US1967708A - Carburetor - Google Patents

Description

y 9 19340 G. E. ERICSON 1,967,708

CARBURETOR Filed Jan. 16, 1931 5 Sheets-Sheet 1 550,245 Hie/550M INVENTOR ATTORNEY 6. E. ERICSON July E934 CARBURETOR Filed Jan. 16, 1.951 5 Sheets-Sheet 2 INVENTOR ATTORNEY J y 24, 1934- G. E. ERIICSON mazms CARBURETOR Filed Jan. 16, 1951 5 Sheets-Sheet 4 Gfiafi E i /650M BNVENTOR I 1 ATTORNEY G. E. ERICSON July 24, 1934.

CARBURETOR Filed Jan. 16, 1951 5 Sheets-Sheet 5 fl 1; v

650265 E ERIC-501V 11v VENTOR A TTRNEY Patented July 24, 1934 UNITED STATES PATENT OFFICE CARBURETOR Application January 16, 1931, Serial No. 509,105

8 Claims.

This invention relates to carburetors and more particularly to downdraft carburetors for internal combustion engines in which the fuel for high and low speed operation is discharged 6 through separate nozzles. In the plain tube type of carburetor, the fuel for low speed operation is ordinarily supplied through an idle" passageway which discharges into the mixing conduit at a point near the edge of the but- 10 terfiy throttle valve when it is in closed or nearly closed position. The fuel for high speed operation is ordinarily supplied through a main nozzle which discharges in the central part of the mixing conduit at a point anterior to the throttle valve.

It is common practice to connect the idle and the main nozzle to each other and then through a common supply passage to the source of fuel supply, and a metering orifice or passageway of 2 calibrated capacity is usually located in the common connection. The reason for this is that it is not desirable to have the main fuel nozzle begin to discharge fuel until a fairly rapid rate of air flow through the mixing conduit has been attained. If the main nozzle were permitted to discharge fuel with the throttle in fully closed position, the fuel would come off irregularly in slugs which would not be vaporized on account of the slow air speed.

Even with this arrangement many difficulties are encountered, for the suction which is built up by the idling conduit tends to withdraw the fuel from the main nozzle so that it contains nothing but air, and if the throttle is suddenly opened, a large amount of air can pass through the mixing conduit of the carburetor while the main nozzle is drawing in enough fuel to fill it to the point where it will begin discharging. This condition causes a lag in the acceleration of the motor which must be corrected by a pump, and places an undue burden on the pump which, in turn, gives rise to serious difficulties due to changing temperature.

It will be understood that when the throttle is suddenly opened, the absolute pressure in the intake manifold of the engine is greatly increased, causing condensation of fuel on the walls of the manifold and a corresponding momentary reduction in the fuel content of the mixture flowing into the engine. A correction for this is ordinarily made by the provision of an accelerating pump, but this is not an ideal solution, for the pump discharges in proportion to the movement of the throttle and not in' proportion to the amount of air flowing through condition.

the carburetor. It is accordingly desirable to keep the pump as small as possible and to avoid placing extra burden on it.

Another difliculty in the operation of downdraft curburetors of the type shown in this application relates to what is known as percolation. Gasoline as ordinarily sold at the present time is a mixture of a number of diiferent hydrocarbons having boiling points ranging from slightly above 100 degrees Fahrenheit to nearly 400 degrees Fahrenheit. Where a small amount of the fuel is contained in the passageways of the carburetor and where the carburetor is subjected to high temperatures as in the case of the downdraft carburetor shown herein, the constituents having lower boiling points tend to form small bubbles in the upwardly extending passageways such as the nozzle and as these bubbles rise in the nozzle they tend to create a flow of fuel out of the nozzle and into the carburetor mixing passages even when the engine is not in operation. This difliculty is especially apparent when the engine is operated in such a manner as to bring it to a high temperature and then stopped for a few minutes. Percolation of this character is frequently suflicient to completely empty the contents of the bowl or float chamber into the intake manifold of the engine, causing an almost impossible starting It is an object of this invention to produce a carburetor in which the discharge of the main nozzle may be delayed until the air speed through the mixing conduit has been increased to such an extent that the fuel discharged from 99 the main nozzle will be properly vaporized under all conditions.

