WO2010116198A1

WO2010116198A1 - Valve bag and method for filling the bag

Info

Publication number: WO2010116198A1
Application number: PCT/HU2010/000038
Authority: WO
Inventors: Zoltán MANDZSU; Jόzsef id. MANDZSU; Jόzsef ifj. MANDZSU
Original assignee: Mandzsu Zoltan; Mandzsu J Zsef Id; Mandzsu J Zsef Ifj
Priority date: 2009-04-08
Filing date: 2010-04-07
Publication date: 2010-10-14
Also published as: HU0900208D0; WO2010116198A4; HUP0900208A2

Abstract

A packing method is provided, involving a plastic valve bag, which valve bag has a filling valve, and dust retaining venting means adapted to provide venting path for conducting air from an inside to an outside of the valve bag. The dust retaining venting means comprise, for dust retaining, one or both of porous filter means and venting channel, the latter comprising flexible walls adapted to be essentially parallel with each other and adjacent to each other, providing venting path between the flexible walls and essentially parallel with the flexible walls. In a filling process, a quantity of a filling mixture of a granular product and air, containing a predetermined filling mass, of the granular product, is filled into the valve bag through the filling valve. After the filling process the valve bag is put into a position suitable for a stacking thereof, and a quantity of air is conducted out there from through dust retaining venting means. In at least a part of a duration of the filling process the valve bag is vibrated. The filling mixture is filled slowly enough to provide a so-called upper venting place inside the valve bag, which, during the filling process, is either prevented from being reached by a level of, and thereby being filled up with, granular product being in one or both of a solid and a fluidized state, or is reached and filled up with such granular product earliest when the valve bag contains at least 70 percent of the filling mass of the granular product. In at least a part of the duration of the filling process, air is conducted out of the valve bag from the upper venting place.

Description

VALVE BAG AND METHOD FOR FILLING THE BAG

TECHNICAL FIELD

The present invention relates to the packaging of granular bulk solids, containing fine powder, into plastic valve bags, and particularly to methods and plastic valve bags useful for such packaging and packages resulting from such packaging.

BACKGROUND OF THE INVENTION

Fine powder products and products containing fine powder components, such as cement, dry concrete mix, dry milk or cocoa powder, starch, dried egg powder, flour etc., are traditionally packed in valve bags. Valve bags are shipping bags with a filling valve, most often comprising a valve tube made of flexible paper or film material, through which the flowable bulk solid product is introduced into the bag. After the bag is filled with the desired mass of product, the bag is simply laid down, by which the contents compress from inside, and thereby collapse, the flexible valve and thereby close the bag. There are several known basic valve bag shapes and structures, for example as illustrated in patent documents US 3,937,395, US 4,759,641, WO 88/05753, WO 92/02428, WO 2005/092724A1 etc.. Because of their fine powder contents, such products are only known to be bagged mixed with air, i.e., in a form of an air-solid mixture containing more mixed- in air during the filling than in a compacted state. That inevitable surplus air results in that during filling the aerated fine powdery product, unlike, for example, a pelletized product, typically behaves like a fluid. The excess air must be removed from the bag during and after the filling operation, as is generally known and confirmed in numerous patent documents. During the filling, the excess air must be removed in order that a sufficient mass of solid contents find room in the bag as soon as possible and thereafter the filling valve of the bag can immediately be closed. At the moment of the closing of the bag, the bag typically still contains more air than the granular solid material, therein, would store in its finally compacted state. The shape and dimensions of the bag are typically designed to fit the volume of fully compacted contents. As it is known, shipping bags are, for cost savings and security purposes, generally designed to provide packages of an approximately brick-like shape of the lowest ,,bag surface area per product volume" ratio that is possible providing an acceptable stack ability on a given pallet type. The packages can only be safely transported in a stacked state if they are compacted otherwise they look and behave like inflated air cushions, instead of ,,bricks", and make the stack collapse. That makes it necessary to conduct some air out of the valve bags also after they are filled, closed and laid down. In this phase typically much less air is removed from the bag than during the filling operation. (Special powder products like hazardous goods may need hermetic packaging whose filling is different, needing suction from within the bag during filling in order that the whole filling mass finds room therein. The problem therewith is, that in addition, the contents of such hermetic packages need to be further compacted with suction, to a final compaction before the bag is closed, because there is not any possibility to vent thereafter, which makes such filling too slow and therefore too uneconomical for ventable, i.e., e.g. non-hazardous, bulk solid products. Packaging which is hermetic after its being closed is out of the scope of our current invention.)

Valve bags made of porous kraft paper have traditionally been the most popular bag type for the filling of such aerated products, because their whole porous surface acts like a filter letting the air out very quickly and retaining the fine powder in the bag. Valve bags made of polymer film have several advantages (e.g. strength, water-resistance, printability, price, recyclability etc.) over paper but their problem is that their walls are impermeable to air. In order of a sufficient venting during filling, plastic walls of the valve bags can, for example, be perforated. Several approaches are known for preventing the fine powder from escaping from the bag with the air. Patent documents US 4,743,123 and US 2008/0273820A1 teach to apply markedly small perforations, directly penetrating the single-film wall of the bag.

A second approach is to provide a bag that has a porous filter layer (e.g. a nonwoven sheet) covering the perforated film wall. For example, the air coming from inside the bag is lead through the filter sheet in a direction perpendicular to the plane of the filter sheet in patent documents US 2007/0248291A1, US 4,441,209, WO 88/08816, DE 4033499A1, US 4,672,684, US 4,215,725 etc. WO 95/09077 discloses a porous filtering venting solution in which yarn fibers are used to lead air from one side of a film-welding line to the other, while retaining solid particles. A further approach is to provide the bag with a (for example pocket-like) venting channel in which approach the air, coming from within the bag and flowing toward the outside, is lead into the venting channel at one point thereof, is conducted between, and parallel with, adjacent film layers (such as overlappig edges of films) making up the venting channel, and is lead out of the venting channel at another point thereof. The aforementioned conducting of the airflow can, for example, be achieved with a staggered perforation pattern of the two adjacent and parallel film layers. The film layers are typically somewhat spaced from each other with some spacer means and thus prevented from a full-surface abutment with each other in order of letting the air flow between them in the venting channel. Embossed projections are utilized as spacer means for example in patent documents US 3,937,395, WO 2007/115538A1, US 2005/0281493 Al, EP 0444261B1, US 3,628,720 etc. While air escapes from within the bag through these venting channels, fine powder particles settle in the channel, as in a pocket, thus they are prevented from getting out to the environment. Venting channels may also contain porous filter means, such as nonwoven sheets or strips, that act as air- permeable spacers and also enhance the dust-retaining capability of the venting channel. In such cases the air coming from the inside of the bag is typically conducted through the porous filter sheet in a direction parallel with the plane of the filter sheet, as is mentioned for example in German utility patent G8133295.5U1 and in patent document US 2005/0281493A1 (paragraph 0026).

The skilled person will always want to fill as fast as possible. Every prior art document, dealing with the filling of aerated fine powdery products into plastic valve bags provided with vent means, teaches to do the filling as fast as possible and, in order thereof, to use, as much as possible, the vent means of the bag for conducting the excess air out of the bag during the filling operation. Examples of such patent documents, teaching to vent the plastic valve bags during filling, are German utility patent G8133295.5U1, US

2007/0248291 Al, US 3,937,395, EP 0444261B1, US 5,493,844, US 4,441,209, US 4,930,904, US 4,672,684, German utility patent G9110645. IUl. Patent documents DE4033499A1, WO 88/08816, WO 2005/092724A1 and US 4,759,641 teach to vent during filling in order of a faster filling. As it is known to the skilled person, a typical, time-efficient filling process has a first, short phase in which the whole volume of the bag is quickly and completely filled with the aerated, fluidized product, which is followed by a second, usually longer phase in which the air is being conducted through the vent means of the bag from the gas-solid-mix-state contents of the bag and thereby the contents are being condensed so that further solid contents can be added, until the full filling weight finds room in the bag which can then immediately be closed. That typical two-phase filling operation is explained, for example, in patent document WO 88/08816 which teaches to fill an industrial-size, vented plastic valve bag with an aerated, pulverulent product within 8 to 12 seconds.

Prior art teaches to always (even if there is an additional artificial sucking means for a faster extraction of the filled-in air) keep the filling valve of the bag tightly fitted around the filling pipe of the filling machine otherwise the overpressure in the bag would drive the dusty air out of the bag causing loss of product and contamination of the environment. See, for example, patent documents US 4,759,641, WO 88/08816, WO 95/03216, US 4,930,904 and US 4,672,684. That tight fit distinguishes the pressurized, therefore fast, valve-bag filling from a typically much slower filling of open-top type bags, like in a form-fill-seal type packaging, where such a high overpressure is generally not utilized. The skilled person, following the technical prejudice, will by all means exploit this advantage of valve bag packaging.

Porous filter media and venting channels, described hereinabove, have been used in order that fine powder product components be prevented from getting, together with the excess air, out to the environment. These filter bodies and venting channels capture and retain dust and therefore they will necessarily contain more or less dust in the end. That fact is confirmed, for example, in patent documents WO 88/08816, US 2007/0248291 Al, US 4,441,209, US 4,215,725, and US 3,628,720. The fact that filter bodies and venting channels accumulate in themselves dust, is only a problem in the prior art either with respect to a potential blocking thereof (stopping venting) or because dust can potentially get out to the environment. In response, prior art solutions cited hereinabove endeavor, on the one hand, to increase the size and therewith the dust holding capacity of the filter bodies and, on the other hand, to prevent dust entering the venting channels from getting out thereof.

Prior art teaches that recyclable plastic valve bags are advantageous. For example, patent documents WO 88/08816 and DE 4033499A1 teach to use the same polymer for the bag wall and the porous filter body so that they can easily be recycled together. Some further prior art documents will also be referred to, later herein under where appropriate, for the sake of clarity.

Technical prejudice concerning packing methods, based on the prior art analyzed hereinabove, will prompt the skilled person, faced with the problem of using plastic valve bags for the packaging of ventable (e.g. not hazardous) fine bulk solids, to:

• use valve bags with venting means capable of letting out as much air as possible during the filling as well as after the filling,

• use dust retaining means, e.g. porous filters and/or venting channels, capable of holding as much fine dust as possible without getting blocked,

• fit the bag's filling valve tightly, possibly air tightly, around the filling pipe of the filling equipment during filling,

• provide the powder product in an aerated, fluidized state for filling, in order of a better flow thereof, • fill as fast as possible, possibly as fast as with full-porous paper valve bags,

• conduct, during the whole process of the filling, as much air as possible from the bag to the environment through the aforementioned venting means,

• exploit, as much as possible, the dust-filtering capability of the aforementioned venting means during and after filling, in order of a clean work environment and product,

• fill, in a first phase, the full volume of the bag quickly with air-solid mixture and then, in a longer-lasting second phase, remove air from the inner space filled up with fluidized air-solid mixture through the aforementioned venting means while adding more solid product thereto through the filling valve, • provide, from a filling pipe, overpressure in the bag during filling, in order to faster expel the air to provide room for the whole filling mass as soon as possible,

• exploit the hydrostatic pressure of the thick, liquid-like fluidized product for expelling air there from through filtering venting means located in the lower region of the valve bag during filling, • close the filled bags and stack them with a cycle time as short as possible, and use the aforementioned venting means to remove residual air from the closed bag in order of a compacted bag that can be stacked safely, • use homogeneous thermoplastic polymer material components in the bag to make it recyclable.

Vented plastic valve bags with dust retaining capabilities are described in several prior-art patent documents. For example, US 4,470,153, German Utility Patents G 8127809.8U1 and G9110645. IUl, EP 0498047, US 4,215,725, US 3,628,720, WO 2007/115538A1, US 2007/0248291 Al, DE 4033499A1, WO 2005/092724A1, US 3,937,395, EP 0444261 etc. provide industrial shipping bags with venting zones located in main surfaces of the bag, the main surface forming a top of the filled bag, or of the package, in a position suitable for a stacking thereof. The venting zones are provided with porous filters and/or multiwall venting channels for a dust retention. The advantage of this approach is that it provides a considerable venting capacity during filling and also after a stacking. However, its drawback is that a lot of openings are provided in the bag walls which is undesired with respect of moisture getting into the bag. Humid air can get into the bag and also, such bags must always be protected from rain, which prevents the user from exploiting the fact that plastic bags can generally be water impermeable. Cement, lime, adhesive powders, for example, are to be protected from moisture as much as possible. Also, the many holes may make the film weaker. On the other hand, for example German Utility Patent G 8133295.5U1, GB2018721A1, US 4,930,904, US 4,441,209, US 4,759,641, WO 88/08816, etc. provide filtered venting means in the corner of the valve bag, possibly adjacent the filling valve, mainly for a venting during filling. This approach has the advantage that it provides a good venting capability during filling, but the location of the venting means is not always suitable for a good venting after stacking, in a horizontal position of the package. Also in this approach the openings expressly provided for venting provide a possibility of moisture getting into the bag. PCT publication WO 88/08816 and German

Utility Patent G8133295.5Ul both describe a filling valve structure in which a tubular sleeve, constituting the filling valve, is (at least partly) made of porous filter web instead of the usual polymer film, with the objective of conducting air through the filter during the filling of the bag. The solution of the former expressly provides means for keeping the filling valve definitely tightly sealed with the filling pipe for any air that could come out of the bag unfiltered. The filtering filling valve of these documents is not believed to be suitable to vent the valve bag in a lying, stacking position thereof, after a filling, because the filling valve is not adapted to reach into a region of the package in which air, separating from the solids by time, usually gathers in a form of a flat bubble. A drawback of the solution is that the dusty contents of the bag contact the whole filter surface, exposed to them, and thereby pollute it with residual powder. Also, a drawback of the solution appears to be that the valve tube filter, necessarily adapted to effectively filter air passing through it perpendicularly to its plane, i.e. necessarily dense enough therefore, is certainly rather expensive, like e.g. Tyvek ™. On the other hand, PCT publication WO 88/05753 describes a valve bag that has a filling valve provided integrated into its top edge, which valve bag is meant to be filled from above, with a vertical filling direction. The said valve bag is not provided with venting means. Generally, filling valves of plastic and paper valve bags do not close well enough to prevent possible very fine granular contents from getting out of the bag through the filling valves, which is known to be caused by the opposed walls of the valve tube, meant to be adapted to flexibly abut each other in their whole contacting surfaces, do not perfectly abut each other and thereby provide for a path, for fine granules of the bag contents, from inside the bag out to the environment.

THE OBJECTIVE OF THE INVENTION

The skilled person who follows the technical prejudice will not be worried about the quantity of dust captured and held within the fibrous filter and/or double-wall venting channel of a bag as long as it does not block them preventing them from breathing.

We, however, consider the quantity, of the captured dust, typical of the prior art practice unacceptable. We have recognized several drawbacks of the prior art caused by the too much captured dust.

The quantity of fine powder product finally contained in the dust retaining filter bodies, venting channels of the bag (hereinafter referred to as the residual powder), is lost for the customer. It is part of the filling weight, whether it is gross-weighed or net- weighed during filling, and the customer pays for it but the end user is unable to pour it out of the bag because it is stuck into the filter body and/or the venting channel. Therefore the residual powder remains in the emptied bags, and is disposed of, creating solid waste, contaminating the environment. It also makes recycling of the used bags difficult. As it is known, used homogeneous thermoplastic packaging bags can simply be physically recycled, i.e. re-extruded into pellets. Prior to re-extrusion, emptied and re-collected plastic bags are chopped into small pieces or flakes of e.g. 10-30 mm in sizes, then any dirt, typically made up by small traces of the original filling product, attached inside and outside the pieces of bag wall, is washed off with water. Those product residues (e.g. sand, stone, cement etc) that are heavier than water are removed with gravity sorting. The thermoplastic flakes are then dried and fed into an extruder where the plastic is melted and pressed through a metal mesh filter, at the exit of the extruder screw, in order of removing any foreign material from the thermoplastic before its re-pelletizing. In case of the currently discussed bags, however, among the chopped film pieces or flakes there are many pieces of filter bodies and/or double-layer venting channels containing embedded dust contamination which is neither washed out of, nor gravity sorted from, the polymer material. Therefore the residual powder enters, together with the useful polymer, the extruder screw and is finally retained in the mesh filter thereafter which is a drawback because it necessitates frequent filter changes in spite of a careful pre-washing. An even much bigger problem, however, is caused if the residual powder is of a hard, abrasive material (e.g. cement, minerals, stone, ores, metals, glass etc.) because it (passing along the extruder before getting caught in the filter) wears out the extruder (barrel and screw) very fast. The costs thereof are even much higher than those of frequent filter changes. In case of the most popular bulk solid products, like building materials etc, the price of the packaging bag makes up a surprisingly considerable part of the price of the packed product. If the emptied, used plastic bags were really well recyclable, they would be valuable, re-collectable raw material for recycling companies, which would add much value to the original packed product, too.

It is our objective to provide methods for packing pulverulent bulk solids into vented plastic valve bags, including conducting air out of the bags during a filling-in of the contents, and also conducting air through dust retaining venting means out of the bags after they are closed, which methods result in clean, vented, compacted and thereby well stackable packages and that result in a decreased quantity of residual powder contained in the filter bodies and venting channels of the bag and thereby eliminate the drawbacks caused thereby (i.e., loss of material for the user, pollution of the environment, increased costs of filtering in the recycling, accelerated wear of the recycling extruder). We believe that the setting of such an objective is in itself inventive. It is also our objective to provide valve bags that are especially suitable for use with our invented method, especially with the preferable embodiments thereof, and which, in particular, have dust retaining venting means suitable to vent the valve bag after its laying down, e.g. onto a stack, retaining dust, and which are possible to be poor in lower- positioned venting openings, more over, possible to be free from any venting openings, other than in the filling valve, possibly involving a moisture hazard and possibly weakening the bag wall. It is our objective to provide improved fine-dust retaining capability in the filling valve in a closed position thereof.

It is also our objective to provide packages comprising granular contents mixable with air packed in a valve bag provided with dust retaining means for a final venting of the package, the package suitable to contain relatively small quantity of residual powder pollution in its dust retaining venting means thanks to a suitable construction of the valve bag.

DESCRIPTION OF THE INVENTION

In our method, like in the prior art, the pulverulent product is aerated, rich in air, when filled into the bag. In order that the packages can, after they are filled and their valve closed, finally be vented, compacted (and safely stacked), the plastic valve bag needs to have venting means capable of conducting the air out of the bag in the long run. In order of a clean, dust-free appearance, the bag must have venting means having porous filter means and/or venting channel(s). Our idea is to possibly protect these dust retaining venting means from the (usually severe) pollution during filling, mainly reserving them for a venting and filtering after the valve bag is filled and laid down. We consider that it can be more important to lessen the quantity of residual powder product captured and contained by the filtering, dust retaining venting means than to fill fast, which is against technical prejudice of the prior art. We believe that if the achieving of this high packaging quality causes a loss of packing speed, a necessary packing throughput can, for example, be provided with several filling stations operated simultaneously. We have recognized that the following factors are beneficial in order of our objective: • It is beneficial to release from the bag, during the filling, as little (most preferably: nearly zero or zero) quantity of internal air as possible through the filtering means (porous filter bodies and venting channels). Namely, the less air (being potentially dusty,) is lead through the filtering means, the less residual powder they capture, during the filling. This is against technical prejudice which prejudice prompts to use the venting means for releasing as much air as possible during filling.

