US2431221A - Centrifugal pump - Google Patents

Description

Nov. 18, 1947. F. B. ALLEN CENTRIFUGAL PUMP 2 Sheets-Sheet 1 Filed March 3, 1945 Om mm W \m MN INVENTOR. FRANK B. ALZE/V M4 H n/ flTTORNEYS Nov. 18, 1947. F. B. ALLEN 2,431,221

CENTRIFUGAL PUMP Filed March 3, 1945 2 Sheets-Sheet 2 INVENTOR. FRANK 5. ALL E/V A TTOE'NE ys Patented Nov. 18, 1947 CENTRIFUGALPUMP Frank B. Allen. Lower Marion Township, Montgomery County, Pa... assignor to The Allen- Sherman-Hoff Company. Philadelphia, Pa., a

corporation of Pennsylvania Application March s, 1945. Serial No. 580,867

This invention relates and more particularly to a new centrifugal pump which has great resistance to abrasion when liquids containing abrasive solids are being pumped.

Many efforts have been made heretofore to provide centrifugal pumps which could be used for long periods of time to pump liquids carrying abrasive solids. One of the first eiforts along this line was to construct the impeller and housing of special steels which were quite hard, such as manganese steel. However, abrasive solids in the presence of the liquid quickly cut and wore away even these hard steels and such wear necessitated replacement of the worn parts.

As a result of experiments, I discovered that such wear of centrifugal pumps, which was quite serious from the standpoint of prolonged pump efficiency, was traceable to the fact, that high pressure liquid in the volute tended to flow between the housing and the suction side shroud plate of the impeller and thence into the intake openingof the impeller; and that abrasive solids in liquid flowing thru that course tended to enlarge the spaces between the impeller and housing at the outer periphery and at the intake opening of the impeller, with the result that as these spaces were enlarged more and more liquid was circulated from the volute back between the impeller and housing to the intake side of the impeller. Liquid and solids so circulating constituted a loss of emciency of the pump and also increased the rate of wear of the pump parts engaged thereby.

As a result of that discovery I have made a number of efforts to solve the problem of preventing such back flow. Some of those efforts are illustrated by the apparatus shown and described in U. S. Patents Nos. 1,967,182; 1,999,163; 2,003,168; 2,021,346; 2,220,669; 2,223,653; 2,232,648 and 2,255,239. The pumps of severaliof these patgenerally to the pump artscams. its-111) I v 2 ring which was carried by the impeller around its intake opening and which cooperated with the rubber liner of the housing to prevent back'flow cuts have, in commercial use, proven to be much more satisfactory than the best prior centrifugal pumps with which I am familiar. However, the pumps of these several patents have worn despite all the precautions taken to prevent such wear and over a considerable period of time expensive repairs or replacements have been required to maintain the efllciency of the pumps above a predetermined minimum amount.

One of the most successful pumps embodying my prior inventions is shown in Patent No. 2,232,648. In that pump the interior of the housing and the exterior of the impeller were covered with rubber which is not worn appreciably by abrasive solids in a liquid. However, the metal from the volute was gradually worn away on the surface disposed at right angles to the axis of rotation of the impeller. This wear occurred despite the facts that the sealing portion of the housing liner was pressed against the ring by clear water under pressure and that some of that water flowed between the liner and ring and into the impeller intake opening. While the pump of that patent was a great improvement over certain prior pumps, yet the ring had to be replaced from time to time and such replacements were expensive in parts and lost operating time.

I have now discovered the reason for such wear of the metal ring of my Patent No. 2,232,648 and by the present invention am able greatly to simplify the construction and lessen the cost of centrifugal pumps while, at the same time, avoiding substantially all wear between the intake side shroud plate of an impeller and the housing which would result in lowered efficiency of the pump. Apparently, fine solids which entered the space between the metal ring and rubber liner were sub- Jected to centrifugal forces which tended to move them radially outward. During this outward progress some of the solids became embedded in the rubber liner and abraided the surface of the ring, and as the surface of the ring'became worn and rough it soon destroyed the rubber, whereupon the seal would fail. The present invention eliminates the metal ring of Patent No. 2,232,648 and prevents the application of centrifugal force to solids seeking to enter the clear water chamber along the outer side of the inlet pipe. Ibelieve that the present invention solves the problem which has confronted the industry for more than ten years; and that this invention provides a pump which will handle liquids carrying abrasive solids for greatly extended periods of time without materially decreased emciency due to wear and abrasion.

