Patent Publication Number: US-7707926-B2

Title: Pressure differential-driven engine

Description:
PRIORITY CLAIM 
   This application is a continuation-in-part of U.S. patent application Ser. No. 10/552,091, filed Sep. 11, 2006, now U.S. Pat. No. 7,246,550, which is a 371 of PCT/US04/10375, filed Apr. 4, 2004; each of which is hereby incorporated herein by reference in its entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to pressure differential-driven engines. More specifically, the invention relates to an engine using a pressurized working fluid to produce cyclic motion. 
   2. Related Art 
   Engines for converting energy from one form to another have been used for many years in a number of applications. Perhaps the best known example, the internal combustion (“IC”) engine, converts energy stored in the form of petroleum-based fuel into mechanical energy. IC engines have been successfully utilized to power vehicles, electric generators, lawn mowers, etc. Typical IC engines convert energy stored in fuel into mechanical energy by burning or detonating the fuel and extracting force generated in a cylinder/piston assembly. Typical IC engines use the force generated in the cylinder/piston assembly to drive some type of output device, such as a rotary crankshaft, a direct rotary output, or other power take-off device. 
   While IC engines have been used with success in a variety of applications, they can be problematic for a number of reasons. One such problem relates to the efficiency of the energy conversion process. For instance, typical IC engines have efficiency ratings in the range of 30-50%, with 50% considered to be highly efficient and generally only achievable by large, highly precise, and, therefore, costly engines. In addition, the process of converting fossil fuels into useful mechanical energy often results in large degrees of pollution released into the atmosphere, which can be detrimental to the environment in general, and particularly to humans who are exposed to or breathe the polluted air. As more and more IC-powered vehicles are produced and operated by an increasingly greater population, the levels of pollution produced by IC-powered vehicles is becoming an increasingly greater concern. In addition, IC engines necessarily create a great deal of heat, as they produce a series of combustion events which generate force and associated byproduct of heat. This can be problematic for applications which benefit from low-heat production engines. 
   In addition to IC engines, a variety of energy transducers have been developed for converting energy from one form to another. Examples of such transducers include heat engines, fluid compressors, hydraulic actuators, etc. 
   SUMMARY OF THE INVENTION 
   It has been recognized that it would be advantageous to develop an engine that produces usable mechanical energy with increased efficiency. In addition, it has been recognized that it would be advantageous to develop a mechanical engine that produces useable mechanical energy while minimizing the byproducts of pollution, high heat generation, and dangerous combustion byproducts. 
   The invention provides a pressure differential-driven engine, including an outer pressurizable enclosure and an actuator enclosure, disposed within the outer enclosure. An actuator can be disposed within the actuator enclosure and a portion of the actuator and the actuator enclosure can cooperatively define a pressurizable cavity cyclable between a first, high pressure state, and a second, low pressure state. The actuator and the actuator enclosure can collectively be restrained by at least one rail to linear, slidable motion within the outer enclosure. The engine can be operable to output usable energy as the pressurizable cavity cycles between the first and second pressure states. 
   In accordance with another aspect of the invention, a method for converting energy from a high pressure fluid into usable translational energy is provide, comprising the steps of: disposing an actuator enclosure within an outer, pressurizable enclosure; disposing an actuator within the actuator enclosure to thereby define a pressurizable cavity between the actuator and the actuator enclosure; collectively restraining the actuator and the actuator enclosure to slidable motion within the outer enclosure; creating a high pressure state within the outer enclosure; and creating a low pressure state within the pressurizable cavity to thereby cause the actuator and actuator enclosure to slide relative to the outer pressurizable enclosure. 
