US2193826A - Centrifugal pump - Google Patents

Description

March 19, 1940. J. MANN cmu'mruw. PUMP Original-Filed July 9, 1937 INVENTOR.

' 'BY'/.-'(Q g lz,'sATTORNEYS Patented Mar. 19, 1940 1 t UNITED STATE CENTRIFUGAL PUMP John Mann, Seneca Falls N. Y., assignor -to Goulds Pumps, Inc., Seneca Falls, 12.1., a corf poration of New York Original application July 9, 1937, Serial No. 152,801. Divided and this application October 10,1938, Serial No. 234,112

'7 Claims. (Cl. 103-111) My.invention relates to new and useful im-\ provements in centrifugal pumps, and is a division of-my application, Serial No. 152,801, filed July 9, 1937.

An object of my invention is to provide an efllcient and simple means for sealing the impeller drive'shaft to, protect the shaft from the corrosive and abrasive action of the liquid bein "Another object of my invention is to provide a seal to prevent access tothe impeller drive shaft of the liquid being pumped without the use of packing between the sealing surfaces.

3 More specifically, 'my invention contemplates a cap having an annular surface adapted to engage thehub of the impeller and be drawn up tightly thereagainst for the purpose of, not only retaining the impeller on its shaft, but also for the purpose of forming a seal without the use of packing between the mating surfaces adapted to withstand high pressures.

Other robjects and advantages of my invention, will be apparent from the following description when taken in connection withthe accompanying drawing, in which: g

1 is a sectional view showing the pump. 08.81118, the impeller, the stufling box. assembly, and other parts of the puinp to which my invention is applied.

' Fig. 2 is an enlarged sectional view ofla portion of Fig. 1 and showing the details of my invention. L 2

Fig.- 8 is a sectional. view somewhat similar to that of Fig, 2 showing a pump impeller, in which the hub of the impeller is solid instead of perforated at shown in Figs. 1 and 2.

While the novel means of my invention may be embodied in any type of centrifugal pump, I have shown the. invention as applied to what is known in the art as a "close coupled pump. The primary'differences between a close coupled Pump and other types of centrifugal pumps are" that, in a close coupled pump, the motor and pump casings are, by what is known' as an adapter,.rigid1y secured closely together and the drive shaft is common to both the motor and The assembly in which the novel means of my invention is incorporated comprises a motor ll, onlythe end of. which is shown, adapter" |2- and a pump casing generally indicated by the numeral l3. The adapter is provided'withhand holes to enable access to thestufling box unit;

The adapter, as showninFig. 2, is rigidly bolted, as indicated at 4, to the motor casing and the pump casing is, in turn, rigidly bolted, as indicated at 16, to the adapter. Any. suitable means may be provided for rigidly securing the pump a and its motor to the floor, no special founda-. tion being required with this type of pump. If

ll and a cover plate l8 which maybe bolted dicated at 34, in an opening in the cover plate" rings 31, and these and other det desired, the pump unit may besecured in a vertical position, as the unit is particularly adapted to operate in any position.

The pump. casing comprises a casing proper" thereto as indicated at I9. The shaft 2|, which "is common to both the motor and the pump,

has a suitable bearing 22 at the pump end of the motor casing and another bearing (not shown) at the other endof the motor casing. 10

That portion of the shaft 2|, which extends'beyond the motor casing H is overhung and extends through the adapter and into'the pump casingl3. To the end of the shaft 2|, by means of a key 23, is secured, against rotation with 18 respect to the shaft, the hub 24 of, an eller 26. The impeller is usually made of bronze and is held, in position on the shaft by means which will be'later described.

The impeller comprisesa web'2'l, a plurality of vanes 28 preferably cast integrally with the web,. and a shroud 29 .which may be riveted or otherwise secured to the vanes. The shroud'as it approaches the impeller axis curves outwardly, as indicated at 3|, to form a smooth entrance for fluidinto the impeller, commonly called the eye ofethe impeller. At its central portion the shroud is flanged outward, as indicated at 32, to provide a fluid entrance or suction opening into theimpeller. The suction pipe 33is threaded, as in--' l8 and is in axial alignment with the-flange 32 oi the impeller so that fluid being drawn through the suction pipe, or flowing thereto by gravity, will smoothly enter the eye of the pump impeller. The pump casing has a volute 6 and wearing s of the pump are-preferably *formed as described in theabovementioned parent application.

The pump is further provided with a stufling box 38 and a packing gland '39, which is adapted,

the stuffing x, and with respect to which the hub 24 of the impeller is rotatable, may be pro-.- vided. i

' In the" past, various methods have been employe'dfor preventing the liquid being pumped 5' from gaining access to the drive shaft. If th'e liquid being pumped gains access to the shaft, corrosion quickly results, and in cases where the, liquid contains solids, such as sand,abrasion of the shaft occurs. In most of the methods or preventin the liquid from gaining access to the shaft, packing is employed. While packing suited to various conditions and of materials designed particularly to resist the action of the various liquids which may be pumped, are available, all types of packing are subject to deterioration, and are a source of trouble. The pump must quite often be dismantled and the packing replaced when it has become worn.

