CA2863245C - Cutter system for pump suction - Google Patents

Abstract

A centrifugal pump with a cutter mechanism having a toothed cutter auger affixed to an impeller, and a toothed cutter stator affixed to the volute casing. The auger is a rotor cutter preferably profiled radially to match the inlet geometry of the impeller vanes while extending along its central axis towards the pump suction. The auger is preferably radially concentric to the impeller and includes vanes numbered preferably to match the number of vanes on the impeller. The auger is affixed to the impeller, preferably with a lockscrew threaded into a common pump shaft. The radial profile of the auger essentially makes a continuous vane with the impeller, and prevents solids from hanging on the inlet vane tip or center void while providing a smooth flow transition into the impeller.

Description

TITLE OF THE INVENTION:
CUTTER SYSTEM FOR PUMP SUCTION
SPECIFICATION
BACKGROUND OF THE INVENTION
1. FIELD OF INVENTION
This invention relates generally to pumps for liquids, and more particularly, to centrifugal pump cutters for cutting solids suspended in the liquid.

2. DESCRIPTION OF RELATED ART
Pumps in both the manure slurry and municipal waste markets are subjcct to clogging due to the nature of stringy materials and other soft solids which tend to restrict or block the impeller passages in a centrifugal pump. This clogging can occur as often as every few days.
One attempt to solve the clogging problem was provided by a drawing of an "A
Series Cutter Assembly: Drawing #046897" to Homa. The Homa assembly is a crude welded device with a single slicer blade welded to a cutter plate, and two flat slicer blades welded inside an impeller and leaving a small opening therebetween. The Homa assembly has operational flaws, including shortcomings present in any welded device designed without thought to hydraulic impact of the cutters. For example, the Homa cutter and stator teeth block flow into the impeller, causing substantial pressure drop as flow enters the pump. This pressure drop will limit the amount of "lift" that the pumps can generate, limit the flow range of a pump, limit the size of a solid that can flow through the pump, and increase the amount of power that would be required to operate the pump. With just one impeller tooth the cutting force is skewed to one side causing life reducing unbalanced loads. The cutter teeth and impeller will have a reduced operational life because of the unbalance.

The Boma mechanism is fabricated with the teeth welded into the impeller and stator.
Welding the teeth adds problem on operation of the pump. For example, welds can be attacked by corrosion causing premature failure. Heating from the welds can damage the impeller and stator.
That is, the heat could warp the teeth and change the base structure of the underlying material. The corrosion resistance near the weld can change because of the heat. In addition, impact loads (from cutting) are concentrated at the weld points leading to reduced impeller/stator life. Further, the welded on teeth are non-replaceable. This means that failure at the weld would likely require a new impeller or plate in order to make a repair that now requires a pump rebuild.
Even prior to failure, the welded-on teeth are wear items and will need to be renewed on a regular basis.
Since pumps can go several years without a major rebuild, the requirement that base parts (impeller/stator) be replaced with the teeth is an expensive time consuming problem for pump users.
In the related art described in U.S. Publication No. 2014/0064929 filed by the same assignee, a cutter device for a centrifugal pump includes an impeller, a cutter ring, a wear ring and a stationary cutter plate. The impeller is concentrically located in a volute of the centrifugal pump. The volute has a front wall with a front flange defining an inlet port. The impeller has a rotational axis about which the impeller rotates within the volute. Further, the impeller has an inlet end that extends into and sits concentrically within the front flange. The cutter ring is releasably attached to the impeller, with the cutter ring concentric with the impeller and including a first set of teeth extending inwards towards the rotational axis of the impeller. The wear ring is located about the cutter ring between the cutter ring and the volute. The stationary cutter plate is releasably attached to the volute, concentric with and adjacent to the cutter ring. The stationary cutter plate includes a plate ring and a second set of teeth extending inwards from the plate ring towards the rotational axis of the impeller. The

