US2306298A - Booster pump - Google Patents

Description

Dec. 22,1942.

Filed Sept. 5, 1941 4 Shee'Ls-Shee*I l Nw, ml//l M Z e w T 1 f mf 4? l T; n

R. R. cum-.ls

BOOSTER PUMP Dec. 22, 1942.

.D E y 4 Sheets-Sheet 2A Zayas IIHliI! Illlllilll Filed sept. 5, 1941 Dec. 22, 1942. R, R. CURTIS 2,306,298

BOOSTER PUMP Filed Sept. 5, 1941 4 Sheets-Sheet 3 .Tiss

A VE Twe wf Patented Dec. 22, 1942 BOOSTER PUMP Russell Curtis, Dayton, Ohio, assigner toy Curtis Pump Company, Dayton, Ohio, a corporation of Ohio Application September 5, 1941, Serial No. 409,647

15 Claims. (Cl. 103--113) This invention relates to booster pump assemblies especially adapted for high altitude aircraft fuel systems. More specifically, this invention relates to centrifugal booster pump assemblies having bubble generating and separating means acting on liquid material before it reaches the pumping vanes of the pump.

In my copending application Serial No. 352,064, led August 10, 1940, entitled Booster pump for aircraft fuel systems, of which the present application is a continuation-in-part, I have described and claimed booster pumps having impeller assemblies for. beating bubbles of gas and vapor out of liquid fuel such as gasoline and for pressuring the bubble freed liquid. In accordance with the present invention, the beating out of bubbles of gas and Vapor from the liquid is augmented by auxiliary means on the impeller assembly which acts on the liquid before it reaches the pumping vanes of the' assembly.'

These auxiliary means may take a number of different forms among which are disclosed herein propellers, auxiliary impellers, shear arms, and vanes. These auxiliary means for beating out the bubbles are positioned above the pumping vanes of the impeller and are closer to the source of liquid than the pumping vanes.

The booster pump has a volute chamber and an outwardlyflared throat converging to a central inlet for the chamber which is in full communication with the liquid. The impeller assembly spans the inlet and the pumping vanes on the assembly underlie the throat to form therewith open ended pumping channels communicating with the inlet at their inner ends and opening into the volute chamber at their outer ends.

In accordance with this invention, the impeller assembly carries the auxiliary means in or ahead of the mouth of the outwardly flaring throat. As a result the liquid is agitated by the auxiliary means to have the entrained gases and vapors therein separated into bubblesfwhich rise through the liquid and escape at the surface thereof. The auxiliary means also serves to liberatexed or dissolved gases or vapors by generating the same into bubble form. Thus by the time the liquid reaches the pumping channels it is in a stabilized or fully liquidcondition sov that only fully liquid material is pressured into the volute chamber of the pump.

It is, then, an object of this invention to provide improved impeller assemblies for booster pumps which are adapted to efficiently beat out bubbles of gas and vapors from liquids while simultaneously pumping the bubble freed liquid. A further object of this invention is to provide improved impeller assemblies for booster pumps wherein auxiliary agitating means act on the liquid before it is pumped. A further object of this invention is to provide, in a booster pump having an outwardly ared throat, a liquid agitating means driven by the. impeller of the pump for beating out bubbles of gas and vapors from the liquid in the throat or about to enter the throat.

A further object of this invention is to provide a booster pump having separate agitating vanes and pumping vanes driven from the same source.

A specific object of this invention is to provide a booster pump assembly adapted for yaircraft fuel systems wherein the fuel about to be pumped is agitated to generate bubbles therein and wherein the bubbles are guided away from the bubble freed liquid.

. Other and further objects of this invention will be apparent to those skilled in the art by the following detailed description of the annexed sheets of drawings which by way of preferred examples show several embodiments of the invention.

On the drawings: Figure 1 is a vertical cross sectional View,

partly in elevation, and with parts broken away,

of a booster pump and fuel tank assembly in accordance with this invention.

Figure 2 is a plan' view of the booster pump assembly shown in Figure 1 taken along the line II--II of Figure 1.

Figure 3 is 'a vertical cross sectional view, with parts in elevation', and' with parts broken away, of a modied form of booster pump and fuel tank assembly in accordance with this invention.

Figure 4 is a plan view of the booster pump impeller assembly shown in Figure 3.

Figure-5 is a fragmentary vertical cross sectional view, with parts broken away, of another booster pump and fuel tank assembly in accordance with this invention.

