| 摘要 |
A valve assembly controls fluid flow between first 77 and second 75 ports of a hydraulic actuator 76 and each of a supply line 38 and a return line 40. A first electrohydraulic proportional valve 30 is connected between the supply line 38 and the first port 77, and a second electrohydraulic proportional valve 60 is connected between the supply line 38 and the second port 75. A first counterbalance valve 73 couples the second port 75 to the return line 40 and operates in response to pressure created by the first electrohydraulic proportional valve 30 and the first port 77. A second counterbalance valve 74 couples the first port 77 to the return line 40 and operates in response to pressure created by the second electrohydraulic proportional valve 60 and the second port 75. Thus operation of the first counterbalance valve 73 is slaved to the first electrohydraulic proportional valve 30, and the second counterbalance valve 74 is slaved to the second electrohydraulic proportional valve 60. |
