US2276077A - Pump impeller - Google Patents

Description

March 10, 1942.

0. JACQBSEN PUMP IMPELLER Filed May 9, 1941 2 Sheets-Shea; l

UNITED STATES PATENT OFFICE PUDIP IMPELLER Oystein Jacobsen, Johnson Road, R. R. No. 5, Ohio, assignor to The Duriron Company, Inc., Dayton, Ohio, a corporation of New York Application May 9, 1941, Serial No. 392,704

7 Claims.

This invention relates to centrifugal pumps, and in particular to such pumps for pumping corrosive fluids.

The centrifugal pump of this invention is intended for the pumping of corrosive fluids, which in prior pumps have leaked along the shaft, past the shaft packing, and have created damage to the parts beyond the pump. The present invention employs a hollow impeller with the vanes thereof dividing the interior of the impeller into two sets of vane chambers. The first set of vane chambers communicates directly with the intake chamber of the pump, whereas the second set of vane chambers communicates with a chamber in communication with the pump shaft packing. The interiors of all of the van chambers are preferably made to diverge outwardly with an approximately Venturi configuration.

The vane chambers of the second set are partially closed at their inner ends, and in some cases completely closed except for a single opening passing through the back plate of the impeller and in communication with the leakage fluid. The pump casing and the impeller are usually cast of high silicon iron to resist corrosion by acids sinee this metal is practically unm able it is necessary to form the vane chambers, and any openings extending from the chambers, by means of cores of sand during the molding operation. Inasmuch as the vane chambers extend from the periphery of the impeller to a position near the center of the impeller, the length of these cores is considerable, and it has been found to b almost impossible to rigidly anchor them in position because they tend to float in the molten metal and thereby cause a variation in thickness of the walls which form the vane chambers.

The primary object of the present invention is to facilitate the manufacture of centrifugal pumps of the open and closed runner types, and in which compartments are provided for draining the fluid which tends to flow along the drive shaft and through the packing thereof.

Another object is to improve the manufacture of pumps having suction compartments interposed between the main flow passageways of an impeller, and in which the suction compartments are employed to drain the leakage fluid from the rear of the impeller.

These objects are attained, in brief, by providing suitably positioned openings at the inner ends of the suction compartments. These openings, when translated in terms of a core, during the molding operation, serve to anchor the inner ends of the core rigidly in position and thus to insure that the metal immediately adjacent the compartments will have a uniform predetermined thickness.

The invention will be better understood when the following specification is perused in connection with the accompanying drawings.

In the drawings:

Figure 1 is a plan view, with the top cover or shroud partially removed to expose the vanes, of a so-called double-shrouded or closed runner type of impeller which has been improved in accordance with the present invention.

Figure 2 is a view, somewhat similar to Figure 1, except that it shows the application of the invention to a so-called open runner type of impeller.

Figure 3 is a cross sectional view of a mold which may be useful in the fabrication of impellers shown in Figures 1 and 2.

Figure 4 is a fragmentary enlarged view of the mold of Figure 3, but shown in horizontal cross section and taken along the line 4-4 in Figure 3.

Figure 5 is an enlarged cross sectional view taken along the line 55 of the impeller shown in Figure 1, but also illustrating the casing.

Figure 6 is a similar view taken along the line 6-6 in Figure 2.

Referring more particularly to Figures 1 and 5, referenc numeral I generally designates an impeller of a centrifugal pump which is useful in pumping acids and other corrosive fluids. The impeller is of the double-shrouded type, having a back plate 2 and a front plate 3, between which the blades 4 are positioned. These blades take on an elliptical or spiral configuration, starting from positions near the center of the impeller and being positioned farther apart as the periphery of the impeller is reached, to form the main flow compartments 5, which ar alternated by the leakage flow suctioncompartments '6.

