Having a patent does not entail competing interests
In many cases papers include a section at the end where authors can declare competing interests, and is normally used for authors to declare if a patent has been submitted or granted as part of the research.
However, I don't see why would that generate any conflicts unless the patent has been licensed. The inventors of a patent get to profit from it only in cases where there are other commercial actors exploiting it, and thus there is an interest not to discredit the original work. In that case, the conflict of interests should state that the patent was licensed and not merely that it was granted.
The patent-based line of thought would lead to previous papers as potential conflict of interest. Discrediting one's own previous work is only damaging for follow up funding.
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