The disclosed embodiments of the present invention relate to an improved design for a diffusion chamber for a centrifugal pump, as well as a centrifugal pump comprising such a diffusion chamber, especially one in which the diffusion chamber is in the nature of a volute. In the disclosed embodiments, the expanding cross-sectional area of the diffusion chamber along a length thereof is achieved by an increase of at least one of: the inwardly-extending width of the chamber in the radial direction and the height of the chamber, in the axial direction. There are a variety of applications for such pumps, particularly in commercial appliances.
The concept of a centrifugal pump is known in the art. Stated very generally, a centrifugal pump with a volute chamber has an impeller, which is typically vaned. When a drive source, typically an electrical motor, rotates the impeller, the pressure decrease from the rotation causes liquid to be sucked into a chamber in which the impeller is arranged, along a suction line that is typically co-axial with the drive source. The impeller rotation throws the liquid outwardly in a tangential manner, the liquid gaining velocity as it is moved outwardly by the impeller. Positioned radially beyond the impeller, the volute chamber has a smoothly increasing volume, terminating at a tangential discharge. As liquid moves around this volute, the velocity head of the liquid is converted to pressure head. Operation of a centrifugal pump is commonly plotted on a graph of total pressure head as a function of pump volumetric flow rate, or impeller speed, which is directly related to pump volumetric flow rate. A particular pump will always operate along this characteristic curve.
In the known art, the volute chamber has a generally constant height in the axial direction and is generally positioned symmetrically to a radial extension of a line defined by a midpoint of the impeller's thickness. To provide the increasing cross-sectional area, the radial extent of the volute chamber increases from the inlet of the volute chamber to the outlet, imparting a spiral shape to the volute chamber, when viewed axially. Indeed, the very term “volute” is derived from the Latin term for “scroll.”
In many applications, but especially with applications for pumping liquids, as in commercial appliances such as washing machines, it is desirable to provide a compact “footprint” to the pump, and especially the pump casing, in the radial direction. It is also desirable to provide a pump casing that is circular in the radial direction. It is also desirable to provide a pump casing in which the ratio of the impeller diameter to the outside pump casing diameter is as large as possible, since pump performance, both in terms of volume of liquid delivered and feet of total head, increases with impeller diameter.
This and other unmet objectives of the prior art are met by a casing for housing an impeller. The casing comprises a first casing element, a second casing element and means for sealingly mating faces of the casing elements intended for that purpose. An interior of the first casing element defines a portion of a chamber for the impeller, the impeller chamber portion being located proximate to the mating face. The second casing element has first and second interior portions. The first interior portion defines the remaining portion of the impeller chamber and is proximate to the mating face of the second casing element. The second interior portion defines a diffusion chamber in fluid communication with the impeller chamber.
In some embodiments, the casing also comprises an opening in the first casing element, co-axial with the impeller chamber, for connecting the impeller in the impeller chamber to a drive source external to the casing.
In some embodiments, a suction inlet in the second casing element, co-axial with the impeller chamber, communicates the impeller chamber with the exterior of the casing.
In some embodiments, the second casing element further comprises a radially-extending disk that separates the impeller chamber from the volute chamber. In some of these embodiments, the radially-extending disk has a diameter that is at least as large as a diameter of a base plate of the impeller. In these embodiments, a gap between a circumference of the radially-extending disk and an interior wall of the second casing element provides the fluid communication between the impeller chamber and the diffusion chamber. When the radially-extending disk and the interior wall are co-axial and circular, the gap is annular.
In some embodiments, the second casing element interior wall is located at a constant radial distance from an axis of the impeller.
In many of the embodiments, the second casing element has a tangential outlet that communicates the diffusion chamber with the casing exterior.
In the embodiments, the cross-sectional flow area of the diffusion chamber increases from a first end thereof to a second end, where the tangential outlet is located, the increase being smooth and monotonic.