The back plate 2 terminates at the center in a rearwardly extending hub I, which is keyed as indicated at 8 to a shaft 9. The right-hand end of the shaft (Figure 5) terminates in a screw threaded shouldered portion H), which carries an interiorly threaded cap II. The inner side of the cap abuts a countersunk surface 12 of the back plate 2. The shaft 9 is also provided with a shoulder 13 which fits against a countersunk surface I4 of a thrust sleeve I5 which bears against the inner surface of the huh I. The arrangement is such that as the cap I I is tightened on the threads ID, the shaft 9 is securely held in its longitudinal position with respect to the back plate 2 of the impeller.

The impeller as a whole is contained within a pump casing, generally designated |6, which comprises a two-part element secured together by the bolts One of these elements comprises a heavy hollow member indicated |8, having a flange |9 which is hollowed out to form a volute chamber in line with the blades 4. This volute chamber communicates with an outlet or discharge pipe 2|, through which fluid under pressure is discharged. The member I8 is provided with a tapered web, as indicated at 22, tapering outwardly away from the impeller and terminating in a hollow hub 23 of greater diameter than the shaft 9 and extending in the direction of the shaft. The innermost portion of the web 22 is extended as an annular flange 24 which barely clears the outer diameter of the huh I. This flange, together with the hub 23, provides a compartment indicated at 25, which contains packing material, preferably in disc form and the purpose of which is to prevent the creepage of the corrosive liquid along the hub 1 and the sleeve IS.

The back plate 2 of the impeller is provided with an annular ring 26 which extends outwardly from the plate and leaving a small clearance from the web 22. There is therefore formed an annular compartment 21 within the ring 26, this compartment being in communication with the packing through the small clearance indicated at 29 between the flange 24 and the hub I. The outer diametral portion of the member I8 is strengthened by an annular flange 29, having enlargements which constitute bosses for receiving threaded bolts 3|. These bolts serve to secure a long extended bearing member, indicated at 32, to the casing, this hearing member including a plurality of ball bearings (not shown) and also a thrust bearing for the shaft 9.

The other portion of the casing l6 comprises a heavy disc-like member 33, having an inturned flat surface 34 against which bears a pair of annular surfaces formed on the front plate 3 of the impeller. As stated hereinbefore, this member is secured to the flange |9 of the pump casing by a number of equi-distantly positioned bolts H. The member 33 is provided at the center with a hub 35 which extends outwardly and terminates in a large flat plate (not shown) suitable for connecting with an intake conduit. The hub 35 is provided with a round intake opening 36 which is in line with the cap member I. Longitudinally extending plates 31, within the opening 36, serve to prevent rotational or swirling movement of the liquid drawn through the intake opening 36.

In operation the shaft 9 is connected to an electric motor, or other source of mechanical energy, which causes the impeller to rotate very rapidly. Liquid is drawn in through the opening 36 and passes through the main flow compartments 5, into the volute chamber 20, from which it is delivered to the outlet pipe 2|. It has been found, particularly when the pump is operating against a high head of fluid, that a certain amount of the fluid will escape around the outer peripheral edge of the back plate 2, into the annular compartment formed on the outside of the flange 26, and this liquid will in time flow through the small clearance between the flange 26 and the web 22, and finally reach the inner annular compartment 21. This leakage fluid may even travel along the hub and get past the packing, where it might come in contact with exposed parts of the shaft 9, and may finally reach the ball bearings on which the shaft is journalled. Inasmuch as this fluid may be of a highly corrosive nature, such as sulphuric acid, considerable damage is likely to result.

In order to prevent leakage fluid from reaching the packing it has been proposed, in accordance with my prior application, Ser. No. 229,470, filed September 12, 1938, which has issued on October 29, 1940, as U. S. Patent No. 2,219,390, to close off the inner ends of one or more pairs of blades 4 by means of a closure member, indicated at 38 (Figure 1), and to provide an opening 39 through the back plate adjacent the closure member and communicating with the leakage fiuid to the rear of the impeller. As the impeller was rotated, for example counterclockwise as seen in Figure 1, the fluid which had collected in the compartment 21 would be drawn through the opening 39 and then caused to pass, under pressure, through the compartment formed by the two adjacent blades 4, and finally expelled from the pump. The path of the leakage fluid through the opening 39, into the volute 20 has been indicated in Figure 5 by the arrows 40.