3 second set of teeth is in shearing communication with the first set of teeth to shear apart solids in the inlet port of the volute.
According to another example described in U.S. Publication No. 2014/0064929, a centrifugal pump includes a volute, an impeller, a cutter ring, a wear ring and a stationary cutter plate. The volute has a front wall with a front flange defining an inlet port. The impeller is concentrically located in the volute, with the impeller having a rotational axis about which the impeller rotates within the volute, and the impeller having an inlet end that extends into and sits concentrically within the front flange. The cutter ring is releasably attached to the impeller, with the cutter ring concentric with the impeller and including a first set of teeth extending inwards towards the rotational axis of the impeller. The wear ring is located about the cutter ring between the cutter ring and the volute.
The stationary cutter plate is releasably attached to the volute, concentric with and adjacent to the cutter ring, with the stationary cutter plate including a plate ring and a second set of teeth extending inwards from the plate ring towards the rotational axis of the impeller. The second set of teeth is in shearing communication with the first set of teeth to shear apart solids in the inlet port of the volute.
The cutter device and centrifugal pump described in U.S. Publication No.

shears apart solids in a centrifugal pump' s suction inlet to prevent restriction or blockage in the impeller passages. The shearing action is accomplished by the mechanical interaction of a cutter ring fastened to the rotating impeller and a cutter plate fastened to the stationary volute of the centrifugal pump. The action of the cutter mechanism disrupts the formation of the clogging action and keeps flow moving through the pump. Some elements of the cutter device may include:
profiled cutter teeth to optimize flow and Net Positive Suction Head (NPSH) characteristics, adjustable cutter clearances to maintain optimal shearing action, keyed engagement that takes impact away from the fasteners on a rotating cutter ring and stationary cutter plate.

4 The cutter device and centrifugal pump described in U.S. Publication No.
2014/0064929 has been successful, especially in light to medium duty services. However, the inventors have recognized that heavier concentration of solids in these applications indicate that the cuter assembly may at some level still be susceptible to the heavier concentration of solids filling in voids at the center of the impeller and around the vane tips, which may restrict the hydraulic flow. Accordingly, the inventors have designed an improved cutter system.
BRIEF SUMMARY OF THE INVENTION
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify essential features of the claimed subject matter, nor is it intended for use in determining the scope of the claimed subject matter.
According to an example of the invention, a cutter device for a centrifugal pump includes an impeller, a rotor, a wear ring and a stationary cutter plate. The impeller is concentrically located in a volute of the centrifugal pump. The volute defines a chamber and has a front wall with a front flange defining an inlet port. The impeller has a rotational axis about which the impeller rotates within the volute. The impeller further includes an impeller vane having an inlet angle.
The impeller also has an inlet end that extends into and sits concentrically within the front flange. The wear ring sits adjacent the impeller between the impeller and the volute. The rotor is a cutter auger releasably attached to and concentric with the impeller. The rotor includes a central section and an auger vane extending away from the central section. The stationary cutter plate is releasably attached to the volute or a suction cover thereof, concentric with and adjacent to the cutter auger. The stationary cutter plate includes a plate ring and teeth extending inwards from the plate ring towards the rotational axis of the impeller and cutter auger. The teeth are in shearing communication with vanes of the auger to shear apart solids in the inlet port of the volute.
According to another example of the invention, a centrifugal pump includes a volute, an impeller, a rotor, a wear ring and a stationary cutter plate. The volute defines a chamber and has a

5 front wall with a front flange defining an inlet port. The impeller is concentrically located in the volute, with the impeller having a rotational axis about which the impeller rotates within the volute, and the impeller having an inlet end that extends into and sits concentrically within the front flange.
The impeller further includes an impeller vane having an inlet angle. The wear ring sits adjacent the impeller between the impeller and the volute. The rotor is a cutter auger releasably attached to and concentric with the impeller. The rotor includes a central section and an auger vane extending away from the central section. The stationary cutter plate is releasably attached to the volute or a suction cover thereof, concentric with and adjacent to the cutter auger. The stationary cutter plate includes a plate ring and teeth extending inwards from the plate ring towards the rotational axis of the impeller and cutter auger. The teeth are in shearing communication with vanes of the auger to shear apart solids in the inlet port of the volute.
The auger may include vanes numbered preferably to match the number of vanes on the impeller. The radial profile of the auger preferably makes a continuous vane with the impeller, and prevents solids from hanging on the inlet vane tip or center void while providing a smooth flow transition into the impeller.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein:

