US2118220A - Carburetor - Google Patents

Description

May 24, 193s.

F. c. MocK CARBURETOR Filed sep@ 52 1935 2 Sheets-Shes?l 1 INVENTOR. `-FRANK A TTORNEY BY 'GJM F. C. MOCK May 24, 1938.

CARBURETOR Filed Sept. 5, 1935 2 sheets-shea 2 ZIj INVENToR. YRANK C. MocK @971 @W( Q ATTORNEY Patented May 24, 1938 NITED STATES PATENT OFFICE CARBURETOR Application'September 5, 1935, Serial No. 39,225

13 Claims.

This invention relates to charge forming de'- vices, and more particularly to carburetors used on internal combustion engines.

An object .of the invention is to produce a carburetor of simplied construction, which will have an increased range of operation, and in which all of the fuel will discharge continuously from one outlet, without transfer spots which give occasional defects in engine operation.

A further object of the invention is to provide a carburetor in which the operation will not be disturbed by the boiling of the fuel in the jet passages.

Further objects and advantages of the invention will be apparent from the following description, taken in connection with appended drawings, in which: l Y,

Figure 1 is a vertical section taken through a carburetor embodying the invention;

Figure 2 is a top plan view of the same;

Figure 3 is a sectional view taken on the line 3-3 of Figure 2;

Figure 4 is a detail View of the cam operating mechanism; and

Figure 5 is a detail View showing a modified form of fuel jet.

In plain tube carburetors as ordinarily constructed, the normal operation of the carburetor is taken care of by means of a main fuel jet discharging into a venturi, the depression at the throat of the venturi giving rise to suction which causes the fuel to flow at a rate corresponding approximately to the rate of air flow. At extremely low speed, however, such an arrangement will not operate satisfactorily, since the depression at the venturi becomes too light to cause any flow of fuel. It is therefore common in many current carburetors to provide a low speed idling jet of considerably smaller capacity than the main fuel jet, and to transfer the fuel delivery to the idlingjet to take care of engine speed corresponding to a car speed of less than M. P. H. This system of a high speed and a low speed jet, however, is not entirely satisfactory, inasmuch as changes in speed and load, along with changes of throttle position, tend to produce occasional periods when the proper amount of fuelis delivered from neither the high speed nor the low speed jet.

The present invention aims to overcome these difli'culties, and also to provide an improved system of fuel delivery and other improved features.

Referring now more particularly to the drawings, the carburetor. comprises an upper body portion I0 consisting of an air horn andv a float chamber cover, a lower body portion I2, and a throttle body I4. The air passage in the lower body portion and throttle body is of circular cross section and is controlled by an ordinary throttle valve i6, mounted on a throttle shaft i8. The 5 air passage in the lower body portion l2 is of rectangular cross section, two of the sides being shaped to give a Venturi cross section when viewed in elevation such as shown in Figure l. One Venturi wall i9 is stationary. but the other 10 wall 2i) is movable according to throttle position in a manner described hereinafter. The carburetor is tted'with a float chamber 2| in which are mounted two floats 22 operating a single float ,valve 24 in the usual manner, the oats being ar- 15 ranged to hold the level, under all inclinations and accelerations of the vehicle, symmetrical vwith respect to the fuel outlet. Y The fuel outlet consists of a siphon delivery passage 25 extending at 28 about three-eighths 20 of an inch above the fuel level, and turned down in the throat of the Venturi air passage to deliver somewhat below the fuel level, at 30. In order to break the siphon and prevent fuel delivery when theA engine is'not generating suc- 25 tion, one or more small holes 32 are provided in the portion 30, slightly above the fuel level. The outlet of the portion may be either single or multiple, but is preferably equipped with a downwardly-extending point 33, for reasons 3o which will be explained hereinafter.

The entrance to this fuel jet is formed by a variable metering orifice 34, which is unobstructed at medium and high speeds but partially closed at smallthrottle opening by a needle valve 36, 35 carried in a sleeve 38, the needle valve and sleeve being threaded together to permit relative ad justment. 'I'he need e valve and sleeve are urged upwardly by a spring 40 against a rocker arm 42 which is operated from the throttle valve by 40 .a rod 44. An adjustable stop screw 46 is provided to limit the upward travel of the needle. The metering orifice 34 is located in aconvenienty central position in the oat chamber below the fuel level, which is indicated by the line L-L.

The movable Venturi wall 20 is xed at its lower e'nd to an arm 50 which is pivoted on a pin 48 extending transversely of the carburetor. The outer end of arm 50 carries a roller 52, which 50 engages in a specially shaped slotted cam member 54 which is `secured to the throttle shaft I8.

