GAS PUMP

Abstract: A gas pump assembly (32, 35) comprises an hydraulically powered gas pump set up in a gas supply system to operate on demand by balancing the hydraulic force against the reactive force of the gas in the pump, the arrangement being that as demand varies, the pumping rate varies correspondingly. The gas supply system may be a return line diving system or a gas regeneration system for an underwater habitat. The pump is constructed from corrosion-resistant materials and can be operated underwater without requiring a protective pressure housing.

Description: GAS PUMP £iSi£!_.2f-- &-ϊ_.lD--£D- i2D This invention relates to gas supply systems, more particularly to "pus-h-pul I" return line diving systems. The invention is especially concerned with providing a gas pump which can fulfil the requirements of compressors and decompressors used in such systems. The pump is primarily designed for supplying breathable gas to a diver working individually outside a submersible vessel or diving bell, or to a group of divers working in a submerged habitat as welders, for example. However, the pump is not limited to such use and may be used in other circumstances requiring gas containment under elevated pressure. iiS_._lE2_iD_J_.2f-._i_lS_.lD___ID_.i2Q Historically bell-mounted "push-pull" diver gas recirculating pumps have been electrically driven compressors mounted inside the gas space, or outside in an external pressure vessel. The problems with * these techniques are noise where the compressor is within the gas space occupied by personnel, a possibility of gas contamination and/or fire hazard for the internal pumps, and heat build-up, increased weight and bulk (because of the protective pressure housing) for externally mounted pumps. In both cases, electrical interference with communications occurs, a substantial power consumption is unavoidable because the known pumps run constantly, and pump damage due to 'water- slugging' following accidental water intake may also occur. Accordingly, it is an object of this invention to obviate or mitigate the aforesaid disadvantages of the known art. Therefore, it is an object of this invention to provide improvements in closed cycle breathing gas systems, especiall those of the type used for life support systems for deep sea divers. More particularly, it is an object of the present invention to provide a pump of substantially lighter weight, reduced size and of considerably more modest power requirements than those presently available in the field. Further, it is an object of this invention to provide a pump of extended operational life expectancy, increased safety, efficiency and economy, in comparison with those currently known. Summar^_of_the < _Inventi > on In accordance with the present invention there is provided a method of supplying gas under elevated pressure to a user, device or location requiring said gas which comprises delivering gas through a system comprising a gas source, ' gas conduits and a gas pump, said pump being a variable-delivery hydrauli ca I ly powered gas pump which is set up to operate on demand in the system by balancing the hydraulic force against the reactive force of gas in the gas pump at a pre-determined system gas pressure. (All pressures mentioned herein are differential or gauge pressures, ie the pressure differential between gas being supplied to a diver and that of the ambient atmosphere in a bell as recorded on a conventional gauge, unless otherwise stated) . Preferably, the hydraulic power is derived from an hydraulic system driven by a variable frequency electric motor, the output of which varies in response to a signal from sensor means sensitive to changes in pressure in the gas system. Preferably also, the said pump is constructed from corrosion-resistant materials to allow operational use involving direct immersion of the pump in water without requiring a protective housing around said pump. Said materials may be plastics, ceramics or corrosion-resistant alloys. In this invention, the hydraulic fluid may be a conventional oil, but economic advantages are obtainable by use of water, eg sea water which is, of course, readily available in the ambient environment of a diver or a submersible. Use of water is particularly preferred in the return line diving bell system use where the umbilical from a support vessel generally includes a hot-water conduit for heating a diver's suit to make good body heat losses. A proportion of this water can be diverted to work the hydraulics and since the pump of this invention works on demand, only small quantities are required. Thus, no additional electrical wires or hydraulic fluid conduits need be provided in the umbilical to operate the pump of this invention. In addition, should any water find its way into the gas system from the hydraulic system, this does not represent a serious contamination problem as would be the case in the use of oil. Since the pump is formed from corrosion-resistant materials, it can be directly exposed to the action of ambient water, even sea water without a reduction in operational efficiency. In fact, such exposure dissipates the heat of gas compression and so provides a positive advantage. Also, being