DIAPHRAGM PUMP
United States Patent 3811803
A diaphragm pump, particularly for use as a fuel pump in an internal combustion engine, comprises upper and lower housing parts separated by a diaphragm which is clamped between them. The upper housing part comprises an intermediate housing and a top cover fixed on top of it. The intermediate housing has a cross wall which extends across the interior of the upper housing part and which, together with a valve plate within the intermediate housing, divides the upper housing part into three separate chambers, a suction chamber to which the pump inlet is connected, a working chamber, and a pressure chamber to which the pump outlet is connected. The working chamber is situated between the valve plate and the diaphragm. A sunken port is press formed or drawn integrally from the cross wall in an eccentric position, the lower lip of this sunken port being sealed to the valve plate around a corresponding aperture in the valve plate. In this way a passageway is formed communicating the chamber above the cross wall, preferably the suction chamber, with the working cyamber. The seal at the lower lip of the sunken port is formed either by a sealing ring or by the lip being directly fixed to the valve plate.
US Patent References:
Diaphragm pumps
Quatredeniers et al. - January 1968 - 3362341
Triple cover fuel pump
Toschkoff - January 1968 - 3364869
Diaphragm pumps
Quatredeniers et al. - January 1968 - 3364870
Diaphragm pumps
Quatredeniers et al. - January 1968 - 3362341
Triple cover fuel pump
Toschkoff - January 1968 - 3364869
Diaphragm pumps
Quatredeniers et al. - January 1968 - 3364870
Application Number:
05/215767
Publication Date:
05/21/1974
Filing Date:
01/06/1972
View Patent Images:
Export Citation:
Assignee:
A. Pierburg Auto-und Luftfahrtgeraete KG (Neuss/Rhein, DT)
Primary Class:
Other Classes:
417/571, 417/507
International Classes:
F02M1/00; F04B43/02; F04B53/00; F04B53/10; F04B21/04
Field of Search:
417/279,308,507,441,458,471
Primary Examiner:
Freeh, William L.
Assistant Examiner:
Smith, Leonard
Parent Case Data:
This is a division of application Ser. No. 864,337, filed Oct. 7, 1969, now abandoned.
Claims:
1. A diaphragm pump having upper and lower housing parts,
2. A diaphragm pump as claimed in claim 1, wherein said pressure reducing valve is controlled by means comprising a housing mounted on said cross wall and projecting into said suction chamber, a control membrane stretched across the interior of said housing, spring means within said housing and acting on one side of said control membrane, and means by which the pressure in said delivery chamber communicates with said housing to act on the opposite side of said control membrane from said spring
3. A diaphragm pump as claimed in claim 2, wherein said housing for said control membrane contains means defining a throttling orifice which connects said suction chamber to the side of the membrane on which said spring means acts.
2. A diaphragm pump as claimed in claim 1, wherein said pressure reducing valve is controlled by means comprising a housing mounted on said cross wall and projecting into said suction chamber, a control membrane stretched across the interior of said housing, spring means within said housing and acting on one side of said control membrane, and means by which the pressure in said delivery chamber communicates with said housing to act on the opposite side of said control membrane from said spring
3. A diaphragm pump as claimed in claim 2, wherein said housing for said control membrane contains means defining a throttling orifice which connects said suction chamber to the side of the membrane on which said spring means acts.
Description:
This invention relates to diaphragm pumps, such as fuel pumps for internal combustion engines, of the kind comprising upper and lower parts separated by a diaphragm, the upper part comprising an intermediate housing upon which is attached a top cover, and the intermediate housing having a cross wall which, together with a valve plate, divides the upper part of the pump into a suction chamber, a working chamber and a pressure chamber, the working chamber being located between the valve plate and the diaphragm.