6 Fig. 1 is a perspective view of an exemplary cutter pump assembly in accordance with the preferred embodiments of the invention;
Fig. 2 is a front view of the cutter pump assembly of Fig. 1;
Fig. 3 is an axial sectional view of the cutter pump taken along line 3-3 of Fig. 2;
Fig. 4 is an isometric exploded assembly view of the cutter pump of Fig. 1;
Fig. 5 is a perspective view of an exemplary cutter auger from the cutter pump of Fig. 1;
Fig. 6 is a top view of the exemplary cutter auger from the cutter pump of Fig. 5;
Fig. 7 is a side front view of the exemplary cutter auger of Fig. 6;
Fig. 8 is a side sectional view of the exemplary cutter auger of Fig. 6 taken along line 8-8 of Fig. 6;
Fig. 9 is a perspective view of an exemplary impeller, cutter auger and cutter ring; and Fig. 10 is an axial side sectional view of an exemplary cutter pump including the cutter auger and cutter ring of Fig. 9.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
1 5 An example of the improved system is shown in the additional figures and includes an auger or auger style part that is profiled radially to match the inlet geometry of the impeller vanes while extending along its central axis towards the pump suction. The auger is preferably radially concentric to the impeller. The auger includes vanes numbered preferably to match the number of vanes on the impeller. The auger depicted in the drawings is axially profiled, top and bottom, at least substantially parallel to the suction flange of the pump, the mating stationary cutter, and the mating surface on the impeller where it registers. The auger acts as a rotating (rotor) cutter, which may replace the toothed cutter from the invention described above. It is affixed to the impeller, preferably with a lockscrew threaded into the common pump shaft. The radial profile of the auger essentially

7 makes a continuous vane with the impeller, and prevents solids from hanging on the inlet vane tip or center void while providing a smooth flow transition into the impeller.
Accordingly, the profile of the exemplary auger design prevents solids from accumulating in at least these locations while also shearing the solids and guiding the flow into the pump. For light and medium applications, the invention described in U.S. Publication No.
2014/0064929 at least achieves this purpose. The auger more efficiently handles heavier duty in more severe applications than prior art pumps, and preferably is retrofitable in common pumps. Further, the auger can be in integral part with the impeller or a replaceable part used with the impeller.
Shearing action is achieved by the interaction of the auger as the cutter rotor and toothed cutter stator. The auger design of the rotor is integral with the impeller and preferably a replaceable part. The cutter pump apparatus is useful especially in extreme service conditions to prevent heavier concentrations of solids from accumulating in the center of the impeller and the leading edge of the impeller vane while guiding the flow into the impeller. In addition, the cutter auger rotor design prevents solids from restricting or blocking the impeller inlet without significant decrease of flow throughput or significant increase in absorbed hydraulic horsepower.
The exemplary embodiments include cutter auger vanes and stator teeth that minimize clogging of the impeller passages into the pump. The size of the teeth is large enough to interrupt clogging, yet small enough to not restrict the original solids capacity of the centrifugal pumps. For example, the teeth project radially inwards preferably less than one-fourth of the diameter of the inlet to the impeller. The vanes are preferably structured with a hydraulic profile that matches the inlet angle of the impeller vanes. In this manner, each pump preferably has an auger interacting with the stator teeth to shear solids entering the cutter pump apparatus. Moreover, the auger has vanes designed to match the impeller inlet vane angles. That is, the teeth and vanes are preferably

