| 摘要 |
A power take-off unit includes a hydraulically actuated brake assembly which is automatically engaged when a hydraulically actuated clutch assembly is disengaged, and further which is automatically disengaged when the clutch assembly is engaged. The power take-off unit includes a housing which contains an input gear and an output shaft. The input gear is adapted to be connected to an engine or transmission of a vehicle or other source of rotational power so as to be rotatably driven in a conventional manner. The output shaft is adapted to be connected to rotatably driven accessory, such as a hydraulic pump. The power take-off unit includes a clutch assembly for selectively providing a driving connection between the input gear and the output shaft and a brake assembly for selectively exerting a braking force to retard rotation of the output shaft. When pressurized fluid is provided from a source to a clutch chamber, the clutch assembly is engaged to cause the output shaft to be rotatably driven by the input gear. Simultaneously, the pressurized fluid is fed to a brake chamber to disengage the brake assembly and permit free rotation of the output shaft. When pressurized fluid is not provided from the source to the clutch chamber, the clutch assembly is disengaged to prevent the output shaft from being rotatably driven by the input gear. At the same time, the lack of pressurized fluid in the brake chamber to engages the brake assembly and exert the braking force to retard rotation of the output shaft.
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