| 摘要 |
There is disclosed herein a brake unit of the oil shear type which is specifically designed for use in controlling the drawworks of drilling rigs or the like. The drawworks brake unit comprises an input shaft driven by the drawworks which operates to drive a gear pump for circulating high volumes of oil under pressure over interposed brake discs and plates and through adjacent restricted orifices during a first direction of rotation such as during lowering of the pipe stands so as to both cool and lubricate the discs and plates. During an opposite rotation of the input shaft, such as during raising of the pipe stands, an alternate flowpath is provided by-passing the restricted orifices so as to reduce the drag placed on the drawworks during raising of the pipe stands. During the first direction of rotation or lowering, the gear pump also operates to provide self-actuating overspeed safety protection as well. A unique stepped oil sealing arrangement is also provided to prevent oil leakage between the input shaft and housing due to the high pressure generated therein.
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