What is the meaning of “consisting essentially of” in patent claims?

The transitional phrase “consisting essentially of” in patent claims occupies a middle ground between “comprising” and “consisting of”. The MPEP explains, The transitional phrase “consisting essentially of” limits the scope of a claim to the specified materials or steps “and those that do not materially affect the basic and novel characteristic(s)” of the claimed invention.

This means that a claim using “consisting essentially of” allows for the inclusion of additional elements or steps, but only if they do not materially change the basic and novel characteristics of the invention. The interpretation of this phrase can be complex and often depends on the specific context of the invention.

It’s important to note that For the purposes of searching for and applying prior art under 35 U.S.C. 102 and 103, absent a clear indication in the specification or claims of what the basic and novel characteristics actually are, “consisting essentially of” will be construed as equivalent to “comprising.” This interpretation guideline is crucial for patent examiners and practitioners to understand.

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Topics: MPEP 2100 - Patentability, MPEP 2111.03 - Transitional Phrases, Patent Law, Patent Procedure
Tags: Claim Interpretation, Consisting Essentially Of, Patent Language, Semi-Open Claims