• It is beneficial if any air that is released from the bag, during the filling, through the filtering means is as clean and dust-free as possible. This is against technical prejudice which prejudice prompts to use the filtering capabilities of the venting means for filtering out as much dust as possible, during the filling.

Further observations being, in combination, parts our recognition are summarized as follows:

Vibrating, during filling, the bag (for example the bottom, or bottom region, thereof) being filled helps the filled-in solid material to separate from the air-solid mixture. For comparison: if, at a given moderate filling speed, there is not any vibration provided during filling, the air-solid mixture fills up the filling space of the bag as a homogeneous fluid. The whole volume of this homogeneous fluid is ready to escape through any venting means, in a form of very dusty air. If, however, at the same moderate filling speed, the bag is being vibrated during filling, then the lower part of the same bag space is being occupied by a quantity of solid, relatively compacted product while the upper part, the rest, of the said same bag space is being occupied by transparent, apparently relatively clean air. With a suitable vibrating (of a suitable duration, frequency and amplitude), the lower, relatively compacted solid is far not as prone to escaping through venting means as in the fluidized state. The upper air, on the other hand, is far much cleaner (hence far less polluting to the filters) than the homogeneous fluidized mass. In addition, the cleaner air needs a lower internal overpressure (being in itself beneficial as explained hereinafter), and fewer and/or smaller openings, for escaping from the bag than a thicker air-solid mixture. A given vibrator has its given capacity and is able to produce its separating effect at a given speed.

If a (momentary and/or average) filling speed low enough with respect to the limited vibrating capacity is selected then the beneficial separating effect can be exploited. It is beneficial to provide the venting means located in the upper region of the bag as far from the bottom of the bag as possible because that way the venting means can longer remain in the clean-air region, free from contacting the solid contents potentially polluting it. It is, as opposed to the technical prejudice, beneficial to provide in the bag, during filling, an overpressure as low as possible because a lower pressure will drive less air and less air- solid mixture (both thus carrying less total contaminant) through the venting means during filling. In order that the excess air is possibly not conducted through the filters and/or venting channels of the dust retaining venting means of the bag during filling, it is beneficial to conduct air out through the open filling valve of the bag, for example by applying a loose fit, providing a free air-path, between the filling valve of the bag and the filling pipe of the equipment. This is also against technical prejudice, but surprisingly, in this case the air escaping at the filling valve does not cause unacceptable pollution because it is kept surprisingly clean inside the bag. It is then beneficial to provide dust retaining venting means of low air permeability (which is, again, against technical prejudice) which will therefore conduct a relatively little quantity of air (and, thereby: of dust) during filling but will well vent, and compact, the bag after its filling and laying down, in the long run.

We exploit the fact that typically much less air needs to be removed, and also much slower, from the bag after its closing than during its filling.

The essence of our method invention is a packing method in which • a plastic valve bag is provided, o the valve bag having a filling valve, o the valve bag having dust retaining venting means adapted to provide venting path for conducting air from an inside of the valve bag to an outside of the valve bag, o the dust retaining venting means comprising, for dust retaining, one or both of

^■ porous filter means and

^■ venting channel comprising flexible walls adapted to be essentially parallel with, and adjacent to, each other providing venting path between, and essentially parallel with, the flexible walls,

• a filling mixture, comprising a mixture of a granular product and air, is provided, and • in a filling process a quantity of the filling mixture, containing a predetermined mass, the filling mass, of the granular product, is filled into the valve bag through the filling valve, and

• after the filling process the valve bag is put into a position suitable for a stacking thereof, and a quantity of air is conducted out therefrom through dust retaining venting means, the method being novel in that

• in at least a part of a duration of the filling process the valve bag is vibrated, and

• the filling mixture is filled slowly enough to provide a place inside the valve bag, so- called upper venting place, which, during the filling process, o is either prevented from being reached by a level of, and thereby being filled up with, granular product being in one or both of a solid and a fluidized state, o or is reached by a level of, and thereby filled up with, granular product, being in one or both of a solid and a fluidized state, earliest when the valve bag contains at least 70 percent of the filling mass of the granular product, and

• in at least a part of the duration of the filling process, air is conducted out of the valve bag from the upper venting place.

The meanings of the terms ,,valve bag" and ,,filling valve" were already mentioned under the ,,Background of the invention" section and are used in this document in a full accordance with their current general technical meaning in the art, which should also be studied in the prior art documents cited in this description. ,,Plastic valve bag" means that it is made of plastic, or at least mainly of plastic which means that a load bearing component of its flexible walls is of plastic, which can be any of the usual forms of plastic valve bags e.g. single- or multiple layered film, monolayer or coextruded, etc. For example, a multiwall paper valve bag typically containing a thin polymer film lining as an intermediate layer is not a plastic valve bag. The filling valve, as is known, can for example be arranged incorporated into a side edge of the valve bag, near an upper corner, providing a horizontal feeding direction or it can be arranged in a top of the bag offering a vertical (downward) feeding direction or it can be of any other suitable form. The filling valve, as is known, most of the times comprises flexible valve films, adapted to be at least partly separated from each other, providing an open path there between for a filling into the valve bag in an open position, state, and also adapted to be rendered into a closed position, state in which the valve films are adjacent to and essentially parallel with each other and are typically pressed to each other by the bulk contents of the valve bag after filling, thereby preventing the contents from getting out of the bag through the valve. However, any other suitable filling valve construction is possible in the plastic valve bag. The valve bag, as provided, has one or more dust retaining venting means. They are suitable to provide, for example they can be put into a position in which they provide, one or more paths through which air can get out from the bag to the environment. They are dust retaining because they are provided with means adapted for retaining dust from the vented air, which can be porous filter means (such as nonwoven sheets, e.g. of spun bond, like Tyvek ™,or SMS i.e. spun bond/melt blown/spun bond type), or venting channels or both. As it is known from the prior art, the flexible walls of a venting channel, if set into a suitable position, are essentially parallel with each other and they are close enough to each other to keep an airflow between them, and essentially parallel with them. A typical, but by not any means limiting, example is that at one point of the venting channel one of the walls (e.g. an inner wall) is adapted to lead air from inside the bag into the venting channel (e.g. the inner wall is perforated there) and at another point of the venting channel the other one of the walls (e.g. an outer wall) is adapted to let air out of the venting channel into the environment (e.g. the outer wall is perforated there), the air being conducted in the venting channel between the two points thereof, while its airborne solid granules are settled, filtered out in the venting channel. In order of the said airflow the walls of the venting channel should be provided with a suitable clearance there between, or should be suitably spaced, which can be provided for, e.g., by the pressure of the conducted air, or for example by suitable spacer means being between the adjacent flexible walls of the venting channel. As the skilled person will know, such spacer means can typically be provided by (e.g. embossed) projections projecting from one or both of the walls into the venting channel or a spacer can be constituted by a porous filter means (e.g. nonwoven sheet) placed into the venting channel. In the latter case the dust retaining is achieved with both a porous filter means and a venting channel. The granular product, in the method, is necessarily provided to be a type of granular product mixable with air, and it is mixed with air in the filling mixture which is provided for a filling and filled into the valve bag. It, in accordance with general knowledge in the prior art, means that the filling mixture is comprised of a certain mass of granular product and of more air than would be contained in that mass of granular product in a compacted state thereof. The filling is facilitated with the mixing with air, fluidizing, of the granular product. In an aerated or fluidized state the granular product is known to be easier (or: at all possible) to fill into a valve bag, i.e., to transport through a filling pipe for example, than in a state poorer in air, in a compacted state thereof. The filling process starts when the filling mixture is started to be filled into the valve bag and it ends by the moment when the necessary filling quantity is filled into the valve bag, this quantity being such a quantity of the filling mixture as contains the predetermined filling mass of the granular product. (The absolute air content of the filling quantity of the filling mixture is usually a function of several parameters of the process, like parameters of the granular product, speed of filling, equipment settings, equipment type such as, for example, pneumatic, combined pneumatic-impeller/pneumatic-auger, or impeller or auger type or any other suitable equipment type etc.) The filling mass can be weighed in any suitable, usual way, e.g. net weighing, gross weighing, with loss-in weight or gain-in weight approach etc. During the filling, the bag can generally be handled in any manner suitable for the purpose. For example, as it is known, during the filling process the valve bag is typically kept in a position suitable for its filling, a filling position, providing an inner space of the valve bag for the filling, the filling space. In this filling position usually the filling valve is positioned at the top of the bag so that filled-in material can fall into the filling space of the bag as easily as possible. The bottom of the bag, in the filling position, is usually, but not necessarily, propped up from underneath in order that the top of the bag where it is suspended (i.e. e.g. the filling valve region) is prevented from a mechanical overload. The valve bags are adapted to be used as industrial shipping bags, therefore their filling mass is known to usually be between about 2 kg and about 55 kg, depending on product type and country. The filling process ends when there are sufficient contents in the bag. After the filling process the filled valve bag, a package, is usually removed from the filling station and put into, e.g. laid down into, a position, or state, suitable for a stacking thereof, a stacking position. In this position usually the biggest, main surfaces of the bag look upwards and downwards. The filled valve bag, the package, can be so laid, for example, onto a conveyer or a table, for a time, or it can be directly placed on top of a stack of similar packages. The bag is kept in this position, suitable for a stacking thereof, and some air is conducted out there from through (one or more of) the dust retaining venting means. It is not necessary that all air conduction is done through dust retaining venting means. Also, it is not necessary that all air, being in the valve bag, is conducted out. Anyway, a certain quantity of air is conducted out in the said manner. While the valve bag is kept in the said position suitable for its stacking, the apparent density of granular product contents in the valve bag is in many cases typically increased. The skilled person will be able to select a suitable arrangement of the dust retaining venting means in the valve bag, for example usually venting means adapted to conduct air, in the stacking position of the valve bag, from a place above the solid contents, i.e. granular product, and under an upper wall of the valve bag. It means that it is useful to vent air from a flat gas bubble that is being formed directly under the top wall of the bag in its stacking position.

Vibrating a bag, or a package, is, in itself, known to a person skilled in the art (for example it is also usual to vibrate packages while they are kept in a horizontal, stacking position, before their actual stacking, in order of giving a regular shape to the packages.) In our method, at least partly during the filling, the valve bag is vibrated, which means that at least a part of the valve bag is exposed to vibration. It is vibrated in order, and in a way, that its granular product contents are, at least partly, also vibrated (probably the parts of the said contents closer to a source of vibration will primarily be vibrated). The vibration can, for example, be easily exerted to the bottom of the bag, from underneath. In this case the usual shelf, propping up the bag from underneath during filling, can be replaced with a vibrating platform. It is also possible to expose sides of the valve bag to vibration. It is useful to expose a part, or parts, of the valve bag filled with granular product to vibration because this way the vibrating effect can directly be transmitted into a bulk of the granular product. The skilled person will be able to select the manner in which the bag and its contents can suitably be vibrated. The skilled person will be able to select a duration for the vibration as a minimum necessary for an acceptable result by trial and error. The vibration can be sinusoidal or of any other suitable form. It is preferable if the direction of the stroke of the vibration is at least approximately normal to the surface, exposed to the vibration, of the valve bag, because this way an undesired shifting, conveying effect of the vibration can be prevented. Generally speaking, the higher the amplitude of the vibration, exerted to the valve bag, the higher its impact on the bag and its contents will be, so the skilled person can set the suitable amplitude to optimize the intensity. The frequency of the vibration can also be optimized by the skilled person, being aware of the given circumstances, by usual trial and error. Like in any practical case of vibrating something in the art, resonance is not desirable. It is preferable for the skilled person to avoid applying a frequency that is too close to a resonance frequency of the partly filled valve bag or of its solid contents because a too intensive vibration of the granules thereof could cause an undesired flow of the excited granules into venting means, similarly to their fluidized state.

Apart from that, generally speaking, the higher the frequency, the higher its impact on the bag and its contents will be, however it should be kept in mind that if the vibration frequency is too far above a resonance frequency of the bag and its contents then it is too difficult to actually bring them into vibration. All this knowledge is believed to be a part of the knowledge of the skilled person. In summary, our experience is that with usual industrial valve bags, our method usually works well with standard 50 Hz, sinusoidal vibrating platforms.

It is an important feature in our method that a filling speed is selected carefully. Namely, the point is that, with respect to the other features of the method, like the vibrating power etc., the filling speed is kept low enough to prevent the level of the granular product in the valve bag from rising too high or from rising high too early. There must be an upper venting place kept, during the filling, that is either totally protected from being reached by a (rising) level of granular product, or is at least protected there from before at least 70 percent of the filling mass of the granular product is filled into the valve bag. The said granular product can either be in a solid or in a fluidized state within the bag, depending on its actual momentary and local air content. A solid state here means a rather compacted, or more or less compact, dense state of the granular product, of a low air content, in which the granular product is unfit to flow like a fluid. On the other hand, a fluidized state here means a state of the granular product in which it has an air content higher than in a solid state thereof, i.e. a more aerated state, in which the granular product is made fit to flow like a fluid, is ready to flow, without respect to whether it is, or is not, actually and momentarily in a flowing motion. The suitable vibration helps the granular product to separate from the air and provides the solid or fluidized granular product filled up to a definite level, a generally horizontal fill level, thereof during the moments of the filling process. The vibration helps to provide a definite phase border with the granular product below and the air above. The air, of course, can be more or less polluted with dust but nevertheless it is definitely separate from the thick fluidized granular product there under. The upper venting place, or in other words upper venting region, therefore is, either during the whole filling process, or at least during a considerable first portion thereof, a place, or spatial region, from which air can be conducted out, at least in a part or parts of the time, during filling. The skilled person will know that, with a given filling mixture and valve bag, the more intensive and effective the vibration is, the faster the filling can be. These features can be optimized with usual trial and error. The upper venting place is typically adjacent the top of the bag during filling. It is possible that there is only one spatial region in the valve bag, qualifying as ,,upper venting place", provided, but it is also theoretically possible that there are more, interconnected or separate, such parts of space provided within a filling space of the valve bag, but at least one of them must be used for conducting air there from in at least a part of the duration of the filling process. Some air is conducted out of the upper venting place, but of course, some further air can also be simultaneously conducted out of the valve bag elsewhere or otherwise. The air can be more or less polluted with dust from the granular product. Air can be conducted out of the upper venting place through dust retaining venting means or otherwise, as will be discussed in more details later herein.

In summary, it is an essential feature of our invention that a suitable, inventive combination of a suitably low filling speed and a suitably effective vibration is applied and thereby a special spatial region, the upper venting place, is provided and maintained in the bag for special venting purposes, all this in order of decreasing the residual powder in dust retaining devices of the bag, which is, in itself, a novel objective in the art. Without a suitable vibration, the method would be too slow therefore too uneconomical. Without the provision of a suitable moderate filling speed our objective could not be sufficiently achieved. Similarly, without a suitable venting from the upper venting place our objective could not be sufficiently achieved. The result, and the advantage of the method, is that the dust retaining venting means remain relatively clean from retained residual powder.

We are providing further particular embodiments of the invention, advantageous with respect to our objectives. As we said, venting from the upper venting place is a clue to achieving our objective and the more it is exploited, the better the result is. It is therefore advantageous if air is being conducted out of the valve bag from the upper venting place in at least 10%, preferably at least 20%, more preferably at least 40%, more preferably at least 60%, more preferably at least 60%, most preferably essentially in 100% of the duration of the filling process.

The longer the upper venting place is being prevented from being flooded by the rising level of the (fluidized and/or solid) granular product, the better the result is. Therefore it is preferable if the upper venting place is, during the filling process, at most reached by a level of, and thereby filled up with, granular product, being in one or both of a solid and a fluidized state, earliest when the valve bag contains at least 75 %, preferably at least 80%, more preferably at least 85%, more preferably at least 90%, more preferably at least 95%, of the filling mass of the granular product. It is even more preferable if the upper venting place is, during the filling process, prevented from being reached by a level of, and thereby being filled up with, granular product being in one or both of a solid and a fluidized state.

This is especially advantageous because the top layer of the granular product in the bag, in other words, the part of the granular product being adjacent the phase border, provided between the solid and the gas phases in the bag, is potentially more flowable, fluidized than the rest of the granular product there under in the bag, therefore it is advantageous if a venting place can be prevented from even a temporary contact with the said fill level or phase border.

We arrived at an insight into the nature of our basic problem, i.e., the particles being accumulated within the dust retaining means, and into why the said problem is more serious if the granular product contains markedly fine powder. Namely, within a particle size interval below 150 microns, the smaller the particles are, definitely the more significant the attracting effect of surface energies of the particles, and of adjacent solid surfaces, is. Therefore the really small particles are much more prone to irreversibly sticking into the pores of the filter and to stubbornly adhering to the inner surfaces of the venting channels. In addition, the adhering effect of electrostatic attraction, very frequent with plastic film bags, also gets much more significant with particles getting smaller. Therefore our method provides a more significant advantage if at least 1 mass percent, preferably at least 2, more preferably at least 3, even more preferably at least 5 mass percent of the granular product has a granule size below 150 microns, preferably 100 microns, more preferably 50 microns, even more preferably 25 microns, even more preferably 10 microns, even more preferably 5 microns. The granule size should preferably be greater than 0.05 microns, under which it is more difficult to filter the dust.

As it is known from the prior art, the powder product is conveyed into the bag together with additional air, the actual quantity of the additional air being a function of the conveying and filling technology. In the prior art, as much (and usually and generally not more) of that excess air is removed from the bag already during the filling, as is enough to provide enough filling space in the bag for filling the whole filling mass, after which the bag is immediately closed, in order of a fast production. The rest of the excess air is lead out, (usually expelled by force,) of the closed bag, through venting means, afterwards. As we said, our newly identified problem originates from airborne powder particles flowing into the porous filter bodies and/or venting channels during filling. After a mixing with air, some granular materials, powders separate, settle, from air relatively easily and quickly while others do not. In prior art valve bag filling technology in which the excess air is forced out with an internal overpressure through the high capacity filters of the bag, any kind of powder that is otherwise slow to separate from air, is also forced to get filtered out (and unfortunately to be stored in the filter means) as quickly as such dust as is prone to a faster separation from air by itself. In other words, in prior art processes for filling fluidized granular products into vented or porous valve bags the significance of the said quality of the granular product (i.e. whether it separates from air quickly or slowly) was in fact low. On the other hand, however, as we said, in our method we want to protect the filter means during filling and therefore we endeavor to decrease the quantity of airborne particles by vibrating and thereby separating the solid granular material from the air. We recognized that our problem to be solved, and therefore also the advantage of our solution, is especially significant with such granular products as are able to take up relatively much additional air and are also able to remain, for a time relatively long with respect to the duration of the filling process, in an aerated state, at rest. The more air is contained, and for the longer time, the higher the significance is. It is therefore preferable if the granular product is suitable to be mixed with air and thereby to be rendered into, and to remain, at rest, at least for 30 seconds, preferably at least for 45 seconds, more preferably at least 60 seconds, more preferably at least 90 seconds, more preferably at least 120 seconds, (preferably, however, at most 168 hours) in an aerated state in which an apparent density of the granular product is at most 98% (preferably at most 95%, more preferably at most 90%, more preferably at most 87%), (preferably, however, at least 15%) of an apparent density of the granular product in a fully compacted state. This specification means that during the specified time interval (e.g. 30 seconds), which the product (about 1 kg of the product) spends at rest, in an open-top, e.g. cube-shaped, vessel in normal atmospheric pressure (i.e. free of artificial over- and under pressure), the apparent density thereof is allowed to increase but at the end of the specified time interval the apparent density must be at most the specified value (e.g. 98% of the compacted apparent density). Apparent density is known to be the density of a loose or compacted granular material determined by dividing actual mass by volume occupied by the material including the voids which are in the material. In a more aerated state the space devoted to cavities between particles, and therefore also the volume occupied, is larger thus the apparent density is lower. A granular product is considered by a skilled person to be in a fully compacted state if it, left at rest in normal atmospheric pressure, is not losing any air any longer, i.e., if its apparent density is constant in time.

