US3133532A

US3133532A - Carburetor choke control

Info

Publication number: US3133532A
Application number: US287628A
Authority: US
Inventors: Thomas M Ball
Original assignee: Chrysler Corp
Current assignee: Old Carco LLC
Priority date: 1963-06-13
Filing date: 1963-06-13
Publication date: 1964-05-19
Anticipated expiration: 1981-05-19

Description

May 19, 1964 T. M. BALL CARBURETOR CHOKE CONTROL 2 Sheets-Sheet 1 Filed June 13, 1963 INVENTOR. 7 %0ma5 M B United States, Patent Ofiice,

3,133,532 Patented May 19, 1964 3,133,532 CARBURETOR CHOKE CONTROL Thomas M. Ball, Bloomfield Hills, Mich., assignor to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Filed June 13, 1963, Ser. No. 287,628 8 Claims. (Cl. 123-119) This invention relates to improvements in carburetors for an internal combustion engine and in particular to an improved automatic choke and means for opening the choke during cranking to prevent flooding of the engine.

A difliculty in the cold weather starting of certain types of automobile engines, arises fromflooding of the engine during cranking, especially if the engine is not in optimum operating condition and an excess quantity of raw fuel is drawn into the inlet manifold. In such engines, it is essential during cold weather when the lubrication is particularly viscous, that each cylinder develop its optimum output during cranking to assist the electric cranking motor.

It is accordingly an important object of the invention to provide improved means for opening the choke valve to a breather position independently of any other actuating device of the carburetor during cranking when the engine is beginning to assist the starting motor but is not yet operating independently. The breather position referred to will be sufiicient to avoid an overly rich fuelair mixture and consequent engine flooding and might be any position of choke valve opening less than the minimum opening during cold idling of the engine.

One of the problems encountered in any attempt to open the choke valve to the breather position during cold weather cranking and before the engine is operating independently of the starting motor is that the most available operating force resulting either from manifold vacuum or the air flow in the inlet induction passage is comparatively small. On the other hand the usual frictio'nal force resisting such opening is comparatively large.

Other important objects are accordingly to provide a particularly low friction device to enable opening of the choke valve to a breather position or range and to provide such a device cooperable with an unbalanced butterfiy type choke valve blade secured to a choke shaft to pivot therewith. A thermostatic lever means is pivoted on a fixed hub of the carburetor housing. The choke shaft extends axially through the fixed hub and has a choke lever'means keyed thereto. The choke and thermostatic lever means are each provided with a pair of radial arms or extensions, the two extensions of the thermostatic lever means being spaced by one of the arms of the choke lever means and serving as movement limiting stops to engage the aforesaid one arm to limit its pivotal movement relative to the thermostatic lever means. The latter is engageable with a fixed stop on the carburetor housing to limit its pivoting in a choke closing or cold operating direction and is operably connected with temperature responsive means to be yieldingly urged into engagement with the fixed stop with increasing force as the temperature decreases. A breather spring interconnects the other arm of the choke lever means with the proximate or a first arm of the thermostatic lever means to urge said one arm in the choke closing direction into movement limiting engagement with the second arm of the thermostatic lever means.

The fixed stop and the arms of the two lever means are I of the air how in the carburetor induction passage against the unbalanced choke blade when the engine is in its partial state of operation (assisting but not operating independently of the starting motor) so as to enable opening of the choke blade to the limit of a breather position determined by interengagement between the corresponding arms of the choke and thermostatic lever means.

By virtue of the thermostatic lever means mounted on the fixed hub, the latter and choke lever means can be arranged co-axially without frictional interference therebetween. Also the force of the breather spring can also be arranged in alignment with the point of movement limiting engagement between the arms of the choke and thermostatic lever means to avoid side loading of the journal mounting for the choke shaft,.thereby to reduce friction and obtain freedom of movement for the choke blade under the comparative light air pressure force available during engine choking.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIGURE 1 is a somewhat schematic side elevation view of a carburetor embodying the present invention, portions being broke away to show details of construction.

FIGURE 2 is a fragmentary enlarged view, similar to FIGURE 1, showing the choke and thermostatic lever means. 7

FIGURE 3 is a fragmentary view taken in the direction of the arrows substantially along the line of 3-3 of FIGURE 2.

