Abstract:
Apparatus and methods for winding wire around the poles and partly within the slots of dynamoelectric machine components, such as stators. Some stators are designed with poles having pole tips that extend relatively far in a peripheral direction, perhaps reaching nearly half way across the stator core. When the pole tips reach so far around the stator core and thus leave little room between opposing pole tips, it may be difficult to use winding technologies with needles that need to move between opposing pole tips. Therefore, stators may be divided into segments for the winding of each pole, and then reassembled to form a complete stator. The segments are wound by rotating the segment and a wire guide structure about an axis, while providing wire to the rotating apparatus from a wire source.

Description:
[0001]    This application claims the benefit of U.S. provisional patent application No. 60/285,064, filed Apr. 19, 2001, which is hereby incorporated by reference herein in its entirety. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention relates to methods and apparatus for winding stators such as electric motor stators.  
           [0003]    The present application concerns solutions for winding wire coils around poles and partly within slots that may be part of lamination cores of dynamoelectric machine components, such as stators. Some stators are designed with poles having pole tips that extend a relatively great distance in a peripheral direction, perhaps reaching nearly half way across the stator core. When the pole tips reach so far around the stator core, it can become difficult to use winding technologies like those described in Luciani et al. U.S. Pat. No. 4,991,782, which is hereby incorporated by reference herein in its entirety. The tips of opposing poles may leave little room between one another for winding needles to access the slots.  
           [0004]    Therefore, stators to be wound by this invention may be divided into separate pole portions, or segments, that need to be wound. Once the separate pole portions have been individually wound, they are joined together to form a single core. By dividing the stator into segments, the difficulty presented by the close proximity of opposing pole tips can be eliminated.  
           [0005]    The solutions presented in this application include forming wire coils in stators of electric motors, and may further include termination of the coils&#39; wire leads to anchoring points that are near, or directly on, the lamination core segment. By terminating one of the wire leads to the lamination core segment, wire is pulled from a source by rotating the lamination core segment. While rotating the lamination core segment, wire is wound around the pole. With the solutions presented in this application, the pole is wound by rotating the segment so that wire is drawn from a source and wound around the pole.  
           [0006]    The segments to be wound in accordance with this invention are segments of a stator that has a central longitudinal axis spaced from the segment but substantially parallel to a longitudinal dimension of the segment. The segment includes first and second, substantially parallel, longitudinal slots on respective opposite sides of a longitudinal pole. The slots may have generally U-shaped cross sections that are inclined toward one another toward the bases of their U shapes. The segment is rotated about an axis substantially perpendicular to the central longitudinal axis. Because the openings of the U-shaped slots may not face in a radial direction with respect to the axis of rotation, it may be difficult to draw the wire into the slots as the segment is rotated without interference from other parts of the stator segment.  
           [0007]    Therefore, it would be desirable to provide apparatus and methods for winding the poles of stators that have pole tips reaching far around the stator core. It would also be desirable to provide apparatus and methods for winding wire in slots having openings that do not face in a radial direction with respect to the axis of rotation.  
         SUMMARY OF THE INVENTION  
         [0008]    It is an object of the invention to provide apparatus and methods for winding the poles of stators that have pole tips reaching relatively far around inside the stator core. When the stator is wound by rotating a segment of the stator, it is a further object of the invention to provide apparatus and methods for winding wire in slots having openings that do not face in a radial direction with respect to the axis of rotation.  
           [0009]    In accordance with the principles of the invention, apparatus and methods for winding a coil of wire on a segment of a stator for a dynamoelectric machine are provided. After winding the segment, the segment is joined to at least one other stator segment to form an assembled stator. The stator typically has a central longitudinal axis spaced from the segment but substantially parallel to a longitudinal dimension of the segment. The segment includes at least first and second slots on respective opposite sides of a longitudinal pole. The first and second slots have openings for the passage of wire. Often, the slots are substantially parallel, longitudinal slots that may have generally U-shaped cross sections inclined toward one another toward the bases of their U shapes. The coil is wound around the pole and partly within the slots.  
