US2343752A - Pump pressure limiting device - Google Patents

Description

March 7, 1944. R, R, CURHS 2,343,752

PUMP PRESSURE LIMITING DEVICE Filed March 26, 1942 /Od Eg.

Patented Mar. 7, 1944.l

UNrEos'rA'rs PATENT -oFFic-s PUMP' PRESSURE LIMITIN G DEVICE Russen n. Carus, nayten, ohio, assignmto Curtis Pump Company, Dayton, Ohio, a corporation o! Ohio v Application March 26, 1942. Serial N 0. 436,265

7 Claims. (Cl. 103.-42)

This invention relates to pump assemblies'of the type especially adapted for use in high altitude aircraft fuel systems.

Morel particularly, the invention relates to centrifugal pump assemblies in which gas and vapors are separated from the liquids so that only fully liquid material is pumped and in which there is provided a pressure relief valve mechanism for limiting the discharge pressure of lthe pumped'material to a predetermined value independent of variations in the speed of rotation of the pump impeller.

In accordance with this invention, a pump casing is so mounted with relation to a source of liquid, such as a fuel tank, as to be below the hydraulic gradient of the liquid.t The casing has an inlet throat communicating with the source of liquid and a pumping chamber receiving pressured liquid from the throat. An impeller disk having pumping vanes thereon centrifugally pumps theliquid from the throat to the pumping chamber. This impeller'also carries an agitatin'g A propeller acting on the liquid before-it reaches the pumping vanes; The propeller is lpreferably positioned at the inlet to the pump between the pump and a guide 'cone carried by the pump. The guide cone is preferably disposed in the fuel in the tank to direct fuel to the 4pump inlet and to deflect bubbles of gas and vapor beaten out of the liquid fuel by the propeller away from the fuel flowing to the pump. A

v As the liquid flows from the fuel tank through the cone and into the pump it is beaten or agitated v and bubbles of. gas or vapor are liberated from w the liquid. Thesebubbles are thrown radially outward from the inlet throat and rise on the youtside of the cone through the liquid in the fuel tank to burst at the surface of the liquid. The gases and vapors are thus liberated from the liquid. Fully liquidA materialis then pumped by the vanes on theimpeller and centrifugally discharged into the pumping chamber of the pump.

In those installations of a ,centrifugal pump in which the motive power is of the variable speed type, or -when the pump is used in aircraft fuel sumoiently great to'upset proper carburetion in the carburetor of the engineto which the fuel is eventually delivered.

In order that the discharge pressure might be limited as the speed of the impeller isincreased,

` It is, therefore, an object of this invention to` provide a pump 4whose discharge pressure is limited to a value below that capable of being produced by the pump.

Another object of this invention is to provide a liquid pump with a discharge by-pass whereby the discharge pressure is variable only to a predetermined value. Y

, A further object of this invention is to provide a ley-pass mechanism between the outlet and the inlet of a pump which is operable at a predetermined discharge pressure.

A still further object of this invention is to provide a spring pressed relief valve mechanism for the volute chamberof a centrifugal pump.

Another and still further object of this invention is' to provide a centrifugal booster pump having a pumping impeller with a spring pressedv relief valve mechanism between the discharge and inlet sides thereof vwhereby the discharge pressurefeiected by the pump impeller is limited systems to pump fuel directly from the fuel tank to the engine carburetor and the vimpellerspeecl is increased to effect a continuous iiow of fuel at high altitudes, the pump discharge pressure changes in proportion to the change in impeller speed. When the impeller speed is increased thel discharge pressure will likewise increase with the result that the discharge pressure might build up above a desired maximum. If uncontrolled, the discharge pressure might even reach a point to a predetermined value. A further object of this invention is the provision, in a centrifugal booster pump, of an inlet throat having a spring pressed relief valve mechansm connecting lthe pumping chamber of the pump with a fuelA tank from which the pump receives liquid.

