US2152950A

US2152950A - Carburetor

Info

Publication number: US2152950A
Application number: US7770A
Authority: US
Inventors: Robert F Bracke
Original assignee: Individual
Current assignee: Individual
Priority date: 1935-02-23
Filing date: 1935-02-23
Publication date: 1939-04-04
Anticipated expiration: 1956-04-04

Description

CARBURETOR Filed Feb. 23, 1935 6 Sheets-Sheet 1 .l a ma? April 4, 1939. R F BRACKE 2,152,950

April 4, 1939.

R. F. BRACKE GARBURETOR Filed Feb. 23, 1935 6 Sheets-Sheet 4 April 4, 1939.

R. F. BRACKE CARBURETOR Filed Feb. 23, 1935 6 Sheets-Sheet 5 April 4, 1939.

R.' F. BRACKE 2,152,950

CARBURETOR Filed Feb. 25, 1955 6 Sheets-Sheet 6 I 00 i J 200 203 .201 d 20g l' vf "u, 202 202 202 0| d 210 i 209 d@ l V l 211 q 2.00 d 207 i y a6 l l Ik I J l ,4/

272 i272 /l/f J) L 7 5 L 1 l I C 1 g i j fi 1; l l 4 213 l I g,JZ/@Jcfv /FOQz/'ZffaC/e.

Patented Apr. 4, 1939 UNITED STATES PATENT OFFICE 10 Claims.

My invention relates to carburetors and is particularly concerned with fuel-lift carburetors having two or more fuel-injecting mechanisms.

An object of my invention is to provide a carburetor having .an improved idling control for the fuel-injecting means.

Another object of my invention is to provide a carburetor having a fuel chamber maintained under suction and a fuel-injecting system always effective to suck fuel from the fuel chamber and capable of idling adjustment independently of the suction existing in the fuel chamber.

'Another object of my invention is to provide a carburetor having a fuel chamber maintained ll" under suction and a fuel-injecting system always effective to suck fuel from the fuel chamber and capable of adjustment for both idling operation and part throttle operation independently of the suction existing in the fuel chamber.

Another object is to provide a carburetor having a fuel chamber maintained under suction and a fuel-injecting system always effective to suck fuel from the fuel chamber and provided with independent idling and part throttle adjustments. 2li both of which are independentof the suction ex istingin the fuel chamber.

Another object is to provide a carburetor having a fuel chamber maintained under suction and two or more independently adjustable fuelinjecting systems supplied from the same fuel chamber.

Another object is to provide a carburetor having multiple fuel-injecting systems, which is simple and rugged in construction, efficient and reliable in operation, and economical to manufacture.

Other objects, advantages and capabilities of the invention Will appear from the following description of preferred embodiments thereof,

` taken in conjunction with the accompanying drawings, in which- Figure 1 is a vertical section through a downdraft carburetor embodying my invention, the same being taken on the line I-l of Figure 2;

Fig. la is a diagrammatic view of the carburetor shown in Fig. 1;

Fig. lb is a diagrammatic view of a detail taken on line Ib-lb of Fig. 1a;

Figure 2 is a fragmentary sectional View, taken on the line 2--2 of Figure 1;

Figure 3 is a sectional view, taken on the line 3-3 of Figure 1;

Figure 4 is a sectional plan View, taken on the line 4-4 of Figure 1, the throttle shaft and econ- 55" omizing mechanism being omitted;

Figure 5 is a sectional detail View, taken on the line 5 5 of Figure 2;

Figure 6 is a sectional elevational view, taken through a modified form of down-draft carburetor embodying my invention;

Figure '7 isa fragmentary sectional View, taken on the line 1-1 of Figure 6;

Figure 8 is a sectional elevation, taken on the line 8 8 of Figure 6;

Figure 9 is a sectional elevation, taken on the line 8-9 of Figure 6;

Figure 10 is a fragmentary elevational view, taken on the line Ill-lll of Figure '7, showing the relation of the choke plate and booster venturi;

Figure 11 is a sectional elevation of a variation of the embodiment shown in Figures 6 to 10, inclusive; and

Figure 12 is a further sectional elevation of the variation shown in Figure 11, being taken in a plane parallel to the plane of Figure l1.

