US3482519A

US3482519A - Liquid fuel pumping apparatus

Info

Publication number: US3482519A
Authority: US
Inventors: Wilfred Edward Walter Nicolls
Original assignee: CAV Ltd
Current assignee: CAV Ltd
Priority date: 1967-03-28
Filing date: 1968-03-13
Publication date: 1969-12-09
Anticipated expiration: 1986-12-09
Also published as: GB1219765A; DE6608181U

Description

Dec. 9, 1.969 w. w. NICOLLS LIQUID FUEL PUMPING APPARATUS Filed March 13, 1968 WILFRED E.w. NICOLLS //VV/V7ZP PM 4709A")? United States Patent 3,482,519 LIQUID FUEL PUMPING APPARATUS Wilfred Edward Walter Nicolls, East Molesey, England, assignor t0 C.A.V. Limited, London, England, a British company Filed Mar. 13, 1968, Ser. No. 712,759 Claims priority, applicatlion Great Britain, Mar. 28, 19 67,

67 Int. Cl. F04b 13/132, 49/00; F04d 15/004 U.S. Cl. 103--2 Claims ABSTRACT OF THE DISCLOSURE This invention relates to liquid fuel pumping apparatus for supplying liquid fuel to an internal combustion engine and of the kind comprising a bore which defines a pumping chamber, a pumping piston slidable in said bore, means for moving the piston inone direction to reduce the volume of said pumping chamber, and a passage extending from said bore and through which fuel flows from the pumping chamber to the engine during movement of the piston in said one direction.

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

According to the invention in an apparatus of the kind specified there is provided a resiliently loaded one way valve having a valve element which is lifted from its seat to permit the flow of fuel from the pumping chamber through said passage and which is further lifted from its seat by physical contact of the piston therewith.

One example of a liquid fuel pumping apparatus in accordance with the invention will now be described with reference to the accompanying drawing which is a partsectional side elevation of the apparatus.

Referring to the drawing there is provided a body part in which is mounted a rotary cylindrical distributor member 11 which is arranged to be driven in timed relationship with the engine with which the apparatus is associated. At one end of the distributor member is formed a transverse bore 12 in which is mounted a pair of reciprocable plungers 50. Surrounding the distributor member at this point is an annular cam ring 51 having a plurality of diammetrically disposed and inwardly extending cam lobes which through the intermediary of rollers 52 respectively act to impart inward movement to the plungers as the distributor member is rotated and the plungers 50 together with the cam ring constitute a pressure pump.

At the opposite end of the distributor member is mounted the rotary part of a fuel supply pump 13 having an outlet which is in communication with a feed passage 14 formed in the body part. The inlet of the feed pump is connected in use, to a source of fuel. Within the distributor member is formed a longitudinally extending bore 15 which at one end is in communication with the transverse bore 12. The other end of the longitudinal bore is closed by a plug member 16 and a portion of the bore adjacent the plug member is of enlarged diameter.

Extending from this portion of the bore 15 is a radially disposed delivery passage 17 which is arranged to register in turn and as the distributor rotates, with a plurality of mice delivery ports 18 formed in the body part. The delivery ports 18 are connected respectively to the injection nozzles of the associated engine.

Slidably mounted within an intermediate portion of the bore 15 is a free pumping piston 19 which has end portions of reduced diameter. Furthermore, the step which is defined between the wider portion and the intermediate portion of the bore 15 constitutes the seating of a one Way valve. The valve element of this valve is defined by a plate 20 which is urged against the seating by means of a coiled compression spring 21. The diameter of the plate 20 is slightly smaller than that of the wider portion of the bore so that fuel can flow past the plate as will be described.

Extending from the bore 15 adjacent the step is an inlet passage 22 and a further inlet passage 23 extends from a further enlarged portion of the bore 15 lying between the aforesaid intermediate portion and the transverse bore 12. The inlet passages 22 and 23 are arranged to register respectively with

inlet ports

24 and 25 which are formed within the body part and which communicate at diametrically opposed points with a cylindrical chamber 26 formed in the body part. Moreover, mounted within this chamber is an angularly adjustable throttle member 53 which is provided with a pair of diametrically opposed and longitudinally extending grooves on its periphery. The inner end of the chamber 26 communicates by way of an annular groove formed in the body part, with the supply passage 14 and the arrangement is such that fuel flowing from the feed pump can be proportioned between the

ports

24 and 25 by adjustment of the throttle member 53.

