Patent ID: 6293329
Filing Date: 2001-09-25
Classification: E06B

Abstract:
A window cover system of the type comprising an extendible window cover and lift means including lift cords attached to the cover for assisting extending and retracting the window cover, the system comprising:a spring drive unit connected to the lift cords for assisting extending and retracting the cover to selected positions, the spring drive unit comprising a shaft mounted to a support member; a coil spring mounted along the shaft and having a fixed end and a rotatable end; and a gear transmission of selected drive ratio; the transmission connected at one output to the rotatable coil spring end and at a second output to the lift means, thereby applying the selected ratio between the coil spring and the lift cords, and determining the ratio of the cover travel distance to the spring winding distance and controlling the force applied to the cover by the spring; andthe transmission having inherent friction opposing movement of the cover from the selected positions.