US2167497A - Carburetor - Google Patents

Description

R. Fv BRACKE July 25, 1939.

GARBURETOR Filed April 18, 1936 0 MB 1 1 @w a w W w 63 w, $4M i i Patented July 25, 1939 UNITED STATES PATENT OFFICE Application April 18,

7 Claims.

My invention pertains to carburetors and is more particularly concerned with carburetors of the fuel lift or self-feeding type.

For use on automobiles and other vehicles it is desirable to have a carburetor which will provide maximum engine acceleration.

An object of my invention is to provide a simple, efficient andreliable carburetor which will afford maximum engine acceleration without the in provision of complicated, expensive or delicate mechanisms.

Other objects and advantages will become apparent as the description proceeds.

In the drawing Figure 1 is a vertical section through a preferred embodiment of my invention and is taken on the irregular line l-l of Figure 2;

Figure 2 is a horizontal section taken on the line 22 of Figure 1; and

Figure 3 is a section through the choking mechanism and is taken on the line 3-3 of Figure 2.

Referring to the drawing, I have shown my carburetor as comprising an upper casting A, a center casting B, and a lower casting C, suitably secured together as by means of bolts ID. A gasket I2 is preferably interposed between the castings B and C. The upper casting A provides primary air inlet l4 and secondary air inlet 16, both of which are so designed that a suitable air cleaner and silencer may be attached to these inlets or to the casting of which they form a part,

The primary air entering through the inlet I4 passes into a chamber l8 therebelow and thence through the nozzle 26 which discharges into a mixing chamber 22. The flow of primary air through the nozzle 2!] creates a vacuum in the throat thereof and this vacuum serves to draw fuel to the nozzle from the fuel chamber 24 in a manner which will presently be described.

The secondary air entering the inlet [6 flows past an air valve 26 and thence through a Venturi-shaped passage 28 and into the mixing chamber 22. It is to be noted that the nozzle discharges into the mixing chamber just beneath the step 30 provided by the Venturi-shaped passage. This is the point of maximum suction for all conditions of operation and provides maximum efficiency for the nozzle 20.

The mixing chamber 22 communicates with the throttle bore 32 containing a throttle valve 34 for regulating the supply of combustible mixture to the internal combustion engine. The casting C is provided with a flange 36 having openings 38 for receiving bolts whereby the carburetor may 1936, Serial No. 75,049

be attached to the intake manifold of the engine. The throttle valve 34 is shown as comprising a balanced butterfly valve controlled through lever 40 from the usual hand and foot throttle controls of an automobile.

The throat of the nozzle 20 is venturi-shaped and has a step below which are located the inner ends of radial passages 42 through which fuel is supplied to the nozzle. These passages communicate with an annular chamber 44 communicating with a horizontal duct 46 connecting with the upper end 48 of a sleeve 56 formed as an integral part of the casting B. The lower end of this sleeve terminates a short distance above the bottom of the fuel chamber 24.

A metal cup 52 is. located in the sleeve about midway of the length thereof, and this cup contains a metered orifice 54 which is controlled by an economizer pin 56 slidable in a tubular guide 58 threaded at 60 into the lower casting C. The guide 58 extends upwardly in the fuel chamber 24 to a point above the maximum height of fuel therein and a passageway is formed between the outer surface of the guide 58 and the adjacent inner surface of the sleeve 56. The lower end of the economizer pin 56 forms a ball and socket connection with the upper end of a rod 62 whose lower end forms a ball and socket connection with an adjustable screw 64 carried by one end of a lever 66. The screw 64 is retained in adjusted position by spring finger 68 which engages the serrated head of the screw 64.

The lever 66 is pivotally mounted on the casting C, as indicated at 16, and is connected to the throttle valve 34 through link 12.

The adjustment of the parts is such that when the throttle valve is closed'and the engine is idling, the tapered portion 14 of the economizer pin 56 is located in the orifice 54, thereby restricting the flow of fuel to the nozzle 26.

When the engine is drawn from this orifice.

The secondary air valve 26 is shown as a balanced butterfly valve carried by a shaft 18 having reduced journals to minimize friction.

One

of these journals 8!) is shown as being pivotally mounted directly in an adjacent portion of the U central casting B whereas the other journal 80 is shown as being pivotally mounted in a bearing member 82 threadedly secured in a boss provided by the casting B. If desired, both journals may be mounted in separate bearing members.

Arm

8G is adjustably secured to shaft I8 by stud 86, and the end of arm 84 receives the horizontal portion of a piston rod 38 whose lower end is universally connected to the piston 99.

