Abstract:
Embodiments of the invention provide an impeller and a method of producing the impeller. The impeller includes a first molded piece coupled to a second molded piece. The first molded piece includes impeller vanes, a motor hub, a nose, and an eye. The second molded piece includes a cover and a hole through the cover. The cover is coupled to the impeller vanes around the motor hub so that the motor hub extends through the hole.

Description:
BACKGROUND 
       [0001]    Conventional plastic impellers are constructed in two parts, often due to the limitations of injection molding and the specific geometries required. As shown in  FIGS. 1-4 , a conventional plastic impeller  10  includes a first piece  12  with impeller vanes  14 , a back plate  16 , and a motor mounting feature  18  (e.g., a motor hub) integrally molded together. The conventional plastic impeller  10  also includes a second piece  20  (e.g., a cover or a shroud) including an inlet nose  22  and an eye  24 . 
         [0002]    Conventional fabrication processes require a minimum of two secondary operations to form a complete impeller  10 . First, the first piece  12  and the second piece  20  are mechanically bonded together. Second, the nose  22  must be machined to be concentric to the hub  18  (e.g., to a specified value A, as shown in  FIG. 3 ). Conventional bonding processes, such as ultrasonic, vibration, hotplate adhesives, etc., use part-holding fixtures. As a result, these processes require clearances in the fixtures and their mating impeller parts, as well as clearances associated with aligning the fixtures relative to each other, in order to maintain concentricity between the hub  18  and the nose  22 . Bonding processes that involve vibration and/or part movement introduce additional issues with regard to maintaining concentricity. General wear from use of the fixtures further impairs the concentric relationship between the hub  18  and the nose  22 . The resulting concentricity issues are corrected by machining additional clearances into the fit between the nose  22  and a wear ring  26  of a diffuser  28 , as shown in  FIG. 4  (e.g., by changing value B in  FIG. 3 ). When the impeller  10  is rotated by an electric motor at relatively high speeds, these additional clearances provide room for vibration. This can result in potential bearing damage, as well as unwanted noisy operation. In addition, these clearances provide room for internal leakage during the pumping process, as shown in  FIG. 4 , which reduces the mechanical efficiency of the pump. 
       SUMMARY 
       [0003]    Some embodiments of the invention provide an impeller including a first molded piece coupled to a second molded piece. The first molded piece includes impeller vanes, a motor hub, a nose, and an eye. The second molded piece includes a cover and a hole through the cover. The cover is coupled to the impeller vanes around the motor hub so that the motor hub extends through the hole. 
         [0004]    Some embodiments of the invention provide a method of assembling an impeller. The method includes molding a first piece including impeller vanes, a motor hub, a nose, an eye, and a front shroud. The method also comprises molding a second piece including a cover and a hole through the cover, and coupling the first piece to the second piece by ultrasonic welding the cover to the impeller vanes around the motor hub so that the motor hub extends through the hole. 
         [0005]    Some embodiments of the invention provide a pool pump including a diffuser, a plastic impeller, and a wear ring. The plastic impeller is positioned adjacent to the diffuser and includes a first piece coupled to a second piece. The first piece of the impeller includes impeller vanes, a motor hub, a nose, and an eye integrally molded together. The wear ring is positioned between an outer circumference of the nose and an inlet portion of the diffuser. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a perspective view of a prior art impeller. 
           [0007]      FIG. 2  is an exploded perspective view of the prior art impeller of  FIG. 1 . 
           [0008]      FIG. 3  is an exploded side view of the prior art impeller of  FIG. 1 . 
           [0009]      FIG. 4  is a partial side cross-section of the prior art impeller of  FIG. 1  assembled with a diffuser. 
           [0010]      FIG. 5  is an exploded perspective view of an impeller according to one embodiment of the invention. 
           [0011]      FIG. 6  is an exploded perspective view of a pump for use with the impeller of  FIG. 5 . 
           [0012]      FIG. 7  is an exploded side view of the impeller of  FIG. 5 . 
           [0013]      FIG. 8  is a perspective view of a piece of the impeller of  FIG. 5 . 
           [0014]      FIG. 9  is a partial side cross-section of the impeller of  FIG. 5  assembled with a diffuser. 
           [0015]      FIG. 10  is a perspective view of another piece of the impeller of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
         [0017]    The following discussion is presented to enable a person skilled in the art to make and use embodiments of the invention. Various modifications to the illustrated embodiments will be readily apparent to those skilled in the art, and the generic principles herein can be applied to other embodiments and applications without departing from embodiments of the invention. Thus, embodiments of the invention are not intended to be limited to embodiments shown, but are to be accorded the widest scope consistent with the principles and features disclosed herein. The following detailed description is to be read with reference to the figures, in which like elements in different figures have like reference numerals. The figures, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of embodiments of the invention. Skilled artisans will recognize the examples provided herein have many useful alternatives and fall within the scope of embodiments of the invention. 
