US2196213A

US2196213A - Automatic carburetor choke

Info

Publication number: US2196213A
Application number: US723284A
Authority: US
Inventors: Clarence H Jorgensen
Original assignee: Individual
Current assignee: Individual
Priority date: 1934-04-30
Filing date: 1934-04-30
Publication date: 1940-04-09
Anticipated expiration: 1957-04-09

Description

April 9, 1940. P. J. JoRGENsEN :TAL 2,196,213

AU'TOMATI CARBURETOR CHOKB med April so, 19:54 :s shuts-sheet 1 P 9 1940 P. J. JoRGENsl-:N er m.' 2,196,213

Au'romrc cAnBunE'roRcHoxs s sheets-sheet 2 Fiied Aril so, 1954 a lllllllllll f 2% ,m e m c 6 e c mw www@ @Hw c e Sc. n n e m a@ J0 l, M f

@fm i P am a April 9,

P. J. JoRGENsEN Er 'AL AUTOMATIC CARBURETOR CHOKE Filed April 30, 1934 3 Sheets-Sheet 3 Patented Apr. 9, 1940 UNITED STATES AU'roMA'rrc cAmsmtEron cnoxE Peter J. Jorgensen, deceased, late of Elmhurst,4

Ill., by Clarence H. Jorgensen, administrator,

Anderson, Ind., and Anderson, Ind.

Clarence H. Jorgensen,

Application Apru so, 1934, serial No. '123,284 Renewed April 16, 1938 23 Claims.

' ing means which is responsive, first, to the temperature of the motor, and second, the factor of whether or not the motor has actually started to run under its own power, in connection with means serving to prevent any sudden opening of the carburetor choke or air valve, whereby any sudden changes in the velocity of the air entering the carburetor will-not displace the control effected by the responsive means or otherwise disturb the fuel ratio established thereby.

Another object of the present invention, particularly in connection with carburetors in which the air valve or choke valve is arranged to automatically open under increased air velocities, is the provision yof a dash pot arranged to prevent sudden changes in air velocities, temporary irregularitles of motor speed, and otherl factors from throwing the air valve out of proper position. Preferably, but not necessarily, the dash pot has suitable valve or other means so that the dash pot is operative only in one direction to restrain any sudden movement of the air valve, this-direction being the opening movement of the valve. 'Ihe dash pot is preferably arranged 35, to allow substantially unrestrained closing movement of the air valve or chokevalve and while the dash pot prevents any sudden opening of the valve, yet gradual movement of the choke valve to the proper open or partially open posi'- tion is not interfered with. For example, when the engine is being cranked, particularly at low temperatures, the choke valve is normally closed, at least a substantial portion, and as soon as the engine begins to re, the increased value of air l drawn in through the carburetor tends to open the choke valve, and this opening of the valve tends to vthin the carburetor mixture to such an extent thatthere is considerable likelihood 'that the engine, which has not yet been brought up to operating temperatures, will stall. 'I'he provision of the dash pot in this connection to prevent the sudden rush of `air as soon as the engine fires from opening the choke valve any appreciable amount beyond the position which the `valve takes in response to the thermostat connected (ci. 12s-119) therewith. As the motor temperature slowly rises the thermostat gradually opens the choke valve to the proper position, and since this movement is more or less gradual the dash pot does not restrainthe same. e v v Another object of the present invention is the provision of such restraining means operative to prevent the over-balanced carburetor choke valve from opening under any sudden rush of air drawn into the carburetor, as by the initial firing of the engine or by sudden acceleration, in connection with means which is responsive to the initial firing of the engine and is operative immediately, or practically so, to adjust the position of the choke valve to meet this condition, that is, the carburetor choke valve is changed from its cranking position to a running position without relinquishing the control of the temperature responsive means on the choke valve and, at the same time, without having the sudden rush of 30 air past the overbalanced valve disturb these adjustments, this latter feature being accomplished by the inclusion of the dash pot referred to.

This application is an improvement on applicants copending application Serial No. 585,510 and the claims presented in this application relate only to such subject matter as is not disclosed in the earlier case, the broad claims readable on subject matter common to the two applications being presented in the earlier application.

These and other objects of the present invention will be apparent from the following detailed description of the preferred form in which the principles of the present invention have been embodied, taken in conjunction with the accompanying drawings illustrating such embodiment.

