US3263972A - Automatic choke mechanism - Google Patents

Description

g- 2, 1966 P. E. BRAUN ETAL 3,263,972

AUTOMATIC CHOKE MECHANISM Filed June 20, 1963 4 Sheets-Sheet 1 PAUL E. BRA UN ALBERT APRUCHIVO ATTORNEYS 1966 P. E. BRAUN ETAL 3,

AUTOMATIC CHOKE umcmmxsm Filed June 20, 1963 4 Sheets-Sheet 2 PAUL E. BRAUN A L BERT A. PRUCH/VO INVENTO ATTORNEYS Aug. 2, I966 P. E. BRAUN ETAL 3,263,972

AUTOMATIC CHOKE MECHANISM Filed June 20, 1963 4 Sheets-Sheet 5 FIG. 6

PAUL E. BRAUN A 1. BERT A. mum/v0 INVENTORS ATTORNEYS Aug. 2, 1966 P. E. BRAUN ETAL AUTOMATIC CHOKE MECHANISM 4 Sheets-Sheet 4 Filed June 20, I963 PA UL E. BRAU/V ALBERT AEBQUCHNO INVE ATTORNEYS United States Patent 3,263,972 AUTOMATIC CHOKE MECHANISM Paul E. Braun, Birmingham, and Albert A. Pruchno, Detroit, Mich., assignors to Ford Motor Company, Dearborn, Mich., a corporation of Delaware Filed June 20, 1963, Ser. No. 289,258 6 Claims. (Cl. 261-39) This invention relates to an automatic choke mechanism for an internal combustion engine carburetor and more particularly to an adjustable linkage for an automatic choke mechanism.

The thermally responsive element of a conventional automatic choke mechanism positions both a choke valve and a fast idle mechanism. The fast idle mechanism increases the engine idle speed during the initial stage of warm up to prevent stalling. It is desirable to provide for adjustment of the choke valve and fast idle mechanism relative to the thermally responsive element to compensate for production variations and differing engine requirements. Adjustment of the choke valve is particularlyrequired when the choke mechanism employs a suction motor to partially open the choke valve when a cold engine first commences to run. The adjustment is necessary to calibrate the degree of choke valve opening or pull down effected by the suction motor.

Automatic choke mechanisms previously known frequently have not permitted the fast idle mechanism and the degree of choke valve pull down to be independently adjusted. In addition it was often necessary to permanently deform a portion or portions of the choke linkage to produce the desired adjustments. Deformation of the linkage could only be accomplished through the use of special tools and did not permit the exacting degree of adjustment required.

It is therefore the principal object of this invention to provide an automatic choke mechanism in which independent adjustment of the choke valve and fast idle mechanism with respect to the thermally responsive element is possible.

It is a further object of this invention to provide a simplified choke linkage adjustment mechanism that permits delicate adjustments to be made.

A carburetor embodying this invention comprises an induction passage containing throttle and choke valves. A temperature responsive element is connected to the choke valve by an adjustable length link to actuate the choke valve in response to temperature variations. A lever rotatable with the throttle valve is adapted 'to engage a fast idle cam to establish a fast idle position for the throttle valve. The fast idle cam is adjustably connected to the temperature responsive element.

Further objects and advantages of this invention will become more apparent when considered in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a side elevational view of an internal combustion engine carburetor incorporating this invention.

FIGURE 2 is a front elevational view of the carburetor shown in FIGURE 1;

FIGURE 3 is an exploded view showing the automatic choke mechanism incorporated in the carburetor.

FIGURES 47 are partially exploded side elevational views of the choke mechanism, with portions shown in cross section, illustrating the sequence of operation.

FIGURE 4 shows the mechanism during cranking of a cold engine.

FIGURE 5 shows the position of the mechanism immediately after the engine has started.

FIGURE 6 shows the choke mechanism as it appears when the engine approaches its operating temperature.

FIGURE 7 illustrates a position the mechanism may take to permit manual opening of the choke valve to start a flooded engine.

FIGURE 8 is a cross sectional view taken along line 8-8 of FIGURE 1.

FIGURE 9 is a cross sectional view in part similar to FIGURE 8 showing the elements prior to fina'l adjustment.

