Note: Standard kickdown valves RQ*B have a long response time of about 20 ms (that can be beneficial) and also have leakage since they are spool-type valves. A circuit with a pressure control valve PR**, a normally open LO*, and a normally closed LK* allows a leak-free kickdown function with optional indication of the valve position.
- Logic valve pilot-to-open: LK*C
- Logic valve pilot-to-close: LO*C
- Pressure control: PR*B
Benefits of this circuit arrangement:
- The pressure P1 on the supply of this circuit sees no leakage into the pilot port (3) of the LKDC and port 2 of the LO*C. The LKDC opens when P1 pressure is 0.55 times larger than the pressure at port 1 of valve LKDC. As soon as the LK opens, the pilot pressure collapses and the LO*C valve will open.
- The logic valve LO*C can be a high-capacity valve - up to 320 gpm. It could also have a position switch to monitor the unloading function.
