US2837070A

US2837070A - Choke control system for carburetors

Info

Publication number: US2837070A
Application number: US602118A
Authority: US
Inventors: Kenneth C Agar
Original assignee: CLINTON MACHINE Co
Current assignee: CLINTON MACHINE Co
Priority date: 1956-08-06
Filing date: 1956-08-06
Publication date: 1958-06-03
Anticipated expiration: 1975-06-03

Description

June 3, 1958 I K, AGAR 2,837,070

CHOKE CONTROL SYSTEM FOR CARBURETORS Filed Aug. 6, 1956 S'Sheets-Sheet l HVVENTUR. 677722 2 6'. #{47' June 3, 1958 K. c. AGAR 2,837,070

CHOKE CONTROL SYSTEM FOR CARBURETORS 5 Sheets-Sheet 2 Filed Aug. 6, 1956 3 INVENTOR.

June 3, 1958 K. c. AGAR CHOKE CONTROL .SYSTEM FOR CARBURETORS 3 Sheets-Sheet 3 Filed Aug. 6, 1956 INVENTOR.

United States Patent CHOKE CONTROL SYSTEM non CARBURETORS This invention relates to a carburetor for an internal combustion engine and has particular reference to an lmproved automatic choke control system for a carburetor.

The carburetor control system of this invention is particularly suitable for use on small single-cylinder engines, although the invention is not limited to use on such engines. Internal combustion engines have many applications wherein it is necessary or desirable to control the throttle by means of a speed-responsive governor driven by the engine. The present invention contemplates a carburetor of this type in which the governor which controls the throttle is also employed for automatically controlling the choke valve in accordance with engine speed and in accordance with engine and ambient temperatures so as to insure easy starting of the engine within a wide range of ambient air temperatures and to properly position the choke valve under the varying conditions of engine operation commonly encountered when the engine is in use.

A principal object of the invention is to provide a new and improved carburetor for an internal combustion engine and more particularly to provide a new and improved choke control system for such a carburetor.

Another object of the invention is to provide an automatic choke control system for a carburetor which is simple in construction and efiicient in operation.

A further object of the invention is to provide a choke control system which automatically operates the choke valve in accordance with the operating condition and temperature of the engine and in accordance with ambient temperatures.

Another object of the invention is to provide a carburetor having a throttle valve and a choke valve and a governor driven from the engine for automatically controlling the position of the throttle and choke valves in accordance with the requirements of the engine.

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 three sheets, which by way of illustration show preferred embodiments of the invention and what I now consider to be the best mode in which I have contemplated applying the principles of my 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 an elevational ing the present invention;

Fig. 2 is a side elevational view of the carburetor shown in Fig. 1 with parts broken away;

Fig. 3 is an enlarged fragmentary elevational view of a part of the choke control mechanism employed in the carburetor;

Fig. 4 is an elevational view partly in section of one type of governor which may be employed in the present invention;

Fig. 5 is a fragmentary elevational view partly in secview of a carburetor embody- 50 being shown in Fig. 4. Each weight 50 2,837,070 Patented June 3, 1958 tion similar to Fig. 1 but showing the parts in the positions they assume during normal running of the engine; and

Fig. 6 illustrates a modified form of the invention.

Referring more particularly to the drawings, in Figs. 1 and 2 there is illustrated a portion of an engine crankcase 10 and a portion of the engine cylinder 12 andthe carburetor 14- embodying the present invention. The invention is illustrated as applied to a single cylinder internal combustion engine having an intake manifold 16 through which a mixture of air and fuel is supplied to the cylinder 12. The body 18 of the carburetor may be more or less of conventional construction and, in the form of the invention illustrated in the drawings, the carburetor is of the updraft type. The carburetor includes an air passageway 20 having an inlet end 22, a Venturi portion 24 and leading at its upper end to the intake manifold 16 which is secured to the cylinder 12 by bolts 26. The carburetor further includes a choke valve 28 within the inlet portion of the air passageway 20 and a throttle valve 30 downstream from the choke valve 28. The fuel supply system of the carburetor may be of conventional design and is therefore not illustrated herein.

