US1712293A - Carburetor - Google Patents

Description

May 7, 1929. M. G. CHANDLER CARBURETOR Filed Sept. 6, 1924 520672 0/: Word 6 flzarzdlefi UWKLQW Patented May '7, 1929.

NITE STATES PATEN mm MILFORD Gt. CHANDLER, OF- CHICAGO, ILLINOIS, ASSIGNOR, BY MESN'E ASSIGNMENTQ, T CURTIS B. CAMP, TRUSTEE, Oh OAK PARK, ILLINOIS.

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Application filed. beptembcr 6, 1924. Serial No. 736,25h.

lily invention relates tocai'buretors of the type which have provision for raising fuel from a low level supply tank to the level of the carburetorby suction obtained from the engine to which the carburetor is attached.

Certain features 'of my invention are applicable to carburetors of the type adapted to receive their fuel by gravity flow froma tank at a higher level.

vhichthe suction available within the mixing chamber on the intake manifold is augmented for lifting fuel from alow level supply to the level of the carburetor,

The advantages to be gained by an augmen-ted suction are fully set forth in my out No. 1,870,947, dated March 8, 1921, and such advantages, therefore, need not be re stated here.

One feature of my invention resides in means for obtaining a readily adjustable'mixture for operating the engine under the sub stantially closed throttle condition known as the idling condition. In accordance with this feature of my invention, a rich mixture of fuel and air is delivered above the throttle,

.while a lean mixture of fuel and air is fed past the throttle. By adjusting the size of the opening through which the rich mixture 16 fed, a correct mixture for any specific engine may be obtained.

Another feature of my invention is the provision of a step herein referred to as a throw-0d at a point of slight restriction in the main induction passage, the purpose of this step being to pick up liquid fuel which may be draining back toward the carburetor along the Walls and to throw that fuel back again into the air stream, this being accomplished by the creation of eddy currents due to the sudden enlargement of the induction passage.

A further feature of my invention resides in the provision of a pressed metal piston for all tails of constructionof the air valve and its supporting parts by means of which it is wholly guided upon its central hollow stem, thus eliminating friction and binding caused by manufacturing inaccuracies.

Still further features of my invention will be more fully pointed out in the following detailed description and the appended claims.

Other features are 10 applicable only to carburetors of the type in the carburetor air valve. and in certain de-' Figure 1 is a section through the induc I tion passage and the float chamber, the latter being shown connected with a low level source of fuel supply;

Figure 2 is an elevation; and Figure 3 is a section through the float valve seat, takenon the line 3-3'of Figure 1.

lfn the preferred embodiment of my invention, the float chamber cover t is cast integrally with the main housing 5, thus providingva structure through which'the various air and fuel passages -may be conveniently formed. Depending from the float chamber cover is an integral pillar 6 carrying a lateral projection 7 to which the float 8 is pivotedat 9. A valve member 10 has a working fit within a cylindricalbore through a part of the lateral member 7 and has a conical point ill 11 which forms a valve for closing the open ing 12 leading from the transverse bore 13 which connects with the hollow portion of the stem 6 into the milled slot ll. The float threaded into the hollow portion of the lower end of the pillar 6, A tubular filter screen 19 is carried upon a threaded plug 20, which is screwed into the member 18, thus providing ready means for removing the screen for cleaning out sediment. Fuel delivery con.- nection to the float chamber is made through a fitting 21 threaded into an opening in the cover 4-. v

The float chamber parts thus described operate in the usual manner to maintain a substantially constant fuel level in the float chamber, whether fuel is fed thereto by gravity or by suction. Valve 10, being cylindrical instead of triangular or slotted, as is customary, presents a larger wearing surface to the guiding opening in the progection than is obtained with the usualconstruction, thus preventing leakage due to cooking of the valve, which is a source of trouble in many carburetors.

The main air passage to the carburetor body 5 is through the conical vhorn 25 which is supported within the groove in the body 5.

