Abstract:
A tool and method for winding and forming a field coil for field assembly, such as a stator, includes separable tool halves defining a winding cavity therebetween. The winding cavity receives magnet wire that is wound therein, such as by rotating the tool or a winding nozzle. The magnet wire generally conforms to the shape of the winding cavity such that when the tool halves are separated, a field coil having a net shape is produced. Once the magnet wire is sufficiently deposited within the winding cavity, wires of the coil may be bonded together either through a resistive heating process such as by passing an electrical current through the coil or through other heating or chemical bonding methods to thereby maintain the net shape of the field coil once it is removed from the tool.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/649,218 filed on Feb. 2, 2005. The disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to manufacturing coils for dynamoelectric machines, and more particularly to improved coil winding tooling and method of using it. 
       BACKGROUND OF THE INVENTION 
       [0003]    Dynamoelectric machines are machines that generate electric power or use electric power. Common types of dynamoelectric machines are alternators, generators, and electric motors. 
         [0004]    Electric motors are used in a wide variety of applications involving power tools such as drills, saws, sanding and grinding devices, and yard tools such as edgers and trimmers, just to name a few. These devices all make use of electric motors having an armature and a field, such as a stator. 
         [0005]      FIG. 1  shows a typical prior art stator  100  for an electric motor. Stator  100  is formed from a lamination stack  102  within which a plurality of windings of magnet wires  104  are wound to form field coils  114 . Lamination stack  102  is formed by stacking together an appropriate number of individual laminations  108  and welding them together. The individual laminations  108  are typically made by stamping them from steel. To do so, loose laminations  108  are loaded in a slacker. The stacker picks up the appropriate number of laminations  108  and places them in a fixture where they are welded together. The laminations  108  are formed with slots so the resulting lamination stack  102  has slots  110  in which the magnet wires  104  are wound. 
         [0006]    Magnet wires, as that term is commonly understood, are wires of the type conventionally used to wind coils in electric machines, such as armatures and stators. Prior to winding the magnet wires  104 , insulating sleeves or insulating slot liners (not shown), such as vulcanized fiber, are placed in the slots  110  and end rings  112  are placed on the lamination stack  102 . End rings  112  are illustratively made of plastic and formed to include coil forms  116 . Field coils  114  are then wound by winding the magnet wires  104  in the slots  110 . After the field coils  114  are wound, the end of the magnet wires  104  are appropriately terminated, such as to terminals  118  in a terminal post  120 . The magnet wires  104  are then bonded together, such as by the application of heat when bondable magnet wires are used. 
         [0007]    Bondable magnet wires are magnet wires layered with a heat activated thermoplastic or thermoset polymer adhesive. One type of bondable magnet wires commonly used is wire available under the trade name BONDEZE from Phelps Dodge of Fort Wayne, Ind. Alternatively, the magnet wires  104  may be bonded by a trickle resin process described below. Where the stator  100  will be used in an application that exposes it to a particularly abrasive environment, such as a grinder, an epoxy coating is applied to the field coils  114  for abrasion protection. 
         [0008]    In the manufacturing process for the stator described above, once the magnet wires have been wound in the slots and the ends of the magnet wires terminated, the magnet wires are bonded, if bondable wire is being used, and a “trickle” resin is applied over the magnet wires, if trickle resin is being used. The process of applying the trickle resin is a somewhat difficult process to manage to obtain consistent results. It also has a number of drawbacks, not the least of which is the cost and difficulty of performing it with reliable, consistent results. 
         [0009]    Initially, the trickle process requires the use of a relatively large and expensive oven to carefully preheat the partially assembled stators to relatively precise temperatures before the trickle resin can be applied. The temperature of the trickle resin also needs to be carefully controlled to achieve satisfactory flow of the resin through the slots in the lamination stack. It has proven to be extremely difficult to achieve consistent, complete flow of the trickle resin through the slots in the lamination stack. As such, it is difficult to achieve good flow between the magnet wires with the trickle resin. A cooling period must then be allowed during which air is typically forced over the stators to cool them before the next manufacturing step is taken. Further complicating the manufacturing process is that the trickle resin typically has a short shelf life, and therefore must be used within a relatively short period of time. 
         [0010]    The end result is that stators must often be designed for the process as opposed to optimum performance and cost. 