A governor is employed for controlling the throttle 30 to regulate the speed of the engine andone type of governor which may be employed is illustrated in Fig. 4 as comprising a centrifugally actuated or fiy-ball type governor driven from the engine. While it is believed that a fly-ball type governor has certain advantages over other type governors in the present invention and is therefore the preferred form of governor, it will be apparent that other type governors might be employed within the scope of the invention. The governor illustrated in Fig. 4 comprises a gear 32 having a hub 34 journaled on a stub shaft 36 suitably supported in one wall of the engine crankcase. The gear 32 may be driven from the engine in any suitable manner such as from the cam gear commonly employed in engines of this type and, in such event, the governor mechanism would be suitably located within the crankcase of the engine. However,

' it will be apparent that the governor might be of a different type or might be located exteriorally of the engine crankcase and driven through a suitable power take-off arrangement from the engine. In the governor illustrated herein, a tubular sleeve 38 is slidably mounted on hub 34 of gear 32 and is provided with a radially extending plate 40 on one end thereof and a similar plate 42 on its other end. The sleeve 38 and the end plates 40 and 42 carried thereby are slidable axially along the hub 34 but are driven with the gear 32 by means of a drive pin 44 having one end 46 secured in an aperture in the gear 32 and its other end received within a slot 48 formed in plate 40. A series of centrifugally respon: sive weights is carried by the gear 32, one of the weights is pivotally mounted on a pin 52 supported by a lug 54 projecting from one face of gear 32. The weight 50 has one arm 56 reacting against the inner surface of plate 40 and the other arm 58 constitutes a relatively heavy mass which effects pivoting of the weight 50 on pin 52 in response to centrifugal force developed by rotation of gear mined by the speed of the engine. A lever 68 is rigidly' secured on governor shaft 64 exteriorly of the engine crankcase and a second lever 70 is loosely journaled on governor shaft 64. The lever 70, which'is'rotatablyjournaled on governor shaft 64, is provided with one or more apertures 72 by means of which one end of a governor spring '74 may be connected to lever 70. The other end of the governor spring 74 is connected to a lever 76 by a selected one of a series of apertures 78. The lever 76 is pivotallymounted on the exterior wall of the crankcase by a bolt 80 and, when the angular position of arm'76 is properly adjusted in a manner to be described, the spring 74 will exert a force on lever 7 0, tending to rotate the same in a counterclockwise direction intothe position shown in Fig. 1, which is the condition of the control linkages when the engine is not operating.

Lever 68 has a projection 82 to which one end of a spring 84 is connected, the other end of spring 84 being connected to the other end 86 of lever .70. The spring 84 reacting between

levers

68 and 70 tends to rotate lever 68 in a counterclockwise direction and, when the engine is not operating, holds the lever 68 in the position shown in Fig. l in which a stop 88 on lever 68 engages the underside 90 of lever 70. Lever 68 may be secured on shaft 64 in the proper angular position by means of a bolt 92 passing through the split-end portion of the lever 68 which is then rigidly clamped on shaft 64 by a nut 94 threaded onto the end of bolt 92.

The throttle valve 30 comprises the usual throttle blade mounted on a throttle shaft 96 which extends across the air passageway 20 formed in the carburetor body 18, the ends of throttle shaft 96 projecting outwardly from the carburetor body, as illustrated in Fig. 2. A throttle lever 98 is'secured on one of the projecting ends of throttle shaft 96 so that rotation of throttle lever 98 will rotate shaft 96 and the throttle blade 30 secured thereon. A throttle link 100 in the form of a rod is connected at its upper end to the end of throttle lever 98 and the lower end of rod 100 is connected to the free end of lever 68.

The governor is shown in its non-operating condition in Fig. 4, and it will be seen that when the engine is running the weights 50 will swing outwardly by centrifugal force to shift the sleeve 38 along hub 34 against crank lever 62, which will swing in a clockwise direction to rotate governor shaft 64 in a clockwise direction, thereby swinging lever 68 clockwise to pull rod 100 downwardly and rotate throttle lever 98 and the throttle shaft 96 and throttle blade 30 in a clockwise direction. Suitable springs may be employed for resisting movement of governor weights 50 outwardly in response to centrifugal force and for holding the weights in their retracted position when the engine is not operating. It will be seen from Fig. 1 that the throttle valve 30 is in a normally open position when the engine is not operating and this normally open position may be about beyond the full open position in which the throttle blade would lie in the plane of the axis of the upper end of the air passageway 20. The throttle blade 30 is rotated in a clockwise direction to effect throttling action.

