| 摘要 |
A block and tackle window sash counterbalancing mechanism 2 disposed between a jambliner 4 and a window sash 6 includes a rod 12 around which a spring 20 and a nonrotating pulley system 30 are disposed. A head block 14 is disposed on the rod for attaching the balance to the jambliner and securing one end of the spring, and a slide block 18 is disposed at about the midpoint of the rod for securing the other end of the spring. The slide block acts in combination with a base block 16 and a pulley cord 28, to create the non-rotating pulley system. The slide block and the base block each have at least one cord-receiving channel 36 formed in a raised U-shaped member 34, for slidably receiving the pulley cord. The base block further includes a bore 52 for securing an end of the pulley cord, and is coupled via the pulley cord to a shoe 40, which moves in response to movement of the window sash. As the shoe moves, the cord slides within the channels, and the slide block moves toward the base block. The displacement of the slide block relative to the fixed head block, results in a change in the length of the spring such that the spring supports the new position of the window sash. |
