US2096273A

US2096273A - Charge forming device

Info

Publication number: US2096273A
Application number: US360404A
Authority: US
Inventors: Fred E Aseltine; Carl H Kindl; William G Pontis
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1929-05-04
Filing date: 1929-05-04
Publication date: 1937-10-19
Anticipated expiration: 1954-10-19

Description

Oct. 19, 1937. F. E. ASELTINE ET AL 2,096,273

CHARGE FORMING DEVICE Filed May 4, 1929 6 Sheets-Sheet l Oct. 19, 19376 F. E. ASELTINE ET AL.

CHARGE FORMING DEVICE Filed May 4, 1923 511eats-Sheei 2 Oct. 19, 1937. RE. ASELTINE ET AL CHARGE FORMING DEVICE F iled May 4, 1929 6 Sheets-Sheet 3 Oct 19, 15937 CHARGE FORMING DEVICE 6 Sheets$heet 4 Filed May 4, 192"- AZLL J. 6

Oct. 19, 1937.

E. ASELTINE ET AL CHARGE FORMING DEVI CE Filed May 4, 1929 6 Sheets-Sheet 5 mum um CHARGE FORMING DEVI 013/ Filed May 4, 1929 6 SheetsSheet 6 25 retors, located adjacent the engine intake ports, vided to render said dash pot substantially in- 25 iii @HARGE FORMING DEVICE Fred E. Ascltine, Carl E. Kindl, and William G.

Pontis, Dayton. Ohio, assignors, by mesne assignments, to General Motors Corporation, Detroit, Micli., a, corporation of Delaware Application May 4, 1929, Serial N0. 360,404

54 Claims. (Cl. 261-41) This invention relates to charge forming demeans for supplying fuel to the primary mixing vices for internalcombustion engines, most parchambers, such means consisting of a plurality tlcularly to that type of charge forming device of fuel jets. one of which is controlled by a fixed which comprises a plurality of primary carbumetering plug and the other of which is conretors, one for each intake port of the engine, trolled by a plurality of valves operated in the and which cooperate respectively with a plurality manner hereinafter described. of secondary carburetors, each of which is A further feature of the invention resides in cated adjacent an engine intake port and receives the provision of improved means for operating a primary mixture of fuel and air from a pipe the two throttle valves and for controlling the connected with one of the primary carburetors, operation of a suction operated auxiliary air valve while receiving additional air when required, in the main air passage. through one branch of an air manifold which A still further feature of the invention consists supplies air to all of the secondary carburetors. of a new and improved pump for supplying ac- An example of a charge forming device of this celerating fuel on opening movements of the character is disclosed in the application of Fred throttle, operated by the primary throttle 15 E. Aseltine, Wilford H. Teeter, and Carl H. Kindl, through the medium of improved operating Serial No. 288,683, filed June 27, 1928, which mechanism and effective to pump the fuel to a matured into Patent No. 1,937,938,- of Dec. 5, 1933. well in which substantially atmospheric pressure In the device disclosed in the above mentioned is maintained and from which it is supplied to 0 application and in other earlier devices of simithe mixing chambers by the action of gravity. lar nature, a plurality of primary carburetors are An additional feature of the present invention provided and the fuel and air mixture is conresides in the provision of a novel form of dash ducted from the primary carburetors through pot for controlling the opening movements of the relatively small conduits to secondary carbuauxiliary air valve, improved means being prowhere it. is mixed with secondary air admitted effective to retard the movement of said air valve to the main air manifold through a single port under certain predetermined operating condicontrolled by a spring held valve. Throttling of tions.

the engine is effected by a single primary throt- A still further feature of the present invention tle which controls all the primary carburetors comprises a suction operated fuel valve in a and a single main air throttle controlling the flow conduit leading to certain of the fuel jets, said of air through the air manifold. These throttles valve being provided with a passage therethrough are operated from a common operating mechato permit a limited flow of fuel when the Valve is nism so constructed that the primary throttle seated and with two exteriorly tapered surfaces moves independently of the main throttle up to which are adapted to variably control the flow 35 a predetermined engine speed, for example, that of fuel when the valve is lifted from its seat.

corresponding to a vehicular speed of 20 to 25 A still further feature of the invention conmiles per hour on a level, after which the two sists in the provision of channels in the surface throttles are operated simultaneously. A pluof the air valve which permit a limited amount 4 rality of means are provided to variably control of air to enter the carburetor when the valve is 40 the admission of fuel and air under different closed to provide the air necessary for starting. operating conditions to provide a mixture of A still. further feature of the invention resides proper proportions to most satisfactorily operate in the provision of means to communicate the the engine. manifold suction to the anterior side of the aux- It is the principal object of the present inveniliary air valve, so as to assist in holding said 45 tion to provide a charge forming device of the valve closed when the throttles are closed, to character above referred to which is simplified in delay the opening movement of the valve and to constrution, is provided with improved means admit air to the primary mixture passages from for controlling the supply of fuel and air by the main air passage under certain operating means of which proper proportioning of the mixconditions.

ture may be secured to most satisfactorily operate Another feature of the invention resides in the the engine under all operating conditions, and provision of improved means for straightening which may be easily and cheaply manufactured. and accelerating the fiow of air past the delivery With these objects in view, one feature of the ends of the primary mixture conduits and for present invention resides in the provision of novel causing such air to move in straight paths.

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

In the drawings:

Fig. 1 is a plan view of a charge forming device embodying this invention, the manifold being broken away in order to show the end branches thereof.

Fig. 2 is a front elevation of the device shown in Fig. 1 looking toward the engine block.

Fig. 3 is a vertical section on the line 3-3 of Fig. 1.

Fig. 4 is a vertical, transverse section on the line 4-4 of Fig. 3.

Fig. 5 is a side elevation of the carburetor unit viewed from the right in Fig. 1 and partly broken away to show certain parts in section.

Fig. 6 is a side elevation of the carburetor unit viewed from the left in Fig. 1 and partly broken away to show certain parts in section.

Fig. 7 is a horizontal section on the line 1--'I of Fig. 2.

Figs. 8 and 9 are fragmentary sections on the lines 8-8 and 9-9 of Fig. '7.

Figs. 10 and 11 are sections on the lines |6-|0 and of Fig. 3.

Figs. 12 and 13 are detail views of the float valve mechanism seen at right angles to each other.

Fig. 14 is a fragmentary, detail view of the throttle operating mechanism seen from the left in Fig. I.

Fig. 15 is a fragmentaryview on the line |5|5 of Fig. 1.

Fig. 16 is a detail view of 'the primary throttle.

Fig. 17 is a diagrammatic view showing in one figure the valve operating mechanism and the fuel passages.

The device disclosed herein comprises a main air manifold l6, having three outlet branches l2, and I3, each of which is adapted to communicate with oneof the intake ports of a multi-cylinder engine in each of which branches is formed one of the secondary mixing chambers to which a primary mixture of fuel and air is admitted in a manner set forth hereinafter. These branches are each provided with an attaching flange l4, which is adapted to be attached to the engine block in the conventional manner. Adjacent its inlet, the manifold is provided with a flange l5, to which the main carburetor unit hereinafter described is adapted to be secured, as shown in Fig. 3.

The main carburetor unit comprises a main housing l6 in the form of a single casting having a flange l1 secured by screws l8 to the flange |5. A valve controlled air inlet, coupling I9, is secured in position over an opening in the top of the housing 5 by screws 20, as shown in Fig. 4, or in any other desirable manner. A casting 2| having a pump cylinder and certain dash pot chambers hereinafter described, formed therein,

' is secured by screws 22 to the bottom of the main housing, a gasket 23 being provided to prevent leakage. A sheet metal fuel bowl forming a main fuel reservoir 24 is held tight against the bottom of the main housing by a screw 25, screwed into the casting 2| and a gasket 26 forms a tight joint between the bowl and the main housing.

