Plastic and nonmetallic article shaping or treating: processes – With severing – removing material from preform mechanically,... – Simultaneous severing and shaping – or severing while work...
Reexamination Certificate
1999-02-08
2001-03-20
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With severing, removing material from preform mechanically,...
Simultaneous severing and shaping, or severing while work...
C264S285000
Reexamination Certificate
active
06203739
ABSTRACT:
TECHNICAL FIELD
This invention relates to insulation, and more particularly to insulation for stator slots in electric motors and generators.
BACKGROUND OF THE INVENTION
Electric motors and generators have many applications. In a typical motor or generator, there is a rotor that rotates within a stator. The stator includes a plurality of fingers that define rotor slots therebetween. Wires are wound around the fingers and through rotor slots to define coils. Each coil must be insulated for proper operation. Insulation, in the form of slot wedges, is inserted into the stator slots to insulate coils from the stator.
It is common to create slot wedges from a strip of insulation that is unwound from a roll. Rolled strips are typically created by (i) unwinding a web of sheet-like insulation from a roll, (ii) passing the web between rolling scissors/knives to cut the web into strips of insulation, and (iii) rolling the strips into individual rolls. Then, as a separate step, a rolled strip of insulation is supplied to a machine that insulates stators. That machine (i) unwinds the strip from its roll, (ii) cuts the strip into “short” lengths, and (iii) inserts the short lengths into stator slots. The short lengths are inserted prior to the installation of the coils onto the stator. During the process of inserting the short lengths, they become somewhat U-shaped in an end profile view. Examples of machines that insert slot wedges or insulating slot cuffs into stator slots are disclosed in U.S. Pat. Nos. 2,340,291; 3,616,512; 3,831,255; 3,778,889; 3,778,890; 4,831,716; 4,878,292; 4,854,033; and U.S. Pat. No. Re. 34,195.
A common manufacturing defect associated with stators has to do with the insulation of stator slots. If a stator slot is not properly insulated, the coil therein electrically shorts/fails. While prior methods and apparatus for insulating stator slots are generally effective, these type of manufacturing defects still occur, and they typically render motors and generators inoperative. Unfortunately, such defects are often not detected until stators are completely assembled. It is typically cost prohibitive to remanufacture a defective stator; therefore, such defects result in considerable waste and expense. Even worse, such defects are often not detected until after electric motors and generators are placed into service.
Accordingly, there is a need for improved methods, apparatus, and articles of manufacture for forming slot wedges to decrease manufacturing defects in stators.
SUMMARY OF THE INVENTION
This invention solves the above-described problems in the art by providing improved methods, apparatus, and articles of manufacture for forming slot wedges to minimize manufacturing defects in stators. Exemplary embodiments of the present invention simultaneously (i) cut a web of insulation into strips, (ii) score the strips to promote the forming of the strips, and (iii) partially form the strips into modified U-shapes. In accordance with a first exemplary embodiment of the present invention, the scored and partially U-shaped strips are rolled into rolls. In accordance with a second exemplary embodiment of the present invention, the strips are flattened and then rolled into rolls. When the rolls of the strips are supplied to a machine that manufactures stators, remarkable savings are achieved because very few of the fabricated stators have manufacturing defects (i.e., the coils do not electrically short/fail).
In accordance with the exemplary embodiments of the present invention, a slitting and scoring machine includes an upper tooling roller and a lower tooling roller that cooperate to define a tooling nip. Each tooling roller includes an alternating series of coaxially arranged annular knives, annular dies, and annular mandrels. A web of insulation is drawn through the tooling nip where it is formed into a plurality of scored strips. Each strip is longitudinally extending and has opposite longitudinally extending edges. While a strip is within the tooling nip, its edges are at least partially bent toward one another so the piece of insulation defines a longitudinally extending channel.
Subsequent to exiting the tooling nip, each strip is drawn through a drawing nip defined between drawing rollers. In accordance with the first exemplary embodiment, the drawing nip generally maintains the U-shape of the strips. In accordance with the second exemplary embodiment, the drawing nip flattens the strips. Subsequent to exiting the drawing nip, each strip is formed into a roll. In each roll, a first length of the strip and a second length of the strip extend around a common point. In accordance with the first exemplary embodiment, at least a portion of the second length is disposed within the channel of the first length.
More particularly, in accordance with the first exemplary embodiment (prior and subsequent to passing through the drawing nip) and the second exemplary embodiment (prior to being flattened in the drawing nip), each strip includes a longitudinally extending middle segment and a pair of longitudinally extending side segments. The side segments extend away from the middle segment in a divergent manner to define the longitudinally extending channel. Longitudinally extending grooves are defined (i.e., formed by scoring) at the junctures of the middle segment and the side segments. The scoring/grooves promote the divergence of the side segments. In an end profile view of a strip, the middle segment and each of the side segments are generally straight, and an obtuse angle is defined between each side segment and the middle segment.
In accordance with the exemplary embodiments, as the web of insulation passes through the tooling nip, each edge of a strip is cut by a separate pair of meshing annular knives. For each pair of meshing annular knives, one knife belongs to the upper tooling roller and the other knife belongs to the lower tooling roller. Each strip is at least partially shaped in the tooling nip by passing between a die and a mandrel that are between the knives that cut the strip. A pair of annular protrusions on the die score the strip to define the grooves. In addition to participating in the cutting, the annular knives that are opposite from the die bend the edges of the strip around the annular protrusions to form the channel of the strip.
Accordingly, an object of the present invention is to provide improved methods, apparatus, and articles of manufacture for forming slot wedges to minimize manufacturing defects in stators.
Another object of the present invention is to provide a roll of shaped insulation, where each successive layer nests into the prior layer.
Still another object of the present invention is to decrease manufacturing defects in stators.
Still another object of the present invention is to minimize waste and expense associated with manufacturing electric motors and generators.
Other objects, features, and advantages of the present invention will become apparent from the following detailed description, drawings, and claims.
REFERENCES:
patent: 5552101 (1996-09-01), Fujii et al.
Hazelton Thomas James
Jeffries Mark A.
Kilpatrick & Stockton LLP
Tentoni Leo B.
LandOfFree
Method of manufacture of insulation for use in stator slot... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of manufacture of insulation for use in stator slot..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of manufacture of insulation for use in stator slot... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2548508