US3133977A - Carburetor - Google Patents

Description

May 19, 1964 CARBURETOR Filed Sept. 25, 1961 J. L. SZWARGULSKI 2 Sheets-Sheet 1 May 19, 1964 J. L. szwARGuLsKl 3,133,977

CARBURETOR Filed Sept. 25, 1961 2 Sheets-Sheet 2 INVENTOR. JESSE L. SZWARGULSKI United States Patent Oiice 3,133,977 Patented May 19, 1964 3,133,977 CARBURETOR Jesse L. Szwargulski, Florissant, Mo., assigner to ACEl Industries Incorporated, New York, N.Y., a corporation of New Jersey Filed Sept. 25, 1961, Ser. No. 140,371 1 Claim. (Cl. 261-39) This invention is directed to a carburetor for an internal combustion engine and particularly to a novel automatic choke construction for such a carburetor.

It has been found that one place where a cost reduction is possible in carburetor design is in the automatic choke structure. An automatic choke designed for present day carburetors utilizes a plurality of levers and linkages, which in some cases result in a rather complex mechanism for automatically checking the carburetor. It is thus desirable as a cost reduction effort to produce an automatic choke having a minimum of parts but one which will operate effectively and withsuicient degree of reliability and effectiveness.

It is therefore an object of this invention to provide a novel automatic choke mechanism for a carburetor.

It is another object of this invention -to provide a novel automatic choke mechanism for a carburetor in which the mechanism has a minimum of parts.

It is a further object of this invention to provide a novel automatic choke mechanism for a carburetor in which the number of parts is minimized and the cost of the mechanism is considerably reduced.

The invention -is directed to an automatic choke mechanism of a carburetor including a choke housing in which is encased a thermostatic spring connected to the choke valve of the carburetor and a small piston and cylinder for operating the choke upon starting or cranking of the engine. Operatively connected with the choke shaft there is provided a novel automatic choke cam slide, which is biased by gravity in one direction when the choke is opened but is operatively moved in the opposite direction by the choke shaft upon the closing of the choke valve. Structure provided on the cam slide and the throttle shaft provides opening of the choke for the unloading of the carburetor, when the engine is flooded, during a cold start. Furthermore, the cam slide provides a stepped stop for preventing the full closing of the throttle valve during a cold kidling condition of the engine.

FIGURE 1 is a plan view of a carburetor embodying the novel features of this invention.

FIGURE 2 is subtantially a longitudinal sectional view of the carburetor of FIGURE 1 and is shown mounted on an engine manifold and with an air filter partially in section.

FIGURE 3 is an end view of the carburetor of FIG- URES 1 and 2 on looking toward the left of FIGURE 1.

FIGURES 4, 5 and 6 are schematic views of the novel choke mechanism of the carburetor of FIGURES 1-3, in various positions of operation.

The carburetor shown in FIGURES 1 and 2 consists essentially of a single casting which is formed with a fuel and air mixture conduit 12 and a fuel bowl cover portion 14 from lwhich is integrally formed a depending accelerating pump cylinder 16, an accelerating fuel passage 18 and a fuel well structure 20. As shown, the mixture conduit 12 is arranged and aligned vertically during operation and is connected by a flange 13 to the intake manifold M of an internal combustion engine E. In the lower part of the conduit 12 there is rotatably mounted a throttle valve 22 fixed to a throttle shaft 24 journaled in appropriately aligned apertures of the body casting 10. In Vvthe upper portion of the fuel-air mixture conduit 12 there is similarly mounted for rotational movement an unbalanced choke valve 26 fixed to a choke valve shaft 28, which is also journaled in aligned apertures through the body casting 10. To the top of the mixture conduit 12 is connected an air filter 29, partially shown in section in FIGURE 2. Between the upper and lower portions of the mixture conduit 12 is formed a venturi or air flow restricting surface portion 30. A small booster venturi 32 is formed integrally with the body casting 12 and has an inner venturi surface 34 coaxially aligned with the mixture conduit 12 and the primary venturi surface 30.

