US2379849A - Internal-combustion engine - Google Patents

Description

July 3, 1945.

G. R. ERICSON 2,379,849

INTERNAL-COMBUSTION ENGINE Filed Nov. 7, 1931 3 Sheets-Sheet 1 H 2E; p GEORGE R. ERICSON INVENTOR ATTORNEY 7, 1931' s Sheets-Sheet 2 Filed Nov.

Ill/II GEORGE i3 ERICSON INVENTOR ATTORNEY ca. R. ERICSON INTERNAL-COMBUSTION ENGINE Filed Nov. 7, 1931 3 Sheets-Sheet 3 N m w R m Rm El G R 0\ u 2 a 5 Z 2 7 5 5 II IlllI-lll I|I|,||l.l.|| aw ,1. 1| lllll 1 r 2 o 4 July 3, 1945.

ATTORNEY Patented July 3, 19 45 INTERNAL-COMBUSTION ENGINE George R. Ericson, Maplewood, Mo., assignor to Carter Carburetor Corporation, St. Louis, Mo., a corporation of Delaware Application November 7, 1931, Serial No. 573,628

33 Claims.

This invention relates to internal combustion engines and particularly to charge forming devices or carburetors for such engines. In the usual present day automotive installation, the carburetor for an internal combustion engine is provided either with a manually operated valve for either increasing the fuel or decreasing the air supply, for use in starting and operating the engine under low temperature conditions. Such installations involve difficulties on account of the fact that the operator has no definite knowledge as to the correct position of the choke valve at any particular instant, and even the most skillful operator can only get a rough approximation of correct operation from his carburetor.

It is an object of this invention to produce a new and improved carburetor capable of automatically varying the fuel mixture ratio in accordance with the requirements of the engine.

Other objects and advantages will appear from the following description and claims taken in connection with the accompanying drawings, in which like reference numerals refer to like parts:

Figure 1 shows a diagram of an internal combustion engine having one modification of my invention applied thereto.

Figure 2 is a side elevation of a carburetor according to one form of my invention, with parts shown in section and others broken away.

Figure 3 is a sectional elevation of the parts shown in Figure 2 taken at right angles to the section of Figure 2.

Figure 4 is a plan view of the parts shown in Figures 2 and 3.

Figure 5 is a fragmentary sectional plan view on line A-A showing the thermostat and parts of the operating cylinder.

Figure 6 is a sectional elevation of one form of operating cylinder.

Figure 7 is a sectional elevation of the carburetor shown in Figures 2 and 3, the section being taken along the line 1-1 of Figure 4.

Figure 8 is a side elevation of the carburetor shown in Figures 2, 3 and '7, with parts broken away and others shown in section.

Figure 9 shows a sectional elevation of the upper part of the carburetor, taken along line I-5 of Figure 8.

Figure 10 is a sectional elevation of the parts shown in Figure 9, with the .valve in closed position.

Referring to the drawings, the reference numeral I indicates the housing of an internal combustion engine. This engine is provided with the usual cylinders or cylinder block 2, an intake manifold I, and an exhaust manifold 4. The exhaust manifold is provided with passages: 5 leading to a stove 6 for heating the intake manifold.

It will be understood that the application of this heat may be varied, and if desired, the heating stove may be applied directly or indirectly to the carburetor. In amr case, a substantial amount of heat will be conducted to the carburetor during the operation of the engine.

The engine is provided with the usual crank case 1 in which an oil pump 8 is located. This pump is operated by a shaft 9 which may be driven from the crank shaft (not shown) or other moving part of the engine. A conventional starter III with a storage battery Il may be provided, and the engine also is provided with the generator H2. The generator is provided with a relay l3 which closes the circuit l4 after the generator has attained a substantial rate of speed. A conventional fuel pump 15 is also adapted to be mounted on and driven by the engine.

