US2481259A

US2481259A - Automatic choke for carburetors

Info

Publication number: US2481259A
Application number: US35638A
Authority: US
Inventors: William H Taylor
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1935-08-10
Filing date: 1935-08-10
Publication date: 1949-09-06
Anticipated expiration: 1966-09-06

Description

Sept w49 W. H. TAYLOR AUTOMATIC CHOKE FOR CARBURETORS 2 Sheets-Sheet 1 Filed Aug. l0, 1935 Sept h5 w49. w. H. TAYLOR 2,431,259

AUTOMATIC cHoKE Foa cARBUREToRs Filed Aug. l0, 1935 2 Sheets-Sheet 2 /sa- L n d1 1:/ x q /66+ M67 INVENTOR ,da ATTORNEYS Patented Sept. 6, 1949 AUTOMATIC CHOKE FOR CARBURETORS William H. Taylor, Anderson, Ind., asslgnor to General Motors Corporation, Detroit, Mich., a

corporation oi' Delaware Application August 10, 1935, Serial No. 35,638

17 Claims. 1

This invention relates to automatic choke devices for controlling the fuel mixture ratio formed by charge forming devices for internal combustion engines.

Choke mechanisms of the automatic type have been provided heretofore for the purpose of automatically increasing the fuel content in the mixture supplied to the engine when the latter is cold so as to facilitate starting and such devices have been provided with means for rendering them inoperative after the engine warms up to normal temperature so that after the warm up period has passed, the mixture provided for the engine by the charge forming device is of normal fuel content. These devices have, in general, been controlled by some thermally responsive means which, when cold, has been utilized either to hold an air valve closed, or a fuel valve open, and when the temperature adjacent such thermally responsive device increases, the device becomes ineffective to position the valves as described, so that the charge forming device thereafter provides its normal mixture.

Certain diiliculties have been encountered heretofore in so constructing such device that the thermally responsive element heats up suiliciently rapidly to enable the valve controlled thereby to be so positioned as to supply a normal mixture sufficiently quickly after the engine begins to operate. In other words the rich mixture is provided for too long a time. Heretofore, the engine has been employed as a heating medium to supply heat to the thermally responsive element and even when the element is mounted on the manifold heater itself, the rise in temperature adjacent such thermal element has been somewhat slow to give the best results under all conditions and this difficulty is even more apparent when the thermally responsive element is mounted on or constructed as a part of the charge forming device itself, which is most desirable for manufacturing purposes.

It is the primary purpose of the present invention to provide improved means for heating the thermally responsive element of an automatic choke device so that such element is subjected to the proper degree of heat to give the best results under all conditions.

It is a further and more specific object of the invention to provide a means for heating the thermally responsive element of an automatic choke mechanism of the character described during the warm up period of the engine by a means other than the engine, itself, and further, to provide means for rendering this heating deating conditions.

According to the present invention, these objects are attained by the provision of an electrical heating device which is positioned immediately adjacent the thermostat, itself, and which is provided with a controlling circuit so arranged that the heating coil becomes edective immediately upon the starting 'of the engine and remains effective until the temperature adjacent the thermally responsive element reaches a predetermined degree when the circuit is broken and remains broken as long as the temperature adjacent such thermally responsive element is above the predetermined degree referred to.

Further objects and advantages of the present invention will be apparent from the following descriptlon, reference being had to the accompanying drawings wherein a preferred embodiment ofA the present invention is clearly shown.

In the drawings:

Fig. l is a diagrammatic view of a charge forming device provided with an automatic choke mechanism equipped witha heating device for the thermally responsive control element constructed in accordance with this invention.

Fig. 2 is a detailed, plan view of the thermally responsive element and a form of heating element associated therewith.

Fig. 3 is a View similar to Fig. 2 showing a modied form of heating device.

Fig. 4 is a section on the line -i of Fig. 5, showing a down-draft type of carburetor provided With a modified form of choke device and heating element for the thermally responsive control member thereof and including a diagram of the control circuit.