FIGURE 4 is an enlarged elevated view taken in the direction of the arrow 4 of FIGURE 3.

FIGURE 5 is a fragmentary enlarged sectional view taken in the direction of the arrows substantially along the line 55 of FIGURE 3. g

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to the drawings, a particular embodiment of the present invention is illustrated by way of example in an automobile carburetor having an air horn body' portion 10 and the usual integral flange 11 for attachment with an air cleaner. The body 10, an intermediate venturi body portion 12, and a lower throttle body portion 13 are suitably secured together to complete a unitary carburetor body. An air induction passage 14 extends through the

body portions

10, 12 and 13, the passage 14 having its air inlet opening into the body 10 and its fuel-air mixture outlet discharging from the body 13.

A'choke shaft 15, FIGURE 3, extends transversely across the passage 14 and is journalled within the opposite side walls of the body 10. In the present instance, the shaft 15 is offset to the left of the center line of the passage 14 in FIGURE 1 and is secured to an unbalanced choke blade 16 to pivot therewith to control the opening of passage 14 and thereby to control the richness of the fuel-air mixture discharged'from the passage 14 in (accordance with customary practice.

The choke shaft 15 extends axially through a fixed hub 10a integral with the body 10 and extending outwardly from one side thereof. The shaft 15 terminates in a flattened end |15a having a choke lever 17 splined thereon for pivoting in unison with the shaft 15 and blade 16.

9 'l'he lever 17 is provided with a pair of generally radial extensions or arms 17a and 17b.

The outer end portion of hub a is reduced in diameter at 10b to effect a radial shoulder 10c and provides a journal for a thermostatic lever 18 seated against the shoulder 10c. The thermostatic lever 18 is provided with a pair of radial extensions or

arms

18a and 1% spaced by an inbent movement limiting projection 170 at the outer end of arm 17b. Lever 18 is also provided with a movement limiting projection 18c engageable with a fixed stop 10d integral with the hub 10a. In addition the lever 18 is provided with extensions 18d and 18s for the purposes described below.

A thermostatic link 19 cooperates with lever 18 to complete a thermostatic lever means and is pivotally secured at its upper and lower ends respectively to extension 18d and to the outer swinging end of an arm 20. The latter is pivotal about a fixed pivot 21 secured to a portion of the engine and also to a fixed end of a spiral bi-metallic thermostatic spring 22. The outer or free end of spring 22 engages the swinging end of arm 20 to urge the latter yieldingly upwardly or counter-clockwise with increasing force as the engine temperature acting on spring 22 decreases. The upward movement of arm 20 and link 19 swings lever 18 counter-clockwise to its limiting position determined by abutment of projection 180 against stop 10d.

Lever 17 is yieldingly urged counter-clockwise by the light force of a breather spring 23 to the limit of movement permitted by engagement between stop 17c and movement limiting arm 18b. Breather, spring 23 is connected under tension between the extremities of

arms

17a and 18a and enables a limited opening of the choke valve 16 until tab 17c engages movement limiting larm \18a. This opening of valve 16 will be independent of any other actuating device for the automatic choke, as for example the closing force applied by thermostatic spring 22 or the manifold vacuum force employed to open the choke to its normal cold idling position as described below. It is also to be noted that spring 23 is a coil spring having its axis in a plane perpendicular to the pivot axis of

levers

17 and 18 and aligned with the point of engagement between stop 17c and arm 18b when lever is at its limit of counter-clockwise movement. This arrangement avoids iany resultant torque in the

levers

17 and 18 about an axis through stop 170, so that side loading of the bearing for shaft is minimized.

Downstream of the choke valve '16, the passage 14 is provided with a throttle valve 24 which may be conventional and which in the present instance is secured to a throttle shaft 25 extending diametrically across the passage 14 and journalled at its opposite ends in the side walls of the body 13. A throttle crank arm 26 splined on one end of shaft 25 is actuated by a foot pedal operated push rod 27 for opening and closing the throttle valve 24. A throttle return spring 28 is secured under tension to an extension of crank arm 26 and to a fixed portion of the engine to yieldingly urge the throttle valve 24 to the closed position.