           [0010]    The apparatus includes a drive structure adapted to rotate the segment about a rotation axis that is substantially perpendicular to the longitudinal axis. The apparatus further includes a wire guide structure adapted for rotation with the segment. The apparatus still further includes a wire source that is located radially out from the wire guide structure but that does not rotate about the rotation axis. The wire source is provided with relative rotation on an orbit with respect to the segment as a result of the rotation of the segment about the rotation axis. The wire guide structure has surface portions that are shaped to guide wire at least between the orbit and the openings of the first and second slots. The winding alternates between the first and second slots, as the segment and the wire guide structure rotate about the rotation axis. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    Further features of the invention, its nature, and various advantages will be more apparent from the following detailed description and the accompanying drawings, wherein like reference characters represent like elements throughout, and in which:  
         [0012]    [0012]FIG. 1 is an elevational view of a stator divided into two stator portions.  
         [0013]    [0013]FIG. 2 is a perspective view of an illustrative embodiment of apparatus in accordance with the principles of the present invention. FIG. 2 and some subsequent FIGS. show some elements as though they were transparent so that other elements can be seen.  
         [0014]    [0014]FIG. 3 is a partial elevational view of the apparatus shown in FIG. 2 taken from line  3 - 3  of FIG. 2.  
         [0015]    [0015]FIG. 4 is a partial elevational view of the apparatus shown in FIGS. 2 and 3 taken from line  4 - 4  of FIG. 3.  
         [0016]    [0016]FIG. 5 is an elevational view of the apparatus shown in FIGS. 2, 3 and  4 , also showing an illustrative embodiment of additional components in accordance with the principles of the present invention.  
         [0017]    [0017]FIG. 6 is an elevational view of a stator divided into two stator portions after being wound with wire in accordance with the principles of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0018]    The invention provides apparatus and methods for winding a coil of wire on a segment of a stator for a dynamoelectric machine. The stator typically has a central longitudinal axis spaced from the segment but substantially parallel to a longitudinal dimension of the segment. The segment includes first and second, substantially parallel, longitudinal slots on respective opposite sides of a longitudinal pole. The slots may have generally U-shaped cross sections that are inclined toward one another toward the bases of their U shapes. The coil is wound around the pole and partly in the slots. The apparatus typically includes a drive structure adapted to rotate the segment about a rotation axis. The rotation axis is generally substantially perpendicular to the longitudinal axis.  
         [0019]    The apparatus further typically includes a wire guide structure adapted for rotation with the segment. A wire source is located radially out from the wire guide structure, but does not rotate about the rotation axis, at least not all the way around the rotation axis. The wire guide structure has surface portions that are shaped to guide wire from the wire source to be wound around the pole. The winding of the wire alternates between the first and second slots, as the segment and the wire guide structure rotate about the rotation axis.  
         [0020]    In some embodiments of the invention, the wire guide structure may include a first substructure adapted to hold the segment. While holding the segment, the first substructure preferably leaves the slots substantially unobstructed. The wire guide structure may include a second substructure spaced from the first substructure so that a passageway for wire is defined between the first and second substructures. In some embodiments, the wire guide structure or a part thereof may be configured to translate along the rotation axis (e.g., to facilitate insertion or removal of a segment relative to the wire guide structure).  
         [0021]    In some embodiments, the wire source may be configured to move in a direction parallel to the rotation axis. This motion, in coordination with the rotation, may help properly distribute the wire around the pole. Altering the motion of the wire source may affect the distribution or density of the coil. Additionally, the distance of the wire source from the rotating apparatus may affect these characteristics of the wound coil. As still another example, some motion of the wire source about the rotation axis may be provided, but preferably the wire source does not move all the way around the rotation axis.  
         [0022]    Because the slots of the segment typically do not open in a radial direction with respect to the axis of rotation, the wire guide structure generally has features that help guide the wire into the slots. These features may help properly distribute the wire within the slots, may help support the coil portion around ends of the poles (i.e., outside of the slots), and may prevent the wire from being caught on a portion of the segment other than within the slots or at the axial ends of the pole. In some embodiments, the wire guide structure may include wings configured to align the wire with an opening to each of the slots.  
         [0023]    In some embodiments, the wire guide structure may include curved surfaces configured to draw the wire into each of the slots. In some embodiments, the wire guide structure may include a ridge configured to keep the wire raised and to draw the wire toward a surface of each of the slots which is radially outermost with respect to the longitudinal axis.  
