US1883095A

US1883095A - Charge forming device

Info

Publication number: US1883095A
Application number: US293424A
Authority: US
Inventors: Wilford H Teeter
Original assignee: Delco Products Corp
Current assignee: Delco Products Corp
Priority date: 1928-07-17
Filing date: 1928-07-17
Publication date: 1932-10-18
Anticipated expiration: 1949-10-18

Description

Oct. 18, 1932. w. H. TEETER Oct. 18, 1932.-

Vl H.TEETER CHARGE FORMING DEVICE 4 Sheets-Sheet 2 Filed July 17, 1928 mma Oct. 18, 1932. w. H. TETER dimer.' FoRING DEVICE 4 Sheets-Sheet 3 lld July 17, 1928 WN kw Oct. I8, 1932. w. H. TEETER CHARGE FORMING DEVICE Filed July 17. 1928 4 Sheets-Sheet 4 Patented Oct. 18, 1932 UNITED STATES PATENT OFFICE WILFORD H. TEETER, OF .DAYTONQ OHIO, ASSIGN OR, BY MESNE ASSIGNMENTS, T DELCO PRODUCTS CORFORATION,

OF DAYTON, OHIO, A CORPORATION 0F DELAWARE CHARGE FQRMING DEVICE Application filed July/1'?,

This invention relates to charge forming devices for internal combustion engines, and more particularly to that type of charge forming device which comprises a plurality of primary carburetors for supplying a primary mixture of fuel and air to a plurality of secondary carbretors located adjacent the engine intake ports, and to which additional air may be supplied under certain operating conditions through a secondary air passage, for admixture with the primary mixture.

Examples of charge forming devices of this type are disclosed in the copending applications of lViltord H. Teeter, Serial No. 221,372. liled September 22, 1927, and Fred E. seltine. et al., Serial No. 288,683, filed June 10, 1928.

It is-.the general object of the present invention to provide improved means for controlling the proportions of fuel and air in the mixture, and more particularly, to provide improved means for enriching the mixture during the acceleration period, to provide a mixture rich enough in fuel content to give the necessary power for smooth and rapid acceleration.

More specifically, it is an object of the invention to provide means for temporarily restricting the admission of secondary air following any opening movement of the throttle, so that the enriched primary mixture is delivered to the intake ports without delay and without dilution by an excess of secondary air.

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

In the drawings: y

Fig. 1 is a plan view of the present invention attached to the engine cylinder head, a part of which is shownV n section.

Fig. 2 is a side elevation looking toward the engine block.

Fig. 3 is a section on line 3-3 of Fig. 1. Fig. 4 is a section on line'4--4 ot' Fig. l.

i928. semi no. 293,424.,

Fig. 5 is a fragmentary detail section on the line of Fig. 3. I

Fig. (5 is a detail view of 'the primary throttle valve.

Fig. 7 is a side elevation of the main carburetor unit looking from the right in Fig. 2.

Fig. 8 is a side elevation of the main carburetor unit looking from the left in Fig. 2. Fig. 9 is a detail sectional view, partly diagrammatic, showing theI means tor retarding the opening ot the secondary air valve. y

Fig. 10 is a section through the secondary mixing chamber on line 10-10 of Fig.

Figs. 11 and 12 are detail sections at right angles to each othei; of the float valve mechanism and fuel inlet passage controlled thereby.l

Fig. 13 is a detail section on the line 13- 13 of Fig. 3. It will be observed that the main air passage which admits air to the secondary mixing chambers has yin some instances in this specification been termed a secondary air passage, while the air flowing through such passage has been termed secondary air. These terms have been used to distlnguish from. the primary air passage and primary air which goes to the primary mixing chambers.

The device disclosed herein comprises a main air manifold indicated in its entirety by the reference character 10', and having three outlet branches 11, 12 and 13 each of which is adapted to communicate with one of the .ports 14 of a multicylinder engine. lach port serves two adjacent cylinders through valve ports 14a and 14?), as clearly indicated in -'Fig..1. The cylinder head is shown in three separate fragments 15, but it will be understood that it may be an integral structure. The branches 11, 12 and 13 are each provided with an attaching flange 16, for attaching the manifoldl to the engine block in the conventional manner. Adjacent the inlet of the manifold is provided a flange 1.7 to which may be secured the main carbure- `tor unit as shown in Fig. 3.

