Abstract:
Method for removing winding conductors from a twisting machine and placing them in a rotor or stator stack. For a plurality of rectangular winding conductors each having a pair of legs separated by an amount equal to the distance between a predetermined number of rotor or stator slots in which they will be inserted, moving a plurality of fingers of a clamping assembly between the legs of a plurality of winding conductors in a twisting fixture to retain the winding conductors, moving the clamping assembly away from the twisting fixture to withdraw the winding conductors from the twisting fixture, providing relative movement of the clamping assembly and a rotor or stator to insert free ends of the winding conductors into a rotor or stator, and moving the fingers of a clamping assembly from between the legs of a plurality of winding conductors. A preferred embodiment of the method is disclosed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of electric motors. 
     2. Prior Art 
     Tecnomatic S.p.A., assignee of the present invention, has in the past made a limited number of motor stators and D.C. motor rotors using flat or square wire for the windings. In that regard, it is to be noted that as used herein, “flat” or “square” wire means wire having four substantially flat sides, each joined to adjacent sides, typically by a rounded edge. In the case of square wire, the wire may be formed in the square shape and then coated with typical winding insulation, or in some cases, pre-coated round wire has been rolled into the square shape. Rolling of round wire to a square shape has definite limits if the insulation is not to be damaged, though smaller rounded edges may be achieved if the wire is first formed by drawing or otherwise formed into the square shape and then coated. Even if the wire is first formed in the desired shape and then coated, some degree of rounding on the edges is desired for various reasons, including prevention of surface tension from pulling the coating away from the sharp edges during coating, preventing the sharp edges from cutting through the coating afterward, and preventing electric field concentration on the sharp edges to induce early breakdown. Thus, as used herein, the words “square” or “flat” or equivalent words used to describe the cross-section of an insulated copper wire are used in the general sense and are not to be construed as excluding significant or substantial rounded corners joining the substantially flat sides. “Flat” as used herein and in the claims means having two opposite sides having a greater separation than the other two opposite sides, its width being greater than its thickness. “Straight” as used herein and in the claims means substantially free of bends. Accordingly, either a flat or a square conductor may or may not be straight. “Rectangular” as used herein is a more general term meaning flat or square, square being a special case of rectangular wherein the dimension between two opposite sides is equal to the dimension between the other two opposite sides. 
     In the prior art stators, the wire has been cut to the desired length and stripped, then bent into a hairpin shape by hand on a one at a time basis, then the two legs of the hairpin separated one hairpin at a time and hand inserted into one end of a stator, with the stripped ends of the wires sticking out of the other end of the stator being all bent all in one row uniformly in one direction and all in the adjacent row uniformly bent in the opposite direction so interconnection of wires in the two rows forming a given phase could be welded, one at a time, to provide the stator windings. However, to bring out the connections to the phases, and to interconnect phases, the corresponding wires needed to be re-bent to isolate them from the connections within each phase, something again previously done by hand. 
     The use of the flat or square wire for the windings produces very efficient and high power to weight ratio motors because of the greater cross-section of copper that can be put into a winding slot. However, the procedure described above is slow and highly labor intensive, and not suitable for a mass produced motor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary hairpin conductor with ends stripped. 
         FIG. 2  shows a twisting fixture for simultaneously bending hairpin conductors to form rotor or stator conductors. 
         FIG. 3  shows a stator or winding conductors as bent in the twisting machine from a hairpin conductors of  FIG. 1 . 
         FIG. 4  is a top view of the overall system in which the exemplary embodiment of the present invention is used. 
         FIG. 5  shows a motor stator with winding conductors therein in an elevated state. 
         FIGS. 6   a  through  6   d  illustrate an extractor for extracting winding conductors from a twisting fixture. 
         FIG. 7  is a view of a guide for the extractor of  FIGS. 6   a  through  6   d.    
         FIG. 8  illustrates a clamp assembly used to remove winding conductors from the twisting fixture and place the same in a rotor or stator. 
         FIG. 9  is a side cross section of the clamp assembly of  FIG. 8 . 
         FIG. 10  illustrates a part of the body member of the clamping assembly of  FIG. 8 . 
