Abstract:
Method and Apparatus for compressing ambient air to a pressure above ambient, directing the compressed air into a portable hyperbaric chamber in which a exothermal chemical reactor is located whereby the air is heated and changed in chemical composition and passing the heated product gas through an expansion motor wherein the work output of the expansion motor is used to help drive the compressor. The exothermal chemical reactor may support combustion or be a person.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Application is a Continuation in Part of application Ser. No. 08/905,156 filed Aug. 1, 1997, now abandoned which is incorporated by reference which Application was a Continuation in Part of Provisional Patent Application Ser. No. 60/023,105 filed Aug. 2, 1996. 
    
    
     BACKGROUND OF THE INVENTION 
     Several underlying principles are key to an understanding of the present invention. 
     It is theoretically possible to pump a volume of fluid such as ambient air into a chamber containing fluid at a second pressure such as a compressed gas chamber with the investment of a certain amount of work which work will be exactly equal to the amount of work which is produced by taking the same volume of fluid and reversing the process, that is, expanding that same quantity of gas from the second pressure to the first pressure. 
     As is known from thermodynamics, adding heat to the gas such as while it is in the pressurized chamber will produce an increment of increased work during the expansion with the amount of work produced during the expansion being a function of the amount of heat added, the pressure ratio, etc. The difference between the expansion work and the compression work may be used to overcome friction and provide a net work output if desired (expansion work less compression work less friction work). The friction work is the friction force times the distance moved by a mass experiencing that friction force. 
     From thermodynamics, greater compression ratios and greater heating of the compressed gas lead to better engines measured with respect to work output per unit fuel used, work output per unit weight, work output per unit volume occupied by the engine, etc. Thus, there has been no motivation to make a collapsible engine and more particularly, an engine wherein the heater for the compressed gas comprises a large flaccid walled airtight container. 
     Rolling diaphragm pumps and expansion motors can be almost frictionless with the friction on the order of 1% of the energy needed to compress a quantity of gas. 
     The embodiments disclosed herein which are heat engines are most closely related to the Brayton cycle which is more commonly embodied as a gas turbine engine. 
     The maintenance of life requires certain supplies and conditions such as oxygen, water, food and an acceptable environmental temperature. As is obvious, such supplies and conditions need not be available except locally such as oxygen in air provided to a SCUBA diver for respiration through his mouthpiece or a suitable temperature maintained next to his skin such as may be obtained by the use of a “wet suit”. 
     Mountain climbers climb mountains which are far from sources of resupply so that they must carry supplies with them, such supplies including food, fuel and, during high altitude climbs, bottled oxygen. 
     The following table suggests the atmospheric pressures (PSIA-lbf/in 2  Absolute) and water boiling points (temperatures) which might be expected at various altitudes: 
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
               
               
                 Pressure 
                 Altitude 
                 Water 
                 Pressure 
                 Altitude 
                 Water 
               
               
                 (PSIA) 
                 (ft) 
                 B.P. (° F.) 
                 (PSIA) 
                 (ft) 
                 B.P. (° F.) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 4.5 
                 29,000 
                 157.8 
                 5.0 
                 26,421 
                 162.2 
               
               
                 5.5 
                 24,085 
                 166.3 
                 6.0 
                 21,951 
                 170.1 
               
               
                 6.5 
                 19,989 
                 173.6 
                 7.0 
                 18,173 
                 176.9 
               
               
                 7.5 
                 16,481 
                 179.9 
                 8.0 
                 14,898 
                 182.9 
               
               
                 8.5 
                 13,412 
                 185.6 
                 9.0 
                 12,012 
                 188.3 
               
               
                 9.5 
                 10,686 
                 190.9 
                 10.0 
                  9,428 
                 193.2 
               
               
                 10.5 
                  8,232 
                 195.2 
                 11.0 
                  7,092 
               
               
                 11.5 
                  6,001 
                   
                 12.0 
                  4,598 
               
               
                 12.5 
                  3,958 
                   
                 13.5 
                  2,071 
               
               
                   
               
             
          
         
       
     
