US1974586A - Carburetor - Google Patents

Description

Sept. 25, 1934. M PRENTISS 1,974,586

CARBURETGR Filed Feb. 1, 1932 2 Sheets-Sheet 2 INVEN TOR. @z/ausr/N MPEf/VT/JS Q. fi Q11:

ATTORNEY Patented Sept. 25, i 1934 PATENT OFFICE CARBURETOR Augustin M. Prentiss, San Antonio, Tex., assignor to Bendix Aviation Corporation, South Bend,

Ind., a corporation of Delaware Application February 1, 1932, Serial No. 590,295

-1 Claim. (01.123-122) This invention pertains to carburetors and more particularly has reference to means for maintaining the temperature of the carburetor and fuel-air mixture within desired limits, irrespective of wide variations in the temperature of the engine and the air surrounding the car-.- buretor.

I It has long been known in the carburetor art that best results are obtained when the fuel-air mixture supplied to the engine is between certain optimum temperature limits and that variations above or below these limits result not only in a marked decrease in power and efliciency but also in other operating difiiculties such as vapor. locks and irregular firing of the engine. The best results are obtained when the fuel-air mixture is between ordinary summer temperature and the boiling point of the lightest fraction of hydrocarbon in the liquid fuel. If the temperature of the fuel-air mixture falls much below normal summer temperature volatilization of the liquid fuel is retarded, whereas if 'the temperature exceeds the boiling point of its lightest fraction, the liquid fuel begins to boil, giving rise to vapor locks in the liquid fuel supply line and also misfires of the engine, whenever a vapor bubble passes through the main fuel nozzle.

\Heretofore the problem has been to maintain the fuel-air mixture within the optimum temperature limits indicated under actual operating conditions 'where the temperature of the carburetor and the air surrounding the carburetor may vary all the way from'20 degrees to 30 degrees below zero Fahrenheit to 150 degrees above zero Fahrenheit.

Due to the large amount of heat radiated by an internal combustion engine, notwithstanding that it may be cooled by a water jacket, and the heat throw-ofi by the radiator, the temperature under the hood of an automobile is always much higher than the atmosphere outside the hood, both in winter and summer. carburetor has always been exposed not only to the heated air under the hood butalso to additional heat transmitted by conduction through the intake manifold from the engine to the carburetor. This latter heat raises the temperature of the carburetor considerably above the air surrounding it, so that often in hot summer weather the temperature of the carburetor is materially above the boiling point of a part of the liquid fuel and unsatisfactory operation results.-

Also in cold winter weather, the temperature of the carburetor, notwithstanding the sources of heat indicated above, is often far below efficient Heretofore, the,

vaporization temperature and loss of power and efliciency occurs.

While it has formerly been proposed to heat the carburetor in cold weather by circulating the exhaust gases or hot water from the engine in a jacket surrounding the carburetor, and to arrange a manually controlled valve so that the amount of such heating fluid may be regulated, so far as I am aware, it has never been proposed to cool the carburetor in hot weather by circulating cold water in a water jacket around the carburetor so arranged as to completely insulate the carburetor from the heated air under the hood and thus maintain the temperature of the carburetor not only below the temperature of the heated air under the hood but also of the outside atmosphere, whenever these temperatures exceed the optimum temperature of i the fuel-air mixture. i

It has also, so far as I am aware, never been proposed to maintain the carburetor and fuel-air mixture between certain desired limits of temperature, necessary for best operating results, by circulating both warming and cooling fluids around the carburetor and automatically controlling -the circulating of these fluids so as to maintain the carburetor and fuel-air mixture within the desired temperature rangeregardless of the temperature of the atmosphere.

An object of this invention is to. provide a carburetor with means for automatically controlling its temperature, and the temperature of the fuelair mixture,-within certain desired operating limits, regardless of the temperature of the atmosphere.

Another object of this invention is to insulate the carburetor from the heated air under the hood by circulating a cooling medium in a jacket completely enveloping the carburetor, so that the temperature of the carburetor and the fuelair mixture will not exceed the boiling point of the lightest fraction of the liquid fuel.

