Abstract:
A flexible pressure vessel is constructed from at least one pair of upper and mating lower dome shaped cell portions. The dome portions are molded from sheets of resilient material and joined together by radio frequency welding or high-strength adhesives. Upper and lower passageway portions extend outwardly from each cell portion to the surrounding sheet material. When the cell portions are joined the passageway portions are joined to form a passageway for connection to a valve or another cell. Upper and lower rings surround the upper and lower cell portions to provide reinforcement for the cells. First and second blankets of heavy-duty fiber reinforced material are attached over the upper and lower cell portions and stitched in place with heavy-duty stitching extending through the resilient material surrounding the cell portions. Cell shaped sponges impregnated with absorbent materials are encased in liquid and gas impermeable plastic tubing and inserted into the cells prior to joining of the cell portions. Heat-reflecting plastic film or metal foil is inserted between blankets and the cell portions. The heavy duty stitching is high-pressure loop and lock braiding. The passageway has a cross-section of between 0.050 and 0.100 inches. An apparatus and method are described for constructing the flexible pressure vessel.

Description:
FIELD OF INVENTION  
   The invention pertains to devices for storing gases and fluids under pressure. More particularly, the invention relates to pressure vessels that are formed out of flexible materials and that can be made to conform to a variety of shapes. 
   BACKGROUND OF THE INVENTION  
   Typically, pressure vessels capable of containing liquids or gases at significant pressures have involved fixed shape cylinders or spheres formed of high-strength metals such as steel or aluminum. Such pressure vessels, while successful for their designed applications, involve a number of problems. First, such metallic cylinders are relatively heavy compared to the gases or fluids that they contain. Second, pressure cylinders contain all of the gas or liquid in a single space. Should the vessel rupture, the entire vessel is destroyed, often with a violent explosion sending shards of metal in all directions. Third, metallic cylinders have a definite shape and cannot be adapted to fit readily in many space-constrained applications. The present invention involves a number of small cells linked to each other by small conduits. The cells are collected in a flexible manifold that allows the collection of cells to be arranged in a variety of different configurations. A pressure vessel of this type can be lightweight, adaptable to a variety of spaces and unusual applications, and is inherently safer in rupture situations. 
   The present invention is easily adapted to a number of valuable applications through the use of modern, high-strength materials and manufacturing techniques. The pressure handling capability of the vessel can be enhanced through the use of braiding, hoop-winding and overlayment with flexible, high-strength fabric and braiding materials. The pressure vessel may then be further strengthened through the use of plastic resin coatings or the addition of external reinforcement rings. The purity of liquids or gases contained in the vessel may be controlled through the use of special lining tubes placed within the vessel cells during construction. The vessel cells may be prevented from collapsing as gasses or liquids are removed by the introduction of special sponges to the cells during fabrication. For certain special applications, the pressure vessel cells may be fitted with removable, resealable ports, permitting the introduction of relatively large matter into the cells. 
   Various designs have been developed using linked cell technologies. U.S. Pat. No. 6,047,860 issued to Sanders, the present inventor, is directed to a container system for pressurized fluids. The system includes a plurality of ellipsoidal chambers connected by a tubular core. The apertures into each of the chambers are of comparatively small size so that the rate of evacuation may be controlled if a single chamber is ruptured. Thus, the vessels are resistant to explosive rupturing. The container system comprises a plurality of chambers and a tubular core. The size of the apertures in the core are pre-selected so as to control the rate of evacuation of pressurized fluid from chambers. Each of the chambers is generally ellipsoidal and molded of a synthetic material with open front and rear ends. The tubular core is sonically welded to the chamber shells and the exterior of the shells are wrapped with pressure resistant reinforcing filaments. A protective plastic coating is applied to the exterior of the filament wrapped shells. 
   U.S. Pat. No. 2,222,762 issued to Bebor et al, discloses hollow metal bodies and means for producing them. The hollow bodies described in this invention are particularly adapted for use as pressure vessels and may be produced from tubular bodies by expanding the walls. The zones may comprise spaced spheroids joined together by parts of the initial tube. The hollow bodies described are made by placing a cylindrical tube into a suitable mold and then heating until the metal possesses the plasticity for expanding. By exerting an axially directed compressive force against the ends of the tube and simultaneously applying a high fluid pressure within the tube, the tube ball is axially compressed or upset while portions of the wall are expanded against the walls of the mold surrounding the tube. By suitably adjusting the axial thrust and expanding pressures, the hollow body is formed to possess the same wall thickness and resistivity to pressure yet to have the form of a plurality of spaced spheroids adjoined together by parts of the initial tube. 
   U.S. Pat. No. 4,946,056, issued to Stannard, is directed to a fabricated pressure vessel that is used for the containment of pressurized fluids. The multi-lobed tank comprises a series of cylindrical lobes connected side by side and separated by a septa. Openings or ports in the septa enable fluid communication between the lobes. 
   U.S. Pat. No. 2,823,668 issued to Van Court et al. describes an inflatable splint. The wrapper of the splint comprises a double layer of material defining a series of flexible fluid chambers divided into elongated enclosures by cementing or heat sealing. It should be noted that the chamber walls are left open at their upper and lower ends whereby all of the elongated fluid chambers are in fluid communication with one another. 
   U.S. Pat. No. 5,704,512 issued to Falk et al., discloses a vessel that is used for a pressure vessel and made of plastic. The vessel includes a centered tubular part interconnected to a plurality of interconnected fluid compartments distributed peripherally in an annular fashion and thus enclosing the central compartment. The vessels described in this invention may be used to hold liquefied petroleum gas, compressed air, as well as various fire-fighting materials. 
   While other variations exist, the above-described designs involving linked cell technologies are typical of those encountered in the prior art. It is an objective of the present invention to provide a flexible pressure vessel that is capable of maintaining gasses or liquids at relatively high pressures. It is a further objective to provide this capability in a vessel that is light in weight and that presents a significantly reduced risk of injury in rupture situations. It is a still further objective of the invention to provide a pressure vessel that may be easily adapted to a variety of space constraints. It is yet a further objective to provide a pressure vessel that is durable, easily serviced, and that may be produced inexpensively. It is still a further objective of the invention to provide means for easily increasing the pressure handling capability of the vessel through the addition of external overwrapping, banding or overlayment with high-strength materials. It is another objective to provide means for controlling the purity of liquids or gasses introduced into the vessel. Finally, it is an objective of the invention to provide means for introducing solid material into the pressure cells of the vessel through resealable ports in the vessel pressure cells. 
   While some of the objectives of the present invention are disclosed in the prior art, none of the inventions found include all of the requirements identified. 
   SUMMARY OF THE INVENTION  
   (1) An ovoid flexible pressure vessel providing the desired features may be constructed from the following components. At least one hollow pressure cell is provided. The pressure cell has symmetrical upper and lower cell portions. The pressure cell is formed of resilient material and has an outer surface, an outer perimeter and at least one opening located at the outer perimeter. A passageway is provided. The passageway has a first end and a second end and is attached to the at least one opening at the first end and extends outwardly for connection to either a passageway of another cell or a valve. At least one reinforcing ring is provided. The reinforcing ring has an inner surface, an outer surface, an outer circumference, is formed of high-strength material and is sized and shaped to fit tightly about the outer perimeter of the pressure cell. The reinforcing ring has an aperture. The aperture extends from the inner surface to the outer surface and is sized, shaped and located to accommodate connection of the passageway to the pressure cell. A valving means is provided. The valving means is capable of controlling a flow of either a liquid or a gas through the passageway and is attached to the second end of the passageway. When the reinforcing ring is located about the outer perimeter of the pressure cell, the pressure handling capacity of the cell is increased. 
   (2) In a variant of the invention, at least one upper dome-shaped cell portion is provided. The upper cell portion is formed from resilient material and has an outer surface, an inner surface, an inner perimeter, an outer perimeter and at least one upper opening portion. The upper opening portion extends outwardly from the inner perimeter. At least one mating lower dome-shaped cell portion is provided. The lower cell portion is formed from resilient material and has an outer surface, an inner surface, an inner perimeter, an outer perimeter and at least one lower opening portion. The lower opening portion extends outwardly from the inner perimeter. The upper cell portion is joined to the mating lower cell portion such that a hollow pressure cell is formed. The cell  15  has at least one opening. A passageway is provided. The passageway has a first end and a second end and is attached to the at least one opening at the first end and extends outwardly for connection to either a passageway of another cell or a valve. 