Referring to the drawings, and particularly to Figures 1 to 5, the carburetor comprises a lower casting element Ill which is provided with two mixing chambers Il arrangedin juxtaposition and separated by a wall l2. Each mixing chamber ll is provided with a relatively large Venturi tube I3. In the lower part of each mixing chamber Il, the carburetor being a downdraft carburetor, is mounted a throttle valve I4. The throttle valves i4 are rigidly mounted on a horizontal shaft I5 which has bearings in the side walls of the casting Ill and also in the partition I2. On one end of the shaft I5 is mounted an actuating arm I6, connected in the usual way to the accelerator controls. On the other end of the shaft l5 is rigidly mounted a short arm l1 which is pivotally connected to a link I8. The link I8 is pivotally connected to a bell crank lever I9 which is pivotally mounted on the casting I6 at 20. The purpose of the bell crank lever I9 will hereinafter be more fully described. It may, however, be here noted that this lever is actuated in accordance with the movement of the throttle.

The casting I!! comprises the float bowl 2|, in which is located an annular float 22. This oat is adapted to engage a forked lever 23 which engages a valve 24 to close same when the liquid level in the bowl is sufficiently high. The seat of the valve 24 is carried in an upper casting 25 and this seat is located at the end of a duct 26 which is adapted to be supplied through pipe 21 with gasoline from the main fuel tank which is below the float bowl 2|.

The casting IIJ is provided with flanges 28 whereby it may be secured to the engine manifold,

which manifold comprises two openings in oontinuation with the throttle bores below the throttle valves E4. The castings i9 and 25 are secured together by screws 29, a suitable gasket being interposed to maintain a tight connection. The casting 25 encloses the fuel bowl 2| and carries a depending cylinder 39 which extends into the opening in the iioat 22, so as to permit free vertical movement of the iioat. Within the cylinder 99 is mounted a depending metering pin 3|. The metering pin 3| is rigidlysecured to a spider 32, which in turn is secured to the casting 25. The openings in the spider permit free communi@ cation between the interior of the cylinder 39 and a small chamber 33 formed in the casting 25. |Iiwo ducts 34 extend from the chamber 33 :for the purpose of supplying gasoline to the jets of the carburetor,

The metering pin 3| extends freely through a metering opening 35 in the center of a piston 39. The piston SS comprises. an outer cylindrical wall 3'1 which works freely in the cylinder 39. Immediately inside the outer wall, the piston comprises an annular well- 38 for the reception of a coil spring 39, which bears against the spider 32. The outer wall of the cylindrical well 38 is con stituted by the cylindrical wall 31. The inner wall of the annular well 38 is constituted by an upwardly extending cylindrical wall 48.

The cylinder 43 is closed by a top wall 4|, in which is formed the metering opening 35. The interior of the cylinder 40 is shouldered at 42. so that it may be engaged by a flange 43 on the upper end of a rod 44. The rod 44 is provided with a central bearing 45 in the oat bowl 2| and its lower end rests upon a screw 46 carried on the end of the bell crank lever i9 previously referred to. The flange 43 is provided with perforations 47, which provide an area considerably larger than the metering opening 35. The rod 44 is provided with a central bore 48 which is adapted to receive the metering pin 3| as the rod 44 is moved upwardly. A duct 49 communicates with the bearing 45 of the rod 44 and with the interior of both of the throttle bores at the base of the casing i9. The high manifold vacuum is thus exerted within the vbearing 45 and prevents air being drawn up past the rod 44 into the float chamber 2|.

The carburetor comprises an air horn 59 through which all the air used by the carburetor is admitted. This horn may be provided with an air cleaner and silencer (not shown) of any suitable type. Inside the air horn 59 is located a valve seat 5| which provides an annular chamber 52 between it and the air horn. The outer end of the valve seat 5| is out away around its periphery to provide openings 53 so that air may pass freely into the chamber 52. The air chamber 52 communicates with an air chamber 54 formed by means of a plate 55 mounted by screws on a ribbed formation on the outside of the casting 25.

