PRIORITY CLAIM This application claims priority to Canadian patent application 2,706,306, filed on Jun. 3, 2010, and this application is also a continuation-in part of U.S. application Ser. No. 12/483,850, filed on Jun. 12, 2009, and hereby claims priority thereto and which applications are incorporated by reference in their entirety.
FIELD OF THE INVENTION The present invention relates to centrifugal pumps, more particularly, the housing design for a magnetically driven centrifugal pump, and to a novel impeller design.
BACKGROUND OF THE INVENTION Centrifugal pumps use an impeller and volute to create the partial vacuum and discharge pressure to move water through the pump. A centrifugal pump works by the conversion of the rotational kinetic energy, typically from an electric motor or turbine, to an increased static fluid pressure. An impeller is a rotating disk coupled to the motor shaft within the pump casing that produces centrifugal force with a set of vanes. A volute is the stationary housing in which the impeller rotates and that collects and discharges fluid entering the pump. Impellers generally are shaft driven, have raised radially directed vanes or fins 1 that radiate away form the eye or center 3 of the impeller, and channels 2 are formed between the vanes. See FIGS. 10 and 11. As the impeller turns, centrifugal force created by the rotating vanes pushes fluid away from the eye 3 where pressure is lowest, to the vane tips where the pressure is highest. Water is directed into the pump via input ports, generally positioned near the impeller eye or center 3, and fluid flows within the pump is generally in the channels 2 between the vanes 1. The pressurized fluid is directed by the volute to the discharge or outlet location of the pump.
Small pump applications, for instance for use in footspas or aquariums, generally are either propeller driven axial pumps, or centrifugal impeller type pumps. Smaller pumps are generally more inefficient, creating heat that must be dissipated. A novel impeller design and housing design are presented that allows for both heat dissipation and smooth flow characteristics suitable for a small pump.
SUMMARY OF THE INVENTION The invention is the combination of a magnetically driven pump, with a motor and a basin, where the motor and pump mount on opposite sides of a mounting plate through an opening in the sidewall of the basin. Mounting plate properly aligns the driven magnet in the pump with the driving magnet on the motor.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front perspective view of one embodiment of the magnet retainer housing.
FIG. 2 is a rear perspective view of the embodiment of the magnet retainer housing of FIG. 1
FIG. 3 is perspective view of a magnetically driven pump system.
FIG. 4 is a cross section through one embodiment of the pump body.
FIG. 5 is a front exploded view of the magnet housing of FIG. 1.
FIG. 6 is a rear exploded view of the magnet hosing of FIG. 1.
FIG. 7A is a front perspective view of one embodiment of the pump body.
FIG. 7B is a partial cutaway view of the pump body of FIG. 7A.
FIG. 7C is a top view of the interior of the pump body of FIG. 7A.
FIG. 8 is a cross section through one embodiment of the magnet retainer housing.
FIG. 9A is a perspective view of one embodiment of the impeller showing fluid flow lines.
FIG. 9B is a cross section through a geometric figure depicting one embodiment of a sloped region.
FIG. 9C is a cross section through a geometric figure depicting a second embodiment of a sloped region, with slightly reduced stability.
FIG. 9D is a cross section through a geometric figure depicting a third embodiment of a sloped region.
FIG. 10 is a perspective view of a prior art vaned impeller.
FIG. 11 is a top view of the impeller of FIG. 10.
FIG. 12 is a perspective view of the rear of one embodiment of a pump impeller.
FIG. 13A is a top view of one embodiment of circle geometric figures, with dimensions disclosed for a small pump application.
FIG. 13B is a side cross sectional view of the embodiment of FIG. 13A showing dimensions for a particular embodiment.
FIG. 13C is an exploded view of one embodiment of a pump with a floating inner assembly.
FIG. 14A is an exploded view one embodiment of mounting a motor through the side wall of a spa using a mounting plate.
FIG. 14B is an assembled view of the motor and mount plate of FIG. 14A.
FIG. 15A is a rear prospective view of the motor and mount plate of FIG. 14.
FIG. 15B is a rear view of the motor and mount plate of FIG. 14.
FIG. 16A is an exploded front view of the motor/mount plate and pump housing.
FIG. 16B is an exploded rear view of the motor/mount plate and pump housing.
