US2230144A - Airplane carburetor - Google Patents

Description

Jan. 28, 1941.

Original Filed Oct. 28, 1936 M. J. KITTLER AIRPLANE CARBURTOR 2 Sheets-Sheet 1 MILTON J. KITTLER.

BY l

Jan. 28; 1941. A M. J. KITTLER 2,230,144

` AIRPLANE CARBURETOR originalriled oct. 28, 193s 2 sheets-sheet 2 MILTON J. KlTfrLER.

BY M 271, M A ATroRNEY.

Patented Jan. 28, 17941 UNITED STATES PATENT vOFFICE AIRPLANE CARBURETOR Milton J. Kittler, Detroit Mich., assignor, by

mesne assignments, to Chandler-Evans Corporation, Meriden, Conn., a corporation of Dela- Application october 28,1936, serial No. 107,961

1 Renewed June 2, 1939 3 Claims. (Cl. 261-34) 'I'he object of this invention is to eliminate one of the` hazards of flying. In the carburetor described herein an automatic fuel pump operated by the vacuum below the throttle delivers 2 extra fuel every time the throttle is opened and substantially atmospheric pressure is restored below the throttle. If landing with the throttle partly closed, the engine ignition is switched oi, the vacuum is destroyed below the throttle and this destruction of the vacuum causes the diaphragm of the pump to function and fuel is ejected into the mixture chamber and drawn into the hot cylinders before the engine has ceased l to rotate. If -one of the engines should have a hot spark plug, ignition might take place at very low engine speed with the result that owing to the high compressions used a very violent shock would be transmitted to the engine and tothe propeller. Alternatively the engine might start up and moveV the plane forward or causethe plane to deviate from 'its path, if there were tion the mixture or altitude fuel control valveV is thrown to the extreme lean position and if means are arranged Yso that'by so doing the accelerating pump is put out of commission (and cf course the accelerating fuel pump is of no value at ceiling altitudes) ,the above mentioned diiiiculty is avoided. When switching oil', the

engine will quit with a lean mixture and whatis more important, and the gist of the invention involved here, .a ymechanical "hookup" is provided whereby the fuel pump is put out of commission when the mixture or altitude fuel control valve is put into the lean position by sealing.

up the Vvacuum chamber` which operates the diaphragm vof the accelerating pump. Then the above mentioned hazards are completely eliminated.

Figure 1 shows the carburetor to which this invention is applied, together with vthe accelerating pump and is a cross sectional elevation taken on the plane of the principal-fuel passage.

Figure 2 Vshows 'the `'corresponding drawing I have taken on the plane parallel to that of Figure 1 through the means for putting the accelerating pump out of action at landing.

Fig. 3 is a plan view of Fig. l with parts broken away and parts in section showing certain features of the invention.

The carburetor chosen for illustration of the invention is of the variable Venturi type in which the throttles serve both as throttles and as walls dening the venturi.v In this carburetor, Y fuel is supplied from a fuel pump and enters the carburetor at A and passes through passages to orices controlled by needle valves C--C into a constant pressure fuel chamber T. Thepressure in the chamber T is maintained constant by mechanism including'levers B plvoted at P and suitably connected with exible diaphragms J and K as more particularly disclosed in my co-pending application Serial No. 107,386 led October 24, 1936 and in vPatent 2,088,464 dated July 2'7, 1937.- The flexible diaphragms J and K constitute the opposite side walls of the constant pressure fuel supply chamber T and each of them forms one wall of one ofv a pair of air chambers L and M which communicate with each other through a passage D and with the carburetor air entrances through a pipeN. Restriction ,'N' restricts the air iiow throughthe pipe N and serves to modify the effects of depression created in the pipe F', passage D which communicates with pipe F', and a pipe F" which communicates with the throat of the venturi, by virtue of the low pressure or suction created inthe 'throat of the venturi. The venturi is formed by throttles 30 and 3|- which areV rotatable between open y and closed positions, the throttles being shown in closed position in Figs. 1 and 2. The flow of air through pipes F' and F" is regulated jby the valve F and lever Z'I. A nozzle bar H provides. the main fuel orifices or .ietsY and is disposed between the vtwo throttles 30 and 3|.

