US2625114A - Fuel pump - Google Patents

Description

Jan. 13, 1953 Filed Feb. 17, 1947 l. E. COFFEY 2,625,114

FUEL PUMP 6 Sheets-Sheet l a Infill] F IG. 4.

' INVENTOR. BY IRVEW E (OF/E 6 Shegts-Sheet 3 I. E COFFEY FUEL PUMP I N V EN TOR.

Jan. 13, 1953 Filed Feb. 17, 1947 n. m C M M M h/fiww I, E. COFFEY Jan: 13., 1953 FUEL PUMP 6 Sheets-Sheet 4 Filed Feb. 1'7. 194? INVENTOR. IRVEN E. COFFEY ATTORNEY Jan. 13, 1953 l. E. COFFEY 2,625,114

FUEL PUMP Filed Feb. 17, 1947 e Sheets-Sheet s L INVENTOR.

- IRVEN E. COFFEY ATTORNEY Jan.,. l3, 1953 1. E. coFFEY 2 ,11

FUEL PUMP Filed Feb. 17. 19.47 s Sheets-Shget 6 INVENTOR.

IRVEN E. COFFEY BY h/FM ATTORNEY Patented Jan. 13, 1953 UN-lT ED STAT-ES RATENT @FFl CE FUEL PUMr Irv'cn E. Coffey, St. Louis, Mo assignor to Carter Carburetor Corporation, St. Louis, Mo., a corporation of Delaware This i ertio r lates o p mp a i larl-y-to fuel pumps for automotive engines and the like and is a continuation in part of my cop ndin app i n, se ia No-, l1s2, fil f y 13-, 1944, now Patent No. 2,426,965, dated September z, 1947. Pumps previously provided for this purpose have not been entirely. satisfactory for a number of reasons, particularly with regard to "capacity and the handling of boiling fuel.

v Another serious trouble with previous designs has been diaphragm failures and short life of the pump, enerally.

A very frequent source of trouble in previous fuel pump designs is the wearing of the valves and valve seats so that the pump will not prime itself at cranking speeds, and will not pump boiling fuel fast enough to run the engine.'

Automotive fuel pumps are ordinarily operated by the engine cam shaft and must have a capacity sufficient to prime the pump, fill the carburetor bowl, and supply all the fuel required to start a cold engine at cranking speeds which may teas low as 40 R. P. M. Since, the pump. isordinarily driven from the cam shaft, the pump. is only operated twenty strokes per minute under these conditions. On the other hand, the pump must be capable of continuous operation at engine speeds of at least 4000 R. P. M. or 2000 strokes of the pump. Such high speed operation results in excessive strains on the diaphrag-ms of pumps of previous designs. 7

When operating at 2000 cycles per minute, the inlet and outlet valves of the pump have to be opened and closed with great rapidity, and this is especially hard on the inlet valve and seat, because its operation of opening and closing must be accomplished in a very small portion of the cycle, when the pump is operating at normal speed andcapacity.

Another difficulty with previous pumps is that they have, in themselves, tended to set up vapor lock or boiling of the fuel by reason of the excessive suction developed in the fuel at the intake connection of the pump and in'the lineleading back tothe tank. In' high Speed operation of the pump, the fuel column leading to the inlet valve must be started and stopped with great rapidity, the only means preventing the separation or boiling of the fuel being the atmospheric pressure in the fuel tank or wherever it can act on the fuel. a

An object of my invention is to produce a new and improved fuel pump capableof lifting and handling volatile fuels.

Another object'of my invention is to produce a new: aridi improved fuel pump for internal co nbustion engii-ics'easa lee qu '-;.I?. i el 2 and filling the carburetor bowl under low speed engine cranking conditions.

Another object of my inventionis to produce a fuel pump for internal combustion engines in which the fuel in the intake conduit is refrigerated by vaporization of fuel in the pumping chamber.

It is a further object of my invent-ion to produce a diaphragm type fuelpump in which the strains on the diaphragm are minimized by providing for the acceleration and deceleration of only short columns of fuel.

It is a further object of my invention to produce a new and improved fuel pump of the reciprocating type in whichthe maximum capacity of the pump is limited by a calibrated restriction at or near the intake valve ofthe pump.

It is another object of my invention to produce a new and improved fuel pump of the reciprocatingtype in which the fuel inlet column or pipe is interrupted by an air chamber near the inlet valve of the pump and in which the inlet passage between the air chamber and the inlet valve has sufficient capacity to contain at least as much fuel as can be discharged at one stroke of the pump during normal and high speed operation.

Another object of my invention is to produce a fuel pump for automotive engines in which the life of the pump may be definitely expected to exceed the life of any engine or vehicleto which it is likely to be applied.

