US2092946A

US2092946A - Carburetor

Info

Publication number: US2092946A
Application number: US756044A
Authority: US
Inventors: Merl R Wolfard
Original assignee: CHARLES F HOPEWELL; HELEN C HOPEWELL
Current assignee: CHARLES F HOPEWELL; HELEN C HOPEWELL
Priority date: 1934-12-05
Filing date: 1934-12-05
Publication date: 1937-09-14
Anticipated expiration: 1954-09-14

Description

Sept. 14, 193,7. M R WQLFARD' 2,092,946

CARBURETOR Filed Dec. 5, 1934 6 Sheets-Sheet l \nvenTr.

by/md M&W A 1 Tys.

Sept. 14, 1937. M. R. WOLFARD GARBURETOR Filed Dec. 5, 1934 6 Sheets-Sheet 4 \nvenTor. Mefl RWoWard b /wd M&W\

ATTyS.

Sept. 14, 1937. M WQLFARD 2,092,946

CARBURETOR Filed Dec. 5, 1934 e Sheets-Sheet; e

Figl. F1 15.

Patented Sept. 14, 1937 UNITED STATES PATENT OFFICE CARBURETOR Application December 5, 1934, Serial No. 756,044

28 Claims.

This invention relates to improvements in carburetors and one of the principal objects thereof is to provide improved simple andeifective means for controlling the ratio of fuel to air in a combustible mixture supplied to an internal combustion engine while operating under changing or transient conditions, such as occur in an automobile engine while operating in traffic, which tend to disturb or upset the normal functioning of c-arbureting devices as .heretofore constructed.

Such changing or transient loads on an engine produce sudden changes in the speed of the air stream, thus causing surges or eddies which momentarily modify the suction head acting at the fuel outlet, thereby producing fluctuating flow of fuel which momentarily disturbs the ratio of fuel to air mixture supplied to the engine.

It has long been assumed that a sudden increase in the suction head is accompanied by a relative lag in the supply of fuel due to the much greater density of the fuel relative to the air, and numerous .fuel accelerating devices have been designed in attempts to overcome thisdifliculty. It is believed that the converse of this proposition, however, has never been recognized in carburetor design, that is, when the suction head suddenly drops, there is a tendency for the fuel to gush or continue to flow by reason of its greater density as compared with that of the air, thuscausing a direct wastage of fuel due to the overenrichment of the mixture at such times. This wastage will be greater as the'length of the high velocity stream in the fuel inlet passage a carburetor with means forcoordinating at all times the rate of fuel flow from the fuel supplychamber into the air stream with the quantity of air flowing through the main passage to maintain the ratio of fuel to air irrespective of sudden changes in the air stream velocity, or suction head, in the main passage resulting from the variations in load on the engine, thereby insuring a continuous carrying forward of the fuel from'the fuel supply chamber into the air stream of the main passage without diminution or .in-

crease relatively to the quantity of air momentarily flowing through the carburetor at any time;

This is attained by a structure in which the fuel passageway is of ample cross Sectional area to insure low velocity therethrough, except for a short restricted fuel metering section which discharges fuel directly into air, and effectively avoids lag or gushing flow of any considerable portion of the fuel, such as would be caused by a sharp or abrupt change or reversal in the direction of flow of fuel in any part of the passageway.

More specifically the present invention relates to certain improvements in the type of carburetor disclosed in my prior Patents Nos. 1,823,017, 1,823,018, and 1,823,019, granted September 15, 1931, in which a unit control is employed for producing a proper proportioning of the fuel-air mixture in combination with means for effecting uninterrupted mixture flow from the fuel inlet and therebeyond under all normal conditions of operation of the engine from idle to full load.

In specific constructions disclosed therein unit control was obtained by varying the area of the fuelmetering section; In the present invention unit control is accomplished by providing means to vary the area of the air metering section.

By the present invention the use of a small valve for controlling the area of the fuel metering section is avoided and inaccuracies in flow resulting from oxidation or gumming of the small valve, which change substantially its flow characteristics, are eliminated; and, inasmuch as the area of the air metering section is many times greater than the area of the fuel metering section, small variations in adjustments of the air metering area are relatively much less disturbing,

thereby permitting a far more trustworthy con-' trol of fuel to air ratio.

Another object of the invention is to provide the main passage of a carburetor with an air metering valveto provide the normal air metering section thereof having a portion thereof ex- 7 in said air metering section is utilized to insure V immediate entraining of the fuel in the air' stream, without subjecting the fuel outlet to the more intense fluctuations in the suction head which are present when the fuel is discharged directly into the higher velocity air stream in the air metering section.

A further object of the inventionis'tq Provide simple and effective means, preferably including thermostatic means, for accurately adjusting the position of said metering valve to determine positively and with precision the area of the air metering section.

Another object of the invention is to provide a fuel metering section through which all the fuel shall pass during idle, light and medium load operations of the engine, in combination with means for producing continuously a predetermined flowing head at said fuel metering section such as will coordinate the rate of fuel flow with the quantity of air flowing through the air metering section of the carburetor at all times.

A further object of the invention is to provide a fuel metering nozzle having its lengthwise wall converging toward its axis near its outlet end at such an angle as will provide a circular knife edge at the discharge end and insure precision of fuel metering when the nozzle is positioned to discharge fuel upwardly and directly into air.

Another object of the invention is to provide novel means for regulating with precision the level of the fuel in the fuel supply chamber relative to the fuel metering nozzle irrespective of changes in velocity or inclination of the supply chamber.

These and other objects and features of the invention will more fully appear from the following descri tion and the accompanying drawings and will be particularly pointed out in the claims,

Illustrative embodiments of the invention are shown in the accompanying drawings, in which,

Fig. 1 is a vertical central longitudinal sectional View of a carburetor embodying a preferred form of the invention;

Fig.2 is a plan view of the same with the cover of the float chamber removed;

Fig. 3 is an end elevation of the construction shown in Fig. 1, a portion of the cover and portions of the wall of the main passageway being broken away to illustrate details of construction therein;

Fig. 4 is a side elevation of the construction shown in Fig. 1;

Fig. 5 is a View mainly in vertical section of a down draft carburetor embodying the invention and to which the controlling mechanism illustrated in Figs. 1 to 4 may be applied;

Fig. 6 is a View mainly in vertical section and partly broken away of another embodiment of the invention characterized mainly in that the air metering section of the main air passage is of rectangular form;

Fig. 7 is a vertical section of the View on lines 1--?, 6;

Fig. 8 is a vertical longitudinal section of the view of a different form of carburetor embodying the invention in which the fuel is introduced into the main passage from below;

Fig. 9 is a top plan view of the fuel supply chamber and the float mechanism therein and also illustrates in dotted lines the relative position of the cylindrical main passage and the mechanism for regulating the throttle valve and the air metering valve;

Fig. 10 is a vertical sectional view of the carburetor shown in Fig. 8 on the broken line l0l9 Fig. 8;

Fig. 11 is a sectional view on lines Hil Fig.

Fig. 12 is a view, partly in longitudinal section, of a modification of the construction shown in Figs. 1 to 4, wherein the throttle valve swings in the'opposite direction with an elbow leading from the carburetor downwardly to connect with the downdraft manifold.

Fig. 13 is a side elevation of the general construction shown in Figs. 8 to 10, but in which the air metering valve and the throttle valve swing in opposite directions to those shown in Figs. 8 to 10;

Fig. 14 is an enlarged detail View of the fuel delivery end portion of the tubular member through which liquid fuel is delivered into the air stream; and,

Fig. 15 is a View of the same at right angles to the position shown in Fig. 14.

The carburetor illustrated in Figs. 1 to 4 of the drawings comprises a casing having a tubular portion I, preferably inclined downwardly, and providing a main air passage 2. The inlet end of the main passage desirably is enlarged and terminates in a cylindrical section 3 adapted to be connected to the usual air cleaner. The opposite end of the tubular section is provided with a peripheral flange l provided with suitable bolt holes for connection to a complementary flange 5 of the continued air passage 6 in the form of an elbow which communicates with the inlet manifold of the engine. The casing I of a fuel supply chamber desirably is formed integral with and superposed upon the tubular portion I of the carburetor casing.

The supply chamber desirably is of a generally rectangular form and is provided with a relatively narrow hollow portion 8 extending lengthwise of the carburetor. The upper wall 9 of the extension 8 is provided with a central aperture having a screw threaded wall which receives the adjustable cylindrical casing l0 which carries the cylindrical. valve seat section II for an inlet valve. The inlet seat section l is enlarged at its upper end to provide a shoulder 12 which engages the upper end of the adjusting valve casing ID. The terminal end of the valve seat section desirably is conical and adapted to receive the flared end of the fuel supply line which is clamped down by the usual cap (not shown).