As it was mentioned, vibration is an inevitable feature of our method. As we said, the skilled person will be able to select a duration for the vibration as a minimum necessary for an acceptable result. Nevertheless, once a suitable vibrating frequency and amplitude is selected, the longer we vibrate the valve bag during filling, the more significant its compacting effect will be. Therefore in order of our objective it is preferable if the valve bag is vibrated in at least 10 percent of the duration of the filling process, more preferably in at least 20 percent, more preferably at least 30 percent, at least 40 percent, 50 percent, more preferably in at least 75 or even better 90 percent, most preferably 100 percent thereof.

As it was said and is also disclosed in the prior art, porous filter means can accumulate in themselves residual powder that is then very difficult, or practically impossible, to remove there from. Venting channels, however, generally accumulate even more dust, due to their generally large inner space acting as a collecting pocket. Therefore, as we recognized, in case of bags having venting channels for dust retaining the significance of our problem and also the advantage of our invention is higher. Therefore it is preferable if at least one dust retaining venting means comprises, for dust retaining, venting channel comprising flexible walls adapted to be essentially parallel with, and adjacent to, each other providing venting path between, and essentially parallel with, the flexible walls. It may, however, also comprise porous filter means, for example inside the venting channel, for example also acting as a spacer providing venting path for air between the adjacent film layers.

As we said, it is an important element of our recognition that suitably slowing down the filling (which is in itself apparently against technical prejudice) is a clue to achieving our objective. According to our experience with industrial size (preferably about 4 kilogram to about 55 kilogram, especially 9 kg to 41 kg) shipping bags, selecting a moderate average filling speed improves our method. Of course a reasonable minimum filling speed should be kept. At filling masses lower than that, even lower average filling speeds could be desirable, due to transient changes of the momentary filling speed (e.g. ,,puffs" of fluid) at start and stop, which would make the process less economical, while at filling masses higher than that, one could possibly fail in effectively vibrating the whole volume of granular material being in the bag. Therefore it is advantageous if the filling mass is between 4 and 55 kilograms (preferably between 9 and 41 kg, more preferably between 19 kg and 31 kg) and the filling mass divided by the duration of the filling process, the average filling speed, is between 0.08 kilograms per second and 2.3 kilograms per second, preferably between 0.11 kg/s and 2.3 kg/s, more preferably between 0.11 kg/s and 1.7 kg/s, more preferably between 0.11 kg/s and 1.3 kg/s.

If, during the filling process, the momentary filling speed fluctuates, i.e. is significantly unsteady, then the vibrating capacity of the vibrator can not be efficiently exploited, because when the momentary filling speed is just low then there is not enough new material coming into the bag to vibrate but when the momentary filling speed is just high then there is not enough momentary vibrating capacity to quickly separate the newly arrived material by vibration, which means that one must wait i.e. slow down the filling. Therefore, and surprisingly enough, in a given combination of filling mixture and vibrating capacity, our objectives can be reached at a higher effective, or average, filling speed with a uniform-speed filler than with a fluctuating-speed filler. Therefore a momentary filling speed, expressed as the momentary value of mass of granular product filled in per unit time, kept as uniform as possible, would be preferable. There are several types of filling systems, technically useful for fine pulverulent products, known. In this case, the main tasks of a filling system are to, on the one hand, aerate the granular product so that it becomes fluidized and thereby fit for a flow through a filling pipe, and to, on the other hand, cause the aerated mass to actually move, flow through the pipe system into the bag. Pneumatic filling systems, which are traditionally known to be the fastest and most popular with, and primarily used for the packing of really fine, pulverulent granular products like e.g. cement, lime hydrate etc., utilize (mainly solely but sometimes also in combination with some other feeding methods) a flow of pressurized feeding air both for aerating/fluidizing the granular product and for transporting it into the valve bag. Pneumatic filling systems are not known to be popular with coarse, pelletized granular products. On the other hand, impeller and auger type fillers, which are known to be popular with pelletized products (like polymer pellets, animal feed, chemical fertilizer etc.), provide a mechanical feeding of the bulk material from a container, e.g. hopper, into the bag. In such systems the aerating, fluidizing of a fine bulk granular product, e.g. in the container or hopper, must be provided for separately. Momentary variations of granular material flow in pneumatic pipe systems inherently causes momentary variations of air pressure and flow rate, which keep an average feeding rate with a feedback between material flow and air pressure, which results in an uneven, non-uniform momentary feeding rate or filling speed. That, however, has never been found to be a drawback in the prior art. On the other hand, impeller and auger type bag fillers provide an essentially uniform volumetric flow of the aerated material and therefore as long as the rate of aeration thereof is at least nearly constant, the mass-filling speed is also at least nearly uniform. This uniformity, especially at our relatively low filling speeds, is believed to be somewhat higher with the auger systems than with impeller type systems. Therefore it is preferable if, in our method, a valve bag filling machine is provided and used for the filling process, which valve bag filling machine is provided with one or both of a feeding auger and a feeding impeller for a forwarding of the filling mixture. It is even more preferable if the valve bag filling machine is provided with a feeding auger for a forwarding of the filling mixture. This selection, from existing valve bag filling approaches, is believed to be non-obvious in this combination of technical features. The selecting of an auger filler, rather than a pneumatic one, for the purpose of bagging granular products containing fine powder with a primary objective of protecting the valve bag from residual powder and with a secondary objective of filling with the highest average filling speed possible in the given circumstances, is believed to be against technical prejudice of the prior art.

Prior art paper, and vented plastic, valve bags have as high air permeability provided, as necessary for a fast and problem-free filling. The whole surface of paper bags is typically breathing. That can also be the case with prior-art plastic valve bags (see e.g. US 2008/0273820A1). The latter, however, can typically also have venting zones of a form of a strip, or strips, positioned all along the length of the bag, from bottom to top, running in the machine direction in which the film of the bag was manufactured. This full-length dimensioning of the venting areas is typical of prior art valve bags and is believed to be necessary for sufficiently venting the pressurized valve bag during a fast filling. (In open mouth or form-fill-seal bags of the prior art, whose filling method has hereinabove been explained to be basically different, the venting zones may be smaller.) The objective of patent application US 2008/0273820A1, well representing the approach of the prior art, is a vented plastic valve bag for packing aerated fine powders, providing, during a filling process, a fast release of entrained air and maximum capturing of the fluidized powder and thereby reduction of dust on the exterior surface of the bag. The document has a claim for a plastic valve bag having an air permeability of at least 30 m³/h, and describes in its examples, as its best practice, plastic valve bags having an air permeability of over 200 m³/h. The values are reported to be measured with the test method standard in the art, the

Haver and Boecker Bag Permeability Test which measures the volume of air, escaping from a bag through its venting means per unit time, under an internal overpressure of 50 mbar. Such air permeability is taught in the prior art to suitably vent the valve bag during a fast filling. We, however, emphasize that a much lower air permeability value can be enough to vent the residual air from the bag after it is closed.

Prior art literature does not consider a dust retaining venting device located near the bottom of a valve bag to be harmful. Namely its task, in the prior art, is venting, and even though it may not vent always as well as a similar device located near the top of the valve bag, it will always vent better than air-impermeable plastic bag wall. We, however, recognized a surprising drawback of dust retaining venting means located near the bottom of the valve bag. During a filling process, an upper part of the bag's filling space, near to the bag's top, is staying filled up with granular product for a relatively short (or even zero) time while a lower part of the bag's filling space, near to the bag's bottom, is staying filled up therewith for a relatively long time, as a fill level of the (fluidized or/and solid) granular product is rising from the bottom upwards, in the bag. As long as the place in the bag, from which a dust retaining venting means conducts air, is being above the level of the granular product, the venting means at most conducts relatively clean air (which is advantageous), but when the said place is being under the level of the (e.g. fluidized) product, it is potentially conducting polluted air from a filling space of the bag which is undesirable for our objective. During a filling process, the closer, to the bag bottom, a dust retaining venting means conducts the air from, the longer it is exposed to potentially fluidized granular product which is undesired. Such problem can be caused, for example, if the air content of the filling mixture happens to rise too high, for example due to an operator error, which may result in a said exposure to fluidized, polluting material. Or, for example, if the vibration frequency happens, also typically due to an operator error, to be selected too near to a resonance frequency of the granular product mass being in the bag then the granular product can unfortunately temporarily become too flowable and can enter the dust retaining venting means in the lower bag region. We recognized that it is desirable to decrease the total venting capacity of such ,,near-the-bottom" dust retaining venting means, and therewith a potential pollution thereof, to a minimum. It is desirable to expose the places, from which the dust retaining venting means conduct air from, to (potentially fluidized) granular product at most for a relatively short time. That can be achieved if these places are rather in the upper region of the bag than in the lower one. Therefore it is preferable if the provided valve bag

• either has dust retaining venting means adapted to conduct air from places of the valve bag which places are, during the first quarter of the duration of the filling process, reached by a level of, and thereby filled up with, granular product being in one or both of a solid and a fluidized state,

• or is free from such dust retaining venting means, and

• if the provided valve bag has such dust retaining venting means then a total air permeability of such dust retaining venting means of the provided valve bag is positive and less than 10 m³/h, preferably less than 8.5 m³/h, more preferably less than 7 m³/h.

Analogously, it is more preferable if the provided valve bag • either has dust retaining venting means adapted to conduct air from places of the valve bag which places are, during the first half of the duration of the filling process, reached by a level of, and thereby filled up with, granular product being in one or both of a solid and a fluidized state, • or is free from such dust retaining venting means, and

• if the provided valve bag has such dust retaining venting means then a total air permeability of such dust retaining venting means of the provided valve bag is positive and less than 20 m³/h, preferably less than 17 m³/h, more preferably less than 14 m³/h, more preferably less than 10 m³/h. The said air permeability values are to be determined with measuring the volume of air escaping from the bag, as it is provided for the method, through the specified venting means per unit time, measured under an internal overpressure of 50 mbar, generally in accordance with the Haver and Boecker Bag Permeability Test. As the skilled person will know, for the test, any other venting means or any other openings that can conduct air out of other places of the bag can be artificially closed, e.g. with tapes.

As we said under the essence of our method invention, a special upper venting place is provided inside the valve bag during the filling process for at least some air to be conducted out there from. We have recognized that it is preferable, if, in our method, in at least a part of the duration of the filling process, air is conducted out of the valve bag from the upper venting place through the filling valve. It means that a quantity of air, i.e. at least some air, is conducted there while some air can also be conducted elsewhere. The advantage thereof is that thereby other venting means can be exposed to less air stream. One possibility therefore is that a filling pipe is provided inserted in the filling valve for a filling of the filling mixture there through and an air removing channel is provided inserted in the filling valve (for example either beside or coaxial with the filling pipe) for a conducting of air from the upper venting place through the filling valve of the valve bag.

If the air removing channel is, in accordance with most of the prior art teachings, provided with a dust retaining filter then the filter can, by time, get blocked with dust which would be difficult to notice by an operator and could cause a hidden rise in the internal pressure of the bag which, as we explained earlier, would be undesirable. Therefore it is advantageous, if (withstanding the technical prejudice) in at least a part of the duration of the filling process, air is conducted out of the valve bag from the upper venting place through the filling valve free from being exposed to a filtering by porous filter means. It means that the said air is left unfiltered by porous filter means, while conducted out through the filling valve. It means that a quantity of air is conducted without such filtering, while some air can also be conducted otherwise. At least a part, preferably the majority, of the air conducted out from the upper venting place through the filling valve is prevented from being filtered by porous filter means, which basically means a direct conducting out thereof and is made possible by the fact that the said air is kept relatively clean, for a relatively long time during the filling process. The advantage of this method is that it decreases a risk of an unnoticed rise in a bag pressure potentially caused by a potentially blocked filter.

As we recognized, another problem, hidden to operating personnel, can potentially be caused by an unwanted rising of the air content of the filling mixture. Namely, if the said air content happens to rise unnoticed, then the level of the granular product in the bag can rise higher than normally which is undesired with respect to our teaching described hereinabove. Also, a generally increased air quantity entering the bag can generally cause an increased air quantity leaving the bag through the dust retaining venting means which has also been explained hereinabove to generally be disadvantageous. Our objective, here, is to provide, in order of quality assurance, a method to make such an unwanted rising of the fill level in the bag or of the air content of the filling mixture immediately visible to the operator. On the other hand, as we said, it would be beneficial to safely provide a relatively low overpressure in the bag during filling. In order of these objectives, it is preferable, if (withstanding the technical prejudice) a filling pipe is provided inserted in the filling valve in a loose manner and thereby a gap, adapted to be permeable for the granular product being in the valve bag, is provided at least in a part of the duration of the filling process within the filling valve at least partly around the filling pipe, and the filling mixture is filled into the valve bag from the filling pipe, and air is conducted out from the upper venting place through the gap. It means that there is a gap provided between the filling pipe and the filling valve, which gap can consist of one opening or of more opening regions which can be interconnected with or separate from each other. The gap is either provided all the time during the filling or only in a part of the duration of the filling process. The gap is permeable for the granular product that can be found in the valve bag which means that if the said granular product happens to rise high enough it is able to find its way out of the bag through the gap. In order thereof, the gap is big enough to let granular product particles pass there through. A quantity of air is conducted out through the gap but of course other quantities of air can be conducted from the upper venting place otherwise. The advantage of this method is that as soon as the level of the fluidized or solid granular product rises as high as it reaches the gap, it gets out of the valve bag through the gap and the appearance of the granular solid from the filling valve immediately tells the operator about the too high fill level who can then intervene. Also, the gap will easily release air and thereby keep internal bag pressure at low levels. On the other hand, the gap area should be smaller than 70 cm² in order to provide sufficient place for the filling pipe in the filling valve. In this respect it is preferable if a total area of the gap is at most 70 cm² and at least 0.1 cm², preferably at least 0.25 cm², more preferably at least 0.35 cm², more preferably at least 0.5 cm². The total area of the gap is meant to include the area of all interconnected or separate openings making up the gap as described above. In order of providing a problem-free operation with a low internal bag pressure it is preferable if the gap is, during the filling process, prevented from being reached by a level of, and thereby being filled up with, granular product being in one or both of a solid and a fluidized state. The said loose fit of the filling pipe in the filling valve is preferably used as a main means for venting the bag during the filling. It is very advantageous because the filling valve is usually among the highest-lying parts of the valve bag during the filling process therefore it is relatively easy to keep it from being flooded by the rising level of the granular product during the filling process. That also means that a dust retaining venting means, provided suitably integrated into the filling valve, will be least exposed to a potential penetration by a polluting flow of fluid or solid granular product. Also, with a suitable arrangement, conducted-out air will rather flow through the (free areas of the) gap than through any dust retaining venting means integrated into the filling valve, due to the former certainly having a lower resistance to air flow. The resistance of the gap to air flow is preferably low and in this case it is preferable if other dust retaining venting means of the valve bag, being elsewhere than, e.g. lower than, the filling valve, are at most exposed to relatively small amounts of air flow penetrating them during the filling process. In order thereof it is preferable if

• either the provided valve bag only has dust retaining venting means positioned in its filling valve, • or in the provided valve bag a total air permeability of dust retaining venting means, being at places of the valve bag other than the filling valve, is positive and less than 30 m³/h, preferably less than 27 m³/h, more preferably less than 25 m³/h, more preferably less than 20 m³/h, more preferably less than 18 m³/h.

The said air permeability value is to be determined with measuring the volume of air escaping from the bag, as it is provided for the method, through the specified venting means per unit time, measured under an internal overpressure of 50 mbar, generally in accordance with the Haver and Boecker Bag Permeability Test. The advantage of this method is that it provides very little, or zero, amounts of potential residual powder finally stored in the dust retaining venting means while, with a suitable arrangement selected by the skilled person, it provides dust retaining venting means for a venting of the bag after the filling and closing thereof, in order of a compaction and safe stacking of the bag.

As we said, it is preferable if the gap is, during the filling process, protected from being reached by a level of the granular product. A valve bag offering, under the given circumstances, room, under the gap, big enough for the whole quantity of the said granular product, is obviously needed therefore. In order of economy it is preferable to possibly avoid using a bag bigger than necessary for a given purpose. With respect to our invented method, a test method which differs from our invented method in that the vibration is totally omitted for test purposes, can be utilized to check the size of a bag: in the test method, at a given filling speed, if such a valve bag is provided as is big enough to receive and hold the full filling mass of granular product without flooding the gap, even with the vibration totally omitted (e.g. switched off) then the said valve bag is bigger than an optimum for our invented method. Namely, any vibration separates, to a certain extent, the solid matter from the air and drives the resulting air out through the gap, thereby somewhat compacts the granular contents, therefore with some vibration the level thereof will be somewhat lower than without vibration. Also, as we said, the vibration keeps the air in the upper part of the space of the bag relatively clean therefore easily flowing, escaping through any venting means being there. Totally switching off the vibration certainly makes the upper part of the contents of the bag more viscous, thicker, and therefore the venting of the bag, through venting means possibly located e.g. in the sides of the bag, slower - apart from how the vibration affects the quantity of residual powder. Therefore it is preferable if, in our invented method, such a valve bag is provided as is small enough to only be adapted to receive the filling mass of the granular product, and keep a level thereof under the gap, by at least a vibration of the valve bag. This means that the provided bag is relatively small therefore it is only made fit for the purpose, i.e. for receiving the filling mass of the granular product and keeping its level under the gap, if the bag is at least vibrated. ,,At least" means that other features of the method can possibly also contribute to the bag being fit for the said purpose but the feature of the bag being vibrated is definitely necessary for the bag being made fit for the said purpose. It means that without the vibration the level of the granular product would reach and flood the gap, due to the size of the bag being relatively small.

