HYDROSTATIC PRESSURE RETAINMENT SYSTEM

Abstract: A pressure vessel comprises a matrix structure extending in three dimensions. The matrix is in generally hydrostatic (triaxial, or three-dimensional) tension when carrying loading induced by pressure of the compressed fluid stored within a series of voids interlinked at their point of contact in the matrix. A fluid impermeable outer covering surrounds, and is contiguously supported by, the matrix. The pressure vessel can assume an irregular shape. Transfer means, including an artery system, is provided for admitting and discharging the fluid. A solid surface component, while in a liquid phase, can be mounted on the matrix and changed to a solid phase, anchoring the component to the matrix with an integral bond.

Description: HYDROSTATIC PRESSURE RETAINMENT SYSTEM CROSS REFERENCES TO RELATED APPLICATIONS This application is based upon a provisional application assigned serial number 60/095,509, filed in the United States Patent and Trademark Office on 08/06/98, by Robert J. Setlock, Jr., and titled "Hydrostatic Pressure Retainment System And High Strength Bonding Method." FIELD OF THE INVENTION This invention relates generally to the field of pressure vessels, and pertains more specifically, to an apparatus and method for retaining pressurized fluid within a three-dimensional structural matrix, and bonding a component to the matrix. BACKGROUND OF THE INVENTION The containment of gases under high pressure generally requires the use of hollow vessels having outer walls in the form of spheres, cylinders, ellipsoids, tori or composites of these shapes. These are the most efficient shapes to withstand the tensile stresses induced in the walls by internal pressure, but they are not the most efficient configurations possible. In addition, these conventional outer shell shapes seldom fit into the available space efficiently. There are many examples in the prior art where interior supports of various configurations have been introduced inside of pressure vessels to facilitate non-conventional shapes. However, all of the non-conventional pressure vessels in the prior art share the characteristic of excessive weight. They all weigh more than equivalent conventional pressure vessels due to inefficient use of the structural material. This invention offers the novel characteristic of weighing less than equivalent conventional pressure vessels fabricated of the same material. Another shortcoming of conventional vessels is that in the event of structural failure of the walls due to stresses induced by pressure, the vessel will fail catastrophically. The sudden release of compressed gas and wall fragments results in an explosion, with serious consequences to nearby personnel and equipment. In my prior Patent Specification No. WO97/27105, USSN 08592004, it describes the possibility of having a high pressure storage tank for gases, in particular having a reinforcement matrix disposed in the tank body and attached to the inner walls thereof, the matrix displacing no more than 50% of the interior volume of the tank. However, the high pressure storage tank suffers from the disadvantages that it is difficult and expensive to manufacture and is in general not of sufficient strength to withstand the high pressures commonly associated with such tanks. The previously disclosed, but unpatented work of ERG Aerospace which specified use of its DUOCEL open cell aluminum foam as an interior support within an irregularly shaped pressure vessel also suffers from the disadvantages that it is difficult and expensive to manufacture and is in general not of sufficient strength to withstand the high pressures commonly associated with such tanks. Patent Specification No. WO98/33004 in the name of Mannesmann AG, describes a container for the storage of compressed gases in which an outer metallic wall encloses a hollow chamber in which is disposed an open-cell metal foam materially connected to the outer wall. However, again, such reinforced containers will again not generally be capable of withstanding the pressures commonly associated with high pressure storage tanks. A homogeneous isotropic material such as steel has mechanical properties, including tensile strength, that are equal at all points (homogeneous) and in every direction (isotropic). Thus, steel can withstand tensile loads in all three Cartesian axes simultaneously. However, materials are seldom used in this manner. Usually, materials are loaded in one direction (axial loading) or in two directions (planar loading). Some portion of the material's capacity to support loading is left unused, thereby limiting structural efficiency. A filament or fiber in tension is under an axial load. The material's capacity to support loading in the remaining two