Abstract:
A power tool includes a motor with a flux ring. The flux ring includes a ring member with a first and second end. The ends are positioned with respect to one another such that the ends move towards and away from one another during compressing and expanding of the ring. At least one anchor is unitarily formed with the ring. A pair of magnets are coupled with unitarily formed anchors to couple the pair of magnets with the ring. The magnets are coupled with the ring such that the ring may be compressed and expanded with the magnets secured in the ring.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION  
         [0001]    The present invention relates to power tools and, more particularly, to motors for the power tools which include flux rings.  
           [0002]    In electric motor construction, the motor magnets must be retained on the housing or on a separate flux ring positioned within the housing. Ordinarily, these magnets have been glued or adhered to the metallic flux ring or housing. When using a flux ring, different methods have been utilized to position the flux ring and magnets in the housing. One such way is to position the flux ring within the housing and then add the magnets onto the flux ring. Another method is to generally adhere the magnets onto a flux ring and then slide the flux ring into the housing. Thus, it would be desirable to provide a flux ring with the magnets positioned on the flux ring which could be positioned into a motor housing and frictionally engage the motor housing to hold the flux ring in place during assembly.  
           [0003]    The present invention provides the art with a flux ring which is capable of radial expansion and contraction with the magnets secured to the flux ring. In order to manufacture a motor with a flux ring, it is desirable to position the flux ring into the housing wherein the flux ring frictionally engages the interior periphery of the housing until the flux ring is secured to the housing. Also, the flux ring minimizes the gap between its ends to provide maximum magnetic flux carrying capacity.  
           [0004]    In accordance with a first aspect of the invention, a flux ring comprises a ring member having a first and a second end. The ends are positioned with respect to one another such that the ends move towards and away from one another during compressing and expanding of the ring during assembly. At least one anchor is unitarily formed with the ring. At least one magnet is coupled with the unitarily formed anchor to couple the at least one magnet with the ring. The magnet is coupled with the ring such that the flux ring may be compressed and expanded with the at least one magnet coupled with the ring during assembly. One of the first or second ends overlaps or meshes with the other end. The at least one magnet is formed on the ring such that the magnet embeds with the anchor to couple the magnet to the ring. The first and second ends may include at least one mating or meshing projection and receiving recess. The at least one magnet is injection molded onto the ring. The anchor may be an aperture in the ring with a counter-sink. Also, the anchor may be a member unitarily formed with the ring and radially projecting from the ring. A combination of the anchors may be used.  
           [0005]    In accordance with a second aspect of the invention, an electric motor comprises a motor can housing with a pair of end caps coupled to the motor can. A flux ring is positioned within the motor can housing. The flux ring includes a ring member having a first and a second end. The ends are positioned with respect to one another such that the ends move towards and away from one another during compressing and expanding of the ring during assembly. At least one anchor is unitarily formed with the ring. At least one magnet is coupled with the unitarily formed anchor to couple the at least one magnet with the ring. The magnet is coupled with the ring such that the flux ring may be compressed and expanded with the at least one magnet coupled with the ring during assembly. One of the first or second ends overlaps the other end. The at least one magnet is formed on the ring such that the magnet embeds with the anchor to couple the magnet to the ring. The first and second ends may include at least one mating or meshing projection and receiving recess. The at least one magnet is injection molded onto the ring. Also, the anchor may be an aperture in the ring with a counter-sink. Also, the anchor may be a member unitarily formed with the ring and radially projecting from the ring. Also, a combination of the anchors may be used. An armature assembly is positioned in the motor can housing.  