Referring now in detail to the drawings, a carburetor is indicated generally by the reference numeral 11. Formed within the carburetor 11 is at least one induction passage 12. A throttle valve 13 is rotatably supported in the induction passage 12 upon a throttle valve shaft 14. The throttle valve shaft 14 extends from each side of the carburetor 11 and one side is connected through throttle linkage 15 to an accelerator mechanism to permit adjustment of the speed of the associated engine (not shown). An inturned tang 16 of the throttle linkage 15 contacts an adjustable screw 17 to establish a normal engine idle speed.

Positioned in the induction passage 12 anterior to the throttle valve 13 is a choke valve 18. The choke valve 18 is rota-tably supported upon a choke valve shaft 19 that extends outwardly at one side of the carburetor 11. The choke valve 18 is rotatably positioned in the induction passage 12 in response to temperature variations by an automatic choke mechanism indicated generally at 21.

The automatic choke mechanism 21 includes a choke housing 22 having a plurality of inwardly extending, apertured bosses 23. Outward-1y extending bosses 24 formed upon the carburetor 11 are tapped to receive bolts 25 that extend through the apertured bosses 23 to secure the choke housing 22 to the carburetor 11. A cover plate 26 encloses the choke housing 22 and is secured thereto by a plurality of bolts 27 that pass through elongated apertures 28 in the choke housing cover 25. The bolts 27 are threaded into tapped holes 29 formed around the periphery of the choke housing 22.

A coiled thermally responsive spring 31 is contained within the cover plate 26 and has its inner end 32 affixed thereto. The thermally responsive spring 31 is insulated from the interior of the choke housing 22 by a composition disc 33 and steel disc 34 that are interposed between the cover plate 26 and the choke housing 22.

The outer end 35 of the thermally responsive spring 31 is aifixed to a bifurcated arm 36 of a choke actuating lever 37. The choke actuating lever 37 is aflixed by a screw 39 to a choke actuating shaft 38 that is journaled in the choke housing 22. The bifurcated arm 36 extends through arcuate slots 40 and 41 formed in the composition and steel discs 33 and 34, respectively.

The choke actuating shaft 38 extends inwardfy toward the carburetor 11 and has a lever 42 affixed to its inner end. A link 43 has an outturned end 44 that extends through an aperture in the lever 42. The outturned end 44 of the link 43 is retained in the aperture by -a snap ring 45 to permit the transmission of motion from the lever 42 to the link 43. The upper end of the link 43 is pivotally connected to a lever 46 that is aflixed for rotation with the choke shaft 19 by an adjustable swivel mechanism indicated generally at 47.

The adjustable swivel mechanism 47, which is shown in greater detail in FIGURES 8 and 9, permits the relative positions of the choke valve 18 and choke actuating shaft 38 to be adjusted. The adjustable swivel mechanism 47 includes a first generally cylindrical shaped element 48 having an inwardly extending boss 49. A headed rivet 51 extends through an aperture formed in the lever 46 and is fixed in an aperture 52 formed in the inwardly extending boss 49. The rivet 51 pivotally connects the lever 46 to the element 48.

A second element 53 of the adjustable swivel mechanism 47 has a cylindrical portion 54 that extends through and is journaled in the internal bore of the first element 48. The second element 53 is axially fixed with respect to the first element 48 by the contact of a shoulder 55 with the upper surface of the eement 48 and the contact of an overturned flange 56 with the lower surface of the element 48. The second element 53 is internally threaded, as at 57, to cooperate with threads 58 formed on the upper end of the link 43.

The relative positions of the choke valve 18 and choke act ating shaft 38 may be adjusted by rotating the internally threaded element 53. Rotation of the element 53 causes the adjustable swivel mechanism 47 to move axially along the link 43 to adjust the effective length of the link 43. Once the desired relative positions of the choke valve 18 and choke actuating shaft 38 are obtained, the adjustable swivel 47 may be rigidly fixed upon the link 43. For this purpose, a groove 59 is formed around the periphery of the element 43 adjacent its internal threads 57. By engaging a tool with the groove 59 and compressing the element 53, the threads 57 are deformed (FIGURE 8) to fix the adjustable swivel mechanism 47 in position. By staking the adjustable swivel mechanism 47 to the link 43, play is eliminated from the choke actuating linkage. The adjustment of the effective length of the link 43 also determines the degree of the vacuum pull down of the choke valve 18 effected by the suction motor now to be described.

