Abstract:
In a method or system for producing a helical stator, a stator core strip is provided having a base portion with spaced tangs extending from the base portion. The strip is driven in a feed direction toward a bending region. At the bending region the strip is bent with an outside pressure member positioned to apply pressure at an outside edge of the strip base portion and with an inside pressure wheel having a plurality of teeth. A backstop surface of the teeth contact an inside edge of the base portion between adjacent tangs to support the base portion as the strip is bent by the outside pressure member. A winding arbor receives the bent strip to collect multiple turns of the bent strip to form the helical stator.

Description:
BACKGROUND 
     It is known to provide a stator core for a motor or alternator which is formed by a stamped helically wound continuous strip. The advantage over a non-helical stator with discrete stacked laminations is less scrap. With a layered lamination stator comprising a plurality of stacked laminations, the center of each lamination becomes scrap material. By stamping a strip and then helically winding that strip, however, there is less scrap loss since only regions between tangs of the stator strip are lost and also perhaps a small scrap strip where the opposite sides of the strip are stamped. 
     In a known method for helically winding a strip for a motor or alternator stator core, it was known to provide an inside pressure wheel which would contact outer ends of tangs of the strip, along with an outside pressure wheel contacting a base portion of the strip. A disadvantage with this known method is that if the tangs are not short, thick, and closely spaced, or the base portion of the strip is too narrow, the tangs can be bent and deformed when the outside pressure wheel applies pressure on the ends of the tangs in a direction of a longitudinal extent of the tang as the strip is being bent. 
     SUMMARY 
     It is an object to improve upon the manufacture of a helical core stator for a motor or alternator, such that tangs of a strip used for the helically wound stator core are not deformed. 
     In a method or system for producing a helical stator, a stator core strip is provided having a base portion with spaced tangs extending from the base portion. The strip is driven in a feed direction toward a bending region. At the bending region the strip is bent with an outside pressure member positioned to apply pressure at an outside edge of the strip base portion and with an inside pressure wheel having a plurality of teeth. A backstop surface of the teeth contact an inside edge of the base portion between adjacent tangs to support the base portion as the strip is bent by the outside pressure member. A winding arbor receives the bent strip to collect multiple turns of the bent strip to form the helical stator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a method and apparatus for helically winding a stator core from a continuous strip; 
         FIG. 2  is a perspective view showing certain operative elements of the method and apparatus of  FIG. 1 ; 
         FIG. 3  is a perspective view of a toothed inside pressure wheel employed in  FIGS. 1 and 2 ; and 
         FIG. 4  is a sectional view showing some of the components of  FIG. 1  taken along line IV-IV in  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the preferred embodiment/best mode illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, and such alterations and further modifications in the illustrated device and such further applications of the principles of the invention as illustrated as would normally occur to one skilled in the art to which the invention relates are included. 
     A method and apparatus or system for producing a helical stator is generally shown in plan view at  10  in  FIG. 1 . A continuous strip of electrical steel is punched in a stamping die  8  to create a stator core strip  11 . The strip  11  comprises spaced tangs  12 , each having a broadened face  12 A, and which project from a base portion  13  of the strip. The strip lies in a channel  14  of a strip guide plate  15 . The channel  14  is covered by a cover plate  16 . The channel has a thickness from a floor  7  to an inside surface of the cover plate which is slightly greater than a thickness of the strip  11 . 
     The strip is moved in a feed direction by use of a strip feed wheel  6  having teeth  6 A. The wheel  6  thus acts like a gear with the teeth  6 A interacting with the tangs  12  to drive the strip forward in the apparatus. The feed wheel  6  is driven via a shaft  17  supported in a bearing block  9  by a drive  18 . A slot  19  in the cover plate  16  shown in  FIGS. 1 and 2  allows the teeth  6 A of the feed wheel  6  to pass down through the cover plate  16  to engage in the regions between the tangs and to exert a force against the trailing edge of the tangs to drive the strip forward. A slot  3  (not visible in  FIG. 1  but shown in  FIG. 2 ) is also provided in floor  7  of channel  14  in line with slot  19  as clearance for teeth  6 A. 
     The bending process is accomplished by a toothed and angled inside pressure wheel  20  and an outside pressure wheel  21 . A vertical surface  20 B (shown in  FIGS. 2 and 4 ) at an outer periphery of each tooth  20 A of the inside pressure wheel  20  extends upwardly through a curved or arcuate slot  22  in the floor  7  ( FIGS. 1 ,  2 ) of channel  14  and serve as a pressure backstop for inside edge  13 A of base portion  13  of strip  11  (see also  FIGS. 2 and 4 ). A similarly arcuate slot  5  in line with slot  22  is also provided in cover plate  16  as clearance for teeth  20 A. The vertical positioning of backstop surface  20 B (see also  FIG. 3 ) is achieved by the design of pressure wheel  20  and by angling a central axis  20 C of shaft  23 , such as 30° from vertical, for example. This is indicated by angle  24  in  FIG. 4 . 
     An outer edge  13 B of strip base portion  13  is in pressure contact with an inner rim  21 B of outside pressure wheel  21 . As shown in  FIG. 2  the outside pressure wheel  21  also has top and bottom circular plates  21 A and  21 C spaced a distance slightly greater than the thickness of the strip  11  and which overlap the strip base portion  13 . 
