Updated: Aug 21, 2020
The Court of Appeals for the Federal Circuit provided some guidance in this case as to how restrictive the limitations in the preamble are when determining the claims scope.
Patent practitioners may be aware that "a preamble limits the invention if it recites essential structure or steps, or if it is ‘necessary to give life, meaning, and vitality’ to the claim." Something that might not be as well known is that "a preamble is not limiting 'where a patentee defines a structurally complete invention in the claim body and uses the preamble only to state a purpose or intended use for the invention.'"