US2841085A - Liquid fuel pumps for internal combustion engines - Google Patents

Description

F. M. EVANS July 1, 1958 LIQUID FUEL PUMPS FOR INTERNAL COMBUSTION ENGINES Filed Jan. 16, 1956 2 Sheets-Sheet 1 July 1, 1958 EVANS 2,841,085

LIQUID FUEL PUMPS FOR INTERNAL COMBUSTION ENGINES Filed Jan. 16, 1956 2 Sheets-Sheet 2 gnm ' Fig.3

United States Patent LIQUID FUEL PUMPS FOR COMBUSTION ENGINES Fraser Mackie Evans, Acton, London, England, assignor to C. A. V. Limited, London, England Application January 16, 1956, Serial No. 559,484

1 Claim. (Cl. 103-37) 3 This invention has for its object to provide in a simple form a self-governing variable delivery pump for supplying liquid fuel to a single-cylinder internal combustion engine.

A pump in accordance with the invention comprises a body part having therein a pair of intercommunicating bores for reception of feed fuel and injection fuel respectively, a plunger in the feed bore, a rotary cam for moving this plunger in one direction and a spring for moving it in the opposite direction, a plunger in the injection bore which is movable in one direction by the feed plunger and in the opposite direction by the feed fuel, and a spring-loaded valve for controlling the rate of flow of fuel from the feed bore to the injection bore.

In the accompanying drawings, Figure 1 is a sectional side elevation of a pump embodying the invention, and Figure 2 is a fragmentary sectional view illustrating a modified form of the valve shown in Figure 1. Figure 3 is a similar View to Figure 1 illustrating an alternative embodiment of the invention.

Referring to Figure 1 the body part a of the pump has formed in it a pair of coaxial bores b, c, of dilferent diameters. The larger bore b is herein referred to as the feed bore, and the other bore c as the injection bore. At one end of the feed bore is provided a liquid fuel inlet d through which fuel is supplied from a supply tank, and from the other end extends a transfer passage e leading to the inlet of the injection bore. Between the transfer passage and the inlet end of the feed bore is provided a restricted vent in the form of bypass passage 1. The latter passage may be of fixed size, or it may be adjustable (as shown) by a manually operable throttle g.

In the feed bore is contained a hollow plunger 11 having at its closed end a port or ports i controlled by a valve j loaded by a spring k and through which fuel can pass from the inlet end to the discharge end of this bore. For actuating this plunger in one direction there is provided a rotary cam m driven by the engine, the cam being so shaped as to effect a rapid movement of the plunger in the direction in which the fuel is caused to move through the plunger, and to control the rate at which the plunger is returned by an associated spring 12. The action of the cam is transmitted to the feed plunger through a cylindrical slide 0 contained in a third (and coaxial) bore p in the body or other associated part, and an intermediate thrust piece q carried by the body part. The range of movement of the thrust piece q in one direction is determined by a collar r on one of its ends which can co-operate with a shoulder in the body part, the range of movement in the opposite direction (under the action of the cam) being determined by an axially adjustable stud s on the slide 0.

The injection plunger t is movable in the direction for discharging fuel from the injection bore by contact of one of its ends with the feed plunger h, movement in the opposite direction being effected by the feed fuel.

.j. In the discharge outlet u of the injection bore is contained a non-return valve v loaded by a spring w. The

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inflow to this bore may be controlled by either of the following devices. In the arrangement illustrated by Figure 1 there is provided a non-return valve x loaded by a spring y and contained in an entrance passage z situated between this bore and the transfer passage 2 and the flow to the entrance passage is controlled by a piston valve 2 in the transfer passage. This valve which is loaded by a spring 3 has formed in it an axial bore 4 leading to a circumferential groove 5 on the valve through which the feed fuel can pass from the transfer passage to the entrance passage. The valve is movable against the action of its associated spring by the pressure of the fuel in the transfer passage, so that the rate of fuel supply to the injection bore is progressively diminished with increasing feed fuel pressure. Alternatively and as shown by Figure 2, a single spring-loaded piston valve is contained in the entrance passage, this being adapted to serve both as a non-return valve and as a control valve responsive to the pressure'of the feed fuel.

