US2840003A

US2840003A - Fuel pump diaphragm assembly

Info

Publication number: US2840003A
Application number: US456360A
Authority: US
Inventors: Eldon A Johnson; Jack M White
Original assignee: ACF Industries Inc
Current assignee: ACF Industries Inc
Priority date: 1954-09-16
Filing date: 1954-09-16
Publication date: 1958-06-24
Anticipated expiration: 1975-06-24

Description

n 24, 1 5 E. A. JQHNSON ETAL 2,840,003

FUEL PUMP DIAPHRAGM ASSEMBLY I Filed Sept. 16, 1954 INVENTOR. ELDON A. JOHNSON JACK .WHITE ATTORNEY 2,840,003 FUEL PUMP DIAPHRAGM ASSEMBLY Eldon A. Johnson, St. Louis, and Jack M. White, Normandy, Mo., assignors, by mesne assignments, to ACF Industries, Incorporated, New York, N. Y., a corporation of New Jersey Application September 16, 1954, Serial No. 456,360

3 Claims. 01. 103-150 This invention relates to engine driven fuelpumps of the diaphragm type and, more specifically, to means for increasing the durability and volumetric efliciency of this type of pump.

In present pulsating fuel pump design, a circular, flexible diaphragm is clamped at its periphery between the circular flanges of the rocker armcasing and the valve casing of the pump. The diaphragm is flexed to produce the pumping action by a stem connected to, the diaphragm and reciprocated from a cam driven rocker arm. This connection with the stem is secured centrally to the diaphram by a pair of backing plates locked to the free end of the stem in clamping relation to the diaphragm. Duringpump assembly, it is usual to provide sufficient slack in the diaphragm outside of the backing plates to accommodate the reciprocating action of the backing plates during their movement from one extreme end of the stroke to the other. Although the diaphragm is of flexible material, it cannot be repeatedly stretched or crimped without fracture. Because there will always be slack in the diaphragm in the midstroke position of the hacking plates,. a circumferential wrinkle or' loop is formed between the backing plates and the pump chamber. On the suction stroke, this wrinkle will form a loop on one side of the backing plates, but, on the pressure stroke, this wrinklewill form a loop in theopposite direction. This inherent back and forth switching of the flexing loop of the diaphragm substantially reduces the life of the diaphragm as well as the capacity, of the pump,

since adequate space must be provided between thesults in a larger loop structure, in orderto. avoid fric tional scraping together of the walls of the loop cessive crimping of the loop. I

This space within the wrinkle contributes to the occurrence of vapor lock. Space must be minimized in order to attain the maximum possible volumetric efficiency to handle modern fuels which contain highly volatile ends. Experiments 7 with larger backing plates to obtain this objective have not been successful, since such plates cause kinking and frictional interference in the flexing portions of the diaphragm. Moreover, when the backing plates exceed a certain size in relation to the pump, the diaphragm acts as an over-center type of spring on each stroke. This is not too important on the suction stroke, because the pump is being actuated by the engine driven eccentric. The discharge stroke of the pump is spring powered, however, and the opposing spring action of the diaphragm can prevent the pump from developing its designed discharge pressure at low speeds and stall the pump at high engine speeds.

This invention has as its object to increase the volumetand exric efiiciency in this type of pump without the disadvan' the wrinkle formed in the diaphragm on each opposite stroke. This arrangement of the backing plates requires that the wrinkle in the diaphragm will form a loop in one direction only in such a manner that its displacement is also utilized toreduce clearance and improve the volumetric etficiency.

The accompanying drawings illustrate one manner in which the invention may be carried out.

In the drawings, Fig. 1 is a side elevation, partly in section, of a pump constructed according to the present invention.

Fig. 2 is a detail of the diaphragm and backing plate assembly for that pump shown in section. V Fig, 3 is a fragmentary view, partly in section, of a, pump according to this invention showing the position of the parts at the discharge end of the stroke.

Fig. 4 is a similar view to Fig. '3 showing the relation of the parts at the extreme opposite end of the stroke.

'Fig. 5 is a view similar to Figs. 3 and 4 showing the position of the parts at midstroke.

Fig. 6 is a view similar to Fig. 5 of a modified form of the invention.

The pump shown in Fig. 1 of the drawings is the same type as that shown in a patent of Irven E. Cofiey, No. 2,625,114 andreference may be made to this patent for the detailed construction not shown in the present application. Y

j The pump shown in Fig. 1 has a rocker arm casingl with a flange 2 having bolt holes (not shown) to secure the pump to the engine of the motor vehicle. Within ,the rocker casing '1 is an arm 3 which is normally discharge stroke. Theintake stroke is etfected by the. action of the rocker arm 3 against theresistance of spring,

10. Stem 9 has a shoulder 11 and a reduced extension 12 extending beyond the shoulder, upon which the backing plates and diaphragm are mounted. Diaphragm 13 is held between an outer or upper backing plate 14 outside the pump chamber and, alower or inner backing plate 15 on the inside of the pump chamber. These plates are mounted on reduced extension 12 by a pair of washers 16 and'17. The diaphragm 13 includes a central portion clamped between the

backing plates

14 and 15, and vouter annular portion of bight form which proscribed in detail, in the application of James L. Edelen,

a in position on the stem 9, and has a similarly turned,

jectstowar'ds the pump chamber, and a peripheral portion whichis clamped between the

flanges

25 and 26 of the, housing. Washer 17 looks with the reversely tapered end of the reduced extension 12, all as illustrated and de- Serial Number 429,343, filed May 12, 1954, for Shaft End; Mounting for Sealing and Loop Forming a Pump Diaphragm. Outer backing plate 14 may be provided with an intermediate rib 19 forming aseat for spring 10.

