Abstract: A steam reciprocating piston engine that uses a pressurized working fluid to drive first and second pistons in reciprocating power strokes is disclosed. A piston is configured for reciprocating motion within the cylinder and traverses between bottom dead center and top dead center positions. An uppermost stop is reached wherein the working fluid is allowed to escape the cylinder through one or more exhaust ports whereby the fluid travels through a closed loop circuit ultimately directing pressurized fluid back into the cylinder inlet. Momentum causes a spring connected mass to continue upward maintaining the piston above the exhaust port so as to allow escape of the working fluid. Return of the piston and mass is caused by opposite movement of a second piston whereby another stroke is initiated. Power output may be transferred to any suitable system.

Abstract: A steam reciprocating piston engine that uses a pressurized working fluid to drive first and second pistons in reciprocating power strokes is disclosed. A piston is configured for reciprocating motion within the cylinder and traverses between bottom dead center and top dead center positions. An uppermost stop is reached wherein the working fluid is allowed to escape the cylinder through one or more exhaust ports whereby the fluid travels through a closed loop circuit ultimately directing pressurized fluid back into the cylinder inlet. Momentum causes a spring connected mass to continue upward maintaining the piston above the exhaust port so as to allow escape of the working fluid. Return of the piston and mass is caused by opposite movement of a second piston whereby another stroke is initiated. Power output may be transferred to any suitable system.

Abstract: A rechargeable pneumatic reciprocating piston engine that uses a mixture of compressed air and water as the working fluid with a combination of gravity and spring force functioning to return the piston after completion of the power stroke whereafter repeated power strokes may be achieved from a single charge of compressed fluid thereby providing a rechargeable pneumatic engine capable of running for an extended period of time on a single charge is disclosed.

Abstract: A pneumatic reciprocating piston engine that uses a mixture of compressed air and water as the working fluid with a combination of gravity and spring force functioning to return the piston after completion of the power stroke is disclosed. A working fluid, preferably comprising a source of compressed air, is in fluid communication with the bottom portion of a generally vertically disposed cylinder via an inlet valve biased to a normally closed position. A piston is configured for reciprocating motion within the cylinder and traverses between bottommost and topmost positions. The piston is configured to engage the inlet valve when at the bottommost position thereby actuating the valve for a limited period of time to an open position so as to allow the introduction of compressed air and initiating of the power stroke to drive the piston upward. In a preferred embodiment, water is injected into the compressed air stream entering the cylinder to provide lubrication for the piston.