The first few degrees of rotation of lever 68 in a clockwise direction from the position illustrated in Fig. 1 will not aflect the position of lever 70, which is retained in the position shown in Fig. 1 by means of governor spring 74. However, an adjusting screw 102 is threadedly supported on lever 68 and, as lever 68 is rotated by the'governor, the lower end 104 of the screw will engage the bottom wall 90 of lever 70 so that thereafter the

levers

68 and 70 will rotate together against the force of governor spring 74 as the engine speeds up. The initial movement of lever 63 from the Fig. 1 position, that is, until the end of screw 102 engages lever 70, is resisted only by spring 84, which is substantially weaker than governor spring 74.

The choke valve 28 is secured on a choke shaft 106 which extends across the air passageway 20 and is journaled in the carburetor body. As shown in Fig. 3, the

choke shaft 106 is provided with a slot 108, receiving one 'end 110 of a spring 112 which has one or more turns around the projecting end of shaft 106 and has its other end 114 reacting against a stop pin 116 formed on the carburetor body. The spring 112 tends to rotate the choke shaft 106 and the choke blade 28 in a clockwise direction or toward the open position of the choke. The pin 116 also provides a stop limiting opening movement of the choke valve, the full open position thereof being illustrated in Fig. 3. A temperature responsive element such as a bimetal element 120 has one end secured to choke shaft 106 and the bimetal element is then coiled around the choke shaft and at its other end carries a clip 122 having a pin 1 24 projecting laterally therefrom and having an enlarged shoulder 126 at its outer end. A link 128 has its upper end secured to an arm 130 secured on the other projecting end 132 of throttle shaft 96. Thearm 130 may be rigidly secured on throttle shaft 96 by a bolt 134 passing through they split end of the arm 130. The other end of link 128 is formed into a loop portion 136 within which the pin 124 is freely slidable. When the parts are in the position illustrated in Fig. l, lever is held in the position shown by governor spring 74 and lever "68 is urged into engagement with lever 70 by spring 84, thereby holding rod in its elevated position to position the throttle valve 30 in its normally open position. Arm 130 turns with the throttle valve 30 and shifts link 128 into a position in which the pin 124 is engaged by the upper end of the loop portion 136 and held thereby in the position shown in Fig. 1. The bimetal element 12.0; wh'ichis responsive to ambient temperatures and possibly to some extent to the radiant heat from the engine, tends to unwind upon a decrease in temperature and, since the end of the bimetal element carrying pin 124 is fixed by the engagement between pin 124 and link 128', the bimetal will then tend to rotate the choke valve in a counterclockwise direction or towards its closed position upon a decrease in temperature. The bimetal 120 acts in a direction opposite to the force of the spring 112, but the bimetal 120 is, of course, considerably stronger than the spring and will rotate the choke valve to a closed position determined by the ambient air temperature. The choke valve as shown in Fig. 1 occupies a closed position which might correspond to approximately 75 F., in which position the choke valve does not completely close thepassageway 20. At lower ambient temperatures the bimetal will turn the choke shaft and the choke valve 28 in a counterclockwise direction to a more fully closed position so that rapid and efiicient starting of the engine may be had within a very wide range of ambient air temperatures.

As soon as the engine is started, the governor will begin to rotate the governor shaft 64 and the lever 68 carried thereby in a clockwise direction against the force of spring '84, which is a relatively light spring. The lever 68 alone will rotate and thereby turn the throttle valve toward its throttling position. This action will cause link 128 to be retracted from the pin 124 carried by one end of the bimetal 120 so as to lessen the choke-closing force exerted by the bimetal and thereby permit spring 112 to move the choke valve 28 towards its open position. Choking of the engine normally should occur only from starting of the engine up to a certain predetermined engine speed, and when-the engine attains such predetermined speed, the choke should be opened and throttle action of the throttle valve under control of v the governor then takes over to regulate operation of the engine. It will be seen that the present control system regulates the choking action of the choke valve 28 from the governor which is responsive to engine speed. In order to enable the choke valve to properly perform its choking function during starting of the engine and operation of the engine up to the predetermined engine speed at which throttling action should begin, the throttle valve 30 is mounted on the throttle shaft 96 at anangular position such that the throttle may move through approximately 20 without in any way restricting the areaof the air passageway 20 or, in other words, without performing any throttling function. After the throttle valve has moved to approximately 20 from its normally open position, continued movement will effect the throttling action required during operation of the engine. During this initial 20 of movement of the throttle valve only the choke valve 28 is performing any choking or throttling function and after the engine attains a predetermined minimum speed, for example, 1000 R. P. M., the choke will be fully open and the throttle valve will take over the throttling action under the control of the governor.

