CAFC Rules Claim Terms Must Be Construed in Context

The 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.