The novel features believed to be character- .I

istic of the present invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and manner of construction, together withfurther objects and advantages thereof, may best be understood by reference to the followingA description taken in connection with the accom panying drawing, in which: v

Figure 1 is a fragmental vertical cross-sectional view along the line I-I of Figure 2, with parts in elevation, of a centrifugal booster pump, a fuel tank` on which the'pump is mounted, and a by-pass valve mechanism between the pumping chamber of the pump and the interior of the fuel tank;

Figure 2 is an enlarged plan view. with the guide cone omitted, of the pump assembly as seen when taken substantially in the plane indicated by the line II--II of Figure 1; and,

Figure 3 i's an enlarged fragmentary vertical cross-sectional view, with parts in elevation, as seen when taken substantially in the plane indicated by the line III-III of Figure 2.

In Figure l, the'reference numeral I0 designates a fuel tank, vented as at |Da, and containing a pond P of liquid fuel, such as gasoline. The bottom wall of the tank has a circular aperture |017 therein. A mounting ring II is positioned in the tank on the bottom wall thereof around the aperture Ib.

A booster pump I2, of the centrifugal type, is suspended on the bottom wall of the tank around the aperture Ib. The pump includes a casing I3 defining a pumping or volute chamber It and a shaft housing I5. The casing |3 is connected with a source of motive power (not shown) which drives a shaft I6 in the housing portion l5 of the casing. The casing has an out-turned annular ange I1 for mounting on the bottom wall of the tank. The flange l1 receives cap screws I8 at spaced intervals therearound which are threaded into blind tapped wells in the mounting ring lI. dered, or otherwise secured to the bottom of the tank.

The casing has a circular opening I9 into which a circular throat ring 20 is seated.

As shown in Figure 1, the throat ring includes a nat bottom wall or horizontal leg 2| and a top wall or leg 22 which extends from the inner end of the leg 2| upwardly and outwardly where it terminates in a horizontal portion in spaced parallel relation above the leg 2|. The outer diameter of the leg 2| is sized to seat within the circular opening I9 of the pump casing and has adannular groove 2Ia (see Figure 3) in the periphery thereof for receiving a seal ring 2lb' preferably formed of resilient material.

The upper leg 22 has a plurality of ears or lugs 22a which partially overlie the flange l1 in spaced relation therefrom. Apertured spacers 23 are interposed between the flange I1 and the lugs 22a. Cap screws 24 are inserted through the lugs 22a, the spacers 23 and into threaded encone C has a plurality of legs L at spaced inter- I vals therearound each of which are equipped with feet F adapted to be bolted on the throat ring. The cone converges toward the aperture 2E to guide fuel to the pump but terminates in spaced relation above the aperture to provide an The mounting ring may be welded, solgagement with blind tapped wells in the pump V acierta open space through which the beaten out bubbles can pass.

'I'he booster pump has an impeller assembly 21 mounted on the drive shaft I6. This impeller assembly includes a disk or flange portion 28 spanning the inlet or aperture 26 in the throat ring and communicating freely around the periphery thereof with the inlet of the pumping lchamber I4. Pumping van'es 29, mounted on the flange 28 around the outer margins thereof, underlie the throat ring 20 and the flange 28, open ended pumping channels communicating at their outer ends with the pumping chamber I4 and at their inner ends with the inlet of the throat ring.

A cap or fairing member 30 extends axially upwardly from the disk or flange portion 28. The cap member 30 receives the shaft i6 therein with the upper end of the shaft having a threaded well for receiving the stem bf a cap screw 3|. The cap screw coacts with the shaft to clamp the cap or fairing member 30 on the shaft.

A propeller assembly 32 has an apertured hub for receiving therethrough the stem of the cap screw 3|. The hub is interposed between the cap screw head and the fairing member 3|) where it is clamped in position. The propeller assembly 32 is illustrated as having four radially extending blades 33. This number may be more or less, it only being necessary to provide as many blades as will eiect proper agitation of liquid fuel flowing towards the inlet mouth of the pump. It is t0 be noted that the cap or fairing member 3D extends upwardly through the throat ring to position the propeller assembly 32 on the side of the throat ring opposite the impeller assembly 21.

The blades 33 of the propeller assembly 32 agitate the fuel flowing down from the fuel tank into the inlet throat for the purpose of beating out bubbles of gas andvapor entrained in the liquid fuel. Rotation of the propeller assembly throws these bubbles outwardly from the inlet side of the inlet throat through the space between the bottom of the cone C and the top of the throat ring where they rise in the pond P around the cone to the surface thereof and burst into the atmosphere.

