Abstract:
An electric motor is provided including a stator and an armature received within the stator for rotational movement within the stator. The armature includes an armature shaft on which a commutator is mounted, and a lamination stack also mounted on the armature shaft and having radially extending teeth that form slots therebetween. The armature further includes end insulator arranged at an end of the lamination stack, the end insulator having a base portion fitted around the armature shaft and insulating teeth corresponding to the radially extending teeth of the lamination stack. A set of coils are wound in the lamination stack slots and the end insulator slots. In an embodiment, at least a portion of the insulating teeth has a greater thickness than at least a portion of the base portion. In another embodiment, at least one of said insulating teeth has a greater thickness than at least another of said insulating teeth. In yet another embodiment, the end insulator has a uniform thickness of at least 5 mm.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This utility application claims the benefit of U.S. Provisional Application No. 61/650,622 filed May 23, 2012. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to power tools, and more particularly to an end insulator for an armature lamination stack of a motor in a power tool. 
       BACKGROUND AND SUMMARY 
       [0003]    Electric motors are used in a variety of applications, including power tools. Electric motors may be brushed or brushless. In a typical brushed motor, the motor includes a motor armature coupled to a commutator assembly and a shaft, and a stator assembly that may include permanent magnets attached to the inner circumference of the stator. Two brushes may be provided in contact with the commutator assembly to drive the motor armature. The commutator is fixed for rotation with the motor shaft and provides an electrical connection between the rotating armature and the stationary brushes. Electrical leads selectively link the brushes to a power source. For a more detailed description of electric motors and power tools utilizing such motors, reference is made to U.S. Pat. No. 7,126,242 issued Oct. 24, 2006, and U.S. Pat. No. 7,893,586 issued Feb. 22, 2011, both of which are assigned to Black &amp; Decker Inc, and both of which are incorporated herein by reference in their entireties. 
         [0004]      FIG. 1  depicts a perspective view of a rotor assembly  100  including a motor armature  102  affixed to the motor shaft  104  for rotation with a commutator  106 . The motor armature  102  may, for example, include a lamination stack that forms a series of peripheral slots  110 .  FIG. 2  depicts a cross-sectional view of the same rotor assembly  100  with a series of insulated conductive wires  108  wound in the armature slots  110  to form armature coils. A layer of insulating material (e.g., insulating paper)  112  is disposed within each lamination slot  110  to insulate the lamination slot  110  from the conducting wires  108 . Ends of the wires are fused to segments of the commutator  106 . Commutator  106  may, by way of example, include 24 independent segments. 
         [0005]    An armature end insulator  114 , commonly referred to as a stack insulation, end fiber or end spider, is provided at one or both ends of the armature lamination stack  102  in order to provide some separation between the lamination stack  102  and the conductive wires  108 . The UL standards as relate to power tool industry safety features require a lamination stack end insulation of approximately 2 mm, although end insulation of 2.5 mm is common to account for material and process tolerances. Once the winding process is complete, a wedge (not shown) is inserted into the peripheral slots above the windings to shield the windings from dust and debris. 
         [0006]    Winding the armature is typically performed in several stages, where a first round of coils is sequentially wound into the peripheral slots  110  followed by another, and this process is repeated until the slots  110  are filled to a desired level. A challenge in winding the armature is that it is difficult to position the wire coils within the peripheral slots in an efficient and compact manner to obtain the maximum amount of wire within each slot fill. Therefore, a mechanism to pack in the most amount of conductive wire into the slots is desirable. 
         [0007]    According to an embodiment of the invention, an electric motor is provided including a stator and an armature received within the stator for rotational movement within the stator. In an embodiment, the armature includes an armature shaft on which a commutator is mounted, and a lamination stack also mounted on the armature shaft and having radially extending teeth that form slots therebetween. The slots are arranged circumferentially around a periphery of the lamination stack. The armature further includes end insulator arranged at an end of the lamination stack, the end insulator having a base portion fitted around the armature shaft and insulating teeth corresponding to the radially extending teeth of the lamination stack that form slots therebetween. In an embodiment, at least a portion of the insulating teeth has a greater thickness than at least a portion of the base portion. A set of coils are wound in the lamination stack slots and the end insulator slots. The shape of the end insulator according to this embodiment guides the coils to be wound more compactly in the lamination stack slots, as will be discussed in detail later. 