   At least one reinforcing ring is provided. The reinforcing ring has an inner surface, an outer surface, an outer circumference, is formed of high-strength material and is sized and shaped to fit tightly about the outer perimeter of the pressure cell. The reinforcing ring has an aperture. The aperture extends from the inner surface to the outer surface and is sized, shaped and located to accommodate connection of the passageway to the pressure cell. A valving means is provided. The valving means is capable of controlling a flow of either a liquid or a gas through the passageway and is attached to the second end of the passageway. 
   (3) In another variant of the invention, a protruding rim is provided. The protruding rim is located at the outer perimeter of the pressure cell. Upper and lower receiving notches are provided. The upper and lower receiving notches are located above and below the protruding rim. Upper and lower projecting ribs are provided. The upper and lower projecting ribs are located upon the inner surface of the reinforcing ring. A central receiving notch is provided. The central receiving notch is located between the upper and lower projecting ribs. The projecting ribs are sized, shaped and located to fit the upper and lower receiving notches of the pressure cell. The central receiving notch is sized, shaped and located to fit the protruding rim of the pressure cell. When the reinforcing ring is located about the outer perimeter of the pressure cell, the pressure handling capacity of the cell is increased. 
   (4) In another variant, at least one upper dome-shaped cell portion is provided. The upper cell portion is formed from resilient material and has an outer surface, an inner perimeter, an outer perimeter and at least one upper passageway portion. The upper passageway portion extends outwardly from the inner perimeter. At least one mating lower dome-shaped cell portion is provided. The lower cell portion is formed from resilient material and has an outer surface, an inner perimeter, an outer perimeter and at least one lower passageway portion. The lower passageway portion extends outwardly from the inner perimeter. The upper cell portion is joined to the mating lower cell portion such that a hollow pressure cell is formed. The cell has at least one passageway extending outwardly from the cell for connection to either a passageway of another cell or a valve. 
   A protruding rim is provided. The protruding rim is located at the outer perimeter of the pressure cell. Upper and lower receiving notches are provided. The upper and lower receiving notches are located above and below the protruding rim. Upper and lower reinforcing rings are provided. Each of the reinforcing rings has an inner surface, an outer surface, is formed of high-strength material and is sized and shaped to fit tightly in either the upper or lower receiving notches. At least one of the reinforcing rings has an aperture. The aperture extends from the inner surface to the outer surface and is sized, shaped and located to accommodate connection of the passageway to the pressure cell. When the reinforcing rings are located about the outer perimeter of the pressure cell, the pressure handling capacity of the cell is increased. 
   (5) In yet a further variant of the invention, means are provided for fastening the upper reinforcing ring to the lower reinforcing ring. 
   (6) In yet a further variant, at least one upper dome-shaped cell portion is provided. The upper cell portion is formed from resilient material and has an outer surface, an inner perimeter, an outer perimeter and at least one upper passageway portion. The upper passageway portion extends outwardly from the inner perimeter. At least one mating lower dome-shaped cell portion is provided. The lower cell portion is formed from resilient material and has an outer surface, an inner perimeter, an outer perimeter and at least one lower passageway portion. The lower passageway portion extends outwardly from the inner perimeter. 
   The upper cell portion is joined to the mating lower cell portion such that a hollow pressure cell is formed. The cell has at least one passageway extending outwardly from the cell for connection to either a passageway of another cell or a valve. A protruding rim is provided. The protruding rim is located at the outer perimeter of the pressure cell. At least one groove located about the outer perimeter above the protruding rim is provided. Upper and lower reinforcing rings are provided. Each of the reinforcing rings has an inner surface, an outer surface, is formed of high-strength material and is sized and shaped to fit tightly about the outer perimeter on either side of the protruding rim. 
   The reinforcing rings have at least one rib located upon the inner surface thereof. The rib is sized, shaped and located to engage the groove. When the reinforcing rings are located about the outer perimeter of the pressure cell, the pressure handling capacity of the cell is increased. 
   (7) In still a further variant of the invention, means are provided for fastening the upper reinforcing ring to the lower reinforcing ring. 
   (8) In another variant of the invention, an overwrapping layer is provided. The overwrapping layer is formed of high-strength braiding material wound around the hollow pressure cell. When the hollow pressure cell is overwrapped with high-strength braiding material, the pressure handling capacity of the pressure cell is increased. 
   (9) In yet a further variant of the invention, hoop winding is provided. The hoop winding is around the hollow pressure cell to increase the pressure handling capacity of the pressure cell. 
   (10) In still a further variant, a plastic overcoating is provided. 
   (11) In yet a further variant, a first flexible blanket is provided. The first blanket has an upper surface, a lower surface and is sized and shaped to cover the upper cell portion and extends outwardly beyond the outer perimeter. The first blanket is fixedly attached at its lower surface to the outer surface of the upper cell portion. A second flexible blanket is provided. The second blanket has an upper surface, a lower surface and is sized and shaped to cover the lower cell portion and extends outwardly beyond the outer perimeter. The second blanket is fixedly attached at its upper surface to the outer surface of the lower cell portion. 
   (12) In another variant, heavy duty stitching is used to attach the first blanket to the second blanket. The stitching penetrates the first and second blankets between the cell portions and serves to further reinforce and increase the pressure-handling capabilities of the pressure cell. 
   (13) In another variant, the heavy duty stitching is high pressure hoop and lock braiding. 
   (14) In still a further variant of the invention, a cell-shaped sponge is inserted between the upper cell portion and the lower cell portion prior to joining the upper and lower cell portions. The sponge serves to prevent the cell from collapsing after either gas or liquid is removed from the cell. 
   (15) In another variant of the invention, the sponge is impregnated with a zeolite compound, a gas or liquid absorbing compound or a reactive fuel cell compound. 
   (16) In still another further variant, either a heat-reflecting plastic film or a metal foil is inserted between at least one of the first blanket and the upper cell portion or the second blanket and the lower cell portion. 
   (17) In yet a another variant of the invention, the upper cell portion is joined to the lower cell portion by either radio frequency welding or high strength adhesive. 
   (18) In still a further variant, either the first and second blankets are formed of high-strength fiber impregnated material. 
   (19) In still another variant of the invention, the passageway has a cross-section of between 0.025 and 0.250 inches. 
   (20) In yet a further variant, an upper retaining plate is provided. The upper retaining plate has a third inner circumference, an outer circumference and a third pre-determined thickness. The upper retaining plate is sized and shaped to fit over the upper cell portion and surround its outer perimeter when the upper cell portion is covered by the first blanket. The third inner circumference is larger than the outer circumference of the reinforcing ring. A lower retaining plate is provided. The lower retaining plate has a fourth inner circumference, an outer circumference and a fourth pre-determined thickness. The lower retaining plate is sized and shaped to fit over the lower cell portion and surround its outer perimeter when the lower cell portion is covered by the second blanket. The fourth inner circumference is larger than the outer circumference of the reinforcing ring. Means are provided for attaching the upper retaining plate to the lower retaining plate. When the upper retaining plate is attached to the lower retaining plate, surrounding the upper and lower cell portions and the first and second blankets covering the reinforcing ring, the pressure capacity of the cell will be increased. 
   (21) In another variant, means are provided for attaching the upper retaining plate to the lower retaining plate. A series of holes are provided. The holes penetrate the upper retaining plate between its outer circumference and the third inner circumference. The holes also penetrate the lower retaining plate between its outer circumference and the fourth inner circumference, the first blanket, a border of sheet material surrounding the outer perimeter of the upper cell portion, a border of sheet material surrounding the outer perimeter of the lower cell portion and the second blanket. The holes are outside of the outer circumference of the reinforcing ring. A series of fastening means is provided. The fastening means are sized and shaped to pass through the series of holes and are capable of securing the upper retaining plate to the lower retaining plate. 
   (22) In yet a further variant of the invention, the fastening means is a series of bolt and locking nuts. 
   (23) In another variant of the invention, the fastening means is a series of rivets. 
