US3279771A

US3279771A - Miniature automatic choke system

Info

Publication number: US3279771A
Application number: US392077A
Authority: US
Inventors: Ronald E Herman; Robert D Mitchell; Frederick J Marsee
Original assignee: Holley Carburetor Co
Current assignee: Holley Performance Products Inc
Priority date: 1964-08-20
Filing date: 1964-08-20
Publication date: 1966-10-18
Anticipated expiration: 1983-10-18

Description

Oct. 18, 1966 HERMAN ETAL 3,279,771

MINIATURE AUTOMATIC CHOKE SYSTEM Filed Aug. 20, 1964 3 o &\ 6 O 1 1 '1 4:41: i) I so 62 ,6 /4 68 56 64 I (2a /8 76 62 72 5'z- 4| 12/00 /6 24 L INVENTORS RONALD E. HERMAN ROBERT D. MITCHELL FREDERICK J. MARSEE m m M United States Patent F 3,279,771 MINIATURE AUTOMATIC CHOKE SYSTEM Ronald E. Herman, Warren, Robert D. Mitchell, Madison Heights, and Frederick J. Marsee, Hazel Park, Mich,

assignors to Holley Carburetor Company, Warren,

Mich, a corporation of Michigan Filed Aug. 20, 1964, Ser. No. 392,077 4 Claims. (Cl. 26139).

This invention relates generally to internal combustion engine carburetors used on the so-called compact cars, and more particularly to a novel automatic choke system for the same.

Smaller type carburetors had to be developed for use with the relatively new compact cars. Consequently, there arose a need for a completely new and more compact automatic choke system which would operate satisfactorily with such -a carburetor and be simple and inexpensive to fabricate.

Accordingly, it is a primary object of the invention to provide a novel automatic choke system which meets the above mentioned requirements.

Other more specific objects and advantages of the invention will become apparent when reference is made to the following description and accompanying illustrations wherein:

FIGURE 1 is .a top view of a carburetor embodying the invention;

FIGURE 2 is an elevational view of the carburetor shown by FIGURE 1;

FIGURE 3 is an enlarged cross-sectional view taken on the plane of line 33 of FIGURE 1 and looking in the direction of the arrows;

FIGURE 4 is an enlarged cross-sectional view of the automatic choke housing assembly, taken on the plane of line 44 of FIGURE 2 and looking in the direction of the arrows; and

FIGURE 5 is a cross-sectional view, taken on the plane of line 55 of FIGURE 4 and looking in the direction of the arrows.

Referring now to the drawings in greater detail, FIG- URE 1 illustrates a compact carburetor mounted on an engine intake manifold 12. The carburetor 10- may comprise upper and

lower portions

14 and 16, separated by a gasket 18 therebetween (FIGURE 2) and secured to each other in some suitable manner, such as by screws 20.

The upper and

lower portions

14 and 16 comprise an induction passage 22, an unbalanced choke plate 24 secured, as by screws 26, to an off-center choke shaft 28, a venturi 30, :and a throttle plate 32. The choke plate 24 contains a bend 33 formed at the point adjacent the shaft 28, for a purpose which will be described later. A fuel reservoir 34 is formed as an integral part of the upper and

lower portions

14 and 16, and it contains the usual float assembly (not shown) and outlets to the various fuel systems.

The automatic choke housing 36 is formed as an integral part of the upper portion 14. The choke shaft 28 is operatively connected to :a bimetallic thermostat element 38, positioned in the automatic choke housing 36, by means of a choke lever which is fixedly attached to the end of the choke shaft 28. The integral choke house ing 36 permits ready alignment of the choke shaft 28 through a single machined hole and eliminates the need for a seal, these being two inherent disadvantages in carburetors wherein the choke housing is a separate body.

It can be seen in FIGURE 1 that the center of the bimetallic thermostat element 38 and the center of the choke shaft 28 are not on the same axis. This particular configuration produces approximately a 2 to 1 leverage advantage, which results in lower costs because less ma- 3,279,771 Patented Oct. 18, was

ice

terial is required in the bimetallic element structure. In other words, the predetermined choke plate movement desired for a particular temperature change is accomplished with a bimetallic thermostat element 38 considerably shorter than would otherwise be required if the centers were on the same axis, since temperature rate of the element 38 varies directly with the length of the element.

The bimetallic element 38 in the choke housing chamber 42 is warmed .by air entering through the choke housing inlet 44 from a suitable stove 46, which could be located in the usual exhaust manifold 48. A cold air tube 50 may, of course, communicate between the exhaust manifold 48 and any suitable cold air source such as some point (not shown) through the wall of the induction passage 22 :above the choke plate 24.