   Additional features and advantages of the invention will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front, partially sectioned view of a pressure differential-driven engine in accordance with an embodiment of the present invention; 
       FIG. 2  is a front, sectional view of one aspect of the engine of  FIG. 1 ; 
       FIG. 3  is rear view of one aspect of the engine of  FIG. 1 , oriented along a plane orthogonal to the generally parallel barrier plate and guide rails of the engine of  FIG. 1 ; 
       FIG. 4  is a more detailed view of one aspect of a lower, collapsible piston of the engine of  FIG. 1 ; 
       FIG. 5  is a front, partially sectional view of the engine of  FIG. 1  including an auxiliary power take-off device; 
       FIG. 6  is a front, sectional view of an actuator and actuator enclosure in accordance with another aspect of the invention; 
       FIG. 7  is a front, sectional view of another actuator and actuator enclosure in accordance with another aspect of the invention; 
       FIG. 8  is a front, sectional view of another actuator and actuator enclosure in accordance with another aspect of the invention; 
       FIG. 9A  is a top view of two of the actuators of  FIG. 8  in a circuit configuration; 
       FIG. 9B  is a top view of the actuators of  FIG. 8  shown in post-actuation position; 
       FIG. 10  is an alternate embodiment of the actuators of  FIG. 8 ; 
       FIG. 11  is a schematic, partially sectioned side view of a pair of actuators and actuator enclosures in accordance with an embodiment of the invention; and 
       FIG. 12  is a schematic, top view of the pair of actuators and actuator enclosures of  FIG. 11 . 
   

   DETAILED DESCRIPTION 
   Reference will now be made to the exemplary embodiments illustrated in the drawings, which are illustrative of the underlying scientific principles thereof; and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Alterations and further modifications of the inventive features illustrated herein, and additional applications of the principles of the inventions as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the invention. 
   As illustrated in  FIG. 1 , a system, indicated generally at  10 , in accordance with the present invention is shown for a pressure differential-driven engine. The system includes an outer, pressurizable enclosure or vessel  12 , which can be configured to be pressurized with a fluid, such as pressurized air, or other gas or liquid. Disposed in the vessel  12  is a pressure barrier plate  14  which, in the embodiment shown, is configured to be stationary relative to the pressure vessel and can be slanted at an angle relative to a lower surface of the pressurizable enclosure or vessel  12 . The pressure barrier plate  14  can include a highly polished or finished upper and lower surface  14   a  and  14   b , respectively. 
   Disposed adjacent the barrier plate  14  is at least one actuator enclosure  16  which can enclose an actuator (not visible in  FIG. 1  but discussed in further detail below). One or more guide or support rails  18  can be disposed adjacent and parallel to the barrier plate. As discussed in more detail below, the actuators enclosed by enclosures  16  can be slidably coupled to the guide rails to constrain the actuator to sliding in a slanted (with respect to the bottom of the enclosure) path along the guide rails  18 . Actuator enclosure seals  22  can be disposed between the actuator enclosures  16  and the barrier plate  14  to facilitate low-friction sliding by the enclosures over the barrier plate; and to allow a substantially pressure-tight cavity to be created within the enclosure. Connecting rods  24  can be utilized to connect the actuator enclosures  16  with a lower, collapsible piston assembly  44 , as discussed in more detail below. In addition, the connecting rods  24  can provide vertical alignment and stability to the actuator enclosures  16  and can be coupled to and connect with guide or support rails  18 , as discussed in more detail below. 
   In use, the pressurizable enclosure or vessel  12  is pressurized with a fluid such as pressurized air, so that the various components enclosed within the vessel are substantially all exposed to a first, higher pressure. In the embodiment shown in  FIG. 1 , a valve  15  can disposed between a high pressure source (not shown) and the vessel to facilitate pressurization of the vessel. By means that are discussed in more detail below, a pressure differential is created within the actuator enclosure which causes the actuator and actuator enclosure  16   a  to slide angledly up or down the barrier plate. In one embodiment, a lower pressure is established in a pressurizable cavity formed between the actuator, the barrier plate, and the actuator enclosure, which causes a pressure differential condition on the actuator and causes the actuator to move. 
   Thus, as the actuator and actuator enclosure  16   a  move upwardly and downwardly along the barrier plate, cyclic motion is produced which includes both a vertical and a horizontal component. As discussed in more detail below, in one embodiment this motion is translated into cyclic horizontal motion, which can be translated to a power take-off device and used to perform mechanical work. 
