Our patent FR2553560 was disparaged by the subsequent patent US5069827. They rejected the use of the best solvent HNO3 of our invention and claimed to use H2SO4 instead of HNO3 in nuclear fuel reprocessing. We believe they are nuclear fuel reprocessing professionals. So that, the inventors of US5069827 must intentionally have rejected our invention, despite it being the best.

Is their patent invalid because of this?

  • What do you mean by "disgrade"? And when you say "they" have rejected our invention, who do you mean by "they"?
    – Maca
    Commented May 18, 2018 at 7:01
  • "disgrade" means they said in their patent that our invention is not of practical and not useless. " they" means the people from France in the patent. Commented May 18, 2018 at 7:32
  • not useless ------> useless Commented May 18, 2018 at 8:16
  • 1
    Since both patents have expired, what possible difference could it make?
    – Eric S
    Commented May 18, 2018 at 13:56
  • Japanese version of our patent was transferred to AREVA in 1997. On the othe hand the US patent from France was lapsed or expired to lifetime. Commented May 19, 2018 at 23:10

2 Answers 2


It's not illegal to say your invention is useless, actually that's quite normal because one wants to argue how their invention is inventive, so naturally the prior art must have drawbacks. It really doesn't matter if that's true-ish or not. The patent attorney writing that probably doesn't even know if your invention or theirs is better. So just ignore that.

If their patent is granted and their way of using H2SO4 works and doesn't infringe your patent, than they can use that. If it's worse than yours, they'll notice on a business level, but for patents, it doesn't matter.

After all, them not using your invention is exactly what your patent is supposed to accomplish. If they find an alternative/better way, well, that's how it goes.


You can say whatever you want about other patents. It might not be sensible for various reasons, but no one will stop you.

However, a patent must also set out the best mode of performing the invention. If it fails to do so, the patent is invalid.

However, best mode is pretty broad. It doesn't just mean highest performing. A cheapest, but lower performing option can be the best mode if you are looking for economy. A safer, but lower performing option can be the best mode if you are looking for safety. An inferior alternative can be the best mode, if you are looking for alternatives. Basically anything can be the best mode under the right lens.

In this case, US5069827 discusses FR2553560, and notes certain problems in it. These problems seem reasonable at first blush. US5069827 also presents a solution that ostensibly doesn't have those problems. So it seems they have disclosed the best mode of performing their invention. This is the case even if FR2553560 discloses a better invention (for some meaning of better).

  • The inventor from France of the patent US5069827 is a professor in nuclear fuel reprocessing, so that they must know that HNO3 is the best solvent of nuclear fuel. There is no alternative to HNO3 as far as known. Nevertheless they proposed H2SO4 insted of HNO3 as solvent. I think they intend to make our invention be useless in practical application. That may be illegal in a patent law. Commented May 18, 2018 at 10:29
  • @AkihikoInoue The point is that everything is "best" in its own way. In any case, they are pursuing their own invention. It doesn't affect your invention. As DonQuiKong notes, if one really is absolutely better than the other, that'll be solved on a business level.
    – Maca
    Commented May 18, 2018 at 11:18
  • @AkihikoInoue their patent has no influence whatsoever on yours.
    – user18033
    Commented May 18, 2018 at 11:49
  • @Maca Just a note on best mode, it is currently no more than a "paper tiger" in the US since AIA. Only an examiner could reject an application for such reasons, and he is unlikely to know whether or not best mode was disclosed unless a third party intervenes during prosecution.
    – user132162
    Commented May 18, 2018 at 15:37
  • @user132162 its more of a cute little paper duck, because best relates to whatever.
    – user18033
    Commented May 18, 2018 at 16:48

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