     (Note that daily weather conditions will provide some variation of these values.) 
     Respiration at High Altitude 
     With respect to respiration, the low pressure effects of living at high altitudes slow the thought processes, make a person more susceptible to frostbite, make sleep more difficult or impossible, interfere with digestion, bring on dehydration, headaches, fluid accumulation in the lungs, etc. These effects among others are collectively identified as being symptoms of “mountain sickness”. 
     Mountain sickness is a danger to persons living at high altitudes and can incapacitate or kill a person. Rarely, death can occur at altitudes as low as 5,000 feet above sea level. However, placing a person suffering from mountain sickness under increased air pressure for only a few hours will typically bring complete recovery. 
     Bottled oxygen is commonly used by mountain climbers climbing the higher peaks to increase the partial pressure of oxygen to counter the debilitation associated with high altitude and the ambient low partial pressure of oxygen but the bottle and oxygen represent heavy consumables. The gradual decline in physical ability which generally occurs as oxygen supplies are husbanded may tempt mountain climbers to make a precipitous “dash” for the peak before the bottled oxygen and physical reserves of strength and health are depleted even if conditions such as weather are marginal. 
     Portable hyperbaric apparatus has been available for several years for use by mountain climbers. Typically, the apparatus comprises a foot operated compressor and a flexible walled collapsible bag having a sealable opening through which a person may enter the bag. In use, a person suffering from mountain sickness enters the bag, the opening is sealed and a second mountain climber on the outside of the bag then operates the compressor whereby air is forced into the bag thereby introducing pressurized air into the bag which air is available for respiration by the bag&#39;s occupant. The pumped air inflates the bag and provides fresh air under pressure in the bag. 
     These bags are typically pressurized to 2 PSI above ambient. In these known portable hyperbaric bags or chambers which are now being used by mountain climbers, a pressure relief valve is used to vent air to the atmosphere. The work required to pressurize a bag is significant and stresses the climber who is manning the compressor. Thus, this apparatus is used only when a climber is ill and the apparatus is otherwise a dead weight for the mountain climbers to carry up and down a mountain. However, it is a needed dead weight since it may be absolutely necessary in an emergency. 
     Patents demonstrating the known prior art relating to portable hyperbaric apparatus such as is used by mountain climbers include: U.S. Pat. No. 4,974,829 to Gamow et al and U.S. Pat. No. 5,109,837 to Gamow. 
     The above table shows that a person in a portable hyperbaric pressure chamber at 29,000 ft altitude at 2 PSIA above ambient pressure would experience a pressure as if he were exposed to the ambient pressure at just under 20,000 ft. At about 24,100 ft in a chamber at 2 PSIA above ambient, a person would be at a pressure equivalent to the ambient pressure at about 16,500 ft altitude. A person at about 22,000 ft altitude would experience a pressure roughly equal to 14,300 ft which is about equal to the altitude of the base camp used for most climbs on Mt. Everest. 
     It would be desirable to allow a mountain climber to rest and/or sleep in a pressurized space using little or no effort on the part of the mountain climber or his fellows. 
     It would thus become possible to wait out a storm at relatively little and possibly no cost in bottled oxygen while maintaining physical strength and reserves. Mountain climbing would become safer since a dash for the top could be delayed until conditions are optimal. This delay would cost only time and only a slight decline in physical strength, health and supplies. Indeed, the physical strength and health of a climber could actually increase through rest during such a delay under many conditions. 
     Cooking under Pressurized Air 
     During mountain climbs, water is typically available from ice and snow on the mountain but must be melted at a cost in the fuel used to heat and melt the snow and/or ice. Hot prepared food is both nutritious and provides warmth and psychological benefits. 
     The fuel needed for a fire is often unavailable from the environment at higher altitudes such as above the “tree line”, and must be carried by the climber. Low ambient pressure and temperature both increase the amount of time and fuel needed for cooking since the boiling temperature of water (which sets the maximum temperature for many cooking processes) decreases with decreased ambient pressure as indicated in the above table. 
     Pressure cookers are known in art. In using such cookers, food and water is placed in the cooker which is then sealed and heated until the water is boiling whereupon the superatmospheric pressure generated within the cooker by the evolved steam raises the boiling temperature of the water and thus the cooking temperature so that the cooking time is decreased. 
     The cooking times for foods increase with increasing altitude and in a non-linear manner. Cooking instructions such as for cake mixes commonly provide for increased cooking temperatures or cooking times at higher altitudes. Three minutes is the approximate time needed to hard boil a chicken egg in boiling water at sea level. However, water boils at about 102° F. at about 65,300 ft altitude so that an egg in boiling water at this altitude is no warmer than when being brooded by a hen which obviously does not hard boil the egg. The quantity of fuel needed for cooking increases with cooking time. 
     The use of a flame to provide heat for cooking and melting snow and ice becomes increasingly difficult as the partial pressure of oxygen available decreases. 
