Abstract:
A heat engine has a region within which a working fluid travels and an hydraulic fluid provided in a reservoir and the output from the heat engine drives the movement of the hydraulic fluid.

Description:
FIELD OF THE INVENTION 
   This invention relates to a new and improved linear hydraulic drive system for use with a Stirling engine. 
   BACKGROUND PRIOR ART 
   Resonant free piston Stirling engine systems are known in the art wherein the load apparatus is hydraulically driven from the periodic pressure wave of the engine. In such known systems the load apparatus is typically disposed within an incompressible fluid-filled space between a pair of flexible diaphragms which seal in and isolate the incompressible fluid, referred to herein as “hydraulic fluid”, from the Stirling Engine. One of the diaphragms is arranged to be acted on by the resulting pressure wave produced in the hydraulic oil and the other diaphragm is arranged as part of a gas spring. The pressure waves produced in the hydraulic oil are operative to reciprocally drive the movable member of the load apparatus in a direction along the same axis as that of the Stirling Engine. Such prior art engine-driven system assemblies were arranged in a stacked, coaxial relationship. While generally satisfactory, the diaphragms employed dramatically limited the useful life of such a device before maintenance was required. Other prior art arrangements had the load components immersed in the hydraulic oil making maintenance, service and repair difficult and expensive. 
   SUMMARY OF THE INVENTION 
   The hydraulic drive system of the instant invention is arranged and constructed to operate from the periodic pressure wave of the Stirling engine to pump the hydraulic fluid through a loop wherein a piston or motor drive is deployed to covert the hydraulic fluid flow to linear or rotary motion. In one embodiment, the hydraulic fluid is acted upon directly by the periodic pressure wave produced by the Stirling Engine. Alternately, the heat engine or Stirling engine may produce mechanical or electrical power that is used to power the hydraulic output system. 
   While the new and improved hydraulic power output and pump system of this invention is capable of use with a Stirling engine, it can be equally well applied in systems wherein fuel explosions or other periodic pressure pulses are available to provide the motive force. Also, while the invention will generally be described in connection with a hydraulic motor, it is understood that the invention could also be applied to compressors, pumps, pistons, linear alternators, and other like load apparatus. 
   In accordance with the instant invention, there is provided a new and improved hydraulic drive system for use with a Stirling engine which reduces the length of the engine-drive assembly. 
   In accordance with the instant invention, there is also provided a hydraulic drive system for use with a Stirling engine wherein the hydraulic oil is positively displaced so as to provide compact, light-weight drive means consisting of few components which can directly provide power to conventional pistons, hydraulic motors, or other like loads. 
   In accordance with the instant invention, there is also provided a hydraulic drive system for use with a Stirling engine which can be readily pressurized to 100 atm for use with a Stirling engine similarly pressurized so as to provide a very high specific power per unit weight and per unit volume in a compact, light-weight drive means. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other advantages of the instant invention will be more fully and particularly understood in connection with the following description of the preferred embodiments of the invention in which: 
       FIG. 1  is a cross section of a heat engine and a hydraulic drive system according to the instant invention; 
       FIG. 2  is a three dimension sketch of a hydraulic pump to be driven by a periodic pressure pulse source such as a Stirling engine wherein the pump employs a tangential inflow and a tangential outflow design; 
       FIG. 3  is a three dimension sketch of a hydraulic pump to be driven by a periodic pressure pulse source such as a Stirling engine wherein the pump employs a tangential inflow and bottom outflow design; 
       FIG. 4  is a three dimension sketch of a hydraulic pump to be driven by a periodic pressure pulse source such as a Stirling engine wherein the pump employs a bottom inlet through a three dimension elbow and a tangential outflow design; and, 
       FIG. 5  is a schematic drawing of an alternate embosiment of a heat engine and a hydraulic drive system according to the instant invention 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The preferred embodiment of the invention is shown in  FIG. 1 . A shroud  11  covers a series of louvred fins  1  which transfer heat from the hot combustion gasses  2  to the heat engine wall  5  and into the louvred fins  6  within the engine which in turn transfer the heat to the working fluid  7 . In addition, the hot combustion gasses  2  transfer heat to the upper end-cap  8  which in turn transfers this heat to the working fluid  7  within the engine. The hot combustion gasses are produced by the flame  3  which is fed by the gas ring burner  4 . The hot combustion gasses exit the system through the chimney  9 . In addition, radiation transfers heat from the flame  3  to the louvred fins  1 . The shroud  11  is supported by a series of louvred fins  12  which are in turn supported by an outer cover  13 . The louvred fins  12  act as a pre-heater for the combustion gasses thereby improving the burner efficiency and also act to support the heated section of the heat engine wall  5  which is weakened due to its heating. The outer cover  13  is substantially colder than the heat engine wall  5  and the louvred fins  12  and  1  serve to mechanically translate the support offered by the outer cover  13  to the heat engine wall  5 . Thus, a cooler metal serves to support the hotter wall. The louvred fins  14  serve as the regenerator section of the heat engine while the louvred fins  15  serve to remove heat from the working fluid and transfer it through the cold section of the heat engine wall  16  and into the hydraulic fluid  40 . It will be appreciated that other construction for a heat engine may be used with the hydraulic drive described hereafter. 