Fig. 5 is a vertical section on the line 5-5 of Fig. 4.

Referring to Fig. l, the reference character l0 indicates a carburetor of the conventional plain tube type which is secured to the riser of an intake manifold I2 and provided with an attaching ange Il adapted to be attached to a corresponding iiange I6 on the manifold.

The carburetor.. being of the conventional plain tube type, has a single air inlet I8 controlled by an unbalanced air valve 20 secured to a shaft 22, which is o!! center with respect to the valve. The valve may be held by a thermostat, later described, and a spring 24 shown diagrammatically in Fig. 1 may be used to aid the thermostat, but may be omitted if desired.

Fuel is supplied from a main fuel tank through a pipe 26 to a float chamber 28 of conventional type, having a float 30 therein which controls a valve 32 to regulate the addition of fuel to the float chamber. Fuel is supplied to the intake passage of the carburetor through a nozzle 34 which terminates in conventional manner within a Venturi tube 36, to create a suction at the end of the nozzle, the flow of mixture from the carburetor being controlled by a throttle valve 38 of conventional form which is secured to a shaft 40 journalled in the carburetor housing and adapted to be operated in the usual Way.

The air inlet valve 20, previously referred to, is variably positioned under different operating conditions to control the ratio of fuel to air in the mixture which is supplied by the carburetor to the engine with which it is associated. Such valve is adapted to be held in closed position when the engine is cold so as to provide a rich mixture at such time to facilitate starting. As the engine warms up subsequent to its starting, the pressure of the thermostat to hold the valve closed is progresslvely reduced and finally the thermostat operates to move the valve to open position against the force of the -spring which holds it closed.

Also in the form of the device shown, a suction.

operated element is provided to move the valve toward open position in the event that the engine fails to start immediately, so as to prevent flooding of the engine under such conditions, while a further suction operated member is adapted to l move the valve temporarily toward closed position upon opening movement of the throttle, the last mentioned device being provided to prevent leaning of the mixture during the acceleration period.

These various control devices are all shown in the earlier application of Clarence H. Jorgensen and Peter J. Jorgensen, Serial No. 585,510, but so far as the present invention is concerned, such suction operated devices are not necessary, and the heating device which forms the present invention may be used without such suction operated device, but when the heating means and such suction operated device are employed in combination the control of the mixture under all conditions is more accurate than if the suction operated devices were omitted.

Referring now to the mechanism for operating the air valve 29, the shaft 22 has secured thereto an arm 42 and connected with the free end of the arm 42 is a. link 44 which extends upwardly and is pivotally connected at its upper end to an arm 46. secured to a shaft 48, journalled for rotation in a housing 50, 'which is secured to the manifold in any desirable manner and in which is contained the control unit for operating the choke valve 20, said control unit comprising the thermostat and the suction operated devices previously referred to.

Connected at one end to the shaft 48 is a bimetallic thermostat 52 of the coil type, the free end of which is pivotally connected to a link 54 which, at its upper end, is secured to an ear 56 projecting from a plate 58 which forms one end of a bellows 60, preferably of metallic construction, and normally held in its expanded position by a compression spring 62 received within the bellows and engaging the top of the housing E0 at its upper end. 'Ihe interior of the bellows communicates with a valve controlled suction .passage 64 through which the suction of the intake manifold may be communicated to the interior of the bellows, the effective area of the suction passage being controlled by a manually adjustable needle valve 66 which is screwed into the housing 50.

Normally, when the device is cold, the parts are in the position shown in Fig. 1. The thermostat, when cold, and the springs 24 tend to hold the valve 20 in closed position with the arm 46 in the position shown. As the engine warms up the thermostat will, of course, expand and the expansion of the thermostat first reduces the force holding the valve closed and eventually causes a clockwise movement of the arm B6 which results in the opening of the valve 20 to a degree determined by the heat to which the thermostat is subjected. Therefore, in any position of the thermostat when the engine is at high temperature which subjects the thermostat, to relatively high temperature would be such as to position the valve either in full open, or in partially closed position dependent upon the degree of heat maintained adjacent the thermostat.

