US1929194A

US1929194A - Charge forming device

Info

Publication number: US1929194A
Application number: US312512A
Authority: US
Inventors: Wilford H Teeter
Original assignee: Delco Products Corp
Current assignee: Delco Products Corp
Priority date: 1928-10-15
Filing date: 1928-10-15
Publication date: 1933-10-03
Anticipated expiration: 1950-10-03

Description

Oct. 3, W H, TEETER CHARGE FORMING DEVICE Filed Oct. l5, 1928 E Lc E` Patented ocr, `3, 1933 'PATENT OFFICE 1,92a194 Y, p A L,

CHARGE Poeme nEvicE Wilford H.. Teeter, Dayton, Ohio,` assignor, 'by

rnesne assignments, to Delco Products 'Corporation, VDayton,"0hio, a corporation of Dela- Y ware Application-october 15, 192s. serial No. 312,512

24 claims. (ci. asi- 34) This invention relates to chargeforming devices for internal combustion engines and, in particular to the type of charge forming device which comprises a plurality of primary carburetors, one

for each intake port of the engine, and which cooperate respectively with a plurality of secondary mixing chambers located adjacent@ the said intake ports. These: mixing chambers are adapted to receive primary fuel mixture from the primary carburetors and under certainr operating conditions,to receive additional air supplied through the branches of an air manifold which supplies air to. all of said mixing cham-` bers and is provided with a single air inlet.

An example of charge forming devices of this character is disclosed in the patent of Wilford H. Teeter and Fred E. ilseltine',` No. 1,819,495 granted August 18, 1931.

In the devices disclosed in the above applica- 2. tions and other devices of this character heretofore designed, various meansare provided for regulating the mixture proportions under various operating conditions in order to provide the mixture necessary to give the most satisfactory engine operation under all conditions of speed and load. These proportioning devices include means for enriching the' mixture on opening movements of lthe throttle to provide a mixture a. rich enough to give the necessary power during the acceleration period. Various forms of fuel pumps have-heretofore been provided to supply additional fuel to enrich the mixture as described. These pumps have not been altogether satisfactory; For instance, it has been found 'necessary to provide check valves .in the delivery conduits of such pumps in order to prevent the liquid in said conduits running back to the source of supply when the pump is not 40 in operation. These check valves were `imseated to some extent byithe vibration of the engine and fail to produce the desired result, hence the pumps aref'not uniform in theirV action and a delay occurs nearly always before the pumped fuel reached the mixture passage after the open- Y ing of the throttle, the arnountoi delay being lvariable and determined bythe degree o f engine vibration and the time interval between opera- 450 tions of the pump. Also'mechanically operated pumps add toV the manufacturing costs andrequire theV provision of parts liable to getfout of proper adjustment, or subject to wear, and are not always eiiective to supply the desired amount of accelerating fuel, since thequantity of buretor unit forming part of said charge forming device.l l.

fuel isdependent` onathe throttle movement instead of the change in engine suction. One of the.. objects of the Vpresent inventio is to provide means for enriching the mixture Y on opening movements of the throttle, which is u elective tosupply the4 desiredV amountof fuel under all operating conditions, is uniform in its action, and simple in construction.V It is another object of this invention to provide means for enriching Athe mixture during theacceleration Q period, which is effective to enrich the mixture on any opening movement of the throttle and substantially simultaneously with such movement. It is a more speciiic object ofv the invention to provide means for enriching the mixture during the accelerating period which is always effective to enrich the mixture an amount proportional to the increase in engine suction on any opening movement of the throttle and is controlled in its action by said throttle` Y According to the present invention, these objects are accomplished by the provision of an auxiliary fuel'reservoir for supplying additional fuel during the acceleratingperiod and into which a fuel delivery ,tube `extends which durm ing normal operation does not reach the fuelin said reservoir, rendering the said reservoir inleective during normal running. This auxiliary vinvention the fuel delivery tube communicates 9' Vwith the primary mixture passages so thatV additional fuel will be discharged into the primary mixture which is passing therethrough at high velocity and is, therefore, supplied at the intake ports almost simultaneously with the opening of sa the primary throttle. l v

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanym0 ing drawing wherein a preferred embodiment of one `form of the present invention is clearly shown.

In the drawing: Y

Fig. 1 is avertical longitudinal section through 105 a charge forming device in which the present invention is incorporated.

, Fig. 2 is an end` elevationof the main .car-

Figs. 3 and 4 are detail sections on the lines 3-3 and 4-4 of Fig. 1.

