Abstract text

A main control valve is actuated by a pilot fluid control signal between open and closed positions to supply fluid to an actuator such as a valve actuator. A stack of logic control valves is supported on the main valve- and controls the flow of the pilot signal. Each of the logic control valves has a housing of common design. Intermediate flow-directing plates of different designs provide fluid communication between adjacent housings. The stack has a common pilot feed passage and a common exhaust passage that are each defined by an annular clearance around supporting tie bars that pass through bores in the stack. Each plate has apertures that form part of the exhaust and pilot feed passages and an aperture that interconnects the returning pilot signal with the pilot inlet of the next valve in the stack. The arrangement allows for simplification of the design of the apparatus with a single housing design and multiple plate designs.