     It would be desirable for mountain climbers to be able to melt snow or ice or cook wherein both the heating flame and the material being heated are under increased pressure relative to the ambient. Again, the maintenance of the increased pressure would be desirably at little or no additional cost in effort or supplies beyond those needed for the cooking or melting process itself. 
     Compressors and Rolling Diaphragm Devices 
     As is known, positive displacement fluid pumps have two distinct portions of the stroke. In particular, the fluid is increased in pressure from the fluid supply pressure to the pressure of the receiver into which the fluid is pumped during the first part of the stroke: During this portion of the stroke, the force needed to continue the stroke of the piston gradually increases. The subsequent portion of the stroke does not increase the pressure of the fluid but only expels the fluid into the receiver: During this portion of the stroke, the force needed to continue the stroke of the piston (assuming constant piston area) is generally considered to be constant. 
     If the fluid is incompressible, the pressurization portion of the stroke is of negligible length and essentially all of the stroke serves to expel the fluid from the pump chamber. 
     If the fluid is compressible, then the two portions of the stroke are distinct. As the pressure difference generated by the pump is increased, the length of the second portion of the stroke, that is, the expulsion portion of the stroke, gradually becomes less and less of the total stroke. 
     Rolling diaphragm devices are known in the prior art. The characteristics of these devices typically limit operation to only a relatively few strokes per minute (up to perhaps several hundred strokes per minute) but rolling diaphragm devices can be very low in friction and operate essentially without leakage. Marsh Bellofram Corporation of Newell, W.V. as of Feb. 6, 1999 maintained a web page describing rolling diaphragms. In this web page on this date, Bellofram Corporation claimed that their “rolling diaphragms can respond instantly to pressure changes as slight as 0.1 inches (0.003 psi) of water.” (www.belofram.com/advantages.htm) 
     A sample calculation is illustrative. If a rolling diaphragm device of 3 inch diameter and 2 inch stroke is used to compress air (standard atmosphere) from 14.69 PSIA at 60° F. (standard atmosphere) to 16.69 PSIA, about 2.28 ft-lbf of work is needed (0.00238 slug/ft 3 ×32.174 lbm/slug×2×3.14159×32/4 in 3 ×((16.69/14.69) a 1)×(460+60)OR×0.238 BTU/(lb m o R×({fraction (1/12)} ft/in) 3  wherein a=(k−1)/k and k=1.40158). This pressurization takes place over the first 0.1736 inches of piston stroke and the additional work needed for expelling the air from the cylinder is 2.152 ft-lbf ((2−0.1736) in×3.14159×3 2 /4 in 2 ×(16.69−14.69) PSIA=25.82 in-lbf) for a total needed energy of 4.43 ft-lbf. 
     If a friction force of 0.01 PSIA must be overcome, the energy lost to friction is 0.283 in-lbf (2 in/stroke×3.14159×3 2 /4 in 2 ×0.01 lbf/in 2 ×2 stroke/cycle) or 0.0236 ft-lbf or 0.533% of the compression work. The Marsh Bellofram web page suggests that the friction may be as little as a third of 0.01 PSI so that the friction work might be as little as about 0.18% of the compressor work. This represents the energy loss per diaphragm used. If a complete motor/compressor such as will be described hereinbelow uses two diaphragms, then the energy loss due to diaphragm friction will be twice the above calculated value or 0.0472 ft-lbf or 1.066% of the compression work. (Calculations performed herein show more places of accuracy than is likely to be obtained in any experiment but are shown to allow reconstruction of the equations and constants used to obtain the calculated numbers.) 
     Patents illustrating the known prior art relating to rolling diaphragm devices include: U.S. Pat. No. 3,375,759 to Smith, U.S. Pat. No. 3,391,644 to Taplin, U.S. Pat. No. 5,255,711 to Reeds and U.S. Pat. No. 5,275,014 to Solomon. 
     (The prior art system as represented by U.S. Pat. No. 4,974,829 to Gamow et al and U.S. Pat. No. 5,109,837 to Gamow is in certain ways analogous to apparatus for lifting a succession of weights which are allowed to fall to the ground after being lifted such that the energy invested in lifting each weight is lost. This is in contrast to lifting each weight by means of a child&#39;s teeter totter wherein the energy obtained in the lowering of one weight is used to partially offset the energy needed to lift the succeeding weight. In this analogy, each weight represents a quantity of gas which is compressed and introduced into a portable hyperbaric chamber while the energy used to “lift” the quantity of air is the energy needed to compress that quantity of air to the desired pressure. It will be seen that the energy requirement wherein the weight is dropped onto the ground includes both friction and the energy needed to lift the weight while, in the second case, the required energy is only that needed to overcome any friction in the teeter totter.) 
     BRIEF SUMMARY OF THE INVENTION 
     It is a first object of the present invention to provide a portable collapsible hyperbaric chamber containing an exothermic chemical reaction heat generator, an expansion motor and a compressor which compressor is driven by the expansion motor to compress air which is introduced into the chamber at an increased pressure to improve the function of the heat generator, the air being heated in the chamber by the heat generator and the heated air passing through the expansion motor wherein a portion of the heat energy produced by the heat generator is used to drive the expansion motor and the compressor. 
