US1578873A - Carburetor - Google Patents

Description

March 30 1926.

H. H. WELCH GARBURETOR Filed Deo. a, 1916 Qld/Kw' Patented Mar. 30, 1926.

'UNITED STATES lPa'rizN'rf.CF1-Ice .f'v

HORACE H. WELCH, 0E DETROIT, MICHIGAN, AssIGNoR'To y.Enna v. oUsTAEsoN, oF

CHICAGO, ILLINOIS. v

CARBURETOR.

To all wimm- 'i muy concern.' v

Be it known that I, HouACEI-I. IVELcH, a citizen of the United States, residing at Detroit, county of Wayne, State of Michigan, have invented a certain new and uscful Improvement in Carburetors, and declare the following to be a full, clear, and4 the vacuum feed type, i. e., carburetors in which a vacuum 1n the float chamber 1s maintained to draw fuel to the said float chamber from a supply tank Situated at a lower leve1. l

The particular object of my invention is to provide a vacuum feed carburetor in which the necessary vacuum in the floatchamber is produced solely bythe aspirating effect of air passing at high velocity through a Venturi or other choke tube. In the ordinary vacuum feed carburetor the vacuum in the float chamber is produced by the vacuum .existing in the intake manifold of the connected engine and as a consequence the vacuum in the float chamber is often too high, causing excessive evaporation of fuel, and often too low, as when the engine is running at loW speed and full load with Wide open throttle. In the improved carlburetor hereinafter described the vacuum in the float chamber is produced by connecting the air space of the closed float chamber to, the restricted portion of a venturi through which air is passing into the mixing chamber at high velocity, thus maintaining a uniform vacuum in the float chamber which is always sufficient to raise the fuel, and never great enough' to cause evaporation of the lighter particles of the fuel. The particular advantage of this means of producing the vacuum in the float chamber lies in the fact that the reduction in pressure at the constricted portion of a venturi is severalI times greater than at the exit end of the venturi. The latter fact is utilized in this invention to provide a vacuum feed cabureter in which.

" speed under load. This means that the fue] Application led December 8, 1916. Serial No. 135,723.

may be lifted with much less throttling of the engine than is possible with the ordinary type of vacuum feed carburetor.

A further object of my invention is to provide a carburetorhaving' a fairly con-- stant vacuum in the float chamber, thus making 1t possible to draw fuel from a supply tank at a lower level under all o-peratlng conditions.

' further object is to provide a carburetor having a venturi through which air passes at about the same velocity regardless of the total amount of air passing through the carburetor. The purpose of this is to. provide a uniform source of vacuum for the float chamber. These and-other objects and the several novel features of the invention in its preferred form are hereinafter more fully described and claimed and shown in they accompanying drawings in Which- Fig. 1 is a vertical section of the preferred commercial form of a carburetor embodying my invention.

F ig. '2 is a diagram illustrative of the principle of operation involved in my izn` proved carburetor. l

The'device herein shown and described differs from the device in my copending application, Serial No. 13,558, principally in that, in the device shown in said pending application, the fuel is supplied in variable quantity to the main air conduit by means of a nozzle situated at or near the point of greatest-variation in pressure in the conduit, the variation in pressure being depended upon to vary t-he flow of fuel in proportion tothe variation inthe volume of the air passing through the air conduit per unit of time. With the device here shown the atomizer is subjected to substantially constant degree of vacuum, the flow through the fuel conduit being varied or controlled by a metering pin positioned variably in the conduit inaccord with variations in the volume of air flowing through-the air conduit per unit of time.

