Patent ID: 6161653
Filing Date: 2000-12-19
Classification: B66B

Abstract:
A selectively operable safety brake apparatus on an elevator car disposed for vertical motion between guiderails in a hoistway, comprising:a safety brake disposed on the car and adapted to be wedged against one of the guiderails when moved from a non-braking condition into a braking condition;a rod disposed on the car for moving said safety brake between said braking and non-braking conditions; anda friction brake attached to said rod and disposed on said car adjacent said one guiderail and moveable between a rail-engaging position and a rail-non-engaging position, said friction brake, when in said rail-engaging position contemporaneously with motion of said car, moving said rod in a direction opposite to the motion of the car to thereby move said safety brake from said non-braking condition into said braking condition;characterized by the improvement comprising:a speed sensor for providing a speed signal indicative of the speed of car motion;a safety controller for comparing the speed represented by said speed signal to speed represented by a threshold signal indicative of an overspeed condition, and for providing a trigger signal in response to said speed signal indicating a speed in excess of said overspeed condition;resilient means for urging said friction brake into said rail-engaging position; andan electromagnet for normally holding said friction brake in said rail-non-engaging position against the urging of said resilient means, and for allowing said resilient means to move said friction brake into said rail-engaging position in the presence of said trigger signal.