     It is another object of the present invention for said heat generator to be a living being such as a mountain climber whereby the heat generated by the living being is due to the metabolism of food which serves as fuel for the heat generator where the normal heat rejection processes of the living being effect transfer heat energy from the living being to the air in the chamber. Such heat energy transfer may be by heat exchange of air which enters the climber&#39;s lungs and/or heat exchange between the air and the climber&#39;s skin. 
     It is another object of the present invention to provide survival apparatus for use by a mountain climber which employs rolling diaphragm devices to perform compressor and expansion motor functions such that the metabolic heat generated by the mountain climber supplies at least part of the power needed to drive the apparatus which apparatus provides compressed air for ventilation and respiration by the mountain climber. 
     It is yet another object of the present invention to provide a heat engine comprising a reciprocation motion compressor, a chamber containing a source of heat and a reciprocating motion expansion motor wherein the source of heat is the metabolic heat of a person living within the chamber. The heat engine thus provides a compressed air chamber in which a person may live under a pressure above ambient and may be used to treat a person suffering from mountain sickness or other effects of low pressure/high altitude. Rolling diaphragm “pistons” are used in the motor and compressor. 
     Yet another object is to provide a portable hyperbaric chamber which may be pressurized by means of a compressor and expansion motor wherein the chamber may contain an oxidizing exothermic reaction such as combustion and a container for effecting a thermally induced change in a material within said container wherein the compressor and expansion motor are driven by a portion of the heat energy produced by the exothermic reaction. 
     Still another object to provide a portable hyperbaric chamber which may be pressurized by means of a compressor and expansion motor wherein the chamber may contain a combustion flame and a container for cooking food placed therein and/or melting snow and/or ice wherein the compressor and expansion motor are driven by a portion of the heat energy produced by the combustion flame. 
     Yet another object is to make a heat engine using a flaccid walled heater for the compressed gas used in the cycle. 
     Still another object of the present invention is to provide a heat engine using a multistage compressor with interstage cooling. 
     Yet other objects will be clear upon reading the following. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 schematically shows one arrangement of basic elements which may be used with apparatus embodying the instant invention. 
     FIG. 2 schematically shows a second arrangement of elements which may be used with apparatus embodying the instant invention. 
     FIG. 3 schematically shows an arrangement of selected elements of the instant invention. 
     FIGS. 4 and 5 disclose various shapes of certain elements of the motor/compressor of the invention disclosed herein. 
     FIGS. 6 a ,  6   b ,  6   c  and  6   d  schematically show a motor/compressor according to the present invention and shows the manner of progressive rolling of the diaphragms used in the motor/compressor. 
     FIG. 7 shows a cut-away perspective view of a hyperbaric chamber which is to be used with a motor/compressor according to the present invention which hyperbaric chamber is particularly shaped for use in melting frozen water or cooking. 
     FIG. 8 shows a motor/compressor with a hyperbaric chamber wherein an air spring is used in the motor/compressor for moving the spindle during the compressor intake/motor expulsion stroke. 
     FIG. 9 schematically shows an arrangement of basic elements which may be used with apparatus embodying the instant invention and which is generally similar to the arrangement of FIG. 1 but using a multistage compressor scheme with interstage cooling. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the various figures, elements having similar functions are assigned the same identifying numbers. Where the functions differ sufficiently or particular feature details need to be identified, additional numbers are assigned as appropriate. A listing of the elements and their identifying numbers appears in the Specification immediately before the claims. 
     While rolling diaphragms are available on the market, the Applicant has made diaphragms according to his particular needs (e.g., unusual shapes) of RTV (Room Temperature Vulcanizing) silicon rubber (such as Silicone II Window &amp; Door Sealant produced by General Electric Company, Waterford, N.Y. 12188 (tube references U.S. Pat. Nos. 4417042 and 4483973) spread over a suitable form such as of paraffin or waxed paper to yield a flexible sheet which may be cut as desired and bonded along seams using RTV rubber. Reenforcing material such a directionally laid threads or fine cloth (such as ersatz silk scarf material) may be incorporated into the sheet before it cures to provide controlled stretch characteristics for the final sheet. 
     The Applicant believes that a person having ordinary skill in the art will be able to construct apparatus according to the instant invention using teachings found herein and in the published literature without undue experimentation. 
     FIG. 1 schematically shows a hyperbaric chamber  10 , expansion motor/compressor  12  comprised of compressor  16  and expansion motor  18 , a heat source  13 , a compressed gas source  2 , a pressure relief valve  4  and a second expansion motor  6 .  10  is a hyperbaric chamber such as but not limited to a Gamow bag as disclosed in U.S. Pat. No. 4,974,829 to Gamow et al and U.S. Pat. No. 5,109,837 to Gamow. The hyperbaric chamber  10  may be sausage shaped like the known commercially available portable hyperbaric chambers or spherically shaped to efficiently contain a small fire in a small camp stove or cooking heater as described hereinbelow. 