Another object of my invention is to produce a new and improved valve capable of maintaining high sealing qualities after long use under high speed operating conditions.

Another object of 'my'invention is to provide a new and improved operating lever for high speed operation.

In order to eliminate the faults of previous designs, and to produce a new and improved pump capable of accomplishing'the above described and other objects, have invented the pump described and show-n in the following spec fication and accompanying drawings; referring to which:

Figure 1 is a seetionalelevation'of arums'ee cording tom'y invention. I

Figure 2 isv a sectional plan view taken along the irregular sectional line 212 of Figure l.

Figure'3is a detailedv plan view of the main air dome member.

Figure 4 is an inverted plan view of the main i deme me rer- Figure 5 is 'a plan View oi/a valve cage.

Figure 6 is a sectional elevation of a valve assembly.

Figure 7 is a sectional view taken along the I line II of Figure 5.

Figure 8 shows the valve spring.

Figure 9 is a sectional view of the valve.

Figure 10 is a sectional view of the valve seat member.

Figure 11 is a plan view of the operating lever or hammer.

Figure 12 is a sectional elevation of the hammer.

Figure 13 is a sectional elevation of the diaphragm assembly.

Figure 14 is a sectional plan view taken along the line I4I4 of Figure 1, parts being broken away.

Figure 15 shows the diaphragm and lower supporting washer.

Figure 16 is a sectional view of th lower supporting washer.

Figure 1'7 is a sectional view of the upper supporting washer.

Figure 18 is a diagram showing the approximate position of the main fuel tank with respect to the engine and fuel pump in an automotive installation.

Figure 19 is a diagram showing the approximate pressure and suction curve existing in the pumping chamber.

Figure 20 is a section similar to Figure 1, taken on line 20-20 of Figure 21 but showing a modifled form of pump.

Figure 21 is a horizontal section taken substantially on line 2I-2I of Figure 20.

Figure 22 is a bottom view showing the dome body of the modified pump.

Figure 23 is a top view of the dome body thereof.

Figure 24 is a partial section taken on line 26-24 of Figure 21.

Figure 25 is a side view and section of the pump shown in Figure 20 but slightly modified and inverted.

Figure 26 is a sectional view similar to Figures 1 and 20 but showing another modification.

Figure 27 is a side view in section similar to Figure 26' but showing the pump inverted.

Figure 28 is a bottom view showing the valve body in Figure 26.

Figure 29 is a top view of the dome body in Figure 26.

Referring first to Figure 18, the reference numeral I!!!) shows a main fuel tank which is normally mounted at a lower level than the pump which is generally indicated by the reference numeral IHI. The pump is mounted on and driven by an internal combustion engine I 02 having the usual carburetor Ilis and float chamber Hi4, the details of which are'not shown but are well understood by those skilled in the art. A fuel conduit I05 of comparatively small diameter and great length leads from the fuel tank to the pump inlet connection 25, and an outlet conduit I06 also of small diameter and considerable length is connected to the fuel pump outlet at 26 and to the carburetor float chamber at I07. It may be noted that the engine is provided with an exhaust manifold I08 which frequently becomes red hot and is likely to cause boiling of the fuel as it passes through the conduit I05 to the pump. inlet. It may also be noted that while boilin occurs in thepump chamber and in the outlet, it isnotof such great importance as boiling in the inlet. This s W W Q any boiling which occurs posterior to the inlet valve creates its own discharge pressure, while boiling in the inlet conduit prevents induction of fuel into the pump chamber and causes vapor lock.

The reference numeral I (Figs. 1-4) shows a main casting having a flange 2, by means of which it is bolted on to the frame of the engine as at 3. It will be understood that while the pump is primarily designed for automotive engines, it is capable of other uses and can be attached to any support 3 so as to be properly positioned with respect to a cam carried by a rotating shaft 5' which preferably turns in a clockwise direction, so that the sweep of the cam will be inward with respect to the hammer or operating lever B, which is pivotally mounted on the body member I by means of the floating pivot shaft I.

This shaft is mounted in the bore 8 (Fig. 14), the ends of which are closed by sealing plugs or rivets 9 which permit substantial end play of the shaft.

The actuating lever or hammer 6 is formed of a curved and channel-shaped sheet metal member having bent-over lugs I0 having central openings I I accurately finished to line up with corresponding holes in the sides of the hammer lever to form bearings for shaft I. One end of the hammer lever rides on the cam, as indicated in Figure l, and the other is provided with a fork or hammer head 12 which is slightly curved on a radius about the point I3, as indicated in Figure 1 It will be noted that the floor of the channel is substantially curved about the bearing I I in such a manner that a diameter of the bearing, produced as indicated by line I4, I5, passes on the same side of the cam contact portion I5 and the hammer head I2, so that a component of the force on the cam necessary to produce the hammerblow is taken in tension and not in pure bending strain. This feature of construction is of importance, because the high speed of operation and the violence of the hammer blow when the hammer encounters the resistance of the diaphragm would otherwise cause crystallization and breakage of the lever.

