| 摘要 |
An emergency overspeed brake is depicted which is mountable onto a shaft rotatable at low speeds in either direction for stopping the shaft when an overspeed condition is obtained. In one embodiment of the invention, the brake features two pawls mounted for movement of the entire pawl in an outward, radial direction in response to centrifugal force acting on said pawl. An annular outer hub rigidly mounted to a stationary frame has a central orifice through which the shaft extends. Two inwardly depending stops are integrally mounted onto an axial flange of the outer hub and engaged by one end of a corresponding pawl when the pawl has been thrown outwardly due to the centrifugal force. A spring member engages each pawl to prevent the outward movement of the pawl until after a predetermined speed has been attained, after which the pawls are thrust rapidly outwardly. The brake also comprises an inner hub rigidly mounted to the shaft, an annular drive plate onto which the pawls are mounted, at least two lugs rigidly attached to the drive plate for engaging one end of corresponding pawls, and a disc brake assembly operatively connecting the outer drive plate and the inner hub. Finally, two symmetric cam surfaces located on the internal side of the flange of the inner hub permit only the leading edge of the pawl to be extended completely outwardly in response to the centrifugal force.
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