     The wall material of the hyperbaric chamber  10  is preferably flaccid so that the chamber may be deflated and folded into a compact portable package. While it desired that the wall material of the chamber  10  be flaccid, it is preferable that the wall material not stretch significantly when stressed so that the volume contained within an inflated chamber 10 is relatively unaffected by variations in the pressure of the inflating gas. 
     FIG. 1 also shows tubes or pipes  28  which are provided to allow passage of gas from a gas supply or source  1  to the compressor intake, conduct compressed gas from the compressor exhaust to the enclosure or hyperbaric chamber  10 , from the hyperbaric chamber  10  to the expansion motor intake and from the expansion motor exhaust to a gas sink or receiver  3 . Tubes  28  are also provided to conduct gas from the compressed gas source  2  to the hyperbaric chamber  10  and from the hyperbaric chamber  10   5  to the second expansion motor  6 . 
     A drive means  9  may assist the expansion motor/compressor  12  at such times as the power produced by the expansion motor  18  is insufficient to drive the compressor  16 . The drive means  9  may be as simple as a rod extending through either end cap (such as end cap  32  as shown) which allows manual longitudinal drive of the spindle  22  or connection to an actuator such as a pneumatic or electric or other motor. 
     The gas normally comprises oxygen mixed with other gases and generally of a composition such that it would be commonly considered to be air. However, the gas flowing to the expansion motors  6  and  16  may be air enriched with products due to respiration or combustion as will be apparent from the following disclosure. The compressed gas source  2  may provide compressed air, compressed oxygen or a mixture of these two gases. The gas compositions appearing in the various elements should not be considered to be limited to those discussed herein above. 
     Looking at FIG. 1, it will be seen that the expansion motor/compressor  12  is located outside of the hyperbaric chamber  10 . FIG. 2 shows an alternate arrangement wherein the expansion motor/compressor  12  is located within the hyperbaric chamber  10 . The compressed gas source  2  and/or the second expansion motor  6  may be located within the hyperbaric chamber  10  if desired. 
     Pressure relief valve  4  is provided as a safety device. Further, if the valve may be manually overridden, the valve may be used to depressurize the hyperbaric chamber  10  by manually opening the valve to allow the escape of pressurized gas from the chamber to the surrounding low pressure ambient. 
     Gas collector  8  is conveniently an extension of the specific tube  28  which conducts gas from the hyperbaric chamber to the intake valve of the expansion motor  18  and may be used to collect heated air from the space immediately near heat source  13  within the hyperbaric chamber  10 . By this stratagem, the gas after heating will not reside in the hyperbaric chamber  10  during which time it may loose heat but go directly to the expansion motor  18  thus retaining maximum enthalpy. 
     The gas collector  8  could be a mask placed over the face of a person  14  if a person is serving as the heater or a collector or hood if the heater is a flame  15  in a camping stove or the like. 
     FIG. 3 is a schematic outline of the a hyperbaric chamber compression system with the various elements shown and numbered. 
     Looking at FIG. 3,  10  is a portable hyperbaric chamber which is conveniently in the form of a flexible wall bag having an opening by which a person may enter the hyperbaric chamber after which the opening may be sealed and air in the hyperbaric chamber pressurized. Such hyperbaric chambers are known and have been called “Gamow” bags. Details of the bag&#39;s construction are not necessary to an understanding of the present invention and will be found in Patents referenced elsewhere as issued to Gamow. 
       12  is an expansion motor/compressor which is comprised of an expansion motor  18  and a compressor  16  which expansion motor/compressor draws air from the ambient, compresses the air in the compressor portion of  12 , passes the compressed air to hyperbaric chamber  10  and receives compressed air from the hyperbaric chamber  10  and expands the air in the expansion motor portion of the motor/compressor  12 . Work produced by the expansion of the gas in the expansion motor  18  of the motor/compressor of  12  is used to provide work to effect the compression of air by the compressor  16  which is part of the motor/compressor  12 . 
     Appropriate tubes  28  are used to carry compressed gas from the exhaust valve  42  of the compressor  16  to the hyperbaric chamber  10  and from the hyperbaric chamber  10  to the intake valve  44  of the expansion motor  18 . 
     In FIG. 3, living creature  14  in the hyperbaric chamber  10  produces heat while changing the composition of the gas as it passes through the chamber  10 . Some of the oxygen in the compressed air entering the hyperbaric chamber  10  will be chemically combined with carbon from food to make carbon dioxide which gradually will foul the air in the chamber  10  if it is not removed and replaced with fresh air. Typically, about 1.7 ft 3 /minute is needed in providing fresh compressed air for use by a person in a Gamow bag. 
     An estimate of the heat and work energies involved is instructive. The ambient air at high altitudes where mountain sickness of concern is typically below 32 degrees F. as evidenced by snow cover and temperatures may be very significantly lower. 
     For purposes of illustration, assume that the temperature of a gas stream heated by a person is about 60 degrees Fahrenheit (significantly less than a person&#39;s body temperature of 98.6 degrees Fahrenheit). 
     For these conservative temperature values, (32 F° and 60 F°), Carnot efficiency Ec is: 
     
