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The judge-made law of double patenting prevents a patentee from obtaining more than one patent for the same invention, and prohibits claims in a second patent that are not patentably distinct from those of the first patent. The purpose of the rule—according to the Supreme Court—is to prevent a patentee from "evergreening" its monopoly by obtaining successive patents for the same invention, or obvious variations. However, the Federal Court of Appeal has recently1 held that double patenting applies to divisional patents—at least those that are considered to be "voluntary" divisionals—that expire on the same date as their parent, and are therefore incapable of "evergreening" a patentee's monopoly.
What you need to know
- "Voluntary" divisional patents can be invalid for double patenting over their parent patents, even though they share an expiry date and therefore do not extend the time of a patentee's monopoly.
- What makes a patent a "voluntary" versus "forced" divisional was not addressed by the Court of Appeal, and remains unclear.
Background
NCS and Kobold are competitors in the oilfield services industry, which both provide specialized "downhole" equipment used in hydraulic fracking. At trial, NCS sued Kobold for infringing five of its patents. Kobold counterclaimed for infringement of two of its own patents (the 830 and 571 Patents). Kobold was successful at trial.
Although NCS originally raised several additional grounds of appeal, the two related substantive issues that remained when the matter was heard were claim construction and double patenting in relation to Kobold's 571 Patent.
Claims construction error
The Court of Appeal allowed NCS's appeal on the claim construction point, holding that the trial judge erred in construing an independent claim as excluding the limitation of a dependent claim. By definition, an independent claim must be broader than claims that depend from it. Put another way, an independent claim must include the subject matter of the claims that depend from it. This error led to additional errors in construing the other claims that had been asserted by Kobold.
Double patenting analysis error
NCS argued that, when properly construed, the asserted claims of Kobold's 571 Patent shared the same inventive concept as certain claims of the 830 Patent, and were therefore invalid for double patenting.
Kobold argued that, although the 571 Patent was a so-called "voluntary" divisional application (i.e., usually one where the claims were divided out of the parent application during prosecution at the instance of the applicant, and not as a result of being required to by the patent examiner), applying the doctrine of double patenting would be an academic exercise since the two patents expired on the same day and did not give rise to "evergreening".
The Court of Appeal rejected Kobold's arguments, finding no basis for rejecting NCS's double patenting arguments. The Court of Appeal agreed that although the Federal Court's conclusion on double patenting rested on an incorrect claim construction, the trial judge was better positioned to decide this validity issue having heard the evidence and testimony at trial. It therefore remitted this issue to the Federal Court for re-determination.
Finding that double patenting applies to divisional patents leaves patent lawyers with a thicket of unanswered questions. Presumably the same reasoning would not have applied to a "forced" divisional patent (i.e., one where the claims were divided out of the parent application during prosecution at the instance of the examiner). But then how does a Court distinguish between a "forced" or "voluntary" divisional? This remains a source of debate in the case law. Moreover, when two patents have the same expiry date and specifications, how could a court decide which claims should be considered the "later" ones for the purposes of obviousness-type double patenting? Does it need to replace the expiry date with the filing date or issue date (and what if they are different?) And then, on what date is the double-patenting assessment being performed—the filling date, the publication date, or the issue date (and, again, of which patent)? These questions fall outside the scope of the redetermination and are likely to remain unresolved, continuing to fuel uncertainty in Canada's law of double patenting.
Given the tendency of patentees in Canada to file multiple divisional applications of a single parent application, we suspect that we have not heard the last word on double patenting.
Footnote
1 NCS Multistage Inc. v. Kobold Corporation,2025 FCA 187.
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