EP0733012A1

EP0733012A1 - Method for inerting packaging covers, devices therefor, and packaging cover used therein

Info

Publication number: EP0733012A1
Application number: EP95901286A
Authority: EP
Inventors: André PATOURAUX; Philippe Patouraux
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-12-08
Filing date: 1994-12-07
Publication date: 1996-09-25
Also published as: IL111934A0; BR9408199A; ZA949803B; JPH09509386A; CA2177707A1; AU685883B2; NZ276347A; AU1059895A; WO1995015887A2; US5794408A; AU5626598A; BE1007847A3; IL111934A; KR960706431A; WO1995015887A3

Abstract

A method for inerting packaging covers, particularly industrial packaging covers, wherein the object to be packaged is placed on at least one composite sheet forming a packaging cover (100) which is completely sealed except for at least two apertures (201, 202) used both for extracting the atmosphere contained in the packaging cover and for injecting an inert gas (1), preferably nitrogen, into said cover; the atmosphere contained in the packaging cover is extracted through a first valve sealingly fitted to a first aperture (202), and inert gas is injected through a second valve sealingly fitted to a second aperture (201) in the cover; a parameter related to the relative humidity level within the packaging cover is continuously measured (11); and both the extraction of the atmosphere contained in the packaging cover and the injection of inert gas are stopped once the relative humidity level required by the customer has been achieved. All the above steps are performed in such a way that a virtual balance is maintained between the pressure inside the packaging cover and the pressure of the surrounding atmosphere.

Description

METHOD OF INERTING PACKAGING COVERS, DEVICES FOR IMPLEMENTING THIS PROCESS, AS WELL AS COVER

PACKAGING USED. Subject of the invention.

The present invention relates to a method of inerting waterproof packaging covers, a machine and valves for implementing such a process, as well as said packaging covers used, which are intended more particularly for industrial packaging. of products liable to deteriorate under the action of humidity, oxygen and external pollution of many types.

In the context of the invention, the expression "inerting" refers to any means making it possible to place products as defined above and detailed in the text below under an inert atmosphere.

State of the art on which the present invention is based.

Various packaging or storage systems are currently used by packaging companies or industrial companies. Most commonly, the products, in particular industrial products, are packed in a solid cover, for example in non-woven fabric, the most delicate or blunt parts are reinforced with "buliepack" or similar materials. Desiccants are placed inside the cover in quantities determined by the manufacturers according to the rate of permeation of the water vapor of the cover, the cubage of the packaging and wedging elements are put in place to wedge the part to be packaged and finally a metallized cover is placed over the whole and a vacuum is applied inside the packaging to protect the packaged part. Finally, the whole is placed in a full wooden case to ensure complete protection of the packaged part. This method of packaging or storage suffers from various drawbacks. First of all, the installation of the non-woven fabric cover and the reinforcing or wedging elements placed inside the packaging are labor-intensive, which results in a cost which n is not to be overlooked. Then, the reinforcing elements are expensive and often introduce moisture or other pollution inside the packaging. In addition, desiccants are rarely heated to make them completely anhydrous and are used as is. As they are themselves packed in packaging containing moisture, they are already saturated with water when they are placed in the packaging and reject their excess moisture in the internal part of the packaging.

In addition, the vacuum is applied using a vacuum cleaner held by a worker above the opening of the cover which remains open after the cover has been partially closed and the whole is sealed by another worker to using heating tongs. Needless to say, this vacuum is only partial, which implies that moisture or other pollution remains in the cover.

Finally, the covers found on the market are relatively porous and allow moisture or other pollution to pass through. In addition, they are very fine and are easily perforated, which has the effect of making them very sensitive to any manipulation, in particular at the welds. In addition, in the case of long-term storage of materials sensitive to humidity or other pollution, it is now necessary to open the covers, remove the desiccants, replace them, close the cover. It takes a lot of manpower and time, even material costs when it is necessary to replace the cover, without giving any guarantees as for the good condition of the materials contained in the covers.

Other industrial companies, in particular in the field of armaments or the metallurgical industry, send their products to specialized companies which grease them or coat them with greased paper. When they reach their destination, the products must be degreased by a specialized company. Needless to say, the costs that add to the prices of industrial products are very significant. Still other companies immerse their products in wax and the extreme costs that result from "waxing" the products when they need to be reused make the process uneconomical.

Other companies keep their products in specially heated rooms or permanently supplied with hot air to remove humidity, which is also very expensive.

Other companies keep their products in containers containing nitrogen. The process is adequate, but requires that the pieces have a size that allows them to enter the container, which is not always the case. This process therefore remains very limited.