Another approach for air removal through the filling valve is that a filling pipe is provided, and the filling mixture is filled through the filling valve into the valve bag from the filling pipe and, in at least a part of the duration of the filling process, air is conducted out of the valve bag from the upper venting place upward through the filling pipe. That can be possible because, thanks to our method, the air in the upper venting place is kept relatively clean and if the pressure of the filling mixture in the filling pipe is not too high for the valve bag to bear, then it can be offset by the air pressure in the upper venting place and the air can, in form of bubbles, flow back upward in the filling pipe in a direction opposite a flow direction of the filling mixture in the same filling pipe. It is a phenomenon driven by gravity, similar to that of air bubbles rising up in the neck of a bottle while water is flowing out downward through the same neck. This would not be possible if the upper venting place was filled with a fluid similar to the fluid coming from the filling pipe, which is typically the case in the prior art. This air-conducting is based on the fact that the air to be conducted out upward through the filling pipe is a material separate from, and having a definitely lower density than, the fluidized granular product conducted into the bag through the same filling pipe. The skilled person will know that, in order of this to work, a way of the air bubbles out to the environment must be provided, for example through the filling pipe and through a mass of fluidized granular product prepared for filling. In this case the air bubbles can also be used to keep the prepared mass in a fluidized, flowable state. The advantage of this method is that it helps to keep the environment of the filling clean and that it does not use any filters which could possibly get blocked. It is preferable if an overpressure in the upper venting place is kept below 2 bars, preferably below 1.5 bars, more preferably below 1.2 bars, more preferably below 1 bar, more preferably below 0.8 bars. The term overpressure means the pressure difference over the ambient pressure. The advantage of this low pressure was explained earlier hereinabove.

The method-embodiments described hereinabove provide compacted packages and a decreased quantity of residual powder contained in the filter bodies and venting channels of the valve bag and thereby eliminate such prior-art drawbacks as loss of material for the user and pollution of the environment. Our problem to be solved (namely to also lessen the costs of filtering in a recycling of the material of the used bag), and thereby also our solution, is more significant if the provided valve bag is of recyclable thermoplastic. This term, in accordance with its current general use in the art, means that the valve bag, as is provided for the method, may also contain non-thermoplastic components, for example, among others, paints, lacquers etc. The usual filtering in a physical recycling process, as we explained earlier, is just meant to remove, among others, these, and other, non- thermoplastic components from the melt. The significance of an efficient recycling is even higher, therefore in our method it is even more preferable if the valve bag at most has such porous filter means as are of a thermoplastic material compatible with the thermoplastic material of a rest of the valve bag. The term ,,at most" means that either the valve bag has such porous filter means as are hereby specified or the valve bag is free from porous filter means. Here the term ,,compatible" has the usual technical meaning: it means that the two thermoplastics can be physically recycled together and they can readily mix in the melt, forming a homogeneous polymer blend. Examples, well known to the skilled person, of pairs of compatible polymers are a polyolefin with another polyolefin, especially a polyethylene with another polyethylene, especially if they have similar melt flow rates.

As we said, the residual powder, for example starch, coca powder, food ingredients etc, in the prior art causes the filters in the recycling technology to be changed more frequently. If, however, as we said, the residual powder comprises hard, abrasive granules, its effect in the recycling is even much more severe, namely it also wears out the extruder screw and barrel of the recycling equipment too fast. Therefore, as we recognized, our problem to be solved (namely to also lessen the wear of the recycling extruder in a recycling of the material of the used bag), and thereby also our solution, is more significant if the granular product contains any one or more of cement, calcium oxide, calcium carbonate, calcium hydroxide, sand, mineral, stone, ore, metal and glass. Due to their very hard material combined with their usually very fine dust structure, the advantage of our method is especially significant if the granular product contains any one or more of cement, calcium oxide, calcium carbonate and calcium hydroxide. Cement is a very abrasive material. It is manufactured to be applied in hydraulic reactions therefore it necessarily has very fine granules. A product having very small granules makes, as we explained earlier, the advantage of our invention more significant. Due to a special combination of small particle size and an extremely abrasive character, cement and other granular products containing cement make the advantage provided by our method especially significant. Therefore it is preferable if at least 1 mass percent, preferably at least 2 mass percent, more preferably at least 3 mass percent of the granular product is cement. It can, for example, be Portland cement or any other kind of cement.

As we said, after the filling process the filled valve bag is put into a position suitable for a stacking thereof, and a quantity of air is conducted out there from through dust retaining venting means. In the prior art this usually means that the filled valve bag is, immediately after the filling is completed, laid down approximately horizontally (usually onto a transporting conveyer belt) and is, usually very soon thereafter, compressed from above, usually by another endless belt, so that most of the air being in the bag is quickly expelled through the dust retaining venting means of the bag. In the prior art, that is a popular way of a quick compacting of the individual packages in order of a stacking thereof with a short cycle time. We, however, recognized that in order of our objective it is preferable if the filled valve bag is left at rest and kept from any extra external compression (e.g. from above) for a while after it is laid down. During that resting time the solid contents of the bag spontaneously separate from the residual air, and the latter is accumulated under a top wall of the valve bag in a form of a flat bubble of relatively clean air. If that relatively clean air is conducted out through dust retaining venting means then very little residual powder gets accumulated therein. Therefore it is preferable if after the filling process the filled valve bag is put into a position suitable for a stacking thereof, and is kept at rest in such a position at least for 60 seconds, preferably at least for 90 seconds, more preferably at least for 120 seconds, more preferably at least for 150 seconds, while with gravity- sorting some air is separated from, and brought above, granular product in the valve bag, and is conducted out there from through dust retaining venting means and thereby an apparent density of the granular product in the valve bag is increased. The valve bag can also be kept at rest much longer than that, depending e.g. on actual logistics, it can for example be kept at rest for up to 168 hours, or even more, unmoved. The term "while" means that at least during a part of the duration, e.g. in a first part of the duration, of the aforementioned time interval some air is separated, brought and conducted. Here the meaning of the term ,,kept at rest" includes that the package is left at rest, unmoved, and is prevented from any such external forces as are not necessarily resulting from its being at rest in such a position. E.g. the package being at rest in a suitable position is necessarily exposed to forces and pressures originating from gravity, including its own weight force and possible static friction forces by its environment, but at the same, time the package, for example, is prevented from being compressed with any additional compressing means, like another package put on its top or a compressing belt etc. The advantage of this method is that the residual air, made relatively clean before being conducted out, exposes the dust retaining venting means to a relatively small quantity of polluting residual powder.

In our comparative Example 1 we illustrate how much residual powder a prior-art valve- bag package of fine granular product can contain in its dust retaining venting means. Our invented method is especially advantageous if during and after the filling process less than a total of 40 g (preferably less than a total of 35 g, more preferably less than a total of 30 g, more preferably less than a total of 25 g, more preferably less than a total of 20 g, more preferably less than a total of 15 g, more preferably less than a total of 10 g, even more preferably less than a total of 5 g) of granular product is accumulated in dust retaining venting means. The lower limit is the ideal zero quantity. It practically means that any and all porous filter means and venting channels of all of the dust retaining venting means of the valve bag at most contain a total of the said quantity of residual powder at the end of the method.

It is preferable if any of the invented plastic valve bags, described hereinafter, is provided for the packaging method.

As we said, we are providing a new valve bag (and preferred embodiments thereof) and also a new package, and its embodiments, all in accordance with a single main general inventive concept, common with that of the method invention. The valve bag and the package have a special relationship to each other. It can, in a first possible approach, be said that both, the valve bag and the package, are a "packaging unit", comprising a valve bag, the valve bag either being essentially free of granular solid contents or containing granular solid contents. The packaging unit can be characterized with features of the valve bag and, if applicable, in combination with those of the contents. However, we believe that is makes the description somewhat clearer and easier to understand if we decide to discuss the valve bag and the package separately. In this second approach, the package is considered as a ventable packaging system, that lets internal air out and compacts its granular contents in its operation, the system containing more than one component, and, as one component, the invented valve bag product. Based on this paragraph, however, the interpretation of the invention can readily be transformed into a form corresponding to the said first approach.

Regarding a valve bag invention, we mentioned that it is our objective to provide a valve bag that needs as few openings in the bag wall as possible for a use in accordance with our method invention hereinabove and especially for a suitable final venting, in order, for example, to improve the bag's moisture resistance. One access opening, however, appears to by all means be necessary, namely that of the filling valve. We recognized that if a dust retaining venting means is provided integrated into the filling valve of the bag then the number and size of further vent openings can be decreased, or they even can preferably be omitted. On the other hand, the filling valve is usually atop the bag during filling, therefore providing a dust retaining venting means there appears to be in an advantageous accordance with our method inventions hereinabove.

The essence of our valve bag invention is a plastic valve bag,

• having a filling valve o for a filling of the valve bag with a granular product and o for a closing of the valve bag for retaining the granular product in the valve bag, • the filling valve comprising an outer opening and an inner opening and a flexible valve tube connecting the outer opening and the inner opening, o the valve tube collapsible for the closing of the valve bag, the valve bag being novel in that • the filling valve has a flexible, porous filter sheet provided, o the filter sheet having two opposed major sheet surfaces o the filter sheet provided at least partly inside the valve tube, suitably fixed,

• the filling valve adapted to provide, at a suitable open state of the valve tube, a filling path inside the valve tube beside the filter sheet for the filling of the valve bag through the outer opening and through the inner opening, and

• the filling valve adapted to provide, at a suitable collapsed state of the valve tube, a venting path for conducting air o inside the valve tube, at least partly through the filter sheet essentially in a direction parallel with the major sheet surfaces of the filter sheet, o from an inside of the valve bag to the outer opening and there through to an outside of the valve bag.

Meanings and details of features like valve bag, plastic valve bag, filling valve have already been mentioned hereinabove. It is known and also we discussed how, in general, a filling valve is used for a filling and a closing of the valve bag. The invented valve bag is suitable to be filled with a granular product which can be, in this product invention, either mixable with air or other granular product. A benefit of the bag, namely its venting capability, however, is better exploited if used with a granular product mixable with air. Like generally in the prior art, opposed ends of the valve tube provide for the inner and outer openings of the filling valve. The inner opening, as well as the outer opening, is preferably a single, unitary orifice, however it can also be divided into separate regions if necessary. The valve tube is preferably, but not necessarily, free from further openings. The valve tube, like generally in the prior art, is flexible and can be collapsed, for closing the bag, or open, to allow a filling of the bag. The valve tube can be made e.g. of plastic film or of any other suitable material. The valve tube can possibly, but not necessarily, partly be constituted by a part of the bag wall, e.g. in a case in which a film sheet is attached, with two edge weldings, to an inner side of the bag wall, the two together forming a valve tube with an inner and an outer opening. An important feature of the invention is that a filter sheet is added to the filling valve. The filter sheet is flexible and is air permeable and suitable to filter the air permeating it. The filter sheet can suitably comprise, e.g., a nonwoven fabric. As in its venting function it is used to filter air that is being conducted in its lateral direction, i.e. essentially parallel with its major sheet surfaces, it is usually sufficient if, (unlike with filter sheets used for filtering air penetrating them in a direction normal to their major surfaces,) the filter sheet is rather thin, lightweight, possibly having a rather uneven fiber distribution possibly resulting in a rather uneven distribution of local thickness, local surface weight and local fiber density. There can even be empty spots, definite macro-cavities, in the filter sheet which would make the filter sheet unsuitable for a filtering in the said normal direction. Therefore, due to this lateral-direction, (as opposed to a normal-direction,) filtering, the filter sheet can be inexpensive, like e.g. a very lightweight (e.g. 10-14 g/m²) spun bond nonwoven which is known to be one of the cheapest nonwovens in the market. At least a part (or parts) of the filter sheet is, importantly enough, inside the valve tube, and the filter sheet performs this laterally directed air conducting inside the valve tube, therefore necessarily surrounded, there, by the valve tube. The said part of the valve tube surrounding the filter sheet keeps the air inside the valve tube, and keeps the filter sheet inside the valve tube, and causes the air to pass through the filter sheet in a lateral direction thereof. (That makes our arrangement differ from such prior art arrangements in which a filter sheet makes up the valve tube, in part or in whole, for example a half of the valve tube is plastic film and the other half of the valve tube is a nonwoven filter.) The filter sheet is suitably fixed, thereby kept at least partly inside the valve tube. It means that the filter sheet has a suitable fixing, attachment with the valve bag, for example with the valve tube. The filter sheet is also fixed suitably for adapting the filter sheet to give a suitable way for a filling path in an open state of the valve tube and to provide a suitable venting path at a collapsed state thereof. In practice, this can, for example, mean that the filter sheet covers a part (e.g. essentially a half) of an inner surface of the valve tube and has attachment with the filling valve along the outer opening and also along lines, generally parallel with the filling path, in the valve tube. The fixing, the attachment is suitable if it at least keeps the filter sheet out of the filling path during filling and keeps it inside the collapsed valve tube for a suitable venting at a collapsed state of the valve tube.

At a collapsed state of the valve tube, the filling valve, with the filter sheet inside the valve tube, provides a venting path for conducting air inside the valve tube, at least partly through the filter sheet. As the skilled person will know, a preferable way therefore is if the filter sheet is adapted to, at a collapsed state of the valve tube, fill a whole cross section of a channel, free for air conducting, provided inside the collapsed valve tube at least somewhere in the valve tube. That arrangement is also advantageous with respect to a retention of fine, dusty granular product contents. As the skilled person knows, though an internal air pressure can possibly separate abutting parts of the collapsed valve tube, in order of air being much easier conducted inside the collapsed valve tube, a space is preferably provided for, between opposed, abutting parts of the collapsed valve tube. If there are parts of the collapsed valve tube provided with spacer means (e.g. with the filter sheet as a spacer) and simultaneously there are other parts of the collapsed valve tube free from any such spacer means then air, and possible granular bag contents, will primarily tend to flow through those parts of the collapsed valve tube provided with a spacer. The filter sheet acts as a suitable spacer providing for such a space, where the filter sheet is.

The skilled person can decide to provide filter sheet all along a venting path, inside the valve tube, from an inside of the valve bag, e.g. through the inner opening, to the outer opening, from which the air can then get out of the valve bag. On the other hand, the skilled person can also choose to provide, e.g. in parts of the said venting path, other spacing means, e.g. embossed projections, alone or together with the filter sheet, hi practice, it can, for example, be a safe solution to provide a filter sheet in a whole length of the valve tube, from the inner opening to the outer opening, e.g. in essentially a half, or in at least a half, of an inner circumference of the valve tube. It is also possible that a part, suitably near to the inner opening, of the valve tube is provided with additional openings, e.g. perforations, for providing an entry point through which air can enter inside the valve tube. In this case at least a venting path starting from that entry point should preferably be provided with a suitable a spacer. Thanks to this venting mechanism, the valve bag, after its filling, with an aerated granular product, and closing, can be arranged in a suitable position which provides the inner opening of the closed filling valve above the solid contents of the bag, and in which air, separating from the solid contents and rising on top of an inner space of the closed valve bag, is collected in a region adjacent to the inner opening of the filling valve through which the air can be conducted out in a filtered manner.

The advantage of this valve bag is that, on the one hand, it can be used to vent, in a filtered manner, a package made there from after a filling and closing thereof, and, on the other hand, it can be formed to have surprisingly few, or even none of, additional venting openings. That, on the one hand, makes the bag preferable to be used with our invented methods and provides a possibility for a surprisingly low level of residual powder pollution in a package made from the bag and, on the other hand, provides a possibility for an improved resistance in the bag against an ingress of humid air and rain and also against a rupture of the bag wall.

With regard to our package objectives, and with advantages originating from those of the valve bag above, the essence of our package invention is a package comprising a vented plastic valve bag and contents of a granular product, mixable with air, in the valve bag, the package being novel in that it comprises the aforementioned valve bag. The venting operation of the package is analogous to that described for the filled valve bag.

Returning now to our valve bag invention; as we said, it is a usual problem of the prior art that the granular contents may exit through the closed, collapsed filling valve. A cause thereof is typically the valve tube being too stiff to close properly. In the prior art, the finer the contents are, the more flexible the valve tube should be to close suitably. Therefore, in the prior art, the skilled person endeavored to provide a valve tube as flexible as possible. The stiffness of the valve tube, however, cannot usually be decreased too much, due to other respects. We recognized that the flexible porous filter sheet, if provided with a suitable low stiffness and if provided with a suitable freedom to move inside the valve tube, can be adapted to retain the granular contents in the bag even if the valve tube is, in whole or in part, relatively stiff. Therefore it is preferable if, in the valve bag,

• the filter sheet has a stiffness lower than a stiffness of at least a part of the valve tube and

• the filter sheet has a marginal portion adapted to be, at least at the collapsed state of the valve tube, inside the valve tube and adjacent the inner opening, and

• at least parts of the major sheet surfaces in the marginal portion are free from direct attachment with the valve tube.

The stiffnesses of the filter sheet and of the valve tube are to be compared in accordance with the standard ASTM D 1388, ,,Option A: Cantilever test". For example, their bending lengths can be compared. This stiffness definition (,,fabric stiffness" or ,,drape stiffness") is generally used for textiles and is also widespread for films and paper, as described in detail in patent documents, e.g., US 6,923,889, US 6,355,344, US 5,607,758, US 6,911,407. Any portion of the filter's major sheet surface is defined to have a direct attachment with the valve tube if the said portion is essentially parallel with and in contact with a portion of the valve tube and they are fixed e.g. adhered, bonded, welded, fused, stuck, sewn etc. to each other. The advantage of this bag is that the innermost edge of the flexible filter sheet, being free of adhesion, bond or fixing with the adjacent, abutting parts of the valve tube, can be freely tucked in, wrinkled to a certain extent by the granular matter trying to enter the valve tube from the bag through the inner opening, which causes the relatively pliable filter sheet to fill up all, or most of, the cavities inside the collapsed valve tube through which the granular product could possibly get out. The filter sheet, however, remains permeable to air. Parts of the filter sheet being farther from the inner opening are preferably fixed to the valve tube for a provision of the said suitable fixing thereof.

In connection with the stiffness of the valve tube we also have further recognition. As we said in our methods, it is preferable if the filling valve is fitted around a filling pipe in a loose manner. The skilled person can, in a given case, design a filling valve having an inner circumference greater than an outer circumference of a filling pipe. In such a case, nevertheless, it is an objective of ours to provide a filling valve construction that inherently facilitates the said loose fit. We recognized that if, (against technical prejudice,) the valve tube is of a stiff material then it often apparently automatically and safely provides for a free space between the filling pipe and the valve tube, if the circumferences are suitably dimensioned. On the other hand, the said stiffness should not be extremely high in order of a practical usefulness. Therefore it is preferable if a bending length of a material of at least a part of the valve tube is smaller than 600 mm and greater than 22.5 mm, preferably greater than 25 mm, more preferably greater than 27.5 mm, more preferably greater than 30 mm, even more preferably greater than 32.5 mm. The bending length is to be determined in accordance with the standard ASTM D 1388, ,,Option A: Cantilever test".

