CAFC Rules Claim Terms Must Be Construed in Context

Cement TruckThe meaning of words often depends on the context in which they appear.  That principle is also true of terms which appear in patent claims.  In Ultimax Cement Manufacturing Corp. v. CTS Cement Manufacturing Corp., the Federal Circuit reaffirmed that the context matters in reversing a district court grant of summary judgment that certain patent claims were not infringed or were invalid for indefiniteness under the second paragraph of 35 U.S.C. § 112.  In fact, the district court in Ultimax Cement repeatedly went astray in failing to interpret two disputed  claim terms in the appropriate context.

In Ultimax Cement, there were three patents involved (the ‘556 patent, the ‘684 patent, and the ‘534 patent) on rapid-hardening, high-strength cement formulations.  Only the ‘556 and ‘684 patents became embroiled in a “claim construction” dispute because of a potential “faux pas” in the choice of claim terms used.

One related to the meaning of the term “soluble CaSO4 anhydride” in Claim 9 of the ‘556 patent.  For those who are not chemists, CaSO4 (calcium sulfate) is commonly known as “plaster of paris.”  But what rings strange in my chemist ears is the word “anhydride” after “CaSO4.”  To a chemist, the term “anhydride” means something obtained from an acid by removing water.  An example of an inorganic anhydride is sulfur trioxide (SO3) which is obtained from sulfuric acid (H2SO4).  An example of an organic anhydride is acetic anhydride which is obtained from acetic acid (present in vinegar).

Under the classical definition of anhydride, CaSO4(which is inorganic) can’t be in an anhydride form, i.e., it can’t be obtained from an acid by removal of water.  In other words, “CaSO4 anhydride” doesn’t exist.  So what did the inventor mean here?  A clue to what was meant comes from the state that CaSO4normally exists in nature, namely the anhydrite (anhydrous) form.  Put differently, “CaSO4 anhydride” was really intended by the inventor to mean “anhydrous CaSO4,” i.e., unhydrated CaSO4.  (CaSO4can be in a hydrated form by adding one or more water molecules, which if removed, provide the unhydrated or anhydrous form of CaSO4.)

Unfortunately, the district court judge, who likely wasn’t a chemist, construed the term “soluble CaSO4anhydride” in a very odd way to find no infringement.  The district court judge started off with very acceptable definition of “anhydride” as “a compound formed from an acid by removal of water.”  But then the district court judge reasoned that if Claim 9 was intended refer to calcium sulfate from which water had been removed (the patentee’s (Ultimax’s) interpretation), the claim drafter would have used the term “anhydrous CaSO4” or “anhydrite,” which, again, is a specific term for “anhydrous CaSO4.”

In fact, the district court judge acknowledged the observation of a neutral court-appointed expert (Dr. Seible) “that ‘given the context in which “anhydride” is used in [the Patent ’556], it is not unreasonable to assume that the author meant anhydrite and not anhydride.’”  Even so, the district court judge held that “it could not substitute terms, as that would constitute redrafting the claims, which was forbidden even when the failure to substitute terms would lead to a strange result.”  Accordingly, “[b]ecause CTS’s cement did not contain an acid from which water had been removed,” the district court judge granted CTS’ motion for summary judgment of no infringement.

The Federal Circuit agreed with Ultimax that the district court judge had gone astray in construing the term “soluble CaSO4 anhydride” to mean “a compound formed from an acid by removal of water.”  Instead, the Federal Circuit ruled that this term should be construed to mean “soluble anhydrous CaSO4,” or “soluble anhydrous calcium sulfate.”  In so ruling, the Federal Circuit emphasized that the district court judge had failed to consider “the context in which the term was used within the claim and the specification.”  As stated by the Federal Circuit, the term “anhydride,” when placed next to “CaSO4,” is intended as a modifier, modifying “CaSO4,” or “calcium sulfate,” thus referring to “calcium sulfate from which any associated water has been removed.”  The Federal Circuit further noted that “[t]he context of the entire specification further supports the conclusion that “soluble calcium sulfate anhydride” means “soluble anhydrous calcium sulfate.”

