Abstract:
A method of fabricating a curvilinear magnet includes forming at least one slot in a material billet. The slotted material billet is inserted into a mold having a curvilinear pocket. The mold is closed around the slotted material billet such that the slotted material billet conforms to the curvilinear pocket and forms a curvilinear billet. The curvilinear billet is arranged in a structure. The curvilinear billet arranged in the structure is then magnetized.

Description:
FIELD 
       [0001]    The present disclosure relates to a curvilinear magnet and a method for fabrication thereof. 
       INTRODUCTION 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0003]    Permanent magnets are found in or used to produce many contemporary technologies from speakers to electric motors used in tools, vehicles, and more. When selecting a magnet for use, design considerations include the magnet strength and the requisite magnetic field arrangement. Certain design considerations and/or packaging constraints dictate the use of curvilinear magnets to meet the requirements. Heretofore, curvilinear magnets have been produced as bonded magnetic powder composites or machined sintered magnet blocks. However, composite magnets generally have inferior magnetic properties, while cutting magnetic arcs from rectangular billets can be costly and do not necessarily provide the requisite magnetic field arrangement. 
       SUMMARY 
       [0004]    A method of fabricating a curvilinear magnet includes forming at least one slot in a material billet. The slotted material billet is inserted into a mold having a curvilinear pocket. The mold is closed around the slotted material billet such that the slotted material billet conforms to the curvilinear pocket and forms a curvilinear billet. The curvilinear billet is arranged in a structure and is then magnetized. 
         [0005]    A method of fabricating a curvilinear magnet includes forming at least one slot in a material billet. The slotted material billet is inserted into a mold having a curvilinear pocket. The mold is closed around the slotted material billet such that the slotted material billet fractures at the at least one slot and conforms to the curvilinear pocket to form a plurality of material segments with openings arranged therebetween. The openings are filled with a binder material to define a curvilinear billet. 
         [0006]    A method of fabricating a curvilinear magnet includes forming at least one slot in a material billet. A backing is inserted into a mold having a curvilinear pocket. The slotted material billet is also inserted into the mold. The mold is closed around the slotted material billet and the backing such that the slotted material billet fractures at the at least one slot. The backing and the slotted material billet conform to the curvilinear pocket to form a plurality of material segments with openings arranged therebetween. The backing and the plurality of material segments are bonded together to define a curvilinear billet. 
         [0007]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0008]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0009]      FIG. 1  is a perspective view of an exemplary kerf-cut material billet according to the present disclosure; 
           [0010]      FIG. 2A  is a schematic view of an exemplary kerf-cut billet before insertion in an exemplary mold press; 
           [0011]      FIG. 2B  is a schematic view of the exemplary kerf-cut segments after closure of the mold press; 
           [0012]      FIG. 2C  is a schematic view of the segments during insertion into a rotor; 
           [0013]      FIG. 2D  is a schematic view of the segments after insertion into the rotor and with the mold press opened for another kerf-cut billet; 
           [0014]      FIG. 3A  is a schematic view of an exemplary kerf-cut billet before insertion in an exemplary mold press; 
           [0015]      FIG. 3B  is a schematic view of the exemplary kerf-cut segments after closure of the mold press; 
           [0016]      FIG. 3C  is a schematic view of a binder filling openings between the segments while in the closed mold press; 
           [0017]      FIG. 3D  is a schematic view of the curvilinear segments with binder after removal from the mold press and with the mold press opened for another kerf-cut billet; 
           [0018]      FIG. 4A  is a schematic view of a pair of exemplary kerf-cut billets before insertion in an exemplary mold press with a form arranged therein; 
           [0019]      FIG. 4B  is a schematic view of the exemplary kerf-cut segments after closure of the mold press and bonding to the form; 
           [0020]      FIG. 4C  is a schematic view of the curvilinear segments bonded to the form after removal from the mold press and with the mold press opened for another pair of kerf-cut billets; 
           [0021]      FIG. 5A  is a schematic view of an exemplary wedge-shaped kerf billet before insertion in an exemplary mold press; 
           [0022]      FIG. 5B  is a schematic view of the exemplary kerf-cut segments after closure of the mold press; 
           [0023]      FIG. 5C  is a schematic view of the segments with a binder filling openings between the segments while in the closed mold press; 
           [0024]      FIG. 5D  is a schematic view of the curvilinear segments with binder after removal from the mold press and with the mold press opened for another kerf-cut billet; 
           [0025]      FIG. 6A  is a schematic view of two alternate arrangements for an exemplary kerf-cut billet with adhesive mat; 
           [0026]      FIG. 6B  is a schematic view of the kerf-cut billet with adhesive mat before insertion in an exemplary mold press; 
           [0027]      FIG. 6C  is a schematic view of the kerf-cut segments with adhesive mat after closure of the mold press; and 
           [0028]      FIG. 6D  is a schematic view of the kerf-cut segments with adhesive mat after insertion into the rotor. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. Further, directions such as “top,” “side,” “back”, “lower,” and “upper” are used for purposes of explanation and are not intended to require specific orientations unless otherwise stated. These directions are merely provided as a frame of reference with respect to the examples provided, but could be altered in alternate applications. 