The choke housing 22 is formed with a cylindrical bore 61 that slidably receives a vacuum actuated piston 62. The piston 62 is pivotally connected by a pin 63 to a link 64. The piston 62 is transversely slotted, as at 65, to provide clearance for the link 64. The upper end of the link 64 is pivotally connected by a pin 66 to an extending arm 67 of the choke actuating lever 37.

The cylindrical bore 61 is exposed to engine intake manifold vacuum by means of a port 68 that opens into one of the longitudinal grooves 69 formed at each side of the bore 61. The port 68 extends through one of the choke housing bosses 23 and carburetor bosses 24 to a point in the induction passage 12 below the throttle valve 13. The lower end of the cylindrical bore 61 is closed by a disc 71. The intake manifold vacuum acting on the head of the piston 62 modulates the position of the choke valve 18 in the manner which will be described as this description proceeds.

The thermally responsive spring 31 is also adapted to provide an increased engine idle speed during the initial stage of engine warm up by means of the fast idle mechanism indicated generally at 72. The fast idle mechanism 72 comprises a lever 73 that is rotatably journaled on the choke actuating shaft 38 between the lever 42 and the choke housing 22. A link 74 transmits motion between the lever 73 and a fast idle cam 75 that is pivotally journaled upon the carburetor 11 by a pin 76. The link 74 is fixed relative to the lever 73 and the fast idle cam 75 by snap rings 77 and 78, respectively. The lever 73 has an inturned tang 79 through which is threaded an adjustable screw 81. The adjustable screw 81 is adapted to abut at times an upper surface 82 of the lever 42. A lever 83 is aflixed to the outwardly extending side of the throttle valve shaft 14 adjacent the automatic choke mechanism 21 by a nut 84. An adjustable screw 85 is threaded through the lever 83 and is adapted to engage the stepped cam surface 86 formed on the fast idle cam 75. Adjustment of the screw 81 permits variation in the position of the fast idle cam 75 with respect to the choke actuating shaft 38.

Operation When the engine has been standing for a long duration under low ambient temperatures, the automatic choke mechanism 21 is permitted to appropriately position the choke valve 18 by opening the throttle valve 13. Opening of the throttle valve 13 permits the linkage to move free of interf ren e rom the fast idle mechanism 72. If the temperature is sufficiently low, the thermally responsive spring 31 will rotate the choke actuating lever 37 and choke actuating shaft 38 in a counterclockwise direction an amount sufficient to fully close the choke valve 18 (FIGURE 4). The contact of the upper surface 82 of lever 42 with the adjustable screw 81 also causes the lever 73 to be rotated in a counterclockwise direction. This motion is transmitted through the link 74 to the fast idle cam 75. When the throttle valve 13 is closed, the adjustable screw 85 will contact the high portion of the cam surface 86 on the fast idle cam 75 to cause the throttle valve 13 to be held in a more fully opened position than the normal idle speed.

The linkage remains in the position shown in FIGURE 4 during cranking of the cold engine. During this time the intake manifold vacuum exerted through the port 68 below the piston 62 is insufficient to have any effect on the position of the choke actuating shaft 38. When the engine commences to run, however, the intake manifold vacuum increases significantly. The increase in vacuum exerted in the cylindrical bore 61 causes the piston 62 to be drawn downwardly and rotate the choke actuating lever 37 in a clockwise direction (FIGURE 5). This motion opens the choke valve 18 slightly to permit suflicient air flow through the induction passage 12 for sustained engine operation. The opening of the choke valve 18 may also be assisted by unbalancing the choke valve 18 upon choke valve shaft 19.

The degree of movement of the piston 62 is limited by registry of the transverse slot in the piston 62 with the longitudinal grooves 69 formed in the cylinder 61. When this happens, a vacuum bleed will occur past the piston 62 and further downward movement of the piston can only occur upon a significant increase in manifold vacuum.