A fuel supply line leading from a main source of fuel supply communicates with a passage in a projecting boss 30, this passage communicating with an angular passage 3| formed in the bottom wall of the main housing. The passage 3| conand 11.

nects with a bore 32 in the casting 2|, a nipple 33 being screwed into the enlarged lower end of this bore. The passage through the nipple is restricted at 33a to form a valve seat with which the valve 34 cooperates. This valve is of square cross section so as to permit the flow of fuel past the valve when it is off of its seat and is controlled by a float 35 secured to an arm 35, pivoted at 31 and engaging the valve 34 to operate said valve in the usual manner to maintain a constant level of fuel within the fuel chamber 24.

A plurality of primary mixture passages indicated in their entirety by the reference character 40, and hereinafter more fully described, are formed in the lower part of the main housing 5. In each of the primary mixture passages are two fuel nozzles 4| and 42, these nozzles being rendered effective successively in a manner to be later described, and constituting low and high speed fuel nozzles respectively. Fuel is conducted from the fuel chamber 24 to the low speed fuel nozzles 4| through a passage 43 and to the high speed fuel nozzles by a separate passage which will be described more fully hereinafter. The passage 43 in the casting 2| extends vertically from the bottom of said casting to a channel 44 formed in the upper surface thereof and extending transversely, as shown in Fig. 10, so as to communicate with all the nozzles 4|. The fiow of fuel through the passage 43 and to the nozzles 4| is controlled by a calibrated metering plug 45 having a fixed orifice therein and screwed into an enlarged portion of the passage 43 adjacent the lower end thereof. It will be understood that the nozzles 4| are in constant communication through the above described passages with the fuel in the fuel chamber and such nozzles are effective at all operating speeds to supply fuel to the afore-mentioned mixture passages.

The high speed fuel nozzles 42 are entirely ineffective during operation at low engine speeds and are rendered effective by means of the valve 46 operated by the throttle in a manner to be later described. The valve 46 is normally held in position to close a fuel supply port 41 in the casting 2|, by means of a spring 48 which is received in a bore 49, in which the valve 46 is slidable, between the lower end of the valve and the plate 50 secured to the bottom of the casting 2|. The passage 41, the bore 49 and a horizontal passage 5|, comprise a fuel passage which communicates with a vertical passage 52, the upper end of which connects with a channel 53 similar in form to the channel 44 and communicating with all of the high speed nozzles 42, which project slightly above the floor of the mixture passages 40, as illustrated in Figs. 3 The flow of fuel through the passages above described to the high speed nozzles 42 is controlled by three elements, the valve 46, above referred to, a calibrated metering plug 54 having a fixed orifice 55 formed therein which controls the maximum flow, and a suction operated metering valve 56 which automatically regulates the flow of fuel to the high speed jets in accordance with the suction effective on the column of fuel flowing through the above described passages to said jets.

The valve 56 is'received in an enlarged bore 51 forming a part of the passage 52 -and fits in said bore loosely enough to permit the passage of fuel around the valve to the high speed jets. The. valve is provided with a passage 58 therein which permits a flow of fuel through the valve when the suction effective on said valve is very low and not enough to lift the valve from its normal seated position. The passage 52 is provided with two shoulders 59 and 88 formed on the Wall of said passage and adapted to cooperate with two tapered surfaces Bi and 62, on the exterior of the valve, while an external rib 63 is provided at thetop of the valve, as indicated in Fig. 9. In its normal position, as shown in such figure, the valve is in its lowermost position with the surfaces 62 engaging the shoulder 60 and the tapered surface 6| spaced slightly from the shoulder 59. Any flow of fuel with the valve in this position must take place through the passage 58 within the valve, but as the throttle valve is opened and the suction communicated to the high speed nozzles is increased in the manner hereinafter described, the valve is lifted so that the passage of fuel around the valve is permitted. The tapered surfaces BI and 62 are of slightly different angularity so as to exert a variable restriction on the fiow of fuel as the valve is lifted. It will be clear from the above that the suction operated valve 56 exerts a variable control on the fiow of fuel to the high speed nozzles after the valve 36 has been opened. Moreover while the valve 46 is stationary, any change in load which would vary the engine speed and, therefore, vary the engine suction, is effective to vary the position of the valve 56 to variably regulate the fiow of fuel.

Each low speed fuel nozzle 4! is provided with a main fuel outlet 64 in the top of the nozzle and a secondary fuel outlet comprising two small holes 85 and 66 diametrically opposite each other in the vertical wall of the nozzle near the bottom of the primary mixture passages. At very low speeds the suction is sufficient to cause a flow through the orifices 65 and 66 only, but on high speeds the suction is great enough in the primary mixture passages to lift fuel through the main fuel outlets as well as from the orifices 65 and 66. Only one fuel outlet is provided in each high speed nozzle 32. The low speed nozzles are each provided with a restricting metering orifice 61, and the high speed nozzles with a similar metering orifice 68. g

The primary mixture passages 48 are enlarged adjacent the fuel nozzles as indicated at 18 and these enlargements constitute the primary mixing chambers. These chambers all communicate with a single chamber H, which for convenience may be termed a primary air chamber and which communicates with a main air chamber in a manner to be described hereinafter. There are three of the primary mixture passages 40 which are parallel to each other and relatively close together, as indicated in Fig. 4. These passages communicate with passages 12 formed in the wall of the manifold and which may be termed for convenience primary mixture conduits. The middle passage 12 is straight and receives a tube 13, which conveys primary mixture to the secondary mixing chamber associated with the middle branch l2 of the manifold. The other two passages 12 are substantially L-shaped and con- 18 for the purpose of materially reducing the velocity of flow through the mixing chambers adjacent the nozzles for a purpose which is fully set forth in the above-mentioned application and need not be repeated herein.

A single throttle valve is rotatably mounted in the main housing l6 and controls all of the mixture passages 80, this valve being provided with grooves 82 which register with the said mixture passages and with spindles 8@, which project from each end thereof outside the housing so that certain valve operating devices hereinafter described may be secured thereto. This throttle controls the flow of primary mixture from the primary mixing chambers through the pipe connections described in the preceding paragraph, to secondary mixing chambers where such mixture is adapted to be mixed with additional air under certain operating conditions in the manner later described.

Substantially all of the air supplied to both primary and secondary mixing chambers is admitted through the coupling i 9 to a. main air chamber from which the air fiows to both the primary and secondary mixing chambers. The flow of air is controlled by means of a valve 85 normally held against its seat 86 by a spring 81 which is receivedbetween the valve and the flange 88 projecting from a sleeve 89, which is slidably mounted on a sleeve 98, fixed in position in the main housing l6. Under normal operating conditions the sleeve 89 is in the position shown in Fig. 3, but may be lifted from this position by means of choke mechanism hereinafter described, to hold the air valve 85 closed to facilitate startmg.

The choke mechanism comprises a lever 9i pivoted on a screw 92, screwed into bosses 93 and 94, formed on the main housing, as indicated in Fig. 5. A suitable operating connection is adapted to extend from the upper end of lever 9! to some position convenient to the operator, while an adjustable stop screw 95 is adapted to engage the main housing and may be adjusted to different positions so as to variably determine the normal position of the lever 9|, and in this manner regulate the normal tension of the spring 81. The lever 9| extends through the wall of the main housing and is provided with a toe 96, which extends beneath the fiange 88 to lift the flange when the lever 8| is rocked in a clockwise direction in Fig. 4, to engage the upper end of the sleeve 89 with the valve 85 to hold the latter closed. When the air valve is held closed in this manner, sufiicient air to carry the starting fuel from the primary mixing chambers to the engine ports is admitted through the air channels 91 formed in the upper surface of the air valve 85.