         [0030]    Electric machines, such as motors or generators, use electric potential energy to produce mechanical energy, or conversely, use mechanical energy to produce electrical energy through the interaction of magnetic fields and current-carrying conductors. Generally, an interior permanent magnet machine includes a rotor having a plurality of magnets of alternating polarity around the outer periphery of the rotor. The rotor is rotatable within a stator, which generally includes a plurality of windings and magnetic poles of alternating polarity. The magnets used in interior permanent magnet machines are often rectangular in shape; however, arc-shaped or parabolic magnets have been found to provide improved performance characteristics. To date, arc-shaped or parabolic magnets have been formed by machining a rectangular material billet to shape or by molding a composite material in a form to achieve the requisite final shape. However, the machining process is materially wasteful and the molding process provides inferior magnetic capabilities. 
         [0031]    Referring now to  FIG. 1 , an exemplary flat, rectangular material billet  10  is shown. The material billet  10  is a commercially available material billet used in magnetic applications, such as with a permanent magnet rotor found in a permanent magnet electric motor or a permanent magnet generator. Permanent magnets may be beneficial for use in the automotive and aerospace manufacturing industries; the pulp and metal processing industries; the agricultural, military, appliance, electronic, power generation, construction/tool, food and beverage, consumer products and medical service industries; and general manufacturing applications. The material billet  10  can be formed from a ferromagnetic material, such as an iron, nickel, or cobalt, or can be formed from an alloy of a rare earth material. The material may be magnetically isotropic, such that the magnetic moments within the magnet have no preferred orientation and the magnet is magnetizable in any direction. In one example, the starting material billet is an oriented magnetic material such that the magnetic moment lies in a specific direction within the billet, and can be magnetized only along that direction. The orientation direction can lie along any direction within the billet. For example, the magnetization may lie perpendicular to the large face (e.g., left and right faces of the material billet  10  in  FIG. 1 ). 
         [0032]    The material billet  10  includes slots  12  arranged to extend partially or completely through the material thickness (e.g., through a kerf-cutting process). The slots  12  may be straight cuts or may take the form of a wedge-shaped cut. In other words, portions of the material billet  10  can be approximated by an array of smaller rectangular prisms or trapezoidal prisms (i.e., “keystone” segments). There may be one or more slots  12  present in the material billet  10  with the slots  12  arranged in a predetermined relationship along the length of the material billet  10  so as to provide a final curvilinear shape after the bending process described below. While the slots  12  are shown equally distributed along the material billet  10 , it should be understood that the slots  12  may also, for example, be biased to one side of the material billet  10 , arranged only near ends or at the central portion of the material billet  10 , be located compactly at a first region and sparsely at a second region of the material billet  10 , or may be located on either side of the material billet  10  (e.g., to create the desired final shape having at least two opposite curvature directions, such as with an “S” shape). 
