| 摘要 |
<p>Two pressure control valves have most components in common. One valve is a direct-acting sequence valve (10) and the other a vented counterbalance valve (7) with pilot assist (76). Both valves have a set opening pressure which is insensitive to secondary port pressure (14). Both valves may provide free reverse flow. The valves include a spring force reduction chamber (48) which receives hydraulic fluid at primary port pressure. Part of the opening force exerted at the primary port (12) is offset by pressure in the spring force reduction chamber (48) so that a spring (22) having a smaller spring constant may be used to resist opening force. This offsetting force may be readily modified by changing the diameter of the piston shaft (52) of the valve.</p> |