set up to work on demand, especially when supplying a single diver, pumping rates are extremely slow in comparison with existing high volume continuously running pumps, so that water ingress will not damage the pump. In such circumstances, the pump merely slows slightly till the water is pushed through. Further, in the event of any leaks occurring in the gas system the pump will automatically respond to increase gas flow to overcome the losses. Thus, in accordance with this invention there s provided a "push-pull" return line diving system comprising a source of breathable gas, gas supply lines, gas exhaust lines, a gas pump, valve means for providing a diver with breathable gas on demand and gas recovery means wherein the gas pump is an hydrauli caI ly powered gas pump designed to operate such that the hydraulic force is balanced against the reactive force of gas in the gas pump at a pre¬ determined user-acceptable gas pressure in the system so that the pump is activated on demand according to the diver's respiratory action. Preferably, the hydraulic power is transmitted by means of an hydraulic motor having an hydraulic piston of relatively small size through a shaft to a gas piston of relatively Large size in order to obtain Large displacements of gas at a breathable pressure with relatively small movements of the hydraulic piston using small quantities of hydraulic fluid at a typical hydraulic pressure. Preferably, the hydraulic motor is activated by an hydraulic system driven by a variable frequency electric motor, the output of which varies in response to a signal from sensor means sensitive to changes in pressure in the gas system. Preferably, a separate pump is provided for both the gas supply ("push") and gas exhaust ("pull") Lines each of said pumps being set up to operate on demand according to the diver's respiratory action. Thus, whenever the diver inhales the gas suppLy pump moves to restore gas inhaled by the diver and maintain pressure in the supply Line, the exhaust pump standing idle (under ideal conditions) and whenever the diver exhales the gas exhaust pump moves to vent the exhaled gas and maintain suction in the exhaust line, the supply pump meantime stalling out and remaining in an inactive mode during the exhaust cycle. It is thought possible that in practice the one pump may not always stop dead whilst the other is performing its required function, but movement thereof would be almost imperceptible unless serious Leaks developed in some part of the gas system. This is in marked contrast to existing compressors which operate continuously at a constant delivery rate regardless of the diver's respiratory action. Preferably, the gas pumps are located on the exterior of a submersible vessel exposed to the action of ambient water for cooling purposes and without any protective pressure housing, the said pumps being constructed from corrosion-resistant materials. Preferably also, the said gas pumps are reciprocating pumps provided with valve means allowing their use as double acting pumps to provide positive gas displacement on both strokes of each pump. The hydraulic fluid chosen may be oil in which case one could operate the hydraulics at a pressure of from 150 to 200 bar and select appropriate hydraulic and gas piston sizes so as to operate the gas supply at from 5 to 15 bar in order to suit ' the diver's equipment, ie depending on the particular demand regulator provided for the diver's breathing apparatus, one may wish to provide the gas supply at say 7 bar or 12 bar. The corresponding suction in the exhaust line need only be in the range of from -1.5 to -2 bar. In fact, in the case where the diver is working some way below the diving belL to which the pumps are attached, the exhaust gas returns without the need for a pump. However should he rise above the Level of the bell, the pump is requi red . In a preferred alternative embodiment of this invention the hydraulic fluid chosen is water in which case the hydraulic pressure lies in the range of from 30 to 40 bar. As before the gas supply pressure is optional and depends on the respective piston sizes ratio, but a preferred pressure s 7 bar. The hydraulic fluid is advantageously obtained by diverting to the pump a proportion of the heated water being passed through the diver's umbilical to heat his suit. Whereas the foregoing discussion relates to supplying a diver with gas, the method of pumping on demand in accordance with the invention has other applications also. The method may also be applied to the regeneration of gas mixtures by means of a gas selective permeable membrane. The gas mixtures concerned may be those required for providing a breathable atmosphere in a submerged habitat or in a compression chamber for use in saturation diving operations. The gas mixtures required vary with the proposed depth of dive, but for the depths currently regarded as "deep sea" diving, gas mixtures based on helium are generally used. The mixture may be 92-98% helium with 2-4% oxygen with small percentages of nitrogen and other gases being tolerable. However, in a welding habitat for example the atmosphere becomes contaminated by the respiratory action of several divers