The adjustable valve casing is provided intermediate of its length with an angular, preferably hexagonal portion l3 to provide means by which the casing may be rotated to adjust it vertically. A look nut [4 upon the threaded portion of the casing beneath the hexagonal portion is adapted to engage the face of the upper wall 9 and secure the casing in adjusted position.

Desirably further locking means for the adjustable casing is provided comprising an angular plate of the form shown in Figs. 1 and 4 having a vertical portion 15 detachably secured to the side of the extension by screws and a hori- Zontal portion l6 provided with a hexagonal aperture adapted to slip over and closely enclose the hexagonal portion l3 of the casing, thus securely holding said casing in adjusted position. In ordertherefore to adjust the valve casing, the screws holding the locking plate must be removed and the plate removed from engagement with the hexagonal portion of the casing.

A conical fuel regulating valve I! engages the lower end of the valve seat member I I and is provided beneath its conical end with a cylindrical portion of less diameter than the inner diameter of the casing. Suitable ports are providr ed in the wall of the casing opposite the cylindrical portion to permit free exit of fuel into the supply chamber I 8. The lower portion of the valve which constitutes the valve stem I9 desirablyis of cylindrical form slidably to fit within the valve casing and preferably has its walls slabbed off to reduce the friction between the valve stem and the wall of the casing and permit the passage of some of the liquid into the supply chamber. The lower end of the valve stem is spherically rounded and engages a convex surface upon a controlling lever 20 in proximity to the pivot or fulcrum 2| thereof. The controlling lever desirably is of bifurcated or yoke form and the ends 22 and 22a: of the yoke are respectively secured to

floats

23 and 24 which are located in the rectangular portion of the supply chamber.

The floats 23 and 24 desirably are of tapering form gradually diminishing in horizontal cross sectional area toward the ends thereof which are remote from the pivot and are symmetrically disposed relatively to a fuel metering nozzle 25 through which fuel is delivered to the air stream in a manner which will hereinafter be more fully described. By reason of this construction, the actuating momentabout the pivot 2| of the controlling lever relatively to the regulating valve remains constant for a predetermined level of liquid relative to the fuel nozzle irrespective of changes in inclination of the supply chamber, thereby insuring precise control of the fuel level in the fuel supply chamber.

The fuel nozzle comprises an upwardly inclined cylindrical tubular portion 26 having an enlarged, preferably hexagonal portion 21, and a screw threaded terminal portion 28 which engages complementary screw threads in an aperture in the inclined side wall 29 of a depression chamber 30, a fibre washer 3| being interposed between the enlarged portion 2'! and the surfaced face of the wall 29, whereby when the nozzle is screwed in place leakage is prevented, from the supply chamber into the depression chamber.

The lengthwise wall of the nozzle gradually and progressively converges toward its axis at its outlet end, where the angle of convergence is more than five and less than twenty degrees to form a restricted fuel metering section through which all of the fuel shall pass during idle, lght and normal load operations of the engine. The depression chamber 30 is located centrally of the width of the fuel supply chamber, its width being relatively small compared with its length, and the walls thereof formed integral with the walls I of the supply chamber. The wall 29 of the depression chamber extends downwardly and merges into an enlarged preferably rectangular boss 32 which extends downwardly to and merges into the wall of the cylindrical portion of the main air passage.

The rectangular boss 32 is provided with a verti cal bore into the upper end of which is inserted the lower end of a deflecting vane 33 having a channel 34 therein, the bottom of said channel presenting a curved surface 35 to deflect the jet of fuel from the nozzle downwardly, during medium and heavier load operations of the engine, into the lower vertical portion of the channel, and thence into a tubular member 36 which extends through the upper wall of and into the main passage. The upper portion of the tubular member is provided with a slightly tapered bore, the upper end of which slightly underlies the bottom of the channel to avoid any projecting edge which would interfere with the entrance of fuel from the deflecting vane. The tapering bore merges into a cylindrical bore 31 in a lower portion of the tubular-member which preferably is of sufficiently smallcross sectional area to produce peripheral surface tension of the liquid fuelflowing therethrough which willeffectively prevent counterflow of air upwardly into the depression chamber during idle and light load operations of the engine.

The tubular member, which is shown .in enlarged detail in Figs. 14 and 15, comprises a cylindrical rod having a conical lower end and is bored axially into but not through its conical lo-wer end. Diametrically opposite sides of the conical lower end portion are cut away thereby providing outlets opening downwardly on opposite sides of a thin flat terminal portion which extends in the general direction of the air current .injthe main passage. The discharge outlet isbelow "the center of the main passage and is-arranged todeliver the fuel downwardly and forwardly beyond the air metering section, so that the air stream in the main passage will carry forward the fuel from the fuel outlet without any tendency to build up back pressure on any portion of the fuel outlet. By reason of this construction the liquid fuel will flow from said outlet in a thin filmover said flat terminal portion during idle and light load operations of the engine, and will tendcto fall or will be carried directly toward the opening between the lower section of the throttle valve and the complementary wall of the main passage.

The throttle valve 38 is of the Butterfly type and desirably is secured to a tapered shaft 39 which is journaled in suitable bosses' lt projecting from the wall of the tubular portion of the casing. The throttle valve preferably presents afiat sur-. face 4! toward the upstream side when in closed position. The upper and lower edgeportions are thin and the valve gradually thickens toward .the middle to present a stream-line contour when the valve is in open position.

when the valve is in closed position the flatsurface is at an angle of about seventy-five degrees to the axis of the tubular portion I of the main passage. When the throttle valve is in idling position its upper edge is substantially in contact with the complementaryupper portion of the tubular wall of the main passage and is ina plane substantially at ninety-degrees or normal with the axis of the main passage. The lower edge of the throttle valve atthe same'time which is nearest its complementary lower portion of the wall of the main passage is in a plane forming an angle of approximately fifteen-degrees with said normal plane, so that when the valve is rotated toward open position the lower edge of the throttle valve moves away from its complementary wall of the passage much more rapidly than its upper edge moves away from its complementary wall. By reason of this arrangement the lower portion of the throttle valve will-concentratethe major portion of the mixture below the throttle valve'and along the lower Wall of the main passage whenin idling and light load-positions, thereby eifectively carrying forward and entraining the fuel in the air stream. As the throttle valve approaches its wide open position the distribution of fuel-air mixture above and below the valve is much more nearly equal in proportion.

The throttle valve 38 is so mounted that when moved from idle toward open position the lower portion thereof moves toward the terminal section of the fuel outlet, thereby facilitating. the entraining and carrying forward of the fuel by the higher velocity of the'air stream-passing beneath the throttle valve during intermediate load operations.

One of the principal objects of the invention is to provide a trustworthy control for regulating the air to fuel ratio from idle to full load opera.- tions of the engine. This is accomplished in the present invention by providing a valve in the main passage to form the normal air metering section thereof and preferably is positioned so that a downstream portion thereof terminates in front of and in proximity to the fuel outlet.

In the construction illustrated in Fig. 1 the air metering valve 42, is fixedly secured to a shaft 43 which is journaled in suitable bearings in bosses 44 and 44x extending from the tubular portion I of the main casing. The shaft 43 preferably has a reduced slightly tapering section 45 which is hammered or pressed snugly into a complementary hole in the valve. The smaller reduced section may be journaled in the boss 44r'or may have an enlarged sleeve 46 secured in place thereon, so that the journaled bearing is of the same size as the other end of the shaft, as illustrated in Figs. 1 and 11. In this method of mounting, valve projections or irregularities of contour on the faces of the valve are avoided and a streamline contour is obtained.

In the particular construction shown in Figs. 1 to 4, the valve 42 is curved in the longitudinal direction of the air passage 2, and is normally positioned at an angle to the longitudinal axis thereof. It has been demonstrated experimentally that if the length of the valve is not substantially greater than its breadth, the turbulence or eddies in the air stream cause an untrustworthy metering of the air in some adjusted positions, and that its length should be more than twenty-five per cent greater than its breadth, so that the valve when in closed position will be at an angle of more than thirty degrees relatively to the longitudinal axis of the main air passage.

The valve is so constructed and positioned that the portion extending from its pivot in a downstream direction presents a convexedly curved surface to the higher velocity portion of the air stream and terminates in front of and in proximity to the fuel outlet. The upstream portion is of relatively shorter length and more abruptly curved, thereby causing the major portion of the higher velocity air stream in the air metering section to pass between the downstream portion of the valve and the adjacent wall of the main passage in adjusted positions.

By reason of the position of the lower end of the valve terminating in proximity to the fuel outlet, the kinetic energy persisting in the air stream from the higher velocity created in the major portion of the air metering section will insure immediate entraining of the fuel in the air stream and the carrying forward of the same to beyond the throttle valve during acceleration and normal load or heavy torque operations of the engine without subjecting the fuel outlet to the more intense fluctuations of the suction head which are present when the fuel is discharged directly into the higher velocity air stream in the air metering section.