   As shown in  FIG. 1 , both an upper enclosure  16   a  and a lower enclosure  16   b  can be provided. Thus, while multiple actuators and actuator enclosures are not necessary, by including one actuator and actuator enclosure on the top of the barrier plate and one on the bottom of the barrier plate, cyclic motion between upward and downward slanted motion can be achieved by alternately creating a pressure differential condition on the upper and lower actuators. Thus, a pressure differential in the top actuator enclosure  16   a  will cause downward slanted motion and a pressure differential in the bottom actuator enclosure  16   b  will cause upward slanted motion. By alternately energizing the two actuators, rapid cyclic motion up and down the barrier plate  14  and guide rails  18  can be effectuated. 
   While the discussion herein will primarily focus on a lower and a higher pressure condition used to create the desired pressure differential, it is to be understood that more than two pressure conditions can be utilized, including variable high or low pressure conditions. However, to simplify the discussion herein, reference will be made to a high pressure, which can be above atmospheric pressure, and a low pressure, lower than the high pressure, which can include, but is not limited to, atmospheric pressure. By establishing the low pressure as atmospheric pressure, only one pressure source, a high pressure source, need be utilized, as the low pressure simply exists in the atmosphere surrounding the vessel  12 . 
   Shown in greater, sectional detail in  FIG. 2 , the system can include an upper actuator  17   a  and a lower actuator  17   b , each of which can be disposed or enclosed within actuator enclosures  16   a  and  16   b , respectively. While actuators and actuator enclosures of any type can be utilized in the present invention, in one embodiment the actuators include a piston-like configuration and are disposed within cylinders, similar to pistons and cylinders which might be included in an internal combustion engine. While not so limited, in the interest of simplicity the following discussion will refer to the actuators as pistons and the actuator enclosures as cylinders. It is to be understood, however, that the invention is not so limited and that other devices can be used for either the actuators or actuator enclosures, as is known in the art. The embodiment of the pistons  17  shown in  FIG. 2  includes pistons having a hollow interior portion, which may be utilized to reduce overall weight and material requirements. However, a solid piston can also be utilized, as can a combination of the two. 
   To further simplify the discussion herein, reference will be primarily made to the piston  17   a  and cylinder  16   a  disposed on top of the barrier plate  14 . It is to be understood that no limitation of the invention is thereby intended, as multiple pistons can be utilized in the present invention, and can be disposed on top or bottom of the barrier plate, as shown in the various figures. 
   As shown in  FIG. 2 , piston seals  28  can be disposed between piston  17   a  and its respective cylinder  16   a . The piston seals serve to limit all or part of the sides of the piston  17   a  from being exposed to a high pressure condition. In this manner, only a top, high pressure exposure surface  30   a  of the piston is substantially continually exposed to the high pressure condition present within the vessel  12 . As indicated in  FIG. 2 , a pressurizable cavity or pressure exchange compartment  34  is formed or defined by a bottom  32   a  of the piston  17   a , the barrier plate  14 , the actuator enclosure seals  22 , and lowermost piston seals  28 . The pressurizable cavity  34  is utilized to alternately expose the bottom  32   a  of the piston  17   a  to the high and the low pressure condition to create an alternating pressure differential condition on the piston. The pressurizable cavity is thus cyclable between a first, higher pressure state and a second, lower pressure state. 
   It will be appreciated that, while movement of the pistons is facilitated by creating a low pressure condition between the barrier plate and piston, when a high pressure condition is present between the two, a more or less “neutral” pressure condition is imposed on the piston. Thus, when high pressure is acting on both the bottom and top of the piston, the pressure forces on the piston are substantially neutralized, and the piston is not disposed to move. When an upper and a lower piston are utilized, a neutral pressure differential on one piston will not significantly impede motion undergone by the other piston. In one embodiment, a neutral pressure differential and a positive pressure differential will alternately be applied to an upper and a lower piston, to alternately move both pistons upwardly and downwardly on the barrier plate between the guide rails. 
   It will also be appreciated that, as the low pressure condition created in the pressurizable cavity results in movement of the pistons, creating a pressure differential between the top and bottom of a piston can be done with relatively little fluid exchange. That is, the pressurizable cavity can be made substantially small in volume, as only a small pocket of low pressure fluid may be required to create an effective pressure differential. Thus, the present invention can be used to provide cyclic movement of the piston/cylinder assembly with relatively low fluid exchange volumes. 