Vacuum operation of the choke blade 16 to open the latter to a predetermined cold idling position against the force of thermostatic spring 22 is accomplished by means of a radial cylinder 29 integral with body 10 and closed at its outer end. The inner end of cylinder 29 opens into the passage 14 upstream of the choke blade 16. A piston 30 reciprocal within cylinder 29 is pivotally connected to one end of a connecting link 31 having its opposite end pivotally connected at 32 to a tab integral with choke blade 16 so as to swing the latter to an open position upon rightward movement of piston 30 and link 31 in FIGURE 1. Vacuum actuation of piston 30 is accomplished by means of a duct 33 extending from cylinder 29 at the right of piston 30 and through the

body members

10, 12 and 113 to port 33a which opens into passage 14 downstream of throttle valve 24.

The engine idling speed is controlled by means of a fast idle cam 34 in accordance with the temperature operating on spring 22. The latter is pivotal on pivot stud 35 secured to body portion 12. The cam 34 is provided with a stepped cam surface 36 comprising a number of circumferentially extended cam portions of progressively increasing radius in the clockwise direction. Approximately diametrically across from the cam surface 36 is an integral counterbalancing extension 37 of the cam 34 which operates to pivot the latter by gravity force in a clockwise or warm direction. An operating link 40 is pivotally connected at its upper and lower ends respectively to extension 18e land to cam 34 within a lost motion slot 41 thereof. Thus upon the cold or counterclockwise closing pivotal movement of lever 18 urged by spring 22 and link 19, the lower end of link 40 will seat against the most counterclockwise end of slot 41 and urge cam 34 in its cold or counter-clockwise direction to the limit of movement determined by the resultant of the forces of spring 22 and the manifold vacuum acting on piston 30. An extension 38 of lever 26 cam'es an adjustable cam follower screw which rides on cam surface 36 when throttle valve 24 moves to its closed position, thereby to limit the closing of throttle valve 24 at a fast idling position determined by the engine temperature. The interrelationship between fast idle cam 34 and follower 39 may be conventional and is not described further.

Spring 22 is located so as to be responsive to an operating temperature of the engine. As this temperature increases to decrease the force urging thermostatic lever 18 in the counter-clockwise or closing direction, the vacuum force acting on piston 30 will tend to open choke valve 16 increasingly and cause clockwise or opening movement of the lever 18 by reason of interengagement between tab 17c and arm 18a. During this movement, the lower end of link 40 will be free to move along slot 41 to enable opening of choke blade 16 freely regardless whether or not cam 34 is immobilized by frictional contact between follower screw 39 and one of the steps of cam surface 36.

In operation of the device described, during cold starting when the usual electric cranking motor is operating without assistance from the engine, a comparative high pressure will exist downstream of throttle valve 24 so that the force on piston 30 will be comparatively slight. Similarly the air flow in passage 14 will be small and the force of this air flow impinging on the unbalanced choke blade 16 will also be comparatively slight. These combined forces will be ineffective to cause opening of choke blade 16 against the light tension of spring 23. In consequence, an optimum choking condition is obtained and a rich fuel-air starting mixture will be discharged from the passage 14 in accordance with customary carburetor operation.

As the engine begins to operate partially to assist the starting motor, both the vacuum force acting on piston 30 and the air flow in passage 14 impinging on choke blade 16 will increase to overcome spring 23 and enable a small predetermined clockwise breather opening of the choke blade 16, thereby to reduce the richness of the fuel-air mixture and prevent flooding of the engine cylinders with raw fuel. The extent of the breather opening of choke valve 16 will be determined by abutment between tab and arm 18a and may be approximately one half the extent that choke valve 15 is opened during cold idling. The breather opening will have no appreciable effect on the valve closing effort of spring 22.

In consequence of the operation described, starting of the engine is materially facilitated. The engine will almost immediately accelerate from its condition of partial operation to an idling condition independent of the starting motor, whereby operation of the latter is discontinued. As soon as the engine is idling, the vacuum force acting on piston 30 resulting from the low pressure downstream of throttle valve 24 will rise to a maxiton 30 and the reaction force of thermostatic spring 22.

