Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Reexamination Certificate
1998-03-24
2002-03-19
Weiss, John G. (Department: 3761)
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
C128S200240, C220S646000, C220S648000
Reexamination Certificate
active
06357439
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a compact gas containment and supply apparatus, particularly one which is readily human portable
2. Discussion of Prior Art
To enhance portability of pressurised gas containment vessels there is a general requirement for high strength combined with relatively low weight. Overwinding around an internal shell is a well established technique both for strength and for weight reduction in the manufacture of cylindrical pressure vessels, such as gun barrels, gas cylinders and the like. Such structures when pressurized are subjected to hoop stresses that are significantly higher than the axial stresses, and the use of an overwinding designed to carry a large part of the hoop load allows the design of the base cylinder to be directed towards meeting only the axial stresses, with a considerable potential for saving in weight. Traditionally such windings were of high tensile strength metal wires. Recent developments in composite material technology have led to the use of composites consisting of fibre windings in a resin matrix.
Toroidal pressure vessels offer an alternative geometry to cylinders. Toroidal vessels comprised of a metal or composite inner toroidal casing overwound with wire or resin matrix fibre composite material are known and are described for example in UK Patent Application 2110566. These can offer some reduction of weight over unwound toroidal shell structures. In the case of composite winding, manufacturing can be complex as conventional winding equipment does not readily allow for the application of resin bonding during winding. It proves difficult to ensure complete wetting of fibre by matrix resin and incompletely wetted fibres constitute zones of weakness in conventional resin matrix fibre composite structures.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a lightweight and compact gas containment and supply apparatus based on a toroidal pressure vessel having fibre overwinding with a reduced weight, and which mitigates some of the manufacturing difficulties encountered in toroidal structures overwound with resin matrix fibre composite material.
According to the invention, a gas containment and supply apparatus comprises a gas reservoir vessel capable of pressurised gas containment fitted with a gas supply aperture, supply means connectable to the gas supply aperture at a first end to provide for supply of the gas through a second end, and control means to control the rate of supply of the gas, wherein the gas reservoir is a toroidal pressure vessel comprising a metallic toroidal shell having wound on the surface thereof a tensile load bearing layer of high tensile strength non-metallic fibre, the fibre being aligned in a substantially meridianal direction on the toroidal shell.
Both the fibre winding and the metal shell are intended to be load bearing. As with simple cylinders, these structures are subjected to significantly higher stresses in the meridianal direction than in the direction perpendicular to the meridian “ringwise” around the torus. The fibre is intended to bear a proportion of the meridianal load only, and is therefore wound in a substantially meridianal direction rather than diagonally round the torus as is the case for prior art composite layers such as described by UK Patent Application 2110566. The metal shell bears the remaining meridianal load and all the load perpendicular to the meridian. The use of winding to take part of the larger meridianal load allows the metal casing to be designed around lower loading parameters, and this produces a lighter vessel than would be possible using a metal construction alone.
The invention offers a compact pressurised gas reservoir which is lightweight and has a toroidal shape, both of which features result in enhanced portability. The toroidal geometry has a flatter profile since it has a smaller minor diameter than a cylinder of equal volume. The shape is thus particular suited to stowage where a flat profile is desired, or to carriage on the human back since it protrudes less behind the wearer in use. The toroidal shape is also advantageous for carriage on a human back as it fits back curvature more easily. The compact shape means that, although some form of harnessing to enable carriage of the tank by the operator will still be needed, this can generally be simpler, and hence lighter, than is needed for conventional cylindrical apparatus, and makes it possible to dispense with the back plate which is traditionally found necessary for at least the larger back mountable cylindrical gas bottles. The ability to dispense with the backplate is an additional factor in both the reduction of overall weight and the lessening of the distance behind the wearer by which the apparatus protrudes, both of which contribute to enhanced portability. The flatter profile of the torus shape also lends itself to being carried in a suitable bag or satchel which offers greater ease of portability whilst still providing the necessary mechanical constraint.
An additional advantage accruing from the toroidal shape lies in the ability for supply means connection to be made on the inside face of the torus affording some protection and reducing the possibility of its shearing off as a result of external impacts. For this purpose the supply aperture is preferably located on the inside face of the torus. The supply means may be permanently connected to the shell but for ease of storage and to allow replacement of gas vessels the gas supply aperture preferably includes means to effect releasable connection of the supply means and a closure valve to prevent release of gas with the supply means disconnected.
A particular advantage of using overwinding accrues from the build-up of thickness of the winding fibre on the inside of the torus. The overwinding is thus able to take a greater proportion of the meridianal load on the inside of the torus, which is the zone where the overall meridianal load is highest. This effect obviates the need for significant extra metal thickness in the higher loaded zones and as a consequence, a metal shell comprising a torus of substantially circular meridianal section and substantially uniform wall thickness gives close to optimum pressure containment performance with minimum redundant metal weight. Some simplification in manufacture results. However, it will be appreciated that a circular cross section is not essential to the effectiveness of the invention, and the invention can be applied to torus-shaped vessels of nonconstant curvature which have non-circular meridianal and/or transverse section where such a shape is more suited to the application of the invention.
Suitable materials for the winding include composites of polymeric, glass and carbon or ceramic fibres in a thermosetting or thermoplastic matrix. A thermosetting resin could be applied to the fibres as a prepreg prior to winding and cured after winding. A thermoplastic resin could be incorporated by using fine impregnated fibre bundles with sufficient flexibility to allow the winding operation, as thermoplastic fibres intermingled with the structural fibres, or as a thermoplastic powder attached to the structural fibres. Regardless of the method used to interlace the thermoplastic the composite will require subsequent consolidation under pressure at elevated temperature. In all cases the fibres are aligned around the meridian of the toroidal vessel.
However, since the invention employs fibres in the overwinding in a meridianal direction to carry loading in that direction only, it offers the additional possibility of dispensing with matrix altogether, or at least for the bulk of the load-bearing depth with only a surface layer applied for protection. In this matrix-free preferred aspect of the invention the absence of a matrix produces a weight saving compared with pressure vessels consisting of a shell overwound with a conventional fibre and matrix composite material and also obviates the requirement that the process must be compatib
Cook John
Richards Brian J
Nixon & Vanderhye P.C.
The Secretary of State for Defence in Her Britannic Majesty&apos
Weiss Joe
Weiss John G.
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