A plastic fuel bowl 36 is fixed beneath the fuel bowl cover 14 and -is held with its rim tightly against a gasket 3S fitted between the rim of the fuel bowl 36 and matching portions of the fuel bowl cover 14. A float structure 40 is pivotally mounted from pin 42 journaled in -a depending portion of fuel bowl cover 14. A lever arm of the float lever 43 fixed to float 40 abuts the lower end of a needle valve 44 having an upper tapered end extending into a valve seat 46 of the inlet 47 to the fuel bowl 36. A fitting may be threaded into inlet 47 to connect the carburetor to a fuel line 48. Fuel is forced under pressure by a pump 50 from a fuel tank 52, both schematically shown, through the fuel line 48 and into the carburetor inlet 47. With the fuel level in bowl 36 low, the fioat 40 is lowered and lever arm 43 allows valve 44 to be pressed by fuel pressure and gravity to an open position. Fuel flows into the bowl 36 and when it reaches a predetermined level, the oat raises lever 43 upwardly against the needle valve 44 to close the inlet to the fuel bowl.

The lower end of the fuel well 20 is closed by a threaded fitting 56 having a central orifice 69 therethrough which is carefully formed to provide a metering jet for the flow of fuel from the fuel bowl 36 to the mixture conduit 12. The upper end of the fuel well 20 intercepts a cross fuel passage 58 directed downwardly into the secondary venturi structure 32. A nozzle fitting 60 is press-'fitted into the end of passage 58 and has one end thereof extending into the center of the secondary venturi surface 34. Pressfitted within the well 20 is a fuel emulsion tube 62 having apertures therethrough along its length.

A metering rod 66 is suspended within .the fuel well 20. The lower end of rod 66 is formed with varying thicknesses and is positioned within the main fuel jet orifice 69 for yoperation in response to engine requirements. Flow or fuel lthrough the main jet fitting 56 is controlled by that portion of the formed end of rod 66 which is positioned within the orifice 69. The metering rod 66 is supported by a retainer in which the upper end 0f rod 66 is frictionally engaged.

A light spring 78 biases the retainer and rod 66 against a diaphragm 80 which is sealed in an air tight manner at its peripheral edge between a shoulder ofthe body casting 10 and a fitting 82 pressed into a matching bore 84 of the body casting. Diaphragm 80 extends across a cavity which is formed from a depression in the bottom of bore 84 and fitting 82. On the upper side of diaphragm 80, a spring is positioned between fitting 82 and the diaphragm to bias the diaphragm 80 in a downward position. The details of this metering rod control is the subject of my copending application, Serial No. 131,175, filed August 14, 1961. v

The space above diaphragm 80 is connected by a cross passage 92 to an annular passage formed in the peripheral surface of the fitting 82. As shown in the above cited copending application, a passage i-s formed through the body casting 10 to the flange portion 13 of the carburetor and opens into the mixing conduit below or downstream of the throttle 22. In this manner, the portion of the space above the diaphragm 80 is connected to manifold pressure of the engine.

A passage 96 (FIGURE 2) is formed between the mixing conduit 12 from a region between the choke valve 26 and the throttle valve 22 to extend downwardly into the upper portion of well 20. Within the passage 96 is press-fitted a restriction element 98 for controlling air fiow through passage 96 into the well 20. t

Mounted within the cylindrical recess 16 formed into body casting is a pump piston 100 (FIGURE .2), which is connected to a pump piston rod 102. A spring 104 is fitted between the upper end of the pump cylinder 16 and the piston 100. The lower end of the pump cylinder 16 is closed by a fitting 106 having a central laperture 108 therethrough above which, biased by gravity, is a ball valve 110. A fuel passage 112 extends between the pump cylinder 16 and the cylindrical passage formed in the body casting 10. Passage 112 permits fuel ow into a fitting 114 closing the lower end of cylindrical passage 18 and having at its upper end a valve seat in which the pointed end of a gravity biased check valve 116 is fitted. The cylindrical passage 18 extends upwardly and intercepts the main fuel passage 58, at which point a closure fitting 118 is fixed. Fitting 118 forms an annular channel 117 with passage 58. Channel 117 is connected with a small aperture 119 through which fuel can be ejected from the cylindrical passage 18 into the main fuel passage 58 under pressure from the pump piston 100. Aperture 119 is formed off axis 'relative to passage 58 so that the ejected fuel will not strike rod 66 and be directed into the well 20.

