WEAR PLATE FOR A CENTRIFUGAL PUMP

Cross-reference to Related Application: This application is a non- provisional application claiming priority to provisional patent application Serial No. 60/967,440 filed September 4, 2007.

BACKGROUND OF THE INVENTION Field of the Invention: This invention relates to centrifugal pumps, and relates specifically to a wear plate for a centrifugal pump having an inner bore edge structured for cutting solids. Description of Related Art: Centrifugal pumps are structured with a pump casing in which an impeller is positioned for rotation. To maximize pump efficiency, the impeller is positioned in close proximity to the pump casing inner surface to provide minimal tolerances between the impeller and the pump casing. When such pumps are used to process fluids with a solids content, the solids tend to erode or wear the inner surface of the pump casing, thereby leading to reduced pump efficiencies.

It is known in the pump industry to position a wear plate between the impeller and the inner surface of the pump casing so that the wear plate is subjected to the erosive effect of the solids. The wear plate can then be easily replaced when worn, rather than attempting to effect a repair or replacement of the pump casing. Certain types of centrifugal pumps are also configured with means for adjusting the position of the wear plate toward the impeller to decrease the gap therebetween as the wear plate becomes eroded.

When centrifugal pumps having wear plates are used to process solids-entrained fluids, especially those containing stringy solids, the solids can become lodged around the smooth inner bore of the wear plate. The stringy solids tend to be pushed and rolled by the edge of the impeller without being cut. The accumulated solids then begin to cause excessive wear between the impeller and the wear plate and the gap between the impeller and wear plate increases, thereby reducing pump efficiency and allowing recirculation of fluid within the impeller.

In recognition of the deleterious effects that solids have on the pump casing, it is known to provide a wear plate that is configured and positioned relative to the impeller to dislodge and direct solids away from the inlet opening or impeller. Examples of such wear plate designs are disclosed in U.S. Patent No. 6,139,260 to Arbeus and U.S. Patent No.

6,464,454 to Kotkaniemi. The wear plates of those inventions provide for an increased space between the wear plate and impeller, but the increased space has the resulting effect of reducing pump efficiencies. U.S. Patent No. 7,037,069 to Arnold further discloses a wear plate for use in a centrifugal pump employing a single vane spiral-type impeller where the wear surface of the wear plate is provided with flow interrupters in the form of notches and recesses that are perpendicular to the axis or rotation, and/or that extend in a direction opposite to the direction of rotation of the impeller. The notches and recesses are provided to interrupt the flow of fluid along the vane of the impeller and to dislodge and clean solids from the impeller to move the solids toward the volute of the pump for discharge. The flow interrupters are positioned on the wear plate to remove solids from the impeller vane; however, they do not provide cutting or chopping of the solids. It is further known in chopper type centrifugal pumps to provide chopper plates with cutter bars or cutting elements that span the eye of the impeller to effect cutting of solids at the eye of the impeller. Such cutter bar arrangements can prove beneficial to effecting the reduction and processing of solids, but also may result in solids, particularly stringy solids, from accumulating at the eye of the impeller.

Thus, it would be advantageous to provide a means for cutting solids at the cutting edge of an impeller in centrifugal pumps that process solids-containing fluids, and to provide such means in a wear plate that can function to withstand the wear of processed solids.

BRIEF SUMMARY OF THE INVENTION

In accordance with the present invention, a wear plate for use in a centrifugal pump is structured with at least one cutting element, but most suitably a plurality of cutting elements, positioned at the inner bore of the wear plate. The cutting elements are positioned to impact the impeller and are oriented in a direction relative to the rotation of the impeller so that the cutting elements can capture the solids and hold them in place until they can be cut by the impeller blade or blades.

Cutting elements on the wear plate of the present invention may be distributed or spaced evenly or unevenly about the inner bore of the wear plate and may have any shape, size, dimension or configuration which will effectively cause cutting of solids at the inner bore of the wear plate. By facilitating the cutting of solids at the inner bore of the wear plate, the solids are more quickly reduced for processing rather than being simply flushed into the impeller, as is the purpose of prior art wear plates. Additionally, the wear on the wear plate and impeller are reduced so that the pump operation life is not decreased.

