Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-03-29
2002-09-10
Ponomarenko, Nicholas (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C370S241000, C370S902000
Reexamination Certificate
active
06448684
ABSTRACT:
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'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's brushes can be an extremely time consuming process, often requiring the removal of the motor'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
Bobbs William C.
Hall Robbie K.
Oehrle Stephen A.
Sutton Dale M.
Bo-Witt Products, Inc.
Bose McKinney & Evans LLP
Dinh Le Dang
Ponomarenko Nicholas
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