The valve 85 controls the admission of air to a. main air chamber I80 formed in the housing l6 and communicating with the primary air chamber H by means of a relatively large orifice II in the floor of said main air chamber. Air also flows from said main air chamber to the secondary mixing chambers through an air conduit I02, which may be termed a secondary air passage and is controlled in a manner hereinafter described, by the manually operable valve I03, secured to the shaft I04, pivoted in the main housing and a suction operated valve I05 secured to a shaft I06, also pivoted in the main housing. The operating mechanism for these valves will be described in detail hereinafter. In addition to the air supplied to the primary mixture passages through the orifice Hll, air is also supplied to these passages from the main air chamber I00 through three passages lII'I, which communicate with the primary mixture passages immediately posterior to the restriction 'Il hereinbefore referred to. These passages serve to admit air to the primary mixture passages for the purposes of reducing the velocity of flow past the fuel jets for a purpose substantially the same as in earlier devices of this character and which is fully explained in the above mentioned application Serial No. 288,683.

During operation at all engine speeds below a certain predetermined speed, such for instance as 20-25 miles per hour on a level, the mixture formed in the primary mixing chambers is of properly combustible proportions and this mixture may be conveyed to the engine without dilution by admixture with the additional air in the secondary carburetors. At all higher engine speeds the primary mixture becomes super-rich in fuel content due primarily to the presence of a velocity head at the nozzles at such speeds. To off-set the too rapid increase in fuel flow and to provide a mixture of properly combustible proportions, the air passage I02 leading from the main air chamber I00 to the air manifold must be opened in order to admit air to the secondary mixing chambers to dilute the primary mixture which is delivered thereto.

The mechanism for operating the valves I03 and I05 will now be described. The valve M03 is operated by means of the primary throttle after the primary throttle has made a certain amount of independent movement, subsequent to which movement the valve I03 is moved with said primary throttle. To this end a throttle operating cam H0 is secured tothe spindle 84 projecting from the right end of the primary throttle shaft as viewed in Fig. l. Thiscam is provided with an orifice II I in which any suitable form of operating connection may be secured. Adjustably secured in an arm II2 projecting from the cam, is a stop screw II3, which is adapted to engage an arm H0, hereinafter more fully described, to determine the position of the cam and the primary throttle when the engine is stopped or idling. By adjusting the screw II3,-the area of the primary mixture passages, when the throttle is closed, may be adjusted and the idling speed of the engine in this manner determined. An operating slot II4, a portion of which is concentric with the spindle 84, is formed in said cam H0 and engages a. pin II5 projecting from an arm IIG, adjustably secured in any desirable manner to the end of the shaft I04 on which the secondary or air throttle I03 is secured. In the normal position of the parts, as shown in Fig. 5, the pin II5 occupies a position adjacent one end of the slot I I4 in that part of the slot which is concentric with the spindle 84. The slot is so designed that the cam I I0 may make some degree of movement before the pin II5 reaches that portion of the slot which is not concentric with the spindle, whereby a certain amount of independent move-' ment of the primary throttle is effected without any corresponding movement of the secondary throttle. After the cam has been moved to a position where the pin H5 is in a portion of the slot I I4 which is not concentric with the spindle, the valve I03 is moved simultaneously with the primary throttle and the degree of movement of such valve is dependent upon the contour of the cam slot II4, which may be made of any desired shape to give the desired amount of movement to the valve I03. It will be obvious that by substitution of a cam having a slot II4 of different contour, the degree of movement imparted to the valve 603 may be changed as desired.

As indicated above, the stop screw I i3 is adapted to engage the arm I It to determine the closed position of the primary throttle. With the parts in normal position, the air valve I03 is fully closed and when the cam is moved in a clockwise direction to move the primary throttle toward its closed position, it may continue to move until the screw l I3 engages the arm H6, which is held stationary when the valve I03 reaches its closed position and thus prevents further closing movement of the primary throttle.

The valve I05 is adapted to be opened entirely by the suction of the engine, but said valve is adapted to be closed by the throttle operating mechanism through the medium of a spring hereinaftelr described. For this purpose an arm II! is adjustably secured to the shaft H04 in any desirable manner, and is connected by means of link H0 with an arm H9 secured on the shaft I00 on which the valve I05 is fixed. The link I I0 is connected to the arms III and M9 by pins I20 and HI respectively, which project through slots I22 and I23 formed in the link H8. "The link is connected to the arm III by means of a spring I24, which tends to pull the link toward the left in Fig. 5, so that the pin I2I occupies the position in slot I23 illustrated in that figure. On operation of the cam IIO to close the primary throttle, the

link I I8 is moved toward the left in Fig. 5 by the spring I24, which is stretched by the clockwise movement of arm Ill, so as to rock the arm H9 in a clockwise direction and close the valve I05, the parts assuming the position shown in Fig. 5 at the end of the closing movement. When the cam IE0 is moved in a counterclockwise direction on opening of the primary throttle, the arm H1 is also moved in a counterclockwise direction and the link I I8 is moved to the right as shown in Fig. 5 without effecting any movement of the valve I05 because of the provision of slot I23, the pin I2I merely moving in said slot during such movement of the link I1 8. After the valve I03 begins to open, the suction effective on the valve I05 will. open said valve and swing the arm H9 in a counterclockwise direction, the movement of said valve being limited by the engagement of the pin I2I with the end of slot I23.

It will be noted that three orifices I25 are provided which connect the space in the passage I02 between the valves I03 and I05 with the three primary mixture passages 40. These orifices communicate the suction of the primary mixture passages to the space between the valves I03 and I05 tending'to hold the valve I05 closed when the throttle I03 is closed and until the pressure differ-. ential on opposite sides of the valve I05-is enough to overcome the resistance of adash pot normally retarding the opening movement of said valve I05. These orifices therefore effect a slight delay in the opening of valve I05 from its closed position, with respect to opening of the air throttle I03.

On opening movement of either or both of the throttle valves, the suction in the main air chamber I00 is increased and the air valve 85 is opened against the tension of its spring permitting an increasing flow of air past said valve. During opening movements of said valve it has been found that the valve will flutter unless means are provided to prevent such action. In order to produce a steady opening movement of the valve, a dash pot of conventional form is provided comprising a cylinder I30 formed in the casting 2| and a cooperating piston I3I secured to the lower and of the air valve stem. This dash pot is of well known construction and is adapted to be filled by leakage around the piston when the valve is stationary, fuel escaping slowly from the cylinder by leakage around the piston during opening of the air valve, whereby the movement of the valve is steady.

On opening movements of the throttle valves it is necessary to provide a somewhat enriched mixture in order to properly operate the engine during the acceleration period. For this purpose the device disclosed herein is provided with a pump operated by the primary throttle and hereinafter more fully described to temporarily supply an additional amount of fuel to the primary mixture passages. It has been found necessary, in order to secure the desired mixture enrichment, to also provide means for retarding the opening of the suction operated valve I05 during opening movements of the main air throttle I03. This is necessary in order to produce a sufficient pressure differential between the inlet and outlet ends of the primary mixture conduits to create a velocity of flow through these tubes great enough to transport the enriched primary mixture from the primary mixing chambers to the secondary mixing chambers almost instantaneously. It is a considerable distance from the point at which the fuel enters the primary mixture passages to the secondary mixing chambers where the primary mixture is mixed with air flowing past the air throttle E03 and if the air valve I05 were allowed I to open freely, an appreciable time interval would be necessary for the rich and relatively heavy primary mixture to travel through this distance, obviously a greater time interval than that required for the pure air to travel from the air throttle I09 to said secondary mixing chambers. By retarding the opening of the valve I 05 the time interval necessary for the primary mixture to reach said secondary mixing chamber is reduced, while that necessary for the air flowing past valve I03 is increased so that these two time intervals approach each other, in fact, are substantially equalized, whereby the enriched primary mixture and secondary air reach the secondary mixing chambers at substantially the same time.