         [0024]    Some embodiments may include the wire guide structure having a support surface configured to support the wound wire at an end face of the pole. In some embodiments, the wire guide structure may include a wall configured to limit bulging of the wound wire at an end face of the pole. Any or all of the above features of the wire guide structure may improve the ability to wind wire on a segment having slots that do not open in a purely radial direction with respect to the axis of rotation.  
         [0025]    In some embodiments, the wire guide structure may be configured to engage the pole. In some embodiments of the invention, the wire guide structure may be configured to clamp the segment. Some embodiments may include a wire guide structure configured to support the segment.  
         [0026]    In some embodiments, the apparatus may include a pulley/belt transmission adapted to drive the rotation. In some embodiments of the invention, the apparatus may include a moveable support for the segment and the wire guide.  
         [0027]    Illustrative examples of embodiments in accordance with the principles of the present invention are shown in FIGS.  1 - 6 .  
         [0028]    [0028]FIG. 1 is an end view of two separate pole portions or stator segments  10  that need to be wound with coils C (shown in FIG. 6) that may be at least partly seated in slots  11 . FIG. 6 is a view similar to FIG. 1 showing coils C after they have been wound around poles  12  and seated in slots  11 . Leads C 1  may be anchored to terminal points (not shown). The terminal points could be on end face  10   a  and/or  10   a ′ of stator segment  10 . For example, the terminal points could be on terminal board structures on end faces  10   a  and/or  10   a ′ of stator segment  10 . Slots  11  may be delimited by curved poles  12  and inner surfaces  13  of the external core structure. Slots  11  occur on respective opposite sides of poles  12  and have openings  11 ′ through which wire can be passed. Coils C wound around poles  12  may have wire turns that are wound around neck portions  14  and seated in slots  11 .  
         [0029]    After winding the coils, pole portions  10  may be joined by press fitting connections, or other joining solutions such as welding or external binding structures (e.g., an external ring). The portions may be joined in areas  15 , to form a closed stator. Arrows  15 ′ and  15 ″ show directions of movement that may be used during a pressing operation to assemble pole portions  10  after they have been wound and terminated.  
         [0030]    Pole tips  12 ′ may extend substantially around central longitudinal axis  10 ′ of the stator. This extension may create maximized spacing of slots  11  and may increase the field performance of the final stator. Consequently, a stator formed of pole portions like those shown in FIGS. 1 and 6 may have a higher number of turns wound within slots  11 . In other words, the completed stator may be capable of producing a higher power output in relation to the stator&#39;s geometric size.  
         [0031]    Bringing the pole tips  12 ′ so far around central longitudinal axis  10 ′ in a closed stator (i.e. a stator which is not divided like shown in FIGS. 1 and 6) may impede winding with needles that traverse the inside and outside of the stator, like those described in Luciani et al. U.S. Pat. No. 4,858,835. This impediment may be due primarily to the lack of space for moving the needles, especially between adjacent pole tips  12 ′. For this reason, the stator core may be divided into two portions like pole portions or stator segments  10  shown in FIGS. 1 and 6 so that access may be created for winding the poles.  
         [0032]    [0032]FIG. 2 is a perspective view showing apparatus that may be used to wind one of the separate pole portions or stator segments  10 . Pole portion  10  in FIG. 2 is shown from direction  2  of FIG. 1. Pole portion  10  may be held by opposite clamp members  20  and  21  so that transverse axis X (FIG. 1) coincides with rotation axis R 1 . Transverse axis X (FIG. 1) may be an axis of symmetry for pole  12 , passing through the center of pole portion  10 .  
         [0033]    Clamp members  20  and  21  may move towards each other, in directions  20 ′, in order to clamp pole portion  10 . Clamp members  20  and  21  may also move in directions  21 ′ (i.e., away from each other) to release pole portion  10 . Clamp members  20  and  21  may be mounted on slide unit  22  to enable these movements for holding or releasing pole portion  10 . Slide unit  22  may be supported by shaft  23 . Shaft  23  may be capable of rotation about axis R 1 . In this way, pole portion  10  may be rotated around axis R 1  when held by clamp members  20  and  21 . Clamp members  20  and  21  may engage the external portions of stator core segment  10 . Clamp members  20  and  21  may extend to areas  15  (FIG. 1) and may have overhanging portions  24 . Overhanging portions  24  may be configured such that the thickness of the core in areas  15  is totally covered.  
