How does the USPTO apply the “Mere Function of Machine” rule during patent examination?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

The United States Patent and Trademark Office (USPTO) applies the “Mere Function of Machine” rule by not rejecting process or method claims solely because they describe the function of a disclosed machine. As stated in MPEP 2173.05(v):

“Process or method claims are not subject to rejection by U.S. Patent and Trademark Office examiners under 35 U.S.C. 112(b) or pre-AIA 35 U.S.C. 112, second paragraph, solely on the ground that they define the inherent function of a disclosed machine or apparatus.”

During examination, patent examiners are instructed to evaluate process claims on their own merits, regardless of whether the application also discloses an apparatus that would inherently perform the claimed steps. This ensures that otherwise patentable process claims are not unfairly rejected and allows for a more comprehensive examination of the invention’s patentability.