Tobacco smoke filters
CA 1235037 A · Owner: British-American Tobacco Company Limited · Inventors: Duke, Martin G.; Horsewell, Henry G.; Phelpstead, James W.P.
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
14-, "Improvements Relating to Tobacco Smoke Filters" A B S T R A C T, Cigarette filters comprise a filter element open, for smoke flow at the mouth end, and smoke passage means of flow impedance less than that of the filter element. The passage means is closed at the downstream end so that smoke is constrained to pass into the element at the downstream end of the passage means. The passage means may be an annular cross-section duct or grooves at the periphery of the element or may be a bore within the element. The filters provide an increasing degree of filtration as smoking proceeds.
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
- Granted April 12, 1988. A Canadian patent filed before October 1, 1989 lasted 17 years from grant, so its term ended April 12, 2005.
- 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.