Other companies manufacture reusable tents or covers that are more or less in the shape of the object to be packed to prevent oxidation under a flow of hot air or continuous nitrogen. This process is very expensive insofar as the cover used is porous, so that there is a gas leak constantly and that, because of the porosity of the cover, ^" " ^1, it is frequently necessary to add gas, which is already expensive in itself; this requires machinery and the intervention of several workers, which only increase costs.

Inerting is already known in the food sector, in particular where nitrogen is blown into sachets of food products such as half-cooked rice, fresh salad, etc. to keep products ready for a limited time. the consumption. This system works in fact continuously and approximately, since the aim is not to keep products indefinitely, but simply to put on the market consumable products in a fresh state. In the interval which elapses between the production of the fresh product and consumption, the products are also stored under nitrogen in cupboards provided for this purpose which are expensive, insofar as they are massive and equipped with complex apparatus. to maintain adequate nitrogen overpressure. These cabinets are stored in fresh produce distribution centers and the nitrogen introduced into the bags is only used for the temporary transport of fresh produce to supermarkets. In summary, current packaging and storage systems are generally expensive and inefficient. In an increasingly internationalized world, there is a need for a packaging and / or storage system that can keep products in good condition, as they left the factory, regardless of the country where they are stored or shipped. In addition, given the pressing demands of customers, the packaging must be reliable and inexpensive, especially in terms of labor. Finally, and this is an important aspect, it must be possible to place nitrogen under the spot, that is to say at the site for industrial products, on the planting sites for fresh products such as fruit, vegetables. , etc ...

Apparently, with the exception of nitrogen containers used mainly by the military and large institutions for industrial products, or large facilities used by producers of products fresh, with the resulting drawbacks of space, nobody has yet used a flexible cover system under nitrogen treated by an efficient and inexpensive machine to inject nitrogen in a precise and measured manner, for the conservation and packaging of any products over a long period of time, in any place where such treatment is required.

Document US-A-4, 344,467 describes a machine which continuously controls the evacuation of oxygen and the filling with inert gas of any cover. This single evacuation / feeding device is introduced into an orifice of the cover in a non-waterproof manner. In particular, no system is provided for closing the cover, which has the drawback that the final oxygen content of the cover is not known with precision. The machine is also fixed and intended ^* to be used continuously on a single package.

US Patent 3,521,806 relates to packaging intended to protect perishable products, such as flowers and food. It also describes the use of a device which simply consists in sending an inert gas via a pipe which expels the air inside the packaging through another pipe without any control.

The document FR-A-2218250 relates to a process in which a certain vacuum is made in a plastic envelope and nitrogen is blown in through air chamber valves after having deposited in said envelope bags of desiccant. Again, no measurement or control, and more particularly of the relative humidity level inside the envelope, is described.

The document FR-A-2653405 effectively relates to industrial packaging in which a forced circulation of air is carried out by expelling the internal atmosphere onto desiccants. A stationary machine is described, which in this way allows the internal atmosphere of the industrial packaging to be dried up and which starts up again each time sensors detect a change in humidity. Document DE-2129706 describes a machine which is intended to allow the conservation of food products. This machine is used for storage and transport in the form of a large cabinet. The internal part can be heated or cooled. Aims of the invention.

The present invention relates to a process for inerting packaging covers, and more particularly industrial packaging, which contain products liable to degrade under the action of humidity, oxygen or any other external pollution.

The present invention aims in particular to propose a method and a device which are simple, very economical and easily achievable on any work site.

The present invention aims to propose a method and an inerting device which can allow very long-term storage. The present invention also aims to propose a method and a device which make it possible to reduce the risks of explosion.

The present invention also aims to protect a machine for implementing the method according to the invention, which must be particularly simple in design, inexpensive and of a very small size.

The present invention also aims to provide valves which can be adapted directly to the packaging cover in a completely sealed manner, and which are intended for the implementation of the method.

The present invention aims in particular to provide valves which are of simple design while being extremely robust.

^" 'Finally, the present invention finally aims at providing a packing case which must be particularly resistant and which is due in in particular a very high tensile strength, a tear resistance and a puncture resistance.

Main characteristic features of the present invention.

The present invention relates firstly to a method of inerting, that is to say of placing under an inert atmosphere, which makes it possible to satisfy the requirements mentioned above. This process is intended for packaging, and in particular for industrial packaging, and is characterized in that the following operations are carried out:

- the object to be packed is placed on at least one composite sheet which serves as a packaging cover, which is closed in a completely sealed manner, with the exception of at least two orifices which are used on the one hand to extract the internal atmosphere present in the packaging cover and on the other hand to inject an inert gas, preferably nitrogen, into said cover, - an extraction of the internal atmosphere present in the cover is carried out packaging, via a first valve adapted in a perfectly sealed manner to a first orifice of the packaging cover and an injection of inert gas via a second valve adapted in a completely sealed manner to a second orifice of the packaging cover,

- a measurement is constantly made of a parameter linked to the relative humidity level prevailing in the packaging cover, the operations for extracting the internal atmosphere present in the packaging and injection cover are completed inert gas when the required relative humidity has been reached according to the needs of the end customer,

"- all the operations described above being carried out so that the pressure present inside the packaging cover is close to equilibrium with that of the external atmosphere.

