US2766698A - Pump - Google Patents

Description

J. C. CARTER Oct. 16, 1956 PUMP 3 Sheets-Sheet l Filed July 18, 1950 22d fnl/5172272" j/7265 Mofa/0 34d 40 39 34e in Oct. 16, 1956 J. c. CARTER 2,766,698

PUMP

Filed July 18, 1950 3 Sheets-Sheet 2 15a fnl/EN fr Oct. 16, 1956 J. c. CARTER 2,766,698

PUMP` Filed July 18, 195.0 3 Sheets-Sheet 3 Jamas' '6T fate/Q United States Patent PUMP James C. Carter, Pasadena, Calif., assigner to The J. C.

Carter Company, Pasadena, Calif., a corporation of California This invention relates to diffuser type centrifugal pumps adapted to deliver volatile liquids at high pressures without becoming gas bound.

Particularly, this invention relates to a diffuser type centrifugal pump with a shrouded impeller spanning the eye f the pump and discharging radially into an axially extending diffuser chamber which, in turn, discharges into a concentric inner annular trough having a peripheral outlet and wherein a deflector ring in the eye of the pump deflects fluid leaking into the inlet from the periphery of the impeller to create a jet pump action which reduces the pressure head requirements at the inlet of the pump and protects the pump from becoming gas bound. This deffection occurs along a diverging path to reduce velocity of the leaking fluid so that it is introduced into the slower moving inlet uid at a reduced velocity.

The pumps of this invention will be hereinafter specifically described in connection with several embodiments of small, compact fuel pumps for high pressure delivery of volatile fuels in aircraft and guided missile fuel systems. It should be understood, however, that the principles of this invention are generally applicable to centrifugal pumps and it is not intended that the illustrated embodiments should limit the invention to any particular use, size, or weight of the pumps.

The preferred forms of pumps according to this invention include mating inlet and bearing pieces. In one form, the inlet piece has a surrounding annular trough, While in another form this annular trough is provided on the bearing piece. In the first form, the bearing piece includes a casing surrounding the trough of the inlet piece and equipped with diffuser vanes for directing fluid discharged from the impeller carried bythe bearing piece into the trough. In the second form, these diffuser vanes are provided on the inlet piece.

A feature of this invention includes the provision of a deflector ring in the intake piece of the pump coacting with a wear ring on the shroud of the impeller and a surrounding seal ring to deflect fluid leaking past the rings in the direction of the intake ow into the pump. Herefofore, the leakage of fluid under pressure from a shrouded impeller was dissipated in the inlet and the kinetic energy of the fluid was lost. The-deflector of this invention, in turning the path of the leakage flow into the direction of the intake ow, creates a jet pump action around the entire periphery of the incoming fiuid to not only reduce the required intake head pressure for efficient operation of the pump but also to prevent the pump from becoming gas bound.

Another important feature of the invention resides in the provision of concentric or nested axial flow paths for converting the velocity head of liquid discharged by the impeller into a pressure head without materially increasing the over-all dimensions of the pump.

Still another feature of the invention is the provision of the mating inlet and bearing pieces so that all surfaces can be easily reached for cleaning and finishing and so that the volume of the diffuser chamber can be easily conece trolled to produce diffuser characteristics which are matched with the impeller characteristics to obtain maximum efficiency.

It is, then, an object of this invention to provide a diffuser type centrifugal pump which utilizes the kinetic energy of fiuid leaking past seals in the pump for preventing the pump from becoming gas bound and for lowering the intake pressure requirements of the pump.

A further object of the invention resides in the provision of a diffuser type centrifugal pump having mating bearing and inlet pieces which are easily matched to balance the diffuser characteristics and impeller characteristics for obtaining maximum efficiency.

A further object of the invention is to provide a compact light weight diffuser type centrifugal pump adapted to deliver volatile fuels at high pressures without becoming gas bound and having concentric diffuser and collecting passages for converting velocity heads into pressure heads.

A still further object of the invention is to provide the wear rings of a shrouded impeller pump with a deflector ring that will direct uid leaking past the wear rings into the impeller for utilizing the kinetic energy of the Huid.

