US2271116A

US2271116A - Carburetor

Info

Publication number: US2271116A
Application number: US314904A
Authority: US
Inventors: Robert F Bracke; Carl W Spohr
Original assignee: Individual
Current assignee: Individual
Priority date: 1938-07-27
Filing date: 1940-01-22
Publication date: 1942-01-27
Anticipated expiration: 1959-01-27

Description

Jan. 27, 1942. R. F. BRACKEETAL 2,271,116

CARBURETOR Original Filed July 27, 1958 6 Sheets--Sheet` l.

R. F. BRACKE ETAL 2,271,116

CARBURETOR v Original Filed July 2'7, 1938 6 Sheets-Sheet 2 l Jan. 27, 1942.-.

Jam 27 1942 R. F. BRAcKE Erm.

CARBURETOR- original Filed `Ju1y 27. 193s 6. sheets-sheet :s

lix

ZOO

.A e 0 2Q@ n wf 0M E; K M2 a f @a HOM 1 u A/ mom 2 6 5 /0 12 2 @a @man Jan. 27, 1942. R. F. BRACKE E-rAL CARBURETOR original Filed July 27, 195e s sheets-sheet 4 AwmlllLlll@ R. F, BRACKE ET AL Jan. 27, 1942.

CARBURETOR Original Filed July 27, 1938 6 Sheets-Sheet 6 g zx Zd. 5 f y fammi,

' @few 7M@- @atented Jan.. 2?, i942 Robert F. Bracke and Carl W. Spohr,

- Chicago, Ill.

Original application July 27, 1938, Serial No.

221,486. Divided and this application January 22, 1940,' Serial No. 314,904

l. Claim.

Our invention'pertains to carburetors and is more particularly concerned with carburetors of the fuel lift type. of our copending application Serial No. 221,486 Illed July 27, 1938.

An object of our invention is to provide a carburetor which will facilitate starting of a hot engine.

Another object of our invention is to provide a carburetor which will improve the starting characteristics of a cold engine.

` Another object of our invention is to provide a carburetor which will give good acceleration.

Another object of our invention i '6o provide a carburetor wherein the fuel in the carburetor 'Ihis application is a division iioat bowl will be maintained at a relatively low y temperature.

Another object of our invention is to provide an improved arrangement of the nozzle Venturi tubes and booster Venturi tube.

Another object of our invention is to provide improved means for adjusting the carburetor whereby it may be calibrated more accurately at the factory.

Another object of our invention is to provide improved means for adjusting the carburetor whereby it may be calibrated `more accurately at the factory.

Another object of our invention is to provide an improved arrangement of the booster Venturi tube and conduits associated therewith to eliminate condensation of gasoline in these passages.

Another object of our invention is to provide an improved accelerator pump which will require less servicing than the accelerator pumps heretofore used.

Another object of our invention is to provide an improved carburetor which is inexpensive to manufacture, trouble-free in use, and which will give more eicient and satisfactory engine operation under all conditions.

Other objects and advantages will become apparent as the description proceeds.

In the drawings, Figure l is a vertical sectional view of a carburetor embodying our invention.

This view is takenon the line I I of Figure 2;`

Figure 2 is an irregular horizontal sectional view taken on the line 2 2 of Figure l;

Figure 2 A is a diagrammatic representation of the .carburetor shown in Figures land 2;

Figure 3 is an irregular vertical sectional view taken on the line 3 3 of Figure 2;

Figure 4 is a vertical sectional view of the upper part of the carburetor shown in Figuresl,

Figure 5 is an irregular vertical sectionalV taken on the line 5 5 of FigureV 6;

Figure 6 is a horizontal sectional viewthe line 6 6 of Figure 1;

Figure 7 is a detailed view,V taken'on the line f 1 1 of Figure 6, showing the adjustment for th'e economizer pin and idling system cut-om' Figure 8 is a partial side elevation and ipartial f sectional view of a modified form of our invenl tion. 'Ihe part of Figure 8 which is'shown'in section is taken on the irregular'line'l8 8 of Figure 9; I

Figure 9 is an irregular generally 'horizontal sectional view of the carburetor shown inFigure 8 and is taken on the irregular line 9 9 of Figure 8;

Figure 10 is a sectionalview` taken on the line v' I l |0 l0 of Figure 8, showing the choke controlv mechanism;l

