US2198676A - Carburetor - Google Patents

Description

April 30,1940 l mi M. MALLQRY ff -2,198,676

...4Mw Elln April 28, 193e 2 ASmets-snee'c 2 Pou/mf:

Pound; af Per #nur M. MALLORY V2,198,676

`'CARBUHETOR Filed April 28, 1938 2 Sheets-Sheet l Aprii 3G,y 1940.

Patented Apr. 30, 194i) UNITED STATES.

PATENT OFFICE CARBURE'I'OR V Marion Mallory, Detroit, Mich.

Application April 28, 1938, Serial No. 204,865

' s claims. (c1. zei- 52) 'I'his invention relates to an improved carburetor having a throttle valve, a fuel metering pin connected thereto, an air .valve and a venturi having a fuel nozzle associated therewith, located between the air valve and throttle valve, and a velocity controlled air valve in the venturi adjacent the fuel nozzle. One important object of the invention is to provide means to control the throttle and metering pin manually to increase or decrease the volume of air and fuel and to open the air valve .by suction and gravity only, but to control the rate of opening of the airvalve in relation to the rate of opening of the throttle valve so as to increase or decrease progressively and in synchronismthe air volume, fuel'volume and suction in the venturi. i 'A further object of the invention is to provide means whereby the throttle and the air valve operate 4in synchronism part of the time as though they were positively connected together and further to provide-means to cause Vthe air valve to lag behind Vthe throttle valve s'o as to automatically enrich the mixture for accelera- 25 tion and to prevent stalling of the engineon which the carburetor is used.

A further object of the invention is to provide means to force most of the air past the fuel nozzle, in this type of carburetor, so as to straighten up the fuel flow and maintain sufficient suction around the nozzle at times when the volume of air passing through the carburetor is low.

l A further object of theinventlon is to control zle does change. from a staticsuction to a dynamic suction as the throttles are opened.`

A further object of the invention is to provide means to offer resistance to the opening of the air valvev for starting and warm-up; this resistance decreasing drapidly as the air valve moves toward an open position and offering no resistance whatever when the air valve is wide open.

. j A further object of the invention is to provide 1 u a metering pin in the form of a slide valve, lso

that the vacuum within the carburetormixing chamber tends to hold the pin against the wall 4of the cylinder in -which it operates, 'to prevent leakage and erratic metering.

A further object of the invention is to provide means between the throttle valve and air valve, whereby resistance is offered to the opening of the Aair valve whenthe throttle valve is closed;

said resistance increasing as the throttle valve 5 is moved away from idle position, then rapidly decreasing, and` finally ceasing altogether by the time the throttle valve is wide open.

A further object of the invention is to provide means whereby the carburetor operates as an 10 air-valve carburetor, regulating the fuel by the metering pin at all positions of the throttle ex.- cept vwhen itis wide open, but for wide open throttle the metering pin and air valve no longer function, the mixture being then controlled en- 15 tirely by the volume of air flowing through the venturi and the size of the nozzle in the venturi, the same as in a plain-tube carburetor.

AV further object of the invention is to provide means whereby the metering pin can be adjusted 20 to regulate fuel flow when the carburetor is operatingas an air-valve'carburetor, and further to provide means to change thedisposition of the fuel nozzle to regulate the fuel flow when the throttle. is wide open and the carburetor 25 operating as a plain-tube carburetor.

Means for carrying out the objects of the invention are clearly explained in connection with the accompanying drawings, in which- Fig l isa side elevation of a carburetor con- 30 structed in accordance with the invention.

Fig. 2 ,is a side elevation looking from the left side of Fig. 1.

Fig. 3 is a central section looking inthe same direction as Fig. ll.

Fig. 4 is'a view of the air velocity valve, looking downwardly into the carburetor.

Fig. 5 is a central sectional view of the venturi, throttle valve, air valve, and the-air velocity valve in the venturi. 40

Fig. 6 is a vertical sectional view showing the metering pin and nozzle bar, some of the other parts being omitted. n

Fig. 7 shows graphs of suction and mixture ratios produced by the invention.