Within the air chamber 54 are located the air supply ends of the fuel supply Venturi tubes or nozzles 56 of the carburetor. These Venturi tubes are provided with extensions 51 which terminate slightly below the throats of the large Venturi tubes |3 previously mentioned. The air chamber 54 is provided on one side with a port 58 through which air is supplied to the booster Venturi tube 59. The open end of the booster 59 is located in the same plane as the port 59 and a rotatable plate 60 is held tightly against the open ends of the venturi and port. The plate 69 is non-rotatably mounted upon the shaft 6|, which shaft has a non-round end which is received in a central opening of similar shape in the plate 69.

A housing member 52 is mounted on the plate 69 by means of a spring washer 63 and a screw 64, which screw is threaded into a central opening in the reduced non-round end of the shaft 6|. The shaft 6| is provided with a bearing 65 in the casting 25 and is provided with a shoulder 66 which bears against the bearing 55 and prevents longitudinal movement of the shaft in one direction, longitudinal movement of the shaft in the opposite direction being prevented by the housing member 62. Inwardly beyond the bearing member 65, the shaft 9| carries a pin 61, the purpose of which will hereinafter appear. The end of the shaft 6| remote from the housing member 62 carries a sleeve 63 into which it partly extends. The portion of the sleeve which projects beyond the shaft 6| is provided with an opening 69. The sleeve 68 is rotatably mounted in a bearing l0 in alignment with the opening 55, and the bearing 1|! is provided with an opening The openings 69 and come into register at a certain position of the shaft 6|.

The opening 1| opens into the secondary air supply chamber 'l2 and when the openings 59 and 'H are in register, which occurs when the carn buretor is choked, the secondary air supply chamber 12 is put into communication with a duct 13 in the casting 25 and a duct 'I4 in the casting I0. The duct 14 terminates in an opening I5 at the base of the casting I9, which opens into both throttle bores. In this way the throttle is bypassed or cracked for the admission of air when the carburetor is choked.

The booster 59 discharges into a passage 'I9 from whence it passes through a metering orifice Ti into a chamber 18. From the chamber 18 the air from the booster passes into an annular chamber 19, then through a port 89 into a duct 8|. The end of the duct 8| turns downwardly, as shown in Fig. 1, and discharges into the secondary air chamber 2 near the upper ends of the mixing chambers I0 at a point immediately above the partition |2. It will be understood that the secondary air chamber l2 extends across the upper ends of the two mixing chambers IU, as best shown invFig, 3. The ports 'i6 and 8|] open to one face of the casting 25, which face is closed by a cover plate 82.

Integral with the cover plate 82 is a cake-like structure 83 which projects into a cylinder 84 in alignment with the air horn 50. The cage-like structure 83 comprises the chamber i8 around which is arranged the annular chamber T9, bot*v previously referred to. The central chamber receives an insert 85 in which is provided the metering orice 17. The cage-like structure 33 is provided with an opening 86 to provide for communication between the duct 16 and the metering orifice Tl. The cage-like structure 83 comprises an inner wall 81 which has a relatively tight nt in the cylinder 84. Inwardly of this wall the cage-like structure 83 is provided with a nipple 88.

The air valve 89 has an exterior of general convexed or mushroom shape. This valve in closed condition provides a small peripheral opening 99 for the admission of a small amount of air into the secondary chamber 12. As the valve is drawn inwardly, the conical shape of the valve seat 5| causes the clearance between the valve and its seat to increase, thereby admitting more and more air into the secondary air chamber 1 2.

The valve 89 is mounted on a rod 9| for free sliding motion in a bearing 92 carried by the casting25. The valve is pressed outwardly to closed position by means of a spring 93, which is protected against the heat of backres by means of telescopic housing 94. One end of the housing 94 bears against the inner side o-f the valve 89. The other end of the housing 94 bears against forked arms 95 which are freely mounted upon the shaft 6I. The arms 95 are connected together by means of a bridge piece 96. As best seen in Fig. 1, when the shaft 6| is turned through a certain angle, which is done by the ordinary choking manipulation of the plate 60. the pin 61 engages the bridge piece 96. Subsequent movement in the choking direction causes the arms 95 to compress the spring 93 so that the choking manipulation applies a greater pressure than that ordinarily exerted by the spring 93 to tend to hold the valve 89 in closed position.