In the drawings:

Figures 1 and 3 show an engine having a carburetor provided with our automatic choke:

Figure 2 is an enlarged fragmentary section 0 taken along the line 2-2 of Figure l;

Figure 4 is a section taken on the line 4-4 of Figure 1;

Figure 5 is'` a section taken on the line 5.-5 of a Figure 4, showing the mounting or base plate and the shaft bracket;

Figure 6 is a section taken along the line 6-6 of Figure 4;

, Figure 7 is a view taken along the line l-I of ,50 Figure 3, looking in the direction of the arrows;

Figure 8 is a fragmentary section taken on the line 8-8 of Figure 6;

Figures 9 and 10 are views of the suction responsive bellows;

` ence numeral i8 and comprises a casing I8.

latter includes a base or mounting plate i1 hav- .ll'iguresli andl2areviewsofthedashpotpis`- metering pin Il includes a tapered I4 ton; and

Figure 13 illustrates a form of the present invention in which the means actuated when the engine starts is a simple connection with the starting motor control, rather than a suction responsive bellows.

Referring now to the drawings', Figures l to 3 show the application of the present invention to an internal combustion engine l having an intake manifold 2 and an exhaust manifold 3 interconnected in such a way that the exhaust gases passing out through the exhaust manifold 3 flow around the central portion of the intake manifold, indicated at .I in Figures 1 and 2. A down draft carburetor l is mounted at the inlet l of the intake manifold 2, as best shown in Figure 1, and includes a draft tube 8 bolted, as at 1', to the upper portion of the exhaust manifold 3 surroundingthe inlet section 4 of the intake manifold 2. The carburetor l is provided with an air inlet- I which is controlled by a choke valve or airvalve l of the unbalanced butterfly type which tends to open under suction. The choke valve 9 is mounted on a shaft to the outer end of which is fixed a valve arm il by which the position of the choke valve l may be controlled, either manually or automatically.

According to the principles 'of the present invention, the choke valve 8 is controlled automatically according totheseveral factors towhich the carburetor i is subjected. The automatic choke is indicated in its entirety by the refer- The ing` a flange section il by which the`automati'c choke control Il is mounted, as by bolts i9, onto the exhaust manifold 2, in the position shown in Figures l to 3. The mounting plate i1 carries a sheet metal shell 2| at the upper portion of which is disposed a cap 22'. A pair of screws 23 dispom in openings in the cap 22 and threaded into the mounting plate I1 serve to hold the shell 2i and cap 22 in place on the mounting plate l1..

A bracket 2l is secured, as by welding or the like, to the bottom of the mounting plate i1, and the bracket 25 includes a pairof downwardly disposed ears 20 in which a shaft 21 is journaled by any suitable form ofbearing means. The shaft 21 extends outwardly of the bottom cover 2B, which encloses the shaft 21 and operating parts associated therewith, and an arm 3U is flxedly connected to the extended end of the shaft 21. A link 2| serves to connect the outer end of the arm 3l with the choke -valve arm a motion restraining dash pot 2l. Referring first to the bellows mechanism 3i, the mechanism includes a flexible bellows 4l having its upper end sealed by s cap 4i which is, in turn. securely fastened, as by soldering, welding or the like,

tothe cover or cap 22 of the casing it. The bellows cap Il includes a central extension 44 of cylindrical formation which is open at its inner end and receives a fitting Il which includes a central section having a tapered bore 41, Y

-in adjusted position. Th) inner portion of the which, corresponding to the taper of the iitting section It, servesto increase or decrease the effective size of the passageway between the tting 4i and the interiorof the bellows Il. The fitting 45 also includes a laterally extending coupling il with which one end of a small tube 6I is connected its by a-bushing I2. The lower or opposite end of thetube Si tcrmlnatesin ahead Il which registers with an opening 84 formed in the casting of which the intake and exhaust manlfolds are constructed and which communicates at its inner end .withthe intake manifold 2,where by the intake suction of the engine i is communicated to the interior of the bellows. Preferably, the end I3 of the tubing Il is so constructed and dispod that when the bolts is, by which'the automatic choke device is mounted on the exhaust manifold l, are tightened, the tube 8l is effectively sealed with respect to-the bore 64. It is to be understood, of course, that any other means for communicating the suction of the intake manifold 2 to the interior of the bel- 'lcws 4I may be employed.

The end of the bellows Il adjacent the coupling f 45 is, as described, sealed to the casing cap piece 22, and the other end of the bellows is movably mounted within the casing and is sealed, as by soldering, to a closure cap 1I to which a bracket 1I is fastened. The bracket 1i includes a pair' of ears 13 and the latter are provided with oppositelyarranged lateral extensions 14,each of which carries an adjusting set screw 1l held in adjusted position by means of a retainer spring 1l. The ears 13 are apertured to receive a pivot pin or rivet Il by which a link Il. connected to the outer end I2 of the thermostat 21 as will be referred to later, is connected to be shifted by the operation of vthe bellows Il. This .endof the bellows, which is movable, is limited in its movements to an inner position. corresponding to the retracted position of the bellows due to the application of suction to the interior thereof. and an outer position to which the movable end of the bellows is moved by a spring Il vdisposed on the interior of the bellows and held in place at its upper end by being disposed around the central portion 4l of the upper closure cap 4i. 'Ihe lower end of the springll is disposed over a i boss or projection l1 formed in' the lower bellows cap -1I.

