US2252958A - Carburetor structure - Google Patents

Description

, G. M. BICKNELL CARBURETOR STRUCTURE Aug.

Original Filed Aug. '7, 1936 2 Sfieets-Sheet 1 INVENTOR.

Geo/:98 M fi/cl-ne/L BY ATTORNEY.

Aug. 19,1941. GMBlCKNELL 2,252,958 VCARBURETOR STRUCTURE" Original Filed Aug. 7, 1936 2 Sheets-Sheet 2' Y INVENTOR. Q6098 M 5/0676.

ATTORNEY.

. Patented Aug. 19, 1941 UNITED STATES PATENT OFFICE CARBURETOR STRUCTURE v I I George M. Biclmell, St. Louis, Mo., assignor to- Carter Carburetor Corporation st. Louis, Mo., a corporation of Delaware Substituted for abandoned application Serial No. 94,764, August 7, 1936. This application July 19, 1939, Serial No. 285,410

2 Claims. (c1. 261-34) This invention relates to carburetors and particularly to arrangements for preventing the withdrawal of fuel through the accelerating pump by suction when the carburetor is passing a large usually provided with accelerating pumps for supplying additional fuel when the engine is being accelerated. Since the carburetor is also provided with a main nozzle and an idling port which, generally, are calibrated for supplying the entire normal requirements of the carburetor during constant speed operation, it is undesirable to have the accelerating pump discharge at such time because the additional fuel would cause the engine to be supplied with an unduly rich mixture. The accelerating discharge nozzle frequently is positioned so as to discharge a compact jet into a part of the mixture conduit where relatively high suction prevails'at least at times, during normal operation of the carburetor, which suction tends to draw fuel from the accelerating system.

In order to avoid such discharge from the acceleratlng passage due to suction, there have been suggestions to provide an air bleed from this passage as, for instance, in Henning Patent No. 1,915,930 which provides an air bleed communicating with the inside of the mixture conduit. This arrangement has proved not wholly satisfactory due to substantial depression whichexists even inthe' air inlet portion of the carburetor at higher speeds of operation. Such depression, though less than that which exists in the high suction zone of the carburetor adjacent the venturls, nevertheless seriously reduces the eflectiveness or the bleed. This difficulty is enhanced by the air cleaner which is always mounted on the air horn of an automobile carburetor and restricts the entering air. Ball Patent No. 1,358,498 provides an outside air bleed for the accelerating discharge passage, but the arrangement is such that the accelerating iuel cannot be discharged in a. jet into the mixture conduit and, indeed, will likely spill out through the air bleed. Other constructions developed for the same purpose require a valve to prevent the squirting of fuel into the outer atmosphere or constant level chamber of the carburetor and this valve is not only expensive but frequently is notreliable.

The object of this invention is to produce an celerating pump which will effectively prevent the pulling over of fuel through the accelerating pump when the carburetor is operated under high suction conditions. V

Other objects and advantages oiv the invention will appear from the following description and accompanying drawings referring to which:

Figure l is a vertical, sectional view ofa' form of carburetor embodying the invention.

Figure 2 is anenlarged view of a portion of the structure in Figure 1.

Figure 3 is an enlarged view of the discharge nozzle of the accelerating pump. l j

The carburetor shown includes. a, downdraft mixture conduit having an air inlet horn I, mixing chamber 2, and a series of venturis 3 and I. A chokevalve 5 is pivotally mountedin the air horn, and a throttle valve 6 is mountedon pivot 6a in the lower part of the mixing chamber. ,The reference character 99- indicates an air cleaner or strainer which is applied to the inlet end of the air horn or mixing condult'.' The interior construction of the air cleaner not shown as it may be of any desired type but it may benoted that the object of this device is to remove dust and dirt from the air and also to silence the flow of air through the carburetor so that there is a certain amount or restricting died on the air flow.

A fuel bowl 1 adjacent the mixture passage encloses an accelerating pump cylinder 8, piston 9, and piston rod l0 controlled from the throttle by means of a crank ll, link l2, and lever l3 pivoted tothe fuel bowl cover. The pump cylinder communicates through passages I4, 15, and I6 withan inclined Orifice I'I leading upwardly and outwardly through the wall of the mixture conduit. Orifice I1 is plugged at its upper end, as at I8. I

During normal operation, fuel is fed from an? other portion of the fuel bowl through calibrated Jet l8, controlled by metering rod 20, and main nozzle 2| discharging into the throat of primary venturl I.

