the invention concerned comprises three components, and one of them is an elastomer which does not contain a functional group (4). I used this term "an elastomer which does not contain a functional group (4)" in claims as well, but now I'm a little bit confused because in Examples, it's basically a past tense and I'm not sure if I should change the tense of (4) (to "did" not) or not. I want to keep the term as it is because it is one element that the invention comprises, but should I change the tense? Or should I change the term (like, elastomer containing no functional group)?

Thank you so much for your help.

  • 1
    “did not contain“ sounds wrong to me, but I'm pretty sure it doesn't matter which tense you use as long as the invention is clear. I bet one could write a patent in first person saying I am the invention. Anyways, what I'm trying to say, I don't think there is an answer to your question.
    – user18033
    Commented Aug 10, 2018 at 17:19
  • Thank you for your answer, DonQuiKong. Ill make it my priority to clarify the invention as much as possible. Commented Aug 17, 2018 at 8:49

1 Answer 1


I do not do chemical patents but have seen "substantially free of XYZ", and "not containing XYZ").You would not use "did not" in a claim ever. If "did" was used in the specification it would imply an actual experiment. It is important to distinguish between actual experiments/data and speculation about what would happen.

  • Thank you for your answer, I'll change the term as you suggested. Thank you! Commented Aug 17, 2018 at 8:50

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