US3284061A - Carburetor - Google Patents

Description

Nov. 8, 1966 Filed March 2, 1964 D. M. rGORDON CARBURETOR 4 sheets-sheet 1 WBV www AGENT Nov. 8, 1966 D, M. GORDON 3,284,061

CARBURETOR Filed March 2, 1964 4 Sheets-Sheet 2 M27 f mlw F162.

INVENTOR. DWIGHT M. GOR DON AGENT Nov. 8, E966 D. M. GORDON 3,284,061

CARBURETOR Filed MarOh 2, 1964 4 Sheets-Sheet 5 INVENTOR. DWIGHT M. GORDON Nov. 8, 1966 D. M. GORDON 3,284,061

CARBURETOR Filed March 2, 1964 4 sheets-sheet 4.

74 INVENTOR.

DWIGHT MGORDON AGENT United States Patent O 3,284,061 CARBURETOR Dwight M. Gordon, Farmington, Mich., assigner to ACF Industries, Incorporated, New York, N.Y., a corporation of New Jersey Filed Mar. 2, 1964, Ser. No. 348,497 5 Claims. (Cl. 261-39) This invention relates -to an automatic choke mechanism for a carburetor, and particularly to linkage modifications applicable to various types of automatic chokes having a predetermined calibration, which linkages are effective in a certain temperature range to provide a modulation of the choke valve temperature responsive element.

An automatic choke mechanism of this type comprises a butterfly type of air valve pivotally mounted in the inlet of the mixture conduit of a carburetor so as to be unbalanced in a direction to be opened on its pivot by suction existing in the mixture conduit upstream of the throttle. This suction is always present if the throttles are partially to wide open due to the pumping action of the engine. The choke valve is biased toward a closed position by a thermostat spring whenever the spring senses engine temperature conditions below the middle seventy range of temperatures Fahrenheit. Usually this thermostat spring holds the choke valve closed by a very light pressure in this range of temperatures and the degree of biasin-g pressure of the spring increases as temperature sensed decreases. Connected directly to the choke valve is a suction motor. yIn many instances, the suction motor has a cylinder connected to engine suction downstream of the throttle to -actuate a small piston which reciprocates in the cylinder and in turn is connected directly to the choke valve. A bypass in the walls of the cylinder is opened by Ea certain predetermined piston movement in response to engine suction moving the piston in the cylinder. The bypass acts to modulate the pull of the suction motor on the valve after a predetermined initial opening of the choke valve.

Calibration of the automatic choke device described, for a particular make, or model, of internal combustion engine involves matters of judicious selection of parts and their proper assembly based upon testings to provide a device having a good margin of operating tolerance for specific engine requirements. Often these requirements so conflict that the calibration gives merely marginal engine performance under some engine operating conditions. For example, a thermostat spring with a certain optimum spring force and rate to provide a -good start for the engine in one te-mperature range would provide marginal choke performance in another temperature range and corresponding to another engine condition.

Such problems often occur and it is one of the objects of this invention to provide modulating linkages for connection with Ia thermostat spring and the automatic choke valve to modulate the thermostat spring action in the choke valve.

Briefly, this invention provides a limit on the closing force exerted by the thermostat spring within a certain operating range of choke valve positions, and specifically, comprises linkage which provide a .variable thermostat spring bias to close the choke valve which is proportional to temperature sensed within one range of decreasing temporatures and, a variable spring bias to close the choke valve within another range of decreasing temperatures which is independent of temperatures sensed.

Conversely, the spring rate provided includes a spring rate resisting initial opening independently of the temperature change Within the second range and a spring rate resisting full opening inversely proportional to temperature change within the first range of temperatures ICC sensed. Since the second range, in most cases, is a lower temperature range than the first, the linkages limit the force of the thermostat spring resisting initial opening of the choke Valve.

Other objects and advantages of this invention will appear from the following detailed description which is in such full, clear and concise terms as to 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 incorporating the invention and shown mounted on an engine manifold.