It should be noted that the process of extracting the internal atmosphere / injecting inert gas can be carried out either simultaneously or in a delayed manner.

In the case of simultaneous operations, it is necessary that the flow rates of inert gas and atmosphere extracted from the cover are equivalent, so that the pressure prevailing inside the packaging cover is equivalent or close to the pressure prevailing in the external atmosphere.

In the case where the operations are carried out in a deferred manner, and more exactly in the form of a cycle, a slight depression is first carried out by extraction of the internal atmosphere present in the packaging cover and then, when the latter is completed, an inert gas injection is carried out so as to immediately compensate for the slight depression created within the packaging cover.

In this case, it will be necessary to carry out this extraction / injection cycle several times until the required relative humidity is obtained inside the packaging cover.

It should be noted that, in a particularly advantageous manner, the two orifices intended to allow the extraction of the internal atmosphere and to inject the inert gas into the packaging cover are disposed in a completely opposite manner on said cover.

The inerting process can also be improved depending on customer needs. For example, we can consider varying the number of sensors to indicate other variables such as pressure, temperature, oxygen, pH, etc ... or to indicate on a liquid crystal display not only the values of these variables , but also other graphical representations as a function of time within the framework of specific customer needs. These variables have their importance when one wants to adjust all these variables according to criteria other than those mentioned above for the transport of products comprising rubber seals which would inevitably dry out if the atmosphere consisted only of nitrogen.

In the context of air transport of industrial products or works of art for example, it is also possible to use purges which are inverted valves and which are preferably calibrated appropriately to compensate for the increase in volume inside. of the cover due to the pressure reduction due to the altitude inside the hold. All these improvements fall within the scope of the present invention.

The inert gas used is preferably nitrogen because it is first of all inert, but also because it is dry and drying. Of course, one could consider according to the invention the use of other gases depending on the end use, but nitrogen is economically as in practical terms the preferred gas. In the case of the presence of rubber seals, a little wet nitrogen will be introduced so as not to dry the seals without there being any real moisture present. The nitrogen used will be almost pure nitrogen according to the recommendations of the company "L'Air Liquide". If necessary, for food preservation uses, food nitrogen will also be used according to the recommendations of L'Air Liquide. For all these types of nitrogen, Air Liquide guarantees the absence of a dew point down to - 60 ° C, which avoids any condensation inside the packaging.

The actual inerting process takes place in such a way that the pressure inside the packaging cover is constantly close to equilibrium with the external atmosphere. Possibly, during the process, and more particularly during a process carried out in the form of a cycle, there may remain a slight depression by relation to the external atmosphere, which aims to create a call for inert gas. This slight depression is always offset by the introduction of inert gas.

According to another preferred embodiment, there may remain, and more particularly at the end of the process, a slight overpressure of inert gas inside the packaging cover, in order to combat possible penetration of the humidity from outside.

The fact that one always works with a pressure close to the external atmosphere makes it possible to reduce the risks of explosion due to the possible presence of fuel during packaging, for example military parts.

As far as the humidity level is concerned, it depends on the needs of the end customer. In the majority of cases, it is desired to obtain a humidity level of less than 30%, so as to avoid any oxidation.

As regards the oxygen content, which of course depends on the relative humidity rate inside the cover, the latter is, according to a preferred embodiment, relatively low, and preferably less than 0, 2%. This advantageously makes it possible to limit the risks of explosion. Another advantage is that the insects are destroyed at such a low oxygen content. According to another embodiment, it will be desired to maintain a minimum oxygen content, and more particularly in the case of perishable foodstuffs such as fruit. Brief description of the figures. The inerting machine as well as the valves used for the implementation of the present invention will now be described in more detail with reference to the accompanying drawings in which: Figure ~ 1 shows a flow diagram of the general structure of the machine , and Figure 2 shows an exploded view of a valve according to The invention. Description of several preferred embodiments of the present invention.

FIG. 1 represents a flowchart of the general structure of the machine of the invention. All the elements which appear there are standard components which exist on the market.

We now refer to this figure, where for the sake of simplicity two dotted speakers are represented which do not correspond to reality. In reality, these two enclosures are normally grouped together within a single entity which constitutes said machine.