The cutting elements of the wear plate of the present invention are further configured with a wall, defined by the thickness of the wear plate and extending from the non-wear surface (i.e., that surface positioned away from the impeller) to the wear surface (i.e., that surface positioned adjacent the impeller), which is angled from the non-wear surface to the wear surface of the wear plate, thereby imbuing the cutting elements with a self-sharpening edge as the wear plate wears.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS In the drawings, which illustrate what is currently considered to be the best mode for carrying out the present invention:

FIG. 1 is a perspective view in partial cutaway of a conventional self-priming pump illustrating the relative positioning of the impeller and wear plate;

FIG. 2 is a perspective view in partial cutaway of a self-priming pump illustrating the placement of the wear plate of the present invention;

FIG. 3 is a perspective view of a prior art wear plate having a smooth inner bore; FIG. 4 is a perspective view of the wear plate of the present invention;

FIG. 5 is a perspective view of the wear plate and impeller as viewed from the wear surface of the wear plate;

FIG. 6 is a perspective view of the wear plate and impeller as viewed from the non-wear surface of the wear plate;

FIG. 7 is a plan view of the non-wear surface of the wear plate of the present invention;

FIG. 8 is an enlarged view of the cutting elements of the wear plate; FIG. 9 is a view in cross section of the radius of the wear plate shown in FIG. 7, taken at line 9-9;

FIG. 10 is a perspective view of a prior art wear plate having a conical shaped wear surface;

FIG. 11 is a perspective view of the prior art wear plate shown in FIG. 10 illustrating the non-wear surface of the wear plate;

FIG. 12 is a plan view of an alternative embodiment of the wear plate of the present invention, the wear plate being generally frustoconical in shape;

FIG. 13 is a view in cross section of the wear plate shown in FIG. 12 taken at line 13-13;

FIG. 14 is a perspective view of the non-wear surface of the wear plate shown in FIG. 12;

FIG. 15 is a perspective view of the wear plate of FIG. 12 shown in position adjacent an impeller; and FIG. 16 is a perspective view of the non-wear surface of the wear plate shown in FIG. 15 illustrating the interaction between the wear plate and impeller.

DETAILED DESCRIPTION OF THE INVENTION The wear plate of the present invention is adaptable for use in any type of centrifugal pump which employs or can employ a wear plate positioned between the impeller and the pump casing or another adjacent structure of the pump. The present invention is described herein with respect to a self-priming pump by way of example only. Those of skill in the art will understand, based on the present disclosure, how to adapt the present invention to other types of centrifugal pumps.

FIG. 1 illustrates a conventional self-priming pump 10 which generally comprises a pump casing 12, an inlet 14 and an outlet 16. The impeller 18 is supported at the end of a bearing housing 20 and is connected to a drive shaft 22 for rotation. A clean out assembly 24 is axially aligned with the impeller 18 and comprises an end cover 26 and a supporting ring 28 that is spaced from the end cover 26 by a plurality of stanchions 30. The supporting ring 28 provides a means for attachment of a wear plate 32, which positions the wear plate adjacent the impeller 18.

As best seen in FIG. 3, the prior art wear plate 32 is generally configured as a flat plate having a thickness T extending between a non- wear surface 34 and an opposing wear surface 36 that is provided for orientation adjacent the impeller. The wear plate 32 is formed with an inner bore 38 that extends through the thickness of the flat plate and is provided with an inner circumferential edge 40 that surrounds the inner bore 38. In the prior art wear plate 32, the inner circumferential edge is smooth. FIG. 3 also illustrates that the wear plate 32 may be secured to the supporting ring 28 by bolts 44.

The wear plate 50 of the present invention is shown in FIGS. 2 and 4. In FIG. 2, where like parts of the pump are referred to by like reference numerals, the wear plate 50 of the present invention is likewise supported by a supporting ring 28 of a clean out assembly 24, and is positioned adjacent the impeller 18.

FIG. 4 more clearly illustrates that the wear plate 50 of the present invention is formed, in this first embodiment, as a flat plate having a thickness T extending between a non-wear surface 52 and an opposing wear surface 54 that is provided for orientation adjacent an impeller. The wear plate 50 is provided with means for attachment of the wear plate 50 to the supporting ring 28 of the clean out assembly, such as bolts 56.

The wear plate 50 has an inner bore 58 formed through the center of the wear plate 50 and the inner bore 58 is formed with an inner circumferential edge 60. The inner circumferential edge 60 of the wear plate 50 is formed with at least one or, as shown here, a plurality of cutting elements 62.

As illustrated in FIGS. 5 and 6, the cutting elements 62 are positioned to interact with the blade 66 or blades of the impeller 18 to produce a cutting action at the inner circumferential edge 60 of the wear plate 50. The cutting action of solids at the inner bore 58 of the wear plate 50 assures that solids, particularly stringy materials, are processed to a smaller and/or more suitable form for movement by and through the impeller 18.