The action of the engine suction upon the bellows is also utilized to move the valve 20 toward its open position under certain circumstances. 'I'he engine suction is communicated through passage 64 to the interior of the bellows as set forth previously and the air within the bellows is slowly exhausted thereby at a rate determined by the position of the valve 66. The flow of air from the bellows is necessarily very slow if the valve is properly adjusted so that there will be a material interval of time before the suction becomes sufficient to open the valve 28 against the closing pressure thereon. The action of the bellows is to lift the free end of the 'thermostat and through the medium of the latter, the shaft 48 is rotated so as to move the arm 46 in a clockwise direction as it is moved when the thermostat expands. This mechanism is provided to permit air to flow into the intake passage to prevent flooding in the event that the engine does not start within a very brief period after the cranking begins. The valve 66 should be adjusted to give whatever time interval is desired before the suction begins to be effective initially.

When the engine begins to run the increase of vacuum effective upon thebellows is very considerable by comparison to the vacuum during cranking and this increased vacuum is eective to operate the arm 46 to move the valve 20 still farther 'toward open position so as to provide a still leaner mixture after the engine begins to run on its own power. The bellows during normal operation of the engine is, of course, elective to hold the free end of the thermostat in whatever position is determined by the degree of suction effective on the bellows.

As indicated previously, means are also pro-- vided to control the action of the valve 2li during the acceleration period and for this purpose the shaft 68 has secured thereto an arm 'l0 one end of which is pivotally connected to a link l2, pivotally connected to a piston 14 slidable in a cylinder 16, formed in the housing 50. The top of the cylinder 16 is connected by a passage T8 with another cylinder 80, also formed within the housing 50. The cylinder is connected at its lower end to a suction passage 82 which, at its upper end, connects with the suction passage 83 leading to the intake manifold and communicat- Vposition by a spring 86 received between the piston and a closure plate 88 at the bottomof the cylinder 80. A valve 80 normally held in closed position by a spring 92 closes a port 94 in the piston |4, and permits the piston to have a dash pot action.

Obviously, the piston T4 will be moved downwardly if the pressure above the piston is increased and on such downward movement of the piston, the valve 20 will be moved toward closed position because the arm 10 is secured to the shaft 48 to which the arm 46 is also secured. The high vacuum existing in the intake manifold when the throttle is closed or partially closed is communicated through the

passages

83 and 82 to the cylinder 80 and pulls the piston 84 downwardly against the pressure of the spring. Any reduction in this vacuum will cause the piston 84 to move upwardly and force air from the cylinder 80 through the passage 18 to increase the pressure above the piston '|4 and close the valve 20 as previously described. This action takes place upon any opening of the throttle valve which causes a reduction in the vacuum between said throttle valve and the engine, such reduction occurring during the acceleration period and the valve 20 is moved by the mechanism just described to compensate for the effect of this decrease in vacuum, which otherwise would cause a leaner mixture to be supplied by the carburetor as is well known in the art.

All of the construction previously described is generally similar in design and yfunction to that shown in the joint application of Clarence H. Jorgensen and Peter J. Jorgensen, which has been referred to above.