The lever is yieldably urged in an anti-clockwise direction by the spring [1, which is seated against the flange 2, and a seatin member I8 which is mounted on .the shaft 1 and provided with a seating fork I9 and an upturned locating member 20, as shown in Figure 1. This detail is covered in my patent No. 2.369,535.

The pump diaphragm 2i is formed of synthetic rubber or the like with a cloth base, and is held in place between the flang 22 on the main actuator casting and a corresponding flange 23 on the valve body 24, which is provided with inlet and outlet connections 25 and 28, respectively. The diaphragm is clamped in position between the flanges, which are held together by any suitable means, such as bolts or rivets (not shown). The center portion of the pump diaphragm is rigidly held in between upper and lower diaphragm washer cups 2? and 28, respectively, which are, in turn, clamped between washers 29 and 3B riveted onto the shaft 3| as indicated in Figure 13. a

The shape and curvature of the washers 21 and 23 are important and form a substantial part of my invention. The lower washer 28 has a slightly convexor conical central portion which is pressed fiat in the'assembly. The diameter of this'washr preferably bears a reason to the workingdirounded byaa-curvedfflans :32-whic has a. se

tionalradiuszot: approxima ely /3 inch.-

i'lrheupper wash r hasa ntral con al portion approximately the. same d amete as he opposi 'lyydisposed surface of .the lower washer, Th surface is surrounded by a flan e .33 which-i curved on a decreasing radius iii-such .a manner that its cross section is a: sectionzof a. parabola .or' ellipse. The'full diameter of the-washer 21 bears. a relation to theworking diameter-of the diaphragm of approximately 8 to .10, and the short radius of the ellipse which. roughly corresponds' to. thecurvature ofthe flange 33 is approximately one fifth of the. fulloperatingzstmke of the pump.

Shaft. 8|. isprovided with an upset .head- 34- at its freeend-against which is seated a metal washer -35. A thin, cushion-washer 36 of shockdamp- =1 ening. material wh-lch is only slightly 'yi-eldable transversely, :is positioned. next to the metal washer, the diaphragmmaterial mentioned being satisfactory, and a third .washer 3] is made :of

hard plastic material suchv as a phenolic. condensate product :with :highly polished surfaces. A discharge spring'tll having sufficientstrength to move the diaphragm in-one direction is compressed between :diaphragm-washer 30 and a metallic washer '39 which rests .on a sealing a washer dil'formed :of synthetic-rubber orlother oil proof sealing'material and'slidably or snugly fitted to the shaft 31 'The sealing washer-40 is mounted on a seat forming shoulder '41 in the actuator casting.

When mounted as shown in, Figure 1, spring '38 acting'against thediaphragm 2! has-suflicient 'force' to produce the pressure in the pumping chamber 42 which the pump is desired to maintain.

An auxiliary operatingleverAS rigidly mounted on a transverse rock shaft having a cam surface 45, as indicated in Figure 1, is provided. The function of the member 43 is to permit the operator to manually rock hammer lever 6 to into the valve body and up into the airdome in a which it is surrounded by a bafiie 52--which extends to a point substantially higher than the passage 53 leading-to the inlet valve 54.. The passage 53 is provided with an upstandingflange 55 over which is fittedthe strainer 56, the latter being held in position by the boss 51 which extends inwardly from the top'of the cover 48.

Space 58above the inlet passage'forms part of the inlet air dome. Ihave discovered; that the relative volumes of the air-domes and pump stroke have-a definite bearing on the life of the diaphragm as well as capacity of the pump, and since these relativevolumes form an important part of my invention, th following examples are given for the assistance of those skilled in the art 1 per-minute: and a. maximum possibledelivery of B lgal ons per hour at. 5000.5- .P. or zmlfl' pump strokes, lhavef und that satisfa tory results can be obtained with the following approximate dimensions and. proportions:

Working diameter of {pump diaphragm inches.- 2.47 Maximum stroke of diaphragm do 125 Diaphragm displacement (full stroke) cc 10 Maximum stroke of diaphragm during high speed operation (-2000 R. Pa-ML) while pumping liquid fuel only inches .03 Discharge spring and exhaust'restr'iction calibration to give diaphragm displacement during high speed operation while pumping liquid fuel only cc 1 Intake air dome volume oc. 62 Outlet air dome volume cc :15