The invention is illustrated as applied to a down draft carburetor, which has an air inlet 5, a mixing chamber 6, and a fuel mixture outlet 'l adapted to be connected with the engine intake manifold. 'I'he mixing chamber is formed 50 with a venturi 8 into which fuel is admitted 'through nozzles 9. v 'I'he throttle valve Il)A within the outlet 'l is mounted on a stem jll which is provided with an arm I2 connected to a throttle control rod 55 I3. An unbalanced air valve I4 within the air inlet 5 is mounted on a stem I5, o n which an arm I6 is secured. A telescopic link connecting the two valve armsAI2 and I6 comprises a rod I1 pivotally connected to the arm I6, with a sleeve I8 threaded on the rod I1 and formed internally with a solid portion I8 normally resting on the upper end of a rod I9 which is pivotally connected to thearm I2 and slidable in the sleeve I8.

The valve I4 is therefore free to close regardlessof the position of the valve I0 and may be opened only by air flow or suction. A cam follower 2Il is slidably mounted on the rod I9 and normally rests against an extension 2| of the arm I2, which is formed with a cam 24. A light coil spring 22 -is disposed between the cam follower 2l!y and the end of the sleeve .I8 and under certain conditions, ashereinafter explained, exerts a light pressure tending t0 close the valve I4. The sleeve I8 has a threaded adjustment on the rod I1 merely to maintain proper length of the linkage between the valves I4 and IIJ and to correct it for wear and manufacturing tolerances. A spring 23 at the upper end of the sleeve retains the latter in its adjusted position.

Fuel is fed from a well 25 through a duct 26 to the nozzle openings 9.in a bar 26, which extends transversely of the mixing 'chamber'. A metering pin 21 in .the Well is connected through a link 28 to one end of a cross arm 29 on the Valve stem II at the opposite side of the carburetor from the throttle arm I2. 'I'hus the pin 21 is raised as the throttle is opened and the tapered iiat surface 30 of the pin allows more fuel to be fed to the nozzle. An accelerator pump 3l is connected by alnk 32 to the opposite end of the cross arm 29 and is adapted to draw fuel from `the well 25 and, as the throttle is opened, to inject it through a duct- 33 and .ietv 34 into the intake passage.

A choke rod 35 is connected to an arm 36 which is mounted on a pivot 31 secured to the carburetor casing. A tension spring 38 connects a pin 39 on the arm 36 to a pin 4I) on a lateral extension 4I of the upper valve arm I6. Normally, the pin 39 is in alinement withthe air valve axis I5 so vthat the spring 38 is radialto the axis and has no eiect on the opening or closing of the air valve.V However, when the choke rod 35, as shown in Fig. 1, is moved to the right, the arm 36 and.

pin 39 are moved to the right and the spring 38 exerts a torque on vthe air valve I4 which tends to hold it closed whenever the throttle is, opened.

A screw 42 threaded into a lug on the arm I2 engages an .abutment 43 to limit the closure lof v the throttle valve Ill to 'idling position. This abutment 43 extends laterally from a bar 44 which is pivotally mounted on the throttle valve axis II. The upper end of this bar has a slot 45 which is engaged by a pin 46 on the arm 36 so that, as the latter is swung in a direction to cause the air valve I4 to act as a choke, the bar 44 is swung slightly in a direction to raise the abutment 43 and open the throttle slightly.A vThis also allows more fuel to pass the vmetering pin 21.

\In the drawings, the carburetor is shown set for idling the engine on which it is used. Air valve I4, throttle valve III and metering pin 21 are not completely closed. There is enough flow pastthe throttle valve I0 to create a vacuum around the nozzle 9. Arm 29 is rigidly connected ,to the valve shaft II and link 28 connects it to metering pin 21. Cam follower 20 is held down on the cam 24 by the spring 22. This spring is' completely collapsed and the partition I 8* in the sleeve I8 is resting on the end oi' the rod I9. At this point, the spring has nothing whatever to do with the suction or vacuum in the mixing chamber. Consequently, it has nothing whatever to do with mixture ratios, because it is in effect cancelled out of the system, and the two valves Ill and I4 operate the same as if they were rigidly linked together.