The valve bag can usually be well used for the packaging of fine aerated granular products in a way in which the valve is collapsed, closed and the bag is laid down into a stacking position and thereafter filtered air is conducted out through the valve tube through the filter sheet. The lower the total momentary venting capacity of the bag is, the longer this final venting can last. It is possible that the package is already put into a stack of packages during this final venting, which involves a temporary (and possibly: latent) risk of the stack collapsing due to the bags temporarily behaving like inflated pillows until they are finally sufficiently vented. Therefore it has a special significance that our valve bag be provided, preferably at least in suitable surface parts thereof, with a static coefficient of friction high enough to stabilize the stack. The lower a total air permeability of the valve bag is, the higher the said significance is recognized to be. The skilled person will know that such suitable surface parts of a bag, and thereby of a package, are, for example, those that look upward and downward and provide for an abutting with further packages within the stack, also referred to as ,,main abutting bag wall parts" later herein. However, the side surfaces of packages can also usefully adhere, with a high friction, to each other. At valve bags venting faster, like usual prior art vented valve bags, this feature does not have such a high significance. Therefore it is preferable if the valve bag has an outer surface having, at least partly, a static coefficient of friction higher than 0.30, preferably higher than 0.33, more preferably higher than 0.36, more preferably higher than 0.40, more preferably higher than 0.43, more preferably higher than 0.46, more preferably higher than 0.49, or possibly even higher. An upper limit for the static coefficient of friction can, for example, be 50.0.

Static coefficient of friction is a feature of the material of the outer surface and does not refer to features of a possible adhesive there, used for stack stabilizing purposes. Static coefficient of friction can be increased with projections, e.g. embossed projections, projecting from the surface. Static coefficient of friction is to be measured according to the standard ISO 8295, and is meant to be an effective measured value reflecting possible antislip effects of possible antislip means in the bag wall surfaces like e.g. projections, e.g. embossed projections.

As we said in discussing our method invention, it is preferable if, during a filling of the valve bag, air is conducted out of the valve bag, from a place as high as possible (in order that the level of the filled-in material cannot, or not too early, reach it), preferably through the valve bag, and preferably in some cases, in a non-horizontal, most preferably vertical, direction in which air bubbles can rise upwards in a thick fluid. It is our objective now to provide a valve bag that is useful for that kind of filling, and also preferable for providing the collapsed inner opening of the filling valve in a preferable position with respect to the previous paragraphs. We recognized that, for this purpose, it is preferable if the filling of the valve bag can be done in the middle of the upper edge of the bag, with a filling directed vertically downwards. That needs a filling valve positioned in a side edge of the bag (to be the upper edge during the filling), preferably approximately in the middle thereof, the filling valve oriented, at least approximately, directly towards the center of the bag. Therefore it is preferable if

• the valve bag has side edges and a center of mass, and • the valve bag has the filling valve integrated into one of the side edges, and

• the filling valve is adapted to provide, at a suitable open state of the valve tube, a filling path for the filling of the valve bag in a direction of an essentially straight line through the outer opening, through an inside of the valve tube and through the inner opening, • the essentially straight line adapted to cross the center of mass of the valve bag.

This arrangement is advantageous for the desired methods and also because it facilitates the provision of a collapsed inner opening with a preferable robust and full overlap with such wall parts of the bag, as serve as horizontal abutting bag surfaces in a stack, defined as main abutting bag wall part later herein.

Analogously to a preferred embodiment of our method invention, it is preferable if

• either the valve bag has dust retaining venting means located in its parts other than the filling valve and providing venting path for conducting air from an inside of the valve bag to an outside of the valve bag, o the dust retaining venting means comprising, for dust retaining, one or both of

^■ porous filter means and

• or the valve bag is free from such dust retaining venting means,

• and if the valve bag has such dust retaining venting means then a total air permeability of such dust retaining venting means is positive and less than 30 m³/h, preferably less than 27 m³/h, more preferably less than 25 m³/h, more preferably less than 20 m³/h, more preferably less than 18 m³/h.

It is even more preferable if the valve bag is free from such dust retaining venting means. It is even more preferable if parts of the valve bag other than its filling valve are essentially air impermeable. The air permeability is measured in the manner detailed earlier hereinabove. The advantages of this bag embodiment are those (e.g. residual powder decrease etc.) detailed in the corresponding method embodiment. In addition, such a bag is less prone to letting moisture into the bag, and to rupture due to perforations, than prior art vented bags. Nevertheless, the bag vents entrapped air from a package in the long run.

Analogously to a preferred embodiment of our method invention, it is preferable if the valve bag at most has such porous filter means as are of a thermoplastic material compatible with the thermoplastic material of a rest of the valve bag. The advantages of this bag embodiment are those (e.g. advantageous recyclability) detailed in the corresponding method embodiment.

With regard to our package objectives, and with advantages originating from those of the aforementioned valve bag embodiments, our package invention is preferable if it comprises a valve bag corresponding to the any one or more of the aforementioned valve bag embodiments.

In analogy to preferred embodiments of our method invention, our package invention is preferable if at least 1 mass percent, preferably at least 2, more preferably at least 3, even more preferably at least 5 mass percent of the granular product has a granule size below

150 microns, preferably 100 microns, more preferably 50 microns, even more preferably 25 microns, even more preferably 10 microns, even more preferably 5 microns. Also, our package invention is preferable if the granular product is suitable to be mixed with air and thereby to be rendered into, and to remain, at rest, at least for 30 seconds, preferably at least for 45 seconds, more preferably at least 60 seconds, more preferably at least 90 seconds, more preferably at least 120 seconds, in an aerated state in which an apparent density of the granular product is at most 98% (preferably at most 95%, more preferably at most 90%, more preferably at most 87%,) of an apparent density of the granular product in a fully compacted state. Also, our package invention is preferable if the granular product contains any one or more of cement, calcium oxide, calcium carbonate, calcium hydroxide, sand, mineral, stone, ore, metal and glass. Also, it is preferable if the granular product contains any one or more of cement, calcium oxide, calcium carbonate and calcium hydroxide. Also, it is preferable if at least 1 mass percent, preferably at least 2 mass percent, more preferably at least 3 mass percent of the granular product is cement. Also, our package invention is preferably such as if the valve bag has dust retaining venting means other than in the filling valve then the filling valve and all the other dust retaining venting means together contain a total quantity of accumulated granular product, and otherwise the filling valve contains a total quantity of accumulated granular product, the total quantity of accumulated granular product being less than 40 g (preferably less than 35 g, more preferably less than 30 g, more preferably less than 25 g, more preferably less than 20 g, more preferably less than 15 g, more preferably less than 1O g, even more preferably less than 5 g).

Returning now to our valve bag invention; as we said about the usage of the valve bag, the filled and closed valve bag can be arranged in a position in which air, separating from the solids in the bag, can escape through the valve tube in a filtered manner. It is our objective to provide a valve bag that is adapted to provide the said filtered conducting-out of residual air, during the use of the valve bag, through the valve tube, at a position and state of the filled and closed valve bag suitable for a stacking thereof, i.e., a stacking position, which is at least approximately horizontal. As is known in the art, in this position usually the biggest, main wall surfaces of the bag are generally approximately horizontal and look upwards and downwards, and the air, released from the aerated contents, gathers directly under a bag wall portion atop the package, the air forming a usually flat shaped bubble there. After a putting of the newly filled bag in a horizontal position, the air will soonest gather in a middle of this main wall surface part. Later, as the solid contents separate from the aerated mixture, their level reach its final, lowest position which, in practice, causes the said air bubble to become rather flat and to essentially be adjacent with the whole of the upper one of the said main wall surface parts. That is the place from which it should be vented, through the valve tube, in the use of our valve bag. In order thereof, as we recognized, the filling valve should be adapted to have the inner opening at least partly where the place of the gathered air bubble is, adjacent the aforementioned bag wall portion atop the package. This can be translated into structural features of the valve bag, as follows.

In a preferable embodiment, our valve bag can be one of three popular, known valve bag types. These types are as follows. The best known type is the block bottom type. Paper valve bags are usually block bottom type bags. A block bottom valve bag, like that illustrated for example in patent documents US 4,049,191 and WO 88/08816, has a block bottom, or more typically two opposed block bottoms. The filling valve is very often, but not necessarily, integrated into a corner of a block bottom. As it is known for the person skilled in dimensioning of such bags, the width of the block bottom corresponds to (i.e. is at least approximately equal to) the height of the package after the bag is filled and kept, and compacted, in a horizontal stacking position, in which state the block bottoms, and also their width dimensions, are vertical. The second possible valve bag type is the gusseted bag. Plastic valve bags of this type are known, like e.g. in patent documents US 4,566,131 and WO 92/02428. The bag usually has two gussets in opposed side edges of the bag, known to be called side gusseted bag, but there are bottom gusseted bags, too, that only have one gusset, in one side edge of the bag. However three, or even all side edges of a bag could comprise gussets. In case of the gusseted bags the gusset has a gusset depth and a double of the gusset depth corresponds to (i.e. is at least approximately equal to) the height of the package after the bag is filled and kept, and compacted, in a horizontal stacking position, in which state the gusset is extended into an essentially vertical plane, wherein its depth dimension is also essentially vertical. The third type is the type that lacks both block bottoms and gussets, for example pillow bag, as illustrated .e.g. in US 3,937,395 patent. Such a bag has simple edges and therefore the height of the package in its filled and stacked, compacted position is not strictly predetermined by the bag's dimensions, but will much depend on the decision of the user on how much the bag is filled up. Nevertheless, in the field of our interest, i.e., in that of heavy duty, industrial shipping bags the height of such bag packages is usually between 45 mm and 250 mm, often between 75 mm and 175 mm. Valve bags, in general, are known to be shipped from bag factories to packers, and stored, in a flat, collapsed state thereof. If, e.g. in a laboratory test, such an empty, collapsed bag is put between two parallel test planes, provided with a clearance corresponding to a predetermined height of a package to be formed from the bag, and the bag is suitably inflated there, then the valve bag will take a shape approximately the same as the desired shape of the desired package. (Such industrial-purpose bags will be strong enough to withstand, and flexible enough to be suitably shaped by, an inner pressure of e.g. 50 mbar.) The surface parts of the bag this way contacting the test planes will approximately be the surface parts forming the horizontal bottom and top of the package, in a horizontal and compacted stacking position, in real use. The air, separating from the solid contents, will gather in, and should be vented from, regions adjacent to one of these surface parts. Therefore it is preferable if

• the valve bag has a flexible bag wall,

• the valve bag is adapted to be in a flat collapsed state suitable for a storing of the valve bag before a filling thereof, the valve bag essentially arranged in a plane, a so- called flat collapsed plane in its flat collapsed state, and

• the inner opening is adapted to, at a collapsed state of the valve tube, be in a collapsed state forming an oblong collapsed inner opening of the filling valve having a collapsed inner opening length and collapsed inner opening widths normal to, and essentially smaller than, the collapsed inner opening length, and

• the valve bag is one of o a block bottom valve bag having at least one block bottom having at least one block bottom width, o a gusseted valve bag free of block bottoms and having at least one gusseted edge having a gusset having at least one gusset depth, and o a valve bag free of block bottoms and gusseted edges, and

• the valve bag is adapted to, in a test, o be placed, in its flat collapsed state, between two suitable solid and parallel planes, so-called test planes, provided for the test essentially parallel with the flat collapsed plane of the valve bag and with a clearance between the test planes, the clearance equaling

^■ a smallest block bottom width in the valve bag if the valve bag is a block bottom valve bag,

^■ a double of a smallest gusset depth in the valve bag if the valve bag is a gusseted valve bag, and

^■ 45 mm if the valve bag is a valve bag free of block bottoms and gusseted edges, and o be brought into a state inflated between the test planes, an inflated state, with collapsed valve tube, with an internal overpressure of 50 mbar, and o have parts of its bag wall, so-called main abutting bag wall parts, contacting the test planes at the inflated state of the valve bag, and o have one or more sections of the collapsed inner opening of the filling valve adjacent to a main abutting bag wall part, a total length of the said one or more sections being at least 1%, preferably at least 2%, more preferably at least 5%, more preferably at least 10%, more preferably at least 25%, more preferably at least 50%, more preferably at least 75%, more preferably at least 90%, more preferably 100% of the length of the collapsed inner opening.

The skilled person is familiar with the shapes of the known valve bag types in their flat collapsed states in which they are essentially not filled, not even with air. Several drawings of patent documents cited hereinabove illustrate such bag states. When the valve tube is collapsed, for a closing of the bag, its inner opening is also collapsed into a gap-shaped collapsed inner opening, of the valve tube. The collapsed inner opening, like gap-shaped things in general, is ,,long" and ,,narrow", i.e. its length is essentially greater than its dimension, or somewhat varied dimensions, normal to the length. A width of the collapsed inner opening can also be zero, which, in practice, means that two abutting films, e.g. compressed to each other, form the collapsed inner opening there. The width of the collapsed inner opening can, in a typical case, correspond to a thickness of a spacer, e.g. the filter sheet, kept in the valve tube. The length of the collapsed inner opening, for example, as it is known to the skilled person, is usually approximately equal to the block bottom width and the desired package height in block bottom valve bags. For example, the valve tube can, near the inner opening, have an inner circumference corresponding to a double of the collapsed inner opening length. The current preferable embodiment of the invented valve bag is suitable to pass the test, described hereinabove. If a bag is not suitable to pass the test then that bag does not conform to our specification. Test planes can be any planes suitably solid, strong and flat for the purpose, like wooden plates, or even better, transparent plates of, e.g., glass or a polymer. Test planes are to be kept essentially parallel to each other, preferably horizontally, with a distance there between. The distance is determined from the given bag. In a given bag, there can be several block bottom width values or several gusset depth values, due, e.g. to there being more than one block bottoms or side gussets or to those dimensions not being quite uniform in a single block bottom or gusset, therefore the lowest value is to be used, if necessary, in determining the said distance. The bag, in our preferred embodiment, is suitable to be kept inflated with 50 mbar, which pressure is in accordance with the value in the Haver and Boecker Bag Permeability Test. The parts of the bag's wall which are, at this inflated state, in contact with the test planes are those as are expected, or would be determined, by the skilled person to serve as the two horizontal main faces of the bag, or package, after the bag is filled, closed, the package laid down horizontally and compacted. The skilled person can certainly forecast which parts of a flat collapsed valve bag will contact the test planes in the test, nevertheless, the aforedescribed test procedure determines/defines the main abutting bag wall parts of a given valve bag in an exact and objective manner. Another advantage of the test approach is that it is uniformly useful for all three types of valve bags. There will typically be parts of the bag qualifying main abutting bag wall parts on two opposed sides, e.g. lower and upper sides, of the bag and in at least one of the two sides, the collapsed inner opening of the filling valve must be adapted to be, in whole or in part, adjacent a main abutting bag wall part. The term adjacent has the usual technical meaning and can, for example, mean that the main abutting bag wall part is forming one border, or lip, for the collapsed inner opening, and typically, one component of the valve tube, while inside the bag another film can form the other border, or lip, for the collapsed inner opening, and typically, another component of the valve tube. The collapsed inner opening, adjacent the main abutting bag wall part can also be realized, for example, in a way in which, inside the bag, a valve tube is provided in a form of a collapsed envelope of films, forming the collapsed inner opening, the envelope attached to an inner surface of the bag's wall with at least a specified part of the collapsed inner opening being adjacent a main abutting bag wall part. A specified portion of the collapsed inner opening is adjacent an inner surface of the specified part of the bag's wall, the main abutting bag wall part, and thereby the filling valve is adapted to provide venting path for conducting out air gathered inside the main abutting bag wall part, which can be well utilized to vent the package while the package can either be horizontal or only has to be suitably tilted from horizontal to a little extent, which is an advantage of this valve bag embodiment. The bigger the overlap between the collapsed inner opening and the main abutting bag wall part is, the more effective the venting will be. For a comparison, in a compacted package made from a typical prior art cross bottom valve bag a (vertical) collapsed inner opening of the collapsed filling valve is completely disjunct from the (horizontal) main abutting bag wall part, just because they are perpendicular to each other. If, however, the whole collapsed valve tube is arranged in a position essentially parallel with and adjacent to a main abutting bag wall part, as is readily possible with side gusseted plastic valve bags, then the whole of the collapsed inner opening can also be adjacent thereto which results in a very effective venting. In practice, for example, the distance between the main abutting bag wall part and the adjacent collapsed inner opening part can be zero, or can correspond to a thickness of one or more layers of films or other webs, and can in general be less than hundred microns as well as for example a couple of hundred microns or even a millimeter or several millimeters or more, up to the decision of the skilled person. The lower the distance between the main abutting bag wall part and the collapsed inner opening part, adjacent thereto, is, the more effective the venting will generally be, because the less air will finally be left unvented from the package. Therefore it is preferable if the distance between a main abutting bag wall part and the collapsed inner opening is lower than 3 mm, preferably than 2 mm, more preferably than 1 mm. Most preferably it is zero. It is our further objective to provide a filling valve that provides a safe venting in a package even if it is somewhat tilted, in a random direction, from a horizontal position. We recognized that in order thereof the filling tube must reach relatively deeply into, i.e. the collapsed inner opening must be relatively deep inside, a region adjacent to a main abutting bag wall part. As we said, the air typically starts to gather in the middle of a main abutting bag wall part.

With respect to a possible inclination of the package from an ideal horizontal position, the highest possibility of air being under a main abutting bag wall part will be in a middle thereof. The closer the collapsed inner opening is, thereto, the more assured the venting therethrough will be. It means that in order of this preferred embodiment of the valve bag, it is not enough to place the collapsed inner opening to an edge of the main abutting bag wall part. Therefore it is preferable if the valve bag is adapted to, in the test,

• have the main abutting bag wall parts bordered with borders and

• have one or more sections, so-called remote sections, of the collapsed inner opening of the filling valve, adjacent to a main abutting bag wall part and of a distance, from all borders of the said main abutting bag wall part, greater than 1 mm, (preferably greater than 2 mm, more preferably greater than 4 mm, more preferably greater than 6 mm, more preferably greater than 8 mm, more preferably greater than 10 mm, even more preferably greater than 12 mm), a total length of the said one or more remote sections being at least 1%, preferably at least 2%, more preferably at least 5%, more preferably at least 10%, more preferably at least 25%, more preferably at least 50%, more preferably at least 75%, more preferably at least 90%, more preferably 100% of the length of the collapsed inner opening. It is clear that the distance of the said collapsed inner opening section(s) from the borders is inherently limited (for example, in practice and in general, is less than 1000 mm), and is maximal if a section of the collapsed inner opening is approximately in the middle of the main abutting bag wall part, which may appear to be optimal in respect of the venting but should be carefully checked by the skilled person with respect to a practical operation of the filling valve during and after a filling. The skilled person will know how far a filling valve can be allowed to protrude into the bag in a given case, as this is already a part of a routine dimensioning. The advantage of this embodiment is that it provides a bag from which such a package can be made that is easily vented through the filling valve after a filling and laying down thereof, even if it happens to be more or less tilted from the ideal horizontal position.

In order, for example, of an assurance of the aforementioned advantageous valve tube configuration, it is preferable if at least a part of the valve tube has an attachment with a main abutting bag wall part. The attachment can, for example, be a welding or an adhered or fused fixing etc. This is advantageous because it secures the said overlap.

