US2387676A - Carburetor - Google Patents

Description

Oct. 23, 1 945 B. c. PHILLIPS CARBURETOR 2 Sheets-Sheet l Filed March 17, 1943 r INVENTOR. W 6% w Oct.j2 3, 1945. B. c. PHILLIPS CARBURETOR 7 Filed March 17, 1943 2 Sheets-Sheet 2 INVENTOR.

Pic. 7

Patented Oct. 23, 1945 CARBURETOR' Bernard C. Phillips, Toledo, Ohio, assignor to The Tillotson Manufacturing Company, Toledo,

Ohio, a corporation of Ohio t l Application March 17, 1943, Serial No. 479,532

, t t t t 1 Claim. This invention relates to carburetors and more especially to aviation carburetors of relatively small capacity.

In carburetors used at ground level elevations,

little eifect on fuel mixtures is encountered due tothe changes in air or atmospheric pressure. In airplanes the carburetor must function properly.at ground levels, at very high altitudes, and at all intermediate positions. In order to obtain the proper mixture ratio, that is the ratio of fuel to air, at all altitudes it is necessary to provide special means to compensate for the change in the density of the air. Numerous devices are in use atthe present time that accomplish this purpose, but all of these devices are used in connection with carburetors for large engines. Many attempts have been made to use the same types of control devices as used on large carburetors, only in smaller sizes. .None of these devices have proven successful on the small carburetor.

One of the objects of my invention is to provide an altitude mixture control that will operate properly on a small capacity. carburetor.

Another objects ofmy invention is to provide an altitude mixture control that can be used with or without a supercharger. 7

Another object of my invention is to provide an altitudemixture control that is simple, durable, dependable and inexpensive.

My invention will be best understood from the detailed description and claim which follows reference being made to the accompanying drawings in which a preferred embodiment of my invention is shown byway of example in which:

Fig. l is a front elevation of a carburetor embodying my novel invention.

Fig. 2 is a top plan view of a carburetor embodying my invention. 3

Fig. 3 is a sectional view taken along line 3-3' of Fig. 2.

Fig. 4 is a sectional view taken along line 4-4 of Fig. 2.

Fig. 5 is a sectional view of Fig. 2.

Fig. 6 is an enlarged sectional view of a portion of the carburetor shown in Fig. 4. 1 i Fig. '7 shows a variation of my novel invention. Referring to the drawings I have shown an taken along line 5-5 aviation carburetor It) provided with a flange ll whereby the carburetor is fastened to an intake manifold I2. Air enters the carburetor Ill through the air horn l3 and passes through the venturi [4, where the air is mixed with the fuel,

and then flows into the intake manifold l2. A

pin 35.

compensating tube l5 has one end opening into the air intake l3 and the opposite end into the passageway IS. The passageway 16 terminates in a control chamber H. A sealed metal bellows I8 is located in the control chamber IT. The sealed metal bellows I8 is held in a definite position by means of the adjusting screw I91 which is screwed into the threaded hole 20. After the initial adjustment, the screw I9 is locked and sealed in position. An air flow control 2| is fastened to the lower end of the sealed metal bellows l8 and operates in a restriction or orifice 22 located in the plug 23. The lower endof the pin 2! is provided with a shoulder 24 which operates in the annular hole 25 to serve as a guide for the air flow control pin 2|. The air chamber 25 is connected to the annular chamber 21 by means of the passageways 28. A passageway 29 connects the annular chamber 2'! to the intermediate chamber 3!]. The intermediate chamber 39 opens into the Venturi or mixing chamber M as shOWn in Fig. 5, by means opening 43. i

The carburetor I0 is provided with a fuel inlet 3!. Fuel is supplied by means of a fuel pump or other suitable means. The fuel inlet 3| leads into a conventional float bowl where a substantially constant fuel level is maintained by means of a float and lever arrangement. The float 33 is fastened to a lever34 which is fulcrumed on a When the fuel flows into the bowl and reaches the desired level the inlet needle 36 is pushed upward closing the fuel inlet. As the fuel level drops the float 33 drops, thus lowering the arm member 34 which in turn allows the inlet needle 36 to drop which opens the fuel inlet and allows more fuel to enter the float bowl 32. In this way a substantially constant fuel level is maintained in the float bowl 32.

A fuel passageway 31 connects the float bowl 32 to the fuel chamber 38. A fuel passageway 40 in the nozzle 39 transmits the fuel to the nozzle restriction 4|. The nozzle restriction 4| is an orifice conventionally used to control the of the quantity of fuel required.

A passageway 42 connects the control cham-- her I! to the float bowl chamber 32.

When air is drawn through the carburetor air intake l3, it flows through the venturi I4 where increased velocity of the air causes a decrease the fuel passageway 31 into the fuel chamber 38. From the fuel chamber 38 the fuel flows into the nozzle passageway 40 through the restriction 4| into the auxiliary mixing chamber 30 where it is mixed with a limited amount of air delivered through passage 29. The mixture then flows through the, opening 43 into the Venturi or mixing chamber l4. Here the fuel is mixed with more air to form a combustible mixture.

After the proper size of fuel restriction or orifice 4|, the amount of air bleed and the outlet 43 have been determined for proper fuel to air mixture ratios, the carburetor will continue to deliver the same mixture ratio as long as the air pressure is not materially changed.