   As discussed in more detail below, particularly in relation to  FIG. 3 , the piston  17   a  can be limited or constrained from absolute vertical movement by guide rails  18 . While the guide rails prevent or limit absolute vertical movement, the piston  17   a  is free to slide along the guide rails in a trajectory substantially parallel to the barrier plate  14 . Thus, as the pressurizable cavity  34  is exposed to the low pressure condition, a force differential results upon the piston  17   a , as the top is exposed to the high pressure force F while the bottom is exposed to the low pressure. This force, which tends to move the piston downwardly, is transferred to the guide rails  18  and the piston moves down the guide rails, which are slanted at approximately the same angle as the barrier plate  14 , with a horizontal component of movement X. Thus, in the embodiment shown, the guide or support rails are substantially parallel to the pressure barrier plate. 
   The low pressure condition created in the pressurizable cavity  34  can be achieved in a variety of manners utilizing a variety of devices. In one embodiment, as shown in  FIG. 2 , a channel  36  or other opening can be formed in the piston. The channel can be operatively coupled to a valve  38  which in turn can be coupled to a hose  39  which is open to the low pressure (as shown in  FIG. 1 ). Thus, when a low pressure condition is desired, the valve  38  can be opened, at which point the high pressure fluid previously contained in the cavity will be vented to low pressure, and a low pressure condition will result in the cavity which causes a pressure differential resulting on the piston. The pressure differential resulting on the piston will then cause the piston to move down the guide rail. 
   The hose  39  can be any type known to those skilled in the art, and in one embodiment includes a relatively flexible material that allows the hose to easily bend and move to enable the hose to follow the movement of the piston and cylinder. Similarly, a variety of means or methods known to those skilled in the art can also be used to create a low pressure condition in the pressurizable cavity  34 . For example, it is contemplated that the pressure barrier plate  14  can include a channel or other opening which can introduce the low pressure condition into the cavity. Other suitable valving and control devices (not shown) can also be included to control the pressure condition within the pressurizable cavities of the piston/cylinder assemblies. As the pressure differential-driven engine may be operated at high speed cycles, a computer-controlled valving system (not shown) may be utilized to facilitate accurate and timely control of the pressure differential. In addition, it is contemplate that a valving or switching system (not shown) can be associated with each of the pistons to facilitate exchange of low pressure and high pressure air between the pressurizable cavities. In this manner, introduction of external air or fluid into the vessel  12  can be reduced or eliminated, and the system can re-use high pressure and low pressure fluid. 
     FIG. 3  illustrates one aspect of the present invention as viewed along a plane parallel to the barrier plate  14  and the guide rails  18 . Thus, the barrier plate  14  and guide rails  18  extend into a plane orthogonal to the page on which  FIG. 3  is disposed. Shown in  FIG. 3  are connecting pins  40  which can be coupled to the piston  17   a  and extend outwardly through channels  42  formed in the cylinder  16   a . The channels  42  can be sized slightly larger than the pins  40 , to allow some movement of the piston without interfering contact with the cylinder  16   a . The pins  40  can be coupled to the guide rails  18  in any manner known to those skilled in the art, and are shown in  FIG. 3  as terminating in annular bearings  44 . Of course, any suitable bearing or other connecting means can also be used. 
   It will be appreciated that, upon being subject to a pressure differential condition, that is, a condition in which the bottom  32  of the piston  17   a  is exposed to the lower pressure state in the pressurizable cavity (not visible in  FIG. 3 ), the piston will apply a downward force in reaction to the pressure force on the top of the piston. This force, which is transferred to slanted guide rails  18 , results in a force component along the longitudinal axis of the guide rails, which in turn results in the piston sliding downwardly between the guide rails. Because the cylinder  16   a  is disposed around the piston  17   a , movement of the piston results in movement of the cylinder. Movement of the cylinder results in downward motion and force applied by the connecting rods  24  to a lower, collapsible piston assembly  44 , as discussed in more detail below. 