As the throttle valve I0 is progressively opened, the metering pin 21 is also opened, and air valve I4 follows throttle valve Il), keeping spring 22 completely collapsed, and the partition I8 in sleeve I8 rests solidly on the end of rod I9. It is understood that the vacuum orA suction under the unbalanced valve I4 keeps spring 22 completely collapsed so that it has no effect on air valve I4 when the throttlev is opened slowly or when it is not being moved at all,.provided that the engine is running.

The angles of the valves I4 and I0 and ofthe arms 29, 2l and I6 are of such a relation to each other that, upon movement of `the throttle valve I 0 toward an open position, the static suction around the nozzle 9 gradually diminishes, and the increased volume of air ilowing past the nozzle 9 through the venturi 8 gradually and progressively changes the static suction around the nozzle to a dynamic suction, as represented graphically by a straight upwardly inclined curve. Naturally, a progressive increase of nozzle suction, a progressive increase of air flow an'd a progressive increase of fuel gives proper mixture ratios in all throttleposltions.

The curves in Fig. 7 show the performance of this carburetor. Curves A and B show the nozzle suction curve and the mixture curve respectively, when the throttle is gradually opened from engine idling to high speed. These curves are prod uced when the carburetor is operating as an airvalve carburetor andthe valves I0 and I4 act as though they were solidly linked together. It Will be observed that the suction curve increases progressively, while the mixture ratio remains the same, until the throttle is nearly Wide open. At that point, the mixtures becomes richer, as indicated by curve B. This is due -to the fact that the metering pin 21 no longer controls the fuel ilow. The ilow is then controlled entirely by the nozzle 9.-

In the event that the throttle is not gradually opened, but opened suddenly for a short distance, the mixture becomes momentarily richer, as indicated at line D. This is because the cam 24 on the arm 2I raises the follower 20 and increases the tension of the spring 22, which tends to delay the opening of the air valve I4, but as soon as the engine speed picks up, the vacuum will in- .crease and again collapse the spring 22, which leans out the mixture again bacl-r down to the line B.

The curves E and F show nozzle suction and `mixture ratios from low to high engine speed,

to obtain the desired performance. and to produce 75 ich curves, the carburetor must be constructed s I have speciiled.

It will be observed that under light loads, the arburetor operates as an air-valve carburetor nd on a lean mixture to give the best economy ut .under full load, when the throttle is wide pen, it operates as a plain-tube carburetor with mixtures for maximum power. This combinalon eliminates the use of step-up jets, power jets r compensating wells, and makes the carburetor ery simple Vto manufacture.

I am aware that other inventors have contructed carburetors having two valves and a nozle between them, and also having spring devices, ut none of these will produce the essential suclon and mixture ratio curves that my carburetor Loes. My construction is not a mere mechanical mprovement upon carburetors heretofore proosed, but involves a new principle in the control f the air valve.

In order to` automatically enrich the mixture or acceleration and to prevent stalling of. the ngine on which my carburetor is used, I have `rovided the spring 22, the cam follower 20 and he cam 24. The spring 22 is located around the od I9, one end resting on sleeve I8 and the other n the follower 2li,v the latter being loose on the od I9. Cam 24 is integral with the arm 2l.

When the engine is idling, the spring 22 is comletely collapsed or compressed and the partition 8 in the sleeve I8 rests solidlyon the end ofthe od I 9. In the event that the engine has a tendncy to stall, due to being cold, the vacuum inA he mixing chamber will naturally decrease and he suction against the air valve I4 will also derease. With this Llow vacuum in themixing bamber, the spring 22 will no longer be colapsed. It will expand against the sleeve I8 and end to close the air valve Il, which in turn will ncrease the suction around the nozzle 9 and enich the mixture to prevent stalling. As the enrine warms up, the vacuum will `Iincrease, which vill again collapse the spring 22, and there will hen be no lost motion in the link that connects he two throttle valves together. In other Words, he two valves will act as though they were linked olidly together.

