US2361521A - Centrifugal pump - Google Patents

Description

Oct. 31, 1944 DE WlTT E. YATES CENTRIFUGAL PUMP Filed Nov. 1, 1943 Patented Oct. 31, 1944 is CENTRIFUGAL PUMP De Witt E. Yates, Chippewa Falls, Wfs., assignor to W. S. Darley & Company, Chicago, 111., a

corporation of Illinois Application November 1, 1943, Serial No. 508,524 7 Claims. (Cl. 103,- -112) The present invention relates generallyto centrifugal pumps. More particularly the invention relates to that type of centrifugal pump which is designed for displacing or pumping a liquid and as the primary or principal parts thereof embodies (1) a volute casing having a cylindrical inlet in the central portion of the front wall thereof and a tangential outlet in the portion of its side wall that is of greatest or maximum radius; (2) a power driven shaft which is in axial alignment with, but of less diameter than, the inlet and extends into the central portion of the casing interior through a stufling box on the central portion of the rear Wall of the easing; and (3) a closed variety, casing-enclosed impeller which comprises spaced apart front and rear shrouds and substantially radially extending blades between the shrouds, is connected for drive by the shaft through the medium of a hub on the central portion of the rear shroud, has on the central portion of the front shroud a forwardly extending sealing ring that fits within the cylindrical inlet in the front wall of the casing, and operates during drive thereof by the shaft to suck liquid into the casing via the inlet and then, due to the actionof the blades, to fling the liquid outwards under pressure so that it travels around the side wall of the casing and is finally discharged through the tangential discharge.

In an elementary centrifugal pumpof this type the impeller and shaft, during pump operation, are subjected to undesirable end thrust in the direction of the inlet in the front wall of the substantially free from end thrust, is subject to several objections. In the first place, the cost of the pump is materially increased because of the addition of the rearwardly extending sealing ring on the rear shroud and the necessity of drilling ports in the central portion of the rear shroud and machining the cylindrical cavity in the rear wall of the casing. Secondly, the pump includes an additional-part which is subject to wear and may require replacement from time to time.

,Thirdly, the efliciency of the pump is reduced by reason of the fact that the space between the rearwardly extending sealing ring and the annular wall of the cylindrical cavity in the rear wall of the casing, the spacewithin the rearwardly extending sealing ring and the ports in the central portion of the rear shroud of the impeller result in a repumping or recirculation of part casing due to the fact that the outer surface of the rear shroud is of greater area than the outer surface of the front shroud and hence the liquid under pressure in the clearancespace between the rear shroud of the impeller and the rear wall of the casing acts with greater force against the impeller than the liquid in the clearance space between the front shroud of the impeller and the front wall of the casing and urges the im- 'peller towards the inlet. It has heretofore been proposed to eliminate such end thrust by providing the rear'shroud of the impeller with a rearwardly extending sealing ring which is the same in diameter as the forwardly extending sealing ring on the front shroud and fits within a cylindrical cavity in the rear wall of the casing, and forming ports in the central portion of the rear shroud in order to establish communication between the interior of the impeller and the space within the rearwardly extending sealing ring. A pump embodying a rearwardly extending sealing ring and ports, although the impeller thereof is of the liquid that is pumped in connection with drive of the impeller. Fourthly, foreign particles in the liquid entering the inner portion of the impeller interior move rearwards through the ports and by lodging in the stufling box produce wearing of the shaft by an abrasive action.

The primary object of the invention is to pro-: vide a centrifugal pump which is more emcient than, eliminates the disadvantages or defections of, and is an improvement upon, previously designed pumps of like character and is characterized by the fact thatit includes simple and novel means whereby end thrust of the impeller and shaft is eliminated without the necessity of em= ploying a rearwardly extending sealing ring on the rear shroud of the impeller together with ports in the inner portion of the rear shroud. In

general such means comprises stationary, radially extending ribs which are formed on the inner surface of the front wall of the casing and serve, in connection with pump operation, to increase the pressure against the front shroud of the impeller by retarding rotation of the liquid under pressure that is in the clearance space between the front shroud of the impeller and the front wall of the casing. It also comprises radially extending vanes which are. formed on the outer surface .of the rear shroud of the impeller and serve, in connection with pump operation, to re duce the pressure on the rear shroud by increasing rotation of the liquid under pressure in the clearance space between the rear shroud of the impeller and the rear wall of the casing. It is contemplated that in certain instances either the static-nary ribs on the inner surface of the front wall of the casing or the radially extending vanes on the outer surface of the rear shroud of the nected to, the rear walls.

