In reference to the patent: US4146939

I don't know much about patents and I can't figure out what the status is on this patent. I'm working on a new invention that attaches to this patent[US4146939]. I want to cut down my costs so my question is am I allowed to replicate and sell the product from the patent?

Many thanks

1 Answer 1


That patent was issued in 1979 and expired 17 years later. The rules changed in 1995 and now patents expire 20 years from their priority date which is usually the filing date.

  • Okay but why does it say new owner? worldwide.espacenet.com/publicationDetails/…
    – user19998
    Commented Oct 24, 2017 at 6:48
  • 1
    That was from 2003.
    – Eric S
    Commented Oct 24, 2017 at 20:48
  • So basically I can't use it till 2023?
    – user19998
    Commented Oct 25, 2017 at 7:17
  • 1
    No, the patent has to expire 17 years after grant (back then). The assignee can change hands at any time, but it doesn’t change the expiration date. This patent must have expired do you can use it. Always be aware that other patents may apply.
    – Eric S
    Commented Oct 25, 2017 at 7:53

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