If the filing date of this patent is on Jun 14, 1994, the patent should have expired on June 14, 2014. Is this right? Also, what is the significance of knowing the assignment of this EXPIRED patent on 2016 if the patent has already expired? Please help. Thank you.

  • This question provides a method to check the date yourself patents.stackexchange.com/q/3801/18033 Normally it's 20/17 years, but the patent term could have been extended. – DonQuiKong Mar 13 '17 at 7:43
  • Yeah, the answer DonQuiKing cited is probably the best on the site. – Eric S Mar 13 '17 at 19:10

Since this patent was filed prior to June 8th, 1995, the term of the patent was 17 years from the date of ISSUANCE, not filing date. Thus if it went through a long examination period, which was common back then (prosecution periods of five or more years were not uncommon), the patent could still be in effect and enforceable. Also, any continuation patent applications would still have that early filing date and the term would be 17 years from the date of ISSUANCE for continuing patent applications. It was common strategy back then to keep continuation applications pending for years after issuance of the parent application. This enabled clever owners to keep amending and prosecuting patent claims in pending applications to cover the attempts of competitors to design around the original patent. This was referred to as "submarine patent applications", that were not published and kept secret from the marketplace, then emerging once a competitor had designed around the original patent. That is one of the major reasons why the patent terms were changed to be 20 years from date of FILING, not issuance and why patent applications are normally published now.

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  • This is a good answer, but is the submarining issue likely to be a problem for a patent first filed in 1994? – Eric S Mar 13 '17 at 19:08
  • Jerome Lemelson was able to keep "submarining patents" alive for decades on such technology as bar code scanners, fax machines, cam corders, walkmans, etc. He made $1.3 billion off of them by suing and licensing the manufacturers of the actual devices. His estate still have applications pending based on filing dates of over 30 years ago. So in the posters case, it is possible that there were continuation applications filed at least for a decade after the original patent application was filed. Thus there may be real value in the patent he referenced or from continuation applications from it – Patent Pending Guide Mar 14 '17 at 1:42

This Wikipedia page provides a good review of patent terms. Essentially in the US, the term is 20 years from the priority date for patents filed on or after June 8th, 1995 or the longer of 20 years from the priority date or 17 years from the grant date for patents filed before June 8th, 1995. Once the patent has expired, you shouldn't need a license so the assignee is irrelevant. This doesn't mean you shouldn't make sure there aren't other relevant patents still in force.

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  • Is there any easy way to check for relevant patents that may still in force? Thank you. – hsieh Jong Yin Mar 14 '17 at 5:35

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