We will first describe the enclosure which connects the source of inert gas (1) which is in this case represented by a nitrogen bottle to the packaging cover (100). This nitrogen bottle (1) is provided with a regulator (2), itself connected to a valve (3). This valve makes it possible to isolate the source of inert gas (1) from the packaging cover (100) or possibly to regulate the flow of inert gas.

The valve (3) can be a modulating valve, and is more particularly recommended in the case where one works in simultaneous mode. In this case, the valve modulates and regulates the flow of inert gas over the volume of the atmosphere simultaneously extracted from the cover, so that the pressure prevailing inside the packaging cover (100) is at roughly equivalent to the external atmosphere.

According to another embodiment, and more particularly in the case where one works in the form of a cycle, the valve can simply be a solenoid valve which controls the opening or closing of the source of inert gas.

This valve (3) is possibly connected to an additional valve which is a manual isolation valve (5).

In addition, a safety pressure switch (6) is also present between the valve (3) and the isolation valve (5), and allows in the event of overpressure to close an additional valve (4) which is in the form of a solenoid and which is a protection valve. The isolation valve (5) essentially makes it possible, during transport, to avoid the introduction of undesirable particles into the internal pipes. This isolation valve (5) is connected to the packaging cover (100) by a flexible connector (21) which is fixed directly on a sealed valve (200) which will be described in more detail below.

The second enclosure as shown in dotted lines in FIG. 1 represents the connection of a vacuum pump (10) or of any device intended to create a slight depression with the packaging cover (100). The vacuum pump (10) or any equivalent device is connected to a flow control valve bearing the reference (15). This valve is connected to a non-return valve (17) via a pressure transmitter (13) which, based on the principle of strain gauges, will give a signal (from 4 to 20 mA or from 0 to 10 V) corresponding to the pressure in the packaging cover (100).

The adjustment valve (15) is connected to the cover (100) via a flexible connector (23), which itself attaches to a valve (202) which will also be described below.

In order to complete the description, it should be noted that a humidity sensor (11) is present between the cover (100) and the adjustment valve (15). According to a preferred embodiment, this humidity sensor (11) can be directly integrated into the valve (202) as described below.

The measurements given by the humidity sensor (11) and the pressure transmitter (13) define either the degree of opening of the valve (3) in the case where this valve is a modulating valve, or the opening time of this valve (3) in the case where this is a solenoid valve, this using the programmable controller.

The non-return valve (17) allows, at the end of the air replacement process with an inert gas, to automatically isolate the internal atmosphere of the packaging cover (100) from the external atmosphere by cutting it of the vacuum pump (10) or any equivalent device. In this way, by closing this valve (17), a pressure and humidity measurement is carried out which reflects the reality inside the packaging cover (100). The non-return valve (17) operates automatically at the end of each replacement of the air extracted with an inert gas. In the case of a longer operation, an additional manual valve is required. It should be noted that the flow rate of the vacuum pump (10) or any equivalent device can be modified depending on the objects to be packed. In most cases, an average power of 35 to 65 m ³ per hour is sufficient. In this case, a normal packaging operation takes a few minutes. The programmable controller present on the face of the machine for implementing the method according to the invention is known per se and will not be described below *.

The machine differs from the machines which are on the market insofar as it does not have an injection pump, the regulator of a nitrogen bottle taking the place of injector can be adjusted to a determined pressure, for example 6 or 8 bars, easily. The machine is compact and can be easily transported in a van on any site, which is not the case with the machines of the prior art.

In addition, the machine according to the invention is inexpensive and can therefore be within the reach of many medium-sized companies or producers, which is not "the case with the machines of the prior art either. Finally , existing machines are almost exclusively intended for food products, while the machine of the present invention has a more general use, in particular in the field of packaging and storage of industrial products. In summary, the machine according to the invention is practical, compact, simple in design and inexpensive.

The valves used are valves specially designed according to the present invention which are simply attached to the material of the cover. These valves allow a simple depression to be carried out by air extraction or to inject an inert gas such as nitrogen into a sealed enclosure which is a packaging cover. They are generally made of a plastic material such as PVC, Teflon or another material of the same type for reasons of economy, but can also be made of other suitable plastics commercially.

