US2277930A - Carburetor - Google Patents

Description

Maid: 31,719.12;v EIC; 9.0@ ml.;

CARBURETOR Filed May 11, '1939 4 vsneets-slmt 1 BY W. Nido/.257-

Q. Q aff ATTORNEY.

March 31, y1942. F1 CMOCK 'E1-AL Y iARBUREToR I F'il'ed May ll, 1939 4 Sheets-Sheet 4 ATTORNEY.;

Patented Maa-3i, i942 illtiiE agirait' 2277,93@ ungenaueren Frank c. Macs aantasten/w. rame, senta Bend, Ind., assgnors te Bendix .aviation Cor-1' poration, South Bend, 3nd., a corporation et Delaware application inayii, isst, seriali no. 272,99@

(ci. esi-ssl 2.1 claims.

This invention relates to carburetors and more particularly to means for supplying an acceler ating charge of fuel to a carburetor under certain conditions of operation;

In all types of carburetors, including the type .wherein the fuel for ordinary operation is injected under pressure, an increase in the rate ci air ilow resulting from rapid opening movement of thethrottle does not immediately produce a corresponding increase in the rate of fuel oiv. r"i'his slight lag in fuel delivery accompanying a suddenfopening of the throttle results in a temporary leanness of the` mixture. In order to overcome this temporary leanness it has beencommon practice'to use a piston type pump directly operable'by the throttle shaft and so arranged that a small amount of extra fuel is mrnediately forced into the air stream as the throttle is opened.

"Acceleration pumps of this type have several inherent disadvantages, especially when applied to carhuretors of the pressure feed type disclosed in the copending application of F. C. Mock, Serial Number 202,206, iiled ,April i5, i938. In this type oi carburetor the throttle and the accelerationlpump maybe at widely spaced points and mechanically connect them would result in the use oi an extensive system oi cooperatingllinnages. VThis is especially hazardous in aircraft use since any sticking orjamming of the piston or linkage Iloclss the throttle. kinematic relationship between the throttle and the pump is diiicult to obtainin the design of some carburetors.

lt is an object oi the invention to provide improved means Whereby the tendency for the mixture ratio to be temporarily lean immediately following an opening of the throttle is overcome. v

It is a further object to provide an acceleration pump having greater accessibility so thaty the pump capacity can be readily adjusted.

A further object is to provide a pressure feed l carburetor having improved acceleration characteristics.

Further objects and advantages oi the invention Will be apparent from the following descrip= bar and nozzle taken on the line 3-3 in Flgure 2; I

Figure 4 is a sectional View of the acceleration pump taken on the line lll-itin Figure l;

Figure 5 is a sectional vievir of another modi-s I cation of the acceleration pump'.

Figure 6 is a sectional view of another modi-= cation of the acceleration pump; and

Figure 7 is a fragmentary view of the adapter flange depicting alternate arrangements for supplying fuel to the acceleration pump.

Referring more specifically to Figure l, the carburetor proper comprises an induction' passage lil leading to a supercharger i2 of an internal combustion engine of any desirable type. The passage i@ is controlled by a throttle lil operable by a rod it extending from the pilots cockpit or drivers compartment. The operator therefore directly controls the air charge to the 2o engine While the fuel charge is automatically venturi throat and communicating through pres-n Also, the necessary a fuel discharge bar 3G.

sure conduit 25. with the control unit hereinafter described. The secondary venturi 22 is formed.-

With an annular chamber 25 communicating through 2, plurality of tubes 2t with the air scoop iB and through pressure conduit 2i with said control unit.

