Abstract:
A flexible impeller pump includes improved flexible impeller geometry, an impeller shaft having protruding portions that produce a stronger and more durable connection between the impeller shaft and the flexible impeller, a smoother housing cam surface, and wear resistant surfaces that are disposed between end faces of the flexible impeller and adjacent housing end walls.

Description:
BACKGROUND 
       [0001]    Flexible impeller pumps are often used to pump fluids. In the flexible impeller pump  10  illustrated in  FIG. 1 , an impellor  12  having flexible vanes  14  extending radially from a central hub is mounted for rotation within an opening of a housing  16 . The impellor  12  is mounted to a shaft, which is mounted for rotation relative to the housing  16  about an axis. The opening is in fluid communication with an inlet  18  and an outlet  20 . As the impellor  12  is rotated (clockwise relative to the view direction of  FIG. 1 ), tips of the flexible vanes interface with sidewalls of the opening to draw fluid from the inlet  18  and discharge the fluid to the outlet  20 . The housing includes a cam portion  22 , which has a sidewall that is disposed closer to the axis than the other sidewalls of the opening, thereby causing increased bending of the flexible vanes  14  as they pass by the cam portion  22 . As the impellor  12  rotates, each flexible vane  14  exits the cam portion  22  in the vicinity of the inlet  18 , travels around an annular portion of the opening to the outlet  20 , and then reengages the cam portion  22  to repeat the cycle. Upon exiting the cam portion  22 , a flexible vane  14  straightens thereby increasing the volume bounded between the flexible vane  14  and the adjacent trailing flexible vane so as to draw fluid from the inlet  18  into the space between the flexible vane and the adjacent trailing flexible vane. The fluid in the space is then propelled around the opening to the outlet  20  by the impellor vanes. At the outlet  20 , the flexible vane reengages the cam portion  22  and is cause to undergo increased bending, thereby decreasing the volume bounded between the vane and the adjacent trailing vane so as to discharge fluid from the space to the outlet  20 . A suction created by the straightening of the vanes upon leaving the cam portion enables self priming of the pump  10  by allowing atmospheric pressure to push the liquid into the pump  10 . 
         [0002]    Existing flexible impeller pumps, however, suffer from a variety of common problems. For example, as illustrated in  FIG. 2 , the repetitive bending of the flexible vanes can lead to fracture of the vanes and/or permanent bowing of the vanes. The sliding of the tips of the flexible vanes along the sidewalls of the housing, especially along the sidewall of the cam portion, can lead to localized wearing, pitting, and/or ripping of the tips of the flexible vanes. 
         [0003]    In addition, relative motion between the end faces of the impellor and adjacent end walls of the housing can result in additional wear damage to the housing end walls. Wear to the housing end walls can be especially significant where the flexible impeller pump is used to transfer abrasive fluids. For example, as a non-limiting example, many dispensable edible fluids contain particulate, some of which are abrasive. And many food dispensing pumps have plastic housings. The plastic end walls of such pump housings can experience significant amounts of wear due to the presence of such abrasive components. 
         [0004]    Thus, there is believed to be a need for improved flexible impeller pumps, particularly flexible impeller pumps suitable for use with abrasive fluids, such as dispensable foods having abrasive components. 
       BRIEF SUMMARY 
       [0005]    The following presents a simplified summary of some embodiments of the invention in order to provide a basic understanding of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some embodiments of the invention in a simplified form as a prelude to the more detailed description that is presented later. 
         [0006]    Improved flexible impeller pumps are disclosed. In many embodiments, wear resistant surfaces are included in the flexible impeller pump such that each end face of the flexible impeller is immediately adjacent to one of the wear resistant surfaces. In many embodiments, the flexible impeller pump includes an impeller shaft that includes an impeller interface portion having one or more protruding portions shaped to interlock with the flexible impeller. And in many embodiments, the flexible impeller pump includes a flexible impeller with improved vane to main body transitions. The wear resistant surfaces decrease the amount of housing end plate wear that occurs, especially when the flexible impeller pump is used to transfer fluids having abrasive components. The wear resistant surfaces may also support the use of moldable housing materials, such as plastic. The one or more protruding portions of the impeller shaft provide a more secure coupling between the impeller shaft and the flexible impeller as compared to existing flexible impeller/shaft assemblies. The more secure coupling is especially beneficial when the flexible impeller pump is used to pump hot abrasive fluids, which may tend to cause the flexible impeller to get hot and become detached from the impeller shaft in existing flexible impeller/shaft assemblies. 