FIG. 17 is a cross section though a spa showing the motor and pump.
DETAILED DESCRIPTION OF THE INVENTION As shown in FIG. 3, the pump system is a magnetically driven pump, such as described in U.S. Pat. No. 7,393,188 (hereby incorporated by reference). The magnetically driven pump system is quiet, efficient, and has a small foot print in the application interior. The magnetically driven pump system includes a driving motor 50 which turns a motor shaft and a driving motor magnet body 51 attached to the motor shaft. The motor magnet 51 is positioned adjacent to the exterior wall 41 of the application enclosure. Adjacent to the motor and driving magnet on the interior wall of the application is the pump, including the pump body 10.
FIG. 4 shows an embodiment of the pump body 10. Shown are the pump front 8 and rear 9 sections, creating a pumping chamber 101 therebetween. In a pump suitable for a spa environment, it is preferred that the pump inlet ports 7 and outlet or discharge ports 6 be located on the pump front portion 8 (see FIG. 7A). For other applications, the discharge port(s) may be located elsewhere, with pump output flow directed by a suitably located discharge diffuser or volute, for instance, for side discharge.
Located in the chamber 101 is a magnet retainer housing 17, comprising a retainer bottom portion 19, and a retainer top portion 18. Impeller 30 is attached to the magnet retainer top portion 18, here shown as integrally molded into the top portion. The bottom and top retainer portions 19 and 18 couple together creating an interior space or volume there between. Located in this retainer interior space is the pump magnet 20. In this embodiment, the magnet 20 is firmly gripped in the interior of the magnet retainer housing 17 (there may be a snap body to snap the magnet in the magnet housing), so that rotation of the magnet 20 causes rotation of the impeller 30, creating a rotative body. The magnet retainer housing may be dispensed with if the impeller is directly attached to the magnet. The magnet retainer housing 17 (or the magnet and impeller if the housing is not used) floats in the interior 101 of the pump housing, as later described. The driven pump magnet 20 and driving motor magnets 51 are of sufficient strength to be magnetically coupled through the application wall. Hence, as the motor magnet rotates, by action of the motor, the pump magnet also rotates by the coupling of the motor magnet with the pump magnet, thereby rotating the impeller. To assist in coupling, each magnet may have multiple N and S domains, where opposite domains face each other—for instance, an “N” domain on the motor magnet that is on the surface facing the pump magnet will align with an “S” domain on the driven pump magnet on the surface of the pump magnet that faces the motor magnet. At least two domains per magnet are desired on opposing faces.
One novel figure of the pump is the means to support the rotative body (here the magnet retainer housing 17) in the pump body. The interior face of the rear portion 9 of the pump body 10 has a center cutout or depression 22, shown lined with a bushing 23 to reduce wear (see FIG. 4), forming a rotation support. The bushing is optional. This support 22 is centered on the impeller 30; that is, the axis of rotation of the impeller 30 aligns with the cutout or support 22 on the interior face of the bottom portion 9 of the pump body 10. The exterior bottom face of the rotative body, here the bottom portion 19 of the magnet retainer housing 17, is generally a flat surface. However, in one embodiment, positioned on this face is a raised shaped rotation center 80 that aligns with the rotation support 22. As shown, the raised rotation center 80 is curved (here, the rotation center 22 is a curved bolt head, forming a portion of a hemisphere). The rotation center 80 has a diameter that is slightly larger than that of the diameter of rotation support 22 diameter. Hence, the rotative body's (magnet retainer housing 17) rear portion 19 is supported above the rear portion 19 of the pump body 10 (in one embodiment, about an ⅛ inch above the face) by the rotation center 80, supported in the rotation support 22. The magnet retainer housing 17, while supported by the housing is detached from the housing, thus the rotating body thus substantially floats in the interior of the pump body 10. When the rotation center 80 includes an opening allowing fluid flow, the rotative body will essentially hydroplane in the rotation support. The rotation center 80 is shaped to allow the magnet retainer housing 17 to pivot in the rotation support 22. Alternatively, the rotation support 22 may be a curved depression surface (such as hemispherical shape, or a truncated hemisphere), of larger diameter than the rotation center, with the rotation center being a cylinder or a curved surface but of sufficient length to allow the magnet retainer housing 17 to pivot in the interior 101 of the pump body 10 about the rotation center 80. Alternatively, the rotation support 22 may be a raised surface, with the rotation center being a depression or cutout in the magnetic retainer housing, with suitable diameters to allow the housing's axis of rotation to pivot about the rotation support 22. The ability of the rotative body, here the magnet retainer housing 17, to pivot about the rotation support 22 allows the driven pump magnet 20 to tilt or pivot its axis of rotation to better align with the axis of rotation of the driving pump magnet 51. The axis of rotation may be tilted or cocked (as measured from a perpendicular from the rear of the pump housing) by several degrees (0-5 degrees, with a upper range of at least 2-3 degrees). Hence, if the plane of rotation of the driven motor magnet 51 is slightly misaligned from that of the rear of the pump body 10 (i.e., not parallel), the rotative body (here the rotating magnet retainer housing 17) will pivot about the rotation support 22 until good magnetic coupling and alignment is achieved between the two magnets (or the edge of the magnet retainer housing 17 contacts the interior wall of the chamber 101).