In the earlier application above referred to, the housing corresponding to the housing 50 is secured directly against the heating chamber for the carburetor, which is customarily known as a hot spot. Exhaust gases are passed through this chamber which heats relatively rapidly as the engin'ebegins to run and such chamber being relatively close to the thermostat, the latter heats up relatively rapidly. It has been found, however, that it does not heat sufficiently rapidly under all circumstances and, moreover, it has also been found that it is somewhat less expensive to manufacture a device in which the choke unit and control unit were constructed as a part of the carburetor than as a separate unit relatively remote therefrom. To overcome these dinicultes, the present applicant has provided a heater comprising an electrical heating element which, in the form shown in Fig. 1, is a form of asbestos strip cemented or otherwise secured to the thermostat itself, and indicated in the drawings by the reference character |00. Incorporated within this strip is a resistance element or wire |02 which comprises anv electrical heater. One end of the wire |02 is grounded as indicated at |04 and its other end is connected by a wire |06 to a contact |08 suitably insulated from the housing 50 and adapted to be engaged by a movable contact carried by and suitably insulated from an arm ||2 pivoted at ||4 to a lug projecting from the housing 50. Connecting this contact with a binding post ||6 suitably insulated from the housing 50 is a wire ||8 and also connected with the binding post is a. wire |20 which extends to the generator. Extending from wire |20 to the cut-out relay is wire |2|. The cut-out relay is of ordinary conventional construction and need not be described specifically more than to say that it comprises a magnet which operates an arm |26 carrying a movable contact |28, adapted to engage a contact |30 connected by the wire |32 to the battery |34 whenever the generator is operating above a predetermined very low speed. The contacts `|28 and |30 are, however, separated whenever the generator is not running to prevent a discharge from the battery back through the generator to ground in a manner well known in the art. The winding of the magnet of the relay is grounded at |36 and the battery is grounded at |38, as indicated in the drawing.

It will be understood that instead of -connecting the terminal ||6 in the manner described it might be connected directly with the battery through the medium of the ignition switch if so desired since such switch is normally open when the engine is not running.

The above described heating device operates as follows. As previously pointed out, the switch comprising contacts |08 and ||0 is normally closed as shown in Fig. 1 when the engine is not` running, but the switch comprising contacts |28 and |30 is open so that no current can flow from the batterythrough the heating element under normal' conditions when the engine is not running. As soon as the engine is started, however, and reaches a predetermined speed, which is relatively low speed, such as the normal idling speed, thc contacts |28 and |30 are closed, at which time current will flow from the battery through the wire |32, contacts |28 and |30, arm |26, the winding of the cut-out relay and Wire |20 to the binding post ||6 from which it flows through wire H8, switch contacts ||0 and |08, and wire |06 to the heating coil |02 and thence to gIOllnd through the connection |04, and from ground back to the battery through the connection |38.

' Thus the circuit throughy the heating element will be established when the motor begins to run at a speed even as low as idling and current will continue to low through the heating element so as to heat up the thermostat quite rapidly, and more rapidly than has been heretofore possible, until the expansion of the thermostat lifts the arm 46, which through the medium of a toe |40 formed thereon lifts the arm 2 to break the circuit by separating the contacts |08 and ||0. Obviously, these contacts will remain separated as long as the heat to which the thermostat is subjected is enough to cause suicient `expansion of the thermostat to lift the arm |2 as described. This degree of heat which is maintained by the engine, itself, after the latter heats up and is operating normally will maintain the contacts |08 and ||0 open as long as the engine continues to run under its own power under normal circumstances. With this arrangement, therefore, the electrical heating device is effective only during the warm up period of the engine, is operative to cause the thermostat to open the valve 20 very soon after the engine becomes self-operative, andI prevents the formation of a too rich mixture within the carburetor for too long a period of time, a difficulty heretofore encountered during 'the operation of the engine with automatic choke trol means for the choke valve is shown and the control mechanism is incorporated as a part of a down-draft carburetor instead ci being an entirely separate unit secured to the manifold as in the form of the invention previously described. The carburetor illustrated comprises an intake passage indicated generically by the number |50 to which fuel is fed by a nozzle ibs, while air is admitted at the upper end of the e IW and is controlled by an unbalanced choke valve |54 secured to the shaft |56 which is suitably journalled in the walls of the intake passage and is ci! center with respect to the vmve as shown. The ilow oi mixture from the carburetor is controlled by a throttle, valve |58 of the usual con? struction secured to a shaft |69 journalled in the housing and adapted to be manually operated by any suitable mechanism. This carburetor is positioned above the manifold to which it is adapted to be attached by means of flange |62 which engages a corresponding ange on the manifold.