plus the gases evolved by or used (eg Argon) in welding. Helium is the gas which must be recovered free of contaminants because of its commercial value and nitrogen and carbon oxides must be excluded because of their deleterious effect on divers. Thus, in accordance with another aspect of this invention, there is provided a method of regenerating a gas mixture for re-use which comprises delivering a gas mixture in need of regeneration to a gas regeneration unit containing a gas selective permeable membrane by means of a system comprising, a variable delivery hydrauli cal ly powered gas pump which is set up to maintain a pre-determined pressure differential across the membrane by balancing the hydraulic force against the reactive force of gas in the pump such that the pump delivers gas on demand. This method may be applied to * _... advantage in the regeneration of gas mixtures for submerged habitats or compression chambers used for commercial or experimental purposes. The gas regeneration may be carried out under water at the habitat or the used gas may be collected and regenerated by a surface or land-based regeneration unit. In the case of a regeneration unit provided, for example, on the deck of a support vessel, the pump of this invention should be provided with cooling leans. preferably, a water jacket. In the case of an i_n s^tu regeneration at a habitat, the pump will be located on the exterior of a submerged habitat so as to be exposed to the action of ambient water for cooling purposes without the need for a protective pressure housing. Thus, in its broadest aspect, the invention provides a gas pump capable of variable delivery in response to a demand which comprises a gas pump, an hydraulic motor for driving said pump, an hydraulic power supply, gas pressure sensitive sensor means and automatic control means for varying the hydraulic power supply in accordance with a signal fed back from said sensor means to said control means. Preferably, the hydraulic power supply is controlled by a variable frequency electric motor. The invention will now be described by way of example with reference to the accompanying drawings. §£_-__!_2S§£rlE£i Q- f____!-:_.££§__!QS§ Fig 1 is a schematic representation of a return line "push-pull" system of this invention shewing in section a demand pump of this invention in which supply and exhaust functions are performed by two gas pistons connected in tandem and driven by a common hydraulic motor. Fig 2 is a side view in section of a pump according to this invention; and Fig 3 is a diagrammatic representat on of another return line "push-pull" system of this invention. 2S§££iB£i _ f_!h§_EE£Ϊ§£I§-!_i2_-2--iffl§Ω£§ Example 1 A "push-pull" return line diving system, referring to Figs 2 and 3 is provided for diver excursions from a diving bell (31) and comprises a demand pump (32) formed from corrosion-resistant materials for supplying gas under elevated pressure through a supply line (33) to a diver demand regulator valve (34) and a demand pump (35) formed from corrosion-resistant materials for exhausting gas under reduced pressure through an exhaust line (36) from a demand exhaust regulator valve C37) . The gas is supplied from a surface support vessel through an umbilical to the bell (31) and from there fed from gas supply regulator means (38) through a heat exchanger C39) in order to pre¬ heat incoming exhaust gas prior to passing said exhaust gas to a water trap (40) and C0 2 scrubber (41). A by-pass valve (42) is provided in the exhaust line for isolating the exhaust pump (35) from the exhaust line (36) in the circumstances where the diver is working below the bell (31) and suction does not need to be applied to the line (36) to assist venting of the exhaust gas. Emergency supplies of gas (43) may be fed into the supply line (33) from the gas supply regulator means (38). The pumps (32) and (35) are hydraulical ly powered reciprocating pumps wherein the hydraulic force is balanced against the reactive force of gas in the supply and exhaust lines respectively. Λ Each pump (32) and (35 " ) comprises a reciprocating gas piston (44) in a cylinder (45) which is provided with inlet and outlet conduit means (46) and (47) respectively and non-return valve means (48), (49), (50) and (51) whereby the pump functions as a double acting pump, the said piston (44) being connected via a shaft (62) to an hydraulic motor ( 63) comprising a reciprocating piston (64) in a cylinder (65 ) which is provided with inlet and outlet means (66) and (67) respectively and valve means (68) for reversing the hydraulic flow. The hydraulic system is driven by a variable frequency electric motor (not shown) which is controlled automatically in accordance with a signal received from pressure-sensiti e sensor means provided in the gas system (not shown). Whereas only one gas piston is shown on the shaft, an identical one may be provided on the opposite end of the shaft to achieve optimum balance in the pump to maintain essentially the same gas pressure on both forward and backward strokes, but it is not essential , because compensations may be made in the hydraulic system instead. A void area C59) separates the hydraulic and gas systems to avoid