   Effectuation of cyclic movement of the pistons in accordance with the embodiments discussed above provides an upper piston assembly  45  that varies between upward and downward movement along or between the slanted guide rails  18 . In order to utilize this cyclic movement, a power take-off device can be operatively coupled to the upper piston assembly. As shown in the various figures, and in more detail in  FIG. 4 , in one embodiment of the invention, the power take-off includes a lower, collapsible piston assembly  44 . The collapsible piston assembly can include an upper piston  46  disposed over or within a lower piston  48 . Seals  50  can be disposed between the upper  46  and lower  48  pistons to limit high pressure fluid from entering the piston assembly. Low pressure shaft  52  can be in fluid communication with the piston assembly  44  to provide a substantially constant low pressure condition within the piston assembly. The low pressure shaft can be vented to an outer, atmospheric pressure state outside of the vessel  12 . One or more outer seals  54  can be disposed in the wall of the vessel to enable lateral travel of the low pressure shaft as the piston assembly moves laterally in the opening in the vessel wall. Linear guide rail  56  can be disposed adjacent the lower piston assembly  44  to provide support for the assembly, and can be coupled to the lower piston assembly through low friction couplings such as bearing assemblies (not shown). 
   As will be appreciated from viewing  FIG. 4 , as the upper piston assembly moves along the barrier plate  14  and guide rails  18 , the connecting rods  24  apply an upward or downward force, respectively, to the top piston  46  of lower piston assembly  44 . Thus, the collapsible piston assembly  44  either collapses or expands, depending on the slanted, lateral movement of the upper piston assembly. Correspondingly, the lateral component of movement of piston assembly  44  causes the low pressure shaft  52  to move laterally side-to-side. As the low pressure shaft  52  provides a substantially constant low pressure state inside the piston assembly  44 , the upper and lower pistons can move relative to each other in a substantially unimpeded manner. Cyclic lateral movement of the shaft  52  can be utilized by an auxiliary power take-off device, such as the rotary crank assembly  70  shown in  FIG. 5 . 
   The size of the lower piston assembly  44  can be altered according to particular applications. For instance, because the upper surface of the upper piston  46  of the lower piston assembly is exposed to the high pressure condition within the vessel, it may be desirable to reduce this surface area, or alter the shape of the exposed surface area, to limit a downward force being applied to the upper piston which may oppose upward movement of the upper piston assembly  45 . 
   As shown at  60  in  FIG. 1 , an additional guide or support rail can be included in the system and can be coupled to the upper  45  and lower  44  piston assemblies or connecting rods  24  to provide additional support or guidance to the components of the system. 
   As shown in  FIG. 5 , an auxiliary power take-off device can be operatively coupled to or associated with the pressure differential-driven engine. The power take-off device  70  shown in  FIG. 5  includes a rotary crank coupled to the shaft  52  in a manner known to those skilled in the art. It is contemplated that any power take-off device can be associated with the present invention, and can be disposed within or external to the vessel  12 . For example, it is contemplated that an electric generator can be associated with the engine to convert cyclic movement of the piston assemblies into electric power. By disposing the generator within the vessel  12 , output of mechanical motion from the vessel can be limited, as it may be necessary only to output an electrical wire from the vessel to which electrically powered devices can be connected. This can be advantageous in that high-quality, dynamic seals may be necessary for mechanical devices moving in and out of openings in the pressure vessel, whereas simpler seals may suffice for devices which are not moving relative to the vessel, such as a power chord. 
   In addition to the collapsible piston assembly discussed above, it is contemplated that a number of power take-off devices can be associated with the pistons  17  and cylinders  18  to convert the cyclic movement of the piston/cylinder assemblies into usable mechanical energy. Examples can include belts or chains associated with the piston/cylinder assemblies to convert the cyclic motion into rotational motion of the chain or belt. Other examples can include ratchet and pawl assemblies, gear and sprocket assemblies, rotary motion converters, etc. 
     FIGS. 6 and 7  illustrate piston and cylinder assemblies utilized in other aspects of the invention. In  FIG. 6 , the piston  80  is configured as a “cap” type device that can be fitted within a cylinder  82 . As it is the area of the upper high pressure exposure surface of the piston  80  that is exposed to the high pressure condition when a pressure differential exists in the pressurizable cavity, increasing or maximizing the surface area of the piston can result in higher power being achieved with lower internal (high) pressure being required in the vessel. Similarly, as shown in  FIG. 6 , the top of the piston can be made parallel to the barrier plate and guide rails, or, as shown in  FIG. 7 , the tops of the pistons  86  can be made substantially parallel to true horizontal. 
