US1930493A - Gas and liquid storage device - Google Patents

Description

Oct. 17, 1933.

J. H. WIGGINS ,930,493 I GAS AND LIQUID STORAGE DEVICE Filed Jan. 2, 1951 2 Sheets-Sheet 1 2y WM 141- TOE/V573 Oct. 17, 1933. J. H. WIGGINS 1,930,493

GAS AND LIQUID STORAGE DEVICE Filed Jan. 2, 1931 2 Sheets-Sheet 2 Patented Oct. 17, 1933 UNITED STATES GAS AND LIQUID STORAGE DEVICE John H. Wiggins, Tulsa, Okla. Application January 2, 1931. Serial No. 506,239

24 Claims.

This invention relates to devices of the kind that are used for storing or holding gases and volatile liquids, and particularly apparatus of the type in which the gas space or chamber of the device is provided with a flexible metallic wall or portion that is adapted to flex so as to vary the volume of said space or chamber.

The main object of my present invention is to provide a storage device of the type mentioned, that is compact and of relatively great capacity, inexpensive to build and easy to maintain in operative condition.

Another object is to increase the capacity of gas and liquid storage devices of the type that comprise a flexible metallic top wall, without increasing the size of the structure, without increasing the area of the surface of same exposed to the rays of the sun, and without adding considerably to the cost of the structure.

Another object is to provide a breather type storage device, which is of such design that when it is under a vacuum the volume of the gas receiving space of same is considerably less than the volume of the gas receiving space of prior storage devices of the breather type, thus producing a device that has a relatively small dead gas space as compared to the internal volume of the holder when it is under pressure.

Another object is to provide a storage device of the breather type which is equipped with mechanically operated valves of the same type or kind for governing the pressure relief and for governing the vacuum relief.

And still another object is to provide a storage device of the breather type that is equipped with a pressure relief valve that is opened or rendered operative by the movement of a flexible metallic wall of the gas receiving chamber, and equipped with a vacuum'relief valve that is opened or rendered operative by the movement of a separate and distinct flexible metallic wall of the gas receiving chamber. Other objects and desirable features of my invention will be hereinafter pointed out. I have herein illustrated my invention embodied in a gas holder, but I wish it to be understood that many features of my invention are applicable to tanks and similar devices that are used for storing or holding volatile liquids.

In the preferred form of my invention herein illustrated the gas receiving space or chamber has two opposed walls formed by metal members that are capable of flexing so as to increase the volume of said chamber, and capable of'flexing so as to reduce the volume of said chamber. In order to prevent said metal members from being strained by excessive movement of flexing of same, the movement of said members is used to operate a pressure relief valve and a vacuum relief valve. Said valves are so arranged that the gas receiving space or chamber will be automatically vented after one of said flexible members has moved into a certain approximate position in the operation of increasing the volume of said chamber, and air wfll be automatically admitted to said chamber after the other of said flexible members has moved into a certain approximate position in the operation of reducing the volume of said chamber. My improved gas holder is capable of various uses, but it is particularly adapted for use in a vapor recovering system or vapor saving system for tanks that are used to store gasoline and other volatile liquids. Therefore, I have herein illustrated it as being used for this purpose.

Figure 1 of the drawings is a fragmentary vertical sectional view of a gas holder embodying my present invention.

Figure 2 is a fragmentary top plan view of the supporting structure for the bottom diaphragm of the gas receiving chamber of the holder.

Figure 3 is a fragmentary vertical sectional view, illustrating the construction and arrangement of the pressure relief valve and the actuating mechanism-for same.

Figure 4 is a vertical sectional view of the vacuum relief valve and the actuating mechanism for same.

Figure ,5 is a fragmentary top plan view of the holder, partly broken away, so as to illustrate the supporting structure for the top diaphragm of the gas receiving chamber; and

Figures 6, '7 and 8 are diagrammatic views, illustrating the action of the holder when it is used in connection with a vapor recovering system or vapor saving system for tanks in which volatile liquids are stored.