The vacuum bleed occurring past the piston 62 is utilized to draw heated air into the choke housing 22 for heating the thermally responsive spring 31 in response to engine operation. Air heated by an exhaust manifold stove (not shown) is drawn through an inlet tube 87 formed integrally with the choke housing 22. The inlet tube is ported through a conduit 88 into the choke housing. The conduit 88 registers with apertures 89 and 91 formed in the steel and composition discs 34 and 33, respectively. The heated air is drawn from the exhaust stove through the inlet tube 87 and conduit 88 into the choke housing cover 26. The heated air passes across a thermally responsive spring 31 and passes through the slotted apertures 39 and 41 into the choke housing 22. From the choke housing 22 the heated air bypasses the piston 62 and is discharged into the induction system of the engine through the port 68.

As the thermally responsive spring 31 is heated in response to engine operation, its tension decreases and the choke actuating lever 37 and choke actuating shaft 38 are rotated in a clockwise direction. The clockwise rotation of the choke actuating shaft 37 is transmitted through the lever 42 and link 43 to the choke valve 18 (FIGURE 6).

The lever 73, link 74 and fast idle cam are unbalanced so that gravity tends to rotate the fast idle cam 75 in a clockwise direction. The clockwise rotation is limited by the contact of the adjustable screw 81 with the upper surface 82 of the lever 42. A fast idle speed is not required after the initial stage of engine warm up and, accordingly, the fast idle cam 75 is permitted to rotate free from contact with the adjustable screw 85. The rotation of the fast idle cam 75 is limited by contact of the fast idle cam 75 with an inwardly extending boss 92 formed on the choke housing 22. The choke actuating mechanism may continue to rotate, however. Continued opening of the choke valve 18 causes the lever 42 to move away from the adjustable screw 81 (FIGURE 6).

If the engine is stopped, the thermally responsive element will cool and cause the choke valve 18 to rotate toward a closed position. Continued rotation will eventually cause the lever 42 to again contact the adjustable screw 81 and actuate the fast idle cam 75. The time of actuation may be varied by adjustment of the screw 81.

It is possible that, due to improper starting procedure, the cold engine may be flooded. Provision is mad-e, therefore, for manual opening of the otherwise closed choke valve 18 to permit unflooding and starting of the engine. For this purpose, the lever 83 is formed with an outwardly extending tang 93. By rotating the throttle valve 13 into a fully opened position (FIGURE 7), the tang 93 is brought into abutment with the fast idle cam 75. The contact causes the fast idle cam 75 to be rotated in a clockwise direction and this motion is transmitted through the link 74 to the lever 73. The clockwise rotation of the lever 73 is transmitted through the adjustable screw 81 to clockwise rotation of the lever 42 to open the choke valve 18 slightly and permit starting.

It is to be understood that various changes and modifications may be made from the described, preferred embodiment of the invention without departing from the spirit and scope of the invention as defined by the appended claims.

We claim:

1. A carburetor for an internal combustion engine comprising an induction passage, a throttle valve and a choke valve rotatably supported in said induction passage, a temperature responsive element, an adjustable length link operably connecting said temperature responsive element to said choke valve for moving said choke valve between an opened and a closed position in response to temperature changes, a lever rotatable with said throttle valve, a fast idle cam adapted to be engaged by said lever to establish a fast idle position for said throttle valve, and an operative connection between said temperature responsive element and said fast idle cam for positioning said fast idle cam to be engaged by said lever at low temperatures, said last named operative connection comprising an adjustable abutment screw to permit adjustment of the relative positions of said temperature responsive element and said fast idle cam independent of adjustment of the relative positions of said temperature responsive element and said choke valve.

2. A carburetor for an internal combustion engine comprising an induction passage, a throttle valve rotatably supported in said induction passage, a choke valve rotatably supported in said induction passage anterior to said throttle valve, a temperature responsive element, a first lever connected to said temperature responsive element for movement in response to temperature variations, an adjustable length link operatively connecting said first lever to said choke valve, a second lever having an adjustable lost motion connection with said link, said lost motion connection being adjustable independently of said adjustable length link, said connection including adjustable screw means, a fast idle cam positioned by said second lever, and a third lever operatively connected to said throttle valve, said third lever being adapted to engage said fast idle cam at low temperatures to establish a fast idle position for said throttle valve.