   As the force or energy output by the engine is primarily a function of the high pressure condition within the vessel, the magnitude of the high pressure can be varied according to desired results. For example, if it is assumed that the surface area of a top of a piston is approximately 50 square inches, a high pressure with a magnitude of 200 psi will apply a force of approximately 10,000 pounds to the top of the piston. By varying either the surface area of the piston or the high pressure magnitude, the force applied to the piston when in the pressure differential condition can be varied. For example, by doubling or halving the high pressure magnitude, the force on the piston can correspondingly be doubled or halved. Thus, the desired output of the engine can be altered and tailored to specific applications. 
   The barrier plate  14  has been described as being substantially stationary relative to the vessel  12 . As shown in  FIG. 1 , for example, the barrier plate can be coupled to the walls of the vessels to hold the plate stationary. In other embodiments, the barrier plate and guide rails can be disposed within a removable frame which can be coupled inside the vessel. In this manner, an engine can be provided that can be relatively easily dismantled, maintained, and repaired. 
   While the barrier plate and guide rails have been shown and described as being slanted from true vertical or horizontal, it is contemplated that they can be of any angle, including vertical or horizontal. In one embodiment the barrier plate and guide rails are formed at angle of about 22 degrees from horizontal. In another embodiment, the angle is 45 degrees. In another embodiment, the angle can range from about 8 degrees to about 45 degrees, depending on particular applications of the engine. 
   Turning now to  FIG. 8 , an alternate piston and cylinder assembly is shown, wherein piston  170  is disposed within cylinder  160 . In this embodiment, the barrier plate  14  and guide or support rail  18  are aligned substantially parallel to a bottom surface of the vessel  12  (not shown in  FIG. 8 ), which corresponds to a substantially horizontal orientation with respect to  FIG. 8 . An upper, high pressure exposure surface  171  of the piston is aligned at an oblique angle with respect to the bottom surface of the vessel (i.e., the upper surface is aligned at an oblique angle with respect to horizontal). Thus, in this embodiment, it is the upper surface of the piston that provides an angled component of pressure-induced force to the assembly. An extension rail  101  extends downwardly from the piston and is slidably and rigidly coupled to guide or support rail  18 . The extension rail shown can be coupled to the rear of the piston in a similar manner as that illustrated discussed in relation to  FIG. 3 . 
   As will be appreciated from  FIG. 8 , the force F 2  applied to the upper surface  171  of piston  170  includes both a vertical and a horizontal component. The vertical and horizontal components of this force are transferred to support rail  18 , which results in horizontal movement of the piston and the cylinder to the left of the page. That is, the piston and cylinder have a direction of positive drive to the left of the page, as that is the direction in which the piston will travel when subjected to a low pressure state in pressurizable cavity  34 . Hose  39  can provide venting and pressurizing of the cavity, as discussed in the embodiments above. 
   As cylinder  160  includes a generally larger frontal outer section  130  (to the left of the page of  FIG. 8 ) than an outer rearward section  132  (the outer section to the right of the page of  FIG. 8 ), the cylinder may be subject to a force differential which may tend to inhibit leftward travel of the cylinder and piston. To aid in overcoming this tendency, piston  120  can be disposed in cylinder  122  which can be coupled to or disposed adjacent to the frontal face  132  of the cylinder  160 . A substantially constant low pressure state can be maintained in cavity  124  to at least partially remove the larger force component on this face  130  of cylinder  160 . Restraining member  126  can be utilized to prevent piston  120  from collapsing upon the low pressure state cavity  124 . 
   The use of restraining member  126  is shown in more detail in top view in  FIG. 9A . In the embodiment of  FIG. 9A , a first piston  170   a  and first cylinder  160   a  are disposed on barrier plate  14   a . A second piston  170   b  and second cylinder  160   b  are disposed on barrier plate  14   b . Each of the pistons have a direction of positive drive to the left of the page of  FIG. 9A . Each of the pistons includes a frontal piston (or auxiliary actuator)  120   a ,  120   b  which are coupled and held from relative movement of each cylinder  160   a ,  160   b , respectively, by restraining member (or connector)  126 . As the frontal face of each piston  120   a ,  120   b  is constantly subjected to the higher pressure state within the vessel  12 , the restraining member  126  is held in a substantially constant tension state about pulleys or guide wheels  130 . Similarly, the rear face  132   a ,  132   b  of each cylinder is restrained by restraining member  128 . Thus, when the piston and cylinders are in a neutral, stationary state, the restraining members restrain pistons  120   a ,  120   b  slightly apart from each cavity  124   a ,  124   b , effectively restraining the pistons from collapsing on their respective cavities. 
