US2627812A

US2627812A - Pump

Info

Publication number: US2627812A
Application number: US595019A
Authority: US
Inventors: Mann John
Original assignee: Goulds Pumps Inc
Current assignee: Goulds Pumps Inc
Priority date: 1945-05-21
Filing date: 1945-05-21
Publication date: 1953-02-10
Anticipated expiration: 1970-02-10

Description

J. MANN Feb. 10, 1953 PUMP Filed May 21, 1945 3 Sheets-Sheet 1 INVENTOR.

JOHN [MANN fair/w J. MANN Feb. 10, 1953 PUMP 3 Sheets-Sheet 2 Filed May 21, 1945 INVENTOR.

JOHN MANN J. MANN Feb. 10, 1953 PUMP 3 Sheets-Shet 3 Filed May 21, 1945 INVENTOR.

BY JOHN AdAN/V bar 2% Patented Feb. 10, 1953 PUMP John Mann, Seneca Falls, N. K, assignor to Goulds Pumps, Inc., Seneca Falls, N. Y., a corporation of New York Application May 21, 1945, Serial No. 595,019

12 Claims.

My invention relates to pumps and more particularly to a pump of the self priming centrifugal type.

One of the distinct disadvantages of a centrifugal pump is that it will not handle large quantitles of air and, therefore, will not prime itself. Various methods of priming centrifugal pumps have been tried. One of these methods requires an additional automatically controlled vacuum pump connected into the suction line of the cen trifugal pump to remove air therefrom and thereby maintain the pump primed or prime it should the pump lose its prime after a period of non-use. This method requires relatively expensive equipment and is, therefore, practical usually only in connection with the larger sizes of pumps.

A second method used is to employ a relatively large storage chamber on the suction side of the pump. The size of the chamber required is the major objection to this method of priming. A third method depends upon maintaining the pump full of water when it is stopped and the recirculation of liquid discharged by the pump back through the pump during the priming cycle.

The self priming pump of my invention relates to this last method of priming. Various adaptations of this method have been attempted and while several of them are in successful commercial use, all of them with which I am familiar result in relatively inefficient pumps. It will be appreciated that liquid recirculated back through the pump represents a loss in energy. While the effort is made to discontinue this recirculation after the priming cycle is completed, in practice either there is some continuous recirculation through the pump afterthe priming has been completed or the optimum centrifugal pump design, particularly of the discharge passageais sacrificed to obtain the desired automatic priming. 1

An object ofmy invention is to provide a simple, positive and efficient self priming pump.

Another object of my invention is to provide a self priming centrifugal pump which departs from the best design for efficiency in only a slight degree so as to provide a centrifugal pump which has all the advantages of self priming with little or no sacrifice in pump efficiency after the priming cycle is completed.

My invention further contemplates the provision of a self priming pump which has twovolute shaped discharge passages designed for maximum pump efficiency, the passages being constructed and arranged so that liquid discharged through one of the passages is recirculated back to the pump through the other passage during the priming cycle andso that, after the priming cycle is completed, both passages become discharge passages which effieiently convert the velocity enorgy imparted by the impeller into pressure energy. I

Other objects and advantages of my invention will be set forth in the claims and will be apparent from the following description, when taken in connection with the drawings, in which:

' Fig. l is a front elevation of the self priming centrifugal pump of my invention partly in section indicating by the arrows the liquid flow during the major phase of priming cycle;

Fig. 2 is a sectional view thereof;

Fig. 3 is a view similar to Fig. 1 in which the liquid flow has been indicated by the arrows when the priming cycle is completed;

Fig. 4 is a sectional view,'similar to Fig. 2, illustrating the self primin pump of my invention combined with a shallow well jet pump; and

Fig. 5 is a view showing the centrifugal self priming pump of my invention combined with a deep welljet pump.

The self priming centrifugal pump of my in vention comprises a casing, generally'ind'icated by the numeral I I, and an impeller 12 mounted in the casing. The impeller is mounted on the end of a drive shaft l3 provided with a suitable shaft seal M.