Figure 11 is a sectional view of the acceleratorY pump Jet and is taken on the line Il ll lof Figure 8;

Figure 12 is a sectional view showing the detail of the hot starting valve and is taken onthe horizontal line I2 I2 of Figurel;

Figure 13 is a detailed sectional view oi the air valve control spring and is taken in the verti cal plane indicated by the line i3 |3 of Figure 2;

Figure 14 is a vertical sectional view of the air valve control mechanism and is taken on the line |4 l4 of Figure 2;

Figure 15 is'a vertical sectional view of a modilied form of air valve control spring and is taken on the line I5 l5 of Figure 16; and

Figure 16 is a horizontal sectional view taken f on the line |6 |6 of Figure 15.

Referring particularly to Figure 1 of the drawings, we have illustrated our carburetor as comprising a castin'g 20 having a flange 22 adapted to be attached to the intake manifoldof an internal combustion engine. A second casting -24 is attached to the upper end of the casting 20 by screws 26 or any other suitable .means and the usual gasket 28 is interposed between the

castings

20 and 24 to insure an air-tight joint. A

third casting 30 depends from the casting 24 and is attached thereto by screws 32, the usualgasket 34 being interposed between the

castings

30 and 24 to. provide a liquid and gas-tightjoint.

It is to be noted that the castingill has the iloat bowl 36 formed therein and that any heat conducted to the float bowl from the engine must.

cross the joint between

castings

20 and 24 and the second-.joint between

castings

24 and 30 be- 2 and 3 and is taken on the line 4 4 ofFgure 2; 5 fore it reaches lthe iloat bowl. We have found Y amount of heat transmitted from the engine to the iloat bowl and that the

gaskets

28 and 34 may be made of any usual material and of any usual thickness, it being unnecessary to provide thick gaskets of special heat insulating material.

As best shown in Figure 3 the casting 24'has an inlet 88 at its upper end through which air is admitted to the carburetor. This inlet may be provided with any suitable air cleaner if desired. The inlet 88 communicateswith a chamber 48 from which air is supplied to the two nozzle Venturi tubes, 42 and 44 and also to the booster Venturi'tube 46 (Figure 4). With this arrangement any eddies which might occur inthe chamber 48 will affect equally the nozzle Venturi tubes 42 and 44 and the booster Venturi tube 46, thereby maintaining a proper balance between these Venturi tubes under all conditions of operation. Air passing to the booster Venturi tube 46 must ilrst pass through a metal cup 48 having slots 58 and attached to a plug 52 threaded in the cover 54 for the chamber 48.` The plug 62 is provided with bores 56 for receiving the prongs of a spanner wrench whereby the cup 48 may be adjusted to admit greater or less air to the booster Ven` turi tube 46 only by a person equipped with the proper tool. The purpose of this particular arrangement is to permit ease of adjustment at the factory and by a service station which is properly equipped, but to prevent tampering by unskilled individuals. The air passing to the booster Venturi tube 46 must also pass through a disk 58 having an orifice of predetermined size.

The nozzle Venturi tubes 42 and 44 discharge into the upper ends of a pair of

throttle boresl

68 and 62 respectively provided with

throttle valves

64 and 66 mounted on a common shaft 68 provided with a lever 18 adapted to be connected to the usual hand and foot controls of an automobile.'

The upper ends of thethrottle bores 68 and 62 1 open into a rectangular chamber 12 at the upper end of which is located an air valve 14. The air valve 14 constitutes an important feature of our invention and comprises a sheet metal valve member 16 which is substantially rectangular in shape and which in the closed position closely fits the seat provided by overhanging

lips

18 and 88. Because of the rectangular shape of the chamber 12, the ends of the valve member 16 may closely fit the ends of the chamber to prevent leakage therepast and in this manner the amount of air .which is admitted to the chamber 12 is regulated by the space between the forward edge 82 of the valve member and the adjacent side wall of the chamber 12, thus providing for more accurate control of the volume of air admitted to the chamber 12 and the throttle bores 68and 63.

The valve member 16 has an extension 64 bent at right angles to themain part of the valve member and adapted to be received in the slot 85 provided in its supporting shaft 86. The extension 84 has generally vertical slots for receiving the screws 88 which extend freely through that portion of the shaft 86 which is to the left of the extension 84 as viewed in Figure 14 and are threaded into that portion of the shaft 86 which is to the right of the extension 84 as viewed in this figure. These screws 88 also pass freely through the adjacent portion of the lever 88 which connects the air valve shaft with thec 2,271,118 that this construction materially reduces the dashpot indicated generally by reference numeral 82.

