GB2056575A - Diaphragm pumps - Google Patents

Abstract

A diaphragm fuel pump has the pump inlet, outlet and working chambers 17, 20, 23 and the inlet and outlet valves 33, 35 all co-axially arranged within the pump housing 1, 15, the inlet and outlet valves being formed as a unitary assembly 30 which also provides a dividing wall between the working and outlet chambers. <IMAGE>

Description

SPECIFICATION Diaphragm pumps This invention relates to diaphragm-pumps and in particular to diaphragm pumps such as are suitable for use as fuel pumps in internal combustion engines. In such pumps the reciprocation of a diaphragm in a working chamber in the housing of the pump opens an inlet valve between the working chamber and an inlet chamber, connected to a fuel supply, to draw fuel into the working chamber on the suction stroke of the diaphragm, and then closes the inlet valve and opens an outlet valve between the working chamber and an outlet chamber of the pump, to discharge fuel from the outlet chamber, upon the delivery stroke of the diaphragm.

In a diaphragm pump according to the present invention the pum-p inlet chamber, outlet chamber and-working chamber, and the inlet and outlet valves which respectively control fluid flow between the inlet and working chambers, and between the work- ing and outlet chambers, are all coaxially arranged within the pump housing.

Preferably, a valve seat plate clamped between a cover portion of the pump housing and the diaphragm is formed with openings therein closable by said outlet valve; a sleeve member coaxial with and clamped between said seat plate and said cover co-operates with said outlet valve to separate said outlet and working chambers; and said inlet valve co-operates with said sleeve and a further valve seat plate within said cover having inlet openings therein, to separate said inlet and working chambers.

Preferably said inlet and outlet valves are formed integral with said sleeve, conveniently by forming the sleeve as a substantially rigid member of elastorneric material such as synthetic rubber, with a flexible radially outwardly extending valve flange at one end and with a central flexible valve disc within, but flexibly connected to, the inner peripheral portion of the sleeve at its other end, said valve disc co-operating with the inlet openings in said further valve seat plate, which is coaxial with, and clamped between, said cover and said other end of the sleeve.

The sleeve and valve members thus form a valve assembly general "top hat" form, providing a substantial simplification in the manufacture and assembly of the pump.

Conveniently, a filter element of general tubular or frusto-conical form, closed at one end and formed at its other end with a radial flange, is clamped by said flange between and coaxial with the cover member and the said ofher end of the sleeve so as to filter out solid particles which pass from the inlet chamber and through the inlet valve into the pump working chamber.

The pump cover member is preferably formed as a sheet metal pressing of stepped cylindrical form, the upper portion of which is of smaller diameter than the adjacent lower portion, so as to form the respective inlet and outlet chambers, and has inlet and outlet stub pipes secured and sealed thereto to provide for connection to a source of fuel and a carburetter respectively.

The cover member is preferably secured to a body member of the pump by deforming a radial flange portion of the-cover member on to a radial flange of the body member of the pump, as by interference staking or crimping. The pump body member houses, in known manner, the parts for effecting reciprocatory movement ofthe pump diaphragm clamped between the cover and body members of the pump.

An embodiment of a fuel pump according to fhe present invention is hereinafter described with refer encetothe accompanying drawings in which Figure lisa vertical section of a-pump according to the invention; Figures2 and 3 arena plan and an inverted plan respectiveíy of the pump of Figure 1, to a reduced scale; -Figure 4 is a vertical section of a valve assembly shown in Figure-1; Figure 5 is an inverted plan of Figure 4; and Figure 6 is a plan of a valve seat member shown in Figure 1.

The fuel pump shown in the drawings has a body 1 with a bore in the lower portion thereof in which a push rod 2is adapted to -be reciprocated, as by a rotary excentric 3, viiithwhich the push rod is kept in engagement by a spring 4.

At its upper end the push rod is retained within interengaged dependent tubular portions 5,6 respectively of an upper clamp plate 7 and a lower clamp plate 8, between which is clamped the central portion of a flexible circular pump diaphragm 10, the outer peripheral portion of the diaphragm being clamped between an annular peripheral flange 11 at the upper end of the housing and an outer peripheral flange on a co-axial valve seat plate 12 and an overlying annularpenpheralflange 14 of a pump cover 15, the cover 15 being secured to the body 1,with the diaphragm 10 and valve seat plate 12 clamped therebetween, by the flange 14 being interference staked at its periphery into the flange 11, as shown at 16.

Thus far described, the pump is, in general, of similar construction to that shown and described in the complete specification of our prior patent 1 065 225.

The cover 15 of the pump is of co-axially stepped cylindrical form having an upper reduced diameter portion within which is the pump inlet chamber 17 and into which opens an inlet pipe 18 secured to the cover.

The lower, wide diameter; portion of the cover 15 has an outlet pipe 19 secured thereto and opening into an output chamber 20 within the lower portion of the cover 15; and also secured to the lower portion of the cover 15is a by-pass pipe 21 which also opens into the output chamber 20.

The seat plate 12 is formed near its outer periphery with a coaxial circular series of openings 22 adapted to provide communication between the output chamber 20 and a working chamber 23 between the diaphragm 10 and the seat plate 12. Coaxially within the series of openings 22 the-seat plate is formed with a further circular series of openings 24 around an upwardly domed coaxial central portion of the seat plate.

Clamped between an annular shoulder 25 intermediate the smaller and larger diameter portion of the cover 10 and a corresponding opposed annular shoulder 26 in the seat plate 12 is a combined inlet and outlet valve assembly 30.