cross-contamination in the event of either of the seals (60) or (61) leaking. In use the system is set up to operate from a hydraulic oil pressure of 200 bar Cin this embodiment) and the respective sizes of the hydraulic and gas pistons are chosen so as to provide a supply pressure to the diver of 12 bar and an exhaust suction of -2 bar. Thus, in this embodiment the "push" supply and "pull" exhaust functions are completely independent of one another, so that the pumps perform very well on demand. By using separate drive means for supply and exhaust pumps the pumps each perform their function in unison with the lungs of the diver, the supply pump (32) moving when the diver is inhaling, and the suction pump (35) when he is exhaling, and both maintaining an effectively constant differential pressure set by the hydraulic supply pressure and the respective ratios of gas to hydraulic pi ston * areas . This embodiment has been described with reference to use of hydraulic oil, but water may be used instead and a suitable adjustment made to the pressures required. It would be particularly advantageous to make use of the heated water normally pumped down from the surface to provide heat for the diver's suit to compensate for body heat losses. Since the pumps are capable of variable delivery and pump only on demand, only small quantities of hydraulic fluid are required. This avoids having to provide separate electrical wires and/or hydraulic hoses in the bell umbilical and this makes the whole system simpler and cheaper. Example 2 In a second embodiment of the invention the supply and exhaust pumps are connected in tandem and driven from a single small hydraulic motor which in turn derives its power from a variable frequency electric motor (not shown). The arrangement comprises an hydraulic motor comprising a cylinder (.4), piston (5), and piston rod 6 , the said cylinder C4) together with the piston (5). defining voids A and B capable of receiving hydraulic fluids which by means of hydraulic valve means (9) can be caused to act alternately on faces (7) and (8) of the piston C5), ie the valve arrangement is such that at either end of its stroke, the in and out on the piston will be reversed, and the piston will be driven in the opposite direction; to the right of Fig 1 of the drawings is shown reciprocating gas pumping means which comprises two cylinders (14) and (24) and two pistons (15) and (25) connected by a common push rod C16) to the piston rod (6) of the hydraulic motor. The cylinders (14) and C24) together with the pistons (15) and (25) define voids (E, F, G, H, ) for receiving gas for compression by the respective faces (17, 18, 27, 28) according to the motion of the pistons (15) and (25) and Λ according to the valve arrangement which comprises non- return valves (11, 12, 13, 19, 21, 22, 23 and 29), which gas when compressed is passed optionally to a supply accumulator (20) which maintains breathable gas at an ovei— pressure (typically circa + 10 bar) for supply to a diver (not shown). In practice it has been found that the accumulator (20) is unnecessary because the gas pumps respond so well to demand that no reservoir is required so that compressed gas can normally be supplied directly to a diver. Air exhaled by the diver may be sucked into an exhaust accumulator (10) maintained at a reduced pressure (typically £Ϊ££§ ~2 bar) and from there drawn by pistons (15) and (25) into the cylinders (14) and (24) and returned to the interior (2) of the submersible. Once again the accumulator (10) is optional. Thus, in operation when the electric motor causes hydraulic fluid to drive piston (5) on its first stroke towards the gas pump (ie fluid is flowing into A and out of B) piston (15) is removing gas from the reduced pressure accumulator (10) through valve (12) into E, thus maintaining the suction or "pull". When on the return stroke, this used gas will be pushed through the valve (11) into the interior (2) of the submersible. Whilst piston (5) is on its first stroke, gas within the cylinder at F will be under compression and will pass out through valve (.19) into the overpressure accumulator (20) thereby maintaining the supply pressure therein at a sufficient level for diver use. On the return stroke fresh gas will be drawn into F through valve (13) from the submersible interior (2) ready for compression on the next stroke. Simultaneously, since pistons ( 15 ) and (25) are connected in tandem but valved differently, on the first stroke of piston (5) gas will be pulled into G through valve (23) from the interior (2) of the submersible, and driven from G through valve (29) into the compression accumulator C20) on the return stroke; and with the piston driving to the right of Fig 1 of the drawings on its first stroke gas in cylinder (24) at H will be expelled through valve (21) into the submersible interior (2), and on the return stroke drawn in through valve (22) from accumulator (10). Thus, in effect G and E, and H and F are equivalent. It will be understood that the diver is breathing from D and exhaling into C all the while, and that the equipment acts on demand, ie the hydraulic piston (5) and the gas pistons (15) and (25) do not move except to make