| 摘要 |
PROBLEM TO BE SOLVED: To reduce a braking initial shock just the same as in time of the starting even if there is large mechanical frinction, in this brake vale gear which is constituted so as to make the shock reducible by performing its relief operations at two high and low stages in time of the starting of a hydraulic actuator and in time of the braking start. SOLUTION: Each of relief valves 4 and 5 is connected to two supply and exhaust passages 2 and 3 to be interconnected to a rotary motor B of a hydraulic shovel-type excavator. Hydraulic pressure at the passage side is led to two spring chambers 8 and 18 of these relief valves 4 and 5 via two orifices 10 and 20, while each of cylinder chambers 12 and 22 is interconnected to these spring chambers 8 and 18, and both the relief valves 4 and 5 are subjected to low-pressure relief operations while two free pistons 13 and 23 in these cylinder chambers 12 and 22 are moved by pressure oil flowing out of the spring chamber side. Then, the free pistons 13 and 23 are energized to each starting end side of the cylinders 12 and 22 by two spring 14 and 24. One side of the spring chambers 8 and 18 is interconnected to a termination of other other side of the cylinders 22 and 12 by two communicating passages 26 and 27.
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