In these embodiments, a fluid conduit through the casing is defined by, in this order, the suction inlet, the impeller chamber, the volute chamber and the tangential outlet.
In some embodiments, the sealingly mating means comprises a radially-extending circular flange at a circumferential edge of the mating face of each of the casing elements. Occasionally, a gasket will be interposed between the respective radially-extending circular flanges.
Further aspects of the invention are achieved by a centrifugal pump, comprising an impeller casing as described above and an impeller arranged for rotation in the impeller chamber.
Other aspects of the invention are achieved by a casing for housing an impeller, the impeller having a base plate that defines a radial direction of the casing, with an axial direction of the casing normal to the radial direction. The casing comprises a body in which the impeller is housed and a fluid conduit formed within the body. The fluid conduit comprises a fluid inlet, an impeller chamber, in which rotation of the impeller imparted velocity to fluid entering through the fluid inlet, a diffusion chamber for volumetrically expanding fluid received from a fluid communication with the impeller chamber along a length of the diffusion chamber, the diffusion chamber characterized by a cross-sectional area that increases from a first end to a second end thereof, the increase in cross-sectional area provided by expansion of the diffusion chamber in at least one of the radially inward direction and the axial direction; and a fluid outlet, communicating the second end of the diffusion chamber with an exterior of the body.
A better understanding of the disclosed embodiments will be obtained from a reading of the following detailed description and the accompanying drawings wherein identical reference characters refer to identical parts and in which:
The first casing element 20 is intended for attachment to the pump motor (not shown), typically by way of mounting feet 22, two of which are visible in
The depicted embodiment 10 shows both casing elements 20, 30 provided with radially-extending flanges 26, 36, respectively, by which the casing elements are mated together in a sealing manner. As depicted, each of the casing elements 20, 30 provide about one-half of the total volume that constitutes primary chamber 50, while all of the volume of diffusion chamber 60 is situated in the secondary casing element 30.
While the depicted embodiment shows radially-extending flanges 26, 36 that are circular, it will be known to those of skill in this art to provide variations on the means for sealingly mating the respective casing elements 20, 30. It will also be known to interpose a gasket or similar sealant between the flanges 26, 36 or other mating means.
The second casing element 30 is also provided with a suction inlet 34, through which fluid is drawn into the center of impeller 70. Accordingly, it is preferred to arrange suction inlet 34 so that it is concentric with the impeller 70 and the drive shaft, such that the liquid is directed onto the vanes 78. A separation disk 38 extends radially from the suction inlet 34. The separation disk 38, which has a diameter that is preferred to be at least as large as the diameter of impeller base plate 72, operates with a radially-extending interior wall of the first casing element 20 to define the primary or impeller chamber 50, which is essentially cylindrical.
At the radially outward edge of separation disk 38, a space 80, which is in this case an annular space, is formed between the disk and an interior axial wall 40 of the second casing element. The annular space 80 communicates the impeller chamber 50 to the diffusion chamber 60, and has a width of one to two times the distance from the first face 74 to the distal end of the vanes 78.
Reference is now made to
Referring now to both
Viewing the disclosed embodiment of
Industrial applicability of the device described herein is found in a number of devices. One example is a pump housed in an industrial/commercial dishwasher and used for pressurizing the hot cleaning water.
Having shown and described a preferred embodiment of the invention, those skilled in the art will realize that many variations and modifications may be made to affect the described invention and still be within the scope of the claimed invention. Thus, many of the elements indicated above may be altered or replaced by different elements which will provide the same result and fall within the spirit of the claimed invention. It is not the intention, therefore, to limit the invention only as indicated by the scope of the claims.
This application is a non-provisional of, and makes claim of the benefit of priority to, U.S. provisional patent application Ser. No. 61/082,711, filed 22 Jul. 2008, which is incorporated by reference as if fully recited herein.
Number | Date | Country | |
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61082711 | Jul 2008 | US |