The main carburetor unit comprises a. main houslng in therform ofa

single casting

18, 100

asv

i attached by screws 19 to theiflange 17 An ings to make a tight joint, and a sheet metal nipple 31, screwed into the main housing 18 .castin and the drill hole on the opposite fuel bowl 27 is held tight against a shoulder 28 on said main hous1ng`18 by means of a screw 29 which is screwed into a post 30 de- I pending from and integral with the casting 25.

A fuel line leading to a main source of fuel supply (not shown) is connected to a as shown in Fig. 1. This nipple may have a screen secured therein in a manner well known so that incoming fuel must pass through the screen and said ni ple communicates with a bore 32 formed 1n the wall of housing 18, the bore 32 connecting with bore 33 also in the wall of said housing as shown in Fig. 12. At its inner end the bore 33 connects with a vertical bore 34,. which in turn `communicates with a bore 35 in casting 25.

. A plug 36'is screwed into the lower end of connects-with each of the nozzles 42 through bore 35 and is provided with lateral fuel outlets 37 through which the fuel Hows into the float chamber. Cooperating with valve seat 38 is a valve 39 controlled by a oat 40 pivoted at 41. The valve operates in the usual manner to maintain a constant fuel level in the said float chamber.

Fuel is conducted from the fuel bowl to a plurality of vprimary fuel nozzles 42 located in the primary mixing chambers 43 formed in the central part of t e main housing which may be termed the distributor block. The construction of the distributor block and co` operating elements comprising the primary carburetors will vbe more fully described hereinafter. To permit the fuel to flow from the fuel bowl to the primary nozzles 42the casting 25 is rovided with a vertical fuel channel 44 which communicates at its uplp'er endwith a horizontal fuel'canal 45 w 1ch holes 46. Fuel is admittedA from the fuel bowl to the channel 44 at low speed through a metering orifice 47. All of the fuel flowing to the fuel nozzles 42 u to a certain predetermined engine speed, or example that corresponding to a vehicular speed of 20 miles per hour passes throleilgh the metering orifice 47. For hi her spe s than said predetermined speer? fuel is also admitted to the fuel channel 44 through an orifice 48 controlledv by a fuel valve 49, operated in a manner fully described hereinafter, and thence through ka.

horizontal channel 50, connecting with the lower end of channel 44.

Fuel is lifted from the fuel bowl through the nozzles 42 to the primar Amixing chambers by the suction therein. hen the throttle is moved toward closed position to reduce the engine speed there is a sudden reduction in suction on the vertical column of fuel between the fuel bowl and the nozzle which mlght permit this column of fuel to drop suf- `iciently to cause a temporary fuel starving of the engine unless means were provided to prevent the dropping of such column of fuel. To prevent this action a check valve 51 is received in an enlarged chamber 52 at the junction of channels 44 and 45 and on reduction of suction in the primary'mixing chambers seats on the bottom of such chamber, preflnting downward flow through the channel The metering orifice 47 is drilled in the ide o the channel 44 is plugged by a screw Each primary fuel nozzle is shown herein as provided with a main fuel outlet in the top of the nozzle and a secondary fuel outlet comprising two holes 54 and 55 formed in the vertlcal wall of the nozzle and diametrically opposite each other as shown in Fig. 3. -At higher speeds there is suiiicient suction in the primary mixing chambers to cause fuel to flow from the main fuel outlet in the top of each primary nozzle, as well as from the holes 54 and 55. At 'idle or very low speed, however, there is insufficient suction to cause such a ow of fuel, the fuel at such time standing in the nozzle at a point between the top of the nozzle and the orifices 54 and 55, flowing connect with L-shaped passages formed in lthe manifold, the outlet ends of such passages terminating in the side walls of the central branch of the manifoldv where they are connected with primary mixture pipes 'hereinafter described. The inlet ends of the primary mixture passages where the nozzles project into such passages are of larger diameterthan the outlet ends thereof and between the inlet and outlet end of each as'- sa e its cross-sectional area is'constricte as in icated at 64, such construction reducing the velocity of the air current passing the nozzle for a purpose. hereinafter set forth.

of a screw 69, adjustable in the casting, to

prevent longitudinal movement ofthe said throttle. The primary mixture passage 62 is in alignment with a tube which is received in a boss in the branch 12, while the passages 61 and 63 communicate with pipes 71 and 72, respectively. These pipesl are connected at one end to the outlets of passages 61 and 63'while the other ends lof such pipes connect with elbows 74 detachably secured to the manifold branches 11 and 13, the outlet ends of such elbows being in alignment with tubes 7 5 andV 76 which are secured inmanifold branches 11 and 13 respectively in any suitable manner.' Primary mixture is drawn by engine suction from the primary mixing chambers through the pipe connections above described, and tubes 70 and 75' to a main air chamber 8O formed in the hous ing 18. An air conduit 81 controlled by a valve mechanism hereinafter described con-v nects the air chamber with the main 'airvmanifold while an orifice 82 in the floor of the air chamber permits a flow of air from the chamber to the primary carburetors.

