US2102361A - Carburetor - Google Patents

Description

Patented Dec. 14, 1937 Y UNITED STATES PATENT OFFICE Application February 7, 1936, Serial No. 62,852 In Great Britain July 18, 1935 4 Claims. (Cl. 261-116) This invention relates to carburetors for interture of the air thus admitted may be from 35 to nal combustion engines, of the type in which the 70 C., for example, in the case of gasoline of fuel is atomized with a primary supply of air at standard quality.

the head of a spraying nozzle and is then mixed 'Ihe cap 2| has a central perforation 3l)` regis-V 5 with the main air supply passing around the noztering With the bore of the fuel tube 22, the parts 5 zle into a Venturi or choke tube. being secured together by means of a boss-3| on According to this invention, the spraying nozzle the bottom of the cap; this boss is shown as being comprises a central tube or passage for the fuel counterbcred, coaxially with the perforation 30, surrounded by an air passage having at its upper to receive the upper end of the tube 22, which is end a perforated cap with a central divergent preferably soldered in place. 'Ihe exterior o'f the l0 cavity, the fuel being delivered axially intothis cap 2l is formed with a rounded rim 32 which is cavity and the air being delivered'through oblique shouldered down at 33 so as to tthe upper end holes in the divergent walls of the cavity. of the outer tube'23, the cap 2I being held down Ihe invention is hereafter more fully described on the latter by the attachment of the inner tube l5 with reference to the accompanying drawing, in 22; theirim 32 producesv a slight restriction of the 15 whiehpassage through the choke tube I1.

Fig. l is a sectional elevation of the body or 'I'he choke tube I 'l has approximately the usual mixing chamber of a vertical carburetor accordventuri-shaped or convergent-divergent interior,

,v ing to one embodiment of the invention. as indicated at 34, but the passage area is con- I'2b Fig'. 2 is a similar view of a modification. trolled by the presence of steel balls 35 loosely en- 20 Fig. 3 is a plan View of the choke tube. v gaged in open-sided cells or flutings 36 formed Fig. 4 illustrates the preferred method of makalong the interior. 'I'he balls project inwardly of ing the choke tube. the choke tube, for'example to the extent of one- Referring to Fig. 1, the carburetor comprises a quarter of their diameter, so as to restrict the pas- 2'5 mixing chamber Ill having its lower portion II of Sage area at their own level, as compared'with'the 25 frusto-conical shape, open to the atmosphere at circular or annular area of a normal choke tube the bottom and formed with a cross-bar I2 which 0f the Same dietlnetel-V The lint/ings 36 :(See Figsuppgrts the spraying nozzle` I3,vv The upper part 3) are preferably part-circular in cross-section,

I4 of the mixing chamber is 0f cylindrical shape', more than semi-circular in extent, and of radius v 3() provided with means, such as a flange V|5cf0r atslightly greater than the balls 35; their open sides, 30 tachment to the' throttle chamber I6 leading to towards the inteor of the choke tube. afford galos the engine. Inside' the cylindrical upper part I4 3l Slightly naITOWeF than the diameter of` the there is mounted a choke tube I'I, resting upon a halls InOunteCl in them- They extend longitudistep ls in the wan 0f the chamber, and retained nally down from the top of the choke tube to the Y by the ange I9 of the throttle chamber, Y level of the throat or narrowest portion 38 of the 35 The spraying nozzle comprises a, Cap 2| secured interior, SO that in the nOIma] pOSilOli ShOWn in to the top of a central tube 22 within an outer Fig. 1, With the balls resting at the bottom ofthe tube'23, the latter being supported by a, polygonal Cells 0I` fllltlngs 36, the area 0f the throat iS rebase 24 of which theshank 25 is screwed into a StIiCted by the inwardly DIOjecting Surfacesof the 4o hole 26 in the hollow cross bar I2 extending from halls; the thlOet 38 may comprise, as' Seen in 40 one side to the other of the mixing chamber be- Fig- 1J a ShOIt Cylindrical DOItiOn betWeen the low the choke tube Il; the lower end of the mixing Convergent and divergent portions of the choke. chamber is Shown as 0f greater Width, toi com- The top of the nozzle cap 2l provides a central pensate'for the restriction formed by the crossdivergent CaVitY 39, 'in the form of a Shallow bar I2. Gasoline or 'other fuel is fed froma float inverted C0ne, COeXel With the DeI'fOIatiOn 30, 45 chamber (not shown) throughA a duct '21 in the the walls of this conical cavity rbeing for example cross bar I2 to a central bore v8 into; which the et an angle 0f 30 t0 the'hOIiZOhtal SO aS t0 lower end of the tube 22 is screwed or otherwise form a Sharp edge vat their junction With the rim secured so as to prevent leakage of fuel at this 32. Oblique hOleS 49, Di'efeiefhly three 0I' mOIe in point. A second ducty 29 eXtending in the opponumber, eVenlY SDaCeCl 'I'Ollnd the aXl'S, and Of a 50 site direction along the cross bar I2 admits air at diameter Which may be IOIn 030 t0 i050 il'leh,A atmospheric pressure to the space around the lowfor example, are formed-in the divergent Walls i er end of the fuel'tube 22, this air being warmed of the cavity 39, these holes connecting with the or heated if desired, for example lby contact with tcp of an annular space or chamber 4I inside the exhaust manifold of the engine; the tempera-` -the .tube 23 and concentric with the fuel tube 65 lil 22; these holes 40 may also be inclined vat an angle of 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 bales, for example of helical form, may. be inserted in the annular chamber 4I, as indicated at 43.