Fig. 5 is a fragmentary detail view showing the construction of thedashpot by-pass.

The device disclosed comprises a main air manifold having three outlet branches, -the mixing chambers, as fully disclosed in the comiddle branch 12 being shown herein.A Each of these branches communicates with one of the intake ports 14 of a multicylinder engine and are each provided with an attaching flange 16 for unitis adapted to be attached,fas shown in Fig. 1. i

The carburetor unit comprises a main housing 20 having an attaching flange 22 adapted to be secured to the flange 18 by screws 24. An air inlet horn 26 is secured in position Ato register withY an opening in the upper wall of the housing 20, in any suitable way.v A'casting 28 supporting the cylinder-of avv dashpot,- hereinafter more fully described, is'secured tothe bottom of the housing `20 andasheet vmetal fuel bowl is held tight against a`v shoulder 30 formed on the casting 28'. Fuel is conducted to the bowl froma main source of supplythroughy aconduit,'not shown herein, and the ow'of fuel is4 controlled by afloat '34 operatingr in the-usual manner to maintain a substantially constant fuel level in the bowl.

e Fuel flows from the bowlvto a plurality of fuel nozzles 36, `one of which is located in each of -the primary mixturefpassag'es 38,1the constructionA o f which`is briefly described hereinafter. The fuel conduit between the fuel bowl and the nozzles -comprises a vertical fuel conduit connecting atlt's upper end with afhorizontal fuel canal 42 formed in a block 43 secured to the bottom rwall ofthe main housing 20 and supporting the conduit 40. The canal 42 communicates with the nozzles 36 through orifices 44 and fuel is admitted to the passage at .low speeds' through'a fixed` metering orifice 46 only,while at higher speeds additional fuel is admitted. .through an oriflce 48-'controlled by a valve 50 in the manner fully set 'forthln the above mentioned copending application Serial No. 221,371.

Fuel is liftedfromV the fuel bowlV throughthe above vdescribedpassages and nozzles 36 to the mixture passages 38 by the suction therein.

Closing movements of theA throttle cause a reducs tion in the suction in the mixture-passages which might permit the fuel column todrop suiciently to cause a temporary fuel starving of the engine unless means were provided to preventit.V Such means comprises a check valve 52 received -in an enlarged chamber 54 at the junction of

channels

40 and 42. On reduction of suction inthe'mixture passages, this valve seats on a rib 56'projectin'g upwardly from the bottom of chamber 54 preventing downward flow of fuel from Asaid chamber. A two stage metering valve 57 regulates the fiow of fuelthrough .conduit 40 in the Vmanner set forth in the copending application, Serial No. 221,371.' Y n I Y ,Each primary fuel nozzle kis provided with a main fuel outlet 58 inthe top "of the nozzle and l a secondary fuel outlet comprising two orifices 60 and 62 in the vertical wall of thenozzle near the bottom of the mixture passage. At relatively high speeds the suction at the nozzles is enough to lift fuel'from the main fuel outlet as well as from holes 60 and 62, but at vidling or low'speed 'operation under load,"the suction is sufficient to lift fuel only to some pointbetween the tops of the nozzles and orifices 60 8.116,62, fuel flowing from such orifices by action of gravity. The primary mixture passages 38 are parallel to each other and close together, as indicated in Fig. 3 and when the carburetor is attached to the mani- `fold, these passages register with conduits which convey the primary mixture to the secondary pending application, Serial No. 221,371. One of these conduits in the form of a tube 68, fixed in the wall of the branch 12 of the manifold and conveying primary mixture to the secondary mixing.l chamber formed in that branch, is shown in Fig. 1. n

Asingle throttlervalve 64 extends across all of theprimary mixture passages to control the flow therethrough and ris provided with grooves 66 which register with the mixture passages. This throttleis journalled in the housing 20 and is operated byrmeans not shown herein and forming no part of the present invention, but fully disclosed in the above application, Serial No.

' Substantially all the air entering 'the carburetor fiows through the air hornz26, controlled by. a main air valve V70, normally held against a seat 72 bya spring 74 received between the valve and 'a flange 76. projecting from a sleeve 78 slidably mounted on a stationary sleeve 80, fixed inthe housing 20: and serving as a guide sleeve for the stem 82 to which the air valve is secured.

When it is desired to choke the carburetor to Afacilitate starting the engine, the flange is adapted to be lifted, by means not shown herein, until the upper end ofthe sleeve 78 engages the valve tov hold .it against vits seat. i Sufficienty air to carry the starting fuel from the nozzles to the venginegintak'e ports is admitted through orifices 84 formed in the housing 20, as shown in Fig. l.

