Schedule a Free Strategy Call Contact Us


What is the Doctrine of Equivalents, and How Can It Prove my Patent Infringement Claim?

Posted by Wes Schwie | Sep 27, 2021 | 2 Comments

What is a patent?

A patent is a grant by a government of the right to exclude others from the manufacture, sale, offer to sell, or unauthorized use (that is, an unlicensed use) of the invention described and claimed in the patent grant. In the U.S., Congress is authorized to enact laws “[t]o promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries.”[i]  Title 35 of the U.S. Code codifies these laws.

A typical U.S. patent includes a detailed description of the claimed invention, one or more drawings illustrating the invention, and concludes with a set of claims that “particularly point out and distinctly claim” the invention. The requirement of distinctly pointing out and claiming the invention exists to notify the public of the scope of protection of exclusive use provided by the patent.

There are three types of patents: utility, design, and plant. Utility patents protect “any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof.”[ii] A utility patent covers a physical article of any size, shape, or weight. Additionally, a utility patent could be a chemical process, such as the steps involved in manufacturing, say, a drug or a paint. Utility patents can even protect business methods, such as Priceline's “Reverse Auction.”

Design patents protect “any new, original, and ornamental design for an article of manufacture.”[iii] In other words, a design patent covers how things look but not any functional features. For example, there are many different drinking mugs available. If someone develops a mug with a new “look,” they could obtain a design patent on it, but it wouldn't cover the fact that it holds fluids because it is related to function.

Finally, the U.S. Patent and Trademark Office may grant a plant patent to anyone who “invents or discovers and asexually reproduces any distinct and new variety of plant, including cultivated sports, mutants, hybrids, and newly found seedlings, other than a tuber propagated plant or a plant found in an uncultivated state.”[iv] For example, if someone develops a new variety of apple, they could obtain a plant patent.

What is patent infringement?

Direct patent infringement occurs whenever someone – whether an individual or business – “without authority makes, uses, offers to sell, or sells any patented invention, within the United States or imports into the United States any patented invention during the term of the patent therefor…”[v]

Other types of infringement include “induced infringement”[vi] and “contributory infringement.”[vii]

  • Induced infringement: A party commits induced infringement when they, for example, pay a manufacturer to make a patented invention.
  • Contributory infringement: A party may commit contributory infringement when they manufacture or import a key or material component of an invention, knowing the component will be used to infringe a patent and it is unsuitable for a substantial noninfringing use.

A patent owner can prove patent infringement in two ways: “literally” and through the “doctrine of equivalents.” An accused device or process literally infringes a patent claim when the patent owner shows the accused device or process includes each claim limitation. For example, suppose a patent for a “seating apparatus” – such as a chair – issued with the following claim:

  • I claim a seating device comprising a substantially horizontal surface and at least one leg supporting the substantially horizontal surface.

Such a claim would be literally infringed, for example, by a bar stool, kitchen chair, bed, or couch. Each of these has a substantially horizontal surface upon which to sit and at least one supporting leg. Now suppose the claim read as follows:

  • I claim a seating device comprising a substantially horizontal surface and at least four legs supporting the substantially horizontal surface.

Most bar stools, kitchen chairs, and couches would literally infringe this claim. However, a three-legged stool would not literally infringe the claim because it lacks the limitation of “at least four legs supporting the substantially horizontal surface.”

In some cases, a claim limitation may not be literally found in an alleged infringing product, though its functional equivalent may be. For example, a claim may recite a nut and bolt for holding two components of a claimed invention together. The alleged infringing article may meet every other claim limitation but use a rivet instead of a screw. In such circumstances, the patent owner will argue that using a rivet infringes the claim under the doctrine of equivalents, which will be discussed in greater detail in our next article.


Gallium Law has extensive experience asserting and defending against patent infringement. If you have patent infringement concerns or questions, please call us at 651-256-9480 or fill out this Contact Form to speak with us before it's too late.

*The information provided in this article is not legal advice and should not be relied on as such. The content of this article is for informational purposes only and is meant as a starting point in your search for answers to your legal questions.

[i] United States Constitution, Art. I, §8, Clause 3.

[ii] 35 U.S.C. 101 Inventions patentable.

[iii] 35 U.S.C. 171 Patents for designs.

[iv] 35 U.S.C. 161 Patents for plants.

[v] United States Code, Title 35, §271(a).

[vi] United States Code, Title 35, §271(b).

[vii] United States Code, Title 35, §271(c).

About the Author

Wes Schwie

Wesley Schwie is the founding Principal of Gallium Law and a registered U.S. patent attorney. Wes' practice encompasses all aspects of intellectual property law, including patent and trademark prosecution, licensing, litigation, portfolio management, due diligence, and infringement and validity counseling...


Knight Reply

Posted Mar 08, 2022 at 04:43:23

Beautiful blog

Wes Schwie Reply

Posted Mar 16, 2023 at 11:08:56

Thank you for your feedback, Knight. We appreciate it.

Leave a Comment

Get Started Today

No matter where you are in your process, we'll help you understand the role of IP in your business. After all, tomorrow belongs to the people who prepare for it today.

Contact Us

Office Location

By appointment only, telephone and virtual meetings available.
445 Minnesota Street
Suite 1500
St. Paul, MN 55101