In the embodiment shown (see FIG. 4), the center cutout 22 forms a through opening in the pump body rear portion 9, allowing fluid communication through the center cutout opening 22. This configuration is preferred, as fluid will flow through the opening 22, reducing the friction caused by the rotation of the rotation support 80 in the center cutout 22. The magnet retainer housing thus “floats” in the interior chamber due to hydroplaning. Fluid transport through this opening 22 also removes heat, providing for longevity of the pump. If the center cutout 22 is an opening in the housing, the housing rear portion 9 should have standoffs 5 to support the rear portion 9 of the pump body 10 away from the application wall so the opening 22 is not blocked by contact with the application wall (see FIG. 12).
A preferred means to allow the magnet retainer housing 17 to tilt about the rotation support 22 and allow for fluid transport through the pump housing is to place an inwardly shaped depression 83 in the center rear of the magnet housing 19 to accommodate a bearing 93, preferably such as a ball bearing having the ability to couple magnetically but not possessing a domain (e.g. high iron content). See FIG. 14C. The depression 83 is shaped to match the portion of the bearing 93 that will reside in the depression 83. Preferably, at least ½ of the bearing (more preferred, ⅔ of the bearing) will protrude above the rear face 19 of the magnet retainer housing 17. For instance, with a spherical ball bearing, the depression will be about ⅓ of spherical surface, with the curvature similar to the curvature of the ball bearing. The center cutout 22 is aligned with the depression in the housing. The center cutout will accommodate a portion of the bearing which protrudes from the rear face of the magnetic housing (or if a bushing 23 is employed, the bushing will accommodate a portion of the bearing). The center cutout 22 may also be shaped to accommodate a portion of the bearing 93 (for instance, the opening 22 may be surrounded by a curved annular depression, where the curvature accommodates the ball bearing. Such curvature is not preferred, as will be later described. Preferably, the center cutout 22 should be smaller in diameter than the bearing 93, so that less than ½ of the bearing will reside within the center cutout 22 (more preferably, about ⅓ or less of the bearing).
As the motor spins, so too will the magnet retainer housing 17 (the magnet 20 is preferably fixed in position within the housing 17) due to coupling of the pump and motor magnets. The end result is a pump internal assembly (magnet retainer housing, impeller and magnet) that has the ability to tilt or pivot within the pump housing 10 about the bearing 93. This pivoting action allows the pump magnet to align substantially parallel with the motor magnet, allowing single arc field coupling between the motor magnet and pump magnet. Further, in operation, as water is pumped into pump housing through the rear cutout 22, the pump internal assembly hydroplanes, resulting in the entire pump inner assembly substantially “floating” within the interior of the pump housing, thereby producing a very low friction pump. In the preferred embodiment, the bearing 93 is magnetic and is retained in the depression 83 in the rear of the magnet retainer housing 17 by magnetic forces. When a magnetic bearing is used, the depression in the rear surface of the housing is preferably lined to prevent wear, such as with non-magnetic stainless steel lining, a hard plastic lining, or otherwise. In one embodiment the entire rear surface of the magnetic housing may be covered with a lining, such as with a 4-5 mil non-magnetic stainless steel lining. As an alternative to a separate bearing, the rear face of the magnet retainer housing 17 may be shaped with a center projection or protrusion, such as a hemispherical shape protrusion, positioned to align with the center cutout 22.
