Abstract:
These and other objects of the present invention are achieved by a brush holder assembly for an electric motor or generator wherein the brush box or holder is arcuate and curved in relationship to a commutator and supports a brush means and a floating constant force spring which allows dynamic movement and control of the brush as it moves towards a commutator.

Description:
RELATED APPLICATIONS 
       [0001]    Applicant claims the benefit of provisional application Ser. No. 61/215,097, filed May 4, 2009. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to electric machines, and more particularly, to a brush holder assembly for an electric motor. 
         [0004]    2. Description of the Prior Art 
         [0005]    Brush holder assemblies which control the movement of the brush against the commutator having a critical affect on overall motor performance. There are numerous designs which are currently used by motor manufacturers including assemblies which use constant force springs to control brush movement against the commutator. Some assemblies limit brush loading to the front, while others can be loaded from the back. On the latter, the constant force spring must be removed to install a new brush. Both designs limit brush movement, resist brush cooling, require complicated brush holder designs, and necessitate substantial space for installation. Previously assemblies restrict how the constant-force spring is held in place because the spring manufacturers recommendations limit the approved method to return the constant-force spring to the outside portion of the coiled sections. There is a need for an improved compact brush holder assembly to hold the inside coil sections of the constant-force spring which do not interfere with brush loading. See Applicant&#39;s prior U.S. Pat. Nos. 5,977,682 and 5,905,323. 
       OBJECTS OF THE INVENTION 
       [0006]    An object of the present invention is to provide for a novel brush box holder assembly in which the brush box has minimal contact with the brush thereby reducing friction and binding. 
         [0007]    A further object of the present invention is to provide for a novel brush box holder assembly which could easily be stamped out of metal. 
         [0008]    A still further object of the present invention is to provide for a novel brush box holder assembly in which the brush box is arcuately curved in relationship to the commutator having side wall members that can be a concave shape, convex shape, or a combination of both to form an S shape. 
         [0009]    A still further object of the present invention is to provide for a novel brush box holder assembly which provides increased brush travel while improving brush alignment with the commutator. 
         [0010]    A still further object of the present invention is to provide for a novel brush box holder assembly which will allow the brush to respond more quickly to radial and axial loads. 
         [0011]    A still further object of the present invention is to provide for a novel brush box assembly which reduces motor noise and improves commutation by allowing the brush to float and thus having a smoother contact with the commutator. 
         [0012]    A still further object of the present invention is to provide for a novel brush box holder assembly, the construction of which reduces brush temperature during operation. 
         [0013]    A still further object of the present invention is to provide for a novel brush box holder assembly which can be installed in a smaller volumetric footprint. 
         [0014]    A still further object of the present invention is to provide for a novel brush box holder assembly wherein the brush box may be fabricated from tubing, thus further optimizing the benefits described hereinabove. 
       SUMMARY OF THE INVENTION 
       [0015]    These and other objects of the present invention are achieved by a brush holder assembly for an electric motor or generator wherein the brush box is arcuately curved in relationship to the commutator and supports a brush means and a floating constant force spring which allows dynamic movement and control of the brush as it moves towards a commutator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    These and other objects of the present invention will become apparent, particularly when taken in light of the following illustrations wherein: 
           [0017]      FIG. 1  is a partial fragmentary, isometric view of a portion of a dynamoelectric machine illustrating a brush and brush holder assembly; 
           [0018]      FIG. 2  is a top elevational view of the yolk of the dynamoelectric machine of  FIG. 1 ; 
           [0019]      FIG. 3  is a front view of the brush and brush holder assembly of the present invention; 
           [0020]      FIG. 4  is a side view of one embodiment of the brush and brush holder assembly of the present invention; 
           [0021]      FIG. 5  is a side view of a second embodiment of the brush holder; and 
           [0022]      FIG. 6  is a side view of a third embodiment of the brush holder. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Referring now to the drawings, and particularly  FIGS. 1 and 2 , there is illustrated a dynamoelectric machine generally indicated as  10 . The dynamoelectric machine  10  may be a conventional DC motor having a tubular frame (not shown) and a cover or end frame  12 , attached to an open end of the tubular frame such as by bolts (not shown) in a conventional manner. An insulated support or yolk member  14  is provided with a plurality of brush and brush holder assemblies, generally indicated as  16 , disposed equidistantly and radially on the yolk  14 . The yolk  14  is fastened to the end frame  12  of the machine  10  in a manner known to one skilled in the art. The yolk  14  is preferably fabricated from a thermoplastic dielectric material and is formed with orifices to provide for the mounting of such brush holder assembly  16 , as well as to provide mounting of the yolk  14  to the end frame  12  of the machine  10 . 
