US1727265A - Charge-forming device for internal-combustion engines - Google Patents

Description

Sept. *1929. F. E. ASELTINE 1,727,265

.CHARGE FORMI'NG DEVICE FOR INTERNAL COMBUSTION ENGINES V Filled sept. 5. 1925 s sheets-sheet 1' 'CHARGE EORMING DEVICE FOR INTERNAL COMBUSTION ENGINES F. E. ASELTINE Sept. 3, 1929.

Filed sept. 5, 1925 s Sheets-sheet 2 Sept; 3, 1929. F. E. ASELTINE 1,727,265 I CHARGE FORMING DEVICE FOR INTERNAL COMBUSTINNGINES 3 Shets-Sheet AS5 FledSept. 5, 1925 \w\ Q WFMQFEM d wh@ w@ HW @Q i m S Y intim Patented Sept. 3, 1929.

UNITED 4STATES 1,727,265 PfiizrvrI OFFICE.

FRED E. ASELTINE, OF DAYTON, OHIO, ASSIGNOR TO GENERAL MOTORS RESEARCH CORPORATION, 0F DETROIT, MICHIGAN, A CORPORATION OF DELAWARE.

CHARGE-FORMING DEVICE FOR. INTERNAL-COMBUSTION ENGINES.

Application filed September 5, 1925. Serial No. 54,592.

This invention relates to charge-forming devices for internal combustion engines, especially such engines as are used for propelling automobiles.

The general object of the invention is to provide a device which will deliver equal quantities of fuel charge of the same mixture ratio to each cylinder of amulticylinder engine under the various conditions of load and engine speed to which the engine may be subjected. This invention provides various iinprovcmeuts over the disclosure in my prior application, Serial No. Qc. 1925.

A special object of this invention is to provide airiniproved liquid dash pot for stabilizing and modifying the action of the suction-actuated main air inlet valve.

Another vobject is to provide an improved engine accelerating device, whereby a richer fuel mixture is momentarily obtained uponthe sudden opening of the manually operated throttles. l

Another object is to provide an improved fuel-distributing means, having a plurality of individual primary carburetors each supplying an overrich fuel mixture to a separate branch ofthe air manifold leading to an engine intake port.

Another object is to provide an auto- 1natically-actuated, passage-restricting means on the engine side of the manually-operated throttle, whereby the entering fuel charge is delivered to the engine inta-ke ports at high velocity. thereby preventing the deposition of liquid fuel particles on the passage walls.

Another object is to provide a compact, rugged structure for carrying out the above objects.

Further objects and advantages ofthe present invention will be apparent from the following description7 reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown. i

ln the drawings:

Fig. 1 is a plan viewof a charge-forming device for a six-cylinder internal combustion engine, built according to this inven- 'tion.

Fig. 2 is a section on line 2 2 of Fig. 1 and shows the relation of one branch of the intake pipe to the engine intake valve of an L-head engine.

4,665, filed January Figs3 is a side elevation of the device shown 1n Fig. l and and .shows the manually actuated arm for changino' the spring tension on the spring closedy main air inlet valve.`

Fig. 4 is a vertical section on the broken line i1 -4 of Fig. land showsin particular the liquid fuel ducts leading from the oat bowl to the two distributing canals'for the primary carburetors.

Fig. 5 is a vertical section on the broken line 5 5-5 of Fig. v1.

Fig. 6 is a section througlrone of the primary carburetors and 'is taken on the line 6 6 of F igs. 1 and 8. Fig. 7 is a plan View of the central part of'the device with, the distributing block containing the primary carburetors removed,

and shows in dot and dash lines the position of the distributing distributing block.

Fig: 8 is an enlarged lan view of the distributinc block containing the distributing canals for the three primary earburetors shown in dotted lines therein.

Fig. 9 is a bottom view of thedistributing block.

' Similar reference'characters refer to similar parts throughout the several views of the drawings.

Numeral 10 designates in its entirety the air manifold provided with the three branches 11, 12 and 13, each of which vbranches connects to an engine intake port, which serves two adjacent cylinders. Since it is well'known in both four and six cylinder engines to provide only one engine intake port to serve two adjacentv cylinders, such engine construction is not shown in detail in the drawings. Fig. 2 shows only. one engine intake valvel of the pair of similar intake valves served by the branchedintake passage 14 and intake port 16 in the cylinder block casting. The air manifold casting10 has a main air inlet opening 17 which is covered by the air inlet fitting 18 having the mainair inlet 19 and the intake valve 20. Located directlynnder the inlet canals contained in said valve 2() is the fuel float chamber 30 which is provided with the annular float 31 and float-- operated fuel inlet valve 32 for maintaining -constant fuel level in chamber 30. Liquid fuel 5 and the two clamping bolts 40 which extend A 18 and the float bowl 30, andv thus through suitable ears on the castings 10 and 36. These clamping bolts 40 also extend through suitable .ears on the air inlet fitting these parts rigidly together, as clearly shown in Fig. 3.

