Patent Claims

Interpreting Patent Claims

201504 LM ApplesThe Meaning of Those Strange Little Sentences –

What’s in a Claim Anyhow –

Claims, those strangely constructed sentences at the end of a patent or patent application, usually get all of the attention.  They define what an invention is, and is not.  While seemingly simple enough, words have their limitations and can be interpreted in differing ways, and the interpretation of claim language is the topic of most struggles within the Patent Office during prosecution or post-grant challenges to validity, as well as in the courts during litigation.

There are differing standards and approaches to interpreting claims, each of which is important to understand if you are involved with patents.  Claim interpretations may vary depending upon the venue where arguments are being made.  While many books have been written on this topic as well as countless litigation and prosecution related documents, our goal is to present a very brief summary of how claims may be interpreted.  (If an initial primer on patent claims in general is needed, that can be found in our two part series “Staking Your (Patent) Claims” 1,2.)

Teflon®, a Claim That Nothing Can Stick To

The more words in a claim, the narrower the scope of the claim tends to be.  Of course more words mean there is more to interpret, and a lengthy claim, while often narrow in scope, provides ample opportunity for scrutiny of each and every word.  And then there is the original patent for Teflon® (a registered trademark of E.I. DuPont de Nemours and Company) granted in 1941 to Roy J. Plunkett and assigned to Kinetic Chemicals, Inc. of Wilmington, Delaware (a subsidiary of E.I. DuPont de Nemours and Company).  Claim 1 reads simply “Polymerized tetrafluoroethylene.” With a claim like that, there is not much left for the imagination to interpret.  Most claims, however, don’t have such brevity and are subject to interpretation. 

Different Standards for Prosecution and Litigation

When interpreting patent claims, different standards apply depending on whether you are prosecuting your patent application before an Examiner in the United States Patent and Trademark Office or litigating an issued patent in court.  A third category, post-grant validity challenges before the USPTO Patent Trial and Appeal Board, has drawn from both standards.  A solid understanding of both of these standards is important when drafting claims in a patent application to ensure successful prosecution, as well as to give claims the best wording possible for any future litigation.   Claim interpretation, the act or process of defining the meaning of a patent claim, may be straightforward, or it may be full of complexities and ambiguities. Knowing the various ways that a claim can be interpreted allows a patent practitioner to write a more robust claim or scrutinize an existing claim.

The Prosecution Standard

Claims in a pending patent application are eventually examined for patentability.  During examination, the pending claims in a patent application must be given their broadest reasonable interpretation in light of the specification as it would be interpreted by one of ordinary skill in the art.3  Furthermore, the words of a claim must be given their plain meaning unless this meaning is inconsistent with the specification.  The plain meaning of a word is the ordinary and customary meaning given to the term by those of ordinary skill in the art at the time of the invention. The specification, drawings, prior art, and the words of the claims themselves are all used to determine the meaning of a claim. However the specification is the best source of meaning, and is relied on heavily by the Examiner in determining patentability.  It is improper for an Examiner to import claim limitations from the specification into the claims4.

Additionally, words of a claim are given their “plain meaning” unless that meaning is inconsistent with the specification5.  The Applicant may also be his own “lexicographer,” defining a term in the specification in such a way that it supersedes the plain meaning of the term6.  There are other rules of claim interpretation in prosecution as well.  For example, the preamble of the claim may be non-limiting. Other words in a claim, such as transitional phrases like “comprising” or “consisting of” have very specific meanings and are used to interpret the claims.

The Litigation Standard

In litigation, claims of issued patents are commonly interpreted in view of the patent specification, the prosecution history record, the prior art, and other claims in the patent itself.  In addition, evidence can be provided to attempt to sway the interpretation in a desired direction.  Often interpretation of a single word in a claim can make or break a desired litigation outcome.  Court cases over the years have molded and shaped claim interpretation, and continue to do so.  The ordinary meaning of a claim term is often used to interpret that claim, and dictionaries are commonly used to assist with that ordinary meaning.  Other outside references may also be consulted, the use of which is referred to as extrinsic evidence.

The use of intrinsic evidence such as the patent specification itself, claim language and prosecution history is generally heavily relied on.  In fact, the U.S. Court of Appeals for the Federal Circuit considers the patent specification to be the best source of guidance for claim meaning, and the Court relies heavily, but not exclusively, on the patent specification.  Prosecution history, the written record of negotiation between the patent examiner and patent practitioner, is also used to show the scope of the invention and how it was understood.   The claims themselves are also used to interpret other claims in the patent.  The words surrounding a term in question as well as usage of the term in other claims are all helpful in interpreting that claim.

Furthermore, the doctrine of claim differentiation looks at the relative scope of each claim in relation to the others.  Essentially, this doctrine says that two claims in the same patent will not have identical scope, but there is in all likelihood an intended difference in scope between the two.  For example, a dependent claim that introduces a further limitation implies that this further limitation was not present in the independent claim to which it refers. This concept is not only important to infringement, but also to validity. If an independent claim is broader than the dependent claim to which it refers, the broadness of that independent claim not only makes it the easier of the two to infringe, it also makes it more vulnerable to an invalidity challenge since its broadness makes it closer to the prior art than its narrower dependent claim counterpart.

While both extrinsic evidence and intrinsic evidence are important to claim interpretation, extrinsic evidence is usually less significant than intrinsic evidence such as the patent specification itself in claim interpretation.

Making a Mountain out of a Word and Sorting it Out at a Markman Hearing

This article provides a brief overview of the various concepts of claim interpretation.  A mountain of evidence and documentation can easily be prepared in defense of a certain position on claim interpretation, or even the interpretation of just one pivotal word in a patent claim.  The stakes in patent litigation are usually high, and often the importance of a broad, well worded claim during prosecution is key to a company’s success, or at least the success of a new product.  Getting the interpretation of a claim sorted out is often no simple task.  One step used by the courts in determining the meaning of claim terms is a Markman hearing.  This is a pretrial hearing in U.S. Federal District Court where a judge considers evidence from both parties regarding the asserted meaning of claim terms. These hearings are named after the Supreme Court case Markman v. Westview Instruments, Inc., 517 U.S. 370 (1996).  Needless to say, claim interpretation can be contentious and costly.  Good practices in prosecution before the patent issues can help if there is ever the need to litigate.

  1. The Limited Monopoly® April 2009
  2. The Limited Monopoly® May 2009
  3. MPEP §2111, 37 CFR 1.75(d)(1)
  4. MPEP §2111.01(II)
  5. MPEP §2111.01(I and III)
  6. MPEP §2111.01(II)
  7. MPEP §2111.01(IV)

Authors Robert D. Gunderman P.E. (Patent Technologies, LLC and John M. Hammond P.E. (Patent Innovations, LLC are both registered patent agents and licensed professional engineers.  They offer several courses that qualify for PDH credits.  More information can be found at   Copyright 2015 Robert Gunderman, Jr. and John Hammond .

Note:  This short article is intended only to provide cursory background information, and is not intended to be legal advice.  No client relationship with the authors is in any way established by this article.

GRAPHIC  CREDIT:  Apples in the Marketplace.  Robert Gunderman. PDF printer wo icon

          For a PDF download of this article or to print a copy , click here →