   (24) In still a further variant, the means for attaching the upper retaining plate to the lower retaining plate further includes a series of holes. The holes penetrate the upper retaining plate between its outer circumference and the third inner circumference, the first blanket, a border of sheet material surrounding the outer perimeter of the upper cell portion, a border of sheet material surrounding the outer perimeter of the lower cell portion and the second blanket. The holes are outside of the outer circumference of the reinforcing ring. A series of pins are provided. The pins are affixed orthogonally along an upper surface of the lower retaining plate and are sized, shaped and located to fit slidably through the series of holes and extends slightly above an upper surface of the upper retaining plate. A series of welds are provided. The welds fixedly attach the pins to the upper retaining plate, thereby securing the upper and lower retaining plates to each other. 
   (25) In yet a further variant of the invention, a series of cell shaped sponges are provided. A tube is provided. The tube is formed of flexible gas and liquid impervious material and is sized and shaped to surround the sponges. The sponges are inserted in the tube at spaced intervals. The encased sponges are inserted between the upper cell portions and the lower cell portions prior to joining the upper and lower cell portions. The tube extends through the passageways. The sponges serve to prevent the cells from collapsing after either gas or liquid is removed from the cells. The tube serves to prevent contamination of either gas or liquid by the inner surfaces of the upper and lower cell portions. 
   (26) In another variant of the invention, the sponges are impregnated with a zeolite compound, a gas or liquid absorbing compound or a reactive fuel cell compound. 
   (27) In another variant, the tube is formed from material selected from the group comprising: thermoplastic polyurethane elastomer, polyurethane polyvinyl chloride, polyvinyl chloride, thermoplastic elastomer, Teflon® and polyethylene. 
   (28) In still a further variant of the invention, upper and lower reinforcing panels are provided. The reinforcing panels are formed of high-strength woven material and are substantially ovoid in shape with extensions projecting from a perimeter of the ovoid shape. The reinforcing panels are adhered to the outer surfaces of the upper and lower cell portions of the hollow pressure cell, thereby increasing the pressure handling capabilities of the pressure cell. 
   (29) In another variant of the invention, the method of adhesion is selected from the group comprising: high-strength adhesive, sonic welding, and RF welding. 
   (30) In another variant, the woven material is prepregnated with either adhesive or laminating material and subjected to heat and pressure. 
   (31) In yet a further variant of the invention, the passageway is removably attached to the hollow pressure cell. 
   (32) In another variant of the invention, the passageway is removably attached to the hollow pressure cell by a threaded fitting. The threaded fitting is sized and shaped to fit a threaded opening at the outer perimeter of the hollow pressure cell. 
   (33) In still a further variant of the invention, an orifice is provided. The orifice penetrates either the upper or lower cell portions. A removable plug is provided. The removable plug is sized and shaped to fit sealably into the orifice, thereby permitting introduction of material into the pressure cell. 
   (34) An apparatus for fabricating an ovoid flexible pressure vessel may be constructed from the following components. An internal core form is provided. The internal core form has the internal shape of a hollow pressure cell, an internal passageway and a plurality of outlet blow holes connected to the passageway. An open top vessel is provided. The vessel contains a solution of liquid plastic. Means are provided for moving the internal core form into and out of the solution. Means are provided for pumping either pressurized gas or liquid into the passageway, thereby causing the liquid plastic to expand about the internal core form to form a hollow pressure cell. The pressure cell has symmetrical upper and lower cell portions, is formed of resilient material and has an outer surface, an outer perimeter and at least one opening located at the outer perimeter. Means are provided for extracting the internal core form from the hollow pressure cell. Means are provided for connecting a passageway to the at least one opening for connection to either a passageway of another cell or a valve. Means are provided for pressing a reinforcing ring onto the outer perimeter. The reinforcing ring has an inner surface, an outer surface, is formed of high-strength material and is sized and shaped to fit tightly about the outer perimeter of the pressure cell. The reinforcing ring has an aperture. The aperture extends from the inner surface to the outer surface and is sized, shaped and located to accommodate connection of the passageway to the pressure cell. Means are provided for attaching a valving means to the passageway. The valving means is capable of controlling a flow of either a liquid or a gas through the passageway and is attached to the second end of the passageway. When the reinforcing ring is located about the outer perimeter of the pressure cell, the pressure handling capacity of the cell is increased. 
   (35) In a variant of the apparatus for fabricating an ovoid flexible pressure vessel, means are provided for forming a protruding rim at an outer perimeter of the hollow pressure cell. The protruding rim has upper and lower receiving notches located above and below the protruding rim. The reinforcing ring has an outer surface, an inner surface, upper and lower projecting ribs and a central receiving notch located between the upper and lower projecting ribs. The projecting ribs are sized, shape and located to fit the upper and lower receiving notches of the pressure cell. The central receiving notch is sized, shaped and located to fit the protruding rim of the pressure cell. 
   (36) In yet a further variant of the apparatus for fabricating an ovoid flexible pressure vessel, first and second symmetrical external mold portions are provided. Each of the mold portions has at least one cavity reflecting the external shape of a hollow pressure cell and a connecting internal passageway. The cavity has at least one vacuum passage connecting to an external vacuum source. First and second sheets of moldable thermoplastic material are provided. Means are provided for inserting the sheets of thermoplastic material between the mold portions. Means are provided for heating the mold portions and the sheets. Means are provided for applying vacuum to the vacuum passages, thereby forming a hollow pressure cell. Means are provided for removing the hollow pressure cell from the mold portions. Means are provided for pressing a reinforcing ring onto the outer perimeter. The reinforcing ring has an inner surface, an outer surface, is formed of high-strength material and is sized and shaped to fit tightly about the outer perimeter of the pressure cell. The reinforcing ring has an aperture. The aperture extends from the inner surface to the outer surface and is sized, shaped and located to accommodate connection of the passageway to the pressure cell. Means are provided for attaching a valving means to the passageway. The valving means is capable of controlling a flow of either a liquid or a gas through the passageway and is attached to the second end of the passageway. When the reinforcing ring is located about the outer perimeter of the pressure cell, the pressure handling capacity of the cell  15  is increased. 
   (37) In another variant of the apparatus for fabricating an ovoid flexible pressure vessel, means are provided for forming a protruding rim at an outer perimeter of the hollow pressure cell. The protruding rim has upper and lower receiving notches located above and below the protruding rim. The reinforcing ring has an outer surface, an inner surface, upper and lower projecting ribs and a central receiving notch located between the upper and lower projecting ribs. The projecting ribs are sized, shaped and located to fit the upper and lower receiving notches of the pressure cell. The central receiving notch is sized, shaped and located to fit the protruding rim of the pressure cell. 
   (38) In still a further variant of the apparatus for fabricating an ovoid flexible pressure vessel, first and second symmetrical external mold portions are provided. Each of the mold portions has at least one cavity reflecting the external shape of a hollow pressure cell and a connecting internal passageway. Means are provided for extruding a plastic tube between the mold portions and pressurizing the plastic tube to form the hollow pressure cell with attached connecting internal passageway. Means are provided for removing the hollow pressure cell with attached passageway from the mold portions. Means are provided for connecting a passageway to the at least one opening for connection to either a passageway of another cell or a valve. Means are provided for pressing a reinforcing ring onto the outer perimeter. The reinforcing ring has an inner surface, an outer surface, is formed of high-strength material and is sized and shaped to fit tightly about the outer perimeter of the pressure cell. The reinforcing ring has an aperture. The aperture extends from the inner surface to the outer surface and is sized, shaped and located to accommodate connection of the passageway to the pressure cell. Means are provided for attaching a valving means to the passageway. The valving means is capable of controlling a flow of either a liquid or a gas through the passageway and is attached to the second end of the passageway. When the reinforcing ring is located about the outer perimeter of the pressure cell, the pressure handling capacity of the cell is increased. 
   (39) In yet a further variant of the apparatus for fabricating an ovoid flexible pressure vessel, means are provided for forming a protruding rim at an outer perimeter of the hollow pressure cell. The protruding rim has upper and lower receiving notches located above and below the protruding rim. The reinforcing ring has an outer surface, an inner surface, upper and lower projecting ribs and a central receiving notch located between the upper and lower projecting ribs. The projecting ribs are sized, shaped and located to fit the upper and lower receiving notches of the pressure cell. The central receiving notch is sized, shaped and located to fit the protruding rim of the pressure cell. 