The valve according to the invention is shown in FIG. 2. The valve (200 or 202) generally comprises a body made up of a series of elements to be assembled beforehand, namely a diffuser (101), a spring (104 ), a shutter in the form of a circular plate (105), a seal (110) preferably made of rubber or of a suitable plastic and a circular ring (109) which allows the sealing to be fixed in the orifice of the packaging cover (100). The diffuser (101) is in the form of a short cylindrical tube, the wall of which has, regularly spaced around its periphery, four circular orifices (102) large enough to allow the application of a vacuum or the injection of nitrogen. The diffuser (101) is externally threaded on its lower part. The diffuser (101) is intended to be mounted on the ring (109) which itself has on its upper part a circular recess

(106) internally threaded which will receive the diffuser (101) by screwing. To reinforce the sealing of the assembly, a circular joint (110) will be mounted in the circular recess (106), between the diffuser (101) and the ring (109). He will be held in place and slightly crushed when the diffuser (101) is screwed onto the ring (109), thereby ensuring a perfect seal.

Before assembling the diffuser (101), the circular seal (110) and the ring (109), the spring (104) and the circular plate serving as a shutter (105) will be placed inside the diffuser (101) in the order shown in figure 2.

The ring (109) generally consists of a circular flange (107) on its upper part - which has the circular recess (106) internally threaded mentioned above - and a short tubular part (108) of smaller diameter on its lower part. This short tubular part (108) is intended to pass through the orifice made in the cover (100) using a cookie cutter. This short tubular part (108) is externally threaded to be screwed onto a nut (111) which is mounted on the other side of the cover (100). The nut (111) is in the form of a ring approximately the same diameter as the circular flange (107) of the ring (109) and is provided with a central hole internally threaded to be screwed on the short tubular part. (108). This short tubular part (108) will protrude slightly from a nut (111) which serves to fix the packaging cover (100). The assembly of the assembly is easy and is done by simple screwing. In addition, the valve takes up little space and merges tightly into the cover.

In conjunction with the valve described above, two elements have been developed which complement the valve and guarantee a better functioning of the latter. A short sleeve (112) internally threaded at one end is able to be screwed onto the short cylindrical part (108). This sleeve (112) is an intermediate piece between the valve and an end piece (115) of a flexible connector leading either to the nitrogen bottle or to the vacuum pump. The sleeve (112 'is not intended to remain on the valve, because the latter overshoot too strongly and could be caught by various objects during crating, which could damage the valve and possibly break the sealing of the cover. The sleeve (112) will be removed each time and can therefore be reused multiple times.

The junction between the sleeve (112) and the end piece (115) must ensure a certain seal between the elements and guarantee rapid disassembly without too great a loss of seal. It is produced by a key system. The outer envelope of the sleeve (112) is slightly frustoconical, the part facing the cover having the largest diameter. The interior of the end piece (115) has the same taper, which ensures better sealing when the two parts are nested one inside the other. The sleeve (112) has a groove (113) which is, in a first part, as shown in Figure 2, parallel to the axis of the sleeve over a distance of a few centimeters and then make an angle of plus or minus 100 ° down from the axial direction in a clockwise direction to form a retaining portion. When the two elements fit one on the other, an adequate tightening is obtained by the engagement of a projecting projection of the internal wall of the end piece (115) in the groove (113). In this case, the end piece (115) is pressed on the sleeve (113) and, when it reaches the end of its travel, it is subjected to a rotation in a clockwise direction until the respective internal and external surfaces of the end piece (115) and of the sleeve (112) stick to one another.

Furthermore, a metal rod (114) projects from the end piece (115) over a determined length. This length is studied so that, when the end piece (115) is fixed on the sleeve (112), the point facing the valve is supported on the spring plate (105) to compress the spring (1 * 04). To promote the compression movement, the end of the rod (114) of the nozzle (115) facing the valve has a flared shape which allows it to rest validly on the circular plate (105), in the center thereof. The metal rod (114) will be fine enough for the most part not to disturb the passage of the gas flows, but care will be taken to avoid any risk of buckling of said rod (114) which is stressed under compression.

When the end piece (115) is plugged in and fixed in the sleeve (112), as indicated above, the rod (114) presses on the circular plate (105) and drives it at the end of its travel to the bottom of the diffuser ( 101), thus revealing the four orifices (102) formed in the wall of the diffuser (101). As a result, the way is free to inject nitrogen or create a vacuum. When the operation is complete, the end piece (115) is undone, the spring relaxes and brings the circular plate (105) back to its starting point, thereby closing the four holes (102) and instantly sealing the cover ( 100).

When the end piece (115) is moved anti-clockwise to disconnect it from the sleeve (112), the diffuser spring expands, quickly pushing back the rod (114), which allows an extremely rapid disconnection of the end piece (115) and an almost instantaneous sealing of the cover, that is to say little loss of gas and, on the whole, a perfect seal is ensured and the gas balance maintained inside of the cover (100).

The nozzle (115) can be incorporated into the flexible connection leading to the vacuum pump or to that leading to the nitrogen bottle. It can also constitute an independent part capable of being connected to the ends of such fittings. In the case of a stock of materials to be checked regularly, the nozzle (115) can be connected to the nozzle of a humidity sensor.