The outlet air dome is closed against the admission of "fuel by means of diaphragm 41. -In order to give this diaphragm substantial workcapacity, I form a substantial part of the air dome volume ina low chamber 59which extends. more than halfway around the base of the air dome casting and terminates in walls 62. In order to prevent-unrestricted movement of the outlet diaphragm beyond the distance which it can .beflexed with safety, I keep the ceiling over the major portion of chamber 59 low, .so as to stop the movement of the diaphragm beyond a predetermined limit, and form the, remainder of the volume in a chamber 6-! which extends. upwardly into the inlet dome space, as shown in Figure 1, but which does not have sulficient diameter to permit undue strain on the diaphragm 41. It will be understood that the greatest strain on the diaphragm ll does not re- :sult from the pumping pressure exerted by spring 38, but from the vapor pressure which builds up as a result of heat when the engine is standing idle, just after a run in which the engine has been thoroughly heated up.

The construction of the valves has an important bearing on the life and operation of the pump. The design of the inlet valve according to my invention is more critical than the design of the outlet valve, because it has to operate at a much higher rate of speed, and also because it is required to perform a restricting function which will be described later. For convenience, I have v.Inacle the eXha-ustvalve identical with the inlet valve.

The valve (Figs. 5-10) comprises a cage 62 having a shoulder 63 which can be seated in corresponding bores formed in the die cast valve body- Strutsts extend upwardly from the body m m r, and om or all of these struts are. in- -tegrally connected with an. annular spring sea and stop member 6.5, as-shown in Figures 5 to 7. A shoulder 66 is formed in the member 65 to receive the spring 61 which normally holds the valve 68' in closed position. The. stop portion 69 must beaccurately and smoothly finished parallel to the Valve 63 and als positionedin-such a m nners t efini ly l mit th op nin movementof the valve to a position substantially less than that which would be required to fully clear the passageway through the valve. The valve cage 62 is preferably formed, of die cast material.

The valve seat member H1 has a shoulder H and ispress-fitted into the bore 12 of the valve ease and'firmly pushed up a ainst the shoulder the valve seat member, and this is carefully lapped to a substantial line contact against the valve 68. This valve is preferably formed of phenolic condensate or other hard, plastic material on a cloth base which is very light so as to move with very little inertia and strike the seat 14 and stop 69 with very little kinetic energy.

Disk valves of the general type shown herein have been previously used, but they have not been satisfactory in regard to wearing quality, as well as for other reasons. It has been assumed by pump and valve engineers that such a disk valve lightly seated by a small spring against a metal seat would present minimum possibilities for wear. There appears to be no rubbing between the valve and the seat. Even in high speed operation, the small inertia of the light valve would seem likely to do no conceivable damage to the seat or to the valve stop.

In previous practice, valves have been sub- .iect to rapid wear and have actually worn out the seats and cages without any apparent reason. I have discovered that the cause of this is that the valve cage and springs of previous constructions cause or permit the valve to assume a slightly angular position with respect to the seat or stop during its opening or closing movement. If this occurs during the movement of the valve from one position to the other, it does not strike dead and fiat, but strikes with a gyrating movement, the same as when a coin is dropped on a table. During this movement, there is a definite rubbing between the valve and seat which is the cause of the surprising amount of wear which has occurred in previous valves of this type. By carefully centering the disk with respect to the valve seat and the spring with respect to the valve, and making the seats and stops absolutely parallel when new, I have eliminated wear on the valves.

A feature of the invention is that the stop 69 is made circular, so that any wear on the valve is distributed on an annular surface. In this way, I avoid throwing the valve slightly out of parallelism with the seat, which would otherwise result from a slight turning of the valve.

' I have also found that a previously unsuspected cause of the tendency of previous disk valves to tilt in operation has been caused by location of the pump fluid connections very close to and directly in line with the valves so that the pump fluid strikes the inlet check valve at an angle as it emerges from the inlet connection and leaves the outlet check valve at an angle as it enters the outlet connection. To avoid this cause of valve failure, I have located the inlet connections 25 and 26 with their axes in planes offset substantially from the valve disks. I also shield the inlet check with the inlet baffle tube 52 and inlet passage 53, so that the entering fuel will approach the inlet check in a direct line therewith. Fuel emerges from the outlet valve seat in substantially all directions around the outlet check through ribs 65 and thence passes from the large space below outlet diaphragm 41 to outlet connection 26. Thus, the fuel does not pass immediately from the inlet connection to the inlet check or from the outlet check to the outlet connection and cannot produce the tilting action mentioned.

