US2980032A - Fuel pump - Google Patents

Description

April 1961 K. c. SCHNEIDER 2,980,032

FUEL PUMP Filed Feb. 27. 1959 FIG. I

INVENTOR KENNETH C. SCHNEIDER ATTORNEYS United States Patent FUEL PUMP Kenneth C. Schneider, Bethe], Conn., assignor to Brown Engine Products, Inc., a corporation of Connecticut Filed Feb. 27,1959, Ser. No. 796,122 6 Claims. (Cl. 103-150) only limited displacement out of the plane of the diaphragm.

In some diaphragm-type fuel pumps, unidirectional flow of fuel is maintained by flap type check valves integral with the diaphragm and operatively associated with the fuel inlet and outlet passages. Such check valve flaps are generally separate from the pumping portion of the diaphragm and are each enclosed in valve chambers formed in the body of the pump. When the pressure in the valve chamber is greater than the pressure in the fuel passage, the flap is urged tightly against its seat around the opening thereby preventing back-flow of fuel from the chamber into the passage. Conversely, when the pressure within the passage exceeds that within the chamber, the flap is unseated and displaced out of the plane of the diaphragm into the chamber thereby permitting the fuel in the passage to flow into the chamber. I

Flap valves of this type are usually formed of very thin sheet material which is highly flexible so that the flaps respond readily to small pressure differentials, and they are uniformly flat so that they can effect a continuous seal around the opening of the fuel passage. It has been found, however, that in diaphragms which have been in operation for long periods of time, the flaps often lose their original flatness and no longer seat readily to seal the fuel passages. Needless to say, this greatly reduces the efliciency of the pump since at each stroke a certain amount of fuel leaks under the distorted portions of the flap and correspondingly less fuel is delivered from the outlet of the pump.

There are many reasons why conventional flap elements lose their flat shape in this manner. The fact that they must be formed of such thin and flexible sheet material gives rise to some of the difliculty because if they are overstressed during the repeated bending of'the flap into and out of the plane of the diaphragm a permanent warped shape is imparted to the thin sheet material. It also appears that the flap elements are sometimes distorted by being unevenly stressed when the pump is assembled, due to excessive tightening together of the pump body members holding the diaphragm in place. Also, the

flaps are generally formed from synthetic elastomers which, if unevenely or excessively heated, are unable to resist curling during use.

One of the primary purposes of this invention, therefore, is to provide a fuel pump of the type described having flap elements integral with the pump diaphragm which remain uniformly flat even after long use. This is accomplished without departing from the use of thin flexible sheet materials from which conventional pumpdiaphragms are presently formed,'and also withoutradically altering the design of ordinary pump body members.

Patented Apr. 18,1961

Moreover, these advantages are achieved without adversely affecting the efliciency or fuel-delivery capacity of the pump.

' The invention provides a unitary flexible substantially flat sheet diaphragm for use in a diaphragm-type pump comprising a displaceable pumping portion adapted to partly define a pumping chamber, and at least one check valve portion adapted to control flow of fluid through the pump. The check valve portion comprises a flat valve flap having a base joined integrally with the diaphragm and a free end essentially separated by cut-out sections from the main body of the diaphragm. The free end of the valve flap is displaceable out of the plane of a cut-out section of the diaphragm; but at least one flexible web finger bridges the cutout section and joins the free end of the valve flap to the diaphragm. By this construction, displacement of the flap element out of the plane of the cut-out section is limited without being prevented, and the flap is restrained from permanently bending, curling, or otherwise becoming distorted out of its original uniformly flat shape.

, Preferred embodiments of the invention are described hereinbelow with reference to the accompanying drawing, wherein- Fig. l is an elevation partly in section of a pump according to the invention;

Fig. 2 is a section taken along the line 2-2 of Fig. l;

and

Fig. 3 is a plan view of a modified form of a pump diaphragm according to the invention.

