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From what I've been reading about US patents, once a patent has expired, it enters the public domain and can be freely used.

The patent I was looking at was filed on 1/1999 and published in 10/2000. So, obviously the 20-year patent term has not yet be reached. However, the status appears to be expired due to non-payment of the maintenance fee.

On google patents, the status is:

12/2008 Expired due to failure to pay maintenance fee

On uspto.gov, the patent's status is shown as:

Patent Expired Due to NonPayment of Maintenance Fees Under 37 CFR 1.362

Has the patent entered the public domain and can it be used freely?

Additionally (and assuming that it is in the public domain), can someone come along at some point and start paying the maintenance fee again and pull it out of the public domain until the 20-year term is reached? It is very unlikely that this patent will be revived by the company that originally filed it since they shut down production of products using the patent in 2000 and moved onto other things.

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2 Answers 2

up vote 3 down vote accepted

Two or three issues involved with this. A patent that expired due to non-payment of maintance fee can be revived by petition as either unintentional or unavoidable. Unintentional has a two-year limit and unavoidable is very hard to establish. Only the patent owner can file these, not just anyone who comes along. Even if revived there are intervening rights (after the 6 mo. grace period) to anyone who started practicing the patent while it was dead to keep doing what they were doing.

All of this pertains to the claimed subject matter. Anything taught in the patent that was never claimed is "dedicated to the public" right away. Of course something taught but not claimed in patent X might very well be patented in some other patent Y.

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George, your answer intuitively sounds correct, and from what I know off the top of my head, the unintentional/unavoidable bit is correct, but I just wanted to clarify the last sentence. If something is taught in patent X, sufficiently to enable someone to practice, than by definition wouldn't that invention not be patentable in patent Y due to anticipation?

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I think the idea was Y predates X in the example. –  Micah Siegel Jan 24 at 20:56
Yes, Y could have been the subject of a completely different patent by a completely different inventor that has an earlier priority date. If the same inventor, Y could be a year later than X. Also, there could be a family of patents, all getting priority back to a common original disclosure. Technologies A and B are taught in the specification and two patents result, one with claims to A and the other with claims to B. A non-payment of maintenance fees or even all claims killed in a re-exam for one patent doesn't affect the other patent (unless they are linked by a terminal disclaimer.) –  George White Jan 24 at 21:17
@Max - Also, Welcome to Ask Patents! You posted your comment to my answer as another answer. This type of post should be a comment on the answer. Everything posted as an "Answer" needs to be something trying to answer the original question. thanks. –  George White Jan 24 at 21:32
@Max - There are also cases where a patentee gets very similar but not identical claim wording allowed in two separate patents. If the second one gets a non-statutory double patenting rejection and a terminal disclaimer is filed then when one patent dies, they both die. This may not be the case in all instances and a patent with slightly different limitations may still be alive after its brother expires due to maintenance fee non-payment. –  George White Jan 24 at 21:38
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