A driving mechanism transforms continuous longitudinal reciprocation of a piston in a chamber into unidirectional rotation. The mechanism utilizes a closed wave-shaped groove defined in either the cylinder or the chamber and adapted to receive guiding members projecting from the other of the piston and...http://www.google.com/patents/US5467684?utm_source=gb-gplus-sharePatent US5467684 - Rotary piston driving mechanism
