US2184349A

US2184349A - Pump

Info

Publication number: US2184349A
Application number: US175187A
Authority: US
Inventors: Bour Harry E La
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-11-18
Filing date: 1937-11-18
Publication date: 1939-12-26
Anticipated expiration: 1956-12-26

Description

Dec. 26, 1939.

H. E. LA BQUR PUMP 3 Sheets-Sheet 2 Filed Nov. 18, 1937 D ec. 2,6, 1939. H. E. LA BouR PUMP' 3 Sheets-Sheet 3 Filed Nov. 18, 1937 Y Patented D ec. 2,6, 1939 UNlTEo STATES PATENT OFFICE PUMP l nem E. Le Bour', Earhart, ma. Application November 1a, 1937, serial No. 175,1s7

16 Claims.

A action, that is, pumping air by recirculation when-the impeller is not supplied with suiiicient liquid at the normal intake tomake up a full discharge, and for automatic and inherent stoppage .of'internal circulationf-.that is, the priming action,-when the impeller receives its full complement of liquid.

In the embodiment ofthe invention 'shown in the aforesaid patent, two separate passageways are employed, that is, a main discharge passageway and anv auxiliary or priming passageway. Also, in that embodiment, the impeller sweeps the casing and the impeller blades are substantially straight for best operation. While that particular form of pump has very effective 'priming action, that is, it has the ability to draw and maintain a very high vacuum, and while it is suitable for fairly high iiuid heads, it involves a rather expensive construction and takes up a relatively large amount of space.

The pump shown in my aforesaid application `also embodies the principle 'of inherent compensation to shift its operation from a recirculation for priming to a straight discharge on liquid pumping;

3 5 For certain classes of work, particularly for large volume 'and moderate or low heads, the volute type of casing, with curved blades, is deriable. This type of construction is also de- *ireble where entrained solids are encountered.

40 However, it` has been found diillcult to get an orderly reintroduction of the priming water into the impeller because of the peripheral position vof the volute in respect to the impeller... Itis therel ore more diiiicultfto secure the same eiectiveness 'in priming,` particularly at high lifts or vacuums. as in the pump employing the two dist'nct and separate passageways.

` The essencel of the fundamental method of nriming according to said prior patent is the in- 50. traduction of thepriming liquid, during priming,

at a point where reversal of hydraulic pressure occursupon the pump receiving its full complement of liquid vNowthe'more sharp and .dei-lnite this region and action canbe made, the

(Cl. 10S-113) of speeds and lifts. Also, it is to be observed that the efficiency of the priming action is dependent upon the degree in which the entrained gas is eliminated in the separator and liquid free of such gas is returned into the impeller for 5- priming. The more definite the control of the reintroduction of gas freed liquid, the better will be the operation of the pump.

The` chief object of the present invention is to provide a structure which will have the ad- 10 vantages of the volute form of pump, together with the advantages of the two-throat action of the pump shown in my prior patent.

A further object of the present invention is to produce a compact form of self-priming cen- 16 trifugal pump suitable for general utility. A further object is to provide suche. `pump having large self-cleaning passageways and atthe same time having an improved priming action whereby it can approximate the performance of the 20 earlier form of pump having the two-separate 'passageways.

A more specific object of the invention is to provide a self-priming pump of the volute type with an improved throat arrangement for. im- 25 proving the effectiveness and eiiiciency of priming and to ,enable the pump to attain relativel high suctions quickly and-easily.

A characteristic of the preferred embodiment of the present invention is -theemployment of 30 a voiute provided with a cut-oil and the'unidirectional ow of uid out of the end of the volute that is beyond the cut-oi. ,.This insures an orderly or organized iiow of fluid in the priming circuit. The iniiowing priming liquid is in 864' troduced under th`e main stream of mixture which hugs thev periphery of the volute. As soon fas this incoming stream of water engages the by the impeller at'the cut-oil, and is added to .45'

the 'mixture discharge coming outof the end of the volute. L

While I speakof unidirectional ilow, it is to be understood that there may be variance from 4continuous 4iiow or yeven ilow in one direction at oo this point/z;v because of the rotating .impeller -blades, particularly at the lowerspeeds. 'I'his variation from strict uniformity is particularly the case with ow at the priming opening. The

lfnumber, inclination andspeed ofA the impeller A One part enters the impeller to form the 4 0 blades determines the iiuctuations of pressure which occur at this point. However, the ow is denitely organized and directed, in the present pump, and thisv presents a distinct advance in pumps of this class.

