In AP&C Advanced Powders & Coatings Inc. v. Tekna Plasma Systems Inc., the Federal Court of Appeal dismissed AP&C Advanced Powders & Coatings Inc. (“AP&C”)’s appeal of the Federal Court’s decision that certain claims in two related patents were invalid for ambiguity. The patents at issue, Canadian Patent Nos. 3,003,502 and 3,051,236, describe metal-powder atomization processes for use in applications such as 3D printing and powder injection molding.

The Federal Court had found that the term “depletion layer” in the claims was not a term of art and could not be given a reliable meaning by a person skilled in the art. As a result, the claims at issue failed to distinctly define the subject matter of the invention in explicit terms, as required by the Patent Act. Since a person skilled in the art could not determine what fell inside the claim and what did not, the claims were invalid for ambiguity.

AP&C argued that the Federal Court erred by effectively requiring a valid patent claim to include a means of proving infringement, but the Court of Appeal rejected that argument. The Court of Appeal referred to the Supreme Court of Canada’s reasoning in Free World Trust v. Électro Santé Inc. that unless the claims of a patent distinctly and explicitly define the invention so that the public knows where it may act with impunity, it will become a “patent of uncertain scope” that is a “public nuisance”. Given its disposition on ambiguity, the Court of Appeal did not address AP&C’s other arguments regarding the Federal Court’s findings on insufficiency or infringement.

The full decision can be found here.