Another object of the invention is to provide a diffuser type centrifugal pump with a smaller overall diameter than a conventional straight volute type centrifugal pump.

Another and specific object of the invention is to provide a ring of axially extending diffuser vanes around the periphery of a centrifugal impeller to change the direction of flow of fluid'issuing from the impeller while converting the velocity head of the fluid into a pressure head and dis-- charging the iiuid radially inward at the and of its axial path.

Other and further objects of the invention will be apparent to those skilled in the art from the following detailed description of the annexed sheets of drawings which, by way of preferred examples, illustrate two embodiments of the invention:

On the drawings:

Figure l is an axial cross-sectional view, with parts in side elevation, of one form of pump according to this invention.

Figure 2 is a fragmentary exaggerated cross-sectional View of the wear ring and deflector ring area of the pump of Figure 1.

Figure 3 is a transverse cross-sectional View, with parts in plan, taken along the line III-III of Figure 1.

Figure 4 is a developed surface view around the circumference IV-IV of Figure 3, but inverted to emphasize that the view is radially inward towardthe center of the assembly.

Figure 5 is an vaxial cross-sectional view, with parts in elevation, of a second form of pump according to this invention.

- Figure 6 is a transverse cross-sectional view, with parts in plan, taken substantially along the line Vl-VI of Figure 5.

As shown on the drawings:

`In the first embodiment of the pump illustrated in Figures l to 4, the reference numeral 10 designates generally a diffuser type shroud-ed impeller centrifugal pump driven by a prime mover 1f1 such as an electric motor, a turbine, or the like.

The pump 10 includes two main casing parts conveniently referred to as a suction inlet piece 12 and a bearing piece 1'3.

The bearing piece 13 has a generally cup-shaped diffuser .chamber defining portion 114 with a circular opening 15 at one end thereof, and a reduced diameter hollow neck portion 16 extending from the center of the closed bottom end 17 thereof. The neck 16 extends to an outturned flat circular flange 18 which, as shown, is connected around its periphery to the casing for the prime mover 11.

An anti-friction `balll bearing assembly 119 is mounted in the neck 16 to rotatably support an impeller shaft 20 driven by the prime mover 11. A shaft seal assembly 21 is disposed around a reduced diameter portion 20a of the shaft in t-he hollow neck 16. A shrouded centrifugal pump impeller 22 is secured on the end of the reduced diameter portion 20a of the shaft in the bottom of the cup shaped portion 14 of the bearing piece. Suitable locking means 23 are provided to secure the impeller and shaft .in non-rotatable rel-ation.y A sleeve 24 bottomed on the bearing assembly 19 holds a shim 25 against a seal ring 26 which is seated in a recess in the flat bottom face of the impeller 22 to maintain the flat disk portion 22a of the impeller in free running clearance relation with the bottom wall 17 of the bea-ring piece 1-3. A seal ring 21a'of the assembly 21 rides on the ring 26. A well 27 in the neck .16 can be drained through a port 28 closed by a plug 29 to prevent fluid leaking .past the seal 21 from entering the prime mover 11. This plug 29 ca-n be replaced with a drain tube if desired.

The flat disk 22a of the impeller 22 has a frustoconical hub portion 22b extending toward the inlet piece 12. A plurality of upstanding curved pumping vanes 22e are provided on the disk 22a in spaced concentric relation around the hub 22b as best shown in Figure 3. These vanes 22e define pumping channels 30 extending radially outward and peripherally lrearward from the -countenclockwise direct-ion of rotation of the impeller. These pumping channels 30 discharge streams of uid in a radially outward and counterclockwise rotating direction into the bottom portion of the cup-shaped end 14 of the bearing piece 113 whereupon the diffuser vanes 31 .change the direction of ilow of the streams into an axially extending spiral around the side wall of the cup 14.

