A control valve for fluid operated circuits for controlling machines and the like which includes a valve member biased to a pressure-off position with a pilot passage and control chamber to effect a line-pressure on-position with a change-over from pilot control to a holding position from line pressure. If line pressure is interrupted for any reason, the valve member returns to a pressure-off position and must be reactivated by an operator, thus preventing an accidental machine start-up when line pressure is restored. The closed center condition as the valve moves to a work position permits change-over from pilot to main pressure control with no pressure loss.
A multiple output modular pneumatic pressure valve has a plurality of modules connected together. Each module has a regulator, shuttle valve and four way solenoid actuated spool valve for provides a plurality of pneumatic pressures to a single outlet which may be quickly selected via the actuation and deactuation of the proper valves. Adjustment of the pneumatic pressures can be easily performed by rotation of a knob of the pressure regulator.
A multiple output modular pneumatic pressure valve has a plurality of modules connected together. Each module has a regulator, shuttle valve and four way solenoid actuated spool valve for provides a plurality of pneumatic pressures to a single outlet which may be quickly selected via the actuation and deactuation of the proper valves. Adjustment of the pneumatic pressures can be easily performed by rotation of a knob of the pressure regulator.
A hydraulic spool valve 40 (FIG. 2(a)) of the edge control type in which the peripheral ends 31, 33 of a spool land 47 cooperate with a radial service port 41 to define by axial spool position the the closure of the port 41 and degree of opening to supply or return port 18, 19. The spool 25 is located in a sleeve 14 itself located in a housing 11 and O-ring seals 22', 22" inhibit leakage between sleeve and housing beyond the seals. Leakage fluid up to the seals exerts a contracting force onto the sleeve and when the spool is in a neutral position closing the service port stiction occurs between the sleeve and the end 36 of the spool land closest to the return port. Both the service port in the sleeve and the spool are constructed such that with the spool in the neutral position the spool groove 48 extends towards the return port so that the end 50 of the groove is at least in line 51 with the O-ring seal 22' and the supporting end region 36 of the spool, inevitably contacting the sleeve, does so at an axial part not subjected to a net contracting fluid pressure.