         FIGS. 11   a  and  11   b  illustrate exemplary clamping fingers used in the clamping assembly of  FIG. 8 . 
         FIG. 12  presents an exemplary stator  32  with insulators therein. 
         FIGS. 13 and 14  illustrate the swaging fixture for swaging one end of insulators in a rotor or stator. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The purpose of the present invention is to simultaneously remove all rectangular winding conductors from a twisting fixture and to place the same in the desired rotor or stator core. In particular, a rectangular insulated conductor with ends stripped is bent into a hairpin conductor  20  as shown in  FIG. 1 . Then all conductors required, except in the case of special length stator conductors used for phase connections in AC motors, are simultaneously bent into rotor or stator conductors  24  ( FIG. 3 ) in the twisting fixture  22  of  FIG. 2 . After the twisting operation, the conductors  24  reside in fixture  22 , with the fixture  22  having a sufficient depth so that the ends of conductors  24  are still within pockets within the fixture. In that regard, the word “pockets” as used herein is used in the general sense to include not only an enclosure on all sides but to further include slots which are open on one side. 
     A top view of the overall system in which the present invention is used may be seen in  FIG. 4 . After the twisting operation, table  26  is rotated so that the fixture  22  will be at the winding conductor extraction station  28 . In that regard, there is a second rotatable assembly  30 , the function of which will subsequently be described. 
     The first part of the extraction process is to raise the winding conductors  24  to provide access to the sides thereof and to provide support for the legs of the winding conductors reasonably close to the ends thereof so that the ends will remain accurately spaced even when removed from the fixture. The result of this operation is much like illustrated in  FIG. 5 , with all winding conductors  24  being substantially elevated in comparison to their position in fixture  22  in  FIG. 2 .  FIG. 5 , however, is illustrating the conductors  24  in a motor stator  32  rather than the fixture, though the Figure may be taken as representative of the position of the winding conductors in either the stator or fixture, depending upon what stage the extraction process is in. 
     To elevate the winding conductors  24  in the fixture  22  at the extraction station  28 , an extractor assembly is positioned immediately below the fixture, and of course, the fixture is accurately angularly indexed to that assembly. The major components of the extractor assembly may be seen in  FIGS. 6   a  through  6   d . In particular, an internal extractor  34  and an external extractor  36  which fits around the internal extractor may be seen in  FIGS. 6   c  and  6   d , respectively. These extractors are mounted on a support  36  ( FIG. 6   b ) which may be moved up and down by actuators  38 . An assembly  40  supports a guide  42  which guides the upper ends of the inner extractor  34  and the outer extractor  36  immediately below the fixture  22  ( FIG. 2 ) to be sure that the individual extractor members are properly guided into the fixture  22 . The guide  42  may be better seen in  FIG. 7 , which is a view thereof corresponding to  FIG. 6 , but taken on an expanded scale. Note that in the preferred embodiment twisting fixture  22 , the inner and outer pockets are actually separated from each other by a wall, and accordingly, separate extractor elements  34  and  36  are provided. Once the extractor is raised, the upper end of extractors  34  and  36 , as well as the ends of the winding conductors  24 , will remain within the fixture, though with the winding conductors substantially elevated, such as by way of example shown in  FIG. 5 . 
     Above the extractor station  28  ( FIG. 4 ) is a clamp assembly shown in side view in  FIG. 8 . This assembly may be raised to allow for rotation of table  26  with the fixture  22  to the extraction station  28  before the wire conductors are elevated from their positions shown in  FIG. 2 , and then lowered so that the bottom thereof is just above the top of the fixture  22 . The clamp assembly, generally indicated by the numeral  44  in  FIG. 8 , has a clamp subassembly  46  on the lower part thereof. The clamp subassembly may be seen in the side cross-section of  FIG. 9 , which illustrates not only the clamp subassembly  46  but also the relative position of the winding conductors  24  therein just before or as clamped. The clamping subassembly  46  has a body member  48 , a part of which is shown in  FIG. 10 . In particular, the body member  48  has a plurality of downward protrusions  50  equal in number to the number of slots in the rotor or stator and in the fixture  22 , sixty in the exemplary embodiment ( FIG. 2 ). As may be seen in  FIG. 10 , each of the projections  50  have a screw hole therein for attachment of stabilizing plate  52  ( FIG. 9 ) in the clamp subassembly. 