As shown in the developed view of Figure 4, the difuser vanes 31 are spirally curved along their length to scoop up the counter-clockwise whirling iluid from the impeller and deliver it to the open end of the cup 14 which has a lip or flange a surrounding the opening thereof. The varies 31 have rounded thickened end portions 31a merging into the range 15a and, as shown in Figure 3, these portions form anchors for studs 32 used to attach the inlet piece 12 to. t-he bearing piece 13.

.The side wall of the cup 14 has an outwardly extending hollow nipple portion 14a providing aI peripheral discharge outlet 33 for the pump. As shown in Figure 4, this outlet 33 is positioned between the vanes 31 and is not bridged by a vane.

The inlet piece 12, as best shown in Figure l, has a cent-ral frustconical port-ion 34 with Van outtur-ned flange 34a at the outer end thereof,V a disk-like portion 34h intermediate the ends thereof, and a shoulder 34e at the small inner end thereof. This shoulder'34c is surrounded by a cylindrical skirt 34d which extends to an outwardly flaring end Wall 34e. The radial outer end of the aring portion 34e has an axially extending rim 34f. A cylindrical Wall 34g surrounds the skirt 34d in spaced concentric relation therefrom and extends beyond the shoulder 34e into spaced relation with the disklike portion 34b. The Wall 34g is on the outer end of the wall 34e. An annular trough 35 is: thereby provided on the small end of the tapered central portion 34 of the inlet piece 12 and this trough surrounds the inlet piece.

The disk portion 34b of the inlet piece 12A overliesl the cup 14 of the bearing piece and is apertured to receive the studs 32 therethrough. Nuts 36 on the studs attach the bearing and inlet pieces together. A peripheral wall portion on the disk 34b snugly fits in the opening 15 of the cup 14 and is ,grooved to receive :a seal ring 37 for preventing leakage between the two pieces. When so mounted, the small end of the conical central portion 34 of the inlet piece extends into the central por-tion of the cup 14 and carries the wall 34g into snug tting relation with the inner walls of the diffuser vanes 31. The diffuser vanes are thereby effective to discharge into the open end of the trough 35 and the trough 35, in turn, has an opening 38 in its outer walrl 34g aligned with the outlet 33 to discharge its contents through the outlet.

The impeller 22 has its shroud 22d overlying the pumping vanes 22C and having close-running clearance rel-ationship with the wall 34e and lip 34f of the inlet piece. This shroud 22d also has an upstanding-cylindrical pon tion 22e extending into the skirt portion 34d of the inlet piece.

A wear ring 39 preferably composed of brass, is pressfitted around the upstanding cylindrical portion 22e of the shroud. This wear ring 39 cooperates with a bearing ring 40 press fitted into the skirt 34d. The two rings 39 and 40 .are in concentric close-'running clearance relationship.

@In accordance with this invention, a deflector ring 41 is seated in the skirt 34d against the shoulder 34e and 'held thereagainst by the bearing ring 40. This deector ring has a lip portion 41a projecting into the vupstanding cylindrical portion 22e of the impeller shroud, in spaced relation inwardly from said shroud. The lip is tap-ered to provide a tapered passageway, between the impeller and lip. It will be noted that the end of the' lip has a smaller diameter tha-n the impeller shroud open- -ing and projects into this opening.

The central frusto-conical portion 34 of the inlet piece provides a converging inlet 42 extending into the central Iportion or eye of the pump and discharging into the shroud of the impeller. At the point of discharge, however, the deector ring 41 projects into the converging end of the inlet passage 42. The luid fed to the eye or shroud of the impeller is acted on by the pumping vanes and discharged into the diluser chamber 14a between the Acup 14 .and the outer wall 34g of the trough. Thev channels 30 into the diffuser chamber 14a and ows in,

an axial spiral path to the end of this diffuser chamber where it again makes a turn a-nd is discharged inwardly into the trough 35.y The uid enters the trough' in a substantially non-whirling condition since the diifl fuser vanes are designed to eliminate the rotational cornponent by the time the fluid reaches the trough. The uid in the trough 35 then discharges through the opening 35 into the outlet passage 33.

