Patent ID: 8540207

Claim:
A device, comprising: a pilot valve responsive to a command signal for supplying a fluid at a command pressure to a pilot valve control port; and a pilot operated spool valve having: a body having a first connector and a second connector, each of said first connector and second connector being adapted for fluid communication with an external circuit; and a spool disposed for sliding movement in said body, said spool having a first end portion and a second end portion opposite said first end portion, said first end portion of said spool being in fluid communication with said pilot valve control port such that said spool is urged to move in a first direction by said fluid at said command pressure, said spool being movable to control a fluid flow between said first connector and said second connector through said body proportionally to said command pressure when said fluid flow is a forward flow from said first connector to said second connector and when said fluid flow is a reverse flow from said second connector to said first connector; said spool valve using negative feedback in the form of fluid at a feedback pressure acting on said spool in a second direction, opposite said first direction, to position said spool in conjunction with said fluid at said command pressure; said spool valve utilizing unstable equilibrium of fluid forces to switch between controlling said forward flow and said reverse flow.