The foregoing arrangement permits easy assembly and adjustment of the air valve, it being only necessary to assemble the partsv and tighten up lightly on the screws 88. The valve member 16 may then be adjusted by sliding its extension l 84 in the slot in the shaft 86 so that the rectangular surface of the valve member 18 contacts l0 with

valve seats

18 and 88 when the valve is in closed position. The screws may then be tightened to lock the valvemember 16 in this position on its shaft 86.

The mechanism for urging the valve to closed position is best shown in Figures Zand 13. The

end of the shaft 86 has a short slot for receiving the inner end of the spiral spring 84 which we have found to have particularly desirable lchar acteristics forV operating the air valve of our improved carburetor. The other end of the spring 84 is bent outwardly as indicated at 86 in Figure 13 and is received in a suitable slot provided in the arm 88 of a generally U-shaped member |88 having a base 88 provided with a central opening pivoted on a forward extension of a bushing |82 surrounding the shaft 88 where it passes through a wall of the casting 24.

The extreme ends of the U-shaped member |88 extend radially outward as indicated at |84 80 and |86 (Figure 135 and are provided with points adapted to be received` in suitable recesses |88 formed in the surrounding portion of 'the casting 24. To adjust the tension of the spring 84 pins are inserted in the holes IIB and |12 formed in the arms |84 and |88 respectively and the pins are then pushed radially inward toward the shaft 86 withdrawing the points of the arms from the recesses |88. While the points are thus retracted the U-shaped member |88 may be 4 rotated about the shaft 86 to increase or decrease the tension on the spring 84. When the U-shaped member |88-has been positioned to give the desired tension on the spring 84, pressure is released on the pins extending into the holes H8 and H2, whereupon the arms of the n U-shaped memberv will expand radially and move the points into the adjacent recesses |88 thereby locking, the' spring in this \adjusted position.

Referring to Figure 2, it will be seen that the U-shaped member |88 is retained in place by a C-spring I4 expanded into a suitable annular groove formed in the adjacentportion of the g casting 24. In order to prevent inexperienced 5" persons from tampering with the air valve spring adjustment, we preferably provide a welsh plug |6 which completely encloses the air valve spring 84 and its adjusting mechanism. o In Figures 15 and 16 we have shown a modication of the spring arrangement for the air valve. This modification has the advantage that it is simpler and less expensive and is equally as advantageous as the form shown in Figures `2 and 13. In Figures 15 and 16 -the air valve shaft 86' is slotted at one end to receive the inner end of the spiral spring 84', the .outer end of this spring being curved as indicated at ||8 for reception in the slots |88' in the casting 24'.

"f5 any adjustment of the air' valve spring will be made at the factory at the time the carburetor is assembled, a welsh plug H6 is pro- `vided to enclose the mechanism and prevent Cil collar |24 located on the piston rod |26 attached to the dashpot piston |28 whereby movement of the air valve causes a corresponding movement of the dashpot piston. l

The dashpot piston |28 is located in a cylinder |30 formed in the casting 24. This cylinder is provided with an atmospheric vent |32 which opens into the cylinder a short distance above the upper end of the piston |28 when the latter is in its lowermost position which corresponds to a closed position of the lair valve 14. of the casting 24 which forms the cylinder |30 is provided with a depending skirt |34 which extends into a depression formed in the upper surface of the casting 20, thereby determining the relative position of the two castings and providing accurate alignment between the same. This skirt |34 has a slot |36 (Figure 14) to admit theY a manner which we shall now describe.

The air entering the booster Venturi tube 46 and flowing through the restricted throat thereof creates a suction which is communicated to the float bowl 36 by means of radial passages |42, annular space |44, and'duct |46. The booster Venturi tube 48 discharges the air passing therethrough and any vapor which 4may have been withdrawn from the float bowl into an inclined passage |48 communicating with a horizontal passage |50. It is to be noted that the passage |50 is merely a recess formed in the lower edge of the casting 24 and that the lower side of the passage |50 is formed by the gasket interposed between the

castings

24 and 20. This manner of forming the passage 50 is advantageous in. re.

ducing the cost of manufacture.