The valve 70 admits air to a main air chamber y88 from'which air flows to the primary mixture passages through an orifice-90 inthe floor of the airgchamber and to the secondary mixing .chambersthrough a passage 92 which communi- Ycates with the inlet of the manifold 10. A manuallyY operable throttle 94Y controls lthe flow of air through passage 92 and the operating connections for the valve are fully shown and described in the above application, Serial 110.221,- 371.

To prevent fluttering of the air valve and to retard its openingA movement Yforr the purpose of forming the' desired mixture for acceleration, a dash pot is provided, including la cylinder located Within the fuel bowl and cooperating with a piston 102, slidable on a sleeve 104, pinned to 'the lower end of the valve stem 82. The sleeve is provided with a flange 106 having an annular bead 108 serving as-a valve seat for the piston which acts asa valve, said piston being' normally held against the bead by a spring 110 received between ther piston and a nut 112 screwed -on the sleeve. The piston is provided with ports 114 and under certain operating conditions, the

Vpiston is :lifted olf the bead 108 permitting fuel ,to pass through the ports 11,4 frornrbelow the 'adapted to be lifted von opening movements of `the throttle by means presently described. A pery tures 122 and'124 in the guide* and cylinder re- :spectively admit fuel to the said vcylinder from `the main fuel bowl.: The cylinder is alsoprovidedwitha by-pass pipe, such as fully shown in Patent No. 1,819,495, the lower end` 126 of Which is shown in dotted lines in Fig. 1.

To lift the cylinder by means of the throttle,

said cylinder is provided adjacent its upper endV with a groove 130 which receives lugs 132 carried by the arms. of a bifurcated lever 134 secured on a rock shaft 136. This shaft `has fixed thereon, outside the housing 20, an arm 138 and projecting therefrom is a lug 140 through which a rod 142 is slidable. One end of the rod is threaded into a lug 144 projecting from a lever 146 loosely mounted on the rock shaft 136. Adjustable nuts 148 are threaded on the other end of thev rod and aspring 150 is received between said nuts and the llug 140. The spring, therefore, urgesthe lug 140Y against a stop member 152 carried by the rod, and by loosening a lock nut 154, normally locking the rod tixedin the lug 144, and turning the rod, the angular relation of the arm 138 and lever 146 may be adjusted and by adjusting the nuts 148 the tension sired positionY in said slot.

o f the spring 150'mayfbe varied. The lever 146 is provided with an arcuate slot 156 which receives va. block 158 -prov'ided with means (not shown) by which it may be clamped in any devThe block provides a bearing for a pin 160 attached to a link 162 pivotally Yconnected at its upper end to a lever 164 pivotally mountedat 166. A cam, 168, secured to a spindle 169 projecting from one end of the primary throttle 64 engages the lever 164, and when the spindle isi turned in a clockwise direction, as viewed in Fig. 2, the lever 164 `is rotated in a counter-clockwise direction. This movement of lever 164 will move the lever 146 counter-clockwise on the rock shaft 136 and through the medium of the spring 150 will move the arm 138 in the same direction rocking the shaft 136 so as to move the bifurcated lever 134 clockwise in Fig. 1,\lifting the dash pot cylinder and increasing the resistance to opening of the air valve whenever the throttle is opened, `so as to enrich the mixturefor acceleration.

The provision of the resilient lifting means for lifting the dash pot cylinder enables the Ylifting movement to take place throughout a. greater period of time than if a positive lifting device were employed. This will cause the` openingmovement of the air valve to be retarded for a longer time, thus providing the richermixture desirable for'acceleration over a longer period.

The above described ydevice is incapable of sufficiently enrichingv the mixture vto secure entirely satisfactory engine operation during the accelerating period and according tothe present invention additional means are provided for enriching the mixture during acceleration, such means comprising an additional fuel jet in each primary. mixture passage which is normally inoperative, `but which is rendered operative on opening movements of the throttle. Positioned immediately in advance of the main fuel jet in each mixture passage is an auxiliary fuel `iet 170l These jets communicate throughV orifices 172 with a fuel canal 174 in the block 143. A bore 176 in the block connects the canal 174 with a vertical passage in `a tube 178 depending from the block 143 and attached to vthe lower face thereof. The dash pot cylinder has formed integral therewith asmaller auxiliary cylinder 180 communicating with the dash pot cylinder by means of a passage 182 and adapted to have fuel standingthereinat vthe same level as in the dash pot cylinder atall times that1the dash pot pistonV is'stationary. -The fuel supply tube 178 projectsinto the upper open end of the auxiliary cylinder to a point above Athe normal level of fuel therein and is A spaced from the wall of said cylinder to admitV passage of. air around the cylinder 100 is lifted, lifting the auxiliary cylin-l der toa position where the lower end of the tube 178iisr immersed in the fuel in said auxiliary cylinder so that the auxilary jets become effective .to supply additional fuel.