A spring urges the piston 99 upwardly to the position shown in Figure 1 of the drawing. In this position of the parts, the end of the arm E l engages the adjacent surface of the upper casting A, as indicated at 9 t, whereby this upper casting forms a limit stop for the arm 84 and determines the closed position of the air valve It is to be noted that in the closed position of this valve, the edges of the valve do not contact with the sides of the passageway in which the valve is located, and thus sticking of the valve is avoided.

In the normal operation of the carburetor, the air valve 26 is opened by downward movement of the piston resulting from the creation of suction in the chamber 95 beneath the piston 90. This chamber communicates with the upper end secondary air valve normally corresponds to the degree of suction existing in the mixing chamber. It is to be noted that the space above the piston 98 normally communicates with atmosphere through passages H32 and I34.

In automotive practice, the carburetor is usually located at some distance from the main fuel tank and at a level well above the level of this tank. Some means must therefore be provided to draw fuel from the main fuel tank to the fuel chamber of the carburetor. I shall now describe this means.

The central casting B is shown as being provided with an inlet passage ldfi terminating at one end in a threaded portion I83 adapted to be connected to one end of the pipe leading from the carburetor to the main fuel tank of the vehiole. An inlet valve IE9 controls communication between the other end of the inlet passage I96 and the fuel chamber 2d of the carburetor. The valve H8 in turn is regulated by the usual float H2 which is shown as being pivotally mounted on a pin ll l carried by the casting B.

Suction is normally maintained in the fuel chamber 2 by a booster Venturi tube I It having an inlet H3 normally communicating with atmosphere and discharging into a conduit I29 leading to a chamber I22 immediately beneath but separated from the chamber $5 of the secondary air valve. The chamber I22 communicates with the mixing chamber 22 through orifice I2 5, space IES, and duct H3. The tapered lower end of a pin I39 attached to the secondary air valve piston 95 varies the effective size of the orifice i2 1 and thus regulates the flow through the booster H8.

The threat of the booster IIS has radial passages 532 leading to an annular space I34 connecting with a vertical passage I36 communicating with the upper end of the fuel chamber 24. The flow of air through the booster I55 creates an enhanced suction at the throat of this booster and this enhanced suction is communicated to the fuel chamber 26 and is normally sufficient to draw fuel thereinto from the main fuel supply tank of the vehicle. 7

In starting a cold motor it is desirable to supply the engine cylinders with an abnormally rich mixture. This I accomplish by providing a choke plate I38 pivoted on a stud I lll threadedly secured to the central casting B. A spring I42 holds the plate 5 firmly against the adjacent portion of the casting. The plate I38 has an arm I44 adapted to be connected to the usual choke control whereby the plate I38 may be shifted to either extreme position, as determined by the engagement of shoulders I46 and I48 with stop pin I50, or to any intermediate position therebetween.

The choke plate I38 has a generally pearshaped opening I52 which in normal engine operation affords free communication between the booster inlet H8 and atmosphere, but in starting a cold engine the choke plate I38 is so shifted that the opening I52 greatly restricts the admission of air to the booster H5, and in extreme position the plate I38 may entirely out off any admission of atmospheric air to the booster H8.

The quantity of fuel supplied by the nozzle is dependent upon the difference in pressure between the mixing chamber 22 and the fuel chamber 24. By reducing the effectiveness of the booster I I6, the suction created in the fuel chamber 24 thereby is correspondingly reduced, whereupon the nozzle 20 supplies an enriched mixture to the engine which facilitates starting.

The choke plate I38 also has a comet-shaped opening I54 which is normally ineffective, but when the choke plate is moved to choking position this opening registers with a passage I56 communicating with the chamber 95 beneath the secondary air valve piston 90. Varying quantities of air are thus admitted to the chamber 95, depending upon the position of the choke plate I38, and the suction created in the chamber 95 is thus correspondingly reduced. This reduces or completely prevents opening of the secondary air valve 26 to facilitate cold starting.

During periods of engine acceleration it is necessary to provide the engine with an enriched mixture and to reduce the suction existing in the mixing chamber to increase the volumetric efficiency of the engine if maximum acceleration is to be obtained. I shall now describe the means which I have provided for accomplishing these results.

I have shown my carburetor as being provided with an air pump, indicated generally by reference character E68, comprising a cylinder I52 and a piston I6 3. The piston is operated by a rod I66 connected to one end of the lever I56, previously described.

