| 摘要 |
PURPOSE:To make it possible to slowly control the ascending and descending speeds of a working machine, by forming the first and second small groups in a manual valve, and arranging a check valve and a throttle valve in series between the manual valve and a hydraulic cylinder. CONSTITUTION:The first and second small groups 921, 922 causing throttle resistance against a hydraulic oil are formed in a manual valve 56. A check valve 58 comprising a main valve 106 and a sub valve 107 opened by a valve opening rod 115 in advance of the main valve 106 and a throttle valve 56 are arranged in series between the manual valve 56 and a hydraulic cylinder. Since the hydraulic oil is therefore subjected to the throttle resistance by the first small group 921 and the throttle valve 57 during the ascending stroke of a working machine, and by the second small group 922, the throttle valve 57 and the sub valve 107 of the check valve 58 during its descending stroke respectively, the ascending and descending speeds of the working machine can be slowly or fast controlled.
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