Posterior to the throttle ll is an adapter section 23 forming a portion of the induction passage l and having a pressure responsive :fuel discharge nozzle indicated generally at 29 which controls the flow of fuel from the conduit 32 to An acceleration pump generally referred to at, 3l is also carried Iby the adapter section 2t and as shown is spaced apl proximately 90 from the nozzle 2li. f

Figure 3 is a sectional view of the discharge 55 The control unit comprises a hollow casing @5, which may be formed from a plurality of diecast sections, assembled and-secured together as shown. The interior of the casing is divided into flve chambers 36, 3i, 33, 39 and lill by the four flexible diaphragms di, d2, i3 and t4, each of which has its outerlend clamped between adjacent sections of the casing .to form a fluid-tight gasket, and its central portion apertured and se:- cured'to a control rod 65 by means of hubs t6, di and it having ian'gesat their ends which clamp the diaphragms between them and limit :dexure thereof to an annular looped portion between the flanges and the casing, which permits vertical movement of the control rod 05. The hubs and diaphragms are held in assembled relation on the control rod by means of a threaded cap i9 which terminates in a spherical end slidably movable in a recess 50 at the upper end of the casing, thus forming a guide bearing for the control rod assembly. A spring 52 in recess 36 yieldingly urges the rod downwardly as shown.

The lower end of the control rod is connected through a double ball-and-socket universal joint 5i, with a fuel valve 52 of the sleeve type having ports 53 controlling the admission of fuel to the lower chamber 00. An adjustable stop 35 limits downward movement of the wcontrol rod and valve 52. An annular fuel chamber 50 surrounds the valve 52, and has an annular groove adapted to register with the ports 53. Any commercial fuel pump arranged to deliver fuel at substan-V tially constant pressure may be used to deliver fuel to the fuel chamber 55|. The one shown at 55 is of a rotary type having a fuel inlet 56, fuel outlet 5l and a by-pass channel 58 controlled by a, pressure responsive valve 59.

The diaphragms used in the control unit are preferably formed of material such as sill: fabric impregnated with Neoprene or other articial rubber compound. Such diaphragme have substantially no inherent resiliency.

In the operation of the device as thus far described, fuel is delivered at substantiallyconstant pressure` to fuel chamber 50. whence it hows through ports 53, the eiective area of which is controlled by the axial movement of the control rod 05, into the unmetered fuel chamber 20, and thence through a passageway E0 containing metering orifice 6|, into the metered Vfuel chamber 39, and thence through passageway 22l to the discharge nozzle 29 and discharge bar 30. Unmetered fuel chamber 00 also communicates, through a longitudinal passage 63 in the control rod 45 and cap t9, with chamber 36, sothat the pressures in the two chambers are at all times equal,

Chamber 3l communicates through passage.

way 21 with the annular chamber 25 in the secondary venturi and is therefore subjected to the pressure existing in the air scoop I8. Chamber 38 communicates through passageway 24| with the annular chamber 23 in the primary venturi` 20 and is therefore subjected to the pressure existing at the throat of said venturi. The diierential in pressure between air scoop and venturi throat is'proportional to the square of the rate of air flow. These two pressures acting on 012901 site sides of diaphragm 02 create a net force on` the control rod which is also proportional to the square of the rate of air ow and is in a. direc-- which is proportional to the square of the quantityof fuel flowing. The fuel pressures in chambers 40 and 39, differing in degree by the pressure drop across the restriction, act on'opposite sides of diaphragm 44 and create a net force on As a-result, for any given conditions of operation, the control rod assembly and attached valve 52 will move to a position such that the force created by fuel flow will be maintained equal to the force created by the air flow. Since these forces are respectively proportional to the squares of the quantities of fuel and air flow, it is apparent that the square of the fuel flow is maintained in constant proportion to the square of the air ow and hence the mixture ratio, that is the ratio of the weight of fuel to the weight of air, is maintained at a. constant value unless a1- tered by extraneous means such. for example, as those disclosed in the copending application of F. C. Mock, Serial Number 202,206.

The` discharge nozzle assembly 29, better shown in Figures 2 and 3, comprises a nozzle body l0, valve 'l2 arranged to seat at 13, cap '-fl,

l a diaphragm 16, and compression Aspring l0, and

the control rod which is proportional to the iof fuel flow increases, thereby opposing the previously mentioned force generated by air ow.

is held securely in place in the adapter section by screws 80, gasket 8|, and packing 82.

