US3588289A - Rotary fuel pump - Google Patents

Abstract

A ROTARY FUEL PUMP OF THE KIND IN WHICH A ROTOR HAVING A PLURALITY OF AXIALLY-EXTENDING BORES THEREIN, EACH CONTAINING A PISTON ENGAGEABLE WITH A CAM-PLATE INCLINED TO THE AXIS OF ROTATION OF THE ROTOR AND COMMUNICATING WITH A PORT AT THE END THEREOF REMOTE FROM THE CAM-PLATE, WHEREBY ON ROTATION OF THE ROTOR, THE PORTS WILL BE CARRIED IN SUCCESSION PAST A FUEL INLET AND A FUEL OUTLET APERTURE AND THE PISTONS WILL BE RECIPROCATED TO EFFECT PUMPING AND IN WHICH THERE IS A CENTRIFUGALLY OPERABLE SPILL VALVE CARRIED BY THE ROTOR AND OPERABLE TO CONTROL FLOW THROUGH A SPILL PASSAGE IN THE ROTOR LEADING FROM THE OUTLET APERTURE TO A SUMP COMMUNICATING WITH THE INLET APERTURE. IN SUCH A PUMP IT IS KNOWN TO APPLY VARIABLE CONTROLLING FORCE ON THE CENTRIFUGALLY OPERABLE SPILL VALVE. THE PRESENT INVENTION PROVIDES A PAIR OF CONCENTRIC, RELATIVELY ROTATABLE, TUBULAR QUILL SHAFTS, OF WHICH ONE IS CARRIED BY THE ROTOR AND COMMUNICATES WITH A PISTON CARRIED BY THE ROTOR AND ENGAGEABLE WITH THE SPILL VALVE AND THE OTHER EXTENDS THROUGH A WALL OF THE HOUSING OF THE PUMP TO RECEIVE AN EXTERNAL CONTROLLING PRESSURE SIGNAL. AN ANNULAR CLEARANCE SPACE BETWEEN THE CONCENTRIC QUILL SHAFTS COMMUNICATES WITH A LEAKAGE PATH FOR FLUID PROVIDING THE PRESSURE SIGNAL.

Description

United States Patent Inventor Mark Cary Sedgwick Barnard 2,838,029 6/1958 Bettoni 285/133 App No 3223: Primary Examiner-William L. Freeh Filed g 22, I969 Attorney-Mawhrnney and Mawhinney Patented June 28, 1971 p H Assignee gfggg Llmlted ABSTRACT: A rotary fuel pump of the kind in which a rotor P Se 1968 having a plurality of axially-extending bores therein, each connori y G P Baum taining a piston engageable with a cam-plate inclined to the 22 5 axis of rotation of the rotor and communicating with a port at the end thereof remote from the cam-plate, whereby on rotation of the rotor, the ports will be carried in succession past a ROTARY FUEL PUMP fuel inlet and a fuel outlet apertureand the pistons will be 2 Chin, 1 Drawing rectprocated to effect pumping and in which there IS a centrifugally operable spill valve carried by the rotor and opera- U.S. Cl. 417/294, bl to t ol flow through a spill passage in the rotor leading 417/270 from the outlet aperture to a sump communicating with the Int. Cl ..F04b 49/00, Met apemlm [n such a pump it is known to apply variable 1 F04! 27/03 controlling force on the centrifugally operable spill valve. The Fkld Discard! present invention provides a pair of concentric relatively 294; 285/134 rotatable, tubular quill shafts, of which one is carried by the R I cued rotor and communicates with a piston carried by the rotor and e "wees I engageable with the spill valve and the other extends through UNITED STATES PATENTS a wall of the housing of the pump to receive an external con- 3,085,6l9 4/1963 Penny etal. 417/294 trolling pressure signal. An annular clearance space between 3,129,960 4/1964 Schrodt 285/134 the concentric quill shafts communicates with a leakage path I 1/1965 Barnard et a1. 417/270 for fluid providing the pressure signal.

SO x 532 "4t 3 3s 5s m 37 31 28 I 3o 27 26 l 9 15 3b 5 l9 5 5 PATENTEUJUH281971 INvENToz MARK CARY Scmawcc EAzu/uzb ROTARY FUEL PUMP The invention is concerned with a rotary fuel pump of the kind (hereinafter called the kind described) employed for supplying liquid fuel to a burner of a gas turbine engine and comprising a rotor having a plurality of axially-extending bores, each containing a piston urged by a spring into abutment at one end with a cam-plate inclined to the axis of rotation of the rotor, each bore communicating with a port at the end thereof remote from the cam-plate, said ports being cireumferentially-spaced around the axis of the rotor so that, during rotation of the rotor, the port of each bore passes successively a fuel inlet and a fuel outlet in the form of circumferentially spaced arcuate apertures, coaxial with the rotor and positioned in a stationary thrust face coacting with the endface of the rotor containing the ports of the bores.

