Patent claim interpretation is the process of giving proper meaning to the claim language. Claim language defines claim scope. Therefore, the language of the claim frames, and ultimately resolves, all issues of claim interpretation. In determining the meaning of disputed claim terms, however, a construing court considers the written description, the drawings, the prosecution history, and extrinsic evidence. These additional sources provide a context to illuminate the meaning of claim terms. Nonetheless, throughout the interpretation process, the focus must and does remain on the meaning of claim language itself. The construction of all of the disputed terms of the claim will govern the court’s validity and infringement analysis at all stages of the case, including trial.
Two-Step Process Used to Analyze Patent Infringement Claims
A two-step process is used to analyze patent infringement claims. First, the asserted claims must be properly construed to determine their meaning and scope, and second, there must be a determination as to whether the claims, as construed, encompass the accused product or process.
The first step, claim construction, is within the province of the court. The language of the claim or claims in the specification of a patent is the measure of the exclusive rights conferred by that patent. Thus, infringement involves construction and interpretation of the language of the claim and a determination as to whether the claim so construed ”reads on” the accused product or process. In construing the claim, the courts consider not only the literal meaning of its terms but also the prior art and the prosecution history of the patent in the United States Patent and Trademark Office (USPTO).
The focus in construing disputed terms of a patent claim is on an objective test of what one of ordinary skill in the art at the time of the invention would have understood the terms to mean.
Giving Terms a Meaning Different from their Ordinary and Customary Meaning
Terms in a claim are generally given their ordinary and customary meaning. However, a patentee may give terms a different meaning, so long as the meaning is stated clearly in the patent specification or file history. The court may also refer to other claims in the same patent to ascertain the intended meaning of a disputed term in a claim, but may not read limitations from other claims into an independent claim. The concept of claim differentiation provides that each claim of a patent constitutes a separate invention and gives rise to separate rights. Claims should also be read in light of the patent’s prosecution history and the patent specification. The specification contains a written description of the invention and includes a best mode or preferred embodiment of the invention.
Prior art may be defined very broadly as the entire body of knowledge from the beginning of time to the present. A person is not entitled to a patent if the invention was known or used by others in this country, or was patented or described in a printed publication in this or a foreign country before the date of invention by the applicant for the patent.
Prosecution history encompasses the negotiations between the patent applicant and examiner at the USPTO during which the scope of the patent is clarified.
Application of Claim as Construed to Accused Product or Process
After the meaning of the claims in issue is determined by a study of all relevant patent documents, the claims must be compared to the accused structures. What is crucial is that the structures must do the same work, in substantially the same way, and accomplish substantially the same result to constitute infringement. This is the general approach used to determine the infringement of all the patent claims.
Doctrine of Equivalents and Doctrine of File Wrapper
In determining infringement, the courts enlist the assistance of two traditional doctrines. Under the doctrine of equivalents, an accused product or process will infringe, though outside the literal terms of the claim, if it does the same work in substantially the same way to accomplish substantially the same result as the patented product or process.
Under the doctrine of ”file wrapper” or ”prosecution history” estoppel, a patent owner may not expand the claim through the doctrine of equivalents so as to recapture subject matter deliberately surrendered during the course of the proceedings in the Patent and Trademark Office to obtain the patent. The burden of proof on factual issues relevant to infringement usually rests on the patent owner.