It will be noted from the above description that the liquid fuel is led from the fuel supply chamber into the main air stream through a fuel passageway comprising a nozzle with a restricted fuel metering section therein, into a depression chamber above the main passage from which it flows through a tubular section preferably having small enough cross sectional area to provide peripheral surface tension of the liquid passing therethrough which is effective to prevent counterflow of air upwardly into said depression chamber. The tubular section extends continually downwardly from the depression chamber and terminates in the main passage.

An air duct leading from the depression chamber to the main passage is so positioned as to be subject substantially to the suction head existing at the terminal end of the tubular section. In the construction illustrated in Figs. 1 to 4, an air duct 41 is provided with a branch communicating with the main passage beyond the throttle valve and has coordinated branches communicating with the main passage in front of the throttle valve in such manner as to produce a staged reduction in pressure between the pressure in the depression chamber and the pressure existing beyond the throttle valve during idle and light load operations of the engine.

The duct 41 comprises a vertical bore in the wall of a casing 1 which communicates at its upper end with the depression chamber 30 through a recess 48 in a boss 49 in the cover 50 of the fuel supply chamber. The duct 41 continues downwardly and may communicate through a port 5! with the main passage 2 beyond the air metering section thereof and in front of the throttle valve 38. The duct 41 has a branch 52 communicating with said main passage beyond the throttle valve and having a portion of its length 52a: of relatively smaller cross sectional area than that of the port 5|. A plug 53 which is inserted across the air duct 4'! has a cylindrical bore 5 5 of approximately the same size as said air duct 41 continuing somewhat more than halfway through said plug, and serves as a means for restricting said air duct to a small cross sectional area intermediate of the depres sion chamber and the port 5|. The plug has an auxiliary port 56 extending axially thereof and communicating with the main passage 2 at a position where the suction head and disturbing eddy currents will be. substantially equal to those at the discharge outlet of the tubular member 36.

The auxiliary port 56 is of larger cross sectional area than the smaller cross sectional area of said duct restricting means so that the relative arrangement and different cross sectional areas of said duct and ports above described will produce a staged reduction in pressure between the pressure in said depression chamber and the pressure existing beyond the throttle valve during idle and light load operations of the engine and will maintain continuously a low flowing head in the depression chamber at the metering section of the fuel nozzle.

If desired, the plug 53 may be omitted whereby the duct 4! will extend continuously downwardly to the port 5i and will communicate with the main passage 2 through the port 5! in front of the throttle valve and also will communicate with the main passage through the restricted port 52 beyond the throttle valve. As the area of the port 52 relative to the area of the port 5| is correspondingly smaller the low flowing head will be continuously maintained, during idle and light load operations of the engine, in said depression chamber, but this low flowing head will not be as steady during sudden changes in the position of the throttle valve as when a staged reduction of pressure, as above described, is used.

Inasmuch as there is a substantial flow of air into the port 5| when the low flowing head is being maintained, the port 5| should be so positioned, in the wall of the main passage 2, that fuel from the discharge outlet will not be drawn the member Gl engages a suitable abutment.

into it during idle and light load operations of the engine. In the preferred construction where a staged reduction in pressure is produced, this port is preferably placed appreciably above the center of the main passage and appreciably forward of the fuel outlet; and the port 56, through which a relatively much smaller quantity of air enters, preferably is positioned in the side wall of the main passage where the suction head and disturbing eddy currents will be substantially :equal to those existing at the fuel discharge out- As an alternative construction, where the air metering valve 42 is moved in coordination with the movement of the throttle valve 38 during idle and" light load operations of the engine as hereinafter more fully set forth, the plug 53 may be employed with the duct restricting means 55 omitted, in which case the duct 41 will communicate through the port 56 directly with the main passage 2 and will remain free of fuel during idle and light load operations of the engine and will be subject to substantially the same suction head and disturbing eddy currents existing at the fuel discharge outlet so that momentary or sudden changes in the suction head in the air metering section are not communicated directly to the fuel nozzle.

Inasmuch as air cleaners are almost universally used at the inlet to the main passage of the carburetor, an air vent desirably is employed to equalize the pressure existing in front of the air metering section in the main passage and the pressure existing above the liquid in the supply chamber. In the present construction, the vent comprises a bore 51 extending upwardly and thence abruptly downwardly in a boss projecting from the cover of the fuel supply chamber. The downwardly extending section of the bore 5'! communicates with the upper end of a bore 58 which extends downwardly and communicates at its lower end with the main air passage in front of the air metering section thereof.

One of the objects of the invention is to provide regulating means for adjusting the air metering valve 42 to-d-etermine positively and with precision the area of the air metering section and preferably includes thermostatic means responsive to changes in temperature of the air entering the carburetor and also may include barometric means responsive to changes in the absolute pressure of the atmosphere in which the carburetor is placed.

In the particular construction illustrated in Figs. 1 to 4, an arm 59 is secured to the end portion of the shaft 43 projecting beyond the cylindrical section of the carburetor casing. The arm 59 preferably is bored to receive the shaft 43 and is slotted and is clamped thereon by a screw 592:. A yoke 60 in the form of a channel is pivotally mounted on the shaft 43 with the inside walls of the channel embracing the edges of the arm 58. A member 6! is suitably secured in the bottom of the channel-shaped yoke 65, as by a rivet 62, and the upper face of the other end of As illustrated in Fig; 4, the abutment comprisesa hook-shaped member 63 which is secured to a sylphon bellows 64, the opposite end of which is fixedly secured to a bracket mounted on the casing I. A screw 65, which is mounted in the arm 58 and engages at its end the under face of themember 5|, provides means for adjusting the arm 58 relative to the member 6 l.

The adjusting screw 65 desirably is provided with a cylindrical notched head 6.1 and suitable means are provided for holding the screw inadjusted positions. As illustrated, the holding means comprises a; spring member 58 which is secured at one end to the arm 58 by the screw 59x,

with the other end suitably positioned to engage the notches in the periphery of the head 51. The end of the screw 66 is maintained continuously in an'engagement with the under face of the member 6| by a spring 69, the lower end of which air metering section in the main passage, and

upon decrease in the temperature of the air to cause the metering valve to restrict the air metering section of the main passage. Adjustment of the screw 66 permits initial position'of'the air metering valve to determine positively and with precision the area of the air metering section to suit the flow of fuel through the fuel orifice to the particular viscosity of the fuel in use and also to suit the idiosyncrasies of the intake system to which the carburetor is attached.

If the barometric pressure of the atmosphere decreases, the sylphon bellows 5 1 will expand thereby permitting the abutment 53 to move upwardly and in turn permitting the valve 42 to increase the area of the air metering section. This is distinctly desirable as an altitude control since as the barometric pressure decreases, the volume of the air perpound'increases. Thus the increase in the area of the air meteringsection tends to maintain a better volumetric efficiency of the engine as compared with any structure where barometriomeans are employed to control the fuel metering area. 7

Desirably, means are provided to enable the air metering valve to be utilized as a choke valve when starting the engine. In the present construction as shown in Fig; 4 a lever H is secured to the arm 58 in any suitable manner as by the screw 59:0. The upper end of the lever "H has attached to it a flexible member, such as a chain 12, which is connected toa control rod 13 extending to the dash of the automobile. The fleX-' ible member 12 is normally in a slack condition to permit automatic regulation of the metering valve 42 through the thermostatic or barometric mechanisms above described.

By reason of the construction above described, a carburetor for an internal combustion engine is provided having a main passage, a valve therein restricting its crOss sectional area to provide the normal air metering section thereof, remaining constant in area irrespective of changes in load during idle, light and medium load operations of the engine, having means beyond said air metering section to control the flow of air therethrough with means effective by the suction of the engine for delivering fuel tosaid main passage comprising a fuel supply chamber, a fuel passageway leading therefrom to the main passage, having a restricted fuel metering section through which all the fuel supplied to the main passage shall pass during idle, light and medium load operations of the engine, with an air duct leading from the depression chamber. through the main passage in combination with coordinating air ducts effective during idle and light load operations of the engine to produce continuously a low flowing head at the fuel metering section to supplement the flow induced by the suction in the air metering section together with thermostatic and/or barometric means acting on said air metering valve to change the area of the air metering section of the main passage in response tochanges in temperature and/or atmospheric pressure .and adjusting means to initially position the air metering valve relatively to the thermostatic and/or barometric controlling means.

The invention is illustrated in Fig. 5 as applied to a down draft carburetor. In this construction the tubular portion 14 of the carburetor casing extends downwardly at a suitable angle tothe vertical and is provided at its lower end with a flange 14 adapted to be bolted or otherwise secured to a complementary flange upon the inlet manifold of an engine. The casing 16 of the fuel supply chamber is mounted upon or preferably formed integral with the tubular portion 14 of the casing.