The rod 9| extends into the cylinder 84 through the nipple 88 and through the metering orifice TI. The free end 91 of the rod 9|. is congured to serve as a metering rod in conjunction with the metering orifice 'I'I for the purpose of maintaining the ilow of air through the booster Venturi tube 59 substantially constant. This results in the maintenance of a substantially uniform depression. or vacuum within the float bowl 2|. This depression or vacuum should ordinarily amount to about fifty inches of gasoline and it is applied to the Miloat bowl 2I by means of a duct 9B which extends through the casting 25 from the top of the float bowl 2| to an annular chamber 99 around the throat of the booster Venturi tube 59. The annular chamber 99 communicates with the Venturi tube through perforations |00.

As best seen in Fig. 5, the plate 60 comprises an arm IOI which may be actuated by a suitable control |02 so as to choke the carburator. The plate 60 is provided with a restricted opening |03 which communicates in all its positions with the port 58 so that the air chamber 54 is in communication with the interior of the housing 62 at all times. Air passes from the interior of the housing 62 into the Venturi tube 59 by means of an opening |04 in the plate 60. As best seen in Fig. 5, the opening |04 is relatively long and of decreasing width so that as'the plate 60 is rotated to choke the carburetor, the amount of air which can be supplied to the booster 59 is progressively decreased until, in fully choked condition, only a little air is being passed therethrough.

The fuel supply Venturi tubes or nozzles 56 are threadedly mounted in bores I 05. Each nozzle cooperates with its bore'to form an annular space |06 which communicates with the interior of the throat of its nozzle by means of small` ducts |01. The ducts open into the throat of their nozzle just below a step therein and supply fuel to such nozzle. l

At a point further away from thethroat of the Venturi tubes in the. down-stream direction, each Venturi tube 56 is providedwith a further annular recess |08 which communicates-to the interior of its Venturi tube through'small ducts |09. Each of the annular spaces I 08 is in communication with a duct IIO in thecasting 25, which duct registers and communicates with a duct III in the casting I0. The duct III communicates with a throttle bore at a point below the throttle valve I4 and each contains a valve seat IIZ (Fig. 4). A valve |I3 is arranged to cooperate with the seat II2 so that the flow through the duct system III, IIO under all conditions can be regulated to a nicety.`

`through passages |99, |68, IE6 and lil.

Within thecylinder 84 the rod.9| rigidly carries apiston" ||4 which has a working t in the cylinder. This cylinder serves as an abutment tending to hold the valve 89 in closed position under the action of the spring 93. This piston II4 cooperates with the cylinder 84 to provide a dashpot effect, which prevents the valve 89 from iiuttering. The rod 9| has a free i'lt within the nipple 88 so that air may slowly pass from and into the cylinder 84.

The operation of the carburetor is as follows: Assuming the engine to be stopped and cold, the valve 89 being, of course, closed, then to start the .engine the plate 60 is manually actuated by the rod |02 so as to limit the amount of air which passes through the opening I 04 into the booster venturi 59. This same movement of the plate 60 rotates the shaft 6I and the throttle valves are b-y-passed through port 'II, port 69, duct 13, duct I4 and opening 15. This by-passing has the same eect as opening the throttle valve slightly. The rotation of the plate 60 also compresses the spring 93 so as to apply greater closing force upon the Valve 89.

During choking, a high vacuum or depression is created in the mixing chambers I and in the secondary air chamber thereabove. This high vacuum would cause a very heavy ow of air through the booster Venturi tube 59 which, in turn, would result in a very high depression or vacuum in the oat bowl 2|. Such an excessively high vacuum or depression would eiectively prevent the supply of any fuel to the Venturi tubes 56. The creation of this high vacuum is prevented by the registry of a narrow part of the opening .|04 with the booster Venturi tube 59. The opening I 04 is conformed so that the vacuum or depression in the bowl 2| is held, during choking, at normal degree, which may, for example, be about fty inches of gasoline.