good a reduction/increase in system pressure created by the diver's respiratory action. The total differential required for pressure and suction to operate the diver's breathing valves is only a small fraction of a typical hydraulic pressure (200 bar vs 12 bar), so the gas piston can be sized accordingly. Indeed, by picking a size whereby the forces on the gas piston counterbalance the forces on the hydraulic piston when those forces correspond to gas pressures only slightly higher than that normally supplied to the diver, the output boost pump will stay reasonably constant in total suction and supply pressure, but the volume pumped (and the amount of hydraulic fluid used) will vary in close proportion to the gas flowing to the diver. With no flow to the diver, the pump stalls out. Also, in the event that water should find its way into the pump, the increased resistance will cause the pump to react simply by slowing down until the water is pushed out of the way. There is no force available to physically damage the pump because it is designed to pump only on demand to a certain maximum pressure towards which pumping rate is slowed. This is in complete contrast to conventional compressors. The usual feature of a hydraulic piston is that the force exerted in one direction is more than the force exerted in the other. This is because the piston rod reduces the area that the hydraulic fluid has to push against on that side. The second of our gas cylinders is sized accordingly, • so as not to waste fluid on one-half of the cycle. Thus, the ratio of piston area (7) of A to the piston area (18) of F is equal (more or less) to the ratio of the piston area (8) of B to the piston area of G. The lack of a piston rod in 4 makes a negligible perturbation to this, as the piston rod area in the gas section is a much smaller percentage of the whole than in the hydraulic section. It should be noted that only one size of pump is working at a time; the other has only friction and low pressure check valves to overcome. In order to set both the suction and supply pressures, suction accumulator (10) C is connected to the submarine interior with a spring-loaded suction relief valve. If the suction dif erential- exceeds this, gas flows through into accumulator C to increase the pressure. Thus, this defines the amount of available suction in C, and, as the total of the suction and supply gas pressures is determined by the hydraulic oil pressure, this determines the supply pressure as well. If the diver descends well below the submersible, he increases his ambient pressure. This has the effect of increas ng the suction and decreasing the supply pressure to his equipment. Decreasing the spring pressure on (40) or even by-passing (40) altogether will tend to restore these. Conversely, if the diver goes above the submersible, the proper flow can be achieved by 2D££§i-iiD9 this spring setting. Lastly, the positions of the various suction and pressure areas have been carefully chosen so that the pressure in E never gets very high. (The. highest it will get relative to the ambient pressure in the sub will be only that little bit caused by the pressure drop across the connection and check valve between E and the sub i nterior) . Thus, a gas leak at the piston seals on E will cause only a very slight loss of gas with negligible pressure. Area J and the tube (30) are connected to the gas booster pump in such a way that gas leaking from these piston seals must get out through hose (30). Hose (30), however, extends downwards to an area of greater hydrostatic pressure, so that any buildup of gas in J will eventually stop due to the increasing back-pressure caused by filling of hose (3), thus stopping the flow through the seals when the driving force vanishes. Example 3 In a third embodiment of the invention a gas regenera¬ tion system is provided in an underwater water welding habitat for regenerating the breathable helium based atmosphere therein. The system comprises a plurality of gas pumps arranged in series to increase the gas pressure from ambient in the habitat to 100 bar above a hient in stages. The compressed gas is delivered to a gas regeneration unit containing a helium permeable membrane, said membrane being impermeable to nitrogen and other undesirable gases such as carbon oxides, nitrogen oxides and inert gases used in welding such as argon. The membrane cannot effectively recover all the helium from the mixture and so for reasons of efficiency approximately 6% of the gas mixture which fails to pass the membrane after a pre¬ determined length of time is removed and collected for regeneration by other means. The remainder is recycled to the habitat after decompression to ambient pressure. The gas pumps are hydrauli cal ly powered reciprocating gas pumps capable of variable delivery to maintain a differential pressure of. about 100 bar over the membrane. As in the diver return line supply use, the pumps, after initial start up, only operate to restore a drop in pressure which saves power. Sensor means responsive to changes in pressure is used to activate a variable frequency electric motor which drives the hydraulics which in turn drive the gas pumps by means of an hydraulic reciprocating motor. The gas pumps are constructed from corrosion-resistant materials, eg plastics, ceramics and alloys and can therefore be mounted exterior of the habitat directly immersed in ambient water to effect dissipation of heat of gas compression and avoiding the need for any form of protective pressure housing. The arrangement may comprise a pair of pumps acting together Cin parallel) to step up ambient gas pressure to an intermediate raised pressure which is then finally elevated to about 100 bar by a third pump which acts on the combined output of the first mentioned pumps. _.d^2 _:29£ 2-E≤ilyE§-i-.2_i-.