Can 3DSystems sue Formlabs over US Patent 5597520? If it was issued in 1997, wouldn't it have expired in 2007?

  • 1
    This patent was filed before June 8, 1995. Its term should be at least 17 years after its issue date. The issue date was January 28, 1997, so the patent should be valid until January 28, 2014.
    – user1876
    Nov 21, 2012 at 23:13
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    @MarkNowotarskipatentagent That is right; you should submit it as an answer.
    – kinkfisher
    Nov 21, 2012 at 23:18
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    The expiry date should have been April 24, 2014. Patents filed before June 8, 1995 have a term which is the longer of 17 years from the date of grant or 20 years from the date of filing. In this case the 20 years is longer. And the final maintenance fee has been paid so it will remain in force until that date. See: ramps.uspto.gov/eram/… Nov 27, 2012 at 3:37
  • The truth is I was assuming 20 years and did the arithmetic in my head wrong. Thanks for all your help, everyone! Nov 28, 2012 at 14:16

2 Answers 2


I don't know about the first question, but the second is no. Calculating a patent term can be complicated, but assuming the maintenance fees were paid, etc., there's no reason it should have expired in 2007.


The 10 years expiration aren't for utility model patents.

  • Welcome to ask patents. I think your answer was down voted as being a very late answer (relative to when the question was asked) and not adding anything to the already good answers.
    – George White
    Jan 1, 2014 at 1:21

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