Diaphragm pumps of this kind for use as fuel pumps are known in which the valve plate, which contains an inlet valve and an outlet valve, separates both the suction chamber situated above the inlet valve, and the pressure chamber situated above the outlet valve, from the working chamber situated above the diaphragm. The suction chamber is separated from the pressure chamber by means of a special part which rests in contact, on the one hand, with the valve plate and on the other hand with the lower surface of the cross wall of the intermediate housing. However, this type of pump is fairly costly to construct, in the first place due to the fact that it consists of four main parts, i.e. the top cover, the intermediate housing, the valve plate and the separating part, and in the second place because a double seal is required at the two ends of the sealing part where it joins the valve plate and the cross wall. A further disadvantage of this known fuel pump is that the top cover, which is mounted concentrically on the intermediate housing by means of an annular flange and which contains the suction chamber, is nevertheless attached to the intermediate housing by a screw inserted eccentrically in the top cover, with the result that the top cover, which contains the fuel inlet connection to the pump, can be mounted on the intermediate housing, which contains the fuel outlet connection, only in one particular position. Any change in the relative angular position of the two parts of the upper housing of the pump is impossible.
According to the invention, in a diaphragm pump of the kind described, the cross wall of the intermediate housing contains a sunken port which is press formed or drawn integrally from the cross wall in an eccentric position, the lower lip of the sunken port resting tightly in contact with or closely adjacent the surface of the valve plate surrounding a corresponding aperture in the valve plate, and a seal being formed between the lower lip and the valve plate so that a passageway is formed between the chamber above the cross wall and the working chamber below the valve plate.
In this way a pump is obtained which consists of only three main parts, the top cover, the intermediate housing and the valve plate, and is thus extremely simple to manufacture and assemble.
Preferably the fluid inlet and outlet connections for the pump are fixed to the top cover and the intermediate housing respectively, and the top cover is mounted concentrically on the intermediate housing by means of a centrally placed screw. Therefore, during assembly of the pump it is quite easy to adjust the angle between the fluid inlet connection and the fluid outlet connection, and also the angle between the fluid outlet connection and the body of the pump. The angle between the two fluid connections is adjusted, during assembly of the pump, by rotating the top cover relative to the intermediate housing and then tightening the screw. The angle between the fluid outlet connection and the body of the pump is adjusted by rotating the intermediate housing relative to the body of the pump. Alternatively, a different angle can be obtained between the fluid outlet connection and the body of the pump, by suitably positioning the opening in the intermediate housing for receiving the fluid outlet connection, i.e., by suitably positioning the fluid outlet connection, relative to the position of the port in the cross wall of the intermediate housing between the suction chamber and the working chamber.
The construction of the pump in accordance with the invention greatly favours application of the building-block principle, so that further structural units can be added to the pump according to requirements, thus greatly increasing the field of application of the pump. This advantage is obtained irrespective of whether the port in the cross wall of the intermediate housing is attached to the valve plate directly, such as by adhesive bonding, braising or welding, or is attached with the interposition of a resilient sealing ring. Direct attachment by bonding is preferred, for the sake of lower manufacturing cost and because it provides a more rigid structure and this method still allows further structural units to be added to the pump. For example the cross wall of the intermediate housing between the pressure chamber and the suction chamber can contain a pressure relief valve, for releasing the excess pressure which can build up in the pressure chamber when the engine is running hot, by evaporation of fuel.
As a further possibility the cross wall of the intermediate housing, between the pressure chamber and the suction chamber, may contain an aperture sealed off by a flexible membrane which is preferably spring loaded by a compression spring on the suction chamber side of the membrane. This construction is arranged to absorb pressure peaks in the pressure chamber and to increase the output of the pump.
As a still further possibility, for releasing excess pressure in the pressure chamber, there may be interposed between the wall of the intermediate housing and the valve plate an auxiliary valve plate to form a pressure chamber and a delivery chamber, the auxiliary valve plate containing a pressure reducing valve. This valve is preferably controlled by a control membrane which is acted on by a spring on one side and by the pressure in the pressure chamber on the other side, the control membrane being arranged in a housing which is mounted on the cross wall and projects into the suction chamber.
As a still further possibility, for certain particular applications, the pump can contain a device for isolating the suction chamber from the pressure or delivery chamber when the pump is not in use. For this purpose a pair of auxiliary plates which enclose a delivery chamber may be arranged in the pressure chamber between the cross wall of the intermediate housing and the valve plate, the pressure chamber communicating with one side of a spring loaded control membrane which, in use, opens a valve under the action of the pressure in the pressure chamber to connect the pressure chamber to the delivery chamber and which, when the pump stops, closes this valve.