FIGURE 2 is a side elevational view-of the carburetor shown in FIGURE 1 with parts broken away to illustrate the choke valve control.

FIGURE 3 is an enlarged view similar to FIGURE 2 showing the construction of the choke valve control in FIGURE 2 in accordance with the invention.

FIGURES 4 and 5 are operational views of the choke valve of FIGURES 1-3 and showing carburetor parts schematically.

FIGURE 6 is a partial top plan view of acarburetor mounted on an engine manifold and showing a modification of the invention.

FIGURE 7 is a side elevational view of the structure of FIGURE 6.

FIGURE 8 and FIGURE 9 are operational views schematically illustrating the positions of the parts in the embodiment shown in FIGURES 6 and 7.

The carburetor to which the invention is applied is of the typel shown and described in patent to L. B. Read 3,030,085 of April 17, 1962. The disclosure of this patent is incorporated by reference here so as to simplify both the following description and the accompanying illustrations in the drawings. The carburetor, shown and described in this patent publication, is basically the same carburetor disclosed in the patent and which is intended to be shown and described but briefly here. The following detailed description will be limited to only so much of the carburetor structure already known by publication as is necessary for an understanding of the construction, application and operation of the instant invention. It is understood, of course, that this application of the invention is exemplary of others and that the instant invention is not restricted in application to the carburetor in the published description.

Turning now to FIGURES 1 and 2 of the drawings, the carburetor therein shown has a body 1 supported on a ange 2 which flange is apertured at 3 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 connected to a fuel line 7a from a fuel pump P and fuel tank T. Fuel bowl cover 5 also includes a generally circular air horn 9. The float bowl cover 5 is secured to the top of the body 1 by screws 10.

This particular carburetor is a dual multistage type referred to as a four barrel carburetor. As viewed in FIGURE 1, there are a pair of primary mixture conduits 12 and 14 located side by side and a pair of secondary mixture conduits 13 and 15 located side by side and all opening within the air horn 9. Air horn 9 is apertured at opposite sides and the oat bowl cover 5 is formed with a pair of spaced bearings 11 and 11 to receive the choke shaft 17. On one end of the choke shaft 17 is a lever and linkage 19 to operate the fast idle mechanism for the throttles in the primary mixture conduits. Primary throttle shaft 2t) is journaled in spaced bearings in 0pposite sides of the carburetor and located in the ange 2. A pair of throttles Z1 and 22 are xed on the throttle shaft 20 within the primary mixture conduits and operated by a lever 23 on throttle shaft 2G provided for connection with a manual control. Within the secondary mixture conduits 13 and 15 are a pair of throttles 24 and 25 in turn mounted upon 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 414 is controlled during cold engine operation by a choke valve 27 secured to the choke shaft 17 and positioned across conduits 12 and 14 upstream of the two throttles 21 and 22. The position of the choke valve 27 is in turn controlled by a thermal responsive spring 35, to be described, through the actuation of lever 28 fixed to the end of the choke shaft 17. Rotation of lever 28 by spring 30 in a counterclockwise direction, as viewed in FIGURE 2, moves the choke valve 27 to closed position. The valve 27 moves to open position by clockwise rotation. A fuel nozzle 12a extends into conduit 12 between throttle valve 22 and the choke valve 27 to bring fuel into conduit 12 from the carburetor fuel bowl. Also fuel nozzle 14a extends into conduit 14 between throttle valve 21 and the choke valve 27 to bring fuel into conduit 14 from the fuel bowl. Air ow through conduits 12 and 14 passes through venturi portions to provide low pressures to suck fuel from the nozzle 12a and 14a. l Referring to FIGURE l, it will be seen that a closed choke housing 30 is provided with a removable cover 32 held in place by a plurality of screws 33. There is a hot air fitting 31 connecting an air line shown at 29 to a stove S on the manifold M, to supply heat within the housing 30.