         [0033]    With reference now to  FIG. 2A , a schematic representation of the kerf-cut material billet  10  before insertion into an exemplary mold press  14  is provided. The mold press  14  as shown includes a first tool  16  and a corresponding second tool  18 . The tools  16 ,  18  move (i.e., first moves toward second, second moves toward first, or both move together) so to close the mold press  14  around the kerf-cut material billet  10  within a pocket  20 , as best shown in  FIG. 2B . The first tool  16  is shown having a convex shape and the second tool  18  is shown having a concave shape such that the pocket  20  is arc-shaped over its length. While the first and second tools  16 ,  18  of the mold press  14  are shown having corresponding arc shapes, it should be understood that any curvilinear shape for the tools is also contemplated. As an example, the first and second tools  16 ,  18  may have a corresponding parabolic shape, arc-shaped end portions with a linear portion therebetween, or a wave shape (i.e., adjoined convex and concave curves). Furthermore, the first and second tools  16 ,  18  may also have shapes that do not correspond, such that the pocket  20  may have another geometric shape (e.g., half circle, polygonal). 
         [0034]    The pocket  20  is sized for receiving the kerf-cut material billet  10 . The material billet  10  is a brittle material that fractures upon a bending action when performed at room temperature (e.g., cold working). Closing the mold press  14  causes a controlled fracture of the kerf-cut material billet  10  at the location of the slots  12  as the material billet  10  is forced to conform to the curvilinear shape of the mold pocket  20 . In this way, the kerf-cut material billet  10  is fractured into a plurality of material segments  22  arranged within the curvilinear pocket  20 . The material billet  10  can be arranged with the slots  12  opening toward either the first tool  16  or the second tool  18 , as preferred. While the material billet  10  is described as being formed from a brittle material that fractures upon bending, it should be understood that certain applications may utilize magnets formed from ductile materials that will yield (i.e., bend). 
         [0035]    Referring now to  FIG. 2C , the plurality of material segments  22  may be moved from the mold press  14  into a rotor  26  (e.g., with a ram). After the material segments  22  are fully inserted into the rotor  26 , the mold press  14  may then be opened for receipt of another kerf-cut material billet  10  (see  FIG. 2D ). After insertion, the material segments  22  are freely movable within the rotor  26 , so an adhesive may be applied to the segments  22  in the rotor  26  to retain the geometry and spacing of the material segments  22  with respect to the rotor  26 . Alternatively, the plurality of material segments  22  may be sized so as to be pressed into the rotor  26  with an interference- or press-fit to retain their orientation within the rotor  26 . Once fixed within the rotor  26 , the material segments  22  may be magnetized with either a steady-state or impulse-type magnetizer. While the material segments  22  are described as being fully magnetized within the assembled state, it should be understood that a partial magnetization process may occur during any of the pre-assembled steps in order to ease the re-magnetization in the final desired magnetic polarity configuration. 
         [0036]    The material billet  10  may be comprised of an oriented magnetic material with the direction of the magnetic alignment perpendicular to the flat surface of the billet  10  (e.g., parallel to the direction of the kerf cuts). After forming the curvilinear magnet, the individual material segments  22  retain the alignment direction perpendicular to the surface, such that when magnetized, the curvilinear magnet has magnetic moment directions that vary with position along the magnet (i.e., perpendicular to the local surface). The ability to spatially vary the magnetic moment directions provides improved motor efficiency. It should be noted, however, that the starting billet can be fabricated with a different direction of magnetic moment if so desired, and the individual segments after forming the curvilinear magnet will retain that orientation. Further, the magnet may also be isotropic, meaning that it can be magnetized in any direction, and the direction of magnetization of the individual segments after forming will be defined by the spatial distribution and strength of the magnetizing field during the magnetizing process. 
         [0037]    With reference now to  FIG. 3A , a schematic representation of a kerf-cut material billet  110  before insertion into an exemplary mold press  114  is provided. The material billet  110  and mold press  114  are similar to the material billet  10  and mold press  14 , and as such, like numbers will be used to describe like parts. The mold press  114  is shown having a first, convex tool  116  and a corresponding second, concave tool  118 . The concave tool  118  moves toward the convex tool  116  to close the mold press  114  around the kerf-cut material billet  110  within a pocket  120 , as best shown in  FIG. 3B . The pocket  120  is sized for receiving the kerf-cut material billet  110 . Closing the mold press  114  causes a controlled fracture of the kerf-cut material billet  110  at the location of kerf-cut slots  112  as the material billet  110  is forced to conform to the curvilinear shape of the mold pocket  120 . The kerf-cut material billet  110  is fractured into a plurality of material segments  122  arranged within the curvilinear pocket  120 . 