The main air inlet valve 20 has a valve steml extendingdown through the guide 51 in casting 36 and 'is provided at its lower end with a dash pot plston 52 which cooperates with the dash'pot cylinder 53 located within the fuel bowl 30 and surrounded by the annular float 31 therein. The piston 52 has one or more holes'54 therein (two being shown in Fig.4) anda loose disk check valve for closing the holes 54 upon downward movement Aofthe piston as will be cl'ea'r from Fig. 4. The dash pot cylinder 53 remains filled with liquid fuel at all times the fuel entering through suitable holes 56 above the piston 52 but below the fuel level 57 in float bowl 30. The wall of the dash pot cylinder 53 is provided with a bv-pass duct 58 of about 1/8-inch diameter, which freely by-passes liquid around piston 52 after the valve 2O has moved down a predetermined amount to uncover the bypass port 59 (see Fig. 5). The air valve 2O is urged toits seat by the coil spring 60 whose upper end engages'the spring seat disc 61 held against a shoulder on the valve stem 50, and whose lower end engages the verticallyadjustable spring cup 62 which slides within guide'cylinder 63 in casting 36. The cup 62 1s adj usted up or down by means of a yoke 64 rigidly secured to a transverse shaft 65 having suitable bearings in the casting 36. The two arms ofthe yoke 64 have slottedextremities 66 engagingdiametrically-opposite pins 67 on the cup 62. These pins 67 project through and ride in the slots 68 in the Walls of the guide cylinder 63 (see Fig. 5). The transverse shaft 65 is actuated by lever arm 69 secured to the projecting end of shaft 65. The tension'- of spring 60 may be adjusted at will b the operator by suitable manually-actuatedI linkage attached to lever 69 and extending to the drivers seat. The minimum or normal tension on spring 60 is adjusted by the screw 70 which limits the downward movement of cup 62, as will be clear from viewing Fig. 3. The air valve 20 is opened according to the depression in the air manifold 10, its opening movement being damped by the leakage of fuel past the dash pot piston 52, the check valve 55 being closed. During its initial opening movement the damping effect is at a maximum, but as the valve 20 opens more and more, the damping effect of the dash pot progressively reduces due to the leakage through by-pass port `59 becoming clamp all v greater and greater as the top edge .of the pis- It will be noted that athin plate is provided to insure that equal parts of the air entering the air inlet horn 19 will flowl through the three outlet branches of the manifold.

This plate is secured between the air inlet horn and the top of the manifold immediately above the middle'outlct branch of said manifold permitting a flow past the air controlling valve directly into this manifold branch. The purpose-of this plate should be obvious. The resistance to flow through the end branches of the manifold is greater than that through the middle branch because of the greater distance through which the air has to flow, and if air were permitted to flow directly into said middle branch the volume of air flowing to the engine through said middle branch would be greater than that flowing' through the end branches. The plate 75 operates as a baille around which the air flowing through the middle outlet branch of the manifold must pass, making the resistance to flow through, and the volume of charge supplied by,.the various branches equal.