Within the housing 30 is the spiral thermostat spring 35 having one end, at the inner end of the spiral, xed to a stud 32a in the cover 32 and its movable free end 36 disposed to engage one side of lug 37 of a lever 3S freely rotatable on the shaft 40, all as shown in greater detail in FIGURE 3. The thermostat spring 35 is constructed so that it unwinds as temperatures decrease and winds up as temperatures increase. As the temperatures decrease to the middle range in the seventies Fahrenheit or below, free end 36 moves into engagement with one side of lug 37 moving the lever 38 clockwise until the lug 37 abuts the stop 42 in the housing 30. As temperatures increase above the said range, the free end 36 of the thermostat moves away from the lug 37 freeing the lever 33 for rotation in a counterclockwise direction.

Fixed to the shaft 40 and in accordance with a feature of the invention, is a lever 44, one end of which is pivotally attached to a link 45 carrying the piston 47. Cylinder 49 has a connection 50 with a suction passage leading posterior of the throttles 21 and 22 so as to communicate engine suction to the cylinder 49 and thereby produce a force drawing the piston 47 into the cylinder 49 during engine operation. The grooves 51 in opposite sides of the cylinder wall provide modulation for the action of the piston 47 because, as the piston 47 is drawn into the cylinder 49, the bypass slots S1 open thereby reducing the suction in the cylinder 49 and, consequently, the pull of the piston 47 on the link 45 and arm 44.

On the arm 38 are a pair of spaced lugs 52 and 53 (FIGURE 3) which straddle the lever 44. A torsion spring 55 has opposite ends hooked around one side of the lever 38 and the opposite side of the lever 44 so as to hold, or tend to hold, the lever 44 in engagement with the lug 53. Since the lever 44 is xed on the shaft 40, rotation of the lever 44 in either direction causes a similar rotation of the shaft 40 which projects through the back of the choke housing 30 as shown in FIGURE 1. The projecting end of the shaft 40 carries arm 56 which is tied by link 57 with choke arm 28 on the choke shaft 17. As heretofore mentioned, as the thermostat spring end 36 moves into engagement with the lug 37, as the temperature sensed thereby decreases below the middle range of seventies Fahrenheit, it rotates lever 38 and lever 44 through spring S5 clockwise as viewed in FIG- URES 2 and 3. This causes the choke valve 27 to move to a Closed position. The thermostat spring 35 is so designed that the biasing force exerted by its movable end 36 against the lug 37 increases as temperature sensed by the thermostat decrease-s so that the relationship between the force exerted by the spring 35 is inverse to temperature sensed. On the other hand, spring 55 is unaffected -by temperature and exerts the same force holding the arm 44 against the lug 53 regardless of temperature.

Assuming that the choke valve 27 has been closed by the springs 35 and 55 so thatthe lug 37 is' held against the stop 42 and the engine is stopped. During the cranking of the engine, suction on the unbalanced valve 27 may cause the spring 35 to yield slightly so as to admit the flow of air past the valve 27, but suction force below the throttle valves is around 1/2 pound per square inch, which is not sufiicient to cause the suction motor to open the choke valve 27. Thus, cranking the engine for a cold start, the suction motor is out of operation. When the engine starts, however, suction builds up rapidly below the throttles to around 6 or 7 pounds per square inch, which pulls the piston 47 into the cylinder 49 until the bypasses 51 are uncovered. This movement of the piston 47 rotates the arm 44 counterclockwise to produce a corresponding rotation of shaft 40 and opening movement of the choke valve 27. The amount of initial opening of the choke valve depends primarily upon the modulation of the power of the suction motor by the piston movement operating the bypass slots 51, as well as the amount of bias in the thermostat spring 35 holding the lug 37 against the stop 42.