The head of the nozzle I3 extends just above the level of the throat38, and the Vcircumferential 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 thethrottle, the increased flow fof air through the choke tube I'I tends to lift the balls 35 inside theirV n Y th1s blank is thenV bored out to form the convergeht-divergent interior vofthe choke tube, as

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 eiIect as the balls rise towards the final position shown in dotted lines at 35a in Fig. l. Y

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 I3, thereby producing a greater restriction, and only thereafter does the passage area become increased; the effect of this intial 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 flat spot which is liable to cause engine stoppage under such conditions. y

In operation, the fuel issuing from the perforation 39 will be met by the oblique streams of air drawn from theholes 40 by the injector effectv 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 I3; the atomizing air, drawn from the duct 29, will have passed through the interior of the'base 24 into the annular space or chamber 4I between the two tubes 22 and 23, so that this air (if sufciently heated) will have raised the fuel inthe tube 22 to a temperature approaching or exceeding its initial boiling point, before it issues from the perforation 30, Vvaporization therefore taking place immediately into the main air current.

VThe number and Vsize 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 basinrfor catching drops of fuel, the sharp edge of thercap above the rim 32 preventing the fuel from dribbling down the outside of the nozzle I3 at low speeds.

In an alternative construction, the Yair passage to the holes 40 may be formed by a pipe coil or spiral closely surrounding the fuel tube 22 and connecting at its upper end with a perforated cap 2| screwed upon the fuel tube 22 and having a similar divergent cavity 39 with axial fuel delivery and oblique air holes. A

.The fuel may be Vsupplied to the nozzle in the form of an emulsion with airr by making use of Y the well-known system Yof compensating Vjets for the same means as the atomizing air supplied to the passage 4I or by a separate heater.

Fig. 2 shows a modified construction suitable for carburetors to be fitted to relatively small engines; in this case the duct 29 for supplying atmospheric air to the nozzle I3 is dispensed with, air being admitted to the annular passage or chamber 4I from the lower part of the mixing chamber, by way of holes 45 formed in the outer Vtube 46. The fuel tube 22 is securedat its lower end in the center of the base 24, which thus supports the complete spraying nozzle, allowing the latter to be removed by unscrewing the base 24 from its hole in the cross bar I2.

The cells or flutings 36 in the choke tube I1 vcan conveniently be formed by drilling evenlyspaced oblique holes 4,1 into the body of a cylindrical metal blank 48, as indicated in Fig. 4;

indicated by the chain-line circles 49---5Il` representing respectively the throat 38 and the top of the choke tube Il, thereby removing the walls of the holes 4'I nearest to the axis for substantially the whole of their axial length. The choke tube will then appear as shown in Fig. 3, with theV open-sided cells or ilutings 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 1/4 inch in diameter, fitted in cells or flutings formed by drilling holes of fr inch diameter at an obliquity of 61/2 ydegrees 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 1/2 inch between their extreme positions. When fully raised, the balls willrbe retained by the connecting flange or facing I9 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 II, and thatit may be applied to vcarburetors of other types than that above described, for Yexample to carburetorshaving tlie axis of the choke tube I1 and spraying nozzle I3 inclined to the vertical; in cases Ywhere the axis approaches" the horizontal position, the gravity control of the displaceable elements may be supplemented or replaced by spring or like control.

What I claim isz- 1. In a carburetor having a spraying nozzle mounted coaxially within a choke, said nozzle comprising two concentric tubes, means for admitting fuel and atmospheric air respectively to the inner one of said tubes and to the annular space between said tubes, and a centrally perforated cap upon the upper ends of said tubes, a. rim around said cap, said rim located above the .narrowest portion of said choke and projecting upper surface of said cap including adepression around the central perforation and a plurality of oblique holes spaced around said central perforation, said holes communicating with said annular space below said cap and converging upon the axis of said central perforation at a point within said depression.

2. In a carburetor having a spraying nozzle mounted coaxially within a choke, said nozzle.

comprising two concentric tubes, a cap upon the upper ends of said tubes, a rim around said cap,

said rim located above the narrowest portion of 7 5 said choke and projecting radially beyond the outer one of said tubes, means for admitting fuelV to the inner one of said tubes, and means for admitting air to the annular space between said tubes, said air-admitting means being independent of the main air supply passing externally of said nozzle, said cap having a perforation in line with said inner tube and also a plurality of converging holes extending from said annular space to the upper surface of said cap, and the air admitted to said annular space being discharged through said holes for mixture with fuel discharged through said perforation prior to meeting said main air supply passing externally of said nozzle.

3. In a carburetor having a spraying nozzle mounted coaxially Within a choke through which the main air supply passes, said nozzle comprising two concentric tubes, means for admitting fuel to the inner one of said tubes, and means for admitting air at atmospheric pressure to the annular space between said tubes, and a cap surmounting said tubes, said cap including a peripheral bead of diameter greater than the exterior diameter of the outerone of said tubes, and the upper surface of said cap being formed as a conical depression having a central perforation communicating With said inner tube and a plurality of oblique holes spaced round said perforation, said perforation being at the bottom of said depression, and said holes communicating with said annular space and converging upon the axis of said perforationrat a point Within said depression. Y A Y 4. In a carburetor having a spraying nozzle mounted coaxially within a choke through which the main air supply passes around said nozzle,

said nozzle comprising a central tube, a passage surrounding said tube, means for admitting fuel and atmospheric air to said tube and passage, and a cap surmounting said tube and passage, said cap having its upper surface formed as a conical depression with a central perforation communicating with said tube and a plurality of oblique holes communicating with said passage, and said cap including a peripheral bead located above the narroWest portion of said choke.

ARTHUR WILLIAM DAVID GLADWELL.

Images