, A further object' of the present invention is the provision of an improved form of separator and the action which occurs therein, particularly looking to the establishment of a so-called dead pocket. By the term "dead pocket I intend to convey the idea of a region wherein the liquid is relatively remote from liquid carrying air, so that the water at that point may carry a minimum amount of air. This dead pocket, in the present structure, is located b'ack of the volute .extension and constitutes a region into which the flow at high velocity expands into a relatively low velocity region after active separation by kinetic eect has had an opportunity to occur, yet there is still suiilcient velocity to prevent accumulation of solids.

Figure 2 is a vertical cross section taken on the:

line 2-2 of Figure 1;

Figure 3 is a top plan view on a reducedl scale;

and

Figure 4 is a front elevational view with a part broken away to` reveal thedetail. Referring ilrst to Figure 1, the pump herein shown comprises the following main parts: I is the main frame casting including a'puinp barrel and various subdivisions later to be referred to.

The second main part is the impeller 2. The third main part is the removable gland structure 3. The fourth main part is the closure member 4 for closing the pump barrel, and the fifth main part is the cover pate 5.

The main frame casting I, in its lower end. defines a pump barrel which includes the back plate 6 and the integral volute the terminal portion of which I designate as the volute extension 8. This pump barrel ,further includes the cut-0119 which extends across the full width of the blades of the impeller 2 and has mechanical clearance only with the tips of the blades III-I of the impeller 2. The volute extension 8 y lmember 4 comprises the generally cylindrical wall I5 which extends inwardly and carries at its inner end the front plate member I3. This front plate member AI6 has the intake opening Il through which the incoming stream of viiuid is supplied to the impeller 2. The flared conical wall I8 provides, in conjunction with the wings v of the blades of the impeller, for an inlet pocket I8 to faciiltate the entry of liquid into the impeller.

The cover member 4 has a peripheral shoulder i a suitable support which, in the present instance, comprises a rearwardly extending flange 40 havvided with a number of openings -25 to form a strainer. This strainer is shown as integral with the closure member 4 but obviously it may be made, for convenience of construction, as a separate part or integral, as desired. A hollow boss 2B formed in the central part of the strainer 24 is provided to receive the compression spring 21 and the bolt 28, the bolt 28 having a head at its outer end and a retaining pin or equivalent fastening means .at its inner end. The compression spring 21 may be suitably pre-stressed so that the f desired pressure upon'the strainer 24 and hence upon the closure member 4, to hold it in place, may be secured by a very small displacement of the pin 28 when the cover plate 5 is fastened in place.

The back plate 6, which is an integral part of the main frame or casting I, has a recess machined at the center thereof for receiving the iiange 23 oi' the removable packing gland cartridge 3. This removable packing gland cartridge 3 is held in place by stud bolts/which may be released from the back side of the pump. This removable packing gland cartridge is accessible from the rear of the pump for servicingand is removable through the main bore of the pump barrel, as will-be described later. A mounting ring V32 for the take-up bolts 33`of the gland follower 3,4 -is held under the stud bolt to the back plate 6.

'I'he particular arrangement of packingin the packing gland 3 is not esse'ntial and various forms of packing may be provided within the scope of the present invention so long as the cartridge is removable, as indicated, through the main bore, whereby the entire pump may be taken apart from the front oi the pump without disturbing its mounting or the suction and discharge connections.

As shown, the removable packing gland cartridge provides an annular recess for fibrous or other packing 34. An intermediate member 3l acts as a follower'for the packing 34 and has a central recess for the introduction of greasel to lubricate the packing, and it, in turn, is packed by fibrous or the like packing 36 and engaged by the gland follower 3|, which is tensioned through the medium of a suitable spring or set of springs 3'I and wing nut 38 on vthe fbolt 33.

