Abstract: A spring drive system useful for window covers is disclosed, which comprises one or more coil spring drives or flat spring drives and the combination whose elements are selected from one or more of a group which includes (1) a band or cord transmission which provides varying ratio power transfer as the cover is opened and closed; (2) gear means comprising various gear sets which provide frictional holding force and fixed power transfer ratios; (3) a gear transmission which provides fixed ratio power transfer as the cover is opened or closed; (4) crank mechanisms; (5) brake mechanisms; and (6) recoiler mechanisms. The combination permits the spring drive force to be tailored to the weight and/or compression characteristics of an associated window cover such as a horizontal slat or pleated or box blind as the cover is opened and closed.

Abstract: A reversible control rod mechanism adapted for selectively and repeatedly rotating a shaft bidirectionally and thereby moving an attached load bidirectionally.

Abstract: A reversible pull cord mechanism adapted for rotating a shaft in one direction when the pull cord is pulled in a first direction and rotating the shaft in the opposite direction when the pull cord is pulled in a second direction.