Fluid pressure relay

A fluid pressure pilot valve, including,

• a housing with a cylindrical bore closed on each end,
• a piston mounted within the housing bore so as to reciprocate within the housing bore while sealed to the housing bore walls and dividing the housing bore into a first chamber and a second chamber,
• a bore extended axially through the piston and axially aligned with the bore through the piston by a counterbore from the direction of the first of the housing bore chambers which forms a seat within the bore through the piston,
• a plug element positioned within the bore through the piston and urged by a spring in the first of the housing bore chambers toward engagement with the seat,
• a spring mounted within the second of the housing bore chambers to apply its force on the piston and move its seat toward the plug element,
• a tube extending through the wall of the second housing chamber and sealed to the chamber wall and extending into the bore through the piston to sealingly engage the plug element while unseating the plug element and its bore connected to exhaust external of the housing which is opened to the second chamber when the tube end disengages from the plug element,
• a supply of power fluid permanently connected to the first bore, chamber,
• and an outlet for the fluid pressure generated in the second bore chamber,
• whereby each position of the tube will initially unseat the plug element and increase the pressure from the supply in the second bore chamber or disengage the end of the tube from the seated plug element and decreases the pressure to exhaust in the second bore chamber, either initial result in pressure change in the second chamber resulting in movement of the piston to both reseat the plug element and engage the plug element with the end of the tube, the pressure in the second chamber representing the new position of the tube and connected to a means manifesting the new tube position.

A control system developing a fluid pressure output in response to a primary element moved over a range of positions, including,

• a primary element responsive to a variable condition in taking up positions over a range,
• a tubular element linked to the primary element and arranged to exhaust the bore of the tube,
• a housing arranged to receive one end of the tubular element through a seal in a wall of the housing and extend the end of the tube parallel the axis of a straight cylindrical bore of the housing,
• a piston positioned in the housing bore in dividing the housing bore into two chambers,
• a seat formed within a bore of the piston and receiving the tubular element,
• a plug member arranged within the piston bore to engage the piston bore seat and to be engaged by the open end of the tubular element,
• a first spring within the housing arranged to urge the piston to engage its bore seat toward the plug member,
• a second spring within the housing arranged to urge the plug member to engage the bore seat,
• a supply of fluid pressure for the housing chamber on the plug side of the piston,
• and an outlet for fluid pressure generated in the housing chamber on the tubular element side of the piston,
• whereby each position of the tubular element will uncouple the plug element from either the piston bore seat or the tubular element to generate the pressure differential across the piston which will move the piston until the plug element reengages the seat and tubular positioner to seal the output chamber with a pressure therein representative of the new position of the tubular element and primary element.