3. A carburetor for an internal combustion engine comprising an induction passage, a throttle valve, a choke valve rotatably supported in said induction passage upon a choke valve shaft, a temperature responsive element, a first lever operatively connected to said temperature responsive element for movement in response to temperature variations, a second lever fixed for rotation with said choke valve shaft, a link having pivotal connections with said levers for transmitting motion between said temperature responsive element and said choke valve, at least one of said pivotal connections comprising a first element pivotally connected to the lever and a second element rotatable with respect to said first element, said first and second elements being connected for simultaneous axial movement, said second element having a threaded connection with said link for adjustment of the axial position of said elements upon said link, a third lever in adjustable abutment with said first lever, and a fast idle cam positioned by said third lever, said cam positioning said throttle valve to establish a fast idle position.

4. A carburetor as defined by claim 3 wherein said second element is permanently deformable to permit it to be locked in its adjusted position upon the link.

5. A carburetor for an internal combustion engine comprising an induction passage, a throttle valve rotatably supported upon a throttle valve shaft in said induction passage, a choke valve rotatably supported upon a choke valve shaft in said induction passage anterior to said throttle valve, a temperature responsive element, a first lever rotatably positioned by said temperature responsive element in response to temperature variations, a second lever fixed for rotation with said choke valve shaft, a link pivotally connected to said first and second levers for positioning said choke valve in response to temperature variations, a fast idle cam pivoted with respect to said carburetor, a third lever pivoted with respect to said carburetor and having an adjustable abutment adapted to contact said first lever, a second link pivotally connected to said fast idle cam and said third lever, said fast idle cam, said second link and said third lever being unbalanced for pivotal movement to bring said adjustable abutment into engagement with said first lever when the choke valve is in a closed position, and a fourth lever fixed for rotation with said throttle valve shaft and having an adjustable abutment adapted to engage said fast idle cam to establish a fast idle position for said throttle valve under low ambient temperatures.

6. A carburetor as defined by claim 5 wherein one of the pivotal connections between said first link and said first and second levers is adjustable to change the relationship between said first lever and said choke valve.

References Cited by the Examiner UNITED STATES PATENTS 2,124,778 7/1938 Hunt 261-52 X 2,136,353 11/1938 Weber 26152 2,555,124 5/1951 Gothberg 74586 X 2,747,848 5/1956 Kehoe 26152 3,151,189 9/1964 McSeveny 261-39 HARRY B. THORNTON, Primary Examiner.

ROBERT F. BURNETT, Examiner.

T. R. MILES, Assistant Examiner.

Claims (1)

1. A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE COMPRISING AN INDUCTION PASSAGE, A THROTTLE VALVE AND A CHOKE VALVE ROTATABLY SUPPORTED IN SAID INDUCTION PASSAGE, A TEMPERATURE RESPONSIVE ELEMENT, AN ADJUSTABLE LENGTH LINK OPERABLY CONNECTING SAID TEMPERATURE RESPONSIVE ELEMENT TO SAID CHOKE VALVE FOR MOVING SAID CHOKE VALVE BETWEEN AN OPENED AND A CLOSED POSITION IN RESPONSE TO TEMPERATURE CHANGES, A LEVER ROTATABLE WITH SAID THROTTLE VALVE, A FAST IDLE CAM ADAPTED TO BE ENGAGED BY SAID LEVER TO ESTABLISH A FAST IDLE POSITION FOR SAID THROTTLE VALVE, AND AN OPERATIVE CONNECTION BETWEEN SAID TEMPERATURE RESPONSIVE ELEMENT AND SAID FAST IDLE CAM FOR POSITIONING SAID FAST IDLE CAM TO BE ENGAGED BY SAID LEVER AT LOWER TEMPERATURES, SAID LAST NAMED OPERATIVE CONNECTION COMPRISING AN ADJUSTABLE ABUTMENT SCREW TO PERMIT ADJUSTMENT OF THE RELATIVE POSITIONS OF SAID TEMPERATURE RESPONSIVE ELEMENT AND SAID FAST IDLE CAM INDEPENDENT OF ADJUSTMENT OF THE RELATIVE POSITIONS OF SAID TEMPERATURE RESPONSIVE ELEMENT AND SAID CHOKE VALVE.

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