| 摘要 |
PROBLEM TO BE SOLVED: To dispense with external return piping used only for optional actuators. SOLUTION: An optional valve 17 is built in a main valve block 5, and the circuit state of a circuit for driving a crushing cylinder 18 and a breaker cylinder 19 serving as the optional actuators is switched by the switching operation of a selector valve 31 into a first circuit state of returning return oil to a tank T via an oil cooler 13, and a second circuit state of returning the return oil directly to the tank T without passing through the oil cooler 13. A selector valve block 32 mounted to the main valve block 5 has return passages 33, 34, and in the second circuit state, return oil from the breaker cylinder 19 is led to a by-pass tank line 11 of the main valve block 5 through the return passage 34. COPYRIGHT: (C)2008,JPO&INPIT
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