The choke valve may be held closed by a spring; not shown, and a thermostat comprising the bi-v metallic coil |6d or the spring may be omitted and the thermostat. itself, may constitute the only means for holding the valve in closed position.

The thermostat is positioned in a chamber |63` which is lined with cork or other suitable mate-y rlals indicated at |65 and is provided with a detachable cover |81. This thermostat is connected at one end directly to the shaft |56, which extends into chamber |63 as indicated in Fig. 4, and at its other end is connected to a. link |66 which extends downwardly and is positively ctm-i nected at |88 to a lug projecting from a, piston |10 slidable in a cylinder |12 formed in the carburetor housing and normally held in its upper posi tion as shown in Fig. 4 by a spring |15 which is received between the piston and the bottom of the cylinder.

Communicating with the bottom of thecylinder is a suction passage I' which communicates with another suction passage |18 leading to the intake passage ist at a point between the throttle valve |58 and the engine. The effective area of this suction passage is controlled by a manually operable needle valve |90 screwed into the housing as indicated in Fig. 5.

The operation of this device is similar to that of the device previously described except for the fact that no means is shown to compensate `for acceleration corresponding to the pistons 84| and 1d of the device shown in Fig. l. When the device is cold and the engine is stationary, the piston |1(|Y is held in its upper position. When the thermostat heats up and expands the expansionl thereof will open the valve |54 to an amount dependent'upon the heat to which the thermostat is subjected until the valve |54 is eventually fully open.

The piston |10 and the suction connections |16 and |18 perform substantially the same function as previously described with respect to bel= lows 60 and the suction connection communicating therewith. If the valve |54 is held closed 70 by the thermostat as previously described with the engine cold the starting motor becomes effective to crank the engine, suction is communicated to the piston |10 which gradually builds up sufascisse so through the medium of the thermostat opens the valve |54 to an extent dependent upon the suction and the force of the thermostat which is eiective on the valve. This device operates to prevent flooding in exactly the same manner as previously described.

The heating element disclosed in this form of the invention comprises a heating coll |82, which is of somewhat arcuate form so as to lie somewhat parallel to the surface of the thermostat in the chamber |63, as shown in Fig. 4. One end of coil |82 ls connected by e. binding post |84, suitably insulated from the housing, in contacting relation with a metallic contact piece of arcuate form |86, which is also suitably insulated from the housing by means of the cork lining |65 of the chamber in which the thermostat is positioned. This contact piece is also secured in position by a rivet ist so as it will be rigidly held in place. Secured to one end of the shaft |56 is a contact arm |92 grounded at ist, which is adapted to wipe over the surface of the contact piece |86, as the arm is moved during movement of the choke valve. The other end of the heating element |82 is connected to a binding post which is suitably insulated from the housing and at its other end is connected to a wire |98 which extends to the generator 20|). A wire |99' connects the cut-out relay, indicated generically by the reference number 2|l2, which is of substantially the same form as that disclosed in Fig. 1, with the wire |98. The generator is grounded at 284 while one end of the winding of the relay magnet is grounded at 206. The contacts of the relay are indicated at 208 and 2|0 and are normally held open by a spring 2|2. The contact 2||| is connected by the wrzeld with the battery 2|6 which is grounded a In Fig. 4 is shown the alternate control circuit employing the ignition switch. When this circuit is used the wire |98 connects with a wire 224 leading to the movable contact 226 of the ignition switch instead 'of extending to the generator and cut-out relay as previously described. The contact 226 is provided with two arms 228 and 23@ adapted to engage xed contacts 232 and 23d from

wires

236 and 238 which lead respectively to the battery and to the ignition system of the engine. The path of current from the battery to the heating element |32 is deemed obvious and need not be discussed.