impeller will suffice to produce the desired results so far as the elimination of end thrust of the impeller and shaft is concerned. It is also contemplated that in other instances, such, for example, as in connection with a pump having a comparatively large inlet in the front wall of the casing, both the stationary ribs on the front wall of the casing and the radially extending vanes on-the outer surface of the rear shroud of the impeller .may be employed in order completely to eliminate end thrust of the impeller and its drive shaft.

Another objectof the invention isto provide portion of the casing side wall I that is of maximum radius and forms the pump outlet. The outer end of the nipple is provided with an internal screw thread in order that it may be connected to a pipe for conducting the pumped liquid to the location or place desired. The rear wall 8 of the casing is formed separately from the end wall 8 and embodies a rearwardly offset, outwardly extending, annular flange l8 which fits against the rear margin ofthe end is removably secured in place by way of bolts ll.

- When the bolts are removed the rear wall 8 of a centrifugal pump which is capable of being produced at a low and reasonable cost and in which simplicity of design or construction. is combined with long life.

Other objects of the invention and the various advantages and characteristics of the present centrifugal pump will be apparent from a consideration of the following detailed description.

- impeller 8 and is driven by the casing may be separated from side walls in order to provide access to the interior oi the casing.

The shaft 5 serves as a driving medium for the any suitable driving means; such, for example, as an internal combustion engine or an electric motor.

- The invention consists in the several novel features whicharehereinafter set forth and are more particularly defined by claims at the conclusion hereof. I v v In the drawing which accompanies and forms a part of this specification or disclosure and in which like numerals of reference denote corresponding parts throughout the several views:

Figure 1 is avertical longitudinal section of a centrifugal pump embodying the invention;

Figure 2 is a vertical transverse'section taken on the line 2-4 of Figure 1 and showing the rib formation which is applied to the inner surface of the front wall of the casing. and serves to in crease the pressure against the front shroud of the impeller by'retarding rotation of the liquid under pressure in the clearance space between the impeller and the front wall of the casing; and

Figure 3 is a rear view of the impeller illustrating in detail the arrangement and design of the radially extending vanes which are formed on the outer or' rear surface of the rear shroud of the impeller and serve to reduce the pressure on the rear shroud by increasing rotation of the liquid under pressure in the clearance space hetweenthe rear shroud of the impeller and the rear wall of the casing.

The centrifugal pump which is shown in the drawing constitutes the preferred form or embodiment of the invention. It is designed to displace or pump a liquid, such as water, andcomprises a volute casing 4, a driving shaft 5 and an impeller 8. a

The casing 4 consists of a front wall I, a rear wall 8, and a side wall 8 and is preferably in the form of a .composite casting.j The front wall I of the casing'is provided at the central portion thereof with an integral forwardly extending sleeve-like part l8 and this defines a cylindrical inlet II which leads from the casing exterior to the central portion of the casing interior. A pipe I2 is attached by way of a screw thread iii to the outer end of the part l8 and serves to connect the inlet I l to the liquid body to be pumped. The rear wall 8 of the casing 4 is disposed in spaced relation with the front wall 'I and embodies at its lower portion a bracket 14 whereby the pump as a whole may be secured to a supporting structure. The side wall 9 is volute' or spiral in form and extends between, and is con- A is connected to. and

'It is journalled in a bearing 18 on the upper portion of the bracket l4 and is of materially less diameter than the cylindrical inlet 10 in the central portion of the front wall 1 of the casing. The front end of the shaft 5 extends through a stuiling box IE on the central portion of the casing rear wall 8 and is provided at its extremity with a reduced stem 5a which is centrally disposed in the interior of the casing. l

The impeller 8 is of the so-called closed variety and comprises a circular front shroud Zt'l, a circular rear shroud 2| and an annular series of substantially radially extending blades 22 between the two shrouds. -It is preferably in the form of a one-piece casting and is located between, but in spaced relation-with, the front and rear walls of the pump casing 4. The central portion of the front shroud 20 embodies a circular opening and in addition a forwardly extending sealing ring 23 which surrounds the opening; fits within the inner end of the sleevelike part in on the central portionof the front wall I of the casing and establishes communication between the cylindrical inlet II and the terially less external diameter than the sealing ring 23 and is fixedly connected to the reduced stem 5a of the shaft 5 by way of a cap screw 25.