         [0018]      FIG. 5  illustrates an impeller  30 , according to one embodiment of the invention, for use in pumps and/or fans. The impeller  30  can be a plastic impeller with a closed, single end suction design. In one embodiment, as shown in  FIG. 6 , the impeller  30  can be used in a pool pump  32  for commercial pools and/or residential pools. As shown in  FIG. 6 , the pool pump  32  can include the impeller  30 , a clamp  34 , a cover  36 , o-rings  38 , a strainer basket  40 , a volute casing  42 , a drain plug knob  44 , nuts  46 , set screws  48 , a stationary diffuser  50 , seals  52 , a gasket  54 , a seal plate  56 , washers  58 , bolts  60 , at least one foot  62 , a foot insert  64 , and a motor  66 . The volute casing  42  and the seal plate  56  can be coupled together to enclose the impeller  30  and the diffuser  50 . A shaft  68  of the motor  66  can extend through the seal plate  56  and can be coupled to the impeller  30  to rotate the impeller  30  during operation of the pool pump  32 . 
         [0019]    In some embodiments, as shown in FIGS.  5  and  7 - 9 , the impeller  30  can include a primary piece  70  and a secondary piece  72 . The primary piece  70  can include substantially critical concentricity features and the secondary piece  72  can include substantially non-critical concentricity features. More specifically, the primary piece  70  can include impeller vanes  74 , a hub  76 , a nose  78 , an eye  80  (as shown in  FIG. 9 ), and a front shroud  82 , and the secondary piece  72  can include a back shroud, or cover  84 . The cover  84  can include a hole  86  through which the hub  76  extends. The hub  76  can be coupled to the motor shaft  68  for operation of the impeller  30 . 
         [0020]    In some embodiments, both pieces  70 ,  72  can be separately molded (e.g., by injection molding or a similar process), and then coupled together. As a result of the impeller vanes  74 , the hub  76 , and the nose  78  being molded in a single piece, the hub  76  can reference the impeller nose  78  to be concentric to threads of the motor shaft  68 . Further, the motor shaft  68  can also be concentric to the impeller vanes  74  as well as the impeller eye  80 . The concentricity can be controlled by the tolerances associated with the plastic resin and the molding process (e.g., to a specified value A′, as shown in  FIG. 7 ), rather than the mechanical joining process, as it is done with conventional plastic impellers. This can reduce the manufacturing cost in joining the two parts together, as well as provide a more accurate process for consistent, reproducible parts. In addition, due to the greater control over the concentricity of the impeller eye  80  relative to an axis of rotation on the motor shaft  68 , machining around the eye  80  of the impeller, as is often required with conventional impellers, may be unnecessary, thus saving operator time and manufacturing costs. 
         [0021]    In some embodiments, the edges  88  of the impeller vanes  74  (as shown in  FIG. 7 ) can be coupled to the cover  84  along grooves  90  (as shown in  FIG. 8 ), for example, by ultrasonic welding or a similar process. As shown in  FIGS. 8 and 9 , the cover  84  can be substantially flat. As a result, the point of coupling (i.e., the weld joint) between the edges  88  and the grooves  90  can be along a substantially flat plane. The ultrasonic welding process can be more precisely controlled due to the weld joint being along a flat plane  91 , in comparison to the non-flat welding plane of conventional impellers. For example, as shown in the conventional impeller of  FIG. 4 , the impeller vanes  14  are mounted to the shroud  20 , resulting in a welding plane  93  that is angled toward the nose  22  by an angle theta. As shown in  FIG. 9 , the flat welding plane  91  of the impeller  30  of some embodiments of the invention can result in a simplified alignment of the two pieces  70 ,  72  during assembly, as well as more consistent and efficient impellers. More specifically, since the depth of the weld is along a single plane  91  (i.e., rather than multiple angled planes), the welding horn can be more consistent. Also, a flat joint is easier to seat into a welding fixture and control, which can result in less flash into the flow channel of the impeller  30 . 
