The Flax and the Foreign: US prosecution history in file wrapper estoppel

  • October 11, 2019
  • Brian Daley, Christopher Guerreiro and Colin Hyslop, Norton Rose Fulbright LLP


The plaintiff, CanMar Foods Ltd., brought a patent infringement action against the defendant, TA Foods Ltd., regarding Canadian Patent No. 2,582,376 (the 376 Patent). Both parties are competitors in the flax seed product industry. The plaintiff’s 376 Patent claims a particular method of roasting flax seeds, and the plaintiff alleged the defendant was producing its roasted flax seeds in a manner that infringed the 376 Patent.

The defendant brought a motion for summary judgment on the basis of non-infringement, arguing that, when properly construed, the only independent claim in the 376 Patent contains two essential elements that the defendant’s flax seed roasting process lacks: (1) heating the oil seed in a stream of air and (2) maintaining the heated oil seed in an insulated roasting chamber or tower. The plaintiff argued that (1) the language of the claim is not limited to a particular type or source of heating and (2) further investigation is required to determine whether the defendant’s method includes an insulated of partially insulated roasting chamber or tower.

Foreign file wrapper estoppel in “extraordinary circumstances”

Relying on the new file wrapper estoppel provision of s 53.1 of the Patent Act, the defendant submitted that these two missing elements were essential in light of the 376 Patent’s Canadian prosecution history and the US prosecution history for the corresponding US application 11/576,405 (US 405 application) filed before the United States Patent and Trademark Office.

Justice Manson held that “[t]he language of section 53.1 is limited to communications between the patentee and the Canadian Patent Office, and generally should be applied in that context,” but ultimately held that prosecution history in foreign jurisdictions may be considered in “extraordinary circumstances.” These extraordinary circumstances arise where, during patent prosecution, (1) the patentee acknowledges it has amended its claims in a substantially similar manner as its claims submitted in another jurisdiction, and (2) the patentee admits the amendments have limited the scope of the claims to make them novel and non-obvious. In these extraordinary circumstances, the prosecution history “of a foreign application is made part of the prosecution history of the Canadian patent [emphasis original].”