The pump also has a novel impeller 30. The surface of the generally circular impeller 30 shown in FIG. 1 does not have radial vanes, but instead includes several raised geometric FIG. 11E having areas interior to the perimeter or edge of the geometric figures and disposed on the surface of the impeller 30. The geometric FIG. 11E are offset from the axial center or eye 31 of the impeller surface, leaving a substantially unobstructed eye. As shown, the impeller has at least three geometric FIG. 11E (here circles) being equally distributed about a periphery or circumference of the impeller. That is, for the number of figures “n”, the circular impeller can be divided into “n” regions (triangular pie shaped areas with the point of the pie at the center) where each region is congruent to every other region (see the three regions dashed depicted in FIG. 13A. Each geometric FIG. 11E has a raised perimeter or edge having a leading portion 11A, opposing a trailing portion 11B, and a proximal portion 11C (closest to the axial center 31), and an interior area 13 between the leading, trailing and proximal portions, where the area interior is at a lower height than the raised perimeter or edge 11. It is preferred that the leading portion 11A has a curvature that curves away from the direction of rotation, while the trailing portion 11B has a curvature that curves into the direction of rotation (but not required, for instance, if the geometric FIG. 11E resembles a kidney bean shape). Hence, it is preferred that the curvature of the leading portion and trailing portion be opposed. The curvature of the leading and trailing portions are not required to be constant (for instance, an oval shaped figure), nor does the curvature of the leading portion have to match or mirror that of the trailing portion. The proximal portion 11C connects the leading portion and trailing portion to create a substantially continuous perimeter or edge, and preferably is also a curved edge. As shown, the interior area 13 is at a height lower then the edge (here at the height of the surface of the impeller exterior to the figures). Each geometric FIG. 11E is separated from the others, creating channels between the figures. Dimensions of one particular impeller embodiment is shown in FIG. 13.
The raised edge 11 may also include a distal portion 11D (closest to the perimeter of the impeller surface and furthest from the impeller center), thereby forming a substantially closed geometric FIG. 11E, such as the circle shaped edge or perimeter shown in FIG. 1. A substantially closed geometric edge 11 is preferred if the pump discharge port(s) face the same direction as the input port(s), as later described. Substantially continuous means that the edge may have minor openings, such as an 1/16-⅛ opening in a ¾ inch diameter circle, as such minor openings do not substantially alter the pumping characteristics of the geometric FIG. 11E (wider openings may be tolerated near the center of the pump, as the fluid velocities are reduced here). Substantially closed means the geometric FIG. 11E has a substantially continuous perimeter and the perimeter generally encloses an area.
As shown, the raised edge 11 also has a sloped portion 12, where the height of the edge decreases away from the eye 31 or axial center of the impeller surface—that is, the highest portion of the raised edge 11 is closer to the eye 31 of the impeller 30, while the lowest portion is closer to the outer edge of the impeller 30. In other words, the slope decreases from the proximal portion to the distal portion, and it is preferred that the slope decrease monotonically (this allows for flat spots near the distal and proximal portions, or elsewhere if desired). That is, both the leading and proximal portions should slope downwardly (preferably monotonically), but the slopes of the two portions do not have to match, although it is preferred that the leading portion and trailing portion be a mirror image (i.e. match). See FIGS. 9B, 9C and 9D for three slopes for the circles). FIG. 9A shows the figure sloped over the entire figure, with a constant slope; FIG. 9B shows the figure with an initial flat spot near the eye, sloping off thereafter at a constant slope; FIG. 9C shows a varying slope over the entire figure, where shape of the edge approximates log(x) or sqrt (X)(x>1) (another shape would be that represented by the negative sloped surface of 1/x). As shown in FIG. 9B, the sloped portion 12 of the edge does not have to extend over the entire length of the edge. A sloped portion is not required on the raised edge, but is preferred. The height of the leading portion does not need to be a mirror image of that of the trailing portion, although it is preferred. Finally, for an impeller that is tilted in the pumping chamber, it is preferred that the edges of the figures decline in height quickly (such as in FIG. 9A, or where the edge of the figures approximates 1/x for instance). As the figures are above the face of the impeller, the figures, with sufficient tilt to the impeller, could contact or rub against the front interior surface of the pumping chamber, an undesired result. For a shaft driven impeller, where impeller tilt is not possible, the shape represented by FIG. 9D is preferred.
