Patent ID: 7143547

Claim:
A motorized operator for a swing door comprising: a frame; a motor supported on said frame; a gear reduction drive mechanism supported on said frame and drivenly connected to said motor, said gear reduction drive mechanism including an output shaft having a part configured for connection to the door for moving said door in one direction and an opposite direction; a sprocket connected to said output shaft and drivingly engaged with a chain partially wrapped around said sprocket, said chain having opposed runs; a single coil spring supported on said frame; an elongated shaft supporting a member engaged with said spring at one end of said spring for transmitting forces to and from said spring through said elongated shaft; and a link member connected to said elongated shaft and directly connected to said opposed runs of said chain, whereby, in response to rotation of said output shaft in a first direction one of said runs becomes taut and the other run becomes slack to compress said spring and store energy in said spring, and said spring is operable to return said energy through said one run to said output shaft to rotate said output shaft in a second direction opposite to said first direction for assisting movement of said door.