Coating apparatus – Work holders – or handling devices – Gripper or clamped work type
Reexamination Certificate
2000-05-31
2001-11-27
Crispino, Richard (Department: 1734)
Coating apparatus
Work holders, or handling devices
Gripper or clamped work type
C118S621000, C118S622000, C211S001530, C211S182000
Reexamination Certificate
active
06322629
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the benefit of the filing date of Japanese Patent Application No. 11-153160, filed in Japan on Jun. 1, 1999, under 35 U.S.C. § 119. The entire content of the Japanese application is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrostatic coating apparatus, which coats an annular article such as a stator core or a driving magnet for an electric motor with electrostatically charged powder, and it pertains to a method for electrostatically coating such an annular article. The present invention also relates to a fixture for holding an annular article for such electrostatic powder coating.
2. Description of the Related Art
Japanese Laid-Open Patent Application No. 60-193560 discloses an electrostatic coating apparatus for coating an armature of an electric motor with electrostatic powder. The electrostatic coating apparatus comprises a chain conveyor for transporting the core to be coated along a transporting path and an electrostatic spray station disposed half way of the transporting path to apply electrostatically charged powder onto the armature. The apparatus also comprises a fixture for holding or supporting the core. The holding fixture is formed of a pair of conductive metallic cylindrical columns, each cylindrical column having a central hole or bore which is open at one end of the column. Both ends of a holding shaft fixed to the center of the armature are detachably fitted to the central holes, respectively. The armature is transported by the chain conveyor along the transporting path with the armature rotating with the cylindrical columns of the holding fixture. While the armature passes through the electrostatic spray station, electrostatically charged powder of solid particulated material are ejected onto the armature to coat the armature with the powder.
However, the aforementioned conventional coating apparatus cannot coat the portion of the armature covered by the holding fixture because the powder cannot reach there, while the exposed portions outside of the holding fixture can be coated. Moreover, since the holding fixture is formed to hold the shaft of the armature, a hollow annular article such as a stator core of an outer-rotor-type spindle motor cannot be held by the holding fixture of the conventional apparatus. When the holding shaft is fitted in the inner diameter of the core, the core can be held thereby. However, the interior surface of the core cannot be coated.
Furthermore, it may be sometimes desirable that the thickness of the coating is changed at portions of the core. As disclosed in Japanese Laid-Open Patent Application No. 10-145988, for example, when a stator of a motor opposes a permanent magnet ring with the stator having coils wound around core sections, it is required that the thickness of the coating on the core is made different, complying with the demand for each portion thereof. For example, the coating on the surface of the core opposing the permanent magnet should be thinner than that on a coil winding portion and interior surface of a mounting hole of the core. In the apparatus disclosed in that patent application, the core held by a particular holding fixture is coated two times, with the second coating being applied after a first coating is removed for some portion where the thickness of the coating is required to be thinner. The portion having one layer of the coating (single coated portion) film and the portion having two layers thereof (double coated portion) are thereby formed on a core such that it has different thicknesses of the coating for the different portions of the core. However, since the prior art does not teach how to hold an annular core during the coating such that the entire surface of the core may be coated, it is likely that the coating is uneven in some portions and un-coated in other portions.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an electrostatic coating apparatus capable of electrostatically coating a desired portion of an annular article.
It is another object of the present invention to provide an electrostatic coating apparatus capable of electrostatically coating the entire surface of an annular article, including the interior surface of an annular article.
It is still another object of the present invention to provide an electrostatic coating apparatus capable of electrostatically coating an annular article to form different thicknesses of the coated layer on different portions of the article.
It is a further object of the present invention to provide an electrostatic powder coating method for coating a desired portion of an annular article.
It is still a further object of the present invention to provide an electrostatic powder coating method for coating the entire surface of an annular article including the interior surface of a central hole of the article.
It is yet a further object of the present invention to provide an electrostatic powder coating method for coating an annular article with the thicknesses of the coating on portions of the article.
It is another object of the present invention to provide a holding fixture for holding an annular article to be coated substantially without covering the surface of the article.
It is further another object of the present invention to provide a holding fixture for holding an annular article to be coated without covering the interior surface thereof.
It is still another object of the present invention to provide a holding fixture for holding an annular article such that a desired portion thereof is electrostatically coated.
It is yet another object of the present invention to provide a holding fixture for holding an annular article such that substantially the entire surface of the article including the interior surface of the article is electrostatically coated.
According to one aspect of the present invention, an electrostatic coating apparatus of the invention comprises a first and second holding fixtures for holding or supporting an annular article to be coated. The first fixture is provided with a plurality of holding hooks which elastically abut against the internal surface of a central hole of the annular article after the hooks are inserted into the central hole of the annular article from one end of the central hole. The second fixture includes a connecting rod for elastically deforming the holding hooks of the first fixture with the connecting rod being inserted into the central hole from the other end thereof to be brought into engagement with the holding hooks. Thus, the annular article is held by the holding fixture, and conveyed to a coating station where a series of treatments including an electrostatic coating is applied while the article is passing through the coating station.
In accordance with another aspect of the present invention, a holding fixture comprises: a first fixture having a plurality of holding hooks which are elastically deformable and is to be inserted into a central hole of an annular article to be coated, from one end to fit loosely thereto; and a second fixture having a connecting rod which is to be inserted into the central hole of the article from the other end thereof to be brought into engagement with the holding hooks to make the latter elastically abut against the internal surface of the article to hold it. The annular article may be a core for a stator of a motor or a driving magnet of the motor for generating a driving force, for example.
In accordance with a further aspect of the present invention, an electrostatic powder coating method for an annular article, comprising the steps of: inserting a plurality of elastic holding hooks of a first fixture into a central hole of the annular article from one end of the annular article; inserting a second fixture into the central hole from the direction opposite from the first fixture so as to be brought into engagement with the holding hooks to make the holding hooks abut against the intern
Inuta Hideo
Okada Shin-ichiro
Burns Doane , Swecker, Mathis LLP
Crispino Richard
Nidec Corporation
T. Yewebdar T.
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