In a known fuel pump of the kind described, the outlet aperture communicates with a spill passage in the rotor leading to the interior of a housing containing the rotor and communicating with the inlet aperture via a centrifugally operable valve member carried by the rotor. The known fuel pump also includes a plunger carried by the rotor and arranged to apply a variable controlling force on the valve member in opposition to the centrifugal force acting thereon. The controlling force is applied by transmitting a fluid pressure to the plunger. In the known pump, the fluid is oil and is applied to the rotor via a passageway defined by a circumferentially-extending seal provided between adjacent rotatable and stationary surfaces on the rotor and the housing respectively. The known arrangement suffers from the disadvantage that friction occurs at the seal. An object of the invention is to avoid the use of such a seal.

According to the invention, a fuel pump of the kind described and including a centrifugally operable valve member, carried by the rotor and arranged to control flow through a spill passage in the rotor leading from the outlet aperture thereof to the interior of a housing containing the rotor and communicating with the inlet aperture thereof, also includes a pressure-operable device arranged to apply a controlling force on the valve member in opposition to the centrifugal force acting thereon, means carried by the rotor defining a chamber in which the device is movable, and means for applying a pressure signal to the chamber, said latter means comprising a pair of concentric, relatively rotatable, tubular quill shafts, of which one is carried by the rotor and communicates with said chamber and the other extends through a wall of said housing to means for producing said pressure signal, and a passage leading .to the outside of the housing from an annular clearance space between the concentric quill shafts for leakage offluid providing the pressure signal.

Conveniently, the fluid providing the pressure signal is compressed air and the passage leading from the space between the quill shafts leads to atmosphere.

Alternatively, another pressurized fluid may be employed and may be permitted to leak through the said passage to atmosphere or to an external supply of said fluid.

By way of example, a liquid fuel pump in accordance with the invention is now described with reference to the accompanying drawing which is a diagrammatic axial section through the pump.

The pump comprises a rotor I mounted in an overhung manner by means of an integral shaft 2 in bearings 3 carried by a pump housing 4. The rotor 1 includes a plurality of axiallyextending bores of which one is indicated at 50 arranged around the rotor and each including a piston 51 arranged to be reciprocated as the rotor and the shaft rotate about their common longitudinal axis. The ends of the piston abut through spherically mounted shoes 52 against a stationary inclined surface 5 of a cam-plate 6 mounted in the pump housing. The left-hand end face 7 of the rotor 1 contains ports, of which one is shown at 55, communicating with the bores 50 and spaced apart circumferentially of the rotor. The ports 55 cooperate with arcuate inlet and outlet apertures 53, 54 through which, respectively, fuel contained in the interior 8 of the housing 4.

is drawn into the axial bores 50 in the rotor and discharged to a delivery pipe (not shown), as the pistons 51 are reciprocated.

As well known in fuel pumps of this kind, the rotor 1 contains a central spill passage 9, communicating at its left-hand end, as shown, with the outlet aperture 54 and through radial branch pipes 10, 11 with ports 12, 13 normally closed by halfball valves 14, 15 carried on leaf-springs 16, 17 supported on arms 18, 19 mounted on the outside of the rotor 1. At predetermined rotational speeds the ports 12 or 13 will open by centrifugal movement of the corresponding half-ball valve 14, 15 against the spring-loading afforded by the respective leaf spring 16, 17. The opening of the port 12 or 13 will result in fuel being returned from the outlet aperture 54 to the interior 8 of the housing 4 through the spill passage 9.

Also as is well known in fuel pumps of this kind, one 14, at least, of the half-ball valves is engaged by a plunger 20, slidable in a chamber 21 defined by the arm 18 and movable by an external fluid pressure signal to oppose the centrifugal force acting on the half-ball valve 14. The plunger 20 carries an O- ring seal 22 to prevent leakage of operating fluid, applied to the chamber 21, past the plunger into the interior 8 of the housing 4. Hitherto, the operating fluid for moving the plunger 20 has been oil applied to the chamber 21 from outside the housing 4 through a quill shaft or equivalent device. To prevent leakage of the oil applied to the chamber 21, it has been necessary hitherto to provide a seal between relatively rotatable parts of the quill shaft or equivalent device, thereby leading to friction and wear at the seal.

