METHOD OF AND MEANS FOR ABSORBING PRESSURE SHOCKS

Abstract: Method and means of absorbing pressure shocks using a gas in which a series of pads (1) containing a gas are stacked one on another, the stack of pads being confined in a two part member (9-10) such as a cage adapted to be contained in a housing or used without a housing, the pads (1) being pre-loaded by the two part member (9-10) and fluid loaded or mechanically loaded to absorb shock.

Description: "METHOD OF AND MEANS FOR ABSORBING PRESSURE SHOCKS" This invention relates to a method of and means for absorbing pressure shocks and in particular, but not exclusively, it relates to the controlling of water hammer normally caused when a shock is applied to water in a system where a sudden variation in pressure occurs, such as when a tap is suddenly closed. The object of the present invention is to provide a simple and effective device, and method of manufacture, which, when arranged to prevent water hammer, can be connected to a line to prevent such water hammer occurring. When used for this purpose, the device according to this invention comprises a housing which can be connected into a pressure line and which is capable of withstanding the pressures developed but into this housing are fitted gas-containing pads which have the water pressure applied to them so that during normal flow the pads remain in a static condition but in the case of a sudden rise, such as occurs during water hammer, the pads are compressed to absorb the pressure shock to thereby relieve the water hammer reaction. The method of absorbing pressure shocks comprises forming a series of pads each comprising flexible membranes marginally joined together and containing a gas, stacking the said pads one on another with the membranes in contact, confining the stack of pads in housing means, such as a cage, and applying to the pads the pressure shocks to compress the pads to absorb at least part of the pressure shocks. The pads are preferably preloaded in the housing means. In its preferred form the device for absorbing pressure shocks comprises a series of pads each comprising flexible membranes marginally joined together and containing a gas, the pads being stacked one on another with the membranes in contact, and held in housing means so that pressure can be applied to the pads to compress the pads to absorb at least part of the pressure shocks. The pads can be preloaded by compressing them in the housing means, or in a fluid pervious cage mounted in the housing means. In order that the invention may be fully under- stood embodiments thereof will now be described with reference to the accompanying drawings in which: FIG. 1 is a part sectional side elevation of a pad which forms the basis of the invention. FIG. 2 is a longitudinal section of a two-part cage with the parts separated and showing a series of pads ready for assembly into the cage. FIG. 3 is a view of the device of FIG. 2 showing the two parts of the cage assembled to compress the pads within it. FIG. 4 is a view showing such a cage located in a housing which is adapted to be connected to a pressure line for absorbing pressure shocks in the line. FIG. 5 is a view similar to FIG. 4 but instead of using the cage, the housing itself supports the pads and includes a screen to protect the pads within the housing. FIG. 6 is a view of a device similar to that shown in FIG. 4 but showing a large capacity unit having a series of cages located in the housing. FIG. 7 shows another form of the device in which the series of cages is placed into a housing surrounding a flow-through tube which is apertured as shown in fragmentary section to allow fluid to flow into the space containing the cages. FIG. 8 is a view showing how the device can be used as a compression member to be placed between two components which are to be separated by a flexible cushion, the device differing from that of FIG. 3 in that pressure can simply be applied endwise. FIG. 9 shows a device similar to that of FIG. 8 but arranged so that the cage can have tension applied to the two opposite sides' thereof to compress the pads. In the form of the invention illustrated particularly in FIGS. 1 to 3, each pad 1 is formed by placing together two flexible membranes 2 and 3 and forming a marginal seal at 4 to form a sealed pad which contains in it a compressible fluid. The pads 1 can be formed of circular sheets of a suitable material which will remain gas-tight. This can be achieved for instance, by having an ^ interleaved construction using two polythene discs with a layer of aluminium between them, such sandwich construction then forming the membrane on one side of the disc with the membrane on the other side of similar construction, the discs being bonded together marginally so that gas can be injected into the space between the two membranes to be permanently held therein at a selected pressure. Thus each pad 1 is of disc like structure with both its sides of convex form. The gas can be nitrogen. It is, of course, possible in some cases to use simply a strength sheet of polythene or similar material and to bond to this aluminium or another material which is impervious to the gas used in the device, but generally it is preferred to protect the aluminium or similar material by outer and inner layers with a suitable water-resistant outer layer and a gas-resistant material on the inner side. The polythene or similar materials can be heat welded together at 4 around or near the periphery to ensure the required strength, and to prevent leakage a rim 6, as indicated by dotted lines in FIG. 1, can be positioned around the periphery of the device which can be crimped or otherwise forced down onto the