In order to retard the opening movement of the valve I05, the shaft I06 on which said valve is secured has attached thereto outside the housing I6 an arm I35,,which is pivotally connected with a link I35, the latter being pivotally connected to one end. of a lever I31 pivoted on a pin I38, screwed into the main housing. The lever I 31 is pivotally connected at its opposite end to a rod I39 connected at its lower end to a dash pot piston I40 slidably mounted in a cylinder MI,

formed in the casting 2|, as indicated in Fig. 8, The piston I40 has a slldable fit within the cylinder MI and sufficient clearance to provide for leakage of fuel past the piston to fill the cylinder when the piston is in its uppermost position. Any opening movement of the valve I05 through the mechanism above described causes a downward movement of the piston I40, which retards the opening of said valve I05 to an extent determined by the amount of clearance between the piston and the cylinder wall. i

In order to variably control the resistance of the above described dash pot to opening movements of the valve I05,'a by-pass passage indicated in its entirety by the reference character I42, is provided in the wall of the cylinder I 4| to permit escape of fuel from below the piston. A valve I43, projecting through the top of the float chamber, so that it may be operated manually, is provided to regulate the area of the passage I02, and it will be observed that by varying the position of the valve, the area of the passage I02 may be correspondingly varied and the resistance of the dash pot regulated as desired.

It has been found desirable under certain op-- erating conditions when the suction effective on the air valve is very suddenly and very greatly increased to permit the valve I05 to open freely. As an example of operating conditions when this action of the valve is desirable, it may be assumed that the vehicle is coasting down hill at a relatively high speed with the throttles closed and the clutch engaged. At such times the engine is running at relatively high speed and if a grade is reached and the throttle is opened, it is not desirable to retard the opening of the air valve because the engine is already running at speed and no enrichment of the mixture is necessary, but at such times suficient air must be admitted to the secondary mixing chambers to provide the necessary volume of charge to give the required power. In order to permit the valve I05 to open freely under the conditions referred to, the dash pot cylinder MI is formed in the casting 29 adjacent an auxiliary cylinder Hi l and communicates with said auxiliary cylinder by means of a passage I05, as shown in Figs. '7 and 8. The cylinder ltd is closed at the top except for a relatively small passage I 46 and slidably mounted within the cylinder I44 is a piston IN, the upper end of which is solid and is normally held in engagement with a circular rib I on the inner surface of thecylinder I04 surrounding the orifice I 36 by means of a spring I09 received between the said closed end of the piston and the plate 50 secured to the bottom of the casting 2i in any desirable manner. The piston It? normally acts as a valve closing the passage I06 and on opening movements of the valve I05, the dash pot piston I40 creates a vacuum within the auxiliary cylinder I44 below the piston tending to pull the piston away from the rib I48. This vacuum is, under all operating conditions except such conditions as above described, insufiicient to overcome the force of the spring I49 so that the dash pot is normally effective to retard the movement of the valve. However, when the throttles are opened under operating conditions such as above described, the suction which 7 is immediately effective on the valve I tending to open same, is sufiicient to overcome the force of the spring I49 and the piston I4? is lifted from the rib I48. The atmospheric pressure of the fuel chamber, therefore, becomes immediately effective over the whole area of the piston head instead of over only the small portion of such head which is directly opposite the orifice I46, and the resistance of the dash pot immediately is correspondingly reduced so that the valve I05 may open substantially freely after the piston has been pulled away from the rib I48. As soon as the suction effective on the valve I05 becomes insufiicient to overcome the action of the spring I09, the piston resumes its position against the rib I48 and the dash pot operates as previously described. Projecting into the cylinder I44 beneath the piston I4! is a pin I50 which limits the downward motion of said piston, the pin being secured in the plate 50 above referred to.

According to the present invention, the pump for supplying additional fuel to the primary mixture passages, as alluded to above, is operated by the primary throttle during its opening movement. For this purpose a cam I55 is secured to the spindle 80 and may be formed integral with the cam H0 or secured to said spindle in any other desirable manner. This cam engages a cam follower I56 rotatably mounted on one end of a lever I51 which is provided intermediate its ends, and pin I58 screwed into the main housing. Pivotally connected to the other end of the lever is a piston rod I59 which extends through the top of the float chamber through a hole I60 of sufficient size to permit lateral movement of the rod and a washer IGI may be provided to'prevent leakage through the hole. The lower end of the rod is pivotally connected to a pump piston I59a which is slidable in a pump cylinder I62 formed in the casting M. The cylinder I62 is connected to a vertical passage I63 bored in the casting 2I, by means of a short horizontal passage I645. The passage I63 is enlarged at its upper end as indicated at Ilita and received therein is a check valve I65, which is normally seated on the shoulder I66, formed at the junction of the passage I63 and the enlargement lfiila, a pin I6'I being provided to limit the upward movement of the check valve. Communicating with the enlargement I60a is a passage I68 which connects with a well Its formed immediately below a channel I'I I of corresponding shape which is formed in the bottom wall of the main housing I6. Communicating with the well I69 are three horizontal passages IN, the opposite ends of which are open to the atmosphere within the float chamber and above the fuel level therein, while intermediate the ends of these passages they communicate with the vertical passages I'IZ drilled in the casting ZI and communicating at their upper ends with corresponding vertical passages I13 in the bottom wall of the main hous ing which have restrictions I10 at the top adjacent the connection of such passages with the primary mixing chambers. On operation of the pump piston I590. fuel is forced through the passages I63 and I68 into the Well I69 from which it flows through the passages III to the vertical passages which communicate with the primary mixing chambers. 'At the same time air enters the opposite ends of passages I II and is mixed with the fuel which is carried through the passages to the mixing chamber. Surplus fuel not carried into the mixing chambers as described, runs out of the passages I'III back into the main fuel chamber 25. The check valve I prevents a downward flow of fuel through the passage I63 and normally maintains a supply of fuel adjacent the well so that said fuel is forced into the well substantially simultaneously with any movement of the throttle. Air is admitted through the passages I'III so that the suction effective on the well I69 and passages supplying fuel thereto is never suflicient to draw fuel from the pump cylinder, the enriching fuel being supplied only by the action of the pump piston when the throttle is open.

In addition to the above described pump for enriching the mixture another means is provided for supplying additional fuel at all engine speeds above that at which the air throttle I03 begins to open. This additional fuel supply means is made necessary by the rapidv reduction in the velocity head at the fuel nozzles which is caused by the opening of the air throttle I03. The fuel metering means is calibrated too small to be theoretically correct in order to compensate for the velocity head, which is present at the fuel nozzles during the operation of the engine at low tively thin sheet metal and the arms of speeds, therefore, the fuel nozzles do not supply sufiicient fuel to form a rich enough mixture for most satisfactory engine operation after the valve I03 begins to open and some means for supplying additional fuel under such conditions must be provided. In order to supply this additional fuel the port 01 controlled by the valve 46 hereinbefore previously described, is provided. The port is normally closed and throttle operated means are provided to open said valve 46 when the valve I03 begins to open. This means comprises a cam I15 secured in any desirable manner to the spin dle 83 projecting from the left \end of the primary throttle as viewed in Fig. 1. This cam is adapted to engage a roller I-l6 rotatably mounted on one end of the bell crank lever Ill," which is pivoted on a pin I16 screwed into the main housing. The other end of the lever Ill is provided with a bent-over toe I19 which lies above the stem of the valve 46 and in which is threaded an operating screw I80, which is adapted to engage the stem of the valve 66 and which may be locked in position by a lock nut NH. The cam Il5 may be of any desirable contour to move the valve at any rate of speed desired and the screw I may be locked in position to engage the stem of the valve 66 at any desired point during movement of the throttle.

