Patent Law For The Lay Person: What Do The Words In A Patent Claim Mean?

An Article in Schott, P.C.’s IP Law For Start-ups Series


Almost weekly, I have a conversation with someone who looks at a single patent drawing or abstract and asks me how someone could get a patent for “that.” I am happy to explain that the inventor didn’t get a patent for what’s in the abstract or drawing, but for what’s in the claims. At the end of the patent, after the abstract, drawings, and description, is a list of numbered sentences called the claims. The claims are the part of the patent that define exactly what the invention is.

With so much importance invested in the language in the claims, it’s no surprise that courts scrutinize the claims during patent litigation. Multimillion dollar litigations often turn on the meaning of a single word in a claim and this article will review the leading case on patent claim interpretation to shed light on how courts interpret patent claims.

Claim Interpretation: A Matter of Law

Claim interpretation, or claim construction as it is sometimes called, is a matter of law. What that means is that interpreting what the words in a claim mean is an issue decided by a judge, not a jury. Put in the context of a patent infringement trial, the judge will tell the jury how to interpret claims and the jury will decide if an accused product falls within the scope of those interpreted claims.

Usually, a judge will hold a separate hearing from the trial to determine the proper claim interpretation. This hearing is either called a claim construction hearing or a Markman hearing, Markman v. Westview Instruments, Inc. being the Supreme Court case that clearly defined the judge as the person responsible for interpreting claim language.

Given that almost all patent infringement cases turn on the meaning of the claim terms, the judge’s claim interpretation is often dispositive of the case, that is, although the judge makes no decision on infringement when deciding the meaning of the claim terms, the claim construction is often the decision that controls which party wins the case.

How the Judge Interprets the Claims

Claim interpretation is always done not from the judge’s perspective, or even the inventor’s perspective. Judges interpret claims from the perspective of a “person of ordinary skill in the art.”  This person is a fictional construct who has normal skills and knowledge in a particular technical field but is not a genius.
From this person’s perspective, a judge can consider two broad categories of evidence when interpreting patent claims: intrinsic and extrinsic evidence.

– Intrinsic Evidence

The judge must favor the intrinsic sources to the extrinsic ones and absent a specific disclaimer of a claim term’s meaning in the specification, a judge may not need to look any further than the claims’ plain and ordinary meaning to interpret a claim.

The patent specification is the next best source for the meaning of a term after the claim itself. The specification may define the term, provide examples related to the term, or may describe the state of the prior state of the art that helps define the term.

Similarly, the record of the patent’s prosecution at the US Patent and Trademark Office may provide evidence of meaning, disclaimer, or what a term means when compared to other references.

– Extrinsic Evidence

The judge can consult extrinsic evidence sources but should generally give them less weight. The rationale for this is that undue reliance on extrinsic evidence poses the risk that it will be used to change the meaning of claims, and one of the critical reasons for claims is that they provide an important public notice function that lets others know the scope of the patent right.

– Dictionaries

Dictionaries are a special case in patent claim interpretation. Technically, they are extrinsic because they don’t make up the patent or its prosecution record. But when a judge wants to look up a word definition, even to determine its plain meaning, where better to look than a dictionary, which provides an objective reference for the words?

Judges have been cautioned by appellate courts not to overly rely on dictionaries but they remain an oft-cited resource for judges determining claims’ plain and ordinary meaning.

Case Review: Phillips vs. AWH Corp.

The leading case that explains how to properly interpret claims is Phillips vs. AWH Corp. The technology in the case involved temporary prison enclosures.

One of the enclosure’s is a sloped steel wall that was helpful in deflecting bullets. This feature became the source of much debate, because the accused product did not have sloped walls but instead uses walls at right angles.

Looking at the claim, the judge had the task of interpreting “internal steel baffles extending inwardly from the steel shell walls.” Phillips, the patent owner, asserted that this language does not specify that the walls are at a specific angle. AWH argued that the walls must extend at an acute or obtuse angle to deflect the bullets effectively.

Taking up the issue, the appellate court (the Federal Circuit Court of Appeals that hears all patent appeals) noted that the claims are silent as to angles, and looked to the specification noting that:

• “the baffles are described as providing structural support,”
• “In Figure 7, the overlapping flanges “provide for overlapping and interlocking the baffles to produce substantially an intermediate barrier wall between the opposite [wall] faces,” and
• “Those baffles thus create small compartments that can be filled with either sound and thermal insulation or rock and gravel to stop projectiles.”

The court described that one of the canons of claim construction is that every claim is presumed valid and thus every claim is assumed to have a different scope. Following this logic, the court noted that there were several other claims that specified angled baffle walls, which implies that no such angular limitation existed in the highlighted language above.

Given that the baffles had purposes other than stopping projectiles and that the claim language itself was not limited as to the angle of the walls, the court concluded “that a person of skill in the art would not interpret the disclosure and claims of the ’798 patent to mean that a structure extending inward from one of the wall faces is a “baffle” if it is at an acute or obtuse angle, but is not a “baffle” if it is disposed at a right angle.”

That’s a summary analysis of how a court interpreted a claim in a single case. If you have questions about other claim construction cases, I would be happy to consider them for a future article.

If you have questions, contact me.
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