The carburetor comprises a main body member it having a flange l1 by means of which it may be bolted or otherwise secured to an internal combustion engine. The carburetor is provided with a constant level fuel chamber I 8 to which fuel is supplied from the fuel pump [5 by means of the connection 19. The fuel is maintained at a substantially constant level A-A as indicated in Figures 2 and 7 by the float 20 which operates the float valve 2 l in a conventional manner. The constant level fuel chamber is vented to the atmosphere thru crevices 84 which are provided between the float chamber and the float chamber cover 85 as indicated in Figures '1 and 8. The normal supply of fuel from the float chamber to the carburetor is delivered through the calibrated jet 22 which is controlled by the metering rod 23 in accordance with the position of the throttle valve 24 which is provided in the outlet of the mixing conduit of the carburetor. This throttle is carried on the shaft 25 which may be operated by any suitable means. Connected to the throttle shaft 25 is a crank member 26 to which is attached a connecting rod 21 so that the rod moves up or down respectively with the opening or closing movements of the throttle.

A shaft 28 is mounted at the upper end of the carburetor and has the rocker member 29 pivoted thereto. The rocker member is operated by the connecting rod or link 21, and the metering rod 23 is connected thereto. Connected to the end of the rocker member 29 opposite the metering rod and link 21 is a flange rod 30 carrying a plunger 3|. This plunger operates to draw fuel from the constant level chamber l8 through the inlet check valve 32, and an outlet check valve 33 is provided, which outlet check valve discharges into the pump nozzle 34. The carburetor is of the plain tube type and is provided with one or more venturis 35. In this instance, three venturis are shown, but it will be understood that the invention is ap licable to plain tube carburetors irrespective of the number of venturis used. The fuel for low speed operation is drawn through the jet 22, passages 36, 31, 38, 39 and 40, and is discharged at the edge of the throttle through the port or ports 4!. These passage ways may be referred to as the idle conduit.

The fuel for normal and high speed operation is drawn from the jet 22 through the passages 36 and 31 to the nozzle 42 which discharges into the air stream at the throat of the smallest venturi.

By this arrangement, it will be seen that the main nozzle and idle draw fuel from the same orifice, and it will be understood by persons skilled in the art that during low speed operation, suction at the port 4| will be so much greater than'the suction in the nozzle 42 that no fuel will be drawn through the nozzle; and when the throttle is opened, the suction on the port 4| will be substantially reduced and only a small quantity of fuel will be discharged at that point, substantially all of the fuel required being discharged at e main nozzle.

For starting purposes, a choke valve 43 is provided. This valve is carried by a shaft 44 and comprises a solid portion 45 which is fixed to the shaft by suitable means, such as screws 46 and a hinged portion 41 which may be opened by suction under conditions hereafter described. The hinged portion is normally held,in the position shown in Figures 2 and 3 by means of a spring 48, but when the choke valve is moved to closed position, the latch 49 contacts with the beveled portion 50 in the air horn and prevents full opening of the hinged portion 41. A slight opening of this portion, however, is provided, as indicated in Figure and the spring 48 is calibrated so that even when the choke valve is in fully closed position and when ,the engine is operated at cranking speeds in the order of forty or fifty revolutions per minute, there will be a slight opening and closing of the member 41 with each suction impulse of the engine. As the choke valve is opened, the latch 49 eventually reaches a position in which it does not interfere with the lug 5| on the member 41, and that member may be opened by suction in accordance with the requirements of the engine. The construction and operation of this choke valve is shown and claimed in the United States patent to Kommer and Henning #1394354 issued January 17, 1933.

In order to control the choke valve 43 in accordance with the temperature and operating condition of the'engine, the following structure is provided. A thermostat 52 of the usual bimetal construction is mounted on a part of the carburetor, and this thermostat may be controlled by varying the conditions of temperature to which the carburetor is subjected.

The thermostat could be mounted on the exhaust pipe of the engine or it could be mounted on the hot spot of the intake manifold, but I prefer to mount it directly on the carburetor, so that the carburetor may be attached and removed as a unit without the necessity for adjusting the thermostat with relation to the choke valve. In

the preferred embodiment the thermostat is carried on a fixed shaft 53 and held in adjusted position by a screw 54, as indicated in Figure 5.

The free end 56 of the thermostat is pivoted to a cam shaft 51 having cam surfaces 58 and 59 thereon. The upper end of the cam shaft is provided with a vertical slot 60 which is slidably mounted on the shaft 44 so as to permit an upward and, downward movement of the cam shaft and cams in response to the temperature changes.