Since the impeller must have good running clearance' relationship with adjacent parts, and since high pressures are created by the pump, some leakage will occur asl illustrated in Figure 2, wherein high pressure liquid from the peripheral outer portion of the impeller can flow between the shroud 22d and Wall 34e and between the rings 39 and 40 as indicated by the arrows. However, the de# flector ring 41 is effective to turn the direction of ow of this leaking uid and cause it to discharge in the same direction as uid fed through the passageway 42 onto the pump. The kinetic energy of the leaking uid thereby.

becomes effective to provide a jet pump action on the incoming fluid in the passageway 42' and since this jet pump action surrounds the incoming uid it will be effective to reduce the required inlet head pressures for eicient operation of the pump. uid before it enters the slower moving stream of incoming tiud in the inlet, the leakage path diverges or widens toward the exit. n

If the pump is handling volatile fluids which tend to form a gas core in the eye of the pump, the diuser ring will prevent the pump from becoming gas bound, since it will discharge the high pressure uid around this core. and cause liquid to be continuously fed into the pump.. AV

drain port 43 closed by a plug 44 isl provided in the.- lower In order to slow up the leakingpart of the side wall of the cup 14, so that the pump can be cleaned without separation of the pieces 12 and 13.

In the embodiment shown in Figures and 6, the pump 50 has a bearing piece 51 carrying the trough and the inlet piece 52 carrying the diffuser vanes. As shown the inlet piece 52 has a cylindrical end portion 52a providing an inlet opening 53 and an enlarged cup shaped portion 521; providing the diffuser chamber 54. The spiral diffuser vanes 55 are formed on this cup portion 52b. The open end of the cup 52h receives the bearing portion 51 and this bearing portion carries a mounting barrel 56 with anti-friction bearings 57 rotatably supporting a drive shaft 5S. A prime mover such as an air turbine 59 drives the shaft 58. A shrouded impeller 60 is mounted on the end of the shaft and overlies the end of the bearing portion in the juncture between the inlet 53 and diffuser chamber 54. The impeller 60 has pumping vanes 60a mounted on a fiat disk 6011 and carrying a top shroud 60e with an upstanding cylindrical portion 60d extending into the inlet 53.

The cylindrical portion 52a of the inlet piece carries a bearing ring 61 surrounding the shroud portion 60d and bottomed against a deflector ring 62 having a lip 62a extending into the inlet 53 for defecting leaking fluid from between the bearing ring 61 and shroud 60d into the direction of fiow of fluid through the inlet S3 for the same purpose as described hereinabove.

The bearing piece 51 provides the annular trough 63 which has its closed end adjacent the disk 60b of the impeller and its open end adjacent the open end of the cup 52b.

As shown in Figure 6, the side wall of the cup 52b has an outlet nipple 64 providing an outlet passage 65 and the trough 63 has an outlet opening 66 aligned with this passage 65.

Fluid flowing through the inlet 53 is received by the pumping vanes 6fm of the impeller and is discharged into the diffuser chamber where it is picked up by the diffuser vanes 55 and directed in an axial spiral path along the outer wall of the trough into the open end of the trough at the other end of the diffuser chamber. The whirling liquid in the trough is then discharged through the opening 66 and passageway 65.

The impeller 6i) has a depending cylindrical skirt 60d on the disk 60b thereof and this skirt has close running clearance relation with a bearing ring 67 carried by the bearing piece 51. This arrangement provides a seal to slow up leakage beyond the impeller into the hollow central portion of the bearing piece. In addition, this hollow central portion of the bearing piece has a seal assembly 68. Bleed holes (not shown) can be provided through the impeller to equalize pressure between the hollow central portion of the bearing piece and the inlet side of the impeller. Therefore, the leakage past the wear ring 67 fiows back to the suction side through the bleed holes and excessive pressure is not placed on seal 68.

A hollow drain pin 69 between the seal 68 and the bearings 57 holds the bearing piece and inlet piece against rotation and provides a drain passageway closed by a plug 70 in the bottom half of the pump.

The pump 50 operates in the same general manner as the pump if) and the deector rings of the two pumps are eective to lower the inlet pressure head requirements for efficient operation of the pump as well as to prevent the pump from becoming gas bound.

