Sleeve for increasing retention value of a screw
CA 2084565 C · Owner: Leibhard, Erich · Inventors: Schwaninger, Thomas; Popp, Franz; Leibhard, Erich
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
The retention value of a screw previously inserted into a wooden railroad tie is increased by an axially extending sleeve (20) having an external thread (24) and an internal thread (25). The thread revolutions of the internal thread (25) are offset axially by half (h) the thread pitch (H) of the external thread (24). due to this offset of the threads, the screw is positioned in the sleeve so that its threads are located between the external thread revolutions affording a new retention while the external thread (24) seats within the thread previously formed in the wooden railroad tie by the screw.
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 4, 1992 and granted July 18, 2000. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended December 4, 2012.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by December 4, 2014.
- 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.