Patent ID: RE39504

Claim:
A counterbalance system for an upward acting door for counterbalancing at least part of the weight of said door when said door is moved between open and closed positions, said system comprising: rotatable drums interconnected by an elongated shaft and supported on spaced-apart brackets adapted to be supported, respectively, generally above and adjacent to said door, said drums having flexible members wound thereon, respectively, the free ends of said flexible members depending from said drums and adapted to be connected to said door, respectively; a torsion spring mounted on said shaft between said drums having opposed end portions, one of said end portions being connected to one of said drums; an elongated tube disposed in sleeved relationship over said spring and operably connected to the other end portion of said spring; and a winding mechanism including a part held stationary with respect to one of said bracket brackets and operatively connected to said tube and operable to hold said tube stationary during normal operation of said counterbalance system, said winding mechanism being operable to rotate said tube, which rotates said other end portion of said spring to adjust the torque applied by said spring to said one drum.