Figure 6 is a plan view of the impeller assembly of the booster pump shown in Figure 5.

Figure 7 is a fragmentary vertical cross sectional view of still another form of booster pump i according to this invention.

Figure 8 is a vertical cross sectional view, with parts in elevation, of still another form of booster Figure 11 is a plan view of the impeller assembly of the booster pump shown in Figure 10.

Figure 12 is a fragmentary vertical cross sectional view of still another form of booster pump according to this invention. Y

Figure 13 is a plan view of the impeller assembly of the booster pump of Figure 12.

Like reference numerals refer to identical parts throughout the drawings.

As shown on the drawings:

In Figure 1 the reference numeral I0 designates a fuel tank. vented as at lila, 'and containing a pond P of liquid fuel such as gasoline. The bottom wall of the tank has a circular aperture therein and a mounting ring I2 is mounted in the tank on the bottom wall around the aperture.

The booster pump I3 is of the centrifugal type and includes a casing I4 defining a volute chamber I5, a discharge outlet |6 for the volute chamber and a shaft housing I1. nected with an electric motor (not shown) which drives the shaft I8 in the shaft housing portion I1 of the casing. The casing I5 has an outturned annular ange I9 for mounting on the bottom wall of the tank I0. The ange I9 receives screws 2li at spaced intervals therearound which are threaded into blind tapped wells in the mounting ring I2. The mounting ring may be welded, soldered or otherwise secured to the bottom wall of thel tank. The casing denes a circular opening 2| into which a throat ring 22 is seated and secured to the casing by means of screws such as 23.

The throat ring 22 has an aperture 24 therethrough for joining the interior of the tank I Il with the volute chamber I 5. The aperture 24 flares outwardly to provide an inlet mouth for the booster pump I3 and is .also undercut or beveled at the bottom thereof to increase the passagewav to the volute chamber I5.

The throat ring has a plurality of standards or ribs such as 25 therearound supporting an imperforate hollow inverted frusto conical shield 26. 'Ihe smaller bottom end of the shield 26 is held by the. ribs 25 in spaced relation above the throat ring 22. The larger or top end of the shield extends fairlv well up into the pond P.

The booster pump I3 has 21 mounted on the drive shaft I8. This impeller assembly includes a disk or flange portion 23 spanning the inlet or aperture of the throat ring and communicating freely around the' periphery thereof with the inner rim I5. Curved pumping vanes 25 are mounted on the flange 28 around the periphery thereof to underlie the throat ring 22. These pumping vanes 29 define with the throat ring 22 and the flange 28 open ended pumping channels communicating at their outer ends with the volute chamber I5 and at their inner ends with the inlet of the throat ring.

The impeller disc 25 can have a dome 28a diverging in a smooth curved path from the axisof the opening 24 to thel inlets of the pumping channels as best shown in Figure 1. This dome. 25a can follow the curvature of the throat ring aperture 24 to'guide the liquid to the pumping channels.

A shaft 30 projects from the top of the dome 28a and has a four-bladed propeller 3| mounted thereon. The blades of the propeller are spaced above throat ring 22 and below 4the shield 25 to act on liquid flowing through the shield to the Pump for beating out bubbles B from the liquid.

The casing I4 is con-A an impeller assembly r ofthe volute chamber ,Y

The propeller blades agitate -the liquid about to enter the pump to separate any entrained gases or vapors from the liquid into bubble form and to generate into bubbles any gases or vapors loosely fixed or dissolved inthe liquid. These bubbles B are thrown outwardly by the propeller blades to the outside of the shield 26 where they rise through the pond P in a widening path around the shield. As the bubbles rise in the pond they become larger as shown in Figure 1 and eventually burst at the surface ofthe pond to liberate the gases or vapors.

The pumping vanes 29 and propeller 3| create a whirlpool in the pond P with the liquid flowing down through the shield 26 and with the bubbles rising outside of the shield to the surface of the pond.

In this manner any liquid about to enter the pump is thoroughly agitated and the gases and vapors are beaten bubbles. Thus the pumping vanes 29 only act on fully liquid bubble freed fuel and pressure this fully liquid fuel into the volute chamber for discharging out of the outlet I6 into the line leading to the fuel pump ofthe engine.

