Electric lamp and discharge devices – With gas or vapor – Having electrode lead-in or electrode support sealed to...
Patent
1991-03-27
1992-04-07
Yusko, Donald J.
Electric lamp and discharge devices
With gas or vapor
Having electrode lead-in or electrode support sealed to...
31323111, 313635, 361120, 361129, 361130, H02H 322
Patent
active
051031353
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to electrical components and, more particularly, to the material design of the external surface of gas-discharge surge arresters.
Gas-discharge surge arresters have a variety of uses including the protection of telecommunication lines, for example. In this application surge arresters are used having electrodes with soldered-on, welded-on or integral leads. Such surge arresters may comprise two opposed electrodes and optionally a third, centrally located annular electrode. German Patent 28 28 650 discloses such a surge arrester. Like the electrodes, the leads attached to them are usually silver-plated if they are made of copper. Occasionally the use of tinned leads is required. In flow soldering the wetting of the leads is required during the soldering operation. If copper electrodes having welded-on copper leads are used, bronze (which is an alloy of copper and tin) may form near the weld when a tinned lead is welded to a copper electrode, weakening the weld mechanically and electrically. It is also known to use surge arresters without leads. With such arresters, the electrodes are contacted by spring action. It is also known to use surge arresters with alloyed-iron electrodes and to coat the electrodes with nickel. Moreover, it is common practice to apply identifying marks to the ceramic insulator of the surge arrester by imprinting it with symbols, numerals and letters.
There is a need for a surge arrester which can be manufactured at low cost and is suitable for automatic bulk processing without degradation of its insulating strength. There is also a need for a surge arrester that can be readily soldered into printed circuits or circuit boards.
SUMMARY OF THE INVENTION
These and other needs are satisfied by the gas-discharge surge arrester of the present invention. The gas-discharge surge arrester includes at least one tubular ceramic insulator having electrodes disposed at its ends. The electrodes are joined to the ceramic insulator in a gastight manner. The external surface of each electrode is provided with a tin protective coating.
An annular insulating protective coating of an acid-resistant and heat-resistant colorant or varnish that is continuous and unbroken in the axial direction of the insulator is applied to the circumference of each ceramic insulator having a width of at least 1 mm.
In this surge arrester the tin coating forms a low-cost metallic coating on the electrodes. Such a tin coating alone entails the risk that when the surge arresters are handled as a bulk material the tin coating will degrade on the rough circumference of the ceramic insulators, which could give rise to insulation faults. The application of the protective colorant or varnish coating eliminates such a risk. The protective coating forms a relatively smooth region on the circumference of the ceramic insulator in which no detrimental degradation of the tin can occur. The width of the protective coating is such that the minimum value of the insulating strength (e.g., 10.sup.10 ohms) is maintained even when degradation of tin does occur in the remaining portions of the circumference of the ceramic insulator.
Optionally, the protective coating may cover the entire external surface of the ceramic insulator. When the width of the protective coating exceeds 3 or 4 mm, the protective coating is utilized as part of the identification of the surge arrester. For this purpose, the protective coating may be reverse imprinted. However, the protective coating may also form a transparent and preferably colorless top coat for a conventional imprint or a substrate for a subsequent conventional imprint.
The acid resistance of the protective coating allows the use of electroplating treatments of the surge arrester. These electroplating treatments are required in the further course of manufacturing the surge arrester. Also, the heat resistance of the protective coating, which is at least 160.degree. C., assures that when the component is subjected to alternating-current stresse
REFERENCES:
patent: 1340657 (1920-05-01), Jacobus
patent: 3904910 (1975-09-01), Schleimann-Jensen
patent: 4266260 (1981-05-01), Lange et al.
Lange Gerhard
Scheidt Andre
Hamadi Diab
Siemens Aktiengesellschaft
Yusko Donald J.
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