, It may here be noted that the valve 89 being held strongly towards its closed position during choking, the metering pin 9'I has a very narrow portion located within the metering orifice II so that the orice is substantially unrestricted during choking. Atthis time, owing to the substanti ally closed condition of the valve 89, practically all the air entering into the mixing chambers II is supplied through the Venturi tubes 56. These Venturi tubes receive their air from the chamber 54 which is open to atmosphere through the openings 53. Consequently, a veryhigh degree of suction is exerted by the Venturi tubes 56 for the supply of the large amount of fuel necessary for the production of a rich starting mixture.

- It is important that both Venturi tubes 55 provide exactly the same idling mixture, and an irnportant feature of my invention lies in providing means whereby the idling operation of each Venturi tube 56 may be adjusted independently of the other. The Venturi tubes 56 are correlated with the booster Venturi tube 59 so that under normal idling conditions the Venturi tu'bes 5,5 would just be unablev to overcome the depression or suction in the float bowl 2|, at least to the extent ci supplying a suciently' rich mixture for normal idling of the engine.

The suction of the Venturi tubes 55 is therefore increased by suction exerted by the engine The increase of suction thus exerted may be very considerable since a high degree of vacuum or depression exists in the throttle bore below the substantially closed throttle valve I4. This increase of suction may be regulated to a nicety by altering the setting of the valves ||3 so that a proper idling mixture is produced. This adjustment is individual to each of the Venturi tubes 56 and, as a result, each may be adjusted independently so that perfect fuel distribution can be attained and the Venturi tubes 56 may be perfectly matched. While the adjustments which I have described are primarly concerned with the idling operation of the engine, these adjustments affect the engine operation to a progressively lesser and lesser extent as the speed of the engine increases until the speed of the engine corresponds to a vehicle speed of approximately twenty-uve or thirty miles per hour, after which the effect of the idling adjustments becomes negligible.

During normal running of the engine, the valve 8S opens to a certain degree, depending upon engine speed, to admit a relatively large amount oi secondary air. This move-ment of the valve 39 from its initial closed position, causes a movement of the metering pin 3l within the metering orice l?. The metering pin 3l is so congured that it provides a variable restriction for the flow of air through the booster Venturi tube 59. This restriction is correlated with the depression existing in the mixing chambers at various speeds, so that the vacuum or depression in the float bowl is maintained substantially constant.

Whenever the throttle is opened rapidly, the rod 44 is moved upwardly and the piston 36 is moved upwardly thereby Within the cylinder 30, so that an extra amount of gasoline is supplied through the ducts 34 tothe venturis 56 in order "f, that the desired acceleration of the vehicle may be quickly accomplished. Since the metering opening S5 is provided in the piston 36, no check valve is needed in this piston.

At part throttle operation, at which practically all ordinary steady driving is done, the pin-3| effectively impedes flow of gasoline through the opening 55, giving a lean mixture best suited for economical operation. During wide open throttle operation, the pin 3| permits a large amount of gasoline to pass through the opening 35, giving a rich mixture and thereby `providing the high torque suitable for high acceleration or i'or heavy load. A

It may here be noted that the improved carburetor is well adapted for touch throttle operation, that is, driving slowly with the occasional slight opening of the throttle. The smooth performance given by the present carburetor under these conditions is due to the fact that all the fuel is fed through two paths, one ior each manifold. As a result, the path of the incoming fuel is always maintained in wet condition, which enables the driving operation mentioned to proceed with smoothness.

The embodiment of the invention illustrated in Figs. 6 to l0, inclusive, comprises an upper casting H5 anda lower casting H5 secured together. The lower casting ||5 is mounted upon the upper end of the dual manifold ||5 with the two throttle bores lll in alignment with the two manifold inlets IIB. The mixing chambers ||9 are provided with relatively large Venturi tube inserts and they contain` throttle valves |2| mounted on a single shaft |22. At one end the shaft |22 carries a cam |23. At the other end it carries an actuating arm |24 whereby the throttles may be opened and closed.

The fuel feed Venturi tubes or nozzles |25 are located above and in alignment with the mixing chambers H9 and they are provided with tubular extensions |25 which terminate slightly below the throat of the Venturi tubes |20. The fuel feed Venturi tubes |25 provide annular spaces |2l' which communicate to the interior of the Venturi tubes near their throats through small passages |28. Two separate ducts |29 lead from the two annular spaces |2l into the upper part of chambers |30, for the supply of fuel to theVenturi tubes |25. As is best seen in Fig. 9, the Venturi tubes |25 are open to the atmosphere.

|4| turns downwardly, as best shown in Fig. 6, and opens into the secondary air chamber |42 at a point above the two mixing chambers ||9 and preferably directly between these two chambers.