The spring (104) will be dimensioned so as to withstand pressure differences between the inside and the outside of the cover (100) of about 1 bar, or a little less. The only pressure of nitrogen, between 6 and 10 bars, could compress the spring (104), open the shutter (105) and allow the valve to operate and this possibility is within the scope of the invention. However, in general, the system described is preferred because it ensures a passage of the gas flow without eddies, or development of forces due to pressure by a simple mechanical action. Furthermore, in the case of the second valve connected to the vacuum pump, the pressure being directed opposite to the pressure of nitrogen, the mechanical system developed in the valve of the invention makes it possible to use a single and same valve for two different operations.

The two complementary elements formed by the sleeve (112) and the end piece (115) will be made of plastic or metal, the rod (114) of metal to ensure greater solidity.

The sleeve (112) and the corresponding end piece (115) can also be made in one piece according to another embodiment, provided that the valve can be actuated by a rod system as described above or another somehow.

This will be the case in particular when we want to connect to the valve any sensor (humidity, pressure, temperature, etc.) as part of the control of long-term stored products.

Finally, the valve according to the invention can be used as a drain when it is mounted upside down, that is to say with the diffuser (101) outside the cover (100). In this case, the spring (104) placed inside the diffuser (101) will be calibrated more or less at a bar if one works with equipressure or more if one works with slight overpressure. This valve mounted upside is of great importance in the case of transport of products ^"flight. The packaged products are placed in the holds of transport aircraft. These compartments are packed, but imperfectly so that during the flight, the decrease in pressure in the hold results in swelling of the cover which can go as far as the bursting of the cover. In this case, the valve according to the invention will serve as a purge to eject the nitrogen overflow outside, even if it means re-inflating the cover on arrival.

The diffuser (101) owes its name to its diffusion action, which disseminates nitrogen regularly in all directions, causing eddies inside the cover (100) which will dislodge moisture in all corners of the cover (100), helped in this by the action of the vacuum pump. Furthermore, if one wants to recover one and / or the other of the valves, it is possible, as mentioned above, to mount them on legs intended to be sectioned subsequently. The lateral arrangement of the orifices (102) allows the valve to fulfill its function, while normal valves with longitudinal flow could not function insofar as they are pressed against the wall of the leg, which would prevent the flow of nitrogen to enter the leg normally and would cause it to rupture. In the case of the valve connected to the vacuum pump, the tab would be pressed against the vacuum port and the action of the vacuum pump would be canceled, which could lead to overheating of the vacuum pump.

These valves are preferably used in number two, arranged diagonally to facilitate the sweeping of the nitrogen and to eliminate the humidity in the smallest corners of the cover. Once the operation has been carried out, they need not necessarily remain on the cover, except in the case of storage where one will be left to allow the nitrogen atmosphere to be checked using a humidity sensor integrated in one of the valves during the checks. To remove the valve (s) from the cover, the operation is simple. It suffices to mount the valve on a projecting tab fitted on the cover and then to weld this tab which will be cut. As the valves are partly recoverable, this further reduces the cost of treatment.

Although the system for quick connection of the nozzle to the valve is described in a particular way in the description and the drawing, the invention also relates to the use of any system using a rod pressing a plate at the bottom. 'against a spring and other variants, in separate or joint form, may be used without departing from the scope of the invention. The present invention also covers the use of a sensor, and more particularly of a capacitive sensor, which allows a measurement of the relative humidity level inside the cover. This sensor will preferably be integrated into the valve described above. According to this embodiment, it is conceivable and even recommended to leave the sensor in the valve after having carried out and completed the inerting process of the packaging cover. In this way, measurements and controls of the relative humidity level inside the packaging cover can be carried out throughout the storage period.

Note that the storage period can be almost indefinite, if the materials under covers are regularly monitored and the covers are not handled.

At present, during long-term storage, conditioned or at least non-humid warehouses are provided. In the context of the invention, it can be stored in any room, or even outside under lean-to, taking normal precautions without more.

The concept explained above, to work, requires good quality covers that prevent moisture from entering the cover.

^" " Have been found particularly suitable in this regard products consisting of at least XF between 70 and 300 g / m ² , an aluminum foil or EVOH or another material capable of improving the gas-tightness and in particular of water vapor-tightness and of any other product capable of improving the appearance, including another XF between 70 and 300 g / m ² . The XF consists of a biaxially stretched laminated film of polyolefins in 3 or 4 layers, the central part of which, present at 70 to 80%, consists of a mixture of olefins so as to obtain, by rolling and drawing , a crisscross arrangement which gives superior resistance.

We can therefore consider the XF as a triaxial or quadrixial film.