The fuel supply chamber may be, and desirably is, the same except as to position of mounting as in the construction disclosed in Figs. 1 to 4. The means for supplying fuel to the main passage of the tubular portion of the casing, the air metering valve, are the same and are designated by the same numerals as in Figs. 1 to 4. The throttle valve 38a: is of the butterfly type and, as illustrated, is secured to a flattened surface of a shaft 39:): which is journaled in bosses projecting from the wall of the casing, as heretofore described. The upper portion of the valve 383: is thickened to delay opening while the lower portion of the valve is bent in an upstream direction whereby the mixture flow is concentrated along the lower wall of the main passage during idle and light load operations of the engine. The mechanisms for regulating with precision the cross sectional area of the air metering section are the same as heretofore disclosed in Figs. 1 to 4 and are not, therefore, illustrated. The operation of the modifled construction illustrated in Fig. 5 is the same as that heretofore described.

Another embodiment of the invention is disclosed in Figs. 6 and '7 in which the air metering section of the main passage is of rectangular cross section in which the air metering valve is mounted near the inlet and extends forwardly between parallel walls with its terminal end in proximity to the fuel discharge outlet.

In this construction the tubular portion 11 of the casing is of rectangular form at the air metering section and has vertical walls 18 and I9 and a flat lower wall 80. The air metering valve 8| is of such width as to fit between the

walls

18 and 79 with a reasonable tolerance and is connected at its front end to a shaft 82 which is mounted in the upper portions of the

walls

18, 19 of the casing in such manner as to seal the passage against the entrance of air over the top of the valve. The lower wall of the tubular section has a downwardly inclined portion extending from the rectangular portion of the passage and merging into a cylindrical inlet section 84 adapted to be connected to the usual air cleaner.

The tubular portion of the casing has at its opposite end a cylindrical section 85 which contains a throttle valve 86 secured to a suitable shaft 81 extending through the wall thereof. The portion of the casing intermediate of the cylindrical section 85 and the portion between the rectangular air metering section and the cylindrical portion 85 merges from the rectangular section into the cylindrical section thereby providing a downwardly inclined wall 88 extending into proximity to the lower end of the throttle valve. The merging of the side walls of the rectangular air metering section into the cylindrical portion is preferably more rapid in'proximity to the air metering section than beyond as illustrated by the shading.

The casing 89 of the fuel supply chamber is superimposed upon and is preferably integral with the tubular portion of the casing and is similar in construction to' that heretofore disclosed in Figs. 1 to 4. In this construction, the fuel supply chamber and the means for delivering fuel therefrom to the main air passage are similar to those illustrated in Figs. 1 to 4 and similar parts are designated by the same numerals. The lower end of the deflecting vane 35 communicates with the tubular section 36:16 which differs from the tubular section 36 shown in Figs. 1 to 4 in that the lower end of the tubular member 36a: is cut at an angle to the axis thereof with the upstream portion longer than the downstream portion whereby the fuel is discharged downwardly and forwardly therefrom without any tendency of the air stream to build up back pressure against any part of the fuel discharge outlet. In the construction disclosed in Figs. 6 and '7, all of the air flowing through the main passage is concentrated beneath the air metering valve into an undivided stream in the air metering section and inasmuch as the air metering valve terminates in front of and in proximity to the fuel outlet, the kinetic energy in the air stream resulting from the high velocity induced in said air metering section effects immediate entraining of the fuel in the air stream without subjecting the fuel outlet to the more intense fluctuations in the suction head which are present when the fuel is discharged directly into the air stream in the air metering section.

Another embodiment of the invention is illustrated in Figs. 8, 9, and 10, in which the fuel supply chamber is located below the main air passage instead of above it as in the embodiments of the invention heretofore described. In this construction the carburetor casing consists of a cylindrical portion 90 which desirably is inclined downwardly relative to the horizontal and has an enlarged cylindrical end 9| adapted to be connected to the usual air cleaner with a tapered portion merging therefrom into the cylindrical inlet portion 90. The casing is provided at its other end with a peripheral flange 92 provided with suitable bolt holes for connection to a complementary flange 93 of the continuing air passage in the form of an elbow-94 which communicates with the inlet end of the manifold of the engine.

In this construction the cover 95 of the fuel supply chamber is formed integral with the tubular portion 90 of the carburetor casing. The fuel supply chamber 96 comprises a reservoir of rectangular form having

vertical walls

91 and 98 provided with suitable bosses 99 which are secured by screws or otherwise to complementary bosses on the cover 95. The fuel supply chamber is provided at one end with an extension I00, the upper wall l0l of which is provided with an aperture having a screw threaded wall which receives an adjustable valve casing I02 which preferably carries a cylindrical inlet valve seat section I03 for an inlet valve. The casing I02 has an integral enlarged head i 04 preferably of circular form and provided centrally with a smaller upwardly extending rectangular boss I05 adapted to be engaged by a suitable tool for adjusting the valve casing. A fuel inlet fitting surrounds the valve casing and comprises a vertical cylindrical portion I06 which is interposed between the head If! of the valve casing and a surfaced portion of the upper wall IilI with a horizontal tubular section It? adapted to be secured to the suitable fuel inlet pipe. The cylindrical section I06 is provided with an enlarged bore I98 extending downwardly from the top nearly to the bottom. The valve casing IE2 is provided with the enlarged bore I E13 with suitable ports I09 to permit the entrance of fuel from the fitting into the valve casing and thence through the valve seat memher.

A conical fuel regulating valve III) engages the lower end of the valve seat member I03 and is provided beneath its conical end with a cylindrical portion of less diameter than the inner diameter of the casing. Suitable ports are provided in the wall of the casing opposite the cylindrical portion to permit free exit of fuel into the supply chamber 96. The lower portion of the valve which constitutes the valve stem III is desirably of cylindrical form slidably to fit within the valve casing and preferably has its walls slabbed off to reduce friction between the valve stem of the wall of the casing and to permit the passage of some of the liquid into the supply chamber. The lower end of the valve stem is spherically rounded and engages a convex surface upon a control lever I I 2 in proximity to the pivot or fulcrum I I3 thereof. The control lever II 2 desirably is of thin channel-shaped metal and extends beneath and is secured to rectangular floats H4 and H5, which are positioned on opposite sides of the fuel nozzle H6. The nozzle may be and desirably is of the same general construction as that shown in Fig. l, and comprises an upwardly inclined cylindrical tubular portion having an enlarged, preferably hexagonal, portion H7, and a screw threaded terminal portion IIB which passes through and engages complementary screw threads in the lower wall of the cylindrical casing SIB, a. fibre washer being interposed between the enlarged portion In and a surfaced face on the casing and acting when the nozzle is screwed in place to prevent leakage from the supply chamber into the main passage.

The lengthwise wall of the nozzle gradually and progressively converges toward its outlet to form a restricted fuel metering section IIQ through which all the fuel shall pass during idle, light and normal load operations of the engine. The floats H4 and H5 are secured to the lever II2 and are located one on either side of the said fuel metering section of the nozzle and at different distances from the pivot H3 of the lever I I2. The float H5 which is more remote from the pivot is of smaller horizontal cross section area than is the float I I4 and their relative cross sectional areas are such as to cause the actuating moment about the pivot I I3 relative to the valve 3 ID to remain substantially constant for a predetermined level of liquid relatively to said fuel metering section, irrespective of changes in velocity or inclination of the supply chamber in the longitudinal direction of said lever.

Preferably the middle portions of the side walls 9! and 98 respectively are made reentrant so that their wall sections I2! and I22 are relatively close to the fuel nozzle for the purpose of reducingthe total free surface of the liquid in the supply chamber and also to act as a sort of baflie toprevent excessive agitation of the surface of the liquid in proximity to the fuel nozzle. It is desirable to keep the free surface of the liquid small in the present construction where all fuel passes through the fuel metering section I I9 during idle and light load operations of the engine so that when the level of the fuel during heavy load operations of the engine drops, the return to the normal idling level is rapid if the load suddenly be decreased.

The normal level of the liquid in the supply chamber may be accurately regulated by placing a suitable shim or shims in the form of thin gaskets I23 between the lower end of the cylindrical wall I06 and the surfaced face of the upper wall In! of the extension of the fuel supply chamber. 7 a

The throttle valve which is located in the tubular section of the carburetor casing beyond the fuel nozzle is mounted upon a shaft I25 which is journaled in bosses projecting from the wall of said casing, as heretofore described. The throttle valve desirably is of the same construction as that illustrated in Figs. 1 to 4 having a flat upstream face I 25, with thin upper and lower edges and thickened toward the center to form a streamline contour on the lower side of the valve when in open position. Desirably a shallow groove I28 extends from the fuel nozzle along the lower wall of the tubular casing 99 to a point beyond the lower end of the throttle valve when. in idling position for the purpose of attenuating any drop or globule of fuel which may tend to form at the lower edge of the fuel nozzle, thereby causing smooth and continuous flow of fuel to beyond the throttle valve during idle and light load operations of the engine. 7

In the construction shown in Figs. 8, 9, and 10, as in that disclosed in Figs. 1 to 4, one ofthe principal objects of the invention is to provide a trustworthy control for regulating the air to fuel ratio from idle to full load operations of the engine. This is accomplished in a similar manner by providing a valve in the main. passage to form the normal air metering section thereof and preferably is positioned so that the downstream. portion of the valve terminates in front of and in proximity to the fuel outlet. In this construction. an air metering valve I29 is fixedly secured to a shaft I353 which is journaled in suit able hearings in the bosses HI and I32 extending from the tubular portion 99 of the casing.