   (40) In still a further variant of the apparatus for fabricating an ovoid flexible pressure vessel, first and second rolls of planar resilient material are provided. First and second thermal die stamping stations are provided. The stamping stations are capable of forming upper and lower cell portions of a hollow pressure cell and a connecting internal passageway. Means are provided for moving resilient material from the first and second rolls of planar resilient material into the first and second thermal die stamping stations. A radio frequency welder is provided. The welder is capable of joining the upper cell portion to the lower cell portion. Means are provided for moving the upper and lower cell portions into the radio frequency welder, thereby joining the upper and lower cell portions and forming the internal connecting passageway. Means are provided for pressing upper and lower reinforcing rings onto the hollow pressure cell adjacent the outer perimeter. The reinforcing rings have an inner surface, an outer surface, are formed of high-strength material and are sized and shaped to fit tightly about the outer perimeter of the pressure cell. At least one of the reinforcing rings has an aperture. The aperture extends from the inner surface to the outer surface and is sized, shaped and located to accommodate connection of the passageway to the pressure cell. Means are provided for attaching a valving means to the passageway. The valving means is capable of controlling a flow of either a liquid or a gas through the passageway and is attached to the second end of the passageway. When the reinforcing rings are located about the outer perimeter of the pressure cell, the pressure handling capacity of the cell is increased. 
   (41) In yet a further variant of the apparatus for fabricating an ovoid flexible pressure vessel, means are provided for forming a protruding rim at an outer perimeter of the hollow pressure cell. Means are provided for forming at least one groove located about the outer perimeter above the protruding rim. Means are provided for forming at least one groove located about the outer perimeter below the protruding rim. Each of the upper and lower reinforcing rings has an inner surface, an outer surface, is formed of high-strength material and is sized and shaped to fit tightly about the outer perimeter on either side of the protruding rim. The reinforcing rings have at least one rib located upon the inner surface thereof. The rib is sized, shaped and located to engage the groove. 
   (42) In another variant of the apparatus for fabricating an ovoid flexible pressure vessel, means are provided for fastening the upper reinforcing ring to the lower reinforcing ring. 
   (43) In yet a further variant of the apparatus for fabricating an ovoid flexible pressure vessel, first and second rolls of high-strength fiber impregnated blanket material are provided. Means are provided for attaching the first and second blankets over upper and lower surfaces of the hollow pressure cell. 
   (44) In still a further variant of the apparatus for fabricating an ovoid flexible pressure vessel, means are provided for overwrapping the hollow pressure cell and reinforcing ring with high-strength braiding material, thereby increasing the pressure handling capability of the hollow pressure cell. 
   (45) In yet a further variant of the apparatus for fabricating an ovoid flexible pressure vessel, means are provided for hoop winding the hollow pressure cell and reinforcing ring, thereby increasing the pressure handling capacity of the pressure cell. 
   (46) In another variant of the apparatus for fabricating an ovoid flexible pressure vessel, means are provided for applying a plastic overcoating. 
   (47) In still a further variant of the apparatus for fabricating an ovoid flexible pressure vessel, a series of cell-shaped sponges are provided. Means are provided for inserting the cell-shaped sponges between the upper and lower cell portions prior to joining the upper and lower cell portions. 
   (48) In yet a further variant of the apparatus for fabricating an ovoid flexible pressure vessel, first and second rolls of either heat-reflecting plastic film or metal foil are provided. Means are provided for attaching either heat-reflecting plastic film or metal foil to the outer surface of at least one of the upper cell portion and the lower cell portion. 
   (49) In still a further variant of the apparatus for fabricating an ovoid flexible pressure vessel, means are provided for moving blanketed cells to a high-pressure hoop and lock braiding machine. 
   (50) In yet a further variant of the apparatus for fabricating an ovoid flexible pressure vessel, a series of cell-shaped sponges are provided. A tube is provided. The tube is formed of flexible gas and liquid impervious material and is sized and shaped to surround the sponges. Means are provided for inserting the sponges in the tube at spaced intervals. Means are provided for inserting the encased sponges between the upper cell portions and the lower cell portions prior to joining the upper and lower cell portions. The tube extends through the passageway. 
   (51) In still a further variant of the apparatus for fabricating an ovoid flexible pressure vessel, means are provided for positioning an upper retaining plate to fit over the upper cell portion and surround its outer perimeter when the upper cell portion is covered by the first blanket. Means are provided for positioning a lower retaining plate to fit over the lower cell portion and surround its outer perimeter when the lower cell portion is covered by the second blanket. Means are provided for producing a series of holes. The holes penetrate the upper retaining plate between its outer circumference and the third inner circumference, the lower retaining plate between its outer circumference and the fourth inner circumference and the first blanket, a border of sheet material surrounding the outer perimeter of the upper cell portion, a border of sheet material surrounding the outer perimeter of the lower cell portion and the second blanket. The holes are outside of the outer circumference of the reinforcing ring. Means are provided for inserting and securing fastening means through the holes, thereby securing the upper and lower retaining plates to each other. 

   
     DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a plan view of a first embodiment of the ovoid flexible pressure vessel illustrating connecting passageways; 
       FIG. 2  is a cross-sectional view of the  FIG. 1  embodiment taken along the line  2 — 2 ; 
       FIG. 3  is a plan view of a series of pressure vessels connected to a manifold and a valve; 
       FIG. 4  is an end view and partial breakaway view of the partial cross-sectional view of the  FIG. 1  embodiment illustrating a first embodiment retaining ring and passageway; 
       FIG. 5  is a side view and partial breakaway view of the partial cross-sectional view of the  FIG. 1  embodiment illustrating the  FIG. 4  retaining ring and passageway; 
       FIG. 6  is a partial cross-sectional plan view of the  FIG. 9  embodiment illustrating the passageway portion of the upper dome-shaped cell portion and upper reinforcing ring; 
       FIG. 6A  is a cross-sectional view of the pressure vessel with second embodiment retaining rings; 
       FIG. 6B  is a cross-sectional view of the  FIG. 6A  pressure vessel with means for attaching the rings together; 
       FIG. 7A  is a cross-sectional view of the pressure vessel with third embodiment retaining rings; 
       FIG. 7B  is a cross-sectional view of the  FIG. 7A  pressure vessel with means for attaching the rings together; 
       FIG. 8  is a partial cross-sectional view of the pressure vessel illustrating a third embodiment of the retaining ring; 
       FIG. 9  is a partial cross-sectional view of the pressure vessel illustrating a fourth embodiment of the retaining rings; 
       FIG. 10  is a partial cross-sectional view of the pressure vessel illustrating a fifth embodiment of the retaining rings including means for fastening the rings together; 
       FIG. 11  is a plan view of a pressure vessel having removable passageways; 
       FIG. 12  is a plan view of the  FIG. 1  embodiment overwrapped with high strength braiding material; 
       FIG. 13  is a plan view of the  FIG. 1  embodiment including hoop winding overwrapping; 
       FIG. 14  is a partial cross-sectional view of the  FIG. 12  embodiment taken along the line  12 — 12 ; 
       FIG. 15  is a partial cross-sectional view of the  FIG. 13  embodiment illustrating a plastic coating; 
       FIG. 16  is a side elevational view with partial cutaway illustrating a flexible blanket disposed over the cells; 
       FIG. 17  is a plan view of the cells with flexible blanket illustrating heavy duty stitching for fastening the blankets over the cells; 
       FIG. 18  is a cross-sectional view of the  FIG. 1  embodiment including a cell-shaped sponge; 
       FIG. 19  is a cross-sectional view of the  FIG. 1  embodiment including a cell-shaped sponge and zeolite compound; 
       FIG. 20  is a partial cross-sectional view of the  FIG. 16  embodiment illustrating a heat reflecting film between the cell and the flexible blanket; 
       FIG. 21  is a plan view of the  FIG. 1  embodiment including retaining plates; 