Several examples of diaphragm pumps in accordance with the present invention are now described with reference to the accompanying drawings, in which:
FIG. 1 is a longitudinal section through a diaphragm fuel pump suitable for use in an internal combustion engine;
FIG. 2 is a longitudinal section through the upper part of a modified form of the fuel pump shown in FIG. 1;
FIG. 3 is a longitudinal section through part of the fuel pump shown in FIG. 1, but illustrating a modification to the pump;
FIG. 4 is similar to FIG. 3, but shows a different modification;
FIG. 5 is a longitudinal section through the upper part of another example of a diaphragm fuel pump in accordance with the invention;
FIG. 6 is a similar view to that of FIG. 5, but shows a further example; and,
FIG. 7 is a longitudinal section through the upper part of the pump shown in FIG. 1, but showing a slight modification.
The diaphragm fuel pump illustrated in FIG. 1 is shown in an upright position and has a diaphragm 1 mounted in a known way between the upper and lower parts of the pump body. The diaphragm 1 is driven in oscillation, when the pump is in operation, through a reciprocating drive rod which slides in a bush in the lower part of the pump body. Above the diaphragm 1 within the upper part of the pump there are three chambers, a suction chamber 2, a working chamber 3 and a pressure chamber 4. The working chamber 3 is situated immediately above the diaphragm 1 and is enclosed by the diaphragm and a valve plate 5 which contains a valve port 5a for an inlet valve 26, and valve port 5b for an outlet valve 26'. The port 5a communicates with the suction chamber 2 and the port 5b with the pressure chamber 4. The upper part of the pump body is formed by two superposed inverted cup-shaped members, i.e., an intermediate housing 6 and a top cover 7. The outer rim of the intermediate housing 6 is rolled over the outer rim of the lower part of the pump body, as shown at 6a in FIG. 1, the outer rims of the valve plate 5 and the diaphragm 1 being secured to the rim of the lower part of the pump body by clamping between the rolled rim 6a of the intermediate housing 6 and the rim of the lower part of the pump body, so as to form a combined sealed joint between these four parts. The top cover 7 is mounted on the intermediate housing 6 with a flange 7a around its rim engaging over the heel of the intermediate housing 6, and is fixed in position by means of a central screw 33 which engages in an internally screw threaded hole in the middle of the cross wall 8 of the intermediate housing 6. The cross wall 8 contains, eccentrically located, a sunken port or aperture 9 formed by a press operation and corresponding to the port 5a in the valve plate 5. The lower rim 9a of the port 9 lies adjacent the upper surface of the rim of the port 5a and a seal is formed between them by means of an elastic sealing ring 10.
With this arrangement the three chambers of the pump, i.e., the suction chamber 2, the working chamber 3 and the pressure chamber 4, are hydraulically separated from each other by the two internal walls in the upper part of the pump body. These are the cross wall 8 of the intermediate housing 6, and the valve plate 5. Thus, the suction chamber 2 is contained by the top cover 7, the working chamber 3 is above the diaphragm 1 and below the valve plate 5, and the pressure chamber 4 is to one side between the valve plate 5 and the cross wall 8. On the right of FIG. 1 the valve plate 5 contains the outlet port 5b. A valve housing 26a, whose upper surface rests against the lower surface of the cross wall 8, contains the outlet valve 26' which is spring loaded towards the closed position by a compression spring 26b. The suction chamber 2 contains a filtering screen 35, and there is a sealing ring 34 interposed between the flange 7a and the heel of the intermediate housing 6. The rim of the screen 35 is squeezed between the sealing ring 34 and the flange 7a.
The top cover 7 has a side opening 36 into which is welded or braised or otherwise firmly secured a fuel inlet connection 28. Similarly, the intermediate housing 6 has a side opening 37 into which is securely bonded an outlet connection 27. This construction has the advantage that the angular positions of the inlet and outlet connections, relative to each other, can easily be adjusted, either during assembly of the pump, or by simply loosening the central screw 33, rotating the top cover 7 relative to the intermediate housing 6, and finally tightening the screw again.
