Cullen v Welsbach Light Co of Australasia Ltd

The High Court of Australia heard an appeal from the Supreme Court of Victoria concerning a patent infringement action. The plaintiff, Welsbach Light Company of Australasia Ltd., had sued Robert Lascelles for infringing its patent for an improved hood for incandescent gas burners. The patent claimed a hood made of pure thorium oxide with a small proportion of other rare metal oxides, prepared as described in the specification.

The central legal issues before the High Court were whether the patent was valid, specifically concerning the novelty of the invention and whether it had been publicly used or published in Victoria prior to the patent's grant. The defence argued that hoods manufactured according to the patent had been publicly sold in Victoria before the patent was obtained, and that the product was such that its composition and method of manufacture could be ascertained by those skilled in the art using common knowledge at the time.

The Court found that hoods manufactured according to the patent had indeed been publicly sold in Victoria prior to the patent's grant. Crucially, the Court determined that the product was of such a composition and construction that any person conversant with the subject, applying the common knowledge of the time, could have reproduced it. This prior public sale of the product, from which the process of manufacture could be deduced, rendered the patent invalid. The Court reasoned that such a sale constituted a disclosure to the public of the invention, thereby negating the novelty required for a valid patent.

Consequently, the High Court allowed the appeal, reversing the decision of the Full Court of Victoria. The patent was held to be invalid on the grounds of prior publication and public use, and the plaintiff's claim for infringement was dismissed.