According to the present invention the secondary mixing chambers have been modified to eliminate as much as possible the restriction of the outlet branches of the manifold, which was effected by the Venturi tubes used therein in earlier forms of this device such as that disclosed in the above mentioned application Serial No. 288,683. In the device herein described, the ends of the primary mixture conduits are Surrounded by a fitting comprising an inner tube I85 which is spaced from the primary mixture conduit and is secured by a spider I86 to an outer tube I81 provided with an enlargement I88 forming a shoulder I89, where it joins with the smaller portion I81. When the device is assembled, this shoulder I89 is adapted to be held against a corresponding shoulder I90, formed in the outlet branch of the manifold and the otherend of the enlarged portion I88 is adapted to engage a similar shoulder in the engine block. The primary mixture conduit terminates about midway of thelength of the inner tube I85 so that the air flowing past the end of said primary mixture conduit is moving in a substantially straight path and since the air flows both within and outside of the tube I85, the fitting restricts the outlet passage very little, the restriction consisting primarily of the ends of the two tubes which are made of relaspider which secure the tubes together. The function of the above described structure is substantially the same as that of the Venturi tube heretofore employed, that is to increase the velocity of the air passing the end of the primary mixture conduit and to cause this air to move in a substantially straight path.

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. A charge forming device for internal combustion engines comprising a mixing chamber, a

fuel reservoir, an air inlet for said mixing chambet, a plurality of fuel inlets discharging fuel into the mixing chamber, separate conduits connectthe ing said inlets respectively with the fuel reservoir for supplying fuel to the fuel inlets, and manually and automatically operable valve means for variably controlling the flow through one of said conduits.

2. A charge forming device for internal combustion engines comprising a mixing chamber,

an air inlet therefor, a plurality of fuel inlets discharging fuel into the mixing chamber, a fuel reservoir for supplying fuel thereto, a throttle, means operated by the throttle for rendering one of said fuel inlets effective and additional means for regulating the flow through said fuel inlet.

3. A charge forming device for internal combustion engines comprising a mixing chamber, an air inlet therefor, a plurality of fuel inlets discharging fuel into the mixing chamber, a fuel reservoir for supplying fuel thereto, valve means for rendering one of said fuel inlets effective at higher engine speeds and additional valve means for automatically and variably regulating the flow of fuel through said inlet.

4. A charge forming device for internal combustion engines comprising a mixing chamber,

fuel and air inlets therefor, a fuel reservoir, a fuel supply conduit connecting the fuel inlet and reservoir, a valve controlling the flow of fuel through said conduit having a passage therethrough and a plurality of external flow controlling surfaces and a plurality of restrictions in said conduit adapted to cooperate with said flow controlling surfaces.

5. A charge forming device for internal combustion engines having a plurality of intake ports comprising an individual primary carburetor for supplying fuel mixture to each intake port, a fuel reservoir, a fuel duct for conveying fuel from said reservoir to all of said primary carburetors, a fuel valve for controlling the flow of fuel through said duct having a plurality of external flow controlling surfaces, and a plurality of shoulders in said duct cooperating with said surfaces.

6. A charge forming device for internal combustion engines comprising a mixing chamber, means for supplying 'fuel and air thereto, a throttle controlling the flow of mixture therefrom, an operating shaft for the throttle, a passage supplying additional air, a valve in said passage and a cam operated by said throttle for operating said air valve, said cam being so designed that the throttle may make a predetermined movement independently of the air valve.

7. A charge forming device for internal combustion engines comprising a secondary mixing chamber, a primary carburetor adapted to deliver a primary mixture of fuel and air thereto, means for supplying fuel and air to the primary carburetor, a primary throttle controlling the flow therefrom, a secondary air passage adapted to supply air to the secondary mixing chamber, a secondary air throttle therein and means foroperating said throttles concomitantly, said means including a cam operated by the pr'jiary throttle and so designed as to permit a predetermined independent movement of said primary throttle.

8. A charge forming device for internal combustion engines comprising a, secondary mixing chamber, a primary carburetor adapted to deliver a primary mixture of fuel and air thereto, means for supplying fuel and air to the primary carburetor, a primary throttle controlling the flow therefrom, a secondary air passage adapted to supply air to the secondary mixing chamber, a secondary air throttle therein, an auxiliary valve in said secondary air passage adapted to be opened as the engine speed increases, a cam operated by the primary throttle for operating said secondary throttle and means controlled by said cam for closing said auxiliary air valve.

9. A charge forming device for internal combustion engines comprising a secondary mixing chamber, a primary carburetor adapted to deliver a primary mixture of fuel and air thereto, means for supplying fuel and air to the primary carburetor, a primary throttle controlling the flow therefrom, a secondary air passage adapted to supply air to the secondary mixing chamber, a secondary air throttle therein, an automatic auxiliary valve in said secondary air passage, a pump for supplying additional fuel during the acceleration period, means for operating said throttles and the pump concomitantly, and means operated by said operating means for controlling the closing of said auxiliary valve.

10. A charge forming device for internal combustion engines comprising a mixing chamber, an air inlet therefor, a plurality of fuel inlets discharging fuel into said mixing chamber, a fuel reservoir, a throttle, separate fuel conduits leading to said fuel inlets, means operated by the throttle for variably controlling the flow of fuel through one of said conduits, and suction operated means for also variably controlling the flow of fuel through sa d last mentioned conduit.

11. A charge forming device for internal combustion engines comprising a mixing chamber, means for supplying fuel and air thereto, a throttle controlling the flow of mixture therefrom, a passage supplying auxiliary air, a valve in said auxiliary air passage, a cam operated by said throttle for operating said auxiliary air valve, a second suction operated valve in said auxiliary air passage and means operated by the cam for controlling the operation of said suction operated valve.

12. A charge forming device for internal combustion engines comprising a mixing chamber, means for supplying fuel and air thereto, a throttle controlling the flow of mixture therefrom, a passage supplying auxiliary air, a valve in said auxiliary air passage, a cam operated by said throttle for operating said auxiliary air valve, a second suction operated valve in said auxiliary air passage, means operated by the cam for controlling the operation of said suction operated valve and a fuel pump also operated by said cam for supplying additional fuel during the acceleration period.

13. A charge forming device for internal combustion engines comprising a mixing chamber, a fuel reservoir, an air inlet admitting air to said mixing chamber, a plurality of fuel inlets discharging fuel into said mixing chamber, separate conduits connecting said inlets with the fuel reservoir, manual and automatic means for controlling the fiow of fuel through one of said conduits, said automatic means comprising a valve operable in accordance with the suction effective on the fuel column in the conduit having the automatic flow controlling means therein.

14. A charge forming device for internal combustion engines comprising a mixing chamber, a fuel reservoir, an air inlet admitting air to said mixing chamber, a plurality of fuel inlets discharging fuel into said mixing chamber, separate conduits connecting said inlets w th the fuel reservoir, means for rendering said fuel conduits successively operative whereby one of said fuel 50 mary carburetor, a fuel reservoir, a plurality and additional means for variably controlling the flow through one of said conduits after said conduits become operative.