Referring first to Figs. 1 and 2, the pump includes a pair ofbody members 10 and 11 which are fastened together in substantially face-to-face relationship by means of a plurality ofscrews 13 disposed about their corresponding peripheries. As seen in Fig. 1, the upper portion of the body member 11 is broken away to indicate that the pump may be incorporated in a larger assembly such as a carburetor. In this embodiment, the pump is of the type actuated by a source of fluctuating fluid pressure, though it can also be mechanically actuated by a cam shaft or similar means.

Separating the facing surfaces of thebody members 10 and 11 is a flat uniformly thinflexible diaphragm 14 of circular shape. Thediaphragm 14 includes acentral pumping portion 15, separate inlet and outlet check valve portions 17 and 18 respectively, and a peripheral gasket portion indicated generally at 19 which makes up the remainder of its area. Thegasket portion 19 of the diaphragm is that area which in the assembled pump underlies agasket 21 positioned against the upper body member 11. Itwill be noted that thescrews 13 extend through corresponding holes in both thegasket portion 19 of the diaphragm and thegasket 21. By this arrangement, the

gasket portion 19 of the diaphragm,,in conjunction with thegasket 21, provides a fluid tight seal which isolates each of the inlet and outlet check valve portions 17 and 18 and thepumping portion 15 from one another when the pump is assembled.

An actuatingcavity 23 is formed in the upper body member 11. This cavity together with the upper side of thepumping portion 15 of the diaphragm defines anactuating chamber 24. The actuatingchamber 24 communicates with a source of fluctuating fluid pressure (such I as the crank-case of a two-cycle engine) through anair passage 25.

Apumping cavity 27 is formed in the otherpump body member 10. This latter cavity, together with the lower side of thepumping portion 15 of the diaphragm, defines apumping chamber 28. As seen most clearly in Fig. 2, the check valve portion 17 includes a valve flap 29 integrally joined at its base to theadjacent gasket portion 19 of the; diaphragm. Its free end isseparat'egl '31 which bridge the cut-out sections 30. The valvefiaps 29'and theweb fingers 31 are of the same uniform thickness as the surrounding portions of the diaphragm, so they can be formed by stamping or punching out the cut-out sections 30.

Similarly, the outlet check valve portion 18 includes avalve flap 32 integrally joined at its base to the diaphragm, with its free end separated from the surrounding portion of the diaphragm by cut-outsections 33. A pair of integral webs 34 connect the free end of thevalve flap 32 to the main body of the diaphragm across the cut-outsections 33.

The element of the fuel system of this novel pump can best be described in-the order in which they are encountered by fuel passing through the pump. Fuel is drawn into the pump through aninlet nozzle 36 into asuitable filter 37 which is held in place by ascrew 38. The fuel then passes into aninlet passage 39 formed in thebody member 10, proceeds through the inlet check valve portion 17 of the diaphragm 19 (as is described in detail below), and enters aninlet valve chamber 40 defined substantially by the body member 11. It is then directed from thevalve chamber 40 through the cut-out section 30 of thediaphragm 14 into intersectingbores 41 and 42 in the body member and then into thepump ing chamber 28. From thepumping chamber 28, the fuel exits under pressure into the intersectingbores 43 and 44 and through the outlet check valve portion 18 of the diaphragm (as is also described in detail below). It then enters anoutlet valve chamber 45 from which it proceeds under pressure to theoutlet fuel passage 46.

The operation of this novel pump is as follows: The cyclically fluctuating air pressure in the actuatingchamber 24 causes the pumping portion of thediaphragm 14 to flex alternately in and out of thepumping chamber 28. At each stroke of thepumping portion 15 out of thepumping chamber 28, the internal pressure in thepumping chamber 28 is decreased. This reduction in pressure is transmitted to theinlet valve chamber 40 and when the pressure therein drops below the pressure in theinlet fuel passage 39, the flap element 29 is lifted and fuel is sucked through into the pumping chamber. The webs 31, however, restrain the free end of the flap element 29 and prevent it from being displaced very far out of the plane of the surrounding portions of thediaphragm 14. At the same time, the webs 31 permit the flap 29 to be raised a sufiicient distance off its seat to allow the fuel to pass easily from thefuel inlet passages 39 into thepumping chamber 40.