-.i3iS_.lDl_£ _;_- D-.-!£S 1 A diver t s gas compressor immersed directly in the sea to effect dissipation of the heat of compression and save weight and space. 2 The system pumps on "demand". A slight drop in the gas pressure increases the pumping rate, an increase slows it. 3 This "demand" principle works in either direction, as the piston sizes are in proportion to the hydraulic piston forces in order to conserve hydraulic oil and thus power. 4 The demand principle also means that this diver boost pump will not be damaged by the intress of water and water "slugging". 5 A suction relief on the "pull" side determines the suction level and thus the supply pressure as well. 6 Means to vary the setting to the relief valve spring in order to track the diver. The total pressure differential remains the * , same. This setting apportions how much of it will be suction and how much pressure, and this in turn reduces the power requirement of the system. 7 Any escaping gas is trapped and the increasing pressure used to balance and stop leaks through the external piston seal. NB Whereas the invention has been described with reference to the use of a variable frequency electric motor, ie an electric motor having a variable frequency drive, the demand operation may be accomplished by other means such as use of a DC motor driven by a chopper or by use of a pressure operated by-pass valve in the hydraulic system itself.

Claims: CLA IMS 1 A method of supplying gas under elevated pressure to a user, device or location requiring said gas which comprises delivering gas through a system comprising a gas source, gas conduits and a gas pump, said pump being a variable-delivery hydrauli cal ly powered gas pump which is set up to operate on demand in the system by balancing the force against the reactive force of gas in the gas pump at a pre-determined system gas pressure. 2 A method according to claim 1 wherein the hydraulic power is derived from an hydraulic system driven by a variable frequency electric motor, the output of which varies in response to a signal from sensor means sensitive to changes in pressure in the gas system. 3 A method according to claim 1 or claim 2 wherein the user is a diver and said pump is constructed from corrosion-resistant materials to allow operational use involving direct immersion of the pump in water without requiring a protective housing around said pump to form part of a "push-pull" return line diving system for supplying breathable gas to the diver. 4 A method according to claim 1 or claim 2 wherein the device is a submersible or diving bell and the pump is constructed from corrosion-resistant materials to allow said pump to be mounted on the exterior of the hull of said submersible or diving bell open to the action of ambient water for operational use without requiring a protective housing around said pump. 5 A method according to claim 1 or claim 2 wherein the location is a submerged welding habitat and at least one pump constructed from corrosion-resistant materials is provided adjacent to said habitat in the ambient water without requiring a protective housing around said pump for supplying gas to said habitat. 6 A method according to any one of the preceding claims wherein a plurality of said pumps are arranged to step up gas pressure in stages to that finally desired. 7 A method according to any one of the preceding claims wherein the hydraulic fluid used is water. 8 A method according to claim 7 wherein the water used is sea water. 9 A method according to any one of the preceding claims wherein the materials used to construct the pump comprise plastics, ceramics or corrosion-resistant alloys. 10 A method according to claim 8 wherein the pump comprises components formed from ceramic materials. 11 A method according to claim 3 wherein the hydraulic fluid used is a quantity of the water normally supplied through the diver's umbilical for heating his suit . 12 A method according to claim 3 wherein a separate pump is provided for the "push" (supply) and "pull" (exhaust) Λ parts of the return line system, each of said pumps being set up to operate on demand according to the diver's respiratory action. 13 A method according to claim 1 wherein the hydraulic power is derived from an hydraulic system including an hydraulic motor for driving the gas pump, said motor comprising a reciprocating piston of relatively small size and said gas pump comprising a reciprocating piston of relatively large size to allow use of typical hydraulic pressures whilst delivering gas to a user at a breathable pressure. 