The operation of the structures described is as follows: Fuel from the fuel bowl 36 flows into both the pump cylinder 16 and the well structure 20, to fill these recesses to the level of the fuel in the bowl. Upon the turning over of the engine, air is sucked through the air filter 29 into the mixture conduit 12 and the intake manifold M. The flow of air through the booster venturi 32 provides a sub-atmospheric pressure within the venturi surface 34 which extends back through the fuel passage 58 to the upper end of fuel well 20. The atmospheric pressure on the surface of the fuel within bowl 36 raises the fuel within the well and simultaneously air is sucked through the restriction 98 and the bleed passage 96 into the upper portion of the fuel well. This air passes around and through the apertures in the emulsion tube 62 to mix with the fuel and its vapor and to form an airfuel emulsion. The emulsion is carried upwardly from the fuel well into the main fuel passage 58 and out the nozzle 60 to form a fuel and air mixture with the air passing through the mixture conduit 12.

At low engine speeds, the throttle 22 is partially closed so that the manifold vacuum in the intake manifold M below the throttle 22 is relatively high. This vacuum is effective upon the upper surface of diaphragm 80 so that atmospheric pressure will press the diaphragm upwardly and permit the metering rod and its retainer to be carried by spring 78 in an upward direction. This brings the thicker portion of the lower end of metering rod 66 into the main jet orifice 69 to cut down the flow of fuel through this orifice in accordance with the lower engine speed. As the throttle 22 is opened progressively from low speed to high speed, the vacuum pressure in the manifold drops and permits spring 90 to bias the diaphragm 80 and the metering rod 66 downwardly until a thinner portion of the lower end of rod 66 enters the jet orifice to provide a greater flow of fuel into the mixing conduit 12.

The accelerating pump rod 102 is connected with a ilost motion connection 124 (FIGURES 1 and 2) by a linkage 126 to the throttle lever 128 which is fixed for simultaneous movement with the throttle shaft 24. Throttle lever 128 has an arm 129 adapted to be connected to any means for manual operation of the throttle 22. Any opening of the throttle by lever 128 will allow spring 104 through the lost motion connection 124 to press accelerating pump piston 100 downwardly and force fuel out of the lower portion of the pump cylinder 16 through passage 112 upwardly past the gravity biased valve 116 and into the annular portion 117 of the fitting 118. This accelerating fuel will spurt out of passage 119 into the nozzle structure 60 to provide additional fuel for the increased air flow due to the opening of the throttle 22. This provides rapid response of the engine upon opening of the throttle.

A low speed or idle circuit is provided in the carburetor and is not shown in this application as it does not constitute a part of the invention. However, it may be similar to that described and disclosed in the copending application of Ralph E. Kalert and Jesse L. Szwargulski, Serial No. 146,896, tiled October 23, 1961.

The choke valve 26 is controlled during cold weather and during cold starts by a thermostatic choke control device enclosed in a housing structure 130. The choke control consists of a thermostatic coiled bi-metallic spring 132 having one end fixed to a stationary stud 134 mounted on the housing 130. The other end of the thermostatic spring rests against one arm 136 of a lever 137 fixed to the choke shaft 28. Lever 137 has an extension, as shown in FIGURE 3, connected by a wire linkage 140 to the piston 142 positioned for sliding motion in the air motor cylinder 144. The lower end of cylinder 144 is closed, as indicated in FIGURE 3, and is also connected through an aperture 146 to a passage 148 leading therefrom to the flange 13 of the carburetor where the lower end of passage 148 is exposed at 149 to manifold pressure below the throttle valve 22.