8 hydraulically profiled to match the impeller. They may even be clocked at installation ¨ oriented such that the teeth minimize the interruption of the inlet flow path.
Accordingly, the exemplary embodiments reduce the impact to suction lift and restricted flows experienced by known designs.
The cutter assembly and cutter system is machined from a casting bolted in, adjustable and preferably symmetrical and retrofitable, leading to predictable mechanical and hydraulic results. Cast and machined parts are not subject to corrosion caused by welding. The impeller and suction case are machined to accept the rotor (e.g., cutter auger, cutter ring) and stator (e.g., cutter plate). This eliminates potential damage caused by welding on the parts. Further, the wear parts are retrofitable.
This will be an incredible benefit to scores of municipal wastewater pump stations that have flow interruptions because of clogging and will be able to quickly add cutters without changing pumps or increasing motor size. When the parts have worn and need to be renewed the impeller and suction piece will be undamaged. The customer will be able to quickly change out the rotor and stator without replacing a damaged impeller or suction piece.
Referring now in greater detail to the various figures of the application, wherein like-referenced characters refer to like parts, a general communication environment including an exemplary cutter pump assembly 10 of the invention is illustrated in Fig. 1.
Fig. 2 depicts the cutter pump device or assembly 10 in front view, Fig. 3 depicts the cutter pump assembly in axial cross view, and Fig. 4 depicts the cutter pump assembly in exploded view. With reference to Figs. 1-4, shown therein in perspective view is a pump volute 12 having a front cover 14, a backplate 16 and a housing 18. The volute 12 defines a chamber 17 within scrolling out to a discharge flange 19.
Typically the volute is made of iron, however, various other metals know in the art for increased hardness or corrosion resistances are acceptable as well. The volute is preferably cast and thus not subjcct to corrosion caused by welding.