With regard to our package objectives, it is our objective to provide a package that is adapted to provide the said filtered conducting-out of residual air through the valve tube at a horizontal position and state of the package suitable for a stacking thereof. Based on an analogy with our recognition in the bag embodiment hereinabove, our package invention is preferable if

• the valve bag has a flexible bag wall,

• the inner opening in the valve bag is adapted to, at a collapsed state of the valve tube, be in a collapsed state forming an oblong collapsed inner opening of the filling valve having a collapsed inner opening length and collapsed inner opening widths normal to, and essentially smaller than, the collapsed inner opening length, and

• the package is adapted to, in a test, o be kept laid down, on a horizontal table provided for the test, in a position of a lowest potential energy, comprising the contents of the granular product in a compacted state thereof and with an essentially horizontal top surface thereof, and o have a part of its bag wall, so-called top bag wall part, essentially horizontal and above a rest of the package, and o have one or more sections of the collapsed inner opening of the filling valve adjacent to the top bag wall part, a total length of the said one or more sections being at least 1%, preferably at least 2%, more preferably at least

5%, more preferably at least 10%, more preferably at least 25%, more preferably at least 50%, more preferably at least 75%, more preferably at least 90%, more preferably 100% of the length of the collapsed inner opening.

A horizontal table is provided for the test. The position of a lowest potential energy means a position whose potential energy is essentially either lower than or equal to potential energies the package has in its other possible positions. It, in case of a practical ,,brick- like" package shape, usually means that the package is lying and its height is selected to be its dimension that is the smallest of its three dimensions. In analogy with the aforementioned valve bag embodiments, it is preferable if the distance between the top bag wall part and the collapsed inner opening is smaller than 3 mm, preferably than 2 mm, more preferably than 1 mm. Most preferably it is zero. It is our further objective to provide a package with an improved filling valve that provides a safe venting of the package even if it is somewhat tilted, in a random direction, from a horizontal position.

Based on an analogy with our recognition in the valve bag embodiments hereinabove, our package invention is preferable if the package is adapted to, in the test,

• have the top bag wall part bordered with borders and

• have one or more sections, so-called remote sections, of the collapsed inner opening of the filling valve adjacent to the top bag wall part and of a distance, from all borders of the said top bag wall part, greater than 1 mm, (preferably greater than 2 mm, more preferably greater than 4 mm, more preferably greater than 6 mm, more preferably greater than 8 mm, more preferably greater than 10 mm, even more preferably greater than 12 mm), a total length of the said one or more remote sections being at least 1%, preferably at least 2%, more preferably at least 5%, more preferably at least 10%, more preferably at least 25%, more preferably at least 50%, more preferably at least 75%, more preferably at least 90%, more preferably 100% of the length of the collapsed inner opening. The advantage of this embodiment is that it provides a package that is easily vented through the filling valve after a filling and laying down thereof, even if it happens to be more or less tilted from the ideal horizontal position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. is a perspective view of a valve bag with one dust retaining venting means in the filling valve, in its flat collapsed state, with the flat collapsed plane illustrated.

FIG. 2. is a perspective view of another side of the valve bag of FIG.1., also in its flat collapsed state, with the flat collapsed plane illustrated.

FIG. 3. is a top view of a gusseted valve bag with one dust retaining venting means in the filling valve.

FIG. 4. is cross section "A-A" of the valve bag of FIG. 3, with details off the section plane omitted in order of an easier reading.

FIG. 5. is cross section "B-B" of the valve bag of FIG. 3, with details off the section plane omitted in order of an easier reading.

FIG. 6. is cross section "C-C" of the valve bag of FIG. 3, with details off the section plane omitted in order of an easier reading.

FIG. 7. is a partial cross section "D-D" of the valve bag of FIG. 3, at an open state of the valve, with details off the section plane omitted in order of an easier reading.

FIG. 8. is a partial cross section "E-E" of the valve bag of FIG. 3, at an open state of the valve, with details off the section plane omitted in order of an easier reading.

FIG. 9. is a partial cross section "D-D" of the valve bag of FIG. 3, at a closed state of the valve and at an inflated state of the valve bag, with details off the section plane omitted in order of an easier reading. FIG. 10. is a top view of a gusseted valve bag with additional venting means adjacent the filling valve.

FIG. 11. is a partial top view, of the additional venting means of the valve bag of FIG. 10., the layers of the additional venting means partly broken away to show top bag wall and porous filter means otherwise hidden.

FIG. 12. is a partial cross section "A-A", of the additional venting means of the valve bag of FIG. 11., with details off the section plane omitted in order of an easier reading.

FIG. 13. is a top view of a valve bag free of block bottoms and gusseted edges, with its lower left corner bent up to show the second main bag wall panel otherwise hidden.

FIG. 14. is a partial cross section "A-A", of the filling valve of the valve bag of FIG. 13., with details off the section plane omitted in order of an easier reading.

FIG. 15. is a partial cross section "B-B", of the filling valve of the valve bag of FIG. 13., with details off the section plane omitted in order of an easier reading.

FIG. 16. is a top view of a block bottom valve bag.

FIG. 17. is a perspective view of a test for defining main abutting bag wall parts in a gusseted valve bag, with the upper test plane partly broken away.

FIG. 18. is a perspective view of a test for defining main abutting bag wall parts in a block bottom valve bag, with the upper test plane partly broken away.

FIG. 19. is a perspective view of a test for defining main abutting bag wall parts in a valve bag free of block bottoms and gusseted edges, with the upper test plane partly broken away.

FIG. 20. is a top view of a gusseted valve bag with additional dust retaining venting means at its bottom. FIG. 21. is a perspective view of a package with a gusseted valve bag, resting on a table.

FIG. 22. is a perspective view of a package with a gusseted valve bag with additional dust retaining venting means, resting on a table.

FIG. 23. is a perspective view of a package with a valve bag free of block bottoms and gusseted edges, resting on a table.

FIG. 24. is a perspective view of a package with a block bottom valve bag, resting on a table.

FIG. 25. is a perspective view of an arrangement illustrating a packing method with a gusseted valve bag lacking additional dust retaining venting means.

FIG. 26. is a central cross section of the package made by the method illustrated in FIG.

25, illustrating a final phase of the packing.

FIG. 27. is a magnified part "A" of FIG. 26., and simultaneously that of FIG.29.

FIG. 28. is a perspective view of an arrangement illustrating a packing method with a gusseted valve bag provided with additional dust retaining venting means near its bottom.

FIG. 29. is a central cross section of the package made by the method illustrated in FIG. 28, illustrating a final phase of the packing.

FIG. 30. is a magnified part "B" of FIG. 29.

FIG. 31. is a perspective view of an arrangement illustrating a packing method with a gusseted valve bag provided with additional dust retaining venting means near its top.

FIG. 32. is a central cross section of the package made by the method illustrated in FIG.

31, illustrating a final phase of the packing.

FIG. 33. is a magnified part "A" of FIG. 32. FIG. 34. is a perspective view of an arrangement illustrating a packing method with a gusseted valve bag and with a feeding impeller.

FIG. 35. is a perspective view of an arrangement illustrating a packing method in which air is conducted out of the valve bag through the filling pipe.

FIG. 35. is a perspective view of an arrangement illustrating a packing method with a horizontal filling pipe and a gusseted valve bag.

EXAMPLES

Example 1 : a comparative example from the prior art

In this comparative Example 1 we illustrate how much residual powder a prior-art valve- bag package of fine granular product can contain in its dust retaining venting means. 25 kg' s of composite Portland cement was filled into a prior art plastic valve bag. We used an auger feeder for the filling in order to provide a fair basis for a later comparison with our invention. We applied a uniform filling speed, and the surplus air content in the filling mixture was about 30 volume percent (i.e. volume of surplus air per volume of aerated mixture).We filled the 25 kg into the bag in 39 seconds. The whole wall of the bag consisted of two layers, separated with spacing projections, of about 250 microns in height, evenly distributed between the two wall layers. The whole surface of the inner bag wall was perforated with pinholes made by steel pins of about 1 mm in diameter, with a density of about 0,66 holes/ cm² of film surface area. The whole surface of the outer bag wall was perforated with similar pinholes, with a density of about 0,066 holes/ cm² of film surface area. In accordance with the prior art practice, we did not apply any vibration, and we fitted the filling valve snugly to the filling pipe. Air was expelled, by the pressure from the filling pipe, from the bag during the filling through the perforations. The big, whole- surface venting channel filtered the dust such that there was not an unacceptable quantity of dust appearing from the pinholes of the outer layer. We filled and closed the bag and then measured the mass of the residual cement powder, collected inside the outer wall and outside the inner wall, to be 40 grams. That illustrates the drawback of the prior art. The quantity would even have been greater with a usual, pneumatic filler and with a usual, faster filling, as we believe.

Example 2 : a comparative example of the invention

We packed cement in order for a comparison with Example 1. In this comparative Example 2 we followed the teaching of our invention. Like in Example 1, 25 kg's of the same composite Portland cement was filled into a plastic valve bag of the same dimensions and shape as in Example 1. We used the same auger feeder and provided the same surplus air content in the filling mixture, i.e., about 30 volume percent. We applied a lower, uniform filling speed: we filled the 25 kg cement into the bag in 150 seconds. In accordance with our invention, we applied a full time vibration of 50 Hz (the bag was propped up on a horizontal vibrating platform), and we always provided a large gap around the filling pipe in the filling valve. The gap and the whole filling valve in general, was prevented from being reached by the level of cement, due to the relatively low filling speed. The whole wall of the bag was a single layer film, air impermeable. There was a 15 g/m2 spun bond nonwoven provided, fixed in the valve tube, covering one half of the inner surface of the valve tube. We filled the bag and collapsed the filling valve into a flat tube whose two abutting halves were separated with the nonwoven. We laid down the package into a horizontal stacking position with the collapsed inner opening of the filling valve provided above the cement at this lying position, adjacent the horizontal top bag wall part of the bag. We kept the bag at rest and thereby compacted the cement and conducted some air out of the bag through the dust retaining venting means (having a venting channel and a porous filter means) incorporated in the filling valve. Then we measured the mass of the residual cement powder accumulated in the collapsed filling valve to be 0.4 grams, which is one percent of the result measured in Example 1.

Example 3: a gusseted valve bag with one dust retaining venting means in the filling valve

A reference is made to the figures, particularly to FIG. 1-9. A valve bag 1 is provided, suitable for packing a granular product 50. It has a flexible bag wall 24 made of a 100 micron thick polyethylene film, impermeable to air. The static coefficient of friction of the outer surface 15 of the valve bag 1 was measured to be 0.51. The valve bag 1 is a gusseted valve bag 32, and can be stored in a flat collapsed state before a filling thereof, in which state it is essentially arranged in a plane, the flat collapsed plane 25. As it can well be seen in its flat collapsed state, the valve bag 1 has opposed, rectangular, first 59 and second main bag wall panels 70 bordered by four bag side edges 60, including two opposed gusseted edges 33, with a gusset 34 in either gusseted edge 33, the gusset depth 35 being

50 mm on either side. The valve bag 1 is of a top valve type, it has a filling valve 2 integrated into one of the bag side edges 60 other than a gusseted edge 33, the top bag side edge 61, approximately in the middle between the two gusseted edges 33. The valve bag 1 has a bottom bag side edge 62 opposed to and parallel with the top bag side edge 61. The length 41 of the top bag side edge 61, and also of the bottom bag side edge 62, is 250 mm.

The length 41 of the gusseted edge 33 is 600 mm. The filling valve 2 comprises a flexible valve tube 5 constituted by a first valve tube wall 63 and a second valve tube wall 64, of different polyethylene films, welded to each other along their two opposed and parallel valve tube side edges 65. Further, in the top bag side edge 61, on the one hand the first valve tube wall 63 is bonded, with a welding line 68, to the first main bag wall panel 59 and the second valve tube wall 64 is bonded, with a welding line 68, to the second main bag wall panel 70. At the flat collapsed state of the valve bag 1 the filling valve 2 is also flat and collapsed, with the valve tube 5 also being in a collapsed state thereof, and is essentially in the flat collapsed plane 25. The valve tube 5 is, in the collapsed state thereof, of a rectangular shape bordered by the said welded valve tube side edges 65 on the one hand and by a collapsed outer opening 66 and a collapsed inner opening 26 on the other hand. The valve tube 5 can be opened from its collapsed state with separating the first 63 and second valve tube walls 64 from each other, for example at their middles 67, whereby the inner 4 and outer openings 3 can also be opened. The opened filling valve 2 provides a filling path 8, parallel with the valve tube side edges 65, for the filling of the valve bag 1 in a direction 10 of a straight line 18 through the outer opening 3, through an inside of the valve tube 5 and through the inner opening 4, the straight line 18 crossing the center of mass 17 of the valve bag 1. A flexible, porous filter sheet 6 of a polyethylene spunbond nonwoven of a surface weight of 14 g/m² is provided in the valve tube 5, the filter sheet 6 having a rectangular shape and a size essentially the same as those of the valve tube 5 in its collapsed state. The filter sheet 6 is between the first 63 and second valve tube walls 64 and is welded to both first 63 and second valve tube walls 64 along the two valve tube side edges 65. The filter sheet 6 is further attached, with a welding line 68, to the second valve tube wall 64 in the outer opening 3, in the top bag side edge 61 of the valve bag 1. This attachment keeps the filter sheet 6 at its place both at an open state of the valve tube 5, when the filter sheet 6 remains parallel with and adjacent to the second valve tube wall 64, partly detached from the first valve tube wall 63, providing a filling path 8 beside the filter sheet 6, between the filter sheet 6 and the first valve tube wall 63, and at a collapsed state of the valve tube 5, closing the valve bag 1 for a retaining of the granular product 50 therein, when the collapsed filling valve 2 provides a venting path 9 for conducting air 51 inside the collapsed valve tube 5, through the filter sheet 6 essentially in a lateral direction 10, parallel with two opposed major sheet surfaces 7 of the filter sheet 6, through the collapsed inner opening 26, from an inside 11 of the valve bag 1 to the outer opening 3 and there through to an outside 12 of the valve bag 1. The filter sheet 6 is fairly pliable while the second valve tube wall 64 is rather stiff. The bending length of the filter sheet 6 was measured to be 22.5 mm and that of the second valve tube wall 64 was measured to be 50 mm. The filter sheet 6 has an inner edge 69 that is adjacent to and parallel with an inner edge 69 of the second valve tube wall 64, they both, together with an inner edge 69 of the first valve tube wall 63, forming the inner opening 4. The first valve tube wall 63 has welded direct attachment 14, consisting of three separate welded regions, with the first main bag wall panel 59 adjacent to the inner edge 69 of the first valve tube wall 63. The inner edge 69 of the filter sheet 6 and the major sheet surfaces 7 of the filter sheet 6 between the valve tube side edges 65 are not fixed directly to the valve tube 5 thus they comprise such a marginal portion 13 of the filter sheet 6 that can flexibly be tucked in or wrinkled, by granular product 50 possibly arriving into the valve tube 5 from the inner opening 4, to an extent sufficient for preventing the fine granular product 50 from getting out of the valve bag 1 through the filling valve 2. As we said, at the collapsed state of the valve tube 5 the inner opening 4 is also in a collapsed state forming an oblong collapsed inner opening 26 of the filling valve 2 having a collapsed inner opening length 27 of about 140 mm (corresponding to a distance 42 between the welded valve tube side edges 65) and collapsed inner opening widths 28 normal to the collapsed inner opening length 27, the said collapsed inner opening widths 28 generally corresponding to thickness 89 values of the filter sheet 6, measured to be between 70 microns and 130 microns. That spacing feature facilitates a flow of vented air 51 through the collapsed inner opening 26 and valve tube 5. In the test, for determining the main abutting bag wall parts 19 of the valve bag 1 (the test is described in Example 7), the valve bag 1 proved to have two opposed main abutting bag wall parts 19, a first main abutting bag wall part 71 in the first main bag wall panel 59 and a second main abutting bag wall 72 part in the second main bag wall panel 70. The main abutting bag wall parts 19 are bordered with borders 43, and for example the first main abutting bag wall part 71 has a border 43, parallel with the top bag side edge 61 provided with the collapsed outer opening 66 of the filling valve 2, and at a distance 42 from the top bag side edge 61, measured along the bag wall 24, of about 50 mm. At the inflated state, prescribed in the test, of the valve bag 1 a section 40 of the collapsed inner opening 26, corresponding to the whole collapsed inner opening 26, is adjacent to the first main abutting bag wall part 71. The distance 42 between the first main abutting bag wall part 71 and the collapsed inner opening 26 essentially corresponds to the thickness of the film of the first valve tube wall 63 and is about 100 microns. The valve tube 5 is suitably long (in particular, it has a length 41 of about 85 mm), therefore, at the said inflated state, a section 40 of the collapsed inner opening 26, corresponding to the whole collapsed inner opening 26 of the filling valve 2 is essentially parallel with the aforementioned border 43 of the first main abutting bag wall part 71 and has a distance 42 from the aforementioned border 43 of about 35 mm, and has distances 42 greater than 50 mm from other borders 43 of the first main abutting bag wall part 71. The aforementioned welded direct attachment 14, between the first valve tube wall 61 and the first main bag wall panel 59 adjacent to the inner edge 69 of the first valve tube wall 63, is also a direct attachment 14 of the first valve tube wall 63 with the first main abutting bag wall part 71.

Example 4: a gusseted valve bag with additional venting means adjacent the filling valve

A reference is made to the figures, particularly to FIG. 10-12. The valve bag 1 of this Example 4 differs from the valve bag 1 of Example 3 in that the valve bag 1 has an additional dust retaining venting means 20 located in its parts other than the filling valve 2. The additional dust retaining venting means 20 comprises perforations 73 penetrating a region, the perforated region, of the first main abutting bag wall part 71 which region is, at a flat collapsed state of the valve bag 1, adjacent to the inner edge 69 of the first valve tube wall 63 but not overlapping with the first valve tube wall 63. The perforated region comprises pin-perforations 73 in a quantity of about 3.1 pieces/cm², covered, for dust retaining, from outside with a porous filter means 21 constituted by a Tyvek ™ spunbond polyethylene nonwoven sheet, which is covered, for further dust retaining, from outside with an unperforated, embossed polyethylene covering film 75, having embossed spacing projections 76 inside. The bag wall 24, in the perforated region, and the covering film 75 form a venting channel 22 providing venting path 9 there between and essentially parallel therewith. The covering film 75 has bonded covering film edges 77 bonded, along welding lines 68, to the porous filter means 21 and there through, indirectly, to bag wall 24. The covering film 75 also has free covering film edges 78 free from a bond with the bag wall, therefore the additional dust retaining venting means 20 provides venting path 9 for conducting air 51 from an inside 11 of the valve bag 1 to an outside 12 of the valve bag 1. We measured the specific air permeability (at 50 mbar internal overpressure) of such a dust retaining venting means 20 to be about 0.004068 m³/h/cm². In the example valve bag 1 the perforated region has a size of approximately 28 cm². As a result, the additional dust retaining venting means 20 has a total air permeability of about 0.114 m³/h.