As shown in Figures 4 and 5 the valve assembly 30 is a unitary member, preferably made from synthetic rubber or like elastomeric material, and has a central cylindrical portion 31,with a wall thickness sufficient to give it substantial axial rigidity, the upper end of the portion 31 being formed with an annular recess 32 at its inner periphery and having co-planar with the lower face of said recess a co-axial valve disc 33 radially spaced from, but integrally connected with, the cylindrical portion31 by four equally spaced radial webs 34.

At its lower end, the cylindrical portion 31 has coaxial therewith an annular valve plate 35 co-planar with the lower face of the cylindrical portion 31, and spaced from, but integrally connected therewith, by a plurality of radial webs 36. As shown in Figure 1, the valve plate 35 normally overlies and closes the seat plate openings 22.

The thickness of the valve disc 33 and valve plate 35 is substantially less than that of the cylindrical portion 30 so as to enable the two valve members 33, 35 to flex under fluid pressure.

Fitting in the annular recess 32 at the upper end of the valve member 30 is a valve seat plate 40 which, as shown in Figures, is in the form of an annulus having therewithin two diametrically extending integral webs 41 intersecting each other at right angles to provide quadrant-shaped openings 42. The valve seat plate 40 is conveniently formed of a rigid plastics material or metal and, as can be seen in Figure 1, the lowerface of the annular seat plate 40 is normally engaged by the central valve disc 33 of the valve member 30 so as to close the openings 42 formed between the webs 41 and the annulus 40.

Arranged coaxially within the inlet chamber 17 is a filter element 50, conveniently formed, as shown in Figure 1, as an inverted cup member having ribs 51 supporting a fine mesh filter gauze 52, the ribs 51 and gauze 52 being integrally moulded with an annular rim flange 53 which overlies the upper end of the tubular portion 31 of the valve member 30 and the outer peripheral portion of the valve seat plate 40, the assembly of the filter flange 53, valve seat plate 40 and the cylindrical portion 31 of the valve member 30 being clamped together in sealing contact with each other between the annular shoulders 25,26 respectively on the cover 15 and seat plate 12.

As will be seen in Figure 1, in this position of the valve member 30 the annular valve plate 35 overlies and closes the circular series of openings 22 in the valve seat plate 12, and the valve disc 33 closes the opening 42 in the valve seat plate 40.

As the inner circular series of openings 24 in the valve plate 12 provide communication between the space within the cylindrical portion 31 of the valve member 30 and the space betweeri the seat plate 12 and the diaphragm 10, it will be seen that the space within the cylindrical portion 31 forms a part of the working chamber 23.

From the above description and the drawings it will be seen that the inlet chamber 17, outlet chamber 20 and working chamber 23 of the pump are all coaxially arranged, as are the filter 50, the seat plate 40, valve member 30 and seat plate 12, and that these are coaxial with the other elements of the pump within the body 1. Such an arrangement provides a substantial simplification in manufacture and assembly as the inlet and outlet valves form part of a unitary member and the concentric arrangement of the parts facilitates assembly by automatic machinery.

In operation, downward movement of the diaphragm under the action of the push rod 2 creates suction in the working chamber 23 causing the valve disc 33 to be unseated from the openings 42 in the seat plate 40 so that fuel is drawn in through the inlet pipe 18 and through the filter 50 into the working chamber 23; the opposite movement of the diaphragm creates pressure in the working chamber 23, which seats the valve disc 30 over the openings 42 and unseats the annular valve plate 35 from the openings 22, through which the fuel is delivered into the outlet chamber 20 and from thence to the outlet pipe 19.

The by-pass pipe 21 enables boiling fuel from the outlet chamber to be returned to the fuel reservoir which supplies fuel to the intake pipe 18 and thus prevent vapour lock.

Claims (8)

1. A diaphragm pump in which the pump inlet chamber, outlet chamber and working chamber, and the inlet and outlet valves which respectively control fluid flow between the inlet and working chambers, and between the working and outlet chambers, are all coaxially arranged within a pump housing.

2. A diaphragm pump according to Claim 1, in which a valve seat plate clamped between an upper cover portion of the pump housing and diaphragm is formed with openings therein closable by said outlet valve; and a sleeve member coaxial with and clamped between said seat plate and said cover co-operates with said outlet valve to separate said outlet and working chambers, and said inlet valve co-operates with aid sleeve and a valve seat in said cover portion having inlet openings therein, to separate said inlet and working chambers.

3. A diaphragm pump according to Claim 2, in which said inlet and outletvalves are formed integral with said sleeve.

4. A diaphragm pump according to Claim 3, in which said sleeve is formed as a substantially rigid member of elastomeric material such as synthetic rubber, with a flexible radially outwardly extending valve flange at one end and with a central flexible valve disc within, but flexibly connected to, the inner peripheral portion of the sleeve at its other end, said valve disc co-operating with valve openings in a further valve seat plate coaxial with and clamped between said cover portion and said other end of the sleeve.

5. A diaphragm pump according to Claim 4, in which a filter element of general tubular orfrusto- conical form closed at one end and formed at its other end with a radial flange is clamped by said flange between and coaxial with the cover portion and the said other end of the sleeve so as to filter out solid particles which pass from the inlet chamber and through the inlet valve into the pump working chamber.

6. A diaphragm pump according to any of Claims 1 to 5, in which said pump cover portion is formed as a sheet metal pressing of stepped cylindrical form, the upper portion of which is of smaller diameter than the adjacent lower portion, so as to form the respective inlet and outlet chambers, and has inlet and outlet stub pipes secured and sealed thereto to provide for connection to a source of fuel and a carburetter respectively.

7. A diaphragm pump according to Claim 6, in which said cover portion is secured to a body member of the pump by deforming a radial flange portion of the cover member on to a radial flange of the body member of the pump, as by staking or crimping.

8. A diaphragm pump constructed and adapted to operate substantially as hereinbefore described with reference to and as shown in the accompanying drawings.