Abstract: A pre-assembled, spring loaded, block and tackle window sash balance assembly is adapted for providing vertical support for a window sash running in an elongated, generally upright sash run having a generally C-shaped guide channel extending along its plow region. The assembly comprises a generally U-shaped housing for a block and tackle spring balance device. The assembly further includes spaced slide means which are discrete from the housing itself and which are slidably interengageable with the guide channel for removeably attaching the assembly to the sash run. Accordingly, the block and tackle balance assembly may be pre-assembled and then conveniently and efficiently attached to the sash run and supported in a position to provide spring balanced support for a window sash mounted in the sash run.

Abstract: An improved window sash balance and components thereof. The balance includes a spring fixed with respect to the frame and a pair of pulley blocks, each containing one or more pulleys. One block is fixed with respect to the frame and the other is disposed on the end of the spring. A cord is secured to one pulley block and trained over the pulleys. The other end of the cord terminates in a hook adapted to be received in an opening in the window jamb channel. The pulley block unit includes a pulley-receiving frame, one, two or three pulleys received therein, and at least one axle for rotatably supporting the pulleys within the frame. The block has one or two pulley-receiving openings therein, and suitable openings for reception and positioning of the axle. The block includes first and second pairs of assembly reference surfaces forming a part of the block and spaced radially from the axle opening.