Preferably, the XF is a film of between 70 and 180 g / m ² . This quality can be used in overpressure or in equippressure according to the needs.

The present invention also relates to all the products produced with films similar to the XF film.

As examples of products which are particularly suitable, mention may be made of the products sold under the names MILPAC 113, MILPAC 113+, MILPAC 143 and MILPAC 153 described in more detail below.

Example 1.

MILPAC 113: compound as follows: - 17 g / m ² metallized polyester

- 20 g / m ² LDPE

54 g / m ² aluminum foil

- 40 g / m ² LDPE

- 150 g / m ² XF Example 2. MILPAC 113- composed as follows

- 17 g / m ² metallic polyester

- 20 g / m ² LDPE

- 70 g / m ² XF

- 20 g / m ² LDPE

- 54 g / m ² aluminum sheet

- 40 g / m ² LDPE

- 90 g / m ² XF

Example 3.

MILPAC 143 composes as follows:

17 g / m ² metallic polyester

- 20 g / m ² LDPE

- 26 g / m ² aluminum foil

- 40 g / m ² LDPE

- 70 g / m ² XF

Example 4. MTT.PAC 153 composes as follows:

- 17 g / m ² metallic polyester

- 20 g / m ² LDPE

- 26 g / m ² aluminum foil

- 40 g / m ² LDPE - 90 g / m ² XF

These various products which constitute the covers according to the invention are manufactured as follows: each layer is fixed to the previous one by extrusion and not by lamination. For this technique, the adhesive often weakens during high temperature welding, thus creating a weakening zone which manifests itself by a very low resistance of the weld to tearing.

^" In order to highlight the specific features and the advantages obtained by using products according to the present invention, comparisons were made with so-called classic products, which are:

Product A:

GM24 (Rhône Poulenc) composed as follows: polyester, aluminum, linear polyethylene, in which the connections between successive layers are carried out by adhesive bonding

Product B:

VACUMATIC (Brangs + Heinrich) composed as follows: polyester, aluminum, - Valéron, in which the connections between successive layers are made by bonding during extrusion

Product C: VALSEM S165 (SNEC) composed as follows: polyester, aluminum,

Valéron, in which the connections between successive layers are made by bonding during extrusion

Product D:

MOISTOP 662 composed as follows: polyester, - aluminum, linear polyethylene, in which the connections between successive layers are made by bonding during extrusion

As will be observed by referring to the various tables below, the products Conventional either consist of linear polyethylene which does not exhibit resistance to initiated tearing, or comprise a Valéron layer which is a biaxial and flat film consisting of two films having fibers in different directions and assembled.

Table I represents the resistance of the welds to pulling out for welds carried out by heating bars under 2 conditions: Condition (1): temperature of 190 ° C. for 3 seconds at a pressure of 3 bar Condition (2): temperature of 170 ° C for 2 seconds at a pressure of 3 bar

Table I.

Condition (1) Condition (2)

MILPAC 143 98.96 N 99.28 N

MILPAC 153 94.65 N 73.35 N

MILPAC 113> 110 N> 110 N

MILPAC 113+> 110 N> 110 N

Product A 61.48 N 76.28 N

Product B 47.75 N 41.10 N

Product C 78.13 N 75.20 N

Table II represents the pull-out and tensile strength for impulse welds.

Table II,

Traction pullout

MILPAC 113 107.1 N 151.9 N

MILPAC 113+ 102 N 177 N

Product A 82.2 N 148 N

Product B 45 N 123.1 N

Product C 73 N 137 N

Product D 47.3 N 101.7 N

Table III represents the resistance to initiated tearing (French standard BS 2782), either in the machine direction or in the transverse direction.

Table III.

Machine direction Cross direction

Product A 1.35 N 2.18 N

Product B 8.49 N 4.55 N

Product C 8.79 N 6.12 N

Product D 1.77 N 1.34 N

MILPAC 143 11.51 N 10.41 N

MILPAC 153 10, 81 N 12.94 N

MILPAC 113 29.12 N 50.16 N

MILPAC 113+ 23.75 N 22.75 N Table IV shows the resistance to dynamic perforation.

Table IV.

Puncture resistance

Product A 1.8 J

Product B 2.6 J

Product D 1.3 J

MILPAC 143 2, 8 J

MILPAC 153 3.5 J

MILPAC 113 4.5 J

MILPAC 113+ 7.5 J

In addition, the mode of. manufacturing and flexibility of the XF film make MILPAC products particularly flexible, and thus ensure perfect support for the aluminum foil which will not be damaged, even if the MILPAC product is crumpled or folded.

The products according to the present invention combine in a particularly advantageous and unexpected manner the following characteristics:

- resistance of the weld to tearing off

- resistance to primed tear - resistance to puncture

- integrity of the aluminum foil.