In the fabrication of the double-shrouded impeller shown in Figure 1, the compartment 6 is obviously formed by a coring job during the molding process. The core of sand would extend from the body of the sand all the way from the periphery of the impeller to the closure member 38, and in the case of large size impellers, this distance is considerable. When it is considered that this core must be arranged exactly in its proper position, and held in that position with respect to the cores which form the passageways 5, the diiliculty of the molding job will be readily appreciated by those familiar with the molding art.

In accordance with the present invention, I have provided an improved method and apparatus for molding an impeller of the type shown in Figure 1, and in carrying out this improvement I provide an opening 4| in the front plate 3 directly in line with the openings 39. The openings 4| are obviously provided in the front plate 3 to communicate only with the closed compartments 6. The purpose of these openings will be described in connection with Figures 3 and 4. In these figures the cope of the mold is indicated at 42, and the drag at 43, the mold being split at 44 and having a pouring hole 45 for the molten metal. The sand of the mold is indicated at 46, and an examination of Figure 3 will show that the space 41, indicated by the absence of stippling, conforms to the shape of the impeller including the spirally-directed blades 4. The horizontal sectional view of Figure 4 Will show the manner in which the compartments 5, 6 are formed by the cores 48, 49, respectively. The cores 49, which form the compartments 5, are preferably molded integral with the main mold but the cores 4B, which form the closed compartments 6, are preferably made separate from the main mold and then baked to harden, and finally placed in position within the main mold by means of small metal rods 50 which can be pressed into the annular ring portion 5| of the sand.

The rods 50 are placed in position within the cores 48 during the separate molding process, and they serve not only to hold the outer end of the core 48 in position with respect to the ring 5| but also to strengthen the long length of core. It is apparent that in addition to rigidly positioning the outer end of the core 48 in the vertical and horizontal directions with respect to the ring of sand it is also necessary to position the inner ends of the core 48 not only in the horizontal direction but also in the vertical direction to assure that a uniform thickness of metal will be provided on all sides of the core 48, by which the compartment 6 is formed. Unless the inner ends of the cores 48 are anchored horizontally and vertically, the force of the molten metal (silicon iron) which is poured into the opening to fill the mold will cause the cores 48 to float, or in any other manner move the inner ends of the cores to an improper distance from the adjacent surfaces of the mold.

Whereas in my prior application referred to hereinbefore, the core portion 52 (Figmre 3), which normally forms the opening 39, would serve to space the inner ends of the cores 48 from the adjacent lower surfaces of the mold, this portion would not prevent the inner ends of the cores from being buoyed upwardly by the metal under the core and thus to render different the distances XY, perhaps causing a decrease in the thickness of that portion of the front plate 3 directly over the closed compartment 6, and a similar increase in thickness of that portion of the back plate 2 which is directly below the closed compartments 6. However, by providing the openings 4| directly in line with the openings 39, the core portion 53, which preferably has the same shape as the core portion 52, serves to definitely space the upper surfaces of the cores 48 from the sand of the cope portion of the mold. In order to strengthen the outwardly and downwardly extending core portions 53, 52, it may be desirable to provide the metal rod 50 with an extension 54 positioned preferably at right angles to the main portion of the rod.

Thus the openings 4| are provided mainly to permit the interposition of the core portion 53 during the molding operation, which together with the core portions 52 serve efiectively to maintain the inner ends of the cores 48 in position. It will be noted from Figure 1 that the necessity for properly positioning the cores 48 by means of the core portion 53 does not arise in the case of the core portions which form the passageways 5, which are open at their inner ends.