From Figures 4 and 6 it will be apparent tha the passage |50 is L-shaped and communicates with a downwardly directed passage |52 leading to a chamber |54 which communicates by way of a metered orifice |56 in a plug |58 with a horizontal duct |60 which communicates' with both throttle bores 60 and 62 as clearly indicated in Figure 6. The tapered metering pin |40 is located in the orifice |56 and variably restricts this orice and the ilow through the booster Venturi tube 46 in accordance with the position of the air valve 14.

The particular arrangement of air valve, dashpot, and booster control of our invention has several important advantages. Since the lower side of the dashpot piston |28 is exposed to the suction existing in the mixing chambers, and the upper ,side of this piston is exposed to atmospheric pressure when the air valve 14 is ,closed or nearly so, the effect of this piston |28 is to impose an additional load on the air valve and thus assist in maintaining a higher degree oi' suction in the mixing chambers when the engine is operating at idle. After the air valve That part i and the mixing chamber of the carburetor.

has opened suiciently to move the piston |28 to a position where it closes the atmospheric vent |32, this additional load is removed from the air valve. It will be understood .that the piston |28 has a clearance of approximately four one-thousandths of an inch, so that after the piston |28 has been raised sufliciently to cover the atmospheric vent |32, both sides of this piston are exposed to equal pressures.

We have previously pointed o ut that the valve member I6 may be easily adjusted to form a perfect contact with its

seats

18 and 80 and that the edges of the valve member 16 iit closely against the ends of the rectangular chamber in which the valve member is located and thus prevent leakage therepast during all positions of the valve. Since the only ow past the air valve is between the free edge of the valve member 'I6 and the seat 18, a relatively large movement of the air valve is necessaryin order to permit an appreciable inflow of air. 'I'his in turn means a relatively large movement of the metering pin which controls the booster Venturi tube and gives excellent calibration of the booster Venturi tube over a very sensitive range. The fact that the free edge of the air valve controls the admission of air to the mixing chamber is important since the particular design of air valve and the particular design of dashpot control cooperate to maintain a relatively high degree of suction in the mixing chamber during idle operation and speeds immediately thereabove and thus insure sufficient flow through the booster Venturi tube to maintain the desired suction in the carburetor iioat bowl.

Attention is also directed to the particular location of the booster Venturi tubetand the passages connecting this Venturi tube with the float bowl The booster Venturi tube 46 is located above the carburetor oat bowland is connected thereto by an inclined passage |46 which is free from pockets in which liquid fuel could collect. The point at which the booster Venturi tube discharges ure 3 that the air valve 14 inclines downwardly to the left as viewed in this figure so that when the air valve is partially open the incoming air is directed against the left-hand wall of the m|x'4 ing chamber. The fuel feeding Venturi tubes, on the other hand, are downwardly inclined to the right and discharge toward the right-hand wall of the throttle bores as seen in this figure. The throttle valves are inclined downwardly to the right to a slight extent when in full closed position, and to a greater extent in part throttle position. A baille plate |62 is preferably located below the air valve 14 to prevent the creation of eddy currents which would interfere with the function of the air valve.

Our improved carburetor has an inlet |64 adapted to be connected with any suitable source of fuel supply which in the present automobile is the main fuel tank usually located at the'rear of the vehicle. Fuel admitted through the intake |64" passes into a filter chamber, |66 containing a screen |68 through which the fuel must pass. After impurities have been removed 4Vbythe screen |68, the fuel flows into a chamber |10 immediately above the xioat valve |12 controlled by a float |14 pivotally mounted on the pin |16.

The fuel owing past the valve |12 enters the upper end of a cylindrical passage |18 which opens at its lower end into the oat bowl 36. The upper end of the cylindrical passage |18 communicates with the throats of -the nozzle Venturi tubes 42 and 44 by way of passages |80, |82, orifice |84, passages |86 and |88. Passage |82 also communicates with a point adjacent the bottom of the oat bowl, by way of the vertical passage |90. 1t will be understood that each nozzle Venturi tube has its throat provided with a step |92 below which are the discharge ends of radially inclined passagesv 84 which communicate with an annular chamber |96. Each annular chamber in turn -is connected to one of the fuel supply passages |88. 'l

YThe particular' varrangement of passages connecting the inlet |64 with the float bowl 36 and the o'at bowl and inlet with the nozzles 42 and 44 is claimed in the copending application of Robert F. Bracke, Serial No. 220,516, filed July We have' provided our improved carburetor with an accelerator pump comprising a cylinder 200 located in the bottom of the float bowl 36 and supplied with the fuel through an inlet passage 202 controlled by a ball valve 204. Fuel discharged from the cylinder 200 flows through an outlet passage 206, past a check valve 208 to a jet 2|0 having a pair of diverting orifices 2|2, each orifice being directed toward one of the throttle bores.