The propeller 3| acts on the downwardly flowing liquid in the center of the whirlpool and throws out bubbles from the outer portion of the whirlpool or outside of the shield 26. The propeller blades are mainly intended for agitating the liquid to beat out bubbles therefrom. The blades of the propeller canv be so pitched as to slightly pressure the liquid through the inlet 24 to the pump for increasing the pumping capacity of the pump.

In the modiflcation shown in Figures 3 and 4, the tank I0 has a conduit 40 extending from a side wall at the bottom thereof and a second conduit 4I extending from this side wall at the top of the tank. A casing 42 has a central inlet 43 receiving the conduit 40 and a peripheral outlet 44 receiving the conduit 4I. The casing 42 can be secured to the flange I9 of the pump casing I4 and provides a throat ring 22a for the pump. The casing 42 defines a volute chamber 45 communicating with the inlet to the pump around its inner periphery and communicating with the discharge outlet 44 at its outer periphery.

The impeller assembly 21 of the pump I3 has the pumping vanes 23 thereon underlying the throat ring-22a. In accordance with this modification, however, additional vanes29a extend inwardly from the pump vanes 29. These vanes taper from the tops of the pumping vanes 29 to the flange 28 .and terminate in spaced relation from the center of the flange.

A shroud ring r rotating throat member 45 is secured on top of the vanet 23 and extends into the throat ring 22a for dening a rotating outwardly dared mouth 41 for the pump. This outwardly ilared mouth defining portion of the ring carries a plurality of inwardly projecting vanes 48 around the periphery thereof to agitate liquid flowing from the inlet 43 to the pump. These vanes 48 liberate bubbles of gases and vapors B from the liquid and centrifugally discharge these bubbles into the chamber 4I of the casing 42. The agitation of the liquid thus induced by the vanes 44 serves to liberate and create bubbles B from gases and vapors which would otherwise enter the pump. At the same timel some liquid is dischriled into the chamber 5. ,-f

The bubble rich liquid in the chamber 4l is somewhat pressured by the-rotating vanes 4l therefrom-in the form of.

this liquid to rise along 49 can be provided in the discharge outlet 44 of the casing 42. The pressure in the casing will be suiiicient to open the valve or flap during operation of the pump.

Any gases or vapors remaining in the liquid after the liquid has been agitated by the vanes 48 will be liberated from the liquid by the vane portions 29a extending into the -inlet of the pump. Thus the liquid is subjected to two agitating treatments before it is acted on bythe pumping vanes 29 and pressured into the volute chamber I5.

The rotating throat ring 41 itself serves as still another agitating means and aids in creating a whirlpool in the conduit 4|) with the bubbles being trapped in the chamber 45 surrounding the vortex of the whirlpool.

In the embodiment shown in Figure 5 the tank I has a conduit or sump portion 50 depending from the bottom thereof and receiving a duct in spaced concentric relation therefrom. The duct 5| extendsv above the bottom of the tank into the pond P of fuel therein.

The booster pump I3 has the throat ring 22 thereof mounted on the bottom of the sump or conduit 5D and provides a frusto conical surface 24a sloping toward the impeller assembly 21 of the pump. The impeller assembly has the pumping vanes 29 on the flange 28 thereof and In the embodiment shown in Figure 7 a modified form of pump casing |4a is used for the pump. This pump casing |4a defines a chamber 6|] between the throat ring 22 and the volute chamber I5. The chamber 60 converges inwardly at the bottom thereof as at 6| to provide the inlet -62 to the impeller assembly 21.

A flaring or domed spacer 63 is disposed around the drive shaft I8 for the impeller assembly 21 and supports a second impellerassembly 64 in spaced relation above the impeller assembly 21. The assembly 64 is mounted in the chamber 60 of the casing and includes pumping vanes 65 which extend only slightly under the throat ring 22. The vanes 65 have agitating portions 65a of appreciable length extending into the path of the aperture 24 of the throat ring 22.

The pump is mounted on the bottom wall of the tank I0 as described in Figure 1 and liquid from the tank flows through the aperture 24 of the throat ring Where it is immediately agitated by' the vane portions 65aof the impeller assembly y 65. These vane portions 65a will beat out bubforming continuations of the sloping surface 24a.

When the booster pump is operating the impeller induces the generation of bubbles at the agitating vane portions 29h thereof and these bubbles are thrown outwardly by centrifugal force to ow along the sloping surface 24a of the throat ring outwardly from the interior of the duct 5I.