The pistonv in the dash pot is moved downwardly when the air valve opens following any opening movement of the throttle, and throughout the downward motion of such piston the level of yfuel in the auxiliary cylinder is maintained above the end of tube 178, because fuel is forced from .thefdash pot cylinder into said auxiliary cylinder as long as the dash pot piston moves, although the dash pot cylinder .may beat rest before the motion of the piston ceases.

The flow of fuel therefrom is determineden- .tirely by the suction in the mixture passages and takes place immediately on opening movement of the throttle, beginning substantially simultaneously with said opening movementl and continuing as long as the lower'end ofthe tube 178 remains immersed in the fuel. Since there is no pumping of fuel into the mixture passages and the flow of fuel from the auxiliary jets is effected solely by the suction, thefflow therefrom is always proportional to the increase in suction and on a given opening movement ofthe throttle under the same operating conditions, the flow from the auxiliary jets. willV` always be fthe same. f Since the device for `supplying additional fuel has no operating parts subject to wear and is very simple in its construction, it is cheap to manufacture and does not Vget outof order, nor need repairs. Moreoveryit is provided with no check valves Yin the delivery conduit to giverise to the difficulties `heretofore mentioned and is always eiTective substantially simultaneously with the opening of the throttle. i

'The flow of fuel continuesasrlong as the level of fuel in the auxiliary cylinder is above the lower end of the tube, and when the throttle is Astationary and the endof said tube" uncovered,

air flows therethrough, but in such small quantities thatit does notinterfere with proper mixture p'roportioning even at low speeds.

vWhilethe form offembodiment ofthe present invention as herein disclosed, constitutes a prefen-ed form, itis to be understood that other vforms might be adopted, all coming within the scope of'the claims=tvhich follow.

air valve controlling the admission of air to the mixture 'passage' andmeans operated Vby said throttle and said'air valve for raising the fuel level-adiacenti said tube.`

2.l A charge forming device `for internal combustion engines comprising! a, mixture passage, means'for supplyingffuel andair thereto, a'throttle, a fuel reservoir, a fuelsupply tuber adapted to supply additionalffuel to said mixture passage on opening of the throttle and normally terminating above the fuel level in said reservoir, an auxiliary reservoir adapted to .supply fuel to said supply tube and means operated by the throttle for-raising:` said auxiliary/reservoir to bring the fuel level above the end of vsaid supply tube.

lil. Azcharge forming device for internal combustionV engines comprisingramixture passage, means for supplying fuel and ai'r thereto, a throttle, a fuel reservoir, a fuel supply tube adapted to supply additional fuelto saidmixture passage on opening of the throttle and'normally terminating above the fuel level in saidreservoir, an auxiliary reservoir adapted to supply fuel to said supplytube, means operated by thethrottle for raising said reservoirv tlift the fuelabove the end of said supply tube, an air valve-and means operated by said Valve for lifting the fuel in said reservoir above the end of saidsupply tube;

4- A charge forming device for internal combustion engines comprising a mixture passage, means for supplying fuel and air thereto, a throttle, means for supplying a quantity of additional fuel to the mixture passage on opening movements of the throttle proportional to the increase in suction inthemixture passage, an air valve controlling admission of airto the mixture passage and means .operated by the throttle for rendering said fuel supply means effective and vsimultaneously increasing Vtheiesistance lto opena movable'cylinder and piston,vmeans forl supplying a quantity of additional fueltothe mixture passage on, opening movements l, of the throttle proportional to theincreaseiin suction in the mixture passage, and means operated by the throttle forsimultaneously moving ther dash pot cylinder to .increase lthe resistanceto opening of the air valve andfor rendering ,said fuel supply means effective. v l