A cam plate 6| is carried by the choke shaft 44, and apair of cams or stops 62 and 63 are carried by the cam plate. The stops 62 and 63 are preferably formed integral'with the cam plate and are simply bent up portions of sheet metal arranged to contact with the cam surfaces 58 and 59.

As will be seen from Figure 2, there is a considerable amount of lost motion between the stops 62 and 63 so that the shaft 44 may be rotated for considerable distances. The arrangement of the stops and cam surfaces is such as to permit a closing movement of approximately 45 degrees of movement of the choke shaft with the cams in the hot position shown in Figure 2, and to permit an opening movement of 20 or 30 degrees when the cam is in its full downward position, that is, when the temperature is at its lowest point.

In order to operate the choke valve, I provide a cylinder 64 having an inlet boss 65 thereon which is screwed into the crank case of the engine by screw threads 66, the crank case being provided with a threaded boss for that purpose. The inner side of the boss is connected by means of screw threads 69, and a conduit (not shown) to the oil pump 8 of the engine. The cylinder 64 is provided with an inlet passageway which is controlled by a check valve II. This check valve is provided with a restricted passageway 12, and the valve is normally held in closed position by springs 13 which, in turn, is held in the threaded end of the box 65 by a perforated plug I4. The cylinder is provided with a slidable piston 15 normally held in its downward position by a spring 16, and the upper end of the cylinder is closed by a combination cap and guide member 11.

The piston is provided with a piston rod 18 which is slidably mounted in the cap 11 and provided at its upper end with a ball and socket joint 19. The ball and socket joint is connected by a link 80, a pivot member 8|, and the cam 6| so that when the piston 15 is inits upward position, the valve 43 will be in open position.

The operation of the device is as follows:

Assuming that thetemperature is low and the engine is not running, the valve 43 and also the valve portion 41, will be closed by the springs 16 before the starting operation is commenced. Fuel is supplied to the pump I5 from the tank diagrammatically indicated in Figure 1, and the engine upon being operated by the starter operates the pump to deliver fuel through the conduit I9 to the inlet valve of the carburetor, which is controlled by the float as shown in Figure 7. 'A comparatively high suction is developed in the carburetor due to the fact that the choke valve is in closed position and substantial quantities of fuel are withdrawn from the nozzles 4| and 42. During the cranking operation of the engine the oil pressure is comparatively low and the spring 16 is of 'sufiicient strength to resist movement thereof by the oil pressure. However, as soon as the enginestarts to fire and run under its own power, the operating speed will increase up to 200 or more R. P. M., and the suction will increase from about lb. per square inch to about six or seven pounds. The oil pressure will then begin to raise the piston 15 and gradually open the choke valve. This movement will bear a certain relation to the temperature at which the operation is started because the oil in the crankcase varies in viscosity according to the temperature, and the restricted passageway 12 will require quite a long interval to pass enough oil into cylinder 64 to fill it. If the temperature is high, the time required to fill cylinder 64 is comparatively short, so that the rate of opening of the choke valve is graduated in accordance with the temperature at which the starting operation is performed.

The segment 41 of the choke valve iaopened against the spring 48 by the increased suction as soon as the engine starts to run under its own I power. It may be noted that the normal cranking suction in the air chamber of the carburetor with the throttle in full closed position, will be in the order of one-half-pound per square inch, which is insuflicient to open the valve 41, but as soon as the engine starts to run the suction will be increased to several pounds per square inch. Under these conditions of increased suction, the valve 41 opens until the member 51 contacts with the latch, when further movement is temporarily arrested.

The opening movement of the choke valve is gradually continued by the movement of the piston I but there is a control on the amount to which the choke valve can open. This control is affected by the position of the cam 59. If the temperature is low, the cam 59 will be lowered with reference to Figure 2, and the stop 63 carried by the choke valve will come iii-contact with the cam before said choke is fully open. The point at which the stop 63 will come into contact with the cam will vary in accordance with the temperature and corresponding position of the cam 59. It will be understood, of course, that when the carburetor has reached normal operating temperature the cam 59 will be in the upward position as shown in Figure 2 and the choke valve will be fully opened, and the carburetor will operate according to the well known lain tube principles.

