| 摘要 |
PURPOSE:To permit safe and efficient operations of an oil-pressure shovel by providing an electromagnetic switch valve by which a working circuit to supply pressure oil to a slewing oil-pressure motor is interrupted usually but led by electric signals. CONSTITUTION:When the circuit of a limit switch 15 is closed by operating the operating lever 16 of an oil-pressure switch valve 4, a relay 14 is excited to open the circuit. The excitation of an electromagnetic switch valve 13 is discontinued, a spool is switched from an E-position to an D-position, oil paths 6 and 7 are interrupted, and an oil-pressure motor 5 is actuated to turn an upper slewing part. When the lever 16 is set to neutral position, the circuit of a limit switch 15 is opened, the circuit of the relay 14 is closed, and the switch valve 13 is excited. A spool is switched from the D-position to the E- position and the oil paths 6 and 7 are led to each other for free rotation of the motor 5.
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