Patent ID: 6516922
Filing Date: 2003-02-11
Classification: B66B

Abstract:
An emergency descent system for elevators using gravitational forces to control the descent of an elevator cab in the event of a loss of power from an outside power source, the system comprising:a counterweight assembly including a counterweight weighing less than the minimum weight of the elevator cab; a generating unit operatively coupled to a drive member and electrically coupled to a load bank; a cable having a first end and second end, the cable operatively coupled to the drive member between the first end and second end, the first end coupled to the counterweight assembly and the second end coupled to the elevator cab such that the weight differential between the counterweight assembly and the elevator cab causes the drive member to rotate, causing the generating unit to produce a first generator torque and a corresponding first current; and an elevator controller having a secondary power source to supply power to the elevator controller, the elevator controller electrically coupled to an outside power source, the secondary power source, the generating unit, and the load bank, wherein the elevator controller configured to detect the speed of the elevator cab and direct a current from the generator to the load bank, and wherein the regulated current produces a generator torque to counteract the cab torque for controlling the rotation of the drive member and the descent of the elevator cab, and wherein the counterweight assembly includes a constant counterweight weighing less than the minimum weight of the elevator cab, a detachable counterweight, and a releasable lock, the constant counterweight coupled to the first end of the cable and the detachable counterweight releasably coupled to the constant counterweight through the releasable lock, and wherein the elevator controller is electrically coupled to the releasable lock and is configured to send a release signal to the releasable lock upon a loss of outside power.