From the above description it should therefore be understood that this invention provides diffuser type cen trifugal pumps which are adapted to handle highly volatile fluids without becoming gas bound and are capable of delivering very high pressures while withstanding very high speed operation.

In describing the relationship between the collecting trough or annulus and the diffusion annulus containing the blades 31, in Figure 1 and the comparable collecting trough or annulus 63 and diffusion chamber containing blades 55 in Figure 5, applicant has referred to' these troughs as concentric or as having common centers or as nested. This nested relationship of the parts, men# tioned supra, provides maximum diffusion and straightenv ing of the fluid prior to its ejection from the pump, with an absolute minimum of space requirement. For purposes of description, the term concentric as applied to the present application has a limited meaning and includes within its scope only parts which are substantially coextensive in an axial dimension and radially spaced from one another thereby providing a true nested relation.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention. i

I claim as my invention: i

l. A diffuser type centrifugal pump adapted to deliver highly volatile fuels at high pressures without becoming gas bound which comprises a pump casing having a bearing piece and an inlet piece, a shrouded centrifugal impeller rotatably carried by the bearing piece, one of said pieces having an annular substantially enclosed trough therein which has a radially extending peripheral opening at the side of the trough remote from the impeller, the other of said pieces having a diffuser chamber surrounding and concentric with the trough and equipped with axially extending helical diffuser vanes for receiving fluid from the impeller to direct the fiuid axially into the open end of the trough.

2. A diffuser type centrifugal pump which comprises a pump casing having a central inlet, a peripheral outlet, and concentric outer diffuser and inner trough chambers connected to each other by an annular cut in the periphery of the trough at one side thereof, a shrouded impeller in said pump positioned to receive fluid from the central inlet and to discharge the fluid into one end of the diffuser chamber for axial fiow through the diffuser chamber to the annular cut, into the trough and thence to the peripheral outlet.

3. A diffuser type centrifugal pump which comprises a pump casing having a central inlet, a peripheral outlet, and nested concentric diffuser and trough chambers communicating with each other at one side by means of an annular cut in the outer periphery of the trough and the inner' periphery of the diffusing chamber and with the peripheral outlet, an impeller in said pump casing positioned to receive fiuid from the inlet and centrifugally dicharge the fiuid into the side of the diffuser chamber remote from said cut, diffuser vanes extending substantially the entire axial width of the diffuser chamber and effective to change the direction of oW of the fluid issuing from the impeller into a helical path along the axis of the impeller for converting the velocity head of the fluid into a pressurehead and for moving the fluid in a spiral path around the outside of the trough and thence into the said cut of the trough for flow back toward said impeller and to a peripheral discharge through the outlet.

4. A diffuser type centrifugal pump which comprises a pump casing having a central inlet and a peripheral outlet, an impeller spanning the central inlet and arranged to centrifugally discharge fiuid transversely of said inlet, means defining a diffuser chamber surrounding the impeller and extending axially of the impeller, spiral vanes on the outer peripheral wall of said diffuser chamber arranged to change the direction of flow of fiuid issuing from the impeller into flow in an axially extending helical path through the diffuser chamber, and means defining an annular chamber having an axial open end receiving the fluid from the diffuser chamber for deflecting the uid inwardly and back upon itself axially to the entrance of a radially directed peripheral outlet in the outer wa'll of said annular chamber for delivering the compressed fluid through both the inside and outside walls of said diffuser chamber.

5. In a diffuser type centrifugal pump, the improvef' ment of a pump casing having a central inlet, a periphcral outlet, and radially nested concentric annular diffuser and collector chambers connected to each other by means of an annular slot at one side of said chambers whereby flow of the fluid during diffusion is axial through said peripheral outlet being connected to said collector chamber.

