| 摘要 |
<p>PURPOSE: To reduce shock and kick in shutting off by providing a variable orifice having a small flow area when a shut-off valve is in an operating position, and expanding to the minimum flow area during the displacement of the shut-off valve from the operating position to a shut-off position. CONSTITUTION: A valve spool 50 having annular grooves 54 and a valve sleeve 26 having an opening 36 are configured and positioned relative to each other to define an orifice having the variable flow area for supplying fluid from a supply passage 16s to a motor passage 16m. This variable orifice is composed of a first orifice means formed by forming one set of opening sets 36, 38 and 44 to be communicated with passages facing the supply passage 16s and the motor passage 16m on the valve sleeve 26, and a second orifice means formed as a valve passage so positioned as to be communicated with the opening sets 36, 38 and 44 except when the valve spool 50 is in the closed position. As a result, when the valve spool 50 is in the operating normally-opened position, the flow area of the variable orifice is decreased, while, when it is displaced to a shut-off position, the flow area has the maximum area.</p> |
