Abstract:
An apparatus for positioning at least one motor brush in an electric motor having a motor housing, comprising a base ring secured to the motor housing, an upper ring disposed adjacent to and moveable relative to the base ring, and an indexing member for aligning the upper ring with the base ring. The base ring includes a first indexing portion, an axially inwardly facing surface disposed adjacent to the motor housing and a second axially outwardly facing surface offset from the first axially inwardly facing surface. The upper ring includes a second indexing portion, a third axially inwardly facing surface disposed adjacent to the second axially outwardly facing surface of the base ring and a fourth axially outwardly facing surface offset outward from the third axially inwardly facing surface.

Description:
CLAIM OF PRIORITY 
     This application claims the benefit of U.S. Provisional Application No. 60/126,691, filed on Mar. 29, 1999. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to an apparatus for holding motor brushes in an electric motor, and more particularly to an insulator/mounting ring for an electric motor that is especially adaptable for use in industrial electric motors. 
     BACKGROUND OF THE INVENTION 
     Today the electric motor is the method of choice to supply mechanical/electrical energy within industrial environments. As with any other electromechanical device, electric motors require periodic maintenance to ensure that they are working properly and at the highest efficiency level possible. One area that requires periodic maintenance is the carbon brushes in the motor. These brushes need to be replaced periodically in order to provide the maximum transfer of electric current between the stator and armature of the motor. 
     The user&#39;s ability to replace the carbon brushes is largely dependent upon the environment in which the motor resides. Some environments permit easy maintenance access to a motor and its brushes, thereby making replacement of the brushes quite easy and quick. However, other environments provide very restricted access to the motor and its brushes. These restricted access environments include those associated with large electric motors such as those found in motors that power heavy industrial machinery and those that power diesel-electric locomotives. In such restricted maintenance access environments, the replacement of the motor&#39;s brushes can be an extremely time consuming process, often requiring the removal of the motor&#39;s housing and insulator ring/brushholder mounting ring. 
     Typically, the electric motors for which the present invention will be most useful contain four or more carbon brushes equally spaced around the commutator of the motor. Usually, the brushes are disposed around the exterior of the cylindrical commutator and are separated by 90°, with a brush being disposed above, below and on each side of the motor. On some motors, the brushes are disposed at about 0°, 30°, 180°, and 240° from top dead center (TDC). The brushes are accessible through an access door located on the side of the motor housing. However, most such access doors allow access to only those two brushes that are mounted on the same side of the commutator as the access door (e.g. at 30° and 240° from TDC) and do not allow access to the other two brushes (e.g. those at 0° and 180°). This makes it very difficult, if not impossible to change all four brushes in an electric motor without completely disassembling the motor, and removing all or part of it from the housing. 
     Additionally, the brushes should not be positioned exactly vertically or horizontally around the armature. Typically, the brushes are rotated approximately three degrees from vertical or horizontal. For example the brush mounted to the top of the motor is not centered on the axis of the motor, but rather is rotated three degrees from vertical about the axis of the motor. Nonetheless, the brushes should maintain the critical ninety degree offset from each other. 
     The difficulty in replacing the brushes results in two undesirable effects. First, motors are not maintained as often as they should be, thereby reducing their efficiency and increasing electricity costs. Second, when a motor is to be repaired, it is typically removed from the environment to which it is operating and replaced by another motor. This requires the factory or industrial facility to maintain a supply of spare motors which therefore increases both labor expense and capital costs. The factory must pay the labor costs to switch out the two motors, transportation costs to move the motor to a repair specialist, as well as the labor costs to have a motor repair specialist disassemble the old motor, replace the brushes and re-assemble the motor. This process typically costs the factory $500.00 to $1,000.00 in extra labor, excessive downtime on the production line due to the added time required to switch out the motors, and the additional costs to maintain a supply of spare motors. 
