US2894459A - Fuel pump - Google Patents

Description

July 14, 1959 A. D. McDU'FFlE FUEL PUMP Filed Jan. 4; 1957 2 Sheets-Shet 1 mwzmox awzadwwwz July' 14, 1959 A. D. MCDUFFIE 2,894,459

FUEL. PUMP Filed Jan. 4, 1957 2 Sheets-Sheet 2 "4' 15% my l/IIIIIIIIIIIIIIA '12 I;

IN VEN TOR.

A TTOE/Vf) United States Patent FUEL PUlVIP Archie D. McDuflie, Berkley, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application January 4, 1957, Serial No. 632,472

1 Claim. (Cl. 103150) The present invention relates to pumps and more particularly to fuel pumps.

In the operation of an internal combustion engine of the spark ignited variety, the combustible charge of air and fuel may be formed by injecting atomized fuel into the charge by means of a pressurized fuel system that includes metering means responsive to the fuel demands of the engine and effective to meter the fuel in proportion thereto. Such a system is disclosed and claimed in copending applications Serial No. 634,915, filed January 18, 1957 and Serial No. 671,933, filed July 15, 1957. Satisfactory operation of such a system is dependent upon the fuel being pumped thereto in sufficient quantity and under adequate pressure to insure proper action of all of the elements in the system. In addition, the pressure should be substantially constant and free from pulsations. Although there are numerous pumps that are suitable for this type of service they are expensive and troublesome in operation and generally not well adapted for use in automotive vehicles.

Due to their simplicity and economy diaphragm type pumps are desirable. However, heretofore, such pumps have employed a pliable member or diaphragm that has the center thereof clamped between a pair of backing plates riveted together and reciprocably driven to produce the pumping action. Although such pumps are adequate at low pressures, at high pressures the perforations in the diaphragm resulting from the riveting frequently produce leaks. This is particularly true when pumping a fuel such as gasoline.

It is therefore proposed to provide an economical and reliable diaphragm pump that is adapted to pump fuels at a substantially constant pressure output free from objectionable pulsations. More particularly, this is to be accomplished by providing a plurality of diaphragm cells that draw fuelfrom a common source and discharge the fuel through a common outlet. Each cell includes an imperforate diaphragm draped over a reciprocating member or backing plate biased by a spring having the desired tension. The diaphragm is retained against the backing plate by the pressure of the fuel or, if necessary, by a second backing plate and spring that are disposed inside of the pumping chamber for biasing the diaphragm against the first backing plate. Since the diaphragm is free of any perforations there will be a hermetical seal that is free of leakage. Each of the several cells produces a substantially constant pressure and if they are properly phased, at least one cell will always be discharging and thus maintaining the pressure.

In the two sheets of drawings:

Figure 1 is a side view, with a portion thereof broken away, of a pump embodying the present invention.

Figure 2 is a cross-sectional view taken substantially along the plane of line 22 in Figure 1.

Figure 3 is a cross-sectional view of the pump housing taken substantially along the plane of line 3-3 in Figure 1.

Figure 4 is a plan view of a cover for one of the cells ICC taken substantially along the plane of line 4-4 in Figure 2.

Figure 5 is an exploded perspective of the cover in Figure 4 and the valves therefor.

Figure 6 is a fragmentary cross-sectional view similar to Figure 2 but of a modification.

Figure 7 is a fragmentary view along line 7-7 of Figure 1.

Referring to the drawings in more detail, the present invention is embodied in a pump 10 having an inlet 12 that is adapted to be interconnected with a source of fuel and an outlet 14 that is adapted to discharge the fuel under pressure therefrom. It has been found desirable for the source of fuel to include a transfer pump 16 that will supply the fuel in large quantities and under a lower pressure. The outlet 14 of the pump may be connected to a fuel system such as that disclosed in the above-identifie d applications.

The pump 10 includes a cylindrical housing 18 having a passage 20 extending axially through the center thereof. The lower end of the housing forms a base 22 that is adapted to be mounted on an engine 24 so that a driveshaft 26 may extend downwardly through the passage 20 and be driven by a suitable source of power such as the engine crankshaft or the camshaft. The center of the driveshaft 26 includes an eccentric 28 having a working surface 30 on the exterior thereof.

A plurality of enlarged bores 32, three in the present instance, are radially disposed about the axial passage 20 so as to form three separate pumping cells. Each of the cells includes a backing plate 34 which is reciprocably disposed in the bore 32. Each plate 34 has a flat end and a rolled collar '36 therearound that is a close fit inside of the bore 32. Each of these backing plates 34 is reciprocably driven by means of a pin 38 that has the upper end 40 thereof riveted to the plate 34 substantially flush therewith while the lower end 42 thereof is attached to one arm 44 of a bell crank 46. The bell crank 46 pivots about a stationary pin 48 so that the other arm 50 thereof engages the working surface 30 of the eccentric 28. The latter arm preferably is bifurcated to provide a lost motion means comprising a spring 52 disposed intermediate the arm and a shoe 54 whereby the shoe will always be kept in contact with the eccentric 28 thereby preventing undue wear of the parts as would occur with intermittent engagement between the arm and the eccentric.

