Patent ID: 7155778

Claim:
A block and tackle window balance device comprising: a channel comprising a first end and a second end; a top guide connected to the first end of the channel; a bottom guide connected to the second end of the channel, the bottom guide comprising: a back portion defining a receiving channel for receiving a portion of a window sash; and a substantially vertical portion opposite the back portion, the substantially vertical portion adapted to guide the balance device along a window jamb surface when the portion of a window sash is received in the receiving channel and the device is installed in a window jamb; a bottom guide roller rotatably mounted relative to and located at least partially within the bottom guide; a fixed pulley block unit connected to the channel; a translatable pulley block unit moveable within the channel; a spring comprising a first end and a second end, wherein the first end is fixed relative to the channel and the second end is connected to the translatable pulley block unit; and a cord comprising a first cord end and a second cord end, wherein the cord is threaded through the translatable pulley block unit and the fixed pulley block unit and extends around the bottom guide roller, the first cord end being attached to the translatable pulley block unit and the second cord end being attachable to a jamb.