The main body or casting I is supported upon ing a shoulder 4I seated in a corresponding rabbet or recess in the mounting bracket 42.

This mounting bracket 42 is annular in shape extension for .securing a suitable mounting r bracket 'or 1a mounting bracket of diii'erent form may be clamped to the ilange' 40, or otherwise arrangements may be'madej for supporting or steadying the pump in the desired position;

'2,104,849 The impeller 2 has an operating shaft 4I viously, instead of a separateshaft the impeller.

and shaft may be constructedtof one casting or otherwise made unitary.

The shaft 46 may be connected in any suitable manner tothe shaft of the driving motor. Thus,

for example, if the shaft is to be connected to an internal combustion engine a disc may be fastened, as by welding or the like, to the righthand end of the shaft and saiddisc then clamped to the fiywheel of the engine, whereby the shaft 46 is supported from the bearings of the engine and need not be self-supporting in the pump One manner of supporting the impeller shaft on the separate set of bearings is shown in my Patent No. 1,993,999.

The main frame casting I comprises, in addition to the pump barrel aforesaid, two other main parts, namely, the separator 41 and the intake trap 48. The separator 41 has a clamping iiange 49 at the top thereof for theconnection of the companion flange 50 of a discharge pipe 52. The discharge opening 53 from the separator 41 faces upwardly, whereas the intake opening 54 for the trap 48 opens horizontally. A clamping ange 55 for cooperation with companion ange 56 of the intake or suction pipe 51 is formed integrally with the walls of the trap 48. The disbe observed that the shape of the separator 41.

while cylindrical in outline, is wedge-shaped in plan,' asmay be seen from Fig. 3. The back wall 58 and the intermediate wall 23 are inclined towards each other in the directionin which the volute extension 8 discharges fluid. The issuing stream of fluid from the volute extension 8 strikes the circular wall 5| and is directed upwardly in :the separator to give the gas which is entrained during priming an opportunity to free itself from the liquid, and the liquid then rises and flows back to the rear ofthe volute extensionY 8, where the casing is wider. as will be seen from Figure 3, and the region indicated by the reference character thereby constitutes the dead pocket where there is the greatest proportion of liquid freed of gas, and

from there to supply'. through the primi |3|3, a stream of'priming iiuid going to the impeller. diate wall 23 are inclined towards each other, the front wall 62 lies substantially at right angles to the axis of the impeller shaft, asv does the mounting flange shoulder 4| (see Figure-19g 'I'he intake trap 48 may, in outline,` substan- -tially overlie, or register with., the separatonand ns portsA While the back wall 58 and intermeber 4, to insure application of the closure mem- .,ber 4 in a definite position, and to prevent accidental rotation. The coverjplate 5 overlies the circular opening 68 which is formed'in the front wall 82, and thiscover plate 5 is held in place by suitable stud bolts 81 which are shown in Figurges 1 and 4.

jObviously, if desired, the intake trap may be made of the same width as the barrel portion throughout its vertical height, or may be otherwise shaped if so desired. However, it is quite ad"antageous to have the intake trap of the s 'A e and configuration shown, so that it may re in a maximum of liquid upon the reux of liquid upon stopping the pump and the carrying of through the separator'and intake trap to break the vacuum in the suction pipe 51. By havi' g the main part of the intake trap dispos above the opening I1' in the front plate il, it can be seen that a maximum charge of liquid will'be retained when the air strikes back through the separator, through the pump, andthrough the opening |1 into the intake trap. Thus no check valve is required in this form of pump and;

yet ample liquid is retained for priming.

A/ removable plug 69 is provided on the separator for charging the pump body with liquid to initiate operation. Draining plugs 10 and 'I2 permit draining of all parts of the pump when it is desired to remove the liquid therefrom.

