By UpCounsel Intellectual Property Attorney Mudit Kakar

Whether you think patents are good for innovation and business or hinder growth, if you are reading this post, odds are you realize their importance. Like many learned academics and practitioners, you may agree or disagree with the patent system, but that is not why you are here. You want to know how to navigate the system to maximize the growth of your business and minimize liabilities.

As an entrepreneur or inventor, you’ve come across patents that might seem to cover your cool product idea. Or, if you are already in the business of making, using, selling, or offering to sell a product, you might have received a cease and desist letter alleging patent infringement. So, what do you do? Anything but ignore the patent. You want to know if you actually infringe this patent? The answer, like everything else in law, is likely not as straightforward as you would like it to be. You can either infringe a patent literally, or under the Doctrine of Equivalents (DOE). This post discusses the latter, which many people don’t know about.

When faced with a patent that allegedly covers your product, you may think that you don’t infringe that patent because a) your product is missing one or more elements of the asserted patent claim(s), or b) your product includes parts that are different from the elements of the asserted patent claim(s). Your analysis is partially correct. The “all elements rule” in patent law requires that when determining infringement, the party asserting a patent must show that the accused product includes each element of the asserted claim either literally or equivalently. This means that even if your product does not include exactly all the elements of an asserted claim, it may still infringe that claim if your product includes features/parts that may be considered equivalent to the “missing” element of the claim.

There are two tests for determining infringement under DOE: (1) Function-Way-Result test – whether the accused product performs substantially the same function in substantially the same way to obtain the same result. (2) Insubstantial Differences test – whether the accused product is substantially different than what is patented. Courts apply either test based on the circumstances of the case and the nature of the infringing product. For instance, for mechanical patents the preferred test is the Function-Way-Result test, whereas for non-mechanical patents, such as chemical patents, the Insubstantial Differences Test is the preferred test.

To understand the application of DOE, let’s consider the below scenario:

You come up with a new kind of stapler and are getting ready to market it— Cool New Stapler®. You come across a patent which claims a stapler with a spring-system to keep stapler pins in place and force them forward as the number of pins deceases (the “Stapler Patent”). You get excited because your Cool New Stapler® does not include a spring-system, which would mean that you don’t infringe the Stapler patent. Not so fast. Your Cool New Stapler® may not infringe the Stapler Patent literally, but what about the DOE?

Applying the Function-Way-Result test begs the question: Does the non-spring system in your Cool New Stapler® that keeps stapler pins in place (function) and forces them forward as the number of pins deceases (function) to maintain a constant supply of pins (result) uses elastic potential energy (way)? The odds are that the non-spring system of your Cool New Stapler® performs the same function and provides the same result as the spring-system in the patented stapler. But does it work in the same way? What if your Cool New Stapler® uses a rubber-band instead of a spring in the non-spring system? Or, how about a vacuum pump? An argument can be made that there is no substantial difference in the spring-system and the rubber-band system because both work by utilizing elastic potential energy. In patent terms, both function in the same way. In this scenario, your Cool New Stapler® may infringe the asserted claim even if it lacks an element of that claim, because it includes an equivalent element.

But, a non-spring system which includes a vacuum pump may not infringe the Stapler Patent. The vacuum pump uses a difference in pressure (way) to keep stapler pins in place (function) and force them forward as the number of pins deceases (function) to maintain a constant supply of pins (result). It does not function in the same way as the spring-system because the spring-system utilizes elastic potential energy, and not pressure difference. In this case, your Cool New Stapler® may not infringe the asserted claim because not only does it literally lack a spring-system, the system it uses, i.e., the vacuum pump, is also not equivalent to the spring-system. Here, even though your Cool New Stapler® may perform the same function and get the same result as the patented stapler, it does not perform the function and achieve the result in the same way as the patented stapler.

Long story short, even if your product is not exactly like a product covered by a patent, and/or is missing an element of a patented claim, don’t ignore the possibility that your product may still be equivalent to the patented claim, under a Doctrine of Equivalents analysis.

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1. This post only discusses product patents, but the concepts discussed apply to process and system patents as well.
2. Nerd alert! Energy stored in springs is called elastic potential energy.

This post is not and does not provide legal advice or opinion, nor is it a comprehensive review of the discussed topic. This post does not create an attorney-client relationship between the author and the reader.

About the author

Mudit Kakar

Mudit Kakar

Dr. Kakar helps clients understand and resolve complex legal issues unique to the technology sector. Particularly, he assists clients manage, grow and commercialize intellectual property in industries ranging from tech startups to multinational pharma and biotech companies. Dr. Kakar also counsel's clients on regulatory and privacy issues.

The combination of scientific and legal experience allows Dr. Kakar explain legal processes to clients in an easily understandable manner. Dr. Kakar brings the big-law experience without the excessive costs associated with it. His practice philosophy is to find the simplest, thorough and most economical resolution for a clients’ legal needs.

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