6. A diffuser type centrifugal pump comprising a pump casing having a central inlet, a pump impeller spanning the inner end of the inlet and adapted to radially discharge fluid transversely of the inlet, said pump casing having an axially extending annular diffuser chamber surrounding the impeller and extending axially away therefrom, helical diffuser vanes in said chamber positioned to convert the centrifugally discharging fluid from the impeller into an axially extending spiral path while changing the velocity head of the fluid into a pressure head, and said casing having an annular collection chamber radially inward of and concentric with said diffuser chamber and the vanes thereof in communication with the diffuser chamber by means of an annular cut in said diffuser chamber at the side thereof remote from the impeller whereby fluid flows axially through the inlet, thence radially through the impeller, thence axially in one direction through the diffuser chamber, thence radially inwardly through said cut, and thence axially in the reverse direction into the collection chamber.

7. A diffuser type centrifugal pump which comprises a pump casing having a bearing piece and an inlet piece, said bearing piece having a cup-shaped end with a flat bottom and a cylindrical side wall providing a diffuser chamber, a hollow neck on the central portion of said flat bottom, a shaft projecting through said hollow neck and rotatably carried thereby, a shrouded impeller mounted on said shaft in close running clearance relation with the bottom of the cup and having pumping vanes between the shrouds thereof arranged to centrifugally discharge fluid from the inlet piece to the periphery of the cup at the flat bottom thereof, said inlet piece having a tapered inlet portion with a trough defining ring surrounding the small end thereof and an outturned disk portion for spanning the open end of the cup for closing the open end of the cup, said trough portion overlying said impeller in close running clearance relation and having a peripheral wall spaced inwardly from the side wall of the cup, diffuser vanes in the cup between the peripheral wall of the trough and the side wall of the cup and arranged to direct fluid from the impeller in an axially extending spiral path into the open end of the trough, said peripheral wall of the trough and said side wall of the cup having aligned openings therethrough for discharge of fluid, and a deilector ring in said central tapered inlet passageway arranged to deflect fluid leaking from the periphery of the impeller back to the inlet passageway in the direction of flow of the incoming fluid for creating a jet pump action on the incoming fluid.

8. A diffuser type centrifugal pump which comprises a casing having a bearing piece and an inlet piece, said bearing piece having a surrounding trough on the end thereof, a pump shaft rotatably carried by the bearing piece, and an impeller on said shaft spanning the end of the` bearing piece and the closed end of the trough, said impeller having a shroud extending axially therefrom, said inlet piece having a cylindrical inlet receiving said shroud and a cup-shaped portion surrounding and concentric with the trough of the bearing piece, axially extending helical diffuser vanes on said cup-shaped portion and extending through the axial width thereof and positioned to deflect fluid from the periphery of the impeller in a helical path axially along the side walls of the cup and thence radially inwardly into the trough through an annular cut in the outer wall thereof, a peripheral outlet for saidtrough, and a deflector ring in said inlet extending into the shroud of the pump for deflecting fluid leaking from the periphery of the impeller back ft? the inlet to utilize the kinetic energy of the leaking fluid for inducing the flow of fluid into the impeller.

9. A diffuser type centrifugal pump comprising a pump casing having axially aligned impeller and collector ring chambers, a surrounding diffuser chamber connecting said chambers and concentric with said collector chamber, a central inlet to the impeller chamber and a peripheral outlet for the collector ring chamber, an impeller in the impeller chamber receiving fluid in the center thereof from the inlet and centrifugally discharging the fluid from the periphery thereof into one side of the diffuser chamber, and vanes in the diffuser chamber extending axially throughout substantially the entire axial width of said diffuser chamber for directing the fluid to the other side thereof and into the collector ring chamber.

lO. in a diffuser-type centrifugal pump, the improvement of a pump casing having a central inlet, a peripheral outlet, an annular diffuser chamber having axially extending helical diffuser vanes extending substantially the full axial width of'said chamber, a collector chamber concentric with said diffuser chamber and an annular opening at one end of said chamber for directing flow from said diffuser chamber to said collector chamber, the inner wall of said diffuser chamber and the outer wall of the collector chamber comprising a single member.