         [0007]    Thus, in one aspect, a flexible impeller pump is provided. The flexible impeller pump includes a shaft configured to rotate about an axis thereof; a rotor that is coaxial with and attached to the shaft; a housing defining an opening with the rotor disposed therein, and a first wear resistant surface. The rotor is configured to be rotated by the shaft. The rotor includes a plurality of vanes extending substantially radially there from. The rotor has a first end face and a second end face opposite to the first end face. The first and second end faces are perpendicular to the axis. The housing defines a fluid inlet and a fluid outlet. The opening includes a cam surface operatically disposed between the outlet and the inlet. The cam surface is configured to interfere with the vanes to bend the vanes toward the outlet. The housing further includes a first end wall and a second end wall that bound the opening in an axial direction thereof. The first wear resistant surface is disposed between the rotor first end face and the first end wall. The first wear resistant surface resides immediately adjacent to a majority of the area of the rotor first end face. The first wear resistant surface has greater wear resistance than the housing first end wall. 
         [0008]    In many embodiments, the first wear resistant surface is immediately adjacent to more than 50 percent of the area of the rotor first end face. For example, the first wear resistant surface can reside immediately adjacent to at least 90 percent of the area of the rotor first end face. As another example, the first wear resistant surface can reside immediately adjacent to at least 95 percent of the area of the rotor first end face. 
         [0009]    A wear resistant member can provide the first wear resistant surface. For example, the housing first end wall can have a recess that at least partially receives an insert having the wear resistant surface. In many embodiments, the insert includes a ceramic material. For example, the ceramic material can include a food grade ceramic material. 
         [0010]    In many embodiments, the flexible impeller pump includes a second wear resistant surface disposed between the rotor second end face and the housing second end wall. The second wear resistant surface resides immediately adjacent to a majority of the area of the rotor second end face. The second wear resistant surface has a greater wear resistance than the housing second end wall. 
         [0011]    In many embodiments, the cam surface is smoothly shaped. For example, the cam surface can have no convex curvature. 
         [0012]    In another aspect, a flexible impeller pump is provided. The flexible impeller pump includes a shaft configured to rotate about an axis thereof; a rotor that is coaxial with and attached to the shaft; and a housing defining an opening with the rotor disposed therein. The shaft includes first and second cylindrical portions and an impeller interface portion disposed there between. The impeller interface portion includes a portion that protrudes by at least 10 percent of the cross-sectional dimension of a central portion of the shaft impeller interface portion. The rotor is attached to the shaft interface portion. The rotor is configured to be rotated by the shaft. The rotor includes a main body and a plurality of vanes extending substantially radially from the main body. The housing defines a fluid inlet and a fluid outlet. The opening includes a cam surface operationally disposed between the outlet and the inlet. The cam surface is configured to interfere with the vanes to bend the vanes toward the outlet. 
         [0013]    In many embodiments, the protruding portion of the shaft protrudes from the central portion by more than 10 percent of the central portion cross-sectional dimension. For example, the protruding portion of the shaft can protrude from the central portion by at least 20 percent of the central portion cross-sectional dimension. 
         [0014]    In many embodiments, the shaft impeller interface portion includes a plurality of protruding portions distributed around the shaft. Each of the protruding portions protrudes by at least 10 percent of the cross-sectional dimension of the central portion of the shaft impeller interface portion. Each of the protruding portions can be aligned with one of the vanes. The number of protruding portions can be equal to or greater than the number of the vanes. The shaft impeller interface portion can include a plurality of rows of the protruding portions. In many embodiments, each of the protruding portions has a constant cross-sectional shape and is aligned with the shaft axis. 
         [0015]    In many embodiments, the flexible impeller pump includes a flexible impeller with improved vane to main body transitions. For example, each portion of the rotor main body disposed between a pair of adjacent vanes can have an external surface having no convex curvature from one of the pair of the vanes to the other of the pair of the vanes. In many embodiments, each of the main body external surfaces has a concave shape with a substantially constant radius. 
         [0016]    In many embodiments, the cam surface is smoothly shaped. For example, the cam surface can have no convex curvature. 
