In a gas turbine engine, a fuel staging valve assembly, for distributing fuel flow to a multiple zone nozzle therein, comprised of a pilot valve operatively interconnected with at least one main valve, each of said valves including:
- a. a dual diameter valve housing;
- b. a dual diameter cylindrical valve sleeve fixedly, sealingly and conformably received within said valve housing, said sleeve having a first diameter portion and a second diameter portion joined via an intermediate annular portion, with a peripheral land cavity being located between sleeve intermediate portion and an adjacent portion of said valve housing;
- and said first diameter portion having a peripheral, recessed, annular gland area with at least an axially spaced first plurality of discrete radial passages therethrough;
- c. a dual diameter hollow cylindrical valve spool, having a central cavity, conformably and slidably received within said cylindrical valve sleeve, said spool having a first diameter portion and a second diameter portion joined via an intermediate annular portion, with predetermined diametral clearance spaces being provided between corresponding adjoining first and second diameter portions of said sleeve and spool, thereby permitting a predetermined amount of fluid leakage therebetween, during operation of said pilot poppet valve;
- and an annular pressure signal cavity, interconnected with said land cavity, being located between intermediate annular portions of said valve sleeve and said valve spool;
- d. a centrally apertured spring retainer fixedly received within said sleeve first diameter portion and closing one end thereof;
- e. a valve spring, interposed between said spring retainer and said spool intermediate annular portion, for preloading said spool against said sleeve;
- f. a centrally-apertured dual diameter valve seat retainer member having a first diameter portion and a second diameter portion joined via an intermediate radial surface portion, said retainer member first diameter portion being fixedly and sealingly received within an open end of said sleeve second diameter portion, with said retainer member intermediate radial surface portion being provided with an inwardly-directed, raised, central contoured seal seat portion adjoining said retainer member second diameter portion;
- g. a generally cup-shaped closure member is fixedly and sealingly received on said retainer member second diameter portion and includes a central main valve discharge orifice;
- h. a multiple diameter poppet member having interconnected first and second diameter portions;
- i. a poppet spring, operatively interposed between said poppet member and a peripheral internal wall portion in said spool member second diameter portion;
- j. a stiff, elastic, annular seal member, contoured in cross-section, fixedly retained within a mating contoured recess within said poppet member second diameter portion, having an axial outer surface adapted to sealingly mate with said raised valve seat portion of said valve seat retainer member;
- k. a shim, fixedly abutting and acting on said retainer member intermediate radial surface portion;
- l. a fluid pilot supply conduit interconnecting said pilot and main valve central cavities at their respective gland areas;
- m. a source of fluid signal pressure connected with said pilot valve peripheral land cavity;
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- n. a fluid pressure signal conduit interconnecting said pilot and main valves at their respective peripheral land cavities, wherein the improvement comprises:
- o. said poppet member first diameter portion being yieldingly, slidably, received within an open end of said valve spool second diameter potion, with the axial movement of said poppet being restricted via a split retaining roll pin press-fitted relative to said valve spool second diameter portion but having a predetermined clearance relative to said poppet member;
- p. said poppet spring axially biasing said poppet member toward said contoured seal seat portion, with said biasing being limited via said predetermined axial clearance, relative to said pin;
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- q. said shim providing an initial, predetermined, sealing force, relative to said seal member axial outer surface, against said retaining roll pin, thereby preventing fuel leaks at low fluid supply pressure, with said predetermined peripheral clearance, relative to said poppet member serving to limit the compression of said elastic member as well as allowing compensation for any seal compression set.