directions is unused. A conventional shell type pressure vessel holding compressed gas is under a planar load. The material at any given point in the wall is stressed in two directions defined by a plane tangent to the outer surface at that point, as shown in FIGS. 1 and 3. The capacity of the material to support loading in the direction perpendicular to the given plane remains unused. Further, axial and planar loading will cause angular distortion in the material, which is a primary trigger of structural failure. It would be advantageous to load materials equally in all three directions (hydrostatic loading, triaxial loading , or three-dimensional loading). Materials under hydrostatic loading (or triaxial loading, or three dimensional loading) are fully utilized, and exhibit no unused capacity for further loading. This ideal condition also presents no angular distortion or deformation. The absence of angular distortion results in the additional benefit of greatly increased yield strength for materials in hydrostatic loading. Thus, less volume of material would be needed to fabricate the vessel, resulting in weight savings when compared to conventional outer shell pressure vessels. Pressure vessels are an ideal application for structural hydrostatic tensile loading, since the fluid (liquid and/or gas) pressure to be counteracted is by definition hydrostatic. Such a structure will take the form of an internal matrix having cavities or interstices for containing the pressurized fluid. The matrix carries most of the pressure induced loading. A lightly stressed thin solid outer covering is attached to the matrix to retain the fluid. The ability of each portion of the matrix material to carry loads in one axis (the worst case), or in all three axes (the best case), depends upon the three-dimensional details (or morphology) of the matrix. An example of a matrix structure which embodies the characteristics required to be a best case matrix is a body of material with a series of substantially spherical voids which are interconnected at their point of contact. These points of contact shall form apertures, wherein the size of the aperture between adjacent voids will generally not exceed more than 10%, preferably 5%, more preferably 2% and advantageously no more than 1%, of the surface area of the void. Such a matrix structure results in a substantial amount of the material being in hydrostatic (triaxial, or three- dimensional) tension. The voids are substantially spherical in shape and preferably of similar size. The voids are substantially uniform in distribution throughout the matrix, and preferably in a face centered cubic orientation. FIG. 6 is a graphic representation showing the desired interior morphology, with homogeneously distributed spherical voids with very small passages 18, connecting each void to the adjacent void at each point of contact. FIG. 7 shows the more preferred face centered cubic orientation. Continuity is maintained in all three dimensions. The structure of this hydrostatically optimized morphology demonstrates substantially ideal structural efficiency, because it places a high proportion of the matrix material under hydrostatic tensile loading when used as an inner matrix in a pressure vessel. FIG. 8 is a photograph of a conventional foam. The support is almost entirely simple axial members because of the irregular structure and absence of cell walls. The morphology of such a structure will not efficiently support hydrostatic tensile loading of the matrix material when used as an inner matrix in a pressure vessel. Relative density is the volume percentage of parent material in the total volume of the matrix. In the situation of a best case matrix morphology, the strength of the matrix will vary linearly with the relative density. The density required is thus the ratio of the required hydrostatic tensile strength (maximum pressure to be stored) to the hydrostatic tensile strength of the parent material (including the design factor). A face centered cubic orientation provides the greatest gas capacity obtainable for a uniform spherical void morphology, about 67%. This equates to a relative density of about 33%. Therefore, the matrix will have a relative density preferably from about 30% to about 35%, or from about 2% to about 30%, or about 35% to about 50%, depending upon the parent material and packing method. Turning now to FIGS. 1 and 2, the volume of parent material required to fabricate a conventional shell type spherical pressure vessel 10 is compared to the volume required to fabricate a matrix type spherical pressure vessel 12. These are approximations for thin walled spheres. pr pr maximum stress: , = σ-, - — shell thickness: t = — — ' 2 It 2σ ■ > pr surface area: S = πr ~ material volume: smll = St = 4π r~ — πpX »» « = 2 (eq, 60) Where: σ= maximum stress, parent material p = maximum pressure stored r = pressure vessel radius t = shell thickness S = surface area mt i = volume of shell material For the matrix type spherical pressure vessel 12, the outer covering is not a critical load bearing structure, and thus will not be considered. The volume of material required to form the matrix is the product of sphere volume and matrix density. 