Siemens Schweiz AG v Thorn Security Ltd

A European patent must be construed through the eyes of the skilled person, purposively and in the context of the patent as a whole. A deliberate claim limitation must be given meaning, and a technically possible interpretation may be rejected where it lacks practical significance. Where the patent and its translation have different legal status under section 80 of the Patents Act 1977, the court must construe each text independently before deciding which confers narrower protection. For infringement, “facilitating” requires a real practical benefit; a merely measurable physical difference is insufficient. Patent ownership transferred by Swiss universal succession was not an “assignment” or an order within section 33(3), so non-registration did not bar recovery of damages under section 68.

The claimant sued for infringement of European Patent No EP 0577094 B1, concerning a wax-containing thermoplastic film used as a protective coating for printed circuit boards. The defendant denied infringement and sought revocation for obviousness over Toshiba patent No 60209884A. The case also concerned competing German and English patent texts, the meaning of “through-plating” and “fused”, and whether successive Swiss company mergers triggered the registration consequences in sections 33 and 68 of the Patents Act 1977.

The court had to determine the proper construction of the patent, whether the defendant’s product and process contained the claimed integers, whether Toshiba made the invention obvious, and whether the claimant’s title and non-registration restricted damages.

1. Construction. The German text was authoritative for revocation unless the English translation conferred narrower protection. Each text had to be construed independently; the German wording could not be used to inform construction of the English wording. The claims were construed purposively, in context and through the eyes of the skilled person, applying the approach in Halliburton v Smith [2005] EWHC 1623 and the practical approach identified in Rediffusion Simulation v Link Miles [1993] FSR 369.
2. “Through-plating” meant carrying out plating or comparable repair operations through the coating, rather than creating plated-through holes. The German term “Durchkontaktierung” had the broader meaning of making contact through the coating. The English meaning was narrower and therefore governed under section 80(2). “Fused” and “aufgeschmolzen” did not require reduction to a fully liquid state. They included heat-softening sufficient to produce close contact and adhesion.
3. Validity and infringement. The claim limitation requiring wax to facilitate through-plating and soldering was a genuine integer, not surplusage. Toshiba did not contain that integer and instead sought to prevent access to the protected circuitry. The obviousness attack therefore failed. The defendant’s wax-containing film improved flow properties and gave practical benefits in repair operations, including easier access at lower temperatures and reduced risk of heat damage. Those benefits were sufficient to establish facilitation, although healing or resealing after invasive soldering was not proved. The application process also satisfied the requirement that the film be fused onto the board by heat. Claim 1 was infringed.
4. Registration and damages. The amended section 68 did not operate retrospectively. Applying the presumption stated in Yew Bon Tew v Kenderaan Bas Mara [1982] AC 553, the former damages restriction governed infringements occurring before the amendment. However, the Swiss mergers transferred the patent by operation of the doctrine of universal succession when registered, not by consensual assignment or an order or direction of an authority. Following Tamglass Ltd v Luoyang North Glass Technology Co Ltd (No 3) [2006] FSR 622, the transfers did not fall within section 33(3). The claimant’s damages were therefore not limited by section 68.
5. The court found for the claimant on validity and infringement and directed that the consequences of the ruling, including damages, be addressed further.