     Another problem with current brush mounting systems is that their mounting bolt arrangements add to the difficulty of replacing the brushes. Current brush mounting systems have a ring made of thermo-setting plastic that is secured to the motor housing. The ring typically has four platforms that extend axially outwardly to provide a seat to attach the brush holders. These platforms have a pair of axially extending apertures through which bolts can pass. These apertures are typically longer than the length of the bolt that passes through them. Because of this, the bolts sometimes recede back into this ring when the brush brackets are removed or installed. If this happens, the factory or industrial facility is often forced to completely disassemble the motor again. This process of retrieving the receded bolts adds both additional time as well as frustration to the motor repair specialist during the brush charging process. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, an apparatus is provided for positioning at least one motor brush in an electric motor having a motor housing. The apparatus comprises a base ring secured to the motor housing; an upper ring disposed adjacent to and moveable relative to the base ring; and a mounting member movable between a fixed position and a released position. The mounting member, when in the fixed position is engagable with the upper ring and the base ring to prevent the relative movement of the upper ring and the base ring. When in the released position, the mounting member releases the engagement between the upper ring and the base ring to permit the relative motion of the upper ring and the base ring. 
     Preferably, the apparatus comprises a two piece, rotatable insulator for holding motor brushes. The insulator is preferably composed of an electrically insulating material such as machinable phonetic, machinable epoxies, polyesters, or other types of insulation material. The insulator includes a lower or base ring and an upper ring. The base ring is secured to the housing in which the motor is placed with two or more bolts, and is fixed in its position with respect to the motor housing. The base ring has a radially inwardly facing surface; three axially facing surfaces, and two radially outwardly facing surfaces of different diameters with the larger diameter surface location positioned for being disposed next to the motor housing. The reduced diameter radially outwardly facing surface provides a centering collar for the upper ring. 
     The outwardly facing outer surface of the base ring is used as mounting lip for positioning and connecting the lower ring to the housing via a bolt and washer combination. 
     The main portion of the upper ring comprises a ring having three axially facing surfaces and three radially facing surfaces. A radially outwardly facing surface is concentric with, and has a smaller diameter than the larger diameter radially outwardly facing surface of the base ring. The diameter is smaller so that the radially outwardly facing surface of the upper ring will be disposed radially inwardly from the radially outwardly facing surface of the base ring, thereby permitting the mounting bolts to clear the upper ring, and permit the upper ring to position itself flush against the base ring. 
     The two radially inwardly facing surfaces of the upper ring have different diameters. The larger diameter, radially inwardly facing surface is concentric with, and approximately the same diameter as the reduced diameter, radially outwardly facing surface of the base ring which is defined as the collar. The diameters of these two surfaces differ enough to allow for a slip fit assembly of the two components and the rotation of the upper ring relative to the base ring, but are close enough to maintain some frictional contact between themselves. The smaller diameter, axially inwardly facing surface of the upper ring in conjunction with the larger diameter, axially outwardly facing surface of the base ring provide a stop axial surface for the axially outwardly facing surface of the base ring. 
     The smaller, radially inwardly facing cylindrical interior surfaces of the upper ring and lower ring preferably have identical diameters that are large enough to provide sufficient clearance within the diameter of the smaller radially inwardly facing interior surfaces to provide clearance for other components of the motor. In addition to the ring portion, the upper ring has four platforms extending axially outwardly from the axially outwardly facing top surface of the ring. These platforms each have two axially extending apertures to accept bolts for securing the motor brush holder to the axially outer end of the platforms. The apertures have a reduced diameter portion through which the tail end of the bolt passes and a relatively enlarged diameter portion for receiving the head of the bolt. The enlarged diameter portion of the aperture is not cylindrical in its configuration. Rather, it should be slotted, ovaloid or hexagonal in cross section and approximately the size of the head of the bolt to provide at least two opposed flat surfaces to grip the flat sides of the bolt to impede rotational movement of the bolt. 