The bubble-freed liquid lenters the pump through theinlet mouth 26 of the throat ring and it is then pressured by the impeller assembly into the pumping chamber.

The pressured liquid then passes into a discharge pipe 34 and from there into a fuel line 35. In the usual aircraft fuel systems, the pressured fuel flows through a fuel line into an engine driven fuel pump and from there directly to the engine carburetor. Should the engine fuel pump fail in operation, the speed of the booster pump can be increased in order to deliver liquid fuel directly to the carburetor of the aircraft engine, either through the inoperative fuel pump or through a by-pass therearound. Any increase In the rotating speed of the impeller will produce a proportionately higher discharge pressure through the pumping chamber. It has been found in high altitude operation of aircraft that a pressure in the discharge side of the booster pump up to a certain value is sufficient for insuring the flow of liquid fuel to the engine carburetor. A maximum discharge pressure can be predetermined for insuring delivery of a full volvume of liquid fuel constantly to the engine driven fuel pump or, if the engine driven fuel pump is inoperative, directly to the engine carburetor. In order to eliminate the necessity for careful control of the speed at which the pump is driven in.

order to attain the predetermined pump pressure, a pressure relief mechanism is provided. This relief mechanism is so regulated as to effect the desired discharge pressure' even though the impeller speed is increased to a value which would normally result in a much higher discharge pressure.

As shown in the figures in the drawing, a plurality of pressure relief valves 36 are provided around the inlet throat ring 20. Each relief valve includes a seat formed by the linner edge of an outwardly tapered aperture 31 through the lower leg 2| of the throat ring. An enlarged aperture is provided in the other leg 2 2 of the throat ring in axial alignment with the aperture 36 for receiving a cup-shaped valve member 38. The valve member 38 has a reduced base 33 at its inner end for receiving one end of a coil spring 4H.` The outer end of the valve member has anenlarged bore 4I for loosely receiving therein a ball 42. The ball 42 is normally held against the valve seat by the spring 40 thereby holding the pumping chamber i4 out of flow communication with the ports 25.

As shown, the valve members 38 are maintained within the leg 22 of the throat ring by a centrally apertured plate 43 overlying the horizontal portion of the leg 22 and clamped thereon by cap screws 44. These cap screws 44 can also be used to extend through the feet F of the cone legs L to bolt the cone on`top of the pump assembly.

It is preferable, although not necessary, that the leg 22 be recessed to provide a shoulder 45 adjacent the inlet aperture' for seating the plate 43 flush with the outer face of the leg 22.

It is to be noted that the opening 31. is so po- .sitioned in the lower leg 2| of the throat ring through the volute chamber by the impeller assembly. When the speed of rotation of the motive power of the pump impeller assembly is increased, the discharge pressure of liquids pumped by the pump impeller into the volute chamber will increase proportionately. When thel discharge pressureiin the volute chamber exceeds the pressure of the coil springs 40, the latter co1- lapse, and the balls 42 are urged away from their valve seats. Liquid under pressure within the volute chamber will then circulate through the av centrifugal pumpl of the type described, the discharge pressure thereof will vary up to a predetermined value as the speed of the impeller is increased. As soon as this predetermined value is reached the discharge pressure of the pump the present invention.

I claim as my invention: l l l. In a. centrifugal type pump including a casing having a central inlet throat opening into a source of fluid supply and a peripheral volute chamber, animpeller with pumping varies between said throat and said volute.chamber for pumping fluids received from said source through the throat into the volute chamber, said inlet throat having a relief passageway joining said volute chamber with said source, and means nor-` mally closing said passageway sensitive to a predetermined pressure in the volute chamber for opening the passageway whereby the pressure in the volute chamber is limited to a predetermined value.

