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The limits of dictionaries in the interpretation of patent claims

17th Jan 2018

In the final days of 2017, the Court of Appeal in the UK issued its decision in Saab Seaeye Ltd v Atlas Elektronik GmbH & Anor [2017] EWCA Civ 2175. The appeal touched on a number of points on claim construction that are instructive.

This case concerned the use of Remotely Operated Vehicles (ROVs) to dispose of unexploded mines and other munitions at sea, either resting on or tethered to the sea bed. In the seas around Europe, for example, industry is keen to exploit oil and gas reserves or to lay international telecommunications cables. This means that the many unexploded mines and other munitions in the seas around Europe, many dating from WW1 and WW2, must be hunted down and destroyed. The use of shaped charges had become popular for the disposal of the mines, but these have only limited range, and thus need to be placed precisely against the target.

In this case under appeal, Atlas had filed a patent covering the use of a nailgun to attach a device containing a shaped charge to a mine, the device having a trigger extending from the from the device to engage the nailgun as the device is placed against the target by an ROV.

The judge at first instance held claim 1 of the patent valid by virtue of claim interpretation. In particular, the judge held that “a trigger mechanism” recited in the claim required an exclusively mechanical arrangement to set off the nailgun, whereas the prior art appeared to use a partially electric system in which a trigger operates a switch in an electric circuit. Saab appealed on this point, that the judge at first instance had interpreted this term incorrectly and come to the wrong conclusion as to novelty of the claim.

The judge at first instance had explained his interpretation as resulting from dictionary definitions of the words “trigger” (“a small device that releases a spring or catch and so sets off a mechanism, especially in order to fire a gun”) and “mechanism” (“a system of parts working together in a machine; a piece of machinery”). On this basis the judge stated that the conventional use of the phrase supports the conclusion that a mechanical mechanism is required, and not, for example, an electrical mechanism.

The judge further stated that nothing in the description of the patent points in any other direction as to the interpretation of this term – a first example system being described as “a plainly mechanical trigger” and a second example system in which force is transmitted axially along an incompressible column of water being described as “obviously purely mechanical”.

Saab argued at appeal that the judge had stuck too closely to the definitions when confronted with the proper context in the light of the patent’s disclosure. Further, Saab argued that the judge had misinterpreted the second example system, which should more properly described as a hydraulic system.

In this case, at appeal, the appeal judges said that, while the judge is entitled to form his judgement by reference to the dictionary definitions, these definitions are acontextual. Those responsible for formulating them are unlikely to have had the patentee’s specific purpose in mind. The judge further stated that, in an appropriate context the words “trigger” and “mechanism” can have a meaning which is wider than the purely mechanical – a gun in which the trigger operates a switch in an electric circuit which in turn releases a striker can properly be regarded as having a trigger mechanism. The appeal judges agreed that the second example employed a column of water to transfer force from trigger to engage the nailgun, and that this was a hydraulic link within the mechanism, and so the mechanism was not wholly mechanical. Reading the description fairly, the appeal judges found it plain that the patentee regarded the hydraulic link as within the claim, although not purely mechanical.

The appeal judges therefore disagreed with the first instance decision that there was nothing in the specification to point away from the purely mechanical arrangement – read fairly it indicated that the patentee was using the expression “trigger mechanism” to encompass more than the purely mechanical. Thus the appeal judges allowed Saab’s appeal on the validity of this claim.

The message from this might be a reminder that, while dictionaries have their place in interpreting a patent claim, the dictionary definitions are not written in the same context as the patent specification and the patent specification might provide context for a different interpretation than that given in the dictionary.

This article is for general information only. Its content is not a statement of the law on any subject and does not constitute advice. Please contact Reddie & Grose LLP for advice before taking any action in reliance on it.

Christopher Smith
Senior Associate
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Would you like to know more? You can talk to Christopher Smith who will be able to help. Call +44 (0)20 7242 0901


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