15. A charge forming device for internal coma bustion engines comprising a mixing chamber, a

fuel reservoir, an air inlet admitting air to said mixing chamber, a plurality of fuel inlets discharging fuel into said mixing chamber, separate conduits connecting said inlets with the fuel reservoir, a throttle, means operated by the throttle when said throttle reaches a predetermined position for rendering one of said fuel conduits effective to supply fuel to the fuel inlet communicating therewith and additional means for regulating the flow of fuel through said last named conduit.

16. A charge forming device for internal combustion engines comprising a mixing chamber, a fuel reservoir, an air inlet admitting air to said go mixing chamber, a plurality of fuel inlets discharging fuel into said mixing chamber, separate conduits connecting said inlets with the fuel reservoir, a throttle, means operated by the throttle when said throttle reaches a predetermined po- 25 sition for rendering one of said fuel conduits e f fective to supply fuel to the fuel inlet communieating therewith, and additional means operable independently of the throttle for variably regulating the flow of fuel through said last named 39 conduit.

17. A charge forming device for internal combustion engines comprising a mixing chamber, a fuel reservoir, an air inlet admitting air to said mixing chamber, a plurality of fuel inlets dis- 35 charging fuel into said mixing chamber, separate conduits connecting said inlets with the fuel reservoir, a throttle, means operated by the throttle when said throttle reachesa predetermined position for rendering one of said fuel conduitseifec- 40 tive to supply fuel to the fuel inlet communicating therewith, and an automatic suction operated valve for variably regulating the flow of fuel through said last named conduit.

18. A charge forming device for internal com- 45 bustion engines comprising a secondary mixing 55 flow of fuel through one of said conduits and a ditional means for also regulating the fiow of fuel through said last named conduit.

19. A charge forming device for internal combustion engines comprising a secondary mixm ing chamber, a primary carburetor for supplying a primary mixture of fuel and air to said secondary mixing chamber, a primary throttle for controlling the flow of fuel mixture from said primary carburetor, a fuel reservoir, a plurality 65 of fuel inlets discharging fuel into said primary carburetor, separate fuel conduits, each of which supplies fuel to one of said fuel inlets, means operated by the primary throttle for controlling the fiow of fuel through one of said conduits, and

. automatically operable means for regulating the rate of fuel flow through said last named conduit.

20. A charge forming device for internal combustion engines comprising a secondary mixing chamber, a primary carburetor for supplying a 75 primary mixture of fuel and. air to said secondary mixing chamber, a primary throttle for controlling the fiow of fuel mixture from said primary carburetor, a fuel reservoir, a plurality of fuel inlets discharging fuel into said primary carburetor, separate fuel conduits, each of which supplies fuel to one of said fuel inlets, means operated by the primary throttle to render one ofv said fuel conduits operative to supply fuel to its associated inlet, and means independent of the throttle for regulating the flow of fuel through said last named conduit.

- 21. A charge forming device for internal combustion engines comprising a secondary mixing chamber, a primary carburetor for supplying a primary mixture of fuel and air to said secondary mixing chamber, a primary throttle for controlling the flow of fuel mixture from said primary carburetor, a fuel reservoir, a plurality of fuel inlets discharging fuel into said primary carburetor, separate fuel conduits, each of which supplies fuel to one of said fuel inlets. means operated by the primary throttle to render one oi. said fuel conduits operative to supply fuel to its associated inlet, and suction operated means for variably regulating the flow of fuel through said last named conduit as the engine suction varies under different operating conditions.

22. A charge forming device for internal combustion engines comprising a plurality of secondary mixing chambers, a plurality of primary carburetors for supplying a primary mixture of fuel and air to said secondary mixing chambers, a fuel reservoir, means for admitting air to said primary carburetors, low and high speed fuel inlets discharging fuel into the mixing chamber of. each primary carburetor, a fuel conduit connecting all of said low speed fuel inlets with said fuel reservoir and a separate and independent fuel conduit connecting all of the high speed fuel inlets with said reservoir.

23. A charge forming device for internal combustion engines comprising a plurality of secondary mixing chambers, a plurality of primary carburetors for supplying a primary mixture of fuel and air to said secondary mixing chambers, a fuel reservoir, means for admitting air to said primary carburetors, low and high speed fuel inlets discharging fuel into the mixing chamber of each primary carburetor, a fuel conduit connecting all of said low speed fuel inlets with said fuel reservoir, a separate and independent fuel conduit connecting all of the high speed fuel conduits with said reservoir, manual and automatic means to variably regulate the flow of fuel through said last named conduit to meet the needs of the engine under varying operating conditions.

24;. A charge forming device for internal combustion engines comprising a plurality of secondary mixingchambers, a plurality of primary carburetors for supplying a primary mixture of fuel and air to said secondary mixing chambers, a fuel reservoir, means for admitting air to said primary carburetors, low and high speed fuel inlets discharging fuel into the mixing chamber of each primary carburetor, a fuel conduit connecting all of said low speed fuel inlets with said fuel reservoir, a separate and independent fuel conduit connecting all of the high speed fuel conduits with said reservoir, manual and automatic means to variably regulate the flow of fuel through said last named conduit, said automatic means comprising a suction operated valve subject to engine suction.

25. A charge forming device for internal comaccuses bustion engines comprising a plurality of secondary mixing chambers, a plurality of primary carburetors for supplying a primary mixture of fuel and air to said secondary mixing chambers, a fuel reservoir, means for admitting air to said primary carburetors, low and high speed fuel inlets discharging fuel into the mixing chamber of each primary carburetor, a fuel conduit connecting all of said low speed fuel inlets with said fuel reservoir, a separate and independent fuel conduit connecting all of the high speed fuel conduits with said reservoir, and a suction operated valve regulating the flow of fuel through the conduit which supplies fuel to the high speed fuel inlets.

26. A charge forming device for internal combustion engines comprising a plurality of secondary mixing chambers, a plurality of primary carburetors for supplying a primary mixture of fuel and air to said secondary mixing chambers, a fuel reservoir, means for admitting air to said primary carburetors, low and high speed fuel inlets dischargingv fuel into the mixing chamber of each primary carburetor, a fuel conduit connecting all of said low speed fuel inlets with said fuel reservoir, a separate and independent fuel conduit connecting all of the high speed fuel conduits with said reservoir, a primary throttle controlling the fiow of fuel mixture from the primary carburetors, means operated by said throttle for rendering operative the conduit supplying fuel to the high speed fuel inlets, and other means for regulating the flow of fuel through said last named conduit.

27. A charge forming device for internal combustion engines comprising a plurality of secondary mixing chambers, a plurality of primary carburetors for supplying a primary mixture of fuel and air to said secondarymixing chambers, a fuel reservoir, means for admitting air to said primary carburetors, low and high speed fuel inlets discharging fuel into the mixing chamber of each primary carburetor, a fuel conduit connecting all of said low speed fuel inlets with said fuel reservoir, a separate and independent fuel conduit connecting all of the high speed fuel conduits with said reservoir, a primary throttle controlling the flow of fuel mixture from the primary carburetors, means operated by said throttle after a predetermined opening movement thereof to render the conduit for supplying fuel to the high speed fuel inlets operative, and other means for variably regulating the flow of fuel through said last named conduit.

