US Patent 7082983 Pre-assembled window shade unit

A window shade component group which includes a window shade supporting windup shaft with bearing devices for rotatably supporting opposite ends of the windup shaft. At least one of the bearing devices is provided with a blocking device, which is effective for maintaining a spring drive of the windup shaft in the wound position after assembly of the windup shaft. Following installation of the window shade component group in a motor vehicle or appropriate housing, the blocking device is releasable as an incident to actuation of the windup shaft.