           [0006]    In accordance with a third aspect of the invention, a power tool comprises a housing with a motor in the housing. The motor comprises a motor can housing with a pair of end caps secured to the motor can. A flux ring is positioned within the motor can housing. The flux ring includes a ring member having a first and a second end. The ends are positioned with respect to one another such that the ends move towards and away from one another during compressing and expanding of the ring during assembly. At least one anchor is unitarily formed with the ring. At least one magnet is coupled with the unitarily formed anchor to couple the at least one magnet with the ring. The magnet is coupled with the ring such that the flux ring may be compressed and expanded with the at least one magnet coupled with the ring during assembly. One of the first or second ends overlaps the other end. The at least one magnet is formed on the ring such that the magnet embeds with the anchor to couple the magnet to the ring. The first and second ends may include at least one mating or meshing projection and receiving recess. The at least one magnet is injection molded onto the ring. The anchor may be an aperture in the ring with a counter-sink. The anchor may be a member unitarily formed with the ring and radially projecting from the ring. Also, a combination of the anchors may be used. An armature assembly is positioned in the motor can housing. A power source is coupled with the housing. An activation member is coupled with the motor and the power source for energizing and de-energizing the motor. An output is coupled with the motor such that the motor drives the output during energizing of the motor.  
           [0007]    In accordance with a fourth aspect of the invention, a method of manufacturing electrical motors comprises the steps of forming a motor can housing. A flux ring is formed having two ends such that the ends move towards and away from one another during compressing and expanding of the ring during assembly. A pair of magnets are coupled with unitarily formed anchors on the flux ring. The flux ring is compressed, if necessary, with the magnets on the flux ring such that the flux ring has an external diameter smaller than an internal diameter of the motor can housing. The flux ring is inserted into the motor can housing. The flux ring is expanded to frictionally engage the motor can housing. The expanding of the flux ring occurs in response to the release of the compression force on the flux ring. The flux ring is secured to the motor can housing preferably by welding, clinching, fasteners or glue. A first motor cap assembly is secured to the motor can housing. A motor armature assembly is inserted into the flux ring in the motor can housing. A second end cap is coupled with the armature assembly and the motor can housing. The magnets are injection molded onto the flux ring. The flux ring is formed such that the first and second ends overlap one another in the expanded condition in the motor can housing. A portion of the overlapped ends are welded to the housing to secure the flux ring in the motor can housing.  
           [0008]    In accordance with a fifth aspect of the invention, a method of manufacturing a power tool comprises the steps of forming a motor can housing. A flux ring is formed having two ends such that the ends move towards and away from one another during compressing and expanding of the ring during assembly. A pair of magnets are coupled with unitarily formed anchors on the flux ring. The flux ring is compressed, if necessary, with the magnets on the flux ring such that the flux ring has an external diameter smaller than an internal diameter of the motor can housing. The flux ring is inserted into the motor can housing. The flux ring is expanded to frictionally engage the motor can housing. The expanding of the flux ring occurs in response to the release of the compression force on the flux ring. The flux ring is secured to the motor can housing preferably by welding, clinching, gluing, mechanical fastening or the like. A first motor cap assembly is secured to the motor can housing. A motor armature assembly is inserted into the flux ring in the motor can housing. A second end cap is coupled with the armature assembly and the motor can housing. The magnets are injection molded onto the flux ring. The flux ring is formed such that the first and second ends overlap or mesh with one another in the expanded condition in the motor can housing. A portion of the overlapped or meshed ends are secured to the housing to fix the flux ring in the motor can housing. A housing half is provided. The motor is positioned in the housing half. An output is positioned in the housing half and coupled with the motor. An activation member is positioned in the housing half and electrically coupled with the motor and the power source to energize and de-energize the motor which in turn drives the output. A second housing half is coupled with the first housing half to form the power tool. A power source is coupled with the housing and electrically coupled with the motor.  
           [0009]    Additional objects and advantages of the invention will become apparent from the detailed description of the preferred embodiment, and the appended claims and accompanying drawings, or may be learned by practice of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a cross-section view of a power tool in accordance with the present invention.  
         [0011]    [0011]FIG. 2 is a perspective view of a flux ring in accordance with the present invention.  
         [0012]    [0012]FIG. 3 is an exploded view of a motor including a flux ring in accordance with the present invention.  
         [0013]    [0013]FIGS. 4 a - 4   c  illustrate assembly steps of a motor in accordance with the present invention.  
         [0014]    [0014]FIGS. 5 a - 5   d  illustrate assembly steps of a power tool in accordance with the present invention.  
         [0015]    [0015]FIG. 6 illustrates another embodiment of a flux ring in accordance with the present invention.  