The primary carburetors fo'r supplying an overrich fuel mixture to each of the branches 11, l2 and 13 of the air manifold will now be described. The casting 36 has an upstanding portion extending upwardly alongside the central branch 12 of the air manifold'lO. This portion 80 contains the two vertical fuel ducts 81 and 82, which branch in parallel relation from the fuel duct 83. Duct 83 is extended to a point below the fuel level 57 by the long metering plug 84 which has the fuelmetering orifice 85 therein. 'The portion 8O .terminates atthe top in a flat table 86 having two screw-ears 87 thereon (see Fig. 7). The distributing block, designated as a whole by numeral 90, has a corresponding flat surface 91 (see Fig. 9), which is rigidly secured upon the table 86 by the two screws 92 which are threaded into the ears 87. 'lhe flat surface 91 of the distributing block 90 is provided with two separate fuel-distributing canals 93 and 94 which register with the vertical fuel ducts 81 and 82, respectively, as shown by the dot and dash lines in Fig. 7. The distributing block 90 contains three - parallel bores 95,96 and 97, of the same diameter, each of which bores extends above and across the fuel-distributing canals 93 and 94 adjacent the open end of each of said bores (see Figs. 8 and 6). 'The fuel canal 93 admits fuel to each of the bores 95, 96 and 97 through a high-speed fuel je't 98, and the canal 94 admits fuel to each of said bores by a lowspeed fuel jet 99, thus forminer three individually-metering primary carburetors 100, 101, and 102. Primary air enters each of these carburetors through -an air-metering bushing 105 which projects into the bores 96 and 97 past both fuel jets 98 and 99 (see Fig. 6). The fuel jets 98 and 99, therefore, deliver fuel to the annular space 106 between the bushing and the walls of the. corresponding bore, and hence the entering air does not impinge directly upon the fuel jets. Any variation in the flow of fuel through these. jets d ue to turbulency in the entering air stream is thus avoided and hence more accurate and uniform metering of the liquid fuel is obtained. The vertical fuel duct 81 contains a gravity metering valve 88 whose tapered end cooperates with the -valve seat 89. During idling or low `engine speeds this valve 88 rests upon its seat 89 and -hence fuel is supplied to the primary carburetors 100, 101 and 102 only through canal 94 and the low-speed jets 99. As the engine speed is in'- creased by opening the manually-actuated throttles, the suction on the primary carburetors is increased sufficiently to cause the liquid fuel to lift valve 88 from its seat and thus permit fuel to also flow through the highspeed jets 98 .in the primary carburetors. The valve 88 is lifted more and more, according to the increase in engine speed and hence acts as a variable restriction or metering orifice for the high-speed jets 98. The weight of the valve 88 is made such that it remains upon its seat at engine speeds below about -100 R. l. M. or a car speed of about 10 miles per hour. At this speed valve 88 begins to pass a small amount of fuel to the high-speed jets 98 and as the speed increases from'this point on the jets 98 supply a progressively increasing amount of fuel to the primary carburetors. Of course, the relative sizes of the various jets and orifices and the weight of valve 88 must be so chosen that the primary carburetors function properly, as described above. T he following weights and sizes have been found to give good results' with a six cylinder 36 H. P. automobile engine: weight of valve 88, 31/2 grams; diameter of valve seat 89, 1% of an inch; size of each of jets 98, No. 60 drill; size of each of jets 99, No. 73 drill; size of fuel orifice 85 supplying total fuel for all three primary carburetors, No. 53 drill; size of each of primary air orifices 105, No. 35 drill.

The overrich air-and-fuel mixture from the primary carburetors 100, 101 and 102 is leddirectly into the throat portion of a relatively large venturi in each of the branches 11` 12 and 13 of the air manifold. The bore 95 of the distributor block 90 leads directly to the hole 111 in the central branch 12, the ldistributor block being rigidly anchored to branch 12 by the screw 112. The bore 96 leads through a small pipe 113, of about the same diameter as said bore, tothe pipe fitting 114, which is rigidly secured to the branch 13 by the screw 115, so that the duct 113 registers with the hole 111 which leads down into the throat'of the venturi 110 in the branch 13. Each of the venturis 110 is held tightly up against a shoulder 116 in each branch by a tapered set screw 117 which rides against a cam surface 118 on the venturi (see Fig. 2). Preferably the floor 120 of the air manifold 10 is raised to lie approximately on a level with the bottom 121 of the throat of venturi 110. This prevents ythe puddling of liquid fuel on the floor 120 ahead of the venturi 110 atlow throttle openings and enables the entering air stream to more easily sweep all liquid fuel which may be deposited upon the fioor of the venturi into the branch 13 and thence into the engine cylinder. The small amount of liquid fuel which may accumulate in the small crescent-shaped depression 122 at low throttle positions will have no deleterious effect. However, this depression 122 may be avoided simply by filling with metal, that is,by designing the venturi 110 so that its bottom por- .tion completely fills the depression 122 and lies flush with the floor 120.