' When the carburetor is choked to start the engine the air valve 77 is held against its i seat by means presently described to conipletely close the main air inlet. To provide sufficient air to carry the starting fuel from the primary nozzles to the engine when the carburetor-is choked as described an air inlet 83 is provided. This inlet is an elongated slot formed in a plate 84 secured to the housing 18 as shown in Fig. 3.

' The main air valve 77 is adjustably secured on a stem 86 slidably mounted in al guide l sleeve 87 xed in the main housing 18. Surrounding the guide sleeve 87 is a slidable sleeve 88, the lower end of which `has a proj ecting disc 89 secured thereto, the disc providing aseat for the air valve spring 79. Means are provided for raising this sleeve toa position where the upper end thereof will engage the air valve to hold it against its seat to choke the carburetor. This means comprises an arm 90 secured to a rock shaft 91 rotatably mounted inthe wallfof the main housing 18. The armv at its inner end has two pins 92 and 93 secured therein between which the disc 90` is received. The shaft 91 projects through the wall of the casing and at its outer end is bent to form an arm 200.

having a hole 201 therein in which some form of operating connection, extending from a point convenient to the operator may be attached. An adjustable stop screw 202 isreceived in a lug detachably secured to the 'air horn asindicated in Fig. 2. By adjustment of the stop screw the normal position of the sleeve 88 may be determined to regu* late the tension of spring 79. Ordinarily the stop screw is so adjusted that the main air valve willopen slightly during idling.

During operation-lat all engine speeds below that corresponding to a vehicular speed of substantially 20-25 miles per hour on a level road the mixture formed in the primary carburetors is of properly combustible proportions and such mixture is conveyed to the engine Without dilution by admixture with additional air in the secondary `mixing chambers. At higher engine speeds, unless means are provided toprevent such action, the velocity of the air current passingthe nozzles becomes so great that a velocity head is built upat the nozzles and increases to such a degree that fuel is caused to iowifrom the nozzles rapidly enough to form a'primary mixture Which is super-rich infuel content.

To prevent this increase in fuel fiow the air passage 81 leading from chamber 80 to the main air manifold is opened in 'a manner hereinafter described, to permit a flow of air through the secondary airpassage. This admission of air through the secondary air passage not only dilutes the mixture but also prevents as great an increase inair velocity at the nozzles as would otherwise occur.

Flow of air from the ychamber 80 to they secondary carburetors is controlled by two valves, a manually operated butterfly throttle 94 and a suction operated valve 95. The valve 94 is fixed on a shaft 96 which is journalled for rotation in the walls of the housing 18, and is operated simultaneously with throttle 65 through connections hereinafter described. -The valve 95 is fixed to a shaft ,97' which is positioned ofi' center with respect to the valve, a greater portion of the valve being below the shaft than above'. The shaft 97 is supported for rotation in the walls of the housing 18 and `is operated primarily by the engine suction, its operation being controlled by devices described later.

The operating connections for the ythrottle valves will now be described.. Fixed on the end of one of the throttlespindles 67 outside the housing 18 is an operating arm 98 having a hole in its free end to be connected toI some suitable form of operating connection extending to a point convenient to the operator of the vehicle. This operating arm 98 is connected through a lost motion connection to an arm 99 secured by a split clamp to the end of shaft 96 outside the casing. An operating link 100 is pivotally connected to the arm 98, and a pin 101 projecting from the free end of arm 99 projects through a slot 102 in the link 100. A regulating screw 103 is threaded in lugs 104 projecting from the operating link and may be adjusted to regulate the length of the slot 102, the upper end of the said screw constituting the lower end of `sai-d slot. A tension spring 105 is connected at one end to the upper end of the link 100 and at its other end to the pin 101. The spring tends to hold the pin 101 against the upper end of slot 102. lVith both throttles closed the parts are in the position shown in Fig. 9, with the pin 101 in engagement with screw 103. As the operating arm 98 is rotated in a clockwise direction to open the primary throttle valve 65 the link 100 moves downwardly to a position where the upper end of slot 102 strikes pin 101 before the operating arm 99 of the air throttle 94 is moved so that the primary throttle is partly opened before the air throttle begins to open. The screw 103 serves as a stop to limit the closing movement of the primary throttle and adjustment of said screw-regulates the throttle opening at idling.

