Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1997-11-10
2001-10-16
Hall, Carl E. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S609000, C156S269000, C156S290000, C156S307700, C310S049540, C310S216055
Reexamination Certificate
active
06301773
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to motor cores and stators and more particularly to a method of manufacturing a motor core by adhesively bonding laminated layers without applying compression to the layers.
BACKGROUND OF THE INVENTION
Motor cores are generally composed of many layers of thin metal plates that are stacked on top of each other to form a laminated stack. Typically, the laminated stack is fastened with welds, rivets, or bolts which hold and/or compress the layers together to permanently maintain the stack in a fixed orientation. Stator windings are then fitted about or wound in place about grooves or slots formed in the inside peripheral surface of the laminated stack to form poles of the motor. During processing of the metal plates and prior to assembly, the plates are annealed to form an oxide layer on the surfaces of each metal plate. The oxide layer effectively insulates one plate from the adjacent plate, provided that the plates are not subject to significant compression. Use of rivets or bolts that compress the stack “shorts-out” the oxide layer causing some or all of the metal layers to be electrically coupled to adjacent layers, essentially “short circuiting” the stack forming a conductor. Welding the layers together similarly creates a short circuit between the plates. In some motor applications this is acceptable, and even desirable.
However, in other motor applications, this is not acceptable, as shorted plates reduce the efficiency of the motor by increasing eddy current loss in the stack. In such applications, the metal layers must be electrically isolated from adjacent layers. Such stacks are referred to as “loosely laminated” stacks because the metal plates are not subject to significant compressive force. Typically, applications requiring a loosely laminated stack are directed toward smaller motors, such as fractional horsepower motors in the range of one-half to one horsepower. However, some loosely laminated stack motors may be as large as five horsepower. The loosely laminated stack must be fixed so as to prevent the metal plates from becoming skewed while simultaneously avoiding detrimental compressive force.
It is known to use clamps to hold the plates in position while the windings are attached or wound about the slots or grooves in the stack. This is costly and labor intensive, and care must be taken not to apply too much compressive force. Application of too much compressive force results in shorting some or all of the laminations, while application of too little compressive force permits the plates to move, resulting in air gaps between the laminations and skewed laminations. Accordingly, use of clamps is disadvantageous in the manufacturing of loosely laminated stacks.
In some applications, large clamping or compressive force is used in conjunction with a chemical adhesive. Of course, a loosely laminated core cannot be manufactured in this way. Such methods use slow-curing adhesives that require the core to remain under compression for relatively long periods of time while the adhesive hardens. Application of such compressive force may involve expensive and bulky fixtures and is an inefficient use of manufacturing floor space. Also, such methods using adhesive are disadvantageous if large compressive force is not used. Without use of substantial compressive force, the cores may suffer from lack of rigidity and lack of squareness if the glue is not permitted to harden, undisturbed, for a relatively long period of time. Therefore, compression of the core is required during this time to insure dimensional accuracy. As described above, such compression causes shorting between the layers, thus this method cannot be used to produce loosely laminated cores.
It is also known to provide a cylindrical bore through the stack that is filled with a chemical adhesive, which when dry, bonds the layers together. Again, this is expensive and time consuming. In known methods, it is difficult to keep all of the metal layers aligned. Failure to maintain alignment between the metal layers results in “skew,” which severely reduces the efficiency of the motor, thus affecting motor performance. Skewed motor cores are unacceptable.
SUMMARY OF THE INVENTION
It is therefore desirable to provide a loosely laminated stack and a method of forming the loosely laminated stack. The cost of manufacturing the loosely laminated stack is significantly reduced because complex and bulky jigs and clamps are not required to hold the laminations in place. Further, there is no expensive welding operation required and no bolts, rivets, or other mechanical fasteners are used. This reduces material and labor costs. Quality control costs are similarly reduced because the laminations are not subject to significant compressive force. This results in fewer rejections due to shorted laminations.
In the present method, the operator need only place the laminations over the alignment post and flow several beads of adhesive material along the outside surface of the laminated stack. The adhesive material cures and hardens in only a few seconds. Accordingly, the laminated stack, once aligned and fixed in place by the adhesive, is ready for the winding process.
More specifically, a method of manufacturing a motor core having a plurality of metallic plate-like laminations includes the steps of a) juxtaposing the laminations in a stacked relation along a central axis, the laminations having a central aperture and an outer peripheral surface, b) placing the laminations over an alignment post of an alignment fixture to align the laminations, until the laminations rest upon a base portion of the alignment fixture, where the alignment post has an outside diameter substantially equal to an inside diameter of the central aperture so as to form a slip fit therebetween to urge the laminations into full alignment, c) flowing at least one bead of hardenable adhesive material along the outer peripheral surface of the laminations in a generally vertical orientation between a top lamination and a bottom lamination where the adhesive material, when cured, fixes the laminations in a predetermined non-moving orientation, d) removing the laminations from the alignment fixture; and e) applying windings to the laminations. Other features and advantages of the invention will become apparent from the description that follows.
REFERENCES:
patent: 1158463 (1915-11-01), Eaton
patent: 1449371 (1923-03-01), Apple
patent: 1654306 (1927-12-01), Paszkowski
patent: 1756672 (1930-04-01), Barr
patent: 1877254 (1932-09-01), Ritter
patent: 1974406 (1934-09-01), Apple
patent: 2057503 (1936-10-01), Sawyer
patent: 2304607 (1942-12-01), Sleeter
patent: 2653208 (1953-09-01), Ballman
patent: 2680285 (1954-06-01), Furnas
patent: 2783404 (1957-02-01), Appenzeller
patent: 3293471 (1966-12-01), De Jean et al.
patent: 3670407 (1972-06-01), Mewhinney et al.
patent: 3778892 (1973-12-01), Ostroski
patent: 3821846 (1974-07-01), Pleiss, Jr. et al.
patent: 4734975 (1988-04-01), Ballard et al.
patent: 5176946 (1993-01-01), Wieloch
General Electric Company
Hall Carl E.
Horton Carl B.
Wasserbauer Damian G.
Welsh & Katz Ltd.
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