The connection of the valve I29 to its shaft I36 desirably is similar to that previously described and illustrated in Fig. 1 1 in respect to the air metering valve 42.

In the construction shown in Figs. 8, 9, and 10, the shaft I39 of the air metering valvel29 has secured to it outside of the casing an arm I33 which is bored to receive the shaft and is slotted and clamped thereon by a screw I 34. A yoke I35 in the form of a channel ispivotally mounted on the shaft I3 with the inside walls of the channel embracing the edges of the arm I33. A bimetallic thermostatic member I 36 is suitably secured in the bottom of the channel shaped yoke I35, as by a rivet I31, and the upper face of the other end of the member I36 engages a suitable abutment to limit the upward movement thereof. A screw I38 which is mounted on the arm I33 provides means for adjusting the arm I 33 relatively to the thermostatic member I35. The adjusting screw desirably is provided with a cylindrical notched head I39, and suitable means may be provided for holding it in adjusting position, as hereinbefore described.

A spring I40, the lower end of which is secured to an eye in the lever of the arm I33 and the upper end of which is secured toa suitable anchorage upon the casing (not shown), maintains the adjusting screw continually against the lower face of the thermostatic member and holds the thermostatic member against said abutment.

The abutment is preferably in the form of a cam I4I which is secured to the shaft I25 of the throttle valve. The cam preferably is bored to receive the shaft I25 and is slotted and clamped thereon by a screw I42. By reason of this connection, adjustment of the cam relatively to the throttle valve upon the shaft I25 can be readily made.

The contour of the face of the cam I43 is such that when the throttle valve is in the middle range of its movement the position of the thermostatic member remains substantially stationary, thereby maintaining the metering valve I29 in normal position throughout a substantial movement of the throttle valve during medium load operations of the engine. The contour of the cam is such as to move said air metering valve from said normal position at a gradual and progressively increasing rate toward a more restrictive air metering position as the throttle valve approaches idling position. Inasmuch as the rate of movement must be relatively much greater as the throttle valve approaches idling position, the main lobe of the cam preferably should extend in a direction to progressively contact with the thermostatic member I35 nearer and nearer to the shaft of the air metering valve, thereby shortening the effective operating length of the thermostatic member as the effective operating length of the cam increases.

There is another important feature inherent in this construction in that the effective length of the main lobe of the cam may be varied if its contour is changed accordingly without changing the relative movement of the thermostatic member as the throttle valve approaches idling position. In other words, the operating lengths of the thermostat at and near idling positions can be changed. This permits reasonable leeway in the positioning of the air metering valve in response to changes in temperature during idling and light load operations of the engine. In this construction, a certain amount of sliding action between the face I43 of the cam and the upper surface of the member I36 will tend to abrade the thermostatic member. To prevent the wearing of the thermostatic member, a thin, flexible, wear-resisting strip I44 is positioned between the thermostatic member and the cam, and may be conveniently secured between the thermostatic member I36 and the bottom of the channel I35 by the rivet I31.

In some installations it may be desirable to increase the richness of the mixture slightly at wide-open position of the throttle, and in the present construction this is conveniently accomplished by providing the cam I4! with a small lobe I45 which when the throttle valve approaches wide-open position will engage the upper surface of the member I35, thus depressing the same, thereby slightly reducing the area of the air metering section.

In some installations where operating conditions are fairly steady and sudden accelerations are not imperative, the throttle valve may be mounted to swing in the opposite direction from that shown in the preceding figures, as illustrated in Figs. 12 and 13.

The carburetor construction illustrated in Fig. 12 is of the same general construction as that shown in Figs. 1 to 4 comprising a casing I having a main passage 2 inclined downwardly which in this case communicates with an elbow I45 which extends downwardly and adapted to be connected to a downdraft manifold. As shown in Fig. 12, the downwardly curved elbow extends into the upper portion of an energy-dissipating section of the mixture receiving chamber of a special manifold having a lower distributing section from which the fuel-air mixture is distributed to the several cylinders of the engine, it being found in actual practice that the special manifold of this construction is desirable inasmuch as the precision attained with the present carburetor construction is such that a refinement in manifold design is desirable to obtain the maximum both in eificiency and in smoothness of operation. The elbow I48 is provided at its end with a flange I41 which is secured by suitable screw bolts to the flange 4 of the carburetor casing. In this construction the air metering valve I48 desirably is of streamline construction adapted to concentrate the major portion of the air flow along the lower wall of the main passage 2.

The throttle valve I49, which is pivotally mounted upon the shaft 39, is adapted to swing in the opposite direction from that shown in Figs. 1 to 4. This valve is of the same streamline construction as that shown in Fig. 1 and will concentrate the flow of fuel to air mixture beneath its lower portion during idle and light load operations of the engine.

In this construction the branch 52 of the air duct 4? leads upwardly instead of downwardly and communicates with the main passage through a restricted portion or port I50 beyond the throttle valve.

The construction illustrated in Fig. 13 corre sponds to that shown in Figs. 8, 9, and 10, except that the air metering valve and the throttle valve swing in opposite directions.

In this construction the casing 95 through which the main air stream passes is inclined downwardly and communicates with a downwardly curved elbow 94. The fuel supply chamber 95 is secured to a cover 95 which is formed integral with the tubular portion 99 of the carburetor casing.

In this construction the throttle valve II is secured to the shaft I25, and the controlling mechanism therefor is so constructed that the lower portion of the throttle valve in moving toward open position swings in the direction of movement of the air stream.

The air metering valve I52 is so mounted upon the shaft I30 that its lower end extends in an upstream direction instead of the downstream direction shown in Fig. 8.

The mechanism for controlling the positions of the air metering valve relative to the throttle valve shown in Fig. 13 is similar in all respects to that shown and described with reference to Figs. 8 to 10, except that the cam MI is secured to the throttle shaft I25 in an upside-down position and must have a slightly different contour I43 in order to compensate the slightly different relation existing between the air metering valve and the throttle valve when swung in opposite di- 433, the yoke I35, the bimetallic thermostatic member I 36, and the adjusting screw I38, and the wear-resisting strip M4, may be the same. as the construction shown and described in Figs. 8 to 10, except that the positions and movements thereof are in the reverse direction and in'that the spring M0 is secured to a lug I53 extending outwardly from the wall of the fuel supply chamher.

In the operation of the invention as disclosed in all the adaptations herein illustrated, an air metering valve is providedto restrict a portion of the main passage to provide the normal air metering section thereof Where the air is metered relative to the fuel; the fuel is delivered into the main passage near the downstream end of the air metering valve and the throttle valve is located beyond the fuel inlet. The fuel is delivered from the discharge outlet forwardly and the arrangement is such that the air stream between the air metering valve and the throttle valve moves across the fuel outlet without any tendency for the velocity of the air stream to build up a back pressure on any part of the fuel discharge outlet.

In all the constructions disclosed herein fuel is delivered from the fuel supply chamber through a restricted fuel metering section in which the fuel is metered relative to the air.

air metering section means are provided for producing continuously a flowing head at said fuel metering section to coordinate the rate of the fuel flow with that of the quantity of air flow through the air metering section during idle and light load operations of the engine to insure the predetermined fuel-air ratio.

In all the constructions means are provided for accurately positioning the air metering valve, preferably including thermostatic means to determine positively and with precision the area of the air metering section.

In the constructions disclosed in Figs. l-"to 7 and 12, the float chamber is mounted above the main passage of the carburetor and the fuel is delivered from the fuel supply chamber through an upwardly inclined nozzle having a fuel metering section into a depression chamber from which it flows continually downwardly through a tubular section of sufiiciently small cross sectional area to produce peripheral surface tension of the liquid fuel passing ther'ethrough effective to prevent counterflow of air upwardly into said depression chamber during idle and light load opl erations of the engine.

During medium and heavy load operation of the engine the fuel' emerges from the nozzle in the form of a jet which impinges against the curved surface of the deflecting vane and is thereby turned downwardly into the tubular section which leads downwardly into the main passage and delivers the fuel into the air stream in a manner above described.

In the constructions disclosed in Figs. 8 to 10 and 13, the fuel supply chamber is located below the main passage of the carburetor and the fuel is delivered therefrom through the fuel metering section of the nozzle directly into the air stream in a manner heretofore set forth.

The essentials of the present invention reside quite as much in the cooperative relation between a number of coordinating parts as in thenovel construction of particular details. The fuel level must be regulated with a degree of precision not attainable when the float chamber is positioned at one side of the main passage. In all the com structions herein disclosed the fuel supply chamher is centrally located relatively to the main 7 passage, either below or above.