       FIG. 22  is a plan view of the  FIG. 21  embodiment including nut and bolt fasteners; 
       FIG. 22A  is a cross-sectional side view of the  FIG. 22  embodiment; 
       FIG. 23  is a plan view of the  FIG. 21  embodiment including rivet fasteners; 
       FIG. 23A  is a cross-sectional side view of the  FIG. 23  embodiment; 
       FIG. 24  is a side cross-sectional view of  FIG. 18  embodiment including a flexible tube encasing the sponge; 
       FIG. 25  is a side cross-sectional view of  FIG. 24  embodiment including a zeolite compound impregnated in the sponge; 
       FIG. 26  is a plan view of a first embodiment of a reinforcing panel for the  FIG. 1  embodiment; 
       FIG. 27  illustrates upper and lower  FIG. 26  reinforcing panels attached to the  FIG. 1  embodiment; 
       FIG. 28  is a plan view of a second embodiment reinforcing panel; 
       FIG. 29  illustrates upper and lower  FIG. 28  reinforcing panels attached to the  FIG. 1  embodiment; 
       FIG. 30  is a partial cross-sectional view of the  FIG. 29  embodiment illustrating a plastic coating; 
       FIG. 31  is a cross-sectional view of an apparatus for forming a seamless pressure cells using a blow-molding technique and an internal core form; 
       FIG. 32  is a cross-sectional view of an apparatus for forming a seamless pressure cell using a blow-molding technique illustrating removal of the internal core form from the cells; 
       FIG. 33  is a cross-sectional view of the pressure cells after removal of the internal core form; 
       FIG. 34  is a cross-sectional view of an apparatus for forming a seamless pressure cell illustrating the introduction of pressure into the cells; 
       FIG. 35  is a cross-sectional view of an apparatus for forming a pressure cell using a vacuum forming technique; 
       FIG. 36  is a cross-sectional view of an apparatus for forming a pressure cell using an extruded plastic tube inflated inside of a two-part mold; 
       FIG. 37  is a cross-sectional view of an apparatus for forming a pressure cell using an extruded plastic tube inflated inside of a two-part mold illustrating the cells after inflation of the tube; 
       FIG. 38  is a side elevational view of an apparatus for forming a flexible pressure vessel cell by thermal die stamping illustrating attachment of reinforcing rings; 
       FIG. 39  is a side elevational view of an apparatus for attaching high-strength fiber impregnated blankets over the pressure cells; 
       FIG. 40  is a plan view of an apparatus for overwrapping the hollow pressure cell and reinforcing ring with high-strength braiding material; 
       FIG. 40A  is a side elevational view of an apparatus for hoop winding the pressure vessel; 
       FIG. 41  is a side elevational view of an apparatus for forming a flexible pressure vessel cell by thermal die stamping; 
       FIG. 42  is a perspective view of an apparatus for stitching the flexible blankets together over the pressure cells; 
       FIG. 43  is a side elevational view of an apparatus for forming a protruding rim and receiving notches on the pressure cell; 
       FIG. 44  is a side elevational view of an apparatus for applying plastic coating the pressure vessels; 
       FIG. 45  is a cross-sectional view of an apparatus for inserting cell-shaped sponges into the pressure cells; 
       FIG. 46  is a cross-sectional view of an apparatus for inserting cell-shaped sponges into the pressure cells inside of a flexible tube; and 
       FIG. 47  is a side elevational view of an apparatus for attaching upper and lower retaining plates to the pressure cells. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
   (1) An ovoid flexible pressure vessel  10 , as shown in  FIGS. 1–4 , providing the desired features may be constructed from the following components. At least one hollow pressure cell  15  is provided. The pressure cell  15  has symmetrical upper  20  and lower cell  25  portions. The pressure cell  15  is formed of resilient material  26  and has an outer surface  27 , an outer perimeter  30  and at least one opening  35  located at the outer perimeter  30 . A passageway  36  is provided. The passageway  36  has a first end  40  and a second end  45  and is attached to the at least one opening  35  at the first end  40  and extends outwardly for connection to either a passageway  36  of another cell  15  or a valve  50 . At least one reinforcing ring  55  is provided. The reinforcing ring  55  has an inner surface  60 , an outer surface  65 , an outer circumference  76 , is formed of high-strength material  70  and is sized and shaped to fit tightly about the outer perimeter  30  of the pressure cell  15 . The reinforcing ring  55  has an aperture  75 . The aperture  75  extends from the inner surface  60  to the outer surface  65  and is sized, shaped and located to accommodate connection of the passageway  36  to the pressure cell  15 . A valving means  80  is provided. The valving means  80  is capable of controlling a flow of either a liquid or a gas through the passageway  36  and is attached to the second end  45  of the passageway  36 . When the reinforcing ring  55  is located about the outer perimeter  30  of the pressure cell  15 , the pressure handling capacity of the cell  15  is increased. 
   (2) In a variant of the invention, as shown in  FIGS. 4 and 5 , at least one upper dome-shaped cell portion  95  is provided. The upper cell portion  95  is formed from resilient material  26  and has an outer surface  100 , an inner surface  116 , an inner perimeter  105 , an outer perimeter  110  and at least one upper opening portion  115 . The upper opening portion  115  extends outwardly from the inner perimeter  105 . At least one mating lower dome-shaped cell portion  120  is provided. The lower cell portion  120  is formed from resilient material  26  and has an outer surface  125 , an inner surface  141 , an inner perimeter  130 , an outer perimeter  135  and at least one lower opening portion  140 . The lower opening portion  140  extends outwardly from the inner perimeter  130 . The upper cell portion  95  is joined to the mating lower cell portion  120  such that a hollow pressure cell  15  is formed. The cell  15  has at least one opening  35 . A passageway  36  is provided. The passageway  36  has a first end  40  and a second end  45  and is attached to the at least one opening  35  at the first end  40  and extends outwardly for connection to either a passageway  36  of another cell  15  or a valve  50 . 
   At least one reinforcing ring  55  is provided. The reinforcing ring  55  has an inner surface  60 , an outer surface  65 , an outer circumference  76 , is formed of high-strength material  70  and is sized and shaped to fit tightly about the outer perimeter  110  of the pressure cell  15 . The reinforcing ring  55  has an aperture  75 . The aperture  75  extends from the inner surface  60  to the outer surface  65  and is sized, shaped and located to accommodate connection of the passageway  36  to the pressure cell  15 . A valving means  80  is provided. The valving means  80  is capable of controlling a flow of either a liquid or a gas through the passageway  36  and is attached to the second end  45  of the passageway  36 . 
   (3) In another variant of the invention, a shown in  FIG. 8 , a protruding rim  145  is provided. The protruding rim  145  is located at the outer perimeter  30  of the pressure cell  15 . Upper  150  and lower  155  receiving notches are provided. The upper  150  and lower  155  receiving notches are located above and below the protruding rim  145 . Upper  160  and lower  165  projecting ribs are provided. The upper  160  and lower  165  projecting ribs are located upon the inner surface  60  of the reinforcing ring  55 . A central receiving notch  170  is provided. The central receiving notch  170  is located between the upper  160  and lower  165  projecting ribs. The projecting ribs  160 ,  165  are sized, shaped and located to fit the upper  160  and lower  165  receiving notches of the pressure cell  15 . The central receiving notch  170  is sized, shaped and located to fit the protruding rim  145  of the pressure cell  15 . When the reinforcing ring  55  is located about the outer perimeter  30  of the pressure cell  15 , the pressure handling capacity of the cell  15  is increased. 
   (4) In another variant, as shown in  FIGS. 6 and 9 , at least one upper dome-shaped cell portion  95  is provided. The upper cell portion  95  is formed from resilient material  26  and has an outer surface  100 , an inner perimeter  105 , an outer perimeter  110  and at least one upper passageway portion  175 . The upper passageway portion  175  extends outwardly from the inner perimeter  105 . At least one mating lower dome-shaped cell portion  120  is provided. The lower cell portion  120  is formed from resilient material  26  and has an outer surface  125 , an inner perimeter  130 , an outer perimeter  135  and at least one lower passageway portion (not shown). The lower passageway portion extends outwardly from the inner perimeter  130 . The upper cell portion  95  is joined to the mating lower cell portion  120  such that a hollow pressure cell  15  is formed. The cell  15  has at least one passageway  36  extending outwardly from the cell  15  for connection to either a passageway  36  of another cell  15  or a valve  50 . 
