| 摘要 |
<p>PURPOSE:To prevent the occurrence of cavitation, by a method wherein, when an oil jack returns after a driving stand of, for example, a cabover type vehicle inclines, one of sweeping chambers of a cylinder becomes a negative pressure resulting from a rapid fall due to a tare. CONSTITUTION:When a driving stand 8 is tilted forward by means of an oil jack 1 from a normal position, a switch valve 14 is set in a position 14A, and a manual pump 15 is actuated. A discharge pressure oil of a pump 15 pushes and opens a pilot check valve 13b, and is fed to a sweeping chamber 11b. A valve 13c is released with an oil pressure in a line 11g, and the oil pressure is fed to a sweeping chamber 11b as well. A piston 12 moves to the left with a difference in a pressure acting area, and the jack 1 expands. In the meantime, when the driving stand 8 is lowered from a tilting condition, the switch valve 14 is set in a position B. A return oil from the chamber 11c is throttled with a throttle resistance thereupon, and the valve 13c is opened. This prevents the chamber 11b from becoming a negative pressure.</p> |