         [0008]    According to an embodiment, the end insulator comprises an inner substantially flat surface mounted on the end of the lamination stack and an outer uneven surface. In an embodiment, each insulating tooth comprises a first extension surface extending from an outer surface of the base portion at a first angle. Each insulating tooth may further include a second extension surface extending from the first extension surface at a second angle. The second extension surface may be arranged at an angle of 0 to 10 degrees with respect to the outer surface of the base portion. In an embodiment, the base portion has a thickness of approximately 1-3 mm and the insulating teeth have various thickness levels between approximately 2 to 5 mm. In an embodiment, wherein each insulating tooth comprises two walls extending longitudinally and substantially in parallel from the inner surface of the end insulator to the outer surface thereof, said walls defining said plurality of slots of the end insulator. In an embodiment, each insulating tooth further includes a support rib corresponding to ribs at the ends of radially extending teeth of the lamination stack, the insulating teeth extending from the inner surface of the end insulator to the outer surface thereof. 
         [0009]    According to an alternative embodiment of the invention, an electric motor is provided including a stator and an armature received within the stator for rotational movement within the stator. The armature includes an armature shaft on which a commutator is mounted, and a lamination stack also mounted on the armature shaft and having radially extending teeth that form slots therebetween. The slots are arranged circumferentially around a periphery of the lamination stack. In an embodiment, the armature further includes end insulator arranged at an end of the lamination stack, the end insulator having a base portion fitted around the armature shaft and insulating teeth corresponding to the radially extending teeth of the lamination stack that form slots therebetween. In an embodiment, at least one of the insulating teeth has a greater thickness than at least another of the insulating teeth. A set of coils are wound in the lamination stack slots and the end insulator slots. 
         [0010]    In an embodiment, at least two of the insulating teeth that are arranged opposite one another have the same thickness as the base portion. In an embodiment, thicknesses of a subset of the insulating teeth gradually increase around the end insulator. In an embodiment, the base layer includes a main portion arranged along a first plane and two stepped surfaces arranged opposite one another along a second plane parallel to the first plane, and at least two of the teeth extend from the stepped surfaces. In an embodiment, the two stepped surfaces comprise a plurality of stepped sub-surfaces, and at least two of the plurality of teeth extend from each of the sub-surfaces. In an embodiment, the coils are wound in the slots adjacent the insulating teeth with the smallest thickness followed by slots adjacent to gradually thicker insulating teeth. 
         [0011]    According to yet another embodiment of the invention, an electric motor is provided including a stator and an armature received within the stator for rotational movement within the stator. The armature includes an armature shaft on which a commutator is mounted, and a lamination stack also mounted on the armature shaft and having radially extending teeth that form slots therebetween. The slots are arranged circumferentially around a periphery of the lamination stack. The armature further includes end insulator arranged at an end of the lamination stack, the end insulator having a base portion fitted around the armature shaft and insulating teeth corresponding to the radially extending teeth of the lamination stack that form slots therebetween. In an embodiment, the end insulator has a uniform thickness of at least 5 mm. A set of coils are wound in the lamination stack slots and the end insulator slots. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  illustrates a perspective view of an armature assembly including a conventional end insulator. 
           [0013]      FIG. 2  illustrates an end view of a fully wound armature assembly including the conventional end insulator of  FIG. 1 . 
           [0014]      FIG. 3  illustrates a perspective view of an end insulator, according to a first embodiment of the invention. 
           [0015]      FIG. 4  illustrates a perspective view of an armature assembly including the end insulator of  FIG. 3 , according to an embodiment of the invention. 
           [0016]      FIGS. 5A and 5B  illustrate end views of armatures having the end insulator of  FIG. 3  and a conventional end insulator, respectively, each with a first pair of coil windings, according to an embodiment. 
