The appellants (Nampak Products Limited and H L & H Timber Products (Pty) Limited) were joint registered proprietors of South African Letters Patent No 90/2427 for a "Pressure Resistant Bag" invention, granted with effect from 27 February 1991. The patent concerned bags used in mine support systems underground. The respondent (Man-Dirk (Pty) Limited) manufactured and sold a competing product. The appellants applied for a permanent interdict restraining the respondent from selling or offering its product for sale and for delivery up of infringing bags. The respondent's product was very similar to the patented product but allegedly lacked one integer of the main claim - specifically, the "second bag" required by integer (iv) of the claim. The respondent's product used a "sleeve" or "sheath" instead of a second full bag. Roux J, sitting as Commissioner of Patents, dismissed the application with costs but granted leave to appeal.
The appeal was dismissed with costs, including the costs of two counsel.
In patent infringement proceedings, the court must first construe the claim and then compare the allegedly infringing article with the claim as construed. All features or limitations of the claim must be present in the allegedly infringing article for infringement to be established. Where patent claims use ordinary English words in an unambiguous manner without technical complexities or esoteric phraseology, the words must be given their ordinary meaning and no aid to interpretation beyond reading the document as a whole is required. The 'purposive construction' approach derived from Catnic is not always appropriate in South African law, particularly where it would require extrinsic evidence on interpretation in circumstances where the claim is clear and unambiguous. To the extent that Lord Diplock's test in Catnic requires extrinsic evidence to be led in all cases, it would not accord with South African law as established in Gentiruco AG v Firestone SA (Pty) Ltd.
The Court made several observations regarding the purposive construction principle: (1) It noted that purposive construction has been invoked in South African cases in different ways - sometimes as a general approach based on the skilled addressee's knowledge of the art, and sometimes where the alleged infringer has appropriated the 'pith and marrow' of the invention by substituting a mechanical equivalent for an inessential part. (2) The Court observed that in all South African cases where purposive construction was applied, it was done in a manner consistent with established principles of claim construction, and generally where evidence was on record for other reasons. (3) The Court noted that the caution sounded by Trollip JA in Gentiruco about the use of English and American decisions remains valid and apposite. (4) The Court acknowledged that a practical construction is obviously desirable in patent cases, but emphasized that care is called for in the manner in which recourse may be had to Lord Diplock's test. (5) The Court commented that the concept of purposive construction has been invoked in cases not concerning patents (such as Public Carriers Association v Toll Road Concessionaries), but indicated it was beyond the scope of the judgment to discuss such applications.
This case is significant in South African patent law for its careful analysis of the 'purposive construction' approach to interpreting patent claims and its limitations. The judgment clarifies that while purposive construction may be appropriate in certain circumstances (such as where claims are ambiguous or where evidence of the prior art is available for other reasons), it is not always appropriate to resort to extrinsic evidence as an aid to construction. The case reinforces the traditional South African approach that where patent claims use ordinary words in an unambiguous manner, they should be given their ordinary meaning. The judgment also highlights the importance of understanding the origins of the Catnic test in the European Patent Convention Protocol and cautions against uncritical adoption of English and American patent law principles without consideration of their compatibility with South African law. The case serves as a reminder that in patent infringement cases, all essential integers of a claim must be present in the allegedly infringing article.