Patent Application
20120251319
The present device relates to centrifugal pumps used for pumping liquids and slurries containing solid matter, including various types of refuse, and for chopping the solid matter which may thereafter be processed for disposal. Particularly, the device relates to a chopper pump which both effectively allows the pump to continue working during heavy chopping, provides better efficiency, and effectively reduces wear on components due to the presence of grit-like material in the liquid.
Generally speaking, U.S. Pat. No. 3,155,046 to Vaughan, issued Nov. 3, 1964, discloses a centrifugal pump having an open impeller with radial vanes. The vane edges adjacent to the pump inlet cooperate with sharpened edges of inlet apertures to cut stringy material or chunks entering the pump. Similarly, U.S. Pat. No. 3,973,866 to Vaughan, issued Aug. 10, 1976, and U.S. Pat. No. 4,842,479 to Dorsch, issued Jun. 27, 1989, disclose centrifugal pumps having impellers with vanes cooperating with inlet apertures to achieve a chopping or slicing action of solid material in a liquid or slurry being pumped. In the case of the pumps of U.S. Pat. No. 3,973,866 to Vaughan and U.S. Pat. No. 4,842,479 to Dorsch, however, semi-open impellers having radial shroud plates are used and external booster propellers may be provided to accelerate flow into the pump. The latter, when used, helps displace chunks of solid matter which become lodged in the inlet apertures and, at least in some instances, cuts solid matter prior to entry into the pump.
Other types of pumps having external cutters rotated with an impeller or propeller are shown in U.S. Pat. No. 2,714,354 to Farrand, issued Aug. 2, 1955; U.S. Pat. No. 3,325,107 to Peterson, issued Jun. 13, 1967; and French Patent No. 1.323.707, issued Mar. 1, 1962. U.S. Pat. No. 3,444,818 to Sutton, issued May 20, 1969, discloses another type of centrifugal pump having an internal impeller with vanes cooperating with the periphery of an inlet aperture to achieve a slicing action. In the Sutton construction, an outer “chopper member” has blades that wipe across the outer surface of the apertured intake plate to assist in chopping solid material to a size small enough to enter the intake aperture. Similarly, in the construction shown in British Patent No. 1,551,918, published Sep. 5, 1979, external blades sweep across small intake apertures to dislodge or gradually cut solid material clogging an intake aperture. In both the construction shown in the Sutton patent and the construction shown in the British patent, the external member is mounted so as to be moveable axially away from the intake plate if a hard obstruction is encountered.
Other types of pumps designed for pumping liquids or slurries containing solid materials are disclosed in Canadian Patent No. 729,917, issued Mar. 15, 1966; Schlesiger U.S. Pat. No. 3,340,812, issued Sep. 12, 1967; Elliott U.S. Pat. No. 4,527,947, issued Jul. 9, 1985; and Corkill U.S. Pat. No. 4,575,308, issued Mar. 11, 1986.
One of the problems with each of these devices is the occurrence of motor overloading during heavy chopping. Where the chopping is not efficient, the motor power increases causing the motor protection controls to trip the motor offline. When the motor goes offline, the chopping stops and operator intervention is required to place the motor back online. The chopping down-time, of course, detracts from the cost effectiveness of the process.
Another problem relates to excessive wear on the cutting parts over time. Fibrous material, such as hair and the like, tend to accumulate in the cutting area, particularly at the cutting parts. The fibrous material collects grit and sand causing the cutting parts to grind down prematurely. A cutter nut and cutter bar assembly at the pump intake has been used to keep the cutting parts clear of such fiber and debris.
Perhaps the most closely related device for this purpose is shown in U.S. Pat. No. 5,460,483 to Dorsch, issued Oct. 24, 1995. The Dorsch '483 patent illustrates a square cutter nut projection (60) in
It is therefore desirable to provide a cutter assembly which helps maintain a clear cutting area, reduces cutting part wear and improves chopping efficiency to reduce motor power load and chopping down-time. It also would be desirable to provide a cutter assembly which aggressively reduces the build-up and collection of grit in the cutting area. The disclosed device affords other structural, manufacture and operating efficiencies not seen in prior art devices, as well.
