Can a preamble be used to distinguish over the prior art during patent prosecution?
Yes, a preamble can be used to distinguish a claimed invention over the prior art during patent prosecution, but doing so may have significant consequences. The MPEP 2111.02 states: “Clear reliance on the preamble during prosecution to distinguish the claimed invention from the prior art transforms the preamble into a claim limitation because such reliance indicates use of the preamble to define, in part, the claimed invention.“
When an applicant uses the preamble to argue that their invention is different from the prior art, they are effectively making the preamble a limiting part of the claim. This can be beneficial if it helps overcome a rejection, but it also narrows the scope of the claim. Applicants should consider the following:
- The preamble becomes part of the claimed invention
- Future infringement analysis will include the preamble
- It may limit the ability to argue for a broader interpretation later
It’s important to carefully consider whether distinguishing based on the preamble is necessary or if there are other ways to overcome the prior art without limiting the claim scope.
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