A chamber 16 is provided" for a purpose which will later appear and the pump shaft extends into a cored out opening in the chamber,'indicated at IT, and as shown in my copending application, Serial No. 577,879, filed February 14; 1945, which has matured into Patent No, 2,440,611, dated April 27, 1948. The shaft of the motor for drivin the pump (not shown) extends into the cored opening l1 and may be coupled tothe pump shaft in the manner illustrated in my above mentioned application. While I have shown a particular arrangement in which the pump and motor shafts are coupled together within a cored opening in the chamber 15, it will be understood that this constitutes no part of my present invention and that if desired a more conventional arrangement of motor, drive shaft and chamber may be provided. 'If desired, the pump casing may be located in the chamber It as shown in my copending application, Serial No. 523,927, filed February 25, 1944, now Patent No. 2,474,539.

The pump impeller may be of the conventional closed type having vanes or blades 18 and a central cylindrically shaped opening constituting the suction entrance or eye IQ of the impeller. The eye of the impeller opens into the suction pipe 2 l which extends to a source of liquid supply (not shown). A check valve 22 is located in the suction pipe and preferably at a point close to the suction entrance or impeller eye of the pump.

The pump casing ll comprises a main casing part 23 and a cover part 24 which may .be secured to the main casing part in any suitable manner.

A pair of volute shaped discharge passages 25 and 27 (Fig. l are provided in themain casing part which are connected by

passages

28 and 29 to the chamber [6 (Fig. 2). As is well known in the art to which this invention applies, the volute discharge passages convert the velocity energy imparted to the liquid by the impeller into pressure energy. The discharge passages are designed for maximum pump efficiency and their design is not sacrificed by reason of the pump being arranged for self priming. In the self priming pumps of the prior art, as previously mentioned, the pump eiiiciency is relatively low because modifications of design are made to make the pump self priming.

I have found that a centrifugal pump may be rendered self priming and still provide a pump of high efficiency. This may be accomplished by providing the pump with two volute discharge passages and spacing the cutwaters 3! and 32 of the pump at different distances from the periph eral edge of the rotating impeller. This construction is combined with an air separating and liquid storage chamber 16 on the discharge side of the pump arranged for the recirculation of substantially air free liquid back to the impeller during the priming cycle.

As shown in the drawings the cutwater 3i lies close to the peripheral edge of the rotating impeller. cutwater may be one sixty-fourth of an inch. Beyond this point the wall of the casing gradually recedes from the periphery of the impeller or the cross section area of the space into which the liquid is thrown by the impeller gradually increases from the cutwater 3| in the direction of rotation to form the volute 27. The cutwater 32 on the other hand is spaced from the peripheral edge of the impeller, ,as shown in the drawings. The clearance at this cutwater may be made, for example, one thirty-second to three sixteenths of an inch with good results being obtained when this clearance is oneeighth of an inch. The clearances mentioned above are not limits but are merely illustrative of clearances Which may be used satisfactorily. Beyond the cutwater 32 in the direction of rotation the volute 25 is formed which is similar to the volute 27.

When it is desired to start the pump the air separating chamber is first filled with liquid, preferably to the level of the top of a discharge pipe 36 located in the air separating chamber. This liquid flows through the impeller and fills the passages to the check valve 22 under which conditions the centrifugal pump is flooded. It will be noted that this priming liquid need only be supplied in the initial starting of the pump or in case, after a long period of disuse, the liquid retained in the air separating chamber should leak past the check valve 22.

When the impeller is rotated the liquid is thrown outward by the impeller and passes out through the volute passages 25 and 27 into the air separating chamber. The pump impeller and the suction pipe above the check valve 22 are soon exhausted of liquid and a vacuum is created therein which is satisfied by a flow of air from the suction pipe beneath the valve 22 into the eye of the impeller. This flow of air is, of course, caused by the atmosphere or pressure on the sur face of the liquid which constitutes the source of supply.

In practice I have found that during the initial priming of the pump there is a tendency for the liquid to flow from the air separating chamber For example, the clearance of this into the pump through the volute passage 28. This may be accompaniedby a discharge of some air and liquid outward from the pump through the volute passage 27. Moreover, until a vacuum of approximately four feet is reached the flow inward and outward appears to be erratic and to alternate between

passages

26 and 21. The exact flow during this period is difiicult to determine.

When the pump is developing approximately a vacuum of four feet, the flow of liquid and air appears to steady down and to be outward through the volute passage 26 and inward through the volute passage 21 from the air separating chamber. The erratic flow, above described, occurs only at the start of the priming cycle and may be due to various factors unnecessary to enumerate herein.

