US 3321193 A
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Description (OCR text may contain errors)
May 23, 1967 w. E. HIGHLEY CARBURETOR 4 Sheets-Sheet 1 Filed March 26, 1964 INVENTOR. E. HIGHLEY WENFORD AGENT May 23, 1967 w. E. HIGHLEY CARBURETOR 4 Sheets-Sheet 2 Filed March 26, 1964 FIG-.2.
INVENTOR. WENFORD E. HIGHLEY BY Q,
AGENT May 23, 1967 w. E. HIGHLEY CARBUHETOR 4 Sheets-Sheet 5 Filed March 26, 1964 INVENTOR. WENFORD E. HIGHLEY AGE N T May 23, 1967 w. E. HIGHLEY 3,321,193
CARBURETOR Filed March 26, 1964 4 Sheets-Sheet 4 INVENTOR. WENFORD E. HIGHLEY AGENT United States Patent 3,321,193 CARBURETUR Went'ord E. Highiey, St. Louis, Mo., assignor to ACF Industries, Incorporated, New York, N.Y., a corporation of New Jersey Filed Mar. 26, 1964, Ser. No. 354,969 4 Claims. ((31. 2261-39) This invention relates to an automatic choke mechanism on a carburetor for a spark ignition engine, and particularly to a power operated mechanism applicable to various types of automatic chokes, which mechanism is effective as a modulator for the closing force imposed on the choke valve by a thermostat spring during the periods of engine starting and warm-up.
The mechanism of his invention is a part of the control connection between a choke valve and a suction motor powered from the engine induction system. Power from the motor is transmitted through this control connection causing a certain minimum choke valve opening after the engine reaches operating speed, and thereafter, provides a selective degree of bias opposing the closing force imposed on the choke valve by the thermostat spring. This bias produced by this mechanism in the control connection can 'be exerted to oppose final closing of the choke valve by the thermostat.
The purpose of an automatic choke on a carburetor is to provide an excess of fuel for priming a cold engine during cranking, to provide an enriched mixture after engine starting in order to keep the engine running during fast idle warm-up and, to provide a mixture on throttle opening to obtain useful power from the engine during warm-up.
Calibration of a carbuertor automatic choke to achieve these three genenal purposes involves extensive testing of various combinations of choke valve control elements to find a combination providing a good margin of operating tolerances for all of the different engine requirements. Often these engine requirements so conflict in different temperature ranges, that the best combination, gives merely marginal engine performance in one range or another either before or after engine start. One example of this would be a situation in which, in order to obtain a good start in one temperature range for the engine, it is necessary to select a thermostat spring with a certain minimum spring force, but this selection has a spring force in another temperature range which would give only marginal performance for another engine condition, causing the engine performance to be unacceptable.
Problems of this nature often arise, and it is one of the objects of this invention to provide :a novel mechanism for a thermostat controlled choke valve by which the thermostat action can be modified in both manner and degree before or after engine speed increases from cranking speed to running speed so as to change the degree of mixture enrichment provided.
It is a further object of this invention to provide a novel control connection between a power operator and a choke valve which can provide a variable degree of vacuum break of at least a selected minimum opening and no more than a predetermined maximum opening.
It is still a further object of this invention to provide a novel control connection capable of modifying the tension holding the choke valve closed during cranking so that some slight breathing is permitted even at low cranking speeds.
It is still another object of the invention to provide a novel control operative in the part throttle range of en gine operation to modulate the action of the temperature control for the choke valve.
It must be kept in mind that operation of an automatic choke is affected by a number of variables. An increase in the closing bias exerted by the thermostat spring on the choke valve will require an increase in suction forces in order to move the choke valve toward open, and the increase in suction forces necessary to cause opening of the valve will increase the rate of fuel flow producing a mixture enrichment. With these facts in mind, it becomes readily foreseeable that a thermostat spring with a biasing force great enough to cause suitable mixture enrichment for engine priming during cranking might not meet the specifications for mixture requirements after the engine begins to operate, or, it might likewise be possible that the reverse condition can exist. In the first case, it would be desirable to modulate the bias of the thermostat spring within the range of operative positions assumed by the choke after the engine began to operate. In the second case, it would be desirable to modulate the action of the thermostat spring only during cranking and possibly the minimum speed ranges of engine operation.