4 Volume of sphere: V h = —π r r 3 Therefore: V mmιi= π r3 x = 1 -33 (eq. 62) Where: V h = volume of sphere V mmύ = volume of matrix material Comparing equations 60 and 62 reveals the material efficiency advantage. An optimum matrix structure can theoretically yield a 33% improvement over a spherical shell. Actual practice indicates an improvement of over 20% is achievable. Turning now to FIGS. 3 and 4, the volume of parent material required to fabricate a conventional shell type cylindrical pressure vessel 14 is compared to the volume required to fabricate a matrix type cylindrical pressure vessel 16. These are approximations for thin walled cylinders, ignoring the end closures. Hoop stress , is twice the longitudinal stress 2 in all outer shell cylinders. pr pr maximum stress: „ m„ax = σ, 1 = — t shell thickness: t = — σ pr surface area: S - 2π rl material volume: ,„,, = St = 2π rl — σ π pr 2 l ™ < = 2 ~ ^ ~ (eq. 66) Where: / = length of cylinder For the matrix type cylindrical pressure vessel 16, the outer covering is not a critical load bearing structure, and thus will not be considered. The volume of material required to form the matrix is the product of cylinder volume and matrix density. Volume of cylinder: n; = π r 2 l v P π p r 2 I Therefore: ' """" = π ' x = (eq. 68) σ σ Where: V nl = volume of cylinder Comparing equations 66 and 68 reveals the material efficiency advantage. An optimum matrix structure can theoretically yield a 50% improvement over a cylindrical shell. Actual practice indicates an improvement of over 40% is achievable. A relatively thin, light outer covering can either be attached to the matrix, or formed monolithically with the matrix as one piece. For purposes of analysis, the thin outer covering can be modeled as many small, interconnected, substantially circular shaped plates. Circles of widely varying radii will be present. The maximum radial size of these circles will be determined by the size of the matrix interstices. FIG. 5 shows a polygon having an inscribed circle of radius = a, and number of sides = n. The required outer covering thickness is a function of the fluid pressure, the allowable material stress, and the polygon radial size. The maximum stress in polygon shaped plates is on the outside edge of each plate, according to Roark's Formulas for Stress and Strain. The following data is from case number 20 of table 26 in Roark's. maximum stress: Where: σ max = maximum allowable stress β 2 = factor from table t = (eq. 72) a = radius of polygon q = fluid pressure t = membrane thickness An example will illustrate the efficiency of a matrix type pressure vessel. The circular polygon, with number of sides = ∞, and radius = matrix void radius, has a β 2 value = 0.75, and will be used as the worst case condition. Assuming a hydrostatically optimized matrix with a void size of 0.0625 inch radius, and made of 6061 T6 aluminum having a yield strength of 40k psi.; thickness from equation 72 is tabulated below for q = 450 psi, 6k psi. and 15k psi. Solid surface components such as the outer covering, fill nozzle, etc., may be formed monolithically with the matrix, or may be attached later. SUMMARY OF THE INVENTION In accordance with the invention there is provided a hydrostatic pressure retainment apparatus for compressed fluid which is capable of withstanding high internal pressure. The pressure retainment apparatus comprises a matrix for carrying loading induced by pressure of the compressed fluid. The matrix structure comprises a body of material with a series of substantially spherical voids which are interconnected at their point of contact. These points of contact shall form apertures, wherein the size of the aperture between adjacent voids will generally not exceed more than 10%, preferably 5%, more preferably 2% and advantageously no more than 1%, of the surface area of the void. Such a matrix structure can be described as one with nearly closed open void morphology resulting in a substantial amount of the material generally in hydrostatic (triaxial, or three- dimensional) tension. The voids are substantially spherical in shape and preferably of similar size. The voids are substantially uniform in distribution throughout the matrix, and preferably in a face centered cubic orientation. Preferably the matrix is a metal, for example