Upward movement of piston '9 draws fuel from bowl 1 through a passage 22, past check ball 23 into passage II, and lowering of the piston forces fuel past check ball 24 into orificeor chamber l1 and the mixture passage through an auxiliary nozzle, generally indicated at 25. The general features of the carburetor structure described arrangement for the discharge outlet of the acbody h i a th e ed p er P on 25 mounted in orifice l1, and a tip 21 discharging into a relatively high suction zone of the mixture conduit adjacent venturis 3. The threaded portion of the auxiliary nozzle also includes a screw driver slot 93. Intermediate its ends, nozzle 25 is provided on its outer surface with an annular recess 28 separated from tip 21 by a collar 29 which substantially seals therecess from the port 91 of passage I1 and themixture conduit. Collar 29 is provided with a very narrow annulus 29a, which, being made of brass is capable of being slightly deformed to fit the exact contour of the bore 91.

Extending longitudinally through the nozzle 22 is a boreor passage 30 having a restriction 3| intermediate its ends. When the nozzle is properly assembled with the carburetor body, as shown in the figures, bore 30 communicates with the atmosphere through radial passages 32, annular recess 28, and a passageway 33 connecting orifice H. with the atmosphere outside the carburetor. The capacity of the vent due to the effective areas ofiradial passages 32, annular recess 28 and the passageway 33 is preferably greater than the capacity of the bore 30 .so that substantially all the suction applied to bore 30 from the mixture conduit is killed by the open vent 33 so that it cannot be-efiective to pull fuel through the orifice 3|. The effectiveness of the air ducts 32, 28 and 33 may be varied to conform with requirements due-to other carburetor features.

During operation of the accelerating pump,

. liquid fuel under pressure will be forced through '1 30 from the mixture passage will be substantially broken by air bleeding through the passages 32 and aperture 33, preventing drawing of fuel from the accelerating system.

The outside vent passageway is shown opening downwardly into a pocket between the fuel bowl and mixture conduitg but the passageway may be otherwise disposed so as to open through any convenient part of the carburetor body. In the arrangement shown, the passageway 33 is substantially protected against dust and foreign matter circulating in the vicinity of the carburetor. The protection is provided, in the present instance, by the location of the inlet of passage 33, but for greater assurance of protection from dust. a strainer or filter 96 may be provided.-

For the convenience of those skilledin the art who wish to use the invention, a practical embodiment may be dimensioned as follows: If the restricted orifice 3| is made not greater in area than .000'75 (#68 drill size) then the passageway 30 may be made .00169 or #56 drill size. The two passageways 32 may be of #58 drill size so as to total .00276 in area, and the passageway 33 may be drilled with a #42 drill which will give the passageway an area of .00686. All of the above areas are given in decimals of.a square inch. It will be understood that the length of these passageways has an effect on the restriction presented thereby but good results were secured with a device constructed in approximate accordance with the scale used in Figure 2.

When the proportions indicated herein are used, the fine stream squirted through the jet 3| will shoot directly through the passageway- 30 so that it will not be impeded by striking the walls thereof and the stream will not, accordingly, be broken into fine drops until it gets out into the mixing conduit beyond the end of the passage 30.

The accelerating nozzle described comprises a relatively simple unit which functions satisfactorily to supply partially atomized fuel to the mixture passage and to prevent pulling over of fuel from the accelerating pump by suction. Obviously, various features of the illustrated structure may be modified as will occur to those skilled in the art and the exclusive use of all such modifications as come within the scope of the appended claims is contemplated.

I claim: 1

1. In a carburetor, a mixture conduit having a restriction forming a suction zone,an accelerating fuel system including a pump, a passage connecting said pump with said conduit at one side of said zone including a discharge nozzle having its bore terminating adjacent and substantially in line with the mixture conduit wall for discharging a jet of accelerating fuel across said conduit, and a suction breaking bleed passage intersecting the. inner end of the bore of said nozzle and communicating with a zone of substantially atmospheric pressure, said nozzle having a restricted fuel orifice immediately anterior to said bleed passage for forming the normal pump discharge into a jet, the portion, of said bore posterior to said bleed passage being coaxial with said orifice and sufiiciently wide and short so that said jet will be projected therethrough and beyond the mixture conduit wall during pump operation substantially without wall friction.

2. In a carburetor, a mixture conduit surrounding a high suction zone including a Venturi tube and a lesser suction zone adjacent the same, a main fuel supply system including a nozzle under the influence of said high suction zone, an accelerating fuel supply system including a pump, an accelerating nozzle having a passage connected with said pump at one end and its other end comprising a bore opening into said lesser suction zone adjacent the conduit wall. a suction breaking bleed passage intersecting the inner end of said bore and communicating with a zone of atmospheric pressure outside the mixture conduit, and said nozzle providing a restricted fuel orifice in said fuel passage adapted to-form a liquid fuel jet immediately anterior vto and coaxial with said bore, said bore bein sufiiciently wide and short so that said jet will be projected through said bore and beyond the conduit wall during normal operation of said pump substantially without striking the walls of said bore. said bleed passage being larger than said orifice so as to substantially satisfy suction applied to said orifice from said mixture conduit.

GEORGE M. BICKNELL.

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