There is disclosed herein an improved centrifugal chopper pump design which avoids the disadvantages of prior devices while affording additional structural and operating advantages.
Generally speaking, the disclosed centrifugal pump comprises a housing having an intake opening and an outlet opening, both in fluid communication with an internal chamber, and an impeller assembly positioned within the chamber.
In an embodiment of the system, the impeller assembly comprises an impeller having a back shroud, an insert cutter positioned on the back shroud to extend in a direction opposite the impeller and having a cutting edge configured for shearing operation, a stationary back plate having a surface adjacent to and facing the back shroud, and a cutting rib attached to the back plate surface and having a cutting edge configured for shearing operation.
In operation, the cutting edge of the insert cutter and the cutting edge of the cutting rib are angled and gapped relative to one another to create a cutting action as the insert cutter passes the cutting rib.
In various embodiments, the cutting rib is aligned radially on the surface of the back plate and a gap between the cutting rib and the insert cutter is preferably in the range of from about 0.005 to 0.050 inches, most preferably in the range of from about 0.010 to about 0.015 inches. Preferably, the insert cutter and the cutting rib are removable and means may be provided to permit the gap to be adjusted, as necessary.
These and other aspects of the invention may be understood more readily from the following description and the appended drawings.
For the purpose of facilitating an understanding of the subject matter sought to be protected, there are illustrated in the accompanying drawings embodiments thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should be readily understood and appreciated.
While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail a preferred embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to embodiments illustrated.
Referring to
As shown in drawing
Referring to
The use of a cutter groove 37 on the cutter bar plate 26 is an optional feature of the present invention and need not be used in all cases. The cutter groove 37 is discussed more fully in U.S. Pat. No. 7,125,221, also assigned to the Assignee of this invention, the disclosure of which is hereby incorporated by reference.
A unique aspect of the present invention is the use of two cutting inserts/ribs, shown in
As previously mentioned, and with reference to
Referring to
It is believed that only a single cutting rib 40 is required with most applications. However, in some instances it may be desirable or necessary to use two back plate cutting ribs. Such additional ribs may be positioned in consecutive or alternate quadrants from one another on the surface 41 of the back plate 28.
As stated above, the insert 40a fits tightly within a groove 42 machined into the surface 41 of the back plate 28. In addition to this friction fit within the preferably dovetailed groove 42, the cutting rib 40 should be held in place using a high-strength adhesive and retained mechanically by obstructions placed at each end of the groove 42. As the cutting rib 40 becomes worn, it can be removed and readily replaced.
As to both cutting areas 29 and 39, a sloping recessed area 43 precedes the groove 42a and b in the surface 35 of the shroud 30 and the surface 41 of the back plate 28, respectively. The sloping recessed areas 43 help to expose more of the cutting rib 40 and insert cutter 24 during the shearing action.
In addition to the sloping recessed areas 43 described above, the cutting rib 40 and insert cutter 24 are also preferably positioned such that they are flush with the respective (shroud 30 and back plate 28) surfaces. This allows the shroud 30 and back plate 28 to be positioned with tighter clearances for better pump efficiency. Solid material is directed downward into the recessed area 43 where it is impacted by the scissoring insert cutter 24 and cutting rib 40.
A gap created between the back cutting rib 40 and the insert cutter 24 is preferably within the range of from about 0.005 to about 0.050 inches (0.0127 to 0.127 cm), and most preferably in the range of from about 0.010 to 0.015 inches (0.0254 to 0.0381 cm). The gap is very important to the efficient operation of the cutting action between rib 40 and insert cutter 24. If the gap is too large, the drive motor power required may be excessive, resulting in motor overload tripping. If the gap is too narrow, metal-to-metal contact problems may result during pump operation.
Alternatively, the recessed areas described may be omitted and the upper edges of the cutting rib 40 and insert cutter 24 may be raised above the surface of the corresponding plate. In this embodiment, a necessary gap, similar to that described above, should be maintained between the cutting edges. However, a larger gap will exist between the hub shroud 30 and back plate 28 surfaces. While this configuration will negatively impact pump efficiency, it may be used with similar success in certain pump applications.