aluminum, steel, stainless steel and the like. An outer covering surrounds the matrix, for retaining the compressed fluid within the matrix. The outer covering has an inner surface attached to the matrix outer boundary surface or region. The outer covering is impermeable to the retained fluid, and is substantially contiguously supported over the matrix outer boundary surface. Transfer means is provided for admitting the fluid into the matrix, and for discharging the fluid from the matrix. A hydrostatic pressure retainment apparatus with a nearly closed void structure is not generally attainable by standard metal (or other) foam manufacturing techniques. Apparatus of this type can be constructed by using an investment casting technique using small uniform spherical balls. For example, a gas containing structure can be made by preparing a shaped outer skin of a metal similar to or compatible with the to be formed internal matrix, generating the internal matrix by coating beads of a volatile substance such as carbamide with powdered metal and then adding these beads to the container, finishing with a layer of powdered metal and also making sure that there is a manifold or tube access to the system. The unit is then heated at about 200°C which enables the metal slurry to stick together whilst the carbamide beads are volatilised and escape through the manifold. This 'green' container can then be subsequently sintered in a higher temperature furnace to provide the finished structure. Internally, because of the method of construction, the cells will all be spherical and inter-connections will be small and at the point of contact with adjacent cells, hence this will produce a porous morphology with only tiny inter-connections between each cell, thereby maximizing the strength of the overall matrix. Addition of the organic spheres to the canister is best achieved by a "snow-storm" packing method to minimize irregularity and structure, however, a simple single sized cellular structure will only leave empty 67% of the volume as free space. This volume fraction can be increased by using spheres of smaller size which will effectively fit in the spaces between the other spheres. Experimental work has demonstrated that this is optimized when the ratio of diameters is between 7:1 and 10: 1 and the proportion of small spheres is 18-20%. Again by using the "snow-storm" packing technique the structure can be made very homogeneous by using the required size range and proportion of spheres. A further embodiment would be to use a powdered metal skin which would avoid any shrinkage problems. The space between the spherical voids orientated in a face centered cubic morphology can also accommodate smaller voids where the radius ratio is d small = d hτse (j2 ~ -1) wherein d small is the diameter of the smaller void and d, arge is diameter of the larger void. This type of procedure could be repeated with ever smaller spherical voids resulting in lower density structures. Alternative manufacturing techniques include, but are not limited to, metal foaming methods as described in U.S. Patent No. 5,151,246 in the name of Fraunhofer-Gesellschaft, the contents of which are incorporated herein by reference. Such methods can be tailored to achieve the necessary structure of the invention, rapid prototype technology and the like. BRIEF DESCRIPTION OF THE DRAWING The invention will be more fully understood, while still further features and advantages will become apparent, in the following detailed description of preferred embodiments thereof illustrated in the accompanying drawing, in which: FIG. 1 is an elevational view of a spherical shell type pressure vessel showing the planar stresses imposed upon the shell; FIG. 2 is an elevational view of a matrix type spherical pressure vessel showing the matrix without the outer covering; FIG. 3 is an elevational view of a cylindrical shell type pressure vessel without the end closures, showing the planar stresses imposed upon the shell; FIG. 4 is an elevational view of a matrix type cylindrical pressure vessel showing the matrix without the outer covering; FIG. 5 is a polygon having an inscribed circle of radius = a, and number of sides = n; FIG. 6 is a graphic representation of a hydrostatically optimized morphology, showing homogeneously distributed spherical voids with very small passages connecting each void to the adjacent void at each point of contact; FIG. 7 is a graphic representation of a hydrostatically optimized morphology, showing the preferred face centered cubic orientation of the spherical voids; FIG. 8 is a photograph of a conventional foam; FIG. 9 is a partial sectional, isometric view of a hydrostatic pressure retainment apparatus constructed in accordance with the invention; FIG. 10 is an enlarged view of detail 12 of FIG. 10, showing an artery in section; and FIG. 11 is a cross-sectional view through a matrix and a solid surface component showing the component material penetration into the matrix. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. 6, 7, 9, and 10, a hydrostatic pressure retainment apparatus for storing a compressed fluid is shown at 20. The apparatus, which weighs less than an equivalent conventional pressure vessel fabricated of the same material, comprises a three dimensional matrix 22, for carrying loads induced by pressure of the compressed fluid (not shown). The matrix can be fabricated in a variety of materials and structural configurations. Polymers, metals and composites can be utilized to form a hydrostatically optimized morphology matrix. FIG. 7 is a graphic representation of a hydrostatically optimized morphology with face centered cubic orientation of the spherical voids, which is the preferred structure to embody the invention. 1 he individual cells are substantially spherical in shape and distributed in a substantially homogeneous fashion throughout the matrix structure. (This shows a nearly closed cell structure) Each cell 26 has a continuous wall 28 almost fully enclosing a space or interstice 30 for containing the compressed fluid. The interstices 30 communicate with one another through relatively small openings or pores 32 in the cell wall 28. The pores 32 ensure generally homogeneous distribution of the fluid throughout the matrix 22. The external dimensional limits of the matrix 22 define an outer boundary surface 34. Substantially all portions of the matrix 22 are in substantially hydrostatic tension when carrying the pressure induced loads, by virtue of the three dimensional nature of the hydrostatically optimized morphology 24. The matrix 22 has a relative density preferably from about 30% to about 35%, or from about 2% to about 30%, or about 35% to about 50%, depending upon the parent material and packing method. However, the novel characteristic of weighing less than conventional pressure vessels is independent of the relative density. The characteristic of lower weight depends entirely upon the structural efficiency of the matrix moφhology. An outer covering 36 surrounds the matrix 22, for retaining the compressed fluid within the matrix 22, and is impermeable to the fluid. The outer covering 36 has an outer surface 38 and an opposite inner surface 40. The outer covering inner surface 40 is attached to the matrix outer boundary surface 34. The outer covering 36 is substantially contiguously supported over the matrix outer boundary surface 34. The outer boundary surface 34, and therefore the outer covering 36, can assume any imaginable shape. This is because most of the stress is carried by the matrix and very little by the outer covering 36, so that hoop stress is no longer a limiting factor. Thus, the outer boundary surface 34 configuration can be symmetrical, or can be of reduced symmetry (irregular shape). The matrix 22 and the outer covering 36 of the hydrostatic pressure retainment apparatus 20 have a total structural mass significantly less than the total structural mass of an equivalent conventional shell type pressure vessel of identical total volume measured over the outer surface 38 of the outer covering 36, made of identical parent material, and designed to withstand identical fluid pressure with an identical design factor. Transfer means is provided for admitting the fluid into the matrix 22, and for discharging the fluid from the matrix 22. Specifically, the transfer means comprises at least one nozzle 42 attached to the outer covering 36. The nozzle 42 has an inner surface 44, and an orifice 46 therethrough communicating with the matrix interstices 30. An optional network of arteries 48 can be provided, communicating with the nozzle orifice 46 and with the matrix interstices 30. FIG. 9 illustrates the artery system 48 in section. The arteries 48 comprise tubes 50 that become ever smaller and more numerous while progressing from the nozzle orifice 46 toward the matrix interstices 30. The tubes 50 include a multiplicity of holes 52 to convey the fluid, as depicted in FIG. 10. The arteries 48 enhance the fluid flow rate throughout the system for more rapidly distributing the fluid to the matrix 22 during admitting, and more rapidly collecting the fluid from the matrix 22 during discharging. The arteries 48 and matrix 22 may be fabricated as one monolithic structure, or they may be fabricated separately. The arteries 48 may be fabricated of the same material as the matrix 22 or of a different material which is compatible with and attachable to the matrix 22 structure. When a solid outer covering 36 is not present as a monolithically formed portion of