         [0024]    Interiorly of the tubular frame of the machine  10  there is provided an armature or rotor, generally indicated as  20 , rotatably positioned within a field structure (not shown). Such field structure is conventional and may include permanent magnetic field or include windings connected to terminally posts leading to the exterior of the housing in a manner known to one skilled in the art. The armature  20  is provided with a shaft  22  journaled for rotation within a recessed portion or cavity  24  formed in the end frame  12 . A thrust washer (not shown) may be provided between a bearing and the rotor  20 . The shaft  22  of the armature  20  is provided with a commutator  26  formed with a peripheral surface which cooperates with equidistantly radially extended brushes  28  mounted on yolk  14  and slidably mounted in a respective brush holder assembly  16  as more fully hereinafter discussed. 
         [0025]    The brush holder assembly  16  of the present invention, referring now to  FIGS. 3 and 4 , is comprised of a preferred generally U-shaped elongated housing member  30 , including an upper and lower U-shaped end wall portion  32 , parallelly-disposed side wall portions  34  and  36  and outwardly extending leg portions  38  and  40  perpendicularly disposed to the side wall portions  34  and  36  respectively. The elongated housing member  30  is radially mounted, such as by nuts and bolts  37  to the yolk  14 , defining a chamber  46 . Housing member  30  with cuvalinear side wall portion  32  is arcuate with respect to commutator  26 , and curves toward commutator  26 . 
         [0026]    An elongated pin member  54  having an upper top head  56  is mounted on both sides of the housing  30  parallelly-disposed to the housing member  30 . Each pin member  54  is mounted within orifices (not shown) in the leg portions  38  and  40  of each side wall member. 
         [0027]    A spring member  60  of constant tension force having a main body position  62  and end coil portions  64  and  66  with each coil portion mounted on a plastic cylindrically-shaped bushing member  68 . The elongated top and bottom U-shaped armature brush member including conductors  72  is positioned within the chamber  46  defined by the housing member  30  and the yoke  14  wherein the main body portion  62  of the spring member  60  is biased against an end portion  74  of the brush member  28 . 
         [0028]    In assembly, the elongated and U-shaped brush member  28  is introduced into the chamber  46  through the front opening of the housing member  30  and inserted against the main body portion  62  of the coil spring member  60  to a point where the brush member is fully inserted within the housing chamber  46 . After mounting the brush and brush holder assemblies on the yolk  14  and positioning of the yolk  14  in the motor assembly  10  with armature  20  suitable positioned therein, the brush member  28  thereby to caused to contact the commutator  26  of the armature  20  under the biased spring force of the spring member  60 . 
         [0029]    Alternately, the brush member  28  may be positioned within the chamber  46  of the housing member  30  by causing the main body  62  if the spring member  60  to be pulled backwards to a point permitting positioning of the brush member  28  at an opening in the rear portion of the housing member  30 . 
         [0030]    The brush holder assembly  16  illustrated in  FIGS. 1-4  is arcuately curved away from commutator  26 . Due to design limitations or space limitations with respect to a particular electrical device, the housing member  30  of brush holder assembly  16  may require a curvature toward commutator  26  or may require a double curve or S-shape.  FIG. 5  illustrates a side profile view of a second embodiment of housing member  30 , designated as housing member  30 A. It functions identically in the brush holder assembly  16  as housing member  30  with the exception that the paralleledly disposed side wall portions  34 A and  36 A are curved forward towards commutator  26  (not shown). Still further, in other design limitations or restrictions, it may be necessary to impart a double curvature to housing member  30 , this is illustrated in  FIG. 6  in which the paralleledly disposed side wall portions  34 B and  36 B are formed with a double curvature  39  and  41 . Again, housing member  30 B functions in an identical manner as respects the housing member  30  as illustrated and explained in  FIGS. 1-4 . 
         [0031]    Therefore, while the present invention has been disclosed with respect to the preferred embodiments thereof, it will be recognized by those of ordinary skill in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore manifestly intended that the invention be limited only by the claims and the equivalence thereof.