         [0038]    Referring now to  FIG. 3C , a binder  130  is added to the mold press  114  at the pocket  120  so as to fill in open spacing  132  between the plurality of material segments  122 . The binder  130  may be any binding material for retaining the curvilinear shape of the material segments  122 , such as an adhesive, a low-temperature solder, a heat-cured material, a neat or reinforced thermoplastic, or neat or reinforced thermoset. After the binder  130  has hardened/cured between and/or around the material segments  122 , the mold press  114  may then be opened to remove the curvilinear magnet  134  (see  FIG. 3D ). The curvilinear magnet  134  will retain its shape after removal from the mold press  114  due to the binder  130 . The curvilinear magnet  134  may be inserted into or fixed on a surface of a rotor or can be used in other permanent magnet applications. Once secured in location, the curvilinear magnet  134  may be magnetized with either a steady-state or impulse-type magnetizer such that the individual material segments  122  have a controlled magnetic moment across the curvilinear shape (e.g., normal to tangent of the curve). As previously noted, it should be understood that a partial magnetization process may take place during any of the pre-assembled steps in order to ease the re-magnetization in the final desired magnetic polarity configuration. 
         [0039]    As previously discussed with respect to the material billet  10 , the material billet  110  may be comprised of an oriented magnetic material with the direction of the magnetic alignment perpendicular to the flat surface of the billet  110  (e.g., parallel to the direction of the kerf cuts). After forming the curvilinear magnet, the individual material segments  122  retain the alignment direction perpendicular to the surface, such that when magnetized, the curvilinear magnet has magnetic moment directions that vary with position along the magnet (i.e., perpendicular to the local surface). The ability to spatially vary the magnetic moment directions provides improved motor efficiency. It should be noted, however, that the starting billet can be fabricated with a different direction of magnetic moment if so desired, and the individual segments after forming the curvilinear magnet will retain that orientation. Further, the magnet may also be isotropic, meaning that it can be magnetized in any direction, and the direction of magnetization of the individual segments after forming will be defined by the spatial distribution and strength of the magnetizing field during the magnetizing process. 
         [0040]    With reference now to  FIG. 4A , a schematic representation of a pair of kerf-cut material billets  210 ,  211  before insertion into an exemplary mold press  214  is provided. The material billets  210 ,  211  and mold press  214  are similar to the material billet  10  and mold press  14 , and as such, like numbers will be used to describe like parts. The mold press  214  is shown having a first, convex tool  216  and a corresponding second, concave tool  218  with a form  236  arranged thereon. The form  236  may be a thin strip of material in a rigid form (e.g., steel, rigid plastic) or in a ductile form (e.g., aluminum, soft polymer, rubber) for securing the material billets  210 ,  211  in a predetermined relationship to one another. The form  236  may be a magnetic material (e.g., iron or steel) or may be a non-magnetic material (e.g., aluminum, stainless steel, other non-magnetic metal, or a polymer) for creating a “magnetic gap” between the material billets  210 ,  211  and a mated structure (e.g., interior wall of rotor). While the form  236  is depicted arranged on the concave tool  218 , it could also be arranged alternatively on the convex tool  216  or a pair of forms  236  could be arranged on both the convex and concave tools  216 ,  218 . Furthermore, the form  236  is depicted having a uniform thickness over its length, but a non-uniform cross-section is also contemplated. 
         [0041]    During operation, the concave and/or convex tools  216 ,  218  move to close the mold press  214  around the kerf-cut material billets  210 ,  211  within a pocket  220 , as best shown in  FIG. 4B . The pocket  220  is sized for receiving the combined kerf-cut material billets  210 ,  211  and form  236 . The material billets  210 ,  211  are formed of a brittle material that fractures upon a bending action. Closing the mold press  214  causes a controlled fracture of the kerf-cut material billets  210 ,  211  at the location of kerf-cut slots  212  as the material billets  210 ,  211  are forced to conform to the curvilinear shape of the mold pocket  220 . In this way, the kerf-cut material billets  210 ,  211  are fractured into a plurality of material segments  222  arranged within the curvilinear pocket  220 . The plurality of material segments  222  are bonded to the form  236  to create a curvilinear magnet  234 . 