The instant invention provides a tool adaptable to both above examples.
Mechanically speaking, the instant invention can be briefly described as a control connection between a choke valve and a suction motor, or the like. Usually the suction motor is one operated by depression in the engine induction system at engine operating speeds and has a predetermined stroke suitable to produce at least the maximum degree of initial vacuum break. This control connection is a lost motion type including a spring, and transmits the force of the motor in a direction to open the choke valve from the closed position against the closing bias imposed on the choke valve by a thermostat spring when temperatures sensed by this spring indicates a cold engine condition, for example, when temperature sensed are in the middle range of seventy degrees Fahrenheit or below.
The spring in the lost motion type connection can act as a yielding force tending to open the choke valve regard less of motor operation, or, only on motor operation, as desired. In the latter case, it applies a yielding force tending to open the choke valve at least within the limits permitted by the lost motion type connection.
Other objects and advantages of this invention will appear from the following detailed description which is in such clear, concise and exact terms as will enable any person skilled in the art to make and use the same when taken in conjunction with the accompanying drawings, forming a part thereof, and in which:
FIGURE 1 is a top plan view of a carburetor to which this invention may be applied and part of the engine on which the carburetor is mounted.
FIGURE 2 is a side elevational view of the carburetor in FIGURE 1 with parts broken away to illustrate parts of a novel choke valve control in accordance with the invention and with parts mounted in the engine induction manifold.
FIGURE 3 is a fragmentary perspective View on an enlarged scale illustrating the parts of the mechanism connected with the choke valve shaft of the carburetor of FIGURES 1 and 2.
FIGURE 4 is an operational view schematically illustrating the position of the parts of the novel automatic choke control at cranking speeds or when the engine is stopped and the temperature sensed by the thermostat is in the range of zero degrees or thereabouts.
FIGURE 5 is an operational view schematically illustrating a position of the parts of the novel automatic choke mechanism after a cold start of the engine when the temperature sensed by the thermostat is in the range of zero degrees or thereabouts.
FIGURE 6 is an operational view similar to FIGURES 4 and 5 schematically illustrating a position. of the parts of the novel automatic choke mechanism during part throttle range of engine operation.
FIGURE 7 is a view similar to FIGURE 6 illustrating a position of the parts when the temperature sensed by the thermostat indicates that the engine is partly to fully warmed u Tf fe carburetor described and shown in this application is essentially the same type as that shown and described in the patent to L. B. Read 3,030,085 of Apr. 7, 1962. The necessary disclosure of this patent is incorporated by reference here so as to simplify both the following description and the accompanying illustrations in the drawing. The instant invention is, however, in no way restricted in application to the particular type of carburetor disclosed in the patent publication and in this application.
Turning now to FIGURES l and 2 of the drawing, the carburetor therein shown has a body 1 supported on a flange 2 which is apertured at 3 around its periphery to receive studs for anchoring the flange to the intake manifold M of an internal combustion engine E. Secured to the top of the body 1 is a float bowl cover 5 having a fuel inlet 7 for connection to a fuel inlet supply line 8, through which fuel is pumped from a tank T by a pump P. A generally circular air horn 9 is formed as a part of the float bowl cover and provides a support for an air filter through which air passes to the engine E. The float bowl cover 5 is secured to the top of the body 1 by a plurality of screws, such as 10.
The carburetor of FIGURES l and 2 is formed with a pair of primary mixture conduits 12 and 14 located side by side and a pair of secondary mixture conduits 13 and 15 also located side by side and all opening within the air horn 9. Apertures in opposite sides of the air horn 9 and the float bowl cover 5 form a pair of spaced bearings 5a to receive a choke valve shaft 17. On one end of the choke shaft 17 is a lever and linkage system, indicated generally as 19, which operates the fast idle cam mechanisms for the throttles in the primary mixture conduits.