When the flow becomes steady it would appear that a sub-atmospheric pressure or lesser absolute pressure is existent just beyond the cutwater 32 in the region of the numeral 37. This subatmospheric (or lesser absolute pressure) appears to be greater than a similar sub-atmospheric (or lesser absolute pressure) existent beyond the outwater 3! in the region of the numeral 38. Moreover, a greater quantity of liquid is carried with the impeller past the cutwater 32 than past the cu-twater 3! due to the greater clearance. This greater quantity of liquid may pull liquid from the passage 2'. or may cause an induced flow from the passage 2?.

Moreover, there is a difference in static head caused by the height of the liquid in the air separating chamber $6 at the points 31 and 38. This difference in head. together with the lesser absolute pressure existent in the region 3?, as compared with the region appears to cause inflow of liquid through the passage 27 and the discharge of liquid through the passage 26. Because the causes of the above action are not definitely known I do not wish to be bound by the above explanation. It is sufficient to state that when the cutwaters are equally spaced from the periphery of the impeller, the priming action is extremely sluggish, whereas when the cutwaters are arranged as above described the priming action is rapid and positive.

The liquid flowing into the pump casing and impeller through the passage 2'! mixes with the air drawn into the eye of the impeller. The recirculated liquid acts as a carrier for the air and as impeller rotation continues. the air is gradually exhausted from the pump casing and the suction lines. The function of the chamber i5 is to maintain a reserve supply of liquid for priming when the pump is not in operation, maintain the pump impeller submerged, and to enable separation of the air from the liquid charged into the chamber by the pump.

The mixture of liquid and air discharged into the air separating chamber 16 is separated, the air rising to the top of the chamber and flowing outward through the discharge pipe 3.. Thus the liquid recirculated back through the pump casing through the volute 21 is substantially air free. t will be particularly noted that the air separating chamber is of relatively large volume as compared to the volume of the pump casing and that the

ports

28 and 29 are separated rather widely with the port 29 at the bottom of the air separating chamber. This arrangement insures adequate air separation and the return of substantially air free liquid to the pump casing.

In the drawings I have shown the air separating chamber as provided with a discharge pipe 35 which rises substantially to the top of the air separating chamber. This height of the pipe determines the normal liquid level in the air separating chamber. If desired the discharge pipe may be eliminated and a discharge outlet provided in the air separating chamber preferably at the top of the air separating chamber or at least at a height sufficient to maintain the pump impeller submerged during periods of nonuse of the pump. The arrangement shown enables the maintenance of a small air. cushion at the top of the air separating chamber.

As the priming cycle continues, as described, the air is exhausted from the suction line and liquid flows into the impeller eye from the source of supply. When the suction pipe and the impeller casing are filled with liquid the flow of liquid inward through the passage 29 and volute 2T ceases and the volute 2'1 becomes a discharge passage. As long as the pump is in operation and substantially air free liquid enters the pump both volutes 26 and 2? act efficiently to convert velocity energy into pressure energy'and the efiiciency of the unit is substantially that of a conventional centrifugal pump designed for high eificiency.

In the drawings I have shown the cutwaters and volutes spaced one hundred and eighty degrees apart. This is not essential but appears to be preferable as this arrangement appears to maintain the pump efficiency at a higher value than other arrangements of the spacing of the cutwaters. I have also found it desirable to locate the cutwater which is spaced further from the periphery of the impeller toward the bottom of the pump. This arrangement enables more thorough separation of air and liquid in the chamber so that substantially air free liquid is supplied to the pump durin priming. Moreover, this arrangement provides a difference in the static head at the wide cutwater as compared to the static head existent at the narrow cutwater.

The arrangement shown may also be incorporated in a vertical pump although in a horizontal unit the priming is faster. Moreover, I have found that when my invention is incorporated in a vertical unit, the time of priming is materially decreased if the level of the volute adjacent the wide cutwater is made somewhat lower than that of the narrow cutwater. That is, by

turning Fig. 2 so that the air separating chamber is uppermost, the unit is viewed as a vertical unit would approximately appear. With this arrangement the surfaces ti and d2 of the wide cutwater should preferably be somewhat lower than the corresponding surfaces 53 and 6a of the narrow cutwater.

