Method of making a variable capacitor microphone
CA 2017185 C · Owner: Cote, Paul L. · Inventors: Sallavanti, Robert A.; Cote, Paul L.
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
A method of making a variable capacitor microphone in which the fixed capacitor element is formed by first coating the metallized surface of a relatively rigid insulating substrate with a polarizable dielectric material and then placing the substrate on one of a pair of spaced electrodes positioned in an ionizable gas and subjecting the gas to the action of alpha rays to produce ions in the space between the electrodes while applying a potential across the electrodes to cause ions to migrate toward the dielectric material to polarize the same to form an electret. After the fixed capacitor element has thus been formed it is mounted, in spaced relationship to a flexible diaphragm to form a …
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Listed from its CIPO record in Patent Yard's archive of Canadian patents past their term. Its claims, description and drawings are in the CIPO record and on Google Patents, and the Claude kit works from them.
Why it's free to use
- Filed May 18, 1990 and granted September 21, 1993. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended May 18, 2010.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by May 18, 2012.
- We check Canadian rights only. A patent in its family in another country could still be in force: check its family on Google Patents.
Timeline
Timeline From CIPO dates
Sources & verification
Official CIPO records
Everything on this page comes from the CIPO record linked above. Contains information licensed under the Open Government Licence – Canada.