| 摘要 |
A compound counterbalance system for window sashes and the like, comprising: a biasing mechanism for easing operation of a window sash and the like, the biasing mechanism being movable at an inherently variable of force; a first biasing force transmission, connected intermediately of the window sash and the like and the biasing mechanism, for increasing the effective range of movement of the biasing mechanism; and, a second biasing force transmission connected intermediately of the first biasing force transmission and the biasing mechanism, the second biasing force transmission having a variable rate of operation predetermined to automatically compensate for the variability of the biasing mechanism, to provide substantial constancy of the biasing force. The biasing mechanism preferably comprises a linearly extensible and contractible spring. In one embodiment, both the first and second biasing force transmissions comprise pulley and cable systems. In another embodiment, only the second biasing force transmission comprises a cable and pulley system and the first biasing force transmission comprises a reduction gear assembly. In each embodiment, the variable rate of the second biasing force transmission comprises a generally conical, spiral-grooved pulley and a cable means affixed at one end to the pulley, affixed at the other end to the biasing mechanism and adapted to wind into and out of the groove. |
