Wealth of Ideas Newsletter, September 2004
There are, unfortunately, no "patent police." When a patentee finds a product or process substantially similar to his or her patented invention, the onus is on the patentee to determine if infringement actually exists.
Infringement is measured by the patent’s claims, which are of two types: dependent and independent. Dependent claims follow and refer to an independent claim and incorporate all of its limitations. Thus, if an independent claim is not infringed, neither will be the dependent claims that refer to it. For this reason, infringement analysis typically focuses on the independent claims.
When analyzing a claim for infringement, remember the all elements rule: each limitation of the claim must be met by the accused product or process. The accused structure (or process) may have additional features that are not found in the claim, but it must meet every limitation of the claim in order to infringe it.
There are two types of infringement: literal infringement, and infringement under the doctrine of equivalents. Literal infringement occurs when the claim language literally reads on the accused device or process. Infringement under the doctrine of equivalents may occur when a product or process does not precisely satisfy the language of one or more of the claim limitations, but nevertheless performs the same function, in substantially the same way, for the same purpose as the claim limitation. The application of the doctrine of equivalents may be limited by factors arising during the prosecution of the patent and also by recent changes in the law (the famous or infamous Festo decision). As a result, literal infringement cases are strongly preferred over those where infringement is found only by application of the doctrine of equivalents.
Once an inventor is reasonably certain that his or her patent is infringed, it is important to determine whether the accused device has been offered for sale in the United States (assuming the infringed patent is a U.S. patent). U.S. patents have effect only within the U.S, but a foreign company may be sued in the U.S. for acts performed here.
When infringement is suspected, a patent attorney or contingency patent enforcement firm such as General Patent Corporation International should be consulted to confirm the infringement and plan and undertake an appropriate enforcement campaign.