Another important and unexpected advantage of the limitation of the movement of the inlet valves is increase in'fuel delivery. The movement of the valves between the seat and stop in 8 my design is so short that the reverse flow through the valve is negligible. I have discovered that by snubbing or limiting this movement, I am enabled to use a spring far lighter than those ordinarily used for similar purposes. In order to hold the end of the spring 61 in fixed position with respect to the valve to prevent wear, I counterbore the valve, as indicated at 75. This counterbore may be made of such a diameter as to snugly fit the end of the spring, but good results may also be obtained by making the shoulders of the counterbore with a radius or chamfer so as to centralize the spring with respect to the valve. i

I have found that the movement of the valve between the seat and stop tends to occur with great violence, and that the valve should be made as light as possible, so that it'will strike the seat and stop with minimum inertia. In order to keep the valve flat and straight, it must have a thickness of at least ,6 at the rim, but by counterboring it, as shown, the diameter of the center can be reduced to approximately or even less. The material used in making the valve should be as light as possible, and I have found that a hard plastic on a cloth base, such as Celleron, Formica, Micarta, or Spauldite, may be used with satisfactory results.

In designing the valve, I have discovered that it i important for a number of reasons to limit the opening movement, and I prefer to make the space between the valve seat and sto approximately 1; of the diameter of the passageway controlled by the valve. The valve will still operate satisfactorily up to an opening movement of /6 of the passage diameter after which further wear occurs very rapidly, resulting in the premature destruction of the valve. When the valve is new, I allow it to open only approximately of the passage diameter. Wear of the valve seat and stop eventually increases the opening to about of the passage diameter during the normal life of the pump, which is greater than the life of any automobile engine to which it is likely to be applied.

In case the wear should be excessive after extreme length of use, it is desirable to provide some means to prevent further wear on the stop. I accomplish this function by making the spring 51 of a suihcient number of turns so that it will go solid when the valve opening reaches approximately of the passage diameter, so that the opening of the valve cannot have become so great as to result in destruction of the valve due to the inertia which it would acquire inopening a substantial distance. It will be understood that the valve is opened by the flow of liquid and that the first part of the liquid flow is comparatively slow and gentle, so. that by snubbing the valve movement during this part of the cycle, it is not subjected to the greater acceleration which it would acquire during the latterpart of the impulse of fuel flow.

One very important function of the inlet valve is to permit free flow of-fuel or vaporinto the pump chamber during cranking of the engine, but to restrict the flow of fuel into the pump chamber during the intake stroke, at least during high speed operation, so as to produce a short period of low pressure in the pump chamber to lower the boiling point of the fuel, to cause some boiling in the pump chamber under incipient boiling conditions, whereby the lowered tem perature resulting from. partial 'vaporization' oi "fuel-in the pump chamber will be transmitted to the walls of the valve body tctne fuel entering at the connection 2-5.

It will be noted that the fuel is led directly into this connection, so as to intimately contact and be cooled by the metal of the valve body before it passes into the dome 58 where it is comparatively insulated from temperature changes. The inlet port, of course, must be sufficiently large to admit the amount of fuel during most rapid operation which. is required to operate the engine. Accordingly,I make this port considerably larger than would be necessary if the valvewere permitted to open far enough to fully clear the port. As is well known; it is necessary that a check valve travel. from itstseat a: distance of at least the diameter of. theseat to. fully clear the same. By providi'ngza much shorter valve stroke, as described, and larger inlet port I provide suitable capacity together with greatly increased valve life. The short valve stroke has another advantage in that it avoids. the possibility of drawing air from the air dome space through the inlet valve in case. of violent pumping action. The air andvapors in the inlet dome will lie above the quantity of fuel in inlet passage 53 and since this passage has more than sufiicient volume to supply the pump during one inlet stroke, there is "littleor no possibility of air being drawn from the inlet dome downwardly into the pump chamber.

In operation, the lever B is held in the position shown in- Figure l by means of the spring ll, so that one end rests on-the cam 4, which preferably rotates in a clockwise direction. Turning the cam rocks the lever onthe-pivot shaft 1 which floats in the bearings -8 andl-l. Assuming there is no resistance pressureor. choking in the passage outlet, the spring '38 moves the diaphragm 2| to the position shown in Figure 1 until it is withdrawn by contactof the hammer 12 with the hammer pad or shock absorber 35363l'.

