Can a product infringe on a patented invention if the two things are different?

A patent is a set of exclusive rights granted to the inventor of an invention by a government. To be granted a patent the inventor must show that their invention is new, novel and not obvious. Getting a patent is a long and expensive process. The inventor must submit a patent application, the patent application must detail exactly why the inventor deserves to be granted a patent on the invention. The patent application must claim every aspect of the invention which the inventor would like to be patented. If the patent application discloses a piece of the invention, but that piece of the invention is not claimed, the unclaimed piece of the invention is not covered by the patent. Inventors must be very careful that their patent application claims every aspect of an invention to which they are entitled.

Writing patent claims is deceptively simple. Drafting valid patent claims that embody an invention completely is an art that takes a patent attorney years to learn. But, even experienced patent attorneys cannot think of every possible way to claim an invention, and the more claims in a patent application has the higher the fee which must be paid to the United States Patent and Trademark Office. This creates a situation where competitors will try to a make their product similar but not identical to a patented invention. Competitors try to make their product perform the function as the patented invention, but not in an identical way to avoid liability for patent infringement.

Can a similar, but not identical, product infringe on a patent? Yes, under the doctrine of equivalents. If an accused product or process does not literally infringe a patented invention, the accused product or process may be found to infringe under the doctrine of equivalents.

The doctrine of equivalents applies when a when a patent holder proves that a product is infringes on their patent by performing the same function.

When a plaintiff in a patent infringement lawsuit claims that a product infringes on their patent the court will ask “Does the accused product or process contain elements identical or equivalent to each claimed element of the patented invention?” Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17, 41 USPQ2d 1865, 1875 (1997). An accused device is “equivalents” if it contains elements that are similar to elements in the patented device. They do not need to be identical. However, they do need to perform the same function. The court will perform an analysis of the role played by each element in the context of the specific patent claim, that will tell the court whether a substitute element matches the function, way, and result of the claimed element, or whether the substitute plays a role substantially different from the claimed element.

Doctrine of equivalents relates to how a product functions not how it looks. When patent infringement through doctrine of equivalents is claimed, the design of the product does not matter, only function. If two products perform the same function in the same way with the same result, doctrine of equivalents applies and it is likely a court will find that patent infringement has occurred.

Generally, there are three limitations on the doctrine of equivalents:

The difference between the infringing product and the patented invention must be minor.
Patent holders are limited by the claims in their patent.
Equivalents cannot be used to encompass prior art.

The burden of proof is on the plaintiff to show that their patent is infringed through the doctrine of equivalents. If the defendant can show that their method of performing the function was in the prior art, or that there is a major difference between the infringing product and the patented invention than they can avoid liability for patent infringement.

Doctrine of equivalents is a complex topic. If you want to avoid patent infringement accusations or want to protect your patent you should consult with an experienced patent attorney.

If you have questions of comments for the authors of this blog please email us at: admin@uspatentlaw.cn