           [0017]      FIGS. 6A and 6B  illustrate the same armatures as  FIGS. 5A and 5B , respectively, each with a second pair of coil windings, according to an embodiment. 
           [0018]      FIGS. 7A and 7B  illustrate the same armatures as  FIGS. 5A and 5B , respectively, each with a third pair of coil windings, according to an embodiment. 
           [0019]      FIGS. 8A and 8B  illustrate the same armatures as  FIGS. 5A and 5B , respectively, each with a fourth pair of coil windings, according to an embodiment. 
           [0020]      FIGS. 9A and 9B  illustrate the same armatures as  FIGS. 5A and 5B , respectively, each with a fifth pair of coil windings, according to an embodiment. 
           [0021]      FIGS. 10A and 10B  illustrate the same armatures as  FIGS. 5A and 5B , respectively, each fully wound, according to an embodiment. 
           [0022]      FIG. 11  illustrates a perspective view of an end insulator, according to a second embodiment of the invention. 
           [0023]      FIG. 12  illustrates a perspective view of an armature assembly including the end insulator of  FIG. 11 , according to an embodiment of the invention. 
           [0024]      FIG. 13  illustrates a perspective view of an end insulator, according to a third embodiment of the invention. 
           [0025]      FIG. 14  illustrates a perspective view of an armature assembly including the end insulator of  FIG. 13 , according to an embodiment of the invention. 
       
    
    
       [0026]    The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       DESCRIPTION 
       [0027]    According to embodiments of the invention discussed herein, improved configurations of armature end insulator are provided to improve the winding process of the armature conductive wires and obtain better slot fill. According to these embodiments, the improved end insulators help route the wires more compactly inside the armature lamination stack slots. 
         [0028]      FIG. 3  depicts a stack end insulator  300  (also referred to as end fiber or end spider) for attachment to an end of a motor armature lamination stack, according to an embodiment of the invention. The end insulator  300  may be made of, for example, plastic or any other insulating material, made via injection-molding or any other known process for obtaining the desired shaped discussed below. 
         [0029]    The end insulator  300  in this embodiment includes a flat base portion  304  and several insulating teeth  306  extending around a circumference of the base portion  304 . The insulating teeth  306  have the same cross-sectional profile as corresponding peripheral teeth of the lamination stack. An inner surface of the insulating teeth  306  and a bottom surface of the base portion  304  are arranged along a single flat plane for attachment to an end portion of the armature lamination stack. The base portion  304  is ring-shaped and has a thickness of approximately 2-3 mm. An outer surface of the base portion  304  is flat in this embodiment, although it is envisioned that a sloped outer surface angled towards the center of the ring is within the scope of this disclosure. Outer surfaces of the insulating teeth  306  protrude outwardly from the outer surface of the base portion  304  at stepped thickness levels. The insulating teeth  306  in this embodiment may thus be referred to as “stepped teeth.” In an embodiment, the outer edge (i.e., outer surface) of each insulating tooth  306  includes a first extension surface  306   a  extending from the outer surface of the base portion  304  at a first angle (e.g., approximately 30-60 degrees with respect to the plane of the outer surface of the base portion  304 ) and a second extension surface  306   b  extending from the first extension surface  306   a  at a second angle (e.g., 0 to 10 degrees with respect to the plane of the outer surface of the base portion  304 ). In an embodiment, the insulating teeth  306  may have a varying thickness of between approximately 2 to 5 mm and more. In an embodiment, the outer walls of the insulating teeth  306  are arranged substantially in parallel. 
         [0030]      FIG. 4  depicts the arrangement of the end insulator  300  with respect to the armature lamination stack  102 , according to an embodiment of the invention. As can be seen herein, a cross-sectional profile of the end insulator  300  matches the profile of the lamination stack. In other words, the insulating teeth  306  have slots therebetween that match the slots of the armature lamination stack  102 . When attached, the slots of the end insulator  300  line up with the peripheral slots of the armature lamination stack. The end insulator  300  may be provided at one or both ends of the armature lamination stack  102 . 