The means whereby fuel is fed into the fuel chamber by a degree of vacuum is shown .in Fig. 2 in which l indicates an air conduit of the general form of a Venturi tube and the upper end of the fuel chamber 2, above the fuel level, is in communication l therewith by means of a tube 3 terminating at about the point of greatest restriction in the conduit l, Whatever degree ofvaeuum is produced at this, point of greatest restriction is likewise produced in the tube `ind in the air space of the fuel chamber 2 which is in communication with the fuel tank by mea-ns of a tube 4. 'The vacuum produced in the fuel chamber is thus utilized to supply the chamber from the supply tank 5 and the level of fuel in the chamber is controlled by a float 6 of common type operating a Valve 7 to close the mouth of the tube 4 wheny the fuel has reached the .desired level. By this arrangement the flo'W into the fuel chamber ceases upon the closing of the mouth of the tube by the valve. The tube 3 may enter the conduit 1 at any desired point preferably as shown in Fig. 2 with the open end pointing in the direction of flow of air therethrough.

In Fig. 2 is shown a second venturi 8 discharging into the main air Aconduit and a third venturi 9 discharging into the venturi 8 at the point of greatest restriction therein. A fuel conduit 10 discharges into the venturi 9 at about the point of greatest restriction, the open end of which points in the direction of flow of air therethrough, and this fuel conduit is connected to the bottom of the fuel chamber of the carburetor. The flow of fuel into the conduit from the fuel chamber is controlled by a metering pin which is connected with a valve 12 controlling the air inlet of the main air conduit, a variation in position of which will vary the volume of flow in the fuelv conduit, as will be readily understood. By subjectingthe air space of the fuel chamber to the aspirating effect of air passing through the Venturi 1 and subjecting the fuel of the fuel conduit to the multiple effect of the two venturis 8 and 9, the pressure to which the fuel conduit is subjected is less than that to which the fuel in the fuel chamber is subjected. The difference in pressure produces a flow of fue-l into the Venturi 9 and consequently, into the main air conduit of the carburetor.

The purpose of the provision of the venturi in the channel between the air space' of the fuel chamber and the main air 'conduit .is to reduce the pressure in the fuel chamber dispensed with and a multiple venturi onlyY is used. In such case the air space is subjected to the degree of vacuum produced by one venturi and the fuel discharge is subjected to the degree produced by both. The

diagram Fig. 2 is believed to make clear this differential condition and the general method vof operation of the dev-ice.

In the preferred commercial .form of the invention as shown in Fig. 1, the main air conduit is indicated at 20 and is provided with a throttle valve 2l adjacent the outlet leading into the intake manifold of the internal combustion engine (not here shown). This main airconduit is only open to atmosphere througli'an inlet normally closed by the spring controlled valve 22 and through an open Venturi tube 23, the preferable form of the conduit and position of this venturi being such that the longitudinal axis of the venturi practically coincides with the longitudinal axis of that portion of the conduit 2() in which it is located and opening in the direction of How of air therethrough. The valve 22 is positioned in a part of the air conduit directly over the center of the fuel chamber 24 which is secured to the lower side of the conduit 20 by the screws 25. The air conduit 2O is closed to the fuel chamber and the joint between the two parts is made substantially air tight to prevent a How of air into the fuel chamber therethrough.

The Venturi tube 23 is preferably threaded in an opening in the lower part of the main air conduit 20 and is formed with a boss 26 at the top thereof threaded to receive an end of the conical defiector member 27 terminating near the point of greatest restriction in the venturi 23. The lower end of the venturi is open to atmosphere as indicated at 28 so that air may flow freely thereinto at all times, and a double walled tubular member 29 is also positioned with the discharge end thereto at about the point of greatest restriction in the Venturi tube. This member 29 is formed of an outer cylindrical member 30 and an inner tubular member 31 having a bell shaped outlet 32 into which the conical end of the deflector 27 extends but spaced from the wall thereof v,substantially as shown. The tube 31 is open to atmosphere at the bottom so that air ma flow through the tube 31 and out throng the bell shaped discharge end aro-'und the deflector. This bell shaped discharge end is also spaced from the end of the surroundf ing tube 3() as indicated, and air may flow into the conduit 35 formed between the two tubes from the apertures 33 provided therefor. Air rushing into the venturi 23 through the mouth 28 and through the tube 31 passes each side of the ring shaped opening 34 formed between the ends of the two tubes 30 and 31 causing a reduction in pressure in the conduit 35 between the two tubes. This conduit is restricted at a point between the openings 33 and the outlet 34 by means of a portion 36. This por'- tion 36 provides a secondary venturi and has a series of radially positioned channels 39 on the fuel chamber.