When the engine is cold, the thermostatic spring is tensioned in one direction to press against the end of the lever 136 and rotate the choke valve 26 into a closed position. The flow of air through the mixing conduit 12 against the unbalanced choke valve 26 and the action of manifold vacuum through passage 148 on piston 142 connected to the choke shaft will partially open the choke valve 26 to permit only sufficient air to pass into the mixing conduit 12 to provide an enriched mixture with the available fuel. As the engine heats up, warm air from a chamber in thermal contact with the exhaust manifold of the engine is sucked through a conduit 150 fixed to fitting 152 leading into a chamber 154 enclosing the piston 142 and cylinder 144. A bypass passage 156 in the cylinder wall permits the passage of air around the piston 142 when it is in the lower portion of cylinder 144. The bypass passage 156 and passage 148 thus expose the chamber 154 to manifold vacuum and enables the warm air from the stove to pass through the chamber 154. Warm air in chamber 154 will pass through an arcuate slot 155 in a divider gasket 156 separating chamber 154 from the spring housing chamber 158 to gradually heat up the thermostatic spring 132. As the spring 132 becomes heated it relaxes and releases the end of the lever 136 so that after a predetermined temperature has been reached, the thermostatic coil 132 has no further effect on the choke 26, which now remains open by gravity and air iiow due to its unbalanced construcion. In accordance with the invention, a novel connection 1s provided between the automatic choke mechanism described above and the throttle valve 22 of the carburetor. This connection is operative to provide positioning of the 'throttle at different openings during idling to provide optimum idling conditions as the engine warms up, during cold operating conditions. Furthermore, the novel connecting means provides structure whereby the choke valve 26 may be opened during cold weather when the carburetor has become flooded and it is necessary to force air through the carburetor by cranking the engine to eliminate the excessively rich air and fuel mixture.

The novel connection between the automatic choke and the throttle 26 of the carburetor comprises essentially a choke cam slide element 160. The slide is substantially a flat piece of metal or of appropriate material, such as a wear-resistant plastic, and as indicated by the side view in FIGURE 2, for example. The cam slide has a deep slot 162 (FIGURE 4) formed in its upper end and a correspondingly deep slot 164 formed in its lower end. The slide 160 is operatively mounted for sliding movement on the choke shaft 28 and a threaded stud 166 threaded into the carburetor body. The choke shaft 28 is received within slot 162 and the mounting stud 166 is received in the lower slot 164. The spacing of stud 166 from the choke shaft 28 is such as to permit only limited movement of the slide 160 along a line connecting the choke shaft 28 and stud 166. As indicated in FIGURES 3 through 6, the stud 166 is mounted slightly displaced from a vertical alignment with the choke shaft 28, but only sufficiently to allow sliding movement of the cam slide 160 under the biasing force of gravity. As an alternative, a biasing spring may be used instead of gravity to move the slide 160 downwardly.

A first lug 168 is formed by upsetting a portion of the outer tine 170 forming the groove 162. A second lug 172 is formed by upsetting a portion of the slide 160 at the lov/er part of the inner tine 174 forming groove 162. A short rod 176 is fixed through the choke shaft 28, as shown in FIGURE 4, between the upset lugs 168 and 172, so that the two ends of rod 176 are respectively in the path of the lugs 168 and 172 as the cam slide 160 is moved from one position to another.

The slide 160 also has a stop 178 (FIGURE 5) on the inner tine and partly defining slot 164 extending away from the direction of movement of the slide 160. A plurality of steps 180 are formed between the stop 178 and an inner edge 182 of the slide to provide additional stop surfaces. Stop 178 and steps 180 are positioned under different conditions of operation in the path of rotation of an idle screw 184 fitted to an arm 186 of throttle lever 128, to operate as described below.

