Cable drum construction of door lift mechanism for multiple horizontal panel garage door with disproportionally heavy top portion

摘要

A cable lift mechanism for a multi panel, overhead garage door includes a drum having a spiral groove comprised of two adjacent sections that are generally coaxial with the longitudinal axis of the cable drum. The groove or grooves in a first section adjacent the attachment end of the cable to the drum have a lesser radius than the remaining grooves of the second section of the drum which have substantially equal radii of greater diameter than the first section radii. As a consequence, initial torque associated with lifting of a garage door is increased to lift a heavier upper or top panel or panels of a multi-panel garage door.