In accordance with the present invention, a pneumatic signal is applied to the chamber 21 from outside the housing 4. The compressed air, or other gas, providing the pneumatic signal, is applied to a connector 23 mounted in an end-plate 24 secured to the housing 4. The connector 23 communicates with passages 25, 26 in the end-plate 24 with a stationary, tubular first quill shaft 27, secured in a plug 28 mounted in a large diameter portion of the passage 26. The plug 28 carries O-ring seals 29; but as neither the quill shaft 27 nor the plug 28 rotates relatively to the end-plate 24 no frictional forces atthe O-ring seals 29 occur. Surrounding the first quill shaft 27 there is a coaxial, second, tubular quill shaft 30, mounted adjacent one end thereof in a seal 31 in the end-plate 24 and adjacent the other end thereof in a bush 32 inserted into a central socket 33 in the right-hand end face of the rotor 1. The second quill shaft 30 carries an O-ring seal 34 engaging the bush 32; but as the latter rotates with the rotor 1 and is not rotatable relatively thereto, no frictional forces occur at the O-ring seal 34. The quill shaft 30 runs freely on the quill shaft 27, there being an annular running clearance space therebetween. The socket 33 is formed coaxially of the spill passage 9 but flow is prevented therebetween by a ball 35 plugging a portion 36 between the passage 9 and the socket 33. A branch duct 37 leading to a socket 38 communicates with the passage portion 36 between the ball 35 and the socket 33. The socket 38 has a tubular connector 39 therein leading to a socket 40 in a portion of the arm 18 adjacent the chamber 21 defined therein. The connector 39 is sealed at its ends by O- ring seals 41, 42 and communicates with a passageway 43 in the arm 18 leading from the socket 40 to the chamber 21. The passageway 43 is closed to the interior 8 of the housing 4 by a ball plug 44.

The end of the running clearance space between quill shafts 27 and 30 at the right-hand end, as shown, of the quill shaft 30 communicates with a cavity 45 in the end-plate 24 and closed by the seal 31. The cavity 45 communicates through a passageway 46 with the outside of the end-plate 24.

When a pneumatic signal is applied through the connector 23, it will be transmitted through the passage 25, the quill shaft 27, the quill shaft 30, the duct 37, the connector 39 and the passageway 43 to the chamber 21. The only place where leakage of compressed air can occur is through the annular running clearance space between the quill shafts 27 and 30 to the cavity 45. From the cavity 45, the leakage compressed air will flow to the outside of the end-plate 24. The leakage is small and is readily replenished without affecting the controlling signal applied to the chamber 21. The seal 31 prevents leakage of compressed air from the cavity 45 into the fuel in the interior 8 of the pump housing.

The only seal acting between rotating and stationary parts in the quill shaft arrangement provided by the present invention is the seal 31; but as this acts between pump inlet pressure and atmospheric pressure, the pressure differential across it is extremely small and therefore there will be substantially no wear at the outer cylindrical surface of the quill shaft 30. The clearance between the quill shafts 27 and 30 avoids wear of the inner cylindrical surface of the quill shaft 30 and the outer cylindrical surface of the quill shaft 27.

Instead of applying compressed air to the plunger 20, via the quill shafts 27 and 30, another pressurized fluid may be applied from a supply externally of the housing and in that case the cavity 45 may communicate with the external supply instead of with atmosphere, so that the leakage fluid will be returned to the supply What I claim as my invention and desire to secure by Letters Patent of the United States is:

Iclaim:

L A rotary fuel pump comprising a housing, a rotor mounted in said housing and having a plurality of axially-extending bores therein, a piston in each said bore, a cam-plate inclined to the axis of rotation of the rotor, a spring in each said bore urging the piston therein into abutment with said cam-plate, each said bore communicating with a port at the end thereof remote from the cam-plate, said ports being circumferentially spaced around the axis of the rotor and cooperable successively with a fuel inlet and a fuel outlet in the form of circumferentially-spaced arcuate apertures coaxial with the rotor, a centrifugally operable valve member, carried by the rotor and arranged to control flow through a spill passage in the rotor leading from'the outlet aperture to the interior of said housing and communicating with the inlet aperture, a pressure-operable device for applying a controlling force on the valve member in opposition to the centrifugal force acting thereon, means carried by the rotor defining a chamber in which the device is movable, and means for applying a pressure signal to said chamber, wherein the improve ment comprises said latter means includes a pair of concentric, relatively rotatable tubular quill shafts, of which one is carried by said rotor and communicates with said chamber and the other extends through a wall of said housing to means for producing said pressure signal, there being an annular clearance space between the concentric quill shafts communicating with a cavity formed in a wall of the housing to receive any fluid providing said pressure signal that may have leaked through said annular clearance space, and an annular seal engaging between said quill shaft carried by the rotor and a peripheral wall of said cavity.

2. A fuel pump as claimed in claim 1 in which the fluid providing the pressure signal is compressed air and a passage leads from said cavity to the outside of said housing to lead leakage compressed air from said cavity to atmosphere.

Images