Abstract: A permanent magnet and an electromagnet actuated mechanical unit that may be secured to an engine block assembly to actuate at least one piston, connecting rod, and drive shaft that forms a part of the assembly to obtain rotary power.

Abstract: A compressor of the resonant type driven by an electrodynamic linear motor incorporates means to control the stroke and to improve the power factor. The spring-mass system of the compressor which is forced into vibration by the motor is arranged to have a selectively variable resonant frequency generally centered on the power line frequency. Means responsive to any overstroking are operative to vary the natural frequency of the spring-mass system, for example by varying the stiffness of the spring means, so as to oppose further overstroking and maintain a high power factor.