Sequence valve for clamping apparatus

摘要

A fluid control valve which operates accurately in response to the pressure difference that exists between a pair of ports in the valve. The valve features a spool which is normally biased to one control position wherein it remains with the sensed pressure difference being below one preselected amount. The spool shifts rapidly to another control position on the sensed pressure difference exceeding this amount. In this other control position, the spool remains until the sensed pressure difference drops to another preselected amount which is significantly lower than the first-mentioned preselected amount. On this latter event occurring, the spool returns to its first-mentioned control position.