| 摘要 |
The lower draft links of a tractor three-point hitch include pivotal draft hooks which are power swung, by a pair of one-way hydraulic actuators, between open and closed positions for respectively receiving and retaining a hitch part of an implement. In the case of an earth-working implement, draft loads imposed on the hooks by the implement may vary during operation and cause variations in the pressure of the fluid in the actuators. A pressure responsive direction control valve is connected to the actuators and is shiftable in response to pressures above and below a preselected pressure for respectively directing fluid pressure to and exhausting fluid from a hydraulic lift cylinder for raising and lowering the draft links for adjusting the implement so as to maintain the preselected pressure in the actuators.
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