       
           Ec= 1−(459.73+32)/(459.73+60)=about 5%  
       
     
     An extremely low friction compressor and expansion motor is needed to make use of the low grade heat represented by the heat released by a living creature such as a person or a camp stove operated to produce minimal wasted heat and thus use minimal fuel. 
     In principle, nearly any compressor/motor of positive displacement type might be used but the practical problems of friction set severe constraints which are not easily met. The valve actuation schedule of such motors and compressors are believed to be well known and determined by the motor and compressor selected. 
     Rolling diaphragm compressors and expansion positive displacement devices can be used to make the desired motor compressor  12 . These devices can have extremely low friction. 
     Assuming a basal (survival level) metabolic rate of a person is 1200 Calories/day, this person produces 4762 BTUs/day equaling 0.05511 BTUs/sec or 42.88 ft lbf/sec of heat. At 5% efficiency, the work available to overcome friction is 5%×42.88 ft lbf/sec 2.2 ft lbf/sec. (This value is approximate since the ambient temperature, the heating temperature and the heating rate are all approximate.) 
     This work is available to overcome friction and other losses in the motor/compressor and to drive the second expansion motor  8  which may be used to provide work for other purposes such as to operate the various valves and/or power the drive means  9 . 
     Roughly 1.7 ft 3 /min of air is required for respiration by a person in a Gamow bag. Using a piston having a 2 inch stroke and 3 inch diameter, about 3.5 strokes per second are needed. Thus, 2.2 ft lbf/sec is 0.6286 ft-lbf/stroke (one work stroke per cycle) which is available to overcome the power lost to friction which is 0.0236 ft-lbf per stroke per diaphragm. This estimate suggests that, for a two diaphragm motor/compressor, about 2×4% or about 8% of the net work output is sufficient to overcome the diaphragm friction. 
     (Note that the diaphragm friction may be only a third of the value used in this calculation, that the food consumption and heat production rate of a mountain climber is low by a factor of more than two and that conservative temperatures for calculating the Carnot efficiency were used so that the motor should have plenty of power to drive the compressor if care is used in the actual design.) 
     It is possible to increase the efficiency of a rolling diaphragm motor/compressor by varying the shapes of certain elements and carefully timing the opening and closing of the valves. Principles of valve scheduling are known in the art. 
     There are two stages in the stroke of a positive displacement gas compressor. In the first stage, the gas is compressed and the pressure of the gas increases while the gas remains in the compression space. In the second stage, the continued stroke causes the gas to be expelled at a constant pressure to a receiver. 
     The compressor used in the present invention uses the major portion of the compression stroke to expel gas which was compressed in the first portion of the stroke. In most compressors, the major portion of the stroke is used to effect high compression and only a small part of the remainder of the stroke used to expel the compressed gas. 
     Likewise, the major portion of the expansion stroke in the expansion motor in the present invention is used to draw compressed air into the motor and only a relatively short final portion of the stroke is used to perform the expansion of the gas. 
     If the motor inlet valve were merely left open during the entire expansion stroke, the gas in the motor would still be under full pressure at the end of the expansion stroke and capable of performing useful work when it is vented upon opening the exhaust valve at the end of the expansion stroke. Thus, closure of the motor intake valve shortly before the end of the expansion stroke is of benefit. 
     The high efficiency/low friction requirements and the compression/expulsion and filling/expansion characteristics are best met by using rolling diaphragm apparatus. 
     Thus, the expansion motor and compressor in the motor/compressor  12  are preferably based on rolling diaphragm positive displacement devices. 
     FIGS. 4 and 5 show different designs of an arrangement of the motor/compressor  12 . The motor/compressor  12  comprises the compressor  16  and the expansion motor  18  which are incorporated in structure including a single containing cylinder  20  which is closed at either end by end caps  30  and  32  with the motor and compressor volumes contained between rolling diaphragms  34  and  36 , the containing cylinder  20  and the end caps  30  and  32 . Spindle  22  serves to couple the displacements of the compressor diaphragm and expansion motor diaphragm and to define the shape of these diaphragms. 
     The containing cylinder  20  and/or spindle  22  (connecting the “pistons” of the compressor and motor) may be given a variation in radius as a function of longitudinal position along these elements. This variation may be selected so that the variation in volume in the compressor displacement volume  24  (located generally between the end cap  30  and the compressor diaphragm  34  and within the containment cylinder  20 ) and the variation in volume in the motor displacement volume  26  (located generally between the end cap  32  and the motor diaphragm  36  and within the containment cylinder  20 ) as a function of displacement of the spindle  22  may be related to the gas pressure in these volumes and the pressure in the volume within  20  and between the diaphragms  34  and  36  to provide a desired force schedule as a function of longitudinal spindle location. 
     FIG. 4 generally illustrates the concept and shows a variation in diameter as a function of longitudinal location for both the containing cylinder  20  and the surfaces of the spindle  22 . 
     FIG. 5 shows an embodiment wherein the diameter of the spindle increases relatively abruptly near the ends and decreases near the center of the spindle. It will be seen that the effective radius of motor “piston” represented by the rolling diaphragm  36  will increase as the diaphragm engages the radially enlarged end R (of radius R 1 ) of the spindle at the end of the motor expansion stroke. Likewise, the effective radius of the compressor piston represented by the roiling diaphragm  34  will decrease as the diaphragm  34  engages the necked down portion (of radius R 2 ) of the spindle  22 . 
