US2182090A - Carburetor - Google Patents

Description

Dec. 5, 1939. M. MALLORY 2,132,090

CARBURETOR Filed Oct. 21, 1936 Patented Dec. 5, 1939 UNITED STATES PATENT OFFICE 4 Claims.

to means for controlling the mixture ratio as the position of the throttle and the load vary.

The primary object of the invention is to pro- 7 vide a carburetor of simple construction, in which the mixture ratio is automatically controlled to insure smooth and economical operation during variations in the throttle opening and in response to variationsin engine speed and load.

A further object of the invention is to provide improved means whereby, upon an increased throttle demand, the mixture will be enriched temporarily until there is a corresponding increase in the speed of the engine.

A still further object of the invention is to provide improved means for adjusting the mixture ratio as affected by an increase in the throttle opening.

The specific construction of the invention in its present embodiment and the principles governing its operation will be more particularly explained in connection with the accompanying drawing in which- Fig. 1 is. a verticalsectional view taken centrally of a carburetor constructed according to. the invention. V

Fig. 2 is an enlarged sectional detail view taken on the line 22 of Fig. 1, showing a means for adjusting the mixture ratio for the higher speeds.

The invention is illustrated in the drawing as applied to a down draft carburetor, which has an air inlet 5, a mixing chamber 6, and a fuel mixture outlet 1 adapted to be connected with the engine intake manifold. The mixing chamber 6 is formed with a venturi '8 and fuel is discharged into the center of this venturi through a jet nozzle 9 from a well l0. The fuelis supplied to the'well I0 through a passage II from a bowl l2, to which the fuel'is admitted through a conduit i3 and a valve l4 controlled by float IS in the usual manner.

The fuel mixture outlet 1 is controlled by a main throttle valve l6 mounted on a stem II, which is provided with an arm l8 connected to a throttle control rod l9. A link 20 connects the arm l8 to a metering pin 2| provided with a fiat taper 22, which opens the port 23 leading to the nozzle 9 in synchronism'with the opening of the throttle valve I6.

An air valve 24 mounted on a stem 25 controls the direct admission of air to the mixing chamber 6. An arm 26 is securedrto the stem 25. A rod 21 pivotally connected to a rearward extension 28 of the arm l8 telescopes into theend of a rod 29 which is pivotally connected to the arm 26 and is provided with an adjustable stop nut 30.

Thus it "will be seen that, when the throttle valve I6 is closed, the valve 24 will be positively 5 closed in synchronism therewith. If the valve l6 is opened slowly, the valve 24, which is unbalanced,*will open at the same time, due .to air flow and pressure thereon. If the valve I 6 is 'opened quickly, however, the valve 24 will lag be- 10 hind, dueto the influence of a dash pot, which comprises a piston 3| reciprocable in a cylinder 32 and connected by a connecting rod 33 to the arm 26. The piston 3| is provided with a relief vent 34 covered by a valve 35 to permit its ready return when the throttle is closed.

A venturi 36 is formed in the air inlet passage above the valve 24 and an air passage 31 with an outlet 38 into the venturi connects the latter to the lower end of the dash pot cylinder 32. As 20 the throttle valve I6 is opened .for acceleration, the lagging of the valve 24 creates an increased vacuum in the vicinity of the nozzle 9, thus temporarily enriching the mixture without imposing a permanent load'upon the valve 24 and without 25 the necessity of using an accelerating pump, until the engine picks up speed, thereby increasing the suction through the venturi 36 and through the passage 31. This in turn hastens the open- .ing of the valve 24, relieving the increased vac- 30 uum around the fuel nozzle and restoring the normalmixture ratio. An adjusting screw 39, extending into the passage 31, determines the rate at which the dash pot permits the valve 24 to open in response to an increase in the main 35 throttle opening.

.As the throttle is opened, the mixture depends in part upon the degree of vacuum around the nozzle 9. If the ultimate opening of the valve 24 with reference to the valve I6 is decreased, the 40 vacuum will be increased and the mixture enriched. In order that this may be adjusted, the arm 26 is provided with a longitudinal slot 40. The pin 4|, which receives the end of the connectlng rod 33, is as shown in Fig. 2, in the form 5 of a shouldered stud 42 with a threaded end-secured in the slot 40 and is adjustable longitudinaly thereof. Thus, by adjusting the pin toward the outer end of the slot, the mixture may be enriched and by adjusting the pin in the opposite 50 direction, it may 'be made leaner.

A by-pass 43 is connected at its-lower end to the fuel nozzle 9 and at its upper end to a nozzle 44, which projects into the upper venturi 36. The eflective capacity of this by-pass is adjusted by a screw 45. when the throttle is in idling position, air is drawn through this by-pass and mixes with the fuel discharged from the nozzle 9 to form when the valve I6 is opened, thereby restricting the supply of air to the fuel mixture.