         [0042]    Referring now to  FIG. 4C , the mold press  214  may be opened to remove the curvilinear magnet  234 . The curvilinear magnet  234  will retain its shape after removal from the mold press  214  due to the structure of the form  236 . The curvilinear magnet  234  may be inserted into or secured on a surface of a rotor, as previously described, or can be used in other permanent magnet applications. Once secured in location, the curvilinear magnet  234  may be magnetized with either a steady-state or impulse-type magnetizer. If the starting magnet is an oriented magnet, the magnetic moment is aligned along a specific direction such that the individual material segments  222  have a controlled magnetic moment across the curvilinear shape (e.g., normal to the surface of the magnet). The spacing between the material billets  210 ,  211  creates an “air gap” in the permanent magnet for overcoming packaging constraints and/or for achieving improved motor efficiency because the magnetic moment of each segment can be controlled across the curvilinear shape. 
         [0043]    With reference now to  FIG. 5A , a schematic representation of a kerf-cut material billet  310  before insertion into an exemplary mold press  314  is provided. Notably, the slots  312  in this representation are in the form of angular openings (e.g., wedge-shaped). The material billet  310  and mold press  314  are similar to the material billet  10  and mold press  14 , and as such, like numbers will be used to describe like parts. The mold press  314  is shown having a first, convex tool  316  and a corresponding second, concave tool  318 . The convex and/or concave tool  316 ,  318  move to close the mold press  314  around the kerf-cut material billet  310  within a pocket  320 , as best shown in  FIG. 5B . The pocket  320  is sized for receiving the kerf-cut material billet  310 . Closing the mold press  314  causes a controlled fracture of the kerf-cut material billet  310  at the location of angular slots  312 . In this way, the kerf-cut material billet  310  is fractured into a plurality of trapezoidal material segments  322  arranged within the curvilinear pocket  320 . The material billet  310  is arranged with the angular slots  312  opening toward the convex tool  316  such that fracturing causes opposing faces of the angular slots  312  to move together, thereby tightly packing the trapezoidal material segments  322  together. While the convex and concave tools  316 ,  318  of the mold press  314  are shown having corresponding arc configurations, it should be understood that any curvilinear shape for the tool is also contemplated. As an example, the convex and concave tools  316 ,  318  may have a parabolic shape, arc-shaped end portions with a linear portion therebetween, or a wave shape (i.e., adjoined convex and concave curves). With these alternately disclosed arrangements, the angular slots  312  may be appropriately arranged on both sides of the material billet  310  so as to provide the tightly packed material segment arrangement. 
         [0044]    Referring now to  FIG. 5C , a binder  330  is added to the mold press  314  at the pocket  320  so as to fill in open spacing  332  between the plurality of material segments  322 . The binder  330  may be any binding material for retaining the final curvilinear shape of the material segments  322 , such as an adhesive, a low-temperature solder, a heat-cured material, a neat or reinforced thermoplastic, or a neat or reinforced thermoset. After the binder  330  has hardened/cured between and/or around the material segments  322 , the mold press  314  may then be opened to remove the curvilinear magnet  334  (see  FIG. 5D ). The curvilinear magnet  334  will retain its shape after removal from the mold press  314  due to the binder  330 . The curvilinear magnet  334  may be inserted into or affixed to a surface of a rotor, as previously described, or can be used in other permanent magnet applications. Once secured in location, the curvilinear magnet  334  may be magnetized with either a steady-state or impulse-type magnetizer such that the individual material segments  322  have a controlled magnetic moment across the curvilinear shape (e.g., normal to tangent of the curve). 