     The upper ring includes one or more axially extending indexing mounting bolt receiving apertures that extend entirely through the upper ring, and are alignable with one or more threaded axially extending indexing bolt receiving apertures that extend through the axially outwardly facing surface of the base ring, and partially through the base ring, thus holding the base and upper ring together. However, the indexing bolt receiving aperture of the base ring does not extend all the way to the axially inwardly facing surface of the base ring which is flush against the motor housing when installed in the motor. 
     These two indexing/mounting bolt receiving apertures also provide a way to index the angular relation between the two rings. When the apertures in each ring align, the upper ring is in its correct operating location relative to the base ring. As stated above, the position of the two rings is maintained by threading an indexing/mounting bolt into the indexing/mounting bolt receiving apertures of the rings. A second locating method calls for the use of a spring loaded detent or spring loaded pin instead of the bolt. 
     One feature of the present invention is that a rotatable insulator assembly is provided to facilitate the easy replacement of all motor brushes without requiring the dis-assembly or removal of the motor to service the brushes. This feature is accomplished through the use of a two ring configuration briefly explained above and in more depth in the following sections. The base and upper rings are held in place relative to each other with one or more indexing bolts. 
     Because of its configuration, removing the access door or doors of a typical motor housing usually allows for the easy replacement of at most two brushes. Once the first two brushes have been replaced with the insulator of the present invention, the indexing/mounting bolts are removed and the upper ring rotated 180° relative to the base ring. 
     When the upper ring is so rotated, the final two brushes are positioned adjacent to the opening in the access door and the first two brushes are positioned away from the access door thus permitting the easy replacement of the final two brushes. After the final two brushes are replaced, the upper ring is then rotated back 180° relative to the base ring and the indexing/mounting bolts are re-inserted. Depending on the position of the motor and the size of the access panel, it may be necessary to replace the brushes one at a time by incrementally rotating the upper ring by 90° three times after removing the first brush. 
     A second feature of the present invention is that the motor brush holder bolts that are passed through the apertures in the platforms of the upper ring to fasten the brush holder to the upper ring are spring loaded, and biased by the spring axially outwardly to maintain the threaded ends of the bolts in a position axially outwardly, and exteriorly of the axially outwardly facing surface of the platforms on the upper ring, while the head of the bolt is fixedly positioned against rotational movement so that the bolt does not freely rotate about its axis when the nut attached is being tightened or loosened. 
     These springs bias the bolts axially outwardly toward their threaded ends. The springs are positioned in the axially inner ends of the apertures of the platforms of the upper ring and are disposed between the axially outwardly facing surface of the base ring, and the head of the bolt to urge the head of the bolt axially outwardly away from the base ring. When the bolt is biased axially outwardly to its forward-most position, the spring should still be under some compression to ensure that the bolt will maintain its forward-most, axially outward position. 
     The enlarged diameter portion of the aperture for receiving the head of the bolt is disposed adjacent to the axially inwardly facing surface of the upper ring, and is not cylindrical in shape but rather slotted, ovaloid or hexagonal. The size of the enlarged portion should be large enough to allow the head of the bolt to pass into and move axially within the aperture, but small enough to engage the flat sides of the head of the bolt to impede the rotation of the head, thereby preventing the bolt from rotating freely in the upper ring. 
     A third feature of the present invention is that it permits the user to repeatably position the brushes in their proper angular position to maximize brush lifetime. The relative rotational (angular) position of the brushes can impact the operation of the motor and the life expectancy of the brushes. By providing an indexing means, such as the indexing bolt, the user can easily place the brush bracket holding upper ring in the same preferred rotational position after replacing the brushes. 
     These and other features of the present invention will become apparent to those skilled in the art through a review of the detailed description and figures set forth below, which set forth the best mode of practicing the invention perceived presently by the Applicant. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side, partly-sectional view of the present invention assembled into an electric motor housing; 
     FIG. 2 is an exploded, assembly view of the present invention with one brush and brush bracket removed for clarity; 
     FIG. 3 is a top view of the present invention in its normal configuration and with brushes and brush brackets shown; 
     FIG. 4 a top, view with the indexing bolt removed and the ring rotated 90° relative to the view shown in FIG. 3; 
     FIG. 5 is a sectional view taken along lines  5 — 5  of FIG. 3; 
     FIG. 6 is a sectional view of the indexing bolt or bolts taken along lines  6 — 6  of FIG. 3; and 
     FIG. 7 is a sectional view taken along lines  7 — 7  of FIG.  5 . 