     In both FIGS. 4 and 5, the motor intake valve  44  and motor exhaust valve  46  are opened such that the motor displacement volume  26  is open to the hyperbaric chamber  10  until near the end of the expansion stroke. At this point, it is preferred but not necessary that the expansion space be isolated by closing the motor intake valve  44  so that the gas in the expansion space may expand during the remainder of the stroke. In the embodiment of FIG. 5, the closure of valve  44  may coincide with the rolling of the diaphragm  36  onto the radial enlargement R on the spindle  22  so that, as the pressure in the motor displacement volume  26  drops on further expansion, the area on which the pressure in  26  increases tending to maintain a constant force acting through the spindle  22  on the compressor  16 . The decrease in radial diameter of the spindle  22  which simultaneously allows a decrease in the effective piston area of the diaphragm  34  at such time as the last of the compressed gas is being expelled from the compress displacement volume into the hyperbaric chamber  10  means that the force (equal to decreased area times the compressor output pressure) may be decreased in this part of the stroke. A great many force schedules as a function of longitudinal position of the spindle  22  may be obtained by tailoring the surface shapes of the spindle  22  and the containing cylinder  20 . 
     On the return stroke, the motor intake valve  44  is closed and the motor exhaust valve  46  is opened. Means such as the piston and spindle motor  50  shown in spindle  22  in FIG. 4 (with appropriate control valves, tubes for carrying the compressed motive gas and exhaust gas, etc. which are not shown), spring, air spring, etc., may be used to drive the spindle to expel expanded gas from the motor displacement volume  26  at the completion of the compression stroke to drawn fresh air into the compressor displacement space  24 . 
     FIGS. 6 a ,  6   b ,  6   c  and  6   d  show different steps in a stroke and schematically illustrate features of interest relative to the function of rolling diaphragm devices having variations in the radius of the inner surface of a containing cylinder  20 . 
     Considering first a compression stroke and beginning at the start of the compression stroke (FIG. 6 a ), the portion of the diaphragm  34  of the compressor “piston” farthest from the compressor end of the device is within a radially expanded region  52  such that the compression displacement volume  24  enclosed by diaphragm  34  includes a toroidal bulge  54 . The motor diaphragm  36  does not have a portion extending into the radially enlarged region  52  so that first motion of the spindle toward the compressor end of the device will pull the diaphragm enclosing the toroidal bulge of the compressor displacement volume  24  into the space between interior surface of the containing cylinder  20  and the exterior surface of the spindle  22 . 
     As noted above, as the spindle  22  moves from the position shown in FIG. 6 a  to the position shown in FIG. 6 b , the compressor diaphragm  34  is pulled so that the toroidal bulge  54  of the compressor displacement volume  24  space is “swallowed” in the space between the containment cylinder  20  and the spindle  22  in the compressor end of the device. The gas in the compression space preferably undergoes compression up to approximately the chamber pressure as the toroid is swallowed. By following this design guideline, it is possible for the entire first part of the stroke represented by FIGS. 6 a  and  6   b  to require an approximately constant pressure in the expansion motor displacement volume  26 . 
     Motion of the spindle  22  expels the already compressed gas through the compressor exhaust valve  42  into the hyperbaric chamber  10  with gas from the chamber flowing into the expansion motor  18  through motor intake valve  44  at the same time. 
     It is preferred that the expansion motor intake valve  46  be closed when the expansion diaphragm starts to form a toroidal bulge of the expansion space as shown in FIG. 6 c . While the pressure will now drop during further expansion, creation of the toroidal bulge during continued expansion will effectively increase the “piston area” so that the decreasing pressure in the expansion chamber will still be able to drive the spindle toward the compressor end of the device to complete expulsion of the compressed gas into the receiver such as hyperbaric chamber  10 . 
     The spindle  22  continues its motion until the apparatus is as shown in FIG. 6 d  whereupon the return stroke of the spindle  22  causes the diaphragms to follow the reverse sequence from FIG. 6 c  to FIG. 6 a  albeit with the valves appropriately opened and closed to suit the return stroke. It will be noted that a toroidal bulge  54  appears in the diaphragm of the expansion motor when the elements are in the position shown in FIGS. 6 c  and  6   d.    
       60  is the space inside the containing cylinder  20 , exterior to the spindle  22  and between the expansion motor diaphragm  36  and the compressor diaphragm  34 . As is known in the art, the diaphragms will be maintained in the proper shape if the space  60  is maintained at a pressure below the pressure in the compressor displacement volume  24  and the motor displacement volume  26 . 
     FIG. 7 discloses a hyperbaric chamber  10  used with a motor/compressor (not shown) according to the instant invention which hyperbaric chamber  10  is shaped and sized to allow cooking under a pressure above ambient while providing pressurized air for combustion by the flame  15 . A motor/compressor and appropriate connecting tubes  28  are provided similar to the arrangements shown in the other Figures. So that the walls of the hyperbaric chamber  10  may best resist the contained pressurized gas, the chamber  10  may be spherical. An access porthole  11  mounted in the wall of the hyperbaric chamber  10  may be opened for access to the interior of the chamber  10  or closed and sealed. 
     A gas collector  8  such as a hood is shown in FIG. 7 as located above the apparatus which contains the flame  15  which apparatus may be a camp stove or the like. The gas collector  8  thus serves as a vent or chimney for the products of combustion released by the flame  15  and conducts them to the expansion motor of the motor/compressor. Details of the camp stove are unnumbered but the figure is intended to show a burner, the flame  15  and a small pot located above the burner with the gas collector  8  located above all of these items. 