The choke housing chamber 42 is subjected to vacuum from the intake manifold 12 through an opening 51 and a vacuum passage 52 in the upper portion 14. As better seen in FIGURE 2, the vacuum passage 52 intercepts a larger passageway 54 extending vertically through the lower portion 16 to the intake manifold 12. A conduit 56 communicates between the top of the passageway 54 and a piston housing 58.

The piston housing 58 comprises a chamber 60, a vacuum responsive piston 62 sliclably mounted therein, a manually adjustable stop 64 extending through the wall thereof, and a press-fitted end cap 66 for sealing off the rear piston cavity from the atmosphere (FIGURE 3). The piston 62 is operatively connected to the choke plate 24 by a link 65. The link 65 is pivotally connected at its one end 67 to a bracket 68 fixedly attached to the smaller side 70 of the choke plate 24, the other end 72 of the link 65 being connected to a pin 74 extending through the front portion of the piston 62. The pin 74 rides in a lost-motion-producing slot 76 in the end 72 of the link 65 for a purpose to be described later.

The throttle plate 32, fixedly attached to a throttle shaft 78, is controlled by a throttle lever assembly 80 rigidly fastened to the throttle shaft 78. Maximum closing movement of the throttle plate 32 is limited by means of an idle adjusting screw 82 abutting against a boss 84 formed on the lower body portion 16. The idle screw 82 is prevented from vibrating loose from the throttle lever assembly 80 by a tension spring 88. A fast idle cam screw is held in adjustment on the throttle lever assembly 80 by a second tension spring 92. The fast idle cam screw 90 is free at times, as will be described later, to abut against some one of the steps of a fast idle cam 94 which is pivotally mounted on the lower body portion 16, as at 96. The fast idle cam 94 is operatively connected to the choke shaft 28 by means of :a bracket 98 and screw 100 and two pivotally connected

links

102 and 104, the latter being free to ride in an override slot 106 in the fast idle cam 94.

Maximum opening movement of the throttle plate 32 is limited by the protrusion 108 on the throttle lever 80 abutting against the boss 84. Also, extension 110 of the throttle lever will at times contact lug 112 formed on the fast idle cam 94, thereby causing deohoking to occur.

FIGURE 2 further illustrates the choke housing cover assembly 114 which comprises a choke housing plate 116, a thermostat cap and baflle assembly 118, a thermostat cap clamp and thermostat cap clamp screws 122.

FIGURE 4 is an enlarged view of the complete automatic choke housing assembly 36 demonstrating the passageway 124 into the choke housing chamber 42 for the hot air which enters through the cap inlet 44. Gaskets 126 and 128 may be located on the two sides of the choke housing plate 116. This figure also illustrates the bimetallic thermostat element 38 mounted on an anchor extension 136 of the thermostat cap and baffle assembly 118. It should be readily apparent that this construction permits ready readjustment of the bimetallic thermostat element 38 setting by loosening the screws 118 so as to disengage the thermostat cap clamp 120 from the serrated outer edge of the cap and bafile assembly I118, and turning the latter to the desired richer or leaner setting before retightening the screws 122.

FIGURE 5 illustrates the routing of the hot air through the thermostat cap inlet 44 and thence through the passageways 124 which may be cast into the thermostat cap and bafile assembly 118.

Assuming, for purposes of illustration, that the engine is cold and is being cranked, the thermostatic element 38 will be in its unwound condition by virtue of the accelerator pedal (not shown) having been depressed, thereby releasing the fast i-dle cam screw 90 from the lowest step 132 of the fast idle cam 94 where it would normally have remained from the previous engine operation. This would rotate the projection 134 of the lever 40 to its extreme counterclockwise position. The lever 40, being secured to the choke shaft 28, rotates the shaft 28 counterclockwise, thereby causing the choke valve 24 to assume a position which substantially closes off the flow of air through the carburetor induction passage 22, as well as causing the fast idle cam high step 136 to be presented to the fast idle cam screw 90 once the accelerator pedal is released.

While the engine is being cranked with the choke plate 24 being biased in a closed position as described above, engine manifold vacuum acting on the piston 62 through the passageway 54 and conduit 56, along with the associated air-flow acting upon the unbalanced choke plate 24, may cause the choke plate 24 to open slightly. Once the engine has fired and becomes self-sustaining, the resulting higher manifold vacuum acting upon the piston 62, against the tension of the thermostatic element 38, will open the choke plate 24 to a position determined by the manually adjustable stop 64. This position is maintained during fast idle while the fast idle cam screw 90 is positioned against the highest step 136 of the fast idle cam 94, the throttle plate 32 being cracked enough to provide the fast idle necessary to run a cold engine.

