Some patents are valuable and some are not.
The claims of a patent determine whether the patent is valuable or not valuable. If the claims are too ‘narrow;’ that is, if the claims protect too little, then the patent is not very valuable and your competitor can make minor changes to a copy of your product and sidestep your patent. If the claims of your patent are broad enough to successfully keep your competitors from making, using or selling a product that competes with your product, then the patent can be very valuable.
But what about when your competitor’s product is similar to, but not exactly the same, as your claimed invention? Say, for example, that technology has changed since your applied for and received your patent and your competitor substituted new technology for a piece of your patented invention? Because of the new technology, your competitor does not literally infringe your patent. Can you nonetheless win an infringement lawsuit against your competitor?
Perhaps you can. For years, inventors could rely on the ‘doctrine of equivalents.’ Under the doctrine, if your competitor’s product performed substantially the same function, in the same way and achieved the same results as your patented invention, then the competitor was liable for infringement even if the competitor did not literally infringe every element of a claim of your patent.
All of that changed in 2002 when the Supreme Court decided Festo Corp v Shoketsu Kinzoku Kogyo Kabushiki Co. The Court decided that if you changed any of your claims during prosecution of your patent application, then you lost all ‘equivalents’ and had no recourse. For example, if an applicant amended the claims to avoid prior art, then the invention owner was limited to the literal words of the claims with no ‘equivalents.’ Patents lost value on that day and for a long time the doctrine of equivalents was of little value to inventors.
The Federal Circuit has re-opened the door to the doctrine of equivalents. In recent cases, including Eli Lilly v Hospira, and Ajinomoto v Federal Trade Commission, the Federal Circuit has found infringement under the doctrine of equivalents if the amendments to the claims during prosecution were ‘tangential’ to the changes made by the competitor. That means that if your claim amendments during prosecution did not relate directly to the differences between the competitor’s product and your patent claims, then the doctrine of equivalents is available to expand your patent claims. This is good news for inventors and invention owners.
Incidentally, in our example, the introduction of new technology is a situation where the Supreme Court’s Festo decision stated that the doctrine of equivalents applied to expand the patent claims, because the inventor could not have anticipated the new technology at the time the inventor filed the patent application. In sum, you may not be limited to the literal language of your claims when it comes time to enforce your patent.
— Robert Yarbrough, Esq.