A throttle valve 125 is located in each of the branches 11, 12 and 13 immediately behind the venturi 110 to controlzthe fuel charge entering each engine intake port 16. Each throttle 125 is mounted upon a separate rotatable sha-ft 126 having bearings in suitable bosses 127 integral 4with l the respective branches. The three shafts" 126 are all interconnected by the two shafts 128 which are connected to the projecting ends of the shafts 126 by means of the universal joints 130. The universal joints 130 each comprise a twoarmed spider 131 rigidly secured to one end of shaft 128, and a similar two-armed spider 132 adj ustably secured to one end of a. throttle shaft 126 by the clamping screw 133. The two spiders 131 and 132 are rigidly riveted to a thin annular ring 135 of flexible metal by means of the rivets 134. It will be clear that.,

these universal joints 130 not only render the exact alignment ofrthrottle shafts 126 un necessary, but also that they'will permit relative longitudinalmovement between the two coupled shafts and hence will eliminate any possible binding of the accurately fitted throttle valves 125 due to unequal expansion of the manifold 10 and the shafts 128 and 126. Each throttle 125 may berotatably adjusted relative to thel universal. coupling 130 by loosening the screw 133 and turning shaft 126 within the boss of spider 132. By this means the throttles 125 may be accurately 4adjusted after assembly, so they will all close exactly together. One of the universal coupling members 132, preferably one attached tothe central throttle shaft 126, isprovided with a depending lever arm 136 by which means all the throttles 125 are concurrently manually actuated. Suitable mechanical linkage (not ports 16, an automatic passage-restricting means is provided in each of the branches 11, 12 and 13 (see Fig. 2). This means comprises a. thin-Walled inner tube 140, of slightly less diameter than the inside diameter of the branch 3, which is held rigidly in place againstthe top wall of the branch by the Soren; 141 and two or more lugs 142 Which'are preferably tongues, cut out of the metal of tube 140 and turned down at suitable angles to fornrlegs for spacing the tube 140 from the bottom of branch 13. W'ithin the tube 140 are mounted two tlapper valves 143 which pivot upon the centrally-mourned shaft 144. The valves 143`are urged to closed position by the small coil tension springs 145 which are suitably fastened atone end to the valves 143 and at the other end to the eyes 146 in the spring support 147 which, preferably, is also pivoted upon the shaft 144 in central slots in the valves 143. The springs 145 are made sufficiently strong to hold valves 143 closed when the throttle 125 is in its nearly closed positions and thus compel all the entering charge to pass through the restricted crescent-shaped passage 148 between the tube 140 and the Walls of branch 13. The velocity of the entering charge is thereby greatly increased and passes up to the engine intake valve 15 at high speed, thus carrying all the unvaporized fuel particles therein in to the engine cylinder and preventing any deposition or accumulation of liquid fuel upon the floor or walls of the engine intake passage 14. Preferably the tube 140 extends a short distance within the passage 14, as clearl shown in Fig. 2, in order to carry the restriction in the intakepassage beyond the engine ports 16, so that the entering charge will be given less chance to slow down materially before entering the valve 15.

As the throttle valve 125 is opened to admit a greater charge to the engine, the springs 145 will yield according to the entering blast upon the apper valves 143 and permit the valves 143 to open to a position to pass this greater' charge at a sufficiently high velocity to pre-d vent deposition of liquid fuel in the passage 14. Vhen the entering charge has reached a maximum value, that is, when the throttle 125 is full open and the engine is running at high speed, the two valves 143 will be' fully open and hence permit the practically unrestricted passage of the charge to the cylinder. The

relative location of the spring eyes 146 and the shaft 144 is such that the springs 145 have their tension increased at a less and less rate as the valves 143 open Wider and wider. The effect of this feature is to cause a relative greater restricting tendency for small incoming charges than for large incoming charges. For large charges no restriction by the valves 143 is needed to prevent deposition of liquid fuel in intake passage 14 and hence the resisting force of springs 145 on valves 143 when in full-open position is made only large enough to properly initiate the closing movenient of the valves upon the next reduction in the amount of incoming charge. Thus any tendency of the valves 143 to reduce the throttle is practically overcome.

A depression-equalizer tube 150 interconnects all the branches 11, 12 and 13 at a point between the throttle 125 and the engine cylinders. At 10W-opening throttle positions this tube150 causes a substantially-constantequal depression on the engine side of the throttles in all the branches 11, 12 and 13, and

volumetric etiiciencv of the engine at full hence causes each ,of the six engine cylin.

ders to draw in equal charges. The method of functioning of this equalizer tube is described in great-er detail in my above-mentioned copending application, vSerial No. 4665.

