US2323721A - Carburetor - Google Patents

Description

July 6, 1943.

W. F. M LINDON CARBURETOR Filed April 10, 1941 v I glnucufot WE MZfzmuzz Patented July 6, 1943 UNITED STATES PATENT OFFICE 6 Claims.

This invention relates to carburetors of the capillary fuel feed type, and it has for its general object the provision of a carburetor of simplified construction and improved efllciency which operates upon the principleof what may be termed controlled accelerated capillarization that makes it for the first time possible to employ a wicktype fuel feed with automatic maintenance of substantially constant mixture proportion throughout substantially the entire speed range of the auto vehicle with which the carburetor may be associated.

Another object of the invention is to provide a carburetor in which the liquid fuel is raised from a supply at constant level by the capillarity of a wick of substantially conical form, the base of which isfsubmerged below the liquid level of the supply, and in which the air constituent of the mixture is passed through an intermediate zone of said wick, which zone, being of less diametc! than the base of the wick, is incapable of passing upwardly toward the apex as much liquid as it receives from the base, whereby in the absence of absorption by the intersecting column of air it becomes supersaturated, assuring an adequate amount of liquid fuel available in the zone of gas and liquid contact to meet the maximum engine demands.

A further object of the invention is to provide a carburetor of the type described, in which the apical region of the cone-shaped wick including the side portions adjacent the apex, is closed by an imperforate cap, the lower edge of said cap defining the upper limit of the zone in which the air passes through the wick in contact mm the liquid to form the combustible mixture.

Still a further object of the invention is to provide a region of subatmospheric pressure automatically maintained during the operation of the carburetor Within the region of the cone occluded by the cap, the function of which is to accelerate the capillary fuel feed by drawing liquid upward through the zone of gas and liquid contact, and to provide within the apical portion of said cone a reserve body of combustible mixture to supply the void or hiatus which occurs at times when the throttle valve is suddenly opened while the cylinders of the engine are operating under a relativelyhigh vacuum.

Still another object of the invention is to provide a choke valve adjustable for varying the volume of air admitted to the carburetor whereby the carburetor may be from time to time set according to the particular engine with which it is employed, the type of fuel used, and atmospheric 1 conditions.

Another object of the invention is the provision of a throttle control auxiliary air inlet whereby additional air is'progressively admitted to the mixture at throttle positions below a determined inturned flange or rim low speed datum, it having been found by experiment that such an adjunct is desirable to prevent undue richness of mixture at verylow operating speeds.

Other objects of the invention wil1-appear as the following description of a preferred and practical embodiment of the invention proceeds.

In the drawing which accompanies and forms a part of the following specification, and throughout the several figures of which the same characters of reference have been employed to designate identical parts:

Figure l is a. vertical diagrammatical section through a carburetor embodying the principles of the present invention;

Figure 2 is a cross-section taken along the line 22 of Figure 1;

Figure 3 is a front view in elevation of the lower part of the carburetor showing the auxiliary air inlet valve;

Figure 4 is a section taken along the line 4-4 of Figure 3;

Figure 5 is a section taken along the line 5-4 of Figure 4; and

Figure 6 is a diagrammatic view showing two carburetor units in tandem arrangement.

Referring now in detail to the drawing, the numeral l represents in general the casing of the carburetor, which as shown is of the down draft type, the lower end 2 being preferably cylindrical for attachment to the manifold fitting, and containing the throttle valve 3. The casing I preferably includes the conical lower portion 3' at the upper end of which is the annular supply chamber 4 having a connection 5 to a float chamber 6 supplied with liquid fuel from' any suitable source. The float 1 at the float chamber inlet rides at such height with reference to the annular chamber 4 that the liquid level I in the annular chamber is preferably close to the top of said annular chamber. A perforate screen baflle 9 of conical form is secured to the inner rim of the annular supply chamber, tapering upwardly to the apex l0. This conical baflie may preferably be made of woven wire mesh material.

A conical wick I l flts upon the screen baflle 9 with its larger or base end l2 submerged below the liquid level in said annular supply chamber. The latter chamber may be provided with the i3 at its upper end, restricting the, opening in its top to an annulus having substantially the width of the wick, so as to prevent the splashing of liquid fuel from the supply chamber 4 due to vibrations or jolts of the auto vehicle.

The casing of the carburetor continues upward from the outer edge of the supply chamber 4 in the form of a frusto-conical hood I 4, the top of which terminates in a cylindrical pipe l5 to which the air cleaner l6 may be fitted.

An imperforate conical cap l1. rests upon the apical portion of the conical wick and extends down upon the sides of the wick to a point determined by the bottom edge l8 of said cap. A zone IQ of the wick intermediate its base and the portion occluded by said cap is left bare and open, and constitutes the region of air and liquid contact. The air for the combustible mixture enters through the pipe i5, passes between the cap I! and hood ll in the form of an annular curtain, and then passes through the wick in the exposed zone l9. Below said zone the carbureted air coming in from all sides becomes intimately mixed and passes down through the throttle control lower end 2 of the carburetor into the manifold.

The cap I! is axially movable to and away from the conical wick, restricting more or less the air passage between said cap and the hood ll, and thus acting as a choke valve to vary the volume of air admitted to the carburetor. The means for operating said cap as a choke valve may consist of-the rod which passes through the pipe l5, extending above the upper end of the air cleaner where it connects with a bell crank 2| rocked by the pull or push of an adlusting rod 22.

The choke valve is designed to be closed through manual or pedal operation of the rod 20 at time of starting, to facilitate starting.

The cap I! is also provided with a setting adiustment whereby it may be given a determined normal axial position with respect to the wick.

A conventional setting adjustment is shown, consisting of a turn-buckle 23 by means of which the rod 20 may be lengthened or shortened, lifting or lowering the cap I'l.

While the wick ll may be made of any suitable material, it is preferably woven or knit from glass fibers or other extruded filaments, for these are free from the fuzziness produced by the ends of the short staples of spun fibers, and will not catch and hold dus etc., so that the glass wick remains clean indefinitely. It also is free from the fire hazard which attends the use of a wick made from vegetable fiber.

It has been found that at very low engine speeds the velocity of the air current through the wick in the exposed zone is slowed to the extent that the air becomes unduly enriched, so that the provision of an auxiliary air inlet becomes desirable.

Such an inlet is shown in Figure 1, consisting of a slot 24 in the lower cylindrical portion 2 of the carburetor casing in the region of the throttle valve. Said slot is controlled by a valve which is here shown as a sliding gate 25, operable in parallel tracks 26 extending along opposite sides of the slot 24. Said gate is normally maintained in inlet closing position by means of the springs 21. It is opened against the tension of said springs by means of a cam 28 rigidly secured to said gate, and which is engaged by an extension 28 on the throttle valve lever 30. Said cam and extension are so relatively positioned with respect to the throttle valve 3 that the extension 2! begins to contact the cam 28 when the throttle valve approaches its closed position. In the closin: movement of the throttle valve thereafter, the extension 29 pushes upwardly against the cam 28, lifting the gate and progressively opening the slot 24. It has been found by experimentation that as the speed of the engine the wick is desirable for several reasons;

decreases beyond the critical point at which it is desirable to begin to admit auxiliary air, the admission of said air should be at a progressively decreasing increment which explains the triangular shape of the slot 24.

The operation of the carburetor is as follows. The wick being of conical form and wider in its submerged portion than it is in the zone of air and liquid contact, has a greater capacity for feeding liquid upward through capillary attraction in its base region than it has in the zone of gas and liquid contact, and therefore, the wick in the exposed zone will be super-saturated with liquid fuel, providing an adequate supply of liquid to properly carburet the maximum amount of air which may be required to satisfy the engine demands under highest speed and load conditions. The converging curtain of carbureted air passing downward through the mixing chamber 23 creates a subatmospheric pressure in that part of the conical chamber occluded by the cap I'I, including the portion of the wick covered by said cap, which subatmospheric pressure draws liquid upward through the wick at the exposed zone, thus accelerating the capillary traverse of liquid fuel across said exposed zone. The subatmospheric pressure also draws the liquid fuel up into that portion of the wick which is occluded by the cap, providing a reserve supply of liquid in said occluded portion of the wick, and maintaining a rich though more or less attenuated body of air in the closed part of the conical chamber inside of the screen bailie 9. In ordinary carburetors, in the absence of special mechanical expedients to prevent it, a hiatus or discontinuity in the flow of carbureted air to the manifold momentarily occurs if the throttle valve is suddenly opened while the cylinders of the engines are working under considerable vacuum so that there is a pause or miss in the operation of the engine. i The subject carburetor avoids this defect, in that when the throttle valve 3 is suddenly opened, producing an attenuation in the mixture at the point 23, the reserve supply of carbureted air in the closed apical portion of the conical chamber within the baflle 9 expands, filling the void until the inertia of the air coming in through the exposed zone of the wick has been overcome.

Regardless of the position of adjustment of the closed cap l'l, axially of the wick, the body of reserve mixture will always have substantially the same volume.

In the normal operation of the engine, that is to say, in any range of speeds above very low speed operation, the velocity of air entering through the wick is so automatically proportioned to the feed of liquid upwardly from the base of the wick into the exposed zone, that the proportion of hydrocarbon gas and air forming the combustible mixture remain constant.

The provision of setting means for adjusting the position of the choke valve with respect to in the first instance to suit the capacity of the particular engine with which the carburetor is used, and thereafter to suit the grade of fuel employed, atmospheric temperature. altitude, etc. When the cap I! is set in a position away from the wick ll, it does not disturb the condition of subatmospheric pressure within the apical portion of the wick for the subatmospheric pressure in the annular space between the cap and wick is substantially the same as that within the wick, so that a substantially static condition of subatmospheric pressure normally persists.

It will be obvious to those skilled in the art that a carburetor operating upon the principle of control accelerated capillarization must be reasonably capacious in order to suit engine demands at high speeds and while a single carburetor need not necessarily be made of an inconveniently large size to suit the demands of any engine, it may be desirable in the case of high speed engines of great cubical capacity, in the interest of space conservation, to provide two similar carburetor units connecting them in tandem as shown in Figure 6, in which the carburetors 3| and 32 are connected by an operating link 33 having a pivot connection 34 with carburetor 3| and a slot connection 35 with carburetor 32, whereby, when the throttle rod 36 is operated, carburetor 34 alone takes care of engine demands up to a determined speed and thereafter, carburetor 32 operates in conjunction with carburetor 3| at higher speeds. Any other multiple arrangement of carburetors may be adopted in the interest of optimum performance without transcending the spirit and scope of the invention as claimed.

It will be understood to those skilled in the art that the details of construction and the arrangement of parts as shown are by way of example and not to be construed as limiting the coverage of the invention.

What I claim as my invention is:

1. Carburetor comprising a casing defining a bore having an air inlet adjacent one end and a combustible mixture outlet adjacent the other,

a liquid fuel reservoir arranged about the inner periphery of the intermediate part of said casing in communication with a float controlled liquid fuel supply whereby a constant liquid level is maintained in said reservoir, a tapered tubular wick having its base immersed below the liquid level in said reservoir for raising liquid fuel by capillarity into said wick, and dividing said bore into air and combustible mixture chambers, a cap enclosing the apical portion of said wick defining an exposed zone between said cap and base through which air must pass in flowing from said air chamber to said combustible mixture chamber.

2. Carburetor comprising a casing defining a bore having an air inlet adjacent one end and a combustible mixture outlet adjacent the other, a liquid fuel reservoir arranged about the inner periphery of said casing in communication with a float controlled liquid fuel supply whereby a constant liquid level is maintained in said reservoir, a tapered tubular wick having its base immersed below the liquid level in said reservoir for raising liquid fuel by capillarity into said wick and dividing said bore into air and combustible mixture chambers, said wick projecting into said air chamber, an imperforate cap enclosing the apical portion of said wick defining an exposed zone between said cap and base through which air must pass in flowing from said air chamber to said combustible mixture chamber, the space beneath said cap into which the apical portion of said wick extends being under subatmospheric pressure due to the venturi action of the convergent air current beneath said wick, whereby the capillary rise of liquid in said wick is augmented by suction.

3. Carburetor comprising a casing including an annular reservoir for liquid fuel, a conical tubular wick having its lower end immersed in the liquid fuel in said reservoir for raising said liquid fuel by capillarity into said wick, said casing including a shell extending above said reservoir having substantially the same taper as said wick, spaced therefrom to form a surrounding air duct and terminating in an air inlet, said casing including also a shell below said reservoir having a combustible mixture outlet, and a hollow conical cap fitting over the apical portion of said wick within said casing defining an exposed zone of saidwick through which air passes to said combustible mixture chamber.

4. Carburetor comprising a casing including an annular reservoir for liquid fuel, a conical tubular wick having its lower end immersed in the liquid fuel in said reservoir for raising said liquid fuel by capillarity into said wick, said casing including a shell extending above said reservoir having substantially the same taper as said wick, spaced therefrom to form a surrounding air duct and terminating in anair inlet, said casing including also a shell below said reservoir having a combustible mixture outlet, and a hollow conical cap fitting over the apical portion of said wick within said casing defining an exposed zone of said wick through which air passes to said combustible mixture chamber, said cap being adjustable axially with respect to said wick.

5. Carburetor comprising a casing including an annular reservoir for liquid fuel, a conical tubular wick, a shape sustaining support therefor, said wick having its lower end immersed in the liquid fuel in said reservoir for raising liquid fuel by capillarity into said wick, said casing including a shell extending above said reservoir having substantially the same taper as said wick, spaced therefrom to form. a surrounding air duct and terminating in an air inlet, said casing including also a shell below said reservoir having a combustible mixture outlet, and a hollow conical cap fitting upon the apical portion of said wick within said casing defining an exposed zone of said wick through which air passes in an annular curtain to said combustible mixture chamber creating suction beneath said cap whereby the capillary feed of fuel to the exposed zone of said wick is augmented by suction on the upper part of said wick.

6. Carburetor comprising a casing including an annular reservoir for liquid fuel, a conical tubular wick having its lower end immersed in the liquid fuel in said reservoir for raising liquid fuel by capillarity into said wick, a perforate shape sustaining support for said Wick circum-- scribing the central opening of said annular reservoir, said casing including a shell extending above said reservoir having substantially the same taper as said wick, spaced therefrom to form a surrounding air duct and terminating in an air inlet, said casing including also a shell below said reservoir having a combustible mixture outlet, and a hollow conical cap fitting upon the apical portion of said wick within said casing defining an exposqi zone of' said wick through which air passes in an annular curtain to said combustible mixture chamber creating suction beneath said cap whereby the capillary feed of fuel to the exposed zone of said wick is augmented by suction on the upper part of said wick, and means for moving said cap axially of said wick to closed position relative'to said shell or to intermediate positions of tions as a choke valve.

WILLIAM F. MOLINDON.

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