As an airplane leaves the ground and. climbs to higher altitudes, the air pressure decreases.

The lowered air pressure decreases the density of the air but has little effect on the density of the fuel. For each cubic foot of air flowing through the venturi a given amount of fuel is metered to the air stream regardless of air pres sure changes. As the air pressure decreases, the air becomes less dense and the mixture ratio becomes richer with fuel; therefore, some means must be provided to prevent mixtures from becoming too rich at higher altitudes. This is done in large capacity carburetors by the use of a metering pin acting directly in the fuel nozzle which decreases the fuel flow as the air pressure decreases. Quite satisfactory results are obtained on large capacity carburetors by this method; however, these structures have not proven practical in small output carburetors due to the difficulty in development and duplication of such. control in combination with the small fuel orifice required.

My invention controls the flow of air that changes the suction on the fuel restriction instead of attempting to vary this restriction. When air is moving through the air horn l3 and venturi [4 the suction at 43 causes air to flow into compensating tube l5 through the passageway IS, into the control chamber I1, and then through the orifice or restriction 22 into the air chamber 26. From the air chamber 26 the air passes through the passageways 28 'into the annular chamber 21 and then through the passageway 29 into the intermediate mixing chamber 30. From the intermediate mixing chamber 3!! the air from the passageway 29 and the fuel from the nozzle restriction 4| pass through the opening or passageway 43 and mix with the main air supply entering through the venturi to form a combustible mixture of fuel and air which is drawn into the intake manifold l2. Since the suction on the passageway 43 remains constant for a given flow of air the suction in the intermediate mixing chamber 30 also remains constant. The amount of fuel drawn through the nozzle restriction 4! will dependupon the amount of air entering the intermediate mixing chamber 30 from the passageway 29. My invention provides a metering pin located in the orifice 22 to control the fiow of air to the intermediate mixing chamber 30. The greater the flow of air from the control chamber the less the suction in the intermediate mixing chamber 30 and hence less fuel flows from the nozzle restriction 4i.

The sealed metal bellows i8 expands as the pressure in the control chamber decreases and contracts as the pressure increases. This expansion and contraction of the bellows causes the conical shaped air flow control pin 2| to move up and down in the orifice 22 and the varying diameter of the control pin 2| changes the effective area of the opening in the orifice 2|, thus regulating the flow of air through the orifice. When my novel carburetor is used at higher altitudes the pressure in the air horn l3 decreases. This pressure is transmitted to the air control chamber I1 and causes the bellows to expand which moves the air flow control pin so that more air is permitted to enter the intermediate chamber' 30, thus reducing the suction on the fuel nozzle restriction 4| and maintaining the proper mixture ratio.

A passageway 42 connecting the control chamber l1 and the sealed float bowl chamber provides a means for equalizing the pressure in the air mitted to the control chamber I! through the compensating tube I 5 and the passageway Hi. This pressure in the control chamber causes the bellows l 8 to contract or partially collapse, which raises the air flow control pin 2|, thus decreasing the flow of air through the orifice 22. This produces a greater suction in the intermediate mixing chamber 30 and as a result more fuel is drawn from the fuel supply through the nozzle restriction 4!. Thus a proper fuel mixture is maintained regardless of the pressure.

Fig. 7 discloses another form of my invention. In this form of my invention the nozzle restriction 45 is at the lower end of the nozzle 46. Fuel flows from the float bowl 32 through the passageway 31 into the fuel chamber 38. The fuel then flows through the nozzle restriction 45 into the auxiliary mixing chamber 41 where air from the air passageway 29 enters through the holes 48. The flow of air from the air passageway 29 is controlled as previously described. The flow of air through the holes 48 controls the suction on the fuel restriction 45 in the nozzle for providing proper fuel mixture ratios as described. This form of applicants novel invention varies from the one described above in that the auxiliary mixing chamber 41 is located within the nozzle 46, instead of between the nozzle and the venturi as shown in Fig. 5.

From the above description it will readily be seen that my novel mixture control device can be used on carburetors of small capacity as well as on large ones and that it will operate properly at all altitudes with or without the use of a supercharger.

While I have described the details of two forms of my invention, I do not wish to be limited to the particular forms shown and described as it will be apparent that many modifications therein can be made without departing from the scope of my invention as set forth in the appended claim.

Having thus described my invention what I claim is:

In a carburetor, an air inlet, a mixture passageway, a float bowl, a mechanism for maintaining a constant fuel level in said float bowl, a fuel passageway extending from said float bowl below said fuel level, a fuel spray orifice in said fuel passageway, an intermediate mixing chamber between said fuel orifice and said mixture passageway having an outlet in line with said orifice, a

In such an ar-' control chamber, a plurality of air passageways communicating with said control chamber whereby the pressure in said float bowl and said control chamber are equalized with pressure in said air inlet, an air passageway extending from said control chamber to said intermediate mixing chamber, a barometric pressure responsive control means mounted in said control chamber, an orifice in said last mentioned air passageway, an air flow control valve directly mounted on said pressure responsive control means, said pressure responsive means adapted to move said flow control valve axially in said second orifice, said axial motion of said air flow control valve varying the effective opening of said second orifice whereby the air flow to said auxiliary mixing chamber is automatically controlled, thereby varying the suction in the intermediate mixing chamber to compensate for variations in fuel mixtures caused by difierent pressures in said air intake.

BERNARD C. PHILLIPS.

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