A rsum of the operation of the device so far described is as follows: With the engine idling, the throttles 125 are in nearly-closed position, hence there is a large depression on the engine side of the throttles 125, but only a relatively small depression in the air manifold 10. This small depression is transmitted through the holes 111 in venturis 110 and the pipes 113 to the primary carhuretors 100, 101 and 102, causing primary air to enter through bushings 105 and fuel to enter through lowspeed jets 99, forming a rich' mixture to be delivered to each venturi 110 through holes .111. At such times only a very small amount of air enters the manifold 10 through the spring-closed air valve 20 since the depression in air manifold 10 is small, and henceA the rich mixture entering the branches through the holes 111 is not over-diluted with air from the main air inlet 19. Now, when it is desired to increase the engine speed, the

' the air valve 20 further and admits a greater amount of air to properly dilute the rich fuel mixture through holes 111, thus maintaining the proper ratio of air and fuel going to the engine. The dash pot 52, 53 prevents possible fie' Ias to bevuncovered by the dash'pot'piston for l port, a main air inlet, a `sprin openingmovement of said to a reducing the damping effect upon the air valve in its more open positions, 1

3. Ina .charge forming device for--an-internalcombustion engine! having .an intake closed valve 1n said main aijr inlet opened y-the engine suction,l opening and closing movement of said valve, said dash pot being so arrangedthat the greater degree than-the closing movement thereof.

the engine sucpot having-aby-pass duct in the Walls there- .of-g for `decreasing tliedamping effect upon Asaidair inletvalve in its more-open positions' @5. .In a charge forming devicefor 'a multi-a cylinderinternal `combustion engine having 4a, plurality of intake ports, anindividual Y primary .carburetor havingan,'.individual ncommonsource t port, allof said primary Y 6.In a-'charge formingdevice for .a mull' Y ticylinder internal combustion engines hav- 'ving a .plurality of intake ports,'an indiv1di ial primary carburetor for supplying a fuel mixture to each intake port, each-primary carburetorj-having a low speed'fuel jet and a high speed fuel jet, and 'a common fuel flow control means-for'all of said high speed jets.

i 7. In a charge forming -device for a multi- *Y .cylinder internal. combustion engine having :fa plurality""`o intake-ports, an individual '-fzprimary carburetorfor supplying a fuel mixport, each primary cartureto each intake buretor having a'lw speedrfuel'jet and. a

high speed fuel jet,

fuel .metering valve for allof said high speed 8. In a `charge forming device for a multicylinder internalfcombustion' engine having A' va pluralit ture -to each intake.v buretor having af-'low speed fuel )et and amary car uretor for supplying a fuelrmixport, eachapri'mary carhigh speed `fuel jet, and. a common gravity actuated fuel flow' restricting valve for' allv of said high speed jets. y

9. Ina charge forming cylinder internal combustionfengine having a plurality ofintake ports, an individual primary carburetor .for supplying a fuel mix- `ture -to each intake ports, each primary carburetor havin a 1 ow speed fuel jet anda hglispeed fue jet, all of saidlow speed jets whereb a dash '.pot for damping both the pipe'for '.supplyin valve is damped engine havin y'fuelagmetering jetforfsupplying a yfuel -mix- ...ture-.to each-intakey =.carburetors bein supplied with fuelfrom a Iirough-fa common meteringy -an thereby dash pot to and a common automatic' `of intake ports, an individual pri-- device for a niiilti.

lternal -fuel with the air passing through. said passage,

highspeed -jets taking fue Ifrom'ao'i'nnoon liquid fuel supply? at closelyrelate'dp'oints,

felini-feet is ythe pressure conditionsinthje liqiiid 10. In a multicylinder ifiternal'fcombstion engine* having-a pluralityaoiintake'fports, a a fuel-A-"Ir'iixtretoA each of. said. ports, av `t rottle'fv-valve in'eaeh of said pi ipes' -located on the engine side of-said -throttles pes,` common means'ft'ir'-v concurrently u actuating all of said throttle'valve's, andan a'utomaticall 11; .In a multicylinder internal-'combustion a pluralit fofkintake ports, a pipe for supp ying a fue mixture to-e'ach of -sa1d'p0rts,1a throttle valve in eachfof said' pipes, common means for concurrently actuating alllof said throttle valves, 'and an automatically 1 closed, suction-ol ened,

sage-restricting valve ineacho said pipes .located on the engine sideof.; said throttles' and relatively close to thev engineintake "ports, Y

