Apparatus for enamelling a conductive wire

Details Apparatus for enamelling a conductive wire Apparatus for enamelling a conductive wire

1998-05-01

2001-02-13

Lamb, Brenda A. (Department: 1734)

Coating apparatus

With heat exchange, drying, or non-coating gas or vapor...

Plural treatments

C118S712000

Reexamination Certificate

active

06186089

ABSTRACT:

The present invention relates to an apparatus for enamelling a conductive wire, the apparatus including an applicator for applying varnish on the wire and an enamelling oven, with the wire travelling through both of them.
BACKGROUND OF THE INVENTION
Document U.S. Pat. No. 5,291,670 disclosed an oven for enamelling conductive wires coated in a layer of resin (or varnish) dissolved in solvents. The oven includes a horizontal main chamber of elongate shape, an auxiliary assembly for sucking in and treating the solvent vapors coming form the main chamber, and a system for hot air convection therein.
The main chamber of the oven is subdivided into a zone for evaporating the solvents form the layer of resin on the wires, and a zone for polymerizing and cross-linking the resin. It is fitted with a horizontal row of electric resistance elements, which are mounted inside the chamber, and with heat exchangers which define two of the opposite longitudinal walls of said main chamber.
The auxiliary assembly has a suction mechanism for sucking in a flow of air and solvent vapor from the main chamber, between the two zones thereof. It also includes a heater mechanism for treating the sucked in flow. It is coupled to one of the ends of the heat exchangers to feed them with hot air provided by the treated flow.
The hot air convection system has a duct which couples the other ends of the heat exchangers to one of the ends of the main chamber. This ensures that the treated flow is recycled, with the flow being reinserted into the main chamber after it has travelled through the heat exchangers along the chamber.
In the main chamber of that enamelling oven, the solvent evaporation zone is maintained at a temperature in the range 150° C. to 350° C. while the resin polymerization and cross-linking zone is maintained in the range 400° C. to 550° C. The flow sucked in from main chamber is treated at a temperature of about 700° C. to 750° C. in the auxiliary assembly. Each of the tow zones in the main chamber is maintained at the desired temperature by the heat delivered form the internal electrical resistance elements, and also to a large extent by the heat exchangers and the convection system.
The enamelling oven makes maximum use of heat exchange between the treated flow fo air and solvents and the wires to be enamelled. Nevertheless, it is complex and bulky in structure.
Document JP-A-01 11671 discloses an assembly for baking a layer of resin (or varnish) on a metal wire, comprising two heating ovens which are mounted one after the other and through which there travels the wire, coated in its resin layer. The first heating oven is a circulating air oven. It ensures that most of the solvents in the layer of resin on the wire evaporate and it maintains resin cross-linking at an insufficient degree, with oxidation of the resin and of the wire remaining below a certain degree. The second heating oven causes the resin to be cross-linked at high temperature, of an the order of 500° C., and is provided with an internal atmosphere having low oxygen content, less than 5%, to hinder oxidation of the resin and of the wire. The enamelling assembly requires a unit for treating the solvent vapor coming from the first heating oven, if pollution problems are to be avoided.
SUMMARY OF THE INVENTION
An object of the present invention is to avoid the drawbacks of the above-mentioned known solution.
The invention provides an apparatus for enamelling a conductive wire, the apparatus including at least one assembly constituted by an applicator for applying varnish on the wire and an enamelling oven with said wire passing through both of the, the oven itself including at least one elongate chamber fitted with a wire inlet and a wire outlet at tow opposite ends and fitted internally with radiant heater elements facing the path followed by the wire between the inlet and the outlet to evaporate the solvents form the varnish on the wire and/or to bake the varnish on the wire, and secondly means for treating the solvent vapor coming form the varnish on the wire, wherein the enamelling furnace includes a single chamber whose internal atmosphere has oxygen content that is low, controlled, and less than 6%, thereby making it possible firstly to evaporate the solvents and bake the varnish on said wire, and secondly to constitute the means for treating said solvent vapor by combustion on contact with the radiant heater elements in the single chamber, without giving rise to any flame.
Advantageously, the apparatus may also present at least one of the following additional characteristics:
the single chamber includes a probe for measuring the oxygen content of the internal atmosphere, and an air feed inlet servo-controlled to the measurement of the probe;
the single chamber is at a pressure lower than the pressure of the outside atmosphere; and
the radiant heater elements are selected to be capable of raising the single chamber to a temperature of not less than 1000° C.


REFERENCES:
patent: 2517024 (1950-08-01), Prescott et al.
patent: 5291670 (1994-03-01), Surra et al.
patent: 39 42 609 A1 (1990-06-01), None
patent: 1 276 775 (1961-10-01), None
patent: 64-11671 (1989-01-01), None
Patent Abstracts of Japan, vol. 013, No. 182 (C-591), Apr. 27, 1989 corresponding to JP 01 11671 A (Furukawa Electric Co., Ltd.) Jan. 17, 1989.

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