While the engine warms up, hot air is circulated through the choke housing 36 via the thermostat cap inlet 44 and the passageways 124 and out through the opening 50. This warms the bimetallic thermostat element 38, causing it to release its tension on the choke shaft 28 via the choke lever 40, allowing the unbalanced choke plate 24 to gradually open under the force of the increased airflow through the induction passage 22. During this Warm-up process while the fast idle cam 94 is being held at some one of its steps by the fast idle cam screw 90, as the choke shaft 28 rotates, the link 16M is free to slide downwardly in the lost motion slot 106 of the fast idle cam 94.

Engine manifold vacuum will of course, still be acting on the piston 62 through the passageway 54 and conduit 56, holding it against the adjustable stop 64. Hence, the lost motion slot 76, along with the hollow piston structure will permit the link 65 to move further into the piston 62.

Referring now to FIGURE 3, it may be noted that the larger and smaller sides of the choke plate 24 are off-set by virtue of a bend being formed therebetween, as .illustrated. The result of this is that, for any particular angular rotation of the plate 24, more air will pass by the upper edge than would be the case if both sides were on the same plane, due to the outer edge of the upper side being automatically displaced further away from the wall of the induction passage 22 than would be the case if it were not off-set from the other side. It should be apparent that this is a very desirable feature, in view of the relatively small diameter induction passage 22 which is inherent in a compact carburetor design. Without the bend, in order to have the plate 24 open far enough during the initial warm-up stage, there would remain only a very small angle in which to rotate to a fully open choke plate position during the remaining warm-up stages.

The movement of the choke plate 24, of course, ties in directly with the various warm-up positions of the throttle plate 32, through the fast idle cam and the associated linkage. Without the offset choke plate configuration, the second step of the fast idle cam 94 would have to be longer than that illustrated, in order for the throttle plate 32 to be maintained open far enough to permit sufficient air to pass by during the initial warm-up process. This, of course, would eliminate some or all of the space available for additional steps, due to the physical limitations, and the engine would be idling much tOo fast during the final stages of warm-up, thereby tending to make it difiicult during the last stages of choking prior to the choke becoming fully open to shift gears, when a standard transmission is involved, and tending to cause the vehicle to creep, at red lights, for example, when an automatic transmission is involved.

From the above, it should be readily apparent that a novel automatic choke system has been provided which is capable of efficient and economical operation in conjunction with a particular compact type carburetor. It is also apparent that simplicity, as well as low construction, operating and maintenance costs, have been emphasized in this automatic choke system so as to further the economy goals behind the development of the relatively new compac cars.

Although but one embodiment of the invention has been shown and described, it is conceivable that various anodifications may be made without exceeding the scope of the appended claims.

What We claim as our invention is:

1. In an internal combustion engine carburetor having an induction passage and adapted to be mounted on an engine intake manifold, an automatic choke system comprising a first housing including a cover assembly with a warm air inlet therethrough and an anchor extension extending from said cover assembly into said first housing; temperature responsive means mounted on said anchor extension; a second housing including a pressure responsive piston; a common passageway adapted to be connected from said intake manifold to a point adjacent said first and second housings; a first conduit communicating between said common passageway and said first housing; a second conduit communicating between said common passageway and said second housing; a choke shaft extending across said induction passage and into said first housing; linkage means between said choke shaft and said temperature responsive means; a choke plate fixedly secured to said choke shaft, said choke plate having the portion on one side of said choke shaft off-set from the portion on the other side of said choke shaft; and second linkage means pivotally connected at its one end to the portion of said choke plate which swings upwardly to open and slidably connected at its other end to said pressure responsive means.

2. In an internal combustion engine carburetor having an induction passage subjected to a source of engine manifold vacuum, an automatic choke system comprising a first housing including a bimetallic thermostat spring; a choke shaft extending across said induction passage and into said first housing, said choke shaft having its axis displaced from the axis of said bimetallic spring so as to provide a leverage advantage in the actuation of said choke shaft by said bimetallic spring, linkage means connecting said choke shaft to the outer end of said bimetallic spring; an unbalanced choke plate fixedly connected to said choke shaft, said unbalanced choke plate having the plane of the smaller side thereof off-set from the plane of the larger side; a second housing including a pressure responsive piston, a manually adjustable stop in said housing for at times being contacted by said piston, additional linkage means connecting the smaller side of said choke plate to said pressure responsive piston, and a lost motion slot in the piston end of said linkage means for receiving said additional linkage means; a first passageway leading from said source of manifold vacuum to a point intermediate said first and said second housing; a second passageway communicating between said first passageway and said first housing; a third passageway communicating between said first passageway and said second housing; and a fast idle cam associated with said choke shaft by means of a plurality of links and a lost motion slot in said fast idle cam.

