US2982275A - Carburetor control - Google Patents

Description

May 2, 196 D. T. DOMAN ETAL CARBURETOR CONTROL Filed Nov. 14. 195.7

2 Sheets-Sheet 1 3 ME/M May .2, 1963 Filed Nov. 14. 1957 D. 'r. DOMAN ETAL 2,982,275

CARBURETOR CONTROL 2 Sheets-Sheet 2 f W M CARBURETOR CONTROL David T. Doman, Ann Arbor, and William L. McNulty,

Tecumseh, Mich., assignors to Clinton Engines Corporation, a corporation of Michigan Filed Nov. 14, 1957, Ser. No. 696,514

Claims. or. 123-119 This invention relates to a carburetor for an internal combustion engine and more particularly to a control means for the choke valve and the throttle valve of such a carburetor.

The invention is particularly concerned with a carburetor for a small internal combustion engine which may be'either a two-stroke cycle or a four-stroke cycle engine, the carburetor having a choke valve and a throttle valve controlled by a speed responsive governor during normal running of the engine. The control mechanism of this invention in general comprises a single manually operable control lever which is operable for positioning the choke and throttle valves in accordance with the desired operating conditions of the engine. The single control lever, in conjunction with the governor which controls the throttle valve during normal engine operation, is operable to position the choke valve and the throttle valve in the correct positions thereof for starting, normal running and idling of the engine, and is also operable for stopping the engine.

A principal object of the invention is to provide a new and improved carburetor control.

A further object of the invention is to provide a carburetor having a single manually operable control means for controlling engine operation. Another object of the invention is to provide a carburetor having a choke valve and a throttle valve and a single manually operable control device for positioning the choke valve and the throttle valve in accordance with the desired operating condition of the engine.

A further object of the invention is to provide a carburetor control device adapted selectively to condition the carburetor choke and throttle valves for engine starting, normal running, idling and stopping.

Other and further objects of the invention will be apparent from the following description and claims and may be understood by reference to the accompanying drawings, of which there are two sheets, which by'way of illustration show a preferred embodiment of the invention and what we now consider to be the best mode in which we have contemplated applying the principles of our invention. Other embodiments of the invention may be used without departing from the scope of the present invention as set forth in the appended claims.

In. the drawings: Fig. 1 is a vertical sectional view through a carburetor embodying the present invention;

Fig. 2 is a top plan view of the carburetor shown in Fig. 1; v

Fig. 3 is an enlarged fragmentary sectional view taken on line 3-3 of Fig. 1; I Fig. 4 is an enlarged fragmentary sectional view taken on line 4-4 of Fig. 1; Fig. 5 is a sectional view taken on line 5-5 of Fig.1;- Fig. 6 is a view similar to Fig. 2 showing the control lever in the starting position; Fig. 7 is an enlarged sectional view similar to Fig. 4 .with the controllever in the starting position;

2,982,275 Patented May 2, 1961 Figs. 8 and 9 are views similar to Figs. 6 and 7, respectively, but showing the control lever in the idle position; and I Figs. 10 and 11 are views similar spectively, showing the control lever in the position for stopping the engine.

The carburetor comprises a carburetor bodycasting 10 provided with an air passage having an inlet end 12 leading from a suitable air cleaner and an outlet 14 leading to a suitable intake manifold in the case of a four-cycle engine, or to the engine crankcase if the car "buretor is used on a two-cycle engine.