Fuel under pressure is received from the control unit through conduit 32, whence it ows into the annular fuel chamber 8d and through ports into the chamber 86, where its pressure is exf erted upon diaphragm 7B to causervalve 'l2 to move oriits seat againstthe action ofthe com pressionA spring l0 and thereby allows the fuel to flow through passageways `liti, 89 and 90 and to discharge through the orices 92 into the air o'wing through the inductionpassage l0. Nozzle cap ld can be-vented through the passageway 92 to either the atmosphere-as shown, or to venturi suction or air scoop pressure to control the fuel delivery pressure characteristic as fully explained in Mock-Partington, application, Serial Number 243,067 iled November 30, 1938. In place of the specific discharge bar and nozzle disclosed herein, any of the nozzleA arrangements disclosed in the above mentioned application may be used# l The acceleration pump 3| (see Figure 4) comprises three chambersi-an' inner chamber |02. an intermediate chamber divided into two portions |04, |06 by a web |30, andan outer chamber |08. Chamber |08 is separated from the intermediate chamber by a diaphragm IIB which has its outer edge clamped between the pump body sections H2 and H4, and its,y center portion apertured and secured between -the diaphragm cup member ||6 and a plate by the nut I I cooperating with the threaded bolt-like extension of the spring retaining cup |20. The diaphragm H0 is formed with an annular groove'as indicated at |22 so as to provide a relatively large stroke-diameter ratio for the diaphragm. A passageway |24 connects the chamber |08 with the air conduit ||l at a point posterior to\ the throttle. The suction transmitted through said passageway urges diaphragm l| |0. to the left, in opposition to 'a compression spring |26, against an adJustable stop |28 which is locked in place bywthe locking nut |29. L

The body member III is provided with an inwardly extending radial flange or web |30 having a relatively large central-aperture |32 and arranged to contact the plate Ill to limit movement of the diaphragm H0 to the right. The flange |30- is also provided with a plurality of apertures IJI to maintain unrestricted communication between the two positions of the intermediate chamber.

Chamber |02 is separated from the intermediate chamber by a diaphragmv |40 which has its outer edge clamped, between the pump body secwelded or riveted to the head of bolt |08 and is adapted to engage an annular groove in a cylindrical cap.v ltlwhich is riveted to the end of the pump valve |52. Lateral clearance as well as a slight amount of end wise or axial clearance is provided between the bifurcated cup |08 and thegroove of cap .|50 to' permit -a'. free but limited lateral movement of the valve |52 relative to the diaphragm after assembly, for purpose of selfalignment. i

The diaphragm U30 can be of formed type since its stroke need only be s ufhcient to move the valve |52 a small distance from the seat ii in the pump nozzle body |56. f

The pump nozzle body is threaded into the adapter section 28 at |51 and is provided with a shoulder |58 cooperating vwith a step in the nozzle cap |50 to securely hold said cap against a shoulder |52 in the adapter section. Gaskets |65 and |65 at shouldersI |50 and |52 prevent any passage of fuel from the chamber |02 into the i. `conduit |0 except by way of the valve |52'and the flat or uri- When the throttle is-suddenly opened the vacuuin in chamber |08 is destroyed and springA |25 urges diaphragm ||0 to the right, thereby forcing fuel from the chamber |06 through the restriction |86 and passageway |80. A pressure is thus createdin chamber |04 in excess of that existing in chamber |02. This difference in pressure `\on opposite sides ofdiaphragm |00 Vurges the diaphragm to the right and opensthe pump discharge valve |52. chamber |02 is under 9, pressure at least equiva-v lent to that in the main fuel nozzle conduit, fuel will issue as a jet from the pump discharge orices H0. After the fuel displaced by diaphragm |80 has been forced through orifice |86 a condi.

tion of Vpressure equilibrium will be re-established across the diaphragm M0, and the valve |52 will close.