In operation, the slide 160 is biased downwardly by gravity so that lug 168 rides on the upper surface of the rod 176. Thus, the position of the choke valve 26 will control the position of the cam slide 160. In cold weather starting, the choke valve 26 is pulled open by the flow of air through the mixture conduit 12 acting against the unbalanced valve portions, as well as the manifold vacuum exerting itself against the piston 142. The choke valve 26, however, is prevented from opening to its full extent because of the tension of the cold thermostatic spring 132. FIGURE 4 indicates an idle condition of the engine during cold operation after starting. In this idling condition, the choke valve 26 is maintained partially opened for the reasons explained above and the throttle valve 22 is also maintained open to permit the air and fuel mixture to pass into the intake manifold of the engine. The operators foot is normaly off the accelerator, and accordingly the throttle lever 128 is released and biased toward closed position by the throttle lever spring. However, the cam slide 160 is held in the position indicated in FIGURE 4 by virtue of the lug 168 resting in contact with the upper surface of pin 176. This positions one of the steps 188 in the path of the idle screw 184 when the throttle lever is released so that the idle screw 184 contacts one of the steps, as shown in FIGURE 4, to hold the throttle 22 in a partially open position necessary for cold engine idling conditions. As the engine warms up during the idling operation of FIGURE 4, the thermostatic spring 132 releases the choke shaft 28 and the choke valve 26 opens up because of air iiow and gravity bias. If the throttle lever is not manually operated, slide 160 will retain the throttle in the fast idle position of FIGURE 4 and yet permit shaft 28 to rotate as the choke valve 26 opens.

After the engine has been warmed up and warm air has passed into the spring housing chamber 158 to heat the thermostatic spring 132 to render it inoperative, the choke valve will be positioned in its full open position, as indicated in FIGURE 3, by the flow of air into the mixture conduit 12 and by manifold pressure exerting a suction on the choke piston 142. In this position, the pin 176 through the choke shaft 28 is rotated in a clockwise direction, from the position in FIGURE 4 to permit the 6. cam slide to be further biased downwardly by gravity until it reaches a position indicated in FIGURE 3 and in which the steps are out of the path of rotation of the idle adjustment screw 184. This permits the throttle to close to its warm idle position as indicated. At this point,

the throttle lever arm 186 abuts the end of a curb idle screw 188 so as to prevent the throttle 22 from completely closing and to permit the flow of sufficient air into the engine manifold to provide a low idle speed.

Provision is also made for the unloading of the carburetor. This is a condition that, upon the failure of the engine to start during cold weather, the mixing conduit 12, as well as the monifold M of the engine, becomes flooded and the air-fuel mixture is too rich as to prevent firing of the engine. This results from an overworking by the operator of the accelerating pedal, which simultaneously squirts fuel into the mixing conduit 12 by action of the accelerating pump piston 180. To eliminate the overly fuel-rich mixture in the carburetor conduit 12 and the engine manifold, it is desirable to force air through these passages to sweep out the unusable mixture. Mere cranking of the engine is not suflicient, as insuicient air is pumped itno the engine during cranking to open the choke valve 26 far enough against the bias of the cold thermostatic spring 132. Accordingly, there is provided on the throttle lever 128 an additional lever arm 189 having at an extreme end a lug 190, shown specifically in FIGURES 4 and 5. Also, fixed to the lower end portion of the inner tine partially defining slot 164 of the cam slide 160 is a lug 192 shown in FIGURES 2 and 5. Lug 192 is formed and positioned in the rotational path of lug 190 when the throttle lever 128 is rotated in a counterclockwise position, as viewed in FIGURE 5. This is only true when the choke valve 26 is closed and the cam slide 160 is raised by pin 176 to the position shown in FIGURE 5. The operator then, upon depressing the accelerator to its fullest extent, will rotate the throttle lever 128 beyond its position, shown in FIGURE 5. The throttle lever lug 190 contacts the cam slide lug 192 and forces the cam slide 160 upwardly until the lug 172 contacts the undersurface of pin 176 to rotate the pin and thus open the choke valve 26. The engine then upon cranking sucks air through the mixture conduit and the engine manifold to sweep out the overly rich mixture and enable an appropriate mixture for starting.