The carburetor includes a choke valve 16 located within the inlet end 12 of the passage through the carburetor and secured on a choke shaft 18 journaled at its opposite ends in the carburetor body 10. The air passage includes a venturi portion 20 and a throttle valve 22 is disposed in the outlet end of the air passage'downstream from the choke valve 16 and the venturi 20. The throttle valve 22 is secured on a throttle shaft 24 rotatably supported at its opposite ends in the carburetor body 10. The carburetor furtherincludes a fuel bowl 26 adapted to be supplied with fuel from the fuel tank in a conventional manner through a suitable valve (not shown) controlled by a float 28. The fuel bowl 26 is supported on the underside of the carburetor body casting 10, which includes an annular peripheral flange 30 surrounding a depending sleeve portion 32 enclosed by the fuel bowl 26. The casting portion 32 is provided with a vertically extending bore 40 receiving a fuel nozzle 34 having a fuel passage 36 andan enlarged shoulder 38 at its lower end which may be threaded into the lower end of the bore 46. The fuel bowl is secured to the carburetor casting by a threaded plug 42, which extends through an aperture in the bottom wall of the fuel bowl and is threaded into vthe lower end of the bore 40, and a nut 44 threaded onto the plug 42 and tightened up against a washer 50 engaging the underside of the bowl 26. As shown in Fig. 5, a passage 52 leads from the fuel bowl 26 to the central bore 40 to supply fuel to the passage 36 in the fuel nozzle 34. A needle valve 54 is threaded into the plug 42 and has a tapered upper end extending into the lower end of the fuel passage 36. The lower end of the needle valve 54 is provided with a knurled head 56 by means of which the valve may be adjusted for regulating the fuel flow into the fuel passage 36. The fuel nozzle 34 opens into the carburetor air passage in the vicinity of the venturi 20 therein and provides the main fuel system of the carburetor. When the choke and throttle valves 16 and 22 are open with the engine running at its governed speed, the air flow past the nozzle 34 will draw fuel from the fuel bowl 26 past the valve 54 and through the fuel passage 36 into the venturi 20 where the fuel will be mixed with the air to form a combustible mixture to be supplied to the engine. An air passage 58 having its entrance facing the air drawn through the carburetor air passage opens into the bore 40 in the body casting 10 and the fuel nozzle 34 is provided with a series of small openings 60 for providing an air bleed into the fuel passage 36 as is conventional in carburetors of this type.

The idle fuel system of the carburetor is illustrated in part in Hg. 5 and comprises an idle fuel passage 62 communicating at one end with the lower end of the main fuel passage 36 and terminating at its upper end in a chamber 64 closed by a plug 65 and which is intersected by a passage 66 formed through a rib 67 on casting 10. The passage 66 has its inlet exposed to the air entering the carburetor air passage and its outlet terminating in two or more idle fuel outlets disposed on either side of the throttle valve 22 when the latter is in its closed posito Figs. 6 and 7, re-

tion. When the throttle valve 22 is closed, the engine vacuum will be transmitted through the passage 66 to draw fuel .upwardly.through the idle fuel passage 62 into the chamber 64 where such fuel will be mixed with a small amount of alr'entering the'chamber 64 in the manner described to provide an idle fuel. mixture for the engine. Carburetors of the general type thus far described are well known in the art and no further description of the details of the fuel supply systems thereof are believed necessary for purposes of this invention.

The present invention is particularly directed to a manual control means for the choke valve 16 and for the throttle valve 22 to obtain positioning of such valves in accordance with the engine operating condition that is required. The control mechanism comprises a mounting post 70 having an enlarged shoulder 72 at its lower end secured within 'a counterbore in the body casting 10. The post 70 is hollow and receives the upper end of the choke shaft 18. The post 70 is fixed against rotation on the casting 10 and a spring 74 has one end received within a slot 76 formed in the upper end of the choke shaft '18. The spring '74 surrounds the reduced upper end of the shaft 18 and has its other end 78 engaging within an elongated slot 80 formed in the post 70. The spring 74 reacts between the post 70 and the choke shaft 18 so as to urge the choke valve 16 toward its open position.

A support plate 82 is seated against the upper surface of the body casting 10 and is provided with oppositely disposed arms S4 which may be crimped over the boss 85 on casting 10, as shown in Fig 3, to secure the plate 82 on the casting It The plate 82 is provided with an opening through which the mounting post 7 extends. A control lever 86 is rotatably journaled on the mounting post 70 above the -support plate 82 and is retained on the post 70 by a split washer 88 received within a groove in the post 70. A suitable cap 90 is fitted over the upper end of the mounting post 70 to seal the interior of the post and the upper end of the choke shaft 18 from the ture in the support plate 82 and is urged upwardly against "the underside of lever 86 by a spring 93. The plunger 92 is adapted to engage any one of four recesses or detents 94, 95, 96 and 97 formed on the underside of the fc'ontrol lever 86 and disposed equidistant from the axis of the choke shaft 18. The spring-pressed plunger and the four recesses together provide a detent means which determines the start, normal running, idle and cutoff positions of the control lever 86.

The upper end of the throttle shaft 24 projects above the body casting and has secured thereon a throttle actuating lever 100 having a depending arm 102 engageable with'a throttle stop screw 104 which is threaded into a vertically extending longitudinal rib 106 formed integrally with the casting It). A spring 108 maintains the screw 104 in its adjusted position and the screw may be adjusted to determine the closed .or idle pos.tion of the throttle valve 22.