         [0034]    Axial surfaces  25  of clamp members  20  and  21  may be flush with end faces  10   a  and  10   a ′ of pole portion  10 . Note that in FIG. 2 (and other FIGS.) certain parts have been shown partially transparent for the sake of clarity. This allows identification of parts and portions which are otherwise hidden.  
         [0035]    Guide member  30  may be positioned opposite to clamp members  20  and  21 . Guide member  30  may be capable of coming into contact with certain parts of pole portion  10  when the latter is held by clamp members  20  and  21 . Once guide member  30  comes into contact with pole portion  10 , guide portions  30  and pole portion  10  may rotate together around axis R 1 .  
         [0036]    In order to enable the synchronous rotation, shaft  31  may be centered on axis R 1  and may be capable of rotating around axis R 1 , when clamp members  20  and  21  rotate around axis R 1 . Guide member  30  may be flanged to shaft  31 , so that guide member  30  is correctly located with respect to rotation axis R 1 . Guide member  30  may be capable of moving in direction  31 ′ (i.e., parallel to axis R 1 ) when required to bring guide member  30  into contact with pole portion  10 . Movement of guide member  30  in direction  31 ″, which is opposite to direction  31 ′, may bring guide member  30  away from pole portion  10  and may create room for transfer of pole portion  10  to and from clamp members  20  and  21 .  
         [0037]    Guide member  30  may be recessed and may have portions that need to be positioned properly with respect to specific portions of pole portion  10 , as will become clear in the following description. In some embodiments, pole portion  10  may have coil holders (not shown, but which may be conventional or substantially conventional). In embodiments having coil holders, guide member  30  may be recessed or otherwise shaped to accept the coil holder. In some embodiments not having coil holders, coils C may be bonded so that they remain in the proper position at the ends of poles  12 .  
         [0038]    Wire W is used to wind pole portion  10  and is delivered from a wire source, like nozzle  40 . Nozzle  40  may be positioned at a distance R from rotation axis R 1 . Wire W may originate at a wire supply (not shown) and pass through a tensioner (not shown) before reaching nozzle  40 . Distance R should be sufficient to avoid collision, during rotation around axis R 1 , between nozzle  40  and the outermost radial portions of the rotating structures. The outermost radial portions may be portions of winding guide  30 , parts of pole portion  10 , or portions of clamp members  20  and  21 .  
         [0039]    In some embodiments of the invention, nozzle  40  may be stationary. In such embodiments, nozzle  40  would appear to be orbiting the rotating segment and wire guide structure to an observer rotating with the segment and wire guide structure. Apparent orbit O of the stationary nozzle, as seen by such an observer, is shown in FIGS. 3 and 4. Representative successive positions of nozzle  40  along its apparent orbit O are denoted  40   a - 40   h  in FIGS. 3 and 4. In other embodiments of the invention, nozzle  40  may be configured to move. For example, path  41  shows the deviation of nozzle  40  from orbit O when nozzle  40  is configured to move in directions  40 ′ and  40 ″.  
         [0040]    Wire W may be delivered for winding around pole portion  10  by anchoring its end to the face of the pole portion where termination occurs such that rotation of pole portion  10  pulls wire from nozzle  40 . Alternatively, the wire may be anchored to other rotating structures like clamp members  20  and  21 . Once the wire end has been anchored, wire W is pulled out of nozzle  40  by rotation of pole portion  10  with guide member  30  around axis R 1 . The wire end may be anchored near the bottom of slots  11  (e.g., in position  11   a  of FIGS. 2 and 4), so that the wire tends to be drawn and laid towards the bottoms of slots  11  when rotation around axis R 1  occurs.  
