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A convertible high or low pressure pilot valve adapted to selectively control fluid flow between a common port and a supply port or exhaust port by moving a band of orifices in a plunger that is slidably disposed within the valve past an O-ring seal disposed between the supply port and the exhaust p

A convertible high or low pressure pilot valve adapted to selectively control fluid flow between a common port and a supply port or exhaust port by moving a band of orifices in a plunger that is slidably disposed within the valve past an O-ring seal disposed between the supply port and the exhaust port so as to establish fluid communication between the common port and the supply port whenever the band is aligned with the supply port through a unitary axial bore in the plunger that maintains fluid communication with the common port or between the common port and the exhaust port through the same axial bore, whenever the band is aligned with the exhaust port or to block fluid communication between the common port, the supply port, and the exhaust port whenever the band is disposed between the supply port and the exhaust port in such manner that the O-ring bridges the orifices in such band.

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A pilot valve for controlling the flow of fluid in a control system in response to pressure variations in a flow line, said valve comprising: a body having an axial bore formed therein, said body having a plurality of body ports including a supply port, and exhaust port and a common port communicati

A pilot valve for controlling the flow of fluid in a control system in response to pressure variations in a flow line, said valve comprising: a body having an axial bore formed therein, said body having a plurality of body ports including a supply port, and exhaust port and a common port communicating with said bore, said body ports being axially spaced, said supply port and said exhaust port communicating with said bore at positions between said common port and an end of said bore; plunger means movably disposed in said bore, said plunger means having an axially extending passageway and first and second bands of radially directed plunger ports communicating with said passageway, said plunger means being positioned in said bore to form an annulus; pressure sensing means at one end of said body, said pressure sensing means being adapted to impart translational motion to the plunger means in response to variations in flow line pressure, said sensing means being adapted to move said plunger between first and second positions, one of said bands of radially directed plunger ports communicating with said supply port when said plunger is in said first position, said band communicating with said exhaust port when said plunger is in said second position; and seal means secured to said body and urged into sealing engagement with said plunger means, said seal means having a dimension measured longitudinally of said bore which is greater than the maximum dimension measured longitudinally of said bore of each of said plunger ports.