A duct I58 connects the upper end of the cylinder 62 with the space I22 into which the booster H6 discharges. The upper end of the cylinder E62 has an outlet I'IB normally closed by a disk valve I'IE held against its lower seat by a spring I'M. This valve is also capable of seating on the lower end of the passage I04 to cut off communication between this passage and the passage IE2.

The operation of my improved carburetor is as follows: Primary air entering the inlet I4 passes into the chamber l8 and thence into the nozzle 20 where it creates sufficient suction in the restricted throat thereof to lift fuel from the fuel chamber 24. The quantity of fuel thus supplied to the nozzle 26 is regulated by the economizer pin 56 in accordance with the position of the throttle valve 34, whereby the quantity of fuel supplied accurately corresponds With the engine needs. The rich mixture of fuel and air supplied by the nozzle 29 discharges into the upper end of the mixing chamber 22 where it mixes with further air supplied through the secondary air inlet IS.

The quantity of secondary air supplied to the mixing chamber is controlled by the valve 26 which is shifted by the piston 90. This piston in turn is drawn downwardly to valve opening position an amount corresponding to the degree of suction existing in the mixing chamber. The combustible mixture passes from the mixing chamber 22 through throttle bore 32 and past throttle valve 34 to the intake manifold of the engine.

Atmospheric air admitted through opening I52 in choke plate I38 passes through booster Venturi tube H6 and creates a high suction in the throat thereof. This suction is communicated through passage I36 to fuel chamber 24 and suffices to draw fuel thereinto from the main fuel supply tank of the automobile at intervals determined by the rate of fuel consumption of the engine. These intervals are regulated by the float I I2 which controls the inlet valve IIEI.

If the accelerator pedal is depressed, the throttle valve M will be opened a corresponding amount to afford freer communication between the mixing chamber 22 and the intake manifold of the engine. The immediate effect of this will be to increase the suction existing in the mixing chamber. At the same time the upper end of the economizer pin will be partially or completely withdrawn from the restricting orifice 55 to permit freer flow of fuel from the fuel chamber to the nozzle 20.

The opening of the throttle valve 34 will also cause an upward movement of the piston I64 of the air pump ififl. At the beginning of this movement the sub-atmospheric pressure existing in the cylinder 532 is equal to the suction existing in the space I22. As the piston I64 moves upwardly, the pressure in the cylinder I62 and space 522 is immediately increased. This immediately reduces the flow through the booster I I6 and correspondingly reduces the fuel chamber suction created thereby. All of these factors combine to cause the nozzle 20 to supply a richer mixture to the engine, and this richer mixture increases the accelerating ability of the engine.

The increase in mixing chamber suction resulting from the opening of the throttle valve 34 is communicated to the chamber 95 beneath the secondary air valve piston and pulls this piston downwardly, thereby opening the secondary air valve 26. This admits a greater quantity of secondary air to the mixing chamber 22 but the admission of this increased quantity of secondary air tends to reduce the suction in the mixing chamber which in turn would result in partial closing of the secondary air valve. My air pump prevents such closing of the secondary air valve.

Continued upward movement of the piston I64 further compresses the air in the cylinder I 62 until the valve I'l2 opens. It is to be noted that the upper side of the valve I'I2'is exposed to atmosphere and is also acted upon by the very light spring I'M so that a pressure slightly in excess of atmospheric pressure must be created in the cylinder I62 before the valve H2 is raised from its seat.

When the throttle valve is opened quickly through a sufiicient angle, pressure above atmospheric is created in the cylinder I62 and the valve I72 is raised from the outlet Ill] and closes the lower end of the passage I04. This permits air to be pumped from the cylinder I62 through outlet I'lil and passage I02 into the space above the air valve piston 90, thereby depressing this piston and causing further opening of the secondary air valve 26. This results in an increased supply of secondary air to the mixing chamber 22 which raises the pressure in this chamber and increases the volumetric efiiciency of the engine, thereby further increasing its accelerating ability.

In the carburetors of the prior art, difficulty has been experienced in providing means which will afford adequate increase in fuel mixture richness for touch throttle operation and which will not supply an excessively rich mixture when the throttle valve is suddenly opened through a Wide range. It is to be noted that my invention overcomes this difficulty.

In touch throttle operation, that is, when the throttle valve is opened only through a small angle, the air pump I83 does not act upon the secondary air valve 26 but only reduces the fuel chamber suction created by the booster I I6. This permits the nozzle 2% to supply a richer mixture which provides the requisite accelerating characteristics. It is to be noted that under these circumstances the only increased opening of the air valve 26 is such as naturally results from the increased suction created in the mixing chamber 22, as a result of the slight opening of the throttle valve 34.