\ Primary throttle shaft 20 is journaled in spaced bearings in opposite sides of the carburetor and located in the flange 2. A pair of throttles 21 and 22 are fixed on the throttle shaft 20 within the primary mixture conduits and operated by a lever 23 apertured at one end for connection with a manual throttle control linkage. Within the secondary mixture conduits 13 and 15 are a pair of throttles 24 and 25 in turn mounted on a pivoted throttle shaft 26 also journaled in spaced bearings in opposite sides of the carburetor and located in the flange 2.
The air flow into the primary mixture conduits 12 and 14 is controlled by a choke valve 27 secured to the choke shaft 17 and located upstream of the two throttles 21 and 22. The choke valve extends across the air horn 9 and closes off conduits 12 and 14 when it is in closed position (FIGURE 2). The position of the choke valve 27 is in turn controlled through, or by, actuation of a lever 28 fixed to the end of the choke shaft 17 by a set screw 28a (FIGURE 1). Rotation of the lever 28 in a counterclock wise direction, as viewed in FIGURE 2, moves the choke valve 27 to closed position. Clockwise rotation of the lever 28 moves the valve 27 toward open position.
When the choke valve 27 is within its range of closed positions, or is operating, it creates some degree of suction effect downstream of the valve 27 in the primary mixture conduits when the engine is running. It is this suction provided by the choking action of the valve 27 which draws the fuel from the main fuel nozzles 12a and 14a located respectively between choke valve 27 and throttle valves 21 and 22 to enrich the mixture delivered to the engine. The amount of suction created and, accordingly, the amount of enrichment depend upon the control mechanism for the choke valve and its resistance to opening in response to suction. This control for the choke valve 27 which determines its position is indicated generally by the reference characters 30 in FIGURE 1 and FIGURE 2.
Freely journaled on the end of choke shaft 17 is a sector-shaped lever 36 spaced from lever 28 by sleeve 31. Between the lever 28 and the sector-shaped lever 26 is a torsion spring 40 with an intermediate coil part loosely mounted around the shaft 17 and having a bent end 41 projecting through an aperture 43 in the sector-shaped arm 36. The opposite end of the spring 40 has a bent end 414 which seats against an adjustable lug 45 fixed to the face of the lever 28 in an adjusted position by a threaded screw 47. The lug 45 is apertured to receive the threaded screw 47 which projects through the lug 45 and a collar 49 into a suitable threaded opening in the face of the lever 28. Spring 40 in turn has a tension which inherently tends to rotate the sector-shaped lever 36 counterclockwise with respect to the lever 28, as viewed in FIGURES 2 and 47, The amount of rotation of lever 36 by spring 40 is limited by a lug 5t), struck out of the sector-shaped lever 36 which will strike the end 44 of spring 46 which will stop relative movement between spring 40 and lever 36. An arm 48 of lever 36 is bent over above the top of lever 28 to provide a stop to limit relative movement of the two levers in one direction. A set screw 48a in arm 48 provides adjustment for this stop.
concentrically formed in lever 36 is an arcuate slot 53, which in turn receives the bent end 54 of a rod 55 connected with the suction motor, generally indicated as 56 in FIGURE '2. This motor has a plunger 58 apertured to receive the opposite bent end on the rod 55 so as to connect the motor 56 with the sector-shaped arm 36. As shown in FIGURE 2, the motor 56 also has a diaphragm 59 connected with the plunger 58 and a suction connection 60 to which hose 61 is connected. This hose 61 connects to a passage 61a through the carburetor flange 2 opening into mixture conduit 14 posterior of the throttles 21 and 22 to communicate engine suction to the motor 56 to act on the diaphragm 59 and retract plunger 58 and diaphragm 59 against the motor spring 59a.
