US2399637A - Carburetor - Google Patents

Description

May 7, 1946. M E, ONE 2,399,637

CARBURETOR Filed Aug. 8, 1942 INVENT OR MALDWYN E.JONES ATTORNEY V for supplying Patented May 7, 1946 CARBURETOR Maldwyn E. Jones, Ferguson, Mo., assignor to Carter Carburetor Corporation, St. Louis, Mo.,

a corporation of Delaware Application August 8, 1942, Serial No. 454,143

2 Claims.

This invention relates to carburetors for internal combustion engines and consists particularly in novel means for supplying fuel and air to the carburetor induction conduit through the a main and idling systems.

Where an automotive vehicle is to be operate on steep inclines, the carburetor should have a main fuel supply nozzle which will prevent the spilling of liquid fuel into the engine intake in case of tilting. An overhead type of nozzle has been found to be effective for this purpose, that is, a nozzle or main fuel passage having a portion which extends sharply upwardly from the fuel bowl to a point above the fuel level and then sidewardly into the induction conduit. With this type of nzzle, the distance the fuel must be lifted by the engine suction is greater than in the case of the inclined main nozzle, such as has been generally used with automotive carburetors. The effect of this increased lift is to decrease the amount of fuel supplied to the engine, particularly at low speeds. This condition is aggravated where the idling fuel system is supplied through the main nozzle metering orifice so that during idling the fuel level in the main nozzle is substantially lowered.

One means of increasing the fuel supply with this type of carburetor, is to provide an idling system which communicates with the fuel bowl independently of the main nozzle so that during idling and low speed operation, the fuel level in the main nozzle passage is not affected. Independent main and idling fuel systems, however, present a problem of providing for proper blending of the discharges from the two systems as the throttle valve is opened or, in other words, at the "transfer pointff The chief problem is to provide for gradual reduction and elimination of the main nozzle discharge during low speed operation when the idling system is functioning.

Accordingly, it is an object the present invention to construct a practical carburetor having an overhead type of main nozzle and indeenrichment of the fuel discharged at low speeds,

particularly when the throttle is opened far enough to cause a discharge through themain nozzle.

It is still another object to provide novel means bleed air to the main and idling systems.

These objects and other more detailed objects hereafter appearing are attained in the carburetor illustrated in the accompanying drawing in which Fig. 1 represents a sectional, partly diagrammatic view of a carburetor illustrating the various features of the .invention.

Figs. 2 and 3 are detailed views illustrating the functioning of the main nozzle passage and air supply means, respectively, at low and high speed operation.

The carburetor illustrated has a downdraft mixture conduit including an air inlet horn portion I, a mixing chamber 2, and an outlet portion 3. A choke valve 4 is mounted in the air horn portion on a shaft 5 and controlled by anysuitable means, either manual or automatic, and a butterfly throttle valve 6 controls the discharge of mixture from the carburetor. Adjacent the mixing chamber are a series of venturis'l into the smallest of whichthe main nozzle I5 discharges. Adjacent the mixture conduit is a constant level chamber or bowl 8 to which fuel is supplied from the usual fuel pump (not shown) through 'a connection 9.

In the lower portion of the fuel bowl there is provided a main metering Jet I2 connected by a cross passage 13 and a vertical. passage M to main nozzle l5 extending sidewardly through Venturi supporting rib l6 into the smallest venturi i, as heretofore noted. Adjacent vertical passage l4, there is a second, parallel passage H in which is secured a iettube l8 forming the idling fuel restriction. Passage ll communicates with the fuel chamber, independently of the main fuel passages, through a port l9. Idling jet tube I8 is connected by passages 20 and 2| to idling port 22 adjacent the edge of the throttle valve when closed. An accelerating pump cylinder 23 is located in the fuel bowl and slidably receives packed piston 24 havinr a piston rod 25. Rod 25 is operatively connected to pump lever 26, pivoted at 21, the lever being connected by a link 28 to an arm 29 rigid with throttle shaft 30. Piston 24 is moved upwardly upon closing of the throttle to draw fuel into the cylinder past inlet check 3!, and is moved downwardly upon closing of the throttlegto force fuel past outlet check 32 and through passages 83 and 34 to nozzle 35 discharging into the mixture conduit.