6,'A chargeforming device for internal combustion engines comprising a mixture passage,

means for supplying fuelrand air' thereto, a throttle, an air valve for controlling the admission .of Vair to the mixturev passage, a dash pot controlling operation'of said air valvecomprising a movable cylinder Vand piston, a. fuel supply tube forsupplying'additional fuel to the mixture passage to enrich the mixture for acceleration, an auxiliary fuel reservoirY movable with said cylinder and' adapted to supply fuel to. said fuel supply tube but being normally ineffective and means `operated on opening lmovements of the throttle to move the dashpot vcylinder to render said fuel supply tube effective.. 7. A ycharge 'forming device for internal combustion engines comprising a secondary mixing .,chamber, means for Vsupplying `air to said secfor regulating the A effective vareabof the primary mixture' passage, lmeansl for supplying fuel and,

air to said primary mixturepassage, and another fuel supply means for ltemporarily supplying additional fuel to Vthe lprimary mixture passage on opening movements of the primary throttle to enrich themixture duringthe acceleration period.

8.' A charge forming device for internal combustion engines comprising a secondary mixing chamber, means for. supplying air to saidl secondary mixing chamber, a primary mixture passage deliveringa primary fuel mixture to said secondary mixing chamber, `a primary throttle forregulating the effective area of the primary mixture passage, means for vsupplying fuel and air to said primary mixture passage, a normally in.- effective Vfuel supply means for temporarily supplying additional .fuel to the primary mixture passage during the acceleration period, and means operated bythe primary throttle for rendering said fuel supply means effective.

9. A charge forming device for internal combustion engines comprising a secondary mixing chamber, means for supplying air to said secondary mixingchamber, a. primary mixture passage deliveringa primary fuel/mixture to said secondary mixing chamber, a primary throttle for regulating the effective area of the primary mixture passage,. means Vfor supplying fuel and air to said primary mixture passage, a normally ineffective fuel supply' meansfor temporarily supplying additional fuel to the primary mixture passage during the acceleration period, and Vmeansoperated as thev primary throttle is opened to render said fuel supply means effective.

10. A charge forming device for internal combustion engines comprising a'. secondary mixing chamber, means for supplying air to said secondary mixing chamber, a primary mixture passage delivering a primary fuel mixture to said secondary. mixing chamber, a primary throttle Yfor regulating the effective area of the primary mixture passage, means forlsupplying fuel and air to said primary mixture passage, a main air valvercontrolling the admission of air to the mixture passage, another fuel supply means for temporarilyisupplying additional fuel lto the primary mixture passage to enrich the mixture during the acceleration4 period, and means operated by the air valve for rendering said fuel supply. means effective, as said primary throttle is opened.' v 115A charge forming device for internal combustion engines comprising a secondary mixing chamber, a primary mixture passage delivering a primary fuel mixture to said secondary mixing chamber, a throttle, means for supplying fuel an'd'lair to .saidvprimary mixture passage, a main air '-valve controlling the admission of air to the mixture passage, means for'supplying additional fuel to the primary mixture passage to enrich the mixture duringtheV acceleration period, and means operated by the throttle and the air valve `for rendering said fuel supply means effective.

' 12. A chargeforming device for internal combustion engines having,v in combination, a plurality'of primary carburetors adapted to supply a primary fuel mixture to a plurality of'secondary .mixing chambers, .means for admitting fuel and air to the" primary carburetors, and a single means for supplying additional fuel to allof said primary' carburetorsl during the acceleration period. i 13. A charge forming device for internal combustion engines having, in combination, a plu. ralityy of primary carburetors .adapted to supply a primary fuel mixture to a plurality of secondary mixing chambers, means for admitting fuel and airv to the primary carburetors, a single lair valve 1.50

controlling the admission. offair. to said primaryA carburetors' a vdaslipot controlling movement of said valve, meansfor supplying .additionalfuel' to the primary carbiuetorsduring the accelera-v '5 tion period, and means associated with said clashpot .for controlling the effectiveness of said fwell supply means.

' 14. VA chargev forming device for eom' bustion engines comprising. 'arsecondary mixing lo chamber,'nieans for supplying air to said secondary mixing chamber, a primary mixture passage delivering a primary mixture of fuel'and air to said secondary mixing chamber, means for Y supplying fuel and air to said primary mixture )i passage, a primary throttle controlling the flow through the primary mixture passage, and means for temporarily supplying additional fuel to the primary mixture passage anterior .to the throttle during the acceleration period.