9 The front cover 14 has a front annular flange 20 partly defining an inlet port 22, and is cast as a separate suction cover that is attached to the volute 12, preferably via front cover bolts 24 threaded into matching bores 26 (Fig. 4) in a forward facing annular flange 28 of the volute housing 1 8. Thus the front cover is an exemplary detachable front wall of the volute 12. It should be noted that the front wall of the volute 12 is not limited to a detachable front wall, as the volute may include a front wall permanently integral with the housing 18.
Now referring to Figs. 3 and 4, the backplate 16 is secured to a rearward facing annular flange 30 of the volute housing 18 where it may be compressed between the volute housing and a motor 32. The backplate 16 has an outward extending center section 34 with an annular recess cavity 36 into which a drive shaft 38 of the motor 32 extends. The backplate 16 is preferably secured to the volute housing via bolts 40 threaded into matching bores (not shown) located in the rearward facing annular flange 30. While not being limited to a particular theory, the backplate 16 also includes an annular extension 44 that in Fig. 3 abuts a spacer bracket 46 fixed between the motor 32 and the backplate, and about the drive shaft 38 to provide stability to the pump.
Other examples of the cutter pump assembly 10 may encompass a wide range of different volute styles and shapes, as many aspects of the invention are not limited to use on centrifugal pumps.
An impeller 48 concentrically sits in the volute 12 rotatable between the backplate 28 and front cover 14. A back wall 50 of the impeller 48 extends radially inwards into an annular collar 52 that defines a bore 54 for attachment to the drive shaft 38 of the motor 32.
The drive shaft 38 is fixed to the impeller 48; preferably via a lockscrew 56 threaded into a matching bore 58 axially located in the driveshaft 38, as will also be described in greater detail below. While not being limited to a particular theory, the impeller 48 is preferably closed vane as it consumes much less energy than open vane impellers. The impeller 48 also includes a front wall 60 and vanes 62 between the front 1_0 wall and the back wall 50. The front wall 60 is turned towards an inlet end 64 that extends into and sits concentrically within and spaced from the front cover 14 by a wear ring 66 therebetween. The impeller 48 is preferably machined from metal or a solid composition including metal. In use, the impeller 48 is rotated by the pump motor 32 to induce a pumping action as understood by a skilled artisan. The pumping action pulls slurry or pumpage into the inlet end 64, through the impeller 34 and out the volute flange 27.
Referring to Fig. 3, a seal structure 42 exposed to the chamber 17 seals the drive shaft 38 and volute 12. This seal structure includes a stationery seal 41 and a rotary seal 43 which rotates with the drive shaft. An urging member, such as a compression spring 45, urges the rotary seal 43 against the stationery seal 41. With the construction described, liquid within the chamber 17 is prevented from leaking outwardly past the backplate 16 of the volute 12. The example depicted in Fig. 3 shows the backplate 16 and impeller 48 having surfaces facing each other that are relatively smooth. It is understood that the invention is not so limited, as the mutually facing surfaces may also have a vane construction distributed circumferentially of the drive shaft 38 effective to produce a circulating action in pumpage moved between the mutually facing surfaces which results in debris leaving the seal structure adjacent the annular collar 52 to move radially outwards to a larger diameter end of the backplate adjacent the rearward facing annular flange 30 and thence out into the main discharge stream of the pump as described in greater detail in U.S.
Patent No. 5,489,187.
The wear ring 66 is disposed concentrically about the front wall 60 of the impeller 48, and is supported between adjacent surfaces of the front wall and the front cover 14 where the wear ring can minimize friction and wear between the rotating impeller and the stationary volute 12. In cross section, the wear ring 66 can be seen as generally rectangular. However, the shape of the wear ring is not limited thereto. For example, the wear ring may be L-shaped with a longitudinally extending portion and a radially extending portion located at a front side of the front wall between the impeller 48 and the volute 12. The wear ring 66 may be a single piece of machined metal or other alloy composition. It is also understood that the wear ring 66 may be a bushing or other multi-piece annular unit.
The impeller 48 and front annular flange 20 define a generally conical shaped interior chamber 68 extending outwards through the inlet port 22. Within the interior chamber 68 resides a cutter assembly 70 supported at least by the volute 12 and the impeller 48. As can be seen in Figs. 3-8, the cutter assembly 70 includes a rotor (e.g., rotating cutter auger 72) and a stator (e.g., cutter plate 74). The cutter auger 72 is preferably machined from a metal casting, and is retrofitably (e.g., releasably) attached to the back wall 50 the impeller 48 preferably by the lockscrew 56. For example, the cutter auger 72 includes a central section of a base portion 76 fixed concentrically against the impeller 48 that extends axially towards the inlet port 22 into a tubular portion 78 ending at a front surface 80 thereof. The base portion 76 and tubular portion 78 define an axial bore 82 (Fig.
8). As can best be seen in Fig. 3, the lockscrew 56 abuts the front surface 80 and extends through the tubular and base portions, and finally through an aperture 84 in the back wall 50 into threaded engagement with the matching bore 58 of the driveshaft 38 to fix the cutter auger, impeller and driveshaft together. Of course the auger 72 can be fixed to the impeller via other ways as readily understood by a skilled artisan, for example, via screws extending through offsetting longitudinal bores in the base portion that attach to matching threaded bores in the impeller 48.
Figs. 5-8 depict an exemplary cutter auger 72 in various views. The cutter auger 72 includes a plurality of vanes 86 that extend outwards spirally from the base and tubular portions 76, 78 of the cutter auger. Preferably each vane 86 has a top spiraled surface 88 having a sharp edge 90 for interacting with the cutter plate 74 to shred solids entering the inlet port 22, as will be described in greater detail below. Each vane 86 also spirals from the base and tubular portions 76, 78 to an outer edge 92. The vanes 86 arc preferably numbered and structured with a hydraulic profile that matches the inlet angle of the impeller vanes 62. Moreover, the auger vanes 86 preferably intentionally match the impeller inlet vane angles. In this manner, the cutter auger vanes 86 remove solids from restricting or blocking the interior chamber 68 before the impeller vanes efficiently without significant decrease of flow throughput. While there is no limitation on the number of auger vanes 86, it is preferred that the auger 72 has at least two vanes 86 equidistantly spaced radially about the base and tubular portions 76, 78 to balance the impact load with the solids or slurry flowing into the impeller 48, which leads to a longer service life of the rotating cutter auger and the impeller. Further, while the front surface 80 of the tubular portion 78 and the tip spiraled surface 88 of the vanes 86 are shown on two different planes in this example, it is understood that the invention does not limit the planar relationship between the surfaces.
