Patent ID: 7536943

Claim:
A steam engine or compressed air motor or compressed gas motor comprising: a piston adapted for reciprocation in cycles, inside a cylinder; said piston having a first end, and second end, and a piston sidewall communicating therebetween; said piston attached to a rod adapted for operative communication with a drive; said cylinder having a first end portion on one side of said piston and a second end portion on the opposite side of said piston; a first intake port communicating with said cylinder at said first end portion and a second intake port communicating with said cylinder at said second end portion; a first exhaust port communicating with said first end portion of said cylinder adjacent to said first intake port said first exhaust port having a determined size to exhaust steam therefrom at a first determined rate; a second exhaust port communicating with said second end portion of said cylinder adjacent to said second intake port said second exhaust port having a determined size to exhaust steam therefrom at a second determined rate; said first and said second determined rates thereby providing means to significantly reduce back pressure only at low speeds of said engine; a valve cylinder adjacent to said cylinder, said valve cylinder having steam inlet ports communicating therewith at first and second ends and also having an exhaust port communicating therewith at a center section; a slide valve slidably engaged in said valve cylinder; said slide valve having a first slide cylinder and a second slide cylinder engaged to said first slide cylinder a fixed distance therefrom defining a gap therebetween; said first slide cylinder having a top surface, a bottom surface, and a first sidewall surface communicating therebetween defining a first length; said second slide cylinder having a top surface, a bottom surface, and a second sidewall surface communicating therebetween defining a second length; said first intake port and said first exhaust port communicating with said valve cylinder at a first distance therebetween; said second respective intake and said second exhaust port communicating with said valve cylinder at a second distance therebetween; said slide valve translating in a reciprocal simple harmonic motion to said piston between said first and second ends of said valve cylinder during each cycle of operation of said steam engine; said first length defining an intake lap and exhaust lap in said first intake and first exhaust port; and said second length determining a second intake lap and exhaust lap in said second intake port and second exhaust port; and wherein steam is communicated to said first end portion and said second end portions of said cylinder through said first and second intake ports, and exhausted through respective separate said first and second exhaust ports of said cylinder during said cycle of operation, for total respective time durations of said first and second intake and exhaust laps determined by said slide valve moving in said harmonic motion.