Nozzle. 35 has an enlarged outlet bore 36 with annularly arranged holes 31 providing communication with atmospheric vent passage 38 for breaking the suction which would otherwise be communicated to the pump nozzle and discharge passages during operation of the carburetor.

Vent passage 38 connects with a passage 39 and a tube 40 which extends into the interior of the air horn and opens against the direction of air fiow therein.

Air passage 39 connects at its lower end with fuel passage M. A restriction element 46 is seated in the upper extremity of passage l4 and has a tubular formation 41 spaced from the wall of the passage and terminating below main nozzle I5,

but above the normal fuel level :r-zr. A passage 48 branches from passage 39 and connects with idling passage ll. Restrictions 49 and 50 provide for metering the idling air and fuel, respectively. Restricting element 46 is removable for adjusting the amount of air supplied to the main nozzle system.

The supply of fuel through main metering jet i2 is controlled by a metering .rod 55 yieldingly connected to lever 26a, operated from the throttle by link 60. The metering rod is provided with an enlargement 56 which is positioned to seat in metering jet -|2 as the throttle is closed so as to substantially cut off the main fuel passage from the fuel bowl and, conversely, as the throttle is opened, communication between the main nozzle and the bowl is gradually opened.

Restricting element 46 in air duct branch 39 serves an important function in properly adjusting the flow of fuel through the main nozzle passages. Tube 41 on this element extends down into passage l4 so that fuel passing upwardly to the main nozzle must go around this tube. ing operation of thecarburetor under low suction conditions, I have found that fuel in passage I4 substantially seals this tube 41, and thus restricts the emission of air into the main nozzle so that, accordingly, a relatively rich mixture is supplied, as is desirable under these conditions. However, as the speed of the engine, and, correspondingly, the suction in the carburetor increases, air is caused to emit from restriction tube 4! in a jet which strikes the surface of fuel in passage I4 and tends to drive this surface downwardly. The effect of this air jet is to substantially lean out the mixture supplied by the carburetor at higher suctions. This leaning out is produced both by the addition of air through the restriction 46 and by the actual retarding effect of the jet upon the fuel. This effectis illustrated diagrammatically by Figs. 2 and 3. Fig. 2 represents the condition.

of the main fuel passage under low speed operation when fuelpassing around air restriction tube 41 substantially seals this tube to prevent bleeding of air therethrough. Fig. 3 represents a condition under high speed operation when the jet of 55 5 atmospheric.

Dur-

Air tube 40 has an inlet opening located substantially inwardly from the wall of the air horn and facing directly against the normal direction of air flow so that the pressure therein approaches This tube supplies air which has passed through the usual cleaner to the main and idling fuel systems and also for bleeding out suction on the accelerating pump nozzle. The arrangement of the air passage is thus substantially The above carburetor, accordingly, has the previously mentioned advantages of an overhead main fuel nozzle and independent main and idling fuel systems while, the disadvantages sometimes accompanying these features, such as the tendency to excessive leanness at low suction with the throttle substantially open, due'to the increased lift of fuel, and the poor blending of the main and idling discharges at the transfer point,

have been largely overcome.

The invention maybe modified as will occur to those skilled in the art and the exclusive use of all modifications as come within the scope of the appended claims is contemplated.

I claim:

1. In a carburetor, an induction conduit, a constant level chamber, a fuel passage having a first portion extending from said chamber upwardly above the normal fuel level therein and a second portion extending sidewardly intd said conduit;

and an atmospheric duct having a tubular element extending into said first portion and opening below the level of said second portion. but above the normal fuel level and facing against the direction of fuel flow in said passage whereby the air and fuel flow, respectively, in said duct and said passage directly oppose and tend to retard each other.

2. In a carburetor, an induction conduit, a fuel bowl, a main fuel passage having a first portion eration at low suction, fuel flows around and substantially ,seals said duct extremity while at relatively high sections the air jet emitted from said element strikes the fuel surface and tends to retard the fuel flow in said passage.

MAIDWYN E. JONES.

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