In carburetors having an air valve of this type. he air stream varies in its course in relation to he fuel nozzle as the` air valve is moved either oward an open or closed position. This causes l variation in suction on the nozzlewhich in turn raries the mixture ratios and aifects distribution.

I have provided means whereby the air always asses the nozzle in the same direction, regardess of air valve position. See Figsgl and 5. I use awo wafers 41 hinged around the nozzle 26a, vhich may be termed an air velocity valve. When he valves I and I l are closed, these wafers are :losed against the venturi by a small spring 48, md even though the air is deected against the :arburetor wall, it is again straightened up and lows vertically past the jets. As the valves Ill md I l are opened further, air velocity forces this difficulty by using a piston-type metering pin 21, as shown particularly in Fig. 6. 'I'his pin has a flat tapered side 30, and with this construction, a long movement can be used to meter fuel, which eliminates sensitivity that is common with the conventional metering pin of this' f, is used in manufacturing, or wear takes place, no

fuel can pass except as permitted by the tapered iiat side.

` I have also provided means for adjusting the mixture ratios or fuel flow when the carburetor is operating as an air-valve carburetor. A piston 49 within the upper end of the pin 21 is formed with a hole 50, which receives the upper end of the link 28. The piston 49 is not threaded, but might be termed floating, since' it is held down against a spring I by a screw 52, which is threaded into the pin 21. If the screw is turned down, the metering pin-is raised to enrich the mixture. If

the screw is backed out, the pin is lowered to.

lean out the mixture.

To adjust the mixture ratios when the carbu-l retor is operated as a plain-tube carburetor, the nozzle bar` 26u can be rotated by loosening a screw 54 and shifting'the arm 53, which is rigidly connected to the nozzlel bar. This changes the angle of the nozzle openings 9, which are in the bar 28a. When t-he openings are at right angles to the air flow, the maximum amount of fuel will be drawn out, but as they are moved toward a position parallel to the air ow, one of them will function as an air bleed and thereby lean out the mixture. This adjustment is very convenient, be-

cause the owner can adjust his own carburetor for altitude or climatic conditions.

In the normal operation of the carburetor, it will be noted that the choke `spring 38 is exactly radial to the axis of the air valve so that it has v no effect. When the choke rod is pulled out, however, the arm 36 is swung about its pivot, moving the lower end of the choke spring to the right,

as shown in Fig. 1, so that it resists the opening illustrative, that the invention can be used for different types of carburetors, whether downs draft, updraft, single or duplex carburetors, and that it also includes such modifications as may be embraced within the scope of the appended claims.

I claim:

1. A carburetor comprising a fuel mixture chamber 'having an outlet adapted to be connected to an engine intake manifold, a venturi in thechamber..` a fuel jet opening into the venturi, an air inlet to thechamber, a throttle valve for vsaid outlet, an unbalanced air valve for `the air inlet adapted` to be opened only by' air ow and suction, each valve having an arm secured thereto for controlling its position, anA

extensible link connecting said arms, a spring exerting pressure tending to extend the link when the valves are nearly closed, the opening of the ftwo valves being substantially the same when the link is of minimum length, the. air valve being open less than the throttle valve when the link is extended), and means actuated by the throttle valve arm to increase the pressure of said spring when the extensible linkis of minimum length such as occurs when the two valves start to open simultaneously and at the same rate whereby the opening of the air valve isdelayed and then to decrease said pressure as they open wider.

2. A carburetor comprising a fuel mixture chamber having an outlet adapted to be connected to an engine intake manifold, a venturi in the chamber, a fuel jet opening into the venturi, an4 air inletl to the chamber, a buttery throttle valve for said outlet, an unbalanced butterfly valve for the air inlet adapted to be opened only by air flow and suction, arms secured to the respective valve axes, a link comprising telescopic sections connected to the respective arms, the opening of the two valves being substantially the same when the link is of minimum length, the air valve being open less than the throttle valve whenever the link is extended, an abutment member slidableon one of the sections, a spring adapted to exert pressure between said abutment member and the other section tending to extend the link, and a cam on the throttle arm operable during the initial opening of the throttle when the extensible link is of minimum length such as occurs when the air valve and throttle valve open simultaneously at the same rate to move the abutment member in a direction to compress the spring whereby opening of the air valve is delayed and upon a wider opening ofthe throttle in a direction to progressively release the spring.

