Special Function Valves

1:0.25 Area Ratio Cartridge: Sizes 16 to 40

This cartridge arrangement has a 1:0.25 area ratio and operates with a pilot flow entering at X, the pilot flow rate being governed by the integral pressure compensated flow control. See Figure 44. Pilot flow passes out of Z1 to an appropriate pilot relief valve which creates pressure on the top of the pilot piston. This means the main valve will open at, and maintain, a pressure at A of 25% of pilot pressure.

When used with an electrohydraulic proportional pressure control (connected to Z1 port), pressures as low as 1,5 bar (22 psi) are controllable at port A, making it ideal for plastics injection molding machine applications. The area ratio of the large piston to sleeve seat is 1:1.1. The Z1 port should never be blocked; doing so could result in pressure intensification at this port. This low pressure relief valve can also be used as a directional control back pressure valve, or as a blocking valve.

When the back pressure function is operational, port Z2 must be drained to the reservoir. The valve can be locked shut by applying at Z2 a pressure greater than any at A.

Normally Open Prefill Valve: Sizes 25, 32, 40, 50 and 63

Normally open cartridge valves require an external pilot signal to close the valve against system pressure. This valve range is ideally suited for applications requiring a prefill valve or decompression valve.

The main spool consists of a sleeve with a sharp edged seat and a piston. A spring holds the piston in the open position. Pressure at control port X forces the poppet against the spring to close the valve.