28. A charge forming device for internal combustion engines comprising a plurality of secondary mixing chambers, a plurality of primary carburetors for supplying a primary mixture of fuel and air to said secondary mixing chambers, a fuel reservoir, means for admitting air to said primary carburetors, low and high speed fuel inlets discharging fuel into the mixing chamber of each primary carburetor, a fuel conduit connecting all of said low speed fuel inlets with said fuel reservoir, a separate and independent fuel conduit connecting all of the high speed fuel conduits with said reservoir, a manually operable valve for rendering operative the conduit for supplying fuel to the high speed fuel inlets, and a suction operated valve for variably regulating the flow of fuel through said last named conduit.

29. A charge forming device for internal combustion engines comprising a mixing chamber,

fuel and air inlets therefor, a fuel reservoir, a

fuel supply conduit connecting the fuel inlet and reservoir, a valve controlling the flow of fuel through said conduit having a plurality of extertrolling surfaces become efi'ective successively to control the flow of fuel through said conduit.

30. A charge forming device for internal combustion engines comprising a mixing chamber, fuel and air inlets therefor, a fuel reservoir, a fuel supply conduit connecting the fuel inlet and reservoir, a valve controlling the flow of fuel through said conduit having a plurality of external flow controlling surfaces tapered at a different angle of inclination to the axis of said valve, and a plurality of restrictions in said conduit of different size cooperating with said flow controlling surfaces, said valve being so constructed that the flow controlling surfaces become efiective successively to control the flow of fuel through said conduit.

31. A charge forming device for internal combustion engines comprising a mixing chamber, a fuel reservoir, an air inlet admitting air to said mixing chamber, a plurality of fuel inlets dis-= charging fuel into said mixing chamber, separate conduits connecting said inlets with the fuel reservoir, a valve in one of said conduits for controlling the flow of fuel therethrough, said valve having a passage therethrough and a plurality of external flow controlling surfaces thereon, and a plurality of restrictions in said conduit adapted to cooperate with said surfaces.

32. A charge forming device for'internal combustion engines comprising a mixing chamber, a fuel reservoir, an air inlet admitting air to said mixing chamber, a plurality of fuel inlets discharging fuel into said mixing chamber, separate conduits connecting said inlets with the fuel reservoir, a valve controlling the flow of fuel through one of said conduits having a plurality of external flow controlling surfaces formed thereon, a plurality of restrictions of difierent size in said conduit and adapted to cooperate with said surfaces, said valve being so constructed that the flow controlling surfaces become efiective successively to control the flow of fuel through said conduit.

33. A charge forming device for internal combustion engines comprising a mixing chamber, a fuel reservoir, an air inlet admitting air to said mixing chamber, a plurality of fuel inlets discharging fuel into said mixing chamber, separate conduits connecting said inlets with the fuel reservoir, a valve controlling the flow of fuel through one of said conduits having a plurality of external flow controlling surfaces tapered at a different angle of inclination to the axis of the valve formed thereon, a plurality of restrictions of difierent size in said conduit and adapted to cooperate with said surfaces, said valve being so constructed that the flow controlling surfaces become efiectlve successively to control the flow of fuel through said conduit.

34. A charge forming device for internal combustion engines comprising a mixing chamber, a fuel reservoir, an air inlet admitting air to said mixing chamber, low and high speed fuel inlets discharging fuel into said miidng chamber, separate fuel supply conduits connecting said inlets with the fuel reservoir, a valve in the conduit supplying fuel to the high speed fuel inlet for controlling the flow of fuel therethrough having a passage therethrough and a plurality of flow controlling surfaces thereon, and a plurality of restrictions in said conduit adapted to cooperate with said surfaces.

35. A charge forming device for internal combustion engines comprising a mixing chamber, a fuel reservoir, an air inlet admitting air to said mixing chamber, low and high speed fuel inlets discharging fuel into said mixing chamber, separate fuel supply conduits connecting said inlets with the fuel reservoir, a suction operated valve in the conduit supplying fuel to the. high speed fuel inlet forcontrolling the flow of fuel therethrough having a passage therethrough and a plurality of flow controlling surfaces thereon, and a plurality of restrictions in said conduit adapted to cooperate with said surfaces.

36. A charge forming devices for internal combustion engines comprising a mixing chamber, a fuel reservoir, an air inlet admitting air to said mixing chamber, low and high speed fuel inlets discharging fuel into said mixing chamber, separate fuel supply conduits connecting said inlets with the fuel reservoir, a valve in the conduit supplying fuel to the high speed fuel inlet for controlling the fiow of fuel therethrough having a plurality of flow controlling surfaces formed thereon, a plurality of restrictions of different size in said conduit and adapted to cooperate with said surfaces, said valve being so constructed that the flow controlling surfaces become effective successively to control the flow of fuel through said conduit.

37. A charge forming device for internal combustion engines comprising a mixing chamber, a fuel reservoir, an air inlet admitting air to said mixing chamber, low and high speed fuel inlets discharging fuel into said mixing chamber, separate fuel supply conduits connecting said inlets with the fuel reservoir, a suction operated valve in the conduit supplying fuel to the high speed fuel inlet for controlling the flow of fuel therethrough, having a plurality of flow controlling surfaces formed thereon, a plurality of restrictions of different size in said conduit and adapted to cooperate with said surfaces, said valve being so constructed thatthe flow controlling surfaces become effective successively to control the flow of fuel through said conduit.

38. A charge forming device for internal combustion engines comprising a mixing chamber, a fuel reservoir, an air inlet admitting air to said mixing chamber, a plurality of fuel inlets discharging fuel into said mixing chamber, separate conduits connecting said inlets with the fuel reservoir, a suction operated valve in one of said conduits for controlling the flow of fuel therethrough, said valve having a passage therethrough I and a plurality of external flow controlling surfaces thereon, and a plurality ofrestrictions in geld conduit adapted to cooperate with said suraces.

39. A charge forming device for internal com bustion engines comprising a mixing chamber, a fuel reservoir, an air inlet admitting air to said mixing chamber, a plurality of fuel inlets discharging fuel into said mixing chamber, separate conduits connecting said inlets with the fuel reservoir, a suction operated valve controlling the flow of fuel through one of said conduits hav-' ing a plurality of external flow controlling surfaces formed thereon, a plurality of restrictions of different size in said conduit and adapted to cooperate with said surfaces, said valve being so constructed that the flow controlling surfaces become effective successively to control the flow of fuel through said conduit.

40. A charge forming device for internal combustion engines having a plurality of intake ports, a plurality of secondary mixing chambers communicating with said intake ports, a plurality of primary carburetors for supplying a primary fuel mixture to said secondary mixing chambers, fuel inlets, one of' which discharges fuel into the mixing chamber of each primary carburetor, a fuel reservoir, a fuel conduit conveying fuel from said reservoir to all of said fuel inlets, a fuel valve for controlling the flow of fuel through said conduit, having a passage therethrough and a plurality of external flow controlling surfaces formed thereon, and a plurality of restrictions of different size in said conduit adapted to cooperate with said surfaces.

41. A charge forming device for internal combustion engines having a plurality of intake ports, a plurality of secondary mixing chambers communicating with said intake ports, a plurality of primary carburetors for supplying a primary fuel mixture to said secondary mixing chambers, high and low speed fuel inlets discharging fuel into the mixing chamber of each primary carburetor, separate fuel supply conduits, one of which supplies fuel to all of the high speed fuel inlets and the other of which supplies fuel to all of the low speed fuel inlets, a valve for controlling the fiow of fuel through the conduit supplying the high speed fuel inlets and having a plurality of external flow controlling surfaces formed thereon and a passage therethrough, and a plurality of restrictions in the fuel conduit cooperating therewith.

