Overhead door operator

摘要: An operator for an overhead door, such as a garage to raise and lower the door. The comprises chain drive which is rotated about upper pulleys powered by motor. Preferably, pair of spaced apart chains are employed. A carriage secured one or releasably connected connecting blocks extending outwardly from carriage. door thereupon raising lowering movement thereof. Each includes double-pitch link ends form continuous loop. block provided with releasable pin extends into securing chains. Removal each will allow manual hence, This construction precludes being driven sprocket where they would attempt around in event that limit switches not properly set. also allows manually disengage order move power failure.