Where a patentee construes an integer as an essential feature of a combination claim, that integer must interact purposefully and functionally with the other integers to produce the claimed result; if it does not, the claim is a mere collocation and invalid. The authorities permitting non-interacting integers as mere limitations on scope (Pugh v Riley; British United Shoe) apply only where the integer is construed as a limitation on the claim, not as an essential feature of the combination. A patentee's construction of a claim for the purposes of infringement binds the patentee for the purposes of validity under both s 18(1)(a) and s 18(1)(b) of the Patents Act 1990 (Cth).
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