Abstract: A lifting jack having a first tubular frame member, a second tubular frame member movably interconnected coaxially with the first frame member, and a selectively operable drive mechanism for moving the second frame member relative to the first frame member. The drive mechanism includes a shaft and a bracket fastened to the second frame member and having two aligned apertures for pivotally mounting a shaft. A protective cover is provided for the drive mechanism and is removably fastened to the shaft.

Abstract: An emergency stop mechanism for a lifting device capable of moving a load along a predetermined path against and with the force of gravity using a primary cable. The emergency stop mechanism includes a secondary cable or line functionally in parallel with the primary cable. The secondary cable is attached to the load and is wound around an idling drum, with means provided to keep the secondary cable taut around the idling drum. In the event of a failure of the primary lifting system, a braking assembly, sensing and actuated by a decrease in tension in the primary cable, arrests the rotation of the idling drum and thus stops or slows the descent of the payload.