The lower position of the bellows ll is shown inrigure2andinthlsfigureitwillbeobserved that the lower position of the bellows is determined by the engagement of the bellows cap 1l with the upper surface of the mounting plate i1.

when the bellows is subjected to suction on its interior, the bellows is collapsed or retracted against the Vtension of the spring 85 and the movable end of the bellowsis drawn upwardly until the adjusting set screws Il engage the abutmentsv Il, thus limiting the retracted position of the bellows so that, even with increasing amounts of suction applied to the bellows. the lower or movable end thereof is held against fur ther movement. LThis limitation ot the movements of the bellows to two deiinite positions by suitable stop means `will be referred to later. r

Refen'ingnowtothethermostatgitwillbe observedfromlligure2thattheinnerend ill ofthe thermostat 31 is anchored in a slot formed intheshaftll. Thethermostat" iscoiled about the shaft 21anumber of times and has its outer end vI2 connected with. the lower end of theiink8i.asmentionedabove.brmeansofa pin I0 By virtue of this construction, the movements of the bellows 40 are communicated to the shaft 2.1 through the interposed thermostat 31. 'I'he bellows 40 is a suction operated device and the thermostat 31 is a temperature responsive device, and it will be noted thatI these devices are arranged in series so far as their control of the shaft 21 is concerned. The casing 28, secured to the lower side of the mounting plate I1, encloses the shaft 21, the thermostat 31 and the link 8|, but the heat from the exhaust mani fold 3 is transmitted to the region of the thermostat 31 by means of a plate ||0 formed of material of high conductivity and having a curved section disposed closely adjacent the thermostat 31 and with ends I2 and ||3 passed through suitable slots formed in the cover 28 and disposed in parallel relation with respect thereto so as to be in contact with the outer wall of the exhaust manifold 3. If desired, the heat transmitting member ||0 may be insulated from the cover 28 proper by suitable insulating means, such as a sheet of asbestos or the like. Small ears ||5 engage the inner surface of the casing 28 and hold the member ||0 in position.

The dash pot device 38 is best shown in Figure 4 and will 'be seen to comprise a cylinder |20- disposed within the casing I8 and including a movable piston |2| having at its upper end a check valve |22 which opens upwardly, against the tension of a light Aspring |23, to permit the free flow of air into the space above the piston |2| when the same moves downwardly in the cylinder |20 but which closes when the piston |2| tends to move upwardly so that there is a cushion of air above the piston |2| which escapes slowly between the piston |2| and the walls of the cylinder |20. To this end, the diameter of the piston |2| is arranged to be slightly less than the interior diameter of the cylinder |20 to provide for the desired current. A leakage groove |24 is formed in the cylinder |20 and has an increasing depth toward the upper end of the cylinder sol 'Ihe lower vend of the piston |2| is formed with a groove |26 in which is fixed a disk |21 having a pair of lugs 28 cut and bent downwardly therefrom and apertured to receive a pivot pin |30 to which the upper end of a link |3| is connected. The lower end of the link 3| is bifurcated and connected, by means of a pin |34, with the outer end of an arm rigidly secured to the end of the shaft 21 opposite the end to which the thermostat 31 is connected, as best shown in Figure 6. Since the arm |35 is rigidly secured to the shaft 21 and since the piston |2| is link connected with the arm, it will be seen that the dash pot device just described serves to oppose any sudden movement of the shaft 21, and since the choke valve is connected to this shaft by the link 3|, likewise any sudden movement of the choke valve 9 is restrained by the dash pot, the greater restraint being imposed upon the choke valve, by virtue of the tapered groove |24, in the lower position of the piston |2 which corresponds to the closed or nearly closed position of the choke valv'e 8.

The cylinder |20 is loosely disposed within the casing I8, and the lower or inner end of the cylinder |20 is provided with a flange |40 which is received within an opening formed in one side of the mounting plate |1, and the bracket 25. which includes a portion covering the cylinder receiving opening, is provided with an opening smaller than but in registry with said cylinder receiving opening, as indicated at |4|. The ears |28 extend through the opening |4|, as best shown in Figure 4. The mounting plate |1 is also provided with a second opening |42 registering with the opening in the mounting plate |1 through which the ears 13 and the link 8| extend, as best shown'in Figure 2; These registering openings are somewhat elongated in formation, as indicated at |45, and adjacent the elongated portions |45 the abutment stops 80 are formed. The elongations |45 provide for the convenient assembly of the device, in that by turning the bellows device BB-Lthrough a small angle,'the lateral extensions 14 will pass downwardly through the opening portions |45, and

then the bellows assembly can be rotated back to its position to dispose the adjusting screws 1l in proper position with respect to the abutment stops 80. Preferably, also, to facilitate assembly, one of the bracket ears 26 is provided with a larger bearing opening than the other, the smaller one receiving the reduced end of .the shaft 21 while the larger opening receives a bearing bushing 5| which is adapted to be inserted over the other end of the shaft 21 after the latter has been disposed in the bearing openings' section so that the angular relation between the arm 30 and the shaft 21 about the axis of the latter is determined. n The choke valve operating arm 30 is securely clamped around this end of the shaft 21 by a clamping screw |55. The bottom cover 28 may be held in place against the lower side of the mounting plate I1 by any suitable means, such as a, screw |51 extending through an opening in the bottom ofthe cover 28 and engaging a threaded opening in the mounting plate |1 or in the bracket 25 secured to the lower space thereof.

