How does the preamble affect the interpretation of apparatus claims?

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.

In apparatus claims, the preamble’s effect depends on whether it recites essential structure or merely states the purpose or intended use of the invention. According to MPEP 2111.02:

“Any terminology in the preamble that limits the structure of the claimed invention must be treated as a claim limitation.”

For example, in Corning Glass Works v. Sumitomo Elec. U.S.A., Inc., the court held that preamble recitations could be structural limitations. However, if the body of the claim fully sets forth all structural limitations, and the preamble merely states the purpose or intended use, it may not be considered a limitation.

It’s important to note that for apparatus claims, a prior art structure capable of performing the intended use stated in the preamble meets the claim, even if it wasn’t specifically designed for that use.