In this order on provisional measures (Rule 206 RoP), the Court of Appeal set aside an injunction granted by the Hamburg Local Division and rejected STEROS’s application for provisional measures based on EP 4 249 647. The patent concerns an electrolytic medium for electropolishing that combines solid electrolyte particles with a “non-conductive fluid” immiscible in the conductive solution.
Two points stand out. First, the headnote states that experimental data not disclosed in the specification are, as a general rule, not relevant to claim interpretation. Secondly, on the merits of claim interpretation, the Court understood the “non-conductive fluid” requirement for emulsions by assessing conductivity at the level of the emulsion as a whole and – crucially – fixed the “not significantly conducting” threshold at ≤ 10 µS/cm by reference to claim language.
Reiterating NanoString v 10x Genomics, the Court held that Art. 69 EPC and its Protocol require claim interpretation in light of the description and drawings (and nothing else…). The parties agreed that the decisive feature was feature [1.2]: a “non-conductive fluid immiscible in the conductive solution”, with [1.2.2] requiring that, at rest and room temperature, the fluid does “not significantly” conduct current.
The Local Division had assessed an emulsion by separating phases (oily vs aqueous) and measuring each phase’s conductivity. The Court of Appeal rejected that approach. The specification expressly treats emulsions as a type of non-conductive fluid and speaks in terms of the emulsion’s non-conductivity at rest. Dependent claim structure supports that reading. Accordingly, the relevant subject of assessment is the overall emulsion as the “non-conductive fluid”, not the conductivity of isolated phases or ingredients.
The Court fixed the boundary for “not significantly conducting electrical current” at ≤ 10 µS/cm. It derived this from the explicit requirement that the set of solid particles retain a “conductive solution” with conductivity “greater than 10 µS/cm” (feature [1.1.2]) and the absence of any contrary indicator in the claims or description. The proprietor’s proposal for a relative, context-dependent threshold (i.e., merely “sufficiently lower” than the particles’ solution) was rejected.
A central submission by STEROS relied on test results it had generated for the litigation, including reconstructions of examples in the tables of the patent to argue that a non-conductive fluid can exceed 10 µS/cm and still meet the claim when viewed relatively. The Court declined to rely on such post-filed experiments for claim interpretation. In line with the headnote, experimental data not disclosed in the specification are generally not relevant to the interpretation of the patent claims. The Court emphasised that illustrative tables list compositions but do not state measured conductivities for the non-conductive fluid at rest; where the patent is silent, litigation-driven measurements cannot modify the ordinary meaning derived from the claims and description.
The Court further observed that, even on the proprietor’s reconstruction, the tested mixture had not been taken to the claimed end-product (electrolytic medium) before measuring the surrounding fluid at rest, whereas the claim concerns the fluid as part of the finished electrolytic medium. By contrast, OTEC’s testing of the surrounding liquid after combining all components yielded emulsion conductivities hundreds of µS/cm—well above the 10 µS/cm threshold.