When the engine starts, manifold vacuum effective in the motor 56 will suck diaphragm 59 to the right as viewed in the figures, This moves plunger 53 a fixed distance which, with a predetermined design of levers 36 and 28 opens the choke valve 27 a predetermined amount to permit a sutficient fiow of air to the engine to keep it running. For some carburetors of the type described the amount of opening of choke valve 27 by the suction motor 56 is around 20 from the closed position of the valve 27. A bracket 63 mounts the motor stationary on the side of the carburetor body 1.
One end of the lever 28 is apertured to receive the bent end 64 (FIGURE 1) of a control rod 65 leading to a thermostat mechanism, generally indicated as (FIGURE 2). The push rod, or control rod, 65 extends through an aperture in a cover plate 73 closing a pocket 71 of the cross-over exhaust passage 72 in the intake manifold M, a part of which is shown in FIGURE 2. The cross-over choke control device has a rotatable carrier 78 which is U-shaped and has opposite legs of the U journaled on a stationary pin 80 supported in spaced legs of a bracket 32 secured to the cover plate 73. At the bridging portion 83 of the U-shaped carrier 78, the opposite legs are apertured to receive the bent end 85 of the push rod 65. A spiral thermostat spring 87 is located between the spaced legs of the carrier 78 and has its inner end held in a slot in the stationary pin 80 and its outer end 86 hooked around the bent end 85 of push rod 65 so as to urge the carrier 78 and bridging portion 83 thereof against the cover 73 when the temperatures sensed by the thermostat are in the middle range of the seventies Fahrenheit, or below, thus, tending to force the push rod 65 upward and arm 28 counterclockwise in the direction to close the choke valve 27. The parts are shown in FIGURE 2 in a position which would occur at temperatures in the range of the middle seventies, or below, with the engine stopped.
. choke valve The above detailed description illustrates the construction of one embodiment of this invention. The schematic showings in FIGURES 4-7 illustrate operational phases of the invention and, from these, others should be self-explanatory.
The automatic choke described is controlled by a thermostat spring having a resist-ance to choke valve opening which varies inversely with temperature and the degree of mixture enrichment increases with increase in resistance to choke valve opening. When the temperature sensed by the thermostat spring 87 is in the neighborhood of zero degrees Fahrenheit, or below, then the resistance of the thermostat spring 87 to choke valve opening is near maximum. Also at these temperatures, the engine is far below its normal ope-rating temperature and, as a consequence, a very rich mixture is required to start the engine and to keep it running after it starts. Accordingly, spring 87 must be selected which will have a force in this temperature range sufficient to hold the choke valve closed fairly tightly against the suction of the engine at cranking speed so as to produce a fuel flow by the engine suction to give a priming mixture. A priming mixture in some instances will be equal parts of air and fuel by weight and one far too rich to keep an engine running once it starts, Since the same thermostat spring remains in control after the engine starts, then since a leaner mixture is now required, the success of the choke valve to maintain operation of the engine will require some modulation of the force exerted by the thermostat spring 87 during starting. Usually this modulation is supplied by suction created by the engine running at operating speed and applied to a suction motor connected to move the choke valve against the resistance of the thermostat spring 87. This suction motor in the present mechanism is indicated as 56, and, when the engine gets to operating speed, there is more than adequate power available in the motor to open the choke valve against the spring bias of the thermostat 87.
A comparison between the position of the parts, shown in FIGURES 2 and 4, will illustrate what happens during cranking of the engine. Note that in FIGURE 2, the diaphragm 59 in the motor 56 is fully rel-axed. This will be the position when no suction is present in the motor 56 and the engine is at rest. Thermostat spring 87 moves lever 28 to close the choke valve 27 and spring 40 expands and rotates lever 36 counterclockwise which positions the end of the rod 55 at the end of the slot 53. Arm 48 will be spaced from the top of lever 28.
