Patent ID: 7966770

Claim:
A tilt-in window having a frame, a guide track in the frame, a window sash, a tilt post extending from the window sash into the guide track, and a counterbalance assembly for guiding movements of the tilt post in the guide track and counter balancing the window sash, said counterbalance assembly comprising: a brake shoe housing positioned within the guide track, said brake shoe housing having a face section that faces the window sash and a rear section that faces away from the window sash, said face section and said rear section being disposed between a first side edge of said housing, a second side edge of said housing, a top edge of said housing, and a bottom edge of said housing, wherein said face section and said rear section are separated by a predetermined distance proximate said bottom edge of said shoe housing and are joined together proximate said top edge of said brake shoe housing, and wherein said first side edge of said shoe housing is a curved surface having a convex curvature; a receptacle disposed within said face section for receiving the tilt post therein; and a curl spring having a free end, wherein said curl spring is anchored in the guide track above said brake shoe housing; wherein said free end of said curl spring engages said brake shoe housing at an eccentric position on said housing, thus said curl spring applies a turning torque to said brake shoe housing that cocks said brake shoe housing in the guide track and physically biases said first side edge into tangential contact with said guide track without moving said tilt post; and a brake mechanism that biases said face section and said rear section apart when the window sash is tilted relative to said frame, therein increasing said predetermined distance between said face section and said rear section and locking said brake shoe housing in a fixed position within the guide track.