The main valve member 26 normally closes the induction opening into the carburetor through the horn 25 and is so shaped that lift as it is raised from its normal position, the

passageway between its own external wall and the inner wall of the horn is increased in area. The inner wall of the horn and the outer wall of the valve are flared at substantially the same angle. so that for all of the different positions of the valve, the passageway created between the valve and the horn enlarges in the direction of flow of the air through the passageway. The rate of enlargement of this passageway is of extreme importance, since for all positions of the valve 26 the passageway between it and the horn constitutes a Venturi tube for creating an augmented suction to draw fuel into the passageway. For this purpose the valve 26 is of hollow construction and is provided with an integral central tube 27 connected by radial holes 28 with the passageway between the valve 26 and the horn. It has been found preferable that the holes 28 discharge into the passage between the valve 26 and the horn at a region immediately down stream from the point of greatest restriction, and to provide this structure, the external end of the valve 26 is formed of such diameter toconstitute a greater restriction than at any other of the positions along the valve. It hasbeen found preferable that the valve be guided upon a hollow tube 27, and, for this purpose, the body is provided with a downwardly projecting cylinder 30 in which the tube 27 has a freely working fit. The external part of the wall of cylinder 30 is provided with a shoulder 31 forming a seat for the pressed cup or piston 32 and forming an abutment for the spring 33 which tends to hold the valve 26 in its normal closed position. The piston 32 substantially closes the open end of the valve member 26, thus forming within the valve member a well 34, the evacuation of which operates the valve, causing it to open and close in response to variations in suction within the mixing chamber. An opening 35 is provided through the wall of the tube 30.

Through this hole the air is withdrawn from the well allowing it to fill with fuel, as hereinafter described. The cup 32 may conveniently be held in placeby a screw 36.

A rich mixture of fuel and air is delivered to the central tube 27 of the valve 26 from a nozzle Venturi tube 38 which is mounted within the bore in the housing 5, which bore connects with the hollow portion of the cylinder 30. The throat diameter of the Venturi tube 38 is small, so that it creates a sufficient restriction to the inflowing air that even for the lowest idling operation of the engine, the valve 26. will be slightly lifted ofi. its seat in the horn 25 to admit some air through thesecondary air passage. Fuel is conducted to the nozzle openings 39 in the wall of the Venturi tube 38v through a passage 40 which is extended through a pipe 41 to the lower part of the float chamber. The external end of the Venturi tube 38 is conically formed at 42, so that when the Venturi tube 38 is tightly screwed into place, a sealed chamber 43 will be formed between the Venturi tube and the bore in the housing to conduct fuel to each one of the plurality of nozzle open ings 39. These nozzle openings 39 are preferably provided with stream line entrance curves, as it is found that this construction materially decreases the resistance to the flow of fuel.

The air entrance to the Venturi tube 38 is provided with a removable cap 45 formed with an inner sleeve 46, so that the air is caused to enter between the cap and the sleeve and reverse in direction before entering the Venturi tube. This construction aids in dampening the noise created by the air rushing through the throat of the Venturi tube 38.

A vacuum Venturi tube 48 is fitted into an openin in the housing 5, so that its discharge enc lies adjacent the outer surface of the valve member 26, the latter being contoured so as to variably obstruct the discharge end of the Venturi tube 48 for different positions of the valve 26. The throat of the Venturi tube 48 is connected through a passage 49 with the upper part of the float chamber for the purpose of creating a suction in the float chamber for drawing fuel thereto from a low level source of supply. The opening at the throat of the vacuum Venturi tube 48 is preferably made very smalh its only function being to admit sufficient air to create an augmented suction in the float chamber.