As this takes place at the inlet check valve portion 17, the reduction in pressure in thepumping chamber 28 is also transmitted to thebore 44 adjacent the outlet check valve portion 18 of the diaphragm. This causes the pressure in theoutlet valve chamber 45 to exceed that in thebore 44 and, as a result, theflap element 32 is forced tightly against its seat to seal off the opening. This prevents back-flow of fuel from theoutlet passage 46 into the pumpingchamber 28 at each intake stroke of the pumpingportion 15 of the diaphragm.

Upon the completion of the intake stroke, the pumpingportion 15 of the diaphragm moves downwardly into the pumpingchamber 28 thereby increasing the pressure of the fuel therein. The eifect of this at the inlet check valve portion 17 is to force theflap element 25 against its seat to seal off the inlet passage. This prevents back-flow of fuel from the pumpingchamber 28 into theinlet passage 39 during the pumping stroke of the diaphragm. At the outlet check valve portion 18 there is a simultaneous increase in pressure in thebore 44 which causes it to exceed the pressure within theoutlet valve'chamber 45. This causes thefiap element-32 to be lifted from-its seat (as shown in Fig. "1)*and permits 4: a some of the fuel in thepumping chamber 28 to be forced out under pressure into theoutlet passage 46. As theflap element 32 is lifted in this manner, however, the webs 34 prevent it from being displaced very far out of the plane of the surrounding diaphragm, yet do not substantially hinder the fiow of fuel into thevalve chamber 45.

Because of the restraining action of the webs 31 and 34, the flap elements 29-and-32' respectively are not excessively displaced. Asa result they do not become so stressed as to warp even after prolonged use. Also, if thermal stresses due to overheating tend to cause curling of the diaphragm material, the webs minimize the deformation of the valve fiaps and insure that they sufiiciently retain their original flat shape to continue to seat eifectively. The webs 31 and 34 likewise compensate for uneven stress which might be imparted to theflap elements 29 and 32 by excessive tightening together of thebody members 10 and 11 during assembly of the pump.

Turning now to Fig. 3, a modified form of thepump diaphragm 50 is shown. Thediaphragm 50 includes acentral pumping portion 52, inlet and outletcheck valve portions 53 and 54 respectively, and aperipheral gasket portion 55 which makes up the remainder of the diaphragms area. Since thediaphragm 50 is to be assembled with a pair of pump body members in the manner described previously, a plurality ofapertures 57 are located in itsgasket portion 55 to accommodate the screws for holding the pump body members together.

The inletcheck valve portion 53 includes a cut-outsection 59 into which extends afiat valve flap 60, which is joined integrally at its base to the main body of the diaphragm. Bridging the cut-outsection 59 and integrally joining the outermost end of thevalve flap 60 to the main body of the diaphragm is asingle web finger 61. This finger limits the displacement of theflap 60 out of the plane of the diaphragm sheet and aids in preventing it from being distorted out of its original flat shape. The cut-outsection 59 shown in Fig. 3 extends to one side of theflap element 60. Hence, this check valve portion is adapted for use in a valve chamber wherein the inlet passage is not in radial alignment with the bores leading from the valve chamber to the pumping chamber.

The outletcheck valve portion 54 is of still different construction. It includes a circular valve flap 63 disposed in a concentric cut-outsection 64. The ,valve flap 63 is integrally joined to the main body of the diaphragm by' a plurality ofweb fingers 66 which bridge thecutout section 64. Any one of these web fingers can be regarded as defining the base of the circular valve flap, and the others as joined to the free end of the valve flap. This type of valve flap is particularly adapted for use in the outlet valve chamber of a pump wherein the fuel enters through the cut-out section and exits from the chamber without passing back through the diaphragm. An example of such arrangement is shown in Figs. 1 and 2 where the pressurized fuel enters from thebore 44 into theoutlet valve chamber 45 and then exits therefrom through theoutlet passage 46 without passing back through the diaphragm. One of the primary advantages of this outletcheck valve portion 54 is that the flap element 63 is lifted substantially evenly from its seat when fuel passes therethrough, thereby tending to insure that the valve flap element seats fiat when it returns to sealing engagement with its associated fuel passage.