Another claim drafting goof which almost led to disaster was Claim 17 of the ‘684 patent.  One basis for the district court judge finding Claim 17 indefinite under the second paragraph of 35 U.S.C. § 112 was the formula “C9S3Š3Ca(f cl)2.”  (Another basis asserted by the district court judge for finding Claim 17 indefinite was the formula recited for “crystal X” because it could yield over 5000 possible compounds and was thus “too broad”; this basis for indefiniteness was also overturned by the Federal Circuit.)  The district court judge found the formula “C9S3Š3Ca(f cl)2 indefinite because it lacked a comma between “f” and “cl” (where “f” stands for fluorine, and “cl” stands for chlorine).  Pretty obvious to a chemist like me that there was a comma missing between “f” and “cl.”  But strangely, the district court judge declined to correct this obvious “claim drafting error” (obvious even to the district court’s neutral expert) because “it was not apparent on the face of the patent, even though it might be clear to one of ordinary skill in the art.”

The Federal Circuit once more had to come to the rescue by putting this obvious “claim drafting error” in the appropriate context.  Regarding the missing comma in the notation (f cl), the Federal Circuit said that this notation “must be viewed through the lens of one of ordinary skill in the art.  While acknowledging that a patent’s claim language can be corrected only when “not subject to reasonable debate,” the Federal Circuit pointed out that even the district court judge recognized that this missing comma was a possible claim drafting error.  In fact, the district court judge had determined that the formula with the notation (f cl) without the comma “corresponds to no known mineral,” and thus “one of ordinary skill in the art would know that the formula should contain a comma.”

The Ultimax Cementcase is instructive on the need to interpret claim terms in the appropriate context (including the context of how that claim term is used in the patent specification), especially when to do otherwise creates “strange results” or impossible meanings for the claim term.  Fortunately for the patentee in Ultimax Cement, the Federal Circuit overcame the “formulistic” approach of the district court judge to correct a potential “faux pas” by the claim drafter to interpret the disputed claim terms in a manner that made sense (even “common sense”) to one of ordinary skill in the chemical arts.

*© 2009 Eric W. Guttag.


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Join the Discussion

11 comments so far.

  • [Avatar for Mike]
    December 11, 2009 09:10 am


    I take nothing personal. I like airing prosecution strategies here, you can see if the strategy is sound and identify alternatives. Often we get a problem solved in one way and fail to see the benefits of alternatives.

    I also think the practice is always changing, so I appreciate the different views.

    Have a great weekend,


  • [Avatar for Jules]
    December 10, 2009 05:46 pm

    Mike, that sounds good. I see you didn’t take it personally, but I might have come off as mischaracterizing your whole comment by addressing only one part of it. That was unintended. It seems like you have a sound approach, including for when BRI becomes BUI. Thanks for the clarification.

  • [Avatar for Mike]
    December 10, 2009 05:18 pm


    The reason to start with a statement defining the term rather than amending the claim is because many BRI rejections come from unreasonable interpretations. I have had an examiner reject a “monomer” protein because all proteins are “polymeric.”

    In that case, simply amending the claim to different language (i.e. the protein of SEQ 1) would have eliminated a variety of other proteins similar to SEQ 1 (i.e. rat, dog, cat, mutant, etc.) unfairly. Making a statement that defined monomer, dimer, trimer, multimer as used by those of skill in protein sciences (not a strictly chemical definition), I was able to maintain a broader scope for my client.

    There are other examples, but the fact is, not all BRI rejections are reasonable and defining the terms creates less estoppel than an amendment. Often the estoppel created is unintended in either case and it would be hard to define what is lost without years of foresight.


    PS I often have many definitions broad to narrow of common and unique terms from my claims and specification. I don’t go as far as to define “a” “an” and “the” but do define most technical terms.

  • [Avatar for Jules]
    December 10, 2009 09:28 am

    Mike, “define the terms in a statement (creates estoppel)”

    This is about the weakest way to get around an examiner’s rejection, because when you are dealing with the examiner you still have a chance to amend. Most examiners will not give in to what you say in passing as a weak attempt to trick the examiner into thinking the claim says something that it doesn’t. If that is your approach, why not cite the court case that says arguments = estoppel in every argument you make.

  • [Avatar for EG]
    December 9, 2009 03:22 pm

    “No doubt the D.C. judge was confused by the inter-panel inconsistencies of the CAFC as to whether or not the court can correct even obvious claim drafting errors.”