The cam 54 is so `shaped that the movable Venturi member 20 remains. in the position shown at full lines in Figure 1 vduring all wide open 55 throttle operation. Also at all wide open throttle operation, the needle valve 36 is raised clear of its seat, so that it does not obstruct the ow of fuel, and the fuel-air ratiois therefore det-ermined merely by the size of the orifice 34. In order to obtain the slightly leaner mixture desired for operation at throttle openings less than wide open, the cam 54 is so shaped that the movable Venturi member 20 is moved to the position indicated at 20A in dotted lines in Figure 1, within throttle angles from nearly full open down to about 20 from closing, or down to a throttle orifice in the particular case described of about :V64 of an inch in width. As the air flow is further reduced, corresponding to a vehicle speed of less than 2O M. P. H., it is desired that the fuel mixture be enriched and, therefore as the throttle is closed below this point, the cam 54 .moves the movable Venturi member 2U tothe right from position 20A; which in decreasing the air orifice exerts more suction on the jet 30 in proportion to the air flow. This action is continued until the throttle reaches a position corresponding to about two and one-half pounds of air per minute, at which point, in order that the restriction at the venturi shall not cause the mixture to be unduly enriched, the needle valve 36 begins to move toward its seat 34. This action is brought about by an arm 55 fixed to the opposite end of throttle shaft |8 which arm at this point comes into contact with and begins to raise rod 44. Further closing of the throttle, down to idle at, say, one-half pound of air per minute, brings the movable Venturi member 20 over to the position indicated in dotted lines at .20B in Figure 1. This restricts the air passage sufficiently to preserve a positive metering suction of adequate value at the fuel jet, while at the same time the needle valve 36 is positioned to give the proper amount of fuel for idling. The proper rate of increase as the throttle is opened from idling or one-half pound of air per minute up to around two pounds of air per minute, may

be obtained by proper selection of the point of the needle valve 36.

It will be noted that at any point in the throttle travel below a position corresponding to about two pounds of air per minute, the needle valve 36 and the Venturi member 20 have been moved in coordination, so that if the throttle be held at any point within this range, and the suction be decreased by lowering the engine speed, the mixture ratio will remain practically unchanged at the value determined by the size of the air and fuel orifices, or become slightly enriched due to the jet outlet being below the fuel level.

Attention is now drawn to the characteristics of the discharge end of the fuel passage. It is known that the ordinary fuel jet must terminate above the fuel level in order that the fuel shall not drain out when the engine is not running. It is also known that the higher the fuel delivery jet is above the fuel level, the greater the deflciency of fuel at low suction. p In the construction shown, the passage 28 extends well above the fuel level, but the antisiphoning vent 32 is placed only slightly above the fuel level, so that even if the siphon were not the taper on in operation the deficiency would be arminimum,

and yet an adequate margin of safety is provided for variations in the fuel level caused by maladjustment of the float valve, etc. An important feature of this structure, however, lies in the fact that the anti-siphoning vent is located in va region of depression preferably equal to or exwith a trough or depression ceeding that on the rjet, so that when the engine is running it does not act as a vent or air bleed, and the downwardly extending jet 30 behaves like a jet positioned below the fuel level, tending to make the mixture rich at very low speeds and wide open throttle; whereas in the common type` of carburetor, the tendency is the opposite. Upon starting, with the Venturi member in position 20B, there is enough suction during cranking to prevent air bleed through vent 32, and to start the siphon.

It is sometimes necessary to close the Venturi member 20 to such a position, as 20B, that it would tend to interfere with the central location of the fuel jet at wide open throttle. To take care of this situation, the member 20 is provided 60 to receive the jet 30. It is also sometimes desirable to employ a jet having two outlets, as shown lat 62 in Figure 5, or more if desired. With such a construction, one of the fuel outlets will be free and unrestricted even though the Venturi member is in the position indicated at 20B in Figure 1.

vA difficulty that has been encountered when relatively small amounts of fuel are drawn from orifices large enough for high speed operation, is that the flow of these orifices at low speed does not occur as a continuous stream; instead, the fuel gathers as a bulb on the tip of the orifice and leaves it in intermittent drops. It has been found that this surface tension effect is overcome if a fine, pointed extension is placed adjashown at 33. The surthen draws it down toit is torn off in the form cent the fuel orifice, as face tension of the fuel ward the point, whence of a continuous spray. v

As best seen in Figure l, the fixed Venturi member I9 is provided at its throat with a small leaf or flap 64 of thermostatic metal, fixed at its upper end and having its lower end free to permit it to decrease the effective Venturi area at low temperatures. The leaf 64 may be sufficiently flexible to be moved back against the Venturi wall at high air velocity. "Ihis change in Venturi orifice is useful in offsetting the change in the air-fuel ratio resulting from the increased density of the air at low temperatures, and should not be confused with a need for enrichment during cranking, due to' the cylinders and manifold being cool, as is done in choking the carburetor. Obviously, a given travel of leaf 64 'will make more difference in Athe fuel-air ratio when the member 20 is in the position 20B than in the position 20. This is compensated for by mounting a pair of pins or stops 66 on the Venturi member 20 in such position that they will 'force the leaf 64 back toward the high temperature position as member 20 approaches the idling posftion 20B.