A chamber |08, which will draw the diaphragm M0 seat ist. apertures les and les in the pump nozzle body |56 afford unrestricted communication between the chamber |02 and the pump valve and seat. f I

The nozzle cap |50 is provided withone o more orifices |10 which can bevaried in size or number and location to respectively control the rate and direction of the acceleration pump fuel delivery.

A compression spring |72 urges the valve |52 and attached diaphragm M0 to the left against the valve seat |513. An extension ile from the end of the valve contacts the inner surface of the nozzle cap |60 to limit the opening movement of the valve.

Chamber |02 is connected` to chamber |0lby the main discharge nozzle supply conduit'l, as

shown in Figure 2; or may lead to a source -of unmetered fuel such as the unmetered fuel chamber ci] of. the control unit or the discharge A againstthe stop |28 and refill chamber i0@ with fuel drawn .from the conduit V32. Since the fuel flowing from the control unit yinto conduitf32 is metered in proportion to the air flowing through the air conduit, any fuel ow into the acceleration pump-resultsin a decreased quantity discharged from' the mainfuel nozzle and hence vin a deficiency of` gasoline discharged into the air stream. The rate of fuel robbing, that is the rate'of 'refilling the pump` chamber, can be controlled by varying the size of restriction l or by using a restriction in the passageway|82';' the majority of engines," however, will continue to operate and no ill? effects are noticed from the "fuel robbing` action following a closing of the throttle even though the restrictions are omitted.

If the pump orifices We have a. combined area which is relatively large as compared to the discharge orice of the main fuel nozzle, the pressure in chamber |02 will decrease upon opening of the valve |52 to a value less thanthe normal fuel nozzle discharge pressure and part of the "metered fuel which would normally be discharged y Conversely, .by `making the pump o rices small and/or increasing the strengthn of Vthe pump spring |12 a part of the fuel displaced by .the

pump diaphragm Hc can be forced to discharge through the lmain discharge nozzle. y

conduit 51 of the engine driven fuel pump 55,

as depicted in Figure 7. :The-principle of operation with each of these arrangements is explained immediately hereinafter. i Operation with fuel supply from metered fuel Assume that the engine is operating at relatively light vload withy a partially closed throttle.

The diaphragm H0 will be-urged to the left, in opposition to the spring |25, against the stop |28 by vacuum transmitted to the chamber |08 from the mixture conduit l0 posterior to the throttle acting ori one side of diaphragm ||0 andby the pressure of the fuelin chamber |06 acting on the other side of the diaphragm. Chambers |02,` |04 and |06 'are filledwith fuelmder -a pressure equal tov that of the fuel in-themetered fuel chamber 39 or main dischargemozzle conduitf?.

`Sincethe pressures acting onopposite'sides of diaphragm |40 are equal, the pump'valv |52 will be held in l.a closedv positionby the spring and full of.fuel when thevacuum is low. RA'

-portion of the metered fuel 'supply is therefore It is apparent` that by proper adjustment of the size of orifices |10, pump spring |12, and restriction |86, the total quantity of -fuel delivered to-` the air stream during the yactive period of' pufnp operation can be apportioned as desired between the main .fuel nozzle and the pump nozzle. It is also apparent that the discharge period of the pump can be lengthened or 'shortened by making the restriction |86 smaller or larger so LAas to vary the time required to re-establish an tically empty of fuell during periods of operation when the vacuum posterior to the uname is high `used vfor filling the bar upon atransfer `from a conditionof high 'vacuum'.operation vto one of 1 low vacuum'operation `as'lis* experienced in any Sincethe fuel in.

' phragm 3 I 0.

conduit during the acceleration peripd is thatv quantity which would normally be supplied by the main control unit, together with the quantity displaced by the diaphragm HU.

