Patent ID: 8381879

Claim:
A drive system for use with a cable and a carrier for raising and lowering a payload between a lower position and an upper position, the carrier being configured to hold the payload, the cable being connected to the carrier, the drive system comprising: a reel configured to receive the cable, the reel being rotatable in each of a winding direction to wind the cable onto the reel to raise the carrier and an unwinding direction to unwind the cable from the reel to lower the carrier; a drive mechanism including a drive member and a motor operable to forcibly rotate the drive member in each of a raising direction and a lowering direction, wherein the drive member is operatively connected to the reel to rotate the reel in the winding direction when the drive member is rotated in the raising direction, and to controllably rotate the reel and/or permit the reel to rotate in the unwinding direction when the drive member is rotated in the lowering direction; a cable slack control mechanism operative to automatically selectively decouple the drive member from the reel while the drive motor is rotating the drive member in the lowering direction when a tension on the cable does not exceed a threshold tension and/or the cable is fully unwound from the reel; and an operator controllable tension adjustment system operable to selectively adjust the threshold tension.