The present invention is also of advantage in clear liquid pumps in sealing the space between the impeller and housing inlet. I

In the drawings accompanying and forming a P rt of this specification,

Figure l'is an end elevational view of the suction side of one form of centrifugal pump embodying the present invention:

Figure 2 is a side elevational view, partly in section, and taken on line 2-2 of Fig. 1;

Figure 3 is an enlarged fragmentary view of the clear water chamber and its seals;

i on bed I.

but showing modified apparatus; and

Figure is a sectional view taken on line 5-5 The centrifugal pump of Figs. 1 and 2 and it 1 driving shaft and associated parts are mounted The shaft 2 is mounted in bearings 3 and is provided with a. keyway 2a at one end for attachment through a coupling to suitable drive means (not shown).

The pump comprises a housing consisting of p a volute 4 partly defining a volute chamber 4a and having a tangential, peripheral outlet portion j 5 for connection to a pipe 6, suction side plate I and shaft side plate 8.

The side plates are in the form of discs with outwardly and axially extheir peripheries are attached to the volute plate tending, radial throats 9 and I9, respectively, and l 4, as by studs II and nuts l2. The throat ||l of j shaft side plate 3 is attached to an annulus l3 2 extends. The annular space between annulus 1 which has an axial opening thru which shaft l3 and shaft 2 is filled with packing H which is l compressed by gland follower I 5 and which serves to prevent escape of liquid from within the hous- 'ing between the annulus and shaft 2.

Shaft 2 is screw-threaded at its end within the housing 1 p and fitting I6 is screwed thereon. The outer cylindrical surface I! of fitting I6 is engaged by 1 i a flexible, rubber-like ring I 8 carried by plate 8.

Side plate 8, annulus l3, fitting l6 and ring l8 1 define a space into which clear water under presa sure may be delivered thru pipe I9. Ring l8 permits this clear water to fiow toward the volute chamber 4a but prevents'entry of water from that chamber into the clear water space.

Side plates 1 and 8 carry on their inner surthe inner periphery of volute plate 4 and have surfaces 2| disposed closely adjacent to and radially outside of the outer periphery of the imfaces metal wear liners 20 which abut against 1 peller, and side surfaces 22 extending along and surface defining the suction inlet of the pump and its outer surface being spaced radially within a surface of the throat 9 to define partly therewith an annular axially extending space 3|.

The impeller comprises a shaft-side shroud attached to fitting l6, as by bolts 21 and nuts 28, a suction side shroud plate 29 having an axial plate 26 having an integral flange 26a which is l intake opening and an axially extending portion 1 3|) which closely surrounds wall 25 and projects into the annular space 3|, and a plurality of 1 blades 32 extending between shroud plates 26 and 29. At the outer end of portion 3|) of plate 29 is mounted a flexible, preferably rubber-like ariat its inner edge. 3'! is mounted in close fitting, liquid tight contact with the inner surface of plate 1. The outer periphery of annulus 35 engages radially with the inner surface of ring 31. The inner surface of flange 36 of member 35 bears against the outer cylindrical surface of wall 25. Ring 31 and annulus 35, with its flange 36,-close the outlet end of space 3|. The inner surface of flange 36 which is opposed to the outer surface of wall 25 may be provided with shallow grooves. The

spiral grooves 38 shown in Fig. 3 extend spirally from their inlet ends in space 3| to their outlet nulus 35 having an axially extending fiange 36 Within space 3| a metal ring ends adjacent the impeller intake and with the intake ends ahead of the outlet ends when the impeller is rotating, so that clear liquid from space 3| is scooped into the grooves and forced therethru. If desired, the shallow grooves may be straight instead of spiral.

Pipe 4|), which may be connected toa suitable source of clear water or other suitable liquid under pressure, leads thru throat 9 of plate 1 into space 3| whence it may flow between ring 31 and annulus 35 to volute chamber 411 and also through grooves 38 into the impeller.

