Occlutech GmbH v AGA Medical Corporation

Patent claims are construed purposively by asking what the skilled person would understand the patentee to mean, reading the claims with the description and drawings under the European Patent Convention 2000. Purpose informs meaning but does not displace deliberate claim language or create a general doctrine of equivalents. A patent may claim less than its specification teaches.

Where a specification distinguishes external clamping from soldering or welding, a clamp means an external device that is the primary and effective means of securing the strands. A claim requiring clamps at opposed ends may therefore exclude a one-ended device whose strands are secured by welding.

Occlutech sought declarations that two medical occlusion devices did not infringe AGA’s European patent. The patent contained a product claim for a collapsible braided-metal device and a method claim for forming it. Mann J upheld Occlutech’s claim for non-infringement in [2009] EWHC 2013.

AGA appealed on the construction of the terms referring to clamps and clamping the strands at the opposed ends of the device. The appeal concerned whether the claims covered Occlutech’s one-ended mesh-sock products, whose loose strands were secured by welding. The issues of obviousness and the meaning of dumbbell-shaped were not pursued on appeal.

Lord Justice Patten gave the leading judgment. Sir Paul Kennedy and Lord Justice Pill agreed. The appeal was dismissed.

1. Construction principles. Under Article 69 of the European Patent Convention 2000, the extent of protection is determined by the claims, read with the description and drawings. The claims must be construed purposively by asking what the skilled person would understand the patentee to mean. Purpose is a contextual aid, not a warrant to extend the claims beyond their language. There is no presumption that the claims have the widest meaning consistent with the teaching, and an obviously deliberate limitation must be given effect.
2. Meaning of clamp. The ordinary meaning of clamp denotes an external device applying pressure or force to hold objects together. The specification distinguished that method from soldering, brazing and welding. In context, clamp therefore referred to an external device of the described kind and did not include a weld or solder. An external sleeve or adaptor attached after the strands had already been welded was not a clamp, because it was not the primary and effective means of securing them.
3. Opposed ends. The claims were directed to the embodiment using a tubular braid cut at both ends and secured by clamps at both ends. The reference to plural clamps and to the opposed ends was a distinctive and necessary limitation. The alternative pocket method for flat fabric in paragraph [0027], which gathered the loose strands at one end, was not thereby brought within the claims. The wording of claim 16 did not alter that result; it was a method claim referring to a device conforming to the preceding claims and had to be read consistently with them.
4. Prosecution file. The court did not rely on the prosecution file. It was not in evidence, no respondent’s notice sought to rely on it, and the court therefore proceeded on the same assumption as the judge below that the skilled person did not have access to it.
5. Result. The old and new Occlutech devices did not infringe claim 1, and the appeal was dismissed.

• Court of Appeal (Civil Division): Appeal dismissed. The court upheld the construction adopted below in [2010] EWCA Civ 702.
• High Court, Chancery Division, Patents Court: Mann J upheld Occlutech’s claim for declarations of non-infringement in [2009] EWHC 2013.