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 transitional phrase “consisting of” in patent claims is significantly different from “comprising” as it creates a closed claim. The MPEP states, The transitional phrase “consisting of” excludes any element, step, or ingredient not specified in the claim.
This means that a claim using “consisting of” is limited to only the elements or steps explicitly recited in the claim. For example, a claim for a device “consisting of A, B, and C” would only cover devices that include A, B, and C, and nothing else. The presence of any additional elements would place the device outside the scope of the claim.
It’s important to note that A claim which depends from a claim which “consists of” the recited elements or steps cannot add an element or step.
This further emphasizes the closed nature of “consisting of” claims.