It will be understood from the foregoing description that the housing has an annular, axially extending space 3| which communicates with the volute chamber 4a and also with the intake opening of the impeller; and that those lines of communication, are controlled by ring 31, annulus 35 and sleeve 25 so that liquids containing abrasive solids are prevented from flowing into the annular space 3 l. I

The operation of the above described pump is substantially as follows; When shaft 2 rotates the impeller liquid is drawn .in thru the inlet passage defined by wall 25 and is impelled out into the volute chamber 4a and thence into pipe 6. Simultaneously clear liquid-under pressure, that is, liquid substantially free from abrasive solids, isdelivered thru pipe 40 into space 3| and tends to escape between ring 31' and annulus 35 and thence flows out into the volute chamber 4a thru the space between the impeller and the adjacent liner 20. This flow preventsthe flow of liquid in chamber 4a in the reverse direction.

impeller intake is overcome; As a result there is practically no wear on the outer surface of wall 25, on ring 31, or on the outer side surface of shroud plate 29, and the efllciency of the pump is not decreased by back flow from the volute chamber and resulting wear. 3

Figs. 4 and 5' show modifications of the apparatus of Fig. 3. In certain respects the apparatus of Figs. 4 and 5 is preferred.

In these figures the suction side plate 1 includes a throat 9 and an axially extending wall 50 whose inner surface defines the suction inlet to the impeller. The outer surface of wall 50 is cut away to form a plurality of shallow, axially extending lubricating grooves 5|. The suctionside shroud plate 29 of the impeller is extended, as at 52, and has an inner surface which is of substantially the same diameter as the inner surface of wall 50 and has an end surface 53 which is substantially parallel to and close to the inner end surface of wall 59. The rubber-like annulus 54 generally resembles annulus 35 of Figs. 1 to 3 but the flange partthereof 55 has a smooth inner surface to engage the smoothouter surface of wall 59 and span the grooves SI-therein. The

arate ring 31 and sleeve 25 of Figs, 1 to 3 have been replaced by the axially extending cylindrical surface 58 and integral wall 50, respectively, and wall 50 is axially grooved and flange 55 has a smooth surface whereas sleeve 25 had a smooth surface and flange 36 was grooved. Wall 50 may be detachably connected to plate I if desired after the fashion shown in Fig, 3.

It will be noted that both forms shown in Figs. 3 and 4 have two axially extending surfaces with which the annulus engages at the outlets from the high pressure clear water chamber 3|. In Fig. 3 these surfaces are the inner surface of ring 31 and the outer surface of sleeve 25. In Fig. 4 these surfaces are the surface 56 and the outer surface of wall 50.

The operation of the apparatus of Figs. 1 and 2 with the apparatus of Figs. 4 and 5 embodied therein is substantially as has been described hereinabove, the main difference being that water escapes from chamber 3| into the impeller intake by flowing thru grooves 5|. Since annulus 54 rotates relative to these grooves water flowing in these grooves axially wipes and lubricates the inner surface of flange 55 once each revolution for each groove. When there are four grooves 5|, the entire inner surface of flange 55 is wiped four times during a single revolution of the impeller. Thus no centrifugal force is applied to solids which may move from .the suction intake of the pump into the space between wall 50 and the impeller, and considerable axial force is applied to such solids by water flowing in grooves 5|. The result is substantially no abrasive wear on the flange 55 or wall 50.

The present invention, as above stated, is advantageous in pumps handling clear liquid, that is, liquid which is substantially free from abrasive solids. In the ordinary centrifugal pump great difficulty has been experienced in effectively sealing the high pressure chamber from the low presv sure chamber, the former being the chamber at the periphery of the impeller and the latter being the chamber at the central inlet of the impeller. The present invention provides an efiicient seal between these chambers and restricts to a small amount the liquid from the high pressure chamber which can enter the low pressure inlet side of the impeller and prevents any marked variation in the amount of such flow.

The adaptation of the present invention to such clear liquid pumps will be readily understood by those skilled in the art from a consideration of Fig. 4. The outer periphery of annulus 54 may be cut away so that it does not engage the axially extending surface 56 of the side plate, such as plate I, but that plate may be formed without a surface 56 to engage the annulus, and the pipe 40 may be omitted.

When such a pump is umping clear liquid, the high pressure liquid from the volute or periphery of the impeller will be prevented from freely flowing into the impeller intake by annulus 54 but small, substantially unfluctuating amounts of liquid will flow thru grooves 5| and into the impeller intake.

Similarly, the apparatus of Fig. 3 may be adapted to pumping of clear liquid by the simple expedient of omitting ring 3-! and pipe 40. Of course, it will be understood that when pipe 40 is omitted the side plate will either not be provided with a hole for pipe 40 or, if it has such a hole, the hole will be plugged.