The assembly and servicing of the present pump is facilitated bythe aforesaid structure. The main bodymember I, including the pump barrel, back plate, supporting flange, the separator and the intake trap, are all formed in-one casting. This greatly facilitates, construction. The machining of the main frame can be accomplished on a boring mill or the like on 'a single axis. That'is to say, the supporting shoulder 4| for the bracket, the recess 29- for the removable packing gland cartridge. the cylindrical surface of the cut-oi! 9,`the bore of the barrel wise are finished by turning on a lathe. or the equivalent.

In assembly, the pump is of the greatest simplicity. 'Ihe impeller and packinggiand cartridge may be inserted as a unit and removed as a unit. or, if desired, the impeller may be removed from the shaft 48 and likewise the packing gland cartridge removed vfrom the shaft through the front opening. The member 4 and the cover plate 5 may be removed and replaced readily without disturbing other parts. Obviously, the details of construction may be varied-that is, for example, the screen 24 may be made a separate part from the closure member and-it may be supported onthe cover plate 5. if desired..

The operation of the pump is as follows: as-

\ sume that the pump has been charged with sum- \ci ent liquid to constitute a 'wai-king charge. Assume that the liquid stands at the same level in the separator and the trap and the shaft 4Q is Liquid will first be drawn out of the trap, down to substantially the.' bottom ofthe opening I1 in the front plate I 8, and `discharged into the trap through the vol'fte extension way of opening I2 and openings |8.

It will be observed that the volute extension 8- does not continue on the same rate of increase as' lby does the main body of the volute, for the reason that the openings I3 constitute additional outlets during the time of liquid pumping. Furthermore, by this construction, the issuing stream of mixture is subjected to an intensified centrifugal effect within the volute extension, i. e., a more pronounced change of direction, and this stream tends, therefore, to hug the outer periphery of the passageway or channel. In the particular construction illustrated the bottoms of the openings I3 are disposed at approximately the periphery of the blade tips, whereby liquid owing in through the openings I 3I3 tends immediately to come under the influence of the pressure conditions within the rotating lmpeller.

The cut-off 9 is shown as disposed slightly below the level of the top of the impeller travel,

although this is-not essential, and itis disposed beyond the openings I3, considered in the direction of travel of the blade tips and of the iiuid ow. Instead of two openings I3, one large opening at one side only might be employed.

The curved blades tend to move the liquid tangentially and radially. By control of the curvature of the blades the ratio of radial throw to circumferential throw may be controlled andthe ratio of pressure to volume vor delivery may Le suitably selected.

Assuming that the priming operation is initiated by 'the rotation of the impeller in a clock- Wise direction as viewed in Figure 2, the blades IS-IV tend to throw the contained liquid radially and circumferentially, discharging the same through the opening I2 of the volute extension 8 and to discharge any excess through the openings I3. As soon as the impeller casing has been substantially emptied of liquid, air takes its place and, since the density of Aair is so much less than the density of water or other liquid which is normally pumped, the pressure developed by the rotating blades will be insumcient to overcome the gravity tendency of the water to-ilow back into the impeller chamber. Hence, liquid will tend to flow into ,the openings I3 into contact with the revolving blades, and liquid also tends to4 enter the opening I2 and ow back into the space occupied by the impeller.