The first part ofthe intake stroke of the diaphragm occurs rather slowly, due to the changing movement of the cam, and during this part of the movement, the intake valve is opened to the fullextent permitted by thestop 69.. As the cam continues in its movement, the diaphragm 2i moves-more rapidly, and the valve is firmly held in. contact with the stop. This somewhat-restricts the movement of the liquid during the central part of the stroke, and produces a sharp pressure drop in the. pump chamber as shown inthe diagram in Figure 19-. The diaphragm or pump chamber 42 is eventually filled due to the dwell at the'end of the stroke, and also due to the fact that this chamber is not emptied. at each stroke except undervery slow speed operating conditions. In other words, the cycle of fuel flow lags slightly behind the cycle of diaphragm operationandsome vapor will appear in the pump chamber duringincipient boiling conditions. During thev next cycle of cam movement, Which-is somewhat less than 180, if the rotation. of the cam is clockwise, thehammer I2 is out of contact with the hammer'pad' (except during some cranking or vapor locking conditions), and the. spring 38 retu-rns the diaphragm 2| todischargethe fuel and any vapor through the exhaust valve 18; This valve functions in substantially thesameway as the intake valve 54', although its. movement against the stop does not. tend to occur withsuchi great violence, the spring 38'havingliinitedi force whilerthemovement of the cam and hammer issubstantially positive. The valve also serves as a restriction onthe amount of fuel discharged; so as to-limi-t thegallons per hour which the diaphragm can be called on to pump, but without placing a corresponding limit on the amount of vapor which can be pumped to get rid of avapor locking condition- The pump diaphragm is accordingly available to pump at least ten times as much volume of vapor as it will of liquid fuel. Of course, this would result in excessive strain and wear of the diaphragm and operating mechanism, except for thefact that vapor lock occurs only occasionally, and vapor does not present great resistance to the movement of the diaphragm.

During the-exhaust stroke, the suction in the dome 58; refills the-dome with fuel from the inlet 25, or at least brings in enough fuel to supplythe next intake stroke of the pump. The exhaust stroke of the pump also displaces the diaphragm A! evenly towards the top of the low chamber 59 and against the'air in the chamber 6| so that the dischargeof fuel from the exhaust of the pump can be continuous throughout the cycle. It will be understood that in a pump of this character, both theinlet and exhaust pipe lines are long and of small diameter, and the fuel has comparatively great inertia, so that without continuity of How at high speeds, the diaphragm and operating mechanism would be subjected to severe stresses;

One of'the most important features of the invention is-the construction of the inlet 53 and air dome- 58 in such" a manner that the column of fuel which must be started in motion at the beginning of the intake stroke is of large diameter and very short, but of volume corresponding to a full charge for normal and high speed operation. Modern motor fuels have comparatively high vapor pressuraand the application of any substantial suction by the'diaphra gm has a great tendency to cause the fuel to separate or' vapor look. This wouldnot be so important, except for the fact that when the fuel is separated, the vapor collects in bubbles which do not disappear as'quickly as they form.

By the construction herein shown and described, thecolumn of fuel present in the dome surface than in thepassage: Bfythis means, the

' power required to acceleratethe fuel column and the internal suction developed within thecolumn, itself, are-held to an absolute minimum;

The device according to this invention departs substantially from priorpractice in the restriction at the inlet'valve and at the exhaust valve The inlet restriction definitely limits or reduces the internal suction which can beplaced on the fuel at the inlet side'of the valve. The amount of suction on the fuel in the pump chamber on the other side of the'restriction is increased, but the formation of vaporin thepumping chamber, if it occurs, doesnot appear to give any serious trouble,- but on the contrary, its formation has a cooling action'which-is helpful 'in preventing the development of vapor'lock'. The diaphragm is capable of discharging the va-por at 'eachstroke and it is not allowed to accumulate. This is because of the selective action of therestricted valve-in passing vapor more freelythan liquid fuel. Excessive pressure in-the--inlet air dome 58,

t9 will lower the level ofuli'quid in passage 53 check. Since both inlet and exhaust: valves-have.

a very selective action in passing a greater volume of vapor than of fuel, it is practically impossible to vapor lock the pump, and yet the diaphragm is not subjected to severe stresses or required to operate through more than a small fraction of its stroke during normal or high speed operation.

In the form shown in Figs. 20-25, inclusive, a modified pump is shown inverted from the position in the previous form with the domes located on the underside of the pumping chamber. The actuator housing I and main body 24 mounting inlet check valve 15 and outlet check valve I8 and forming pumping chamber 2'! closed on one side by pumping diaphragm H are substantially identical with the corresponding parts in the previous form and will not be described in detail here. Dome-forming structure H is secured to the underside of main or valve body 24 and is of general cylindricalform with its transverse area extending substantially coextensively with the flexing part of the pumping diaphragm. A horizontal web I I 4 extends intermediately across the dome structure and has depressed side portions I52 on each side forming therebetween a diametral ridge H3.

