US2232351A - Fuel control means - Google Patents

Description

Feb. 18, 1941. s. M. UDALE FUEL common MEANS Original Filed Feb. 1 1937 "I-NVENTOR Patented Feb. 18, 1941 UNITED STATES PATENT OFFICE mesne cuts, to Chandler-Evans Co ration, Meriden, Comm, a corporation of Delaware Application February 1, 1937, Serial No. 123,358 Renewed April 13, 1939 2 Claims. (01. 261-41) This invention is an improvement on the carthrough the passage K, which passage comburetor shown in the Milton J. Kittler application, Serial No. 107,386. In a carburetor of this type it is desirable that-the mixture ratio be 5 richer at maximum power than it is under throttle, because the engines towhich these carburetors are applied are built so closely to their safety limit that unless excess fuel is used, the

engines fallbecause' under excessive heat. the

10 strength of, the parts subjected to the heat is reduced below the safe limit. I

The applicant has discovered that the required additional fuel can be obtained by admitting fuel to the mixing chamber through a valve 15 controlled by the air flow in the air entrance,

the valve being so loaded that imtil a certain minimum air flow is reached, no additional fuel is added. By utilizing the Pitot tube effect and a diaphragm responsive to this effect, a con- 20 venient method is available with the fewest squared would be four times and the relative- Pitot tube effect would be doubled as the product of four times one-half equals two. There- 35 fore, the additional fuel received would be excessive unless means were provided to correct this excess fuel. Hence I o'ppou to the Pitot tube effect the effect of increased altitude, that is,v the effect of reduced atmospheric pressure by 4 employing a suitable sylphon bellows containing air at atmospheric pressure.

In the figures:

Figure 1 shows diagrammatically the fuel control means. f Figure 2 shows diagrammatically the altitude control.

mule flguresAisthefuelpump, Bisthe.

fuel outlet leading to a pair of needle valves C, C, which admit fuel to a diaphragm chamber l5 bounded on one side by the diaphragm E and on the other side by the diaphragm F. .Levers G, G engage with the center portions of the diaphragms E and I" and also with the needle valves C, C. Air chambers H, J enclose the 55 diaphragm F, E and are connected together municates with the air entrance passage L. The fuel outlet M from the upper portion of the diaphragm chamber D communicates with the center of the variable venturi N through the 5 nozzle passage 0. The flow is controlled by a needle valve P. The venturi N is formed of two movable curved elements Q and Q linked together. One of the elements Q engages with the needle valve P so that the needle valve P into the center of the venturi N. v

The fuel is supplied through the fuel. outlet B from the fuel pump A. A valve T is provided in the passage 8 and is controlled by a diaphragmU. Thediaphragm'flrespondstoa differential pressure created by the air flowing into and through the entrance e L which has a portionof Venturi-shape, the differential or Pitot tube effect being obtained by the use of the Pitot tubes VI and V2, VI facing downstream! substantially in the throat of the venturi portion of the e and V2 facing upstream to receive air at atmospheric pressure. An adiustable spring Y regulates the opening of the needle valve T. The pressure in the fuel outlet a from the fuel pump A is regulated by means of'a Bylphon bellows W responsive to atmospheric pressure and arranged to by-pass the fuel from the fuel outlet 3 backto the fuel. pump A when the pressure in Wexceeds a predetermined amount. Thusthc pressure in B is maintained a constant amount above that of the atmosphere. 1

In order to correct the mixture ratio for the variations in atmospheric pressure, the fuel control means is modified as shown in Figure 2. 40 Another Sylphon bellows x is placed back of the needle valve T. In order to regulate the effect of this Sylphon bellows, the spring Y is arranged to-cnsas with the diaphragm (I [through a lever z. The lever Z also transmits the movement from the diaphragm U to .the

needle T. The tendency that would otherwise exist as described abovefor the mixture ratio to get rich athigh altitudes is thus counteracted by the increase in pressure in the air enclosed in the Sylphon x at high altitudes. This increase in pressure is a relative increase, that is to say, an increase with relation to the pressure derived from the Pilot tube VI.

In the operation of the carburetor when the throttle elements Q. Q are moved towards each other, the needle valve P restricts the flow from the fuel. passage M to the fuel outlets O, 0. As the throttle elements Q, Q are opened and the valve P is opened, the fuel flow increases through M. At the same time, the air flow increases through L. The pressure differential acting on the diaphragm U also increases. If the air flow exceeds, for example, 4000 pounds of air per hour, the valve T will open slightly and as the quantity of air increases to 6000, the valve T becomes more and more open. There is thus an increase in fuel flow through the passage S from the fuel pump A. When the plane is flown at high altitudes, the same volume of air produces a less pressure differential, but a less quantity of fuel is required to counteract the tendency of the engine to overheat. The means for maintaining the mixture ratio constant at altitude is controlled by the Sylphon bellows X which reduces the opening of the needle valve T whenthe atmospheric pressure falls. v

What I claim is:

1. In a carburetor having a mixing chamber, an air entrance leading thereto, and a source of fuel supply under substantially constant pressure, a fuel supply chamber connected thereto, a pressure reducing valve for the fuel, said valve being adapted to maintain a relatively low pressure of substantially constant value in said chamber, a fuel outlet passage from said chamber adapted to discharge into said carburetor, a second fuel passage connecting the high pressure fuel supply directly to the carburetor, a valve in said second passage, and means directly responsive to the flow of air through said air entrance for operating said valve in said secon passage forthe purpose described.

2'. A carburetor as described in claim, 1 together with means responsive to variations in atmospheric pressure for opposing the action of the means responsive to air flow for the purpose described.

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