         [0022]    As shown in  FIGS. 5 and 9 , the cover  84  can be coupled to the primary piece  70  around the hub  76  so that the hub  76  extends through the hole  86  in the cover  84 . A main purpose of the cover  84  can be to improve pumping performance by preventing vane bypass and to reinforce the impeller vanes  74  so that they do not flex under the stress of operation. However, the cover  84  may not be vital to the rotation of the impeller  30 , resulting in the cover  84  being a substantially non-critical concentricity feature of the impeller  30 . More specifically, the impeller  30  may be able to operate in a pump without the cover  84 . In conventional impellers, alignment and concentricity between all pieces is vital to their rotation and they are unable to rotate without both halves assembled. 
         [0023]    During use in a pump, such as the pump  32  shown in  FIG. 6 , the impeller  30  can be positioned adjacent to the diffuser  50 . In operation, fluid can follow a flow path from an inlet  94  of the volute casing  42 , through the strainer basket  40 , through an inlet  95  of the diffuser  50  (as shown in  FIG. 9 ), through the impeller eye  80  (as shown in  FIG. 9 ), and radially outward from the impeller vanes  74  toward an outlet  96  of the volute casing  42 . As shown in  FIG. 9 , a stationary wear ring  92  can be positioned between the rotating nose  78  of the impeller  30  and the stationary diffuser  50 . As shown in  FIGS. 4 and 9 , the clearance between the impeller nose  22  or  78  and the diffuser wear ring  26  or  92  provides a primary internal leakage path  98 . The size of this primary internal leakage path  98  can have a significant impact on a pump&#39;s operating efficiency because that gap allows bypass from the high pressure side of the discharge back to the inlet, requiring the bypass liquid to be pumped twice. 
         [0024]    For example, as described above, conventional impellers  10  must be machined around the nose  22  to achieve proper concentricity with the motor hub  18 . This machining causes a greater and/or uneven clearance gap  98  between the nose  22  and the wear ring  26 , as shown in  FIG. 4 , causing vibration during rotation of the impeller  10  and increased wear on motor bearings as well as the wear ring  26 . In some embodiments of the invention, the clearance (i.e., the primary leakage path  98 ) between the nose  78  of the impeller  30  and the stationary wear ring  92  can be reduced due to the control over the runout and concentricity, as described above. By tightly controlling the concentricity of the impeller nose  78  to the impeller hub  76  (e.g., by molding the substantially critical concentricity features in a single piece  70  and removing the need to machine the nose  78 ), the clearance between the impeller  30  and the wear ring  92  can be minimized (as shown in  FIG. 9  in comparison to  FIG. 4 ). This can result in less internal leakage and a more efficient hydraulic system (e.g., due to less energy being wasted pumping bypass liquid). Also, the tighter concentricity control can allow the proper balance of the impeller  30  during rotation and reduced vibration, allowing a reduction in noise and less wear on motor bearings. 
         [0025]    In some embodiments, the impeller vanes  74  can extend outward from the front shroud  82  and/or inside the nose  78 . In addition, as shown in  FIG. 10 , leading edges  100  of the impeller vanes  74  can extend from inside the nose  78  to the motor hub  76 . The leading edges  100  of the impeller vanes  74  can be close to or approximately parallel with an axis of rotation  102  of the impeller  30 . In some embodiments, the leading edges  100  can be slightly sloped inward toward the center of the hub  76  so that the fluid is swirled into the impeller vanes  74  after it enters the impeller eye  80 . This is more difficult to achieve in conventional molded impellers because it produces an undercut for the molding tool. 
         [0026]    In addition, as shown in  FIG. 9 , the impeller  30  can include a substantially smooth transition from the nose  78  to the front shroud  82 , thus providing a smooth transition through the flow path  104  from the fluid inlet (i.e., the impeller eye  80 ) to the fluid discharge (i.e., radially outward from trailing edges  106  of the impeller vanes  74 , as shown in  FIG. 4 ). This can allow for a slower relative velocity change of fluid as it travels through the impeller  30  and therefore avoids uneven and drastic pressure drops that are tied to rapid velocity changes. As a result, in warmer water temperatures and lower suction pressure, the impeller  30  can provide a better performance curve compared to conventional impellers which have a flow path  108 , as shown in  FIG. 4 , with a sharper change in direction from inlet to discharge. For example, the NPSHR (Net Positive Suction Head Required) curves of a pump using the impeller  30  of some embodiments rather than a conventional impeller can be improved due to this smooth transition. 
         [0027]    It will be appreciated by those skilled in the art that while the invention has been described above in connection with particular embodiments and examples, the invention is not necessarily so limited, and that numerous other embodiments, examples, uses, modifications and departures from the embodiments, examples and uses are intended to be encompassed by the claims attached hereto. The entire disclosure of each patent and publication cited herein is incorporated by reference, as if each such patent or publication were individually incorporated by reference herein. Various features and advantages of the invention are set forth in the following claims.