The example shown in FIG. 2 differs from FIG. 1 in that the sunken inlet port 9 has a different lip 9a, and is sealed to the valve plate 5 in a different manner. Furthermore the fuel inlet and outlet connections to the pump are differently attached to the upper part of the pump. In FIG. 2 the lip 9a of the inlet port 9, which is an essentially cylindrical extension formed by a drawing operation, rests directly on the upper surface of the valve plate 5 surrounding the port 5a without any intermediate seal, the two surfaces being bonded together by means of an adhesive, or by being braised or welded together. With regard to the inlet and outlet fuel connections, in FIG. 2 each connection 29, 30 has an external flange 31, 32, which is braised or welded to the housing part 6, 7 around the ports 36, 37 respectively. This arrangement still allows the housing parts 6 and 7 to be easily adjusted in angular position relate to each other merely by first loosening the central screw 33.
The way in which the diaphragm fuel pump shown in FIGS. 1 and 2 functions is as follows:
On the down stroke of the diaphragm 1 as it is oscillated by the driving shaft, fuel is sucked into the chamber 2 through the inlet connection 28, 30. The fuel in the suction chamber 2 flows through the filter screen 35 and through the inlet valve 26 into the working chamber 3, situated above the diaphragm 1. During the driving or up stroke of the pump the diaphragm 1, moving upwards, closes the inlet valve 26 and opens the outlet valve 26'. The fuel is expelled from the working chamber 3 into the pressure chamber 4 and from there is delivered through the outlet connection 27, 29. The outlet connection is connected by a pipe to the carburettor or fuel injection pump of the Otto cycle or Diesel cycle engine (not shown).
In the example shown in FIG. 3 the part of the cross wall 8 of the intermediate housing 6 which bounds the pressure chamber 4 contains a pressure relief valve 11, consisting of a ball 11b loaded by a compression spring 11a and seating on an orifice 12 forming a passage through the cross wall 8 and through the top of the housing 26a of the outlet valve 26'. The pressure relief valve 11 prevents an excessive pressure from building up in the pressure chamber 4 when fuel evaporates from a hot engine. As soon as the pressure increases to beyond the permitted value it lifts the ball 11b allowing fuel to escape from the pressure chamber 4 through the orifice 12 into the suction chamber 2 under the top cover 7.
The pump shown in FIG. 4 provides for absorption of the pressure peaks in the pressure chamber 4, thus increasing the output of the pump. An elastic membrane 13 is stretched across an opening in the cross wall 8 between the pressure chamber 4 and the suction chamber 2, and is spring loaded by a compression spring 14 situated on the suction chamber side of the membrane 13 and contained in a support housing 14a. The elastic membrane 13 absorbs pressure peaks in the pressure chamber 4 by flexing elastically upwards.
In certain cases it is desirable to absorb an excessive pressure build up within the pump before it reaches the outlet connection of the pump. An arrangement for doing this is shown in FIG. 5. An auxiliary valve plate 15 containing a pressure reducing valve 16, is interposed between the cross wall 8 of the intermediate housing 6 and the valve plate 5 to form a pressure chamber 4 and a delivery chamber 18. The pressure reducing valve 16 consists of a housing 16a containing a spring loaded ball 16c, loaded by a compression spring 16b. The ball 16c rests against the end of a plunger 17a attached to a control diaphragm 17 mounted in a housing 17b. The upper surface of the control diaphragm 17 is spring loaded by a compression spring 17c contained in the upper part of the housing 17b, which has an orifice 19 opening into the suction chamber 2. The pressure in the delivery chamber 18, acting on the lower surface of the control diaphragm 17 controls the flow of fuel delivered by the pump. The ball valve therefore acts as a pressure control valve, controlling the pressure in the delivery passage 18. It should be observed that in the example of FIG. 5 the central screw 33, which holds the top cover 7 down on its seat, screws into a stirrup 38 resting on the intermediate housing 6.
In some cases it is necessary to block the passage between the suction chamber and the pressure chamber of the pump, when the engine is at a standstill. This is obtained in the example shown in FIG. 6 by interposing between the cross wall 8 and the valve plate 5, two separating plates 20, 21 which enclose between them a chamber 22 which forms the delivery chamber of the pump.