I claim:

1. In a carburetor for an internal combustion engine, an air induction passage, means for providing a predetermined breather opening in said passage for air flow therein during cranking of said engine in a cold condition when said engine is in a partial state of operation to assist the cranking but is not operating independently of the cranking comprising a pivotal choke shaft extending into said passage, a butterfly type choke valve in said passage having an unbalanced choke blade secured to said shaft to pivot therewith and adapted to pivot in an opening direction in response to the pressure of air flow in said passage impinging on saidblade, a pivotal thermostatically actuated lever means, a fixed stop engageable by said lever means to limit pivoting thereof in one direction, temperature responsive means for yieldingly urging said lever means in said one direction with increasing force in response to a decreasing operating temperature of said engine, crankarm means secured to said choke shaft to pivot therewith, said crankarm and lever means having first and second interengaging portions to limit relative pivoting of said shaft in choke closing and choke opening directions respectively, and means yieldable under the pressure of said air flow impinging on said unbalanced choke blade when said engine is in said partial state of operation for opening said choke blade to a predetermined breather position determined by said second interengaging portions including resilient means yieldingly urging pivoting of said shaft in said choke closing direction.

2. In the combination according to claim 1 said chokeblade being in the closed position when said shaft is at the limit of its choke closing position determined by said first interengaging portions and said lever means is at its limit of pivoting in said one direction determined by said fixed stop.

3. In a carburetor for an internal combustion engine, an air induction passage, means for providing a predetermined breather opening in said passage for air flow therein during cranking of said engine in a cold condition when said engine is in a partial state of operation to assist the cranking but is not operating independently of the cranking comprising a pivotal choke shaft extending into said passage, a butterfly type choke valve in said passage having an unbalanced choke blade secured to said shaft to to pivot therewith and adapted to pivot in an opening direction in response to the pressure of air flow in said passage impinging on said blade, a pivotal thermostatically actuated lever means, a fixed stop engageable by said lever means to limit pivoting thereof in one direction, temperature responsive means for yieldingly urging said lever means in said one direction with increasing force in response to a decreasing operating temperature of said engine, choke lever means secured to said choke shaft to pivot therewith, first interengaging means on said thermostatic lever and choke lever means to limit pivoting of said choke blade in said one direction to a closed position when said thermostatic lever means is at its limit of pivoting in said one direction, second interengaging means on said thermostatic lever and choke lever means to limit pivoting of said choke blade in the direction opposite said one direction to a breather position, and means yieldable under the pressure of said air flow impinging on said unbalanced choke blade for opening the latter to said breather position when said engine is in said partial state of operation in- 6 eluding resilient means yieldingly urging pivoting of said shaft in said one direction.

4. In a carburetor for an internalcombustion engine, an air induction passage, means for providing a predeterminedbreather opening in said passage for air flow therein during cranking of said engine in a cold condition when said engine is in a partial state of operation to assist the cranking but is not operating independently of the cranking comprising a pivotal choke shaft extending into said passage, a butterfly type choke valve in said passage having an unbalanced choke blade secured to said shaft to pivot therewith and adapted to pivot in an opening direction in response to the pressure of air flow in said passage impinging on said blade, a pivotal thermostatically actuated lever means, a fixed stop engageable by said lever means to limit pivoting thereof in one direction, temperature responsive means for yieldingly urging said lever means in said one direction with increasing force in response to a decreasing operating temperature of said engine, choke lever means secured to said choke shaft to pivot therewith, first interengaging means on said thermostatic lever and choke lever means to limit pivoting of said choke blade in said one direction to a closed position when said thermostatic lever means is at its limit of pivoting in said one direction, second interengaging means on said thermostatic lever and choke lever means to limit pivoting of said choke blade in the direction opposite said one direction to a breather position, means yieldable under the pressure 'of said air flow impinging on said unbalanced choke blade for opening the latter to said breather position when said engine is in said partial state of operation including resilient means yieldingly urging pivoting of said shaft in said one direction, a throttle valve in said passage, and pressure actuated means operatively coupled with said choke'valve and responsive to the pressure in said passage downstream of said throttle valve when said engine is idling to openvsaid choke valve and pivot said lever means in opposition to said temperature responsive means to a predetermined position beyond said breather position.