If the head of liquid is insufhcient to force liquid suiciently far into the impeller to secure a denser working medium than air, and of a volume -suicient to establish an orderly flow, the pump may exhibit the well known action of low vacuum or startingstall. The present construction of pump exhibits substantially no tendency to stall at this point, but immediately begins to form a working fluid more dense than air and less dense than liquid, by the inow of liquid through theA openings I3 into contact with thel impeller. The pressure upon the front faces of the blades Ill-IIJ is that due to the rapidly rotating blades working against the liquid which is moving more slowly, or which may be substantially stationary at this point. The pressure upon the back sides of the blades Ill- I0 is below the mean pressure in the impeller chamber justas the pressure upon the advanced faces operated upon by the impeller blades, tends to be thrown to the periphery of the channel or volute passageway II, and where, as in the case of priming, the charge of liquid is insulcient to completely ll the volute channel- II, the space between adjacent blades as the same approaches the passageways I3 gives room and a pressure reduction which tends to draw the liquid from the separator through the ports or passageways I3 into the interior of the impeller to form a working mixture. The liquid so drawn in is mixed orchurned up with airand is discharged as a stream Whichhugs the outer periphery of the volute passageway I I and is driven out through the opening I2. The priming liquid which is admitted through the openings I3 into contact with or under the inuence of the impeller, enters below the issuing stream of mixture and such part of the entering stream of priming liquid as can be taken into the impeller is so taken in, but that part of the liquid which is engaged on the front sides of the blades as the blades approach the cut-0H 9 is rejected by the impeller at this point and forms a stream which slides over the top edge of the cut-ofi` 9 and follows the wall 5I upwardly. Thus, out of the opening I2, during priming, there are two distinct flow streams, first, the flow stream of mixture which hugs the outer wall of the volute channel II and passes through the opening I2 into the separator above the openings I3 or the major part of the same, and the second ow is that which is rejected by the impeller over the cut-oil 9 and follows up the wall 5I. The issuing stream of mixture is thus bent upwardly by the adjacent walls of the separator and by the stream of rejectedliquid, and it flows upwardly along this curved wall, tending to agglomerate the bubbles and free them by the action in the separator. The practical effect of these two streams is to form an outward unidirectional flow of uid (liquid and gas mixture) at all times during priming. Thereby the opening I2 is lfilled with outwardly flowing iluid and hence none of the heavy gas laden liquid can be sucked back into the impeller. By this arrangement an orderly ow of priming liquid which is largely freed oi gas is provided and as a consequence the pump primes more rapidly and is able to attain higher suctlons than would be the case if heavily gas laden liquid could `reenter the impeller.

The action in this separator is unique. 'Ihe stream of iiuid issuing from the endv I2 of the volute comprises,` first, the rejected priming water, which flows at fairly high velocity due to the fact that it has been directly under the inuence of the blades. Second, there is the issuing stream of mixture which is more remote from the iniiuence of the blades. These two streams are not readily distinguishable and by the time they issue and strike the wall 5I, they are merged. Following the curved wall 5I the velocity at the narrowest part (the right in Figes the dead pocket 60. The dead pocket is by no means a quiet body or region, but only relatively so. Liquid substantially freed of gas ows along the two sides of the volute extension in the '5 channels 59-59 through the openings I3, and again into the impeller. This action ofthe travel of theliquid in a path which may be described roughly as a gure 8, clockwise in the impeller chamber and counterclockwis'e in the separator, with a crossing of the two streams at the volute extension 8, proceeds until the vacuum is highl enough to pull water over-through the suction pipe 51 or to draw as high a dry vacuum as the pump is capable of exerting in case liquid is not I available. When liquid comes over through the charge. Due to the reversal Jof pressure occuring at the ports I3, the tendency for solid mai terial to lodge is counteracted. Likewise, the

flow along the channels 59--59 at each side of the volute extension 8 and over the same is quite rapid at all times, whereby any tendency for the deposit of solid material and debris is overcome,

. the same being expelled through the opening 5 3 with the water being pumped..

Any material which is capable of passing through the strainer openings 25 can be handled by the pump, and material which cannot pass the strainer openings 26 is held in the bottom part d of the intake trap, from which it may be removed by opening the cover plate 5. The openings in the strainer 25 present a much greater aggregate than the opening I1 and hence partial clogging of the same will not stop the operation of the pump.

I do not intend to be limited to the precise forms or details herein disclosed, except as called for by the appended claims, as the disiting. p

I claim:

1. A self-priming centrifugal pump compris- `ing an impeller chamber having a cutoff and a volute extending over the cutoff. an impeller oooperating with said cuto and said volute, aseparator having a curved end wall ,leading from the cutoi for receiving and leading the liquid passing out of the volute and over the cutoff in a curved path from a substantially horizontal diline with the cutoff and the end of the volute extending into the separator above said bottom wall, the separator having a lateral wall which is spaced away from a side of the volute and va sidewall of the volute having a tranverse opening communicating with the inside of thev separator adjacent the bottom wall for leading priming liquid from the separator into the impeller 7'0- in advance of the cutoff.