         [0016]    [0016]FIG. 7 illustrates an additional embodiment of a flux ring in accordance with the present invention.  
         [0017]    [0017]FIG. 8 illustrates an additional embodiment of a flux ring in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]    Turning to the figures, FIG. 1 illustrates a power tool, particularly a drill, which is designated with the reference numeral  10 . The power tool  10  includes a housing  12  which includes two halves which are integrally connected to one another. A motor  14  is positioned within the housing  12 . The motor  14  is coupled with an output  16  which includes a chucking end  18 . Also, the motor  14  is electrically coupled with an activation member  20  as well as a power source  22 , in this case a battery. The activation member  20  energizes and de-energizes the motor  14  which, in turn, ultimately rotates the chuck  18 .  
         [0019]    The motor  14  includes a stator assembly  30  which includes a motor can housing  32 , flux ring  34 , and magnets  36  and  38 . An armature  40  includes a shaft  42 , a rotor  44  with laminations  46  and windings  48 , and a commutator  50 . The armature  40  is coupled with the shaft  42  and positioned inside of the motor can housing  32 . The motor also includes end plates  52  and  54 . End plate  52  includes a bearing  56  which balances one end of the shaft  42 . The shaft  42  is coupled with a pinion  60  which is part of the power tool output. Brushes  62  and  64  are associated with the commutator  50 . A bearing  70  is also coupled with the end plate  54  to balance rotation of the shaft  42 .  
         [0020]    Turning to FIG. 2, the flux ring  34  is illustrated with magnets  36  and  38 . The magnets  36  and  38  are of a molded magnetic material. Preferably, the molded material is an injection molded material. The ring  34  is stamped and rolled and positioned within a die and the magnetic material is molded onto the flux ring. Also, the ring could be a machined part. Further, the magnets could be preformed and glued in place on the ring.  
         [0021]    The flux ring  34  includes anchors  80  to retain the magnets  36  and  38  onto the ring  34 . The anchors  80  may be of two types. First, anchor  82  is an aperture formed in the flux ring  34 . The aperture has a first portion  84  and a second counter-sink portion  86 . The counter-sink portion  86  extends to the exterior  88  of the ring  34 . As the molded magnetic material is received in the anchor  82 , the molded material embeds with the ring and has a neck  92  and a head  94 . The neck  92  and head  94  provide an overall rivet appearance. Thus, the head  94  acts to retain the magnets  36  and  38  on the ring  34 . The ring  34  may be comprised of just a plurality of aperture anchors  82  to retain the magnets on the ring  34 .  
         [0022]    Additional anchors  96  may be utilized on the ring. Anchors  96  are shown radially projecting from the interior surface  98  of the ring  34 . However, the anchors  96  could project radially outwardly from the ring  34 . Ordinarily, the anchors  96  are stamped or the like into the ring  34  forming an aperture  100  immediately adjacent the projecting anchor  96 . Thus, when the molded magnetic material forms around the projecting anchor  96 , it likewise goes under the anchor to fill-in the aperture  100  to embed the molded magnetic material with the anchor  96 . This provides for a firm securement of the magnet onto the ring  34 .  
         [0023]    The ring  34  includes a pair of ends  102  and  104 . The ends  102  and  104  overlap one another. The overlapping enables a substantially continuous magnetic flux around the ring  34 . Also, the ends  102  and  104  enable overlap when the ring is compressed or expanded during positioning of the ring  34  into the motor can housing  32 . Note that the ring  34  may be compressed and expanded with the magnets  34  and  36  already secured to the ring. Also, the ends  102  and  104  provide a surface on the ring  34  to be welded to the motor can  32 .  