The amount of biasing force in the thermostat spring 35 depends upon engine requirements which dictate the choice of spring rates required. It often occurs that the required biasing force from a thermostat spring 35 in the seventy degree range of temperatures sensed thereby, dictates the use of a spring whose bias becomes excessive by the time that the temperatures sensed are in the neighbodhood of zero degrees Fahrenheit, for example. This invention offers a solution because the spring 55 can be chosen so that, when the biasing force of the thermostat spring becomes excessive in this lower range of temperatures, spring 55 will take over and yield to permit arm 44 to move from its position against lug 53 to a position against lug 52. In the particular instances illustrated, this amounts to a turning movement of about nineteen degrees of the shaft 40 and a similar amount of initial opening movement of the choke valve 27. Spring 55 is chosen so that its biasing force between arms 38 and 44 is always less than the force exerted by the suction motor on the arm 44. Consequently, the use of the second spring means 55 in the linkage between the thermostat and the choke valve provides a modulating effect in the linkage and thereby in the biasing force produced by the thermostat spring 35. After arm 44 moves into engagement with lug 52, further opening of the choke valve 27 will be against the biasing force exerted by the thermostat spring 35.

In FIGURES 4 and 5, the dotted line position is the closed position for the choke valve 27. This would be the position for the choke valve after the engine has stopped and the temperature within the housing has decreased from a range of temperatures below the middle seventies Fahrenheit.

The full line position for the choke Valve 27 indicates the approximate initial opening of the choke after the engine starts with the throttle cracked to the fast idle position. Assuming that the temperature sensed by the thermostat 35 in FIGURE 4 is in a range below the middle seventies but above zero, then after the start, the piston 47 is pulled down by suction as shown until slots 51 are uncovered decreasing the suction force on the piston to modulate the action of the suction motor. Lever 44 is moved by the piston to rotate shaft 40 and through spring 55'to rotate lever 38 to move lug 37 against the bias of spring 35. Rotation of shaft 40 thus opens choke valve 27 against the closing force of the spring 35 in this range of temperatures since the biasing force of the thermostatic spring 35 on the lug 37 is less than the biasing force of spring 55 between the two arms 44 and 38. Consequently, only spring 35 yields and alone imposes the biasing force tending to close the valve 27 against any force produced by engine suction tending to open the valve 27. In this rst range of temperatures, the spring 55 is inactive on initial opening of the choke valve 27. On further opening of the throttle 22, however, suction acting on the choke valve increases and the valve 27 moves further open. At some point and temperature, the resistance of spring 35 may become excessive and at this point spring 55 yields to modulate the action of the thermostat spring 35.

Assume now that the temperature sensed by thermostat spring 35 decreases to a range below zero degrees Fahrenheit. Since, as the temperature drops, the biasing force exerted by the spring 35 increases, then at sorne temperature slightly below the arbitrarily chosen limit for the first range of temperatures, the biasing force of thermostat 35 becomes equal to the biasing force of spring 55 in the control linkage between the thermostat spring 35 and the choke valve 27. This can be referred to as a transition condition in the control linkage action. During transition, the force of the suction motor will deect either spring 35, or spring 55, or both,and, consequently, such a condition would be difficult to illustrate. However, assuming that the transition condition is in a very narrow temperature band, once the temperature sensed by the thermostat spring 3S becomes subzero in any substantial amount, a second range of temperatures exists in which the action of the control linkage can be depicted as in FIGURE 5.

With particular reference to FIGURE 5, the parts are shown schematically in full line position after the engine starts. The force of the piston 47 in the suction motor no longer deects spring 35 because of its increasing bias. Spring 55 becomes the first to yield as the piston moves the arm 44 out of contact with the lug 53 and eventually into engagement with the lug 52. This condition of the parts imposes the added resistance of spring 35 which forms a yielding limit for further piston movement. In moving from lug 53 against lug 52, arm 44 rotates shaft 40 about nineteen degrees in the illustrated example and this produces an equal rotation of the choke valve 27 to a partially open position as in FIGURE 5 which corresponds to a partially open position shown in FIGURE 4. The spacing of the lugs 52 and 53 depends upon engine requirements. Spacing is a calibration point in the linkage which can be set arbitrarily to suit engine requirements. Thus, initial choke opening in the second temperature range could be less than in the first, or equal as shown. It could be greater, but this is rather unlikely. The degree of initial opening of the choke valve in any temperature range is a matter of calibration and what has been illustrated here in FIGURES 4 and 5 is merely exemplary.