It is a further object of this invention to produce a carburetor of the above described type in which the main nozzle will not be emptied of fuel during the operation of the idle tube, whereby the main nozzle may begin to discharge instantly when the throttle is opened.

It is a further object of this invention to produce a carburetor in which the main nozzle and 100 the idle tube are supplied through separate calibrated passageways so that each may be controlled or adjusted without affecting the other.

It is a further object of this invention to produce a carburetor in which the flow of fuel from the float chamber to the main nozzle is cut oil whenever the engine is not in operation, so that the emptying of the bowl or float chamber into the mixing conduit by percolation thru the main nozzle will be prevented.

Other objects of.the invention will appear from the following description and the accompanying drawings, referring to which:

Figure 1 is a vertical sectional view of a downdraft carburetor embodying oneform of my invention, the section being taken along the line 1-1 of Figure 2.

Figure 2 is a plan view of the carburetor shown in Figure 1.

Figure 3 is a side elevation of the carburetor shown in Figure 1, with parts in section for better illustration thereof, the section being taken along the line 3-3 of Figure 2.

Figure 4 is a side elevation of the carburetor shown in Figures 1 to 3 with parts in section, the section being taken along the line 4-4.

Figure 5 is a side elevation of the adjustable coupling for the metering rod, with parts shown in section for better illustration thereof.

Figure 6 is a diagrammatic view of the device.

The reference numeral 1 indicates a lower casting forming the main body member of the carburetor. This casting is provided with a flange 2 by means of which it may be attached to the intake manifold '70 of an internal combustion engine. An upper casting 3 is attached to the upper end of the body member 1 and forms an air inlet or air horn. A downdraft mixing conduit 4 having its inlet end in the upper end of the air horn and its outlet in the flange 2 is formed in the carburetor; the lower part of the mixing conduit, as indicated at 5, may be considered the main mixing chamber of the carburetor. A choke valve 6 is provided for controlling the admission of air through the air horn, and a throttle valve '7 is provided to control the rate of discharge of the air and fuel mixture to the engine.

In this embodiment of the invention, a nest of three venturis is used comprising a primary venturi 8, a secondary venturi 9, and a main venturi 10. Each of the first two venturis discharges at a point adjacent the throat of the next larger venturi. The lower casting 1 has a float chamber 11 made integral therewith, and fuel is supplied to the float chamber through a connection 12 from any suitable source. A valve 13 controlled by a fioat 14 controls the admission of fuel to the float chamber and maintains the height of the fuel substantially at the level shown in Figure 4. This level is also indicated by the broken line A-A in Figure 3.

The fuel for the low speed operation of the carburetor is supplied through a passageway 15 which receives the fuel below the fuel level in the float chamber 11 and is connected to a metering orifice 16 in a cross passageway 17 which leads to the downwardly extending idle passage 18 from which the fuel is discharged at the edge of the'throttle valve '7 through an elongated port 19. An adjusting screw 20 controlling the admission of air at the upper part of the idle passage 18 is provided to prevent syphoning of the fuel when the carburetor is not in operation. The air for this purpose is admitted to the port 21 and adjusted by the tapered end of the screw 20 which acts as a valve. It will be obvious that the fuel supply for low speed operation can be fully controlled by suitably calibrating the capacity of the restriction 16 and the shape, size, and position of the port 19, and the adjustment of the screw 20.

The fuel for high speed operation is supplied through a nozzle 22 which is connected by means of the passageways 23 to the fuel chamber. A metering plug 24 is mounted-in the inlet end of the passageways 23 and has a calibrated passageway extending therethrough to control the admission of fuel to the main nozzle. A metering rod 25 provided with one or more steps 26 of different diameter extends into the metering plug 24, and a valve portion 2'7 is formed on the metering rod just above the steps 26 so that when the rod is pushed all-the way in -to the metering plug, the flow of fuel will be entirely out off, as indicated in Figure 4. The position of the metering rod is controlled by the position of the throttle in the following manner:

