Case Comment
M & I Heat Transfer Products Ltd. v. Airseal Controls Inc.

citation(s): A-36-94
date: October 8, 1997

Judges: Strayer, J.A. (Linden & Robertson JJA concurring)

copyright 1997 Donald M. Cameron, Aird & Berlis



The Court of Appeal agreed with the Trial Judge that the patent was infringed. The patent was given a purpose of instruction based on expert evidence. Infringement was determined by comparing the claim language with the allegedly infringing device and not by comparing the infringing device with embodiments illustrated in the patent or with the plaintiff's product.


The Decision

This is an appeal from a trial decision in which the appellant's (defendant's) damper was held to infringe the respondent's (plaintiff) Canadian patent. At trial, the patent was also held to be valid. Validity was not an issue on the appeal.

Held, the appeal is dismissed with costs.


Claim Construction

The trial judge did not err in law in his analysis. He relied on the plain wording of claim 1 but with appropriate reference to the disclosures and drawings of the patent.

At p.2:

"In this he was obviously much assisted by the evidence of the experts, particularly that of Mr. Hubbert, the respondent's expert. He obviously relied a great deal on Hubbert's evidence as to the meaning of certain terms of art in claim 1, the claim in issue. This was entirely appropriate."

The Court quoted the case of Procter and Gamble Inc. v. Unilever PLC, et al (1995) 61 C.P.R. (3d) 499 at p. 506 that a patent is to be construed with the knowledge of the skilled worker to the extent that such knowledge is revealed by expert evidence accepted at trial. Claim construction turns heavily on the evidence of persons skilled in the art.

The trial judge gave a purpose of construction to the patent: the purpose of translation was to move the closure member away from the frame sufficient to facilitate its rotation without breaking the frame. The precise sequence of translation and rotation was not otherwise important. All of the trial judge's conclusions as to construction were open to the learned trial judge.

It was open to the trial judge to find infringement as he did.

At p.3:

"In this he was correct to compare the appellant's allegedly infringing device with claim 1 and not with particular embodiments of the claim either as illustrated in the patent or as found in the respondent's product based on the patent."

Return to:

Cameron's IT Law: Home Page; Index

Cameron's Canadian Patent & Trade Secrets Law: Home Page; Index

JurisDiction Home Page