       SUMMARY OF THE INVENTION 
       [0011]    A tool for forming a field coil for a field assembly, such as a stator, in accordance with the invention has separable tool halves defining a winding cavity therebetween. The winding cavity receives magnet wire that is wound therein. The magnet wire generally conforms to the shape of the winding cavity such that when the tool halves are separated, a field coil having a net shape is produced. 
         [0012]    In an aspect, once the magnet wire is sufficiently deposited within the winding cavity, the coil is bonded either through a resistive heating process, such as by passing an electrical current through the coil, or through other heating or chemical bonding methods to thereby maintain the net shape of the field coil once it is removed from the tool. 
         [0013]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0015]      FIG. 1  is a perspective view of a prior art stator; 
           [0016]      FIG. 2  is a flow chart of a method for forming a stator with pre-formed field coils that are formed in accordance with an aspect of the invention; 
           [0017]      FIG. 3  is an exploded assembly view of a stator having pre-formed field coils formed in accordance with the method of  FIG. 2 ; 
           [0018]      FIG. 4  is a perspective view of a pre-formed field coil prior to molding; 
           [0019]      FIG. 5  is a perspective view of a coil tool for forming a field coil in accordance with an aspect of the present invention; 
           [0020]      FIG. 6  is a front view of the coil tool of  FIG. 5 ; 
           [0021]      FIG. 7  is an exploded view of the coil tool of  FIG. 5  oriented to show a perspective view of a male tool half; 
           [0022]      FIG. 8  is an exploded view of the coil tool of  FIG. 5  oriented to show perspective view of a female tool half; and 
           [0023]      FIG. 9  is a side view of a forming tool used in compression of a field coil. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
         [0025]    Referring to  FIGS. 2-9 , a process for making a field assembly, such as stator  300  is shown. At step  210 , a coil, such as coil  301 , for field coils  304  of stator  300  is wound to a predetermined shape, preferably net shape, by winding magnet wires  303  to the predetermined shape. “Net shape” means the final shape of the field coils  304  in an assembled stator  300 . At step  212 , the magnet wires  303  are bonded together. The magnet wires  303  are preferably bondable magnet wires such as BONDEZE wires, having a layer of heat activated thermoplastic or thermoset adhesive thereon and heat is applied to the formed coil  301  to activate the adhesive on the magnet wires  303  to bond them together. 
         [0026]    Field coils  304  have coil ends  305  with lead wires  302  extending therefrom which are brought out at step  214  from the formed coil  301 . Lead wires  302  can be brought out using different alternatives. Coil ends  305  may illustratively be terminated at terminals  307  and lead wires  302  attached to the terminals  307 . Lead wires  302  can be attached directly to coil ends  305 . Lengths of coil ends  305  can be insulated by various methods, such as shrink tubing, various wall thickness TFE or PTFE tubing, and the insulated lengths provide the lead wires  302 . The use of tubing, such as TFE or PTFE tubing, in addition to insulating the coil ends  305 , further provides the advantages of strain relief and added rigidity to lead wires  302 . Sliding tubing such as TFE or PTFE tubing over the coil ends  305  shields them and the tubing can be retained by any type of end termination. 
         [0027]    At step  216 , the formed coil  301  is insulated to form field coil  304 . The formed coil  301  can be insulated by encapsulating it with an encapsulation material  309  that forms an encapsulation  313 . The encapsulation material  309  is illustratively an elastomeric thermoplastic or thermoset plastic, such as thermoset liquid silicon rubber. Encapsulation material  309  is illustratively injection molded around field coils  304 . It should be understood that other processes and materials can be used to encapsulate the formed and bonded coils with encapsulation material  309 , such as transfer molding or spraying the encapsulation material  309 . The encapsulation material could also be a more rigid thermoset. The encapsulation material may illustratively be thermally conductive and could also be a more rigid type of thermally conductive plastic, such as a Konduit® thermoplastic commercially available from LNP Engineering Plastics (GE Plastics) of Exton, Pa. The encapsulation material may illustratively be applied using the known vacuum impregnation process. The formed field coil  301  would be placed in a vacuum chamber and the encapsulation material wicks onto the field coil  301 . It should be understood that the coil  301  can be insulated in ways other than encapsulation, such as with paper insulation wrapped or otherwise disposed around it. 
         [0028]    Insulated field coils  304  are assembled with stator core pieces  306  to form stator  300 , as shown in step  218 . Stator core pieces  306  include pole pieces  308  and back iron or return path pieces  310 . 