Operation with fuel supply from u'nmelered fuel If the acceleration pump supply conduit |84 communicates with the unmetered fuel chamber 40, fuel at unmetered fuel pressure will be delivered to the orices |10 during the entire period that the valve |52 is open'ed in response to a differential in pressure across the diaphragm |40, created as previously explained. The rate.

of discharge of this acceleration fuel will depend upon the difference in pressure between the fuel pressureV in the unmetered chamber and the pressure in the air conduit and the size of the restriction through which the fuel must ow such as orices |10. The quantity of extra fuel delivered into conduit l0 by this arrangement will depend not only upon the rate of discharge but also upon the length of time valve |52 remains open. The time available for discharge can be varied by adjustment of the size of restriction |86 since decreasing or increasing said restriction will respectively increase or decrease the time required for pressure equalization across the diaphragm |40. The quantity of extra fuel for acceleration purposes is therefore not dependent upon the volume displaced by diaphragm H0, and hence large'quantities of acceleration fuel can be handled with but a very small pump structure, L

Since the pressure in the unmetered fuel chamber varies with the rate of air and fuel flow, and since the quantity of acceleration fuel delivered into the air conduit depends upon the unmetered fuel pressure, it is apparent that the quantity of acceleration fuel will vary somewhat with the rate of air flow at the time of the acceleration. This variation has been found desirable on certain engines and undesirable on others and may be eliminated`if desired by the arrangement of Figure 7 in which the acceleration pump receives fuel from the discharge conduit of a constant pressure fuel supply pump.

A modified form of the invention is shown in Figure 5 in which the reference numerals of Figure 4 with the addition of 200 have been used to designate similar parts.

The pump is composed of the four chambers 302, 304, 306 and 308 separated respectively by the diaphragm 340, a solid web 330, andv the dia- Chamber 308 communicates through passageway 324 with the airl'conduit posterior to the throttle. A passageway 402 in the web 330 connects chambers 308 and 304 and is provided with a one-way check valve 404 to prevent ow of fuel from chamber 306 to chamber 304 and to permit flow in the reverse direction. Chamber 306 is also connected to chamber 302 by a passageway 406 which may be provided with a restriction 408. Passageways 382 and 384 connect the chamber 304 with a source of fuel which may either be metered or mime# l tered fuel as previously explained in connection opened,- the vacuum in chamber 308 will be destroyed and spring 326 will urge the diaphragm 3| 0 to the right, thereby forcing the fuel from chamber 306, through passageway 406, restric tion 408 and into chamber 302 where it Will increase the pressure on the right side of diaphragm 340 and open the valve 352, thereby allowing the fuel to discharge into the air conduit. 4

Check valve 404 prevents any of the fuel displaced from chamber 306 by diaphragm 3|0 during the pump dischargeperiod from entering the chamber 304. I1; is apparent that the additional fuel delivered to the air conduit during the acceleration period, irrespective of whether the fuel source is from metered or unmetered fuel, is merely the volume of fuel displaced by the diaphragm 3|0, and the entire quantity is discharged through the pump discharge nozzle. The

rate of delivery of the acceleration pump charge can be increased or. decreased by respectively increasing or decreasing the size of the restriction 408. f

Upon a subsequent closing of the throttle the diaphragm 3|0 is drawn to the `left by the vac- -uumI transmitted to chamber 308 and fuel is is 'forced-through passageway 384 to the fuel source and the balance through the pump discharge nozzle. The actual apportioning of the acceleration `pump charge between these two available paths of flow can be accomplished by adjustment of the relative sizes of the restrictions 408 and.404'.

In the description of the several embodiments of the invention, the terms upward and downward as well as left" and right have been used for convenience, but it Will be understood that the control mechanism'may be inverted relative to the carburetor, or the control unit and carburetor inverted relative to the engine, or the engine and all its accessories maybe inverted gas in acrobati-c'flight) without greatly affecting the operation as above described.