In the accompanying drawings which illustrate the preferred form of my invention, A and B' designate opposed walls of a gas receiving space or chamber :2. Each of said walls is made up of ,a plurality of metal plates joined together by gas tight joints in such a manner as to produce a substantially imperforate diaphragm that is capable of flexing in opposite directions relatively to the peripheral edge of the diaphragm. The walls A and B may be disposed either approximately horizontally or approximately vertically and the peripheral edge portions of said walls are attached-to a circumferential member that holds the edge portions of said walls spaced far enough apart to permit the central portions of said walls to move inwardly towards each other, so as to reduce the volume of the gas receiving space or chamber 0:. Usually, the walls A and B will be of approximately circular shape or disk shape in general outline, but the particular shape or form of said walls is immaterial, so long as they are of such construction that they are capable of flexing so as to increase the volume of the gas receiving space or chamber :1: of the holder and are capable of flexing so as to reduce the volume of said space or chamber.

In the form of my invention herein illustrated the flexible metallic members A and B of the holder are arranged approximately horizontally in superimposed relation so as to form the top and bottom walls, respectively, of a relatively shallow horizontally-disposed gas receiving chamher :0 that may often be of several hundred feet in diameter. Each of said walls is constructed in the form of a metal diaphragm that has a natural tendency to assume a substantially con cave shape or form, and the peripheral edge portions of said diaphragms are joined by gas-tight joints to a circumferential member C, herein illustrated as consisting of an annular shell provided at its top and bottom edges with reinforcing members 1 and 2, preferably commercially rolled angles, that hold said shell in shape.

As shown in Figure 1, the top and bottom diaphragms A and B have a natural tendency to assume a downwardly flexed condition, shown in full lines, wherein they are of substantially concave shape, but they are capable of assuming an upwardly flexed condition, shown in broken lines, wherein they are of substantially convex shape.- Usually, the diaphragms A and B will be so constructed that they are of substantially frustoconical form when they are flexed downwardly and are of substantially inverted frusto-conical form when they are flexed upwardly. In order to adequately support the bottom diaphragm B and prevent it from being strained when the holder is operating under a positive pressure, a rigid supporting structure D is provided for the bottom diaphragm, and in order to adequately support the top diaphragm A and prevent it from being strained when the holder is operating under a vacuum or minus pressure, a supporting structure E is provided for the top diaphragm A. Said supporting structures D and E can be made in various ways, and in building the holder said supporting structures are preferably used as frames on which the plates constituting the diaphragms are supported during the operation of connecting said plates together. The supporting structure D for the bottom diaphragm B may be conveniently formed by erecting a plu- 'rality of circular rows of posts 2 on the ground, and then attaching to same radially-disposed frame members 3 and braces 4 so as to produce a skeleton like frame (see Figure 2) whose top .surface is inclined downwardly from its peripheral edge towards its center, as shown in Figure 1. The supporting structure E for the top diaphragm A is of similar shape or form and may be conveniently constructed from radially-disposed members 3* combined with intermediate frame members 4. The peripheral edge of the skeleton-like frame that constitutes the supporting structure E is sustained preferably by an inwardly-projecting angle or brackets 5 on the shell C of the holder, and the central portion of said frame is sustained by a stationary center post 6 that projects upwardly through the bottom diaphragm B and which is provided at its upper end with a flange 6 (see Figure 3) to which the central portion of the supporting structure E is attached. In order to prevent the supporting structure E from deflecting intermediate its center and peripheral edge, an annular row of intermediate supporting posts or uprights 7 are provided, which posts 7 project upwardly through the bottom diaphragm B and, have their upper ends attached to the intermediate frame members 4 on which the radial members 3* rest.

Various means 'may be used to provide for the flexing or movement of the bottom diaphragm B without liability of gases escaping through the openings in said diaphragm through which the supporting posts 6 and '7 pass, but I prefer to use liquid seals for said openings. Thus, as shown in Figures 1 and 3, the center post 6, which is set in the ground, has its lower end portion surrounded by a tubular member 9 whose upper end is attached to the central portion of the supporting structure D for the diaphragm B. Said tubular member 9 contains a body of sealing liquid, designated by the reference character 10 in Fig-. ure 3, and the bottom diaphragm B is provided with a sleeve 11 that projects downwardly into the sealing liquid 10. The body of sealing liquid 10 in the well formed by the tubular member 9 is maintained at such a level, and the depending sleeve 11 on the bottom diaphragm B is made of such length, that the lower end of said sleeve will always remain submerged in the sealing liquid 10, even when the bottom diaphragm B is in its extreme upwardly flexed condition, shown in broken lines in Figure 1, thereby effectively preventing gases from escaping from the chamber or gas space a: of the holder through the opening in the bottom diaphragm that receives the center post 6. Usually, the bottom diaphragm B will be provided with an upwardly-projecting collar 12, shown in Figure 3, that surrounds the center post 6, and thus prevents any condensate that collects on the bottom of the chamber a: from mixing with the sealing liquid 10, and thus impairing the efliciency of said sealing liquid. The supply of sealing liquid in the well or tubular member 9 may be replenished through a supply pipe 13 that extends outwardly from the upper end of the tubular member 9 to a reservoir 14 located at or adjacent to the peripheral edge of the holder, as shown in Figure 1. The openings in the bottom diaphragm'through which the intermediate supporting posts '7 project are provolume of the gas receiving chamber, or in the operation of decreasing the volume of said chamber, I have equipped the holder with a pressure.

