CA2569061C - Containers for granular or pulverulent material - Google Patents

Abstract

A flexible container for the repeated filling and draining of granular, powdered or finely-divided solids having a high air content. The container consists of at least two plies, one ply being made of an air-permeable, supporting material, and the other ply consisting of a filter material. The plies allow air to move quickly therethrough, and the granular, powdered or finely-divided solids, having a high air content, to be highly compacted.

Description

Containers For Granular Or Pulverulent Material The invention relates generally to the filling of containers with granular or powdered materials, in particular with finely-divided solids with a high air content, as well as to features of the container itself.
This application is divided from and comprises the disclosure of Canadian Patent Application 2,452,775, filed July 9, 2002. Consequently the expression "the invention"
and the like, as used herein, is not restricted to subject matter specifically claimed in this divided application, but may encompass subject matter also described but not claimed.
The handling of pourable finely-divided solids having a high air content and low pour density such as, for example, finely-divided silica, poses various problems.
Producers as well as final consumers are faced with the fact that these materials raise dust even in the slightest air convection. The formation of dust must be avoided to protect the personnel dealing with the product from possible damage to their health by breathing in the dust.
In addition, the low pour-density increases transportation costs, because the ratio of container weight to filling weight is high and a correspondingly large amount of packaging material is required.
Owing to its three-dimensional spatial branch structure, finely-divided silica is a product having a very Iow compacted bulk density of about 40 to 50 g/l. Owing to its fine structure, finely-divided silica is capable of binding a very large amount of gas, for example air, so the

2 product is put into a quasi-fluid state of about 20 to 30 g/l.
Spontaneous escape of this removable air content takes place only very slowly and incompletely. The dust problem is also increased in this fluid state because the mobility of the finely-divided silica is extremely high.
Pourable finely-divided solids with a high air content and very low pour-density are therefore introduced into air-permeable bags predominantly by means of an externally applied vacuum. The duration of filling increases as the air content increases.
The bags typically consist of three to four plies of paper, and one ply of the paper may additionally be laminated with polyethylene as a barrier against penetrating moisture. To achieve the desired air permeability during the filling process, all plies are microperforated. This has the effect that the product is compressed as it is introduced into the bag and its filling density increases relative to the natural pour density.
It also is possible to carry out preliminary deaeration using special press rollers, but this can always give rise to structural damage which may adversely affect the properties of the solids in use.
The higher proportion of the product in the container weight reduces transportation costs, but this saving is offset by additional expenditure for procuring the special container and the necessary filling devices.

3 A method and a receptacle for repeated filling with and emptying of pourable product having a low pouring density is known from EP 773,159. The woven fabric receptacle described therein, the so-called big bag or also super bag, consists of flexible air-permeable woven fabric, preferably a single or multiple ply of plastic woven fabric with at least one inlet. This woven fabric receptacle also is filled using vacuum filling systems. A vacuum is applied to the woven fabric receptacle, and the product is aspirated through the open inlet into the woven fabric receptacle until a predetermined filling weight is achieved. The issuing gas is distributed over the entire surface of the woven fabric receptacle. During the filling process, the product is reversibly compacted, as when being poured into bags, without its structure being destroyed in the process.
DE-A-198 39 106 describes flexible large containers for finely-divided solids having a high air content for repeated filling using vacuum filling systems, which consist of at least two superimposed plies, an inner ply consisting of uncoated air-permeable woven fabric and an outer ply being dustproof and being coated with a moisture barrier and these plies being mutually connected by a special seam in such a way that the container may only be aerated through it.
With this design of containers, in particular the increase in moisture in the filling product during storage in the large container could be reduced.
As the air no longer is able to escape over the entire surface of the woven fabric receptacle, however, a drawback