14 A method according to claim 13 wherein the hydraulic fluid is oil and the hydraulic pressure lies in the range of from 150 to 200 bar and the gas supply pressure lies in the range of from 5 to 15 bar whilst the gas exhaust suction lies in the range of from -1.5 to -2 bar. 15 A method according to claim 14 wherein the gas supply pressure is 12 bar. 16 A method according to claim 14 wherein the gas supply pressure is 12 bar. 17 A method according to claim 13 wherein the hydraulic fluid is water and the hydraulic pressure lies in the range of from 30 to 40 bar. 18 A method according to claim 17 wherein the gas supply pressure is 7 bar. 19 A method of regenerating a gas mixture for re-use which comprises delivering a gas mixture in need of regeneration to a gas regeneration unit containing a gas- selective permeable membrane by means of a system comprising a variable-delivery hydrauli cal ly powered gas pump which is set up to maintain a pre-determined pressure differential across the membrane by balancing the hydraulic force against the reactive force of gas in the pump such that the pump delivers gas on demand. 20 A method according to claim 19 wherein the hydraulic fluid is oil and the hydraulic pressure is 200 bar, and the respective gas pressures for-supply to the' " membrane and waste gas collection are 100 bar and 0.6 bar. 21 A method according to claim 19 or 20 wherein the gas mixture is that for providing a breathable atmosphere in a submerged habitat or a compression chamber. 22 A method according to claim 21 wherein the gas mixture is based on helium. 23 A method according to claim 21 wherein the pump is located on the exterior of a submerged habitat exposed to the action of ambient water without requiring a protective housing, said pump being formed from corrosion-resistant materials. 24 A method according to any one of claims 19 to 23 wherein a plurality of said pumps are arranged to step up gas pressure in stages to that finally desired. 25 A method according to any one of claims 19 to 24 wherein said pump is formed from plastics, ceramics or corrosion-resistant alloys. 26 A gas pump capable of variable delivery in response to a demand which comprises a gas pump, an hydraulic motor for driving said pump, an hydraulic power supply, gas pressure sensitive sensor means and automatic control means for varying the hydraulic power supply in accordance with a signal fed back from said sensor means to said control means. 27 A gas pump according to claim 26 wherein the hydraulic power supply is controlled by a variable frequency electric motor. 28 A gas pump according to claim 26 or claim 27 wherein the materials used to construct the pump are corrosion-resistant so as to withstand operational use involving direct immersion in water without requiring a protective housing. 29 A gas pump according to any one of claims 26 to 28 wherein the gas pump is a reciprocating pump and. the hydraulic power is transmitted by means of an hydraulic motor having an hydraulic piston of relatively small size through a shaft to a gas piston of relatively large size in • said pump in order to obtain large displacements of gas with relatively small movements of the hydraulic piston, the gas pressure being substantially less than the hydraulic pressure. 30 A gas pump according to claim 24 wherein the gas pump is a double acting reciprocating pump. 31 A gas pump according to any one of claims 26 to 30 wherein the hydraulic motor is separated from the gas pump by a chamber for trapping any hydraulic fluid leaking from the motor or any gas leaking from the pump thereby preventing cross-contamination of the hydraulic and gas systems. 32 A gas pump according to claim 31 wherein said chamber is provided with conduit means which in underwater use of the pump extends beneath the compressor to a region of greater hydrostatic pressure in order to provide a means of limiting the amount of any gas leaking from the gas pump into the chamber. 33 A gas pump according to any one of the preceding claims wherein the hydraulic fluid used is water. 34 A gas pump according to claim 33 wherein the water used is sea water. 35 A gas pump according to claim 34 wherein the pump comprises components formed from ceramics and/or corrosion- resistant alloys. 36 A "push-pull" return line diving system comprising a source of breathable gas, gas supply lines, gas exhaust Lines, a gas pump, valve means for providing a diver with breathable gas on demand and gas recovery means wherein the gas pump is an hydrauli cal Ly powered gas pump designed to operate sucti that the force delivered by the hydraulic system is balanced against the reactive force of gas in the gas pump at a pre-determined diver-acceptable gas pressure in the system so that the pump is activated on demand according to the diver's respiratory action. 37 A. "push-pull" return line diving system according to claim 36 wherein the pump is formed from corrosion- resistant components so as to withstand operational use involving direct immersion in water without requiring a protective housing. 