Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Reexamination Certificate
1999-05-25
2001-06-19
Ortiz, Angela (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
C264S272150, C264S272190, C264S278000, C264S346000
Reexamination Certificate
active
06248279
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for encapsulating a ring-shaped member, such as a wound coil of wire, with a casing having a relatively constant thickness and rounded edges, and wherein the encapsulated ring-shaped member is stress-relieved.
1. Description of Prior Art
Conventional methods have been used to encapsulate ring-shaped members, such as wound coils of wire. For example, wound coils have been dipped in an epoxy material or an enamel material. The dipping process results in a coated or encapsulated wound coil. However, the wall thickness of the coating can significantly differ because of manufacturing inconsistencies associated with different variables, such as materials and gravity effects.
In other conventional methods, a wound coil is encased by positioning the wound coil within a prefabricated casing or housing having two or more pieces. The multiple casing or housing pieces are then welded, adhered or otherwise sealed or mechanically connected with respect to each other.
The different conventional methods for encapsulating a ring-shaped member produce casings with variable wall thicknesses and casing that have exposed sharp edges. Encapsulated wound coils are used to manufacturer toroidal coils, wherein a wire is wound in a toroidal fashion about the casing of an encapsulated wound coil. Inconsistent casing thicknesses can result in inaccurate toroidal windings. Because tension is applied to a toroidal wire during a winding process, a sharp casing edge can sever and thus break the toroidal wire during the winding process.
There is an apparent need for a method and apparatus for encapsulating a wound coil, wherein the casing has a relatively constant thickness with no exposed sharp edges, to provide a base for winding a consistent and accurate toroidal coil, particularly without breaking the toroidal wire. Also, there is a need to provide a method and apparatus for mass producing at relatively high production speeds an encapsulated ring-shaped member, such as a wound coil.
SUMMARY OF THE INVENTION
It is one object of this invention to provide a method and apparatus for encapsulating a ring-shaped member using a controlled injection molded thermoplastic material.
It is one object of this invention to provide a method for annealing or heat treating on encapsulated ring-shaped member to stress relieve the ring-shaped member.
It is another object of this invention to provide an encapsulated ring-shaped member which has a casing with rounded external comers or edges.
It is another object of this invention to provide an encapsulated ring-shaped member having a casing of relatively constant wall thickness.
It is another object of this invention to provide a method and apparatus for precisely reproducing a particular size and shape of a casing used to encapsulate a ring-shaped member.
As used throughout this specification and in the claims, the term ring-shaped member can be interchanged with the term wound coil. It is apparent that the ring-shaped member and/or the wound coil can have any suitable cross-sectional shape, as further discussed later in this specification.
The above and other objects of this invention are accomplished with a method for mass producing large quantities of encapsulated ring-shaped members, particularly at relatively high production speeds, using controlled injection molding techniques as described in this specification.
In one preferred embodiment of this invention, a mandrel is positioned within an opening formed by a ring-shaped member. The mandrel can be shaped to form a first inner void between the mandrel and at least a portion of an inner surface of the ring-shaped member. The first inner void preferably extends about an entire periphery of and between an external surface of the mandrel and an internal surface of the ring-shaped member. Thus, the first inner void is preferably formed as a peripheral void or an annular void.
The mandrel and the ring-shaped member mounted with respect to the mandrel are positioned within a first mold. In one preferred embodiment according to this invention, the first mold and the ring-shaped member form a first outer void about a periphery of the ring-shaped member. The first mold and the ring-shaped member also preferably form a first annular void that joins both the first inner void and the first outer void.
In a first fill, a thermoplastic material is injected into and fills or occupies the first inner void, the first annular void and the first outer void.
In one preferred embodiment according to this invention, a sleeve is positioned over the mandrel, near the ring-shaped member. A peripheral edge of the sleeve preferably forms a boundary of the first inner void. The peripheral edge has an undercut that forms a curved surface at the boundary of the first inner void. The curved surface forms a rounded corner on an external surface of an inner periphery of the casing.
After forming the first fill, the mandrel, the mounted ring-shaped member and a partially formed casing are removed from the first mold. The mandrel is then moved with respect to the ring-shaped member to form a second inner void between the mandrel and a second portion of the peripheral inner surface of the ring-shaped member. Then, the mandrel and the re-mounted ring-shaped member are positioned in a second mold. In one preferred embodiment of this invention, the second mold and a remaining portion of the peripheral outer surface of the ring-shaped member forms a second outer void. The thermoplastic material of the first fill occupying the first outer void is exposed to the second outer void, which preferably extends about a periphery of the outer surface of the ring-shaped member. The second mold and the ring-shaped member preferably form a second annular void that joins both the second inner void and the second outer void.
The thermoplastic material, which can be the same or a different thermoplastic material as used in the first fill, is injected into and occupies the second inner void, the second annular void and the second outer void. In one preferred embodiment according to this invention, the second fill joins, knits or bonds with the first fill and encases the ring-shaped member, preferably but not necessarily in an air-tight manner.
Depending upon the design of the second mold, the sleeve can be removed before or after the mandrel and the ring-shaped member are positioned within the second mold. After the second fill is complete, the mandrel and the encased ring-shaped member are removed from the second mold. After removing the mandrel and the ring-shaped member from the second mold, a comb or a knockout device can be used to eject the coil from the mandrel.
In one preferred embodiment according to this invention, the encapsulated ring-shaped member can then be annealed or heat treated, for example, to a temperature that is sufficient to anneal and thus stress-relieve any undesirable tension within the ring-shaped member. Undesirable tension may be caused by the injection molding method of this invention.
Because the casing is injection molded, according to this invention, wall thicknesses along the casing are relatively constant. Also because of the injection molding according to this invention, the casing can be reproduced with precise dimensions and shapes. By using the sleeve with the undercut, according to this invention, all external edges of the casing can be rounded.
With the method and apparatus according to this invention, the mandrel can be moved with respect to the ring-shaped member, such as a wound coil, without friction or shear forces distorting the shape of the wound coil. Also, with the method and apparatus according to this invention, the encased wound coil can be stress-relieved with a heat treating or an annealing step.
REFERENCES:
patent: 1808047 (1931-06-01), Littleton, Jr. et al.
patent: 2058938 (1936-10-01), Apple
patent: 3311690 (1967-03-01), Fischer
patent: 3351691 (1967-11-01), Wilford
patent: 3484516 (1969-12-01), Simons
patent:
Ortiz Angela
PANZER Tool Works, Inc.
Pauley Petersen Kinne & Fejer
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