1. Field of the Invention
The invention pertains to the field of windows. More particularly, the invention pertains to a window balance.
2. Description of Related Art
Block and tackle window balances are compact in size and relatively easy to install. They use a system of pulleys and an extension spring to convert high spring tension applied over a short working distance to a lower spring tension applied over a longer working distance. Both the spring and the pulley system are arranged within a rigid U-shaped balance channel. One end of the extension spring is anchored at a first end of the balance channel, while the other end of the extension spring is mounted to an intermediate pulley or middle carriage of the pulley system. The second pulley of the pulley system is anchored at the second end of the balance channel. Generally, the balance channel is mounted in the jamb of the window frame and the cord for the pulley system is attached to a sash shoe that slides in the jamb with the sash. However, this arrangement can be reversed with the cord anchored to the top of the frame and the sash shoe anchored to the opposite end of the balance channel. In all cases, the extension spring and the pulley system are sized so that a desired lifting force is applied to the window sash throughout the entire range of sash travel in the window frame.
Referring to FIG. 1, a prior art block and tackle balance 110 is constructed from a channel 112, commonly formed from sheet metal, into which a spring 114 is assembled. The first spring end 114A of the spring 114 may be affixed by various means proximate a first end 112A of the channel 112. The second spring end 114B of the spring 114 is attached to a middle carriage 116, the middle carriage 116 including the first portion of a multi-part balance tackle assembly. An end axle 118, including a second portion of the multipart balance tackle assembly is affixed proximate a second end 112B of the channel 112. In conventional block and tackle balances, a sash cord 120 is affixed at one end to the middle carriage 116 and twice passes alternatively around sheaves including the end axle 118 and the middle carriage 116, exiting finally at the second end 112B of the channel 112, to form a five-part balance tackle assembly. A cord terminal 122 is affixed to the second end of the sash cord 120, to facilitate attachment of the sash cord 120 in the application of the counterbalance and to prevent the second end of the sash cord 120 from being retracted into the second end of the channel 112. The cord terminal 122 is then mounted in a carrier or balance shoe, which slides up and down a frame channel when the window is opened and closed.
In another prior art block and tackle balance, a cord terminal is mounted in a balance shoe 128, the top surface of which is shown in FIG. 2. The balance shoe 128 has a gap 146 for insertion of the cord terminal (not shown) and a pocket 148 for mounting the cord terminal in the balance shoe 128. The balance shoe 128 has flexible tabs 132, which help to maintain the mounted cord terminal in the pocket 148 of the balance shoe 128. The tabs 132 are flexible primarily in a direction perpendicular to the long axis of the pocket 148. These tabs 132 do not sufficiently limit motion of a mounted cord terminal in the pocket and have been found to break during usage in a block and tackle balance assembly. These tabs 132 also bear some of the load from the upward force of the block and tackle assembly as applied to the shoe by the cord terminal during operation.
There is a need in the art for a balance shoe design that durably and flexibly maintains a cord terminal in a mounted position in a balance shoe of a block and tackle balance assembly.