This arrangement of the fuel nozzle in the central portion of the fuel supply chamber between float sections on either side is imperative not only for the reason that the float levelmay change due to variations in inclination of the carburetor; but in operating an automobile under traffic conditions the sudden acceleration or deceleration of the car, as well as swerving or turning the car quickly either to the right or the left, may cause a banking of the fuel which is even more serious than normal changes in the inclination of the carburetor.

The total arrangement of parts necessary to deliver liquid fuel into the main air stream, in proper proportions at all times, is such that at no time, even during idle and light load operations of the engine, is a small portion of theair passing through the carburetor required to pickup, accelerate and carry forward the entire fuel supply.

These cooperating elements make'it possible to provide the regulating means which accurately positions the air metering valve so as to determine with precision the area of the air metering section, thereby providing a ,unit control to vary the ratio of fuel to air from idle to full load operations of the engine.

This unit control permits a single adjustment which from a practical standpoint is capable of being set by an ordinary operator with a degree of precision quite unattainable even by an experienced engineer, without an extended period of tests, where a plurality ofcoordinated adjustments are required to properly proportion the fuel to air mixture over the whole range of operations of the engine. This unit control also permits the application of a single thermostat to regulate the ratio of fuel to air in a carburetor thereby enormously increasing the practicalvalue of the thermostatic regulation. I

It will be understood that the particular embodiment of the invention disclosed herein is of an illustrative character and is-not restrictive, and that various changes in form, construction and arrangement of parts may be made within the spirit and scopeiof the following claims;

Having thus described the invention, what is claimed as new, and desired to be secured by Letters Patent, is: a

1. A carburetor for an internal combustion engine having a main passage, an air metering valve therein restricting its cross sectional area to provide the normal air metering section thereof, a throttle valve beyond saidair metering section to control the flow therethrough,-the bottom of said main passage being inclineddownwardly from said air metering valveto said throttle valve, means eifective by the suction of the engine for deliveringliquid fuel to said main passage intermediate of said valves comprising a fuel supply chamber, a fuel passageway leading from said supply chamber to said main passage having a restricted fuel metering section through which all the fuel shall pass during idle, light and medium load operations of the engine, means in said supply chamber to maintain the liquid level therein with precision slightly below said restricted fuel metering section, and means effective during idle and light load operations of the engine for producing continuously a flowing head at said metering section effective to coordinate the rate of flow of fuel with that of the quantity of air flowing through the air metering section.

2. A carburetor for an internal combustion engine having a main passage, an air metering valve therein restricting its cross sectional area to provide the normal air metering section thereof, a throttle valve beyond said air metering section to control the flow therethrough, the bottom of said main passage being inclined downwardly from said air metering valve to said throttle valve, means effective by the suction of the engine for delivering liquid fuel to said main passage intermediate of said valves comprising a fuel supply chamber, a fuel passageway leading from said supply chamber to said main passage having a restricted fuel metering section through which all the fuel shall pass during idle, light and medium load operations of the engine, means in said supply chamber to maintain the liquid level therein with precision slightly below said restricted fuel metering section, means effective during idle and light load operations of the engine for producing continuously a flowing head at said metering section effective to coordinate the rate of flow of fuel with that of the quantity of air flowing through the air metering section, and means for adjusting said air metering valve to determine positively and with precision the area of the air metering section, thereby acting as a unit control to change the ratio of fuel to air from idle through light and heavier load operations of the engine.

3. A carburetor for an internal combustion engine having a main passage, an air metering valve therein restricting its cross sectional area to provide the normal air metering section thereof, a throttle valve beyond said air metering section to control the flow therethrough, the bottom of said main passage being inclined downwardly from said air metering valve to said throttle valve, means effective by the suction of the engine for delivering liquid fuel to said main passage intermediate of said valves comprising a fuel supply chamber, a fuel passageway leading from said supply chamber to said main passage having a restricted fuel metering section through which all the fuel shall pass during idle, light and medium load operations of the engine, means in said supply chamber to maintain the liquid level therein with precision slightly below said restricted fuel metering section, means effective during idle and light load operations of the engine for producing continuously at flowing head at said metering section effective to coordinate the rate of flow of fuel with that of the quantity of air flowing through the air metering section, and thermostatic means acting on said air metering valve to change the area of the air metering section in response to changes in temperature.

4. A carburetor for an internal combustion engine having a main passage, an air metering valve therein restricting its cross sectional area to provide the normal air metering section thereof, a throttle valve beyond said air metering section to control the flow therethrough, the bottom of said main passage being inclined downwardly from said air metering valve to said throttle valve, means effective by the suction of the engine forv delivering liquid fuel to said main passage intermediate of said valves comprising a fuel supply chamber, a fuel passageway leading from said supply chamber to said main passage having a restricted fuel metering section through which all the fuel shall pass during idle, light and medium load operations of the engine, means in said supply chamber to maintain the liquid level therein with precision slightly below said restricted fuel metering section, means effective during idle and light load operations of the engine for producing continuously a flowing head at said metering section effective to coordinate the rate of flow of fuel with that of the quantity of air flowing through the air metering section, thermostatic means acting on said air metering valve to change the area of the air metering section in response to changes in temperature, and adjusting means to initially position said valve relatively to said thermostatic means.

5. A carburetor for an internal combustion engine having a main passage, an air metering valve therein restricting its cross sectional area to pro vide the normal air metering section thereof, a throttle valve beyond said air metering section to control the flow therethrough, the bottom of said main passage being inclined downwardly from said air metering valve to said throttle valve, means effective by the suction of the engine for delivering liquid fuel to said main passage intermediate of said valves comprising a fuel supply chamber, a fuel passageway leading from said supply chamber to said main passage having a restricted fuel metering section through which all the fuel shall pass during idle, light and medium load operations of the engine, means in said supply chamber to maintain the liquid level therein with precision slightly below said restricted fuel metering section, means effective during idle and light load operations of the en gine for producing continuously a flowing head at said metering section effective to coordinate the rate of flow of fuel with that of the quantity of air flowing through the air metering section, and barometric regulating means for adjusting said air metering valve to determine positively and with precision the area of the air metering section in response to changes in pressure of the ambient air.

6. A carburetor for an internal combustion engine having a main passage, an air metering valve therein restricting its cross sectional area to provide the normal air metering section thereof, a throttle valve beyond said air metering section to control the flow therethrough, the bottom of said main passage being inclined downwardly from said air metering valve to said throttle valve, means eifective by the suction of the engine for delivering liquid fuel to said main passage intermediate of said valves comprising a fuel supply chamber, a fuel passageway leading from said supply chamber to said main passage having a restricted fuel metering section through which all the fuel shall pass during idle, light and medium load operations of the engine, means in said supply chamber to.maintain the liquid level therein with precision slightly below said restricted fuel metering section, and means effecthrough which; all the fuel shall pass during idle,

tive; during idle and: light q load; operations: of: the engine for'producing continuously a flowing, head;

at said, metering section effective to coordinatethe rate of flow of ,fuel with: that: of: the quantity of air flowing through the air metering section,

said throttle valve being constructedandmounted to concentrate the flow of; fuel-air; mixture beneath it when in idle, and light: loadoperating. positions.

7. A carburetor for an internal combustion en gine having a mainpassage, an airmeteringvalve thereinrestricting its cross; sectional areato prO..- videthe normal air metering section thereof, at

throttle valve beyondsaid air'metering sectiontot. ,control the flow therethrough-, the bottom of said.

main passage being inclined downwardly" from said air; metering valve to said throttle valve, means effective by the suction of the enginefor delivering liquidfuel tosaid main passage intermediate of' said valves comprising a fuel supply chamber, a fuel passagewayleading from said supply chamber to said main passage having a restricted fuel metering section through which all the fuel-shall pass, duringidle, light and me-r dium loadoperations of the engine, means in said, supply chamber to maintain the-liquid level therein with precision slightly below said restricted fuel meteringsection, and means effective-during idle and light load operations, of the engine for producing continuously a. flowing head at, said metering sectionv effective to coordinate the-rate of flow. of fuelwith that of the quantity, of air. flowing through the air metering section, said. throttle valve being constructed and, mounted to concentrate the flow of" fuel+air mixture beneath it when in idle andlight load operating: positions, and anelbow forminga continuation of said main passage beyond and adjacentrtosaid'. throttle valveacting to divert the fuel andair mixture from saidmain passage toward a: verticaldirection.