the matrix, a novel attachment system, shown in FIG. 11, is employed to integrally mount a solid outer covering 36, or a solid surface component 54 to the outer boundary surface 34 of the matrix 22. The outer covering 36 or component 54 is fabricated onto the solid phase matrix 22 while the component inner surface, or the entire component 54, is in a liquid phase. The component inner surface is allowed to penetrate or extend a predetermined distance 56 into the matrix 22. The component then solidifies so as to anchor the component to the matrix 22. A strong integral bond structure results. This inexpensive attachment is compatible with irregular outer boundary configurations. Application methods include, but are not limited to, potting, dipping, spraying, brushing, vacuum dipping and the like. The outer covering can also be thick enough to provide mechanical protection from impacts, piercing and the like. Further, labels can be introduced providing information on identity, safety instructions and the like. The covering may also have cosmetic properties and in some systems biocompatable material can be employed. A hydrostatic pressure retainment method is disclosed for storing a compressed fluid. The method comprises the steps of: extending a matrix structure 22 in three dimensions to an outer boundary surface 34; surrounding the matrix 22 with an outer covering 36 impermeable to the fluid; attaching an inner surface 40 of the outer covering 36 to the outer boundary surface 34 of the matrix 22; supporting the outer covering 36 substantially contiguously over the matrix outer boundary surface 34; admitting the fluid under pressure into the matrix 22; retaining the compressed fluid in interstices 30 within the matrix 22; retaining the compressed fluid within the matrix 22 with the outer covering 36; inducing substantially hydrostatic loading in the matrix 22 material by the pressure of the compressed fluid; carrying the loading in substantially hydrostatic tension in substantially all portions of the matrix 22 material; and discharging the fluid from the matrix 22. Further steps include: attaching a nozzle 42 to the outer covering 36; and communicating an orifice 46 through the nozzle 42 with the matrix interstices 30. Still further steps include: communicating a network of arteries 48 with the nozzle orifice 46 and with the matrix interstices 30; distributing the fluid through the arteries 48 to the matrix 22 during admitting; and collecting the fluid from the matrix 22 through the arteries 48 during discharging. Additional steps include: juxtaposing an inner surface of a component with the outer boundary surface 34 of the matrix 22 while inner surface material is in a liquid phase; impregnating the matrix interstices 30 to a predetermined depth with the inner surface material; and changing the inner surface material to a solid phase, thereby anchoring the component to the matrix 22. Another step comprises forming the outer boundary surface in an irregular configuration. Yet further steps include forming the matrix 22; and forming the matrix by using an investment casting process. Yet further steps include forming the matrix 22; and forming the matrix from a Fraunhofer type metal foam which has been modified to open small apertures between adjacent voids. Yet further steps include forming the matrix 22; and forming the matrix by using a rapid prototyping process. As seen from the foregoing description, the present invention satisfies the need to provide a system for retaining pressurized fluid that does not induce planar loading in a relatively thick wall, but that utilizes more efficient hydrostatic loading with less material to significantly reduce weight; that is not limited to the form of spheres, cylinders, ellipsoids, or tori, but could assume a reduced symmetry configuration to fit within any given envelope; that will not explode in the event of structural failure of the walls; and that includes a method for attaching solid surface components securely to a matrix of any surface configuration. Although the invention has been described and illustrated in the preferred embodiments, those skilled in the art will make changes that will be seen to be functional equivalents to the present invention. For example, the hydrostatic pressure retainment apparatus described above and depicted in FIG. 9 is a rectangular parallelepiped. It will be appreciated that any shape or configuration, symmetric or unsymmetric can be utilized. It is therefore to be understood that the above detailed description of embodiments of the invention is provided by way of example only. Various details of design and construction may be modified without departing from the true spirit and scope of the invention as set forth in the appended claims.

