US2979047A

US2979047A - Automatic choke for small carburetors

Info

Publication number: US2979047A
Application number: US670452A
Authority: US
Inventors: Eugene L Rapplean; Wenford E Highley; Martin E Fuchs
Original assignee: ACF Industries Inc
Current assignee: ACF Industries Inc
Priority date: 1957-07-08
Filing date: 1957-07-08
Publication date: 1961-04-11
Anticipated expiration: 1978-04-11

Description

April 11, 1961 E. L. RAPPLEAN ETAL AUTOMATIC CHOKE FOR SMALL CARBURETORS Filed July 8, 1957 Wan @IIIIA MARTIN 2 Sheets-Sheet 1 INVENTORS EUGENE L. RAPPLEAN WENFORD E.HIGHLEY E. FUCHS elland/ M ATTORNEY A ril 11, 1961 E. L. RAPPLEAN ETAL 2,979,047

AUTOMATIC CHOKE FOR SMALL CARBURETORS 2 Sheets-Sheet 2 Filed July 8, 1957 FlG.6

INVENTORS EUGENE L. RAPPLEAN WENFORD E. HIGHLEY MARTIN E. FUCHS u wf/mwd ATTORNEY re tates 2,979,047 AUTOMATIC CHOKE FOR SMALL CARBURETORS Filed July 8, 1957, Ser. No. 67%,452 6 Claims. (Cl. 123-119) This invention relates to carburetors of the type employed for supplying a fuel-air mixture to small two or four cycle internal combustion engines, and is more particularly, concerned with automatic choke contiol devices for small carburetors.

In the operation of small internal combustion engines, carburetor choke valves are usually provided with manual control means, whereby the choke valve may be closed to enrich the fuel mixture to facilitate starting of the engine. After starting of the engine, the choke valve is manually opened to lean out the fuel mixture. As engine driven devices are now commonly operated by those unskilled in carburetion, it is an object of the invention to provide an automatic choke control means particularly adapted for use in starting small engines.

Another object of the invention is to provide an automatic choke control device embodying a temperature responsive means and a suction responsive means coacting to regulate the position of the choke valve during startmg and running of an engine to provide the proper fuela1r mixture.

A further object of the invention is to provide an automatic choke control device adapted to prevent immediate complete closing of the choke valve when the engine is stopped to thus provide a leaner mixture for restarting of the engine when it is hot.

Another object of the invention resides in the provision of an automatic choke control device in which the operation of the suction responsive means is controlled by a thermostatically controlled air bleed valve.

Another object of the invention is to provide a device operable responsive to intake manifold suction for opening the choke valve, and means for dampening manifold pulsations to prevent fluttering of the choke valve.

Another object is to provide an automatic choke control which is relatively simple, inexpensive to manufacture, and reliable in use.

The invention embodies other novel features, details of construction, and arrangement of parts which are hereinafter set forth in the specification and claims, and illustrated in the accompanying drawings, wherein:

Fig. l is an elevation, partly in section, illustrating a carburetor choke control embodying features of the in-' vention, the choke valve being shown in its closed position for starting a cold engine.

Fig. 2 is an elevation, corresponding to Fig. 1, showing the choke valve in its slightly open position for restarting a heated engine. I

Fig. 3 is a fragmentary elevation showing parts of the control structure.

Fig. 4 is a sectional view showing a thermostatically controlled air bleed valve structure.

5, 6, and 7 are elevationsillustrating a modified form of the invention.

Referring now to the drawings for a better understanding of the invention and, more particularly, to Figs. 1 to 4, therein, the automatic choke control is shown as applied to a small carburetor comprising a body 6 having r 2,979,047 Patented Apr. 11, 1961 a mixture conduit 7 provided with an inlet 8, outlet 9, and a venturi 11. A choke valve 12 is disposed within the inlet 8 and fixed on a shaft 13 journaled at its ends in the body 6 in a manner to be opened by engine suction. A throttle valve 14 is disposed within the outlet 9 and fixed on a shaft journaled at its ends in the body 6.

The body 6 is formed with an annular recess 16 to receive the rim of a constant level fuel bowl 17 which is secured to a tubular boss 18 on the body by means of a screw 19. A float 21 is pivotally mounted within the bowl to actuate a conventional fuel inlet needle valve (not shown). A main fuel nozzle 22-is threaded into the tubular boss 18 and formed with a fuel metering orifice 23 to receive the tapered end of a hollow metering rod 24.