The arrangement shown and above described is capable of priming from levels of approximately 27 to 28 feet suction lift. The length of time required to prime increases with increases in suction lift.

In Figs. 3 and 4 I have shown the self priming centrifugal pump of my invention combined with a shallow well jet pump. The jet and diffuser are indicated respectively by the numerals it and H. The jet pump receives its supply of liquid for creating a sub-atmospheric pressure in the suction pipe from the air separating chamber 16. Because a jet pump is an extremely eilicient air pump, the unit of Figs. 3 and 4 primes much more rapidly than the unit of 'Figs. land 2. Moreover, the unit of Figs. 3 and i will automatically prime with a total suction lift of approximately thirty-one feet of liquid and in fact substantially to the vapor tension of the liquid.

The operation of the jet pump system is described in my Patent No. 2,257,507, issued September 30, 1941. As in the unit of Figs. 1 and 2, liquid enters the port 29 and volute 21 during the priming cycle, commingles with the air in the pump casing and the mixture flows to the air separating chamber. When the priming cycle is completed both

ports

28 and 29 become discharge ports.

In Fig. 5 I have illustrated the self priming pump of my invention combined with a jet pump of the deep well type the action of which is also described in my prior patent. Liquid is supplied to the jet pump from the air separating chamber through a pressure pipe 5| and the jet pump is located usually at a level well below that from which a shallow well jet pump is capable of drawing liquid. 7

While I have shown and described the preferred form of my invention, it-will be appreciated that various changes and modifications may be made therein, particularly in the form and relation of parts, without departing from the spirit of my in vention as set forth in the appended claims.

I claim:

1. A pump of the character described comprising, in combination, a casing; an impeller mounted in said casing, said casing having at least two volute passages'into which liquid is discharged by the impeller and said volute passages each having a cutwater, the spacing of said cutwaters from the peripheral edge of the impeller being different.

2. A pump of the character describedcomprising, in combination, a casing, an impeller mounted in said casing, said casing having at least two volute passages into which liquid is discharged by the impeller and said volute passages each having a cutwater, the spacing of said cutwaters from the peripheral edge of the impeller being different, and an air separating chamber with which each of said volute passages communicates.

3. A pump of the character described comprising, in combination, a casing, an impeller mounted in said casing, said casing having at least two volute passages into which liquid is discharged by the impeller and said volute pas-sages each having a cutwater, the spacing of said cutwaters from the peripheral edge of the impeller being different, an air separating chamber with which each of said volute passages communicates, and means including said air separating chamber arranged so as to maintain said casing flooded during period of non-use of the pump.

4. A pump of the character described comprising, in combination, a casing, an impeller mounted in said casing, said casing having at least two volute passages into which liquid is discharged by the impeller and said volute passages each having a cutwater, the spacing of said cutwaters from the peripheral edge of the impeller being difierent, an air separating chamber with which each of said volute passages communicates, said air separating chamber being arranged so that its normal liquid level is above the major portion of the pump casing, and means for maintaining the liquid level approximately at said normal level during periods of non-use of the pump.

5. A self-priming centrifugal pump having an impeller chamber, an intake connected to said impeller chamber, a rotatableimpeller mounted in said impeller chamber, a discharge chamber,

a cut-off at one side of said impeller chamber and related to the orbit of said impeller, and an arcuate wall in said impeller chamber on the output side of said impeller and in the plane thereof, said wall being spaced from the orbit of said impeller and the adjacent end wall of said impeller chamber and forming on. its opposite sides flow passages connected to said discharge chamber.

6. A self-priming centrifugal pump having an impeller chamber, a rotatable impeller mounted therein, a separation and discharge chamber, and an arcuate wall spaced from the impeller orbit on the output side of the impeller forming on its inner and outer sides liquid flow paths having connection at their inner ends with the lower portion of said impeller chamber and communicating at their outer ends with said separation and discharge chamber, whereby liquid from the impeller will separate and move proportionately in the paths in the same direction toward a point of discharge into said discharge chamber under conditions of balanced liquid density and pres sure within and adjacent to said respective discharge paths, and will reverse the direction of fluid flow in one of said paths upon the unbalancing of said liquid density and pressure.

