Seismic vibration generating device used particularly in oil wells

Read the whole patent

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 December 18, 1990. No grant is recorded for it in Canada; had it been granted, its 20-year term would have ended December 18, 2010.
• A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by December 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.