In NCS Multistage Inc. v Kobold Corporation, 2025 FCA 187, the Federal Court of Appeal provides a helpful reminder on claims construction, including that dependent claims should generally be construed more narrowly than independent claims and that limitations in dependent claims should not be excluded from embodiments encompassed in the claims from which they depend.
In the underlying Federal Court decision, the Court held that claims 6, 11, 12, and 16 of Kobold’s Canadian Patent No. 3,027,571 were infringed by NCS.
The claims were directed to a downhole apparatus for hydraulic fracturing of oil- and gas-bearing rock formations that included first and second annular chambers between a housing and a moveable sleeve (claim 6) separated by an annular barrier (claim 11 depending from claim 6). The annular barrier was moveable (claim 12 depending from claim 11) and further included “at least one metering passage fluidly connecting the first and second chambers across the barrier” (claim 16 depending from claim 11 or claim 12).
While not at issue, claim 13 (depending from claim 12) was relevant to the Federal Court’s reasoning and recited “a seal arrangement … between the sleeve and the housing.”
Before the Federal Court, NCS argued that claim 12 could include embodiments having an annular barrier seal as well as a metering passage. However, the Court ruled this was a “violation of [the principle of] claim differentiation” because claim 13 would be redundant if claim 12 included an annular barrel seal. Accordingly, the Court held that claim 12 could not include embodiments having an annular barrel seal.
On appeal, the Federal Court of Appeal determined that the Federal Court had incorrectly applied the principle of claim differentiation when construing claim 12. Claim differentiation prohibits reading limitations from dependent claims into the claims from which they depend as limitations of those preceding claims. However, it does not act to exclude the limitation of the dependent claim as a feature of an embodiment covered by the preceding claim. That is, in the present case, “claim 12 encompasses two embodiments of the annular barrier, one that has a gap and one that is sealed…[;] claim 12 encompasses, but is not limited to, the seal embodiment contemplated by claim 13.” This construction of claim 12 better follows the principle that dependent claims should generally be construed more narrowly than the claim from which they depend.
The Federal Court of Appeal remitted the matter back to the Federal Court for reconsideration using the correct construction of claim 12.
The full decision is reported here.