Enhanced crush strength construction multi-grade paperboard tubes
CA 2124700 C · Owner: Johnson, Charles G. · Inventors: Mccarthy, Monica; Wang, Yiming; Gerhardt, Terry D.
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
The invention provides multi-grade spirally wound paperboard tubes of enhanced flat crush strength construction. The multi-grade spirally wound paperboard tubes of the invention include a plurality of structural paperboard plies having at least two predetermined densities including a lower density and a higher density wherein the higher density is at least about 3% greater than the lower density. The cylindrical bodywall is defined in radial cross section by at least one centrally located paperboard layer disposed between at least one radially inwardly located structural paperboard layer and at least one radially outwardly located structural paperboard layer. The centrally located …
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 May 31, 1994 and granted November 3, 1998. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended May 31, 2014.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by May 31, 2016.
- 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.