As shown in FIG. 9A, the geometric FIG. 11E are substantially circles, the preferred embodiment, although other curved geometric FIG. 11E could be used. Preferably, geometric FIG. 11E having leading portions and trailing portions with the curvature of these two being opposed, are preferred. Preferably the trailing portion curvature is concave to the direction of rotation, with the leading portion curvature being convex to the direction of rotation (i.e., from the center of the figure, the leading and trailing portions appear concave). For instance, geometric FIG. 11E having teardrop shapes (with the broad part of the teardrop near the eye of the impeller) or wide oval shapes (with the long axis of the oval along a radial line from the center of the impeller) will give certain of the desired flow characteristics provided by circle geometric FIG. 11E. Straight line segmented geometric figures are not preferred as two straight line segments create potential turbulence generated at the intersection or join of two line segments, particularly on the trailing edge.
As shown in the embodiment of FIG. 1, the distal portion 11D of the geometric FIG. 11E is also raised above the impeller surface 30 and the interior area. Water pumped through the interior region 13 of the raised perimeter, when encountering the distal portion 11D, will be given a velocity component perpendicular to the impeller surface. Such a velocity component is preferred when the outlet ports are directed perpendicular to the impeller surface, as in the embodiment shown in FIG. 7A. Also as shown in FIGS. 7C and 7B, the interior face of the rear portion 90 of the pump body 10, has two arcuate volute channels 40 formed adjacent the periphery of the impeller. Each volute channel encompasses about 180 degrees with the widest part of the volute terminating near the outlet ports 6. Each volute thus helps channel fluids exiting the impeller to one of the outlet ports 6.
Flow patterns using circular geometric figures are depicted in FIG. 9A. As shown, fluid is drawn in from the input port(s) into the eye or center region 31 of the impeller by the reduction in pressure near the impeller eye resulting from rotation of the geometric FIG. 11E. The smooth interior face 11G of edge 11 directs water outwardly through the interior region 13 of the geometric FIG. 11E. The velocity of fluid directed outward in the channels between the geometric FIG. 11E is less then that of waters exiting the impeller through the interior of the geometric FIG. 11E, as the discharge area is greater at the channel periphery than it is through the interior of the geometric FIG. 11E. Additionally, the channels are not as efficient as capturing and accelerating fluid as is the concave curvature of the trailing portion of a figure.
The pressure differential across the impeller surface having geometric figures (i.e. from the center to the periphery) is not as great as that created by a radially vane impeller, and hence the flow produced by the present impeller is believed to be slower, smoother and less turbulent and more suited for small applications, such as a spa or aquarium. Additionally, the edge or perimeter forming the rotating figure preferably presents less of a profile (i.e., it is not as high) with distance from the center of the impeller. Hence, the rotating geometric FIG. 11E has less direct fluid contact with fluid away from the impeller eye, providing for smoother discharge of water from the impeller surface. Additionally, this decrease in contact surface area between the rotating impeller and flowing fluid, with distance from the eye, produces less drag on the impeller than would be present without the sloped region. This reduction in drag helps keep the driven pump magnet aligned with the driving motor magnet, which is not subject to any fluid drag force. To assist in directing the flow of water away from the pump, shaped nozzles 2007 may be mounted on the discharge ports. One such shaped nozzle 2007 is shown in FIG. 13C and FIG. 15A. The nozzle has a shaped opening 2008 (depicted as an oblong rectangular opening). Preferably, the nozzle is rotatably mounted to the discharge port 6. The nozzle face may be constructed an angle α, (see FIG. 17) such as 20-45 degrees, to assist in directionally directing pumped water away from the pump in a desired selected direction.
Finally, any raised geometric figure on an open rotating impeller will form a bow wave generated by the top edge of the rotating figure. The sloped design of the applicant's geometric figure helps shape a bow wave that is more even and better formed with less turbulence. The bow wave generating figure edge reduces in height with distance from the center of impeller, helping to counter the effects of an increase in velocity of the figure with distance from the impeller center. The impeller is shown on a magnetically driven pump, but it could be used on any pump where low turbulence is desired. That is, the impeller may be adapted to be driven by a motor directly (shaft driven) or indirectly, for instance, magnetically driven.