The operation of this heating element is substantially the same as that previously described. When the engine ia at rest, if the ,thermostat is cold, the contact arm |92 engages the contact piece |86 but the circuit is broken because of separation of the contacts 208 and 2|@ of. the cut-out relay as previously described. When the engine starts to run under its own power these contacts 208 and 2|!) are closed and current will flow from the battery through the relay, the

'wire |98, and binding post |96 to the heating element |82, thence through contact piece |86, arm I 92 and the connection |94 to ground, and back to the battery through the connection 2| 8. As the thermostat warms up and expands to open the valve |54 as previously described, the contact arm |92 is moved in a counter-clockwise direction and nally is moved entirely out of engagement with the contact piece |86 so as to break the circuit of the heating element at such point and such circuit will remain broken until the thermostat is again sulciently cool for the arm to engage ilciently to pull the piston |10 downwardly and 75 the contact piece |86. As long as the engine runs 9 under its own power after the warm up period is over. the heat which the thermostat gets from the engine, itself, is sulcient to keep the circuit of the heating element open so that it is not eil'ectlve until after the thermostat again cools down subsequent to the stopping of the engine.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A choke mechanism for the charge forming device of an internal combustion engine having in combination means for varying the fuel to air ratio in the mixture formed by said charge forming device, a thermostat for operating said ratio varying means, relatively remotely located with respect to the engine, heating means `for raising the temperature adjacent the thermally responsive means more rapidly than the temperature adjacent the engine is raised and means other than the thermostat for rendering the heating means inoperative after a predetermined effect on the thermally responsive means.

2. A choke mechanism for the charge forming device of an internal combustion engine having in combination means for varying the fuel to air ratio in the mixture-formed by said charge forming device, thermally responsive means for op- 1 the temperature adjacent the engine is raised, :l

means operable when the engine operates at a predetermined speed for rendering the heating means inoperative after a predetermined effect on said thermally responsive means.

3. A choke mechanism for the charge forming device of an internal combustion engine having in combination means for varying the fuel to air ratio in the mixture formed by said charge forming device, a thermostat for operating said ratio varying means, an electric heating device for heating the thermostat, and means comprising an element separate from but operable by the thermostat for rendering the said heating device inoperative.

I 4. A choke mechanism for the charge forming l device of an internal combustion engine having in combination means for varying the fuel to air ratio in the mixture formed by said charge forming device, thermally responsive means for controlling the position of said ratio-varying means,

means for heating said thermally responsive means, means for rendering said heating means inoperative after its heating effect on said thermally responsive means reaches a predetermined degree,`and suction operated means also controlling the position of said ratio varying means, effective on the latter during the entire operation of the engine under its own power.

`5. A charge forming device for an internal combustion engine having, in combination. means for varying the fuel to air ratio of the combustible mixture formed by said charge formingl device and comprising a choke valve adapted to variably restrict the air inlet of said charge forming device and movable to different positions in response to variations in temperature and engine suction, a thermostat for controlling the position of the choke valve, an operative connection between the .thermostat and the choke valve, means for rendering said thermostat eiective to hold the choke valve closed at low temperatures and to move said valve to open position as the -temperature is increased, heating means other than the engine for heating the thermostat when the engine is in operation, and means for rendering said heating means ineffective as the choke valve is moved toward open position by the thermostat.

6. A charge forming device for an internal combustion engine having, in combination, means for varying the fuel to air ratio of the combustible mixture formed by said charge forming device and comprising a choke valve adapted to variably restrict the air inlet of said charge forming device and movable to different positions in response to variations in temperature and engine suction, a thermostat for controlling the position of the choke valve, an operative connection between the thermostat and the choke valve, means for rendering said thermostat effective to hold the choke valve closed at low temperatures and to move said valve to open position as the temperature is increased, an electric heating device for heating the thermostat when the engine is in operation and means for opening the circuit of said heating device to render said device inoperative as the choke valve is moved toward open position by the thermostat.

