GB2135739A - Improvements in fuel pumps for motor vehicles - Google Patents

Abstract

A fuel pump for a motor vehicle, wherein a unitary stepped body shell 9 has swell 12 dividing the shell into inlet and outlet chambers, the latter incorporating a diaphragm 21 which provides excess pressure compensation by allowing variations in volume in a closed chamber 22 defined between said diaphragm and the dividing wall. A pumping chamber 11 communicates with the inlet and outlet chambers through valves 15, 16. <IMAGE>

Description

SPECIFICATION Improvements in fuel pumps for motor vehicles This invention relates generally to a fuel pump and, inparticular, a diaphragm pump of the type common ly used to provide a regular supply offuel to the carburettorofa motor vehicle.

The invention has for its objecttoofferimprove- mentswhich basically affect the structure which ] rnakesup and/or delimits the entry and supply chambers which itforms, in such a way that the overall-unit has the special feature of offering notable simpli'fication in assembly, high operating safety underrtormal conditions and, in case of unexpected conditionssuch as in accidents involving the overturn ofthevrffiicleinwhich it is installed, providing in all instancesa perfectlyfuel-tight block, together with better regularityof operation than that ofconventional pumps.These improvements are primarily achieved bytheintroductionwithin the supply chamber of a diaphragm, defining an excess pressure compensation chamber,this means being very simply made and of highly efficient function for the object intended.

The diaphragm petrol pump envisaged possesses a special characteristic in that its body is completely fuel-tight as it is made up of a single-blockshell within which the two chambers for entry and supply are contained and these are sealed from the outside as well as from each other even if the pump should come to be in an inverted position, as well as in certain operating conditions, being of superior reliability so far as concerns flow and static pressure than conventional pumps.

In essence, the diaphragm pump of this invention possesses a special characteristic in that the air intake and supply chambers which itforms are made up basicallyofasingleone-piece shell with a configura tion incorporating two coaxial tubular sections of different diameterjoined by means of a simple step, with the respective chambers being defined within each of these tubularsections which, joined by welding ontheirside, carry parallel fuel lines horizon 'tally positioned with both emerging towards one side, both ofthe aforementioned chambers being kept separate by a circular plate provided with a cylindrical peripheral flange and surrounded by a collar coupled by a connecting joint within the smaller section which defines the entry chamber and which incorporates a conventional filter, with the aforementioned step supporting the collar, while this plate incorporates a depression of circular shape with an invertedtrun- cated cone shaped wall having an opening at the base in the form of a funnel terminating with a cylindrical neckvia a stepped linkage, wherebythe funnel configuration cooperates with a third pump part coupled within the supply cavity, this part being a carrierforthevalves and which has the shape of an inverted cup with its base at two levels, with the surrounding rim projecting at the edge and resting on a step at the perimeter of the mouth ofthis lower cavity, this third piece also having on each of its base planes an opening which determines the seating of the aforementioned valves while providing in one of these a tubular extended collar designed to cooperate with the said throat which communicates with the air intake cavity, while its edge is supported on the annular plate which surrounds it.

Thus, a special characteristic of this diaphragm pump is the single block nature of its body without screw couplings orjoints interposed between pieces.

ltthus possesses completefuel-tightness in relation to the exterior even should the said pump cometo be in an inverted position as a consequence of an unexpected accident in the motorvehicle in which it is installed, which provides a notable increase in safety.

Another characteristic of this unit is the placing between the carrying element of the valves and the piece which divides the interior of the one-piece body into two chambers of a diaphragm ofwhich the periphery incorporates a shaped gasket which is defined on the ringed edgewhich surrounds the circular opening with which it is provided,to allow passage by means of the throat ofthe funnel shape.

The tubular collar rests on the periphery in such a way thatthe said diaphragm provides a closed air chamber in relation to the lower surface of the aforementioned transverse plate, this air chamber being of variable volume depending on the pressure which is applied to the diaphragm atthe expulsion phase and on the subsequent elastic response on recuperation following expulsion, this air chamberthereby providing an efficient compensation for the expulsion pressure.

The compensation chamber also works to provide a noticeable improvement in the reliability of the unit and in the static pressure it offers.

To provide a better understanding ofthe invention reference is made to the accompanying drawing, which shows in axial section a diaphragm pump incorporating all the improvements set out, byway of illustration, not intending to be limitative and in accordance with the following details.