The adjustment of screw 102 controls the point at which levers 68 and 70' begin to move together, and this adjustment is such that this engagement between

thelevers

68 and 70 is at the end of the initial approximately 20 of travel of the throttle valve. It is to be noted that the initial movement of lever 68 and throttle valve 30 is restrained only by spring 84 and that, after such initial movement has taken place and the choke is fully opened, further movement of

levers

68 and 70 is resisted by the governor spring 74 which is calibrated so as to obtain in conjunction with the governor the predetermined running speed of the engine which will normally be considerably higher than the previously mentioned minimum engine speed of 1000 R. P. M. at Which throttling action begins to'take place.

Under certain operating conditions such as extreme cold, the choking period may prove insufficient to obtain a proper fuel mixture and in such event the engine will slow down after the choke has been opened and slowing down of the engine will cause the throttle valve to move toward its open position and thereby re-engage link 128 with pin 124 to move the choke valve towards closed I position through the bimetal element 120 which connects the choke valve with the link 128. The choking action thus obtained will enrich the fuel mixture and consequent speeding up of the engine will again permit the choke to open in the manner previously described. The choking action will take place automatically and may be repeated a number of times until the proper fuel requirements of the engine are met.

The choke control arrangement described may be adjusted to suit various operating conditionsrwhich will be encountered in use of the engine. The force exerted by the governor spring 74 and by the spring 84 controls the throttling action and, as shown, the force exerted by spring 84 may be varied by connecting one end thereof to either of a series of notches 140 formed in the end 86 of lever 68. In a similar manner the spring 74 may be connected to lever 70 by means of either of the apertures-72 to obtain the pro er spring tension and the other end of spring 74 may be connected to a selected'one of the apertures 78 in the arm 76. As previously mentioned, the arm '76 is pivotally mounted on bolt 80 and provides a means for adjusting the forceexerted by spring 74 and consequently a means for adjusting the throttle. A rod 142 has its lower end secured within a suitable aperture 144 in the end of arm 76 and a suitable means not illustrated herein may be employed for raising or lowering the rod 142 to increase or decrease the tension on spring 74 to obtain the proper throttle adjustment or to adjust the governed speed of the engine.

It may be desirable in some applications to prevent the choke from returning to its closed position when the engine is running down afterbeing stopped, thereby preventing choking action and consequent enriching of the fuel mixture. In Fig. 6 there is illustrated a mechanism suitable for accomplishing this result and, as showntherein, the throttle lever 198 which corresponds to the throttle lever 98 described in connection with Figs. 1 to has one end connected to therod 100 and is provided at itsother end with a pin 200 received within a 'slot 202 formed on one end of a link 204. The other end of link 204 is secured to an arm 206 having a shaft 208 projecting therefrom and to which is secured one end of a temperature-responsive device such as a bimetal element 210. The other end of the bimetal element 210 reacts against a pin 212 and the bimetal 210 may be positioned at a hot spot on the engine such as the exhaust port bossor the cylinder head. When the engine is hot, the bimetal 210' rotates arm 206 in a counterclockwise direction to cause link'204 to engage pin 200 and hold throttle lever 198 in the position shown in which the throttle valve 30 is in a fully open position but is about 20 fromits normal open position previously described. The bimetal element 210 reacts against the force of spring 84 and holds the throttle valve 30 in the position shown which in. turn prevents link 128 from reacting against the bimetal element in a choke-closing direction. The choke spring 112 will retain the choke in its open position while the engine is running down so as to prevent a choking action from taking place at such time. As soon as the engine cools sufficiently, the bimetal 210 will shift link 204 in a direction to permit throttle lever 198 and the throttle valve 30 to return to their normal open positions. This modification is otherwise the same as in Figs. 1 to 5 and may be desirable in certain applications in which the engine is driving a load having a large amount of inertia and in which the momentum of the load may turn the engine over many times before the engine can be brought to a complete stop.

The normal open position of the throttle may be determined by suitably locating a stop pin 148 which is engaged by lever 70 to prevent further rotation of the

levers

68 and 70 under the influence of spring 74.