- 2. A self-priming centrifugal'pump ing an impeller casing having a cutoff and a volute of progressively increasing cross section, an impeller having a plurality of backwardly curved blades cooperating with the cutoi! and y closure herein is`illustrative, rather than limrection to substantially a vertical direction, the i separator having a bottom wall substantially in v compris'- l receives a full complement of liquid sucient to produce outiiow whereby said passageway tends .to clear itself of entrained solids.

3. A pump comprising an impeller casing having a volute, an impeller in said casing cooperating with said volute, a separator, a portion oi the volute projecting ii'ito and terminating within the separator .above the bottom wall thereof, said separator having a wedge shape with the narrower part thereof facing the discharged end of the volute and the wider` part'behind the projecting portion of the volute to form a dead pocket of minimum velocity during priming'.

'4. 1n a pump, a body casting having a pump barrel at its lower end and a pair of chambers thereabove constituting an intake trap and aseparator, a transverse bore in the lower `part of said casing extending into the pump barrel, the bore on the back side being closedby an integral backwall vhaving a central openin a packing gland secured to the back wall and removable through said. bore, k an impeller insertable through said bore and having a shaft extending through said gland, a circular intake member forming a front wall for the\impel1er .and having an inlet opening, a strainer member extend-` ing forwardly of the intake member, a cover plate closing the outer end of the bore.'

5. In a pump a body casting comprising a. pump barrel including a back plate and a volute,

integral extensions dening a hollow body and l comprising a front intake trap wall, a. back separator'wall and an intermediate dividing wall back of which lies a separating chamber and in front of which lies an intake trap, there being concentric openings through the front wall Vand the intermediate wall and through the backplate, a circular intakemember having a cylindrical pluglike portion for closing the opening in the intermediate wall, and having a front plate portion with a. central intakev opening, an impeller disposed between said back plate and said front plate portionand cooperatingV with the volute portion of the pump4 barrel, a shaft for the impeller extending .through the back plate wall, said impeller being removable through said concentric openings inthe intermediate wall and the front wall, and a cover plate for the opening in the iront wall.

6. In a pump, a pump barrel member'` comprising an integral volute, back plate and vertical walls dening a separator communicating v with the outlet of the volute and 'having its side walls spacedfrom the sidewalls of the volute, and an intake trap which lies partly in front oi' and partly-above the pump barrel, an opening extending through the trap concentric with plate for the impeller and having a central intake opening, a strainer member extending over the front plate, and a closure plate for the opening through the iront trap wail.

7. The combination-of claim 6 combined with a separable packing gland cartridge removable through. the pump barrel, and a circular mounting extension. surrounding the removable packing gland cartridge. y

8. In a pump, a pump .barrel comprising a volute and back plate, a mounting extension integral with the back plate, an intake chamber having walls integral with the pump barrel and having an opening concentric with the pump barrel, a' circular closure member for the pump barrel comprising a front plate for the impeller, said front plate having an inlet opening, an impeller removable through the barrel and the concentric opening disposed between the back plate and the iront plate, said closure member bearing a strainer member, a cover plate for the concentric opening in the intake chamber and compression spring means between the coverv plate and the strainer member.

` 9. In a pump, a body comprising a pump barrel with integral iront and back Walls rising above the vpump barrel and deiining a wedgeshaped separator chamber disposed wholly above the pump barrel, and an intake trap disposed in front of and above the pump barrel, the pump barrel comprising an integral back. plate and a volute, the volute having a terminal portion which extends into the lower part of the separator and has its discharge directed into the narrow portion of the wedge -shaped separator, there being an opening through the trap to the pump barrel, a closure member bearing a iront plate for closing the pump barrel and having a central inlet opening, a cover plate for the outer ,end of said trap opening, and means disposed between the cover plate and the closure member for holding the closure member in seated position.