   The displacer  19  is supported by a shaft  20  which is supported by member  21  and is attached to an eccentric drive  18  which is mounted on an electric motor  37  which is immersed in the hydraulic fluid  40  within the main pump chamber  34  whereby eliminating the need for a pressure seal within the displacer drive system. 
   When the engine is hot and the displacer  19  moves to its bottom dead centre position the working fluid  7  expands thereby exerting pressure on the hydraulic fluid  40  within the main pump chamber  34 . The hydraulic fluid  40  begins to flow in response to this pressure. The hydraulic fluid  40  flows through the pipe  38  through the one way check valve  39  through pipe  22  through the heat exchanger  23  through pipe  24  into accumulator  25  through pipe  26  and through the motor  27  (which provides useful work—i.e. the output to a load) through pipe  28  into accumulator  29  through pipe  30  through check valve  31  through pipe  32  through the cooling section  17  and through pipe  33  back into the main pump chamber  34 . 
   The accumulator  29  maintains a pressure greater than the engine buffer pressure so that when the displacer travels to the top dead centre and the pressure within the engine is reduced to the buffer pressure, the hydraulic fluid  20  can flow through pipe  30  through check valve  31  through pipe  32  through the cooling section  17  and through pipe  33  back into the main pump chamber  34  to refill the main pump chamber  34  in preparation for the next cycle. The size of the reservoirs  25  and  29  and of the entire hydraulic piping must be sufficient to allow the rate of flow required to deliver the power output from the engine to the motor  27 . One major advantage of this system is that the accumulators  25  and  29  and the working fluid  7  can all be pre-pressurized to a high pressure thereby yielding a very high specific power output for a small engine. The hydraulic fluid may be an oil or an aqueous fluid. If the hydraulic fluid is an oil, then the preferred hydraulic oil is silicone oil. If the hydraulic fluid is aqueous, then the preferred hydraulic fluid comprises water, an antifreeze and a corrosion inhibitor. In some applications, the aqueous hydraulic fluid may be buffered. 
   Optional floating splash guard  35  minimizes splash within the engine. The member  21  also serves to trap a small amount of gas in a head space above the hydraulic fluid thereby ensuring that the fluid level can never rise above member  21 . Alternatively, a float mechanism may be employed to limit the amount of hydraulic fluid which will flow in during the refilling cycle although the buffer pressure should control this as well. 
   An embodiment for the hydraulic pump to be driven by a periodic pressure pulse source such as a Stirling engine wherein the hydraulic pump employs a tangential inflow and a tangential outflow design is shown in  FIG. 2 . In this embodiment the fluid to be pumped  40  enters the pump housing  45  through tangential inlet  41  and follows a spiral path  42  to the tangential outlet  43  where the fluid  44  exits the pump. A check valve (not shown) may be used at one or both of the inlet  41  and the outlet  44  to maintain unidirectional flow within the pump. 
   An embodiment for the hydraulic pump to be driven by a periodic pressure pulse source such as a Stirling engine wherein the hydraulic pump employs a tangential inflow and an axial outflow design is shown in  FIG. 3 . In this embodiment the fluid to be pumped  46  enters the pump housing  51  through tangential inlet  47  and follows a spiral path  48  to the bottom outlet  49  where the fluid  50  exits the pump. A check valve (not shown) may be used at one or both of the inlet  47  and the outlet  49  to maintain unidirectional flow within the pump. 
   An embodiment for the hydraulic pump to be driven by a periodic pressure pulse source such as a Stirling engine wherein the hydraulic pump employs an axial inflow and a tangential outflow design is shown in  FIG. 4 . In this embodiment the fluid to be pumped  52  enters the pump housing  58  through a bottom inlet  53  and through a three dimensional elbow  54  which sets the flow onto a spiral path  55  to the tangential outlet  56  where the fluid  57  exits the pump. A check valve (not shown) may be used at one or both of the inlet  53  and the outlet  56  to maintain unidirectional flow within the pump. 
   In the alternate embodiment of  FIG. 5 , a hydraulic power deliver system utilizes mechanical energy output from a heat engine. As shown therein, a heat engine  60 , which may the same or different to the heat engine shown in  FIG. 1 , has a linear to rotary converter. Linear to a rotary converter may be provided integrally with heat engine  60 . For example, as shown in  FIG. 5 , linear to rotary converter is designated by reference numeral  62  and is enclosed in container  64  which may be the outer shell of heat engine  60 . Mechanical energy from linear to rotary converter  62  is supplied by output shaft  66  which is drivingly connected to pump  68 . Output shaft may be directly drivingly coupled to pump  68  or, alternately, it may be indirectly coupled such as through a transmission or other power regulation means. In a further alternate embodiment, heat engine  60  may include a linear generator (e.g. the power piston of heat engine  60  may comprise a portion of a linear generator). In such a case, heat engine  60  would produce electricity which could be used to power pump  68 .