relief valve and a vacuum relief valve that are combined with said diaphragms in such a way that the movement of the top diaphragm A is used to cause the pressure relief valve to open automatically and vent the chamber a: when said diaphragm A reaches a certain approximate position when it is flexing in a direction to increase the volume of said chamber, and the movement of the bottom diaphragm B is used to cause the vacuum relief valve to open automatically and admit air to the chamber a: when said bottom diaphragm is flexing in a direction to decrease the volume of said chamber. I prefer to use mechanically-operated valves of the same type or kind for controlling the pressure relief and the vacuum relief and maintain said valves in their closed position by springs that are strong enough to absolutely eliminate the possibility of said valves opening accidentally. In Figure 3 I have illustrated a pressure relief valve F that I have found to be very satisfactory for venting the chamber 1:, which valve is composed of a substantially flat or disk-shaped valve element 15 that bears against the underside of an annular valve seat 16 carried by a casing 17 that is attached to the top side of the top diaphragm A at a point in alignment with a vent opening 18 in the center of said top diaphragm. The valve element 15 is provided with a stem 19 that projects upwardly through a guide 20 carried by the valve seat member 16, and a spring 21 is interposed between the guide 20 and a stop 22 on the valve stem 19. Said valve element 15 is so arranged with relation to its seat 16 that the internal pressure of the chamber :0 exerts pressure on said valve element in a direction tending to hold it seated, and the spring 21 is strong enough to efiectively resist any minus pressure or vacuum in the chamber a: tending to open the valve element 15. or move it away from its seat. The valve element 15 is unseated or moved away from its seat 16 during the upward movement of the top diaphragm A by a rod 23 attached to the valve element 15 and provided at its lower end with a head piece 24 that is adapted to strike against a stop or abutment 25 carried by the center post 6 and arranged adjacent the upper end of said post, as shown in Figure 3. Due to the fact that the valve element 15 is carried by the top diaphragm A and the actuating rod 23 is attached to said valve element, the pressure relief valve will remain closed during the upward movement of the top diaphragm A until said diaphragm reaches such a position that the head piece 24 on the valve rod 23 comes into engagement with the abutment 25. Thereafter, any further upward flexing of the top diaphragm will cause the rod 23 to exert a pull on the valve element 15 in a direction to unseat said valve element, and thus vent the chamber at. As soon as said chamber is vented the upward flexing of the top diaphragm ceases, with the result that said diaphragm will not be strained, as might occur if it were permitted to flex upwardly too great a degree. A mechanically-operated vacuum relief valve G of similar design is provided for automatically admitting air to the chamber :1: during the upward flexing of the bottom diaphragm B, before said bottom diaphragm has moved upwardly to such an extent or degree as to strain thesame. As shown in Figure 4, the vacuum relief valve comprises a valve element 15 a valve seat 16, a spring 21 for holding the valve element 15 seated, and a housing 17 that is attached to the bottom diaphragm B at a point in alignment with an air inlet 18 in said bottom diaphragm, the valve element 15 being so arranged that a minus pressure in the chamber 1: tends to hold said valve element tightly on its seat. The housing 1'7 projects downwardly from the bottom diaphragm B, and the valve element 15 is provided with an actuating rod 23 that has a head piece 24 which is adapted to strike against an abutment 25 carried by a tubular housing 6 in which the actuating rod 23 reciprocates, said housing 6 being imbedded in the ground, as shown in Figure 1. During the upward flexing of the bottom diaphragm B the valve element 15 of the vacuum relief valve will remain seated, until the head piece 24 on the valve actuating rod comes into engagement with the stop or abutment 25 after which any further upward flexing of the bottom diaphragm will cause the valve element 15* to unseat and admit air to the gas receiving space or chamber 1:. From the foregoing it will be seen that in myimproved gas holder it is impossible for the diaphragms A and B to be subjected to destructive strains produced by excessive flexing or movement of said dia phragms, due to the fact that the movement of the top diaphragm A is utilized to positively unseat a pressure relief valve, after the top diaphragm has reached a certain approximate position when it is moving in a direction to increase the volume of the gas receiving chamber 3:, and the movement of the bottom diaphragm B is utilized to positively unseat a vacuum relief valve when said bottom diaphragm reaches a certain approximate position during the movement of same in a direction to reduce the volume'of the chamber :c.