10. In a pump of the class described, a main body member comprising a pump barrel portion having a front opening and an encircling volute portion, an `impe1ler adapted to be inserted through said barrel opening, a closure member for the opening forming a front plate for the barrel.

of a diameter substantially greater than the pump` barrel and of an axial depth approximately equal to that of the pump barrel, an intake trap lying at its upper end against the separator andbeing oi' substantially the same' outline. and at its lower end forming substantially a continuation of the pump barrel, whereby the major part of the capacity of the intake trap is above the pump barrel, the lower end oi the intake trap having an opening registering with the opening in the pump barrel for removal of the cover member and the impeller from the pump, and a cover plate for closing the opening in the lower end of the separator.

12. In a pump of the class described, a main body member comprising a pump barrel portion having a front opening and an encircling volute portio an impeller adapted to be lnsterted throu h said barrel opening, a closure member for the. opening forming a front plate for the impeller, said front plate having an intake opening, said main body member having walls delining a separator of generally cylindrical outline disposed above the pump barrel and being of a diameter substantially greater than the pump barrel and of an axial depth approximately equal to that of the pump barrel, an intake trap lying at its upper end against the separator and being of substantially the same outline and at its lower end forming substantially a continuation of the pump barrel whereby the major part of the capacity of the intake trap is above the pump barrel, the lower end of the intake trap having an opening registering with the opening in the pump barrel for removal of the cover member and the impellerfrom the pump, a cover plate for closing the opening in the lower end of the separator, and a screen overlying the Aclosure member and being held in place by the cover plate.

13. Self-priming pump having a separator and a volute with a volute extension disposed in the separator, said volute having a progressively increasing cross section to the volute extension, said volute extension having openings through the side walls and having a cross section of substantially the same value throughout its length, and a cutoff for the volute disposed beyond said openings in the volute extension.

14. In a self-priming centrifugal pump, a separator chamber having at its lower end a slot in a wall thereof, an impeller casing of thevolute type joined to the walls of the chamberabout.

said slot, an impeller rotatable in a plane at substantially right angles to said wall and having its periphery projecting into said' slot, said volute casing having a cutoff at one end of the slot, a hoodlike volute extension extending from the other end of the slot and directing the stream of mixture from the volute over the cutoff, saidy volute extension having a peripheral wall for guiding the mixtureradially far enough away from the periphery of the impeller to produce a region of reduced pressure between said guided stream of mixture and the cutoi, said volute extension having side walls disposed at the sides of the slot, and slots formed in said side walls at said region of reduced pressure for permitting the entry of priming liquid directly from the lower end of said separator into engagement with the periphery of the impeller in advance of said cutoii', said priming liquid engaged by the periphery of the impeller at said region of reduced pressure being divided by said cutoi whereby part enters the impeller casing to form a mixture and a part is rejected and ilows along with said issuing stream of mixture over the cutoii.`

15, A self-priming centrifugal pump of the volute type comprising a gas and liquid separator, an impeller, an impellerhousing provided with a cutoi, and a volute having a terminal lportion extending over the cutoff to deiine a periphery of the impeller and being disposed in advance of the cuto for admitting priming liquid from the separator into the vperiphery of the impeller in advance of the cutoii, said discharge outlet being substantially completely lled with outwardly iiowing iiuid during priming to prevent sucking back of liquid heavily laden with gas.

16. A self-priming `centrifugal pump oi' the volute type comprising an impeller chamber having a cutoff, an impeller having mechanical clearance only with the cutoff,l a volute having a terminal portion cooperating with the cutoff to deiine a discharge opening and having an intermediate portion yin advance of the cutoif spaced radially lfrom the impeller to produce a region of reduced pressure at the periphery of the impeller in advance of the cutoff. there being a passageway'from the separator through the side wall of the volute openingl into the periphery of the impeller' at said region of reduced pressure to. admit priming liquid, a part of said admitted priming liquid being rejected over the cutoff and driven out ol.

Isaid discharge opening along with said stream of mixture during priming to preventI sucking back of a part of said stream of mixture.

HARRY E. LABOUR.