The fuel from the constant pressure supply chamber T flows through a restriction R, the

Vopening in which is controlled by a needle III which is moved toward or from a position clos- 4- ing the oriiice R- by mechanism including a. double thrust collar I2 which is engaged4 by a lever I3 pivoted at 28, which lever carries a cam follower Il at all times engaged in afcam track formed in a cam track member I5. The cam track member I5 is carried by a pivoted shaft I6 which also carries a gear I l which meshes with a gear 2li in turn meshed with a gear I9. As

Vthe gear 2D is secured toga stub shaft on the throttle member AI0 and asthe gear I 9 isA simitsV nsl

larly secured to a stub shaft on the throttle mem- `ber 3|, rotary movement of the shaft I6 will open or close the throttle members 30 and 3| and simul- ,of the device to which this invention is more ,particularly directed, that is, the accelerating zfuel pump and associated mechanisms. A cavity or chamber in the carburetor body is divided Ainto an accelerating fuel chamber 54 and a pres- .sure chamber 58 by means of a diaphragm 55. The

accelerating fuel pump chamber 54 is connected with the constant pressure fuel chamber T by a passage controlled by a valve 53. 'I'he diaphragm 55 is normally urged toward the left (Fig. 2) by springs 52 while a reduction of pressure in cham` ber 58 tends to move diaphragm 55 to the right (Figs. 1 and 2). Chamber 58 (Figs. 2 and 3) communicates through passages 80-8I with the inside of the hollow throttle 3|, the down stream face of which is of Venturi form and communicates through a series of openings 59 with the mixture outlet O which leads to the engine. A valve 82 is mounted on the end of a shaft 83 in turn mounted in a sleeve guide 84 secured within the body f the carburetor. An extension 85 from the lever 21 is arranged to engage with the end of shaft 83 when the lever is moved to the leftor counterclockwise (Fig. 3) into a position which opens valve F the arrangement being such that when the valve F is opened the valve 82 is closed against its seat. A spring 86 tends to open the valve 82 when the extension 85 is .disengaged from the `end of the shaft 83, that is, when the lever 21 is moved to the right or clockwise (Fig. 3): A take-up springj-81 permits a limitedmovement of lever 21 after the valve 8-2 has been seated. A spring loaded valve 51 normally closes an outlet orice from a passage leading from accelerating fuel chamber 54 to the space above the throttles 30-3I so that under certain conditions additional fuel may be supplied to the engine.

The automatic pump constituted by the diaphragm 55 and its related mechanisms normally discharges fuel past t he valve 51 every time the throttle is opened and the pressure in the mixture outlet O increases since such increased pressure effect is transmitted into the chamber 58 thereby to permit the springs 52 to movewthe diaphragm 55 to the left. Alternative means or supplemental means are provided for closing the valve 82 when the throttles are closed.

nevertheless, is arranged to engage withthe shaft Voperating mechanismV so that when the throttles are closed the engagement of projection '90 with lever 88 will effect closing of the valve 82.

Operation When landing and immediately before turning o ff the ignition, the valve F is moved to "the extreme counterclockwise position that isto say, the valve Fis opened Wide. This operation closes the valve 82 thereby sealing off chamber 58 $0 as to maintain the low pressure therein and to hold the diaphragm 55 as far to the right (or against moving to the left) as its position then is. This prevents the springs from moving the diaphragm to the left (Fig. 2) so that no fuel from chamber 54 will be ejected pastvalve 51. If this safety device were not provided then ifthe engine were shut off (especially with the throttle partly closed) the low pressure in chamber 58 would be broken at about the time the engine was coming to a stopl but before the engine actually had stopped. Under such circumstances of ordinary conditions the diaphragm 55 would be moved to the left and the fuel in chamber 54 would be suddenly discharged through the outlet nozzle 51, and, if there were suiicient heat in any engine' cylinder to cause ignition of the fuel thus supplied, a very dangerous result could obtain. Such possibilities are entirely obviated by the invention.

