Design patents (most obviously indicated by the “D” preceding the patent number) protect the ornamental design5 of an object and are enforceable for 15 years6 from the date they are issued. Utility patents (most typically considered “inventions”), in contrast, protect the invention’s described functionality and are enforceable for up to twenty years from their earliest effective (e.g., non-provisional) filing date.
Patent infringement occurs when one, without authorization, makes, uses, sells, offers to sell, or imports into the United States a patented invention during the term of that invention’s protection.7 Liability for patent infringement applies to direct infringers and can also extend to those who actively induce others to commit patent infringement. Furthermore, infringers do not have to infringe the entirety of a patent to be found liable; so long as they are found to infringe a material part of an enforceably-patented invention, they may be found liable.
The claims of a patent are what define a patent’s protected subject matter. For a design patent, the claims are the drawings themselves. The test for design patent infringement is simply whether, in the eye of an ordinary observer, giving the attention a purchaser usually gives, the accused design and patented designs are substantially the same. The resemblance between the accused and patented designs must be such as to deceive the ordinary observer and induce him to purchase one supposing it to be the other. Depending on the jurisdiction in which the lawsuit is brought, the test may be supplemented with the “point of novelty” test that requires, for infringement to be found, that the accused design include the particular features that distinguished the patented design over the prior art.
The claims of a utility patent are sequentially numbered sentence-like phrases which appear at the end of an issued patent. Terminology in a utility patent claim is given ordinary meaning unless the inventor has expressly or implicitly used the term in a manner that is inconsistent with its ordinary meaning in either the specification (another part of the patent) or the throughout the patent application’s prosecution. Extrinsic evidence, such as technical treatises, dictionaries, and even expert testimony, may be used to construe the claims’ terminology only if the patent’s specification, prosecution history, and the prior art fails to resolve the ambiguity.
To be found literally infringing a utility patent, the accused product must include each and every element of a claim following the transitional phrase (i.e., it “reads on”).8 Thus, if one or more of the structural or functional limitations of the claim are not present in the accused invention, there is no literal infringement. Even if a claim does not literally “read on,” however, an accused invention may still be infringing under Doctrine of Equivalents which looks at whether the differences between the accused and patented inventions are insubstantial. Differences are insubstantial where the compared elements perform substantially the same function, in substantially the same way, to achieve substantially the same result. Evidence of interchangeability, copying, and designing around claims is considered under the Doctrine of Equivalents.
Occasionally, an element in a utility patent claim is expressed as a “means” or a step for performing a specified function (i.e., “means-plus-function”). In this case, the element will be construed to cover the corresponding structure, materials, or acts described in the patent’s specification, and equivalents thereof, so long as the alleged “means-plus-function” claim element does not recite a definite structure, material, or act which in the claim. To literally infringe a “means-plus-function” claim, an accused invention must perform the identical function specified in the claim element by virtue of a corresponding structure, material, or act that is disclosed in the patent’s specification for performing that function, or an equivalent of that corresponding structure. A structure, material, or act disclosed in the specification is deemed to be a “corresponding structure” only if the specification clearly links or associates that structure to the function recited in the claim.
The standard for determining whether such literal equivalence exists in a means-plus-function limitation is whether the differences between the pertinent structures disclosed in the specification and the structure of the accused device are, again, insubstantial. An insubstantial change is one that adds nothing of significance to the structure, materials or acts disclosed in the specification.
Those who are found liable for patent infringement can be held accountable for their profits or a retroactively-applied “reasonable royalty” for their infringing activity. Where an infringer is found to have willfully infringed, the court may increase the damages award upon to three times. Courts may also award attorneys’ fees in exceptional cases and issue injunctions either stopping the allegedly infringing activities while a lawsuit goes on or after the lawsuit to permanently cease the infringer’s judicially-determined infringing activity.