    Or possibly “gun-shy”! I suspect district court judges feel a sense of “whiplash” whenever they try to deal with a claim construction issue, and try to divine which panel decision they should go with.

    Also thanks for the comments about the potential hazard of doing a certificate of correction. That’s interesting that the COC isn’t retroactive, but after reading COC statutes (35 USC 254 or 255), it looks like once the alleged infringing starts, any COC granted afterwards has problems.

  • [Avatar for A curmudgeon]
    A curmudgeon
    December 9, 2009 02:55 pm

    No doubt the D.C. judge was confused by the inter-panel inconsistencies of the CAFC as to whether or not the court can correct even obvious claim drafting errrors. Prof. Wegner argues that it may be “luck of the panel draw” whether or not a CAFC panel will help you fix obvious claim drafting formal errors, or render your claim fatally defective instead. To wit, in the Energizer Holdings decision there was no antecedent literal expression at all for the words of a claim element following “said.” However, the panel held that a prior claim expression using very different words was intended to be the antecedent, and saved the claim on that basis. In contrast there is the notorious “burned buns” dough baking patent that even a judge with no technical education could understand in the Chef America case that the claimed temperature was of the oven, not the buns.
    The unstated lesson is to avoid this dangerous unpredictability by fixing formal claim drafting errors with a “certificate of correction” before suit. However, note that that there is another CAFC decision [Southwest Software] holding that a certificate of correction is not retroactive. Thus, you may not be able to recover back damages from before the certificate of correction issues. Thus, that Southwest Software decision might be inhibiting some attorneys from using pre-trial certificates of correction where significant potential back damages are present?

  • [Avatar for EG]
    December 9, 2009 02:23 pm

    Michael Feign,

    Thanks for the comment. I use the same approach as you do: an extensive defintion of terms section. That should negate any attempt by the Examiner to assert BRI. And you’re correct, many Examiners won’t read them (and even say no defintion exists in the patent spec); that just makes it easier to hit them with a written “two by four” response.

    Mike: What Michael Feign and I do is what you suggest (argue against the interpretation) but does it in a way that allows us to dictate the playing field. The days of being able to rely upon extrinsic evidence, including dictionaries (the Ultimax Cement case is the rare exception), to “rescue” claim term ambiguity are just about over. In the term isn’t defined in the patent spec either explicitly or by exemplification through disclosed embodiments, you’re usally going to be in trouble.

  • [Avatar for Michael Feigin, Esq.]
    Michael Feigin, Esq.
    December 9, 2009 01:55 pm

    “Often the first office action is not reasonable, the BRI is out of context and off- point. I spend the first office action “teaching” the examiner about the technology and what the true scope of the claims are.”

    I try and add very clear definitions to every team I can think of in case I need to fall back on it… though it doesn’t mean they’ll be read, at least that response to the first office action becomes either to, as you say, “teach” the examiner.

  • [Avatar for Mike]
    December 9, 2009 08:42 am

    To get around BRI you can either argue against the interpretation (least limiting), define the terms in a statement (creates estoppel), or amend the claims (again, creates estoppel). The patent office has to go with BRI because that is how the patent holder will apply those claims.

    Often the first office action is not reasonable, the BRI is out of context and off- point. I spend the first office action “teaching” the examiner about the technology and what the true scope of the claims are. An interview often helps to clear the air and get the prosecution started on the right track.

  • [Avatar for EG]
    December 9, 2009 07:47 am


    How “appropriate context” would be “measured” by BRI is anyone’s guess. Frankly, I find the whole concept of BRI to be odd. So does Chris Cotropia in the article he cowrote on the BRI standard in the most recent AiPLA Quarterly Journal.

    But the Federal Circuit in Ultimax Cement does give clues that claim constructions that create strange or impossible meanings won’t fly, even under BRI. Also, if the so-called BRI is contrary to how the claim is defined in the patent speciication, that shouldn’t fly either. If you have any other thoughts, please do provide them.

  • [Avatar for Noise above Law]
    Noise above Law
    December 8, 2009 05:27 pm

    How is “appropriate context” measured in light of the Office protocol of Broadest Reasonable Interpretation (often confused with Broadest Possible Interpretation)?