The fact that these passageways are open permits the core portions 49, which alternate with the core portions 48, to be integrally joined by sand to the main portion of the mold so that the core portions 49 are automatically held in position. However, in the case of compartment 5, the closure member 38 prevents'any integral connection between the cores 48 and the main parts of the mold except through the core portions 52, 53. It has been found that while the opening 4| serves a very useful purpose in the molding of the impeller, for reasons stated hereinbefore, this opening produces practically no deleterious effect on the suction action of the closed compartments 6 in drawing fluid from the compartment 21, through the openings 39 and expelling this fluid at the periphery of the impeller. Any small amount of fluid which may leak at the surface 34 will promptly be caused to flow through the closed compartments 6.

In Figures 2 and 6 I have shown the application of my invention to the so-called open runner type of pump which was disclosed in my prior application Ser. No. 352,237, filed August 12, 1940 which has issued on September 9, 1941, as U. S. Patent No. 2,255,287. The impeller in this type of LAGHHHUI pump has a back plate 55 but no front plate 3, except that there is a cover 56 which spans the two adjacent vanes of each closed compartment 51. The open compartments which constitute the passageway for the main flow are indicated at 58. The vanes 59 which form the closed compartments 51 are joined together at their inner ends by a closure member 69. There is an opening 6| through the back plate 55 which is in communication with the leakage fluid which normally collects in the annular space 62 (Figure 6). Directly above the openings GI, and passing through the covers 56, there is an opening 63, preferably of a shape similar to the opening 6|, the purpose of which is to permit the use of a sand core portion 53 (Figure 3) similar to that which was described in connection with the closed runner pump of Figure 1.

In the case of the open runner type of impeller, I prefer to provide openings 64 through the back plate 55, and positioned within the open and closed compartments 58, 51, respectively, near the periphery of the impeller. These openings may have any desired shape or size and are located in a position so as to communicate with the leakage fluid in the annular space indicated at 65. The purpose of these openings 64 is to provide a suction effect on the leakage fluid which collects in the annular space 65 and which normally passes through the clearances between the outer edge of the impeller and the casing member l8. It has been found that the presence of these openings does not affect, in any manner, the force with which the open compartments 58 serve to expel the main body of fluid entering the pump through the opening 36, and neither do these openings cause any depreciation of the suction effect of the closed compartments 51 on the leakage fluid which collects in the space 62 and is forced through the openings 5|.

Thus in the pump shown in Figures 2 and 6 there is provided the openings 64 and 61, which serve to empty the annular spaces 65 and 62 respectively, thereby positively preventing even the slightest amount of fluid from passing along the hub 1 and through the packing to damage the bearing surfaces beyond the packing. It should also be noted that the openings 64 permit the use of a core portion (not shown) during the molding operation, by which the outer ends of the cores which form the compartments 51, 58 are held in proper position. Figures 5 and 6 show a threaded opening 66 directly below the volute chamber 20 for the purpose of draining the chamber when desired.

It will be understood that I desire to comprehend within my invention such modifications as come within the scope of the claims and the invention.

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

1. In a centrifugal pump, a casing and a double-shrouded impeller adapted to rotate in said casing, said impeller including a back plate and a front plate, vanes secured therebetween to provide passageways across the radial width of the impeller, the inner ends of at least one pair of adjacent vanes being joined by a closure plate whereby a compartment is formed closed on all sides except at the outer end, an opening in said back plate which communicates with the leakage fluid to the rear of the impeller and is positioned within said compartment adjacent said closure plate, and an opening in said front plate directly in line with the opening in the back plate.

2. In a centrifugal pump, a casing and an impeller adapted to rotate in said casing, said impeller'including a back plate, vanes secured thereto to provide passageways across the radial width of the impeller, the inner ends of at least one pair of adjacent vanes being joined by a closure plate, a cover plate spanning said pair of adjacent vanes at their edges ODD Site the back plate whereby a compartment is formed closed on all sides except at the outer ends, an opening in said back plate which communicates with the leakage fluid to the rear of the impeller and is positioned within said compartment adjacent said closure plate, and an opening in said cover plate directly in line with the opening in the back plate.