A manually rotatable cam 50 is pivoted on the housing 5 by means of a screw 51, and is held in spring' contact with a flat surface on the housing by means of the star spring washer 52. The rotation of this cam varies the size of the entrance openin to the Venturi tube 48, thus altering the egree of suc tion augmentation produced by this Venturi tube. When it is desired that the mixture shall be richer, the entrance to the Venturi tube 48 is held nearly closed, thus cutting down the flow of air and decreasing the Venturi action. WVhen the cam is rotated to an extreme position, the entrance to the Venturi tube 48 is entirely closed so that the suction in the upper part of the iioat chamber is thus entirely unaugmented and is the same as that existing in the body of the carburetor. When the cam is in this latter position, the opening 53 comes opposite the duct 54 which leads to the chamber 34 within the valve 26, thus opening an atmospheric communication which prevents the valve 26 from being lifted off its seat. This causes a high suction within the mixing chamber, drawing a rich mixture into the carburetor for cold starting.

The shape and proportions of the air passage through the body of the carburetor are of primary importance in securing performence and in the prevention of loading. After the air becomes charged with fuel, part of which is in the form of vapor and part of which is in the form of finely divided particlcs held in suspension, it has been found advantageous to prevent swirls, eddy currents and back flows, as these are likely to cause the deposit of liquid fuel upon the walls of the carburetor. [is an aid to the columnlike flow of fuel and air toward the engine, the cross sectional area of the passageway which conveys the mixture toward the engine is maintained substantially constant, the form of the housing 5 and that of the plunger support 56 being such that the area of the passage is not materially altered from the region in which the mixture leaves the space between the valve 26 and the horn to the region immediately below the throttle 57. Since it is not convenient to maintain the column movement of the mixture past the throttle, and since a part of the liquid fuel is consequently deposited on the induction passage walls at this point, it has been found expedient to provide means for re-atomizing the liquid fuel which is thus deposited on the walls. The means herein provided comprises a suddenslight enlargement of the parsageway by means of a shoulder 58 followed by a gradual enlargement of the passageway for a distance of one-half inch or more. This construction causes a definite baclr draft along the wallson the engine side of the step 58 and likewise creates a high suction or depression at the region immediatelyabove the step The liquid fuel running back along the walls entering this region of high depression is again whipped off the corner of the step 58 and carried into the air stream in an atomized form, thus effectively preventing the collection of large drops of fuel, which, when carried into the engine cyllnders, dis

turb the combustible qualities of the mixture."

In this embodiment of my invention, l have provided a duct 60 leading from the space immediately beyond the discharge end of the Venturi tube 38 and discharging on the en gine side of the throttle 57. A screw 61 in tercepts this passage 'andby its position obstruets the same to a greater or less degree, as conditions demand. The discharge end of the'passage 60 is subjected to high suction when the throttle 57. is closed, thus drawing a rich mixture of fuel and air into the mani fold on the engine side of the throttle. The size of this passage is so small that the amount of mixture passing through it is insufficient for the operation of the engine, so that a quantity of leaner mixture is of necessity allowed to enter the manifold around the throttle 57. The adjustment of the screw 61, therefore, controls the richness of the mixture and serves as a ready means to compen sate for the air leakage around the engine intake valve stems, which leakage changes with the wear of the stems. Thus the idling mixture can be readily altered to properly proportion it for different engine conditions.

When the engine demand is low, as, for example, when the throttleis one-fourth open and the valve 26 will assume a position somewhat above normal and the major portion of the air. for supplying the engine will enter the induction passage of the carburetor through the opening between the valve 26 and the horn 25. As this air rushes past the openings 28 through the valve 26, it creates a suction which, from experience, isfound to be substantially. twice as great as the suction in the induction passage above the upper limits of the valve 26. The suction produced on the ends of the passages 28 prevails throughout substantially the entire length of the tube 2? and acts upon the discharge end of the nozzle Venturi tube 38, creating a flow of air through that tube which creates a suction at the nozzle openings 39 which is substantially twice as great as the suction within the tube 27. The suction, therefore, on the nozzle openings 39 is substantially four times that prevailing in the induction passage of the carburetor below the throttle. The suction in the chamber 34E within the valve 26 is substantially equal to that of the induction passage immediately above the edge of the valve 26, because the space between the valve 26 and the piston 32 is suflicient to cause a substantial equalization of suction within and without the chamber 34. The fit between the tubes 27 and is sufficiently free that the high suction in the passage through the tube 2'? causes a flow from the chamber 34 into the tube 27. The flow being in this direction carries with it liquid fuel which flows along the outside of the valve 26 and along thegap between the valve 26 and the plunger 32, This fuel entirely fills the chamber 34, the opening 35 serving as a passage for the withdrawal of air from this chamber until the chamber is filled with car speed is 15 miles per hour, the