materials which are to be held together in the leak-proof fashion, and this rim 6 can contain a sealant or gasket means, if such is required. It would also be possible to position a ring 7 of a soft plastic material or the like, as indicated OMPI by dotted lines in FIG. 1, inside of each of the pads near the perimeter where the layers are joined, this being for the purpose of controlling the type of deflection of the wall of the pac.s which will give best results and ensure long life for the unit. These pads 1 are placed one on another in the manner shown in FIG. 2 and are then compressed in a cage 8 consisting of a pair of interengaging cage members 9 and 10 which when pushed together have interengaging ends 11 and 12 which move past each other as shown in FIG. 3 so that they interlock to hold the two cage members 9 and 10 of the cage together against outward movement. The enlarged perspective view of the interengaging ends 11 and 12 show the taper which allows the ends 11 and 12 to move past each other and then interlock. The action of confining the pads 1 in the cage 8 results in a precompression of the pads and this precompression can be selected to suit the particular conditions and pressures to which the device is to be subjected and in connection with which it is to form shock absorbing means. By making the cages 8 with rigid end plates 13 and 14 and extending projections 15 and 16 which are disposed in a generally axial direction and which terminate in the interengaging ends 11 and 12 so that the interengaging ends 11 of the projections 15 of the end plate 13 pass and then interlock with the ends 12 of the other extending projections 16 of the end plate 14 so that a safe and rigid structure results to which water has access through the spaces 18 between the extending projections 15 and 16 from the two ends plates 13 and 14. In FIG. 4 the cage 8 containing the pads 1 is held in a housing 20 having a removable end closure 21 and supplied with a fluid inlet 22 which allows fluid to flow into the housing 20 to extend around the cage 8 and thus to apply pressure to the pads 1, the pads 1 of course being further compressible beyond the initial loading which exists when the pads are forced together within the cage so that when for instance pressure in a water main to which the device is connected suddenly rises to produce a shock wave, the compression of the pads 1 absorbes this shock and prevents the water hammer action which would otherwise cccur. In the device shown in FIG. 5 the housing 20 contains the pads 1 without being held in a cage, but to protecc the edges of the pads, partic¬ ularly at the inlet 22, a mesh 24 surrounds the perimeter of the assembled pads 1 and lies against the inner wall of the housing 20, the end closure 21 in this case serving to compress the pads 1 when the end closure 21 is assembled on the housing 20. In the form shown in FIG. 6, which is generally adapted for industrial use, a larger housing 25 is used again with a fluid inlet 26 and in this case a series of cages 8 are positioned within this housing. In the form shown in FIG. 7 the housing 28 surrounds a pipe 29 to form a cavity around the pipe 29 in which cavity a considerable number of cages 8 are placed and in this case the pipe 29, within the area bound by the housing 28, has a series of apertures 30 through it so that liquid OMH_ flowing through the pipe 29 has access to the chamber formed by the housing 28 to again act to prevent water hammer when such a device is applied to a water pipe. The device of FIG. 8 is similar to the device of FIG. 3 but in this case the one interengaging cage member 32 is connected to the other inter¬ connecting cage member 33 by having hook-shaped ends 34 of extending projections 35 interengage with hook-shaped ends 36 on the extending circular projection 37, shown enlarged in the circle, of the other cage member 33 so that pressure exerted on the pads 1 can be increased by moving the two cage members 32 and 33 towards each other and this movement again has the required ability to absorb shocks which is the basis of this invention. The pressure is in this case is applied to the ends 40 in the direction of the arrow 41. In .the device shown in FIG. 9 the one inter- connecting cage member 42 has extending projections 43 which extend the full depth of the cage 8 and are turned inwards at their ends to engage the opposite side of the cage 8 while the other inter¬ engaging cage member 44 has extending projections 45 which turn over at 46 to engage the top of the cage 8, the cage members 42 and 44 being provided with anchors 48 and 49 respectively to allow the cage members 42 and 44 to be pulled apart against the compression resistance of the pads 1 in the cage 8. OMPI

Claims: THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. The method of absorbing pressure shocks which comprises forming a series of pads each comprising flexible membranes marginally joined together and containing a gas, stacking the said pads one on another with the membranes in contact, confining the said stack of pads in housing means, and applying to the said pads the pressure shocks to compress the said pads to absorb at least part of the said pressure shocks. 2. The method of claim 1 characterised in that the said housing means comprise a cage having at least two interengaging members, and by placing the said pads between the said Interengaging members and compressing the said pads by moving the said Interengaging members towards each ether and inter¬ connecting the said members to maintain the said pads under a preloaded pressure condition. 3. The method of claim 2 characterised by placing the said cage in a housing and applying a pressure fluid to the said housing to further compress the said pads when pressure shocks occur. 