The throttle shaft 28 is provided with a' crank 29 which is connected by means of a link 30 to the crank 31 on the rock shaft 32 which is mounted on a pillow block 33 on the member 34 which forms the cover of the float chamber of the carburetor. The crank 31 is provided with a clip 35 carrying a pintle or crank pin 36 which is pivotally engaged with the upper end of the tube 37, as shown in Figures 1 and 4. The lower end of the tube is turned in to slidably fit the metering rod 25, and the upper end of the metering rod is headed, as indicated at 38. A spring 39 is placed in the tube 37 between the pin 36 and the head of the metering rod so that the rock shaft 32 and throttle shaft 28 may have a continued movement after the valve 27 has come in contact with the metering plug 24.

It will be noted that the rock shaft 32 is pro vided with a crank 40 connected by means of a link 41 to the rod 42 which operates the piston 43 in the cylinder 44. These parts belong to the accelerating pump of the carburetor and form no part of this invention. It will be understood that my invention is to be applied to carburetors, irrespective of whether they are equipped with an accelerating pump or not, and that one of the objects of the invention is to make it possible to use a smaller accelerating pump, or, in some cases, to eliminate it altogether. For the purpose of this specification, it will sufficient to say that on the up-stroke of the piston 43, fuel is withdrawn from the float chamber 11 and on the down-stroke of the piston 43, fuel is discharged through a nozzle 48 to the mixing conduit of the carburetor.

The operation of the device is as follows:

When the throttle is in the position shown in Figure 3, the suction on the outlet side of the throttle valve will draw air and fuel through the port 19 to supply the needs of the engine, and as the throttle valve is gradually opened, this fuel supply is continued until the throttle valve has moved far enough from the port 19 to partially relieve the suction at that point or at least to relieve it to such an extent that the air flowing through the passageway 21 will kill the suction in the idle tube 18 to such a point that it will no longer pull liquid fuel up to the level of the cross air passage 1'7. It will be obvious that the idle tube will discontinue its operation gradually and not abruptly during gradual opening movements of the throttle.

As the throttle is opened, the throttle shaft 28 turns in a clockwise direction (with reference to Figure 1) pushing the link 30 upwardly and rocking the shaft 32 in a clockwise direction. During the first stages of the opening movement of the throttle, the spring 39 retains the valve 27 on its seat, preventing the discharge of fuel from the nozzle 22, but as the opening movement is continued, the valve 27 is gradually lifted off its seat and the nomle 22 comes into operation. The nozzle is always filled with fuel, because there is no way of getting it empty, and even if an air bleed to the nozzle is provided, there will generally be sumcient leakage at the valve 27 to keep the nozzle full.

After the valve 27 has started to open, a very slight further movement of the throttle will bring it to fully open position. It will be understood, however, that the extent of throttle movement necessary to fully open the valve 27 can be made to depend upon the taper of the valve 27, the diameter of the valve, and the length of thecranks 29 and 31. The carburetor will be so calibrated by adjustment of these various elements that the main nozzle will begin to discharge fuel in the same ratio as the idle ceases to discharge.

In case an adjustment is desired for the position of the valve 27, the metering rod and operating means therefor may be formed in the manner shown in Figure 5. The tube 45 is substituted for the tube 37 in the other figures. The tube 45 is threaded at its lower end and provided with a cap member 46 which may be adjusted up or down on the tube and held in place by a lock nut 47. The-spring 39 may be the same as used in the device shown in Figure 4, and the metering rod may also be the same. It is obvious that many other forms of adjustment will suggest themselves to a mechanic skilled in the art.

I claim:

1. In a downdraft carburetor of the plain tube type, means forming a downdraft mixing conduit, a throttle valve near the lower end of said conduit controlling the flow of mixture therethrough, a plurality of coaxial venturis in said conduit above said throttle valve, means forming a main fuel supply chamber, a main fuel supply nozzle leading from said fuel supply chamber and discharging into the inner of said venturis, a valve for controlling the flow of fuel through said nozzle, said valve being adapted to entirely cut off the flow of fuel through said nozzle in one operated position thereof, said valve being operatively connected to said throttle and being moved to fully closed position by a closing movement of said throttle.