    
    
     DETAILED DESCRIPTION 
     The insulator/brush holder (“insulator”)  10  of the present invention is shown in FIG.  1  and FIG.  2 . In FIG. 1, the insulator  10  is shown as being mounted in a motor housing cover  13 . The motor components are visible through an access door  12  in the motor housing cover  13 . The basic electric motor parts include: a motor housing ring  14  for housing the motor of the present invention, commutator  16 , motor output shaft  18 , and motor brushes  20 . The insulator  10  includes the following components: a base ring  40 ; an upper ring  80 , four bolts and washers  60   a-d  for fixedly clamping base ring  40  flushly to the motor housing ring  14 , eight bolts  120   a-h,  eight nuts  200   a-h  and eight springs  180   a-h.    
     Referring now to FIGS. 1-2 and  5 - 6 , the base ring  40  includes three planar, radially extending, axially facing surfaces; three axially extending, radially facing surfaces; and a blind depth aperture for the indexing/mounting bolt or bolts  220 . The axially inwardly facing underside surface  42  is positioned flush against the axially outwardly facing mating surface  22  of the motor housing ring  14 . The axially outwardly facing surface  46  is offset from surface  42  by a distance sufficient to impart sufficient thickness to the base ring  40  to provide for rigidity of the base ring  40 . The inner, axially outwardly facing surface  50  is offset from surface  42  by a distance sufficient to produce a collar for the upper ring  80  to slide onto. The collar is formed by an inwardly disposed, radially outwardly facing collar surface  48 , that extends between the outer and inner axially outwardly facing surfaces,  46 ,  50  and whose extent is defined by the offset distance of surface  46  from surface  50 . 
     The radially outwardly facing, perimetral surface  44  has a diameter larger than that of the collar surface  48 . The diameter of the perimetral surface  44  is large enough to allow for sufficient room between the upper ring  80  and the perimetral surface  44  for the mounting bolts and washers  60   a-d  to engage the radially outer edge portion of the outer axially outwardly facing surface  46 . The radially inwardly facing interior surface  52  has a diameter large enough to provide clearance for receiving other components of the motor. 
     The base ring  40  includes an indexing portion  54 . The indexing portion  54  is an axially extending aperture  54  which extends through surface  46 , but not all the way through to underside surface  42 . As best shown in FIG. 6 axially outwardly facing aperture base surface  56  defines the depth of the aperture  54  and illustrates that the indexing/mounting bolts receiving aperture  54  only extends through a portion of the base ring  40 . The indexing/mounting bolt receiving aperture  54  allows the indexing bolt  220  to pass partway into the base ring  40 , and to tighten rings  40  and  80  together. 
     The base ring  40  is fixedly coupled to the motor housing ring  14  with four bolt and washer combinations  60   a-d.  Bolt and washer  60   a  demonstrates this in FIG. 1 as being clamped onto surface  46  when threading bolt  60   a  into motor housing ring  14 . 
     The four bolt and washer combinations  60   a-d  are each positioned about the base ring  40  by approximately 90° of separation, and are thereby cooperatively positioned about the base ring  40  to maintain the base ring  40  in its proper position on the motor housing ring  14 . 
     Once all four bolt and washer combinations  60   a-d  have been positioned properly about the base ring  40 , the bolts and washer combinations  60   a-d  secure the base ring  40  to the motor housing ring  14  in a fixed position. 