4 is that the period of time required to reach a predetermined pouring density is considerably extended, and the filling capacity therefore reduced. To compensate for this, DE-A-198 39 106 describes a particular process for filling this large container, with which the filling material is subjected to preliminary deaeration prior to filling, and a further deaeration via the seams of the fabric is carried out during filling. The preliminary deaeration and therefore partial compaction of the filling product are also effected by the application of vacuum.
A drawback of the process described in DE-A-198 39 106 is the extremely high expenditure on apparatus, as vacuum systems are required for both preliminary compaction and filling of the large container. Despite this expenditure, the filling capacity is still too low, so the process described in DE-A-198 39 106 is uneconomical overall.
The invention provides apparatus for filling a container with granular, powdered or finely-divided solids having a high air content; with which a high filling capacity with adequate compression of the solids to be poured may be achieved with low expenditure on apparatus and therefore low capital outlay. The apparatus can comprise a feed nozzle for introduction of the solids into a feed orifice of the container under positive pressure, the feed nozzle comprising a flexible sealing skin which provides dust-free pressure filling of the container, and the container being surrounded by a two-part or multi-part cage which is gas-permeable.
The invention also relates to a method for filling containers, in particular with finely-divided solids having a high air content, by arranging an air-permeable container in an apparatus according to the invention, air-tight connection of the container to the feed nozzle, filling of the container under pressure, and removal of the filled container.
Finely-divided solids having a high air content may be poured with adequate compression of the solids in high capacities using the apparatus and method according to the invention, without high expenditure on apparatus. In particular, finely-divided granular powdered solids having a high air content may be pyrogenic oxides, precipitated oxides, carbon blacks and modifications thereof.
In particular, with pneumatic conveyance of the filling product, the resultant pressure is sufficient to achieve appropriate filling of the container. According to a preferred embodiment of the invention, the apparatus has a special feed nozzle which is equipped with a flexible sealing skin and therefore allows dust-free pressure filling. The feed nozzle may be deformable and may therefore allow the filling of containers of various sizes.
The cage, which is an important component of the apparatus according to the invention has to withstand, in particular, the pressure required. At the same time, the cage gives the container adequate support during the filling process, to ensure that the container withstands the pressure applied and keeps its shape during the filling process.
Containers of a wide variety of shapes and of various materials may be filled in the apparatus according to the invention. The materials may be: air-permeable plastic woven fabric, preferably polypropylene woven fabric, plastic woven fabric, textile woven fabric, cardboard, paper, paper plastic woven material, plastic non-woven fabric, textile non-woven fabric or composites of the aforementioned materials. The filling pressure is generally 0 to 8 bar, preferably 0 to 2 bar, and particularly preferably 0.2 to 1.2 bar.
The containers employed in the apparatus and method according to the invention may be of any conventional shapes and materials. For example, the containers may have a base area selected from a group consisting of polygon, circle, semicircle, ellipse, trapezium, triangle, rhombus, square and rectangle or a star-shaped base area. The containers may also have the shape of a hood, of assembled pockets or the shape of a tied-up bag. To ensure safe handling even during pressure filling, however, it is advantageous if, during the filling process, the cage contacts the container to be filled, as uniformly and snugly as possible. It is therefore expedient if the cage substantially corresponds to the shape of the container.
Additional fittings in the cage allow adaptation to the respective container to be filled.
Owing to the excess pressure prevailing in the interior of the container, the air is carried off over the surface of the container. As the excess pressure is able to escape, compression of the filling product is also achieved. To enable the excess pressure to escape as rapidly as possible from the container, in particular in the case of a snugly fitting cage, it is expedient if the cage itself is also gas-permeable. The cage may have walls with openings or with adequate porosity. This may be achieved, for example, by openings in the cage walls. It is particularly advantageous if the cage walls are produced from a material selected from perforated plate, mesh or netting, woven fabric or sintered material or a mesh material, because this allows high gas permeability with adequate stability to ensure that the container does not explode even under high filling pressures. The cage may be in several parts, preferably two parts. The cage may have a bottom and may be designed without a bottom. Preferably, the cage has no bottom.
According to a preferred embodiment of the apparatus according to the invention, the cage may be in two or more parts and the apparatus comprises additional devices with which the two parts of the cage may be separated from one another and may be driven apart manually or automatically, preferably electro-pneumatically, to release the filled container. In particular in the case of cage shapes with a polygonal base area, it is expedient if the cage can be separated along a diagonal as~this prevents damage to the container.
According to a particularly preferred embodiment of the present invention; the cage has no bottom, in other words the cage is open at the bottom. This embodiment allows particularly simple management of the filling process. After the two-part cage has been closed and the two parts have been connected to one another, the actual filling process can-begin. For example, the container can then be positioned directly on a plate or a pallet, the feed nozzle can then be introduced into the feed orifice of the container and can be connected in an airtight manner to g the container. On completion of the filling process, the two cage wedges can then be separated from one another and driven apart to release the filled container. As the filled container is then standing on a plate or pallet, it can easily be removed by a transportation device.
In another aspect the invention also contemplates a flexible container for finely-divided solids for repeated filling and draining, characterized in that it consists of at least two plies, one above the other, wherein one ply consists of an air-permeable supporting material that is preferably non-coated and the other ply consists of a filter material.
According to one embodiment, the air-permeable, supporting material can be~arranged on the outside and filter material on the inside. However, other combinations of the plies, from the inside toward the outside, are possible, wherein the combination of supporting and filtering element of the container is present. The material used for each ply can be commercially available material.
The container can be designed for optional amounts of finely-divided filler materials. The container preferably can be used for amounts up to 1,200 kg. In contrast, containers according to prior art could only accommodate filling amounts of 90 to 100 kg.
The container permits a dust-free filling through compacting on the inside of the container, in particular using the apparatus according to the invention, wherein clearly higher bulk weights can be achieved.

