Stretchline Intellectual Properties Ltd v H & M Hennes & Mauritz UK Ltd

Patent claims must be construed purposively by asking what the skilled person would understand the patentee to mean in context. A claim requiring a fusible yarn capable of forming a penetration barrier does not necessarily require a discrete, continuous layer of fused material. Where the technical function of the yarn is to bond other yarns, the relevant barrier may be formed by the resulting composite fabric structure. General claim language should not be limited by details of a preferred embodiment unless the patentee has chosen to include those limitations. A construction is not rejected merely because it might expose the patent to invalidity, particularly where the validity issue is unavailable or the evidence does not establish the alleged common general knowledge. Product descriptions used instead of disclosure must be complete and accurate; samples may be required where they materially assist the infringement inquiry.

The claimant owned a patent for tubular fabric used to encase underwires in garments. Earlier infringement proceedings were settled by an agreement under which the defendant undertook not to deal in products falling within the patent claims, subject to a limited sell-through period and an exclusion for low-volume fabric.

The claimant later alleged that bras sold by the defendant breached the settlement agreement. The defendant disputed whether the garments fell within the patent claims and relied on a construction requiring the fusible yarn to form a discrete layer or liner. The central issues were the construction of the expression penetration barrier, the relevance of common general knowledge and validity, the adequacy of product descriptions, and whether the products infringed.

1. Construction. The claims were construed purposively in accordance with Kirin-Amgen Inc and Others v Hoescht Marion Roussel and Others [2005] RPC 9. The skilled person would understand fusible yarn to bond the other yarns in the fabric. The penetration barrier was therefore formed by the composite fabric structure, with the fusible yarn acting as the cause or trigger of the increased resistance to penetration. The claims did not require a discrete, continuous layer of fused material.
2. The preferred embodiments, the expert evidence and common general knowledge all supported that construction. A discrete layer was impractical in woven tubular fabric, and the preferred percentages of fusible yarn would not have produced such a layer. The claim required a material increase in resistance to penetration, but imposed no minimum percentage, no absolute barrier requirement and no requirement to use the L+M sewability test.
3. The court rejected the proposed non-infringement and invalidity squeeze. The settlement agreement precluded the defendant from raising invalidity. In any event, the court would have adopted the same construction, and the evidence did not establish that using fusible yarn to increase penetration resistance in tubular fabric formed part of common general knowledge.
4. Product descriptions. A defendant electing to serve a product description instead of disclosure must provide complete and accurate information sufficient to resolve infringement issues. The duty is equivalent to the duty relating to disclosure. Where appropriate, samples should be provided at an early stage, particularly where they would make the composition and manufacturing process intelligible.
5. Infringement and outcome. The products contained significant quantities of fusible yarn woven into the fabric. The expert evidence, adhesive bonding shown in some images and M&S pin penetration testing established increased resistance to penetration. Each of the Devsel, Rimteks and Takefast bras fell within the patent claims. Their sale breached the Settlement Agreement.

The defendant’s invalidity defence and counterclaim had previously been struck out by Sales J. That decision was affirmed by the Court of Appeal in Stretchline Intellectual Properties Ltd v H&M Hennes & Mauritz [2015] EWCA Civ 516. Following the appeal, the claimant discontinued its patent infringement claim and pursued only breach of the Settlement Agreement.