- During operation of the pump liquid is drawn or outer margins of the front and v sucked into the central portion of the impeller interior by way of the inlet II and the central opening in the front shroud and is then flung outwards under pressure by the blades 22 against the end wall 9 of the casing. Because of the shape or volute character of the side wall the liquid travels around the side wall and then'is discharged via the tangential discharge nipple l5. During operation of the pump there is liquid under pressure in the clearance space between the rear shroud 2| of the impeller and the, rear wall 8 of the casing and there is also liquid under pressure in the clearance space between the front shroud 20 of the impeller andthe casing front wall 1. Due to the fact that the outer surface of the rear shroud is ofgreater area than the outer surface of the front shroud the liquid under pressure in the rear clearance space, i. e., the space between the rear shroud and the casing rear wall, acts with greater force on the impeller than the liquid under pressure in the front clearance space and tends to urge the impeller and shaft towards the inlet H. With a view of eliminating or counteracting end thrust of the impeller and wall and the front and k shaft the inner surface of the front wall 'I of the casing is provided with an integral rib structure 26 and the outer surface of the rear shroud 2| of the impeller 8 is provided with an annular series of radially extending vanes 21. The rib structure 28 on the. inner surface of the front wall of thepump casing comprises an annular series of equidistantly spaced radially extending ribs 28 and a circular rib 29. The radially extending ribs 28 project outwards from the inner end of the sleeve-like part '10 and terminate adjacent the outer marginal portion of the inner surface of the front wall I of the casing. The circular rib 29 extends around, and is joined to the outer ends of, the radially extending ribs 28 as shown in Figure 2, and forms with such ribs wedge shaped pockets 30. When the pump is in operation the liquid under pressure in the clearance space between the front shroud of the impeller and the front wall of the casing tendsto swirl or rotate. The rib structure 26, however, retards swirling of the liquid in the front clearance space and thus increases the pressure against the front shroud. By increasing the pressure of the liquid in the front clearance space against the front shroud end thrust of the impeller and shaft in the direcwall and an outlet at its outer portion: a drive shaft of less diameter than the inlet extending through the rear wall of the casing and arranged in axial relation with said inlet; a closed variety impeller disposed in the casing and embodying a front shroud arranged in opposed and spaced relation with the casing front wall and provided with a central opening in communication and substantially sealed relation with the inlet, a rear shroud arranged in opposed and spaced relation with the casing rear wall, having the outer surface thereof of greater area than the outer surthe casing operative during drive of the impeller tion of the inlet l l is counteractedt The pockets serve to trap a portion of the liquid in the front clearance space and thus coact with the rib structure 26 to retard rotation of the liquid in such clearance space and increase the pressure against the front shroud of the impeller. The radially extending vanes 21 on the outer surface of the rear shroud 2| of the impeller are formed integrally with the rear shroud and extend outwards fromthe rear end-of the hub 24. During operation of the pump the vanes 21 serve to increase rotation of the liquid under pressure in the clearance spacebetween the rear shroud 2| of the impeller and the rear wall 8 of the pump casing and thus reduce the pressure against the rear shroud. By increasing the pressure against the front shroud 20 by the stationary rib structure 25 and decreasing the pressure against the rear shroud by means of the vanes 21 end thrust of the impeller and drive shaft in the direction of the inlet I is effectively eliminated or counteracted. In certain instances the desired results may be obtained by using either the rib structure 26 or the vanes 2'1. In other cases, such, for example, as in connection with a pump havinga comparatively large inlet, both the rib structure 26 and the vanes 21 may be employed so as fully to 'coun-,

teract end thrust on the part of the impeller and its drive shaft.