In order to control the mixture ratio automatically during variations in the throttle opening and in response to variations in engine speed, the invention comprises a main throttle valve and an air valve with a fuel jet nozzle between them. The main throttle valve, which is on the engine side of the fuel nozzle, is positively actuated through the throttle control rod. The air valve, which is unbalanced, is positively closed by the closure of the main throttle valve, but is opened only by air flow or suction. A dash pot connected to the air valve retards the opening of the latter if the main throttle valve is opened quickly, thereby maintaining a suificient suction.

around the nozzle to temporarily enrich the mixture until the engine picks up speed. Unlike a spring loaded valve, however, the dash pot does not impose a permanent load and does not permanently increase the vacuum around the fuel nozzle. 7

In the operation of noted that all of the fuel foridling, for acceleration or for operating under a heavy load is always supplied from the well It) through a single port to the nozzle 9. No accelerating pump or power jet piston is necessary. The fuel is metered by the pin 2| in proportion to the opening of the throttle valve 16.

The air for the idling mixture is drawn through the by-pass 43 and mixes with and atomizes the fuel before it leaves the nozzle 9. As the valves l6 and 24 are opened, there is a suction through the venturi 36 which, as the speed increases, becomes suflicient to stop the air flow through.the by-pass 43. The suction through the venturi 8 is then suflicient to atomize the fuel as it leaves the nozzle 9.

Since the unbalanced valve 24 may be opened only by air flow or pressure, if the throttle valve I6 is opened quickly, the valve 24, temporarily retarded by the dash pot, lags behind the valve l6 until the engine picks up speed. The suction developed by the increasing speed of the engine first acts directly upon the valve I6 and then,

as suction is developed through the venturi 36 and in the passage 31, accelerates the bleeding of the dash pot. As a result, the mixture is temporarily enriched for acceleration without the use of an accelerating pump. Since the .yalve 24 is not spring loaded, the mixture ratio again becomes normal as soon as the desired acceleration is effected. If, however, it should be desirable to have a slightly richer mixture for high speed, this may be obtained by adjusting the pin 4! so that the valve 24 will not open as wide as the valve l6. This increases the suction around this carburetor, it will be the fuel nozzle 9, with a consequent increase in the mixture ratio. 4 While I have shown and described in detail one specific embodiment of the invention, it is to be understood that this is merely illustrative and that the invention also embraces such modifications as may be made within the scope of the appended claims.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent, is: y

l. A carburetor comprising a fuel mixture chamber with a venturi having a fuel inlet, an air inlet, and an outlet adapted to be connected to an engine intake manifold, a main throttle valve controllingsaid outlet, an unbalanced valve controlling the air inlet, a dashpot tending to retard the opening of the unbalanced valve, means for closing both valves in unison, said means serving to open the throttle valve but held, out of operative relationship with the unbalance. valve during opening movement of the throttle valve, another venturi on the atmospheric side of the unbalanced. valve, and a passage connecting the dash pot to the last mentioned venturi, whereby suction through the said venturi tends to accelerate the movement of the piston as the unbalanced valve opens.

. 2. A carburetor comprising a passage having an air inlet and a fuel mixture outlet with two venturis between them, a fuel supply duct with a nozzle discharging into the second venturi, a main throttle valve on the engine side of the second venturi,'an auxiliary unbalanced valve between the first venturi and the fuel nozzle adapted to be opened by air flow and pressure alone, an idling air by-pass from the first venturi into the fuel supply duct, and means for positively closing the unbalanced valve in synchronism with the closure of the main throttle valve, said means serving to open the throttle valve but being out of operative relationship with the unbalanced valve during said opening movement.

.3. A carburetor comprising a passage having an air inlet and a fuel mixture outlet with two venturis between them, a fuel supply duct with a nozzle discharging into the second venturi, a

main throttle valve on the engine side of the second venturi, an auxiliary unbalanced valve between the first venturi and the fuel nozzle adapted to be opened by air flow and pressure alone, a dash pot with a piston connected to the unbalanced valve to retard the opening of the latter, means for bleeding the dash pot into the first venturi, and means for positively closing the unbalanced valve in synchronism with the closure of the main throttle valve.

4. A carburetor comprising a passage having an air inlet and a fuel mixture outlet with two venturis between them, a fuel supply duct with a nozzle discharging into the second venturi, a main throttle valve-on the engine side of the sec.- ond venturi, an auxiliary unbalanced valve between the first venturi and the fuel nozzle adapted to beopened by air flow and pressure alone, a dash pot with a piston connected to the unbalanced valve to retard the opening of the latto the opening of the main throttle valve.

MARION MALLORY;

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