Inlet connection 25 on the valve body opens into a cavity H4 aligned with a tubular passage H5 having its lower end opening into the space H6 beneath transverse web III. A tubular boss H! formed adjacent passage H5 in the dome structure forms an extension of inlet passage I I8 in the main body and port '54 controlled by the inlet check valve. An elongated wire screen H9 is lodged inthe diametral recess below central part H3 of the transverse web and between the floor of the same and a washer I20 resting on a boss I2I projecting from removable bottom wall or cap I22 of the dome structure and secured in place thereby. The dome structure itself is secured to the main body by a bolt I23 extending through a central boss I24 and having an internally threaded extremity I25. The lower cap is secured to the threaded end of bolt I23 by a capscrew I26. I

Flexible sealing diaphragm 41a is secured between the main or valve body and the dome structure. The diaphragm is apertured to provide for inlet passages H5 and III, as shown, but otherwise covers the dome structure. The elevated central portion H3 of transverse web I II is slightly spaced beneath diaphragm 41a to form air space 59a which also extends laterally on both sides above the depressed portions H2 of the transverse web to form the outlet air dome between the web and diaphragm 41a. (See Fig. 24.) Diaphragm 41a, of course, separates the fuel emerging from the outlet port from the outlet dome space. On the other hand, inlet boss H1 projecting below transverse web I H forms pockets at the sides thereof and above the open lower extremity thereof which traps a quantity of air and vapor to form the cushioning inlet dome between the web and the surface of liquid accumulated in'the bottom of the casing Ht. A tube I2! is lightly pressed into the lower end of the inlet III to form the lower portion of the inlet passage, providing greater dome space. The length of this tube is varied in accordance with the stroke of the pump for the particular engine to which the pump is applied, and both the capacity of the inlet charge chamber and the air dome may be thus regulated. Screen I I9 provides for filtering fuel before it enters inlet tube I21 and the pumping chamber. Y

It should be noted particularly that inlet connection 25 and outlet connection 26 are disposed in both forms of the invention with their axes in planes substantially offset, respectively, from the inlet and outlet check valves. In the case of the inlet connection, this offsetting together with inlet passage H5 and tube I21 insures that the fuel entering the pump approaches the. inlet check valve directly in axial alignment therewith so as to avoid any tendency to tilt this valve with attendant excessive wear thereof. In the case of the outlet check, fuel emerges therepast from the pumping chamber evenly in all directions so as to fill space 5% between diaphragm 41a, and the outlet check and apply the pump pulsations evenly to the exposed part of the diaphragm. Thus, the pumped fuel does not directly enter outlet connection 26 from the outlet port of the pump so that any tendency to. tilt the valve because of an immediate unsymmetrical change of direction of the pumped liquid is avoided. The tendency to tilt is much more serious in case of the inlet check in fuel pumps-heretofore known and thus tubular inlet passage I21, H1, H8 is provided in connection therewith to avoid this tendency.

Figs. 24 and 25 show the modified pump inverted; in this figure extension tube I21 or inlet passage I I! is omitted, the inlet air dome forming beneath cap I22 on the dome structure and extending down to the approximate level of the top of the passage III, the spaces about and at the sides of inlet boss I I! now being filled with liquid.

The modified form in Figs. 26-29, inclusive, is substantially flattened vertically to provide greater clearance for contiguous parts of the engine. Main or valve body I34 has a diametral rib I35 forming a pocket I36 adjacent outlet valve I8 on one side thereof and forming, with curved walls I31 of inlet passage I38, a pair of pockets I39 at the other side thereof. Walls I31 form a tubular inlet boss or passage, the open lower end of which is closed by a screen I40.

Dome-forming cap structure I4I has a transverse, diametral rib I4Ia which registers with main body rib I35 and forms pockets or recesses I42, beneath pocket I36, and I43 beneath pockets I39 and passage I38. Flexible sealing dia-- phragm I44, while extending entirely across the main body and dome-forming structure and "clamped therebetween by screws (not shown) is cut out adjacent pockets I39 and inlet passage I38. Inlet connection I46 is formed in the dome structure and opens into pocket I43 and outlet connection I4! is formed on the body structure and opens into pocket I35. The axes of these connections are in planes disaligned from the axis of corresponding valves, as in the previous form.

In operation of the third form of invention, fuel entering pocket I43 is guided through screen inlet I40 and inlet passage I38 directly against inlet valve disk 15 and thence passes into the pumping chamber. Fuel is discharged past outlet check 18 into space I36 extending from side to side of the main body where its pressure is applied evenly to the exposed part of sealing diaphragm I44 and thence through outlet connection I41. Space I42 beneathdiaphragm I44 and in the dome structure holds cushioning body of air which forms the outlet dome extending the full width of the dome structure. Pockets I39 at the sides of inlet passage I38 provide for trapping air or vapors on the inlet dome.

inlet side to form an 15 used in inverted position with said element extending upwardly and said tubular element is unnecessary to maintain an inlet dome.

