Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-06-23
2001-06-26
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S090000, C310S091000
Reexamination Certificate
active
06252321
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to electric motors and more particularly, to an endshield assembly for an electric motor.
Known electric motors typically include a motor housing, a stator, and a rotor assembly The rotor assembly includes a rotor core and a rotor shaft extending through the core. The housing includes a shell and two endshields and houses at least a portion of the rotor assembly. Electric motors also include at least one bearing sized to receive the rotor shaft. Typically the bearings are coupled to the endshields with springs, brackets or other mountings. The endshields attach to ends of the housing shell. For optimum operation of the motor, the bearings need to align with the rotor shaft, i.e., the center of the bearing cartridge opening needs to align with the centerline of the rotor shaft.
Each part of the endshield and bearing assembly is manufactured to a tolerance, and the tolerance of the assembly is the sum of the tolerances of the parts. Known cartridge bearing and endshield mounting configurations result in additive tolerances. Additive tolerances of the parts of the assembly can result in misaligned bearings and associated wear and motor performance problems.
It would be desirable to provide an endshield and bearing assembly that would not produce additive tolerances, therefore, resulting in lower tolerances in the final motor assembly. It would also be desirable to provide an endshield and bearing assembly that has a reduced number of parts and that provides accurate support of the bearing element and that permits limited bearing alignment.
BRIEF SUMMARY OF THE INVENTION
In an exemplary embodiment, an endshield assembly for an electric motor includes a metal endshield, a bearing assembly, and an injected molded metal center housing that couples the bearing assembly to the metal endshield. The bearing assembly is sized to receive a center shaft of the electric motor and includes a cylindrical housing having an outer surface.
The center housing includes a plurality of projections extending from the inside surface of a cylindrical wall. The projections are positioned around the circumference of the inside surface of the center housing to engage the outer surface of the bearing housing. The projections are staggered around the center housing circumference so that every projection contacts the outer surface of the bearing housing on an opposite side of a bearing housing circumferential centerline than an immediately adjacent projection.
The endshield assembly is fabricated by positioning the metal endshield in a mold/fixture. The bearing assembly is also positioned in the mold/fixture so that a centerline of the bearing assembly opening is aligned with a centerline of the center opening of the endshield. The center housing is then formed around the bearing assembly by the known process of injection molding. Molten metal is injected into the mold so that the metal forms an injected molded metal housing that contacts the metal endshield and the bearing assembly to couple the bearing assembly to the metal endshield.
The above described endshield assembly includes a reduced number of parts than known end shield and bearing assemblies. Because the endshield assembly uses a mold/fixture to align the metal endshield and the bearing assembly during the injection molding of the center housing, the are no additive tolerances. The tolerances of the bearing assembly and the endshield are absorbed by the injection molded metal center housing. The endshield assembly also provides accurate support of the bearing assembly and permits limited bearing alignment.
REFERENCES:
patent: 3875436 (1975-04-01), Macfarland
patent: 4420703 (1983-12-01), Adam et al.
patent: 4823032 (1989-04-01), Ward et al.
patent: 5127148 (1992-07-01), Lykes et al.
patent: 5917258 (1999-06-01), Kershaw et al.
patent: 5945759 (1999-08-01), Tanaka et al.
patent: 5969447 (1999-10-01), Periyathamby et al.
patent: 6040649 (2000-03-01), Horng
Fisher L. Edwin
Pape Marc D.
Armstrong Teasdale LLP
General Electric Company
Horton, Esq. Carl
Lam Thanh
Ramirez Nestor
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