Unresolved Means-Plus-Function Issues Post-Williamson

Dec 30, 2020

Michelle Xu

What are the benefits of means-plus-function claiming?

Claims written this way allow the patentee to describe their invention in terms of a “step” or “means” for performing a specified function without limiting the patent scope to the specific structures disclosed in the patent for performing that function. Means-plus-function claiming is beneficial because it allows patentees “to express those elements that can be performed by many different types of structures or devices” and claim the scope of those structures or devices. The language of the statute permits this broad scope, stating that functional claims “shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof.” Another benefit is that functional claiming does not require a patentee to “explicitly disclose[]” all of the possible structures for performing the desired function. “In this manner a claim can cover a relatively large number of possible structures without the patent application becoming excessively detailed.” However, as this Comment will describe, while means-plus-function claiming allows for broad claims, this broad scope comes at the high price of future invalidity challenges. For this reason, functional claiming is usually not a risk worth taking.

This Comment analyzes the current landscape of means-plus-function claiming in the courts in an effort to illuminate ambiguities and unfairness in the courts’ current interpretation of means-plus-function claims. The purpose of this Comment is to persuade the federal court system to reconsider its framework on means-plus-function claims and to persuade patentees to avoid functional claiming whenever possible. A critical point throughout my arguments is that in many cases, the challenge occurs after the USPTO has examined and allowed the patent. Thus, courts should not so readily interpret these claims to be subject to means-plus-function analysis and subsequently invalidate the claims. The proper presumption of patent validity must attach to the issued patent, especially in the patent realm of confusing case law and wavering burdens of proof.