         [0041]    Wire guide member  30  may have features that deviate wire W from orbit O to slot openings  11 ′. Nozzle  40  may be aligned with wings  30   a  of guide member  30  so that when pole portion  10  rotates with guide member  30 , wire W runs along wing  30   a  to enter slots  11 . This may be particularly useful in drawing wire W through opening  11 ′ that extends along length L of pole portion  10  (see FIG. 3). FIGS. 3 and 4 show the wire stretching from opening  11 ′ to nozzle  40  in various instances (denoted by  40   a - 40   h ) of the rotation around axis R 1 . In FIGS. 3 and 4, it appears that nozzle  40  is rotating around pole portion  10  and wire guide member  30 . However, it is actually pole portion  10  and wire guide member  30  that are rotating. FIGS. 3 and 4 are illustrated this way for the sake of clarity and simplicity. FIGS. 3 and 4 show illustrative relative positions of nozzle  40  with respect to rotating pole portion  10  and wire guide member  30 . The rotation direction of pole portion  10  with guide member  30  is indicated with reference letters RO. Wings  30   a  may lead to pole tips  12 ′ and may be slanted to act as a continuation of pole structure  12 . This helps ensure that wire W becomes aligned with slot openings  11 ′. This configuration may also assure that wire W runs smoothly through slot openings  11 ′ to reach its resting location within slot  11 . Overhang  24  of clamp member  20  may mask pole portion  10  in area  15  and may act as a guide surface to keep wire W aligned with opening  11 ′. When nozzle  40  is substantially aligned with end face  10   a  of pole portion  10  (see corner A), guide member  30  may present curved surface  30   b  that continues to draw wire W into slots  11 , towards neck  14 , and towards end face  10   a  of pole portion  10 . Curved surface  30   b  may generally rise to ridge  30   c  (see also FIG. 4) that keeps wire W raised and draws it towards surface  13  of the external core structure surrounding slots  11 .  
         [0042]    This helps ensure that the wound coil will be sufficiently raised above pole  12 . Ridge  30   c  may be above and in front of curved support surface  30   d  of winding guide  30  as viewed, for example, in FIG. 4. In other words, curved support surface  30   d  may be adjacent the axial end of pole  12 , while ridge  30   c  is axially spaced from the axial end of the pole. Accordingly, support surface  30   d  can act as a support for the coil portion being formed around end face  10   a  of pole portion  10 . Wall  30   e  extending from support surface  30   d  and up to ridge  30   c  may act as a front-containing surface to limit the external bulge of the coil from axial end  10   a  of the coil portion. Ridge  30   c  may reduce in height with respect to support surface  30   d  where the wire tends to enter opening  11 ′ on the opposite side of pole  12  (see corner B in FIGS. 2 and 4). This may bring wire W towards opening  11 ′ on the opposite side of pole  12 , at corner B.  
         [0043]    Inviting bulge  21   a  on clamp member  21  may assist in bringing wire W towards opening  11 ′ on the opposite side of pole structure  12  at corner B. Without bulge  21   a , wire W may miss opening  11 ′ and be wound outside slots  11 .  
         [0044]    Nozzle  40  may be moved in direction  40 ′ (i.e., parallel to axis R 1  and towards pole structure  12 ) to assist in drawing wire W towards the bottom of slots  11 , and towards surface  13  of the core structure.  
         [0045]    Movement in reverse direction  40 ″ may assist in bringing wire W towards opening  11 ′ on the opposite side of pole structure  12  at corner B. An example of the relative movement of nozzle  40 , which is the combined effect of nozzle  40  moving in directions  40 ′ and  40 ″ and pole portion  10  rotating about axis R 1 , is shown by dashed line  41 . Thus, the movement of nozzle  40  may need to be synchronized with the rotation of pole portion  10  around axis R 1 . In other words, the axial position of nozzle  40  may be a predetermined function of the angular position reached by pole portion  10  around axis R 1  during rotation.  
         [0046]    In summary, portions  30   b  and  30   c  of guide member  30  are encountered when wire W leaves slot  11  and needs to be drawn around end face  10   a . Other portions, like a final portion of ridge  30   c  and invitation bulge  21   a  are encountered by wire W when it needs to renter slot  11  on the opposite side of pole  12 .  
         [0047]    These specific portions are also typically present on opposite end face  10   a ′ of pole portion  10  to provide similar functions when wire leaves and reenters the slots at opposite end face  10   a ′. Similarly, portions like  30   b  and  30   c  are typically present on guide member  30  in corner D at opposite end face  10   a ′. Furthermore, invitation bulge  21   a  is typically present in corner E at opposite end face  10   a ′. Portions like ridge  30   c  and support surface  30   d  may by located adjacent opposite end face  10   a ′ by extending from corner D to corner E in a manner similar to that that has been described for corner A to corner B of end face  10   a.    