Still another object of my invention is to provide means for automatically controlling, within certain limits, the temperature of the air entering the carburetor so as to obtain in hot weather air cooler than that under the hood and in cold weather warmer than that under the hood.

With these and other objects in view which may be incident to my improvements, my invention consists in the combination and arrangetom of the hood space.

of an automobile in which are located a conventional water-cooled internal combustion engine.

and radiator, in operative connection with a carburetor embodying my improvements.

Figure 2 shows in central longitudinal section, on an enlarged scale, the carburetor shown in Figure 1;

Figure 3 shows a front elevation of the same partly in section along the line 33 of Figure 2.

Figure 4'is an enlarged, vertical section of thermostat valve shown in Figure 1.

Referring to the drawings and particularly to Figure 1, the reference numeral 1 denotes the hood and 2, the dashboard, of an automobile having a multicylinder internal combustion engine 3 which is located within the hood 1 and cooled by a radiator 4 and fan 5 inthe usual way. The hot water manifold 6 is connected to the top of the radiator 4 by a pipe '7 in'which is located a valve 8 controlled by a thermostat 9 in the radiator, as clearly shown in Figure 1. The function of valve 8 is to prevent circulation of water from the engine to the radiator until the temperature of the water reaches a certain point sufficient to operate the thermostat 9 and open valve 8. This hastens the warming up of the engine. The same results may also be obtained by providing thermostaticallyoperated shutters in front of the radiator cutting off the circulation of air therethrough until the temperature of the water in manifold 6 is sufliciently highto operate the thermostat actuating the shutters. These are conventional features associated with my invention but forming no part thereof.

The bottom of the radiator 4 is connected to the bottom of the water jacket surrounding the cylinders of the engine by a pipe 10 having a bleed pet cock 11 and circulating pump 12 connected thereto. Below pipe 10-, radiator 4 has a separate section 4a having a pipe 10a and circulating pump 12a connected thereto, for cooling the carburetor as hereinafter described.

The reference numeral 13 denotes the carburetor as a whole, connected in the usual manner to the riser 14 of the intake manifold (not shown) and to an air cleaner 15. While I have shown an updraft carburetor in the drawings, it will be apparent from the description hereinafter that my invention is equally applicable to downdraft carburetors and to pressure feed carburetors as well as suction feed types. The intake pipe 16 of the air cleaner extends downward-1y below the pan 17 of the automobile which encloses the bot- Intake pipe 16 is connected by a pipe 18 to an air heater or stove 20 surrounding the exhaust manifold 21 of the engine in the conventional manner. At the junction of pipes 16 and 18, a flap valve 22 is so arranged as to alternately cut off the entrance of air to the air cleaner through either pipe 16 or 18 or toregulate the proportion of air entering through each pipe. In this way the temperature of the air entering the carburetor is regulated. Since the outside air under the pan is cooler than the heated air under the hood, valve 22 closes pipe 18 in hot weather and permits air to enter only through pipe 16. Conversely, in cold weather, when heated air is desired, valve 22 closes pipe 16 and permits. air to enter only through pipe 18 which connects with heater 20. In moderate weather valve 22 would have an intermediate position, as shown in Figure 1 permitting a mixture of cool air through pipe 16 and hot air'through pipe 18. It is obvious that valve 22 thus controls, within the limits of the temperature of the outside air on the one hand and the temperature of the stove 20 on the other, the

"temperature of the air entering the carburetor.

The operating mechanism of valve 22 will be hereinafter described.

The carburetor 13 is provided with an integral water jacket 23 which completely surrounds and envelops the body of the carburetor, including the fuel reservoir, as clearly shown in Figure 2. This water jacket 23 is connected by a pipe 24 to the pump 12a on its high pressure side, and by a pipe 25 to the radiator 4a. Pipe 25 is also connected to pipe 10 on the low pressure side of pump 12 and is provided with a two-way thermostat valve 25a which is adapted to open communication be-' tween pipes 25 and 10, and close communication through pipe 25 to the radiator 4a, in cold weather, and to close communication between pipes 25 and 10 and open communication through pipe 25 with radiator 4a in hot weather, as clearly shown in Figure 1, for a purpose to be more fully explained hereinafter.