The metering rod 24 extends upwardly through the main fuel nozzle 22 and across the mixture conduit 7 for engagement at its end with an adjustment screw 26 threaded-into the body 6. A fuel passage 27 is provided in the boss 18 for the flow of fuel from the bowl upwardly through the orifice 23 and main fuel nozzle 22 into the mixture conduit 7. An air bleed passage 28 leads from the inlet 8 into the annular space 29 between the boss 18 and main fuel nozzle 22, the nozzle having air bleed apertures 31.

Fuel for idling operation of the engine passes intothe hollow metering rod 24 through apertures 32, and thence outwardly through openings 33 in the adjustment screw 26 into an idle passage 34 to an idle port 36 for discharge into the mixture conduit 7 adjacent the edge of the throttle valve 14 when the latter is disposed in idling position. Idle air bleed apertures 37 are provided in the metering rod 24.

In Figs. 1 and 2 in the drawings, the automatic choke control is shown as comprising a lever 38 fixed on the choke shaft 13 and provided with a slot 39 to receive an offset end 40 on the upper end of a link 42. An inturned lug 4-3 is formed on the lever 38 for engagement by one end of a bimetallic strip 41 which has its other end secured to the olfset end 40 of the link 42. If desired, the medial portion of the strip 41 may extend around the shaft 13.

The lower end of the link 42 is pivotally connected to the upper end of a rod 44 secured to and actuated by a diaphragm 46 of a suction motor 47. The marginal portion of the diaphragm is clamped between upper and

lower housing sections

48 and 49, respectively, by means of cap screws 51. The upper section of the motor 47 is secured to a bracket 52 by a nut 53, and the bracket is secured to the body 6 by cap screws 54. A compression spring 56 is seated on the lower housing section 49, within a suction chamber 57, to engage and yieldably resist downward movement of the diaphragm.

The lower housing section 49 is provided with an inlet nozzle 58 having an upwardly seating check valve 59 therein for the purpose of dampening pulsations of the diaphragm during operation of the engine, the check valve seat being scored to provide a slow leak of air past the valve into the suction chamber 57 when the engine stops operating to cause the spring 56 to close the choke valve.

A conduit 61 leads from the nozzle 58 to one end of a suction passage 62 in a thermostatically controlled air bleed device 63, the other end of the passage being connected to an engine intake manifold 64 by a conduit 66. The device 63 ismounted on an engine exhaust manifold 67 and provided with a bimetallic strip 68 pivotally mounted intermediate its ends on a pin 69. One end of the strip 68 engages an adjustment screw 71, and theother end of the strip is adapted to engage a valve member 72 to open a port in an air bleed passage 73 leading from atmosphere to the suction passage 62. A spring 74 is provided to yieldably resist opening movement of the valve member 72.

When the engine is not operating, the thermostat 41 will cool, rotating the choke lever 38 and valve 12 in a counter-clockwise direction toward closed position as far as permitted by the engagement of the end of slot 39 with the offset end 40 of link 42, which will be moved to its extreme position in one direction by spring 56 acting on plunger 44. Bleed valve72 will be held open by flexed thermostat 68, so that insufficient suction will be applied to diaphragm 46 during cranking to affect the choke position. When the engine starts direct action of air flow on the unbalanced choke, itself, will cause partial opening of the choke. As long as the valve 72 remains open, engine suction has no effect upon the position of diaphragm 46 and plunger 44, so that the choke valve 12 and lever 38 are limited to a movement corresponding to the axonate length of slot 39. The left end of slot 39 engaging the end of link 40 limits choke valve opening. 7

As the engine becomes heated, thermostat 68 will straighten, permitting closure of bleed valve 72, and, ultimately, the effect of increasing manifold suction applied to the diaphragm will cause corresponding movement of plunger 44 and rod 42 as spring 56 is compressed. Concurrently, choke thermostat 41 will expand to shift lever 38 and the choke valve relative to link 42, as in Fig. 2, but, of course, the valve cannot open faster than the end I 40 of rod 42 permits.

spring 76 are provided to move the choke valve 12 betweenits closed and partly open position, as illustrated in Figs. ,5 and 6, respectively. The torsion spring 76 is connected at one end thereof to the choke shaft 13 and at its other end to the body 6 to yieldably resist opening movement of the choke valve 12.