FIGURE 6 illustrates a condition of the carburetor in which the engine is operated at high speed with a wide open throttle and choke valve. In this position gravity has biased the cam slide 160 downwardly so that the lug 192 of the slide has passed beyond the rotation of path of lug 19t) and such that when the throttle lever 128 is operated in this position of FIGURE 6, there is no interference of lug 192 with lug 190.

The above described choke mechanism is one which utilizes a simple connection between the choke and the throttle lever. The slide 160 provides a simple construction for controlling the positioning of the throttle lever during fast idle conditions when the engine is operated in a cold condition. Furthermore, the cam slide 160 provides means for unloading the carburetor and engine during cold starting when necessary. Thus, the operative connection between the automatic choke mechanism described and the throttle operating mechanism consists of a simple cam slide 160 having a plurality of projections or lugs which are operatively positioned at different times to provide the necessary control of the throttle by the automatic choke mechanism and also to provide opening 0f the choke by the throttle for unloading. The cam slide structure shown utilizes a minimum of parts and does not require a plurality of levers and connecting links between the automatic choke mechanism and the throttle lever as has been used previously.

I claim:

A carburetor for an internal combustion engine, said carburetor comprising a body formed with an air and fuel mixture conduit adapted to be connected to the intake manifold of said engine, a throttle shaft journaled in aligned bearing apertures in said body and positioned transversely of said mixture conduit, a throttle valve fixed to said throttle shaft within said mixture conduit and rotatable from a position closing to a position fully opening said mixture conduit, a choke shaft journaled in aligned bearing apertures in said body and positioned transversely of said mixture conduit, a choke valve xed to said choke shaft within said mixture conduit and movable from a closed to an open position, a slide member having bifurcated upper and lower ends defining inner and outer tines and a longitudinal slot at each end of said slide member, the lower portion of the inner tine and the upper portion of the outer tine at the upper end of said slide member each being formed with a projecting lug portion, a stud member axed to said body between the choke shaft and the throttle means and laterally thereof, the upper slot of said slide receiving the choke shaft and the lower slot receiving said stud whereby said slide is positioned on said body for movement along a line transverse to said mixture conduit, said slide having a projecting lug portion on the lower end of the inner tine partially defining the lower slot adapted to be positioned in the apth of a portion of said throttle means, a plurality of inwardly facing steps on said lower inner tine above said lug portion adapted to be positioned in the path of a portion of said throttle means to prevent full closing of said throttle valve, said slide being biased in one direction toward an inoperative position, a pin extending transversely through said choke shaft with its ends projecting laterally each side thereof for engaging one lug portion of the bifurcated upper end of said slide for moving same into an operative position and thermal responsive means operatively connected to said choke shaft to move said pin into engagement with the lug portion of the other tine of the bifurcated upper end of said slide to move said slide into an operative position to prevent full closing of said throttle during relatively cold ambient temperature conditions, said thermal responsive means including a thermostatic coil having one end iixed to the body, said choke shaft and said pin connecting the other end of said coil to said slide to move said slide into said operative position.

References Cited in the le of this patent UNITED STATES PATENTS 2,010,206 Timion Aug. 6, 1935 2,124,777 Hunt et al July 26, 1938 2,160,411 Blattner et al. May 30, 1939 2,166,899 Blattner July 18, 1939 2,302,245 Mosely et al Nov. 17, 1942 2,302,527 Coffey Nov. 17, 1942 2,307,486 Carlson Jan. 5, 1943 2,518,794 Kittler et al Aug. 15, 1950 2,867,424 Sutton Jan. 6, 1959 2,943,848 Gordon et al July 5, 1960

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