The vertical section indicated shows two superimposed coaxial chambers 10, 11, linked by a stepped shape which a one-piece body9 incorporates, thereby defining the proposed diaphragm pump, from which emerge respectivetubular passages 10',11'for circulation ofthefluid handled by the unit. The said chambers 10, 11 are separated by a plate 12 furnished with a peripheral skirt 12', which is inserted as a fit in the smaller cavity 10, while a collar which surrounds its periphery rests on the step 13. The second chamber 11, of larger diameter, is coupled to a piece 14 carrying valves 15, 16, having springs 17. The piece 14 defines the seating for both the said valves, from one of which projects a tubular collar 18 which receives as a connecting linkthe extremity (which forms part of the throat 19) of a depression in the form of a funnel 20 provided on the plate 12 thereby allowing com munication between the two chambers. The drawing also shows the diaphragm 21 which is interposed between the part 14 and the plate 12, delimiting a closed chamber 22 of variable volume which tends to compensate the action of the diaphragm of the pump (notshown), principally at the expulsion phase, tending, as can be understood from the illustration, to regulate the supply of petrol to the carburettor, thereby improving the performance and useful life of the unit The said diaphragm 21 is furnished with a reinforced periphery 21', thereby to make it operate as a gasket extending to the partwhich lies held between the collar 18 and the external ring-shaped part ofthe depression 20 ofthe plate 12.

Optionally, it is possible to eliminate the circular plate 12, in this case making the join between the projecting tubular collar 18 with the diaphragm 21 by means of a conventional rivet arrangement.

Claims (8)

1. A diaphragm fuel pump of the alternating type forsupplyingthecarburettorofa motorvehicle, comprising a unitary body shell stepped to define two cylindrical sections respectively of smaller and larger dimeter, a dividing wall within the body shell in the region ofthe step, and an associated diaphragm dividing the interior into principal chambers, one on one side ofthe dividing wall and the other on the other side thereof, fluid inlet and outlet passages communicating with the respective principal chambers, a first valve providing for communication between the two principal chambers, a closed chamberofvariable volume defined between the diaphragm and the dividing wall, and a second valve operable principally in the expulsion phase to control the response ofthe diaphragm at said closed chamber, thereby to provide compensation for excess pressures.

2. Afuel pump according to claim 1, wherein the dividing wall has a flanged periphery bearing a radial lip and cooperating with the step in the body shell.

3. Afuel pump according to claim 2, whereby the dividing wall has a funnel-shaped depression provid ing for communication between the two principal chambers via the first valve.

4. Afuel pump according to any ofclaims 1 to 3, wherein the first and second valves are carried by a support member located in the principal chamber of larger cross-section.

5. Afuel pump according to claim 4, wherein the supportmemberactsto locate a reinforced periphery of the diaphragm against the said step in the body shell.

6. Afuel pump according to claim Swhen appen- dantto claim 3, wherein the support member has an axial projecting collar serving to locate the internal periphery of an aperture in the diaphragm around the funnel shaped depression in the dividing wall.

7. An entrylexpulsion chamberfor an alternating pump comprising a one-piece shell in the interior of which the air-intake and expulsion chambers are defined bytwo coaxial cylindrical sections of different diameter joined by means of a step, with fuel lines being linked on the same side of the body shell to the two chambers by means of welding,the said cham bers being separated by an annular plate provided with a cylindrical peripheral flange surrounded by a collarwhich is engaged in the smaller section which defines the entry chamber and which incorporates a filter, the collar seating on the step intersection ofthe two chambers, said plate having an inverted truncated cone-shaped depression with a funnel shaped opening atthe base terminating in a cylindrical shaped throatwhich coperates with a valve holder which takes the shape of an inverted stepped cup having its base attwo levels, and with a projecting flange surrounding its edge which rests on a peripheral step at the mouth of the larger chamber, this valve holder having at each of its base levels a passage adjacentto which is formed the seating forthevalves, and one base level also having a projecting tubular collar suitable for cooperating with the throat communicating with the air-intake cavity, there being provided between the valve holder element and the annular plate an apertured diaphragm of which the periphery incorporates a shaped gasketwhich is also located on the ringed edge which surrounds the aperture to permit passage by means ofthe throat of the funnel of the dividing plate with the tubular collar cooperating therewith, the diaphragm in relation to the annular plate providing a closed air chamberofvariable volume according to the pressure appliedto the diaphragm during the explusion phase and the subsequent elastic response, this chamberthereby providing an effective compensation for such active pressure and helping to regulatetheflowonexpulsion, thereby increasing the reliability and static pressure ofthe unit.

8. Afuel pump substantially as hereinbefore described with reference to the accompanying drawing.