The thermostat 41a has its inner end connected to the choke shaft 13, and its outer end in abutting engagement with an adjustment screw 77 threaded through a boss 78 on the body 6. The thermostat 41a acts to prevent complete closing of the choke valve 12 upon stopping of a heated engine to provide a proper fuel-air mixture for restarting of the engine in a heated condition. When a cold engine is not operating, the opening force exerted by the torsion spring is overcome, and the thermostat holds the choke valve in closed position. This form of the invention is otherwise similar to the form heretofore shown and described.

Certain structures have been described herein which will fulfill all the objects of the present invention, but it is contemplated that other modifications will be obvious to those skilled in the art which come within the scope of the invention as defined by the appended claims.

We claim:

1. In a carburetion system for an internalcombustion engine, a choke valve, suction means including a diaphragm motor responsive to manifold suction for opening and closing said choke responsive to starting and stopping of the engine, heat responsive means interposed between said suction means and choke valve to resistfull closing movement of said choke valve upon stopping of the engine to providea leaner fuel mixture for restarting of the engine in a heated condition, and means for varying the suction applied to said motor responsive to variations in temperature of the engine.

2. In a carburetion system for an internal combustion 4 engine, a carburetor body having a. mixture conduit, a choke shaft journaled in said body, a choke valve fixed on said shaft, a lever fixed on said shaft, suction responsive means having a lost-motion connection with said lever tending to open and close said choke valve, and temperature responsive means interconnecting said lever and said suction responsive means for varying the position of said lever relative to said suction responsive means, whereby said choke valve is biased to a slightly open position to provide a leaner fuel mixture for restarting a heated englue.

3. In a carburetion system for an internal combustion engine, a carburetor body having a mixture conduit, a

choke shaft journaled in said body, a choke valve fixed on said shaft, a lever fixed on said shaft, suction responsive means having a lost-motion connection with said lever for opening and closing said choke valve, and temperature responsive means for varying the position of said lever relative to said suction responsive means, whereby said choke valve is held in slightly open position to provide a leaner fuel mixture for restarting a heated engine, said suction responsive means having a link slidably engaged in a slot in said lever whereby said choke valve is movable between closed and slightly open position responsive to movements of said temperature responsive means.

4. In a carburetion stystem for an internal combustion engine, a carburetor body having a mixture conduit, a choke shaft journaled in said body, a choke valve fixed on said shaft, a lever fixed on said shaft, suction responsive means having a lost-motion connection with said lever for opening and closing said choke valve, temperature responsive means for varying the position of said lever relative to said suction responsive means, whereby said choke valve is held in slightly open position to provide a leaner fuel mixture for restarting a heated engine, and means responsive to variations in temperature of the engine for varying the suction force applied to said suction responsive means.

5. In a carburetion system for an internal combustion engine, a carburetor body having a mixture conduit, a choke shaft journaled in said body, a choke valve fixed on said shaft, a lever fixed on said shaft, suction responsive means having a lost-motion connection with said lever for opening and closing said choke valve, temperature responsive means for varying the position of said lever relative to said suction responsive means, whereby said choke valve is held in slightly open position to provide a leaner fuel mixture for restarting a heated engine, and means including a thermostatically controlled air-bleed valve structure responsive to variations in temperature of the engine for varying thesuction force applied to said suction responsive means.

6. In a carburetion system for internal combustion engines, a choke valve, suction means to open said choke valve, spring means to close said choke valve, means responsive to variations in engine temperature for moving said choke valve between closed and slightly open positions, and other means responsive to variations in engine temperature for varying the force exerted by said suction means.

References Cited in the file of this patent UNITED STATES PATENTS 2,030,331 Smith Feb. 11, 1936 2,222,865 Chandler Nov. 26, 1940 2,309,419 Sisson Ian. 26, 1943 2,361,132 Smith Oct. 24, 1944 2,362,346 Blake Nov. 7, 1944 2,403,720 Hunt July 9, 1946 2,408,349 Stanton Sept. 24, 1946 2,421,733 Henning June 3, 1947