2. In a centrifugal type of pump havingl a casing defining an inlet opening and a discharge volute chamber, a throat ring in said inlet openllng having spaced legs connected by a curved web portion, one of said legs overlapping said discharge volute chamber, the space between said legs andthe inlet of said pump opening into a source of fluid supply, an impeller with pumping 'vanes between said -throat ring and said volute openings 3l and the ports 25 into the Vfuel tank I0. Consequently, the pressure exerted by the coil springs 40 determines the maximum dis-l charge pressure of liquids pumped by the impeller` assembly through the volute chamber and into the dischargeline 34. Obviously, this maximum pressure may be changed as desired, either bythe ball 42 whilethe bore 39 issmaller in diameter to limit the inward movement of the ball. Furthermore, the valve member projects into the space between the legs 2l and 22 to loosely hold the ball 42 in proper -alignment with its valveseat. This eliminates any possibility ofthe ball being laterally displaced in the ports 25 and into' the interior of the tank l0.

It will be apparent from the foregoing that in chamber receiving uids from said source through the throat and pumping the fluids into the volute chamber, at least one opening through said overlapping leg of the throat ring connecting the discharge volute chamber and the source of fluid supply to now therebetween, a ball seated on a seat defined by the edge of said opening on the side of said one leg opposite the side overlap# ping the volute chamber, and a coil spring normally maintaining said ball on the seat4 to close said opening, said ball being urged away from said seat when the pressure in said volute chamber exceeds the pressure of said spring whereby the volute chamber is vented through the opening into the'source of fluid supply.

3. In a. centrifugal type of pump having 'a casing dening an inlet and a discharge volute chamber, a circular throat ring of U-shaped secmeans between` said one vleg and'said inlet, an

impeller with pumping vanes between said throat ring and said volute chamber receiving fluids from said source through the inlet opening and pumping said fluids into said volute chamber, openings through said one leg spaced around said throat ring for connecting the space between said legs and the volute chamber to uid flow, a ball for each of said openings seatable on the side of said one leg opposite the side overlapping said volute chamber, and a coil spring for each ball having one end seated on a ball and its other end seated in a recess in the other leg of said throat ring for normally maintaining the opening in said one leg closed, said ball being urged away from said opening when the pressure in said volute chamber exceeds the pressure of said coil spring whereby pressure in the volute chamber is released into the space between said legs.

4. In a pump having a casing dening an opening, a hollow throat ring arranged to be seated in said casing opening, said throat ring having spaced superimposed legs connected b'y a curved web whose inner surface defines a ilared inlet for the pump, one of said superimposed legs being sized to seat within said casing opening, an

v radially extending legs on the other of the superimposed legs on said throat ring, said radially extending legs overlapping said pump casing, spacers between said radially extending legs and said casing, and means for connecting said radially extending legs and spacers to said casing, the space between said radially extending legs deil'ning ports communicating with the space between the superimposed legs of the throat ring.

5. A throat ring construction comprising a. hollow ring member having spaced radially extending legs connected at their inner ends by a curved web, radially extending legs spaced circumferentlally around one of said legs 4for connecting the ring member to a support, aligned openings in said legs, and a valve mechanism in an opening in one of said legs for normally closing an opening in the other of said legs, said valve -mechanism including a cup-shaped member inserted in said opening of said one leg and opening toward said opening in the other leg. a ball, and spring means carried by said cup-shaped member for normally urging said ball against the edges of said opening in the other leg to close the same.

6. A throat ring construction comprising a hollow ring member having spaced radially extending annular legs connected at their inner ends by a curved'web defining a ared surface extending axially through the ring member, circumferentially spaced apertured legs on one annular leg adjacent the flared end oi the ring member, pairs of aligned openings through said spaced legs, the openings in the other annular leg being tapered away from said one leg, a ball for each tapered opening in said other leg and being sized for seating on the edges of the opening at its largest end, a cup-shaped member in l each opening in said one leg extending into the space between said legs, said cup-shaped member opening toward the aligned tapered opening in said other leg and having a bore at its outer end for loosely receiving said ball, a coil spring in said cup-shaped member for normally maintaining said ball against said tapered opening to cover the same, and a ring plate seated on and connected to said one leg for maintaining said cupshaped members in the openings therein.

7. In a pump construction having a central inlet throat adapted to communicate with a pond of liquid and a, peripheral pumping chamber communicating with said throat and adapted to receive liquid therefrom, the improvements of communicating relief passageways adapted to join said pumping chamber with the pond of liquid feeding the inlet throat to discharge liquid from the pumping chamber back into the pond at a point radially outward of the inlet throat, and

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