         [0017]    In another aspect, a flexible impeller pump is provided. The flexible impeller pump includes a shaft configured to rotate about an axis thereof, a rotor that is coaxial with and attached to the shaft, and a housing defining an opening with the rotor disposed therein. The rotor is configured to be rotated by the shaft. The rotor includes a plurality of vanes extending there from. The housing defines a fluid inlet and a fluid outlet. The opening includes a cam surface operationally disposed between the outlet and the inlet. The cam surface is configured to interfere with the vanes to vend the vanes toward the outlet. The cam surface has no convex curvature surface that interfaces with the vanes. 
         [0018]    For a fuller understanding of the nature and advantages of the present invention, reference should be made to the ensuing detailed description and accompanying drawings. Other aspects, objects and advantages of the invention will be apparent from the drawings and detailed description that follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  illustrates the operation of a flexible impeller pump. 
           [0020]      FIG. 2  is a perspective view of a flexible impeller illustrating common types of damage that can occur. 
           [0021]      FIG. 3  shows components of an existing flexible impeller pump illustrating deformation of the flexible impeller. 
           [0022]      FIG. 4A  is a perspective view of an existing impeller assembly that includes a flexible impeller attached to an impeller shaft. 
           [0023]      FIG. 4B  is an end view of the impeller assembly of  FIG. 4A . 
           [0024]      FIG. 4C  is a cross-sectional view of the impeller assembly of  FIG. 4A . 
           [0025]      FIG. 4D  is a side view of the impeller shaft of the impeller assembly of  FIG. 4A . 
           [0026]      FIG. 5A  is an end view of an impeller assembly that includes an improved flexible impeller mounted to an improved impeller shaft, in accordance with many embodiments. 
           [0027]      FIG. 5B  is a cross-sectional view of the impeller assembly of  FIG. 5A . 
           [0028]      FIG. 5C  includes various views of the improved impeller shaft of  FIG. 5A . 
           [0029]      FIG. 6  includes various views of an existing housing assembly of a flexible impeller pump. 
           [0030]      FIG. 7  includes various views of an improved housing assembly of a flexible impeller pump, in accordance with many embodiments. 
           [0031]      FIG. 8  shows components of an improved flexible impeller pump illustrating deformation of the improved flexible impeller, in accordance with many embodiments. 
           [0032]      FIG. 9  includes a top view and a cross-sectional view of a housing end plate assembly that includes a wear resistant insert, in accordance with many embodiments. 
           [0033]      FIG. 10  includes a top view and a cross-sectional view of a housing base plate assembly that includes a wear resistant insert, in accordance with many embodiments. 
           [0034]      FIG. 11  includes a top view and a cross-sectional view of the wear resistant insert of  FIGS. 9 and 10 . 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    In the following description, various embodiments of the present invention will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to one skilled in the art that the present invention may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified in order not to obscure the embodiment being described. 
         [0036]    Referring now to the drawings, in which like reference numerals represent like parts throughout the several views,  FIG. 3  shows the configuration of an existing flexible impeller pump  30 . The impeller pump  30  includes a housing  32  defining an opening  34 , an impeller shaft  36  mounted to rotate relative to the housing  32 , and a flexible impeller  38  mounted to the impeller shaft  36  to be rotated by the impeller shaft  36 . The flexible impeller  38  includes vanes  40  that extend radially from a cylindrically-shaped main body of the flexible impeller  38 . The opening  34  is sized to induce significant amount of bending in each of the vanes  40 . The geometry of the transition between each of the vanes and the main body results in significant stress concentrations at the roots of each of the vanes. The opening  34  includes a cam surface  42 , which induces yet further levels of bending in the vanes as the vanes move over the cam surface  42  during rotation of the flexible impeller  38  within the opening. The geometry of the opening  34 , including the cam surface  42 , coupled with the geometry of the flexible impeller  38 , results in high stress cycles in the flexible impeller, particularly at the roots of the vanes, as well as high contact stresses between the tips of the vanes and the cam surface  42 . These high stress cycles and high contact stresses contribute, over time, to damaging the impeller  38 . 