fuel, and after the chamber is thus filled with fuel, serving as a passage through which a slight amount of fuel continuously circulates due to the higher suction within the tube 2'? than that prevailing at the upper edge of the valve 26.'

f The flow ofair through the Venturi tube 48 creates a suction upon the surface of the fuel in the fioatchamber. This suction being augmented by the Venturi tube 48 is about twice as great as that-existing in the body of the carburetor at the opposite end of the Venturi tube l8. This suction is available for lifting fuel from the low level supply tank to the float chamber of the carburetor, but, since it is not as great as the suction prevailing at the nozzle openings 39, it does not prevent the feeding of fuel from the float chamber to the carburetor; The adjustment of the suction on the fuel in the float chamber by means of the cam and by means of the contoured external surface of the valve 26 createsa proper fuel feeding diiierential to maintain the correct proportion of fuel to air.

lVhe-n, the throttle 57 is more widely opened, the higher suction preyailing on the engine side of the throttle is conveyed to the induction passage through the carburetor and is thence conveyed to the interior of the valve 26, causing that valve to raise to a more widely open position. The movement of the valve ejects a portion of the fuel from the chamber 34 into the air as it passes through the carburetor, thus supplying the amount of fuel necessary to prevent leanness during engine acceleration. Conversely as the throttle is closed and the engine speed is, consequently, decreased, the valve 26 moves downwardly, drawing additional fuel into the chamber 34, thus preventing overrichness incident to the decelerating condition of an internal combustion engine.

As formerly stated. for cold starting, it is desirable that the mixture shall be extremely rich. To provide this rich mixture-the cam 50 is moved so that the opening 53 comes in alignment with the passage 54, thus relieving'the suction within the chamber 34 and preventing the valve 26 from opening at least to the same degree that it would were the suction not thus relieved.

It will be understood that many features of the invention herein described are applicable to carburetors of the gravity feed type, though some of the features are applicable only to carburetors of the suction feed type. In order to convert this carburetor into one of the gravity feed type, it is necessary only that air be admitted to the float chamber to prevent the suction therein from rising to as high proportions as when the carburetor is used for suction delivery of fuel to the bowl. lVith this alteration, the spring 33 may have a less compression than when the carburetor is used for suction feed. All other features of the device may remain entirely unchanged.

lVhile I have shown and described my invention with respect to certain details, it is to be understood that these may be modified in many respects without departing from the spirit or scope of my invention.

\Vhat I claim 1s:

1. In a carburetor. the combination with a casing including an induction passage. apiston member supported centrally within said induction passage, a hollow valve member operating about said piston member and controlling the fiow of secondary air to said induction passage, the support for said piston being fixed and substantially cone-shaped and the outer walls of the induction passage contracting about the conical support for the piston whereby the cross sectional area of the induction passage is maintained substantially constant around the piston and piston support and immediately above the piston support.

2. In a carburetor, 'the combination with a casing forming an induction passage, of a hollow piston support within the induction passage, a hollow cup-shaped piston attached to the piston support, a valve member operating about said .piston, said valve member being adapted to regulate the flow of secondary air into said induction passage.

In witness whereof, I hereunto subscribe -my name this 4th day of September, 1924.

MILFORD G. CHANDLER.

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