'Ihe operation of the device described above is substantially as follows. The bellows device 38 has its lower movable end 10 held against the upper face of the mounting bracket I1 by the spring so long as there is no suction in the intake manifold 2, and this disposes the outer end 82 of the thermostat 31 inthe lower position of the two f positions it is desired to occupy, the upper position being when the bellows 40 is drawn upwardly by the application of suction so that the adjusting screws 15 engage the abutments 90.

When outside temperatures are low and when the outer end 82 of the thermostat 31 is in its lower position, the position of the shaft 2'| is such that the choke valve 8 is held by the thermostat 31 in its closed or substantially closed position. This adjusts the carburetor 5 for cranking under low temperature conditions. As the starting motor is energized and the engine cranked, a small amount of suction will be established in the in- -take manifold 2, and this will serve to contract the bellows 40 slightly so asl to raise the link 8|' i and the outer end of the thermostat l2. This will rock the shaft -21 a corresponding amount since the temperature to which the thermostat' I1 is subjected has not been changed. Now as the engine iires'and begins to run under its own power, the suction in the intake manifold 2 is materially increased the moment the engine fires. This suddent increase in the suction is immediI ately applied to contract the bellows 4I, the rate of application being governed by the setting of the metering pin 50 which serves, in'the first instance, toprevent the sudden building up of suction in the intake manifold 2 from swinging the shaft 21 to suddenly open the choke valve l, it being obvious that the farther in the metering pin 5I is adjusted, the greater the restriction established thereby will be and the greater will be length of time required for the suction to lift the bellows 4l. However, the moment the engine fires the suddenly created suction in the intake manifold 2 and the sudden rush of air past the choke valve v9 in the air inlet 8 of the carburetor tends to swing the valve to its open position, as a result of the use of the overbalanced type of valve'. At this moment, however, the dash pot device Il comes into action and, being directly connected with shaft 21, which in turn is directly connected with the arm I0 of the choke valve, the dash pot device is immediately effective to prevent any sudden opening of the choke valve the moment the engine begins to lire. In the absence of a dash pot or the equivalent, the moment the en gine would begin to lire, the sudden rush of air would swing the choke valve open and the fuel mixture would be too lean, with consequent danger of the engine stalling. The dash pot, constructed according to the principles of the present invention, effectively prevents the sudden opening of the choke valve but allows the same fea to slowly open as the engine warms up, the grad'- ual opening of the choke valve being predetermined by the characteristics of the thermostat 31. According to the principles of the present invention, therefore, as soon as the engine begins to nre, the bellows device 38 operates to shift the outer end 82 of the thermostat through a fixed distance, corresponding to the spacing between -the stops associated with the movable end of the bellows, but neither this sudden movement nor the eifect of the sudden application of suction to the choke valve itself will cause any immediate or instantaneous change in position of the chokevalve. due to the restraining action of the dashpot, particularly the more eifective restraint established by the dash pot in the lower positions of the piston I2I. Gradually, however, as the motor warms up and the thermostat 31, reacting against the lower end of the link Il, exerts a force to rotate the shaft 21 and also as the dash pot'l gradually gives way to the effect of the air pressure on the choke valve I itself, the latter opens to progressively reduce the amount of choking at practically exactly the rate best suited .to adjust the carburetor for the change in temthe thermostat 31 is to gradually open the chok valve, to which gradual movement the dash pot offers substantially ro resistance. The metering pin Il and associated parts are such that minor fluctuations in the intake suction do not affect the setting of the outer 'end of the thermostat l2',

and even though the intake suction should drop appreciably for a short length of time, the lower end of the bellows Il will not move downwardly away from the abutments Il for an appreciable length of time, due to the fact that the diameter of the bellows Il and the restriction established by the metering pin I0 serve to prevent the bellows from returning the end l2 of the thermostat to cranking position, that is, to its lower position, unless the cessation of suction continues for some little time. However, if the engine should stalll and the suction in the intake manifold be cut oi! for a short time, then the bellows 4I acting through the thermostat 31 as a lever, operates to the return choke valve toward its cranking posi` tion. However, as long as the engine I is actually running, the bellows Il serves to hold the screws 1I up against the abutments IG, thereby holding the thermostat end l2 in running position.

