| 摘要 |
A continuously driven gear pump includes an internal bypass valve for selectively controlling the supply of pressurized fluid to a hydraulically actuated device. The internal bypass valve includes a movable spool which is spring-biased to a first position, wherein the flow of fluid is bypassed from the outlet port back to the inlet port, and no fluid is delivered to the actuated device. The spool has an internal passageway formed therethrough which permits a relatively small amount of fluid to pass from the outlet port back to the reservoir when the gear pump is operated in the bypass mode. To replenish this small amount of fluid which is returned to the reservoir from the outlet port, the gear pump draws a corresponding small amount of fluid to the inlet port. Thus, a small amount of fluid circulates between the gear pump and the reservoir when the gear pump is operated in the bypass mode. This circulation cools the pump without causing a significant load to be placed on the engine. The spool can be moved to a second position against the urging of the spring, wherein the entire flow of fluid is directed to the actuated device.
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