Any preferred or suitable means may be used to conduct rain water from the top surface of the top diaphragm A when said diaphragm is in its extreme downwardly flexed condition or partly downwardly flexed condition, the means herein illustrated for this purpose consisting of a flexible pipe 26 attached to the top diaphragm A in alignment with a drain hole in said diaphragm and having its lower end portion projecting through the bottom diaphragm B and connected to said bottom diaphragm by a liquid and gas-tight joint.

As previously stated, my improved gas holder is particularly adapted for use in a vapor recovering or vapor saving system having tanks in which volatile liquids are stored. Accordingly, in Figures 6, '7 and 8 of the drawings I have shown diagrammatically how my holder operates when it is connected with one of more milks H that are used for storing gasoline or other volatile liquids. The storage tank or tanks H are connected by means of a gas pipe 27 with the gas chamber or space a: of the holder, said pipe 2'7 being preferably attached to the shell 0 of the holder. During the daytime, when the gases or vapors in the tanks H expand, said gases or vapors escape into the chamber :r of the holder. At such times gravity causes thebottom diaphragm B to assume its downwardly flexed condition and remain at rest on the supporting structure D that is used to sustain the bottom diaphragm and prevent it from being strained when the chamber or space a: of the holder isunder pressure. The top diaphragm A will assume various positions, depending, upon the internal pressure of the space :r. When the internal pressure of said space a; overcomes the weight of the top diaphragm A, said top diaphragm will flex upwardly more or less, and thus automatically increase the volume of the space x. During the night time the gases previously admitted to the space or chamber a: of the holder will escape from said chamber and return to the storage tanks H through the pipe 2'7, due to the suction or vacuum created by the condensing and thermal contraction in the tanks H. At such times, i. e., during the night, gravity causes the top diaphragm A of the holder to assume its downwardly flexed the chamber :0, but said vacuum will never become high enough to strain the bottom dia phragm, because the vacuum relief valve will open before the bottom diaphragm flexes upwardly to such an extent or degree'as to strain the metal of same. As the day proceeds the vapors or gasesin the storage tanks H expand and flow into the chamber a: of the holder, with the result that the bottom diaphragm B will flex downwardly, as shown in Figure 6, thereby increasing the volume of the chamber. x. As the gases and vapors in the storage tanks H continue to expand, they escape into the chamber a: of the holder, with the result that the top diaphragm A of the holder will flex upwardly, as indicatedin Figure 8, thus adding materially to the volume of the chamber :r and producing a gas receiving space or chamber that is of suflicient volume to takecare of the expansion of the storage tanks H'. When the top diaphragm A reaches a certain approximate position during its upward flexing, the valve element 15 of the pressure relief valve F is pulled positively off its seat, thereby automatically venting the chamber a: and preventing the top diaphragm from flexing upwardly to such a degree or extent as to strain the metal of same. At such times, i. e., when the holder is operating under pressure, there is no liability of the metal of the bottom diaphragm being strained, due to the fact that the bottom diaphragm is supported throughout its entire area by the supporting structure D.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

l. A device of the kind referred to, having a storage space or chamber provided with opposed metallic walls, one of which is adapted to flex to increase the volume of said chamber under pressure and the other being adapted to flex to reduce the volume of said chamber under vacuum, and means for restricting the flexing of said walls so as to prevent said walls from being subjected to destructive strains.

2. A device of the kind referred to, having a storage space or chamber provided with opposed metallic walls, one of which is adapted to flex in one direction to increase the volume of said chamber and the other being adapted to flex in the opposite direction to reduce the volume of said chamber, a pressure relief valve arranged so that pressure in said chamber tends to hold said valve seated, a vacuum relief valve arranged so that a vacuum in said chamber tends to hold said valve seated, and means operated by the movement of said walls for unseating said valves.