Above the outlet port 5b leading into the pressure chamber 4 there is an aperture 23 passing through the two auxiliary plates 20, 21 which are in contact with each other around the periphery of the aperture 23 to form a seal against each other. The aperture 23 connects the pressure chamber 4 to the lower surface of a control diaphragm 24, whose upper surface is loaded by a compression spring 39 contained in a housing 40. The housing 40 contains an orifice 41 which connects the suction chamber 2 to the space above the diaphragm 24. This diaphragm controls a valve 25 consisting of a valve seat 25a mounted in the separating plate 21, a valve disc 25b and an inner valve housing 25c. When the pump is at a standstill the valve 25 is closed, as long as the pressure is not excessive in the pressure chamber 4. However, a pressure build up in the pressure chamber 4 acts on the control diaphragm 24, lifting the valve disc 25b and opening the valve 25 so that a connection between the delivery chamber 22 and the pressure chamber 4 is established, allowing fuel to flow out into the carburettor. In the pump shown in FIGS. 6 and 7 the ports 5a and 5b are provided with valve members 5a' and 5b' respectively which are made of conventional elastomer material, thereby causing the respective valves to act unidirectionally.
The pump shown in FIG. 7 is substantially the same as the pump shown in FIG. 1, but with the difference that in FIG. 7 the inlet valve 26 is not located in the valve plate 5, but rather in the interior of the sunken port 9, which is a part of the intermediate housing 6. This pump, however, still functions in the same way as the pumps shown in FIGS. 1 and 2.
The main advantages of the diaphragm pump according to the invention are that, in the first place, the pump contains few parts and is easy to manufacture and assemble. A further great advantage is that the construction of the pump greatly favours application of the building-block principle, so that further parts can easily be added to the pump, at very little extra cost.
Diaphragm pumps of this kind for use as fuel pumps are known in which the valve plate, which contains an inlet valve and an outlet valve, separates both the suction chamber situated above the inlet valve, and the pressure chamber situated above the outlet valve, from the working chamber situated above the diaphragm. The suction chamber is separated from the pressure chamber by means of a special part which rests in contact, on the one hand, with the valve plate and on the other hand with the lower surface of the cross wall of the intermediate housing. However, this type of pump is fairly costly to construct, in the first place due to the fact that it consists of four main parts, i.e. the top cover, the intermediate housing, the valve plate and the separating part, and in the second place because a double seal is required at the two ends of the sealing part where it joins the valve plate and the cross wall. A further disadvantage of this known fuel pump is that the top cover, which is mounted concentrically on the intermediate housing by means of an annular flange and which contains the suction chamber, is nevertheless attached to the intermediate housing by a screw inserted eccentrically in the top cover, with the result that the top cover, which contains the fuel inlet connection to the pump, can be mounted on the intermediate housing, which contains the fuel outlet connection, only in one particular position. Any change in the relative angular position of the two parts of the upper housing of the pump is impossible.
According to the invention, in a diaphragm pump of the kind described, the cross wall of the intermediate housing contains a sunken port which is press formed or drawn integrally from the cross wall in an eccentric position, the lower lip of the sunken port resting tightly in contact with or closely adjacent the surface of the valve plate surrounding a corresponding aperture in the valve plate, and a seal being formed between the lower lip and the valve plate so that a passageway is formed between the chamber above the cross wall and the working chamber below the valve plate.
In this way a pump is obtained which consists of only three main parts, the top cover, the intermediate housing and the valve plate, and is thus extremely simple to manufacture and assemble.
Preferably the fluid inlet and outlet connections for the pump are fixed to the top cover and the intermediate housing respectively, and the top cover is mounted concentrically on the intermediate housing by means of a centrally placed screw. Therefore, during assembly of the pump it is quite easy to adjust the angle between the fluid inlet connection and the fluid outlet connection, and also the angle between the fluid outlet connection and the body of the pump. The angle between the two fluid connections is adjusted, during assembly of the pump, by rotating the top cover relative to the intermediate housing and then tightening the screw. The angle between the fluid outlet connection and the body of the pump is adjusted by rotating the intermediate housing relative to the body of the pump. Alternatively, a different angle can be obtained between the fluid outlet connection and the body of the pump, by suitably positioning the opening in the intermediate housing for receiving the fluid outlet connection, i.e., by suitably positioning the fluid outlet connection, relative to the position of the port in the cross wall of the intermediate housing between the suction chamber and the working chamber.
