CA2023296A1

CA2023296A1 - Collapsible container and check valve

Info

Publication number: CA2023296A1
Application number: CA 2023296
Authority: CA
Inventors: John K. Bethune
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-08-13
Filing date: 1990-08-15
Publication date: 1992-02-14
Also published as: GB9102901D0; GB2261206A

Abstract

COLLAPSIBLE CONTAINER AND CHECK VALVE

ABSTRACT
The collapsible bag-like container (20) includes a flat profile collapsible check valve (21) at the fill end (32) of the container. A fused line of connection (60) anchors the check valve to the container (20), with a tab (56) inserted in the open ended fill passage (54) of the check valve. The tab weakens the seal formed by the line of connection (60) across the bag and check valve and assist the user in opening the fill passage.

Description

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OLLAPSIBLE CONTAINER AND CHECK VALVE
FIELD OF THE INVENTION
The present invention generally relates to disposable collapsible containers for holding fluids and check valves mounted to the containers and used for filing the containers and holding the fluids in the containers. More particularly the invention relates to an improved low profile check valve mounted in one end of a flexible plastic bag container which permits the movement of fluid into the container and prevents the fluid from moving back through the valve when the fluid in the container is pressurized.

BACKGROUND OF TTIE INVENTION
Flexible plastic bags have become popular for use in containing flowable materials, such as liquids, ~els and other fluids. The plastic materials used to fabricate the bags are inexpensive and the equipmen-t and procedures used in fabricating the bags are relatively inexpenslve when used on a mass produc-tion basis. I-lowever, it is still somewha-t difficult to fill and -then close the bag so that its contents will not escape.
In some instances rigid valve structures, fabricated of hard plastics or o-ther hard materials, have been utilized as bag closure means. Some of these structures have been constructed as check valves which permit the ~ 9 ~

ingress of fluid but prevent the escape of fluid. The hard valves are somewhat expensive to construct and connect to the bag material, and the hardware is cumbersome and bulky when stacked with the empty bags.
Several flexible, low profile collapsible check valve structures have been disclosed in the prior art which can be used with collapsible bags. For example, U.S. patent ~,674,532 discloses a check valve that can be utilized at an end of a collapsible bag container. Such valves typically are heat welded or fused to the bag material, with a portion of the check valve protruding into the bag so that the contents of the bag, when pressure is applied, tend to collapse and close the valve.
One of the problems with the prior art low or flat profile check valves used with collapsible containers is that the valves sometimes evert when excess pressure is applied to the container. Eversion of the check valve causes leakage from the container. Further, when the check valve is hea-t welded to the container, care must be exercised so as to avoid welding the check valve closed or in failing to completely weld the check valve to the container.
Another problem with some of the prior art low profile flexible check valves is that the valves are constructed so that they are not sealed before use and they will admit fluids or moisture inadvertently before the fluid of choice is admitted into the container. For example, the container can be partia:Lly fillecl with a hygroscopic material at the production plant and stored and later delivered to the customer who will fill the container with a liquid. If the check valve is not maintained in a sealed condition, there is some hazard that moisture laden atmospheric air will enter the container through the check valve and prematurely contact -the hygroscopic material. This tends to render the product unacceptable to the customer.

This invention therefore is generally directed to the provision of a collapsible container and a flat profile check valve that are heat welded together in such a manner that the check valve is not likely to evert when experiencing excess internal pressure within the container, and a check valve that is closed at the production plan-t with a releasible flangible seal that maintains the chamber of the container closed to the atmosphere until purposely opened by the user.