     The hyperbaric chamber  10  in FIG. 7 may be provided with ribbing in the chamber wall to help it maintain its shape when it is unpressurized such as when the access porthole is open when the flame  15  is lighted, extinguished or adjusted or the material being heated is moved. Any suitable supports for the spherical hyperbaric chamber  10  of this FIG. 7 may be used or rocks and/or snow may be piled up to provide the desired support. 
     FIG. 8 shows an embodiment of a expansion motor/compressor  12  wherein the expansion motor end of the spindle  22  is of a greater diameter than the compressor end of the spindle  22  so that the effective areas of the expansion motor “piston” is greater than the effective area of the compressor “piston” so that the motor will be able to move the spindle  22  on a compression stroke when the compressor displacement volume  24  and the expansion motor displacement volume  26  contain gas at the same pressure such as the gas pressure in the hyperbaric chamber  10 . When the pressures in these two volumes are decreased such as down to the ambient pressure, then the gas pressure acting on the effective piston area of the air spring will effect a return stroke of the spindle  22 . The compressor intake and exhaust valves  40  and  42  may be check valves as is known in the compressor art while the expansion motor intake and exhaust valves  44  and  46  may be actuated such as manually or by an available work output such as by a second expansion motor (as second expansion motor  6  shown in other Figures) or by a mechanism transmitting motion appropriately from the spindle  22 . 
     The air spring comprises air spring diaphragms  62  and  64  and tube  66  by which gas pressure is communicated into the cylindrical cavity  68  which contains the diaphragms  62  and  64 . The space  72  between the diaphragms  62  and  64  should be at a low pressure so that the diaphragms will stay flexed properly. Communicating passages through the spindle  22  such as the representative communicating passage  70  may be provided so that the space  60  and space  72  will be at the same pressure. 
     The end of tube  66  could terminate within the compressor displacement volume  24  with the desired air spring function obtained by making tube  66  long and of two diameters. Alternately, a constant diameter tube  66  could be used with a direct fluid communication made between the space in the hyperbaric chamber  10  and the cylinder cavity  68 . However, in both cases, the diameter of the diaphragms  62  and  64  and the tube  66  become small so that the length to diameter ratio of the diaphragms is great and the diaphragms do not want to roll freely. 
     Instead, a pressure reducer  74  may be used as shown in FIG. 9 to lower the pressure applied to the cylinder cavity  68  of the air spring thus allowing the use of larger diameter diaphragms. 
     FIG. 9 schematically shows expansion motor/compressor apparatus which comprises expansion/motor  12  and expansion motor/compressor  12 ′ wherein the compressor of the expansion/motor  12 ′ receives ambient air and compresses the air which is caused to pass through heat exchanger  17  whereby heat appearing in the compressed air due to the compression is transferred to the ambient air before the compressed air is passed to the intake of the compressor of the expansion motor/compressor  12  wherein the air is further compressed before passing to the hyperbaric chamber  10 . The air leaving the hyperbaric chamber  10  passes through the expansion motors of the expansion motor/compressors  12  and  12 ′ successively. Tubes, valves etc., are provided as needed and in accordance with teachings found hereinabove with respect to these elements. It will be seen that the arrangement of the elements in FIG. 9, apart from the heat exchanger  17  and the second expansion  15 ′ motor/compressor  12 ′ is substantially the same as shown in FIG.  1 . 
     It will thus be seen that the present invention allows efficient supply of compressed air to a living being or other exother microprocessor in a portable hyperbaric chamber. 
     Certain of the tubes  28  may be deleted. FIGS. 1 and 2 show such tubes as passing gas to and from the intake and exhaust valves of the compressor and expansion motor  12 . However, if the appropriate source of gas (pressurized or ambient) is immediately available at the intake or exhaust valves of the expansion motor/compressor, then that tube may be omitted. Thus, the valves  40  and  46  in the embodiments of FIGS. 4,  5 ,  6   a ,  6   b ,  6   c ,  6   d , and  8  and  9  and  5  are not connected to tubes. If any of the expansion motor/compressors  12  in these Figures is located within a hyperbaric chamber  10  (similar to the embodiment of FIG.  2 ), then tubes  28  will be connected to the valves  40  and  46 . 
     The following is a list of the elements and features discussed in my disclosure of my invention and their identifying numbers and labels: 
       1 —gas source or supply (typically the atmosphere) 
       2 —compressed gas source 
       3 —gas sink or receiver (typically the atmosphere) 
       4 —pressure relief valve 
       6 —second expansion motor 
       8 —gas collector (e.g., mask, hood, etc.) 
       9 —drive means (for the motor/compressor  12 ) 
       10 —hyperbaric chamber 
       11 —access port hole 
       12 —expansion motor/compressor (also  12 ′) 
       13 —heater 
       14 —living creature 
       15 —flame 
       16 —compressor 
       17 —heat exchanger 
       18 —expansion motor 
       20 —containing cylinder 
       22 —spindle 
       24 —compressor displacement volume 
       26 —motor displacement volume 
       28 —tubes 
       30 —end cap on compressor 
       32 —end cap on motor 
       34 —compressor diaphragm 
       36 —motor diaphragm 
     R 1 , R 2 —effective spindle radii 
     R—radial enlargement on spindle  22   
       40 —compressor intake valve 
       42 —compressor exhaust valve 
       44 —motor intake valve 
       46 —motor exhaust valve 
       50 —spindle motor 
       52 —radially expanded region 
       54 —toroidal portion of a diaphragm 
       60 —vacuum space 
       62 —air spring diaphragm 
       64 —air spring diaphragm 
       66 —air spring tube 
       68 —air spring cavity in spindle  22   
       70 —communicating passage between vacuum space  60  and space  72   
       72 —pressure reducer 
     I do not wish for my invention to be defined or limited by the above description but rather by the following claims.