On opening movement of either throttle Valve the suction below the air valve 7 7 is increased and the air valve is opened against the tension of its spring permitting an inrush of air to the secondary mixing chambers which will be suiiicient to lean the mixture unless means are provided to retard the opening movement of said valve. By retarding the opening of the valve the leaning of the mixture as well as fluttering of the air valve may be prevented. lIt will be understood, of course, that opening of the air valve may be sufficiently retarded on opening of the throttle to enrich the mixture for acceleration, but in this particular embodiment of the invention opening of the air valve is not retarded to that extent.

To retard the opening movement of the air valve the lower end of the valve stem 86 has secured thereto a piston 106 which slides in a cylinder 107 formed in the casting 25. The

piston is securedto the stem l86 by means disclosed in the copending case above referred to,- a nut 109 holding the piston in place.

`The lower end of the cylinder is closed by a closure member 110, having a valve controlled inlet (not shown) therein, and permitting free upward movement of said piston, but retarding the downward movement thereof andopening movement of the valve.

The dashpot cylinder 107 may be provided with a by-pass in its wall which allows liquid to pass around the piston when the piston passes below the upper end of said by-pass, thus relieving the dashpot. As this by-pass forms no part of the present invention and its construction and function is fully described in the above mentioned application it is not shown herein.

lrVhcn the main vthrottle valve 94 is opened the suction in the chamber 80 below the air valve 7 7 is so greatly increased that although the suction at the nozzles is increased and at the same time the opening movement of the main air valve is retarded to some extent to prevent leaning of the mixture the additional air iiow into the secondary mixing chambers through the main air passage, past the throttle valve 94 would be so rapid as to prevent any enrichment of the mixture imto provide sufficient fuel for proper engine acceleration.

The opening movement of the air valve is retarded primarily for producing at all times, when the throttle 94 opened, a sufficient pressure differential between the inlet and outlet ends of the primary mixing tubes to create a velocity of flow through such tubes great enough to transport the primary mixture from the primary mixing chambers to the secondary mixing chambers almost instantaneously. In the device disclosed herein an accelerator pump forces, fuel for acceleration into the primary mixing tubes to form a super rich mixture therein. It is a considerable distance from the point where fuel enters the primary mixture passages to the valve 95 relative to throttle 94: two results are accomplished, first the production of a high pressure differential between the inlet and outlet ends of the primary mixtuge passages which maintains a high velocity of flow through such-passages at all times second the retarding of the inflow of pure air to the secondary mixing chambers. By maintaining the high velocity of flow through the primary mixture passages the timeinterval reuired for the primary mixture to travel the istance above referred to is greatly reduced.

At the same time the retardation ofthe air flow by means of valve 95 increases the time interval necessary for pure air to reach the secondary mixing chambers, so that these two time intervals approach each other, in fact p primary mixture and the air flowingvpast throttle 94 reach the secondary .mixing chambers at substantially the same time.

According to this invention means are provided to retard the opening of the valve 95 which comprises an arm 120 secured outside the housing 18 to the end of shaft 97 on which the valve 95 is mounted. A rod 121 is bent at its upper end to forni a short horizontally extending leg 122 which projectsthrough a suitable slot 123 in the free end of arm 120. The slot permits movement of the leg 122 relative to the end of arm 120 as the latter moves in an arcuate path, enabling the rod t'o move in a rectilinear path. Atits lower end the rod 121 is connected to a piston 124 preferably by meansv of a flanged coupling memben 125 pinned to the rod and a nut 126 screwed onsaid coupling member, the piston being securely clamped between the iange on said coupling member and the nut. The piston has a close sliding fit within a cylinder 127 rovided withan attaching flange 128 projecting therefrom which is bolted to the housing 18as shown in Fig. 8. A vent 129 is provided in the cylinder 127 to allow escape of air on descent of the piston and a spring 130 is received in said cylinder between its bot toni and the bottom of the piston, said spring acting to normally hold the valve 95 closed.

lt will be noted that according to the present invention the valve 95 is positioned anterior to the throttle 94 and the shaft 97 on which said valve is mounted is placed close to the floor of the passage 81, so that the valve when fully open lies flat on the licor of said passage, the passage 81 being formed with a. flat bottom for some distance posterior to said valve as indicated in Fig. 9 to permit the mounting of said valve as described.