         [0031]    In an embodiment, as shown in  FIGS. 3 and 4 , each insulating tooth  306  may further include a support rib  308  extending from the bottom surface of the insulating teeth  306  to the end of the second edge  306   b . The bottom sides of the support ribs  308  rest on corresponding ribs of the lamination stack teeth above the peripheral slots. The support rib  308  may be V-shaped in a longitudinal direction of the lamination stack  102 , with its width narrowing as it projects away from the lamination stack  102 . 
         [0032]    As previously discussed, lamination stack insulating paper ( 112  in  FIG. 2 ) is inserted inside the lamination stack slots before winding the coils in order to provide double-insulation between the lamination stack  102  and the conductive wires  108 , and the ribs of the lamination stack teeth are provided on the outer periphery of the lamination stack  102  to partially enclose the lamination stack slots  110 , thus keeping the insulating paper inside the slots. The support ribs  308  have the same cross-sectional profile as the ribs of the lamination stack slots  110 . The support ribs  308  also provide further support for the insulating teeth  306  against the lamination stack to prevent the teeth  306  from bending or breaking. In one embodiment, the lamination stack insulating paper may be extended slightly (e.g., 0.5 to 1 mm) from the ends of the lamination stack slots to allow for proper alignment of the support ribs  308  of the end insulator  300  with the lamination stack slots. 
         [0033]      FIGS. 5A-10B  depict the winding steps of armature coils  310  on an armature using the end insulator  300  of  FIGS. 3 and 4  discussed above, shown step by step in  FIGS. 5A ,  6 A,  7 A,  8 A,  9 A, and  10 A, compared to winding of armature coils  108  on an armature using the conventional flat end insulator  114  of  FIG. 1 , shown step by step in  FIGS. 5B ,  6 B,  7 B,  8 B,  9 B, and  10 B. It must be noted that the same size conductive wires and the same number of turns per winding step are used for these two armatures. 
         [0034]      FIGS. 5A and 5B  depict the competed winding of a first pair of coils at eight turns per coil.  FIGS. 6A and 6B  depict the completed winding of a second pair of coils at sixteen turns per coil. As can be seen in  FIG. 6A , the first extension surface  306   a  of the end insulator  300  is already beginning to guide the coil winding closer to the lamination stack core.  FIGS. 7A and 7B  depict the completed winding of a third pair of coils at sixteen turns per coil.  FIGS. 8A and 8B  depict the completed winding of a fourth pair of coils at sixteen turns per coil. 
         [0035]      FIGS. 9A and 9B  depict the completed winding of a fifth pair of coils at sixteen turns per coil. By the end of the fifth pair winding, it is clear that the wires  310  in  FIG. 9A  are wound closer to the core of the lamination stack than wires  108  in  FIG. 9B , as the extension surface  306   a  forces the wires  310  towards the base portion  304  of the end insulator  300 . 
         [0036]      FIGS. 10A and 10B  depict the completed windings after several additional winding steps, clearly showing bigger gaps  312  within the laminations stack slots of  FIG. 10A  above the windings  310  than the gaps  120  within the lamination stack slots of  FIG. 10B  above the windings  108 . It was found that, given the same amount and size of conductive wire, winding the wires over the end insulator  300  reduces the total amount of space occupied by the coil wires by approximately 15%. This allow for a wider gap on top of the slots, which can accommodate insertion of thicker and stronger wedges into the armature slots. Alternatively, the more compact winding of the coils according to this embodiment enables using either thicker coil wires or more number of coil windings, which would increase armature performance. 
         [0037]      FIG. 11  depicts an end insulator  600 , according to an alternative embodiment of the invention. In this embodiment, the end insulator  600  includes a base portion  604  and several insulating teeth  606 - 612  extending around a circumference of the base portion  604 . The insulating teeth  606 - 612  follow the same cross-sectional profile as corresponding peripheral teeth of the lamination stack. A bottom surface of the insulating teeth  306  and a bottom surface of the base portion  606 - 612  are arranged along a flat plane for attachment to an end portion of the armature lamination stack. 