7. A charge forming device for an internal combustion engine having, in combination, means for varying the fuel to air ratio of the combustible mixture formed by said charge forming device and comprising a choke valve adapted to variably restrict the air inlet of said charge forming device and movable to different positions in response to variations in temperature and engine suction, a thermostat for controlling the position of the choke valve, an operative connection between the thermostat and the choke valve, means for rendering said thermostat effective to hold the choke valve closed at low temperatures and to move said valve to open position as the temperature is increased, heating means other than the engine for heating the thermostat when the engine is in operation, and means operable by the thermostat to render the heating means ineffective when the choke valve is moved by said thermostat toward open position through a predetermined distance.

8. A charge forming device for an internal combustion engine having, in combination, means for varying the fuel to air ratio of the combustible mixture formed by said charge forming device and comprising a choke valve adapted to variably restrict the air inlet of said charge forming device and movable to different positions in response to variations in temperature and engine suction, a thermostat for controlling the position of the choke valve, an operative connection between the thermostat and the choke valve, means for rendering said thermostat effective to hold the choke valve closed at low temperatures and to move said valve to open position as the temperature is increased, an electric heating device for heating the thermostat when the engine is inoperative, and means operable by the thermostat to open the circuit of ther electric device torender said device inoperative when the choke valve is moved by said thermostat through a predetermined d istance toward open position.

9. A charge forming device for an internal combustion engine having, in combination, means for varying the fuel to air ratio of the combustible mixture formed by said charge forming device and comprising a choke valve adapted to variably restrict the air inlet of said charge forming device 75 and movable to different positions in response to variations in temperature and engine suction, a thermostat for controlling the position of the choke valve, an operative connection between said thermostat and the choke valve, means for rendering the thermostat eective to move said choke valve' toward both closed and open positions, `a heating means other than the engine for heating the thermostat during engine operation, and means also operated by the thermostat for rendering said heating means ineective when the choke valve is moved a predetermined distance toward open position.

10. A charge forming device for an internal combustion engine having, in combination, means for varying the fuel to air ratio of the combustible mixture formed by said charge forming device and comprising a choke valve adapted to variably restrict the air inlet of said charge forming device and movable to diiierent positions in response to variations in temperature and engine suction, a thermostat for controlling the position oi the choke valve, an operative connection between said thermostat and the choke valve, means rendering the thermostat effective to hold the valve closed at low temperatures, to move the valve toward open position upon increase of temperature and to hold said valve in relatively wide open position as long as normal or higher engine operating temperatures are maintained, heating means other than the engine for heating the thermostat during engine operation, and means operable by the thermostat for rendering the heating means ineffective as the choke valve is moved by said thermostat a predetermined distance toward open position.

11. A charge forming device for an internal combustion engine having, in combination, means for varying the fuel to air ratio of the combustible mixture formed by said charge forming device and comprising a choke valve adapted to variably restrict the air inlet of said charge forming device and movable to diil'erent positions in response to variations in temperature and engine suction, a thermostat for controlling the position of the choke valve, an operative connection between said thermostat and the choke valve, means rendering the thermostat effective to hold the valve closed at low temperatures, to move the valve toward open position upon increase of temperature and to hold said valve in relatively wide open position as long as normal or higher engine operating temperatures are maintained, heating means other than the engine for heating the thermostat during engine operation, means operable by the thermostat for rendering the heating means ineffective as the choke valve is moved by said thermostat a predetermined distance toward open position and for preventing operation of the heating means as long as the choke valve remains open to an extent equal or greater than said predetermined distance.