- A piston 2|4 is mounted in the cylinder 200 and is reciprocated by a piston rod 2 |6 having an enlarged head 2 I8 located in a bore 220 in the piston f 2|4. The piston` rod 2|6 is normally held in its upper position by a spring 22| and is moved downwardly by the roller 222 carried by a lever 224 attached to shaft 226 pivotally mounted in the casting 24. An arm 228 (Figure 7) is attached toone end of the shaft 226 and is adjustably connected to a lever 230 which is .freely mounted on the shaft 226. The adjustable connection between the arm 228 and lever 230 comprises a screw the arm 228 and threadedly engages the lever 230. A relatively heavy spring 234 surrounds the screw 232 and is interposed between the arm 228 and lever 230 in such manner as to maintain tension on the screw 232 and thus impose suiiicient Vfrictional resistance to rotation of this screw to maintain the desired adjustment of the parts. A rod 236 connects the lever 230 with the arm 238 attached to one end of the throttle valve shaft.

Opening movement of the throttle valve shaft causes a downward movement of piston rod 2|6 whose lower end slides freely in the bore 220 of the piston 2 |4. The downward movement of the piston rod 2|6, however, carries with it the plate 240 which compresses spring 242 whose lower end rests upon the piston 2M and thereupon urges this piston downwardly in the cylinder 200. The piston 2|4 has a sealing member 244 which is held in engagement with the cylinder wall by an annular spring 246 sc that downward movem'ent of the piston discharges incl from the cylinder 200 through passage 266, past check valve 208 and thence through the orifices in the jet 232 which passes freely through Attached to the plate 240 is a metering pin 248 `having a tapered upper end which lies in the orice |84 and serves as a means for controlling the quantity of fuel supplied to the nozzle Venturi tubes 42 and 44 under different conditions of engine operation. One of the important functions of the adjustment shown in Figure 7 isto shift the position of this metering pin with respect to the orifice |84.

All fuel lift carburetors having booster Venturi tubes provide an inherently rich mixture for starting and this increases the difculty of starting a hot 'engine provided with such a carburetor. In order to overcome this difficulty with the prior art carburetors, we have provided special means for reducing the richness of the starting v mixture supplied to the internal combustion engine provided with our novel carburetor.

Referring particularly to Figures 2, 2-A and 12, it will be seen that we have provided a passage 250 which communicates with the mixing chamber at a point below thedashpot 92 as is most clearly vshown in Figure 2 and leading to a valve chamber 252 containing a check valve 254 adapted for engagement with a seat 256 and guided in its movement by a pin 258 formed on a plug 260. A second passage 262 connects the valve chamber 252 with the throttle bores 60 and 62 at a point below the

throttle valves

64 and 66 as clearly indicated by reference numeral 264 in Figure 2A.

When the engine is not operating, the spring 266 which is confined between one end of the chamber 252 and the valve 254 holds this valve in open position a's clearly shown in Figures 2-A and 12, and thus provides relatively free com-l:`

munication between the intake manifold and the mixing chamber even though the

throttle valves

64 and 66 be in closed position. This means that by leaving the throttle valves closed, a relatively large volume of lean mixture is supplied to the engine, since the metering pin 248 is in its uppermost position and reduces the quantity of fuel supplied to the nozzle Venturi tubes 42 and 44, thereby reducing the volume of fuel discharged into the mixing chamber 'by these nozzle Venturi tubes. As soon as the engine res; the suction created by the operation of the engine closes and the valve 254 against the resistance of its spring 266 and retains this valve closed throughout part throttle engine operation.

We have also provided a novel mechanism for supplying 4fuel to the engine while idling, this system beingspecially designed to provide easy starting of a hot engine. We shall now describe this novel idling system.