The construction of the pump in accordance with the invention greatly favours application of the building-block principle, so that further structural units can be added to the pump according to requirements, thus greatly increasing the field of application of the pump. This advantage is obtained irrespective of whether the port in the cross wall of the intermediate housing is attached to the valve plate directly, such as by adhesive bonding, braising or welding, or is attached with the interposition of a resilient sealing ring. Direct attachment by bonding is preferred, for the sake of lower manufacturing cost and because it provides a more rigid structure and this method still allows further structural units to be added to the pump. For example the cross wall of the intermediate housing between the pressure chamber and the suction chamber can contain a pressure relief valve, for releasing the excess pressure which can build up in the pressure chamber when the engine is running hot, by evaporation of fuel.
As a further possibility the cross wall of the intermediate housing, between the pressure chamber and the suction chamber, may contain an aperture sealed off by a flexible membrane which is preferably spring loaded by a compression spring on the suction chamber side of the membrane. This construction is arranged to absorb pressure peaks in the pressure chamber and to increase the output of the pump.
As a still further possibility, for releasing excess pressure in the pressure chamber, there may be interposed between the wall of the intermediate housing and the valve plate an auxiliary valve plate to form a pressure chamber and a delivery chamber, the auxiliary valve plate containing a pressure reducing valve. This valve is preferably controlled by a control membrane which is acted on by a spring on one side and by the pressure in the pressure chamber on the other side, the control membrane being arranged in a housing which is mounted on the cross wall and projects into the suction chamber.
As a still further possibility, for certain particular applications, the pump can contain a device for isolating the suction chamber from the pressure or delivery chamber when the pump is not in use. For this purpose a pair of auxiliary plates which enclose a delivery chamber may be arranged in the pressure chamber between the cross wall of the intermediate housing and the valve plate, the pressure chamber communicating with one side of a spring loaded control membrane which, in use, opens a valve under the action of the pressure in the pressure chamber to connect the pressure chamber to the delivery chamber and which, when the pump stops, closes this valve.
Several examples of diaphragm pumps in accordance with the present invention are now described with reference to the accompanying drawings, in which:
FIG. 1 is a longitudinal section through a diaphragm fuel pump suitable for use in an internal combustion engine;
FIG. 2 is a longitudinal section through the upper part of a modified form of the fuel pump shown in FIG. 1;
FIG. 3 is a longitudinal section through part of the fuel pump shown in FIG. 1, but illustrating a modification to the pump;
FIG. 4 is similar to FIG. 3, but shows a different modification;
FIG. 5 is a longitudinal section through the upper part of another example of a diaphragm fuel pump in accordance with the invention;
FIG. 6 is a similar view to that of FIG. 5, but shows a further example; and,
FIG. 7 is a longitudinal section through the upper part of the pump shown in FIG. 1, but showing a slight modification.
The diaphragm fuel pump illustrated in FIG. 1 is shown in an upright position and has a diaphragm 1 mounted in a known way between the upper and lower parts of the pump body. The diaphragm 1 is driven in oscillation, when the pump is in operation, through a reciprocating drive rod which slides in a bush in the lower part of the pump body. Above the diaphragm 1 within the upper part of the pump there are three chambers, a suction chamber 2, a working chamber 3 and a pressure chamber 4. The working chamber 3 is situated immediately above the diaphragm 1 and is enclosed by the diaphragm and a valve plate 5 which contains a valve port 5a for an inlet valve 26, and valve port 5b for an outlet valve 26'. The port 5a communicates with the suction chamber 2 and the port 5b with the pressure chamber 4. The upper part of the pump body is formed by two superposed inverted cup-shaped members, i.e., an intermediate housing 6 and a top cover 7. The outer rim of the intermediate housing 6 is rolled over the outer rim of the lower part of the pump body, as shown at 6a in FIG. 1, the outer rims of the valve plate 5 and the diaphragm 1 being secured to the rim of the lower part of the pump body by clamping between the rolled rim 6a of the intermediate housing 6 and the rim of the lower part of the pump body, so as to form a combined sealed joint between these four parts. The top cover 7 is mounted on the intermediate housing 6 with a flange 7a around its rim engaging over the heel of the intermediate housing 6, and is fixed in position by means of a central screw 33 which engages in an internally screw threaded hole in the middle of the cross wall 8 of the intermediate housing 6. The cross wall 8 contains, eccentrically located, a sunken port or aperture 9 formed by a press operation and corresponding to the port 5a in the valve plate 5. The lower rim 9a of the port 9 lies adjacent the upper surface of the rim of the port 5a and a seal is formed between them by means of an elastic sealing ring 10.