         [0045]    As previously discussed with respect to the material billet  10 , the material billet  310  may be comprised of an oriented magnetic material with the direction of the magnetic alignment perpendicular to the flat surface of the billet  310  (e.g., parallel to the direction of the kerf cuts). After forming the curvilinear magnet, the individual material segments  322  retain the alignment direction perpendicular to the surface, such that when magnetized, the curvilinear magnet has magnetic moment directions that vary with position along the magnet (i.e., perpendicular to the local surface). The ability to spatially vary the magnetic moment directions provides improved motor efficiency. It should be noted, however, that the starting billet can be fabricated with a different direction of magnetic moment if so desired, and the individual segments after forming the curvilinear magnet will retain that orientation. Further, the magnet may also be isotropic and the direction of magnetization of the individual segments after forming will be defined by the spatial distribution and strength of the magnetizing field during the magnetizing process. 
         [0046]    With reference now to  FIG. 6A , a schematic representation of a kerf-cut material billet  410  having a backing mat  438  is provided. The backing mat  438  can be a flexible backing for design and dimensional flexibility (e.g., aluminum foil or a fiber bonded with a polymer) and may be coated with an adhesive on a first surface  440  for securing the backing mat  438  to the material billet  410 . An opposing, non-adhesive surface  442  of the backing mat  438  can be coated with a material having either a low surface energy (e.g., for facilitating insertion) or a high surface energy (e.g., for increasing retention after insertion). The backing mat  438  is secured to one or both sides of the material billet  410  prior to insertion within a mold press  414 . The material billet  410  and mold press  414  are similar to the material billet  10  and mold press  14 , and as such, like numbers will be used to describe like parts. 
         [0047]    Referring now to  FIGS. 6B and 6C , the mold press  414  is shown having a first, convex tool  416  and a corresponding second, concave tool  418  movable for closing the mold press  414  around the kerf-cut material billet  410 . A pocket  420  is sized for receiving the combined kerf-cut material billet  410  and backing mat(s)  438 . Closing the mold press  414  causes a controlled fracture of the kerf-cut material billet  410  at the location of kerf-cut slots  412  so as to conform to the curvilinear shape of the mold pocket  420 . In this way, the kerf-cut material billet  410  is fractured into a plurality of material segments  422  arranged within the curvilinear pocket  420 . 
         [0048]    Referring now to  FIG. 6D , the curvilinear magnet  434  with backing mat(s)  438  can be flexed into an appropriate shape for insertion into a rotor  426  due to the structure of the backing mat(s)  438 . The curvilinear magnet  434  may be inserted into the rotor  426 , as previously described, or can be used in other permanent magnet applications. Once secured in location, the curvilinear magnet  434  may be magnetized with either a steady-state or impulse-type magnetizer such that the individual material segments  422  have a controlled magnetic moment across the curvilinear shape (e.g., normal to tangent of the curve). As can be seen, the backing mat(s)  438  allow the curvilinear magnet  434  to be moved without the need for using binder, while still maintaining the integrity of the magnet (i.e., no loose parts). Notably, a binder material can be added after the curvilinear magnet  434  is arranged in a final location in order to alleviate any dimensionality issues that could arise. Furthermore, the backing mat(s)  438  can be used to create an “air gap” in the permanent magnet for overcoming packaging constraints and/or for achieving improved motor efficiency because the magnetic moment of each segment can be controlled across the curvilinear shape. 
         [0049]    As previously discussed with respect to the material billet  10 , the material billet  410  may be comprised of an oriented magnetic material with the direction of the magnetic alignment perpendicular to the flat surface of the billet  410  (e.g., parallel to the direction of the kerf cuts). After forming the curvilinear magnet, the individual material segments  422  retain the alignment direction perpendicular to the surface, such that when magnetized, the curvilinear magnet has magnetic moment directions that vary with position along the magnet (i.e., perpendicular to the local surface). The ability to spatially vary the magnetic moment directions provides improved motor efficiency. It should be noted, however, that the starting billet can be fabricated with a different direction of magnetic moment if so desired, and the individual segments after forming the curvilinear magnet will retain that orientation. Further, the magnet may also be isotropic, meaning that it can be magnetized in any direction, and the direction of magnetization of the individual segments after forming will be defined by the spatial distribution and strength of the magnetizing field during the magnetizing process. 
         [0050]    Embodiments of the present disclosure are described herein. This description is merely exemplary in nature and, thus, variations that do not depart from the gist of the disclosure are intended to be within the scope of the disclosure. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for various applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations.