US2102362A

US2102362A - Carburetor

Info

Publication number: US2102362A
Application number: US62853A
Authority: US
Inventors: Gladwell Arthur William David
Original assignee: Individual
Current assignee: Individual
Priority date: 1935-07-18
Filing date: 1936-02-07
Publication date: 1937-12-14
Anticipated expiration: 1954-12-14

Description

6L vuul h" IUU APPARATUS.

1937- A. D. GLADWELL 2,102,362

GARIURETOR Filed Feb. 7, 1936 'LUI. H0 6L L|QU|U CUNTACT APPARATUS.

Patented Dec. 14, 1937 UNITED STATES UVUI VII I IV CARBURETOR Arthur William David Gladwell, London, England Application February 7, 1938, Serial No. 62,853

In Great Britain July 18, 1935 Claims.

This invention relates to carburetors for internal combustion engines and has for its object to provide improved automatic means for varying the choke area so as to afford a varying passage area dependent on the suction or depression, the variation preferably comprising a slight initial reduction of the original area for accelerating and a subsequent steady increase for high speed and maximum power up to the full area available.

According to this invention, the spraying nozzle is mounted within a choke tube having its upper or divergent portion fitted internally with displaceable elements adapted to be drawn alon by the air current past the nozzle. The displaceable elements may consist for example of metal balls loosely engaged in open-sided cells orfiutings formed along the interior of the choke tube, the width of the openings at the surface of the tube being slightly less than the diameter of the balls.

The invention is hereafter described with reference to the accompanying drawing, in which:-

Fig. 1 is apart sectional elevation of the body or mixing chamber of a vertical carburetor having a variable choke tube according to the invention.

Fig. 2 is a plan view of the choke tube.

Fig. 3 illustrates the preferred method of making the choke tube.

Referring to Fig. 1, the carburetor comprises a mixing chamber I0 having its lower portion H of frusto-conical shape, open to the atmosphere at the bottom and formed with a cross-bar |2 which supports the spraying nozzle l3. The upper part [4 of the mixing chamber is of cylindrical shape, provided with means, such as a flange l5, for attachment to the throttle chamber |6 leading to the engine. Inside the cylindrical upper part M there is mounted a choke tube I1, resting upon a step |8 in the wall of the chamber, and retained by the flange IQ of the throttle chamber.

The spraying nozzle comprises a cap 2| secured to the top of a central tube 22 within an outer tube 23, the latter being supported by a polygonal base 24 of which the shank 25 is screwed into a hole 26 in the hollow cross bar l2 extending from one side to the other of the mixing chamber below the choke tube I1; the lower end of the mixing chamber is shown as of greater width, to compensate for the restriction formed by the cross-bar l2. Gasoline or other fuel is fed from a float chamber (not shown) through a duct 21 in the cross-bar |2 to a central bore 28 into which the lower end of the tube 22 is screwed or otherwise secured so as to prevent leakage of fuel at this point. A second duct 29 extending in the opposite direction along the cross-bar |2 admits air at atmospheric pressure to the space around the lower end of the fuel tube 22, this air being warmed or heated if desired, for example by contact with the exhaust manifold of the engine; the temperature of the air thus admitted may be from 35 to 70 C., for example, in the case of gasoline of standard quality.

The cap 2| has a central perforation 30 registering with the bore of the fuel tube 22, the parts being secured together by means of a boss 3| on the bottom of the cap; this boss is shown as being counterbored, coaxially with the perforation 30, to receive the upper end of the tube 22, which is preferably soldered in place. The exterior of the cap 2| is formed with a rounded rim 32 which is shouldered down at 33 so as to fit the upper end of the outer tube 23, the cap 2| being held down on the latter by the at tachment of the inner tube 22; the rim 32 produces a slight restriction of the passage through the choke tube II.

The choke tube I! has approximately the usual Venturi-shaped or convergent-divergent interior, as indicated at 34, but the passage area is controlled by the presence of steel balls 35 loosely engaged in open-sided cells or flutings 38 formed along the interior. The halls project inwardly of the choke tube, for example to the extent of one-quarter of their diameter, so as to restrict the passage area at their own level, as compared with the circular or annular area of a normal choke tube of the same diameter. The flutings 36 (see Fig. 2) are preferably part-circular in cross-section, more than semi-circular in extent, and of radius slightly greater than the balls 35; their open sides, towards the interior of the choke tube, afford gaps 31 slightly narrower than the diameter of the balls mounted in them. They extend longitudinally down from the top of the choke tube to the level of the throat or narrowest portion 38 of the interior, so that in-the normal position shown in Fig. 1, with the balls resting at the bottom of the cells or flutings 36, the area of the throat is restricted by the inwardly projecting surfaces of the balls; the throat 38 may comprise, as seen in Fig. 1, a short cylindrical portion between theconvergent and divergent portions of the choke.

The top of the nozzle cap 2| provides a central divergent cavity 39, in the form of a shallow inverted cone, coaxial with the perforation 30, the walls of this conical cavity being for example at an angle of 30 to the horizontal so as to form a sharp edge at their junction with the rim 32. Oblique holes 40, preferably three or more in number, evenly spaced round the axis, and of a diameter which may be from .030 to .050 inch, for example, are formed in the divergent walls of the cavity 39, these holes connecting with the top of an annular space or chamber 4| inside the tube 23 and concentric with the fuel tube 22; these holes 40 may also be inclined at an angle of 30 to the horizontal, and they are arranged in radial planes so that their axes and that of the fuel tube 22 and perforation 30 intersect at a point 42 within the cone 39. Partitions or baflles, for example of helical form, may be inserted in the annular chamber 4!, as indicated at 43.

The head of the nozzle I3 extends just above the level of the throat 38, and the circumferential rim 32 of the cap 2| projects about one or two millimeters radially beyond the outer tube 23; this rim 32 lies at a slightly higher level than the restricted area provided by the projecting surfaces of the balls 35 in their normal position. When more suction is applied by the opening of the throttle, the increased flow of air through the choke tube ll tends to lift the balls 35 inside their cells 36 and carry them along to the upper and wider part of the choke tube, thus removing the restriction from the throat and reducing its proportional effect as the balls rise towards the final position shown in dotted lines at 35a in Fig. 1. But at the initial opening of the throttle from the idling position, the lifting of the balls first carries them to the level of the rim or bead 32 at the head of the nozzle l3, thereby producing a greater restriction, and only thereafter does the passage area become increased; the effect of this initial restriction is to provide a richer mixture at the moment of opening the throttle for acceleration after a period of slow running, and thus to avoid the fiat spot which is liable to cause engine stoppage under such conditions.

In operation, the fuel issuing from the perforation 30 will be met by the oblique streams of air drawn from the holes 40 by the injector effect of the engine suction, these streams breaking up the fuel into a fine mist (as indicated at 44) which mixes with the main air supply passing round the exterior of the nozzle l 3; the atomizing air, drawn from the duct 29, will have passed through the interior of the base 24 into the annular space or chamber 4| between the two

tubes

22 and 23, so that this air (if sufiiciently heated) will have raised the fuel in the tube 22 to a temperature approaching or exceeding its initial boiling point, before it issues from the perforation 3U, vaporization therefore taking place immediately into the main air current.

The number and size of the oblique air holes 40 may be varied; these holes have a limiting effect upon the quantity of fuel passed at high speeds, so that the fuel consumption remains approximately proportional to the power developed. The divergent cavity 39 also acts to some extent as a basin for catching drops of fuel, the sharp edge of the cap above the rim 32 preventing the fuel from dribbling down the outside of the nozzle [3 at low speeds.

The cells or fiutings 36 in the choke tube I! can conveniently be formed by drilling evenlyspaced oblique holes 41 into the body of a cylindrical metal blank 48, as indicated in Fig. 3; this blank is then bored out to form the convergent-divergent interior of the choke tube, as indicated by the chain-line circles 49-50 representing'respectively the throat 38 and the top of the choke tube l1, thereby removing the walls of the holes 41 nearest to the axis for substantially the whole of their axial length. The choke tube will then appear as shown in Fig. 2, with the open-sided cells or fiutings 36 each adapted to receive one ball. With a choke-tube having a. 24 millimeter throat and an internal diameter of 28 millimeters at the top, there may be employed nine balls each A, inch in diameter, fitted in cells of fiutings formed by drilling holes of inch diameter at an obliquity of 6%; degrees to the axis, corresponding to the divergent side of the choke, the pitch circle of the balls varying by about 3 millimeters in diameter with an axial movement of about inch between their extreme positions. When fully raised, the balls will be retained by the connecting flange or facing l9 to which the carburetor body is secured, so that they cannot slip out of place.

It will be understood that the invention is not limited to the use of steel balls as displaceable elements controlling the passage area through the choke tube l1, and that it may be applied to carburetors of other types than that above described, for example to carburetors having the axis of the choke tube l1 and spraying nozzle [3 inclined to the vertical; in cases where the axis approaches the horizontal position, the gravity control of the displaceable elements may be supplemented or replaced by spring or like control. The choke tube may be adapted to any existing carburetor having the usual form of choke, the dimensions being arranged to suit the carburetor to which the choke is to be fitted.

What I claim is:-

1. In a carburetor having a spraying nozzle mounted coaxially within a choke, a choke member having a convergent inlet portion and a divergent outlet portion, said outlet portion having its inner surface formed with fiutings extending approximately from the throat of said choke member to the end of said outlet portion, said fiutings being open for their entire length inwards of said surface, and elements loosely confined in said fiutings, said elements partly projecting from the open sides of said fiutings to restrict the passage through said outlet portion and being controlled by the air current through said choke.

2. In a carburetor having a spraying nozzle mounted coaxially within a choke, a choke member having a convergent inlet portion extending from below the outlet of said nozzle and an upper outlet portion extending to above the outlet of said nozzle, said outlet portion having its inner surface formed with longitudinal fiutings, said fiutings being open for their entire length inwards of said surface, and displaceable elements confined in said fiutings, said elements partly projecting from the open sides of said fiutings to restrict the passage through said divergent portion and being lifted by the air current through said choke, said air current having free access to the upper faces of said elements through the open sides of said fiutings.

3. In a carburetor having a spraying nozzle mounted coaxially within a choke, a choke member having a convergent inlet portion and a divergent outlet portion, displaceable elements loosely mounted at the inner surface of said di-' vergent portion, said displaceable elements being adapted to restrict the passage through said di- 7 aus. GHQ QL LEL 'LiU (JUNIAQI APPARATUS.

UUIII UH ii i' vergent portion and having their position controlled by the air current through said choke, said nozzle extending above said dispiaceable elements in their normal position, and a peripheral enlargement at the upper end of said nozzle for restricting the passage through said choke at a transverse plane of said divergent portion corresponding to the position of said displaceable elements when initially displaced by the air current.

4. In a carburetor having a spraying nozzle mounted'coaxially within a choke, the combination of a nozzle having a peripheral enlargement adjacent to its outlet, a choke member having its throat below the plane of said enlargement, and displaceable elements loosely mounted in said choke, said elements partly projecting from the inner surface of said choke to restrict the passage therethrough and being controlled in position by the air current longitudinally of said choke, and

the displacement of said elements with increase of said air current carrying them from a position below said enlargement to a position above said enlargement.

5. In a carburetor having a spraying nozzle mounted coaxially within a choke, a choke member having a convergent inlet portion extending from below the outlet of said nozzle and an upper outlet portion extending to above the outlet of said nozzle, said outlet portion having its inner surface formed with open-sided flutings extending to the upper end of said outlet portion, and displaceable balls loosely engaged in said flutings, the opening along the inner side of each fiuting being substantially parallel and of width slightly less than the diameter of the ball engaged in the respective fluting.

ARTHUR WILLIAM DAVID GLADWELL.