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. The piston is drive upward by the
working fluid until an uppermost stop is reached wherein the piston head has cleared an exhaust port formed in the cylinder thereby allowing the working fluid to escape. A
mass is connected to the piston, in overhead relation, by a spring connection. When the piston reaches the uppermost stop,
momentum causes the spring connected
mass to continue upward thereby placing the spring in compression and maintaining the piston above the exhaust port so as to allow escape of the working fluid therethrough. Return of the
mass downward, caused both by gravity and spring energy, causes the mass to engage the piston and return the piston to its bottommost position whereby another
stroke is initiated.
Power output may be transferred to any suitable
system.