As can best be seen in Figs. 1, 2 and 4, the cutter plate 74 is preferably annular, stationary and retrofitably (e.g., releasably) attached to the front annular flange 20 of the volute 12 by cutter plate cap screws 94 threaded through bore walls 96 (Fig. 4) of the cutter plate into screw fixing bores 98 (Fig. 4) of the front annular flange 20. The stationary cutter plate 74 is preferably machined from a metal casting with three integrally formed stationary teeth 104 provided to engage with the sharp edges 90 of the auger vanes 86 for cutting or shearing solids flowing into the inlet port 22 of the volute 12. The teeth 104 are machined from a casting with a profile that allows entry of solids/slurry into the chamber 68 while extending into the inlet port 22 far enough to match against the sharp edges 90 of the top spiraled surface 88 for shearing action. The stationary teeth 104 each have a sharp edge closest to an approaching sharp edge 90 to maximize the cutting and shearing action there between. While there is no limitation on the number of stationary teeth 104, it is preferred that the cutter auger 72 has one more or less vane in comparison to the number of teeth. The stationary teeth 104 are equidistantly spaced about the stationary cutter plate 74 to balance the impact load with the solids or slurry flowing into the impeller 48 and to balance the shearing action between the stationary teeth and the auger vanes, which leads to a longer service life of the stationary cutter plate and the rotating cutter auger 72.
Sct screws 100 are threadingly disposed through the cutter plate 74 to adjust a clearance 102 between the top spiraled surface 88 of the auger 72 and the cutter plate 74.
In particular, the set screws 100 are threaded through threaded bores 106 (Fig. 4) in the cutter plate 74 and into abutment against a recessed annular face 108 (Fig. 4) of the front cover 14 to spatially set the cutter plate at a distance from the recessed annular face as the cutter plate is attached to the front annular flange 20 via the cap screws 94 threaded into the screw fixing bores 98. The set screws 100 are designed to set the distance between the cutter plate 74 and the recessed annular face 108 to provide the clearance 102 between the stationary teeth 104 and the top spiraled surface 88 of the rotating cutter auger 72 to allow a shearing interaction in use therebetween when the auger vanes 86 are rotated adjacent the stationary teeth. Preferably this clearance is set to bctween 0.01 and 0.02 inches. While the exemplary embodiment shows four set screws 100, it is understood that the invention is not limited thereto and that any number of set screws is within the scope of the invention. Preferably the number of set screws is plural and spaced equidistantly about the stationary cutter plate 74 to provide equal clearance between the stator teeth 104 and the sharp edges 90.
As discussed above, the rotating cutter auger 72 and the stationary cutter plate 74 are retrofitable. For example, the cutter auger 72 and cutter plate 74 are releasable with the impeller 48 and front cover 14, respectively, here via the lock screw 56 and the cap screws 94 (Fig. 4). This is beneficial since both of these members include wear parts (e.g., vanes, teeth) that wear out over time and generally quicker than the other parts of the cutter pump assembly 10. As the sharp edges 90 of the cutter auger 72 and teeth of the stationary cutter plate 74 become dull, break, or wear down, the members can be removed and replaced with a new or refurbished auger or plate having sharp edges and teeth effective for shearing the slurry. This extends the life of, for example, the impeller 48 and volute 12, which have a longer service live than the auger 72 and cutter plate 74, because a plurality of augers and cutter plates may be retrofitted and used. This also adds flexibility to the cutter pump assembly 10 as differently configured augers and cutter plates can be used with the assembly based on which configuration (e.g., number of vanes/teeth, angle of teeth blades, size of teeth, shape of vanes) may be preferred for a specific slurry, suction level, or output.
As can best be seen in Fig. 3, during pump operation, the slurry or pumpage, including suspended solids and stringy materials, enters thru the inlet port 22 of the pump volute 12. The slurry then is drawn into the cutter assembly 70 by the pumping action of the impeller 48. The slurry passes between the stationary cutter plate 74 and the rotating cutter auger 72, at which point the suspended solids are sheared into smaller segments and pulled into the auger.
The sheared pumpage then flows through the impeller 48, is discharged out into the volute chamber 25 and exits the volute 12 through the discharge flange 27.
It should be noted that in the examples of the cutter assembly may also include a toothed cuter ring similar to the cutter ring disclosed in U.S. Publication No.
2014/0064929. Figs. 9 and 10 depict an example with such a cutter ring integrated into the cutter pump assembly 10 between the cutter auger 72 and the cutter plate 74. While not being limited to a particular number, a rotating cutter ring 110 includes two integrally fon-ned profiled teeth 112 for cutting or shearing solids and two projections 114 designed to provide a keyed engagement with the impeller 48 as discussed in greater detail below. The profiled teeth 112 are machined from a casting with a hydraulic profile that preferably matches an inlet angle of the impeller vanes 62 and the auger vanes 86. For example, the profiled teeth 112 have a cutting edge 116 and a blade 118 angled rearward from the cutting edge towards the impeller back wall 50 at an angle that matches the inlet angle of the impeller and auger 5 vanes. This matching hydraulic profile minimizes any impact to suction lift and restriction flow and minimizes pump efficiency loss. The profiled teeth 112 may be oriented with the auger vanes 86 to minimize the interruption of solids and slurry into the inlet flow path partly defined by the inlet port 22 and the chamber 68.
While there is no limitation on the number o f pro file teeth 112, it is preferred that the rotating