ll. A diffuser-type centrifugal pump which comprises a pump casing having a central inlet and a peripheral outlet, an impeller spanning the central inlet and arranged to centrifugally discharge fluid radially of said inlet, means defining a diffuser chamber surrounding the impeller and extending axially of the impeller, spiral axially extending vanes on the outer peripheral wall of said diffuser chamber arranged to change the flow of fluid issuing from the impeller into flow in an axially extending helical path through the diffuser chamber, and means defining an annular collector chamber Within and concentric with said diffuser chamber having an axial open end receiving the fluid from the diffuser chamber for deflecting the fluid radially inwardly and back upon itself to discharge through a peripheral. outlet in said diffuser and collector chambers,y each of said diffuser and collector chambers having an axial dimension substantially greater than its radial dimension and the opening between said chambers having an axial dimension substantially less than the axial dimension of said collector chamber.

12. A diffuser-type centrifugal pump which comprises a pump casing having a central inlet, a peripheral outlet, and concentric outer diffuser and inner trough chambers connected to each other by an annular cut in the periphery of the trough at one side thereof, an impeller in said pump positioned to receive fluid from the central inlet and discharge the fluid into the side of the diffuser chamber opposite from said cut for axial flow through the diffuser chamber to the annular cut, into the trough and thence to the peripheral outlet, each of said diffuser and trough chambers having an axial dimension substantially greater than its radial dimension and the annular cut between said chambers having an axial dimension substantially equal Vto the radial dimension of said diffuser chamber.

13. A diffuser-type centrifugal pump which comprises a pump casing having a central inlet, a peripheral outlet, and concentric outer diffuser and inner trough chambers connected to each other by an annular cut in the periphery of the trough at one side thereof, an impeller in said pump positioned to receive fluid from the central inlet and discharge the fluid into the side of the diffuser chamber opposite from said cut for axial flow through the diffuser chamber to the annular cut, into the trough and thence to the peripheral outlet, each of said diffuser and trough chambers having an axial dimension substantially greater than its radial dimension and the annular cut between said chambers having an axial dimension substantially less than the axial dimension of either of aaid diffuser or trough chambers.

14. A diffuser-type centrifugal pump which comprises a pump casing having a central inlet, a peripheral outlet, and concentric outer diffuser and inner trough chambers connected to each other by an annular cut in the periphery of the trough at one side thereof, an irnpeller in said pump positioned to receive iluid from the central inlet and discharge the uid into the side of the diffuser charnber opposite from said cut for axial flow through the diffuser chamber to the annular cut, into the trough and thence to the peripheral outlet, said diffuser chamber having an axial dimension several times as great as its radial dimension and overlying said trough chamber throughout a majority of its axial dimension, and said annular cut having an axial dimension substantially less than the axial dimension of either of said chambers.

15. A diffuser-type centrifugal pump which comprises a pump casing having a central inlet, a peripheral outlet, and concentric outer dituser and inner trough chambers connected to each other by an annular cut in the periphery of the trough at one side thereof, an irnpeller in said pump positioned to receive Huid from the central inlet and discharge the fluid into the side of the diffuser chamber opposite from said cut for axial flow through the diiuser chamber to the annular cut, into the trough 10 and thence to the peripheral outlet, said ditfuser chamber having an axial dimension several times as great as its radial dimension and overlying said trough chamber throughout a majority of its axial dimension, and said annular cut having an axial dimension substantially equal to the radial dimension of said diffuser chamber.

References Cited in the le of this patent UNITED STATES PATENTS 717,096 Harris Dec. 30, 1902 786,384 Richards Apr. 4, 1905 815,540 Krogh Mar. 20, 1906 1,072,650 Price Sept. 9, 1913 1,525,884 Plummer Feb. 10, 1925 2,018,092 Rickert Oct. 22, 1935 2,207,317 Gear July 9, 1940 2,405,048 Nickerson July 30, 1946 2,436,514 Jennings Feb. 24, 1948 2,444,100 Hill June 29, 1948 2,450,143 Howard Sept. 28, 1948 2,684,634 Schneider July 27, 1954 FOREIGN PATENTS 786,795 France June 17, 1935

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