After the arm 44 contacts the lug 52, further choke valve movement will be resisted by the spring 35. When the throttle valve is opened toward its wide open position and engine speed increases, the suction of the air ow on the choke valve beyond the range shown in full lines. This further opening movement is under the control of the spring 35.

This invention is capable of taking various forms and to illustrate this fact a second embodiment is shown in FIGURES 6-9 Again, the invention is illustrated in these figures as applied to a carburetor of the type described above, wherein the same reference numbers indicate identical structures. The automatic choke mechanism is the carburetor of FIGURES 6-9 if of the crossover type. The description below is limited to the automatic choke specically which differs from that already described.

With reference to FIGURES 6 and 7, on the end of the choke shaft 17 which mounts the choke Valve 27 is a compound lever 65 having a sector shaped arm 66 and an arm 67 angularly related thereto. The sector shaped arm 66 has an arcuate slot 69 in which the bent end 70 of a link 72 is held captive. The end 70 is freely slidable between the ends of slot 69, and, when the choke valve is'fully closed and the engine stopped, the end 70 abuts the right end of slot 69 (FIGURE 7). The slot is long enough so that the choke valve can open wide without interference between the end 70 and the left hand end of slot 69.

The suction motor 7S is a diaphragm type in which a plunger 73 is reciprocated by the action of suction on a exible diaphragm 73a. Plunger 73 is fixed to the center of diaphragm 73a by support plates 73b. Diaphragm 73a is sealed around its edge to the housing of the motor '75 to provide a closed chamber 75a. A suction connection 77 extends from the motor to connect chamber a with a passage 50 .in the carburetor body opening posterior of the throttles 21 and 22. The link 72 has a bent end 74 secured in an aperture of the plunger 73, so that link 72 moves with plunger 73. The power stroke of the motor 75 is such that it moves the arm 66 and choke valve 27 to a partially open position from a -fully closed position. The slot 69 then permits movement of valve 27 to full open position under control of a thermostat spring. Motor 75 is supported in a fixed position on the carburetor body l by a bracket 79.

A spring link 80 has one end 81 bent at right angles to fit in an aperture in the end of the arm 67. The other end 84 of spring link 80 passes through an aperture in a cover plate 82 of a cross-over choke control device 83 mounted in a pocket 85 of the cross-over exhaust passage in the intake manifold M of an engine E, or the like, a part of which is shown in FIGURE 7. Carrier 88 is U-shaped and has opposite legs of the U journaled on a stationary pin 90 supported in spaced legs of bracket 91 on cover plate 82. At the bridging portion 92 of the U of the carrier 88, the opposite legs are apertured to receive the bent end `84 of spring link 80. A spiral thermostat spring 94 has its inner end held in a slot in pin 90 and its outer end 84 shaped to hook around the right side of the bent end 84, as viewed in FIGURE 7, so as to urge the carrier portion 92 against cover 82 when the temperatures sensed by the thermostat are in the middle range of the seventies Fahrenheit or below, thus forcing spring link 80 upward and arm 67 counterclockwise in a direction to close choke valve 27, The parts are shown in FIGURE 7 in a position which would occur .at temperatures in the range of the middle seventies or below with the engine stopped.

Spring link 80 is formed with a ilexible resilient loop type spring 95. For example, if the link 80 is a round rod, the spring loop 95 can be made by attening the rod into a spring strip between bends 96 and 98 which are opposite one another and act as limit stops for deflection in the spring loop 95.

The operation of the embodiment, shown in FIGURE 7, is exactly the same as that previously described here in detail. As temperatures sensed decrease to, and below, the middle seventy range, thermostat spring 94 winds up after the engine stops raising link 80 to close the choke valve 27 to the dotted line position, shown in FIGURES 8 and 9.