SUMMARY OF THE INVENTION
Briefly described, the present invention comprises a collapsible container and its collapsible and flexible flat profile check valve which are adapted to receive and contain fluids such as liquids, gels and gases, with the components of the container and valve being fabricated from sheet materials suitable for forming lines of conne,ction between the layers of material. For example, heat fusible thermoplastic sheet material can be used for both the container and the check valve. When being constructed, a separator tab is placed in the open ended fill passage of the check valve and the check valve is placed in the fill end of the plastic container, and a heat formed line of connection is extended across the fill end of the container, check valve and tab, causing heat fusion and welding of the plastic materials. The separator tab, being formed of a non-heat bondable porous material, such as a ply of paper, reduces the strength of the connection across the open ended fill passage of the check valve, thereby forming a releasable closure across the check valve. With this arrangement, the bag can be filled by the manufacturer with, for example, hygroscopic materials, the bag closed as described, and the materials will not be exposed to the atmosphere until the user oE the bag opens the check valve.
This protects the materials for later use. Later the bag can then be filled with water or other fluids, and the pressure of -the fluids within the bag will tend to collapse the check valve and therefore close the fill passage, thereby retaining the fluid within the bag.
The check valve in accordance with the present invention can be used for a coolant/refrigerant bag, for example. The economical check valve having a very simple structure is capable of preventing a leak from the fluid-filled bag or other collapsible container, such as a balloon toy, a yel pack, a water bag, or a coolant bag. In o one form of the lnvention, the check valve for a collapsible container filled with fluid can be easily opened by the insertion of a rod or tube through the fill passage of the check valve, thus forcing the collapsed side walls of the check valve to part and form a passage through which the fluid can escape. However, when the tube or probe is retracted from the fill passage of the check valve, the pressure of the fluid medium contained within the container collapses and closes the check valve.
The collapsible check valve is formed of a width greater than the width of its open ended fill passage, and the excess width of the check valve is heat welded to the fill end of the container. This construction tends to avoid any tendency of the check valve everting due to pressure applied by the fluid contents of the container.
Thus, it is an object of this invention to provide a collapsible container and an improved collapsible check valve which is sealable at the factory, easy to open by the user and which functions to reliably contain liquid or other fluids within the container.
~nother object of this invention is to provide an improved collapsible check valve usable with a fluid-filled collapsible container which is sealable at the manufacturing plant, which is easy to open by the user and which forms a reliable seal responsive to the pressure of the fluid contents of the container.

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Another object of this invention is to provide an inexpensive and reliable collapsible container that is compatible with mass production procedures, which can be filled with a preliminary material at the production plant and closed about the material, and which can be easily opened and filled by the purchaser.
Other objects, features and advantages of this invention will become apparent upon reading the following specification, when -taken in conjunction with the accompanying drawings~

BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of the collapsible container and check valve, showing the fill end and top surface of the container.
Fig. 2 is an exploded perspective illustration of the collapsible container and check valve, showing the check valve spaced in front of the fill end of the container.
Fig. 3 is a detail perspective illustration, with parts removed for clarity, of the fill end of the collapsible container and the check valve.
Fig. 4 is an end view of the fill end of the collapsible container, showing the placement of the check valve within the container.
Fig. 5 is a side cross-sectional view of the fill end of the container, showing how a person's hands are used to open the check valve, appearing with Figs. 1, 2 and 3.
Fig. 6 is a perspective illustration of the fi]l end of the container with parts broken away to show the check valve and the placement of a fill tube in the open ended fill passage of the check valve.
Fiy. 7 is a side cross-sectional view of the container, showing the check valve in its open expanded condition as the container is filled with fluid.

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Fig. 8 is a side cross-sectional view of the container, showing how the pressure of the fluid within the container collapses and closes the check valve.
Fig. 9 is an expanded perspective illustration of the container and its check valve, similar -to Fig. 2, but showiny a second embodiment o-f the check valve.
Fig. 10 is an expanded perspective illustration of the container and its check valve, simllar to Figs. 2 and 9, but showing a third embodiment of the check valve.
Fig. 11 is an expanded perspective illustration of the container and check valve, similar to Fiy. 2, 9 and 10, but illustrating a fourth embodiment of the check valve.
Figs. 12, 13 and 14 are perspective illustrations of other forms of the check valve usable with a collapsible container similar to those illustrated in Figs. 1-11.

DETAILED DESCRIPTION
Referring now in more detail to the drawings in which liXe numerals indicate like parts throughout the several views, Fig. 1 illustrates the collapsible container 20 and the check valve 21, with the collapsible container in the form of a bag or pouch having opposed side walls or panels 22 and 24 which are in overlying juxtaposed relationship, with the side panels 22 and 24 joined at side edges 26 and 28, joined at the base end 30 and having a fill end 32.
The connection along base end 30 is a line of ccnnection formed by heat sealing of the material. The material forming the bag 20 is a thermoplastic, such as transparent polypropylene, and typically the thickness of the material ~0 will be matched with the use of the bag, so that the material is of sufficient strength to withstand the handling of the bay when filled with Eluid. ~or example, from 0.5 to six millimeter polyethylene sheet plastic is suitable for most small bag structures that are to contain up to one quart of liquid such as water. As the weight and quantity of the contents of the bag are increased, the 3 ~ ~ ~