     Referring again to  FIG. 9 , the clamp subassembly  46  has a plurality of outer fingers  54  and inner fingers  56 , only one of which is visible in  FIG. 9 . The outer fingers  54  fit between projections  50  and are captured for rotation between parts  58  and  60  and driven in rotation by arm  62  when the assembly including members  58  and  60  is raised or lowered. Similarly, fingers  56  are mounted for rotation between members  64  and  48  and are captured and driven in rotation by members  66  and  68 . Exemplary fingers may be seen in  FIGS. 11   a  and  11   b . Finger  54  of  FIG. 11   b  slides between each group of four legs of the winding conductors and thus are equal in number to the slots in the rotor or stator and in the fixture  22 . For that purpose, they are tapered on surfaces  60  to hold the winding conductors in the proper spaced apart condition while assuring that when the clamp subassembly is raised, the winding conductors must also be raised because of the shape of the surface of the wedge  60  and region  62 . Fingers  56  shown in  FIG. 11   a  have a surface  64  that will span two slots, and accordingly, only thirty such fingers are used in the exemplary embodiment. The surface  64  is appropriately curved so as to radially contact the inner surface of the legs of the inner winding conductors to support the same, thereby preventing the inadvertent deflection of the winding conductors radially inward when the clamping subassembly clamps the wire conductors. In that regard, to clamp the wire conductors, members  58  and  66  are moved downward to cause fingers  56  to move outward to support the inner diameter of the conductor wires, and members  58  and  60  are also moved downward to cause fingers  54  to move between conductor wires to both properly grip and space the conductor wires. 
     While the extraction station  28  ( FIG. 4 ) is operating as described above, a stator core having insulators therein is loaded into the system at station  70  ( FIG. 4 ), either manually or automatically, into a fixture providing precise positional and angular location thereof. A portion of an exemplary stator  32  with insulators  72  therein may be seen in  FIG. 12 . The insulators are of typical insulation paper commonly used, and are automatically placed in the stator slots in other equipment. As may be seen in  FIG. 12 , the insulators are slightly longer than the stator core itself, and accordingly, somewhat project out of the stator core on both sides thereof, one side being visible in  FIG. 12 . Once the stator with insulators is loaded into station  70 , a swaging assembly  74 , shown in  FIG. 13 , with four rows of projections  76 , shown in  FIG. 14 , extending into the insulators to swage or expand the same in the circumferential direction. During this operation, movement of the insulators deeper into the stator slots is prevented by a backup plate supporting the opposite ends of the insulators. The swaging as described has at least two advantages. First, it assists in the feeding of the ends of the winding conductors into the appropriate insulator opening. Secondly, it prevents a winding conductor from simply pushing the insulator deep into the slot. 
     Once the conductor wire extraction at station  28  and the swaging operation at station  70  ( FIG. 4 ) are complete, assembly  30  is rotated to bring the clamp subassembly  46  ( FIGS. 8 and 9 ) over the insulated stator or insulated rotor and lowered so that the lower ends of the winding conductors extend into the appropriate insulator in the insulated slots. Thereafter, members  58  and  60  ( FIG. 9 ) are raised, as are members  66  and  68 , releasing the winding conductors  24 , with an extractor  78  visible in  FIG. 9  being lowered to be sure none of the winding conductors remain retained by any of fingers  54  or  56 . The entire clamp assembly  44  ( FIG. 8 ) is then raised and rotatable assembly  30  is rotated back through 180° for the repeat of the process. 
     Thus in accordance with the present invention, rectangular winding conductors formed in a twisting fixture are all simultaneously removed from the twisting fixture and automatically placed in an insulated stator or insulated rotor, with the winding conductors  24  standing relatively high in the rotor or stator as shown in  FIG. 5 . In a later stage of the fabrication process, the winding conductors  24  will be pushed down into the stator or rotor to their final elevation, ready for connections to be made at the other side of the stator or rotor. 
     While a preferred embodiment of the present invention has been disclosed and described herein for purposes of illustration and not for purposes of limitation, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.