Referring to Figures 1, 2A, and 3, it will be noted that one side of the operating rod 2|6 of the accelerator pump is cut away as indicated at 268 to permit fuel in the oat bowl36 to enter the annular chamber 210 surrounding the rod 2|6 when the rod is in the raised position which it assumes when the throttle valves are closed. The passages 212 and 214 connect the chamber 210 with a transverse passage 216 leading to vertical passages 218 and-280. A needle valve 282 is interposed between one end of passage 216 and passage 218 whereby the quantity of fuel supplied to passage 218 may be varied at will. A spring 284 holds the needle valve 282 in adjusted position. A similar needle valve 286 is interposed between the other end of passage 216 and vertical passage 288.

The lower end of the passage 218 vcommuni-- cates with the throttle bore 60 below the throttle valve 84 by way of a small hole 288 and a second small hole 298 connects the passage 218 with the throttle bore 88 immediately above the throttle valve 84 when the latter is in closed position.

A very small drill. hole 292 connects the upper end of the passage 218 with the mixing chamber and prevents the creation of a siphoning action. The other vertical passage 288 is similarly provided with openings 294 and 298 connecting with the throttle bore immediately below and above the throttle valve 88 and is also provided with a small anti-siphoning opening 298.

'I'he carburetor is so designed that when the throttle valve is Wide open and the engine is being turned over by the electric starter. the carburetor delivers a lean mixture to the 4internal combustion engine unless the choke mechanism to be hereinafter described is in operating position. The lean mixture thus supplied to the engine for starting purposes facilitates starting a hot engine. art carburetors were designed to supply such a lean mixture during starting, the mixture supplied to the engine during normal operation would be so lean that the engine would not accelerate properly when the throttle valve is opened slightly. In' other words, the engine would not accelerate properly to "touch throttle operation. A feature of our invention lies inthe design of our idle system which overcomes this difficulty.

It is to be noted that the

openings

298 and 298 communicate with their respective throttle bores immediately above the upper sides of the throttle valves therein when these valves are in closed or substantially closed position. Thus. in starting a hot engine with the throttle valves closed, air is drawn into the

openings

288 and 298 and a mixture of air and fuel is delivered by the lower openings 288 and 294 to the intake manifold of the engine. As soon, however, as the throttle valves are opened a slight amount, the upper edges of these valves are above the

openings

298 and 298 Iwhereupon these openings, as Well as the openings 288 and 294, become fuel delivery openings and thereby increase the quantity of fuel supplied to the engine. In touchthrottle operation, the movement of the throttle valves which converts the

upper openings

298 and 298 from'air inlet openings to fuel delivery openings thereby supplies suilicient additional fuel to the engine to provide the desired increase in engine power. It is to be noted that the float bowl 38 is located ahead` of the throttle bores when the automobile is traveling in a forward direction so that the inertia of the fuel tends to increase the quantity supplied to the engine during acceleration of the automobile.

On the otherhand, if the priorv mounted on a pivot 388. The plate 384 has a downwardly projecting portion 388 provided with a knob 3| 8 adapted to be connected with the usual manual control on the instrument board of the automobile. When the knob 3|8 is moved toward the right, as indicated by the small arrow in Figure l, the pear-shaped depression 3I'2 in the plate 384 is shifted to establish communication between the passage 388 and the upper end of a duct 3|4 whose lower end communicates with the passage |58 which connects the booster Venturi tube 446 with'the mixing chamber. In this position Yof the plate 384, air is admitted to the passage |58 thereby' reducing the flow of air through the booster Venturi tube' 48 and thus reducing the ability of this booster Venturi tube to create suction in the carburetor float bowl with the result that 'the nozzle Venturi tubes and the idling system supply the engine with an unusually great quantity of fuel, thereby facilitating starting of the engine whenvcold.

'I'he plate 384 has a cam-shaped'edge 3|8 adapted to engage thel part 3I8 of the lever 238 when the plate 384 is shifted to operative position. Such engagement moves lever 238 about its pivot and causes a corresponding opening of the buretor inlet 38' with a chamber 382' closed by a sheet metal member 384 pivotally mounted on a sleeve 388' surrounding a screw 388. An ordinary lock washer 3I8 is interposed between the After the throttle valves have been opened an l amount corresponding to a predetermined road speed, such for example as forty miles per hour on the level, the accelerator pump operating rod 2 I6 moves to a position to cut off communication between the float bowl and theannular chamber 218, whereupon the

openings

288, 298, 294,' and 288 cease to function and all of the fuel requirements of the engine are supplied by the nozzle Venturi tubes 42 and 44 except during an accelerating movement of the throttle valve suiciently great to actuate the accelerator pump.