strength and therefore the thickness of the bag material necessarily will increase for strength purposes. Usually the material of the check valve 21 will be thinner than the material of the bag 20 so that its sealing characteristics will complement with the bag. However, the check valve material can vary with respec-t to the bag material in accordance with the contents to be contained within the bag and the use of the filled bag.
As shown in Fig. 2, the bag can be formed of fl.at sheet material folded over on itself and formed in a tubular shape with a longitudinally extending seam 34, or the bag can be chosen from a tubular stock material of indefinite length and cut to length o-ther bag structures may be used as may be desirable.
As illustrated in Fig. 2, check valve 21 comprises two overlying plies of sheet material 36 and 38, with the plies of material 36 and 38 being bonded toyether with fused lines of connection 40 and 42. In the embodiment of Fig.
2, the fused lines of connections 40 and 42 are parallel to each other and are spaced from the side edges 44 and 46 of the plies of material, thereby forming three pairs of overlying layers of material, side layers 48 and 50 and central layers 52. Central layers 52, being ordered by fused lines of connection 40 and 42 form an open ended fill passage 54, having an external opening 53 and an internal opening 55.
A tab 56 formed of cellulose paper material or other suitable porous material is inse:rted in the fill opening 54, with the distal end 58 pro-truding through the ex-ternal opening 53 of the open ended fill passage. When collapsible bag container 20 is being assembled, the tab 56 is inserted into the open ended fill passage of the check valve 21 and the chec]c valve is inserted in the fill end 32 of the collapsible bay container 20, with the extern~l opening 53 of the fill passage 54 facing outwardly of the fill end 32 of the bag, and with the edyes of the check ~ 5-.

valve and of the bag substantially aligned. When in this position, the heat induced fused line of connection 60 is formed across the fill end of the bag. The fused line of connection 60 closes the fill end of the bag about the check valve 21, and the heat applied during the fusing process causes the side walls 22 and 24 of the bag material on opposite side of the check valve to fuse together, causes-the side walls 22 and 24 to fuse to the check valve, and causes the plies of material 36 and 38 of the check valve to fuse together, thereby closing the passayes through the check valve and sealing the bag material to the check valve. This completely closes the fill end of the bag against the check valve and completely closes the check valve, creating a low profile check valve in the fill end of the bag.
The tab 56, being placed in the fill passage of the check valve also becomes sealed in the fill passage;
however, the seal of the fill passage is not as strong as the seal formed elsewhere by the line of connection 60 because of the presence of the non-heat sealable porous material of the tab 56. The material and thickness of tab 56 is chosen so as to create a weakened seal across the open ended fill passage 54 during the heat sealing function. For example, the tab 56 can be formed of conven-tional paper material of sufficient porosity to permit the hea-t sealing of the layers of material through the paper, yet the paper should be strong enough to resist tearing when the paper is grasped and pulled to open -the releasable seaL fcrmed through the paper. The paper does not make a permanent bond wit:h the bag material.
As illustrated in F'ig. 5, when -the check valve of the container is to be opened, a person grasps a protruding end 58 of the tab 56 and an adjacent side layer 36 or 38 of the fill passage, pulling these layers of ma-terial apart. This breaks the seal between the tab 56 and the adjacent ply of check valve material, thereby opening the Eill passage 54.