When the throttle 94 is closed the engine suction is not communicated to the valve 95 and the spring 130 holds the valve closed. As the throttle 94 opens, however, the engine suction is communicated to points in the passage anterior to the throttle and as soon as the throttle is opened suihciently for the engine suction effective on said valve 95 to become greater than the force of the spring 130 the valve is opened, moving piston 124.

downwardly and forcing the air in the cylinder 127 out through the small hole 129. Owing to the small size of hole 129 it is impossible to lower the piston rapidly and the opening of the' air valve is therefore delayed, no matter what the degree of opening of the throttle 94` may be.- This retarding means is a simple, efficient and inexpensive form of air dash pot. 'On closing of throttle 94 the spring 180 will lift the 'piston and close valve 95. R

As previously stated the opening of the valve 95 is temporarily retarded on opening of the main air throttle accelerate the flow of rimary mixture sufficiently to prevent sai mixture from lagging behind the flow of air through the manifold duringthe acceleration period, thus preventin the formation of a lean mixture at the secon ary mixing chambers during the acceleration period. In the ydevice disclosed in this application the priv106 and cylinder 107 constitutes the pump which operates when the piston' moves downwardly on opening of the air valve. A fuel delivery conduit 140 is received at its lower end in a hole in the cylinder 107 near the bottom thereof while the upper, outlet end of said conduit connects with a fuel channel 141 in a block 142, secured in any desirable mannerrto the bottom ofthe distributor bloclr in a position somewhat posterior to the primary throttle as indicated in Fig. 3. The block 142 extends across all ofthe primary mixture passages and

fuel passages

143, 144 and 145 formed in said block communicate with

passages

146, 147 and 148 drilled in the bottom wall of the distributor block, and communicating with the primary mixture passages 61, 62 and 63 respectively, as shown in Figs. 3 and 13. Two air channels 149-, one of which is shown in 'F ig. 3 admit air to the fuel channel 141 the entering air forming an emulsion with the fuel which issues from

passages

146, 147 and 148 into the primary m1x' ture passages.

The reason for admission of air to the fuel channel 141 is to prevent the high suction maintained in the primary carburetors acting to draw fuel from the dash pot cylinder independently ofthe pumping action of the piston 106. 1t will be understood that under all conditions of operation a very con-` siderable degree of suction is maintained in the primary mixing chambers and unless the fuel delivery passage between the dash pot cylinder and the primary mixture passages is vented to atmosphere at some point therein, this high suction would operate to lift fuel from the dash pot cylinder at all times, whereas it is desirable to deliver fuel from the dash pot cylinder to the primary mixture passages only when the throttle is opened to cause downward motion of the piston 106. By admitting air to the fuel channel 141 the suction effective to'lift fuel throuvh the conduit 140 is never great enough to hft the fuel to the channel 141, but is sufficient to lift fuel only to some point intermediatethe dash pot cylinder and said channel preferabl to a ton 106 is in position to close the upper end 4of the by-pass. As soon as the by-pass is uncovered the pumping action ceases and further downward movement of the piston operates merely to force fuel from the lower part of the cylinder through the by-pass to the upper part of the c linder.

In addition to the a ove described devices operating to enrich the mixture for acceleration means is provided for supplyin additional fuel at high speed by opening t e fuel `valve 49 previously referred to. This means comprises an arm 150 pivoted at 151 on the outside of housing 18 Vas shown in Fig. 8. Projecting from the opposite end of the arm 150, is a pin 152 which is receivedvin a bore in an enlarged head 153 into which the valve 49 is screwed. A cam 154is fixed on the spindle 67 projecting from the end of the throttle shaft opposite to that on which its operating arm 98 is secured, and cooperating with this, cam is a roller 155 mounted for rotation on a pin projecting from theearm 150. A considerable portion of the cam is concentric relative to its operating shaft, so that it is ineffective to raise arm 150 to open the fuel valve until a certain predetermined speed is reached, for example an engine speed corresponding to a vehicular speed of 20-25 miles per hour. By using a cam of different shape the engine speed at which the fuel valve begins to open may be regulated as desired. Also by adjusting the valve in its head153 the normal position of e valve prior to the opening of said valve y arm 150 may be determined.