i 5. In a carburetor for an internal combustion engine, an air induction passage, means forproviding a predetermined breather opening in said passage for air flow therein during cranking of said engine in a cold condition when said engine is in a partial state of operation to assist the cranking but is not operating independently of the cranking comprising a pivotal choke shaft extending into said passage, a butterfly type choke valve in said passage having an unbalanced choke blade secured to said shaft to pivot therewith and adapted to pivot in an opening direction in response to the pressure of air flow in said passage impinging on said blade, a pivotal thermostatically actuated lever means, a fixed stop engageable by said lever means to limit pivoting thereof in one direction, temperature responsive means for yielding urging said lever means in said one direction with increasing force in response to a decreasing operating temperature of said engine, choke lever means secured to said choke shaft to pivot therewith, first interengaging means on said thermostatic lever and choke lever means to limit pivoting of said choke blade in said one direction to a closed position when said thermostatic lever means is at its limit of pivoting in said one direction, second interengaging means on said thermostatic lever and choke lever means to limit pivoting of said choke blade in the direction opposite said one direction to a breather position, means yieldable under the pressure of said air flow impinging on said unbalanced choke blade for opening the latter to said breather position when said engine is in said partial state of operation including resilient means yieldingly urging pivoting of said shaft in said one direction, a throttle valve in said passage, a pivotal fast idle cam having a lost motion slot and a cam surface and being pivotal between warm and cold positions, means yieldingly urging pivoting of said cam toward its warm position, a link having one end movable along said slot and bottoming at one end of the latter to limit pivoting of said cam to its warm position, said thermostatic lever means being operably connected with the other end of said link for yieldingly urging the latter and said cam to its cold position upon pivoting of said thermostatic lever means in said one direction, said one end of said link being movable along said slot upon pivotal opening of said choke blade beyond said breather position, and a cam follower operably connected with said throttle valve for operation therewith and engageable with said cam surface for selectively holding said throttle valve open to a fast idling position determined by said operating temperature.

6. In a carburetor for an internal combustion engine, an air induction passage, means for providing a predetermined breather opening in said passage for air fiow therein during cranking of said engine in a cold condition when said engine is in a partial state of operation to assist the cranking but is not operating independently of the cranking comprising a pivotal choke shaft extending into said passage, a butterfly type choke valve in said passage having an unbalanced choke blade secured to said shaft to pivot therewith and adapted to pivot in an opening direction in response to the pressure of air flow in said passage impinging on said blade, a pivotal thermostatically actuated lever means, a fixed stop engageable by said lever means to limit pivoting thereof in one direction, temperature responsive means for yieldingly urging said lever means in said one direction with increasing force in response to a decreasing operating temperature of said engine, choke lever means secured to said choke shaft to pivot therewith, first interengaging means on said thermostatic lever and choke lever means to limit pivoting of said choke blade in said direction to a closed position when said thermostatic lever means is at its limit of pivoting in said one direction, second interengaging means on said thermostatic lever and choke lever means to limit pivoting of said choke blade in the direction opposite said one direction to a breather position, spring means connecting radial extensions of said thermostatic and choke lever means and yieldable under the pressure of said air flow imping on said unbalanced choke blade for opening the latter to said breather position when said engine is in said partial state of operation, said spring means comprising a coil spring having its axis in a plane perpendicular to the pivot axis of said choke shaft and extending through said first interengaging means when said thermostatic lever means is at its limit of pivoting in said one direction.

