Can the transitional phrase “consisting of” ever be interpreted as open-ended in patent claims?

Can the transitional phrase “consisting of” ever be interpreted as open-ended in patent claims?

While “consisting of” is generally considered a closed transitional phrase, there are rare circumstances where it might be interpreted as open-ended:

• Dependent claims: A dependent claim using “consisting of” might be interpreted as open-ended if its base claim uses an open-ended transition.
• Specification context: If the specification clearly indicates an open-ended interpretation, this might influence the claim’s scope.

However, these are exceptional cases. The MPEP 2111.03 emphasizes:

“The transitional phrase ‘consisting of’ excludes any element, step, or ingredient not specified in the claim.“

In general, “consisting of” is treated as a closed transition, limiting the claim to only the specified elements. Examiners and practitioners should be cautious about interpreting “consisting of” as open-ended without clear and compelling evidence from the specification or prosecution history.

To learn more:

• transitional phrases
• consisting of
• open-ended interpretation
• closed transition
• claim scope