10 cutter ring 110 has at least two profiled teeth 112 equidistantly spaced about the cutter ring and aligned with the auger vanes 86 to balance the impact load with the solids or slurry flowing through the impeller 48, which leads to a longer service life of the rotating cutter ring and the impeller. Like the cutter auger 72 and the cutter plate 74, the cutter ring 110 is preferably retrofitable, as it is releasably coupled to the impeller 48, for example, via cap screws 122 that extend through apertures 15 126 in the cutter ring into threaded engagement with bolt fixing bores 124 in the impeller. This prolongs the service life of the impeller 48, as a plurality of cutter rings 110 can be used with the same impeller 48.
As can best be seen in Fig. 9, the projections 114 of the rotating cutter ring 110 are machined to fit into notches 120 at the inlet end 64 of the impeller 48. The projections 114 are sized to fit snuggly into the notches 120 in a keyed engagement and take impact away from the fasteners (e.g., cap screws 122) attaching the rotating cutter ring 110 the impeller 48.
Preferably the projections 114 and the notches 120 are squared to permit a snug fit and maximize the impact transfer, here from the cap screws 122 and bolt fixing bores 124 of the impeller 48, to the projections and notches, which minimizes impact damage and wear at the cap screws and bolt fixing bores.
While the exemplary embodiment shows two sets of matching notches 120 and projections 114, it is understood that the invention is not limited thereto and that any appropriate number of sets of matching notches and projections is within the scope of the invention. Preferably the number of sets is plural and spaced equidistantly about the impeller 48 and rotating cutter ring 110 to equally distribute the impacts.
Fig. 10 also shows that the wear ring 66 may be set between the cutter ring 110 and the impeller 48 to reduce wear there between. Here, the wear ring 66 is disposed concentrically about the cutter ring 110, and supported between abutting surfaces of the cutter ring and the front cover 14, where the wear ring can minimize friction and wear between the rotating cutter ring and the stationary volute 12. As noted above, the wear ring 66 may be a single piece of machined metal or other alloy composition. It is also understood that the wear ring 48 may be a bushing or other multi-piece or shaped annular unit.
It is understood that the cutter apparatus for a centrifugal pump and thc cutter system described and shown are exemplary indications of preferred embodiments of the invention, and are given by way of illustration only. In other words, the concept of the present invention may be readily applied to a variety of preferred embodiments, including those disclosed herein. While the invention has been described in detail and with reference to specific examples thereof, it will bc apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. For example, the number, location and shape of the vanes, teeth, projections, notches and channels described may be altered without departing from the scope of the invention. Without further elaboration the foregoing will so fully illustrate the invention that others may, by applying current or future knowledge, readily adapt the same for use under various conditions of service.