Claims: CLAIMS The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 1. A pressure retainment apparatus comprising a matrix for carrying loading induced by pressure of the compressed fluid, the matrix structure comprising a body of material with a series of substantially spherical voids which are interlinked at the point of contact wherein these points of contacts form small apertures and wherein the size of the apertures between adjacent voids does not exceed more than about 10% of the internal surface area of the void. 2. The apparatus of claim 1, wherein the matrix structure comprises voids that are substantially spherical in shape and are substantially uniform in distribution throughout the matrix. 3. The apparatus of claim 1 , wherein the matrix structure comprises the voids are a similar size. 4. The apparatus of claim 1, wherein the matrix structure comprises voids that are in a face centered cubic orientation. 5. The apparatus of claim 1 , wherein a substantial amount of the material in the matrix is in tension selected from the group consisting of hydrostatic, triaxial, three-dimensional or combinations thereof. 6. The apparatus of claim 1, wherein the size of the apertures between the adjacent voids does not exceed more than about 5% of the internal surface area of the void. 7. The apparatus of claim 1, wherein the size of the apertures between the adjacent voids does not exceed more than about 2% of the internal surface area of the void. 8. The apparatus of claim 1, wherein the size of the apertures between the adjacent void does not exceed more than about 1% of the internal surface area of the void. 9. The apparatus of claim 1, wherein there is an outer covering surrounding the matrix, for retaining the compressed fluid within the matrix, the outer covering having an inner surface attached to the matrix outer boundary surface, the other covering being impermeable to the fluid, the outer covering being substantially contiguously supported over the matrix outer boundary surface. 10. The apparatus of claim 1, wherein there is a transfer means for admitting the fluid into the matrix and for discharging the fluid from the matrix. 11. The apparatus of claim 1, for storing compressed fluid. 12. The pressure retainment apparatus of claim 1 , wherein the transfer means further comprises at least one nozzle attached to the outer covering, the nozzle having an inner surface, the nozzle having an orifice therethrough communicating with the matrix interstices. 13. The pressure retainment apparatus of claim 2, wherein the transfer means further comprises a network of arteries communicating with the nozzle orifice and with the matrix interstices, for distributing the fluid to the matrix during admitting, and collecting the fluid from the matrix during discharging. 14. The pressure retainment apparatus of claim 1, wherein the inner surface extends a predetermined distance into the matrix so as to anchor the inner surface to the matrix. 15. The pressure retainment apparatus of claim 1, wherein the outer boundary surface configuration is irregular. 16. The pressure retainment apparatus of claim 1, wherein the matrix includes a structural foam. 17. The pressure retainment apparatus of claim 6, wherein the matrix is a Fraunhofer type metal foam. 18. A hydrostatic pressure retainment apparatus for storing a compressed fluid, the pressure retainment apparatus comprising: (a) a matrix for carrying loading induced by pressure of the compressed fluid, the matrix extending in three dimensions to an outer boundary surface, the matrix having a series of voids throughout interlinked at their point of contact for containing the compressed fluid, the voids communicating for substantially homogeneous distribution of the fluid, substantially all portions of the matrix being in substantially hydrostatic tension when carrying the pressure induced loading; (b) an outer covering surrounding the matrix, for retaining the compressed fluid within the matrix, the outer covering having an outer surface and an opposite inner surface, the outer covering inner surface being attached to the matrix outer boundary surface, the outer covering being impermeable to the fluid, the outer covering being substantially contiguously supported over the matrix outer boundary surface; and (c) transfer means for admitting the fluid into the matrix, and for discharging the fluid from the matrix; wherein (d) the matrix and the outer covering of the hydrostatic pressure retainment apparatus have a total structural mass less than a total structural mass of an equivalent conventional shell type pressure vessel of identical total volume measured over the outer covering outer surface, made of identical parent material, and designed to withstand identical fluid pressure with an identical design factor. 19. The pressure retainment apparatus of claim 18, wherein the transfer means further comprises at least one nozzle attached to the outer covering, the nozzle having an inner surface, the nozzle having an orifice therethrough communicating with the matrix interstices. 20. The pressure retainment apparatus of claim 19, further comprising a network of arteries communicating with the nozzle orifice and with the matrix interstices, for distributing the fluid to the matrix during admitting, and collecting the fluid from the matrix during discharging. 21. The pressure retainment apparatus of claim 18, wherein the inner surface extends a predetermined distance into the matrix so as to anchor the inner surface to the matrix. 22. The pressure retainment apparatus of claim 18, wherein the outer boundary surface configuration is irregular. 