It will be noted that the Venturi member 20 in its travel passes across the air vent hole 32. This may be employed if desired to obtain a regulation of the mixture ratio by making an air bleed effective only at the lower throttle openings.

Although the invention has been described only with reference to certain embodiments thereof, it will be understood that it is not limited to the modifications disclosed, nor otherwise except in accordance with the language of the appended claims.

I claim:

1. In a carburetor, an induction passage including a venturil haying a movable portion, a manually operated throttle controlling the lntol duction passage, and a connection between the throttle and said movable portion for varying the cross sectional area of the venturi from a minimum at minimum throttle opening to a maximum at a throttle opening slightly less than maximum, and to less than maximum at maximum throttle opening.

2. In a carburetor, an induction passage including a venturi, a fuel jet, a throttle controlling the induction passage, means controlled by the throttle position for varying the cross sectional area of the venturi from a minimum at minimum throttle opening to a maximum at a throttle opening less than maximum and to less than maximum at maximum throttle opening, and means controlled by throttle opening for controlling the flow of fuel to said fuel jet.

3. In a carburetor, a tubular downwardly extending fuel jet having a downwardly facing fuel discharge opening provided with an integral extension tapering to a point and extending from one side of the opening to receive drops of fuel therefrom.

4. In a carburetor, an induction passage including a venturi, a fuel jet discharging posterior to the throat of said venturi, a throttle controlling the induction passage, and means becoming operative as the throttle is moved from wide open to closed position to first increase the cross-sectional area of the Venturi throat, then decrease the same, and finally to decrease-both the crosssectional area of the Venturi throat and the flow of fuel to the jet.

5. In a carburetor, an induction passage including a venturi having a movable portion, a fuel jet discharging within said induction passage, a valve controlling the flow of fuel to said jet, and connections from the throttle to the movable portion and to the valve operative as the throttle opening is decreased from maximum to idling speed to rst increase the cross-sectional area of the venturi, then decrease the same to a minimum, and as said cross-sectional area approaches minimum to move said valve toward closed position.

6. In a carburetor, an induction passage including a venturi of variable cross section, a throttle controlling said induction passage, a fuel jet discharging within said venturi, a valve controlling the -fiow of fuel to said jet, and means becoming operative as the throttle is moved from wide open to closed position to first increase the cross-sectional area of said venturi, then gradually decrease the same to a minimum, and as said cross-sectional area approaches minimum to move said valve toward closed position.

'7. 'I'he method of supplying a carbureted fuelair mixture to an internal. combustion engine which comprises introducing liquid fuel at a variable Venturi restriction in a stream of air to form a fuel mixture, inducing the flow of fuel as a function of air-flow speed, slightly restricting the flow of air at said Venturi restriction while providing an unrestricted flow of mixture from the Venturi restriction to the engine, restricting the flow of air to aless degree while providing a restricted flow of mixture from the Venturi restriction to the engine, and radically restricting both the flow of air and of fuel while providing a radically restricted ow of mixture from the Venturi restriction to the engine.

8. In a carburetor, a venturi comprising a wall movable in'response to temperature changes, a second movable wall, manual means for moving the second movable wall, and means carried by the second movable wall for limiting movement of the first mentioned Wall.

9. In a carburetor, a venturi comprising a flexible wall movable in accordance with air velocity through the venturi to modify the shape of the Venturi restriction, said wall being of thermo-sensitive material whereby its degree of response to a given air velocity varies with temperature, and a second wall movable manually and provided with a member adapted to contact the flexible wall and positively limit its movement.

10. In a carburetor, a throttle, a venturi comprising a wall movable in response-to air velocity through the venturi, a second Wall movable in accordance with throttle position, a fuel nozzle discharging at the restriction of the venturi, and means carried by the second Wall for limiting the movement of the i'lrst wall.

11. The invention defined in claim 10, wherein the degree of responsiveness of the rst wall varies with temperature.

12. The invention defined in claim 10, wherein the first wall comprises a flexible bimetallic sheet adapted to be deflected by the iiow of air through the Venturi restriction.

13. The invention dened in claim 10, wherein the second wall is connected to the throttle by a cam -mechanism adapted to move the second wall into a position of maximum restriction at closed' throttle, an intermediate position at wide open throttle, and a position of minimum restriction at intermediate throttle positions.

FRANK y C. MOCK.

CERTIFICATE OF CORRECTION."

Patent No. 2,118,220. May 2LP, 1958. i

of the above numbered ypatent requiring correction as follows: Page 5,y second column, lines l2 and l5, claim?, after the word "air" insert at said venturi restriction; and that the said Lett-ers Patent should be read with this correction therein that the-same may conform to the record of the case in the Patent Office.

Signed and sealed this 25th day of July, A. D. 1959.

Henry Van Arsdale (Seal) Acting Commissioner of Patents.

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