Patent ID: 6446757
Filing Date: 2002-09-10
Classification: B66F

Abstract:
A lift, comprising:a plurality of substantially vertical posts, each including a latch plate defining a plurality of vertically-spaced openings; a lift platform, including a plurality of yoke ends, each of said yoke ends supported on its respective post; a plurality of lift cables, one of said lift cables supporting each yoke end; each of said yoke ends including a main sheave, which receives its respective lift cable for raising and lowering the yoke end relative to its respective post; a dog, which pivots into the openings of the latch plate as the yoke end moves upwardly relative to its respective post; a first actuator, which extends and retracts the dog during normal, taut cable operating conditions; and a slack cable actuator which extends said dog in response to a slack cable condition, even when the first actuator has retracted the dog; each of said slack cable actuators including a pivot arm having a secondary sheave in contact with its respective lift cable, which, when the lift cable is taut, biases said pivot arm in a first direction; and a spring, which biases said pivot arm in a second direction; wherein, when the lift cable is taut, the lift cable acting against the secondary sheave maintains said pivot arm in a normal operating position, and, when the lift cable is slack, the spring rotates said pivot arm to a locking position; wherein the rotation of said pivot arm to the locking position mechanically extends said dog; and wherein each of said slack cable actuators operates independently of the other slack cable actuators.