I claim:

1. For use in a diaphragm-type pump, a unitary flexible substantially flat sheet diaphragm comprising a displaceable pumping portion adapted to partly define a pumping chamber, at least one check valve portion adapted to control flow of fluid through. said pump, said check'valve portion comprising a fiat valve flap having a base integral with said diaphragm and an end portion essentially separatedby cut-outsections from the main body of said diaphragm, the end portion of said valve flap being dis.-

placeable out of the plane of said diaphragm, and at least one flexible web finger bridging said cut-out sections and joining the end portion of said valve flap tosaid diaphragm, said web finger limiting without preventing displacement of said end portion of the valve flap out of the plane of the diaphragm.

2. A diaphragm-type fuel pump comprising two body members joined together in substantially face-to-face relationship, a flexible diaphragm separating the substantially cojoined faces of said body members, said diaphragm including a pumping portion which partly defines a pumping chamber in one of said body members, both of said body members having fuel inlet and outlet passages formed therein communicating with said pumping chamber, said diaphragm also including check valve portions located in said fuel passages for controlling flow of fluid through said pump, at least one of said check valve portions comprising a flat valve flap having a base integral with said diaphragm and an end portionressentially separated by cut-out sections from the main body of said diaphragm, the end portion of said valve flap normally being in sealing relation with the fuel passage with which it is associated and being displaceable out of the plane of said diaphragm to permit flow of fuel through its associated fuel passage, and at least one flexible web finger bridging said cut-out sections and joining the end portion of said valve" flap to said diaphragm, said web finger limiting without preventing displacement of said end portion of the valve flap out of the plane of the diaphragm.

3. For use in a diaphragm-type fuel pump, a diaphragm of substantially flat flexible material comprising a displaceable pumping portion adapted to partly define a pumping chamber, and two separate check valve portions adapted to maintain unidirectional flow of fuel through said pump, each of said check valve portions comprising a valve flap having a base joined integrally to said diaphragm and an end portion essentially separated by cut-out sections from the main body of the diaphragm, the end portion of said valve flap being displaceable out of the plane of said diaphragm, and restraining means comprising at least one web finger integrally joined both to the end portion of said valve flap and to the main body of the diaphragm bridging said cut-out sections and limiting without preventing displacement of said end portion of the valve flap out of the plane of the diaphragm.

4. For use in a diaphragm-type fuel pump, a diaphragm according to claim 3 wherein the restraining means in at least one of said check valve portions comprises two integral separate web fingers bridging the cut-out sections from opposite sides of the end portion of the valve flap to the main body of the diaphragm.

5. For use in a diaphragm-type fuel pump a diaphragm according to claim 3 wherein the restraining means in at least one of said check valve portions comprises a single integral web finger bridging the cut-out sections from the outermost end of the valve flap to the main body of the diaphragm.

6. A diaphragm-type fuel pump comprising two body members joined together in substantially face-to-face relationship, a substantially fiat flexible diaphragm separating the substantially cojoined faces of said'body members, said diaphragm including a pumping portion which partly defines an actuating chamber in one of said body members and a pumping chamber in the other of said body members, said actuating chamber being adapted to communicate with a source of fluctuating fluid pressure, both of said body members having fuel inlet and outlet passages formed therein communicating with said pumping chamber, said diaphragm also including two separate check valve portions located in the respective fuel passages for maintaining unidirectional flow of fuel through said pump, each of said check valve portions comprising a flat valve flap having a base integral with said diaphragm and an end portion essentially separated by cutout sections from the main body of said diaphragm, the end portion of said valve flap normally being in sealing relation with the fuel passage with which it is associated and being displaceable out of the plane of said diaphragm to permit flow of fuel through its associated fuel passage, and at least one flexible web finger bridging said cut-out sections and joining the end portion of said valve flap to said diaphragm, said web finger limiting without preventing displacement of said end portion of the valve flap out of the plane of the diaphragm.

References Cited in the file of this patent UNITED STATES PATENTS Scholer Apr. 29, 1958 i

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