2. In a downdraft carburetor of the plain tube type, means forming a downdraft mixing conduit, a throttle valve near the lower end of said conduit controlling the flow of mixture therethrough, a plurality of coaxial venturis in said conduit above said throttle valve, means forming a main fuel supply chamber, a main fuel supply nozzle leading from said fuel supply chamber and discharging into the inner of said venturis, a valve for controlling the fiow of fuel through said nozzle, said valve being adapted to entirely cut off the flow of fuel through said nozzle in one operating position thereof, said valve being operatively connected to said throttle and being moved to fully closed position by a closing movement of said throttle, said valve being moved into fully closed position before the throttle valve reaches fully closed position, and resilient means in the connection between said throttle and said valve for permitting the throttle to continue its closing movement after said valve is entirely closed.

3. In a carburetor, means forming a mixing conduit, a throttle valve controlling the flow of mixture therethrough, a fuel nozzle for discharging fuel into said conduit, a metering device for controlling the admission of fuel to said nozzle, said metering device comprising means forming a calibrated passageway, a metering rod having a portion of smaller diameter than saidpassageway normally extending therein, a valve portion on said metering rod of larger diameter than said passageway, a connection between said throttle valve and said valve, said connection closing said valve before said throttle reaches closed position, and said connection comprising a yieldable member and adapted to be compressed after said valve has been closed to permit the completion of the closing movement of the throttle.

4. In a carburetor, means forming a mixing conduit, a throttle controlling the passage of mixture through said conduit, a single means for supplying fuel to said carburetor during low speed operation comprising a passageway discharging adjacent the edge of said throttle, a single means supplying all of the fuel required for said carburetor for constant speed operation while said throttle is in open position comprising a main fuel nozzle discharging anterior to said throttle, and a valve for cutting off one of said fuel supply means as the other of said fuel supply means goes into operation.

5. In a plain tube downdraft carburetor, means forming a downdraft mixing conduit, a throttle valve controlling the flow of mixture through said conduit, means forming a fuel supply chamher, an idle passage in the general form of an inverted U receiving fuel from said supply chamber and discharging adjacent the edge of said throttle, said throttle being located below the level of fuel in said supply chamber, an air bleed in said idle passage above the level of fuel in said supply chamber, a venturi in said conduit having its throat slightly above the level of the fuel in said supply chamber, said venturi discharging downwardly and terminating below the level of the fuel in said supply chamber, a main fuel nozzle connected to said supply chamber independently of said idling passage and discharging near the throat of said venturi,

said idling passage and said main nozzle forming respectively the sole means for supplying fuel to said carburetor at constant low speed operation and constant high speed, and a valve operated by said throttle for controlling the flow through one of said fuel supply means, said valve being adapted to prevent the simultaneous operation of said supply means. I

6. In a carbureteor of the plain tube type,

means forming a mixing conduit, a throttle controlling the passage of mixture through said conduit, means forming a constant level fuel supply chamber, a main nozzle connected to said fuel supply chamber and discharging in said mixing conduit slightly above the level of fuel in said supply chamber, a venturi surrounding the discharge outlet of said nozzle, means for supplying fuel to said carburetor for low speed operation, and means to prevent the discharge of fuel from said main nozzle until a flow of air through said mixing conduit has been produced of sufficient velocity to vaporize fuel discharging from said main nozzle.

7. In a downdraft carburetor, means forming a constant level liquid fuel chamber, means forming a downwardly directed mixing conduit, a throttle valve near the lower end of said conduit, a main fuel nozzle connected to said fuel chamber at a point below the fuel level' mounted in said mixing conduit, a main nozzle for conveying fuel from said constant level fuel chamber to said mixing conduit, said main nozzle having its discharge outlet just slightly above the fuel level of said chamber, a valve for cutting off the flow of fuel from said constant level chamber thru said main nozzle, connections between said throttle and said valve for closing the throttle when the valve is closed, an idling passageway leading from said constant level chamber upwardly to a point above the fuel level and then downwardly to a point adjacent the edge of the throttle when same is in closed position, said idling passage having a vent at a point above said fuel level and being supplied with fuel from said constant level fuel chamber independent of said main nozzle.

GEORGE R. ERICSON.

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