Drew, Robinson and Co v Shearer

Drew, Robinson & Co. (appellants) appealed to the High Court of Australia from a decision of the Supreme Court of Western Australia, which had found them liable for infringing letters patent held by John Shearer and David Shearer (respondents) for an improved ploughshare and footpiece. The respondents sought an injunction, damages, and other relief. The appellants denied infringement and also challenged the validity of the patent on several grounds, including lack of novelty and prior publication.

The central legal issue before the High Court was the construction of the patent claims, specifically claims 2 and 3, and whether the appellants' ploughshares infringed these claims. This involved determining whether the "tongue" described in the patent specification was an essential element of the invention claimed. The appellants argued that their ploughshares, which featured a flange but lacked the upwardly projecting tongue, did not infringe because the tongue was an essential part of the patented invention. The respondents contended that the tongue was not an essential feature and that their patent should be construed broadly to cover their invention.

The High Court, in allowing the appeal, reasoned that the patentee, by their specification, had clearly defined the "tongue" as an essential element of the invention. The Court applied the principle that a patentee delimits the area of their monopoly through their claims, and if an element is described as essential, there can be no infringement if that element is not used by the alleged infringer. The Court found that the appellants' ploughshares possessed the flange but lacked the upwardly projecting tongue, which was considered the substance of the invention. Therefore, as the appellants had not used this essential element, they had not infringed the patent.

Consequently, the High Court allowed the appeal, setting aside the judgment of the Supreme Court of Western Australia. The Court found that the appellants had not infringed claims 2 and 3 of the patent because they had not incorporated the essential "tongue" feature of the patented ploughshare.