Assuming, for example, that the temperatures sensed by the thermostat 94 is in a rst range of temperatures from the middle seventies to zero Fahrenheit, then, when the engine starts, the suction motor 75 moves plunger 73 to the right in FIGURE 8 pulling arm 66 clockwise and moving choke Valve 27 to the partially open position, shown in full lines in FIGURE 8. The rotation of the choke valve 27 and arm 66 is resisted by the end 84 of thermostat spring 94 acting on the end 84 of spring link 80. In this range of temperatures, the bias of spring 94 is less than the spring resistance of loop spring 95 and, consequently, link 80 acts as a more or less positive linkage between spring 94 and arm 67. In this first range of temperatures, the loop spring 95 is inactive on initial opening of the choke valve 27 but may come into action later as the throttle is opened. When suction on the choke valve increases due to throttle opening, choke valve 27 also opens and at some point the resistance of thermostat spring 94 may become excessive. At this point, loop spring 95 yields'to modulate the action of thermostat spring 94.

As the temperatures sensed decreases to zero, again there will be a transitional condition as explained above in which bot-h springs 94 and 95 could be deflected. However, this condition would probably be in a very narrow band of temperatures, at, or near, zero in this example, and a true representation of the part positions would be dii'cult to illustrate here. Consequently, FIGURE 9 is illustrative of the operation at a second range of tem-` peratures below zero and below this transitional band of temperatures.

In the example chosen, the bias of spring 94, as shown in FIGUR-E 9, 'has increased -to the degree that spring 95 yields rst. As the engine starts, suction motor 75 rotates arms 66 and 67 together with the choke valve 27 in a clockwise direction. The valve moves from the dotted line position tothe full line position, but this move ment has no eiiect on thermostat spring 94 w'hose end 9 y84 stays against cover 82 which forms la limit stop. Spring l-ink 80 is compressed in length because spring loop 95 iiexes until stops 96 and 98 abut one another. Link 80 becomes a solid link in this condition with bends 96 and 98 together and thermostat spring 94 can act as a yielding limit stop for `the choke valve. The spacing between bends 96 and 98 can be equal to, les-s th-an, or greater than, the stroke of the motor 75 measured in degrees of initial choke valve opening. This is wholly a matter of calibration, but by proper selection of springs and spacing of bends 96 and 98, engine requirements, as to uel ratios at various temperature conditions, are more easily met and better results attained by using a modulated linkage between the thermostat spring and the choke valve. This is true whether the spring is like 55 or 95 and whether the limits are 4lugs 52 and 53 or bends 96 and 98.

Changes in and modifications of -this invention may be made without departing from the spirit of the invention or sacricing its advantages.

I claim:

1. A carburetor comprising -a body having an air and fuel mixture conduit therethrough, a throttle valve movably mounted within said mixture conduit, a choke valve mounted for movement within said mixture cond-uit from an open to a closed position, means responsive to engine operation to move said choke valve to an open position, a temperature responsive spring to resist opening .movenient 'of said choke valve below a predetermined range of engine temperatures with a force inversely proportional to engine temperature, means exposing said temperature responsive spring to engine temperature, an elongated connection joining said temperature responsive spring to said choke valve, said connection including a partially rigid member, and a spring like yieldable link integral therewith, said link exhibiting a greater resistance to yield above zero degrees Fahrenheit than at temperatures below bero degrees Fahrenheit, whereby said link will yield at temperatures below Zero degree-s Fahrenheit and not transmit force exerted by said spring to said choke, but at .temperatures above zero degrees Fahrenheit, said link will not yield and thereby ltransmit the force exerted by said spring to said choke.

2. The combination as defined in claim 1 in which said linkage inclu-des a pair of rigid rods, a spring like yieldable link connected to adjacently positioned ends of said rods, the opposite ends of said respective rods being connected to said respective choke and temperature responsive springs.

3. The combination as deiined in claim Z wherein said yieldable link is adapted to yield a predetermined amount thereby bringing the ends of said rigid rods int-o abutment thus forming a rigid connection between said choke and said temperature responsive spring.