The finely-divided material can be drained from the container through a preceding fluidization and simultaneous conveying. For this, known drainage devices can be used.
Another embodiment is a corrugated-cardboard container (carton) for finely-divided solids, which can be ventilated.
One side of the container consists of a highly air-permeable paper, and the inside undulations) as well as the other sides and intermediate plies consist of non air-permeable standard corrugated cardboard with microperforation.
Optional combinations of the outer plies, the inner plies and the intermediate plies are possible, wherein the container (corrugated cardboard container) has a supporting as well as filtering design.
This results in the following advantages as compared to the known technology:
The highly air-permeable inner ply acts as a filter for the product and permits the air to escape;
The outer ply and the intermediate ply (plies) and the undulations) absorb the forces, but permit the air to escape.
As a result of this configuration, air is moved quickly through the walls and the product can be highly compacted inside the container with considerably higher filling weights than is possible with known systems (up to 1,200 kg as compared to the known 90-100 kg, depending on the product type).
The invention will now be described in further detail with reference to the accompanying drawings, in which:

l~
Figure 1 is a side view of a preferred embodiment of the present invention;
Figure 2 is a plan view of the embodiment according to Figure 1 with opened cage;
Figure 3 shows schematically a representation of a container according to the invention;
Figure 4 shows the drain of Figure 3 in schematic detail;
Figure 5 shows a schematic representation of a corrugated cardboard container according to the invention.
As shown in the Figures, a preferred embodiment of the invention comprises a framework 1 with two rails 2 at the top, along which the two halves 3a and 3b of the cage 3 which may be moved by conventional drive devices.
In the embodiment shown in Figures 1 and 2, the cage has a square base area and is divided along the diagonal into the two halves 3a and 3b. This ensures that two halves easily can be separated from the filled container, even when the container has been pressed against the cage owing to a high filling pressure.
The cage also has two half shells 4a and 4b which surround the feed nozzle (not shown) when closed.
As shown in Figure 2, the cage 3 is open at the bottom and the container is positioned on a pallet or plate during the filling process. It also is advantageous, as shown in the drawings, if the filling nozzle is arranged symmetrically with respect to the frame 1, so a cage half 3a may be removed further from the pallet or plate 5 to allow easy access, for example, for a transportation device for removing the filled container.
A container according to the invention is shown schematically in Figure. 3.
On the one hand, a container 6 according to Figure 3 consists of two plies, namely a supporting, air-permeable outer material 7 (PP woven ribbon material with a weight of 75 to 300 g/m3) .
The material is not coated so that air can pass through.
This outer layer is supporting as well as carrying for product amounts up to 1,200 kg.
On the other hand, a second ply, the inner ply 8 (inliner), consists of a filter material (e. g. HDPE nonwoven TyvekT"' by DuPont, which holds back the finely-divided product, but permits the air escaping from the product to pass through.
The drain 9 is shown schematically in Figure 4A. The drain has a conical design and is thus particularly suitable for a special draining apparatus according to EP 761,566. Sticky tapes 10 and 11 are provided, and Figures 4B and 4C are a side view and a view from above, respectively, of the tape 11 which is equipped with a D-ring.
Another container according to the invention is shown schematically in Figure 5, with highly permeable paper 12 on the product side, microperforate undulation 13, and non-porous paper 14.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A flexible container for the repeated filling and draining of finely divided silica and to be used for amounts up to 1,200 kg having a high air content and extremely low pour density, consisting of at least two plies, wherein one ply is made of an air permeable, supporting material PP woven ribbon material with a weight of 75 to 300 g/m3 and the other consists of filter material HDPE nonwoven Tyvek.TM. by DuPont, wherein the air permeable supporting material is arranged on the outside and the filter material on the inside, and permitting a dust-free filling through compacting on the inside of the container, wherein clearly higher bulk weights can be achieved, wherein the highly air-permeable inner ply acts as a filter for the product and permits air to escape, wherein the outer ply absorbs the forces, but permits air to escape, and wherein the outer ply is hot coated so that air can pass through.