12. A charge forming device for an internal combustion engine having, in combination, means for varying the fuel to air ratio of the combustible mixture formed` by said charge forming device and comprising a choke valve adapted to variably restrict the air inlet of said charge forming device and movable to diil'erent positions in response to variations in temperature and engine suction, a thermostat for controlling the position of the choke valve, an operative connection between said thermostat-and the choke valve, means rendering the thermostat eiective to hold the valve closed at low temperatures, to move the valve toward .open position upon increase of temperature and l2 to hold said valve in relatively wide open position as long as normal or higher engine operating temperatures are maintained, an electric heating device for heating the thermostat during engine operation and means operable by said thermostat for opening the circuit of said heating device as the choke valve is moved a predetermined distance toward open position by said thermostat.

13. A charge forming device for an internal combustion engine having, in combination, means for varying the fuel to air ratio of the combustible mixture formed by said charge forming device and comprising a choke valve adapted to variably restrict the air inlet of said charge forming device and movable to different positions in response to variations in temperature and engine suction, a thermostat operatively connected to said valve, said thermostat being effective to hold the valve closed at low temperatures so as to form a rich mixture, to move the valve toward open position upon increase of temperature in order to lean the mixture and to hold said valve in relatively wideopen position as long as normal or higher 4engine operating temperatures are maintained,

an electric heating device for heating theA thermostat during engine operation, means operable by said thermostat for opening the circuit of said l heating device as the choke valve is moved a predetermined distance toward open position by said thermostat, and for maintaining said circuits open as long as vthe choke valve remains open to an extent equal or greater than said predetermined distance.

14. A charge forming device for an internal combustion engine having, in combination, means for varying the fuel to air ratio of the combustible mixture formed by said charge forming device and comprising a choke valve adapted to variably restrict the air inlet of said charge forming device andmovable to different positions in response to variations in temperature and engine suction, a thermostat for positioning said choke valve and operatively connected to an operating arm whereby said arm is moved in response to variations in temperature, a suction operated element movable in response to variations in engine suction and connected to said arm through the medium of said thermostat, so as to move the arm upon variations in suction, means connecting said operating arm to the choke valve so that movements of said arm bring about movements of the choke valve, a heating device for heating the thermostat during engine operation, and means also operable by said arm for rendering said heating device ineiective as said choke valve is moved toward open position.

l5. A charge forming device for an internal combustion engine having, in combination, means for varying the fuel to air ratio of the combustible mixture formed by said charge forming device and comprising a choke valve adapted to variably restrict @e air inlet of said charge forming device and movable to diierent positions in response to variations in temperature and engine suction, a thermostat for positioning said choke valve and operatively connected to an operating arm whereby said arm is moved in response to variations in temperature, a suction operated element movable in response to variations in engine suction and connected to said arm through the medium of said thermostat, so as to move the arm upon variations in suction, means connecting said operating arm to the choke valve so that movements of said arm bring about movements of the choke valve, an electric heating device for heat- 13 ing the thermostat during engine operation, a switch for controlling said electric heating device and means also operable by said arm for opening said switch as the choke valve is moved toward open position.

16. A charge forming device for an internal combustion engine having, in combination, means for varying the fuel to air ratio of the combustible mixture formed by said charge forming device and comprising a choke valve adapted to variably restrict the air inlet of said charge forming device and movable to different positions in response to variations in temperature and engine suction, a thermostat for controlling the position of said choke valve in accordance with temperature variations, an electric heating device for heating said thermostat during engine operation, a circuit for said heating device lying entirely outside the thermostat, whereby the current for heating said thermostat does not pass therethrough and means for controlling said circuit.

17. A charge forming device for an internal combustion engine having, in combination, means vfor varying the fuel to air ratio of the combustible mixture formed by said charge forming device and comprising a choke Valve adapted to variably restrict the air inlet of said charge forming device switch.

WILLIAM H. TAYLOR.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,719,103 Dickey July 2, 1929 1,805,207 Drury May 12, 1931 1,913,131- Sisson June 6, 1933 1,969,358 Coffelder Aug. 7, 1934 2,071,633 Hunt Feb. 23, 1937 2,245,672

Hunt June 17, 1941