Solution "Consisting of a Sodium Phosphate" Required Single Solute
In Norian Corp. v. Stryker Corp. (Fed. Cir.; December 6, 2005) the court concluded that the term "a solution consisting of water and a sodium phosphate" could include only a single sodium phosphate in the following "kit" patent claim:
The solution in the kit sold by Stryker was made from two different sodium phosphates: monobasic sodium phosphate monohydrate and dibasic sodium phosphate heptahydrate. The question before the Federal Circuit was whether that solution was "consisting of water and a sodium phosphate."
8. A kit for preparing a calcium phosphate mineral, said kit consisting of:
at least one calcium source and at least one phosphoric acid source free of
uncombined water as dry ingredients; and
a solution consisting of water and a sodium phosphate, where the concentration of said sodium phosphate in said water ranges from 0.01 to 2.0 M and said solution has a pH in the range of about 6 to 11.
The court began by noting that the patent contains multiple references to various different sodium phosphates. "In that context," Circuit Judge Alsup wrote, "the reference in the claim to 'a sodium phosphate' is most naturally understood as a reference to one of the different sodium phosphates. Judge Alsup also differentiated terminology in different paragraphs of the claim. "If the patentee had meant to claim the use of at least one type of sodium phosphate in the recited solution, it would have been simple to use the same ["at least"] language in the second portion of the claim that was used in the first":
Even aside from the departure from the "at least one" phrase used in the first
limitation, the word "a" is conspicuous in the phrase "a sodium phosphate."
Although the word "a" generally means "one or more" in open-ended claims
containing the transitional phrase "comprising," that general rule does not apply
when the specification or the prosecution history shows that the term was used
in its singular sense. In particular, this court has interpreted the word "a" in its singular sense when, as in this case, it has been used in conjunction with the closed transitional phrase "consisting of." Thus, the claim language "consisting of . . . a sodium phosphate," on its own, suggests the use of a single sodium phosphate.
That interpretation is consistent with the specification, as the district court ruled. In particular, example 3 of the specification includes a chart listing the different setting times that are associated with different solutions. Each of the listed solutions contains a single solute, which is either a type of sodium phosphate or a type of sodium carbonate. While the scope of a claim is not necessarily limited to the examples disclosed in the specification, nothing in the ’065 patent specification points away from the district court’s construction limiting claim 8 to single-solute solutions. Rather, each of the solutions described in the specification uses only a single solute, and the specification makes no reference to using a mixture of multiple solutes in a single solution.
. . . The district court was also correct to rely on the prosecution history, which reflects a series of patentability rejections, followed by narrowing amendments and clarifying explanations from the prosecuting attorney. The prosecution history shows that through the series of amendments, Norian surrendered significant scope for what became claim 8. In response to one series of rejections, Norian narrowed the claim by changing the transitional phrase in the claim’s preamble from "comprising" to "consisting essentially of" and then ultimately to "consisting of." In response to another rejection, Norian amended the critical claim language by replacing the words "a sodium phosphate solution" with the words "a solution consisting of water and a sodium phosphate." The prosecuting attorney advised the examiner that the amendment "limit[ed] the claimed kit to one in which the solution is made of water and a single solute, where the solute is either a sodium phosphate or a sodium carbonate, which solute is completely dissolved in the water" (emphasis added).
If there were any doubt that the reference to "a sodium phosphate" meant a single type of sodium phosphate, the prosecuting attorney directed the examiner to the specification’s tables for examples of the single-solute solutions to which the amended claim was limited. As the prosecuting attorney noted, the tables disclose "solutions of different sodium phosphates": one solution is made from monobasic sodium phosphate, another from dibasic sodium phosphate, and a third from trisodium phosphate. But none of the solutions is made from a mixture of different sodium phosphates. In other words, the specification contemplates the use of various forms of sodium phosphate, but used individually, not simultaneously in the same solution.
As the prosecuting attorney explained, the claim was limited "with the incorporation of the additional limitation limiting the solution to one that consists of water and a sodium phosphate." Other references in the prosecution history underscore the restrictive scope that was accorded to the claim language. Thus, the prosecuting attorney explained that "the solution is limited to one that is made of water and a solute selected from a sodium phosphate or sodium carbonate," and that "the claimed kits of the present application are limited to kits in which the setting liquid is a solution of water and a solute, where the solute is either a sodium phosphate or a sodium carbonate." The district court properly construed that language to limit the scope of the claim at issue in this case to a single solute in the water solution, i.e., to a single type of sodium phosphate.