Although the invention has been described with specific reference to certain embodiments thereof, it should not be inferred that the invention is limited thereto nor otherwise except in accordance with the following claims.

We claim:

l. In a charge forming device for an internal combustion engine, an induction passage, a throttle controlling the same. and an acceleration open said valve upon a sudden rise in pressure in pump comprising a pressure chamber connected to said induction passage posterior to the throttle, a fuel chamber separated from the pressure chamber by a diaphragm, a second fuel chamber connected to said rst fuel chamber by a passageway and to a source of fuel, a third fuel chamber separated from the second fuel chamber by a diaphragm, a duct connecting said rst andl third fuel chambers, a conduit connecting said third fuel chamber with the induction passage, and ayv'alve attached to said second diaphragm controlling said conduit.

2. The invention dened inclaixn 1 together with checkvalve means in said passageway to prevent fuel flow in the direction of the fuel source upon fuel chamber reducing movement of said first-named diaphragm. .Y

3; In a charge forming device for an internal combustion" engine, an induction passage, a throttie controlling said induction passage, and an acceleration pump comprising a pressurechamber connected to saidzinduction passage posterior to the throttle, a fuel chamber separated from the pressure chamber by a diaphragm, a secondfuel chamber separated from said first fuel chamber by a diaphragm, said fuel chambers being adapted to contain fuel under superatmospheric pressure, a passageway connecting said fuel chambers, a

said ,pressure chamber.

6. The invention dened in claim 5 together with yieldingI means urging said valve toward a closed position.

'1. In a charge forming device for an internal combustion engine, an induction passage, a throttle controlling the same, and an acceleration pump comprising a pressure chamber connected to said induction passage posterior ifo the throttle, a fuel chamber separated from said pressure chamber by a movable wall, yielding means urging said movable wall in a direction to decrease duct for supplying fuel under superatmospheric pressure to said second fuel chamber, a conduit connecting said second fuel chamber with the induction passage, av valve oper-ably connected to said second diaphragm controlling said lastnamed conduit, and a Y spring urging the nrst named diaphragm in a direction to decrease the volume of the rst na'med fuel chamber whereby a sudden rise in pressuredn the pressure chamber will increase the pressure in the rst named fuel.`

chamber tothereby urge the second diaphragm in a direction to open the valve.

d. In a charge forming devicevfor an internal lcombustion engine,l an induction massage, a throttle controlling said induction passage, and an acceleration pump' comprising a pressure chamber connected to said'induction passage pos- A terior to the throttle, a secondchamber separated from the pressure chamber by a movable wall and having an outlet, resilient' means urging -said wall in a direction to decrease the size of the second chamber. a fuehchamber separated from said second chambereby a movable wall and containing fuel under superatmospheric pressure, a passageway connecting said fuel chamber with a source of fuel under pressure, a conduit connecting said fuel chamber with the induction passage, and a valve operably connected to said secthe size ofsaid fuel chamber, a second fuel chamber having a movable Wall and being closed 'to atmosphere to be thereby adapted to contain fuel under superatmospheric pressure, a passage-` way interconnecting said fuel chambers, a conduit connectingone of said ffuelchambers Withy said second movable wall to control the ow of fuel through said duct.

8. In a chargv forming device, an induction passage, a throttle controlling the same, a source of fuel under pressure, a fuel conduit connecting said source with the induction passage, a second fuel conduit connecting said rst fuel conduit at a point at which the fuel pressure is superatmospheric to the induction passage, a valve in said second-named fuel conduit, and means responsive to variations inthe pressure in the induction passage posterior to the throttle for temporarily openingsaid valve to thereby permit fuel under superatmospheric pressure to discharge into the induction passage through said second fuel conduit, said last mentioned means comprising a variable pressure chamber connected to the induction passage posterior to the throttle, a second chamber separated from the pressure chamber by a movable wall capable of relatively large displacements, and a second Amovable wall capaing the valve.

ond-named movable wall controlling said conduit.

