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US 4,407,849 AGranted
Process for improving electrode coatings
AssigneeBell Telephone Laboratories, Incorporated
InventorsLaird K. S. Haas, Larry H. Herring, Yoshinao Nakada
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AssigneeBell Telephone Laboratories, Incorporated
InventorsLaird K. S. Haas, Larry H. Herring, Yoshinao Nakada
Estimating the term…
Disclosed is a method of improving the coating on electrodes (11 and 12) in spark gap devices which minimizes filament formation, densifies the coating, and ensures a good bond between the coating and underlying electrode. The device is coupled to a circuit (FIG. 2) which includes appropriate components so that a rapid sequence of current pulses having large amplitudes during arc initiation is passed through the device. The coating bonds with a different area of the cathode for each current pulse. The signal may be applied with appropriate reversal of polarities so that essentially the entire surface of both electrodes is thus reacted. Subsequently, the device may be subjected to an additional pulse in order to leave asperities on the surface which will increase field emission and ensure a low surge limiting voltage.
A method of fabricating a sealed gas surge limiter having two electrodes (11 and 12) with a coating (21) on a portion of at least one electrode and a spark gap (19) between said electrodes comprising the step of applying a pulsed signal to the electrode by means of a circuit including an AC current source (23), first means (portion I) for causing a relaxation oscillation waveform across the electrodes throughout each half-cycle of the current, second means (portion II) for producing a plurality of current spikes through the electrodes at the end of each period of the relaxation oscillation waveform and to produce a small polarity reversal each time the waveform goes to zero, and third means (portion III) for producing current spikes of high amplitude, such that a limited portion of the coating bonds with the electrode for each conduction so that said coating is bonded over essentially the entire interface with the electrode.
A method for fabricating a sealed gas surge limiter having two electrodes (11 and 12) with flat and sloped portions and with a coating (21) on the facing portions of the electrodes and a spark gap (19) between the flat portions of less than 75 .mu.m comprising the steps of:
Dependencies are inferred from the claim text.