4. The method of claim 1 characterised by placing the said pads into a two-part cage forming the said housing means and compressing the said cage to achieve a preloaded pressure condition in the said pads 5. A device for absorbing pressure shocks in which gas cushion means are used characterised by a series of pads each comprising flexible membranes OMP marginally joined together and containing a gas, said pads being stacked one on another with the membranes in contact, means housing the said pads, and means to allow pressure to be applied to the said pads to compress the said pads to absorb at least part of the said pressure shocks. 6. A device for absorbing pressure shocks according to claim 5 wherein the said housing means are dimensioned to preload the said pads. 7. A device for absorbing pressure shocks according to claim 5 wherein the said pads are held in a fluid pervious cage arranged to preload the said pads, and the said cage is disposed in the said housing means, 8. A device for absorbing pressure shocks according to claim 5 wherein the said housing means for the said pads comprise a pair of interengaging cage members dimensioned to compress the said pads when the cage members are interengaged. 9. A device for absorbing pressure shocks according to claim 8 arranged to counter water hammer characterised in that the said interengaged cage members are fluid pervious and are supported in a housing having a fluid inlet thereto. 10. A device for absorbing pressure shocks according to claim 5 arranged to counter water hammer comprising at least a cage to house a series OMPI of the said pads, said cage or each said cage being water pervious, a housing enclosing the said cage or cages, and means on the said housing to connect It to a water supply pipe. 11. A device for absorbing pressure shocks according to claim 10 arranged to counter water hammer wherein the said pads are partially compressed In the said housing. 12. A device for absorbing pressure shocks according to claim 5 wherein the said means for housing the said pads comprise a cage formed of a plurality of cage members adapted to support the said stack of pads, and means on the said cage members to interengage when the said pads are partially compressed to limit separation of the said cage members whereby to hold the said pads in the said partially compressed condition. 13. A device for absorbing pressure shocks according to claim 12 wherein the said cage is fluid-pervious, and by a housing surrounding the said cage and having fluid inlet means thereto whereby fluid pressure can be applied to the said pads to absorb pressure shocks by further compression of the said pads. 14. A device for absorbing pressure shocks according to claim 5 wherein a plurality of fluid- pervious cages each contain a series of partly compressed pads, and wherein the said plurality of cages are held in a housing adapted to be connected to a pipe carrying pressure fluid. OMPI 15. A device for absorbing pressure shocks according to claim 14 wherein the said housing has the fluid carrying pipe project through it and the said pipe is apertured within the said housing and the said cages are disposed around the said pipe in the said housing. 16. A device for absorbing pressure shocks according to claim 5 arranged to counter water hammer and comprising a series of the said pads stacked one on another in a water pervious cage arranged to hold the said pads compressed and means on the said housing to connect it to a pressure water line. 17. A device for abosrbing pressure shocks according to claim 5 arranged to counter water hammer and comprising a series of said pads stacked one on another in the said housing to hold the said pads compressed, means on the said housing to connect it to a pressure water line, and a screen in the said housing interposed between at least the said water inlet and the said stack of pads. 18. A device for absorbing pressure shocks according to claim 7 wherein the said housing means comprise a first part and a second part each having rigid end plates and peripheral extensions projecting in an axial direction therefrom, said extensions having hook-shaped interengaging ends arranged to allow compression of the said housing in an axial direction beyond the interenegaging position of the said hook-shaped interengaging ends. 19. A device for absorbing pressure shocks according to claim 7 wherein the said housing means comprise a first cage member and a second cage member each having rigid end plates and peripheral extensions projecting in an axial direction and having inturned ends to engage the said cage at an end remote from the said rigid end, and means on the said ends to apply tension to the ends of the said housing means. 20. A device for absorbing pressure shocks according to claim 5 wherein the said pads each comprise flexible membranes marginally joined together and containing a gas characterised by a ring between the membranes adjacent the marginal joining whereby to further control the action of the membranes and further characterised by a ring to seal the membranes together marginally. 21. A device for absorbing pressure shocks to prevent water hammer constructed and operating substantially as described with reference to FIGS. 1 to 3 or any one of FIGS. 4 to 7. 22. A device for absorbing pressure shocks constructed and operating substantially as described with reference to FIGS. 1 to 3 or any one of FIGS. • 4 to 9.

Inventors: RAST WLODZIMIERZ, RAST, WLODZIMIERZ
Applicants: RAST PTY LTD W, W. RAST PTY. LTD.
Application year: 1983
Main classification: F16L55
IPC codes: F04B11, F16L55