37 formed therein extending through the wall of the tube 30. The channels 37 are By the arrangement described air flowing at high velocity through the main venturi 23 from the inlets 31' and 28 tends to produce the greatest possible degree of vacuum in the conduit 35 between the two the bottom of the fuel chamber to the chan-- nel 38' in communication with vthe radial.

channels 37. These channels 37 are slightly above the normal level of the fuel in .the fuel chamber, as indicated by dotted lines a-a and, by reason of the formationof these channels 37 in the secondary venturi, the fuel in the channel 41 is subjected to a higher degree of vacuum than is produced in the upper end of the fuel chamber. The

fuel is thus introduced into the channels or' atomizer 37 by difference in pressure and flows into the conduit 35 at a right angle to the direction of flow of air therethrough. It is thus atomized in the tube 35 and is again further broken u on 'its discharge throuofh the ring shape discharge end-34 into the main venturi 23.

As .heretofore stated, the channel 41 leads into the bottom of the fuel chamber through a vertical conduit 42. This conduit has an inletl aperture 43 after the nature of a valve seat and a pin 44 having a long taper is positioned within this aperture. This pin, under normal conditions and with the valve 22 closed, does not quite contact with the wall of the aperture 43, allowing a flow of vfuel therebetween sufficient to supply the At ordinary idling engine while idling. speed of operation of the engine, suilicient air is supplied through the Venturi tube arrangement above deseribed, and this metering pin is unaltered in position and flow is therefore restricted in quantity depending upon the setting of the pin 44. As the volumel of airvreqnired by the engine per unit of time is increased beyond that which the Venturi tube arrangement is capable of supplying, the increased demand causes suf.- icient degree of vacuum in the main air conduit 20 to open the valve 22 to a greater or less extent depending upon the demand. This valve 22 is lprovided with a vertical stem 45 extending through the wall of the conduit 20 and into the fuel chamber and the pin 44 is threaded into the end of this stemA so that, upon the valve 22 being deressed -to allow a greater volume of air l into the air conduit, the meteringpin is' retracted from the aperture 43 increasing the area of the space between the valve 44 andthe surrounding wall by reasonof the taper. of the pin and-thus allowing for an increased flow of fuel through the passageway. As'before stated, the taper of the valve isa long taper and is such that the flow is increased in relation to the lift of the valve 22. ume ofwair flowing through the conduit per unit of time, the volume of flow of fuel is also increased in proportion to maintain the required percentage of fuel to air flowing into the'intake manifold of the engine, and by altering the vertical position of the in 44 in relation to the seat 43l by screwing it into or out of the end of the stem 45 considerable variation in fuel flow may be produced, as may be required for adjustmen l The valve 22 is 'normally closed by means,-

of the cage is chambered and the upper end of the valve stem is provided with a vplunger 49 fitting the chamber and forming what may be termed a dash-pot, adapted to prevent fluttering of the valve under variation 1n pressure in the conduit 20. While this dash-pot arrangement is not essential to the operation of the carburetor I prefer to use an instrumentality of such character to prevent a fluttering of the valve which would affect the flow of fuel into the conduit 41.

The float 50 in the fuel chamber is pivotally supported on the wall thereof, as indicated at 51 and controlsl a valve 52 seating in the upper end of a channel 53 in communication with the fuel supply tank. The float 50 is centrally apertured to allow the stem of the valve 45 to pass therethrough, and on a fall in the level of fuel the valve 52 may lift due-to the vacuum produced by means of the passageway 40 heretofore described which draws the fuel into the chamber. On the fuel reaching normal level the lever 54 connected with the float forces the valve on ,to the seat and closes the channel 53 to the vacuum produced in the fuel chamber.