While I have illustrated and described preferred embodiments of my invention, it is understood that these are capable of modification, and I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes and alterations as fall within the purview of the following claims.

I claim: s

1. In a carburetor for an internal combustion engine having an air passageway, a choke valve in said passageway and a throttle valve in said passageway downstream from said choke valve, means urging said throttle valve toward open position, a speed responsive governor driven by said engine and operably connected to said throttle valve and said choke valve, said governor being operable for positioning said, throttle valve in accordance with the speed of the engine and for holding said choke valve in a less than full open position when the engine speed is below a predetermined speed, temperature responsive means in the connection between said governor and said choke valve for varying the closed position of said choke valve in accordance with ambient temperatures, and means for opening said choke valve as said throttle valve is moved from its said open position by said governor during operation of said englue.

2. In a carburetor for an internal combustion engine having an air passageway, a choke valve in said pas-' sageway and a throttle valve in said passageway downstream from said choke valve, means urging said throttle valve toward open position, a speed responsive governor driven by said engine and operably connected to said throttle valve and said choke valve, said governor being operable for positioning said throttle valve in accordance with the speed of the engine and for holding said choke valve in a less than full open position when the engine speed is below a predetermined speed, temperature responsive means in the connection between said governor and said choke valve for varying the asszovo closed position of said choke valve in accordance with ambient temperatures, said throttle valve being movable through an initial distance by said governor and until said predetermined engine speed is attained without efiecting a throttling action, and means for opening said choke valve as said throttle valve is moved from its said open position by said governor during operation of said engine.

3. Ina carburetor for an internal combustion engine having an air passageway, a choke valve in said passageway and a throttle valve in said passageway downstream from said choke valve, means urging said throttle valve toward open position, a governor driven by said engine and operably connected to said throttle valve and said choke valve, said governor being operable for positioning said throttle valve in accordance with the speed of the engine and for holding said choke valve in a less than full open position when the engine speed is below a predetermined speed, temperature =responsive means for varying the closed position of said choke valve in accordance with ambient temperatures, and means biasing said choke valve toward full open position as said throttle valve is moved from its said open position by said governor during operation of said engine.

4. In a carburetor for an internal combustion engine having an air passageway, a choke valve in said passageway and a throttle valve in said passageway downstream from said choke valve, means urging said throttle valve toward open position, a speed responsive:governordriven by said engine and operably connected to said throttle valve and said choke valve, said governor beingoperable for positioning said throttle valve in accordance with .the speed of the engine and for holding said choke valve in a less than full open position when the engine speed is below a predetermined speed, temperature responsive means for varying the closed position of said choke valve in accordance with ambient temperatures, and means for opening said choke valve as the engine attains said predetermined speed.

5. A carburetor according to claim 4 including temperature responsive means responsive to the temperature of the engine for preventing closing of said choke valve when the engine is hot and stops running.

6. In a carburetor for an internal combustion engine having an air passageway, a choke valve in said passageway and a throttle valve in said passageway downstream from said choke valve, acentrifugally actuated governor driven by the engine for positioning said throttle valve in accordance with the speed of the engine, means connecting said throttle valve and said choke valve and operable for closing said choke valve when the engine is not operating, said means connecting said throttle valve and choke valve including a temperature responsive element for varying the closed position of said choke valve in accordance with ambient temperatures, and means for opening said choke valve when said throttle valve is under control of said governor during operation of said engine.

7. In a carburetor for an internal combustion engine having an air passageway, a choke valve in said passageway and a throttle valve in said passageway downstream from said choke valve, a centrifugally actuated governor driven by the engine for positioning said throttle valve in accordance with the speed of the engine, means connecting said throttle valve and said choke valve and operable for closing said choke valve when the engine is not operating, means for biasing said throttle valve toward open position and acting against the force exerted by said governor, initial movement of said throttle valve from said open position being operable to permit choking action of said choke valve without effecting throttling action by said throttle valve, and means for opening said choke valve when said throttle valve is under control of said governor during operation ofsaid engine.

8. In a carburetor for an internal combustion engine having an air passageway, a choke valve in said passageway and a throttle valve in said passageway downstream from said choke valve, means urging said throttle valve toward open position, a centrifugally actuated governor driven by the engine and operably connected to said throttle valve for positioning said throttle Valve in accordance with the speed of the engine, means connecting said throttle valve and said choke valve and operable for closing said choke valve when the engine is not operating, and means for opening said choke Valve when said t rottle valve is under control of said governor during operation of the engine.