The secondary air is controlled by a valve |53 which is similar to the valve 39 of the modication first described. This valve is of general mushroom shape and in its fully closed position its periphery is located within the restricted part of the air inlet |54. When the valve |53 is drawn inwardly by the suction of the engine, its periphery moves away from the narrowest part of the air inlet |54 and the secondary air inlet opening increases in size, depending upon the degree of suction to which the valve is subjected. The valve |53 is mounted on a shaft |55 which has a bearing |55` in the casting. The end of the shaft |55 remote from the valve |53 extends into a cylinder |51 in alignment with the air inlet |54. Within this cylinder the shaft |55 rigidly carries a piston |58 which limits the movement of the valve in the outward direction. The valve |53 is provided with a coil spring |59 which tends to force the valve |53 outwardly. The spring |59 is enclosed within a telescopic housing |60 and The end of the duct y fifi oil

in the casting I I5. When the plate |33 has been rotated towards carburetor choking position a certain extent, the arm |52 engages one of the housing lelements |56 and further movement in the choking direction eifectsa further compression of the spring |59 so that the valve |53, during choking, is held very strongly towards its most fully closed position, a position at which very little air is admitted into the secondary air chamber |42.

The portion of the shaft |55 which cooperates with the metering opening |45 is congured so that under normal running conditions, that is, during all engine operation except with choking, the air passing through the booster venturi I3| is substantially constant. As a result of this feature, a substantially constant depression or vacuum is maintained within the float chamber |31. This depression or vacuum may suitably amount to about fifty inches of gasoline. During choking, the secondary air valve |53 is held towards its closed position by the arm |52 with a force greater than that exerted by the spring |59 in non-choking operation. Consequently, during choking a very substantial depression is created within the secondary air chamber |42 and a very strong flow of air would occur through the booster venturi |31 if the plate |33 were not adjusted. This strong flow of air would create very great depression within the float bowl |31, that is, a depression which would render the fuel supply venturis i 25 incapable of taking fuel from the bowl. The configuration of the opening |32 is such that during choking the normal iioat bowl depression or Vacuum is not exceeded, but is maintained in substantially the normal degree, for example, about fty inches of gasoline.

It will be noted that when the opening |45 is brought into register with the opening |48, which occurs during choking, the by-pass which is thus completed between the secondary air chamber |42 and the throttle bore is effectively the same as cracking the throttle valves 52|.

Two metering rods I8| are secured yto the upper side of the piston i1 I, for example, by means of enlarged heads |82 which are located beneath the flange |19, this flange having openings cut in its edge to permit the vertical portions of the rods |8I to pass therethrough. These rods extend freely through openings |63 into the chambers |35 previously referred to. The chambers |36 open to the upper side of the carburetor and are internally threaded both below and above the position at which the ducts |23 communicate with the chambers.

The metering rods |81 extend through metering orifices |84 provided in cage-like structures |85 which are threaded into the chambers |30. The cage-like structures have upward extensions |86 which are hollow, in order to accommodate the upper portions of the metering rods lili, which move with the piston i'li. At their upper ends these extensions |86 are provided with kerfs whereby the cage-like structures |85 may be adjusted in position by means of a screw driver. As best seen in Fig. 8, the extensions |86 project through packing glands |81 which tightly enclose the upper ends of the chambers |36.

A sealing duct |88 is provided from the interior of the bearing |16 to an opening |83 which extends into both throttle bores adjacent the lower edge of the carburetor. This sealing duct prevents leakage of air into the float chamber along the rod |69.

Each metering rod |8l has a slightly tapered portion i90 which lies in the corresponding metering orice |84 when the engine is idling, and by adjusting the orifice |84 up and down the idling operation of the corresponding nozzle Venturi tube |25 can be varied by varying the amount of fuel supply thereto. Just below the slightly tapered portion |90 of each metering rod |8| is a more steeply tapered portion I9| which is located in its corresponding orifice when the engine is operating at part throttle.