3. In a centrifugal pump, a casing and an impeller adapted to rotate in said casing, said impeller including a back plate, vanes secured thereto to provide passageways across the radial width of the impeller, the inner ends of the alternate pairs of adjacent vanes being joined by a closure plate, cover plates spanning said pairs of adjacent vanes at their edges opposite the back plate whereby compartments are formed closed on all sides except at the outer ends, openings in the back plate which communicate with the leakage fiuid to the rear of the impeller and are positioned within said respective compartments adjacent their closure plates, and openings in said cover plates directly in line with the openings in the back plate.

4. In a centrifugal pump, a casing and a double-shrouded impeller adapted to rotate in said casing, said impeller including a back plate and a front plate, vanes secured therebetween to provide passageways across the radial width of the impeller, the inner ends of the alternate pairs of adjacent vanes being joined by a closure plate, openings in the back plate which communicate with the leakage fluid to the rear of the impeller and are positioned within said respective compartments adjacent their closure plates, and openings in said front plate directly in line with the openings in the back plate.

5. In a centrifugal pump, a casing and an impeller having a hub portion and adapted to rotate in said casing, said impeller including a back plate having a pair of longitudinally directed rings of different diameters, the outer ring extending asfar as the periphery of the impeller whereby an annular space is provided between said rings and the casing, and a second annular space is formed by the inner annular ring, the hub of the impeller and said casing, vanes secured to said back plate to provide passageways across the radial width of the impeller, the inner ends of at least one pair of adjacent vanes being joined by a closure plate, a cover plate spanning said pair of adjacent vanes at their edges opposite the back plate whereby a compartment is formed closed on all sides except at the outer end, an opening in said back plate which communicates with the leakage fluid within the space formed by the inner annular ring, the hub of the closed compartments.

impeller and the casing, an opening in said cover plate directly in line with the opening in the back plate, and an opening in the back plate which communicates with the space formed between the inner and outer annular rings of the back plate, all of said openings communicating with the closed vane passageways.

6. In a centrifugal pump, a casing and an impeller having a hub portion and adapted to rotate in said casing, said impeller including a back plate having a pair of longitudinally directed rings of different diameters, the outer ring extending as far as the periphery of the impeller whereby an annular space is provided between said rings and the casing, and a second annular space is formed by the inner annular ring, the hub of the impeller and said casing, vanes secured to said back plate to provide passageways across the radial width of the impeller, the inner ends of the alternate pairs of adjacent vanes being Joined by closure plates, cover plates spanning said pairs of adjacent vanes at their edges opposite the back plate whereby compartments are formed closed on all sides except at the outer ends, openings in said back plate which communicate with the leakage fluid in the space formed between the inner annular ring, the hub of the impeller and the casing, said openings being positioned within said compartment adjacent said closure plates, openings in said cover late directly in line with the openings in the back plate, and openings in the back plate which communicate with the leakage fluid in the space formed between said annular rings.

7. In a centrifugal pump, a casing and an impeller having a hub portion and adapted to rotate in said casing, said impeller including a back plate havin a pair of longitudinally directed rings of difierent diameters, the outer ring extending as far as the periphery of the impeller whereby an annular space is provided between said rings and the casing, and a second annular space is formed by the inner annular ring, the hub of the impeller and said casing, vanes secured to said back plate to provide passageways across the radial width of the impeller, the inner ends of the alternate pairs of adjacent vanes being joined by closure plates, cover plates spanning said pairs of adjacent vanes at their edges cpposite the back plate whereby compartments are formed closed on all sides except at the outer ends, openings in said back plate which communicate with the leakage fluid in the space formed between the inner annular ring, the hub of the impeller and the casing, said openings being positioned within said compartments adjacent said closure plates, openings in said cover plate directly in line with the openings in the back plate, and openings in the back plate which communicate with the leakage fluid in the space formed between said annular rings, said lastmentioned openings being provided in said back plate at positions between the adjacent clo ed compartments as well as at positions within the OYSTEIN J ACOBSEN,

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