:12..Ina charge forming device'for'an iu-- ternalcombustion engine,-a main air inlet, an automatically .closedvalve' insaid i'inlet opened by thev engine suction, avd'ash pot for modifying themovement ofsaid valve, and the amount of charge-drawn` into the engine for momentarily increasing the resistance of said dash pot tothe opening .movement of said air valve, whereby a tem orary enrichening of the charge is'obtaine 13. I n a charge'forming device for-'an internal combustion engine, .-a main air inlet, an automatically closed valve in said inlet opened by the engine suction, a dash pot for modifying the movement of said valve, and mean's actuated upon a sudden increase in the amount of charge drawn into the en ine for pumping fluid into said dash pot increasing 'the resistance of said the openingh .ovement -of said airvalve." v v #-14.. In a chargeiforming deviceI for'anin- =terna1fcombstionengine, a main air inlet,

'means'actuated 'upon a sudden .increase ini.

an'automatically closed valve in said inlet opened bythe engine suction, a dash pot for' an intake; pas-- 120. Y umping fluid into said dash pot -4 l j f.increasing the resistance to the ing means, an automatically closed air valve in said passage on the inlet side of said as-- pirating means, and suction-operated means actuated upon the opening movement of said throttle for urging said air valve toward closed position.

16. In combination with an internal combustion engine, a 4charge intake. passage, a.- carburetor, a throttle in said passage' on the engine side of said carburetor, an air inlet valve for said carburetor, and suction-operated means actuated upon the opening movement of said throttle for-urging said air valve toward closed position.

17. In a charge forming' device for an internal combustion engine, an intake passage, a fuel aspirating means 4for mixing fuel with the air passing to the engine through said passage, a throttle' valve in said passage onthe engine side of said aspirating means, an automatically closed air valve 1n said passage on the inlet side of saidl aspirating means, and means actuated by the change of depresvsion above the throttle' upon the opening movement of said throttle for resistingv the opening movement of said vair valve.

1.8. In a charge forming device for an intcrnal combustion .engine,'.a main air duct having a suction controlled .air inletvalve and a throttle therein, a fuel supply passage leading into said air duct between said inlet valve and throttle and subject to the suction between said inlet valve and throttle, andan independent suction actuated fuelvalve 88 metering the flow of fuel to said fuel supply passage.

19. In a charge forming device for an internal combustion engine, a main air. duct having a suction controlled air inlet valve etween said inlet valve and throttle, said primary carburetor having a low speed 'fueljet and a high speed fuel jet, and an independent suction. controlled fuel valve'88v controlling the fuel supplythrough said high speed fuel jet.

21. A charge forming device for internal combustion engines comprisin a mixing chamber, a fuel inlet therefor, a -el chamber supplying fuel to-said inlet and an air inlet bushing rejecting into said mixing chamber,

said bus ing extending over said fuel inlet and spaced therefrom whereby the incoming air is prevented from passing directly in contact with saidl fuel inlet.

v 22. A- charge'forming device forinternal combustion' engines comprising a mixing chamber,'a plurality of fuel inlets admitting fuel to said mixing chamber, a fuel chamber supplying fuel to said inlets, and an air inlet bushing projecting into said mixing chamber to admit-air thereto, said bushing extending over both said fuel inlets and spaced .therefrom whereby the incoming. air is' revented from assing directly in Contact wlth either of sai fuel inlets.

23. A charge forming device for internal combustion engines comprising a secondary mixing chamber, a primary carburetor adapted to deliver a mixture of fuel and air to said secondary mixing chamber, said pri-mary carburetor comprising a mixing chamber, a fuel inlet therefor, a .fuel chamber supplying fuel to said inlet and an air inlet bushing projecting into said mixing chamber, said bushinlT extending over said fuel inlet and spaced therefrom whereby the incoming air is prevented from passing directly in contact with said fuel inle 24. A charge forming device for internal combustion engines com rising a plurality of 5 secondary mlxing cham ers one of which is associated with each engine intake port, a plurality of individual primary carburetors,

each of which is adapted to deliver a mixthre of fuel and air to one of said secondary mixing chambers, each of said primary carburetoors comprising a mixing chamber, a fuel inlet therefor, and an air inlet bushing rojecting into said mixing chamber, said ushin extending over said fuel inlet and space therefrom, whereby the incoming air is prevented from passing directly in qontact with said fuel inle i 25. A. charge forming device for an internal combustion engine having in combination a mixing chamber a fuel inlet therefor, a main air inlet, a suction operated spring controlled valve therein, means for retarding the o ening of said ,valve on opening of the thrott e to enrich the mixture for acceleration, andmeans for rendering the retarding means ineffective after a predetermined movement of the air valve.

In testimony whereof I hereto affix my signature.

FRED E AsnLfrInE'.

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