Referring now to Figure 2, the reference numeral 2'7 denotes the body of a carburetor having an air intake 28, a Venturi throat 29, a mixing chamber 30 and mixture outlet 31 controlled by a throttle valve 32 in the usual manner. A main liquid fuel nozzle 33 communicates through a passageway 34 and port 35 with an integral liquid fuel reservoir 36. A needle valve 37 controls the flow of liquid fuel through port 35 from reservoir 36 to nozzle 33.

Reservoir 36 is supplied with liquid fuel through inlet 38 and pipe 39 by a liquid fuel pump (not shown). A valve 40, actuated by float 41, maintains the liquid in reservoir 36 at a constant level. A vacuum controlled acceleration pump 42 opens an auxiliary port 43 in the bottom wall of reservoir 36 and supplies additional fuel as required for acceleration, as clearly shown in Figure 2. The slow speed or idle fuel feed is supplied through a plurality of ports 44 which bestride the throttle 32 (in closed position) and are connected by a passageway 45 with fuel nozzle 33.

Reservoir 36 is closed by a cover 46 held in place by a plurality of screws 47 and sealed by a gasket 48. Cover 46 is also provided with a water jacket 49 which is connected to water jacket 23 by a plurality of passages 50 as shown in Figure 2. The mechanism controlling the temperature of the water circulating in jackets 23 and 49 is contained in a housing 51 which is cast integral with carburetor body 27 and is closed by a cover plate 52, as shown in Figure 2. Integral with plate 52 is a circular valve housing 53 which encloses a valve 54 as shown in Figures-2 and 3. Valve 54 is fixed to a shaft 55 which is journalled in the body of the carburetor 27 and inplate 52. Near its inner end shaft 55 carries a spiral thermostat 56 which is coiled around shaft 55 and attached at its inner end to said shaft by a plurality of screws 57. At its outer end coil 56,is attached by a pin 58 to the body of the carburetor 27 as clearly shown in Figure 2. The thermostat coil 56, thus mounted is enclosed by a chamber 59 forming part of the jacket 23 and communicating therewith through ports 60. The coil 56 is thus immersed at all times in the water circulating through jacket 23, and is subject to the temperature of this water.

When the temperature of the water rises, coil 56 expands, unwinds, and moves valve 54 in a clockwise direction to the position shown in full lines in Figure 3, whereupon communication is established between cold water supply pipe 24 and jacket 23 through ports 61 and 62 in valve housing 53. Conversely, when the temperature of the water circulating through jacket 23 falls, coil 56 contracts, winds up, and moves valve 54 in a counterclockwise direction to the position shown in dotted lines in Figure 3, whereupon communication between cold water pipe 24 and jacket 23 is cut olf and hot water enters jacket 23 from pipe 26 through ports 64, 62 and 63. It will also be noted fromFigure 3 that when valve 54 is in the position shown in full lines, permitting the circulation of cold water around the carburetor, the hot water entering from pipe 26 is discharged directly out through port 65 in valve housing 53, and pipe 25 to pipe 10 on the low pressure side of pump 12, and conversely when valve 54 is in the position shown in dotted lines, permitting thecirculation of hot water around the carburetor, the cold water from pipe 24 is discharged directly out through port 65 and pipe 25 in the same manner.

Since valve 54 is thinner than the width of ports 62 and 65, when valve 54 is in a vertical position, midway between the positions shown in Figure 3, both hot and cold water will enter housing 53 and will discharge through ports 62 and 63 into jacket 23 where they will commingle and result in water having a medium or intermediate temperature. In this way, the temperature of the water circulating around the carburetor is regulated and controlled by valve 54 which is in turn actuated by thermostat 56 responsive to the temperature of the carburetor.

Shaft 55 carries fixed to its outer end an arm 66 which is connected by an adjustable link 67 to an arm 68 on air valve 22, so that as valve 54 is moved by thermostat 56 in a clockwise direction, valve 22 is raised so as to restrict pipe 18 and open pipe 16 and, conversely, when valve 54 is moved in a counterclockwise direction, valve 22 is lowered to cut off pipe 16 and open pipe 18.

