# Patent expiry question

**URL:** <https://boards.straightdope.com/t/patent-expiry-question/396363>\
**Category:** Factual Questions\
**Created:** [March 17, 2007, 8:41pm UTC](https://boards.straightdope.com/t/patent-expiry-question/396363 "2007-03-17T20:41:37Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\
**Post date:** [March 17, 2007, 8:41pm UTC](https://boards.straightdope.com/t/patent-expiry-question/396363/1 "2007-03-17T20:41:37Z")

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Question… is it really true that US patents expire 20 years after filing? Can they be re-newed or is the invention public domain at that point? I’m wondering if the inventor of a patent granted in the 1950’s could claim damages against someone using that invention in the present day.