US3513475A

US3513475A - Liquid fuel pumping apparatus

Info

Publication number: US3513475A
Application number: US773497A
Authority: US
Inventors: Alan Ewart Walter Austen
Original assignee: CAV Ltd
Current assignee: CAV Ltd
Priority date: 1967-11-06
Filing date: 1968-11-05
Publication date: 1970-05-19
Anticipated expiration: 1987-05-19
Also published as: DE1806922B2; GB1243184A; DE1806922A1; FR1590821A; ES360489A1

Description

May 19, 1970 A. E. .w. AUSTEN 3,513,475

I LIQUID FUEL PUMPING APPARATUS Filed Nov. '5, 1968 INVENTOR 4/, 144 4/4144 Md ATTORNEYS United States Patent 3,513,475 LIQUID FUEL PUMPING APPARATUS Alan Ewart Walter Austen, Sunbury-on-Thames, England, assignor t0 C.A.V. Limited, London, England,

a British company Filed Nov. 5, 1968, Ser. No. 773,497

Claims priority, application Great Britain, Nov. 6, 1967, 50,289/ 67 Int. Cl. F04b 1/00, 13/00; F04d 15/00 US. Cl. 417-252 4 Claims ABSTRACT OF THE DISCLOSURE A liquid fuel pumping apparatus including a plunger formed by two cup shaped parts axially slidable one within the other and loaded apart by a coiled compression spring, the plunger being mounted within a bore and actuated by a cam the pressure of fuel supplied to the bore acting when it attains a sutficiently high value to effect compression of the spring so that the effective displacement of the plunger is increased.

This invention relates to liquid fuel pumping apparatus of the kind comprising in combination, a pumping plunger movable within a bore, a cam for imparting movement to the plunger in one direction to pump fuel from the bore, the motion of the plunger in the opposite direction being under the influence of fuel under pressure entering said bore and acting upon the inner face of the plunger, the pressure of the fuel being dependent upon the speed at which the apparatus is driven and stop means for limiting the extent of movement of the plunger in the other direction.

The object of the invention is to provide such an apparatus in a simple and convenient form.

According to the invention the plunger has associated therewith a part which is axially movable relative to the plunger and there is provided spring means for urging the plunger and the part relative to each other so that said part projects beyond the outer face of the plunger, the arrangement being such that in use, when the fuel pressure is low the stop will be effective upon said part to limit the movement of the plunger in said other direction, and when the fuel pressure is high the spring means will be overcome so that the stop will be effective upon the plunger to limit the movement thereof.

In the accompanying drawings:

FIG. 1 is a sectional side elevation of one example of a pumping apparatus in accordance with the invention,

FIG. 2 is a section on the line 22 of FIG. 1, and

FIG. 3 is a view to an enlarged scale of part of the apparatus shown in FIGS. 1 and 2.

In one example of a liquid fuel pumping apparatus in accordance with the invention, there is provided a body part 1 in which is mounted a rotary cylindrical distributor member 2 which is adapted to be driven in timed relationship with an engine with which the apparatus is associated. At one end of the distributor member there is formed a head 3 having a transversely extending bore 4. In the bore 4 is mounted a pair of reciprocable pumping plungers 9. The space defined between the plungers is in communication with a longitudinal passage formed in the body part 1 and which at one point is in communication with a radially disposed delivery passage 17. The delivery passage is arranged to register in turn and as the distributor member rotates, with a plurality of equiangularly spaced delivery ports 18 formed in the body part and which, in use, are in communication respectively with injection nozzles (not shown) mounted so as to direct fuel into the combustion spaces of the associated engine.

For effecting inward movement of the plungers, there is provided in the body part, an annular cam ring 15 on the internal periphery of which are formed a plurality of pairs of inwardly extending cam lobes seen in FIG. 2. Moreover, at their outer ends the plungers bear upon slidable carriers respectively, each carrier mounted a roller 16 which bears upon the cam lobes. The outward movement of the carriers is limited by an adjustable stop plate 19 which is mounted upon the distributor member.

Also in communication with the longitudinal passage is a plurality of inlet passages 11 which are arranged to register in turn and as the distributor rotates, with an inlet port -12 formed in the body part.