     Significantly, gaps  20 D ( FIG. 3 ) between teeth  20 A of the inside pressure wheel  20  permit engagement of the leading side edges of the teeth  20 A with trailing side edges of the tangs  12 . The inside pressure wheel  20  is not driven by the shaft on which it is mounted, but rather turns freely as the tangs push against the teeth, with the respective tangs being received in the respective gaps  20 D between the teeth  20 A of wheel  20 . 
     As shown in  FIG. 4 , the shaft  23  is received in a bearing block  25 .  FIG. 4  also shows the angle of inclination  24  of the axle  23  relative to vertical, which is preferably 30° in this embodiment. Also  FIG. 4  clearly shows how the inner edge  13 A of base portion  13  of the strip strikes the vertical surface  20 B at the outside periphery of each tooth  20 A of inner pressure wheel  20 . 
     As shown schematically in  FIG. 1 , the outside pressure wheel  21  is rotatably driven by a drive  26  by a shaft  4 . 
     After the strip  13  has been bent by the inside and outside pressure wheels  20  and  21 , it is deflected upwardly slightly by an inclined ramp  27  ( FIG. 2 ) and then begins winding around an arbor  28  having teeth  28 A. This arbor is shown in fragmentary view in  FIG. 2  at the top, but also in cross-sectional view in  FIG. 4 . The arbor is driven by a shaft  29  mounted in bearing block  30 . A drive  31  rotates the shaft  29  and thus the arbor. As the arbor turns, the helical winding of the stator, with the arbor teeth  28 A between the widened tang faces, is thus built up on the arbor until the stator desired height has been reached, at which time the strip is cut off and no further winding occurs. 
     When the teeth  28 A of the arbor engage between the tang end faces  12 A, the helical winding process occurs after the bending process described above. 
     The inside pressure wheel  20  is also shown in perspective view in  FIG. 3  where the teeth  20 A and gaps  20 D between the teeth are illustrated. The peripheral length of each tooth  20 A at the backstop surface  20 B substantially corresponds to a length of the spacing between the tangs  12  at the strip base portion inside edge  13 A. This inside pressure wheel is mounted on shaft  23  mounted in bearing block  25  as shown in  FIG. 4 . Inside pressure wheel  20  is formed not only of the teeth  20 A but also of a circular base portion  20 E from which the teeth  20 A extend in an upwardly angled or transverse direction. The wheel  20  is designed such that, with the shaft  23  arranged at a 30° angle relative to vertical, the outside backstop surface  20 B near the upper peripheral edge  20 F of the teeth is vertical. Also by angling the shaft  23 , the upper edge of each respective tooth  20 A extends up through the slot  19  in the floor  7  as the tooth rotates up to and then past the slot. 
     The cover plate  16  shown in  FIG. 1  extends laterally to near the outside pressure wheel  21  peripheral surface and has a conforming circular arc segment  16 A shown in  FIG. 1  conforming to the outer periphery of the outside pressure wheel  21 , and more particularly to the outer circumference of the disks  21 A and  21 C. Thus the strip is entrained between the cover plate  16  and the floor  7  of channel  14  of plate  15  throughout the bending process so that steel “ripples” or “folds” are minimized at the base portion  13  of strip  11 . 
     It will be appreciated that the inside pressure wheel  20  supports the base portion  13  during the bending forces exerted by the outside pressure wheel  21 . It should further be noted that the inside pressure wheel  20  does not exert a radial pressure on the tangs during the bending process, so that the tangs are not deformed in an undesirable fashion. Further, the gaps  20 D between the teeth  20 A in the inside pressure wheel receive the tangs  12  during the bending of the strip, these tangs driving the inside pressure wheel to rotate freely since the inside pressure wheel mounting shaft is free to rotate. 
     With the apparatus and method of the preferred embodiment, helical stator cores can be manufactured with relatively long and thin tangs with relatively narrower base portions supporting the tangs since radial forces, that is forces acting along the longitudinal extent direction of the tangs, are substantially not present. The creation of such helical wound stators having relatively long and thin tangs allows for additional winding wire to be employed in the gaps or coil areas between the tangs, thus permitting larger horsepower motors or alternators to be manufactured with stators constructed of helically wound cores. 
     The drive  18  for the strip feed wheel  6 , drive  26  for the outside pressure wheel  21 , and drive  31  for the winding arbor  28 , have only been shown schematically. These drives are synchronized with one another. The form and structure of these drives and the method of synchronization has not been described in detail since various different kinds of synchronization or drives can be employed and are well known by one skilled in the art such as gears, belts, synchro-motors, and electronic control of the various drives. 
     The strip feed wheel  6  may take various forms and other types of strip drives may be employed. Similarly, other shapes and designs may be employed for the outside pressure wheel  21  and for the inside pressure wheel  20 . Similarly the winding arbor may have various designs and shapes. Finally, the strip guide plate  15  with its channel  14  and the cover plate  16  may also be designed in other ways to accomplish appropriate confinement of the strip as it is being bent to provide the helical winding. Also, the bearing blocks for the shaft of the inside pressure wheel and the shaft of the outside pressure wheel may take various forms and may be located in different regions. Also the bearing block  9  for the shaft  17  of the strip feed wheel  6  may be located at different regions. 
     While a preferred embodiment has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention both now or in the future are desired to be protected.