_9_ As illustrated in Figs. 6 and 7, when the fill passage 5~ is open, it tends to for a cylindrical shape suitable for receiving the end of a conduit 62, such as the delivery end of a flexible hose, a hard faucet conduit, etc. When the fill passage is first opened, typically the tab 56 will remain adhered to one of the plies of material 3~ or 38, so that the tab can be used to yuide the fill passage to the delivery end of the conduit 62, so as to extend the fill passaye about the delivery end of the conduit.
When fluid moves in the direction as indicated by arrow 63 through the fill conduit 62 and through the open ended fill passage 54, the fluid accumulates at 66 in the container, and the side walls 22 and 2~ of the container move apart to accommodate the inflow of fluid. Thus, the side walls 22 and 24 form a variable volume chamber 64.
Once the fluid has been p]aced in the container 20, the level of liquid or quantity of gas within the container can be adjusted by simply squeezing the container and the open ended fill passage 54 being held open by the conduit 62, permits the escape of the fluid back through the check valve 21. Once the proper level of liquid or quantity of gas has been achieved witl.in the container 20, the fill conduit 62 is withdrawn from the check valve 21, and the check valve is free to collapse and close. As illustrated in Fig. 8, the internal pressure of the gas or liquid 66 applies pressure as illustra-ted by arrows 68 to opposite sides of the collapsible check valve, which causes the walls of the fill passage 5~ to collapse and close. This forms a closure at the fill end 32 of the container 20.
The more pressure applied, the stronyer the seal.
As illustrated in Fiy. 6, the fused line of connection 60 ex-tends across bo-th the central layer 52 and the side layers ~8 and 50 of the check valve. The connection of the side layers ~8 and 50 tends to stabilize the position of the check valve 21 in the container 20, helpiny prevent the check valve from everting in the event of excessive pressure applied by the fluid 66 in the container 20. The fluid pressure tends to cause the fill end 32 of the collapsible container to retain its shape, and the anchoring of the pairs of side layers 48 and 50 of the 5 check valve 21 by the -fused line of connection 60 requires that the check valve retain its shape under relatively extrerne pressures applied by the fluid 66. The side layers 48 and 50 therefoxe stabilize the central layer 52 of the check valve material so as to avoid distortion of the check val,ve.
Fiy. 9 illustrates another embodiment of the check valve, whereby a check valve 121 is formed of separate overlying juxtaposed plies of material 136 and 138 bonded together by the fused line of connection 160. The structure of the check valve 121 is otherwise similar to the check valve of Fig. 1-8 in that a tab 156 is inserted into the open ended fill passage 154 and the material at the fill end 132 of the bag 120 is heat fused to the check valve at the line of connection 160.
Fig. 10 discloses a third embodiment of the check valve. The check valve 221 is similar to the check valve 21 of Fig. 1-8, except that the fused lines of connection 240 ancd 242 are not parallel but converge toward each other to form a truncated conical open ended fill passage 254.
The tab 256 is also tapered so as to correspond to the shape of the fill passage 254. The fused line of connection 260 also mounts the check valve 221 in the end of the container 220 and crosses the tab 256 to form a temporary seal of the open ended fill passage. The tapered shape of the fill passage 254 permits the eas~
rnounting of the fill passage about the nozzle of a fill conduit during filling yet the size of the interna:L opening 255 is relatively small, thus minimizing the tenclency of any leakage of the fluid from the collapsible container 220 in low internal pressure conditions within the container.

Fig. 11 shows yet a fourth embodiment of the check valve. The check valve 321 comprises two plies of material 336 and 338, with the fusecd lines of connection 340 and 342 positioned at the edges of the plies of material, with one line of connection 340 being interrupted so as to form a side opening 355. An intermediate fused line of connection 357 is formed adjacent the opening 355, so that the flow path through -the open ended flow passage 354 is approximately L-shaped. The base end 329 of the check valve 321 is heat sealed to the base end 330 of the container 320, thus holdiny the check valve 321 firmly in place in the container and avoiding any tendency of the check valve to evert in response to excessive internal fluid pressure within the container 320. The tab 356 is similar to tabs 56 and 156 of the prior embodiments and becomes sealed in the open ended fill passage 35~ by the fused line of connection 360.
Fig. 12 shows another embodiment of the check valve.
Check valve 421 is formed of two plies of material 436 and 438 being folded over at fold 437 in overlying, juxtaposed relationship, with the plies of material being connected together by the parallel spaced fused lines of connection 440 and 442. This forms the first portion of the open ended fill passage 454. Outboard fused lines of connection 439 and 441 also are parallel to the internal lines of connection 440 and 442, with the outboard lines of connec-tion being interrupted to form side openings 443 and 445. Because the lines of connection 440 and 442 stop short of the fold ~37, the open ended fill passaye 454 extends from the external opening 453 inwardly -toward the fold 437, and then the fill passage turns both right and left to move back between the lines of connec-tion 439, 440 and 4~1, 442, respectively so as to pass through the side openings 443 and 4~5. This structure tends to form a more secure seal of the check valve in response to excessive fluid pressure within the container. Further, this ~ 9 ~