It frequently happens that when the engine is started to run under its own power, it will run for a few seconds and then stop. If this occurs, the

choke valve may be slightly opened by the oil pressure and if the operator should again attempt to start the engine within two or three seconds after the stoppage thereof, the mixture would be too lean if the choke valve 43 remains in partially open position. The construction of the check valve -'H is such that an immediate return of the piston 15 is permitted, the oil flowing around the check valve through the inlet 65 and back into the oil system of the engine.

After the engine has been stopped, the temperature of the carburetor may not decrease as rapidly as the temperature of the combustion chamber, and moreover it is desirable upon restarting the engine, to have a slightly higher restriction in the air inlet than would be desirable for the same temperature with the engine in operation and running under its own power. As soon as the engine stops, the oil from cylinder 64 is permitted to flow back into the oil system as hereinbefore stated. However, if the carburetor is hot the choke valve is not fully closed by reason of the fact that the cam 58 is in its upward position and the member 52 comes in contact with the cam, thereby piston 15. If the engine is restarted almost immediately after stopping, with the temperature fairly high, the choke valve is only partially closed, so that the mixture supply for starting will not be too rich, in view of the hot condition of the engine. As the engine cools off, the thermostat moves the cam shaft 51 and the cam 58 downwardly, and closing of the choke valve is permitted in the measure in which the engine has cooled off. a

The invention is not limited to the structural details shown but may be modified in various respects as will occur to those skilled in the art and the exclusive use of all such modifications as come within the scope of the appended claims is contemplated.

I claim:

1. In an internal combustion engine having an intake manifold, a carburetor attached to said manifold, and a pump driven by said engine; a constant level fuel chamber for said carburetor, said constant level fuel chamber being vented to the atmosphere, a fuel supply nozzle for said carburetor, a choke valve controlling the admission of air to said carburetor at a point anterior to the discharge outlet of said fuel supply nozzle whereby the richness of the fuel mixture delivered by said carburetor is controlled, a thermostat for controlling the movement of said choke valve, a spring for closing said choke valve, and means operated by pressure derived from said pump for opening said choke valve.

, 2. In an internal combustion engine, having an intake manifold, a carburetor attached to said manifold, a throttle valve for said carburetor, a fuel mixture controlling choke valve for said carburetor, means for delivering fuel by suction to said carburetor at a point between said throttle and choke valve, a pump driven by said engine, means operated by said pump to open saidl choke valve, spring means for closing said choke valve, means for limiting said closing of said choke valve, and a thermostat for varying the position of said closure limiting means.

3. In a device of the class described, means forming a mixing conduit, a throttle valve controlling the discharge of mixture from said conduit, an air valve controlling the admission of air to said conduit, means forming a source of fuel supply, a pair of fuel discharge conduits discharging fuel into said mixing conduit at spaced points, a pair of stops carried by said choke valve, cam

means for limiting the movement of said choke valve in either direction by contact with saidstop, and heat controlled means for varying the position of said cam means.

4. In an internal combustion engine having an intake manifold, a carburetor attached to said manifold, said carburetor having a fuel chamber and a mixing conduit therein, a choke valve for controlling the admission of air to said mixing conduit, said fuel chamber having a nozzle discharging into said mixing conduit at a point posterior to the choke valve, and said fuel chamber having a vent for admitting air thereto regardless of the position of said choke valve, spring means tending to close said choke valve when said engine is not in operation, means operated by power derived from said engine for opening said choke valve when the engine is in operation, and a heat responsive device for limiting the opening movement of said choke valve in accordance with the temperature.