11. A fuel pump as described in claim 10 in which space is provided adjacent said removable tubular element and communicating therewith in the upper part of said dome structure serving to trap a cushioning body of air as an inlet dome.

12. In a fuel pump, means forming a pumping chamber having a flexible pumping wall, inlet and outlet check valves for said chamber, domeforming structure adjacent said chamber, a transverse wall extending across said dome structure and forming separate inlet and outlet domes respectively, adjacent said check valves, a pocketed end wall for said dome structure having cavities forming extensions of said inlet and outlet domes, and means securing together said pumping chamber forming means and said end wall structure.

13. In a fuel pump, a main body structure having a flexible pumping wall and inlet and outlet ports controlled by check valves, dome-forming structure beneath an inlet connection in one of said structures, a tubular inlet passage extending from said inlet port into said dome-forming structure, and a substantial pocket at the side of said inlet passage and also communicating with said inlet connection for trapping a volume of vapor and ai as an inlet air dome.

14. An invertible fuel pump of the vapor dome type comprising a main body structure having a flexible wall and inlet and outlet ports with con trolling check valves, a dome-forming structure adjacent said main body and having pockets located, respectively, opposite said ports, a wall in said dome structure separatin said pockets, and a tubular inlet element projecting from said inlet port and opening into one of said pockets, said last-mentioned pocket having substantial portions at the sides of said tubular element and beyond the open end thereof, said portions serving for trapping volumes of dome-forming vapors, respectively, when said dome structure is m=ount ed below or above said main body structure.

15. In a fuel pump, a body structure having a flexible pumping wall and inlet and outlet ports with controlling valves, a dome structure mounted adjacent said body, a flexible diaphragm secured between said body and dome structure, a rib extending across said dome structure and forming separate cavities therein, a tubular inlet passage element extending from said inlet check valve through said diaphragm, into one of said cavities, a fluid inlet connection communicating with said last mentioned cavity, the other cavity extending along said diaphragm and forming therewith a cushioning outlet air dome extendin in juxtaposition to said outlet valve.

16. In a fuel pump, a main body structure having a flexible pumping wall and an opposite stationary wall, inlet and outlet ports in said stationary wall controlled by check valves, domeforming structure beneath said main body structure, an inlet connection in one of said structures, a tubular inlet passage on said stationary wall and extending from said inlet port into said dome-forming structure, and a substantial pocket at the side of said inlet passage and also communicating with said inlet connection for trapping a volume of vapor and air as an inlet air dome.

17. In a fuel pump, a main body structure having a flexible pumping wall and a stationary wall, inlet and outlet ports in said stationary wall and check valves for said ports, a dome-forming structure adjacent said main body structure, registering ribs traversing said structures and forming inlet and outlet pockets each open to one of said valved ports, an inlet fuel connection in one of said structures and opening into said inlet pocket, and a tubular inlet passage extending from said main body structure adjacent said inlet port and opening into said inlet pocket, said inlet pocket having portions within said main body structure and at the sides of said inlet passage andalso in said dome structure beyond the open end of said passage to form fuel trapping and inlet vapor dome spaces between said inlet port and said inlet connection.

18. A fuel pump as described in claim 17 in which the pump is mounted with said dome structure depending therefrom, saidtubular inlet passage extending downwardly into said inlet pocket and the pocket portions in said main body structure at the sides of said passage serving to trap a substantial volume of vapor to form an inlet dome.

19. A fuel pump as described in claim 17 in which the pump is mounted with said dome structure above said body structure, the upper end of said tubular inlet passage opening into the inlet pocket portion in said dome structure and the inlet pocket portion above said open end of said inlet passage serving to trap a volume of vapor to form an inlet dome.

20. A fuel pump as described in claim 17 further including a flexible diaphragm traversing said outlet pocket and received between said main body and dome structures, said diaphragm sealingly trapping a quantity of gaseous fluid in the portion of said outlet pocket opposite said outlet port and forming therewith a resilient outlet dome.

21. A fuel pump as described in claim 17 in which said main body and dome forming structures are of circular section, said registering ribs being substantially diametral so as to form similar spaces on opposite sides thereof for pocketing.

' IRVEN E. COFFEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,957,753 Babitch May 8, 1934 2,003,420 Babitch et al June 4, 1935 2,005,206 v Rockwell June 18, 1935 2,104,446 Babitch Jan. 4, 1938 2,203,464 Harry June 4, 1940 2,242,582 Jencick May 20, 1941 2,269,625 Erickson Jan. 13, 1942 2,285,163 Knott et a1 June 2, 1942 2,344,287 Creveling Mar. 14, 1944

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