   In one exemplary use, the pistons can originally be held in a neutral, i.e., immobile state. Upon creating a low pressure state in the pressurizable cavity of first piston  170   a  and cylinder  160   a , the first piston will move to the left of the page of  FIG. 9A . After reaching full travel to the left, the pressurizable cavity of the first piston can be neutralized (i.e., pressurized to equal the high pressure state of the vessel), causing the first piston to stop moving. At that point, the lower piston  170   b  and cylinder  160   b , which will have moved in neutral state to the position shown in  FIG. 9B , can be energized to drive it to the left of the page of  FIG. 9B . This cycle can then be repeated to create cyclical motion of the piston assemblies over the barrier plates. 
   An alternate embodiment of the piston arrangement of  FIGS. 9A and 9B  is shown in  FIG. 10  (note that barrier plates and guide or support rails are omitted from this view). In this aspect of the invention, a master restraining member  180  can be disposed about pulleys or guide wheels  131 . The master restraining member can include a chain or generally slack-resistant conveyor structure to which each cylinder  160   a ,  160   b  can be substantially rigidly connected. The master restraining member can stabilize the travel path of the cylinders and can also be used as a power take-off device. For example, the master restraining member can be coupled to sprockets or other known devices to convert the cyclic, back-and-forth motion of the cylinders and pistons into useable mechanical energy. 
   The various components described herein can be formed of a variety of materials. However, in one embodiment, the barrier plate is formed of high-strength steel and provided with a highly polished surface to facilitate easy sliding of the cylinders over the surfaces of the barrier plate. Similarly, any of the surfaces described herein can include a highly polished finish to facilitate low friction movement of other components. Also, where relative motion between two components is illustrated, it is contemplated that bearing structures as known in the art can be incorporated to improve efficiency of the engine by reducing losses due to friction. 
     FIGS. 11 and 12  illustrate yet another aspect of the present invention. The inventive concepts illustrated in  FIGS. 11 and 12  share many of the features and advantages of above-discussed embodiments, particularly the embodiments illustrated in  FIGS. 8 ,  9 A,  9 B and  10 ). Importantly, it is noted that, while  FIGS. 11 and 12  adequately disclose and enable the inventive concepts associated therewith, for the sake of clarity some physical components associated with the embodiments illustrated in  FIGS. 11 and 12  are omitted. For example, in order for the system to function properly, pressurizable cavities  225   a  and  225   b  will, of course, be in operable communication with one or more vent/pressurization lines (not shown in these figures) and a valve system (not shown in these figures). Also, rails  200   a  and  200   b  will be rigidly coupled to the pressure vessel  12 : also these rails are omitted from view in  FIG. 12 . Similarly, while the auxiliary pistons or actuators  224   a  and  224   b  are shown in relatively close proximity to one another, it is to be understood that the connecting member  230  that connects the auxiliary pistons may, in fact, be much longer. In some aspects of the invention, the connection member  230  will be serpentine in nature, similar to the connectors  126 / 128  of  FIG. 9A . 
   In the embodiment of  FIGS. 11 and 12 , the system includes outer pressurizable enclosure  12  and at least one actuator enclosure  272   a ,  272   b  disposed therein. An actuator  270   a ,  270   b  can be disposed within each actuator enclosure. The actuators and actuator enclosures each define a pressurizable cavity  225   a ,  225   b  that can be cyclable between a first, high pressure state, and a second, low pressure state. The actuator and actuator enclosure can collectively be restrained by at least one rail  200   a ,  200   b  to linear, slidable motion within the outer enclosure. The engine can be operable to output usable energy as the pressurizable cavity cycles between the first and second pressure states (note that the power output system is not illustrated in these figures). 