A governor actuated link 110 has one end pivotally connected to the throttle lever 164) and, as illustrated schematically in Fig. 2, the other end 112 of the governor link 110 is pivotally connected to an arm 114 secured to an air'vane 116 pivoted on a pin 118 supported at a suitable place on the engine. A spring 120 urges the vane 116 and the governor link 110 in a throttle opening di- 'from the fan is indicated by the arrow 122 so that as the engine speed increases the vane 116 will pivot in a clockwise direction against the force of spring 128 to actuate the governor link 11 0 in a direction to rotate the throttle 'lever 100 and the throttle valve 22 'connec'ted'thereto' toward the closed position of the throttle. When the engine speed decreases, the spring 120 will actuate the governor link 110 in a direction to open the throttle valve 22,. It will be apparent that the air vane 116 illustrated schematically in Fig. 2 is merely representative of one type of engine speed responsive governor that may be employed for controlling the throttle valve 22 and that other types of governors may be employed within the scope of this invent on. It is also contemplated that the governor may be provided with an adjustment for regulating the governed speed of the engine.

The control lever 86 is provided with a stop arm 124 engageable with the rib 106 to limit pivoting of the lever in one direction and a second stop arm 126 engageable with the rib 106 to limit pivoting of the lever 86 in the other direction. Between the arms 124 and 126 the lever 86 is provided with a rounded end 128 for rotating the throttle lever 100 and the thottle valve 22 'to the idle position thereof. 'A thin resilient or springlike sheet metal plate 130 is secured on the upper end of the throttle shaft 24 and includes a depending arm 132 adapted to be engaged by the rounded end 128 of the control lever 86 when the latter is moved to the idle position.

The control lever 86 and the choke and throttle valves 16 and 22 are illustrated in Figs. 1 to 4 in the position that they occupy during normal engine operation. The cold starting position of the control device is illustrated in Figs. 6 and 7 in which the control lever 86 is rotated in a counterclockwise direction to the position determined by the detent'94. In this position the throttle valve 22 will be full open and the choke valve 16 will be closed so that the full vacuum developed as the engine is turned over by the starting mechanism will be applied to the fuel outlets in the mixture passage to provide fuel for starting the engine. As shown in Fig. 7, the lever 86 has an arcuate slot 134 into which projects a pin 136 which is secured to and projects laterally from the upper end of the choke shaft 18. The pin 136 projects from the upper end of the choke shaft through the slot in the mounting post 70 and into the arcuate slot 134 in the control lever 86. When the lever 86 is swung to the starting position thereof indicated in Fig. 7, the left-hand edge of the slot 134 engages the pin 136 to rotate the same and the choke valve 16 in a counterclockwise direction to the closed position of the choke valve. The control lever 86 does not engage the throttle lever at this time and the throttle position is determined solely 'by the governor mechanism which, when the engine speed is below a predetermined speed, holds the throttle valve in its full open position, as shown in Fig. 6.

After the engine is started the control lever may be swung in a clockwise direction to the run position illustrated in Figs. 2 and 4, or to the idle position of Figs. 8 and 9. In the run position of the control lever, which is determined by detent 95, the pin 136 follows and re mains in engagement with the left-hand end of the slot 134 in the lever 86 since the spring 74 urges the choke shaft 18 in a'clockwise direction. As shown in Fig. 3, the slot 80 in the post 70 has a lateral extension 138 at at its lower end into which the pin 136 moves as the choke shaft is rotated to the open position of the choke valve. When the lever. 86 is in the run position shown in Fig. 2, the throttle lever 100 is not yet engaged by the end 128 of the lever 86 and the throttle valve 22 will at such time be under control of the governor mechanism described.

