US2418184A - Pumping mechanism - Google Patents

Description

April 1, 1947- J. w. M CONAGHY 2,418,134

PUMPING MECHANISM Filed Nov. 18, 1945 INVENTQR IIZWIZGSWJI ms ATTORNEY.

Patented Apr. 1, 1947 PUMPING MECHANISM James W. McConaghy, Phillipsburg, N. J., as-

signor to Ingersoll-Rand Company, New York, N. Y., a corporation of New Jersey Application November 1 8, 1943, Serial No. 510,713

6 Claims.

This invention relates to pumps, and more particularly to a pumping mechanism for use in the fuel system of an air craft.

As is well known, the tendency of the lighter fractions of gasoline to evolve from the'liquid varies with variations in the pressure to which the gasoline is subjected. Thus, in the fuel system of an air craft the formation of vapor bubbles in the fuel supply increases with the increased altitude at which the air craft is being operated, and if bubble-laden fuel is delivered for distribution to an engine the fuel pump often becomes vapor-bound and is unable to effect delivery in the form and quantities required for the efiicient operation of the engine.

With a view to overcoming this objectionable occurrence it has been proposed heretofore to incorporate a booster pump in the fuel line for delivering the liquid under pressure to the fuel pump. Under certain conditions of operation this expedient serves, to prevent the occurrence of vapor lock at the fuel pump, but it is not altogether satisfactory for the reason that the booster pump itself may become vapor-bound. This condition arises from the violent agitation of the liquid by the pump impeller and the bubbles thus created collect at the inlet opening of the pump and break the continuity of flow of liquid fuel to the engine.

In accordance with the practice of the invention it is contemplated to assure the delivery of fuel to the booster pump in a substantially bubblefree form. This is accomplished by providing the mechanism with a reservoir serving the function of a stand-pipe that opens directly into the fuel supply tank and through which theliquid passes to the pump inlet. The fuel is delivered to the reservoir in the form of a rising column to which is imparted a whirling motion that tends to separate the lighter fractions from the fuel and causes them to accumulate in the zone of minimum pressure in the rising column of liquid, namely, the central portion.

The liquid constituent of the fuel Spills into the reservoir to maintain a constant net positive suction head for the booster pump and the bubbles of vapor and gas pass freely through the upper end of the reservoir into the fuel tank, whence they may escape through the tank vent to the atmosphere.

The stream of liquid pumped into the reservoir is of such a volume that a constant and full flow may be maintained from the upper end of the reservoir into the fuel tank in order to preclude the admission of gasoline directly from the fuel tank through the reservoir to the booster pump.

One object of the invention is to deliver the fuel to the fuel pump in a fully liquified state.

A more specific object is to prevent the delivery of fuel to the fuel pump of an engine in a vaporous or gaseous state.

A further object is to maintain a constant suction head on the booster pump of an. air craft irrespective of the level of the liquid in the supply tank or the altitude to which the air craft may rise.

Other objects will be in part obvious and in part pointed out hereinafter.

In the drawings accompanying this specification and in which similar reference numerals refer to similar parts,

Figure 1 is an elevation, partly in section, of a pumping mechanism constructed in accordance with the practice of the invention and a fuel tank to which the pump is attached,

Figure 2 is a view similar to Figure 1 taken on the line 22 in Figure 1 and looking in the direction indicated by the arrows, and

Figures 3 and 4 are transverse views taken through Figure 1 on the lines 3-3 and 44, re-

spectively.

Referring more particularly to the drawings, 20 designates a fuel tank, and 21 is a pumping mechanism for pumping liquid fuel, as for example gasoline, from the tank 20 and is driven by a suitable motor 22 only a portion of which is shown in the drawings.

The pumping mechanism comprises a casing 23 that is arranged in a vertical position on the fuel tankand consists of upper and lower sections 24 and 25, respectively. The confronting ends of bolts 29.

the sections 24 and 25 are in telescopic engagement with each other and are secured together by bolts 26 and 21. The lower section 25 carries an external flange 28 that seats against the bottom of the tank 20 and is secured thereto by The casing section 25, in turn, supports the motor 22 which is secured to said section by bolts 30. p

The section 25 serves as the casing of the booster pump and is recessed to provide an impeller chamber 3| having an outlet 32 for the discharge of liquid from the impeller chamber. Within the chamber 3| is an impeller 33 that is mounted upon the shaft 34 of the motor 22. The impeller is of the open-type and the ends 35 of the. portions of its vanes adjacent the inlet end of the impeller preferably extend slightly above the inlet opening 36 of the impeller chamber so that vapor bubbles breaking back from the impeller chamber along the wall or the inlet opening 36 will be fanned outwardly away from the stream of liquid entering the impeller.

Suitable provision is made for the escape of the bubbles rising from the impeller chamber by forming an annular. chamber 31 in the adjacent end of the casing section 24 and in the outer wall of the chamber 35 are outlet openings 38 through which the vapor may escape into the fuel tank 20. Preferably, only two outlet openings 38 are provided for this purpose and they are disposed in diametrically opposite sides of the casing section 24.

The inner surface 39 of the annular chamber 31 is tapered toward the inlet opening 36, and the external diameter of the end Portion 40 thereof is slightly smaller than the diameter of the inlet opening 36 and is spaced a sumcient distance from the end of said inlet opening to provide an unrestricted annular path 4| through which the bubbles of ,vapor may pass from the inlet opening 36 into the chamber 31.

