Dismissing an appeal from a decision of Mr Justice Mann, the Court of Appeal, in Occlutech GmbH v AGA Medical Corp [2010] EWCA (Civ) 702, has decided that, although in a suitable context the word "clamp" could be understood to carry an extended meaning, in the context of the patent in suit, a "clamp" meant a "clamp" in the everyday sense of the word, and not an all-inclusive term for means of securing things together.


AGA Medical owns a patent relating to a device designed to be placed inside blood vessels to block them in order to treat certain medical conditions, such as holes in the heart. The device is made from a sheet of fabric consisting of interwoven metal wires. To prevent the ends of the wires from unravelling, the metal strands were "clamped" at both ends of the device by means of an external clamp and this was claimed in Claim 1. Claim 16 was to a method of manufacture of a device as set out in the earlier claims, including Claim 1.

Occlutech GmbH, a manufacturer of a similar device, used another method to prevent unravelling. In its devices, there were cut strands only at one end and these were secured by welding. AGA Medical claimed that Occlutech's devices infringed its patent. In turn, Occlutech sought a declaration of non-infringement, asserting that the loose ends of their products were welded instead of clamped and, furthermore, their devices were formed like a sock, so there were loose strands to be secured at only one end of the device. As such, Occlutech argued that the differences in the products took them outside the scope of AGA Medical's patent.


The High Court of England and Wales ruled in favour of Occlutech, with Mr Justice Mann preferring the evidence of Occlutech's expert, who defined a clamp as an object that exerts force upon two or more other objects in order to keep them together. AGA Medical appealed.


As the appeal turned on the definition of the term "clamp", Lord Justice Patten, giving the leading judgment of the Court of Appeal, considered the issue of claim construction.

The focus was on determining what the skilled addressee would have understood the language of the claim to mean. In Kirin- Amgen v Hoechst Marion Roussel [2005] RPC 9, Lord Hoffmann stated that "there is no presumption about the width of the claims. A patent may, for one reason or another, claim less than it teaches or enables". He went on to note that courts in Germany, the Netherlands and the United Kingdom prohibit the use of file wrappers as an aid to construction.

Patten LJ upheld Mann J's view that "clamp" was used commonly to describe something that bound together other objects by applying a degree of external pressure or force, but he held that it could also, in a suitable context, be understood to carry an extended meaning that might include the use of a device that physically bound the strands together, even if that was not the only means used to secure them.

Patten LJ held that the skilled addressee would understand the language of the patent description to mean that a clamp meant the application of an external device to hold the strands together as opposed to fusing them together with solder or a weld and that it excluded an external device that was placed over and physically attached to the welded ends after completion of the moulding process.

Patten LJ also found for Occlutech on the basis that its device, which attached the strands at one end only, fell outside the patent claims, which called for two clamps at opposing ends. This conclusion was reinforced by the knowledge that AGA had sought a divisional patent that had since been granted as a patent for an occluding device with only one clamp. This offered an explanation of why the claims in the patent in suit were limited to the teaching contained in the earlier paragraphs of the description.

Accordingly, Patten LJ upheld the decision of the High Court that Occlutech's devices did not infringe AGA Medical's patent.


It is noted that this is yet another case where various European courts have interpreted the same patent claim differently. The Dutch and English Courts held that there was no infringement, whereas the German courts have held that infringement occurred.