   A protruding rim  145  is provided. The protruding rim  145  is located at the outer perimeter  110  of the pressure cell  15 . Upper  150  and lower  155  receiving notches are provided. The upper  150  and lower  155  receiving notches are located above and below the protruding rim  145 . Upper  181  and lower  185  reinforcing rings are provided. Each of the reinforcing rings  181 ,  185  has an inner surface  190 , an outer surface  195 , is formed of high-strength material  70  and is sized and shaped to fit tightly in either the upper  150  or lower  155  receiving notches. At least one of the reinforcing rings  181 ,  185  has an aperture (not shown). The aperture extends from the inner surface  190  to the outer surface  195  and is sized, shaped and located to accommodate connection of the passageway  36  to the pressure cell  15 . When the reinforcing rings  181 ,  185  are located about the outer perimeter  30  of the pressure cell  15 , the pressure handling capacity of the cell  15  is increased. 
   (5) In yet a further variant of the invention, as shown in  FIG. 10 , means  182  are provided for fastening the upper reinforcing ring  181  to the lower reinforcing ring  185 . 
   (6) In yet a further variant, as shown in  FIGS. 6 ,  6 A and  7 A, at least one upper dome-shaped cell portion  95  is provided. The upper cell portion  95  is formed from resilient material  26  and has an outer surface  100 , an inner perimeter  105 , an outer perimeter  110  and at least one upper passageway  175  portion. The upper passageway portion  175  extends outwardly from the inner perimeter  105 . At least one mating lower dome-shaped cell portion  120  is provided. The lower cell portion  120  is formed from resilient material  26  and has an outer surface  125 , an inner perimeter  130 , an outer perimeter  135  and at least one lower passageway portion  180 . The lower passageway portion  180  extends outwardly from the inner perimeter  130 . 
   The upper cell portion  95  is joined to the mating lower cell portion  120  such that a hollow pressure cell  15  is formed. The cell  15  has at least one passageway  36  extending outwardly from the cell  15  for connection to either a passageway  36  of another cell  15  or a valve  50 . A protruding rim  145  is provided. The protruding rim  145  is located at the outer perimeter  110  of the pressure cell  15 . At least one groove  205  located about the outer perimeter  110  above the protruding rim  145  is provided. Upper  181  and lower  185  reinforcing rings are provided. Each of the reinforcing rings  181 ,  185  has an inner surface  190 , an outer surface  195 , is formed of high-strength material  70  and is sized and shaped to fit tightly about the outer perimeter  110  on either side of the protruding rim  145 . 
   The reinforcing rings  181 ,  185  have at least one rib  210  located upon the inner surface  190  thereof. The rib  210  is sized, shaped and located to engage the groove  205 . When the reinforcing rings  181 ,  185  are located about the outer perimeter  110  of the pressure cell  15 , the pressure handling capacity of the cell  15  is increased. 
   (7) In still a further variant of the invention, as shown in  FIG. 6B  and  FIG. 7B , means  211  are provided for fastening the upper reinforcing ring  181  to the lower reinforcing ring  185 . 
   (8) In another variant of the invention, as shown in  FIG. 12  and  FIG. 14 , an overwrapping layer  215  is provided. The overwrapping layer  215  is formed of high-strength braiding material  220  wound around the hollow pressure cell  15 . When the hollow pressure cell  15  is overwrapped with high-strength braiding material  220 , the pressure handling capacity of the pressure cell  15  is increased. 
   (9) In yet a further variant of the invention, as shown in  FIG. 13 , hoop winding  225  is provided. The hoop winding  225  is around the hollow pressure cell  15  to increase the pressure handling capacity of the pressure cell  15 . 
   (10) In still a further variant, as shown in  FIG. 15 , a plastic overcoating  230  is provided. 
   (11) In yet a further variant, as shown in  FIG. 16 , a first flexible blanket  235  is provided. The first blanket  235  has an upper surface  240 , a lower surface  245  and is sized and shaped to cover the upper cell portion  95  and extends outwardly beyond the outer perimeter  110 . The first blanket  235  is fixedly attached at its lower surface  245  to the outer surface  100  of the upper cell portion  95 . A second flexible blanket  250  is provided. The second blanket  250  has an upper surface  255 , a lower surface  260  and is sized and shaped to cover the lower cell portion  120  and extends outwardly beyond the outer perimeter  135 . The second blanket  250  is fixedly attached at its upper surface  255  to the outer surface  125  of the lower cell portion  120 . 
   (12) In another variant, as shown in  FIG. 17 , heavy duty stitching  265  is used to attach the first blanket  235  to the second blanket  250 . The stitching  265  penetrates the first  235  and second  250  blankets between the cell portions  95 ,  120  and serves to further reinforce and increase the pressure-handling capabilities of the pressure cell  15 . 
   (13) In another variant, the heavy duty stitching  265  is high pressure hoop and lock braiding  270 . 
   (14) In still a further variant of the invention, as shown in  FIG. 18 , a cell-shaped sponge  275  is inserted between the upper cell portion  95  and the lower  120  cell portion prior to joining the upper  95  and lower cell  120  portions. The sponge  275  serves to prevent the cell  15  from collapsing after either gas or liquid is removed from the cell  15 . 
   (15) In another variant of the invention, as shown in  FIG. 19 , the sponge  275  is impregnated with a zeolite compound  280 , a gas or liquid absorbing compound  285  or a reactive fuel cell compound  300 . 
   (16) In still another further variant, as shown in  FIG. 20 , either a heat-reflecting plastic film  305  or a metal foil  310  is inserted between at least one of the first blanket  235  and the upper cell portion  95  or the second blanket  250  and the lower cell portion  120 . 
   (17) In yet a another variant of the invention, the upper cell portion  95  is joined to the lower cell portion  120  by either radio frequency welding or high strength adhesive. 
   (18) In still a further variant, as shown in  FIG. 16 , either the first  235  and second  250  blankets are formed of high-strength fiber impregnated material  315 . 
   (19) In still another variant of the invention, the passageway  36  has a cross-section of between 0.025 and 0.250 inches. 
   (20) In yet a further variant, as shown in  FIGS. 21 ,  22 A and  23 A an upper retaining plate  320  is provided. The upper retaining plate  320  has a third inner circumference  325 , an outer circumference  330  and a third pre-determined thickness  335 . The upper retaining plate  320  is sized and shaped to fit over the upper cell portion  95  and surround its outer perimeter  110  when the upper cell portion  95  is covered by the first blanket  235 . The third inner circumference  325  is larger than the outer circumference  76  of the reinforcing ring  55 . A lower retaining plate  336  is provided. The lower retaining plate  336  has a fourth inner circumference (not shown), an outer circumference (not shown) and a fourth pre-determined thickness  350 . The lower retaining plate  336  is sized and shaped to fit over the lower cell portion  120  and surround its outer perimeter  135  when the lower cell portion  120  is covered by the second blanket  250 . The fourth inner circumference is larger than the outer circumference  76  of the reinforcing ring  55 . Means  318  are provided for attaching the upper retaining plate  320  to the lower retaining plate  336 . When the upper retaining plate  320  is attached to the lower retaining plate  336 , surrounding the upper  95  and lower cell  120  portions and the first  235  and second  250  blankets covering the reinforcing ring, the pressure capacity of the cell  15  will be increased. 
   (21) In another variant, as shown in  FIG. 22 ,  FIG. 22A  and  FIG. 23 , means are provided for attaching the upper retaining plate  320  to the lower retaining plate  336 . A series of holes  360  are provided. The holes  360  penetrate the upper retaining plate  320  between its outer circumference  330  and the third inner circumference  325 . The holes  360  also penetrate the lower retaining plate  336  between its outer circumference and the fourth inner circumference, the first blanket  235 , a border of sheet material (not shown) surrounding the outer perimeter  110  of the upper cell portion  95 , a border of sheet material (not shown) surrounding the outer perimeter  135  of the lower cell portion  120  and the second blanket  250 . The holes  360  are outside of the outer circumference  76  of the reinforcing ring  55 . A series of fastening means  365  is provided. The fastening means  365  are sized and shaped to pass through the series of holes  360  and are capable of securing the upper retaining plate  320  to the lower retaining plate  336 . 
   (22) In yet a further variant of the invention, as shown in  FIG. 22  and  FIG. 22A , the fastening means  365  is a series of bolt and locking nuts  370 . 
   (23) In another variant of the invention, as shown in  FIG. 23 , the fastening means  365  is a series of rivets  375 . 