The fact that the engine is stopped under the extreme lean condition is an additional safety device because it causes the mixture in the cylinder after the engine is switched off to be less liableto explode than if the normal mixture were present and therefore the engine will stop promptly with the turning. off of the ignition, which is the object of this invention. Alternatively, even if the operator forgets to put the lever 21 into the lean position provided he closes the throttle 3|, the Valve 82 will still be shut off and the engine will quit promptly immediately the ignition is switched off. i

In the event that the pilot changes his mind and decides not to make a landing, he immediately throws the valve 21 into the rich position for low altitude, that is to say, he closes the valve F and at the same time he opens the throttles 3| and 32. The result of these maneuvers is to admit atmospheric air past the throttle through the opening 59, along the-passage 8|, past the valve 82, down the passage 80, into the chamber 58, re-establishing atmospheric pres# sure in this chamber. The springs 52 and diaphragm 55 then move to the left and eject fuel through the nozzle 51 in Fig. 1 into the air entrance of the carburetor. In' the event that the pilot changes his mind and Wishes to re-ascend and make a second attempt to land, it is of the utmost importance that the engine shall pick up without any hesitation.

What I claim is:

1.`In a carburetor having an air entrance, a throttle valve, and a .jmixture outlet, fuel supply means for said carburetor, a spring operated accelerating fuel pump including a displacement member and a fuel chamber into whichsaid displacement member may be moved by action ef the spring, a fuel passage connecting said fuel supply means with said fuel chamber, a nonreturn valve in said fuel passage for admitting fuelv to said fuel chamber, a fuel outlet leading from said pump, a lvariable pressure chamber into which said displacement member may be drawn for operating said pump on its suction "stroke, a passage connecting said variable pres- 'sure chamber with said mixture outlet, a valve in the vsecond said passage, means for closing the last said valve, a mixture vcontrol valve for valtitude effective to vary the flow through said fuel supply means, and means interconnecting .said mixture control valve with said valve closing means whereby as the altitude control is moved to the high altitude position the valve in l the second said passage is closed.

. 2. In a carburetor having an air entrance, a throttle valve and a mixture outlet, fuel supply means for said carburetor, a differential pressure operated accelerating fuel pump, a fuel passage connecting said fuel supply means with said pump, a non-return valve in said fuel passage, a fuel outlet leading from said pump, means for operating said fuel pump including a passage connected with said mixture outlet for subjecting the pump to pressure variations in said mixture outlet, a valve in the second said passage, manual means for closing the last said valve, a mixture control valve for altitude eective to vary the fuel flow through said supply means, said mixture control valve being interconnected with said manual means and the throttle valve being also interconnected with said manual means whereby when the throttle valve is closed and alsowhen the altitude control is moved to the high altitude position the first said valve is closed.

3. In a carburetor having an air entrance, a throttle valve and a mixture outlet, a primary fuel supply chamber, a flexible diaphragm forming one wall of said primary chamber, said chamber having a connection with a source of fuel and being adapted to receive fuel at one side of said diaphragm, means providing an air chamber at the other side of said diaphragm,.a passage connecting said air chamber with the air entrance of said carburetor, a second passage connecting said air chamber with the mixture outlet,

a valve in the second passage, a secondary fuel supply chamber having a flexible diaphragm forming one wall thereof, means for delivering ture outlet, a valve controlling the connection` between said second air chamber and said mixture outlet, a fuel passage connecting the two fuel supply chambers, a check valve in said connecting fuel passage, a fuel discharger nozzle, a valve for controlling air ow through said connection between said second air chamber and said mixture outlet, and means adapted to close said air flow control valve and to open the valve controlling said passage connecting the rst mentioned air chamber and the mixture outlet.

l l Y MILTON J. ICI'I'ILER.

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