5. In an internal combustion engine having an intake manifold and an oil pump operated by said engine, a carburetor attached to said intake manifold, a choke valve for said carburetor, a cylinder connected to said oil pump, a piston in said cylinder for operating said choke valve, means comprising a highly restricted passageway for in operation, a thermostat mounted on and car-.

ried by said carburetor, and cam means operated by said thermostat for limiting the opening and closing movements of said choke valve in accordance with the temperature, irrespective of whether said engine is in operation or not. 7Q In an internal combustion engine having an intake manifold, a. carburetor atttached to said manifold, said engine having an oil pump, a choke valve for controlling the admission of air to said carburetor, a suction operated valve carried by said choke valve, means operated bypressure derived from said oil pump forcontrolling said choke valve, and means comprising a thermostat carried by said carburetor for controlling movement of said choke valve.

8. In an internal combustion engine having an intake manifold, a carburetor attached to said manifold, said engine having an oil pump, a choke valve for cbntrolling the admission of air to said carburetor, a suction operated valve carried by said choke valve, means operated by pressure derived from said oil pump for controlling said choke valve, means comprising a thermostat carried by said carburetor for controlling a movement of said choke valve, and spring means for normally closing said choke valv when said engine is not in operation.

9. In an internal combustion engine having an intake manifold, a carburetor attached to said manifold,. said engine having an oil pump, a choke valve for controlling the admission of air to said carburetor, a suction operated valve carried by said choke valve, means operated by pressure derived from said oil pump for controlling valve for suddenly reducing the suction applied to said nozzles when said engine starts to run under its own power.

11. In a device of this class described, a downdraft miXing conduit, a throttle valve near the lower end of said conduit, a choke valve 'near the upper end of said conduit, a pair of fuel nozzles discharging by suction into said ixing co u t, one of said nozzles discharging adjacent said throttle and the other discharging at a point between said throttle and said choke valve, suction operated means calibrated to Open only when said choke valve is closed and only when said engine is operating under its own power, for admitting air to said mixing conduit, means operated by said engine for gradually opening said choke valve after the engine starts to operat under its own power, said meansv being constructed and arranged to permit a quick closing of said choke valve, when said engine ceases to operate under its own power.

12. In an internal combustion engine, a carburetor, a choke valve for said carburetor, operating means including a pump operatedby said engine for controlling said choke valve, said operating means tending to close said choke valve when said engine is operating at 100 R. P. M. or less and said means tending to open said choke valve when said engine is operating at speeds substantially above 100 R. P. M., and means for preventing the complete closing of said choke valve when the temperature is high, regardless of the operating speed of said engine.

13. In an internal combustion engine, a carburetor, a suction operable choke valve for said carburetor, means in addition to the suction and operated by said engin for controlling said choke valve, said controlling means tending to close said said choke valve, means comprising a thermostat carried by said carburetor for controlling'a movement of said choke valve, and spring means for normally closing said choke valve when said engine is not in operation, said thermostat controlling both the opening and closing movement of said choke valve.

10. In an internal combustion engine, having an intake manifold, a downdraft carburetor connected to said manifold, a throttle and choke valve for said carburetor, a plurality of venturis in said carburetor between said throttle and choke valve, a fuel nozzle discharging into the upper one of said venturis near throat thereof, a second fuel nozzle discharging into said carburetor adjacent to said throttle valve and below said venturi, said choke valve simultaneously controlling the suction applied to both of said fuel discharge nozzles, means for closing said choke valve when said engine is not in operation, means tending to open said choke valve when said engine is in operation, means comprising a thermostat for limiting the opening and closing movements of said choke valve, and means comprising a suction operated choke valve when said engine is operating at R. P. M. or less and said means tending to open said choke valve when said engine isoperating at speeds substantially above 100 R. P. M., and temperature controlled means for limiting the movement of said control means.

14. In a carburetor, means forming a mixing conduit, a throttle valve controlling the outlet of said mixing conduit, a choke valve controllin the admission of air to said conduit, a shaft connected with said choke valve, a cam plate carried by said shaft, cams carried by said cam plate, a thermostat mounted on said carburetor, a cam shaft carried by said thermostat, a cam surface on said cam shaft, said cam surface being adapted to contact with said cams on said cam plate to limit the movement of said choke valve.