' In this way, the temperature of the air entering the carburetor is controlled and made to vary directly and proportionately with the temperature of the water circulating around the carburetor. Since the water jackets 23 and 49 surround and completely insulate the float reservoir 36, the temperature of the liquid fuel in the float reservoir is sensibly that of the water in jackets '23 and 49, since the capacity of reservoir 36 is made sufficient to insure an adequate period of time during which the liquid fuel remains in the reservoir in contact with the walls of jacket 23.

The operation of my device is as follows. In cold weather, when the engine is first started, the engine, carburetor and water in both cooling systems are all at the temperature of the atmosphere, valve 8 is closed and valve 25a cuts off radiator 4a and opens communication between pipes 25 and 10. The first explosions in the cylinders of the engine quickly heat the water in manifold 6 which is held therein and prevented from circulating to the radiator by valve 8. Part of this hot water travels down pipe 26 and since valve 54 is in its cold (dotted) position, it circulates around the carburetor and is discharged out through pipes 25 and 10 to the low pressure side of the pump 12. As pump 12 runs continuously whenever the engine is running, it creates a higher pressure in manifold 6 than exists in pipe 10 between the radiator 4 and the pump, and thus causes a vigorous circulation of hot water around the carburetor. Since the superior pressure in manifold 6 is greater when valve 8 is closed than when it is open and the water is circulating through the radiator, it follows that the most vigorous circulation of hot water takes place when the engine is first started in cold weather, which is as desired because the carburetor then requires the most heat. After valve 8opens, the same circulation continues around the carburetor but in a lessened degree. The temperature of the water in the engine cooling system is largely determined in cold weather by the adjustment of thermostat 9 or the shutters on the radiator if such are used, and can be regulated as desired. However, the water in manifold 6 is always appreciably hotter than that in any other part of the engine cooling system.

When the engine has been operating a sufficient time to bring the water in its circulating system to a uniform temperature the carburetor is also at its optimum temperature. While the carburetor is thus maintained at its optimum temperature, the air entering the carburetor is also brought up to the same temperature by stove 20 and hence the fuel-air mixture delivered by the carburetor to the engine is at substantially the same temperature, regardless of the temperature of the atmosphere. Thermostat 56 may be calibrated to maintain any desired constant temperature near that of the carburetor temperature in winter, which gives optimum operatingresults.

In hot weather, when the engine is started, the engine, carburetor and water in both cooling systems are also at the temperature of the atmosphere. Valve 25a opens communication with radiator 4a and cuts 01f communication between pipes 25 and 10, and the water in the carburetor cooling system is free to circulate through the radiator 4a where it is cooled below atmospheric temperature by radiation losses. 1

Cold water from pipe 10a travels up pipe 2 under the pressure created by pump 12a and since valve 54 is in its warm (full line) position, it circulates around the carburetor and is returned through pipe 25 back to radiator 4a and pipe 10a to the low pressure side of the pump. Since there is a great difference in temperature between the water in jacket 23 and that in radiator 4a, circu-. lation will also be caused by convection and pump 12a might be omitted. By this continuous circulation of cold water, the carburetor is maintained at a temperature far below engine temperature and much cooler than the heated air under the hood to which the carburetor has been heretofore exposed. At the same time, the air entering the carburetor is taken from under the pan and is at atmospheric temperature which again is much less than that of the heated air under the hood. As the liquid fuel in reservoir 36 is also cooled by the circulation of water around the carburetor, it is maintained at a temperature lower than the boiling point of its lightest fraction and in this way vapor locks and misfires due to vapor bubbles are prevented. In order to prevent heating of the liquid fuel before it enters reservoir 36, the portion of pipe 39 exposed to the air under the hood should be reduced to a minimum and the fuel pump either located below the pan 17 or provided with a water jacket connected in series with the carburetor water jacket.

I have found by the means described above that, notwithstanding the heated air under the hood, and the heat transmitted by conduction from the engine through the intake manifold to the carburetor, the carburetor can be maintained at an I claim:

In an automobile, an internal combustion engine, a carburetor operatively connected thereto, separate liquid cooling systems connected to said engine and carburetor respectively, and means for selectively heating said carburetor from said engine cooling system or cooling said carburetor from its separate cooling system depending upon the temperature of said carburetor.

- AUGUSTIN M. PRENTISS.

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