Liquid fuel from the pond P flows downwardly through the duct 5| to the inlet to the pump and is beaten or agitated by the agitating vanes. The bubble freed liquid is then pressured by the pumping vanes 29 into the volute chamber I5 of the pump.

In this modification, therefore, the bubbles are guided outwardly of the duct 5| while the liquid from the pond flows downwardly through the duct to the pump. The agitating vanes 29h on the impeller act on the liquid from the duct 5| before it reaches the pumping vanes 29 and free the liquid from gases and vapors. These gases and vapors are caused to separate in the form of bubbles B and rise through the space'in the sump around the duct 5|. After rising above the bottom wall of the tank 'the bubble path widens out as shown in Figure 5 and the bubbles become larger as they rise to the surface. Upon reaching the surface the bubbles burst discharging the gases and .vapors entrapped therein to the atmosphere. The liquid then recirculates down through the duct 5|.

.As shown in Figure 6 both the pumping vanes s 29 and the agitating vane portions 29h are curved. f

bles B of gas and vapor from the liquid fuel. Simultaneously with the agitation of the liquid 'flowing through the throat, the vane portions which it flows downwardly through the inlet 62 to be acted on by the impeller assembly 21.

The throat ring 22 is very open so that at this first stage of operation the liquid is mainly agitated to eliminate the bubbles. The opening 62 to the volute chamber I5 is more closed so that the pumping vanes 29 of the impeller 21 underlie this throat ring to further pressure the bubble freed liquid into the volute chamber I5. Thus the vane portions 55a of the first impeller 64 beat out bubbles from the liquid, the vane portions 65 of the impeller next pressure the bubble freed liquid into the chamber 69, the flaring spacer 63 guides the liquid to lthe pumping vanes 29 of the impeller 21 and these vanes 29 pressure the liquid into the volute chamber |5. The initially pressured liquid does not further vaporize as it is acted upon by the impeller assembly.

the throat ring 22 receives thereon the flange 10 of a cylindrical screen 1| Avhaving a screened top wall 12 spaced materially above the bottom wall of .the tank I0.

The screen 1| carries an inverted frusto conical hollow shield 13 in spaced relation above the throat ring. As is best shown in Figure 8, the throat ring 22 extends upwardly as at 14 into the screen 1| for defining an outwardly fiaring mouth 15 of appreciable length. The mouth converges toward the axis of the pump and then is undercut or beveled as at 15a into communication with the volute chamber I5 of the pump. The pumping vanes- 249 of the pump assembly 21 underlie the throat ring for pressuring the liquid into v olute chamber.

The impeller assembly 21 has a curved dome portion 28a extending upwardly into the inlet mouth of the throat ring 22 and a spacer 28o is provided'thereabove around the shaft I8.- A propeller 16 is mounted on the shaft I8 above the spacer 15 and is disposed above the throat the ring 22 but below the shield 13 within the screen 1I.

.Liquid from the pond in the tank is screened through the screen 1I and then flows downwardly through the shield 13 where it is agitated by the propeller 16. The propeller .18 then throws the bubbles of gases and vapors outwardly back through the screen 1I Wherethey can rise along a gradually widening path to the top of'the pond in the tank I0. The bubbles, as they rise, become larger and will not again pass through the screen so that recirculation of bubbles back to the propeller is eliminated, or at least minimized.

The agitated fuel, freed from the bubbles, then flows downwardly through the mouth 15 of the throat ring and is pressured by th.: pumping vanes 29 into the volute chamber I5.

In this embodiment as shown in Figures 8 and 9, therefore, the fuel in the tank is filtered before it is agitated and the filter aids in maintaining the bubbles separate from liquid entering the throat ring.

In the embodiment shown in Figures 10 and l1 the impeller assembly 21 of the pump has the pumping vanes 29 and agtating vanes 29a thereon as described in Figures 3 and 4. vIn this modiiication, however, an arm assembly 80 is mounted on the top of the impeller 21 around the drive shaft I8 which projects above the impeller fiange 28. The assembly 80 has four arms 8| extending over the sloping agitating vanes 29a and overlying the. conical mouth 24a of the throat ring 22. These arms are held rather close to the surface 24a of the throat ring and serve to shear off bubbles liberated by the agitating vanes 29a from the surface so that the bubbles will rise into the pond of fuel. In addition, the arms have some agitating action on the fuel and augment the vane portions 29a in beating out bubbles from the fuel.