In the pump of my invention I have provided novel means for retaining the impeller on the shaft, and at the same time preventing access of the liquid being pumped to the shaft. This construction is more clearly shown in Fig. 2. A shaft sleeve 5| is mounted on the shaft 2| and confined against movement along the shaft in a direction to the right, as viewed in Fig. 1, by butting it against a shoulder 52 on the shaft. The

other end of the shaft sleeve, which, as is the usual practice, is made of bronze, has a tapered countersuction portion, as indicated, at 53, so as to provide an annular bearing surface 54 of restricted area which is ground and finished.

A threaded bore 56 is provided in'the end of the shaft along the axis thereof into which is threaded a socket head tap bolt 51. The bolt '51 has a suitable opening 58 for the reception of a wrench. A sealing member or washing 59 is confined between the head of the bolt and the hub 24 of the impeller. The washer is provided with an annular sealing surface SI of restricted area, which is ground and finished. The mating face 82 of the hub with the sealing surface GI,

and the mating face 63 with the sealing surface 54 formed on the sleeve 5|, are preferably ground and finished. It will'be particularly noted that the annular sealing surface 6| is the only portion of the washer which engages the hub of the impeller. The washer does not engage the shaft at any point. It will further be noted that when pressure is applied on' the washer, the hub of the impeller is pressed tightly-against the sealing surface 54 formed on the sleeve 5|, and that the sleeve 5| is pressed tightly into engagement with l the shoulder 52 on the shaft 2 I.

In practice, particularly in small pumps, since access to the bolt must be had through-the eye or suction opening of the impeller, the size of the bolt is within rather small limits fixed by the diameter of the impeller suction opening.

Moreover, the diameter of the shaft in small pumps does not permit the use of a large diameter bolt, and further, as is apparent upon consideration of Fig. 1, a bolt with a large diameter head restricts the freeflow of water. through the impeller.

- made equal to the area of the bolt at the root of the thread.

When the bolt is tightened up by a man, in the ordinary manner, so that the bolt is loaded within the elastic limit of the -material of the bolt, the pressure applied on the bolt is transmitted to the sealing surfaces BI and 54. This places the maximum pressure possible at thev seal points without destroying the surface contacts between the sealing surfaces and the hub.

It will be appreciated that if the areas II and With these considerations limiting the size of the bolt in mind, the bolt head and the- 54 are made larger than the area of the bolt at the root of the thread (the dimension N), the pressure at the sealing surfaces will not be the maximum amount possible. If the areas SI and 54 are made smaller than the bolt area at the root of the thread, then the pressure'applied on the sealing surfaces may be sufliciently great to destroy the surface contacts at the sealing surfaces. When the sealing surfaces are loaded just within their elastic limit, the whole area of the machine surfaces at the sealing points will be in contact because any slight unevenness of the surfaces will be crushed out for the reason that the areas of these uneven surfaces will be less than the area of the bolt at the root of the thread and the sealing surfaces 6| and 54 will imbed themselves slightly into the hub of the impeller. The seal thus provided effectively prevents the liquid being pumped from gaining access to the shaft and is capable of withstanding a pressure of approximately three hundred pounds per square inch, a pressure far above the pressure which the seals may be called upon to withstand. The shaft seal described eliminates the use of troublesome packing. A copper sealing ring 66 is interposed between the head of the tap bolt 51 and the washer 59 which effectively prevents leakage along the threads of the bolt. If desired, the bolt and washer may be made integral, although I do not consider this construction as desirable, because it is preferable that, in drawing up'the tap bolt 51, rotation of the tap bolt with respect to the washer 59 be permitted. Also if desired, instead of using a tap bolt threaded into a threaded bore in the shaft, as shown herein, the end of the shaft may project slightly beyond the hub of the impeller. The

projecting end may then be threaded to receive anut and there may be interposed between the nut and the hub of the impeller a washer havsides of the hub will be the same and the impeller will, therefore, be substantially hydraulically balanced since the pressures in the discharge chamber on opposite sides of the impeller are the same. In Fig. 3 I have shown how the shaft seal above described may be applied to an impeller in which the apertures through the hub of the impeller are omitted and the impeller is not, therefore, hydraulically balanced; The construction is the same as that described above, differing therefrom only in the omission of the apertures and in the omission of an impeller wearing ringcorresponding to the wearing ring '44 of the structure shown in Fig. 1.

It will be appreciated that I have'provided a novel construction for preventing access to the shaft of the liquid being pumped, and that while I have shown my invention as applied to a close coupled centrifugal pump, the invention has other applications, particularly to other types of centrifugal pumps. It will further be appreciated that various modifications may be made in the form and relation of parts of the structure shown and described without departing from the spirit of my invention as set forth in the appended claims.