   (24) In still a further variant, as shown in  FIG. 23A , the means for attaching the upper retaining plate  320  to the lower retaining plate  336  further includes a series of holes  360 . The holes  360  penetrate the upper retaining plate  320  between its outer circumference  330  and the third inner circumference  325 , the first blanket  235 , a border of sheet material  236  surrounding the outer perimeter  110  of the upper cell portion  95 , a border of sheet material (not shown) surrounding the outer perimeter  135  of the lower cell portion  120  and the second blanket  250 . The holes  360  are outside of the outer circumference  76  of the reinforcing ring  55 . A series of pins  380  are provided. The pins  380  are affixed orthogonally along an upper surface  385  of the lower retaining plate  336  and are sized, shaped and located to fit slidably through the series of holes  360  and extends slightly above an upper surface  390  of the upper retaining plate  320 . A series of welds  395  are provided. The welds  395  fixedly attach the pins  380  to the upper retaining plate  320 , thereby securing the upper  320  and lower  335  retaining plates to each other. 
   (25) In yet a further variant of the invention, as shown in  FIG. 24 , a series of cell shaped sponges  275  are provided. A tube  400  is provided. The tube  400  is formed of flexible gas and liquid impervious material  405  and is sized and shaped to surround the sponges  275 . The sponges  275  are inserted in the tube  400  at spaced intervals (not shown). The encased sponges  275  are inserted between the upper cell portions  95  and the lower  120  cell portions prior to joining the upper  95  and lower  120  cell portions. The tube  400  extends through the passageways  36 . The sponges  275  serve to prevent the cells  15  from collapsing after either gas or liquid is removed from the cells  15 . The tube  400  serves to prevent contamination of either gas or liquid by the inner surfaces  116 ,  141  of the upper  95  and lower  120  cell portions. 
   (26) In another variant of the invention, as shown in  FIG. 25 , the sponges  275  are impregnated with a zeolite compound  280 , a gas or liquid absorbing compound  285  or a reactive fuel cell compound  300 . 
   (27) In another variant, the tube  400  is formed from material selected from the group comprising: thermoplastic polyurethane elastomer, polyurethane polyvinyl chloride, polyvinyl chloride, thermoplastic elastomer, Teflon® and polyethylene. 
   (28) In still a further variant of the invention, as shown in  FIGS. 26–30 , upper  411  and lower  415  reinforcing panels are provided. The reinforcing panels  411 ,  415  are formed of high-strength woven material  420  and are substantially ovoid  425  in shape with extensions  430  projecting from a perimeter  435  of the ovoid shape  425 . The reinforcing panels  411 ,  415  are adhered to the outer surfaces  100 ,  125  of the upper  95  and lower  120  cell portions of the hollow pressure cell  15 , thereby increasing the pressure handling capabilities of the pressure cell  15 . 
   (29) In another variant of the invention, the method of adhesion is selected from the group comprising: high-strength adhesive, sonic welding, and RF welding. 
   (30) In another variant, the woven material  420  is prepregnated with either adhesive or laminating material  422  and subjected to heat and pressure. 
   (31) In yet a further variant of the invention, the passageway  36  is removably attached to the hollow pressure cell  15 . 
   (32) In another variant of the invention, as shown in  FIG. 11 , the passageway  36  is removably attached to the hollow pressure cell  15  by a threaded fitting  440 . The threaded fitting  440  is sized and shaped to fit a threaded opening  445  at the outer perimeter  30  of the hollow pressure cell  15 . 
   (33) In still a further variant of the invention, as shown in  FIG. 11A , an orifice  450  is provided. The orifice  450  penetrates either the upper  95  or lower  120  cell portions. A removable plug  455  is provided. The removable plug  455  is sized and shaped to fit sealably into the orifice  450 , thereby permitting introduction of material  460  into the pressure cell  15 . 
   (34) An apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIGS. 31–34 , may be constructed from the following components. An internal core form  465  is provided. The internal core form  465  has the internal shape of a hollow pressure cell  15 , an internal passageway  470  and a plurality of outlet blow holes  475  connected to the passageway  470 . An open top vessel (not shown) is provided. The vessel contains a solution of liquid plastic (not shown). Means are provided for moving the internal core form  465  into and out of the solution. Means (not shown) are provided for pumping either pressurized gas or liquid into the passageway  470 , thereby causing the liquid plastic  485  to expand about the internal core form  465  to form a hollow pressure cell  15 . The pressure cell  15  has symmetrical upper  20  and lower  25  cell portions, is formed of resilient material  26  and has an outer surface  27 , an outer perimeter  30  and at least one opening  35  located at the outer perimeter  30 . Means  463  are provided for extracting the internal core form  465  from the hollow pressure cell  15 . Means (not shown) are provided for connecting a passageway  36  to the at least one opening  35  for connection to either a passageway  36  of another cell  15  or a valve  50 . Means (not shown) are provided for pressing a reinforcing ring  55  onto the outer perimeter  30 . The reinforcing ring  55  has an inner surface  60 , an outer surface  65 , is formed of high-strength material  70  and is sized and shaped to fit tightly about the outer perimeter  30  of the pressure cell  15 . The reinforcing ring  55  has an aperture  75 . The aperture  75  extends from the inner surface  60  to the outer surface  65  and is sized, shaped and located to accommodate connection of the passageway  36  to the pressure cell  15 . Means  471  are provided for attaching a valving means  80  to the passageway  36 . The valving means  80  is capable of controlling a flow of either a liquid or a gas through the passageway  36  and is attached to the second end  45  of the passageway  36 . When the reinforcing ring  55  is located about the outer perimeter  30  of the pressure cell  15 , the pressure handling capacity of the cell  15  is increased. 
   (35) In a variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIG. 43 , means  473  are provided for forming a protruding rim  145  at an outer perimeter  30  of the hollow pressure cell  15 . The protruding rim  145  has upper  150  and lower  155  receiving notches located above and below the protruding rim  145 . The reinforcing ring  55  has an outer surface  65 , an inner surface  60 , upper  160  and lower  165  projecting ribs and a central receiving notch  170  located between the upper  160  and lower  165  projecting ribs. The projecting ribs  160 ,  165  are sized, shape and located to fit the upper  150  and lower  155  receiving notches of the pressure cell  15 . The central receiving notch  170  is sized, shaped and located to fit the protruding rim  145  of the pressure cell  15 . 
   (36) In yet a further variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIG. 35  and  FIG. 38 , first  490  and second  495  symmetrical external mold portions are provided. Each of the mold portions  490 ,  495  has at least one cavity  500  reflecting the external shape of a hollow pressure cell  15  and a connecting internal passageway  36 . The cavity  500  has at least one vacuum passage  505  connecting to an external vacuum source  510 . First  515  and second  520  sheets of moldable thermoplastic material are provided. Means  512  are provided for inserting the sheets of thermoplastic material  515 ,  520  between the mold portions  490 ,  495 . Means  522  are provided for heating the mold portions  490 ,  495  and the sheets  515 ,  520 . Means  523  are provided for applying vacuum to the vacuum passages  505 , thereby forming a hollow pressure cell  15 . Means (not shown) are provided for removing the hollow pressure cell  15  from the mold portions  490 ,  495 . Means  501  are provided for pressing a reinforcing ring  55  onto the outer perimeter  30 . The reinforcing ring  55  has an inner surface  60 , an outer surface  65 , is formed of high-strength material  70  and is sized and shaped to fit tightly about the outer perimeter  30  of the pressure cell  15 . The reinforcing ring  55  has an aperture  75 . The aperture  75  extends from the inner surface  60  to the outer  65  surface and is sized, shaped and located to accommodate connection of the passageway  36  to the pressure cell  15 . Means (not shown) are provided for attaching a valving means  80  to the passageway  36 . The valving means  80  is capable of controlling a flow of either a liquid or a gas through the passageway  36  and is attached to the second end  45  of the passageway  36 . When the reinforcing ring  55  is located about the outer perimeter  30  of the pressure cell  15 , the pressure handling capacity of the cell  15  is increased. 
   (37) In another variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIG. 43 , means  473  are provided for forming a protruding rim  145  at an outer perimeter  30  of the hollow pressure cell  15 . The protruding rim  145  has upper  150  and lower  155  receiving notches located above and below the protruding rim  145 . The reinforcing ring  55  has an outer surface  65 , an inner surface  60 , upper  160  and lower  165  projecting ribs and a central receiving notch  170  located between the upper  160  and lower  165  projecting ribs. The projecting ribs  160 ,  165  are sized, shaped and located to fit the upper  150  and lower  155  receiving notches of the pressure cell  15 . The central receiving notch  170  is sized, shaped and located to fit the protruding rim  145  of the pressure cell  15 . 