In addition, MILPAC products have improved gas, and in particular water vapor, tightness compared to technical products. Table V describes the transmission to water vapor for products according to the state of the art and oroducts according to the invention. Table V.

Transmission to water vapor (g / m ^2/24 h)

Product B 0.06

Product C 0.05

MILPAC 113 0.018

MILPAC 143 0.001

MILPAC 153 0.007

Claims

CLAIMS.

1. Method for inerting packaging covers, and in particular industrial packaging covers, characterized in that the operations are carried out: - the object to be packed is placed on at least one composite sheet which serves as packaging cover, which is closed in a completely sealed manner, with the exception of at least two orifices which are used on the one hand to extract the internal atmosphere present in the packaging cover and on the other hand to inject an inert gas, preferably nitrogen, into said cover, an extraction of the internal atmosphere present in the packaging cover is carried out, via a first valve adapted in a perfectly sealed manner to a first orifice of the cover packaging and an injection of inert gas via a second valve adapted in a completely sealed manner to a second orifice of the packaging cover,

- all the operations described above being carried out so that the pressure present inside the packaging cover is close to equilibrium with that of the external atmosphere.

2. Method according to claim 1, characterized in that one carries out the operations of extraction of the internal atmosphere and injection of inert gas simultaneously, the flow rates of inert gas and atmosphere extracted from the cover being equivalent.

3. Method according to claim 1, characterized in that one carries out the extraction operations of the internal atmosphere of the packaging and inert gas injection cover in a delayed manner in the form of a cycle.

4. Method according to any one of the preceding claims, characterized in that the two orifices intended to allow the extraction of the internal atmosphere from the cover and to inject the inert gas are arranged opposite on the packaging.

5. Method according to any one of the preceding claims, characterized in that the valve intended to extract the internal atmosphere of the cover is in the form of a purge.

6. Method according to claim 5, characterized in that the valve in the form of a drain is calibrated so as to be able to compensate for any increase in volume inside the cover due to a reduction in pressure.

7. Device for implementing the method according to any one of the preceding claims, characterized in that it comprises a source of inert gas (l), such as a nitrogen tank provided with a pressure reducer (2), which is connected to a valve (3) which makes it possible to regulate or close the injection of inert gas, the valve (3) being connected via a flexible connector (15) to the waterproof packaging cover (100), and that it includes a vacuum pump (10) or any other device intended to create a slight depression in the packaging cover (100) connected to said cover (100) via a flexible connector (23) a flow control valve (15) and a non-return valve (17).

8. Device according to claim 7, characterized in that the flexible connections (21 and 23) are connected to the cover (100) in a completely sealed manner by valves (200 and 202).

9. Device according to claim 7 or 8, characterized in that a humidity sensor is directly present and integrated in the valve (202) intended to extract the internal atmosphere of the packaging cover (100).

10. Valve adaptable to waterproof packaging covers (100), characterized in that it comprises a body made up of elements to be assembled beforehand which consists of a diffuser (101), of a spring (104) which applies to a shutter (105) which is in the form of a circular plate, a seal (110) and a circular ring (109), this ring (109) allowing the fixing of the valve on the waterproof packaging cover (100).

11. Valve according to claim 10, characterized in that the diffuser (101) is in the form of a short cylindrical tube whose wall has regularly and spaced around its periphery four circular orifices (102) large enough to allow the application of a vacuum or injection of an inert gas, and in that this diffuser (101) is externally threaded on its lower part (103) so as to be mounted on the ring (109) which has itself on its upper part a circular recess (106) internally threaded, which will itself receive the diffuser (101) by screwing.

12. Valve according to claim 11, characterized in that the circular seal (110) is mounted in a circular recess (107) between the diffuser (101) and the ring (109) and is held in place slightly crushed when the diffuser ( 101) is screwed onto the ring (109), thereby ensuring a perfect seal.

13. Valve according to any one of claims 10 to 12, characterized in that it comprises an element (120) which allows it to be connected directly to a humidity sensor (11).

14. Packaging cover, and more particularly industrial packaging, characterized in that it consists at least of an XF film between 70 and 300 g / m ² , and preferably between 90 and 180 g / m ² , an aluminum foil or EVOH or another material capable of improving the gas-tightness, and in particular water vapor-tightness, as well as any product capable of improving the appearance, including another XF film between 70 and 300 g / m ² , the XF film being a product consisting of a laminated film biaxially stretched from polyolefins in 3 or 4 layers, of which the central part, present at 70 to 80%, consists of a mixture of olefins so as to obtain, by rolling and drawing, a crisscross arrangement which gives a higher resistance.