With this arrangement the three chambers of the pump, i.e., the suction chamber 2, the working chamber 3 and the pressure chamber 4, are hydraulically separated from each other by the two internal walls in the upper part of the pump body. These are the cross wall 8 of the intermediate housing 6, and the valve plate 5. Thus, the suction chamber 2 is contained by the top cover 7, the working chamber 3 is above the diaphragm 1 and below the valve plate 5, and the pressure chamber 4 is to one side between the valve plate 5 and the cross wall 8. On the right of FIG. 1 the valve plate 5 contains the outlet port 5b. A valve housing 26a, whose upper surface rests against the lower surface of the cross wall 8, contains the outlet valve 26' which is spring loaded towards the closed position by a compression spring 26b. The suction chamber 2 contains a filtering screen 35, and there is a sealing ring 34 interposed between the flange 7a and the heel of the intermediate housing 6. The rim of the screen 35 is squeezed between the sealing ring 34 and the flange 7a.
The top cover 7 has a side opening 36 into which is welded or braised or otherwise firmly secured a fuel inlet connection 28. Similarly, the intermediate housing 6 has a side opening 37 into which is securely bonded an outlet connection 27. This construction has the advantage that the angular positions of the inlet and outlet connections, relative to each other, can easily be adjusted, either during assembly of the pump, or by simply loosening the central screw 33, rotating the top cover 7 relative to the intermediate housing 6, and finally tightening the screw again.
The example shown in FIG. 2 differs from FIG. 1 in that the sunken inlet port 9 has a different lip 9a, and is sealed to the valve plate 5 in a different manner. Furthermore the fuel inlet and outlet connections to the pump are differently attached to the upper part of the pump. In FIG. 2 the lip 9a of the inlet port 9, which is an essentially cylindrical extension formed by a drawing operation, rests directly on the upper surface of the valve plate 5 surrounding the port 5a without any intermediate seal, the two surfaces being bonded together by means of an adhesive, or by being braised or welded together. With regard to the inlet and outlet fuel connections, in FIG. 2 each connection 29, 30 has an external flange 31, 32, which is braised or welded to the housing part 6, 7 around the ports 36, 37 respectively. This arrangement still allows the housing parts 6 and 7 to be easily adjusted in angular position relate to each other merely by first loosening the central screw 33.
The way in which the diaphragm fuel pump shown in FIGS. 1 and 2 functions is as follows:
On the down stroke of the diaphragm 1 as it is oscillated by the driving shaft, fuel is sucked into the chamber 2 through the inlet connection 28, 30. The fuel in the suction chamber 2 flows through the filter screen 35 and through the inlet valve 26 into the working chamber 3, situated above the diaphragm 1. During the driving or up stroke of the pump the diaphragm 1, moving upwards, closes the inlet valve 26 and opens the outlet valve 26'. The fuel is expelled from the working chamber 3 into the pressure chamber 4 and from there is delivered through the outlet connection 27, 29. The outlet connection is connected by a pipe to the carburettor or fuel injection pump of the Otto cycle or Diesel cycle engine (not shown).
