Patent ID: 7967051
Filing Date: 2011-06-28
Classification: E05D,E05Y

Abstract:
1. In an upward acting door, a counterbalance mechanism comprising: an elongated shaft supported generally above said door; spaced apart cable drums mounted on said shaft for rotation therewith, said cable drums supporting flexible cables depending therefrom and connected to said door respectively; at least one torsion coil spring having a plurality of coils and being operably connected to said shaft for exerting a torsional effort on said shaft to counterbalance at least a portion of the weight of said door to assist in opening movement of said door, said spring being anchored to a spring support member at an end opposite that connected to said shaft; and at least one sleeve member having an unobstructed central axis, said at least one sleeve member removably disposed between said shaft and at least some of the coils such that said at least one sleeve member is interchangeable with another sleeve member and engageable with the at least some of the coils of said spring, the at least one sleeve member being positioned to allow for reduction of a spring diameter of said spring and to inhibit further reduction of a coil diameter of the at least some of the coils to modify the rate of said spring as said spring is loaded.