5. In a'charge forming device for an internal,

combustion engine, an induction passage, a throttle controlling the induction passage, and an ac- -cleration pump comprising a pressure chamber connected to said induction passage posterior to the throttlei a second chamber separated'from the pressure chamber by a movable wall, a second A movable Wall arranged to'be subjected` to pressures created in 'saidsecond/chamber, a pump Y. dischargenozzle in the induction passage, a conf duit leading from a source of fuel under pressure v t to said nozzle to supply fuel under super-atmospheric pressure thereto, a valve cpnnectedto said second movable' wall-and normally closing said s ,'conduit, -and spring means "ux-ging* said first v named movablel wallA in a direction to. increase .the pressure in 'said second chamber to thereby 75 9'. In a charge forming device, an induction passage; a throttle controlling the same, a fuel nozzle discharging into said induction passage,- a pressure responsive valve controlling said nozzle, a fuel conduit connecting a source of fuel under pressure with said fuel nozzle, a second fuel con# Y duit connecting the induction passage with said first-named fuel conduit anterior to said nozzle, a

normally closed Vvalve in said second fuel conduit,

and means responsive to an increase in the pressure in the induction pamage posterior to the Y' throttle for temporarilyopening said valve comprising ajvariable pressure chamber connected to the induction' passage posterior to the throttle, a fuel chamber connected -toreceive fuel from one of said conduits, a movable wall separating said pressure and. fuel chambers and capable of relatively large displacements towvary substantially the volume 'of said fuel chamber, a second fuel chamber forming a portion of said second fuel conduit and having Aamovable wallconnectedfto lthe valve, and'means effective upon fuel chamber reducing movement of the rst movable wall fuel chamber to the said second fuel conduit.

for opening said lvalve` by subjectingv the lastl named movable'wall to vfor transmitting 1 ,a fuel regulating means in said duct including a metering restriction,.and an acceleration pump comprising a pump discharge nozzle, a conduit connecting said pump discharge nozzle with the fuel duct posterior to the metering restriction, a valve in said conduit, a diaphragm attached to said valve, a variable capacity chamber associated with said conduit and having a movable wall operable in the chamber increasing direction in response to suction in the induction passage posterior to the throttle and spring urgedin the chamber reducing direction upon a decrease in said suction, hydraulic means connecting said movable wall and said diaphragm to temporarily open the valve upon chamber reducing movement of the movable wall, and means to apportion between the main fuel nozzle and the pump nozzle the total fuel flowing through the metering restriction during the period said valve is opened.

11. In a charge forming device for an internal combustion engine, an induction passage, a throttle controlling the same, a fuel nozzle discharging into said induction passage, a fuel duct connecting a source of fuel under pressure and the nozzle, regulating means in said duct including a metering restriction, a conduit connecting the induction passage with the duct posterior to the metering restriction, a valve in said conduit, a diaphragm attached to said valve, a variable capacity chamber associated with said conduit having a movable wall operable in a chamber reducing direction upon increase in the pressure in the induction passage posterior to the throttle, and

' hydraulic means associated with the movable wall leading from asource of fuel under pressure to l theinduction passage posterior to the throttle, and a pressure responsive valve in said duct whereby the fuel in said duct anterior to said valve is maintained under. superatmospheric pressure: the combination therewith of an acceleration pump comprising a pressure chamber connected to said induction passage posterior to the throttle, a second chamber separated from the pressure chamber by a movable'wall. a 'second movable wall arranged to be subjected to pressures created in said second chamber, a valve connected to said second movable wall to be actuated thereby, and a fuel conduit controlled by vsaid yvalve and leading from the fuel d'uct anterior to said pressure responsive valve to the induction passage posterior to the throttle whereby fuel under superatmospheric pressure will be discharged therefrom into the induction passage upon a sudden' rise in pressure in said pressure chamber.

