Saint-Gobain Isover G+H and Saint-Gobain Construction Products Nederland B.V. v. Knauf Insulation S.P.R.L., Liège Court of appeals, Belgium, 19 September 2013, Case No. 2011/RG/1503
Saint-Gobain is the holder of a European patent (EP 0 399 320) claiming the use of glass fibres with a certain composition and which have a diameter of < 8 µm, wherein more than 10% of the glass fibres have a diameter of < 3 µm, as glass fibres which exhibit no carcinogenic potential. After having ex parte descriptive measures executed at Knauf’s plant near Liège (Belgium) and on the basis of the expert report obtained, Saint-Gobain filed a claim for infringement before the Liège commercial court.
Knauf filed a counterclaim for revocation of the patent, but only in subsidiary order, because the patent has expired in the meantime. In main order, Knauf contested the infringement on the basis of the finding of the expert report, that more than 10% of the glass fibres contained in Knauf’s products had a diameter thicker than 8 µm. Saint-Gobain stated this did not prevent the infringement, as the wording “which have a diameter of < 8 µm” in the patent claim must be interpreted in a technically meaningful sense and therefore understood as “which have an average (or median) diameter of < 8 µm”.