| 摘要 |
A fluid-operated piston is mounted on a driven shaft for joint rotation therewith and for sliding motion in its axial direction. Driven from a first drive shaft, a bevel gear is rotatably mounted on the driven shaft, while being locked against axial displacement, and held opposite to one end of the piston via a first clutch. A rotor on a second drive shaft is opposed to the other end of the piston via a second clutch. A hydraulic control circuit is provided for selective delivery of a hydraulic fluid under pressure into a pair of opposed fluid chambers in order to urge the piston into engagement with either the bevel gear or the rotor via the corresponding one of the clutches. Normally held engaged to allow the first drive shaft to drive the driven shaft, the first clutch disengages automatically against the fluid pressure in one of the fluid chambers when the torque being transmitted from the bevel gear to the piston exceeds a predetermined limit, thereby avoiding the overloading of the driven shaft by the first drive shaft. The driven shaft can then be driven from the second drive shaft with reduced torque.
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