3. A device of the kind referred to, having a storage space or chamber provided with opposed metallic walls, one of which is adapted to flex in one :1 direction to increase the volume of said chamber and the other being adapted to flex in the opposite direction to reduce the volume of said chamber, a spring seated pressure pressure relief valve arranged so that pressure in said chamber tends to hold said valve against its seat, a springseated vacuum relief valve arranged so that a vacuum in said chamber tends to hold said valve against its seat, means for utilizing the movement of one of said walls to unseat said vacuum relief valve.

4. A device of the kind referred to, having a storage space or chamber provided with opposed metallic walls constructed and arranged so that one of said walls is capable of flexing outwardly when the other wall is in an outwardly flexed conchamber and the other wall is capable of flexing inwardly when the opposed wall is in an inwardlyflexed condition, thereby reducing the volume of said chamber.

5. A device of the kind referred to, having a storage space or chamber provided with opposed flexible metallic walls, both of which are capable of assuming an outwardly flexed condition when said chamber is under a positive pressure and both of which are capable of assuming an inwardly flexed condition when said chamber is under a minus pressure.

6. A device of the kind referred to, having a storage space or chamber provided with opposed flexible metallic walls, both of which are capable of assuming an outwardly flexed condition when said chamber is under a positive pressure and both of which are capable of assuming an inwardly flexed condition when said chamber is under a minus pressure, and means for preventing said walls from being strained when they are in either an outwardly flexed condition or in an inwardly flexed condition.

'7. A device of the kind referred to, having a storage space or chamber provided with opposed flexible metallic walls that are adapted to assume an outwardly flexed condition when said chamber is under a positive pressure and to-assume an inwardly flexed condition when said chamber is under a minus pressure, a supporting structure for one of said walls that prevents it from being strained when said chamber is under a positive pressure, and a supporting structure for the other wall that prevents it from being strained when said chamber is under a minus pressure.

8. A device of the kind referred to, having a storage space or chamber provided with'opposed flexible metallic walls that are adapted to assume an outwardly flexed condition when said chamber is under a positive pressure and to assume an inwardly flexed condition when said chamber is under a minus pressure, a pressure relief valve operated by the movement of one of said walls, a vacuum relief valve operated by the movement of the other wall, and supporting structures for said walls arranged so that when said chamber is under a positive pressure, the wall that operates the vacuum relief valve will be supported throughout substantially its entire area, and when said chamber is under a minus pressure, the wall that operates the pressure relief valve will be supported 7 throughout substantially its entire area.

9. A device of the kind referred to, having a storage space or chamber provided with a metallic top wall of substantially concave form that is capable of flexing upwardly so as to increase the volume of said chamber, a metallic bottom wall for said chamber of substantially concave form that is capable of flexing upwardly to reduce the volume of said chamber, and supporting structures .on which said walls rest when said walls are of substantially concave form.

10. A device of the kind referred to, having a storage space or chamber provided with a metallic topwall of substantially concave form that is capable of flexing li ipwardly so as to increase the volume of said chamber, a metallic bottom wall for said chamber'of substantially concave form that is capable of flexing upwardly to reduce the volume of said chamber, supporting structures on which said walls rest when said walls are of substantially concave form, a pressure relief valve operatedby the movement of said top wall for venting said chamber, and a vacuum relief valve operated by the movement of said bottom wall for admitting air to said chamber.

11. A device of the kind referred to, having a storage space or chamber provided with opposed metallic flexible walls constructed and arranged so that when said chamber is under a vacuum or minus pressure both of said walls will be flexed inwardly and when gases are admitted to said chamber one of said walls will flex outwardly, and if the admission of the gases is continued, the other wall will thereafter flex outwardly.

12. A device of the kind referred to, having a storage space or chamber provided with opposed flexible metallic walls constructed and arranged so that as the pressure in said chamber is reduced one of said walls will flex inwardly, and if the diminution of the pressure is continued to a point below atmospheric pressure, the other wall will then flex inwardly.

13. A device of the kind referred to, having a storage space or chamber provided with a plurality of flexible portions constructed and arranged so that during the operation of admitting gases to said chamber one of said portions will flex or move in a direction to progressively increase the volume of said chamber, and during the operation of withdrawing gases from said chamber one of said portions will flex or move in a direction to progressively decrease the volume of said chamber.