Now when the engine is being cranked and the temperature sensed by the thermostat 87 is in the zero range of engine temperatures, the parts will take the position depicted in FIGURE 4. Choke valve 27 is still held tightly closed by the thermostat 87, but there is some suction acting on the diaphragm 59 in the motor 56 which tends to tension the spring 40 and move the finger 48 toward the top of lever 28. The force exerted by the motor 56, however, is far from sufficient to move the 27 open in any amount. FIGURE 4 illustrates the throttle valve 22 in a partially open position so as to communicate manifold suction posterior of the choke valve 27 on the fuel nozzles 13a and 14a in the mixture conduits 13 and 14 so as to draw fuel therefrom and prime the engine.
FIGURE 5 discloses the position of the choke and carburetor parts after the engine has started and when the thermostat coil 87 is still sensing low temperatures in the neighborhood of Fahrenheit. Immediately upon the engine starting, the manifold vacuum downstream of the throttles 21 and 22 rises to a value of more than minus 19 inches of mercury. This is suflicient vacuum to draw the diaphragm 59 of the air motor 56 down wardly against the bottom of the housing of the motor. This action rocks the lever 36 clockwise as viewed in FIGURE and with the adjusting screw 48a contacting the top of lever 28 will also pull lever 28 simultaneously in the clockwise direction. This action of the two levers snaps open the choke valve 27 to a minimum amount as indicated in FIGURE 5, which, under the described conditions, is in the order of 15 from the closed position of valve 27. This opening valve 27 is against the stitf biasing eifect of thermostat spring 87 and] provides for a necessary flow of air to the engine for its operation. This action leans out the rich starting mixture of the carburetor and provides an enriched operating mixture for the continuous running of the engine at low temperatures.
A further feature of the invention is the provision of a compensating action of spring 40, when under the abnormal cold conditions described above, the throttle is opened and the operator attempts to drive the vehicle away. Under such conditions the engine is placed under a load requiring a greater output of power for moving the vehicle. For this reason it is necessary that additional air be mixed with the enriched idle mixture to provide the required power for the drive-away function. Accordingly, upon opening of the throttles 21 and 22 a greater manifold vacuum is effected immediately downstream of the choke valve 27. Atmospheric pressure on the top of the valve rocks the unbalanced valve in a clockwise direction, as viewed in FIGURE 5, and permits a greater flow of air to the engine. However, under extremely cold conditions around 0 Fahrenheit the thermostatic spring 87 exerts an abnormal closing bias on the valve 27 and will under extreme cold prevent the valve from opening to an optimum amount. However, spring 40 was placed under tension when lever 36 was rocked by the motor 56 from its inoperative position shown in FIGURE 2 to its position shown in FIGURES 4 and 5, where the adjustment screw 48a strikes the top of lever 28. This loading of spring 40 then in accordance with a feature of the invention, opposes the undue bias of the cold spring 87 during this drive-away condition of operating a vehicle and thus aids in opening the valve 27 to an optimum position against the bias of spring 87 for increasing air flow to the engine for drive-away operation.
FIGURE 6 schematically illustrates the probable position of the choke parts when the throttles are opened wide enough for power. Air flow and manifold suction acting directly on valve 27 together with the helping bias of spring 40, rotate the choke valve to a wider open position than its position during idle warm-up shown in FIG- URE 4 and than the position the choke valve 27 would assume without the help of spring 40. Thus, an optimum amount of air will flow to the engine to lean out the mixture resulting in greater available power. In this manner, spring 40 compensates for the overchoking condition that valve 27 would have under the control of an overstiff thermostat spring 87 at around 0 F.
As the engine warms up and the closing effect of spring 7 on the choke valve 27 lessens, the opposing modulating force of spring 49 and the air pressure on the unbalanced valve 27 will slowly move valve 27 in an open direction until lug 50 strikes the end 44 of spring 40 to stop relative to rotation of levers 36 and 28. At this point further opening of the valve 27 is under full control of the thermostat spring 87 which will continue to unwind as engine heat increases until choke valve 27 is in its full open position as indicated in FIGURE 7. Since lever 36 is carried along with lever 28 in this operation, slot 53 accommodates the stationary end 54 of rod 55.