23. The pressure retainment apparatus of claim 18, wherein the matrix is a structural foam. 24. The pressure retainment apparatus of claim 23, wherein the matrix is a Fraunhofer type metal foam. 25. A hydrostatic pressure retainment method for storing a compressed fluid, the method comprising the steps of: (a) extending a matrix structure in three dimensions to an outer boundary surface; (b) surrounding the matrix with an outer covering impermeable to the fluid; (c) attaching an inner surface of the outer covering to the outer boundary surface of the matrix; (d) supporting the outer covering substantially contiguously over the matrix outer boundary surface; (e) admitting the fluid under pressure into the matrix; (f) containing the compressed fluid in a series of voids interlinked at their point of contact within the matrix; (g) retaining the compressed fluid within the matrix with the outer covering; (h) inducing loading in the matrix by the pressure of the compressed fluid; (i) carrying the loading in substantially hydrostatic tension in substantially all portions of the matrix; and (j) discharging the fluid from the matrix. 26. The pressure retainment method of claim 24, further comprising the steps of: (a) attaching a nozzle to the outer covering; and (b) communicating an orifice through the nozzle with the matrix interstices. 27. The pressure retainment method of claim 26, further comprising the steps of: (a) communicating a network of arteries with the nozzle orifice and with the matrix interstices; (b) distributing the fluid through the arteries to the matrix during admitting; and (c) collecting the fluid from the matrix through the arteries during discharging. 28. The pressure retainment method of claim 25, further comprising the steps of: (a) juxtaposing an inner surface of a component with the outer boundary surface of the matrix while inner surface material is in a liquid phase; (b) impregnating the matrix interstices to a predetermined depth with the inner surface material; and (c) changing the inner surface material to a solid phase, thereby anchoring the component to the matrix. 29. The pressure retainment method of claim 25, further comprising the step of forming the outer boundary surface in an irregular configuration. 30. The pressure retainment method of claim 25, further comprising the step of forming the matrix from a structural foam. 31. The pressure retainment method of claim 30, further comprising the step of forming the matrix from a Fraunhofer type metal foam. 32. A hydrostatic pressure retainment apparatus for storing a compressed fluid, the pressure retainment apparatus comprising: (a) a matrix for carrying loading induced by pressure of the compressed fluid, the matrix extending in three dimensions to an outer boundary surface, the matrix having interstices for containing the compressed fluid, substantially all portions of the matrix being in substantially hydrostatic tension when carrying the pressure induced loading; (b) an outer covering surrounding the matrix, for retaining the compressed fluid within the matrix, the outer covering having an inner surface attached to the matrix outer boundary surface, the outer covering being impermeable to the fluid, the outer covering being substantially contiguously supported over the matrix outer boundary surface; and (c) transfer means for admitting the fluid into the matrix, and for discharging the fluid from the matrix. 33. A method of filling a pressure vessel which incoφorates a hydrostatic pressure retainment apparatus with a fluid under pressure, said method comprising: (a) obtaining a pressure vessel which incoφorates a hydrostatic pressure retainment apparatus comprising: (i) a pressure vessel having a fill opening and a tank body having at least two opposing inner walls defining an interior volume; and (ii) a reinforcement matrix disposed in said tank body and attached to said inner walls, said reinforcement matrix structure comprising a body of material with a series of substantially spherical voids which are interlinked at the point of contact wherein these points of contacts form small apertures and wherein the size of the apertures between adjacent voids does not exceed more than about 5% of the internal surface area of the void, (b) at least partially filling said pressure vessel with said fluid under pressure. 34. A method of storing a fluid under pressure in a pressure vessel which incoφorates a hydrostatic pressure retainment apparatus, said method comprising: (a) obtaining a pressure vessel which incoφorates a hydrostatic pressure retainment apparatus comprising: (i) a pressure vessel having a fill opening and a tank body having at least two opposing inner walls defining an interior volume; and (ii) a reinforcement matrix disposed in said tank body and attached to said inner walls, said reinforcement matrix structure comprising a body of material with a series of substantially spherical voids which are interlinked at the point of contact wherein these points of contacts form small apertures and wherein the size of the apertures between adjacent voids does not exceed more than about 5% of the internal surface area of the void. (b) placing a fluid under pressure in said pressure vessel; and (c) allowing said fluid under pressure to remain in said pressure vessel.

Inventors: GARRETT MICHAEL ERNEST, SETLOCK ROBERT JOSEPH JR, GARRETT, MICHAEL, ERNEST, SETLOCK, ROBERT, JOSEPH, JR.
Applicants: BOC GROUP PLC, SETLOCK ROBERT JOSEPH JR, SETLOCK, ROBERT, JOSEPH, JR., THE BOC GROUP PLC
Application year: 1999
Main classification: F17C1
IPC codes: F17C1, F17C11