14. A device of the kind referred to, having a storage space or chamber provided with flexible metallic top and bottom walls that are capable of moving so as to vary the volume of said chamber, a supporting structure for the top wall, sustaining posts or uprights for said supporting structure that project upwardly through the bottom wall, and means for sealing the openings in said bottom wall through which said posts project.

15. A device of the kind referred to, having a storage space or chamber provided with flexible metallic top and bottom walls that are capable of moving so as to increase and decrease the volume of said chamber, a supporting structure on which the top wall is adapted to rest under certain conditions, sustaining posts or uprights for said supporting structure that pass through openings in the bottom wall, and liquid seals for preventing gases from escaping from said chamber through said openings in the bottom wall.

16. A device of the kind referred to, having a shallow gas receiving chamber of relatively great diameter having flexible metallic top and bottom walls that have a natural tendency to assume a substantially concave shape, but which are capable of flexing upwardly into a substantially convex shape, a pressure relief valve carried by'said top wall, means operated by the movement of said top wall for causing said valve to open, a pressure relief valve carried by said bottom wall, and means operated by the movement of said bottom wall for causing said pressure relief valve to open.

17. A device of the kind referred to, having a storage space or chamber, comprising a metallic wall that is adapted to flex in a direction to increase the volume of said chamber when the medium to be stored is being supplied to the chamber and when the chamber is under pressure, and said chamber also comprising an opposed metallic wall that is adapted to flex in a direction to reduce the volume of said chamber when the stored medim is being withdrawn or when the chamber is under a minus pressure.

18. A device of the kind referred to, having a storage space or chamber, comprising a metallic wall that is adapted to flex in a direction to increase the volume of said chamber when the medium to be stored is being supplied to the chamber and when the chamber is under pressure, said chamber also comprising an opposed metallic wall that is adapted to flex in a direction to reduce the volume of said chamber when the stored medium is being withdrawn or when the chamber is under a minus pressure, and an automatic pressure relief device and an automatic vacuum relief device for said chamber.

' 19. A device of the kind referred to, having a storage space or chamber provided with a flexible metallic bottom wall that has a natural tendency to flex downwardlyat its center and assume a substantially concave-shape, said bottom wall being constructed so that it will be flexed or pulled upwardly when the vacuum or minus pressure in said chamber overcomes the weight of said wall, thereby causing the volume of said chamber to be automatically reduced.

20. A device of the kind referred to, having a storage space or chamber provided with a flexible metallic bottom wall that has a natural tendency to flex downwardly and assume a substantially concave shape, said bottom wall being constructed so that a certain approximate vacuum or minus pressure in said chamber will cause said wall to flex upwardly and thus reduce the volume of said chamber, and a vacuum'relief valve operated by the movement of said bottom wall.

21. A device of the kind referred to, having a storage space or chamber provided with a flexible metallic bottom wall that has a natural tendency to flex downwardly, said wall being constructed so that a vacuum or minus pressure in said chamber will cause said wallto flex upwardly more or less and thus reduce the volume of said chamber, a vacuum relief valve for admitting air to said chamber, and means for causing said valve to operate automatically after said bottom'wall has flexed upwardly a certain approximate degree.

22. A deviceof the kind referred to, having a storage space or chamber provided with a flexible metallic bottom wall constructed so that a certain approximate minus pressure or vacuum in said chamber will flex or pull said wall upwardly and thus reduce the volume of said chamber, a supporting means on which said bottom wall rests when said chamber is under atmospheric pressure or positive pressure, and means for restricting or limiting the movement of said bottom wall upwardly away from said supporting means.

23. A device of the kind referred to, having a shallow chamber of relatively great diameter provided with a flexible metallic bottom wall constructed so that gravity tends to cause said wall to assume a downwardly flexed condition and a vacuum or minus pressure in said chamber tends to cause said bottom wall to assume an upwardly flexed condition, and a vacuum relief valve that operates automatically to admit air to said chamber during the upward flexing of said bottom wall.

24. A device of the kind referred to, having a storage space or chamber provided with a metal portion that is adapted to flex in a direction to increase the volume of said chamber, due to the internal pressure of said chamber, a separate metal portion that is adapted to flex in a direction to :reduce the volume of said chamber, due to the vacuum or minus pressure in said chamber, and meansfor restricting the flexing of said

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