'Ihe suddenhullding up of the intake suction after the motor ilres and begins to run is only one means for shifting the thermostat device l1 from its cranking position toits starting position or, in other words, for automatically shifting the choke valve 9 from its cranking position to its starting position. Other means may be employed which in a general sense are responsive to crankconnection with the starting motor of the engine I or any of the associated controls, as illustrated in Figure 13. In this 'gure the bellows 36 and associated connections have been omitted. Instead, the end I2 of the thermostat is connected to the upper end of a Bowden wire I which is suitably enclosed in a casing IGI. The lower end of the wire is connected by a lug |63 with the plunger |32 of the mechanism which controls the starting motor for the engine I. In operation, when it is desired to start the engine I the plunger |82 is premed downwardly, the position shown in Figure 13, by any suitable means so as lto cause the starting motor I to crank the engine I. The downward movement of the plunger Il! to the position shown in Figure 13 exerts a pull on the wire III, and this swings the thermostat 21 downwardly substantially to a position like that shown in Figure 2. As soon, however, as the engine begins to fire, the plunger |02 is released and the spring I I forces the same back.A

to its original position. This movement of the plunger |62 is transmitted through the wire Ill to the end I2 of the thermostat 31 and moves the same through substantially the same extent 'that the thermostat in Figure 2 is shifted by the contraction of the bellows Il which, as described above, is also responsive to the starting of the engine I. Thus, where in one case I have utilised the increase in suction to cause a shift of the thermostat I1 whenever the engine begins to run, and in Figure 13 I have illustrated a construction in which the movement of the' starting motor control mechanism from a cranking position to s. position corresponding to the running of the engine for causing the same shift of the associated thermostat, it is to be observed that in each case the parts constitute means for shifting the thermostat from one position to another whenever the engine I begins to nre.

The dash pot device 3l, both in the form of the invention shown in Figure 2 and the form shown in Figure 13, also serves another important function in automatically controlling carburetor adjustmenta The primary object of the dash pot is to prevent suddm'iiuctuatiom-of air pressure on,

the choke valve l from shifting the same out of the desired position to which it has been moved by the temperature responsive thermostat 31. For example, after a cold motor has been started and has been running for a short length of time, it may be that sudden acceleration of the motor and the resulting rush of air past the choke valve 9, would tend to swing the same to` an open position which would thin the fuel mixture to such a point that the motor would not operate properly. The dash pot device 38 under such conditions functions to prevent such sudden opening of the choke valve and therefore, operates during periods of acceleration to maintain the proper fuel ratio. In this connection, it is to be noted, that the'dash pot 3Q is more effective in its lower positions, which correspond to the more closed positions of the choke valve, than when the piston I2| is in its upper range of movements.

While we have shown and-described above the preferred structure in which the principles of the present invention have been embodied, it is to be understood that our inventionis not to be limited to the specific vdetails shown and described, but that, in fact, widely different meansmay be employed in the practice of the broader aspects of our invention.

What we claim, therefore, and desire to secure by Letters Patent is: v i

l. An automatic choke for carburetors for internal combustion engines in which the carburetor is provided with an unbalanced air valve, said automatic choke comprising a casing, a shaft vjournaled in one section of said'casing and having an arm adapted to be connected with said air valve, a thermostat anchored at one end t o said and rigidly connected withthe shaft therein,`

means in the second section of said casing serving as a dash pot and operatively connected with said second arm, and means adapted to communicate the intake suction of the engine to said bellows.

2. An automatic choke for carburetors for internal combustion engines in which the carburetor isprovided with a choke valve, saidA auto-- matic chokecomprisinga casing, a shaft journaled therein and provided with an arm `secured thereto and adapted t'o be connected with said choke valve to vcontrol. thel position thereof, a

thermostatic spring connected'at one end with said shaft, a bellows carriedby said casing and having a movableend connected with the other end of said thermostatic spring, means serving as Y a pair of spacedstops for the movable end of said bellows to limit the movement' thereof, spring means tensioned to shift the movable end of said bellows against one of said stop means, -means providing forthe communication of intake suction from the engine to said bellows; andmeans incorporated therein and including a metering pin for restricting the application of'suction Ato said bellows, the intake suction acting to-draw :the movable end of said .bellows giDSt the other of said stop means, the tension of saidspring means and the setting of Vsaid vmetering pin being correlated with the amount of intake suction so that the spring will not move'thc movto move the same.

able end of the bellows againstsald nrst stop means for a length of time greater than that requiredfor the suction to draw the movable end of' the bellows from said first stop means up against said second stop means.