Since the tapered portions |66 and |9| of the metering rods are provided by the saine member, any adjustment of the corresponding orifice |84 with respect to one of these tapered portions necessarily produces a corresponding adjustment of this orifice relative to the other of these tapered portions. In other words, the metering pins I8| and adjustable orifices I constitute a means whereby each nozzle Venturi tube may be adjusted for both idling operation and part throttle operation independently of the other nozzle Venturi tube, but the idling and part throttle adjustments for a given Venturi tube are not independent of each other. When the engine is operating at full throttle, the small lower ends of the metering rods |8| are located in the orifice |84 so that the fuel may flow freely to the Venturi tubes |25.

The present embodiment of the invention operates in substantially the same way as the embodiment rst described. It is to be noted, however, that the individual and separate control which is necessary for the satisfactory operation of the two nozzles or fuel Venturi tubes |25 is attained in a different way.

In the embodiment rst described, the idling operation of the fuel feed Venturi tubes was independently controlled by independently adjusting the flow of air through each Venturi tube and a common metering pin was used for Varying the fuel supply to the two fuel feed Venturi tubes during part throttle operation, whereas in the present embodiment a separate metering pin is provided for each nozzle, each metering pin being adjustable independently of the other and adjustably controlling the supp-ly of fuel to its nozzle during both idling and part throttle operation.

In Figures 11 and 12 I have shown a variation of the embodiment illustrated in Figures 6 to 10, inclusive. In this variation the idling control means utilized in the embodiment of Figures 6 to 10, inclusive, is eliminated, and the idling control means utilized in Figures 1 to 5, inclusive, is substituted therefor.

Figure 11 corresponds generally to Figure 8 which shows a section of the second embodiment of my invention. In the present variation of that embodiment, eachrmetering pin 200 has the lower portion of its large cylindrical upper end lying in its associated orifice 20| when the engine is idling. Below the enlarged upper end of each metering pin 200 is a tapered portion 202 which regulates the supply of fuel to the associated nozzle during part throttle operation of the engine. Vertical adjustment of the orifices 20| does not change the idling operation of the nozzles but only affects the part throttle operation, and in this respect the metering pins 200 differ from the metering pins |8| of the preferred embodiment since the latter adjusts both the idling operation and the part throttle operation of the nozzles with whichthey cooperate.

'I'he nozzles or fuel feed Venturi tubes 203 of the present variation are identical with those disclosed in Figure 3. Each nozzle has a throat 204 terminating in a step just below which is located the rdiagonal fuel feeding passages 205 which draw fuel from the fuel chamber or float chamber 206, cylinder 201 and through one of the orifices 20|. Below the fuel feeding passages 205 each nozzle is provided with a series of radial ports 208 communicating with an annular chamber 209 connected to a short horizontal bore 2|0.

The upper end of a vertical passage 2|| connects with one end of each horizontal bore 2|() and the lower end of each passage 2H opens into a diagonal conduit 2|2. Each conduit 2|2 communicates with a throttle bore at a point 2|3 located below the corresponding throttle valve. A separate needle valve 2|4 adjustably controls communication between the lower end of each conduit 2|2 and its corresponding throttle bore.

Except for the differences which I have pointed out, the Variation shown in Figures 11 and 12 is substantially identical with the embodiment shown in Figures 6 to 10, inclusive. It Will be noted that the structures of Figures 11 and 12 provide an independent idling adjustment for each nozzle and an independent part throttle adjustment for each nozzle. Furthermore, the idling adjustment and the part throttle adjustment for the same nozzle are independent of each other.

While I have illustrated and described several embodiments of my invention, it is to be understood that my invention is not limited to the particular details shown but may assume numerous forms, and that the scope of my invention is to be limited solely by the following claims.

I claim:

1. In a carburetor of the class described, the combination of a plurality of nozzles, a fuel chamber from which said nozzles are supplied, a common accelerator pump for all of said nozzles, and a separate metering means for each nozzle, said pump controlling all of said metering means.