structure is useful when it ls desirable to avoid direct access through the check valve to the container, as by the use of a tube extending directly through the check valve.
Fig. 13 shows another check valve 521 that is similar to check valve 421 except that the lines of connection 540 and 542 are not parallel but converge toward each other as they extend away from the external opening 553 of the open ended fill passage 554.
Likewise, the check valve of Fig. 14 shows another embodiment of a check valve 621 which is similar to the check valve of Fig. 13, but which includes additional lines of connection 631 and 632 on one side and 633 and 634 on the other side. These additional lines of connection tend to make the check valve more durable and to provide additional obstruction of the passage of fluid through the check valve, thereby tending to increase the resistance of the check valve to reverse flow of fluid therethrough.
As with the check valves of Figs. 1-11, the check valves of Fig. 12, 13 and 14 each include the fused line of connection 460, 560 and 660 which temporarily closes th~
open ended fill passage of each check valve and anchors the tab 456, 556 and 656 in the fill passage to form the temporary closure of the check valve.
Because the check valves of Fig. 12-14 define serpentine fill passages, it is more difficult to open the fill passage when attempting to create exhaust flow from within the container back through the check valve. This is desirable in those instances where it is anticipated that the fluid within the container should never be removed.
The foregoing description seks forth the container being a collapsible thermoplastic transparent sheet material; however, other type materials can be used for the container. I-t i5 anticipated that the container must be flexible and therefore substantially collapsible so that at least atmospheric pressure will be present in the chamber formed by the container, so that at least atmospheric 2 ~

pressure will be applied to the check valve, thus holding the check valve closed.
While the inven-tion has been disclosed as embodying heat fusibl.e material, the lines of connection of the material can be adhesively formed or pressure formed or formed by other procedures as may be compa-tible with the material. Moreover, while specific embodiments of the invention have been disclosed and illustrated herein, it should be apparent to those skilled in the art that variations and modifications of the disclosed embodiments can be made without departing from the scope o:E the invention as set forth in more detail by the following claims.

Claims

1. In combination, a collapsible fluid-holding container and collapsible check valve for filling the container, said container comprising a base end and a fill end and including overlying juxtaposed side panels connected together at lines of connection along opposite side edges and along their base edges with portions of the side panels positioned away from the lines of connection being movable toward and away from each other to form therebetween a variable volume fluid-holding chamber open at the fill end of said container, said check valve comprising juxtaposed side walls connected together with spaced lines of connection and forming between the lines of connection an open ended fill passage, said check valve being positioned between said container side panels at said fill end of said container with the open ended fill passage protruding in one direction outwardly from the fill end of said container and protruding in the other direction inwardly through the fill end and into said variable volume fluid-holding chamber, the side panels of said container and the side walls of said check valve being connected together by a line of connection extending across said fill end of said container and across said check valve so that said fill end of said container is closed about said check valve and the line of connection across the fill passage is weaker than the remaining portion of the fill end line of connection for releasably closing the fill passage of said check valve, so that when the chamber is to be filled with fluid the line of connection across the check valve is opened and fluid is passed through the fill passage into the chamber of said container, and pressure of the fluid in the chamber tends to collapse and close the inwardly protruding end of the open ended fill passage.

2. The combination of claim 1 and wherein the spaced lines of connection of said check valve are spaced inwardly away from the edges of the side walls of said check valve, and wherein said line of connection extending across said fill end of said container and across said check valve extends to the edges of the sidewalls of said check valve for prohibiting the check valve from everting in response to pressure in the fluid-holding chamber of said container.

3. The combination of claim 1 and further including a separator tab positioned in and protruding from the external end of said fill passage, with the line of connection extending across said fill end of said container crossing said tab so that said tab can be grasped and pulled in an effort to open said fill passage.

4. The combination of claim 1 and wherein the spaced lines of connection connecting together the side walls of said check valve are substantially parallel and said open ended fill passage when inflated assumes a substantially cylindrical shape.

5. the combination of claim 1 and wherein the spaced lines of connection connecting together the side walls of said check valve converge toward each other as they extend into the fluid-holding chamber of said container and said open ended fill passage when inflated assumes a substantially truncated conical shape.

6. The combination of claim 1 and wherein said check valve extends to and is connected to the base edges of the side walls of said container for prohibiting the check valve from everting in response to pressure in the fluid-holding chamber of said container.

7. The combination of claim 1 and wherein said check valve is characterized by having been formed of open ended tubular stock material.

8. The combination of claim 1 and wherein said check valve is characterized by having been formed of overlying juxtaposed sheets of flexible material.

9. The combination of claim 1 and wherein the side walls of said container are formed of transparent thermoplastic material and wherein said lines of connection extending along the opposite sides, base and fill end of said side walls of said container are characterized by having been fused by the application of heat.

10. The combination of claim 1 and wherein the side walls of said check valve are connected together with spaced lines of connection that form an approximately L-shaped open ended fill passage.

11. The combination of claim 1 and wherein the side walls of said check valve are formed of a single sheet of flexible material folded into overlying plies of material, and wherein at least one of the spaced lines of connection extends from the free ends of the plies of material toward the fold of the material without intersecting the fold of the material forming an opening between the plies of material.