The herein described centrifugal pump is characterized by extremely high efliciency by reason of the fact that end thrust of the impeller is eliminated while at the same time there is a minimum amount of repumping of the liquid. It is further characterized by the fact that it is simple in design or construction and hence may be produced at a low cost. L D

The invention is not to be understood as re stricted to the details set forth since these may be modified within the scope of the appended claims without departing from the spirit and scope of the invention. x

Having thus described the invention what I claim as new and desire to secure by Letters Patent is: I

1. A centrifugal pump adapted to displace or pump a liquid and comprising a volute casing embodying spaced apart front and rear walls and having an inlet in the central portion of its front to retard rotation of the liquid in the clearance space between the front shroud of the impeller and the front wall of the casing so as to increase pressure on the front shroud and thus counteract end thrust of the impeller and shaft in the direc tion of the inlet.

" 2. A centrifugal pump adapted to displace or pump a liquid and comprising a volute casing embodying spaced apart front and rear walls and having an inlet in the central portion of its front wall and an outlet at its outer portion; a drive shaft of less diameter than the inlet extending through the rear wall of the casing and arranged in axial relation with said inlet; a closed variety impeller disposed in the casing and embodying a front shroud arranged in opposed and spaced rela tron with the casing front wall and provided with a central opening in communication and substantially sealed relation with the inlet, a rear shroud arranged in opposed and spaced relation with the casing rear wall, having the outer surface thereof of greater area than the outer surface of the front shroud, and provided at its central portion with a hub mounted fixedly on the shaft, and an annular series of substantially radially extending blades extending between the two shrouds and adapted in connection with drive of the impeller to draw liquid into the impeller interior via "said inlet and opening and to fling the liquid outwards against the outer portion 'of'the' casing for discharge through the outlet; and a rib structure formed on the inner surfaceof the front wall 01 the casing and operative during drive of the inrpeller to retard rotation of the liquid in the clearance space between the front shroud of the impeller and the front wall of the casing so as to increase p essure on the front shroud and thus counteract end thrust of the impeller and shaft in the direction of the inlet;

3. A centrifugal pump adapted to displace or pump a liquid and comprising a volute casing embodying spaced apart front and rear walls and in axial relation with said inlet; a closed. variety impeller disposed in the casing and embodying a front shroud arranged in opposed and spaced relation with the casing front wall and provided with a central opening in communication and of the impeller to draw liquid into'the impeller interior via said inlet and opening and to fling the liquid outwards against the outer portion of the casing for discharge through the outlet; and a rib structure formed on, and integrally with, the inner surface of the front wall, embodying an annular series of substantially radial ribs, and operatlve during drive of the impeller to retard rota-r tion of the liquid in the clearance space between the front shroud of the impeller and the front wall of the casing so as to increase pressure on the front shroud and thus counteract endthrust of the impeller and shaft in the direction of the inlet.

4. A centrifugal pump adapted to displace or pump a liquid and comprising a volute casing embodyingspaced apart front and rear walls and having an inlet in the central portion of its front wall and an outlet at its outer portion; a drive shaftof less diameter than the inlet extending through the rear wall of the casing and arranged in axial relation with said inlet; a closed variety the outer surface of the front shroud, and provided at its central portion with a hub mounted fixedly on the shaft, and an annular series of substantially radially extending blades extending between the two shrouds and adapted in connection with drive of the impeller to draw liquid inimpeller disposed in the casing and embodying a front shroud arranged in opposed and spaced relation with the casing front wall and provided with a central opening in communication and substantially sealed relation with the inlet, a rear shroud arranged in opposed and spaced relation with the casing rear wall, having the outer surface thereof of greater area than the outer surface of the front shroud, and provided at its central portion with a hub mounted fixedly on the shaft, and an annular series of substantially radially extending blades extending between the two shrouds and adapted in connection with drive of the impeller to draw liquid into the impeller interior via said inlet and opening and to fling the liquid outwards against the outer portion of the casing for discharge through the outlet; and a rib structure on the inner face of the front wall of the casing embodying an annular series of radially extending ribs and a circular rib around the outer ends of the radially'extending ribs, and operative during drive of the impellmto retard rotation of the liquid in the clearance space between the front shroud of the impeller and the front wall of the casing so as to increase pressure on the front to the impeller interior via said inlet and opening and'to hing the liquid outwards against the outer portion of the casing for discharge through the outlet; and means on the outer surface of the rear shroud of the impeller extending inwards to the central portion of said rear shroud and operative during drive of the impeller to increase rotation of the liquid in the clearance space between the rear shroud of the impeller and the rear wall of the casing so as to decrease pressure on the rear shroud and thus counteract end thrust of the impeller and shaft in the direction of the inlet.