When the throttle valve is suddenly opened through a wide range, the air pump I60 opens the secondary air valve 26 to its maximum extent. When the accelerating action begins, the engine is operating at less than full speed, and when the engine is operating normally at less than full speed, even with the throttle wide open, thesecondary air valve is not completely opened. Therefore, while the air pump I66 is effective in holding the secondary air valve wide open, the opening of this valve is greater than normal for the corresponding engine speed, even under full throttle conditions.

The result is that large quantities of secondary air are admitted to the mixing chamber 22 which reduce the suction existing in this mixing cham- 7 tity of fuel to the engine when the throttle valve is suddenly opened through a wide range. My accelerator air pump is thus effective in meeting the exacting requirements of an engine to afford maximum acceleration under all conditions.

My invention is not limited to the details shown and described but may assume various forms, and the scope of my invention is to be limited solely by the following claims.

I claim:

1. In a carburetor of the class described, the combination of a nozzle, a fuel chamber from which said nozzle is supplied, a mixing chamber into which said nozzle discharges, a booster for creating a suction in said fuel chamber, said booster having an outlet communicating with said mixing chamber through a duct, a throttle valve controlling communicattion between said mixing chamber and an intake manifold of an engine to which said carburetor is attached, an air pump discharging into said duct, and an operating connection between said air pump and said throttle valve.

2. In a carburetor of the class described, the combination of a nozzle, a fuel chamber from which said nozzle is supplied, a booster for creating suction in said fuel chamber, a mixing chamber into which said nozzle discharges, said booster having an outlet communicating with said mixing chamber through a duct, a restriction in said duct, an air pump, said air pump communicating with said duct between said booster and said restriction, and means for operating said air pump.

3. In a carburetor of the class described, the combination of a nozzle, a mixing chamber into which said nozzle discharges, an air valve controlling the admission of air to said mixing chamber, a fuel chamber from which said nozzle is supplied, a booster for creating suction in said fuel chamber, said booster discharging into a duct communicating with said mixing chamber, a restriction in said duct, a pin controlling said restriction, said pin and air valve being interconnected, an air pump discharging into said duct between said restriction and booster, a valve opening piston operated by said pump, means connecting said piston and air valve, a throttle valve interposed between said mixing chamber and an intake manifold of an engine to which said carburetor is adapted to be attached, and an operating connection between said air pump and said throttle valve.

4. In a carburetor of the class described, the combination of a nozzle, a fuel chamber from which said nozzle is supplied, a booster for creating suction in said fuel chamber, a mixing chamber into which said nozzle discharges, an air valve, an air pump in open communication with said booster whereby any compressive operation of said air pump tends to reduce the effectiveness of said booster, valve opening means operated by said air pump, a second valve interposed between said means and said air pump and opened by air pressure created by said pump whereby said air pump operates said means only after creation of a predetermined pressure in said pump, a throttle valve, and an operating connection between said pump and said throttle valve.

5. In a carburetor of the class described, the combination of a nozzle, a fuel chamber from which said nozzle is supplied, a booster for creating a suction in said fuel chamber, a mixing chamber into which said nozzle and booster discharge, an air valve, an air pump in open communication with said booster, piston and cylinder means for opening said air valve, said piston and cylinder means designed for communication with and operation by said air pump, a loaded valve interposed between said air pump and said piston and cylinder means, a throttle valve, and a connection between said throttle valve and said air pump.

6. In a carburetor of the class described, the combination of a nozzle, a fuel chamber from which said nozzle is supplied, a mixing chamber into which said nozzle discharges, a booster for creating suction in said fuel chamber, a valve for admitting air to said mixing chamber, a throttle valve interposed between said mixing chamber and an intake manifold of an engine to which said carburetor is adapted to be attached, an air pump connected with said throttle valve to operate upon opening of said throttle valve, a discharge conduit for said booster connecting said booster with said mixing chamber, a connection between said air pump and said discharge conduit whereby said pump discharges into said conduit, and means operated by said pump for opening said air valve.

7. In a carburetor of the class described, the combination of a nozzle, a fuel chamber from which said nozzle is supplied, a mixing chamber into which said nozzle discharges, a booster for creating suction in said fuel chamber, a discharge conduit for said booster connecting said booster with said mixing chamber, a valve for admitting air to said mixing chamber, an air pump connected to said discharge conduit for discharge thereinto, control means for opening said air valve, said control means being operated by said air pump, and means for actuating said air pump.

ROBERT F. BRACKE.

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