In accordance with the practice of the invention, means are provided for effecting the separation of vapor and gas from the liquid prior to its delivery to the booster pump and to assure a substantially constant net positive suction head for the booster pump, irrespective of the level of the fuel in the tank 20. To these ends the pumping mechanism is provided with a second pumping chamber 42 in the upper portion of the casing section 24 and in communication with the lower portion of the fuel tank 20 through inlet passages 43, in the section 24. The inlet passages are located diametrically opposite each other and at right angles to the openings 38' to prevent the vapor bubbles issuing from the latter openings from being drawn into the inlet openings 43.

The pumping chamber 42 is defined by an annular skirt 44 at the upper end of the section 24. It accommodates a propeller 45 that is secured, by meansof a nut 46, to a shaft 41 extending downwardly through the section 24 and connected to the motor shaft 34 by a pin 48 extending through the two.

4 stant stream of liquid will flow from the upper end of the tubular member 50 into the tank 20 to prevent liquid from flowing from the tank directly through the annular chamber 52 to the booster pump.

In the operation of the device, liquid entering the pumping chamber 42 through the inlet passage 43 is pumped upwardly through the discharge conduit 49 and a rotary motion is imparted to the liquid by the propeller 45 to cause the lighter fractions to flow toward the center of the rising column of liquid and pass through the central portion of the' tubular member into the fuel tank 20.

Upon issuing from the discharge conduit 49 the liquid spills over the upper edge of the discharge conduit against the inner surface of the portion of the tubular member 50 lying above the discharge conduit. Some of this liquid will fill the chamber 52, the passages 53 and the chamber 54 to maintain a substantially constant head of vapor-free fuel upon the booster pump.

During the operation, the portion of the liquid in excess of the requirements'of the booster pump The propeller is situated below the upper end of the skirt portion 44 and pumps the liquid through a discharge conduit 49 that is in telescopic engagement at its lower end with the inner On the outer surface of the skirt portion 44,

and arranged concentrically with the discharge conduit 49, is a tubular member thatis connected thereto by radially extending ribs 5 I. The tubular member 50 cooperates with the discharge conduit 49 to define an annular chamber 52 that communicates at its lower end with the inlet opening 36 of the impeller chamber 3| through passages 53 in the casing section 24 and a chamber 54 connecting the lower ends of the passages '53 and lying directly over the inlet opening 35.

The lower end of the tubular member .50 is secured to the skirt portion 44 by screws 55, and its upper end extends above the discharge conduit 49 and opens directly into the tank 20. Thus, by the arrangement described and with a propeller 45 of greater pumping capacity than the impeller 33 the liquid rising in the discharge conduit 49 will spill over the edge of the free end thereof into the tubular member 50 and a conwill flow from the outer end of the tubular member 50 into the container and prevent the charging of the booster pump directly from the supply tank 20. As will be apparent, therefore, only liquid of lower vapor pressure than that present in the supply tank will be delivered to the booster pump whether the level of liquid in the tank lies above or below the upper end of the tubular member 50; and a constant net positive suction head may at all times be maintained for the booster pump irrespective 'of the variations of the atmospheric pressure in the supply tank.

I claim:

1. Pumpin mechanism for liquid-fuel, comprising a casing'having an impeller chamber and an outlet for the chamber, .an impeller in the chamber, a reservoir above the impeller chamber constituting a supply passage therefor and having an opening at its upper end to permit liquid to spill from the reservoir, and pumping means for pumping liquid into the reservoir and having greater pumping capacity than the impeller,-and a discharge conduit for the pumping means having its discharge end within the reservoir below the opening to deliver liquid to the reservoir and to the opening.

'2. Pumping mechanism for liquid-fuel, com-v prising a casing having a propeller chamber and an inlet passage therefor, an'impeller chamber and an outlet therefor in the casing, an impeller in the impeller chamber, a discharge conduit for the propeller chamber having its discharge end at a higher elevation than the propeller chamber, a propeller for pumping liquid from the propeller chamber through the discharge conduit,

and means cooperatin with the discharge conduit to define asupply passage for-the impeller .chamber and the inlet end of said supply passage a higher elevation than the propeller, and means defining a supply passage for the impeller chamher and the inlet end or said supply passage being Positioned to receive liquid Welling from the discharge conduit.

- 4. Pumping mechanism for liquid-fuel, comprising a casing having an impeller chamber and an outlet therefor, an impeller in the chamber, a

tion oi gas and vapor from the liquid prior to the delivery of the liquid to the reservoir.

5. Pumping mechanism for liquid-fuel, comprising a casing having an impeller chamber and an outlet therefor, an impeller in the chamber, a reservoir above the impeller chamber constituting a supply passage for the impeller chamber and being open at its upper end to permit the 25 flow oi excess liquid from the reservoir, a supply cmduit for the reservoir extending through the reservoir and terminating at it discharge end below the upper end of the reservoir, and a propeller for pumping liquid from the container through the supply conduit into. the reservoir and for imparting a whirling motion to such lid- 30 Number ma in the supply conduit to cause the separation of gas and vapor from the liquid prior to the delivery of the liquid to the reservoir, said propeller having greater pumping capacity than the impeller to effect the constant flow of liquid from the upper end of the reservoir.

6. Pumping mechanism for liquid-fuel, comprising a casing having an impeller chamber and an inlet and an outlet therefor, an impeller in the chamber, means forming an annular reservoir above the impeller chamber and being open at its upper end p. propeller to pump liquid from the container into the reservoir and to impart a whirling motion to such liquid for causing the separation ofvapor and gas from the liquid, said propeller having greater pumping capacity than the impeller to effect the constant flow of liquid from the upper end of the reservoir, and .a discharge conduit extending through the reservoir to convey liquid from the propeller into the reservoir and having its discharge end located below the upper end of the reservoir.

, JAMES W. McCONAGHY.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Name Date 2,806,301 Curtis Dec. 1942

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