'By reason of the channel 40 communicating with the Venturi tube at the point of the greatest restriction therein the degree of vacuum produced in the top ofthe fuel chamber is greater than the degree produced in the main conduit 20. A further decrease of pressure in the conduit 41 is caused by the secondary venturi formed in the lconduit 35 below the point of communication of the Thus with an'increased volj passageway 40 therewith. I The quantity of from the supply tank to the carburetor and at the same time does not unduly throttlethe engine i. e., there is but a slight degree' of vabuum inthe intake manifoldand a considerably higher degree of vacuum in the fuel chamber.

vacuum in the fuel chamber, therefore, does \s'uction lof not act as a drag on the engine.

From the foregoing description it becomes evident thatmy improved carburetor is comparatively simple and inexpensive to manufacture and is highly efficient in operation` by'reason of embodying features of established superiority, as the metering pin controlling the fuel flow in relation to variation in volume o f air demanded, and incorporating therewith such an arrangement of parts as to utilize the aspira-ting effect of air passing through the carburetor to produce a flow ofl fuel into the fuel chamber thereof and from'the fuel chamber to the atomizer. This latter function is performed in the carburetor herein described by subjecting the fuel of the discharge conduit to a less degree of pressure than the fuel in the chamber. It is to be considered within the spirit of this invention as defined in the appended claims, however, to produce a flowv of fuel into the atomizer or jet of the carburetor by any approved means in combination with the means for utilizing the aspirating effect to 'produce a flow of fuel into the fuel chamber.

Having thus fully described my invention, its utility and mode of operation, what I claim and desire-to secure by Letters Patent of the United States isl. A carburetor comprising a casing, an anterior valve for restricting the flow of air into said casing, a p-air of Venturi tubes leading into said casing, a fuel supply reservoir, one of said venturi tubes having a suction port leading to said reservoir at apoint below the fuel level thereof, the other'of said Venturi tubes having a suction port leading to said reservoir at a point above the fuel level thereof.

2. A carburetor comprising a casing, an anterior valve for limiting the air passage into said casi-ng, a small Venturi tube extending into said casing and having a` s uc-` tion orifice for the delivery of fuel to said casing, a second Venturi tube extending into said casing and having a suction orifice for the maintenance ofa partial vacuum upon the) fuel for delivery to the first Venturi tu e.

3. A carburetor comprising a casin forming the enclosure for the `mixing c amber and its appartenant "airinduction chamber, a fuel sup ly reservoir, a small Venturi tube exten ing into'- the chamber of said carburetor .appurtenant to the mixing chamber and having a suction opening connecting with the upper spaces'of said reservoir, and other means for admitting all of the fuel to said mixing chamber.

4. In -a carburetor, the combination with a supply reservoir sealed against atmospheric communication, of .a small Venturi tube for The increaseddegree of the passage of air into the carburetor by the the suction producingl means for the carburetor, said Venturi tube being provided with an opening near the throat thereof connecting with the upper space of said reservoir, r whereby the partial vacuum crea-ted in the upper space of said reservoir will be-maintained greater than the partial vacuum in thebody of the carburetor and other means conducting all of the fuel into the carburetor.

5. In a carburetor the combination with a Abody portion forming'the main air passage for the carburetor, an anterior and a posterior throttle fo-r said passage, two Venturi tubes leading from atmosphere into said passage, a fuel reservoir, one of said Venturi tubes being connected with the lower part of the fuel reservoir and serving to deliver fuel into said passage, the other of said Venturi tubes being connected with the up` per space of said fuel reservoir, and serving to create a partial vacuum therein for raising fuel from a low 'level source to the fuel reservoir.