As described, the pump body may be held in place adjacent the motor through the spa wall by magnet forces alone, although this is not preferred. The pump may be fixed or coupled to the spa via a handle, arm or other mechanical coupling of the pump to the spa. However, if magnetic forces alone are used, or even a mechanical couple of the pump to the spa, alignment problems between the pump magnet and the motor magnet are common, and particularly troublesome when the spa sidewall is curved or cut at an angle. To help alleviate misalignment issues, it is desired to allow the pump magnet to tilt until proper alignment is made with the motor magnet, as described above with a “floating” pump magnet. An alternative arrangement is to mechanically couple the motor to the pump housing, thereby forcing alignment between the pump magnet and motor magnet. To mechanically couple the motor and pump, holes must be cut into the spa sidewall.
One method of mechanically coupling the pump to the spa and motor is shown in FIGS. 14A and 14B. Shown is a portion of the spa sidewall 1000, with an opening 1001 cut therethrough. A mounting plate 2000 sealing couples against the opening 1001 in the spa sidewall 1000. The mounting plate 2000 may be glued (such as using silicon caulk), or epoxied in place, or may be coupled via a gasket and mounting nuts to a rear mounting ring positioned on exterior of the spa wall (not shown), and should seal against the spa sidewall. As shown, the mounting plate 2000 has four openings 2001 through which bolts 2005 are inserted to couple to the motor housing 3000. The mounting plate 2000 front face also has several projections 2002 used to couple the pump housing to the mounting plate 2000.
Details of the mounting plate 2000 are shown in FIGS. 15A and B. As shown, the rear or exterior face of the mounting plate has a series of standoffs 2003 around the periphery of the mounting plate, that are positioned to interface with the motor housing 3000. The mounting bolts 2005 couple to the motor housing 3000 mounting face through these standoffs 2003. The standoffs 2003 provide for even contact of the mounting plate 2000 to the mounting face of the motor housing 3000, and allow the motor magnet 3001 to be placed between the standoffs 2003 and adjacent the underside of the mounting plate 2000 for efficient coupling to the pump magnet. As shown in FIG. 14A, the motor may have an additional support on the exterior surface of the spa to avoid unnecessary flexing of the mounted motor/mounting plate with respect to the spa sidewall. As shown, one such support is a brace 4000 that mounts to the motor and spa exterior sidewall.
The pump housing 5000 has an interior and exterior face, with rear facing projections, the coupling members 5002, on the interior face of the pump housing (the side adjacent the basin). These projections are hollow, and allow the pump housing projections or coupling members 5002, to couple (here by snapping into place) with the mounting member 2002 on the mounting plate 2000, as depicted in FIGS. 16 and 17. Preferably, the pump housing projections 5002 are long enough so that the interior face back portion 5003 of the pump housing 5000 (wherein pump magnet is located) remains in fluid communication with the exterior face of the of the pump housing 5000 (that is, the center of the interior face near 5010 is not flush against the mounting plate 2000) to allow water to be pumped through the opening 5010 in the rear of the pump housing 5000. Other means to couple the pump housing 5000 to the mounting plate 2000 can be used, for instance, by having the mounting member 2002 on the mounting plate 2000 be a depression or slot into which the coupling member 5002 is inserted or snapped into place. This method of mounting a pump can also be used with a disposable spa liner, where the pump housing snaps into position on the mounting plate with a liner positioned between the pump housing and mounting plate.
The combination of pump housing 5000 mechanically coupled to the mounting plate 2000 which is mechanically coupled to the motor housing 3000 forces alignment of the pump and motor, and hence the pump magnet and motor magnet. In this embodiment, it is preferred that a hole or aperture be cut in the spa sidewall to accommodate the mount and mounting plate (preferred). A close alignment may be made without a large cutout or hole opening, if the mounting plate is still mechanically coupled (such as by long bolts) to the motor housing through small openings or apertures through the spa sidewall (such as four small openings to accommodate 4 bolts through the sidewall). This is not preferred.