From the foregoing description of the present invention as applied to clear liquid pumps it will be understood that it may be applied to pumps in I stages, that is, wherethe high pressure liquid from one pump is fed into the impeller of an adjacent pump and its pressure increased in that stage and perhaps delivered to another pump for further increase in pressure. The present invention may be utilized in the pumps of each stage substantially as just described.

Having thus described my invention so that others skilled in the art may be able to understand and practice the same, I state that what I desire to secure by Letters Patent is defined in what is claimed.

V\ .at is claimed is: I

1. A centrifugal pump comprising a housing including a suction-side plate having an axially enlarged throat and' an inlet defining, cylindrical wall extending axially in said throat, said throat and wall defining an annular space therebetween, axially extending, radially spaced, cylindrical surfaces on said throat and wall, an impeller mounted for rotation in the housing with its suction side opposed to said cylindrical wall, a rubber-like annulus attached to the impeller and bearing against said cylindrical surfaces, said cylindrical walland annulus defining therebetween an outlet passage which extends axially for its full length and connects said annular space with the suction side of said impeller, and means to deliver clear liquid under pressure into said annular space.

2. A centrifugal pump comprising a housing including a suction-side plate having an axially enlarged throat and an inlet defining, cylindrical wall extending axially in said throat, said throat and wall defining an annular space therebetween, axially extending, radially spaced, cylindrical surfaces on said throat and wall. an impeller mounted for rotation in the housing with its suction side opposed to'said cylindrical wall, a rubber-like annulus attached to the impeller and having an axially extending flange near its inner periphery, the outer periphery of said annulus bearing on the said axially extending surface of said throat and the inner surface of said flange of said annulus bearing on the said axially extending surface of said wall, and means to deliver clear liquid under pressure into said annular space.

3. A centrifugal pump comprising a housing including a suction-side plate having an axially enlarged throat and an inlet'defining, cylindrical wall extending axially in said throat, said throat and wall defining an annular space therebetween, axially extending, radially spaced, cylindrical surfaces on said throat and wall, an impeller mounted for rotation in the housing with its suction side opposed to said cylindrical wall, a rubber-like annulus attached to the impeller and having an axially extending flange near its inner periphery, the outer periphery of said annulus bearing on the said axially extending surface of said throat and the inner surface of said flange of said annulus bearing on the said axially extending surface of said wall, there being shallow grooves between the opposed surfaces of said flange and said wall and extending from said annular space to said impeller, and means to deliver clear liquid under pressure into said annular space.

4. A centrifugal pump comprising a housing including a suction-side plate having an axially enlarged throat and an inlet definin cy ind ical wall extending axially in said throat, said throat and wall defining an annular space therebetween,

axially extending, radially spaced, cylindrical surfaces on said throat and wall, said cylindrical surface of said wall having small axially extending grooves therein, an impeller mounted for rotation in the housing with its suction side op-; posed to said cylindrical wall, a rubber-like annulus attached, to the impeller and having an axially extending flange near its inner periphery;

the outer periphery bearing on the said axially extending surface of said throat and the said flange bearing on the said grooved cylindrical surface of said wall, and means to deliver clear liquid under pressure into said annular space.

i 5. A centrifugal pump comprising a housing including a suction-side plate having an axially enlarged throat and an inlet defining, cylindrical wall extending axially in said throat, said throat and wall defining an annular space therelietween,

axially extending, radially spaced, cylindrical surfaces on said throat and wall, an impeller mounted for rotation in the housing with its suction side opposed to said cylindrical wall, a rub-;

6. A centrifugal pump com rising a housing including a suction-side plate having an axially enlarged throat and an inlet defining, cylindrical wall extending axially in said throat, said throat and wall defining an annular space therebetween,

said wall havingan outer, axially extending,

cylindrical surface, a ring bearing against said throat-in said annular space and having an axially extending cylindrical surface, an impeller mounted for-rotation in the housing with its $110- tion side opposed to saidcylindrical wall, a rubber-like annulus attached to the impeller and bearing against said cylindrical surfaces on said ..wall.and said ring, and means to deliver clear her-like annulus attached to the impeller and" bearing against said cylindrical surfaces, said annulus having an axially extending flange near its inner periphery to engage said cylindrical surface of the wall and having grooves in its surface engaging said wall to direct clear liquid therethru out of said annular space, and means to deliver clear liquid under pressure into said annular space.

"liquid'under pressure into said annularspace.

FRANK B. ALLEN.

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

UNITED STATES PATENTS

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