Importance

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Abstract

A hoist having a motor, gear reduction unit, drum, and an emergency brake on the drum or on a drive-coupled element close to the drum. A brake-actuating mechanism is operated in response to a mechanical out-of-sync detector with mechanical inputs directly from the motor shaft and drum shaft or a shaft coupled to the drum. The detector has an output shaft which signals to actuate the brake actuator when there is a variation in the relative angular velocities between the two input shafts to the detector to set the brake. In one embodiment, the output shaft rotation provided from the variation in the relative velocities of the input shafts also provides the force for applying the emergency brake. In another embodiment, the brake is set by a large force spring which is controlled by a trigger mechanism. In still other embodiments, the mechanical detector is driven by an overspeed or speed-sensitive clutch, and/or by an electrically operated clutch.

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First Claim