3. A carburetor comprising a fuel. mixture chamber having an outlet adapted to be connected to an engine intake manifold, a venturi in the chamber, a fuel jet opening into the venturi, an air inlet to the chamber, a butterfly throttle valve for said outlet, an unbalanced buttery air valve for the air inlet adapted to be opened only bylair flow and suction, an arm secured to the air valve axis and extending radially therefrom, a tension spring connected at its outer end to said arm, and a choke actuating member to which the inner end of said spring is connected at a point normally in line with the air valve axis so that the spring has no effect upon the opening or closing of the air valve, said choke actuating member .being shiftable to move the inner end of said spring away from the valve axis in a direction to cause the spring to exert a torque on the air valve tending to hold itlosed., whereby the air valve functions as a choke.

4. A carburetor comprising a fuel mixture chamber having an outlet adapted to be connectedI to an engine intake manifold, :a venturi in the chamber, a fuel jet opening into the venturi, .an air inlet to the chamber, a butterfly throttle valve for said outlet, an unbalanced butterfly air valve for the air inlet adapted to be opened only by air ilow and suction, each valve having an `arm secured theretojor controlling its position, an extensible link connecting said arms,

a light spring exerting pressure tending to extend said link and thereby 'retard the opening of the air valve when the throttle valve is partly opened from idling position, an independently pivoted choke actuating member, a tension choke spring with its inner end anchored to a point onsaid member normally in line with the air valve axis and its outer end anchored to the air valvel arm at a distance from the valve axis so that it has no effect upon the opening or closing of said valve, and means for shifting the choke actuating member and thereby moving the inner end of the choke spring in a direction to cause the Alatter to exert a torque on the air valve tending to hold it closed, whereby the air valve functions as a choke.

5. A carburetor comprising a fuel mixture chamber having an outlet adapted t0 be connected to an engine intake manifold, a venturi in the chamber, a fuel jet opening into the venturi, an air inlet to the chamber, a buttery throttle valve for said outlet, an unbalancedbutteriiy air valve for the air inlet adapted to be opened only by air flow and suction, each valve having an arm secured thereto for controlling its position, an extensible link connecting said arms, a light spring exerting pressure tending to extend said link and thereby retard the opening of the air valve whenever the throttle valve is vpartly opened from idling position, means to increase the pressure of said light spring as the twov valves start to open simultaneously and then to'decrease said pressure as they open wider, an independently pivoted choke actuating member, a tension choke spring with its inner end anchored to-a point on said member normally in line with the air valve axis and its outer end anchored to the air valve arm at a distance from the valve axis so that it has no effect upon the opening or closing of said valve, and means for shifting the choke actuating member and thereby moving the inner end of the choke spring in a direction to cause the latter to exerta torque on the air valve arm connected to and arranged to swing about the same axis as the throttle valve, an unbalanced auxiliary valve controlling the air inlet and adapted 'to be opened only by air flow and suction, an extensible push connection consisting of two relatively movable members, the rst of which is pivotally connected to the throttle valve arm and the second 0f which is pivotally connected to the auxiliary valve, cooperating stop means carried by said extensible members for limiting the opening of the unbalanced valve to the same degree as the throttle valve, Aresilient means carried by the extensible push connection which exerts a force tending to extend the extensible connection and' retard the opening of the unbalanced valve as the throttle valve is opened, a follower movably mounted on the first of said members and positioned between the resilient means and the ar'm for operating said v throttle valve, a cam having an uphill and downhill portion carried by the throttle valve arm, said uphill portion arranged to engage the follower during the initial opening of the throttle to move the follower away from the point at which the rst member is` connected to the throttlegvalve arm whereby the resilient means is stressed to retard the opening of the auxiliary valve and upon a wider opening of the'throttle said downhill portion of thecam engaging the follower whereby the spring is progressively relieved of said stress and the follower moves in a direction toward the point at which the first member is pivoted to the throttle valve arm. r

MARION MALiloRY.

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