I claim:

1. A pump of the character an overhung shaft extends'into a casing comprising, in combination, an. impeller having a described wherein shaft, said hub having a plurality of apertures 'to permit the free fiow of liquid from the back of the impeller to equalize the pressure on opposite sides of the impeller, a sleeve mounted on said shaft and confined against movement along the shaft, a bolt threaded into the end of the shaft concentric with the axis thereof, said bolthaving a head, a cap confined between the head of said bolt and the end of the shaft, said cap being out of contact with the end of the shaft and engaging the hub of the impeller, said bo lt having a cross sectional area at the root of the thread equal to the area of contact between the cap and the hub of the impeller and equalto the area of contact between the hub of the impeller and the end of said sleeve whereby when the bolt is drawn up tightly, the impeller is secured to said shaft and the pressure applied seals the surfaces between the cap and the hub and between the hub and the sleeve to prevent access to the shaft of the liquid being pumped.

2.- A pump. of the character described wherein an overhung shaft extends into a casing-cornprising, in combination, .an impeller having a hub mounted in said casing on the end of said shafiba bolt threaded into the end of the shaft concentric with the axis thereof, said bolt having ahead, a cap confined between the head of said bolt and the end of the shaft, said cap being out of contact with the end of the shaft and engaging the hub ofthe impeller, said bolt having a cross sectional area at the root of the thread substantially equal to the area of contact between the cap and th'e hub of the impeller whereby when the bolt is drawn up tightly the pressure applied seals the surfaces between the cap and the hub to prevent access to the shaft of the liquid being pumped. 3.-In a machine of the class described, a shaft, an impeller having a hub mounted on said shaft,

said hub having a ground and finished surface,

means for preventing leakage of fluidshaft comprising a cap having an annular ground of the liquid being pumped.

bination a pump shaft, an

and finished contact surface engaging the ground and finished surface of the hub and encircling the end of the shaft, and means for applying pressure on said cap, said pressure being sumcient to crush out any unevenness between the matins surfaces of the cap and the hub whereby a' liquid seal is formed to prevent access to the shaft 4. In apump of the class impeller having a hub mounted on said shaft, means for preventing leakage of fluid along the shaft comprising a-caphaving an annular contact surface of limited area engaging the hub of the impeller encircling the end of the shaft, said cap being out of con-' tact with the end of the shaft, and means comprising a bolt threaded into the end of the shaft for applying pressure on said cap. said bolt having a cross-sectional area atthe root of the thread substantially equal to the .area of contact between the cap and the hub of the impeller, the pressure applied between the mating surfaces of said 'cap and hub beinmsuificient to crush out any unevenness between the matingso that a liquid seal is-formed to-prevent access to the shaft of the liquid being pumped without the use of packing.

. a cap having a small along the described. in coms. s pump ofths character described wherein finished surfaces of the hub in engagement with the end of the sleeve comprising a cap having a ground and finished surface of limited area adapted to engage the other ground and finished surface ofvthe hub, said cap being out of contact with the end of the shaft, and means for applying pressure on said cap comprising athreaded member between the cap and the end of the shaft, said cap when pressure is applied applying pressure between'the ground and finished surfaces of said cap and hub and between the meeting surfaces of said hub and sleeve.

6. A pump of the character described wherein an overhung shaft extends into a casing comprising, in combination, an impeller having a hub mounted in said casing on the end of-said shaft, said hub having a plurality of apertures to permit the free flow of liquid from the back of the impeller to equalize the pressure on opposite sides of the impeller, a sleeve mounted on said shaft and confined against movement along the shaft, said sleeve engaging one side of thelhub, area of'contact with the other side of the hub and being out of contact with the endof the shaft, said cap and hub having ground and finished cooperating engagingsurfaces, and means including a threaded member between the end of the shaft and the cap for applyingpressure between said ground and finished surfaces and between the hub and the end of the sleeve, said threaded member having a cross sectional area at, the root of the thread substantially equal to the area of contact besubstantially equal to the area of contact between the hub of the impeller and the end of said sleeve whereby when pressure is applied the impeller is secured to said shaft and the pressure applied seals the surfaces between the cap .and

the hub and between the hub and the sleeve to prevent access to the shaft of the liquid being pumped.

7. In a pump of the class described, in combination, a pump shaft, an impeller having a hub mounted on said shaft, said hub having a ground and finished surface, means for preventing leakage of fluid along the shaft comprising a cap having an annular ground and finished. contact surface of'limited area engaging the ground and finished surface of the hub of the impeller, said cap being out of contact with the end of the shaft, and means comprising a threaded member between the endof the shaft and the cap for applying pressure on said cap, said, threaded member having a cross sectional area at the root of the thread substantially equal'to the area of contact between the cap and the hub of theimpeller, the pressure applied between the mating surfaces of said cap and hub being sufiicient to crush out any unevenness between the mating surfaces of the cap and the hub so that a liquid seal is formed to prevent access to the shaft of the liquid being pumped without the use of packing.

' JOHN MANN.

tween the cap and the hub of the impeller and

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