During a filling stroke of the apparatus the

ports

24 and 25 are in communication with the passages 22 and 23 respectively whilst the passage 17 is out of register with an outlet port 18. As fuel flows through the passages 22 and 23 the free piston 19 moves to the left from the position in which it is shown in the drawing and at the end of the filling stroke the bore 15 is completely filled with fuel as also is the bore 12. As the distributor rotates the passages 22 and 23 are moved out of register with the ports, 24 and 25 and the delivery passage 17 is moved into register with an outlet port 18. During further movement of the distributor member the plungers are moved inwardly and fuel under pressure moves the free pumping piston to the right and in so doing fuel is displaced from the pumping chamber defined at the right hand end of the piston through the delivery passage 17 and the delivery port 18. During this time the plate 20 is lifted from the seating against the action of the spring 21. Towards the final movement of the pumping piston the reduced end thereof contacts the plate 20 and lifts it further from its seating.

The free pumping piston continues to be moved by the action of fuel under pressure expelled from the transverse bore 12 until spill passages 30 which extend from the bore 15, are exposed by the left hand end of the piston. As soon as this occurs the pressure at the left hand end of the pumping piston is relieved and any surplus fuel escapes through the spill ports 30 which during this time are in communication with spill ports 31 formed in the body part.

The delivery of fuel to the engine ceases as soon as the piston is brought to rest and when the excess fuel has been discharged the piston is moved in the reverse direction by the action of the spring 21. During this movement a quantity of fuel flows from the pipe line which interconnects the outlet port 18 with the nozzle, into the bore 15. After a predetermined quantity of fuel -has returned the plate 20 will be urged back onto its seat. When this occurs no further fuel can flow from the pipe line. It will thus be seen that the quantity of fuel which is returned from the pipe line to the bore 15 depends upon the movement of the piston during the movement of the plate onto its'seat. 4

If the piston is of sufficient mass its inertia will cause it to continue its movement to deliver fuel to an outlet after the spill port 30 has been opened. The inertia depends upon the speed at which the piston moves and since this is dependent upon the speed at which the apparatus is driven the degree of unloading of fuel from the pipe line can be made to vary in accordance with the speed at which the apparatus is driven.

If desired a pressurising valve 54 may be provided in the spill passage 31. The effect of this valve is to assist the inertia of the pumping piston 19 since it will ensure that pressure is always applied to the left hand end of the piston even though this pressure may be considerably lower than the pressure which is attained during the injection stroke. The characteristic of the pressurising valve may be adjusted to provide any required degree of unloading.

As the distributor member is rotated from the position in which it is shown in the drawing the delivery passage 17 is moved out of register with the delivery port 18 and the inlet passages 22 and 23 are brought into register with the

inlet ports

24 and 25 respectively to fill the bore 15 with fuel for the next injection stroke.

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

1. A liquid fuel pumping apparatus for supplying fuel to an internal combustion engine and comprising in combination, a pressure pump arranged to be driven in timed relationship with an engine with which the apparatus is associated, a bore, and to one end of which fuel is delivered by the pressure pump during a pumping stroke thereof, a pumping piston slidable in said bore and movable towards the other end of said bore during a pumping stroke of the pressure pump, a passage extending from said other end of the bore and through which fuel flows to the engine during movement of the piston towards said other end of the bore, a seat defined about said bore adjacent the other end thereof, a spring loaded valve element which is lifted from the seat to permit the flow of fuel from the other end of the bore through said passage and which is further lifted from the seat by physical con tact of the piston therewith, the piston under the action of the spring loading of the valve element moving towards said one end of the bore at the end of the pumping stroke of fuel to flow into said otherend of the bore throughsaid passage before the valve element contacts the seat.

2. An apparatus as claimed in claim 1 including a port formed in the wall of said bore, said port being uncovered to a drainby the end of the piston adjacent said one end of the bore when the piston attains a predetermined position after contacting said valve element and .during its movement towards the other end of the bore, the final position at which the piston stops being determined by the inertia thereof.

3. An apparatus as claimed in claim 2 including a pressurizing valve operable to limit the extentof the reduction in pressure of fuel acting on the end of the piston adjacent said one end of the borewhen said port is uncovered.

4. An apparatus as claimed in claim 3 including a rotary cylindrical distributor member mounted in a body part and arranged to be driven in timed relationship with the engine with which the apparatus is associated, said passage breaking out onto the periphery of the distributor member, and being arranged to register-in turn as the distributor member rotates, with a pluralityof outlet ports formed in the body' part-and which in use, are connected respectively to the' injection nozzles of the associated en gine,'the action ofthe' piston and valve element when moving in the other direction being to allow a returnflowv of fuel through said passage before the valve closes, the

volume of such return flow being substantially constant for each outlet port.

References Cited UNITED STATES PATENTS Q g Harris 103-41 X DONLEY J. STOCKING, Primary Examiner W. J. KRAUSS, Assistant Examiner US. Cl. X.R.