The inlet port 12 is in communication with the outlet 7 of a feed pump 5, the rotary part of which is secured to the distributor member. The inlet 6 of the feed pump is connected to an inlet connection formed in the body part and the inlet and outlet of the feed pump are in communication with each other by way of a relief valve 8. The feed pump is of the vane type and the relief valve as shown, is in the form of a simple spring loaded relief valve. Alternatively it may be in the form of a centrifugally operable relief valve. In each case the output pressure of the feed pump varies in accordance at the speed at which the apparatus is driven.

For controlling the quantity of fuel which is fed to the space between the pumping plungers, an adjustable throttle 14 is provided intermediate the inlet port 12 and the outlet 7 of the feed pump. The throttle offers a variable restriction to the flow of fuel and the setting of the throttle is controlled by a speed sensitive governor (not shown) the characteristic of which can be adjusted by the engine operator. In use, fuel enters the space defined between the plungers by way of the inlet port 12 and an inlet passage 11 and moves the pumping plungers 9 outwardly. Subsequently, inward movement is imparted to the pumping plungers 'by the action of the cam lobes and fuel is discharged from the space between the plungers and flows by way of the longitudinal passage 10 and the delivery passage 17 to an outlet port 18. If the throttle is set to permit the maximum rate of flow of fuel the extent of outward movement of the plungers is limited by the stop plate 19.

In some applications it is desirable that the maximum quantity of fuel which can be delivered to an engine at low speeds is smaller than that which can be delivered at high speeds. Such a condition arises when the engine is provided with a turbo supercharger which is relatively ineffective at low speeds. In order to provide for this, one of the pumping plungers 9 and as shown in FIG. 3, is modified by making it of two parts, one part 20 is of cup-shaped form and forms the plunger, the base wall of the cup being directed towards the other plunger. Slidably mounted within the cup-shaped part 20 is a further cup-shaped part 21. Moreover, the base wall of the cup-shaped part 21 is provided with an extension 22 and mounted between the two cup-

shaped parts

20, 21 is a coiled compression spring 23 'which acts to urge the part 21 outwardly from the part 20. This movement is resisted by a circlip 24 which is located within a groove formed in the wall of the part 20. When the part is in contact with the circlip, the extension 22 of the base wall thereof projects slightly beyond the adjacent annular end face of the part 20.

At low speeds the fuel pressure which is applied to the end face of the part 20 during the filling stroke is insuf- (ficient to compress the spring 23 with the result that when the rollers move inwardly under the action of the cam lobes the spring 23 is compressed before actual inward movement of the part 20 occurs. At high speeds when the fuel pressure is higher, the spring 23 is compressed during the filling stroke so that the outward movement of the part 20 is slightly larger and the result of this is that an increased quantity of fuel is fed to the engine on the next filling stroke. Since the variation in fuel pressure with increasing speed is progressive so also is the increase in the quantity of fuel deliv red by the apparatus to the engine.

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

-1. Liquid fuel pumping apparatus for supplying fuel to an internal combustion engine and comprising a body part, a rotary fuel distributor member mounted in said body part and arranged to be driven in timed relationship with the engine with which the apparatus is asso ciated, a feed pump, the distributor member being provided with a cross bore in which is mounted an injection pumping plunger, an annular cam ring having cam lobes formed on the internal periphery thereof and which as the distributor member is rotated effects inward pumping movement of said plunger, said cross bore further being provided with a part which movably connects with said plunger by means of a spring means which urges said part and plunger relative to each other, the part, and spring means acting to limit the outward movement of said plunger toless than full stroke during low pressure pump operation but becoming inactive and allowing a full plunger stroke during high pressure pump operation.

2. A liquid fuel pumping apparatus as claimed in claim 1 in which the plunger and part of the interengaging cupshaped form, with the spring means in the form of a coiled compression spring acting between the plunger and said part.

3. A liquid fuel pumping apparatus as claimed in claim 2 in which the relative movement of the plunger and part under the action of the spring is limited by a circlip retained within a groove formed in the internal periphery of the plunger.

'4. A liquid fuel pumping apparatus as claimed in claim 3 in which the part is provided with a projection for contact with said cam ring.

References Cited UNITED STATES PATENTS 2,922,371 1/1960 Bischoif 103161 X 3,161,138 12/1964 Koster. 3,166,063 1/1965 Schettler. 3,338,168 8/1967 Davis l03-16'6 X 3,392,634- 7/1968 Tobias 106l61 X WILLIAM L. F'REEH, Primary Examiner W. J. 'K-RAUSS, Assistant 'Examiner US. Cl. X.R.