The mode of action of the pump is as follows:

Assuming that both of the bores have already been filled with fuel, the effect of the action of the cam is to impart to the feed plunger through the thrust piece, a movement in the direction which causes fuel to be displaced through this plunger from one end of the feed bore to the other. The length of the stroke of the plunger in this direction is determined by adjustment of the above mentioned stud s on the slide relatively to the adjacent end of the' thrust piece. The maximum stroke is obtained when (prior to the commencement of the action of the cam) the thrust piece is in contact with the said stud. Simultaneously with this movement of the feed plunger, the latter transmits movement to the injection plunger and so effects discharge of the content of the injection bore. The manner in which the stroke of the injection plunger is automatically varied will become apparent in a later part of this description.

After the cam has performed its above mentioned duty, the feed plunger is returned by its associated spring at a rate determined by the contour of the cam. During this movement fuel is discharged from the feed bore along the transfer passage to the injection bore and the effect of this is to move the injection plunger in the same direction as the feed plunger. Assuming that the pump is working at a slow rate the injection plunger will move at the same rate as the feed plunger, and the injection bore will receive its maximum amount of fuel. Any excess of this amount will be returned to the inlet end of the feed bore through the by-pass passage 1.

With increasing rate of rotation of the cam, the pressure of the fuel in the transfer passage will increase, until a predetermined pressure is reached when the control valve 2 will move against the action of its spring, in the direction for reducing the rate at which the fuel can enter the injection bore. Consequently the extent of movement of the injection plunger and the amount of fuel which enters the injection bore before the cam exerts its next action on the slide Will be diminished, thus providing the desired automatic governing action of the quantity of fuel discharged from the injection bore. The speed at which the governing action occurs may be varied by appropriate setting of the manually operable throttle g or, in the case of a fixed throttle, by appropriate adjustment of the loading of the spring 3 which opposes the movement of the control valve 2, this adjustment being conveniently effected by appropriate manipulation of a screw-threaded bush 3a (Figure 1) which serves as an abutment for the end of the spring remote from the control valve.

In the example illustrated by Figure 3, the above mentioned valve j on the plunger 11 is substituted by a non-return valve 6 loaded by a spring 7 and contained in a side passage 8, between the fuel inlet d and one end of the bore b. In the discharge end of the injection plunger-t is formed an" axial spill bore 9 leading to a circumferential groove 10, and in the body part is formed a spill port 11, so that when the plunger 2 approaches the end of its discharge stroke, excess fuel can be diverted from the bore c'to the passage e; The control valve 2 is supported at its lower end on a shoulder 12 in the passage 2 and is provided with an axial bore 4 which is fed through a side port 13. The valve isheld in the position shown by the spring 3, and at the upper end of the bore 4, there is mounted a non-return ball valve 14. Further the thrust piece q is permanently in contact with the parts It and s and the effective length of stroke of the plunger t is determined by the spill groove 10 and port 11.

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

A liquid fuel pump comprising in combination a fuel inlet, a body part provided with a first bore for receiving fuel from said fuel inlet, a second bore arranged co- 4 axially with and extending from one end of .said first bore, and a fuel transfer passage leading from said first bore to the remote end of said second bore and having a restricted vent associated"'ther"ewitli, afuel outlet leading from the last mentioned end of said second bore, a fuel feed plunger slidable in said first bore, a spring acting on said plunger, a rotary cam for moving said plunger against the action of said spring, a fuel injection plunger slidable in said second bore in one direction by said fuel feed plunger for discharging fuel through said outlet, and in the opposite direction'by the pressure of fuel transferred by said fuel feed plunger from said first bore to said second bore through said passageway, and a spring-loaded valve arranged in said passageway and movable by fuel pressure in said first bore to reduce the rate of fuel flow therefrom to said second bore.

ReferencesCited in the file of this patent UNITED STATES PATENTS 2,582,535 Drouot Ian. 15, 1952

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