US3097607A - Liquid fuel pumps - Google Patents

Description

F. G. FREEMAN LIQUID FUEL PUMPS I July 16, 1963 Filed Feb. 28, 1961 2 Sheets-Sheet 1 July 16, 1963 Y F. s. FREEMAN LIQUID FUEL PUMPS 2 Sheets-Sheet 2 Filed Feb. 28, 1961 United States Patent 3,097,607 LIQUID FUEL PUMPS Frank G. Freeman, Solihull, England, assignor to Joseph Lucas (Industries) Limited, Birmingham, England Filed Feb. 28, 1961, Ser. No. 92,220 Claims priority, application Great Britain Mar. 1, 1960 1 Claim. (Cl. 10341) This invention relates to pumps for supplying liquid fuel to gas turbine or other engines, the pump being of the kind comprising in combination a hollow body pant having an inlet and outlet, a rotor mounted in the body part for rotation by the engine, a plurality of plungers occupying a plurality of bores in the rotor respectively, and a cam surface against which the plungers are urged, the arrangement being such that as the rotor is rotated, fuel will flow from the inlet into the bores in turn during the "outward movements of the plungers and be discharged through the outlet by the inward movements of the plungers due to their interaction with the cam surface.

The object of the invention is to combine with such a pump convenient means for governing the speed of the engine.

According to the invention a pump of the kind specified includes a bleed passage in communication with the pump outlet, a valve member for controlling the escape of fuel through said bleed passage, said valve member being rotatable with, but axially movable relative to, the rotor, and centrifugally operable means on the rotor for moving said valve member axially in a direction to uncover said bleed passage as the speed of the engine increases.

More specifically the valve member comprises a piston movable in a cylinder by said centrifugally operable means, the bleed passage terminating in the wall of the cylinder and the pump further including a restricted orifice through which the inner end of the cylinder is in communication with the pump outlet, and an adjustable relief valve for controlling the pressure of fuel in the inner end of the cylinder, and hence the engine speed at which the bleed passage is uncovered.

An example of the invention is illustrated in the accompanying drawings in which FIGURE 1 is a sectional side view, FIGURES 2, 3 and 4 respectively are sections on the lines 2-2, 3-3 and 4-4, in FIGURE 1, and FIG- URE 5 is a section on the line 5-5 in FIGURE 4.

Referring to the drawings, the pump illustrated is intended for supplying liquid fuel to a gas turbine engine for a road vehicle, and comprises a hollow body part 6 provided with a fuel inlet 7 and a fuel outlet 8. Within the body part is a rotor 9 which is mounted or formed on a shaft 10 extending at one end from the body part 6 and adapted to be driven by the engine. In the rotor 9 are formed a plurality of angularly spaced parallel bores 9a extending parallel to the shaft 10. In each bore is a plunger 11 having at one end a shoe 12 which is held by one of a plurality of springs 13 against a cam surface 14 disposed obliquely to the axis of the shaft 10. Moreover at the end of the rotor 9 remote from the cam surface 14 is formed on the body part 6 a segmental valve (FIGURE 2) in which is formed an arcuate port 15 in communication with the outlet 8, the arrangement being such that as the rotor 9 is rotated fuel will be drawn into the bores 9a in turn by the outward movements of the plungers 11 under the action of their springs 13 and will be discharged through the port to the outlet 8 as the plungers 11 are moved inwardly by the cam surface 14.

In the end of the body part 6 containing the cam surface 14 there is formed a valve cylinder 16 which is coaxial with the rotor 9. In the cylinder 16 is a piston 17 having a stem 18 which extends into the centre of the rotor and is provided with a foot 19. The piston 17 is 3,097,607 Patented July 16, 1963 ice spring-loaded towards the rotor by means of a coiled compression spring 20 acting between the foot 19 and an abutment ring 21 in the rotor, and on the rotor is pivoted a centrifugally operable mass 22 which, as the angular velocity of the rotor increases, is adapted to exert an increasing axial force on the foot 19 through the intermediary of a ball 23, this force acting in opposition to the spring 20.

In the wall of the cylinder 16 is an annular groove 24 which is covered by the piston 17 when the pump is at rest, and which is in communication with the pump outlet 8 through a bleed passage 25 (FIGURE 5) communieating with a further passage 26. The passage 26 is also in communication with the other end of the cylinder 16 through a restricted orifice 27 (FIGURE 5) and a further passage 28. Moreover for controlling the pressure of fuel in the inner end of the cylinder there is provided a relief valve (FIGURE 4) the setting of which can be adjusted by the driver.

