| 摘要 |
PURPOSE:To extend the life span of a mechanical braking device by supplying discharge oil of a pilot pump to a brake releasing cylinder during and before the operation of a hydraulic motor. CONSTITUTION:In the case of switching a directional changeover valve 15 into a position G and operating a hydraulic motor 1, at the position B of the directional changeover valve 15, an intake port 15d and a discharge port 15h are cut off from communicating with each other, and discharge oil of a pilot pump 9 is supplied to a line 3c through a line 9a in order to flow into the cylinder chamber 3a of a brake releasing cylinder 3 through a check valve 10 for releasing locking. Since the control by a mechanical braking device can be certainly released before the hydraulic motor 1 is started to rotate by the above mechanism, a mechanical braking device is never dragged in starting the hydraulic motor 1, operating performance is improved and the life span of a mechanical braking device can be extended.
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