3. In an internal combustion engine carburetor body having an induction passage therethrough, an automatic choke assembly, said assembly comprising a housing integral with said carburetor body; a cover on said housing; a cap assembly rota-tively mounted on said cover; said cap assembly having a warm air inlet therethrough, an extension into said housing and an outer serrated face; clamp means positioned in a constant location against said serrated face and having notches for mating with said serrated face; temperature responsive means mounted on said extension; a choke shaft extending through said induction passage and into said housing at a point intermediate said extension and the outer end of said temperature responsive means; linkage means connecting said choke shaft to said outer end of said temperature responsive means; and a choke plate fixedly secured to said choke shaft in said induction passage, said choke plate having the portion on one side of said choke shaft off-set from the portion on the other side of said choke shaft; and second linkage means pivotally connected at its one end to the portion of said choke plate which swings upwardly to open and slidably connected at its other end to said pressure responsive means.

4. In an internal combustion engine carburetor body having an induction passage therethrough, an automatic choke assembly, said assembly comprising a housing integral with said carburetor body; a cover assembly rotatively mounted on said housing; said cover assembly having a warm air inlet therethrough, an extension into said housing and an outer serrated face; clamp means positioned in a constant location against said serrated face and having notches for mating with said serrated face; temperature responsive means mounted on said extension; a choke shaft extending through said induction passage and into said housing at a point intermediate said extension and the outer end of said temperature responsive means; linkage means connecting said choke shaft to said outer end of said temperature responsive means; and a choke plate fixedly secured to said choke shaft in said induction passage, said choke plate having the portion on one side of said choke shaft off-set from the portion on the other side of said choke shaft; and second linkage means pivotally connected at its one end to the portion of said choke plate which swings upwardly to open and slidably connected at its other end to said pressure responsive means.

References Cited by the Examiner UNITED STATES PATENTS 1,034,531 8/1912 Stump 251-305 X 2,026,947 1/1936 Leibing 261- 2,771,282 11/1956 Olson et al. 261--39 X 2,776,821 1/1957 Davis 251305 X 2,918,266 12/1959 Hamilton 261-39 3,180,576 4/1965 Herman 26139 X ROBERT F. BURNETT, Primary Examiner.

T. R. MILES, Assistant Examiner.

Claims

1. IN AN INTERNAL COMBUSTION ENGINE CARBURETOR HAVING AN INDUCTION PASSAGE AND ADAPTED TO BE MOUNTED ON SAID ENGINE INTAKE MANIFOLD, AN AUTOMATIC CHOKE SYSTEM COMPRISING A FIRST HOUSING INCLUDING A COVER ASSEMBLY WITH A WARM AIR INLET THERETHROUGH AND AN ANCHOR EXTENSION EXTENDING FROM SAID COVER ASSEMBLY INTO SAID FIRST HOUSING. TEMPERATURE RESPONSIVE MEANS MOUNTED ON SAID ANCHOR EXTENSION; A SECOND HOUSING INCLUDING A PRESSURE RESPONSIVE PISTON; A COMMON PASSAGEWAY ADAPTED TO BE NNECTED FROM SAID INTAKE MANIFOLD TO A POINT ADJACENT SAID FIRST AND SECOND HOUSINGS; A FIRST CONDUIT COMMUNICATING BETWEEN SAID COMMOM PASSAGEWAY AND SAID FIRST HOUSING; A SECOND CONDUIT COMMUNICATING BETWEEN SAID COMMON PASSAGEWAY AND SAID SECOND HOUSING; A CHOKE SHAFT EXTENDING ARCOSS SAID INDUCTION PASSAGE AND INTO SAID FIRST HOUSING; LINKAGE MEANS BETWEEN SAID CHOKE PLATE AND SAID TEMPERATURE RESPONSIVE MEANS; A CHOKE PLATE FIXEDLY SECURED TO SAID CHOKE SHAFT, SAID CHOKE PLATE HAVING THE PORTION ON ONE SIDE OF SAID CHOKE OFF-SET FROM THE PORTION ON THE OTHER SIDE OF SAID CHOKE SHAFT; AND SECOND LINKAGE MEANS PIVOTALLY CONNECTED AT ITS ONE END TO THE PORTION OF SAID CHOKE PLATE WHICH SWINGS UPWARDLY TO OPEN AND SLIDABLY CONNECTED AT IS OTHER END TO SAID PRESSURE RESPONSIVE MEANS.