42. A charge forming bustion engines having a plurality of intake ports, a plurality of secondary mixing chambers communicating with said intake ports, a plurality of primary carburetors for supplying a primary fuel mixture to said secondary mixing chambers, high and low speed fuel inlets discharging fuel into the mixing chamber of each primary carburetor, separate fuel supply conduits, one of which supplies fuel to all of the high speed fuel inlets and the other of which supplies fuel to all of the low speed fuel inlets, a valve for controlling the flow of fuel through the conduit supplying thehigh speed fuel inlets and having a pluralityof external flow controlling surfaces formed thereon, and a plurality of restrictions of different size in the fuel conduit adapted to cooperate with said surfaces, said valve being so constructed that the flow controlling surfaces become effective successively to control the flow of fuel.

43. A charge forming device for internal combustion engines having a plurality of intake ports comprising an individual primary carburetor for supplying fuel mixture to each intake port, a fuel reservoir, a fuel duct for conveying fuel from said reservoir to all of said primary carburetors, a suction operated valve for controlling the flow of fuel through said duct having a plurality of external flow controlling surfaces formed thereon and restrictions in said duct adapted to cooperate with said surfaces, the valve being moved by suction so as to render the surfaces effective successively to control the flow of fuel.

44. A charge forming device for internal combustion engines having a plurality of intake ports,

a plurality of secondary mixing chambers communicating with said intake ports, a plurality of primary carburetors for supplying a primary fuel 1 mixture to said secondary mixing chambers, high device for internal com-' Gil Separate fuel supply conduits, one of which supplies fuel to all of the high speed fuel inlets and the other of which supplies fuel to all of the low speed fuel inlets, a suction operated valve for controlling the flow of fuel through the conduit supplying the high speed fuel inlets and having a plurality of external flow controlling surfaces formed thereon, and a plurality of restrictions in the fuel conduit adapted to cooperate with said surfaces, the valve being moved by suction to render said flow controlling surfaces efiective successively.

45. A charge forming device for internal combustion engines comprising a plurality of secondary mixing chambers, a plurality of primary mixing chambers adapted to deliver a primary mixture of air and fuel to said secondary mixing chambers, fuel and air inlets therefor, a fuel reservoir, a primary throttle controlling said primary mixing chambers, a well for supplying additional fuel to all of said primary mixing chambers, a plurality of outlet passages leading from the well to said mixing chambers, and a plurality of vent passages each of which communicates with one of said outlet passages between the well and the mixing chamber whereby equal distribution of fuel from said well to the various mixing chambers is secured, and a pump operated by the primary throttle for forcing fuel into the well.

46. A charge forming device for internal combustion engines comprising a fuel reservoir, a mixing chamber, a fuel inlet therefor, a suction operated valve controlling admission of air to said mim'ng chamber, a dash pot for resisting opening movements of said valve comprising a cylinder and a piston slidable therein, an auxiliary cylinder communicating with the dash pot cylinder, a piston in said auxiliary cylinder, a spring normally holding said last named piston in position to render the dash pot effective, said spring being adapted to yield to permit movement of the piston to a position where the dash pot is rendered inefiective when the suction on the valve is sufficient to overcome the pressure of said spring.

47. A charge forming device for internal combustion engines comprising a fuel reservoir, a secondary mixing chamber, a primary carburetor adapted to deliver a primary mixture of fuel and air to said secondary mixing chamber, means for supplying fuel and air to the primary carburetor, a secondary air passage supplying air to said primary carburetor, a secondary air valve admitting air to said secondary mixing chamber, a dash pot for resisting opening movements of said secondary air valve comprising a cylinder having a piston slidable therein and connected to the secondary air valve for movement therewith, an auxiliary cylinder communicating with the dash pot cylinder, a piston in said auxiliary cylinder, a port in said auxiliary cylinder communicating with the fuel reser voir and adapted to control the resisting effect of" the dash pod-means normally holding the last named piston in position to close the port to render the dash pot effective, said means being rendered ineifective by a predetermined degree of suction on the air valve.

for resisting opening movements of said secondary air valve comprising a cylinder having a piston slidable therein and connected to the secondary air valve for movement therewith, an auxiliary cylinder communicating with the dash pot cylinder, a piston in said auxiliary cylinder, resilient means normally holding the piston in said auxiliary cylinder in position to close the port and render the dash pot effective to resist normal opening movements of the air valve, said resilient means being adapted to yield to permit movement of the last named piston to position to open the port and render the dash pot ineffective when I the suction on the air valve is suflicient to over- 49. A charge forming device for internal com means on the bustion engines comprising a fuel reservoir, a

secondary mixing chamber, a primary carburetor adapted to deliver a primary mixture of air and fuel to said secondary mixing chamber, means for supplying fuel and air to said primary carburetor, a primary throttle controlling'the flow from the primary carburetor, a secondary air passage supplying air to the secondary mixing chamber, a secondary air throttle therein, an additional suction operated valve in said secondary air passage, a dash pot for resisting opening movements of said suction operated valve comprising a cylinder having a piston slidable therein and connected to said suction operated valve for movement therewith, an auxiliary cylinder communicating with the dash pot cylinder, a piston in said auxiliary cylinder, a port in said auxiliary cylinder communicating with the fuel reservoir and adapted to regulate the admission of fuel from the reservoir to control the resisting effect of the dash pot, and means normally holding the last named piston in position to close the port to ren der the dash pot effective.

50. A charge forming device for internal combustion engines comprising a fuel reservoir, a mixing chamber, a fuel inlet therefor, a suction operated valve controlling admission of air to said mixing chamber, a dash pot for resisting opening movements of said valve comprising a cylinder and a piston slidable therein, an auxiliary cylinder communicating with the dash pot cylinder, a piston in said auxiliary cylinder, a port in said auxiliary cylinder communicating with the fuel reservoir, an annular projecting flange on the interior of said auxiliary cylinder surrounding said port and forming a seat for said last named piston when the piston is held against said seat whereby the pressure of the fuel reservoir is effective on a relatively small part of the piston head, means normally holding the piston inicontact with said flange but constructed to permit the piston to be moved away from said flange when the suction on the air valve is relatively great so that the pressure of the fuel reservoir is communicated to the entire surface of the piston head in order to reduce the resisting effect of the dash pct.

51. A charge forming device for internal combustion engines comprising a mixing chamber, means for supplying fuel and air thereto, a throttle controlling the flow of mixture therefrom, an operating shaft for the throttle, a passage supplying additional air, a valve in said passage, a fuel pump for supplying additional fuel during the acceleration period, and cams operated by the throttle and adapted to operate the air valve and the fuel pump.

52. A charge forming device for internal com- Eli valve.

53. A charge forming device for internal combustlon engines comprising a secondary mixing chamber, a primary carburetor adapted to deliver a primary mixture of fuel and air thereto, means for supplying fuel and air to the primary carburetor, a primary throttle controlling the flow therefrom, a secondary air passage adapted to supply air to the secondary mixing chamber, a secondary throttle therein, a c operated by said primary throttle for operating the air throttle after a predetermined movement of the primary throttle, a fuel pump for supplying additional fuel during the acceleration period, a fuel valve for controlling the admission of additional fuel at relatively high speeds and other cams operated by the primary throttle and adapted to operate the fuel pump and the fuel valve.

54. A charge forming device for internal combustion engines comprising a mixing chamber, an air inlet therefor, a plurality of fuel inlets discharging fuel into the mixing chamber, a throttle controlling the flow of fuel mixture from said 'mixing chamber, a plurality of fuel passageways supplying fuel to said fuel inlets, throttle operated means for rendering one of said fuel passages eiiective, and fixed and variable flow controlling restrictions in said last named passageway.