Efficient lightweight hoist with multiple-cable-size traction and safety systems

摘要

This scaffold hoist uses a transmission mechanism whose output shafts are fastened to the hoist housing, and whose case rotates, carrying a sheave which impels the mechanism along the cable. The transmission mechanism is advantageously a quadrant drive for extremely high torque-to- weight ratio.PPThe sheave has a peripheral groove, tapered and deep enough to seat a cable having any of three different diameters, at different depths in the groove.P PThe cable wraps around three-fourths of the sheave. Around five- eighths of the sheave, a chain presses the cable into the groove. The chain rollers enter the groove deeply enough to engage even the smallest- diameter cables of interest, while clearing the sheave periphery. The chain side bars ride along the sides of the sheave, holding the chain and cable in position.PPA resettable overspeed brake uses a rotary cam that jams a cable of any of the three sizes, at correspondingly various cam angles. The cam is cocked out of contact with the cable, and immediately spring-driven against the cable when triggered by a centrifugal sensor. A backup block--which keeps the cable from retreating from the cam--slides away from the cable at an angle during resetting, to facilitate unjamming the cable by moderate force.