4. The combination as dened in claim 2 wherein said yieldable link is in the form of a resilient loop having opposite sides connected to the adjacent ends of said rigid rods, said loop being adapted to be deormed by opposing -iorces applied to opposite ends of said rigid rods, until opposite ends of said loop come into engagement.

5. A carburetor comprising a body having an air and fuel mixture conduit therethrough, a throttle valve mov- :ably mounted within said mixture conduit, a choke valve mounted Afor movement Within said mixture conduit from an open to a closed position, means responsive to engine operation for moving said choke valve 4to an open lposition, a temperature responsive spring -to 4resi-st opening movement of said choke valve below a predetermined range of engine temperatures with a force inversely proportional -to engine temperature, means exposing said temperature responsive spring to engine temperature, a connection joining said temperature responsive spring and said engine operation responsive means to said choke valve, said connection including a partially rigid member, and la spring like yieldable link, integral therewith, said link exhibiting a greater resistance .to yield at temperatures yabove zero degrees Fahrenheit than at temperatures below zero degrees Fahrenheit, whereby at ternperatures below zero degrees Fahrenheit, said link will yield and not transmit fonce exerted by said temperature responsive spring to said choke, but at temperatures above zero degrees Fahrenheit, said link will not yield and thereby transmit the force exerted by said temperature responsive springito said choke, said link being adapted to yield a predetermined amount at temperatures below zero degrees Fahrenheit, thereby lforming subsequent to said yielding, a rigid connection between said thermal-ly responsive spring :and said choke.

References Cited by the Examiner UNITED STATES PATENTS 2,421,733 6/ 1947 Henning 2'6'1--39 `2,774,343 12/ 1956 Schaffer 261-39 2,979,047 4/ 1961 Rapplean et al. 2611--39 2,998,233 8/1961 Marsee 261-39 3,076,639 2/196-3 Szwargulski et al 261-39 3,137,889 `6/1964 Sogoian 267--10 3,167,254 1/ 1965 Goodyear 261-39 HARRY B. THORNTON, Primary Examiner.

T. R. MILES, Assistant Examiner,

Claims (1)

1. A CARBURETOR COMPRISING A BODY HAVING AN AIR AND FUEL MIXTURE CONDUIT THERETHROUGH, A THROTTLE VALVE MOVABLY MOUNTED WITHIN SAID MIXTURE CONDUIT, A CHOKE VALVE MOUNTED FOR MOVEMENT WITHIN SAID MIXTURE CONDUIT FROM AN OPEN TO A CLOSED POSITION, MEANS RESPONSIVE TO ENGINE OPERATION TO MOVE SAID CHOKE VALVE TO AN OPEN POSITION, A TEMPERATURE RESPONSIVE SPRING TO RESIST OPENING MOVEMENT OF SAID CHOKE VALVE BELOW A PREDETERMINED RANGE OF ENGINE TEMPERATURES WITH A FORCE INVERSELY PROPORTIONAL TO ENGINE TEMPEATURE, MEANS EXPOSING SAID TEMPERATURE RESPONSIVE SPRING TO ENGINE TEMPERATURE, AN ELONGATED CONNECTION JOINING SAID TEMPERATURE RESPONSIVE SPRING TO SAID CHOKE VALVE, SAID CONNECTION INCLUDING A PARTIALLY RIGID MEMBER, AND A SPRING LIKE YIELDABLE LINK INTEGRAL THEREWITH, SAID LINK EXHIBITING A GREATER RESISTANCE TO YIELD ABOVE ZERO DEGREES FAHRENHEIT THAN AT TEMPERATURES BELOW ZERO DEGREES FAHRENHEIT, WHEREBY SAID LINK WILL YIELD AT TEMPERATURES BELOW ZERO DEGREES FAHRENHEIT AND NOT TRANSMIT FORCE EXERTED BY SAID SPRING TO SAID CHOKE, BUT AT TEM-

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