         [0029]    With particular reference to  FIGS. 5-9 , a coil forming or winding tool  500  in accordance with the invention for use in forming the field coils  301  will be described in detail. The tool  500  includes a male tool half  502  and a female tool half  504 . The male tool half  502  is matingly received by the female tool half  504  such that a winding cavity  506  is formed generally therebetween. 
         [0030]    The male tool half  502  includes a main body  508  and a projection  510  extending from the main body  508 . Projection  510  may illustratively be integrally formed with main body  508 , or it may be a separate part that is affixed to main body  508 . The main body  508  may illustratively include a plurality of attachment apertures  512  ( FIG. 8 ) formed on a face  513  that aid in selectively fixing the male tool half  502  to a winding machine (not shown). The projection  510  includes a generally arcuate surface  515  ( FIG. 7 ) extending between shoulders  516  of projection  510  with a recess  518  illustratively in the center thereof. The arcuate surface  515  cooperates with the female tool half  504  to define the winding cavity  506  with the recess  518  matingly receiving a projection  524  of the female tool half  504  to properly align the female tool half  504  with the male tool half  502 , as will be described further below. It should be understood, however, that the male tool half could include projection  524  and the female tool half include recess  518 . 
         [0031]    The female tool half  504  includes a main body  520  having opposed shoulders  521  having arcuately inwardly facing surfaces  523  ( FIG. 8 ) that together define a generally arcuate concave surface  528 . Arcuate surface  528  cooperates with arcuate surface  515  of the male tool half  502  to define the winding cavity  506 . Main body  520  also has projection  524  extending from main body  520  illustratively at a center between opposed shoulders  521 . Projection  524  may illustratively be formed integrally with main body  520  or may be a separate piece that is affixed to main body  520 . The main body  520  may also illustratively include a plurality of attachment apertures  526  formed on a face  527  generally opposite from the projection  524  to aid in attachment of the female tool half  504  to a winding machine (not shown). 
         [0032]    It should be understood that tool  500  can be secured in the winding machine in other ways. For example, tool  500  may be provided with a self locking mechanism, such as a twist-lock mechanism, so that male and female tool halves  502 ,  504  can be locked together and tool  500  then placed in the winding machine. 
         [0033]    It should be understood that tool  500  can be configured so that the formed coil  301  is not symmetrical. For example, formed coil  301  may have end coils of different shapes. In which case, the elements of male and female tool halves  502 ,  504  are configured to provide the desired shape of formed coil  301 . Projection  524  of female tool half  504  and recess  518  of male tool half  502  may then not be centrally located in their respective tool halves. 
         [0034]    In operation, the male and female tool halves  502 ,  504  are fixedly attached to a winding machine by fasteners (not shown) inserted into attachment apertures  512 ,  526 , respectively. The tool halves  502 ,  504  are aligned in the tool  500  such that the recess  518  of the male half  502  opposes the projection  524  of the female half  504 . When the winding machine brings the tool halves  502 ,  504  together, the projection  524  is seated within the recess  518  to align the tool halves  502 ,  504 . Alternatively, as discussed above, male and female tool halves  502 ,  504  may be placed in the winding machine after being locked together. 
         [0035]    Once the projection  524  is fully received by the recess  518 , the tool  500  is in a closed position. At this point, the arcuate surface  515  of the male tool half  502  opposes the concave surface  528  of the female tool half  504  such that a gap is formed between the two tool halves  502 ,  504 . The gap defines the winding cavity  506  in which the magnet wire  303  is wound during formation of the field coils  301 , as will be described further below. Alternatively, the two tool halves  502  and  504  may be secured together by alternate means such as screws (not shown), and then inserted and aligned into the winding machine for winding. After the winding step  210  is completed, the tooling can be removed from the machine for the bonding operation  212 . Alternatively, the bonding operation may be performed prior to removing the tool  500  from the winding machine. 
         [0036]    With particular reference to  FIGS. 5-9 , the operation of the tool  500  is described. The magnet wire  303  is inserted into the winding cavity  506  of tool  500 . The leading end of the magnet wire  303  is secured. It may be secured to tool  500  such as by securing it to a tool half  502 ,  504 , or by clamping it between tool halves  502 ,  504  as the winding machines closes the tool  500  (i.e., moves the tool halves  502 ,  504  in direction Z of  FIG. 6 ). It may otherwise be secured such as by as by clamping it to an element of the winding machine. At this point, the magnet wire  303  is prevented from disengaging the tool  500 . 