The secondary mixing chambers comprise Venturi tubes 160 (as shown) or other fiow accelerating elements. these venturis 160 which are identical in construction and are positioned in the branches 11, 12 and 13 of the manifold 10, in such relation to the primary mixing tubes, that the point.` of greatest depression or suction in each Venturi tube is immediately adjacent the outlet end of the primary mixture tube associated therewith. Each venturi is provided .with an annular projecting rib 161 which fits, when the manifold is attached to the engine block, both inthe engine intake port and in a recess 162 in the end of the associated branch of the manifold the rib engaging shoulders 163 and 164 in the manifold and intake port respectively when the venturi is in position. A channel 165 is There are three of formed in the outer wall of said venturi at the bottom of said element when t-he device is assembled,I to permit any fuel which precipitates out of the mixture and collects on the wall of the manifold branch to flow into the engine intake port. The Venturi tubes,

cause the air entering the air manifold to move past the ends of

t'ubes

70, 75,'and 76 at high velocity creating in each of the tubes a high suction at all times'.

It will be understood that while the device,

for retarding the passageof air through the secondary air passage on opening of the air throttle, which constitutes the present invention, is disclosed, for convenience, in this application as embodiedin a charge forming device having means for enriching the primary mixture,the invention is in .no way limited to` such a charge forming device. Such invention will produce desirable results when embodied in a charge forming devlce in which enriching fuel is not injected into the primary mixture concurrently with the retardation of air flow through the secondary air passage. It will be clear that such air should not be permitted to reach the secondary mixing chambers on opening of the air throttle, before the increased quantity of primary mixture resulting from opening ofthe primary throttle reaches said mixing chambers, Whether said primary mixture is in-v creased in vfuel content or not.

While the form of embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In ay charge forming device for a multicylinder engine having a plurality of intake ports the combination of a main air manifold having branches leading to said intake ports and forming secondary mixing chambers, a plurality of primary carburetors for supplying fuel mixture to said secondary mixing chambers, a single air intake passage admitting auxiliary air to all of said secondary carburetors,'a throttle for controlling the flow through said passage and a`suction op-A erated valve in said passage for modifying the effect of said throttle.- 3. `In a charge forming device for a multicylinder engine having a plurality of intake ports', the combination of a main air inanifold having branches leading to said intake ports and forming secondary mixing chainbers, a plurality of primary carburetors for supplying fuel mixture to said secoi'idai'y mixing chambers, a single air intake passage admitting auxiliary air to all of said secondary carburetors, a throttle for controlling the flow through said passage, a suction operated valve in said passage for modifying the effect of the throttle and means for retai-ding the opening movements of said valve.

4. In a charge forming device. for a multicylinder engine having a plurality otl intake ports, the combination of a main air inanifold having branches leading to said intake ports and forming secondary mixing chambers, a plurality of primary carburetors for supplying fuel mixture to said secondary mixing chambers, a single air intake passage admitting auxiliary air to all of said secondary carburetors,.a throttle for Controlling the flow through said passage, a suction operated valve in. said passage for modifying the etliect of the throttle and a dash pot for retarding the opening movements` of said valve.

5. A charge forming device for internal combustion engines hav-ing in coinbnation a plurality of secondary mixing chambers, a plurality oi primary carburetors for supplying fuel mixture thereto, conduits for conveying the primary mixture to said second-A ary mixingchambers, means in said secondary mixing chambers for maintaining a high vacuum at the outlets ot' said primary mixture conduits, a passage for applying auxiliary air to all said secondary mixing chambers only under certain operating conditions and automatic means for retarding the flow or" air through said passage when the latter becomes eective to prevent reduction of the vacuum at the outlets of said primary mixture passages.

6. A charge forming devicel for internal combustion engines having in combination a plurality of secondary mixing chambers, a plurality of primary carburetors for supplying 'fuel mixture thereto, conduits for conveying the primary mixture to said secondary mixing chambers, means in said secondary.

mixing chambers for maintaining a high vacuum at the outlets of said primary mixture conduits, a passage for supplying auxiliary air to all said secondary mixing chambers, a normally closed throttle in said passage, means for opening said throttle at a predetermined enginel speed,- and automatic means for retarding the iow ot air through ,said passage when the throttle is openeihto prevent reduction oit the vacuum at the outlets of the primary mixture passages.

