| 摘要 |
PURPOSE:To make speed change gearing performable in a smooth manner, by installing a small groove part being small in a traverse area in a return communicating groove formed in a spool of a valve. CONSTITUTION:A small groove part which is small in a traverse area is installed in a return communicating groove 35 formed in a spool 32 of a valve 27. With this constitution, when a speed change from a low speed state to a high speed one in the middle of running, even if a cylinder at the low speed side is changed over to a state of drain oil, resistance is added to the drain oil by means of the small groove part 35a whereby a half-clutching state comes out, changing the speed into a state of high-speed running so that speed change gearing can be smoothly carried out.
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