38 A "push-pull" return line diving system according to claim 36 or 37 wherein the- gas pump is a reciprocating pump. 39 A "push-pulL" return Line diving system according to claim 38 wherein the hydraulic power is transmitted by means of an hydraulic motor having an hydraulic piston of relatively small size through a shaft to a gas piston of relatively large size in said pump in order to obtain large displacements of gas at a breathable pressure with relatively small movements of the hydraulic piston using small quantities of hydraulic fluid at a typical hydraulic system pressure. 40 A "push-pull" return line diving system according to claim 39 wherein the hydraulic fluid is oil and the hydraulic pressure lies in the range of from 150 to 200 bar, the gas supply pressure lies in the range of from 5 to .15 bar, and the gas exhaust suction lies in the range of from -1.5 to ^2 bar. 41 A "push-pull" return line diving system according to claim 40 wherein the gas pressure is 7 bar. 42 A "push-pull" return line diving system according to claim 40 wherein the gas pressure is 12 bar. 43 A "push-pull" return line diving system according to claim 39 wherein the hydraulic fluid is water and the hydraulic pressure lies in the range of from 30 to 40 bar and the gas supply pressure is 7 bar. 44 A "push-pull" return line diving system according to claim 43 wherein the water used is a quantity of the hot water normally supplied through an umbilical to the diver for heating his suit. 45 A "push-pull" return line diving system according to claim 43 wherein the water used is sea water. 46 A "push-pull" return Line diving system according to claim 36 wherein the gas pump comprises an hydrauli cal Ly powered motor and a reciprocating gas pump comprising first and second gas compression means connected in tandem, and connected thereto gas conduit and non-return valve means arranged such that the reciprocating gas pump is a double- acting pump wherein each of said first and second gas compression means alternately perform supply and exhaust functions thereby maintaining a substantially uniform positive pressure in the supply lines and a correspondingly uniform negative pressure in the exhaust Lines of the system. 47 A "push-pull" return Line diving system according to claim 46 wherein a chamber is provided between the hydraulica I ly powered motor and the gas pump in order to provide a trap for any hydraulic fluid leaking from the motor and any gas leaking from the pump. 48 A "push-pull" return line diving system according to claim 47 wherein said chamber is provided with conduit means which in use extends beneath the pump to a region of greater hydrostatic pressure in order to provide a means of limiting the amount of any gas Leaking from the gas pump into the chamber. 49 A "push-pull" return line diving system according to claim 46 wherein gas accumulators are provided, one in the supply line and one in the exhaust line. 50 A "push-pull" return line diving system according to claim 49 wherein the gas compressor is mounted on the exterior of a submersible vessel and a spring-l.oaded exhaust suction relief valve is provided within trie submersible interior, which valve is connected to the exhaust accumulator. 51 A "push-pull" return line diving system according to claim 36 wherein at least two gas pumps are provided, one in the supply ("push" ) Line and one in the exhaust ("pull") line, each comprising an hydrauli ca I ly powered motor and a reciprocating gas pump connected with conduit means including non-return valve means arranged such that the said reciprocating gas pump is a double acting pump, each of said pumps being designed such that in use the hydraulic force is balanced against the reactive force of the gas in the pump at a pre-determined gas pressure so that the pumps each operate on demand to maintain a substantially uniform positive pressure in the supply line and a substantially uniform negative pressure in the exhaust line in response to a diver's respiratory action. 52 A "push-puLL" return Line diving system according to claim 51 wherein the pumps are each formed from corrosion- resistant materials so as to withstand operational use involving direct immersion in water without requiring a , protective housing and are mounted on the exterior of a submersible diving vessel hull. 53 A "push-pull" return line diving system according to claim 51 wherein the supply gas is brought into indirect heat exchange contact with the exhaust gas to pre-heat same prior to passing said pre-heated exhaust gas through a water trap and CO. scrubber. 54 A "push-pull" return line diving system according to any one of claims 51 to 53 wherein a by-pass valve is included in the exhaust line to allow isolation of the exhaust pump from the exhaust line. 55 A "push-pull" return line diving system according to any one of claims 51 to 54 wherein the hydraulic fluid used is a quantity of the hot water normally supplied to the diver through an umbilical for heating his suit. 56 A "push-pull" return line diving system according to any one of claims 51 to 54 wherein the hydraulic fluid used is sea water and the pump comprises components formed from ceramics and/or corrosion-resistant alloys.

Inventors: KRASBERG ALAN, KRASBERG, ALAN
Applicants: KRASBERG ALAN, KRASBERG, ALAN
Application year: 1985
Main classification: B63C11
IPC codes: B63C11