According, to this invention, outer backing plate 14 is larger than inner'backing plate 15, and is provided adjacentits periphery with a downturned lip 20 which erminates in a reversely rolled edge or curved lip 21.

Inner backing plate 15 is substantially flat when secured complementarylip 22 disposed in parallel relation and radially inwardly of or underlying the overhanging lip 20 ,of .outer backing plate 14. h

As can be seen from Fig. 2, the complementary lips on the backing plates grip and stress the diaphragm 13 to effect a distinct frusto-conical deformation or bight 30 in the diaphragm from a normally flat condition. This distortion is clearly illustrated in Fig. 2. Referring again to Fig. 1, the periphery of the diaphragm 13 is clamped between the circular peripheral flange 25 of the rocker arm casing 1 and the corresponding flange 26 of the il'a'lve'chaiiiber casing 27'by a series of cap screws 28. Sufficient. slack is provided in the flexingportion 'or bight 300i the diaphragm between the backing plates and the casingsoas tapermit the full stroke of the pump without stretching this part ofthe diaphr'agmi.

A dome jformin'g cover31' with an outlet is secured to theva1ve"body 2 7infahy suitable mannei Iui'nin'g jnow to'FigsI 3fto5, Fig. 3' illustrates the operation of thediaphr'agrn within theipump chamber 35 at the extreme, end of the discharge stroke of the chamber 35 to provide full volumetricefiiciency. This is important since it enables the pump to better handle gases to prevent vapor lock. s

Fig.1 4 "illustrates the pump elements atlthe extreme end oft he' suction stroke. In this position, the bight 30 in the diaphragm 13 is in the same relation tothe backing plates as in Fig; 3, due, to the'st'resses produced on the diaphragm by the backing plates.

Fig. 5 illustrates the, position'of the pumping elements at midstroke, and here again the position of the bight 30 in the diaphragm 13 is shown maintained in the same looped relation to the backing plates as in the previous views. 7 'It .will be noted that the action of the diaphragm phragm, and permits use of larger backing washers with:

out undue kinking" or scraping "of the diaphragm during operation. V

In Fig. 6 is shown a modification of the invention wherein lip 21 of the outer backing plate has a cylindrical outwardextension 21A disposed. closely adjacent to the walls of the pumping chamber. This flange will further assist in precluding reversal in the position of the bight 30, should there be anytendency for this effect.

structure has beenfshown which will fulfill all the objects of the present invention as defined by the appended claims, but it iscontemplated that other embodiments of the same invention will occur to those skilled i'n'the art. l

We claim; I M g 1. A fuel pump comprising a casing forming a pumping chamber, said pumping chamber having its end wall portion provided with inletand outlet openings, a diaphragm forming a pumping element and one wall of said chamber, said diaphragm havingitsfouter peripheral portion secured to the casing, said diaphragm being provided with aninwardly projecting bight at its outer portion, backing plates disposed upon the inner and outer sides of a central portion of the diaphragm, a centrally positioned'operating stem connected thereto, spring means on the stem normally urging said diaphragm into said pumping chamber, the peripheral edge of said inner plate being spaced a sutficient distance from the wall of said portion normally projecting into the concave portion of' said bight and engaging the adjacent face of the diaphragm defining the bight for retaining said bight against substantial deflection regardless of pressure in said pumping chamber.

2. A fuel pump comprising a casing forming a pumping chamber, said pumping chamber having its end wall portion provided with inlet and outlet openings, a diaphragm forming a pumping element and One wall of said chamber, said diaphragm having its outer peripheral portion secured to the casing, said diaphragm being provided with an'i'nwardly projecting bight at its outer portion,"

nating in a reversely curved lip, and said peripheral por-' tion normally projecting into the concave portion of said' bight and engaging the adjacent face of the diaphragm defining the bight for retaining said bight against substantialdeflection' regardless of pressure in said pumping chamber." V i 3. *A fuel pump comprising a casing forming a pumping chamber, said pumping chamber having its end wall portiomprovided with inlet and outlet openings, a dia-' phragrn forming a pumping element and one wall of said chamber; said diaphragm having its outer peripheral portion secured to the casing, said diaphragm being provided with an inwardly projecting bight at its outerportion, backing plates disposed upon the inner and outer sides of acentral portion of the diaphragm, a centrally positioned operating stem'connected thereto, spring means on the stemnormally urging said diaphragm into said pumping chamber, the peripheral edge of said inner plate being spaced asuflicient distance from the wall of said chamber.

to provide an annular area between said wall and said plate topermit said bight in said diaphragm to project therebetween in the direction of the pumping chamber,

said peripheral portion of the inner backing plate extending alongjthe adjacent inner face of the bight to guide and retain the same againstdefiection inwardly, and the peripheral portion -'of the outer backing plate being spaced References Cited in the file of this patent f V "U ITED STATES PATENTS Pounds May 4, 1875 1,466,242 Neal Aug. 28, 1923 1,811,557 Ove a June 23, 1931 2,080,391 i Rockwell May 11, 1937 2,169,862 Whitted Aug. 15, 1939 2,185,784 Corydon et al. Ian. 2, 1940 2,464,196 Van Ranst Mar. 8,' 1949 2,623,726 Suska Dec. 30, 1952 FOREIGN PATENTS 102,368 Great Britain Nov. 30, 1916 405,686 Great Britain Feb. 12, 1934 616,053 France Oct. 25, 1926