6. A centrifugal pump adapted to displace or pump a liquid and comprising a voiute casing embodying spaced apart front and rear walls and having an inlet in the central portion of its front wall and an outlet at its outer portion; a drive shaft of less diameter than the inlet extending through the rear wall of the casing and arranged in axial relation with said inlet; a closed variety impeller disposed in the casing and embodying a front shroud arranged in opposed and spaced relation with the casing front wall and provided .with a central opening in communication and substantially. sealed relation with the inlet, a rear shroud arranged in opposed and spaced relation with the casing rear wall, having the out er surface thereof of greater area than the outer surface of the front shroud, and provided at its central portion with a hub mounted fixedly on the shaft, and an annular series of substantially radially extending blades extending between the two shrouds and adapted in connection with drive of the impeller to draw liquid into the impeller interior via said inlet and opening and to fling the liquid outwards against the outer portion of the casing for discharge through the outlet; means on the inner surface of the front wall of the casing operative during drive of the impeller to retard rotation of the liquid in the clearance space between the front shroud of the imshroud and thus counteract end thrust of the impeller and shaft in the direction of the inlet.

5. A centrifugal pump adapted to displace or pump a liquid and comprising a voiute casing embodying spaced apart front and rear walls. pro! vided with an inlet in the central portion of its front wall and an outlet at its outer portio and having the inner face of its rear wall smooth; a

drive shaft of less diameter than the inlet extending through the rear wall of the casing and arranged in axial relation with said inlet; a closed variety impeller disposed in the casing and embodying a front shroud arranged in opposed and spaced relation with the casing front wall and provided with a central opening in communication and substantially sealed relation with the inlet, a rear shroud arranged in opposed and spaced relation with the casing rear wall, having the outer surface thereof of greater area than peller and the front wall of the casing so as to increase pressure on the front shroud and thus counteract end thrust of the impeller and shaft in the direction of the inlet; and means on the outer surface of the rear shroud of the impeller operative during drive of the impeller to increase rotation of the liquid in the clearance space between the rear shroud of the impeller and the rear casing wall so as to decrease pressure on said rear shroud and thus further counteract end thrust of the impeller andshaft.

7. A centrifugal pump adapted to displace or pump-a liquid and comprising a voiute casing embodying spaced apartfront and rear walls, provided with an inlet in the central portion of its front wall and an outlet at its outer portion, and having the inner face of its rear wall smooth; a drive shaft of less diameter than the inlet extending through the rear wall of the casing and arranged in axial relation with said inlet; a closed variety impeller disposed in the casing and embodying a front shroud arranged in opposed and spaced relation with the casing front wall and provided with a central opening in communication and substantially sealed relation with the inlet, a rear shroud arranged in opposed and spaced relation with the casing rear wall, having the outer surface thereof of greater area than the outer surface of the front shroud, and provided at its central portion with a hub mounted fixedly on the shaft, and an annular series of substantially radially extending blades extending between the two shrouds and adapted in connection with drive of the impeller to draw liquid into the impeller interior via said inlet and opening and to fling the liquid outwards against the outer portion of the casing for discharge through the outlet; a rib structure formed on the inner surface of the front wall of the-casing and operative during drive of the impeller to retard rotatlon'of the liquid in the clearance space beof the impeller to increase rotation of the liquid in the clearance space between the rear shroud and the casing rear wall so as to decrease pressure on said rear shroud and thus further counteract end thrust of the impeller and shaft.

DE WITT E. YATES.

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