We have also provided novel means to facilitate starting of the engine when cold. Referring particularly to Figures 1, 2-A and 4, a passagev 388 connects the carburetorinlet 88 with a circular chamber 382 which is closed by a plate 384 member 384' and a handle 3|8' which engages the head of the screw 388. The lock washer 3|8' formsl a convenient and inexpensive means of firmly holding the member 384' in sealing en gagezrient with the adjacent surfaces of the casting In the drawings, the parts are shown in the inoperative position. When it is desired to provide an lexcessively rich mixture, as when the engine is cold, the knob 3|2' on the handle 3l8 is shifted to the left. as viewed in Figure 8, by the usual linkage (not shown) which connects this handle with the instrument board of the automobile. When the lower end of the handle 3|8 is thus moved to the left, the irregular cupshaped depression 314' provided by the member 384' is moved to establish communication between the chamber 382' and a passage 3| 8' to admit air to the passage |58. This admission of air to the passage connecting the discharge of the booster Venturi tube 48 with the mixing chamber reduces the flow through the booster Venturi tube and thereby reduces its ability to create a suction in the carburetor float bowl. The pressure existing inthe carburetor oat bowl is accordingly higher than normal and the nozzle Venturi tubes and idling system, therefore, receive additional quantities of fuel so that the engine receives an unduly rich mixture whic facilitates starting in cold Weather. Y

The upper end of the handle member 318 is provided with a shoulder 318' for engaging the projection 3|9` on'a' lever 238 pivotally mounted on shaft 226' and connected with the throttle valves by link 320 and throttle valve shaft 324 and adapted to be connected to the usual manual and foot controls.

The lever 230 is connected to the shaft 226' through the adjusting means 326 similar to that of the previous embodiment and a lever 328 rigid with the shaft 226 is connected by link 330 to a rod 332 carrying a plate 334. This plate carries the metering. pin.336 for controlling the quantity of fuel supplied to the nozzle Venturi tubes. The plate 334 has an opening in which is located the accelerator pump cylinder 338 which re-Y ciprocates relative to a fixed piston 3,40, a spring Y 342 being interposed between the plate 334 and a flange formedat'the upper en d of the cylinder whereby upward movement of the plate 334 tends to raisethe cylinder 338 to expel fluid therefrom.

The lower'end of the cylinder 33t is provided with a port 344 normally closed by a. disk valve 346 which, is urged -to its seat by gravity and also by anyfback flow voi fuel which may occur. The fixed4` piston 340 is hollow, .providing a passage 348 communicatingwith a second passage 350 leading to the accelerator jet 2 l0. A check valve 35| prevents backv-ow of fuel to the accelerator pump. vThe accelerator pump operating rod 332 has a notch 352 formed in one side thereof to control communication between the interior of the float bowl 36' and the annular chamber 354 which supplies fuel to the idling system'which is identical with that previously described.

Our invention is not vlimited to the details shown in the drawings, but may assume numerous forms and is limited solely by the scope of the appended claim.

In a carburetor of the class described, the combination of a mixing chamber, an inclined nozzle for supplying fuel to said chamber, a oat bowl from which said nozzle is supplied with fuel, a booster Venturi tube for maintaining suction in said float bowl, a passage for supplying air to said booster Venturi tube, said passage having portions of different cross-section, a'slotted cup closely fitting one portion of said passageway and extending into the other portion thereof, an adjustable support for said cup to vary the position of the cup in said portions and thereby vary the amount of air supplied to said booster Venturi tube, a passage connecting said Venturi tube with said mixing chamber, an inletfor said last-named passage intermediate said booster and chamber, arcold starting valve for opening and closing said inlet, means for operating 'said valve, a rectangular air inlet for said mixing chamber, a sheet metal valve closely fitting said inlet, said valve being inclined oppositely to said nozzle and having a free edge adjacent saidrnozzle, a shaft having a slot adjustably receiving a bent portion of said last-named valve, a spiral spring for urging sadshaft to valvefclosing position, means for adjusting said spring, a dashpot connected to said valve shaft, and a throttle valve inclined in the same direction as said nozzle.

ROBERT F. BRACKE. CARL W. SPOHR.