As best seen in FIG. 7, the cutting elements 62 are generally produced by forming notches 70 in the inner circumferential edge 60 of the inner bore 58. The notches extend from the inner circumferential edge 60 toward the outer edge 74 of the wear plate 50. Two adjacently- formed notches 70 produce a tooth 72. As illustrated in FIG. 7, there may be more than one tooth 72 formed at the inner bore 58; however, a single tooth 72 may be formed in the inner bore 58. Further, as illustrated in

FIG. 7, the plurality of teeth 72 may be spaced evenly about the inner circumferential edge 60. However, alternatively, the cutting elements 62 may be spaced unevenly about the inner circumferential edge 60.

The notches 70 formed in the inner circumferential edge 60 are preferably formed at a tangential angle to the inner circumferential edge

60 such that a center line 76 (FIG. 7) of the notch 70 extends in the direction of rotation of the impeller, as shown in FIG. 5. The angle of the

notches 70 facilitates the capture of solids material in the notch to enable cutting by the blade or blades 66 of the impeller 18.

As further illustrated in FIGS. 7-9, the notches 70 and teeth 72 are formed with a wall surface 80 that is defined by the thickness between the wear surface 54 and the oppositely-facing non-wear surface 52 of the wear plate 50. The notches 70 are formed by cutting or machining through the thickness of the wear plate 50 at an angle to a plane 82, formed through the thickness of the wear plate 50, that is perpendicular to the planes of the wear surface 54 and non-wear surface 52 of the wear plate 50. That is, the angle A of the wall 80 is directed toward the center

84 (FIG. 7) of the wear plate 50 in a direction extending from the non- wear surface 52 to the wear surface 54 of the wear plate 50. Notably, the center 84 of the wear plate 50, when positioned in a pump, is co-axial with the rotational axis of the impeller. As best seen in FIG. 8, the angle A of the wall 80 of the notches

70 produces a tooth 72 having an edge 86 formed by the wear surface 54 which is greater than an edge 88 formed by the non-wear surface 52 of the wear plate 50. Consequently, the cutting elements 62 or teeth 72 of the wear plate 50 are self-sharpening as the wear plate 50 becomes worn by its interaction with the impeller (it being understood in the art that the wear plate 50 is axially adjusted toward the impeller from time to time as the wear plate 50 becomes worn).

The wear plate 50 described thus far, which is in the form of a flat plate, is suitable for use in smaller sizes, and certain types, of centrifugal pumps. In larger sizes or different types of centrifugal pumps, the wear plate may be formed in a generally frustoconical shape. FIGS. 10 and 11 again illustrate a frustoconical wear plate 90 that is known in the prior art. The wear plate 90 has an inner bore 92 with a smooth inner circumferential edge 94. FIG. 10 illustrates the wear surface 96 of the frustoconical wear plate 90 and FIG. 11 illustrates the non-wear surface

98.

FIGS. 12-14 illustrate a frustoconically-shaped embodiment of the wear plate 100 of the present invention where the inner bore 102 has an inner circumferential edge 104 that is formed with at least one cutting element 106, or a plurality of cutting elements 106 as shown. FIG. 12 illustrates the wear surface 108 of the wear plate 100 and FIG. 14 illustrates the non-wear surface 110 of the wear plate 100. The cutting elements 106 are formed in the manner previously described with respect to the flat plate embodiment illustrated in FIGS. 7-9, including the formation of the cutting elements to provide a self-sharpening capability. FIG. 15 further illustrates the frustoconically-shaped wear plate

100 of the present invention where the wear surface 108 is positioned adjacent an impeller 120 of a larger size pump. FIG. 16 illustrates the non-wear surface 110 of the wear plate 100 and illustrates the interaction of the cutting elements 106 with the blades 122 of the impeller 120. FIGS. 15 and 16 illustrate the position and direction of the cutting elements relative to the direction of rotation of the impeller 120, as denoted by arrow 126. It can be appreciated from the view of FIG. 16 that the notches 128 formed between the cutting elements 106 effectively trap solids therein for cutting by the leading edge 130 of the impeller blades 122 as the impeller rotates.

The wear plate of the present invention can be adapted for use in any type of centrifugal pump having an impeller, and especially a pump that is used to process fluids which are laden with solids material. Thus, reference herein to specific details of the illustrated embodiments are by way of example only and not by way of limitation.