   (38) In still a further variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIGS. 36–38 , first  490  and second  495  symmetrical external mold portions are provided. Each of the mold portions  490 ,  495  has at least one cavity  500  reflecting the external shape of a hollow pressure cell  15  and a connecting internal passageway  36 . Means  524  are provided for extruding a plastic tube  525  between the mold portions  490 ,  495  and pressurizing the plastic tube  525  to form the hollow pressure cell  15  with attached connecting internal passageway  36 . Means (not shown) are provided for removing the hollow pressure cell  15  with attached passageway  36  from the mold portions  490 ,  495 . Means (not shown) are provided for connecting a passageway  36  to the at least one opening  35  for connection to either a passageway  36  of another cell  15  or a valve  50 . Means  501  are provided for pressing a reinforcing ring  55  onto the outer perimeter  30 . The reinforcing ring  55  has an inner surface  60 , an outer surface  65 , is formed of high-strength material  70  and is sized and shaped to fit tightly about the outer perimeter  30  of the pressure cell  15 . The reinforcing ring  55  has an aperture  75 . The aperture  75  extends from the inner surface  60  to the outer surface  65  and is sized, shaped and located to accommodate connection of the passageway  36  to the pressure cell  15 . Means are provided for attaching a valving means  80  to the passageway  36 . The valving means  80  is capable of controlling a flow of either a liquid or a gas through the passageway  36  and is attached to the second end  45  of the passageway  36 . When the reinforcing ring  55  is located about the outer perimeter  30  of the pressure cell  15 , the pressure handling capacity of the cell  15  is increased. 
   (39) In yet a further variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIG. 43 , means  473  are provided for forming a protruding rim  145  at an outer perimeter  30  of the hollow pressure cell  15 . The protruding rim  145  has upper  150  and lower  155  receiving notches located above and below the protruding rim  145 . The reinforcing ring  55  has an outer surface  65 , an inner surface  60 , upper  160  and lower  165  projecting ribs and a central receiving notch  170  located between the upper  160  and lower  165  projecting ribs. The projecting ribs  160 ,  165  are sized, shaped and located to fit the upper  150  and lower  155  receiving notches of the pressure cell  15 . The central receiving notch  170  is sized, shaped and located to fit the protruding rim  145  of the pressure cell  15 . 
   (40) In still a further variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIGS. 38 and 41 , first  530  and second (not shown) rolls of planar resilient material are provided. First  540  and second (not shown) thermal die stamping stations are provided. The stamping stations  540  are capable of forming upper  95  and lower  120  cell portions of a hollow pressure cell  15  and a connecting internal passageway  36 . Means (not shown) are provided for moving resilient material  26  from the first  530  and second rolls of planar resilient material into the first  540  and second thermal die stamping stations. A radio frequency welder  550  is provided. The welder  550  is capable of joining the upper cell portion  95  to the lower cell portion  120 . Means  513  are provided for moving the upper  95  and lower  120  cell portions into the radio frequency welder, thereby joining the upper  95  and lower cell  120  portions and forming the internal connecting passageway  36 . Means  517  are provided for pressing upper  181  and lower  185  reinforcing rings onto the hollow pressure cell  15  adjacent the outer perimeter  30 . The reinforcing rings  181 ,  185  have an inner surface  190 , an outer surface  195 , are formed of high-strength material  70  and are sized and shaped to fit tightly about the outer perimeter  30  of the pressure cell  15 . At least one of the reinforcing rings  181 ,  185  has an aperture  200 . The aperture  200  extends from the inner surface  190  to the outer surface  195  and is sized, shaped and located to accommodate connection of the passageway  36  to the pressure cell  15 . Means are provided for attaching a valving means  80  to the passageway  36 . The valving means  80  is capable of controlling a flow of either a liquid or a gas through the passageway  36  and is attached to the second end  45  of the passageway  36 . When the reinforcing rings  181 ,  185  are located about the outer perimeter  30  of the pressure cell  15 , the pressure handling capacity of the cell  15  is increased. 
   (41) In yet a further variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIG. 43 , means are provided for forming a protruding rim  145  at an outer perimeter  30  of the hollow pressure cell  15 . Means  523  are provided for forming at least one groove  205  located about the outer perimeter  30  above the protruding rim  145 . Means are provided for forming at least one groove  205  located about the outer perimeter  30  below the protruding rim  145 . Each of the upper  181  and lower  185  reinforcing rings has an inner surface  190 , an outer surface  195 , is formed of high-strength material  70  and is sized and shaped to fit tightly about the outer perimeter  30  on either side of the protruding rim  145 . The reinforcing rings  181 ,  185  have at least one rib  210  located upon the inner surface  190  thereof. The rib  210  is sized, shaped and located to engage the groove  205 . 
   (42) In another variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIG. 10 , means  527  are provided for fastening the upper reinforcing ring  181  to the lower reinforcing ring  185 . 
   (43) In yet a further variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIG. 42 , first  555  and second  560  rolls of high-strength fiber impregnated blanket material are provided. Means  529  are provided for attaching the first  555  and second  560  blankets over upper  100  and lower  125  surfaces of the hollow pressure cell  15 . 
   (44) In still a further variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIG. 40 , means  531  are provided for overwrapping the hollow pressure cell  15  and reinforcing ring  55  with high-strength braiding material  220 , thereby increasing the pressure handling capability of the hollow pressure cell  55 . 
   (45) In yet a further variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIG. 40  A, means  533  are provided for hoop winding  225  the hollow pressure cell  15  and reinforcing ring  55 , thereby increasing the pressure handling capacity of the pressure cell  15 . 
   (46) In another variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIG. 44 , means  537  are provided for applying a plastic overcoating  230 . 
   (47) In still a further variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIG. 45 , a series of cell-shaped sponges  275  are provided. Means  539  are provided for inserting the cell-shaped sponges  275  between the upper  95  and lower  120  cell portions prior to joining the upper  95  and lower  120  cell portions. 
   (48) In yet a further variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIG. 39 , first  575  and second  580  rolls of either heat-reflecting plastic film  305  or metal foil  310  are provided. Means  541  are provided for attaching either heat-reflecting plastic film  305  or metal foil  310  to the outer surface  100 ,  125  of at least one of the upper cell portion  95  and the lower cell portion  120 . 
   (49) In still a further variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIG. 42 , means (not shown) are provided for moving blanketed cells  15  to a high-pressure hoop and lock braiding machine  590 . 
   (50) In yet a further variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIG. 46 , a series of cell-shaped sponges  275  are provided. A tube  400  is provided. The tube  400  is formed of flexible gas and liquid impervious material  405  and is sized and shaped to surround the sponges  275 . Means  549  are provided for inserting the sponges  275  in the tube  400  at spaced intervals  410 . Means  543  are provided for inserting the encased sponges  275  between the upper cell portions  95  and the lower cell portions  120  prior to joining the upper  95  and lower  120  cell portions. The tube  400  extends through the passageway  36 . 
   (51) In a final variant of the apparatus for fabricating an ovoid flexible pressure vessel  10 , as shown in  FIG. 47 , means are provided for positioning an upper retaining plate  320  to fit over the upper cell portion  95  and surround its outer perimeter  110  when the upper cell portion  95  is covered by the first blanket  235 . Means are provided for positioning a lower retaining plate  336  to fit over the lower cell portion  120  and surround its outer perimeter  135  when the lower cell portion  120  is covered by the second blanket  250 . Means are provided for producing a series of holes  360 . The holes  360  penetrate the upper retaining plate  320  between its outer circumference  330  and the third inner circumference  325 , the lower retaining plate  336  between its outer circumference and the fourth inner circumference and the first blanket  235 , a border of sheet material  236  surrounding the outer perimeter  110  of the upper cell portion  95 , a border of sheet material  237  surrounding the outer perimeter  135  of the lower cell portion  120  and the second blanket  250 . The holes  360  are outside of the outer circumference  76  of the reinforcing ring  55 . Means  597  are provided for inserting and securing fastening means  365  through the holes  360 , thereby securing the upper  320  and lower  336  retaining plates to each other.