In the modification shown in Figures 12 and 13 a reduced portion of the drive shaft I8 or an extension I8a extends above the impeller flange 28 through the aperture 24 of the throat ring 22. This shaft I8@ carries a plurality of vanes 85 around the top end thereof to agitate the fuel entering the pump I3 before the fuel reaches the pumping vanes 29. 'I'he vanes 85 lie partially within the aperture 24 of the throat ring. The

vanes 85 serve to beat out bubbles of gases and vapors from the liquid fuel while Athe bubble freed liquid is then pumped by the pumping vanes 29 into the volute chamber I5.

From the above descriptions it will be understood that this invention provides many forms of impeller assemblies for booster pumps wherein volatile fuels such as gasoline are agitated before being pumped. The agitating means are carried by the impeller of the pump but act on the fuel before it reaches the pumping vanes of the impeller. The agitating means either lie within or `above the inlet to the pump. The inlets themselves may take many forms but are especially shaped so as to permit the beaten out bubbles to rise away from the bubble freed liquid.

The booster pumps of this invention when mounted below the hydraulic gradient of a fuel system will beat out gases and vapors from the fuel and will then pressure the thus stabilized fuel to the fuel pump of an airplane or other vehicle engine. The fuel is pressured to a value greater than its vapor pressure so that additional liberation of bubbles is prevented.

When incorporated in aircraft fuel systems, the booster pumps of this invention stabilize the fuel as the aircraft is flying toward high altitudes so that vapor lock in the fuel system will be eliminated. When an altitude is reached where the fuel in the tank starts breakingup the booster pump will prevent passage of gases and vapors to the fuel line. At the same time the booster pumps serve to pressure the fuel in the fuel line thereby preventing further vaporization.

When the booster pumps are inoperative the same provide free iiow channels for the gasoline so that the pumps need only be operated when high altitude performance is contemplated.

'I'he beaters or agitators of the pumps of this invention not only beat out bubbles of gases and vapors dispersed in the fuel, but also induce bubble formation from gases and vapors loosely fixed or dissolved in the liquid.

It will, of course, be understood that various details of construction may be varied through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

l. A pump assembly comprising a casing dening a volute chamber having a central inlet and a peripheral outlet, a pump impeller in said casing for centrifugally discharging liquid from the inlet into the volute chamber, and a propeller mounted on said impeller and disposed in the path of liquid to the inlet, said propeller being arranged for transverse communication with a body of liquid surrounding the incoming liquid to the inlet, and said propeller having blades adapted to beat out bubbles of gas and vapor from the guid before the liquid reaches the volute cham- 2. A booster pump construction including a casing defining a volute chamber, a throat ring defining an inlet to said chamber, an impeller assembly having vanes underlying the throat ring to impel liquid from the inlet into the volute chamber, a propeller disposed above the throat ring mounted on said impeller assembly for transverse communication with a body of liquid surrounding the incoming liquid to the inlet, and an open ended shield mounted above said throat ring to guide the liquid to said propeller.

3. A booster pump construction including a casing defining a volute chamber having a peripheral outlet and an annular inner opening, a throat ring defining a central inlet to the annular opening of the volute chamber, an impeller havingl peller through the inlet of the throat ring, and a propeller mounted on said shaft having blades disposed above the throat ring arranged for free transverse communication .with a body of liquid surrounding the liquid flowing to the inlet.

4. A pump comprising a casing defining a volute chamber having an inner annular opening and an outer peripheral outlet, a throat lring deiining a central inlet to said opening, and an impeller assembly having blade portions on both sides of the throat ring, said blade portions on one side of the throat ring being arranged for communication with the volute chamber, and said blade portions on the other side of the throat ring being arranged for transverse communication with a body of liquid surrounding the incoming liquid to the throat ring.

5. Ina fuel system, a fuel tank, a centrifugal pump secured to the outside of the tank comprising a casing, a vaned impeller, a throat member having one side adjacent the impeller-vanes and the other side facing toward the fuel in the tank, a shield mounted in the tank in spaced relation from the throat member defining a localized fuel path to the pump, and fuel agitating means intermediate the throat member and shield positioned for transverse communication with fuel in the tank surrounding the shield.

6. In a fuel system, a fuel tank, a centrifugal pump secured to the outside of the tank comprising a casing, a vaned impeller, a throat member having one side adjacent the impeller vanes and the other side facing toward the fuel in the tank, a shield mounted in Athe tank in spaced relation from the throat member dening a localized fuel path to the pump, a shaft extending from the impeller into the tank, and agitating means on said shaft between the shield and throat member positioned for transverse communication with fuel in the tank surrounding the shield.