         [0038]    In this embodiment, unlike the embodiment of  FIG. 3 , the teeth  606 - 614  have different thicknesses around the base portion  604 . Specifically, in an exemplary embodiment, end insulator  600  is provided with two insulating teeth  606  arranged opposite each other and extending from the main plane as the base portion  604 . In an embodiment, both the base portion  604  and the insulating teeth  606  have a thickness of approximately 2-3 mm. 
         [0039]    In an embodiment, the base portion  604  further includes a stepped surface  604   a  arranged at opposite peripheral potions of the base portion  604 . Two additional insulating teeth  608  extend from the stepped surface  604   a  adjacent teeth  606 . The thickness of the insulating teeth  608  is slightly greater than the thickness of the insulating teeth  606 , and top surfaces of the insulating teeth  608  are on a second plane slightly distanced from the plane of the base portion  604 . 
         [0040]    Similarly, in an embodiment, the stepped surface  604   a  includes a stepped sub-surface  604   b  arranged at a plane farther from the bottom surface of the end insulator  300 . Two insulating teeth  610  extend from the stepped sub-surface  604   b  adjacent teeth  608 . The thickness of the insulating teeth  610  is slightly greater than the thickness of the insulating teeth  608 , and top surfaces of the insulating teeth  610  are on a third plane slightly distanced from the second plane formed by the top surface of insulating teeth  608 . 
         [0041]    In an embodiment, the stepped surface  604   a  includes an additional stepped sub-surface  604   c  arranged at a plane ever farther from the bottom surface of the end insulator  300 . The remaining insulating teeth  612  extend from the stepped sub-surface  604   c  between respective insulating teeth  610  and  606 . The thickness of the insulating teeth  612  is slightly greater than the thickness of the insulating teeth  610 , and top surfaces of the insulating teeth  612  are on a fourth plane slightly distanced from the third plane formed by the top surface of insulating teeth  610 . 
         [0042]      FIG. 12  depicts the arrangement of the end insulator  600  with respect to the armature lamination stack  102 , according to an embodiment of the invention. As can be seen herein, a cross-sectional profile of the end insulator  600  matches the profile of the lamination stack. In other words, the insulating teeth  606 - 612  have slots formed therebetween that match the slots of the armature lamination stack  102 . When attached, the slots of the end insulator  600  line up with the peripheral slots of the armature lamination stack. The end insulator  600  may be provided at one or both ends of the armature lamination stack  102 . 
         [0043]    Similarly to the end insulation of  FIGS. 3-10A , the end insulation  600  of this embodiment allows the coils to be wound more compactly near the core of the armature. Specifically, in this embodiment, the coils are wound in steps, starting with the slots having low clearance, i.e., those adjacent teeth  606 , followed by the slots along the first stepped surface  604   a , i.e., between teeth  608  and  610 , followed by slots along the second stepped surface  604   b , i.e., between teeth  610  and  610 , etc. In this manner, at each step the coil windings overlap the previously wound coils at the ends of the armature, which allows the coil windings to be formed closer to the armature core. 
         [0044]    It is noted that while end insulator  600  shown herein does not include support ribs at the ends of the insulating teeth  606 - 612 , support ribs having the same lateral profile as the ribs of the lamination slack teeth may be provided and the ends of the insulating teeth  606 - 612 . Each support rib may be V-shaped in a longitudinal direction of the lamination stack  102 , with its width narrowing as it projects away from the lamination stack  102 . 
         [0045]      FIGS. 13A and 13B  depict a stack insulation  702 , according to yet another embodiment of the invention. In this embodiment, the stack insulation  702 , including the base portion and the teeth, are provided with a uniform thickness of at least 5 mm. It was found by the inventors that this design extends the winding turns at the ends of the lamination stack away from the lamination stack to allow more compact winding of the coils inside the lamination stack slots. 
         [0046]    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 scope of the invention.