Example 5: a valve bag free of block bottoms and gusseted edges

A reference is made to the figures, particularly to FIG. 13-15. A pillow type valve bag 1 of 140 micron thick polyethylene film is provided, with a size, in its flat collapsed state, of 350 x 600 mm. It has a first main bag wall panel 59 and a second main bag wall panel 70 and four bag side edges 60, all bag side edges 60 closed, hi its first main bag wall panel 59 it comprises a strip of overlap 79, comprising two overlapping film layers 80. The overlapping film layers 80 are fully adhered, with two welding lines 68 along the margins of the strip of overlap 79, to each other except in the filling valve 2. The unadhered overlapping film layers 80 form the valve tube 5 and the inner opening 4 and the outer opening 3. There is a porous filter sheet 6 between the overlapping film layers 80 in the valve tube 5 with a solution analogous to that of Example 3. The sides of the valve tube 5 are closed with two parallel welding lines 68 where the overlapping film layers 80 and the porous filter sheet 6 have common bonds. The porous filter sheet 6 is bonded, with a welding line 68, to the overlapping film layer 80 providing the outer surface 15 of the valve bag 1 in the outer opening 3 to provide a filling path 8 beside the porous filter sheet 6. Example 6: a block bottom valve bag

A reference is made to the figures, particularly to FIG. 16. This valve bag 1 differs from the valve bag 1 of Example 5 in that this valve bag 1 is further provided with two opposed block bottoms 30 whose block bottom width 31 dimensions are, at a flat collapsed state of the valve bag 1, parallel with the strip of overlap 79. The block bottom width 31 of both block bottoms 30 is 100 mm.

Example 7: a test for defining main abutting bag wall parts in a gusseted valve bag

A reference is made to the figures, particularly to FIG. 17. The valve bag 1 of Example 3, as we said, is a gusseted valve bag 32 and has a gusset depth 35 of 50 mm on either side. Two glass plates 81, suitably strong with respect to expected main abutting bag wall part 19 sizes and the 50 mbar inner pressure, of a suitable size can be provided, in a horizontal position, for the test providing their inner surfaces 82 as test planes 37. A clearance 38 of

100 mm, equaling the double of the 50 mm gusset depth 35 of the valve bag 1, is set between the parallel test planes 37. The flat collapsed valve bag 1 is inserted, laid horizontally, there between and inflated with 50 mbar. The bag wall 24 parts now contacting the test planes 37 are defined as main abutting bag wall parts 19.

Example 8: a test for defining main abutting bag wall parts in a block bottom valve bag

A reference is made to the figures, particularly to FIG. 18. This example differs from Example 7 in the following. As valve bag 1, the block bottom valve bag 29 of Example 6 is provided. A clearance 38 of 100 mm, equaling the block bottom width 31 of the valve bag

1, is set between the parallel test planes 37. As in this example a bag wall 24 forms a part of the valve tube 5, the distance 42 between a main abutting bag wall part 19 and the collapsed inner opening 26 is zero.

Example 9: a test for defining main abutting bag wall parts in a valve bag free of block bottoms and gusseted edges A reference is made to the figures, particularly to FIG. 19. This example differs from Example 7 in the following. As valve bag 1, the valve bag 1 of Example 5 is provided. A clearance 38 of 45 mm is set between the parallel test planes 37. As in this example a bag wall 24 forms a part of the valve tube 5, the distance 42 between a main abutting bag wall part 19 and the collapsed inner opening 26 is zero.

Example 10: a gusseted valve bag with additional dust retaining venting means at its bottom

A reference is made to the figures, particularly to FIG. 20. The valve bag 1 of this Example

10 differs from the valve bag 1 of Example 4 in that the additional dust retaining venting means 20 of the valve bag 1 is located adjacent the bottom bag side edge 62 of the valve bag 1 and overlapping with the first main bag wall panel 59.

Example 11: a package with a gusseted valve bag

A reference is made to the figures, particularly to FIG. 21. The example package 44 comprises the valve bag 1 of Example 3 as a vented plastic valve bag 1. The package 44 further comprises contents 45 of granular product 50 in the valve bag 1, the contents 45 being a granular, cement based dry adhesive powder, containing e.g. some quartz sand, and with a total cement content of about 30 mass percent. At least 1 mass percent of the adhesive powder is believed to have a granule size below 5 microns. At least 10 mass percent of the adhesive powder is believed to have a granule size below 150 microns. In our test, the adhesive powder proved suitable to be mixed with air and thereby to be rendered into an aerated state in which an apparent density of the adhesive is about 79% of its apparent density in a fully compacted state thereof. We found that 120 seconds after the aerated adhesive powder was put at rest, its apparent density was still far lower than 87% of its apparent density in its fully compacted state. The closed filling valve 2 is realistic to contain less than 1 gram, e.g. about 0.4 g, of accumulated granular product 50. In the package 44, the valve bag 1 has a flexible bag wall 24. At a horizontal resting position of the package 44, the valve tube 5 is collapsed. The inner opening 4 of the filling valve 2 is in a collapsed state forming an oblong collapsed inner opening 26 of the filling valve 2 having a collapsed inner opening length 27 and collapsed inner opening widths 28 corresponding to those of the valve bag 1 in Example 3. If the package 44 is kept lying on a horizontal table 46, with the second main bag wall panel 70 of its valve bag 1 in contact with the table 46, then it is in a position of a lowest potential energy. It is suitable to comprise the contained adhesive powder in a compacted state thereof and with an essentially horizontal top surface 47 thereof. At this position, a part of its bag wall 24, its top bag wall part 48, is essentially horizontal and above a rest of the package 44. Due to a suitable quantity of adhesive powder contents 45 in the valve bag 1, the top bag wall part 48 essentially corresponds to the first main abutting bag wall part 71 of the valve bag 1. The top bag wall part 48 is bordered with borders 43. A section 40 of the collapsed inner opening 26, corresponding to the whole collapsed inner opening 26 of the filling valve 2 is adjacent to the top bag wall part 48. The distance 42 between the top bag wall part 48 and the collapsed inner opening 26 is about 100 microns. The valve tube 5 is suitably long, therefore, at the horizontal resting state of the package 44, the whole collapsed inner opening 26 of the filling valve 2 is essentially parallel with the border 43 of the top bag wall part 48 closest to the collapsed inner opening 26 and essentially parallel with the dimension of the collapsed inner opening length 27, and a section 40 of the collapsed inner opening 26, corresponding to the whole collapsed inner opening 26, has a distance 42 from the aforementioned border 43 of about 35 mm, and has distances 42 greater than 50 mm from other borders 43 of the top bag wall part 48. This feature provides for a venting, through the filling valve 2, of the package 44 which compacts the contents 45 after the package 44 is closed and laid down horizontally, with the collapsed inner opening 26 positioned atop the granular product 50 contents 45.

Example 12: a package with a gusseted valve bag with additional dust retaining venting means

A reference is made to the figures, particularly to FIG. 22. The package 44 of this example differs from the package 44 of Example 11 as follows. This example package 44 comprises the valve bag 1 of Example 4 as a vented plastic valve bag 1. The closed filling valve 2 and the additional dust retaining venting means 20 are together realistic to contain a total of accumulated granular product 50 of a mass less than 2 grams, e.g. about 0.8 gram. Example 13: a package with a valve bag free of block bottoms and gusseted edges

A reference is made to the figures, particularly to FIG. 23. The package 44 of this example differs from the package 44 of Example 11 as follows. This example package 44 comprises the valve bag 1 of Example 5 as a vented plastic valve bag 1. As in this example a bag wall

24 forms a part of the valve tube 5, the distance 42 between the top bag wall part 48 and the collapsed inner opening 26 is zero.

Example 14: a package with a block bottom valve bag

A reference is made to the figures, particularly to FIG. 24. The package 44 of this example differs from the package 44 of Example 11 in that this example package 44 comprises the block bottom valve bag 29 of Example 6 as a vented plastic valve bag 1.

Example 15: a packing method with a gusseted valve bag lacking additional dust retaining venting means

A reference is made to the figures, particularly to FIG. 25, 26, 27. This example is based on our actual test results. A valve bag filling machine 54 is provided for and used in the method, the valve bag filling machine 54 provided with a hopper 83 for holding the prepared filling mixture 49 and a feeding auger 55 for forwarding the filling mixture 49. As plastic valve bag 1, the gusseted valve bag 32 of Example 3 is provided. As we said in Example 3, the valve bag 1 has a filling valve 2 integrated into the top bag side edge 61 of the valve bag. The filling valve 2 also provides a dust retaining venting means 20 in the valve bag 1. The valve bag 1 only has dust retaining venting means 20 positioned in its filling valve 2. The filling valve 2, at a closed state thereof, and at a collapsed state of the valve tube 5, provides a venting path 9 for conducting air 51 from an inside 11 of the valve bag 1 to an outside 12 of the valve bag 1, through the collapsed valve tube 5 and the outer opening 3. The filling valve 2, as dust retaining venting means 20, comprises, for dust retaining, both a flexible porous filter sheet 6, as porous filter means 21, and a collapsed valve tube 5, as venting channel 22. The collapsed valve tube 5, as venting channel 22, comprises flexible first 63 and second valve tube walls 64, as flexible walls 23 of the venting channel 22, which are, at a collapsed state of the valve tube 5, essentially parallel with and adjacent to each other and provide the said venting path 9 between, and essentially parallel with, the flexible first 63 and second valve tube walls 64. In this example, a filling mixture 49 comprising a mixture of air and the adhesive powder of Example 11, as granular product 50, is provided for a filling, prepared in a hopper 83. The filling mass is 25 kg. In the filling process as much filling mixture 49 is filled, with a feeding auger 55, into the valve bag 1 as contains 25 kg of the adhesive powder. A steel filling pipe 57, of a vertical position, is provided for the filling, inserted in the filling valve 2. The filling mixture 49 is filled in a vertical direction 10 into the valve bag 1, through and from the filling pipe 57, downward, through the filling valve 2 at an open state of the filling valve 2. The inner opening 4 is under the rest of the filling valve 2 and the outer opening 3 is above the rest of the filling valve 2, during the filling. A horizontal vibrating platform 84 is provided and the valve bag 1 is propped up on the vibrating platform 84 during the filling process so that the vibrating platform 84 holds a part of the weight of the valve bag 1. The beginning of the filling process is the moment at which the filling mixture 49 first reaches into the valve bag 1, and the end of the filling process is the moment at which the filling of the valve bag 1 is stopped. During the whole duration of the filling process, the valve bag 1 is vibrated with the vibrating platform 84 at a frequency of 50 Hz, with a vertical stroke 85 of vibration, with an amplitude usual with such vibrating platforms 84 and sufficient to at least partly shake the valve bag 1 and to shake at least a part of the granular product 50 in the valve bag 1, the amplitude being about 1 mm. The vibration keeps the granular product 50 essentially separated from air 51 inside the valve bag 1, a part, typically a lower portion 86, of the granular product 50 being in a solid, not flow able, state and the rest of the granular product 50 being more in a fluidized state, these two states not being apparently sharply separable. The momentary top of the granular product 50, its actual fill level 53, however, is a definite phase border separating the granular product 50 from air 51 there above. The duration of the filling process is 53 seconds. The filling mixture 49 is filled with a uniform volumetric filling speed. This average filling speed, of about 0.47 kg/s, proves to be slow enough to provide, inside the valve bag 1, a place, the upper venting place 52, being a spatial region under, and adjacent to, the inner opening 4 of the filling valve 2, which is prevented from being reached by a level 53 of, and thereby being filled up with, granular product 50 being in one or both of a solid and a fluidized state. At the end of the filling process, when there is 25kg of granular product 50 in the valve bag 1, the level 53 of the granular product 50 is some 20 millimeters under the inner opening 4 of the filling valve 2. The valve bag 1 is held with two fixing sticks 87 at its two gusseted edges 33, adjacent its top bag side edge 61, i.e. it does not hang on its filling valve 2 as usual. During the whole filling process the filling pipe 57 is provided inserted in the filling valve 2 in a markedly loose manner and thereby a gap 58 is provided within the filling valve 2 at least partly around the filling pipe 57, which is facilitated by the valve tube 5 partly having a rather stiff material, as we said in Example 3. The gap 58 essentially consists of two main parts around the filling pipe 57 and the total area of the gap is about 5 cm . This gap 58 is apparently a gap 58 permeable for the granular product 50 being in the valve bag 1, i.e., if the level 53 of the granular product 50 should rise to reach the gap 58 then the granular product 50 would necessarily and readily penetrate the gap 58 and leave the valve bag 1 through the gap 58. The gap 58, and the whole filling valve 2, however, is prevented from ever being reached by the rising level 53 of the granular product 50 during the filling. On the other hand, during the whole filling process air 51 is conducted out from the upper venting place 52 through the open filling valve 2, namely through the gap 58. It means that during the whole filling process air 51 is conducted out of the valve bag 1 from the upper venting place 52 through the open filling valve 2 free from being exposed to a filtering by any porous filter means 21. In this Example such a valve bag 1 is provided as is small enough to only be adapted to receive the filling mass of the granular product 50, and keep a level 53 thereof under the gap 58, by at least a vibration of the valve bag 1. In other words, if we omit the vibration from the method, the level 53 of the granular product 50 reaches the gap 58 and passes through it. This is demonstrated in comparative Example 16. After the filling process the filling valve 2 is closed with putting the valve tube 5 into its collapsed state. Thereafter the filled valve bag 1 is laid down on a table 46 in a horizontal position, with its second main bag wall panel 70 contacting the table 46 and its first main bag wall panel 59 essentially being atop the valve bag 1. The top surface 47 of the granular product 50 in the valve bag 1 is horizontal. This position of the filled valve bag 1 is suitable for a stacking thereof. The filled valve bag 1 is kept at rest in such a position for 48 hours, while with gravity-sorting some air 51 is separated from, and brought above, granular product 50 in the valve bag 1, and is conducted out there from through the dust retaining venting means 20 incorporated in the filling valve 2 and thereby the apparent density of the granular product 50 in the valve bag 1 is increased essentially to its compacted apparent density. In the method, during and after the filling process a total quantity of granular product 50, measured to be about 0.4 grams, is accumulated in dust retaining venting means 20.

Example 16: a comparative example for a packing method without vibration

This example method has an essential difference compared to that of Example 15, namely the vibration is totally omitted. Other essential primary parameters are unchanged. According to our test results, during the filling process the level 53 of the granular product 50, being in one or both of a solid and a fluidized state, and having a mass in the valve bag 1 less than the specified 25 kg filling mass, reaches the inner opening 4, fills up the open filling valve 2 and the gap 58 and a quantity thereof leaves the valve bag 1 through the gap 58. The vibration is necessary for a successful packing of 25 kg material with this valve bag 1 size and at this filling speed.

Example 17: a packing method with a gusseted valve bag provided with additional dust retaining venting means near its bottom

A reference is made to the figures, particularly to FIG. 28, 29, 30. This Example 17 differs from Example 15 in that in this Example 17 the gusseted valve bag 32 of Example 10 is provided for the filling. This valve bag 1 has an additional dust retaining venting means 20 close to its bottom bag side edge 62, adapted to conduct air 51 from places of the valve bag 1 which places are, during the first quarter of the duration of the filling process, reached, in this Example method, by a level 53 of, and thereby filled up with, granular product 50 being in one or both of a solid and a fluidized state. The total air permeability of the said dust retaining venting means 20 is about 0.114 m³/h. This method is also an example for a method in which the provided valve bag 1 has a dust retaining venting means 20 adapted to conduct air 51 from places of the valve bag reached by a level 53 of, and thereby filled up with, granular product 50 being in one or both of a solid and a fluidized state, during the first half of the duration of the filling process, the total air permeability of the said dust retaining venting means 20 being far less than 10 m³/h. In this method, therefore, the total air permeability of dust retaining venting means 20, being at places of the valve bag 1 other than the filling valve 2, is about 0.114 m³/h , being less than 18 m³/h specified in the invention. In the method, during and after the filling process a total quantity of granular product 50, certainly realistic to be less than 1 gram, is accumulated in all dust retaining venting means 20.

Example 18: a packing method with a gusseted valve bag provided with additional dust retaining venting means near its top

A reference is made to the figures, particularly to FIG. 31, 32, 33. This Example 18 differs from Example 15 in that in this Example 18 the gusseted valve bag 32 of Example 4 is provided for the filling. This valve bag 1 has an additional dust retaining venting means 20 relatively near to its top bag side edge 61. Further differences from the method of Example

15 are as follows. During the filling process, the feeding auger 55 is kept revolving at a constant speed which speed results in a typical filling speed of 0.52 kg/s during a first phase of the filling process, in which first phase the gap 58 around the filling pipe 57 in the filling valve 2 is maintained like in Example 15 and the upper venting place 52, constituted in this example by the places in the valve bag 1 adjacent to the inner opening 4 of the filling valve 2 and to the additional dust retaining venting means 20, is prevented from being reached by the level 53 of granular product 50. With the said, relatively high, filling speed the rising level 53 of granular product 50, being in one or both of a solid and a fluidized state, is caused to reach and fill up the upper venting place 52 at a moment which moment is the end of the first phase of the filling process and a beginning of a second phase of the filling process. Two seconds before this moment the filling valve 2 is snugly fitted to the filling pipe 57 and thereby the gap 58 is closed to prevent granular product 50 from flowing out of the valve bag 1 through the filling valve 2. From the beginning of the filling process, up to the moment of the closing of the gap 58, air 51 is conducted out of the valve bag 1 from the upper venting place 52, primarily through the gap 58 and theoretically to a minimal extent also through the additional venting means 20. At the end of the first phase of the filling process, i.e. when the upper venting place 52 is filled up, the valve bag 1 contains 24.6 kg of the granular product 50 which is 98.4 percent of the 25 kg filling mass. During the second, final phase of the filling process further filling mixture 49 is filled into the valve bag 1 through the snug filling valve 2 and air 51 is conducted out from the valve bag 1 through the additional dust retaining venting means 20, until the moment at which the valve bag 1 is provided with the full 25 kg filling mass of the granular product 50. After the filling process the filling valve 2 is closed and the method is continued like in Example 15 with the difference that in this Example 18 during and after the filling process a total quantity of granular product 50 of about 1 gram, is accumulated in dust retaining venting means 20.

Example 19: a packing method with a gusseted valve bag and with a feeding impeller

A reference is made to the figures, particularly to FIG. 34. This Example 19 differs from Example 15 in that in this Example 19 a valve bag filling machine 54 is provided for and used in the method, the valve bag filling machine 54 provided with a hopper 83 for holding the prepared filling mixture 49 and a horizontal feeding impeller 56 for forwarding the filling mixture 49, and the filling mixture 49 is filled, with a feeding impeller 56.

