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| Olefin polymerization catalyst component |
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Process for producing an insulated twisted electric wire
| Details |
Inventors: Masuda, Shigeo; Katsuda, Morihiko; Ueoka, Isao;
Assignee: Sumitomo Electric Industries, Ltd. (Osaka, JP)
Primary Examiner: Newsome; John H.
Assistant Examiner:
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak & Seas
A process for producing an insulating twisted electric wire having a reduced overall diameter with an insulating coating of high quality. The insulating coating has a thickness in a range of 3 to 100% of the radius of a smallest circle circumscribing the assembled set of twisted conductors. The insulating coating is formed by two or more cycles of coating and curing an insulating paint. Preferably, a bottom layer of the insulating coating is formed by applying a heat-curable insulating paint with a felt applicator or with a roller coating device. The heat-curable insulating paint should have a viscosity of not more than about 300 cps at 30.degree. C. |
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DETAILED DESCRIPTION In order to solve the problems described above, the present inventors have conducted various studies to find an effective method to produce twisted wires with a thin insulating coating and have successfully developed a method capable of forming an insulating coating on twisted metal conductors without causing blistering or leaving air bubbles entrapped within the coating.
As mentioned above, when an insulating coating is formed on twisted conductors by the conventional method of applying and curing insulating paint, air left in gaps (indicated at 2 in FIG.
1) between conductors expands upon heating and causes frequent blistering.
When air is heated at a given pressure from, for example, room temperature (20.
degree.
C.
) to 250.
degree.
C.
, its volume increases by a factor of about 1.
8.
The present invention has been accomplished as a result of the intensive studies conducted by the inventors to develop techniques for preventing the occurrence of a blistered insulating coating resulting from such an increase in air volume to thus eliminate entrapped air bubbles.
The insulating coating formed in accordance with the present invention is characterized by being thinner than the coating formed by conventional extrusion techniques, specifically, the coating thickness is within a range of 3 to 100% of the radius of the smallest circle that circumscribes the set of twisted conductors.
If the coating's thickness is less than 3% of the radius of the circumscribing circle, a highly reliable insulated wire will not be obtained, and if the thickness of the insulating coating is more than 100% of the radius of the circle, the method of the present invention provides no specific benefits as conventional extrusion techniques will serve as well.
In accordance with one aspect of the present invention, at least the bottom layer of the insulating coating on the twisted conductors is formed by applying a thin layer of heat-settable insulating paint with a felt applicator or by roller coating, and then hardening the applied layer so as to produce an insulated twisted wire having no blistered insulating coating
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Adhesives and Rubbers 