   This embodiment differs from other embodiments in that a barrier plate is not required for this system. Instead, one or more independent cylinder/piston assemblies is provided. In the embodiment shown, cylinder  272   a  is operably coupled to a chain drive  280  (or some functionally similar structure), as is cylinder  272   b . Piston  270   a  is slidably coupled (by way of slidable coupler  202   a ) to rail  200   a . Piston  270   b  is slidably coupled (by way of slidable coupler  202   b ) to rail  200   b . Each of the pressurizable cavities  225   a ,  225   b  is varying in volume, depending upon the position of the respective piston within the cylinder. It will be appreciated that, as cylinder/piston assembly  270   a / 272   a  moves to the right of the page of  FIG. 11 , the piston  270   a  will move downward into cylinder  272   a . The reverse is true of cylinder/piston assembly  270   b / 272   b.    
   Thus, in the case where a low pressure state exists in pressurizable cavity  225   a , piston  270   a  will be driven downwardly into cylinder  272   a . As the piston is driven downwardly, the slanted rail  200   a  forces the assembly to move in the direction of the right of the page of  FIG. 11 . As the two cylinder/piston assemblies are coupled by way of connector  230 , and pistons  224   a  and  224   b  (as discussed in more detail below), they complement one another in movement. In practice, a low pressure state can first be established in cavity  225   a  (while a high pressure, or neutral, state is maintained in cavity  225   b ). This will result in piston  270   a  being driven downward into cylinder  225   a  while piston  270   b  tends to remain in place relative to cylinder  272   b . Thus, only the leftmost cylinder/piston assembly is in a non-neutral force condition, and it will drive both cylinder/piston assemblies to the direction of the right of the page of  FIG. 11 . 
   Once travel to the right of the system has been completed, cavity  225   a  can be pressurized (causing that piston/cylinder assembly to be neutralized), and a lower pressure state can be established in cavity  225   b  (causing that piston/cylinder assembly to drive both units to the direction shown as the left of the page of  FIG. 11 ). These conditions can be cycled continuously to continuously drive the system back-and-forth within the pressurizable enclosure  12 . As discussed in detail above, this continuous cycle of motion can be extracted by a power take-off system so that the energy can be utilized by an external system. 
   Similar to the system described in connection with  FIGS. 8 ,  9 A,  9 B and  10 , in the event a pressure differential exists on the outer surfaces of cylinders  272   a  and  272   b , the respective piston/cylinder assemblies may tend to be forced in one direction or another, leading to inefficiencies in the system. Auxiliary piston/cylinder assemblies  222   a / 224   a  and  222   b / 224   b  can coupled to sides of the cylinders  272   a ,  272   b  to offset this condition. The auxiliary pistons  224   a ,  224   b  can be coupled via connector  230  and prevented from collapsing upon the lower pressure state established in the pressurizable cavities  231   a ,  231   b . Thus, connector  230  is generally maintained in a substantially constant state of tension, restraining each piston  224   a ,  224   b  from moving relative to respective cylinder  222   a ,  222   b.    
   Each cylinder  272   a ,  272   b  is generally coupled to chain  280  on only one side of the chain (as shown in top view in  FIG. 12 ), such that the chain can provide a positive transfer of the to-and-fro motion of the cylinder/piston assemblies. It is to be understood that the chain drive/restraint system can be replaced with a variety of similar structures known to those having ordinary skill in the art. 
   In addition to the structural features discussed, the present invention also provides a method for converting energy from a high pressure fluid into usable translational energy, comprising the steps of: disposing an actuator enclosure within an outer, pressurizable enclosure; disposing an actuator within the actuator enclosure to thereby define a pressurizable cavity between the actuator and the actuator enclosure; collectively restraining the actuator and the actuator enclosure to slidable motion within the outer enclosure; creating a high pressure state within the outer enclosure; and creating a low pressure state within the pressurizable cavity to thereby cause the actuator and actuator enclosure to slide relative to the outer pressurizable enclosure. 
   It is to be understood that the above-referenced arrangements are illustrative of the application for the principles of the present invention. It will be apparent to those of ordinary skill in the art that numerous modifications can be made without departing from the principles and concepts of the invention as set forth in the claims.