15. In an internal ombustion engine, a carburetor, choke valve means for controlling the admission of air to said carburetor, said choke valve means including a valve eccentrically mounted on a transverse shaft whereby it may be moved toward open position by the direct action of suction, and a second valve member, said valve members being movable to closed position to restrict the admission of air to said carburetor and also being movable to an open position whereby the admission of air to said car-' buretor is substantially unrestricted, aheat responsive device constructed and arranged to control movements of at least one of said choke valve members, and means including a device adapted to be actuated by an engine driven pum for controlling the movement of at least one of said members.

16. In an internal combustion engine, a carburetor, means for controlling the. admission of air to said carburetor comprising separately movable choke valve members, one of said members buretor having an air inlet, choke valve means for restricting said air inlet, a shaft for said choke valve means, an operating member mounted on said shaft, said operating member having a pair of abutments, a heat responsive device, a member connected for operation by said heat responsive device and having a portion mounted between said abutments to limit the opening and closing movements of said choke valve according to temperature.

18. In a device of the class described, a carburetor having an air inlet, valve means for restricting the said air inlet, a shaft for said valve means, a control member mounted on said shaft, said control member having a pair of abutments, a heat responsive device, a member connected for operation by said heat responsive device and having a portion mounted between said abutments to control the action of the choke valve in accordance with temperature, and means whereby the choking effect of said choke valve will be reduced at each suction impulse of the engine when the motor is cranked with the choke valve in closed position.

19. In a carburetor for an internal combustion engine, a choke valve, a temperature-responsive member positioned to be influenced by temperatures generated during operation of the engine, and a connection between the temperature-responsive member and the choke valve operative to urge the latter toward closed position at low temperatures and toward open position at high temperatures, and inoperative to urge the choke valve to either of said positions at intermediate temperatures.

20. In combination with a carburetor having a pressure responsive choke valve, control means for the choke valve comprising a thermostat having an unyielding lost motion connection with said valve for positively controlling its operation in both directions.

21. In combination with a carburetor having a pressure responsive choke valve, control means for the choke valve comprising a thermostat and a pressure sensitive member both connected to said valve by u yielding connections and simultaneously effective under predetermined conditions of engine operation to move said valve toward open position.

22. A combination as defined in claim 21 wherein the thermostat is connected to the choke valve by a lost motion connection.

23. In a plain tube carburetor for use on an internal combustion engine, means forming a mixing conduit, air and fuel inlets for said conduit, a throttle valve in said conduit, an unbalanced valve for controlling said air inlet, said valve being moved toward open position by fluid pressure developed by the engine upon operation under its own power; means tending to close said valve for cold starting, thermostatic means for varying the efl'ective action of said closing means in accordance with temperature during cold starting, and means for causing said valve to move'to and remain in its fully open position during normal operating temperatures of said engine.

24. In a plain tube carburetor for use on an internal combustion engine, means forming a mixing conduit, air and fuel inlets for said conduit, a throttle valve in said conduit, an unbalanced valve forcontrolling said air inlet, said valve being moved toward open position by fluid pressure developed by the engine upon operation under its own power, means tending to close said valve for cold starting, thermostatic means for varying the effective action of said closing means in accordance with temperature during cold starting, means for causing said valve to move to and remain in its fully open position during normal operating-temperatures of said engine, and means responsive to operation of the carburetor in the full throttle range for enriching the fuel and air ratio.

25. In an internal combustion engine, a downdraft carburetor of the plain tube type, means forming a mixing conduit, said mixing conduit having an air inlet and a mixture outlet, a choke valve controlling said inlet, a throttle valve controlling said mixture outlet, a'suction operated fuel nozzle discharging in said mixing conduit at a point between said valves, fuel supply means comprising a fuel supply chamber, an idling fuel passageway having a fuel inlet and a discharge outlet in said mixing conduit adjacent said throttle valve, a source of energy for use in tending to close the choke valve for starting purposes, heat responsive means for limiting effective application of said energy to close the choke valve, and means yieldable to admit a limited amount of air at said air inlet when said choke valve is in closed position.