'7. In a fuel system, a fuel tank, a first conduit extending .from the bottom portion of the tank, a second conduit extendingfrom the top portion of the tank, a casing defining an annular chamber with a central inlet and a peripheral outlet respectively receiving said first and second conduits, a pump having an inlet throat in communication with the central inlet of the casing, a pump'impeller having pumping vanes underlapping said throat and agitating means on said impeller,A extending into the throat and in communication with the annular chamber for beating bubbles from fuel delivered through the first conduit into the annular chamber to liow back to the tank through said second conduit.

8. A pump construction comprising, means defining opposed annular chambers with a central connecting throat therebetween and a central liquids inlet to one of said chambers, and an irripeller rotatably mounted in said means having vanes for pumping liquid into the other one of said chambers together with agitating means communicating with said liquidsv inlet and said one chamber for `beating bubbles from lthe liquid into said one chamber. A f

9. A pump construction comprising means defining opposed annular chambers each having inlet openings around theirl inner peripheries and discharge outlets on their outer peripheries, a throat'member between the chambers deninga restricted passage between the inlet openingsan impeller spanning said passage having pumping vanes underlying the throat member to pump liquid into the adjacent chamber, a ring on 'said impeller extending into the restricted passage of the throat and vanes on the inside of the ring communicating with the` other chamber for agitating the liquid before it reaches the pumping vanes to beat bubble rich liquid into said other chamber.

10. A device adapted forI discharging fully liquid material, such as volatile fuel, whichl comprises a pump having an inlet throat adapted for receiving liquid material, an impeller assembly adjacent the inlet throat, vane portions on the impeller assembly underlapping the throat to define walls of open ended liquid ow pumping channels, andv means on the impeller assembly arranged for transverse communication with a body of the liquid material surrounding the liquid material entering the inlet throat and effective for agitating the liquid material to beat out bubbles of gas and vapor before the vliquid reaches the outlet of said inlet throat.

11. A device adapted for discharging fully liquid material, such as volatile fuel, from a source of liquid material which comprises a pump having an inlet throat adapted to receive liquid material from said source, an impeller assembly adjacent the inlet throat, vane portions on the imy the throat.

12. A device adapted for discharging fully liquid material, such as volatile fuel, from a source of liquid material which comprises a pump having an inlet throat adapted for communicating with Y said source, an impeller adjacent the inletthroat,

pumping vanes on the impeller underlapping the throat andv agitating mechanism positioned in advance of the discharge end of the throat arranged for transverse communication with a body of the liquid surrounding the incoming .liquid to the pumping vanes and `effective for beating out bubbles of gas and vapor from the liquid before it is discharged out of the throat.

13. A pump assembly comprising a casing delining a pump chamber, a throat ring defining a liquids inlet to said chamber, an impeller assembly spanning the inlet and having pumping vanes thereon to centrifugally discharge liquids from said inlet into said chamber, and agitating vanes positioned ahead of the discharge end of the liquids inlet and arranged for transverse communication with a body of liquid surrounding the liquid iiowing through the inlet to be effective for beating out bubbles of gas and vapor from the liquid before the liquid. reaches the pumping vanes.

14. A pump assembly comprising a casing delining a pump chamber with a liquids inlet, an impeller assembly spanning the inlet and having pumping vanes thereon to centrifugally discharge liquids from the inlet into the chamber, and agitating vanes positioned ahead of thedischarge en d of the liquids inlet and arranged for transverse communication with a body of liquid surrounding the liquid iiowing to the inlet to be effective for beating out bubbles of gas and vapor from the liquid before the liquid reaches the pumping vanes.

15. Apump assembly comprising a. casing dening a pump chamber having a liquids inlet, a 'guide shield dening with its inner face a localized flow path to the inlet, an impeller assembly spanning the inlet having pumping vanes thereon to centrifugally discharge liquids from the inlet into said chamber, and agitating vanes 'positioned ahead of the discharge end of the liquids inlet and arranged for transverse communication with a body of liquid surrounding the guide shield to be effective for beating out bubbles of gas and vapor from the liquid before the liquid reaches the pumping vanes whereby the beaten i out bubbles can be deected by the outer face of the guide shield away from the incoming liquid to the inlet.v

RUSSELL R. CURTIS.

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