     Turning now to FIGS. 2,  5  and  6 , the upper ring  80  includes a generally washer-shaped body portion  81  and four axially outwardly extending platform members  240   a-d.  The body portion  81  includes three axially facing, radially extending surfaces and three radially facing, axially extending surfaces. A radially outwardly facing perimetral surface  82  is concentric with, and has a smaller diameter than the perimetral surface  44  of the base ring  40 . The diameter of the perimetral surface  82  of the upper ring  80  is smaller to allow the radially outer edge of the outer, axially outwardly facing surface  46  to be exposed so that the bolt and washer combination  60   a-d  can grip the outer axially outwardly facing surface  46  of the base ring  40 , to position the base ring  40  flush against the motor housing ring  14 . 
     The two radially inwardly facing surfaces  84 ,  86  of the upper ring  80  have different diameters. The larger diameter radially inwardly facing surface  84  is concentric with and approximately the same diameter as the reduced diameter, radially outwardly facing collar surface  48  of the base ring  40 . The radially inwardly facing surface  84  has a slightly greater diameter than the collar surface  48  to allow the radially inwardly facing surface  84  to interiorly receive the collar surface  48  to permit assembly of the base ring  40  and upper ring  80 , and to permit the rotation of the upper ring  80  relative to the base ring  40 , while maintaining the two surfaces  84 ,  48  close enough to maintain a frictional contact there between. The smaller diameter, radially inwardly facing interior surface  86  is concentric and approximately equal in diameter to the interior surface  52  of the base ring  40 . As in the case of the interior surface  52  of the base ring  40 , the diameter of the interior surface  86  of the upper ring  80  is chosen to ensure sufficient clearance for other electric motor components. The axially inwardly facing base surface  88  of the upper ring  80  is placeable flushly against the axially outwardly facing top surface  46  of the base ring  40 . The outwardly facing top surface  92  of the upper ring  80  provides a surface for the indexing/mounting bolt  220  to tighten together base ring  40  and upper ring  80 . 
     The upper ring further includes an indexing portion  94 . The indexing portion  94  is an axially extending threaded indexing/mounting bolt receiving aperture  94  that extends entirely through the upper ring  80  from the axially outwardly facing top surface  92  of the upper ring  80  to the axially inwardly facing surface  88  of the upper ring  80  which is disposed flush against the base ring  40 . The indexing/mounting bolts aperture  94  of the upper ring  80  is alignable with the indexing/mounting bolt receiving aperture  54  of the base ring  40 . When the apertures  94 ,  54  in each ring  80 ,  40  align, the upper ring  80  is in its correct operating location relative to the base ring  40 . The position of the two rings  80 ,  40  is maintained by threading the indexing bolt  220  through the apertures  94 ,  54  of each ring  80 ,  40  until the bolt head surface  58  bottoms out onto surface  92  of upper ring  80 . 
     The upper ring  80  also includes four platforms  240   a-d  that extend axially outwardly from the axially outwardly facing top surface  92  of the upper ring  80 . The height, H, of the platforms  240   a-d  is governed by the required position of the motor brushes  20   a-d  relative to the commutator  16  (FIG.  1 ). Each platform  240   a-d  is generally rectangular in cross-section, with the exception of radially inwardly facing interior surface  246  which is arcuatly concave in cross-section, and is concentric with the other radially inward facing surface  86  of the upper ring  80 . The distance between the radially inwardly facing interior surfaces  246  of a pair of opposed platforms (e.g.  240   a  and  240   c ; or  240   b  and  240   d ) is equal to or greater than the diameter of radially inwardly facing interior surface  86  of the upper ring  80 . 