Claims (20)

17What is claimed is:

1. A cutter pump device for a centrifugal pump, comprising:
an impeller concentrically located in a volute of the centrifugal pump, the volute defining a chamber and having a front wall with a front annular flange defining an inlet port, the impeller having a rotational axis about which the impeller rotates within the volute, the impeller including a plurality of impeller vanes, each impeller vane having an inlet angle, the impeller having an inlet end that extends into and sits concentrically within the front annular flange;
a wear ring adjacent the impeller between the impeller and the volute;
a rotor releasably attached to the impeller, the rotor being a cutter auger radially concentric within the impeller in the volute and including a central section and a plurality of auger vanes, each auger vane extending spirally away from the central section, the auger vanes numbered to match the number of impeller vanes and structured with a hydraulic profile that matches the inlet angles of the impeller vanes; and a stationary cutter plate releasably attached to the volute, concentric with and adjacent to the cutter auger, the stationary cutter plate including a plate ring and a first set of teeth having at least onc tooth extending inwards frorn the plate ring towards the rotational axis of the impeller, the first set of teeth bcing in shearing cornmunication with the auger vanes to shear apart solids in the inlet port of the volute.

2. The cutter pump device of Claim 1, the cutter auger having a base portion and a tubular portion, the base portion fixed concentrically against the impeller and extending axially into the tubular portion ending at a front surface thereof

3. The cutter pump device of Claim 2, the base portion and the tubular portion defining an axial bore, the cutter auger further comprising a lockscrew abutting the front surface and extending through the axial bore and through the impeller into engagement with a driveshaft of the cutter pump to fix the cutter auger and the impeller together.

4. The cutter pump device of Claim 1, the impeller and the front annular flange defining a conical shaped interior chamber extending outwards through the inlet port, the cutter auger being located within the conical shaped interior chamber.

5. The cutter pump device of Claim 2, wherein the cutter auger has at least two auger vanes equidistantly spaced radially about the base portion and the tubular portion.

6. The cutter pump device of Claim 1, wherein the cutter auger has one more or one less auger vane than the number of teeth in the first set of teeth on the stationary cutter plate.

7. The cutter pump device of Claim 1, each auger vane having a profile that matches the inlet angle of one of the impeller vanes.

8. The cutter pump device of Claim 1, further comprising a cutter ring releasably attached to the impeller between the cutter auger and the cutter plate, the cutter ring being concentric with the impeller and including a second set of teeth extending inwards towards the rotational axis of the impeller.

9. The cutter pump device of Claim 1, wherein the impeller is a closed vane impeller.

10. The cutter pump device of Claim 1, wherein the front wall is detachable.

11. A centrifugal pump, comprising:
a volute defining a chamber, the volute having a front wall with a front annular flange defining an inlet port;

an impeller concentrically located in the volute, the impeller having a rotational axis about which the impeller rotates within the volute, the impeller including a plurality of impeller vanes, each impeller vane having an inlet angle, the impeller having an inlet end that extends into and sits concentrically within the front annular flange;
a wear ring adjacent the impeller between the impeller and the volute;
a rotor releasably attached to the impeller, the rotor being a cutter auger radially concentric within the impeller in the volute and including a central section and a plurality of auger vanes, each auger vane extending spirally away from the central section, the auger vanes numbered to match the number of impeller vanes and structured with a hydraulic profile that matches the inlet angles of the impeller vanes; and a stationary cutter plate releasably attached to the volute, concentric with and adjacent to the cutter auger, the stationary cutter plate including a plate ring and a first set of teeth having at least one tooth extending inwards from the plate ring towards the rotational axis of the impeller, the first set of teeth being in shearing communication with the auger vanes to shear apart solids in the inlet port of the volute.

12. The centrifugal pump of Claim 11, the cutter auger having a base portion and a tubular portion, the base portion fixed concentrically against the impeller and extending axially into the tubular portion ending at a front surface thereof.

13. The centrifugal pump of Claim 12, the base portion and the tubular portion defining an axial bore, the cutter auger further comprising a lockscrew abutting the front surface and extending through the axial bore and through the impeller into engagement with a driveshaft of the centrifugal pump to fix the cutter auger and the impeller together.

14. The centrifugal pump of Claim 11, the impeller and the front annular flange defining a conical shaped interior chamber extending through the inlet port, the cutter auger being located within the conical shaped interior chamber.

15. The centrifugal pump of Claim 12, wherein the cutter auger has at least two auger vanes equidistantly spaced radially about the base portion and the tubular portion.

16. The centrifugal pump of Claim 11, wherein the cutter auger has one more or one less auger vane than the number of teeth in the first set of teeth on the stationary cutter plate.

17. The centrifugal pump of Claim 11, each auger vane having a profile that matches the inlet angle of one of the impeller vanes.

18. The centrifugal pump of Claim 11, further comprising a cutter ring releasably attached to the impeller between the cutter auger and the cutter plate, the cutter ring being concentric with the impeller and including a second set of teeth extending inwards towards the rotational axis of the impeller.

19. The centrifugal pump of Claim 11, further comprising a seal structure exposed to the chamber that seals the volute with a drive shaft from a motor, the seal structure including a stationary seal abutting the volute, and a rotary seal adjacent the stationary seal that rotates with a drive shaft.

20. The centrifugal pump of Claim 19, the seal structure further including a compression spring urging the rotary seal against the stationary seal.