3. The combination for use with an internal combustion engine having an exhaust manifold' and an intake passageway, and a carburetor having an air valve which tends to open by suction in said intake passageway, of a casing adapted to be secured to said exhaust manifold, a shaft journaled in said casing and having an arm secured thereto and connected with said air valve, a thermostat disposed in said casing and connected at one end with said shaft, means providing for the transmission of heat from the exhaust manifold to said thermostat, a bellows carried by said casing and having a movable end connected with the other end of said thermostat, stop means limiting the movements of said movable end in both directions, one of said stop means being adjustable, and conduit means leading from the interior of said intake passageway to the interior of said bellows.

4. The combination for use with an internal combustion engine having an exhaust manifold and an intake passageway, and a carburetor having an air valve which tends to open by suction in said intake passageway, of a casing adapted to be secured to said exhaust manifold, a shaft journaled in said casing and having an arm secured thereto and connected with said air valve, thermostat disposed in said casing and connected at one end with said shaft, means providing for the transmission of heat from the exhaust manifold to saidthermostat, a bellows carried by said casing and having amovable end connected'with the other end of said thermostat, stop means limiting the movements of said movable end in both directions, one of said stop means being adjustable, conduit means leading from the interior of said intake passageway to the interior of said bellows, a metering pin disposed in said conduit means for governing the rate of application. of

5. 'Ihe ycombination/for use with an internal combustion engine having an exhaust manifold and an intake passageway, and a carburetor having an air valve which tends to open by suction in the intake passageway, of -a casing adapted tobe mounted on said exhaust manifold, a rotatable shaft journaled in said casing and having an arm adapted to be connected to said air valve to .position the same, a thermostat mountedon said arm. means providing for the transmission` of heat I from the exhaust .manifold to said thermostat, va dash pot conthe'position of the latter, to change the position of 4said air valve, means providing denite stops in-vboth directions for-'said movable member,` one positioncorresponding to the desired position' of said-air valveduringcranking of the engine and theA other position corresponding .to the de'- lired'position of the .air valve when the engine begins to fire, and means for shifting said movable member from one position to another.

6. The combination for use with an internal combustion engine having an exhaust manifold and an intake passageway, and a carburetor having an air valve which tends to open by suction in the intake passageway, of a thermostat. means connecting one end of said thermostat with the air valve to govern the position of the latter, means subjecting the thermostat to the heat from the exhaust manifold, a dash pot for resisting sudden opening thereof, said dash pot comprising a cylinder, a piston slidable therein and connected to the air valve, said cylinder having a tapered groove formed in the inner wall thereof adjacent the piston to vary the resistance of the dash pot to movement of the valve, a movable anchoring member to which the other end of the thermostat is connected, stop means providing two definite positions for said movable member, one position corresponding to the position of the air valvev when the engine is being cranked and the other position corresponding to a position of the air valve when the engine begins to run, means biasing said movable member to yieldingly hold the same in one position, and means for moving said movable member from said one position to the other position.

7. The combination for use with an internal combustion engine having an exhaust manifold and an intake manifold, and a carburetorv having an air valve which tends to open by suction inthe intakemanifold,ofacasing adaptedtobe secured to the exhaust manifold and including a lower portion, a shaft iournaledin said lower portion, an arm on the outer end of s aid shaft operatively connected with the air valve of said carburetor, means providing for the transmission of heat from said exhaust manifold to the lower portion of said casing, a thermostat anchored at its inner end to and coiled around saidshaftand subjected totheheat from said exhaust manifold, an arm fixed to said shaft in the lower portion of said casing, a pair of chambersformedintheupperportionofsaidcasing and disposed alongside one.` another, a dash pot piston mounted in one of said chambers and connected with said last mentioned arm, valve means carried bysaid tension and providing for the restraint of movement of said arm and shaft in one direction only, a bellows disposed in the other ofY lsaid fchambers and anchored at its upper end to said casing, the ylower end being movable therein, link means connecting the movable end of said bellows with the outer end of said thermostat. means carried by said casing' and serving as a pair of stops limiting the movement. of the outer end of said thermostat in both directions, and means subjecting the interior. of said bellows to the suction in said intake manifold. Y

8. An automatic choke for carburetors for internal combustion engines in which the carburetor is provided with an unbalanced air valve, said automatic choke comprising a casing, a shaft journaled in one section of said casing and having an arm adapted to be connected with said air valve, a thermostat anchored at one end to said shaft, a bellows disposed in the other section of said casing and having one end fixed thereto and the other end movable, and means connecting the movable end of said bellows with the other end of said thermostat, whereby by shifting said thermostatthe movement of said bellows shifts said shaft and the arm carried thereby.

9. An automatic choke for carburetors for lnternal combustion engines having an exhaust manifold and in which the carburetor is provided with an unbalanced air valve, said automatic cho e comprising a mounting bracket adapted to secured to said exhaust manifold and having depending ears, a shaft journaled in said ears and having an arm adapted to be connected with said carburetor air valve, a thermostat anchored at one end to said shaft and disposed on the under side of said bracket, a bellows disposed on the other side of said bracket, an upper casing section mounted on said bracket and enclosing said bellows, the latter having one end fixed to said casing and the other end movable, a lower casing section enclosing said shaft and thermostat, means connecting a movable end of said bellows with the other end of said thermostat, whereby movement of said bellows shifts said shaft and the arm can'ied thereby, and means serving to transmit heat from said exhaust manifold to said thermostat.