     The platforms  240   a-d  each have a brush coupling member receiving portion  242   a-h  for receiving a brush coupling member  120   a-h.  Each of the platforms  240   a-d,  contain two axially extending platform apertures  242   a-h  to accept brushholder mounting bolts  120   a-f  ( 120   h  not being shown) for securing the motor brush brackets  100   a-d  to the axially outer ends  244  of the four platforms  240   a-d  respectively. The platform apertures  242   a-h  each have a reduced diameter portion  248  through which the tail end of the brush holder mounting bolts pass and a relatively enlarged diameter portion  250  for receiving the heads of the brush holder mounting bolts  120   a-h.  The enlarged diameter portions  250  of the platform  242   a-h  apertures are not cylindrical in their configuration, but rather should be slotted, ovaloid or hexagonal and sized to receive a head of one of the brush holder mounting bolts  120   a-h,  and to grip the opposed flat sides of the brush mounting bolts  120   a-h  to impede the free turning of the brush mounting bolts  120   a-h  about their longitudinal axis. As best shown in FIG. 7, the enlarged diameter portion  250  is slotted (ovaloid in cross-section) and has two flat, parallel surfaces (or “flats”)  252  whose spacing is only slightly larger than the width of the head of the brush holder mounting bolts  120   a-h  to receive the head of the brush mounting bolts  120   a-h,  but will not permit rotation of the head of the brush mounting bolts about their longitudinal axis. 
     The eight brush holder mounting bolts  120   a-h  are biased axially outwardly in the enlarged diameter portion  250  of the platform apertures  242   a-h  with a biasing member such as springs  180   a-h.  FIG. 4 shows this configuration for brush holder mounting bolt  120   a  and  120   f.  Looking at brush mounting bolt  120   a- as an example, it is seen that the spring  180   a  is seated, at its axially outer end, on the axially inwardly facing surface of the head of brush holder mounting bolt  120   a , and at its axially inner end on the axially outwardly facing top surface  46  of the base ring  40 . To maintain the brush holder mounting bolt  120   a  in its forward-most position, spring  180   a  should still be under some compression even when the brush holder mounting bolt  120   a  is in its forward most position. 
     Brush holder mounting brackets  100   a-d  are attached to the axially outwardly facing end surface  244  of the platforms  240   a-d  of the upper ring  80  through the passage of the brush mounting bolts  120   a-h  through first and second brush holder bracket apertures  295 ,  297  that are found in each of the four brush mounting brackets  100   a-d.  Nuts  200   a-h  are secured to the tail ends of the brush mounting bolts  120   a-h.    
     FIGS. 3 and 4 illustrate the operation of replacing the motor brushes. In FIG. 3 the indexing/mounting bolt  220  is in its proper operating position. Brushes  20   a  and  20   b  are accessible to the repair person through the access door  12 . After these brushes  20   a,    20   b  are replaced, the indexing/mounting bolt  220  is removed. The upper ring  80  is then rotated 90° relative to the base ring  40  as shown in FIG. 4 in a direction indicated by arrow R. This 90° rotation places brush  20   d  in a position where it is accessible to be replaced through the access door  12 . Once brush  20   d  is replaced, the upper ring  80  is then rotated another 90° in the direction shown by arrow R to place brush  20   c  in an easily accessible position, adjacent to door  12  to facilitate its  20   c  replacement. After brush  20   c  is replaced, the upper ring  80  is rotated back 90° (in a direction shown by arrow S) relative to the base ring  40  to align apertures  54 ,  94 . 
     The indexing/mounting bolt  220  is then re-inserted and tightened into its apertures  94 ,  54  to thereby fixedly positioning together the upper ring  80  and lower ring  40 , to prevent any further rotation of the upper ring  80 . When the indexing/mounting bolts  220  are reinserted into apertures  54 ,  94 , the apparatus has been returned to its proper operating configuration as shown in FIG.  3 . This method allows for easy brush replacement, and also maintains the proper critical position of the brushes relative to the commutator. Alternately, if the repair specialist finds it too difficult to replace brush  20   b  when it is in its fixed position (shown in FIG.  3 ), the upper ring  80  can be rotated forward in the direction of arrow R, 90° further than it is rotated to obtain access to brush  20   c , to permit brush  20   b  to be positioned adjacent to access door  12 , similarly to the position of brush  20   a  of FIG.  3 . 
     Although the invention has been described in detail with respect to certain preferred embodiments, it will be appreciated by one skilled in the art that modifications and variations exist within the scope and spirit of the claims.