In FIGURE 7 a condition is illustrated in which the engine if fully warmed up and the thermostat 87 has wound up removing all bias tending to close the choke valve 27. The engine is under the control of the throttle alone and is operating with the throttle 22 in the part throttle position.
Another condition which is typical is also schematically represented in FIGURE 6. In this view, the approximate relation of the parts is illustrated after the engine speed increases from cranking to running speed at the fast idle setting indicated by the throttle at 21 and when the temperature sensed by the spring 87 is in the range above zero to the middle seventies. In this temperature range, the mixture does not have to be as rich to keep the engine running as in the condition illustrated in FIG- URE 5, when the temperature sensed by spring 87 was around F. Consequently, the initial choke valve opening, or vacuum break, should be greater. Since the bias imposed tending to close the choke valve 27 and exerted by the thermostat spring 87 is considerably less than when the range of temperature sensed was much lower, the strength of spring 40 is chosen to be greater than that of spring 87 above zero to the middle seventies temperature range so that the full stroke of motor 56 will act to open choke valve 27 and levers 36 and 28 will rotate together against the bias of thermostat spring 87. Thus, valve 27 opens more than under the condition when thermostat senses a temperature near 0 F. as illustrated in FIGURE 5.
This greater degree of vacuum break is a feature of the control linkage including the spring 40 because, although the motor 56 has a predetermined stroke, it can act through the connecting spring 40 to produce a variable vacuum break. Of course, the amount of initial choke valve opening on the vacuum break depends upon the resistance of the thermostat spring 87 as it senses various temperatures in the illustrated range selected. Suppose, however, that in the range selected, spring 40 can expand its full amount against the resistance of the thermostat spring 87. This is indicated in FIGURE 6 by the spacing between the screw 48a and the top of the lever 28 which incidentally is the distance permitted for full expansion of the spring 40 from the position in which it is shown in FIGURE until it strikes the stop 50 on the segmental shaped lever 36. It will be noted that the stop 50 does not prevent the choke valve 27 from full opening. Stop 50, however, sets the maximum movement by the spring 40. Thus, in the control linkage, just described, the minimum movement of the choke valve 27 during vacuum break is set by the screw 48a and its adjustment. The maximum movement of the choke valve 27 on the vacuum break is set by the maximum movement of plunger 58 through the action of motor diaphragm 59. Neither one of these elements in the control linkage is such as to interfere in any way with full opening of the choke valve 27 against the resistance of the thermostat spring 87. Depending upon the temperature sensed by the thermostat spring 87, the degree of vacuum break can be any amount in between these two limits. However, the limits may be varied by the adjustment of screw r 48a, as well as the adjustable position of lug 45 on lever 36. Changing the position of lug 45 changes the relative spacing between stop arm 50 and spring end 44. Thus, lug 45 can be set to increase or decrease the modulating force exerted by the spring 40. A movement of the lug 45 clockwise as viewed in the figures increases the tension in the spring 40 and its modulating force. This increase in modulation can mean a leaner mixture at the vacuum break and a definitely leaner condition during the driveaway at part throttle. Less modulation effect of spring 40 means a richer mixture and this could be effective in the vacuum break position of the choke as well as in the part throttle drive-away condition.
The stop 50 may be omitted, as a modification of the invention in which the spring 40 is operative throughout all, or nearly all, of the entire range of operative positions of the choke valve 27 to modulate the effect of the thermostat spring 87. For example, spring 40 would be active throughout the range of open positions of the choke valve from the closed position of FIGURE 4 to the wide open position of FIGURE 7. However, without lug 50 the end 54 of rod 55 would retain lever 36 in a fixed position of FIGURE 5, and spring 40 would rotate lever 28 clockwise as viewed in the figures and an amount allowed by the varying strength of thermostat spring 87. The range of action depends only on the characteristics of the spring chosen to perform the functions of the spring 40. The spring chosen could be relatively stiff or relatively weak, depending on requirements. Spring 40 is also variable as to the angle of wind-up, or unwind. In other words, the spring 40 could be chosen to have a small active angle, a few degrees, or, the spring 40 may be chosen to have a wide active angle. Of course, no matter what choice is made, finger 45 can be adjusted to modify the resulting spring action.