         [0037]      FIGS. 4A through 4D  illustrate details of the attachment of the existing flexible impeller  38  to the existing impeller shaft  36 . The flexible impeller  38  is coaxial with and attached to the impeller shaft  36 . As shown in  FIG. 4D , the impeller shaft  36  has an impeller interface portion  44  that includes a knurled surface  46  that interfaces with the flexible impeller  38 . The flexible impeller  38  can be bonded to the impeller shaft  36  over the knurled surface  46 . The flexible impeller  38  can, however, become detached from the impeller shaft  36  over time, particularly when the flexible impeller pump is used to move a hot, viscous, and abrasive fluid (e.g., a hot food condiment having an abrasive component). The heat may weaken the bond between the flexible impeller  38  and the knurled surface  46 . The viscosity and abrasiveness of the fluid may increase the torque required to rotate the flexible impeller  38 , thereby increasing the torsion that must be transferred from the impeller shaft  36  to the flexible impeller  38 . The combination of reduced bond strength and increased load transfer may result in detachment of the flexible impeller  38  from the impeller shaft  36 . 
       Improved Impeller and Shaft Assembly 
       [0038]      FIG. 5A  shows an improved flexible impeller  50  mounted to an improved impeller shaft  52 , in accordance with many embodiments. The improved flexible impeller  50  includes six vanes  54  that extend radially from a main body  56 . The flexible impeller  50  includes improved vane to main body transition regions, which include larger fillet radiuses relative to the fillet radiuses of the flexible impeller  38 —0.215 inch for the improved flexible impeller  50  as compared to 0.070 inch for the existing flexible impeller  38  (illustrated in  FIG. 4B ). The larger fillet radiuses of the flexible impeller  50  reduce the stress concentrations at the root of the vanes  54 , thereby reducing the resulting root stress generated by the bending of the vanes  54 . While the flexible impeller  50  employs a single constant radius that extends from one vane to the next, variable curvature can also be used. For example, a variable curvature concave surface that extends from one vane to the next and includes no regions of convex curvature can also be used to reduce the stress concentrations at the root of the vanes  54 . In contrast, in the existing flexible impeller  38 , the external surface of the main body between each vane has a cylindrical shape (0.780 inch diameter), thereby interposing an area of convex curvature between the 0.070 inch fillet radiuses. 
         [0039]    The improved flexible impeller  50  can be made from a suitable material. For example, when the pump is used to transfer a hot food condiment, the flexible impeller can be made from a suitable food grade material (e.g., FDA grade Viton Shore A, DUR075 material). 
         [0040]    As shown in  FIGS. 5A through 5C , the improved impeller shaft  52  includes a first cylindrical portion  58 , a second cylindrical portion  60 , and an impeller interface portion  62  disposed there between. The impeller interface portion  62  includes a plurality of protruding portions  64 . In the embodiment shown, each of the protruding portions  64  has a constant approximately trapezoid-shaped cross section and extends along the impeller shaft  52  parallel to the centerline of the impeller shaft  52 . The protruding portions  64  have an outside diameter of 0.450 inches and extend from a 0.301 inch diameter base. In the embodiment shown, eighteen protruding portions (three rows of six) are equally distributed around the shaft and are separated by six slots  66  (0.125 inch wide) that extend along the impeller shaft  52  and two radial grooves  68  (0.090 inch wide) that separate the rows. The slots  66 , the grooves  68 , and the distributed protruding portions  64  combine to define a stepped interface between the flexible impeller  50  and the impeller shaft  52 . The stepped interface provides increased bonding area and provides a more positive mechanical connection between the impeller shaft  52  and the flexible impeller  50  that is capable of transmitting torque and preventing axial movement of the flexible impeller  50  along the impeller shaft  52  even in the absence of a bond between the impeller shaft  52  and the flexible impeller  50 . 
         [0041]    In the embodiment shown, each of the eighteen protruding portions  64  extends from the base by approximately 25 percent of the cross-sectional dimension of the base. Other suitable number and size of protruding portions can also be used. For example, one or more protruding portions that protrude by at least 10 percent of the cross-sectional dimension of a central portion of the shaft impeller interface portion can be used. And in many embodiments, the protruding portion(s) protrudes from the central portion by at least 20 percent of the central portion cross-sectional dimension. 
         [0042]    As shown in  FIG. 5A , each group of three of the protruding portions (one protruding portion in each of the three rows) is aligned with one of the six vanes  54  of the flexible impeller  50 . By aligning the vanes  54  with the protruding portions  64 , the protruding portions  64  are disposed under the vanes  54  where the local thickness of the main body of the flexible impeller  50  is greater and therefore provides greater room to accommodate the protruding portions  64 . 
