| 摘要 |
PURPOSE: To provide a fail safe circuit having a sub circuit made to reliably function when abnormalities are generated on a main circuit even if the fail safe circuit has one supply source of pressure oil. CONSTITUTION: A plurality of electromagnetic control valves 3, 6 connected to an actuator 1 in parallel are provided with centering springs and maintain the neutral positions in the normal state. A feed port and a return port and two actuator ports are provided on each control valve, the feed port and the return port are communicated with each other in the neutral position, and the feed port and the return port are shut off from respective actuator ports. A feed port 3a of the control valve 3 of the most upstream side is connected to a supply source P, a return port 6b of the control valve 6 of the most downstream side is connected to a tank T, and the return ports 3b of respective control valves is connected to the supply port 6a of the control valve 6 downstream of it.
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