Abstract: A safety brake of the type for use in hoist. As a hoist cage descends or ascends faster than a predetermined safety speed, a corresponding high speed motion is transmitted to a main shaft of the safety brake through a input pinion gear connected to the main shaft for engagement with a vertical rack attached to a hoist tower. Movable braking disks are attached to the main shaft for rotation therewith. Fixed braking disks are interleaved with the movable disks. Such high speed motion causes a dog retained in the main shaft to centrifugally move outwardly to engage the drum. The actuator assembly connected to the drum acts to cause the drum to move against the fixed and movable braking disks.

Abstract: Antifrictional screws are used to permit the resetting of safety brakes of the type used in hoists. As in prior brakes, centrifugally operated dogs connect braking members, but in the present brakes the dogs also engage actuating members of the antifrictional screws, the screws being rotatable independently of their respective braking members. The dogs can be disengaged from the actuating members by merely operating the usual controls to raise cages of the hoists. The antifrictional screws in one embodiment are then free to be turned automatically independent of the rate of rotation of a braking member by force of usual spring washers disposed between the screws and respective braking members until the brakes are normally released. In modified types, dogs or pawls for controlling the amount of braking continue to engage respective actuating members for controlling rate of rotation of the screws until the cages have been raised sufficiently to release the brakes.