Kwikbolt Ltd v Airbus Operations Ltd

A patent claim must first be construed purposively in accordance with its ordinary meaning in context. The court must then ask whether a variant which does not infringe on that construction nevertheless falls within the scope of the claim as an immaterial variation. A fastener described as removable must be suitable for removal in its entirety from the workpieces without significant damage to the fastener or the workpieces. The inventive concept must be identified without reference to the alleged variant. On the facts, the alleged product did not satisfy a claim integer and did not achieve the inventive concept under the doctrine of equivalents. The patent was valid but not infringed.

Kwikbolt owned a patent for a removable blind fastener used in aerospace assembly. Airbus used the Centrix Free Spin Fastener, which Kwikbolt alleged infringed claims 1, 8, 16 and 18. Airbus counterclaimed for invalidity based on lack of novelty, lack of inventive step and insufficiency, relying principally on McClure 1, the E-Nut, McClure 2 and Wylie.

The court determined the meaning of disputed claim integers, considered infringement under normal construction and the doctrine of equivalents, and assessed the pleaded prior art. The central issues were whether the Centrix Fastener satisfied the requirement that the screw head be adjacent to the first member head, whether it was removable as a unit, and whether the patent lacked novelty, inventive step or sufficiency.

1. Construction. Following the two-stage approach in Actavis UK Ltd v Eli Lilly and Co [2017] UKSC 48, the claims were first construed purposively according to their ordinary meaning in context, informed by the specification, drawings and the skilled person’s common general knowledge. If there was no infringement on that construction, the court considered whether the alleged variant was nevertheless an immaterial variation.
2. Meaning of “removable”. A fastener was removable within the patent if it was suitable for removal in its entirety from the workpieces which it clamped, without significant damage to the fastener or the workpieces. The term did not impose a requirement that removal occur before flight or at any particular time.
3. Disputed integers. “Elongate” bore its ordinary meaning and required each relevant member to be longer than it was wide. The head of the first member was defined by its function of bearing against a workpiece. “Adjacent” meant adjoining or bordering but not necessarily touching. The three members had to be insertable and removable as a single unit, although individual members need not each pass through both workpiece apertures.
4. Infringement. The Centrix Fastener satisfied most disputed integers, including removability, but its screw head adjoined the opposite end of the first member rather than the head end. It therefore did not satisfy integer 1(8), or its equivalent in claim 18. Claim 16 was also not embodied because the first member head was not adapted to receive the anti-rotation tool.
5. Doctrine of equivalents. The inventive concept had to be identified through the eyes of the skilled person using the claim, specification and common general knowledge, without knowledge of the alleged variant. The inventive concept was a blind removable fastener which, in clamping mode, was substantially flush with the upper workpiece. The disputed adjacency integer was important to that concept. Since the Centrix Fastener did not achieve that result, the first reformulated Improver question was answered negatively and there was no infringement by equivalence.
6. Validity. McClure 1 did not disclose a removable fastener as construed; its central teaching was to anchor the sleeve to a workpiece. The E-Nut added nothing. McClure 2 taught isolation of the collet fingers from torque, and it would not have been obvious to abandon that teaching. Wylie did not make the claims obvious, including because its first member head was not adjacent to the screw head on the correct construction. The patent was neither insufficient nor invalid for lack of novelty or inventive step.
7. Disposition. The patent was valid but was not infringed. The claim and invalidity counterclaim were determined accordingly.