12. The combination of claim 11 and wherein the spaced lines of connection are substantially parallel.

13. The combination of claim 11 and wherein the spaced lines of connection converge toward each other.

14. The combination of claim 1 and further including a hygroscopic material in said variable volume fluid-holding chamber.

15. The combination of claim 1 and further including a separator tab positioned in the fill passage of said check valve, with the line of connection extending along the fill end of said container crossing said tab.

16. The combination of claim 15 and wherein said separator tab comprises porous sheet material that weakens the connection of the line of connection extending along the fill end of said container for forming a releasable seal across the fill passage.

17. The combination of claim 1 and wherein the portion of the line of connection extending across the fill passage of said check valve is weaker than the remaining portion of the line of connection extending across the remainder of said check valve for permitting the fill passage to be opened while retaining closed the remaining portion of the line of connection.

18. In combination, a collapsible fluid-holding container and collapsible check valve for filling the container, said container comprising a base end and a fill end and including overlying juxtaposed side panels connected together at lines of connection along opposite side edges and along their base edges with portions of the side panels positioned away from the lines of connection being movable toward and away from each other to form therebetween a variable volume fluid-holding chamber open at the fill end of said container, said check valve comprising juxtaposed side walls connected together with spaced lines of connection positioned inwardly of the side edges of the side walls and forming between the lines of connection an open ended fill passage, said check valve being positioned between said container side panels at said fill end of said container with the open ended fill passage protruding in one direction outwardly from the fill end of said container and protruding in the other direction inwardly through the fill end and into said variable volume fluid-holding chamber, the side panels of said container and the side walls of said check valve being connected together by a lien of connection extending across said fill end of said container and across the fill passage and across the side edges of said check valve so that the fill end of said container is closed about said check valve and the line of connection releasibly closes the fill passage of said check valve and anchors the side edges of the check valve to said container, so that when the chamber is to be filled with fluid the line of connection across the check valve is opened and fluid is passed through the fill passage into the chamber of said container, and pressure of the fluid in the chamber tends to collapse and close the inwardly protruding end of the open ended fill passage.

19. The combination of claim 18 and further including a separator tab positioned in and protruding from the external end of said fill passage, with the line of connection extending along said fill end of said container crossing said tab so that said tab can be grasped and pulled in an effort to open said fill passage.

20. The combination of claim 18 and wherein the spaced lines of connection connecting together the side walls of said check valve are substantially parallel and said open ended fill passage when inflated assumes a substantially cylindrical shape.

21. The combination of claim 18 and wherein the spaced lines of connection connecting together the side walls of said check valve converge toward each other as they extend into the fluid-holding chamber of said container and said open ended fill passage when inflated assumes a substantially truncated conical shape.

22. The combination of claim 18 and wherein said check valve is characterized by having been formed of open ended tubular stock material.

23. The combination of claim 18 and wherein said check valve is characterized by having been formed of overlying juxtaposed sheets of flexible material.

24. The combination of claim 18 and wherein the side panels of said container are formed of transparent thermoplastic material and wherein said lines of connection extending along the opposite sides, base and fill end of said side panels of said container are characterized by having been fused by the application of heat.

25. The combination of claim 18 and wherein the side walls of said check valve are connected together with spaced lines of connection that form an approximately L-shaped open ended fill passage.

26. The combination of claim 18 and wherein the side walls of said check valve are formed of a single sheet of flexible material folded into overlying plies of material, and wherein at least one of the spaced lines of connection extends from the free ends of the plies of material toward the fold of the material without intersecting the fold of the material forming an opening between the plies of material.

27. The combination of claim 26 and wherein the spaced lines of connection are substantially parallel.

28. The combination of claim 26 and wherein the spaced lines of connection converge toward each other.

29. The combination of claim 18 and further including a hygroscopic material in said variable volume fluid-holding chamber.

30. The combination of claim 18 and further including a separator tab positioned in the fill passage of said check valve, with the line of connection extending along the fill end of said container crossing said tab.

31. The combination of claim 30 and wherein said separator tab comprises porous sheet material that weakens the connection of the line of connection extending along the fill end of said container for forming a releasible seal across the fill passage.

32. The combination of claim 18 and wherein the portion of the line of connection extending across the fill passage of said check valve is weaker than the remaining portion of the line of connection extending across the remainder of said check valve for permitting the fill passage to be opened while retaining closed the remaining portion of the line of connection.