Abstract: A hoist having a worm safety device in which the worm is continuously meshed with a worm wheel coupled to the drum. The worm is accelerated to a speed greater than that of the worm wheel and at a torque sufficient to overcome the frictional contact between the worm and worm wheel when the hoist direction is reversed.

Abstract: The safety system in a hoist having a motor with a motor shaft, a gear reduction unit, a drum, a safety brake drivingly coupled on an operating element on or close to the drum in which a mechanical out-of-sync detector produces a unidirectional brake-setting output from inputs from the drum and the motor shaft, the unidirectional brake-setting rotational output for setting the brake. In a preferred embodiment, an error correction is made into the detector for obtaining a first unidirectional output during normal operation, and the brake-setting unidirectional rotation is in the opposite direction for setting the brake. One form of detector is a mechanical differential assembly and another form of detector is a set of coaxial shafts that measure differential rotation between the drum and motor input shafts. A unique brake actuator is provided and is easily reset remotely after the brake has been set.

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.

Abstract: A system is provided for automatically clamping a cable drum in the event of mechanical failure of the drive train that connects the cable drum to its prime mover. The system monitors the mechanical continuity of the drive train by comparing the number of revolutions of the prime mover with the number of revolutions made by the cable drum in the same time interval. The system actuates a caliper disc brake mounted with the drum if a discontinuity of the drive train is detected. In the electrica system, shaft encoders are used on both the cable drum axle and prime mover shaft. The cable drum encoder is selected such that the number of pulses it produces per revolution of the cable drum is approximately equal to the number of pulses produced by prime mover shaft encoder per revolution of its shaft divided by the speed reduction ratio of the drive train.

Abstract: A synergistic safety system is incorporated in a crane driven by a high-speed motor which requires both an energy-absorbing torque-limiting device in the speed reduction unit and a drum emergency holding device. The energy-absorbing torque-limiting device transmits the static and dynamic torque required to rotate or hold the drum against the maximum carried load, but will slip at a pre-determined setting to absorb high-speed rotational energy of the drive train and/or torque of the drive motor in the event a two-blocking, load hang-up, overload, or engagement of the drum emergency holding device occurs. The drum emergency holding device is set automatically when the energy-absorbing torque-limiting device is actuated and/or any drive train component fails, which are detected by one or more sensing sub-systems.

Abstract: A convertible crane is provided with a main trolley which carries a powered hoist along a horizontal path. A trailer trolley also carries a hoist which is powered from the main trolley. Each of the hoists thus have a powered drum which will increase the total line capacity of the crane allowing the crane to be used for temporary longer load travel or higher capacity lifting depending upon the amount of reeving or parts of line used to support the load from the trolleys.