The relief valve takes the form of a stepped cylinder 29 formed within the body part and extending at right angles to the axis of the rotor. The narrower end of the cylinder is connected to the passage 28 and contains a cylindrical valve member 30 having a head adapted to seat against a shoulder defined between the narrower and wider part of the cylinder. The valve member 30 is loaded against its seating by means of a coiled compression spring 31 interposed between its head and an abutment piston 32 in the wider part of the cylinder, and between the valve member and the abutment piston is an outlet 33 through which fuel can escape through a passage 34 to the inlet side of the pump.

The wider end of the cylinder 29 is adapted for connection to a cylinder or other device (not shown) Whereby fluid pressure can be applied to the opposite side of the piston 32 in accordance with the setting of a throttle pedal or other control operable by' the driver, the arrangement being such that as the control is moved to increase the speed of the engine the compression of the spring 31 increases.

The relief valve 29, 30 is operable by a predetermined pressure of the fuel in the fuel outlet 8 of the hollow body part 6, and thereby serves to reduce the pressure of the fuel which occupies the inner end of the governing valve cylinder 16 remote from the interior of the hollow body part 6, and which is supplied from the fuel outlet 8 to this end of the governing valve cylinder through the restricted orifice 27 for opposing opening movement of the governing valve 16, 17.

Moreover, the governing valve 16, 17 is operable under the action of the centrifugally operable mass 22 carried by the rotor 9, and thereby serves to reduce the fuel pressure in the fuel outlet 8.

In operation the centrifugally operable mass 22 acts in opposition to the spring 20 and also the pressure of fuel at the inner end of the valve cylinder 16. Therefore, assuming that the drivers control is kept at a constant setting, the relief valve will open at a predetermined speed and permit fuel to escape fro-m the inner end of the valve cylinder 16 until the piston 17 uncovers the annular groove 24 and permits fuel to flow from the pump outlet 8 through the passages 26, 25 to the inlet 7. As a result the quantity of fuel fed to the engine is reduced and the engine speed falls thereby allowing the relief valve to close and the pressure of fuel fed through the restricted orifice 27 to the inner end of the valve cylinder 16 to return the piston 17 to its initial setting. By this means the speed of the engine will be governed to accord with the setting of the driver operated control, which determines the pressure at which the relief valve opens.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

A liquid fuel pump of the kind specified, comprising in combination a hollow body provided with a fuel inlet, a fuel outlet, an internal cam surface, and a bleed passage communicating at one end thereof with said outlet, a rotor mounted within said hollow body, and provided with a plurality of longitudinal bores which are angularly spaced relative to the axis of said rotor, and each of which communicates alternately, at one endof said rotor, with said inlet and said outlet during rotation of said rotor, a plurality of spring-loaded plungers respectively mounted within said bores, and extending from the other end of said rotor into contact with said cam surface which is disposed so that rotation of said rotor is accompanied by reciprocation of said plungers for enabling fuel from said inlet to be admitted to said bores in turn, and to be discharged from said bores in turn through said outlet, a valve member in the form of a piston which is coaxial with said rotor, and which serves to control the escape of fuel from the end of said bleed passage remote from said outlet, means whereby said piston is connected to said rotor so as to be rotatable therewith, and capable of axial movement relative thereto, centrifugally operable means which is carried by said rotor, and under the action of which said piston is movable axially to permit escape of fuel from said bleed passage when said rotor attains a predetermined speed, a valve cylinder in which said piston is mounted, and which at one end communicates through the interior of said hollow body with said inlet, and an adjustable pressure-responsive relief valve for controlling pressure in the other end of said cylinder, the latter being provided adjacent the first mentioned end thereof with an opening which communicates with the end of said bleed passage remote from said outlet, and through the medium of which communication is establisha'ble between said bleed passage and the first mentioned end of said cylinder by movement of said piston under the action of said centrifugally operable means, said hollow body being provided with a restricted orifice in communication with said outlet, and being also provided with a second passage which communicates at opposite ends respectively with the said other end of said cylinder and the end of said restricted orifice remote from said outlet, and said second passage being also in communication with said relief valve.

References Cited in the file of this patent UNITED STATES PATENTS 654,140 Diesel July 24, 1900 2,251,552 Purdy Aug. 5, 1941 2,357,563 Truxell Sept. 5, 1944 2,501,054 Huber Mar. 21, 1950 2,590,853 Fulton Apr. 1, 1952 2,706,384 Schott Apr. 19, 1955 2,922,370 Bischotf Jan. 26, 1960

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