15. A charge forming device for internal combustion engines comprising a secondary mixing chamber, a primary mixture passage delivering a primary mixture of fuel and air to said secondary mixing chamber, means for supplying fuel and `l air to said primary rmixture passage, a primary throttle controlling the flow lthrough the primary mixture passage, a secondary'air passage supplying air to the secondarymixing chamber, a secondary throttle controlling the flow of air therewr'through, meansfor supplying additional fuel to the primary' mixture passage during the acceleration period and means operated by the primary throttle for rendering said fuel supply means, effective. Y ,l

16. A charge forming device for internal combustion engines comprising a secondary mixing chamber, -a primary mixture vpassage delivering a primary mixture of fuel and air ,to said secondary mixing` chambermeans for supplying C fuel and air to said primary mixture passage, a primary throttle controlling ythe now through the primary mixture passage, a secondary air passage supplying air to the secondary mixing chamber, ,a secondary throttle controlling the flow of -air therethrough and adapted to be opened after the primary throttle has made a predetermined opening movement, means for supplying additional fuel to the primary mixture passage during the acceleration period, and means operated by the primary throttle both before and after the opening of the secondary throttle for ren chamber, a primary mixture conduit adapted to.

@fl-deliver a primary fuel mixture to said secondary mixing chamber, a primary throttle in said mixture passage for controlling the flow therethrough, means for supplying fuel and air to said primary mixture passage, and another fuel supply means for temporarily supplying additional lfuel to the primary mixture passage on opening supply a primary fuel mixture to said secondary' mixing chamber, means for supplying air to said secondary mixing chamber, means for supplying Q 5 air and fuel to said primary mixture passage at 'mixture during the acceleration period.

`mixing chamber, a secondary air passage for supa,` point relativehr V` remote Vfroxnfthe secondary mixing, chamber, and another fuel supply means Aforv temporarily supplying y*additional fuel toi the,

primary mixture passage ,on openingmoyeme'nts of Athe primary throttle, to emichthe mixture during theac :celerationI period. f

' 19. A charge 4forming device for'internal com. lmstionengines` comprising al secondary mixing a. primary mixture passage adapted to supply auprimary `fuel mixture to the secondary mixing chamber, a secondary air passage for supplying air to said secondary'mixing chamber, means for supplying air and fuel to saidrprimary mixture passage, said primary mixture passage and said primary air passage being of substantially the same length and another fuel supply means for temporarily supplying additional fuel to the primary mixture passage on opening movements of the primary throttle, to enrich the 20. A charge forming device for internal combustion engines comprising a secondary mixing chamber, a primary mixture passage adapted to supplya primary fuel mixture to the secondary 1N plying air to said secondary mixing chamber, a fuel'inlet for supplying fuelto the primary mixture passage, a single air inlet admitting air to both said secondary air passage and said primary mixture passage, and another fuel supply means for temporarily supplying additional fuel to the primary mixture passage on opening movements of the primary throttle to enrich the mixture during Vthe acceleration period.

2l. A charge forming device for internal combustion engines havingin combination a plurality of secondary mixing chambers, a plurality of primary mixture passages for supplying a primary mixture of fuel and air to said secondary mixing chambers, one of said primary mixture passages being associated with each of said secondary mixing chambers, means for supplying fuel and air to all of said primary mixture passages, a single secondary air passage for supplying air to all of said secondary mixing chambers and a single fuel supply means for supplying additional fuel to all of said primary mixture passages.

22. A charge forming device for internal combustion engines having in combination a plurality of secondary mixing chambers, a plurality of primary mixture passages for supplying a primary mixture of fuel and air to said secondary mixing chambers, one of said primaryV mixture passages being associated with each of said secondary mixing chambers, means for supplying fuel and air to all of said primary mixture passages, a single secondary air passage for supplying air to all of said'secondary mixing chambers,V and a single fuel supply means for supplying Y additional fuel to all of said primary mixture passages, said means comprising a fuel supply Aconduit having a single inlet and a branched outlet comprising a plurality of branches each of which supplies fuel to one of said primary mixture passages.

23. .A charge forming device for internal combustion engines comprising a mixture passage, means for supplying fuel and air thereto during 4normal operation, a throttle, another normally inoperative fuel supply means adapted to supply additional fuel to the mixture passage during the acceleration period, said means being constructed to supply during each acceleration period a total quantity of fuel which is proportional to the increase in suction in the mixture passage i ture passage during the acceleration period, ysaid means including a separatefuel. jet for delivering.

fuel tothe mixture 'passage and being constructed to supply during eachaeceleration period a total quantity of fuel which is proportional to the increase of suctionin said mixtureipassage adjacent saidjet during the acceleration period, and

means operated by the throttle on opening move.

ments thereof for. rendering said additional .fuel supply means operative. Y