         [0043]    The impeller shaft  52  can be made from a suitable material. For example, when the pump is used to transfer a hot food condiment, the impeller shaft  52  can be made from a suitable food grade material (e.g., 300 series stainless steel). 
       Improved Housing Assembly 
       [0044]      FIG. 6  shows an existing impeller pump housing assembly  70  for comparison with an improved housing assembly  72  that is shown in  FIG. 7 . In both of the housing assemblies  70 ,  72 , a housing defines an opening in which the flexible impeller is disposed. The opening includes a main cylindrical portion (0.748 inch radius) and a cam portion. In the existing housing assembly  70 , the cam portion has an aggressive concave ramp surface  74  (0.433 inch radius) at both ends, a central concave section  76  (0.627 inch radius) with an intermediate convex surface  78  (0.118 inch radius) disposed between each end ramp surface  74  and the central concave section  76 . In contrast, in the improved housing assembly  72 , the cam portion has no convex curvature. A less aggressive ramp surface  80  is disposed on both sides of a central concave section  82 . The less aggressive ramp surface  80  includes only concave surfaces (a  0 .433 inch curved section joined to a 2.000 inch curved section). Accordingly, when the vanes are bent by the cam portion in the improved housing assembly  72 , the vanes do not have to travel over an area of convex curvature (e.g., the intermediate convex surface  78  in the existing housing assembly  70 ), and are therefore less likely to break or experience early wear. 
         [0045]      FIG. 8  shows deformation of the improved flexible impeller  50 , which is disposed in the improved housing assembly  72 , in accordance with many embodiments. In contrast to the existing impeller pump shown in  FIG. 3 , the improved flexible impeller  50  is subjected to less severe localized strain, thereby decreasing the failure rate of the improved flexible impeller  50  relative to the existing flexible impeller  38 . 
         [0046]    The housing assembly  72  can be made from a suitable material. For example, when the pump is used to transfer a hot food condiment, the housing assembly  72  can be made from a suitable food grade material (e.g., acetal thermoplastic with  13  percent Teflon FDA grade). 
         [0047]      FIGS. 9 and 10  show a housing end plate assembly  84  and a housing base plate assembly  86 , respectively, for the improved housing assembly of  FIG. 7 , in accordance with many embodiments. The housing end plate assembly  84  includes a housing end plate  88  and a wear resistant insert  90  (shown separately in  FIG. 11 ) received within a recess of the housing end plate  88 . In a similar manner, the housing base plate assembly  86  includes a housing base plate  92  and a wear resistant insert  90  received within a recess of the housing base plate  92 . The wear resistant insert  90  has a circular disk configuration with an outside diameter (1.600 inch) that exceeds the diameter (1.496 inch) of the opening in the improved housing assembly  72  so that the wear resistant insert  90  extends past and overlaps the opening. The wear resistant insert  90  has a central aperture, which accommodates the impeller shaft  52 , which is supported by the housing end plate  88  and the housing base plate  92 . The wear resistant insert  90  provides a wear resistant surface, which resides immediately adjacent to and can interface with a majority of the area of an end face of the flexible impeller  50 . For example, in the embodiment shown, the wear resistant surface interfaces with at least 95 percent of the area of the adjacent end face of the flexible impeller  50 . 
         [0048]    The housing end plate  88  and the housing base plate  92  can be made from a suitable material. For example, when the pump is used to transfer a hot food condiment, the housing end plate  88  and the housing base plate  92  can be made from a suitable food grade material (e.g., acetal thermoplastic with 13 percent Teflon FDA grade). 
         [0049]    The wear resistant inserts  90  can be made from a suitable material. For example, when the pump is used to transfer a hot food condiment, the wear resistant inserts  90  can be made from a food grade material (e.g., AL995 FDA grade hard fired alumina ceramic). 
         [0050]    Other variations are within the spirit of the present invention. Thus, while the invention is susceptible to various modifications and alternative constructions, certain illustrated embodiments thereof are shown in the drawings and have been described above in detail. It should be understood, however, that there is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined in the appended claims. 
         [0051]    The term “force” is to be construed as encompassing both force and torque (especially in the context of the following claims), unless otherwise indicated herein or clearly contradicted by context. The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
         [0052]    Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context. 
         [0053]    All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.