In the present embodiment, the cutting rib 40 and insert cutter 24 are preferably made of one of either a hardened steel or hardened stainless steel. As a hardened steel, the finished cutter preferably has a hardness measure of at least HRC 60, and as a hardened stainless steel, a measure of about HRC 40. Such hardness gives both the cutting rib 40 and the insert cutter 24 the necessary durability to operate effectively and efficiently before needing replacement.
As stated above, the insert cutter 24 and cutting rib 40 fit tightly within the corresponding groove 42 machined into the surfaces of the back shroud 30 and back plate 28, respectively. In addition to this close fit within the preferably dovetailed grooves 42a and b, the insert cutter 24 and cutting rib 40 should be held in place using a high-strength adhesive and may be further retained mechanically by obstructions placed at each end of the respective groove 42. As the insert 24 and rib 40 becomes worn, they may be removed and readily replaced.
In operation, liquids or slurries including solid waste material (collectively “fluid”) enter the chopper pump 10 at the inlet opening 14 as a result of the suction created by the impeller 22 motion turned by motor 50. While the present system may be employed for most any chopper pump operations, it is particularly useful for small electric motor systems.
By “small motors” it is meant to include such motors rated under 30 horsepower (hp), especially those in the 5 to 10 hp range. The reason for particular application to these motors relates to the overload tendency of such motors due to the additional torque required to overcome the binding caused by solid waste gathering between the back shroud 30 and the stationary back plate 28 as previously mentioned. The disclosed invention is certainly suitable for motors of greater than 30 hp, including large pumps in the 60 to 200 hp range, but such motors are less affected by power increases and are, therefore, less susceptible to going offline due to such an increase.
Continuing, the fluid enters the chamber 18 at the first or primary cutting zone where the fluid is subjected to a first shearing action between the impeller blades 31 and the components of the cutter bar plate 26, including the internal cutter groove 37, the shear fingers 39 and also the tooth of the cutter nut 47, which cuts against the ends of the shear fingers 39. From there, most fluid travels from the chamber 18 to the outlet port opening 16. Some of the fluid ends up at the second cutting zone where it goes through another shearing action between the insert cutter 24 and the cutting rib 40 and also between the rotating impeller hub and the upper cutting ring. These components should be carefully gapped to provide the most efficient and effective cutting of difficult material—i.e., material which is not readily broken, but must be cut with scissor like action. Eventually, the fluid in the second cutting zone is also delivered to the outlet port opening 16 for discharge.
While the present invention is exclusively described herein for use on a chopper pump, the inventors concede that it may have practical uses on other types of pumps as well. For example, a raised cutting rib may be used on a screw-centrifugal pump-currently sold as TRITON® pumps by Vaughan—or on vortex (i.e., recessed impeller) pumps to pump relatively “clean” sludge in a system. By “clean” it is meant that the sludge has no large debris to be chopped by the pump. Such sludge is still replete with fine fibers, such as hair, strands of fabric and the like. The use of a cutting rib exclusively for such pump systems would be useful.
The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While particular embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of applicants' contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.
The present application is a continuation-in-part of and claims priority to U.S. patent application Ser. No. 13/350,874, filed Jan. 16, 2012 and titled “Screw-Type Centrifugal Pump With Cutting Inserts,” which is a continuation in part of U.S. patent application Ser. No. 12/220,829, filed Jul. 29, 2008 and titled “Centrifugal Chopper Pump with Impeller Assembly,” now U.S. Pat. No. 8,105,017. The present application is also a continuation-in-part of U.S. patent application Ser. No. 13/273,452, filed on Oct. 14, 2011 and titled “Internal Cutter on Submersed Mixer,” which is a continuation of U.S. patent application Ser. No. 12/721,602, filed Mar. 11, 2010 and titled “Internal Cutter on Submersed Mixer,” now U.S. Pat. No. 8,118,244. The '017 patent, the '452 application, and the '244 patent are all hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12721602 | Mar 2010 | US |
| Child | 13273452 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13350874 | Jan 2012 | US |
| Child | 13492470 | US | |
| Parent | 12220829 | Jul 2008 | US |
| Child | 13350874 | US | |
| Parent | 13273452 | Oct 2011 | US |
| Child | 12220829 | US |