When the control lever is rotated further in a clockwise direction to engage the detent 96 with the plunger 92, the choke and throttle valves will be positioned for idle engine operation. This position of the control lever is illustrated in Figs. 8 and 9 from which it will be seen that the pin 136 and the choke shaft 18 are prevented from further rotation by the engagement of the pin with the end of the slot extension 138 in the post 70. In the idle position of the lever'the'end 128 thereof engages "the spring arm 132 secured on the throttle lever 100 to rotate the throttle valve 22 to its closed or idle position against the force of the governor spring. Fuel is then supplied through the idle fuel passage 66 to the idle fuel outlet into the mixture passage, which outlet is controlled by the usual idle adjusting screw 140. I

The control lever 86 may be rotated to a fourth position illustrated in Figs. and 11 for stopping the engine, and this position of the lever is determined by the detent 97. The choke valve 16 remains in its open position when the lever 86 is swung to the cut-off position since the pin 166 is still in engagement with the slot extension 138 as shown in Fig. 11. The end 123 of the lever 86 continues to engage the spring arm 132 to hold the throttle valve 22 in its closed position. The engine is killed by the engagement of control lever 86 with a shorting clip 142 which is secured on a lateral extension 144 of the support plate 82. The shorting clip 142 is electrically connected to a wire 146 connected into the primary winding of the magneto of the engine ignition system for grounding the same when the clip is engaged by the control lever 86.

In the event that the engine is still hot when it is to be restarted, it may be that, if restarting is attempted with the choke in the closed position, too much fuel will be supplied to the engine and therefore the engine may be started when hot by positioning the control lever 86 in the run position shown in Figs. 2 and 4. The control means described herein is particularly suited for use with an internal combustion engine of the relatively low horsepower single cylinder type commonly employed on power lawn mowers and otherdevices. The control means permits the engine to be operated under the control of a suitable governor during normal running of 'the engine and at the same time provides a means for positively and accurately positioning the choke valve and throttle valve of the carburetor in the correct positions thereof for starting the engine and for idling engine operation and for shutting off the engine. The above operations are obtained with the use of only a single manually operable control lever which may be associated with a suitably marked control panel to indicate the various positions to which the control lever may be moved according to the engine operation that is desired.

While we have illustrated and described a preferred embodiment of our invention, it is understood that this is capable of modification, and we therefore do not wish to be limited to the precise details set forth but desire to avail ourselves of such changes and alterations as fall within the purview of the following claims.

We claim:

1. In a carburetor having a body defining an air passage, a choke valve and a throttle valve journaled in said body and disposed in said passage; a control for said choke and throttle valves comprising a spring for biasing said choke valve toward its open position, a manually operable control lever rotatably mounted on said carburetor body, detent means cooperable with said lever for determining a plurality of operable positions thereof, said choke valve having a pin rotatable therewith, said lever having an arcuate slot into which said pin projects and one end of which slot is engageable with said pin to rotate said choke valve to its closed position against the force of said spring when said lever is rotated into one of its said positions, stop means against which said choke valve is opened by its spring when said lever is moved to a second position thereof, said throttle valve having an arm thereon, said lever being engageable with said arm for rotating said throttle valve to its closed position when said lever is rotated to a third position thereof, said slot in said lever permitting movement of said lever to said third position without corresponding movement of said choke valve.

2. A carburetor according to claim 1 wherein said arm on said throttle valve comprises a spring member.

3. In an internal combustion engine carburetor having a body defining an air passage, a choke valve and a throttle valve journaled in said body and disposed in said passage, and a shaft on which said choke valve is secured; a control for said choke and throttle valves comprising a hollow post secured on said carburetor body and into which one end of said choke shaft projects, a spring reacting between said choke shaft and said post for biasing said choke valve toward its open position, said post having a slot therein, a pin projecting from said choke shaft through said slot and engageable with one end of said slot to limit opening movement of said choke valve, a manually operable control lever rotatably mounted on said post, detent means cooperable with said lever for determining a plurality of operable positions thereof, said lever having an arcuate slot therein one end of which is engageable with said pin to rotate said choke valve to its closed position against the force of said spring when said lever is rotated into one of its said positions, said choke valve being opened by its spring when said lever is moved to a second position thereof, in which position said pin engages said one end of the slot in said post to determine the open position of said choke valve, said lever being engageable with said throttle valve for rotating the latter to its closed position when said lever is rotated to a third position thereof, said slot in said lever permitting movement of said lever to said third position without corresponding movement of said choke valve.

4. In a carburetor according to claim 3 wherein the engine is provided with an ignition system; a means for shorting the ignition system mounted on said carburetor body and engageable by said lever for stopping the engine in a fourth position of said lever.

5. A carburetor according to claim 4 including a resilient, deflectable member connected to said throttle valve and which is engaged by said lever to close said throttle valve, and wherein said lever continues to engage said resilient member to hold said throttle valve closed when said lever is moved into engagement with said ignition shorting means.

Thrasher June 17, 1930 Richardson Feb. 17, 1959

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