In the modification as shown in FIGURES 2 and 3, the stop 50 limits the angle of spring action. In other words, the active angular expansion of spring 40 is limited to a fixed angle. Because of this feature, the linkage can be set so that spring 40 does not oppose the bias exerted by the thermostat spring to move the choke valve 27 fully closed. In other respects, the spring 40 performs in the same manner as without stop 50, except for the distinction that adjustment of finger 45 can operate to change only the degree of spring force exerted, or spring loading, but not active angle. The bias produced by the spring 40 can be either restricted to opening movement only of the choke valve and to only a part of the full operating range of movement of the choke valve opening, or to the full range of opening during operation of the choke valve. Under any circumstances, the degree of bias is subject to variation as described. Thus, this control connection of spring 40 is one readily modified in both the manner and degree in which the baising force may be applied to modulate the thermostat spring, and, in this respect, it provides for the requirements of various makes, or models, of Cllgll'lES.
Although the invention has been described in connection with a cross-over choke spring 87 mounted in the engine manifold, this should not be limiting, as the invention can also be used with a temperature sensitive spring mounted on the carburetor body and responsive to air sucked up from a stove on the exhaust manifold of the engine, as disclosed in the above mentioned Patent 3,030,085 of L. B. Read. Also, the invention could be used with a temperature sensitive spring which is heated by electrical means responsive to the ignition system of the engine, for example.
Thus, changes in and modifications of the constructions described may be made without departing from the spirit of my invention or sacrificing its advantages.
1. A carburetor device having a body, a mixture conduit extending through said body, a moveable throttle valve in said mixture conduit, a choke valve shaft journaled for rotation in said body and extending across said mixture conduit upstream of said throttle valve, a choke.
valve in said mixture conduit and fixed for rotation on said choke valve shaft from an open to a closed position, a suction motor, means including a suction passage extending from said motor to an opening in said mixture conduit posterior of said throttle, a mechanical connection between said suction motor and said choke valve to move said choke valve to a partially open position in response to engine suction posterior of said throttle, a temperature responsive spring connected to said choke valve for biasing said choke valve closed at temperatures below a predetermined value, said mechanical connection including a first lever connected for rotation with said choke valve shaft and a second lever freely mounted for rotation on said carburetor body, a second spring having one end fixed to said first lever and the other end fixed to said second lever to resiliently hold said first and second levers together against the bais of said temperature responsive spring, said second spring having a resistance to expansion less than the bias of said temperature responsive spring below said predetermined temperature value and greater than the bias of said temperature responsive spring above said predetermined temperature value, and stop means cooperative with said first and second levers for limiting relative movement of said respective levers against the bias of said second spring when said choke valve is partially opened by said suction motor.
2. In a carburetor device as defined in claim 1 wherein said stop means is adjustable to permit regulation of the relative movement of said levers against the bias of said second spring.
3. In a carburetor device as defined in claim 1 wherein said first lever includes an arm (48) having a portion thereof overhanging said second lever (28), and a screw (48a) carried in said arm and threadably positioned therein to engage a portion of said second lever to adjust the relative movement of said levers against the bias of said second spring.
4. The invention of claim 1 wherein said second spring is a coil spring, said first and second levers and said coil spring include said stop means limiting relative move- 10 ment of said levers against the bias of said coil spring when said choke valve is partially opened by said suction motor.
References Cited by the Examiner UNITED STATES PATENTS HARRY B. THORNTON, Primary Examiner.
T. R. MILES, Assistant Examiner.