7. In a carburetor for an internal combustion engine, a body, an air induction passage in said body, means for providing a predetermined breather opening in said passage for air flow therein during cranking of said engine in a cold condition When said engine is in a partial state of operation to assist the cranking but is not operating independently of the cranking comprising a choke shaft extending into said passage pivotally mounted on said body, a butterfly type choke valve in said passage having an unbalanced choke blade secured to said shaft to pivot therewith and adapted to pivot in an opening direction in response to the pressure of air flow in said passage impinging on said blade, 21 fixed pivot hub extending from said body and having said choke shaft extending axially therethrough, a thermostatically actuated lever means pivotally mounted on said hub, a fixed stop on said body engageable by said lever means to limit pivoting thereof in one direction, temperature responsive means for yieldingly urging said lever means in said one direction with increasing force in response to a decreasing operating temperature of said engine, choke lever means secured to said choke shaft to pivot therewith, first interengaging means on said thermostatic lever and choke lever means to limit pivoting of said choke blade in said one direction to a closed position when said thermostatic lever means is at its limit of pivoting in said one direction, second interengaging means on said thermostatic lever and choke lever means to limit: pivoting of said choke blade in the direction opposite said one direction to a breather position, said thermostatic lever and choke lever means having radial arms respectively, spring means connecting said arms under tension yieldingly urging pivotal closing of said choke valve in said one direction to the limit enabled by said first interengaging means and being yieldable under the pressure of said air flow impinging on said unbalanced choke blade for opening the latter to said breather position when said engine is in said partial state of operation including resilient means yieldingly urging pivoting of said shaft in said one direction.

8. In the combination according to claim 7, the connection between said spring means and radial arms being in alignment with said first interengaging means and in a plane perpendicular to the axis of said choke shaft.

No references cited.

UNITED'STATES PATENT OFFICE CERTIFIGATE OF CORRECTION Patent No 3,133, 532 May 19, 1964 Thomas MO Ball It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as correctedbelow.

Column 2, line 18, for "choking" read cranking line 26, for "broke" read H broken column 5, line 55, strike out "to", second occurrence; column 7, line 43, for "imping" read impinging a Signed and sealed this 12th day of October 1965a (SEAL) Attest:

ERNEST "W; 'SWIDER EDWARD J. .BRENNER Attesting Officer Commissioner of Patents

Claims

1. IN A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE, AN AIR INDUCTION PASSAGE, MEANS FOR PROVIDING A PREDETERMINED BREATHER OPENING IN SAID PASSAGE FOR AIR FLOW THEREIN DURING CRANKING OF SAID ENGINE IN A COLD CONDITION WHEN SAID ENGINE IS IN A PARTIAL STATE OF OPERATION TO ASSIST THE CRANKING BUT IS NOT OPERATING INDEPENDENTLY OF THE CRANKING COMPRISING A PIVOTAL CHOKE SHAFT EXTENDING INTO SAID PASSAGE, A BUTTERFLY TYPE CHOKE VALVE IN SAID PASSAGE HAVING AN UNBALANCED CHOKE BLADE SECURED TO SAID SHAFT TO PIVOT THEREWITH AND ADAPTED TO PIVOT IN AN OPENING DIRECTION IN RESPONSE TO THE PRESSURE OF AIR FLOW IN SAID PASSAGE IMPINGING ON SAID BLADE, A PIVOTAL THERMOSTATICALLY ACTUATED LEVER MEANS, A FIXED STOP ENGAGEABLE BY SAID LEVER MEANS TO LIMIT PIVOTING THEREOF IN ONE DIRECTION, TEMPERATURE RESPONSIVE MEANS FOR YIELDINGLY URGING SAID LEVER MEANS IN SAID ONE DIRECTION WITH INCREASING FORCE IN RESPONSE TO A DECREASING OPERATING TEMPERATURE OF SAID ENGINE, CRANKARM MEANS SECURED TO SAID CHOKE SHAFT TO PIVOT THEREWITH, SAID CRANKARM AND LEVER MEANS HAVING FIRST AND SECOND INTERENGAGING PORTIONS TO LIMIT RELATIVE PIVOTING OF SAID SHAFT IN CHOKE CLOSING AND CHOKE OPENING DIRECTIONS RESPECTIVELY, AND MEANS YIELDABLE UNDER THE PRESSURE OF SAID AIR FLOW IMPINGING ON SAID UNBALANCED CHOKE BLADE WHEN SAID ENGINE IS IN SAID PARTIAL STATE OF OPERATION FOR OPENING SAID CHOKE BLADE TO A PREDETERMINED BREATHER POSITION DETERMINED BY SAID SECOND INTERENGAGING PORTIONS INCLUDING RESILIENT MEANS YIELDINGLY URGING PIVOTING OF SAID SHAFT IN SAID CHOKE CLOSING DIRECTION.