10. An automatic choke for carburetors for internal combustion engines in which the carburetor is provided with a choke valve, said automatic choke comprising a casing, a shaft journaled therein and provided with an arm secured thereto and adapted to be connected with said choke valve to control the position thereof, a thermostatic spring connected at one end with said shaft, a bellows carried by said casing and having a movable end connected with the other end of said thermostatic spring, means serving as a pair of spaced stops for the movable end of said bellows to limit the movement thereof, means tending to hold the movable end of said bellows against one of said stop means, and means providing for the communication of intake suction from the engine to said bellows.

11. 'Ihe combination for use with an internal combustion engine having an exhaust manifold and an intake passageway, and a carburetor having anairvalvewhichtendstoopenbysuction insaid intake passageway, of a casing adaptedtobesecuredtosaidexhaustmanifold,ashaft journaiedinsaidcasingandhavinganarmsecured thereto and connected with said air valve, athermostatdisposedinsaidcasingandconnected at one end with said shaft, means providing for the transmission of heat from the exhaust manifold to said thermostat, a bellows carried by said casing and having a movable end connected with the other end of said thermostat, stop means limiting the movements of said movable end in both directions, and conduit means leading from the interior of said intake passageway to the interior of said bellows.

12. The combination for use with an internal combustion engine having an exhaust manifold, and a carburetor having an air valve which tends to open by suction in said intake passageway, of a casing adapted to be secured to said exhaust manifold, a shaft journaled in said casing and having an arm secured thereto and connected with said air valve, a thermostat disposed in said casing and connected at one endwith said shaft, means providing for the transmission of heat lfrom the exhaust manifold to said thermostat, a

bellows carried by said casing and having a movable end connected with the other end of said thermostat, and means operable through said bellows when the engine begins to run for imparting a given shift to the position of said ther- 2.1mm l i "r mostat, independent of the temperature of said exhaust manifold.

13. The combination for use with an internal combustion engine having an exhaust manifold I and an intake passageway, and a carburetor having an air valve which tends to open by suction in the intake passageway. of a spring thermostat, means connecting one end of said thermostat with the air valve to govern the position of the latter, means subjecting the thermostat to the heat from the exhaust manifold, a movable anchoring member to which the other end of the thermostat is connected, stop means providing two denite relatively fixed positions for said movable member, one position corresponding to the position of the air valve when the engine is being cranked and the other position correspending to a position of the air valve when the engine begins to run, means for moving said movable member from said one position to the other position, dash pot means connected to said air valve for cushioning the movement of said air valve against the tension of said spring thermostat occasioned by variations in suction in the lo intake passage, and means for reducing the cushioning effect of said dash pot as said valve is moved toward open position. y

14. In a charge forming device for internal combustion engines, means for automatically determining the ratio of air to fuel in the mixture supplied to such engine comprising a suction-4 operated air valve for regulating the supply of air, thermally responsive means operative to move said air valve toward open position upon 88 increase of engine temperature and a dash pot operable to oppose the movement of said valve toward open position upon increase in the suction effective on such valve. and means for varying the resistance of the said dash pot as the valve moves toward open position.

15. In a charge forming device for internal combustion engines, means for automatically determining the ratio of air to fuel in the mixture supplied to such engine comprising a suctionoperated air valve for regulating the supply-of air, thermally responsive means operative to move said air valve toward open position upon increase of engine temperature and a dash pot operable to oppose the movement of said valve tol0 ward open position upon increase in the suction effective on suchvalve. and means for progressively reducing theresistance of the dash pot as the valve moves toward open position comprising a tapered slot in the wall of the dash Dot Il cylinder to permit escape of air therefrom.

16. An automatic choke mechanism for the charge forming device of an internal combustion engine having an intake manifold provided with a heating chamber for heating the combus- 00 tible mixture supplied to the engine and comprising, in combination, a mixture proportioning means, a control unit for operating said mixture proportioning means and including a housing, thermally responsive means mounted in said housing adapted to position said mixture proportioning means in accordance with engine temperature. a suction operated means also positioned within said housing and adapted to vary 'o the setting of the mixture proportioning. means as determined by said. thermally responsive means in accordance with engine suction. means for securing.v said housing directly to the wall of the heating chamber in auch position that the n thermally responsive means is relatively close to said wall and a metallic heat conducting element between the walland the thermostat.

