“Consisting essentially of” in Canadian Claim Construction15/01/2018
Due to the flexible nature of the law of claims construction in Canada, the construction of the commonly used transitional phrase, “consisting essentially of,” may surprise those not familiar with Canadian patent practice. As such, when preparing patent applications for filing in Canada, the term should be used with caution.
The use of the phrase “consisting essentially of” in claims is common in other jurisdictions, particularly in the United States. Thus, practitioners often assume that this term has the same meaning in Canada as in the United States. In the United States, the phrase limits the scope of a claim to the specified materials or steps “and those that do not materially affect the basic and novel characteristic(s)” of the claimed invention.1 In Europe, the phrase is held to mean that “specific further components can be present, namely those not materially affecting the essential characteristics” of the specified materials or steps. However, this phrase does not necessarily have a similar meaning in Canada.
In section 11.01 of the Canadian Patent Office Manual of Patent Office Practice; “consisting essentially of” is listed with “consisting of,” which appears to suggest that “consisting essentially of” has the same meaning, or close to the same meaning, as “consisting of,”: a term that is well established to limit the scope of a claim to the specified materials or steps.2 However, the Patent Appeal Board has variously interpreted “consisting essentially of” to mean “comprising,”3,4 to exclude materials or steps not specified in the claim5, or to have a meaning similar to that in the US or Europe.6
Courts in Canada have also flexibly interpreted the term “consisting essentially of”. The Federal Court has rejected the US interpretation.7 In a recent decision, the Federal Court interpreted “consisting essentially of” to exclude materials and steps not specified in the claim.8 In another decision, the Federal Court construed a claim directed to “[a]n abridged … composition” in view of the description, another dependent claim, and “abridged” in the preamble of the claim to determine that “consisting essentially of” included other materials and steps not specified in the claim.9 On the other hand, both decisions state that in line with the Supreme Court of Canada’s decision in Free World Trust,10 the claims should be purposively construed and the whole disclosure must be considered.
Thus, the phrase “consisting essentially of” is not likely to have the established meanings as it does in the United States and Europe. Rather, the term will be interpreted in view of the whole disclosure of the particular specification. English is a widely used and adaptable language but those using it would do well to keep in mind that Canadians, Americans and the English themselves adapt it and interpret it according to their own needs.
Authors: Lei Gao, Andrew Kaikai (former associate)
This article is for information purposes only and does not constitute legal or professional advice.