In the example shown in FIG. 3 the part of the cross wall 8 of the intermediate housing 6 which bounds the pressure chamber 4 contains a pressure relief valve 11, consisting of a ball 11b loaded by a compression spring 11a and seating on an orifice 12 forming a passage through the cross wall 8 and through the top of the housing 26a of the outlet valve 26'. The pressure relief valve 11 prevents an excessive pressure from building up in the pressure chamber 4 when fuel evaporates from a hot engine. As soon as the pressure increases to beyond the permitted value it lifts the ball 11b allowing fuel to escape from the pressure chamber 4 through the orifice 12 into the suction chamber 2 under the top cover 7.
The pump shown in FIG. 4 provides for absorption of the pressure peaks in the pressure chamber 4, thus increasing the output of the pump. An elastic membrane 13 is stretched across an opening in the cross wall 8 between the pressure chamber 4 and the suction chamber 2, and is spring loaded by a compression spring 14 situated on the suction chamber side of the membrane 13 and contained in a support housing 14a. The elastic membrane 13 absorbs pressure peaks in the pressure chamber 4 by flexing elastically upwards.
In certain cases it is desirable to absorb an excessive pressure build up within the pump before it reaches the outlet connection of the pump. An arrangement for doing this is shown in FIG. 5. An auxiliary valve plate 15 containing a pressure reducing valve 16, is interposed between the cross wall 8 of the intermediate housing 6 and the valve plate 5 to form a pressure chamber 4 and a delivery chamber 18. The pressure reducing valve 16 consists of a housing 16a containing a spring loaded ball 16c, loaded by a compression spring 16b. The ball 16c rests against the end of a plunger 17a attached to a control diaphragm 17 mounted in a housing 17b. The upper surface of the control diaphragm 17 is spring loaded by a compression spring 17c contained in the upper part of the housing 17b, which has an orifice 19 opening into the suction chamber 2. The pressure in the delivery chamber 18, acting on the lower surface of the control diaphragm 17 controls the flow of fuel delivered by the pump. The ball valve therefore acts as a pressure control valve, controlling the pressure in the delivery passage 18. It should be observed that in the example of FIG. 5 the central screw 33, which holds the top cover 7 down on its seat, screws into a stirrup 38 resting on the intermediate housing 6.
In some cases it is necessary to block the passage between the suction chamber and the pressure chamber of the pump, when the engine is at a standstill. This is obtained in the example shown in FIG. 6 by interposing between the cross wall 8 and the valve plate 5, two separating plates 20, 21 which enclose between them a chamber 22 which forms the delivery chamber of the pump.
Above the outlet port 5b leading into the pressure chamber 4 there is an aperture 23 passing through the two auxiliary plates 20, 21 which are in contact with each other around the periphery of the aperture 23 to form a seal against each other. The aperture 23 connects the pressure chamber 4 to the lower surface of a control diaphragm 24, whose upper surface is loaded by a compression spring 39 contained in a housing 40. The housing 40 contains an orifice 41 which connects the suction chamber 2 to the space above the diaphragm 24. This diaphragm controls a valve 25 consisting of a valve seat 25a mounted in the separating plate 21, a valve disc 25b and an inner valve housing 25c. When the pump is at a standstill the valve 25 is closed, as long as the pressure is not excessive in the pressure chamber 4. However, a pressure build up in the pressure chamber 4 acts on the control diaphragm 24, lifting the valve disc 25b and opening the valve 25 so that a connection between the delivery chamber 22 and the pressure chamber 4 is established, allowing fuel to flow out into the carburettor. In the pump shown in FIGS. 6 and 7 the ports 5a and 5b are provided with valve members 5a' and 5b' respectively which are made of conventional elastomer material, thereby causing the respective valves to act unidirectionally.
The pump shown in FIG. 7 is substantially the same as the pump shown in FIG. 1, but with the difference that in FIG. 7 the inlet valve 26 is not located in the valve plate 5, but rather in the interior of the sunken port 9, which is a part of the intermediate housing 6. This pump, however, still functions in the same way as the pumps shown in FIGS. 1 and 2.
The main advantages of the diaphragm pump according to the invention are that, in the first place, the pump contains few parts and is easy to manufacture and assemble. A further great advantage is that the construction of the pump greatly favours application of the building-block principle, so that further parts can easily be added to the pump, at very little extra cost.