Example 20: a packing method in which air is conducted out of the valve bag through the filling pipe

A reference is made to the figures, particularly to FIG. 35. This example is based on our actual test results. This Example 20 differs from Example 15 in the following details. The momentary filling speed values were not measured. The feeding auger 55 is revolved with a uniform revolution speed during the whole filling process. During the whole filling process the filling pipe 57 is provided inserted in the filling valve 2 with a snug, practically airtight fit, at which the valve tube 5 is kept pressed to the filling pipe 57 in such a manner at which the porous filter sheet 6 of the filling valve 2 is prevented from conducting out an essential amount of air 51, as will be demonstrated by an internal overpressure provided in the valve bag 1 later herein. The duration of the whole filling process is 70 seconds. During the whole filling process the upper venting place 52, being a spatial region under, and adjacent to, the inner opening 4 of the filling valve 2, is prevented from being reached by a level 53 of, and thereby being filled up with, granular product 50 being in one or both of a solid and a fluidized state. During the whole filling process relatively clean air 51 is kept around and under the inner opening 4 of the filling valve 2. In a first phase, lasting for about 40 seconds, of the filling process not any air 51 is conducted out of the valve bag 1, but an inner overpressure in the valve bag 1 is developed. At the end of the first phase an internal overpressure, measured to be about 0.1 bar, is provided and the valve bag 1 is provided with an inflated shape and is filled with granular product 50, of a mass less than the 25 kg filling mass, and pressurized air 51, the two separated, thanks to the vibration, by a definite and sharp phase border at the level 53 of the granular product 50 definitely under, and separate from, the inner opening 4 and the filling pipe 57. After the first phase, a second phase of the filling process is provided, lasting for about 30 seconds. During the whole time of the second phase of the filling process air 51 is conducted out from the upper venting place 52 through the open filling valve 2, through the vertical filling pipe 57, in a form of air bubbles 88 rising up in the filling pipe 57, into, and up through, the prepared filling mixture 49 being in the hopper 83. The conducted air 51 is kept free from being exposed to a filtering by any porous filter means. The air bubbles 88 flow upward in the filling pipe 57 while filling mixture 49, being a definitely thicker, fluidized phase of granular product 50, flows downward in the same filling pipe 57, this phenomenon probably driven by gravity and the overpressure in the valve bag 1, balancing a pressure of filling mixture 49 in the filling pipe 57. At the end of the second phase of the filling process, and of the filling process, when there is 25kg of granular product 50 in the valve bag 1, the level 53 of the granular product 50 is some 20 millimeters under the inner opening 4 of the filling valve 2, from which time the method is continued in a way similar to that of Example 15.

Example 21 : a packing method with a horizontal filling pipe and a gusseted valve bag

A reference is made to the figures, particularly to FIG. 36. This Example 21 differs from Example 15 in the following details. As plastic valve bag 1, the gusseted valve bag 32 of Example 5 is provided. As we said in Example 5, the valve bag 1 essentially has a filling valve 2 adapted for a horizontal filling direction 10. A steel filling pipe 57, of a horizontal position, is provided for the filling, inserted in the filling valve 2. The filling mixture 49 is filled in a horizontal direction 10 into the valve bag 1, through and from the filling pipe 57, through the filling valve 2 at an open state of the filling valve 2. The valve bag 1 is fixed in a hanging manner suspended at its filling valve 2 so that the filling valve 2 is essentially atop the valve bag 1 during filling. At the end of the filling process, when there is 25kg of granular product 50 in the valve bag 1, the level 53 of the granular product 50 is some 10 millimeters under the inner opening 4 of the filling valve 2. During the whole filling process the filling pipe 57 is provided inserted in the filling valve 2 in a markedly loose manner and thereby a gap 58 is provided within the filling valve 2 under the filling pipe 57. The gap 58 essentially consists of one main part under the filling pipe 57 and the total area of the gap 58 is about 5 cm².

Example 22: a packing method with a horizontal filling pipe and a block bottom valve bag

This Example 22 differs from Example 21 in that as plastic valve bag 1, the block bottom valve bag 29 of Example 6 is provided.

Claims

1. A packing method in which

• a plastic valve bag is provided, o the valve bag having a filling valve, o the valve bag having dust retaining venting means adapted to provide venting path for conducting air from an inside of the valve bag to an outside of the valve bag, o the dust retaining venting means comprising, for dust retaining, one or both of

^■ porous filter means and

^■ venting channel comprising flexible walls adapted to be essentially parallel with each other and adjacent to each other, providing venting path between the flexible walls and essentially parallel with the flexible walls,

• a filling mixture, comprising a mixture of a granular product and air, is provided, and

• in a filling process a quantity of the filling mixture, containing a predetermined mass, a filling mass, of the granular product, is filled into the valve bag through the filling valve, and

• after the filling process the valve bag is put into a position suitable for a stacking thereof, and a quantity of air is conducted out there from through dust retaining venting means, characterized in that • in at least a part of a duration of the filling process the valve bag is vibrated, and

• the filling mixture is filled slowly enough to provide a place inside the valve bag, an upper venting place, which, during the filling process, o is either prevented from being reached by a level of, and thereby being filled up with, granular product being in one or both of a solid and a fluidized state, o or is reached by a level of, and thereby filled up with, granular product, being in one or both of a solid and a fluidized state, earliest when the valve bag contains at least 70 percent of the filling mass of the granular product, and • in at least a part of the duration of the filling process, air is conducted out of the valve bag from the upper venting place.

2. The method according to claim 1, wherein air is being conducted out of the valve bag from the upper venting place in at least 10% of the duration of the filling process.

3. The method according to any of claims 1-2, wherein the upper venting place is, during the filling process, at most reached by a level of, and thereby filled up with, granular product, being in one or both of a solid and a fluidized state, earliest when the valve bag contains at least 75 percent of the filling mass of the granular product.

4. The method according to any of claims 1-3, wherein the upper venting place is, during the filling process, prevented from being reached by a level of, and thereby being filled up with, granular product being in one or both of a solid and a fluidized state.

5. The method according to any of claims 1-4, wherein at least 1 mass percent of the granular product has a granule size below 150 microns.

6. The method according to any of claims 1-5, wherein the granular product is suitable to be mixed with air and thereby to be rendered into, and to remain, at rest, at least for 30 seconds in an aerated state in which an apparent density of the granular product is at most 98% of an apparent density of the granular product in a fully compacted state thereof.

7. The method according to any of claims 1-6, wherein the valve bag is vibrated in at least 10 percent of the duration of the filling process.

8. The method according to any of claims 1-7, wherein at least one dust retaining venting means comprises venting channel for dust retaining.

9. The method according to any of claims 1-8, wherein the filling mass is between 4 and 55 kilograms and the filling mass divided by the duration of the filling process, an average filling speed, is between 0.08 kilograms per second and 2.3 kilograms per second.

10. The method according to any of claims 1-9, wherein a valve bag filling machine is provided and used for the filling process, which valve bag filling machine is provided with one or both of a feeding auger and a feeding impeller for a forwarding of the filling mixture.

11. The method according to claim 10, wherein the valve bag filling machine is provided with a feeding auger for a forwarding of the filling mixture.

12. The method according to any of claims 1-11, wherein the provided valve bag

• or is free from such dust retaining venting means, and

• if the provided valve bag has such dust retaining venting means then a total air permeability of such dust retaining venting means of the provided valve bag is less than lθ m³/h.

13. The method according to any of claims 1-12, wherein the provided valve bag

• either has dust retaining venting means adapted to conduct air from places of the valve bag which places are, during the first half of the duration of the filling process, reached by a level of, and thereby filled up with, granular product being in one or both of a solid and a fluidized state,

• or is free from such dust retaining venting means, and

• if the provided valve bag has such dust retaining venting means then a total air permeability of such dust retaining venting means of the provided valve bag is less than 20 m³/h.

14. The method according to any of claims 1-13, wherein

• either the provided valve bag only has dust retaining venting means positioned in its filling valve,

• or in the provided valve bag a total air permeability of dust retaining venting means, being at places of the valve bag other than the filling valve, is less than 30 m /h.

15. The method according to any of claims 1-14, wherein in at least a part of the duration of the filling process, air is conducted out of the valve bag from the upper venting place through the filling valve.

16. The method according to claim 15, wherein in at least a part of the duration of the filling process, air is conducted out of the valve bag from the upper venting place through the filling valve free from being exposed to a filtering by porous filter means.

17. The method according to any of claims 1-16, wherein a filling pipe is provided inserted in the filling valve in a loose manner and thereby a gap, adapted to be permeable for the granular product being in the valve bag, is provided, at least in a part of the duration of the filling process, within the filling valve at least partly around the filling pipe, and the filling mixture is filled into the valve bag from the filling pipe, and air is conducted out from the upper venting place through the gap.

18. The method according to claim 17, wherein a total area of the gap is at most 70 cm² and at least 0.1 cm².

19. The method according to any of claims 17-18, wherein the provided gap is prevented from being reached by a level of, and thereby being filled up with, granular product being in one or both of a solid and a fiuidized state.

20. The method according to claim 19, wherein such a valve bag is provided as is small enough to only be adapted to receive the filling mass of the granular product, and keep a level thereof under the gap, by at least a vibration of the valve bag.

21. The method according to any of claims 1-20, wherein a filling pipe is provided, and the filling mixture is filled through the filling valve into the valve bag from the filling pipe and, in at least a part of the duration of the filling process, air is conducted out of the valve bag from the upper venting place upward through the filling pipe.

22. The method according to claim 21, wherein an overpressure in the upper venting place is kept below 2 bars.

23. The method according to any of claims 1-22, wherein the provided valve bag is of recyclable thermoplastic.

24. The method according to claim 23, wherein the valve bag at most has such porous filter means as are of a thermoplastic material compatible with a thermoplastic material of a rest of the valve bag.

25. The method according to any of claims 23-24, wherein the granular product contains any one or more of cement, calcium oxide, calcium carbonate, calcium hydroxide, sand, mineral, stone, ore, metal and glass.

26. The method according to claim 25, wherein the granular product contains any one or more of cement, calcium oxide, calcium carbonate and calcium hydroxide.

27. The method according to any of claims 25-26, wherein at least 1 mass percent of the granular product is cement.

28. The method according to any of claims 1-27, wherein after the filling process the filled valve bag is put into a position suitable for a stacking thereof, and is kept at rest in such a position at least for 60 seconds, while with gravity-sorting some air is separated from, and brought above, granular product in the valve bag, and is conducted out therefrom through dust retaining venting means and thereby an apparent density of the granular product in the valve bag is increased.

29. The method according to any of claims 1-28, wherein during and after the filling process less than a total of 40 g of granular product is accumulated in dust retaining venting means.

30. The method according to any of claims 1-29, wherein a plastic valve bag according to any of claims 31-44 is provided.

31. A plastic valve bag (1),

• having a filling valve (2) o for a filling of the valve bag (1) with a granular product (50) and o for a closing of the valve bag (1) for retaining the granular product (50) in the valve bag (1),

• the filling valve (2) comprising an outer opening (3) and an inner opening (4) and a flexible valve tube (5) connecting the outer opening (3) and the inner opening (4), o the valve tube (5) collapsible for the closing of the valve bag (1), characterized in that

• the filling valve (2) has a flexible, porous filter sheet (6) provided, o the filter sheet (6) having two opposed major sheet surfaces (7), o the filter sheet (6) provided at least partly inside the valve tube (5), suitably fixed,

• the filling valve (2) adapted to provide, at a suitable open state of the valve tube (5), a filling path (8) inside the valve tube (5) beside the filter sheet (6) for the filling of the valve bag (1) through the outer opening (3) and through the inner opening (4), and • the filling valve (2) adapted to provide, at a suitable collapsed state of the valve tube

(5), a venting path (9) for conducting air (51) o inside the valve tube (5), at least partly through the filter sheet (6) essentially in a direction (10) parallel with the major sheet surfaces (7) of the filter sheet (6), o from an inside (11) of the valve bag (1) to the outer opening (3) and there through to an outside (12) of the valve bag (1).

32. The valve bag (1) according to claim 31, wherein

• the filter sheet (6) has a stiffness lower than a stiffness of at least a part of the valve .tube (5), and

• the filter sheet (6) has a marginal portion (13) adapted to be, at least at the collapsed state of the valve tube (5), inside the valve tube (5) and adjacent to the inner opening

(4), and

• at least parts of the major sheet surfaces (7) in the marginal portion (13) are free from direct attachment (14) with the valve tube (5).

33. The valve bag (1) according to any of claims 31-32, wherein a bending length of a material of at least a part of the valve tube (5) is smaller than 600 mm and greater than 22.5 mm.

34. The valve bag (1) according to any of claims 31-33, wherein the valve bag (1) has an outer surface (15) having, at least partly, a static coefficient of friction higher than 0.30.

35. The valve bag (1) according to any of claims 31-34, wherein

• the valve bag (1) has bag side edges (60) and a center of mass (17), and

• the valve bag (1) has the filling valve (2) integrated into one of the bag side edges (60), and

• the filling valve (2) is adapted to provide, at a suitable open state of the valve tube (5), a filling path (8) for the filling of the valve bag (1) in a direction (10) of an essentially straight line (18) through the outer opening (3), through an inside (11) of the valve tube (5) and through the inner opening (4), • the essentially straight line (18) adapted to cross the center of mass (17) of the valve bag (l).

36. The valve bag (1) according to any of claims 31-35, wherein

• either the valve bag (1) has dust retaining venting means (20) o located in its parts other than the filling valve (2), o providing venting path (9) for conducting air (51) from an inside (11) of the valve bag (1) to an outside (12) of the valve bag (1), o the dust retaining venting means (20) comprising, for dust retaining, one or both of

^■ porous filter means (21) and

^■ venting channel (22) comprising flexible walls (23) adapted to be essentially parallel with each other and adjacent to each other, providing venting path (9) between the flexible walls (23) and essentially parallel with the flexible walls (23),

• or the valve bag (1) is free from such dust retaining venting means (20),

• and if the valve bag (1) has such dust retaining venting means (20) then a total air permeability of such dust retaining venting means (20) is less than 30 m³/h.

37. The valve bag (1) according to claim 36, wherein the valve bag (1) is free from such dust retaining venting means (20).

38. The valve bag (1) according to any of claims 31-37, wherein parts of the valve bag (1) other than its filling valve (2) are essentially air impermeable.

39. The valve bag (1) according to any of claims 31-38, wherein the valve bag (1) is thermoplastic and at most has such porous filter means (21) as are of a thermoplastic material compatible with a thermoplastic material of a rest of the valve bag (1).

40. The valve bag (1) according to any of claims 31-39, wherein

• the valve bag (1) has a flexible bag wall (24),

• the valve bag (1) is adapted to be in a flat collapsed state suitable for a storing of the valve bag (1) before a filling thereof, the valve bag (1) essentially arranged in a plane, a flat collapsed plane (25) in its flat collapsed state, and

• the inner opening (4) is adapted to, at a collapsed state of the valve tube (5), be in a collapsed state forming an oblong collapsed inner opening (26) of the filling valve (2) having a collapsed inner opening length (27) and collapsed inner opening widths (28) normal to, and essentially smaller than, the collapsed inner opening length (27), and

• the valve bag (1) is one of o a block bottom valve bag (29) having at least one block bottom (30) having at least one block bottom width (31), o a gusseted valve bag (32) free of block bottoms (30) and having at least one gusseted edge (33) having a gusset (34) having at least one gusset depth (35), and o a valve bag (1) free of block bottoms (30) and free of gusseted edges (33), and • the valve bag (1) is adapted to, in a test, o be placed, in its flat collapsed state, between two suitable solid and parallel planes, test planes (37), provided for the test essentially parallel with the flat collapsed plane (25) of the valve bag (1) and with a clearance (38) between the test planes (37), the clearance (38) equaling

^■ a smallest block bottom width (31) in the valve bag (1) if the valve bag (1) is a block bottom valve bag (29), " a double of a smallest gusset depth (35) in the valve bag (1) if the valve bag (1) is a gusseted valve bag (32), and

^■ 45 mm if the valve bag (1) is a valve bag (1) free of block bottoms (30) and gusseted edges (33), and o be brought into a state inflated between the test planes (37), an inflated state, with collapsed valve tube (5), with an internal overpressure of 50 mbar, and o have parts of its bag wall (24), main abutting bag wall parts (19), contacting the test planes (37) at the inflated state of the valve bag (1), and o have one or more sections (40) of the collapsed inner opening (26) of the filling valve (2) adjacent to a main abutting bag wall part (19), a total length of the one or more sections (40) being at least 1% of the collapsed inner opening length (27).

41. The valve bag (1) according to claim 40, wherein a distance (42), between the adjacent main abutting bag wall part (19) and collapsed inner opening (26), is smaller than 3 mm.

42. The valve bag (1) according to claim 41, wherein the distance (42) is zero.

43. The valve bag (1) according to any of claims 40-42, wherein the valve bag (1) is adapted to, in the test,

• have the main abutting bag wall parts (19) bordered with borders (43) thereof and

• have one or more sections (40) of the collapsed inner opening (26) of the filling valve (2) adjacent to a main abutting bag wall part (19) and of a distance (42), from all borders (43) of the main abutting bag wall part (19), greater than 1 mm, a total length of the one or more sections (40) being at least 1% of the collapsed inner opening length (27).

44. The valve bag (1) according to any of claims 40-43, wherein at least a part of the valve tube (5) has an attachment (14) with a main abutting bag wall part (19).

45. A package (44) comprising a vented plastic valve bag (1) and therein contents (45) of a granular product (50) mixable with air, characterized in that it comprises a valve bag (1) according to any of claims 31-44.

46. A package (44) according to claim 45, wherein at least 1 mass percent of the granular product (50) has a granule size below 150 microns.

47. A package (44) according to any of claims 45-46, wherein the granular product (50) is suitable to be mixed with air and thereby to be rendered into, and to remain, at rest, at least for 30 seconds, in an aerated state in which an apparent density of the granular product (50) is at most 98% of an apparent density of the granular product (50) in a fully compacted state.

48. A package (44) according to any of claims 45-47, wherein the granular product (50) contains any one or more of cement, calcium oxide, calcium carbonate, calcium hydroxide, sand, mineral, stone, ore, metal and glass.

49. A package (44) according to claim 48, wherein the granular product (50) contains any one or more of cement, calcium oxide, calcium carbonate and calcium hydroxide.

50. A package (44) according to claim 49, wherein at least 1 mass percent of the granular product (50) is cement.

51. A package (44) according to any of claims 45-50, wherein • if the valve bag (1) has dust retaining venting means (20) other than in the filling valve (2) then the filling valve (2) and all the other dust retaining venting means (20) together contain a total quantity of accumulated granular product (50), and

• otherwise the filling valve (2) contains a total quantity of accumulated granular product (50), • the total quantity of accumulated granular product (50) being less than 40 g.

52. A package (44) according to any of claims 45-51, wherein

• the valve bag (1) has a flexible bag wall (24),

• the inner opening (4) in the valve bag (1) is adapted to, at a collapsed state of the valve tube (5), be in a collapsed state forming an oblong collapsed inner opening

(26) of the filling valve (2) having a collapsed inner opening length (27) and collapsed inner opening widths (28) normal to, and essentially smaller than, the collapsed inner opening length (27), and

• the package (44) is adapted to, in a test, o be kept laid down, on a horizontal table (46) provided for the test, in a position of a lowest potential energy, comprising the contents (45) of the granular product (50) in a compacted state thereof and with an essentially horizontal top surface (47) thereof, and o have a part of its bag wall (24), a top bag wall part (48), essentially horizontal and above a rest of the package (44), and o have one or more sections (40) of the collapsed inner opening (26) of the filling valve (2) adjacent to the top bag wall part (48), a total length of the said one or more sections (40) being at least 1% of the collapsed inner opening length (27).

53. A package (44) according to claim 52, wherein a distance (42) between the adjacent top bag wall part (48) and collapsed inner opening (26) is smaller than 3 mm.

54. A package (44) according to claim 53, wherein the distance (42) is zero.

55. A package (44) according to any of claims 52-54, wherein the package (44) is adapted to, in the test, • have the top bag wall part (48) bordered with borders (43), and

• have one or more sections (40) of the collapsed inner opening (26) of the filling valve (2) adjacent to the top bag wall part (48) and of a distance (42), from all borders (43) of the said top bag wall part (48), greater than 1 mm, a total length of the one or more sections (40) being at least 1% of the collapsed inner opening length (27).