-6. In a carburetor, the combination with a body forming a main air passage, of a large Venturi tube in said passage, a small fuel delivery Venturi tube having its posterior end located at substantially the point of greatest suction in said large Venturi tube, a fuelreservoir, and a third Venturi tube having its internal en'd positioned at a' point in said passage anterior to the point of maximum suction of thelarge Venturi tube, said third Venturi tube being connected for producing a partial vacuum in the upper space of the said fuel reservoir.

7 In a carburetor, a chamber. adapted to be connected with the intake of an internal combustion engine, two fixed Venturi tubes chamber to the Venturi tube in which the lesser depression obtains. t

8. In a carburetor, a chamber adapted be connected with the intake of an internal combustion engine, two fixed Venturi tubes discharging into said chamber, said Venturi tubes being'of different characteristics whereby different degrees of depression obtain therein respectively when the-pressure in said chamber is reduced, a constant level liquid fuel chamber, a passageway for liquid fuel leading from below the liquid fuel level' in said constant level chamber to the Venturi tube in which thev greater depressiony obtains, a passageway leading `from above the liquid fuel level in said constant level chamber to the Venturi tube in which the lesser depression obtains, a liquidl yfuel supply tank in which the level of liquid fuel is below the level of liquid fuell in said constant level chamber, and afuel supply passageway leading from said supply tank to saidconstant level chamber.

9. In a carbure-tor, a chamber adapted to be connected with the intake of an ,internal combustion engine, two Venturi tubes discharging into said chamber, said Venturi tubes being of dierent characteristics whereby diferent degrees of depression obtain therein respectively when the pressure insaid chamber is reduced, a constant level liquid fuel chamber, a passageway for liquid fuel leading from below the liquid fuel level in said constant level chamber to the Venturi tube in which the greater depression obtains, a passageway leading from above the liquid fuel in said constant level chamber to the Venturi tube lin which the lesser depression obtains, :and a suction responsive valve controlling air admission to said chamber.

10. In a carburetor, a chamber adapted to be connected with the intake of an internal combustion engine, two Venturi tubes discharging into said chamber, said Venturi tubes being of different characteristics whereby different degrees of depression ob? tain therein respectively when the pressure in said chamber is reduced, a constant level liquid fuel chamber, a passageway for liquid fuel leading from below the'liquid fuel level in said constant level chamber to the Venturi tube in which the greater depression obtains, and a permanent passageway leading from above the liquid fuel level in-said constant level chamber to the Venturiy tube in which the lesser depression obtains.` v

11; In a carburetor, a chamber adapted to combustion engine, two Venturi: tubes discharging into said chamber, said Venturitubes being of different characteristicswhereby differenty degrees of depression obtain therein respectively when the pressure in said chamber is reduced, a constant level liquid fuel chamber, a passageway vfor liquid fuel leading from below lche liquid fuel level in said constant level chamber to the Venturi l tube inwhich the greater depressionobtains,

.a passageway leading from above the liquid be connected with the intake of an 'internal fuel level in said constant level chamber tubes being of different characteristics whereby different degrees of depression obtain therein-respectively when the pressure in lsaid chamber is reduced, a constant level liquid fuel chamber, a passageway for liquid fuel leading. from below theliquid fuel level i .in said constant level chamber to the Venturi tube in which the greater depression obtains, a the liquid' uel level in said constant level chamber to the Venturi -tube in which the lesser depression obtains, the atmosphere being suitably. excluded fromsaid constant level chamber so that the depression in said assageway vleading' from above last named Venturi tube may have effect therein, a liquid fuel supply tank in which thel level ofmliquifd fuel is below the level of liquid fasi Hr 'aidualacant,item1` chamber, and 'af fuel supply passageway leading directly from said supply tank to said constant level chamber whereby the feed of fuel tdsaid constant level fuel chamber is by suction.

In testimony whereof, I sign this specication.

HORACE H. WELCH.

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