9. A carburetor according to claim 8 wherein said throttle valve is movable an initial distance from said open position without efiecting a throttling action.

ll). A carburetor according to claim 9 including temperature responsive means for preventing closing of said choke valve when the engine is hot and stops running.

ll. A carburetor according to claim 9 including temperature responsive means connected to said throttle valve to prevent said throttle valve from returning to said open position and thereby prevent said connecting means from closing said choke valve when the engine is hot and stops running.

12, In a carburetor for an internal combustion engine having an air passageway, a choke valve in said passageway and a throttle valve in said passageway downstream from said choke valve, means urging said throttle valve toward open position, a speed responsive governor driven by the engine and operably connected to said throttle valve and said choke valve for positioning said throttle valve in accordance with the speed of the engine and for holding said choke valve in a less than full open position when the engine speed is below a predetermined speed, said throttle valve being movable in initial distance from said open position and until said predetermined cngine speed is attained without etfecting a throttling action, and means for opening said choke valve during said initial movement of said throttle valve.

13. A carburetor according to claim 12 including temperature responsive means connected to said choke valve for varying the less than full open position of said choke valve in accordance with ambient temperatures.

14. A carburetor for an internal combustion engine comprising means defining an air passageway leading to the intake manifold of the engine, a choke valve in said passageway, a throttle valve in said passageway downstream from said choke valve, a governor operable in accordance with the speed of the engine and operably connected to said throttle valve to position said throttle valve in accordance with the speed of the engine, means urging said throttle valve toward open position, means biasing said choke valve toward open position, said governor being operably connected to said choke valve, temperature responsive means in said connection between said governor and said choke valve to position said choke valve in a closed position determined by ambient temperature conditions when the engine is not operating, actuation of said governor being operable to move said throttle valve toward a throttling position and to reduce the force exerted on said choke valve by said temperature responsive means so as to permit said biasing means to open said choke valve.

15. A carburetor according to claim 14 wherein said throttle valve is movable through an initial distance from said open position without effecting a throttling action;

16. A carburetor for an internal combustion engine comprising means defining an air passageway leading to the intake manifold of the engine, a choke valve in said passageway, a throttle valve in said passageway downstream from said choke valve, linkage means connected to said throttle valve, a governor driven by the engine and reacting against said linkage means to position said throttle valve in accordance with the speed of the engine, means reacting on said linkage means against the force exerted by said governor and urging said throttle valve toward open position, means biasing said choke valve toward open position, temperature responsive means reacting between said throttle valve and said choke valve against the force of said biasing means to position said choke valve in a closed position determined by the ambient temperature when the engine is not operating, movement of said throttle valve from said open position by said governor and linkage means being operable to reduce the force exerted on said choke valve by said temperature responsive means so as to permit said biasing means to open said choke valve.

17. A carburetor for an internal combustion engine comprising means defining an air passageway leading to the intake manifold of the engine, a choke valve in said passageway, a throttle valve in said passageway downstream from said choke valve, a centrifugally actuated governor driven by the engine for positioning said throttle valve in accordance with the speed of the engine, means for urging said throttle valve toward open position, means biasing said choke valve toward open position, temperature responsive means connected to said choke valve, link means connected between said throttle valve and said temperature responsive means, said temperature responsive means reacting between said link 10 means and said choke valve to position said choke valve in a closed position determined by the ambient temperature when the engine is not operating, movement of said throttle valve from said open position by said governor being operable to shift said link means in a direction to reduce the force exerted on said choke valve by said temperature responsive means so as to permit said biasing means to open said choke valve.

18. In a carburetor for an internal combustion engine having an air passageway, a choke valve in said passageway and a throttle valve in said passageway downstream from said choke valve, a speed responsive governor driven by said engine and operably connected to said choke valve for holding said choke valve in a less than full open position when the engine speed is below a predetermined speed, means for opening said choke valve as the engine attains said predetermined speed, said governor being operably connected to said throttle valve for positioning said throttle valve in throttling position thereof at engine speeds above said predetermined speed.

References Cited in the file of this patent UNITED STATES PATENTS 1,155,094 Podlesak Sept. 28, 1915