PRETORQUE TO UNLOAD ELEVATOR CAR/FLOOR LOCKS BEFORE RETRACTION

To prevent elevator rope stretch effects when a horizontally transferable elevator cab (18) is rolled onto and off of an elevator car frame (10), an elevator car/floor lock (31) includes a bolt (47) which extends across the interface between the car frame and the building and engages a strike (39). Jack screw (44) and solenoid (60) embodiments are shown. To take the weight off the lock bolts so that they may be retracted to permit moving the car frame vertically in the hoistway, strain gages (64, 65) or load sensors (62, 63) provided in or adjacent the bolts sense the weight supported thereby, and a pretorque program (Fig. 6) provides armature current to the hoisting motor to raise or lower the car frame sufficiently to reduce the load on the bolts to nil.