2. In a carburetor of the class described, the combination of a fuel chamber, a booster Venturi tube for maintaining a suction in said chamber, a nozzle supplied from said chamber, a mixing chamber into which said nozzle discharges, a secondary air inlet for said mixing chamber, a valve for said inlet, a spring tending to close said valve, choke means for restricting the inlet to said booster Venturi tube, and mechanism operated by said choke means for increasing the tension of said spring.

3. In a carburetor of the class described, the combination of a plurality of nozzles, a fuel chamber from which said nozzles are supplied, an independent idling adjustment for each nozzle, a common accelerator pump for all of said nozzles, and a separate metering means for each nozzle, said pump controlling all of said metering means.

4. In a carburetor of the class described, the combination of a plurality of nozzles, a fuel chamber from which said nozzles are supplied, means for maintaining a suction in said fuel chamber, a common acelerator pump for all of said nozzles, and a separate metering means for each nozzle, said pump controlling all of said metering means.

5. A multiple carburetor comprising a fuel chamber, means for creating a depression therein for the elevation of fuel thereinto, a plurality of fuel feed Venturi tubes for supplying fuel to a plurality of manifolds, a throttle valve controlling the supply of mixture to each manifold, a suction passage communicating with the interior of each Venturi tube and with the throttle bore posterior of the throttle valve, for augmenting the amount of fuel supplied by said Venturi tubes, a common accelerator pump for all of said nozzles, and a separate metering means for each nozzle, said pump controlling all of said metering means.

6. In a carburetor of the class described, the combination of a fuel feeding venturi, a fuel chamber, means for maintaining suction therein, said means consisting of a booster venturi discharging through an orificev into the carburetor throttle bore, means to keep the flow of air through said booster substantially constant regardless of variations in the air iiow through said throttle bore, said means comprising an element for progressively restricting sai-d orifice as the air flow through the carburetor throttle bore becomes progressively greater, a fuel-injecting system always effective to suck fuel from said fuel chamber, means for adjusting the idling operation and part throttle operation of said fuelinjecting system independently of said fuel chamber suction, said means providing separate and independent adjustment for idling operation and part throttle operation.

7. In a carburetor of the class described, the combination of a fuel feeding venturi, a fuel chamber maintained under suction, a fuel-injecting system always effective to suck fuel from said fuel chamber, separate means for maintaining a suction in said fuel chamber, said means consisting of a booster venturi discharging through an orifice into the carburetor throttle bore, means to keep the flow of air through said booster substantially constant regardless of variations in the air ow through said throttle bore, =said means comprising an element for progressively restricting said orice as the air flow through the throttle bore becomes progressively greater, and means for adjusting` the idling operation and part throttle operation of said fuelinjecting system independently of said fuel chamber suction, said means providing separate and independent adjustments for idling operation and part throttle operation.

3. In a carburetor of the class described, the combination of a fuel feeding venturi, a fuel chamber, means for maintaining a suction therein, said means consisting of a booster venturi discharging through an orfice into the carburetor throttle bore, means to keep the flow of air through said booster substantially constant regardless of variations in the air flow through said throttle bore, said means comprising an element for progressively restricting said orice as the air flow through the throttle bore becomes progressively greater, a plurality of nozzles supplied from said fuel chamber, an independent idling adjustment for each nozzle, an independent part throttle adjustment for each nozzle, the idling adjustment and part throttle adjustment for a given nozzle being independent of each other.

9. In a carburetor of the class described, the combination of a fuel feeding venturi, a fuel chamber, a pair of nozzles' supplied therefrom, means for maintaining a suction in said fuel chamber, said means consisting of a booster venturi discharging through an orifice into the carburetor throttle bore, means to keep the flow of air through said booster substantially constant regardless of variations in the air flow through said throttle bore, said means comprising an element for progressively restricting said orifice as the air flow through the throttle bore becomes progressively greater, an independent idling adjustment for each nozzle, and an independent part throttle adjustment for each nozzle.

10. In a fuel-lift carburetor of the class described, the combination of a fuel chamber, means for maintaining a suction therein, a pair of nozzles supplied with fuel from said chamber, an independent idling adjustment for each noz zle, a common accelerator pump for all of said nozzles, and a separate metering means for each nozzle.

ROBERT F. BRACKE.