Courts will presume different meanings attach to different words when construing claim language. See, e.g., Ethicon Endo-Surgery, Inc. v. U.S. Surgical Corp., 93 F.3d 1572, 1579 (Fed. Cir. 1996) (reversing lower court’s ruling that a “pusher assembly” and a “pusher bar” have the same meaning). But a recent Patent Trial and Appeal Board decision construed the claim terms “permeation barrier” and “substantially impermeable barrier” to “refer to essentially the same thing.” Air Liquide Large Indus. U.S. LP v. Praxair Tech., Inc., IPR2015-01075, Paper 11 at 8 (Oct. 26, 2015).
In Air Liquide, Petitioner sought inter partes review of U.S. Patent No. 8,690,476 claims 1-12 and 15. Independent claim 1 of the ‘476 patent includes a step of “maintaining the stored hydrogen at a pressure between [certain limits], whereby the salt cavern forms a substantially impermeable barrier to the stored hydrogen therein.” In contrast, independent claim 12 includes a step of “forming a permeation barrier . . . so as to prevent substantially all of the stored hydrogen from passing therethrough.” Id. at 5.
The ‘476 patent specification defined a “permeation barrier” as a salt cavern that when pressurized or thermally activated, would restrict the passage of hydrogen flow through the salt walls. The parties and the PTAB agreed that a “permeation barrier” is a structural phenomenon formed in a salt cavern’s walls when subject to sufficient pressure or thermal activity. Id. at 6.
On the other hand, the ‘476 patent did not define a “substantially impermeable barrier.” The Petitioner thus argued that the phrase’s broadest reasonable interpretation should be that the salt cavern walls did not display a higher impermeability to hydrogen than the walls of any other salt cavern. The PTAB disagreed. Id. at 6-7.
According to the PTAB, Petitioner’s proposed construction was unwarranted. The PTAB reasoned that the construction failed to address the fact that the claim also requires that a “barrier” be formed by maintaining the salt cavern at certain pressures. Moreover, while the term “substantially” indicates the barrier is not 100% impermeable, interpreting “substantially impermeable barrier” to mean a barrier that merely retains “a large majority” of the stored hydrogen “gives an unduly broad scope to the claim phrase.” Id. at 7.
The takeaway from Air Liquide is two-fold. First, the presumption that different claim terms will be given different meanings is just that, and can be rebutted. Second, the PTAB will (sometimes at least) consider context when construing claim language, even under the auspices of a broadest reasonable interpretation.