         [0037]    Once an end of the magnet wire  303  is secured to the tool  500 , the winding machine rotates the tool  500  about axis “X” ( FIG. 6 ). Rotation of the tool  500  about axis X causes the magnet wire  303  to be placed under tension. The tensile force exerted on the magnet wire  303 , due to rotation of the tool  500 , causes the magnet wire  303  to wrap around the projections  510 ,  524  and begin to fill the winding cavity  506 . It should be understood that the tool  500  could be kept stationary and a winding nozzle rotated about tool  500  to wrap the magnet wire  303 . 
         [0038]    The tool  500  (or the winding nozzle) is continuously rotated until the desired number of turns of magnet wire  303  is achieved in the coil  301 , thus filling the winding cavity  506 . The winding of magnet wire  303  is then stopped and an outermost portion, referred to as a trailing edge, of the magnet wire  303  in the winding cavity  506  is secured. The trailing edge of magnet wire  303  may be secured to the tool  500 , such as by securing it to a tool half  502  or  504 , or otherwise secured such as by clamping it to an element of the winding machine. The magnet wire  303  is then cut from the wire supply (i.e., spool, etc.). 
         [0039]    The magnet wire  303  is wound around the projections  510 ,  524  and has a wound shape similar to that of the winding cavity  506 . At this point, winding and forming of the magnet wire  303  is substantially complete and takes the basic form of the coil  301 . 
         [0040]    Coil  301  may preferably be bonded prior to separation of the tool halves  502 ,  504  and removal from the tool  500 . Magnet wire  303  of coil  301  is bonded together either by sending a current through the wire  303  (i.e., resistance heating) or by chemically bonding, as previously discussed. It should be understood that while the magnet wire  303  has been described as being bonded while the coil  301  is still in the tool  500 , it should be understood that the coil  301  could alternatively be bonded after the coil  301  has been removed from the tool  500 . However, it should be further noted that one advantage of bonding the magnet wire  303  when the coil  301  is still in the tool  500  is that it ensures that the coil  301  maintains its precise shape when it is removed from the tool  500 . The coils  301  may also be compressed during bonding to minimize the air gaps between the magnet wires, resulting in improved heat transfer between adjacent magnet wires  303  and improved bonding strength between adjacent magnet wires  303 , and increasing slot fill when coil  301  is placed in a slot of a field. 
         [0041]    Compression of the coil  301  may be accomplished by the winding machine exerting a compressive force on the tool halves  502 ,  504  in the Z direction once the magnet wire  303  has sufficiently filled the winding cavity. As can be appreciated, further compression of the tool halves  502 ,  504  in the Z direction causes the projection  524  to traverse farther into the recess  518  and thereby move the tool halves  502 ,  504  closer together thus applying a compressive force a coil  301 . 
         [0042]    Alternatively, the two halves  502 ,  504  could be completely compressed during winding and bonding through interaction of a forming tool  507  ( FIG. 9 ) with the coil  301 . The forming tool  507  includes a pair of forming blades  509  that are interconnected by a cross-member  517 . The forming blades  509  are inserted through slots  519  ( FIG. 7 ) in the male tool half  502  of the tool  500  and engage the coil  301 . The blades  509  enter the tool  500  and compress the coil  301 , illustratively just after the bonding current is stopped while the thermoplastic bonding layer (adhesive) is still in the softened state, thereby compressing the coil  301  while still in the tool  500 . The coil  301  may also be compressed while it is still being heated. 
         [0043]    It should be understood that the forming tool may illustratively be part of one or both male and female tool halves  502 ,  504 . For example, forming blades similar in shape to forming blades  509  may illustratively be entrained in slots  519  of male tool half  502  and urged against magnet wire  303  at an appropriate point in the winding cycle. 
         [0044]    Once formation of the coil  301  is complete, the forming tool  507  is removed from slots  519 , the tool halves  502 ,  504  are separated, and the coil  301  is removed from the tool  500 . At this point, assuming that the coil  301  was bonded in the tool  500 , the coil  301  is complete and is ready for testing at step  213  prior to being assembled into the stator  300 . 
         [0045]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.