26. In an internal combustion engine, a downdraft carburetor of the plain tube type, means forming a mixing conduit, said mixing conduit having an air inlet and a mixture outlet, a choke valve controlling said inlet, a throttle valve controlling said mixture outlet, a suction operated fuel nozzle discharging in said mixing conduit at .a point between said valves, fuel supply means comprising a fuel supply chamber, an idling fuel passageway .having a fuel inlet and a discharge outlet in said mixing conduit adjacent said throttle valve, a source of energy for use in tending to close the choke valve for starting purposes, heat responsive means for limiting effective application of said energy to close the choke valve, means yieldable to admit a limited amount of air at said air inlet when said choke valve is in closed position, and additional means to admit a limited amount of air regardless of the position of the choke valve and said yieldable means.

27. In an internal combustion engine, a downdraft carburetor of the plain tube type, means forming a mixing conduit, said mixing conduit having an air inlet and a mixture outlet, a choke valve controlling said inlet, a throttle valve controlling said mixture outlet, a suction operated fuel nozzle discharging in said mixing conduit at a point between said valves, fuel supply means comprising a fuel supply chamber, an idling fuel passageway having a fuel inlet and a discharge outlet in said mixing conduit adjacent said throttle valve, a source of energy for use in tending to close the choke valve for starting purposes,

tially closed position.

28. In a plain tube carburetor for use on an internal combustion engine, means forming a mixing conduit, air and fuel inlets for said con' duit, a throttle valve in said conduit, an unbalanoed choke valve for controlling said air inlet, automatic means tending to close said valve for cold starting, temperature responsive means for limiting the action of said closing means, said choke valve being constructed and arranged to be moved toward open position by the direct action of suction, and to fully open position when the engine reaches normal operating temperature and to remain in such fully open position as long as the engine continues to operate under its own power. v

29. In a charge forming device for internal combustion engines, means forming a mixing conduit,.a choke valve for said mixing conduit, means for closing said valve for starting purposes, a heat responsive device for limiting the effective action of said closing means when the temperature is high, means for providing a bypass to admit air under the influence of suction when the choke valve is in substantially closed position, and means constructed and arranged to be operated in accordance with fluid pressure developed during operation of the engine for moving said choke valve in a direction to lean out the mixture.

30. In a charge forming device for internal combustion engines, means forming a mixing conduit, a choke valve-for said mixing conduit, means for closing said valve for starting purposes, a heat responsive device for limiting the effective action of said closing means when the temperature is high, means for providing a by-pass to admit aid under the influence of suction when the choke valve is in substantially closed osition, and means constructed and arranged to be operated in accordance with fluid pressure developed during operation of the engine for moving said choke valve in a direction to lean out the mixture, said last named means being constructed and arranged for more rapid operation when the temperature is high than when the temperature is low.

anced valve for controlling said air inlet, said valve being moved toward open position by fluid pressure developed by the engine upon operation under its own powers, means tending to close said valve for cold starting, and thermostatic means for varying the effective action of said closing means in accordance with temperature and means for causing said valve to move to and remain in its fully open position during normal operating temperatures of said engine.

32. In a plain tube carburetor for use on an internal combustion engine, means forming a mixing conduit, air and fuel inlets for said conduit, a throttle valve in said conduit, both of said inlets being of constant size regardless of suction to give a predetermined fuel mixture ratio during normal operation, an unbalanced valve for controlling said air inlet, said valve being moved toward open position by fluid pressure developed by the engine upon operation under its own power, means tending to close said valve for cold starting, thermostatic means for varying the effect of said closing means in accordance with temperature, and means for causing said valve to move to and remain in its fully open position during normal operating temperatures of said engine.

33. In a plain tube carburetor for use on an internal combustion engine, means forming a mixing conduit, air and fuel inlets for said conduit, a throttle valve in said conduit, both of said inlets being of constant size regardless of suction to give a predetermined fuel mixture ratio during normal operation, an unbalanced valve for controlling said air inlet, said valve being moved toward .open position by fluid pressure developed by the engine upon operation under its own power, means tending to close said valve for cold starting, thermostatic means for varying the effect of said closing means in accordance with temperature, means for causing said valve to move to and remain in its fully open position during normal operating temperatures of said engine, and means controlled by the movement of said throttle to wide open position for enriching the fuel mixture.

GEORGE R. ERICSON.

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