17. An automatic choke mechanism for the charge forming device of an internal'cox'nbustion engine having an intake manifold provided with a heating chamberfor heating the combustible mixture supplied to the engine and comprising, in combination, a 'mixture proportioning means, a control unit for operating said mixture proportioning means and including a housw' ing, a suction operated element in said housing for operating said vmixture proportioning means, thermally responsive means in said housing for determining the position of said mixture proportioning means in accordance with engine temu perature to modify the position of said mixture proportioning means as determined by temperature, a suction passage for communicating the suction of the intake manifold to said suction operated element, and a manually adjustable go metering valve in said suction passage to control the effective area thereof and to vary the effect of engine suction on said mixture proportioning means.

18. An automatic choke mechanism for the g5 charge forming device of an internal combustion engine having an intake manifold provided with a heating chamber for heating the combustible mixture supplied to the engine, and comprising, in combination, a. mixture proportioning ,o means, a control unit for operating said mixture proportioning means and including a housing, a thermally responsive element in said housing adapted to hold said mixture proportioning means in position to form a rich mixture when the temperature is low, a suction operated element in said housing adapted to move said mixture proportioning means through the medium of the thermostat toward position to form a lean mixture as the engine suction increases, a suco tion passage for communicating `the manifold suction to said suction operated element and a manually adjustable metering pin in said passage to control the suction effect on said suction operated element. s

19. An automatic choke mechanism for the charge forming device of an internal combustion engine having an intake manifold provided with a heating chamber fort heating the combustible mixture supplied to the engine and comprising, w l

in combination, a mixture proportioning means, a control unit for operating said mixture .proportioning means and including a housing, a suction operated element adapted upon increase of engine suction to move the mixture proportioning means toward a position to form a lean mixture and upon decrease of suction to control the movement of said mixture proportioning means toward a position to form a rich mixture, a suction conduit to communicate manifold suction to the o suction operated element, said conduit having a portion with a gradually tapered Wall forming a valve seat, a manually adjustable valve 'received within the'conduit and extending longitudinally thereof, said valve having a surface substantially g5 parallel to said valve seat, whereby adljustment of said valve may effect minute variations in the area of the passage between said valve and seat to accurately determine the rate of movement of the mixture proportioning means as brought about by variations in suction.

20. An automatic choke mechanism for the charge forming device of an internal combustion engine having an intake manifold provided with a heating chamber for heating the combustible mixture supplied to the engine, and comprising, in combination, a mixture proportioning means, a control unit for operating said mixture proportioning means and including a housing, thermally responsive means in said housing adapted to operate the mixture proportioning means, means directly securing said housing to the wall of said heating chamber, and a metallic gasket adapted to be secured between said housing and the heating chamber, said gasket being provided with aprojecting surface extending toward said thermally responsive means whereby said gasket acts as a metallic heat conductor for conducting heat from said heating chamber to the thermally responsive means'. y

21. An automatic choke mechanism for the charge forming device oi! an internal combustion engine having an intake manifold provided with a heating chambersfor heating the combustible mixture supplied to the engine, and comprising, in combination, a mixture proportioning means, a control unit for operating said mixture proportioning means and including a housing, thermally responsive means in said housing adapted to operate the mixture proportioning means. means directly securing said housing to the wall oi.' said heating chamber, and a metallic gasket adapted to be secured between said housing and the heating chamber, said gasket being provided with a projecting surface which extends partially around the thermostat, whereby said gasket acts as a metallic conductor of heat from the heating chamber to the thermally responsive means and also as a shield for said thermally responsive means.

22. An automatic choke for carburetors for internal combustion engines in which the carburetor is provided with an unbalanced airvvalve. comprising the combination oi' thermostat means responsive to engine temperature, means yieldingly connecting the thermostat means with said valve for shifting the same to a position corresponding to engine temperature and providing for movement of the valve relative to said thermostat means throughout the range of the latter under the influence of air pressure against the valve, dash pot means having a rigid connection with said valve to prevent sudden changes of air velocities from sluiting said valve out of the position determined by said spring thermostat means and means for reducing the resistance oiIered by the dash .pot to movement of the valve as the said valve is moved toward its open position.

23. An automatic choke for carburetors for in- -ternal combustion engines in which the carburetor is provided with an unbalanced air valve tending to open by the iiow of air past said valve. said automatic choke comprising the combination oi thermostat means responsive to engine temperature, means yieldingly connecting the thermostat means with said valve for shifting the same to a position corresponding to engine temperature, means operable between two deilnite limits intermediate the range of movement of said valve for shifting the latter from one of said deilnite positions to the other when the engine begins to run, dash pot means having a rigid connection with said valve and adapted to oppose sudden movements of the valve inside said limits of movement thereof whereby the opening of said valve under the influence of air flow past the same and under the iniiuence of sudden decreases in the intake suction is resisted by said -dash pot means and means for reducing the resistance oiered by the dash pot to movement o! the valve as the said valve is moved toward its open position.