         [0048]    Wings like  30   a  may be present from corner B to corner D to keep the wire aligned with the slot openings on the opposite side of pole  12 .  
         [0049]    The internal structure of guide member  30  presents a seat configured to closely match the described portions and surfaces of guide member  30  with the surfaces of pole portion  10  that they need to be adjacent to. The curved underside of pole  12  may match the bottom of the cavity (see FIG. 4 in which pole  12  is shown in dashed line representation). The bottom of the cavity may mate with underside surface  12 ″ of pole  12 .  
         [0050]    [0050]FIG. 5 is a view showing an illustrative embodiment of assembly units that can be used to rotate clamp members  20  and  21  and guide member  30  around axis R 1 . Shaft  23  carrying slide unit  22  is supported in bearings  51  of casing  52 . End  23 ′ of shaft  23  carries a pulley driven by pulley/belt transmission  53 . Shaft  54  for driving pulley/belt transmission  53  is supported in bearings  55 . Pulley/belt transmission  56  rotates shaft  54 , thereby rotating shaft  23  around axis R 1 . Pulley/belt transmission  56  is driven by motor  56 ′.  
         [0051]    Shaft  31  carrying guide member  30  is assembled in sleeve  65 . Sleeve  65  is supported on bearings  57  of casing  58 . Sleeve  65  is driven to rotate around axis R 1  by pulley belt transmission  62 , which is also connected to shaft  54  for obtaining rotation from motor  56 ′. Shaft  31  has keys received in ways of sleeve  65  so that rotation imparted to sleeve  65  around axis R 1  is also imparted to shaft  31 . The keys of shaft  31 , received in the ways of sleeve  65 , allows shaft  31  to be moved in directions  31 ′ and  31 ″ (FIG. 2) mentioned in the foregoing. Linear actuator  59  is connected to shaft  31  through rotating coupling  60 , to cause shaft  31  to move in directions  31 ′ and  31 ″.  
         [0052]    Furthermore, support plate  61  may be moved in directions  40 ′ and  40 ″ (FIG. 4) mentioned above, as an alternative to moving nozzle  40 .  
         [0053]    The solution of rotating pole portion  10  with respect to nozzle  40  to wind coils C also may allow the winding of coils C with multiple wires. The various wires are drawn from respective nozzles, like nozzle  40 , without the problem of twisting them around each other. This may facilitate separating the wires when required to accomplish termination with equipment like has been described in U.S. Pat. No. 5,193,755. Once the wires have been terminated, lead pulls or manipulation robots like those described in Luciani et al. U.S. Pat. No. 5,065,503 and Luciani et al. U.S. Pat. No. 5,245,748 may be used to anchor the leads C 1  to required anchoring points.  
         [0054]    The surfaces and portions of guide member  30  that have been described to draw wire W into slots  11  may need to be configured to suit the geometry of the stator that needs to be wound. It has been contemplated that some of the surfaces or portions may be omitted, and that others may be added depending on the geometry of the pole portion. It would be desirable for the wire to run smoothly from one surface to another of the guide member in order to possibly avoid jerks that may over-tension the wire. Regularity of the turn distribution and correct depositing of the coils&#39; turns in wanted areas of slots  11 , and also around end faces  10   a  and  10   a ′ of pole portion  10 , may depend on tailoring the surfaces and portions of guide member  30  to the geometry of pole portion  10  and the position of nozzle  40  with respect to pole portion  10  when it is rotating around axis R 1 . At certain times during the rotation of the stator segment  10  and elements  20 ,  21 , and  30 , the wire going from nozzle  40  to stator segment  10  may contact and thus be guided by portions of elements  20  and  21 . These elements may therefore be referred to as part of the wire guide structure of the apparatus. In other words, elements  20  and  21  may constitute a substructure of the wire guide structure. Element  30  may constitute another substructure of the wire guide structure.  
         [0055]    Thus it is seen that apparatus and methods for winding the poles of stators that have pole tips reaching far around the stator core have been provided. Apparatus and methods for winding wire in slots having openings that do not face a purely radial direction with respect to the axis of rotation when the stator is wound by rotating a segment of the stator have been provided. One skilled in the art will appreciate that the present invention can be practiced by other than the described embodiments, which are presented for purposes of illustration and not of limitation, and the present invention is limited only by the claims which follow.