8. A carburetor for an internal com-bustionengine having a main passage; an air metering-valve therein restricting its cross sectional areatoprovide the normal air metering. section thereof, a.

throttle-valve-beyond said air metering-sectiontocontrol the flow'therethrough, the bottom of: said main passage being inclined; downwardly from.

said air metering valve to said throttle valve;. means effectiveby the suction Of'QthG, engine for delivering liquid fuel into the lower portion of. the main: passage near the downstream, endof'the air, metering valve and in proximity; tothe, throttle valve, comprising a fuelsupply'chamber, a fuel passageway leading from said; supply chamber to said main'passagehaving a restricted: fuel metering section through which allthe; fuel shall pass during idle, light and medium load; opera? tions of the engine, means in saidsupply chamber to maintain the liquid level therein with precision slightly below said restricted fuel, metering section, and means effective during-idleand light load operations of the engine for producing continuously a flowing, head at said metering section'- efiective to coordinate the rate of flow offuelwith; that of the quantity of air flowing through the air meteringsection.

9. A carburetor-for an internal combustion enginehaving a downwardly inclined main passage:

through which the air stream: shall pass, means for delivering liquid fuel to saidair stream comprising a fuel supply chamber, a fuel passagewayleading, therefrom, having a restricted fuel me.- tering section remaining constant in area and light? and; normal loadmperationsof: the engine and having a fuel;outlet infsaid, main passage, an, air metering: valve in said, mainpassage to provide the normal air metering. section thereof having a;.portion extending in a downstream; di-

rection andterminating infrontof and in proximity. to said fuel. outlet, and a; throttle valve located beyond: and in proximity to said; fuel outlet, whereby the kinetic energy persisting; in the-air stream from the-high velocity created in the air, metering section will insure immediate entraihingof the fuelin the air stream and. the carrying forward of the same beyondthe throttle valve during acceleration and normal load or heavy torque operations of the engine.

1021A. carburetor for an. internal. combustion engine having a downwardly inclined main passage through which the air stream shall pass, means for: delivering liquid fuel to-said-airstream comprising: a fuel supply chamber, a fuel passageway leading therefrom having a restricted fuel metering section remaining constant in area and-through which all the fuel shall pass during idle, light and normal loadoperations of the engine and having a fuel outlet in said main passage, anair metering valvein said main passage to provide the normal air metering sectionthereof' having a portion extending in a downstream-direction and terminating in front ofand in proximity to said fuel outlet, and a throttle valve located beyond and in proximity to said fueloutlet, being constructed and mounted to concentrate'the flow-of fuelair-mixture beneath it during idle and light load operations of the engine;

1l-. A- carburetor foran internalcombustion enginehaving a downwardly inclined: main passage through which the air stream shall pass, a throttle valve in said mainpassage, means for delivering liquid fuel I to said air stream comprising a fuel supply chamber, a fuelpassageway leading therefrom having a restricted fuel metering section remaining constant in area and through which all the fuel shall pass during idle, light and normal load operations of the engine and having a fueloutlet in said main passage, an air metering valve in said mainpassage to provide the" normal air metering section thereof having a portionextending in a downstream direction and terminating in front of and in proximity to said fuel outlet, and regulating means for adjusting said air metering-valve to'determine positively and with precision'the' area of the air;

metering section.

12. A carburetor for an internal combustion engine havinga downwardly inclined main passage throughwhich the airstream shall pass, a throttleval-vein said' main passage, means for delivering liquid fuel to said air stream comprising a fuel supplychamber, a fuel passage leading therefrom having a restricted fuel metering section remaining constant in area and through which all the fuel shall pass during idle, light and normal load operations of the engine and having afuel outlet, insaid main passage, an air metering valve in said main passage to provide the normal air metering section thereof having a portion extendingin a downstream direction and terminatingin front of and inproximity to said fuel outlet, and thermostatic regulating means for adjusting said valve to: determinepositively, andtwith precision the area of theair metering section in response-to changes inr-temperature. 7

13; A carburetor for an internal combustion engine having a main passage, an air metering valve therein restricting its cross sectional area to provide the normal air metering section thereof, a throttle valve beyond said air metering section to control the flow therethrough, the bottom of said main passage being inclined downwardly from said air metering valve to said throttle valve, means effective by the suction of the engine for delivering liquid fuel to said main passage intermediate of said valves comprising a fuel supply chamber, a fuel passageway leading from said supply chamber to said main passage having a restricted fuel metering section.

through which all the fuel shall pass during idle, light and medium load operations of the engine, means in said supply chamber to maintain the liquid level therein with precision slightly below said restricted fuel metering section, and means to maintain said air'metering valve in normal position throughout a substantial movement of said throttle valve during the medium load operations of the engine, and to move said air metering valve from said normal position at a gradually and progressively increasing rate toward a more restricted air metering position as the throttle valve approaches idle position, thereby effectively to coordinate the rate of flow of fuel with the quantity of air flowing through the air metering section.

14. A carburetor for an internal combustion engine having a main passage, an air metering valve therein restricting its cross sectional area to provide the normal air metering section thereof, a throttle valve beyond said air metering section to control the flow therethrough, the bottom of said main passage being inclined downwardly from said air metering valve to said throttle valve, means effective by the suction of the engine for delivering liquid fuel to said main passage intermediate of said valves comprising a fuel supply chamber, a fuel passageway leading from said supply chamber tosaid main passage having a restricted fuel metering section through which all the fuel shall pass during idle, light and medium load operations of the engine, means in said supply chamber to maintain the liquid level therein with precision slightly below said restricted fuel metering section, means for regulating said air metering valve operable in conjunction with the throttle valve to maintain said air metering valve in normal position throughout a substantial movement of said throttle valve during medium load operations of the engine and to move said metering valve from said normal position at a gradually and progressively increasing rate toward a more restricting air metering position as the throttle valve approaches idle pro-t sition.

15. A carburetor for an internal combustion engine having a main passage through which the air stream shall pass, a throttle valvein said main passage having a shaft extending through the wall thereof, a pivoted air metering valve in said main passage, in front of said throttle valve to provide the normal air metering section thereof, having a shaft rigid therewith extending throughthe wall of said passage the bottom of said main passage extending downwardly toward said throttle valve, means for delivering fuel to said main passage intermediate of said valve, means for regulating said air metering valve comprising an arm fixedly connected to the shaft" of said air metering valve outside of said passage, a thermostatic member pivotally mounted at one end relatively to the shaft of saidair metering valve, a'cam secured to the shaft of said throttle valve engaging said member at progressively decreasing distances from said pivot as the throttle is moved toward idle position, yieldable means tending to'force said arm into contact with said member and to hold said member against said cam, and shielding means permitting free action of said thermostatic member while protecting the same from the abrading action of said cam.

16. A carburetor for an internal combustion engine having a main passage through which the air stream shall pass, a throttle valve in said main passage having a shaft extending through the wall thereof, a pivoted air metering valve in said main passage, in front of said throttle valve to provide the normal air metering section thereof, having a shaft rigid therewith extending through the wall of said passage the bottom of said main passage extending downwardly toward said throttle valve, means for delivering fuel to said main passage intermediate of said valves, means for regulating said air metering valve comprising an arm fixedly connected to the shaft of said air metering valve outside of said pas-- sage, a thermostatic member pivotally mounted at one end relatively to the shaft of said air metering valve, a cam secured to the shaft of said throttle valve engaging said member at progressively decreasing distances from said pivot as the throttle is moved toward idle position, yieldable means tending to force said arm into contact with said member and to hold said memberagainstsaid cam, and a thin, flexible, wearresisting strip of material positioned between said thermostatic member and said cam for protecting said thermostatic strip from the abrading action of said cam.

17. A carburetor for an internal combustion engine having a main passage through which the air stream shall pass, a throttle valve in said main passage, a pivoted air metering valve in front of said throttle valve to provide the normal air metering section thereof, having a shaft rigid therewith extending through the wall of said passage,'the bottom of said main passage extending downwardly toward said throttle valve, a fuel supply chamber, means for conducting liquid fuel therefrom to said main passage intermediate of said valves comprising a fuel passageway leading from said supply chamber and having a restricted fuel metering section through which all the fuel shall pass during idle, light and normal load operations of the engine, means for regulating said metering valve comprising a member connected to the shaft of said metering valve, a cam operable in conjunction with the movement of the throttle valve having a contour acting upon said member to maintain said metering valve in normal position throughout a substantial movement of said throttle valve during medium load operations of the engine and to move said metering valve from said normal position at a gradually and progressively increasing rate toward a more restricting air metering position as the throttle valve approaches idle position, thereby insuring coordination of the rate of flow of fuel with that of the quantity of air flowing through therair metering section during idle and ber and having a restricted section acting as a fuel metering nozzle through which all the fuel shall pass during idle, light and normal load'op- 'erations of the engine, means for regulating said metering valve comprising a member connected to the shaft of said metering valve, a cam operable in conjunction with the movement of the throttle valve having a contour acting upon said 'member to maintain said air metering valve in normal position throughout a substantial movement of said throttle valve during medium load operations of the engine and to move said air metering valve from said normal position at a gradually and progressively increasing rate toward a more restricting air metering position as the throttle valve approaches idle position, thereby insuring coordination of the rate of flow of fuel with that of the quantity of air flowing through the air metering section during idle and light load operations of the engine and operable when the throttle valve approaches wide open position to cause said metering valve to slightly decrease said metering section.

19. A carburetor for an internal combustion engine having a main passage through which the air streams shall pass, a throttle valve in said main passage, a pivoted valve in said main passage in front of said throttle valve to form an air metering section thereof having a shaft rigid therewith, the bottom of said main passage extending downwardly toward said throttle valve, means for delivering fuel to said main passage intermediate of said valves, means for regulating said valve comprising a bimetallic member of thermostatic metal pivotally mounted at one end and contacting at the other end with an abutment, and means connected to said shaft contacting with said thermostatic member intermediate of said pivot and said abutment to position said air metering valve in response to changes in temperature, whereby the stiffness of said thermostatic member is increased for a given deflection as compared with a thermostatic member fixedly secured at one end.

20. A carburetor for an internal combustion engine having a main passage, an air metering valve therein restricting the cross sectional area to provide the normal air metering section there- 'of, a throttle valve beyond the air metering section to control the fiow therethrough, a fuel supply chamber, means for conducting liquid fuel therefrom to said main passage comprising a fuel passageway leading from said supply chamber tosaid main passage having a section provided with a fuel metering nozzle with its axis inclined upwardly, a depression chamber beyond said nozzle and a deflecting vane in said depression chamber having a channel therein the bottom of which presents a curved surface to deflect the jet of fuel from said nozzle downwardly toward the air stream in said main passage beyond'the air metering valve duringmedium and heavier load operations of the engine.

21. A'carburetor for an internal combustion engine having a main passage, an air metering valve therein restricting the cross sectional area to provide the normal air metering section thereof; a throttle valve beyond the air metering section to: control the 'flowtherethroughfmeans for "delivering liquid fuel to said passage comprising a' fuel supplychamber, a fuel passageway leading from said'supply chamberto said' main pas"- s'age having an-upwardly extending restricted section acting as a fuel metering nozzle, a depression chamber'beyond said nozzle, means to 'producepersistent fuel flow 'through said nozzle into said depression chamber during idle and light load operations of the engine, a tubular section of suiiiciently small cross sectional area toprovide peripheral surface tension upon the liquid fuel passing therethro'ugh effective to prevent pounterfiow of air upwardly, said tubular sectionextending downwardly from said depression chamber into said main passage, and a defiectingiv'ane in said depression chamber acting to change the direction of fiow-of'fuel from said nozzle into said tubular section during medium and heavier load operations of the engine.

22.'A carburetor for an internal combustion engine having a main passage, an air metering valve therein restricting the cross sectional area 'to provide the normal air metering section thereof, a throttle valve beyon'd'the air metering section to control the flow therethrough, means for delivering liquid fuel to said main passage comprising a 'fuel supply chamben'a fuel passagewayleading from said supply chamber to saidmain passage having a fuel metering section-remaining constant in area irrespective of changes in load during idle, light and normal'load operations of the engine and through which all the fuel shall 7 pass, a depression chamber beyond said fuel metering section, a tubular section extending continually downwardly from said depression chamber into said main passage, and having its discharge outlet below the middle of said main passage and arranged to discharge the fuel downwardly-and forwardly and having a continuing structural wall with gradually reduced cross sectional area extending from said outlet downwardly and terminating near the lower wall of 'said'mainpassage, whereby the fuel will flow from said outlet in a thin film over said structural wall during idle and light load operations of the engine.

23. A carburetor for an internal combustion engine having a main passage, an air metering valve therein restricting the cross sectional area to provide the normal air metering section thereof, a throttle valve beyond the air metering sec- 'tion to control the fiow therethrough, means for delivering liquid fuel to said main passage comprising a fuel supply chamber, a fuel passageway leading from said supply chamber to said main.

sage so positioned as to be free; of fuel during idle 1 I and light load operations ofithe engine and-to be subject. substantially to the suction head existing 'at' the terminal .end of said tubular section.

24. A carburetor for an internal combustion enginehaving a main passage, an air metering valve to restrict a portion thereof to provide the normal air metering section; a throttle valve beyond the air metering section to control the flow therethrough produced by the suction of the'engine, means for delivering liquid fuel to said main passage comprising a fuel supply chamber, a fuel passageway leading from said supply chamber to said main passage having a fuel metering section and a depression chamber beyond said fuel metering section, means effective by the suction head in the air metering section in conjunction with the suction head beyond the throttle to produce persistent fuel flow into said depression chamber during idle and light load operations of the engine, said fuel passageway having a section extending continually downwardly from said depression chamber to said main passage and of small cross sectional area providing peripheral surface tension of liquid fuel passing therethrough effective to prevent counterflow of air upwardly into said depression chamber during idle and light load operations of the engine.

25. A carburetor for an internal combustion engine having a main passage, means to restrict a portion thereof to form an air metering section, a throttle valve beyond the air metering section to control the flow therethrough, means for delivering liquid fuel to said main passage comprising a fuel supply chamber, a fuel passageway leading from said supply chamber to said main passage having an upwardly extending restricted section acting as a fuel metering nozzle,

a depression chamber beyond said nozzle, means effective by the suction head in the air metering section in conjunction with the suction head beyond the throttle to produce fuel flow into said depressionjchamber during idle and light load operations of the engine, said fuel passageway having a tubular section of substantial length extending downwardly from said depression chamber to said main passage and of a small cross sectional area providing peripheral surface tension of the liquid fuel passing therethrough effective to prevent counterflow of air upwardly into said depression chamber during idle and light load operations of the engine, and a deflecting vane in saiddepression chamber to change the direction of flow of fuel from said nozzle into said tubular section during medium and heavier load operations of the engine.

26. A carburetor for an internal combustion engine having a main passage, means to restrict a portion thereof to form an air metering section, a throttle valve beyond the air metering sectionto control the flowtherethrough, means for deliveringliquid fuel to said main passage comprising a fuel supply chamber, a fuel passageway leading from said supply chamber to said main passage having a fuel metering section through which all the fuel shall pass during idle, light and normal load operations of the engine, a depression chamber beyond said fuel metering section, a tubular section extending continually downwardly from said depression chamber to said main passage having a small cross sectional area to provide peripheral surface tension of the liquid fuel passing therethrough effective to prevent counterflow of air upwardly into said depression chamber during idle and light load operations; of the engine, and an air duct leading from the depression chamber and communicating with the main passage in front of said throttle valve so positioned as to be free of fuel during idle and light load operations f the engine and acting to stabilize the equalizaengine'having a main passage, means to restrict a portion thereof to form an air metering section, a

throttle valve beyond the air metering section to control the flow therethrough, means for delivering liquid fuel to said main passage comprising a fuel supply chamber, a fuel passageway leading from said supply chamber to said main passage having a fuel metering nozzle, a depression chamber beyond said fuel metering nozzle, a section of said fuel passageway extending continually downwardly from said depression chamber to said main passage and having a small cross sectional area to provide peripheral surface tension of the liquid fuel passing therethrouglr effective toprevent counterflow of air upwardly into said depression chamber during idle and light load operations of the engine, an air duct leading from the upper portion of the depression chamber having a port communicating with said main passage beyond the air metering section and in front of the throttle valve, and a branch communicating with said main passage beyond the throttle valve having a portion of its length of relatively smaller cross sectional area than said port, thereby to maintain continuously a low flowing head in said depression chamber to supplement the suction head induced by the air metering section during idle and light load operations of the engine, and to produce a gradual diminution in said low flowing head as the load isincreased beyond idle through light load operations of the engine and without momentary or sudden changes in the suction head acting upon the fuel nozzle.

28. A carburetor for an internal combustion engine having a main passage, means to restrict a portion thereof to form an air metering section, a throttle valve beyond the air metering section to control the flow therethrough, means for delivering liquid fuel to said main passage comprising a fuel supply chamber, a fuel passageway leading from said supply chamber to said main passage having a fue1 metering nozzle, a depression chamber beyond said fuel metering nozzle, a section of said fuel passageway extending continually downwardly from said depression chamber to said main passage having a small cross section area to provide peripheral surface tension of the liquid fuel passing therethrough is effective to prevent counterflow of air upwardly into said depression chamber during idle and light load operations of the engine, an air duct leading from the upper portion of the depression chamber and having a port communicating with said main passage beyond the air metering section and in front of the throttle valve, and a branch communicating with said main passage beyond the throttle valve having a portion of its length of relatively smaller cross sectional area than said port, and means restricting said air duct to a small cross sectional area intermediate of said depression chamber and said port, and an auxiliary port leading from said duct intermediate of said depression chamber and said duct-restricting means to said main passage, said auxiliary port being of larger cross sectional area than the smaller cross sectional area of said duct-restricting means and acting to produce a staged reduction in pressure between the pressure in said depression chamber and the pressure existing beyond the throttle valve.

MERL R. WOLFARD.