7. In a centrifugal pump, a casing shaped to form atone end thereof an impeller chamber having an end wall and a separation and discharge chamber at the other end of said casing, a rotatable impeller mounted in said impeller chamber, and means in said impeller chamber and disposed substantially concentric to the output side of said impeller, and spaced from the impeller orbit and the adjacent portion of said end wall, to provide a pair of inner and outer paths outwardly of the impeller orbit for liquid flow toward said discharge chamber under balanced conditions of liquid density and pressure.

8. A self-priming centrifugal pump having an impeller chamber, an intake connected to said impeller chamber, a rotatable impeller mounted in said impeller chamber with its axis of rotation horizontal, a discharge chamber, a cut-oi contiguous to the orbit of said impeller at one side of said impeller chamber, and an arcuate wall mounted in said impeller chamber opposite the output side of said impeller and extending from the lower portion of said impeller chamber toward said discharge chamber, said wall being spaced from the impeller orbit throughout its extent a distance greater than the spacing of said cut-oif from said impeller and forming in the space between the latter and the adjacent end wall of said impeller chamber flow channels or passageways for the liquid leading toward said discharge chamber, and means for rotating said impeller.

9. A self-priming pump consisting of a casing shaped to provide a volute impeller chamber at one end and a discharge chamber at its opposite end, one side wall of said casing between said chambers being provided with a cut-off, a rotatable impeller in said impeller chamber related to said cut-off, an arcuate wall in said impeller chamber opposite the output side of said impeller and spaced from the end wall of said impeller chamber and the impeller orbit and extending from the lower portion of said impeller chamber toward said discharge chamber in spaced relation to said cut-off to form liquid flow passages for discharging liquid toward said discharge chamber, the spacing of said arcuate wall from the impeller at all points being greater than the spacing of said cut-oil from said impeller, and means for rotating said impeller.

10. In a centrifugal pump, a casing shaped to provide a chamber for an impeller and a discharge chamber, a cut-off at one side of said casing between said chambers, a rotatable impeller mounted in said impeller chamber related to said cut-off, said impeller chamber having a wall extending from said cut-off around said impeller in volute relation to its orbit to provide a liquid flow space opening into said discharge chamber, and an arcuate wall in the flow space opposite the output side of said impeller, the inner portion of said wall being spaced from the impeller orbit and its outer portion extending toward said chamber, said Wall dividing the flow space into inner and outer passageways to provide for flow of liquid therethrough to said discharge chamber under conditions of normal liquid density and pressure and reverse flow of liquid in the outer passageway responsive to an unbalance of liquid density and pressure, both of said passageways being volute shaped throughout the major part of their extent and means for rotating said impeller.

11. A self-priming centrifugal pump having a rotatable impeller, means including a shaft rotat able about a horizontal axis for driving said impeller, a chamber for said impeller having an end wall in the plane of said impeller, an intake connected to said chamber, an air separation chamber at least partly above said impeller chamber, cut-off in close spaced relation to the impeller orbit, said end wall being of volute form and extending from said cut-ofi around the axis of said impeller and forming a flow space outwardly of the impeller orbit, and an arcuate wall in the flow space opposite the output side of said impeller and spaced from the impeller orbit and adjacent end wall of said impeller chamber to divide said flow space into inner and outer liquid flow passages communicating at their outer ends with said air separation chamber.

12. In a centrifugal pump, the combination of an impeller chamber, an intake connected thereto, an air separation chamber having an outlet, said chambers being in connected relation, a cutoff at one side of said impeller chamber, a rotatable impeller in said impeller chamber having close clearance with said cut-off, said impeller chamber having an arcuate end wall in the plane of said impeller extending from said cut-ofi around said impeller and connected to said air separation chamber and forming a flow space contiguous to and outwardly of the impeller orbit, and an arcuate wall in said flow space extending from a point anterior to said cut-oil in the direction of rotation of said impeller toward said air separation chamber and providing flow paths of substantially volute shape for the liquid, the direction of flow along the outer side of said wall being dependent on the density of the liquid supplied by said intake.

JOHN MANN.

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

UNITED STATES PATENTS Number Name Date 2,287,397 Rupp June 23, 1942 2,291,760 Rupp Aug. 4, 1942 2,335,109 Conery Nov. 23, 1943 2,375,571 Mann May 8, 1945