14. In a charge forming device having an induction passage, a throttle therein, a fuel source, a fuel conduit leading from the source and havt ing a pair o'f branches discharging in the induction passage posterior to the throttle. a control lll) unit including a valve responsive to the rate of air flow through the induction passage for controlling the fuel flow through the conduit, a pressure responsive valve controlling one of said branches, a second valve controlling the other of said branches, and means for actuating said second valve including a pressure chamber connected to the induction passage posterior to the throttle. a second chamber separated from the pressure chamber by a movable Wall, and a second movable Wall arranged to be subjected to pressures created in said second chamber and connected to said second valve for actuating the same.

15. In a charge forming device for an internal combustion engine having an induction passage, Y

a throttle therein, a main fuel nozzle discharging in said induction passage posterior to the throt-v tle, and a control unit responsive to the rate of air flow through the induction passage for supplying fuel under superatmospheric pressure to said nozzle comprising a fuel conduit having a metering restriction therein, unmetered and metered fuel chambers in communication with the conduit respectively anterior and posterior to the metering restriction, a fuel control Valve, and movable wall means in said chambers for actuating said valve: in combination therewith of an acceleration pump including a fuel duct leading from said fuel conduit at a point a which the fuel pressure is superatmospheric to the induction passage, a valve in said duct, and means responsive to a sudden increase in the pressure in the induction passage. posterior to the throttle for temporarily opening said valve;

16. In a charge forming device having an induction passage, a throttle therein, a fuel nozzle discharging fuel into the induction passage, a source of fuel, a fuel conduit connecting said source and the nozzle and having a metering restrictiomand a control unit for controlling the flow of fuel to said nozzle in response to the air flow through the induction passage and to the fuel flow through the metering restriction: in combination therewith of an acceleration pump comprising a pressure chamber connected to said induction passage posterior to the throttle, a fuel chamber separated from said pressure chamber by a movable Wall, yielding means urging said wall in a direction to decrease the size of the fuel chamber, a second fuel chamber having a' movable wall, a passageway interconnecting said fuel chambers, a fuel passage connecting one of said fuel chambers with the fuel conduit posterior to the metering restriction, a duct connecting the second fuel chamber with the induction passage. and Valve means attached to the second movable wall to control the flow of fuel through said duct.

17. The invention dened in claim 16 comprising in addition a one-way check valve in said fuel passage.

18. In a charge forming device, an induction passage, a throttle controlling the same, and an acceleration pump comprising a pressure chamber connected to the induction passage posterior to the throttle, a fuel chamber separated from the pressure chamber by a movable wall, a second fuel chamber having a movable Wall adapted to be subjected to pressures created in said first fuel chamber, a fuel conduit including at least one of said fuel chambers for conducting fuel under positive pressure from a source to an outlet in the induction passage, and a Valve closely adjacent said outlet for controlling the flow of fuel therefrom. said valve being connected to the second named movable wall to be actuated thereby. 19. The invention defined in claim 1.8 comprising in addition a check valve in said fuel conduit.

20. 4The invention dened in claim 18 comprising in addition a pair of restrictions in said fuel conduit respectively anterior and posterior to a fuel chamber included thereby.

21. In a charge forming device, an induction passage, a throttle controlling the same, a fuel nozzle discharging therein, a fuel pump, a conduit connecting the pump and nozzle, a valve for varying the fuel flow through said conduit, means responsive to the rate of air flow through the induction passage for controlling said valve, a duct connecting the conduit with the induction pasconnected to the 'induction passage posterior' to the throttle, a second fuel chamber separated -from the pressure chamber by a diaphragm, an

annular groove in said diaphragm to permit substantial displacements thereof, a spring urging the diaphragm in a direction to decrease the volsage, a valvein said duct, a fuel chamber in the duct having a movable wall connected to the second named valve, a variable pressure chamber the said second valve upon fuel chamber decreasing movement of the diaphragm.

FRANK C..MOCK.

ROBERT W. MOORE.

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