         [0024]    Turning to FIG. 4, a better understanding of the manufacturing of the motor  14  will be had. The motor can housing  32  is provided with two open ends. However, a drawn motor can could be used with a unitary end on the motor can. The ring  34  with the magnets  36  and  38  already on the ring  34  is compressed, if necessary, such that the ring  34  has an outer diameter less than the inner diameter of the motor can housing  32 . The ring  34 , in a radially compressed condition, is placed inside of the motor can  32 . The compressive force is removed from the ring  34  enabling it to expand. As the ring  34  expands, it frictionally engages the motor housing  32  maintaining it in position on the housing  32 . Also, the ring could have an outer diameter less than the inner diameter of the motor can. Thus, the ring would be forcibly expanded to frictionally engage the motor can. The ring  34  is then secured to the motor can housing  32  by welding, clinching (e.g. extruding the motor can housing into the flux ring or vice versa), gluing, mechanical fastening (e.g. rivets) or the like. The ring is welded at ends  102 ,  104  to secure it with the motor can housing  32 . Also, the ring  34  may be welded to the motor can at a position 180° from the ends. After welding, the end plate  52  is positioned on one end of the motor can housing  32 . The armature  40  with the end plate  54  which includes the brushes  62  and  64  as well as the bearing  70  is inserted into the motor can housing  32 . The end plate  54  is coupled with the motor can housing  32  forming the motor  14 .  
         [0025]    Turning to FIG. 5, the above described motor  14  is positioned into a housing half. The power tool output  16  with the chucking end  18  is coupled with the motor  14 . In turn, the activation member  20  is positioned into the housing half and electrically coupled with the motor  14 . The second housing half is coupled with the first housing half. Thereafter, the power source  22 , in this case a battery, is inserted into the housing  12  and electrically coupled with the activation member  20  which, in turn, is electrically coupled with the motor  14 . Also, the motor, output and chuck, and activation member may be assembled together so that it is positioned as a unit into a housing half. The other housing half would then be coupled with the first housing half and the battery would be added. When the activation member energizes the motor  14 , the output  16  rotates the chuck  18 .  
         [0026]    FIGS.  6 - 8  illustrate different ring embodiments. The difference between the rings is at their ends.  
         [0027]    [0027]FIG. 5 illustrates a ring  34 ′ which has ends  102 ′ and  104 ′. The end  104 ′ includes a cut-out portion  206  with a projecting member  208 . The projecting member  208  serves as a weld location. While a single projecting member  208  is shown, multiple members could be used.  
         [0028]    [0028]FIG. 7 illustrates an additional embodiment of the present invention. Here, the ends  102 ″ and  104 ″ have alternating projections  304 ,  306  and recesses  308 ,  310 . The fingers and recesses enable meshing of the ends  102 ″ and  104 ″. Gaps  312  and  314  are formed between the ends  102 ″ and  104 ″. As the ring  34 ″ expands into the motor housing  32 , the gap  312  increases in size, while the gap  314  remains substantially constant in size. The gap  314  is maintained sufficiently small such that a weld easily bridges between ends  102 ″ and  104 ″ to the motor housing  32 .  
         [0029]    [0029]FIG. 8 illustrates an additional embodiment of the ring  34 ′″. Here, end  102 ′″ includes a pair of recesses  402  while end  104 ′″ includes a pair of projecting members  404 . The projecting members  404  project into the recesses  402  and provide a weld location to weld the ring  34 ′″ to the motor can  32 . Also, each end could include one projection and one recess. Gaps  406  and  408  are formed between the ends  102 ′″ and  104 ′″. As the ring  34 ′″ expands into the motor housing  32 , the gap  406  increases in size, while the gap  408  remains substantially constant in size. The gap  408  is maintained sufficiently small such that a weld easily bridges between ends  102 ′″ and  104 ′″ to the motor housing  32 .  
         [0030]    Applicants would like to incorporate by reference the specification and drawings of U.S. patent application Ser. No. 09/492,059 filed Jan. 27, 2000 and entitled “ANCHORING SYSTEM FOR INJECTION MOLDED MAGNETS ON A FLUX RING OR MOTOR HOUSING”. The embodiments of the flux ring illustrated in the 09/492,059 application may be equally substituted in the present invention with the exception that the ends of the rings would be modified as described above with respect to FIGS.  2  or  6 - 8 .  
         [0031]    While the above detailed description describes the preferred embodiment of the present invention, the invention is susceptible to modification, variation, and alteration without deviating from the scope and fair meaning of the subjoined claims.