7. A charge forming device for internal combustion engines comprising a plurality of secondary mixing chambers, a plurality of primary carhuretors for supplying fuel mixture thereto, a primary throttle controlling the flow from all the primary caburetors, a secondary air passage for supplying auxiliary air to all' said secondary carhuretors, a secondary throttle controlling the How' of air therethrough. means operated by the primary throttle for opening said secondary throttle after said primary throttle has opened a predetermined amount, and means for retarding the flow of air through the secondary air passage, on opening movement of the secondvary throttle.

8. A charge forming device for internal combustion engines comprising, a plurality of secondary mixing chambers, a plurality of primary carburetor-s in which a primary mixture of fuel and air is formed for delivery to the secondary mixing chambers, a secondary air passage adapted to supply auxil- -iaiy air to all'of said secondary mixing chambers, a single main air inlet supplying air to all the primary mixing chambers, a/tlirottle for controlling the supply of mixture, and devices for retardingthe'flow of air through the main air inlet and secondaryl air passage on opening movement of' the throttle.

9. Av charge forming device for internal combustion engines comprising, a plurality of secondary mixing chambers, a plurality of primary caiburetors in which a primary mixture of uel and air is fori'ned for delivery to the secondary mixing chambers, a secondary air passage adapted to supply auxiliary air to all of said secondary mixing chambers. a single main air inlet supplying air to all the primary mixing chambers. a throttle for controlling the supply of mixture, nieansitoiretarding the fioiv of air through the main air inlet on opening movements of the throttle under all operating conditions,and means for retarding the flow of air through the secondary air passage on opening movements oi the throttle under certain operatingconditions only.

10. A charge forming device for internal combustion engines comprising, a plurality of secondary mixing chambers, a plurality or primary carburetors in which a primary ymixture offuel and air is formed for delivery -for modifying the effect of the air throttle.

1l. A charge forming device for internal combustion engines comprising, a plurality Y of secondary mixing chambers, a plurality of primary carburetors in which a primary mixture of fuel and air is formed for delivery to the secondary mixing chambers, a secondary air passage adapted to supply auxiliary air to all of said secondary mixing chambers, a single main air inlet supplying air to all the primary mixing chambers, a prilnary throttle for controlling the How of primary mixture from all of the primary carburetors, an air throttle for controlling thel flow through the secondary air passage and an automatic suction operated valve in said air passage. A

12. A charge forming device for` interna-l combustion engines comprising, a plurality ot secondary mixing chambers, a plurality of primary carburetors in which a primary mixture of fuel and air is formed for deliver to the secondary mixing chambers, a secon ary air passage adapted to supply auxiliary air to all of said secondary mixing chambers,a single main air inlet supplying air to all the primary mixing chambers, a primary throttle for controlling the flow of primary mixture from all of the primary carburetors, an air throttle for controlling the flow through the secondary air passage, an automatic suction operated valve in said air passage, and means for temporarily retarding the opening movement of said valve on opening movement of the air throttle.

13. A charge forming device for internal I combustion engines comprising, a plurality of secondary mixing chambers, a plurality of primary carburetors in which a primary mixture of fuel and air is formed for delivery to the secondary mixing chambers, a secondary air passage adapted to supply auxiliary air to all of said secondary mixing chambers, a single main air inlet supplying 'air to all the primary mixing chambers, a primary throttle for controlling the iiow of primary mixture from all of the primary carburetors, an air throttle for controlling the flow through the secondary air passage, common operating means for opening said primary and air throttles, and means for temporarily retarding the How of air through the secondary air passage on opening movements of the air throttle.

14. A charge forming device for internal combustion engines comprising, a plurality of secondary mixing chambers, a pluralityn of primary earburetors in which a primary mixture of fuel and air is formed for delivery to the secondary mixing chambers, a secondary air passage adapted to supply auxiliary air 'to all of said secondary mixing chambers, a single main air inlet supplying airtoall the primary mixing chambers, a primary y throttle for controlling the fiow of primary mixture from all of the primary earburetors, an air throttle for controlling the How through the secondary air passage, common operating means for opening said primary In testimony whereof I hereto alix my signature.

YVILFORD H. TEETER.