A coil spring 55 is disposed in each bore 32 so as to be supported by a seat 56 pressed into the inner end of the bore 32. The other end of the spring 55 engages the inside of the backing plate 34 and urges it radially outwardly. It may be seen that when the spring 55 urges the backing plate 34 outwardly, it will tend to retain the arm 50 against the eccentric and rotation of the eccentric 28 will produce a reciprocating motion or a pumping action in the backing plate 34.

As best seen in Figures 2, 5 and 7, in order to form a pumping cell a cover plate 58 is secured over the outer end of each bore 32 by cap screws. Each cover plate 58 has a recessed center portion 60 registering with the bore 32. An inlet passage 61 in each cover 58 communicates with an intake or supply manifold in the housing 18 and has an intake valve 64 therein. In addition, an outlet passage 66 is provided which includes an outlet valve 68 and discharges into a high pressure outlet manifold 62.

In order to seal the pumping chamber a diaphragm 70 is provided so that the periphery 72 thereof is clamped and sealed between the cover 58 and the side of the housing 18. The center portion 74 is merely draped over the end of the backing plate 34 and since there is not a second backing plate riveted to the first plate, there are no troublesome perforations in the center portion 74. By

supplying the fuel to the pumping chamber under a slight pressure, for example, by a transfer pump 16, the diaphragm 70 will be retained against the backing plate.

Normally the fuel pressure produced by the transfer pump 16 will retain the diaphragm 70 against the backing plate even during the intake strokes. However, if a transfer pump 16 is not employed or such a pump fails to-insure the desired action, the modification disclosed in Figure 6 may be employed. This embodiment is substant-ially identical to the foregoing arrangement except that a secondary backing plate 76 and spring '78 are disposed inside of the pumping chamber. This spring 78 biases the secondary plate '76 against the diaphragm 70 and retains it on the first backing plate 34 at all times. Thus even though a secondary backing plate 76 is employed the diaphragm 70 will still remain imperforate and free of any openings that might tend to develop into leaks.

It may thus be seen that a high pressure diaphragm pump has been provided in which a plurality of pumping cells are provided. Each of these cells has a substantially identical output pressure and they are fixed with respect to each other so that at least one cell will always be discharging the fuel and therefore the output pressure will be substantially free of any pulsations therein. Also the plurality of cells will permit a very short stroke for each individual backing plate. As a result of this there will be a amount of flexing of the individual diaphragms and since the periphery of the backing plate is a close fit in the radial passage, the diaphragm will have support over its entire area and therefore will be able to withstand the higher pressures. In addition since there are no perforations in the center portion there is no chance of any leakage occurring at the higher pressures. I

It is to be understood that although the invention has been described with specific reference to particularembodiments thereof it is not to be so limited since changes and alterations therein may be made which are within the full intended scope of this invention as defined by the appended claim.

I claim:

A pump comprising a housing having an axial passage with a rotating eccentric member therein a plurality of passages radially disposed about said eccentric member forming openings in the side of said housing a cover closing each opening to form a pumping chamber fuel inlet and outlet valves disposed within said chamber, a member reciprocably disposed in each of said radial passages, a flexible diaphragm disposed in each of said chambers and peripherally clamped between said cover and said housing, said diaphragm having an imperforate center portion adapted to overlay said reciprocable member, pressure means adapted to act upon said diaphragm to maintain the latter in engagement with said recipro cable member, spring means in each of said radial passages for resiliently biasing the associated reciprocable memher into said pumping chamber, and drive means for each reciprocable member comprising a bell crank lever, a pin articulated between one arm of said lever and said reciprocable member, a follower pivotally connected with the other arm of said lever, spring means biasing said follower into continuous engagement with said eccentric member, said bell crank lever being pivotally supported upon said housing intermediate said arms whereby rotation of the eccentric member causes said bell crank lever to compress said spring to draw fuel into said inlet valve into said pumping chamber, each of said drive means being equally spaced about the circumference of said eccentric.

References Cited in the file of this patent UNITED STATES PATENTS 1,639,623 White Aug. 16, 1927 1,871,040 Carter Aug. 9, 1932 2,027,979 Hopkins Jan. 14, 1936 2,463,486 Johnson Mar. 1, 1949 2,702,006 Bachert Feb. 15, 1955 FOREIGN PATENTS 283,021 Great Britain Jan. 5, 1928

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