These proceedings were brought as an application for leave to appeal and an appeal against a declaration and consequential orders made on 23 May 2022 to the effect that Airco Fasteners Pty Ltd infringed claims 1, 2, 3, 17 and 20 of Illinois Tool Works Inc’s patent number 2005232970. The patent, titled “in-can fuel cell metering valve”, describes a fuel cell for use with a combustion tool (such as a nail gun) which includes an internally mounted metering valve arranged so that a metered dose of fuel is dispensed each time the stem is pressed into the “open” position. The invention was said to reduce the risk of leakage found in prior art systems which used two valves, the second metering valve sitting outside the fuel cell. Figure 1 of the patent is set out below.

The primary judge provided the following description of the invention:

… the Patent explains that the function of the fuel metering chamber (38) is to facilitate the storage and subsequent dispensation of a measured amount of fuel through the outlet [(28)] of the fuel cell. In the preferred embodiment depicted in Fig 1, the fuel metering chamber [(38)] engages an outlet seal [(42)], which is adjacent to the closure (16) of the fuel cell [(10)]. However, the Patent explains that the fuel metering chamber [(38)] may be located within the housing and is preferably located within the valve body (34) and in close proximity to the closure [(16)]. Locations [of the fuel metering chamber] external of the valve body (34) are also expressly contemplated.

The appeal raised two issues of construction, concerning the primary judge’s determination that Airco’s combustion tool fuel cell has “a fuel metering chamber disposed in close proximity to said closure” (the close proximity integer) and “a valve body having a second end opposite said fuel metering chamber located within said container” (the second end opposite integer), as required by each of the relevant claims.

The Full Court rejected Airco’s criticisms of the primary judge’s findings on construction.

Airco submitted that the primary judge erred in construing the close proximity integer as requiring an assessment of the relative nearness of the fuel metering chamber and the closure within the context of the fuel cell as a whole, arguing that the construction of the primary judge failed to give effect to the natural meaning of “close proximity” as emphasising the requirement of “closeness” rather than simply proximity. It submitted that the primary judge ought to have construed the close proximity integer as requiring an assessment of the relative nearness of the fuel metering chamber and the closure “within the context of the location of the fuel metering chamber in the fuel metering valve” (emphasis added).

Airco argued that the assessment of “close proximity” must be undertaken in circumstances where it is “already a given” that the fuel metering chamber is contained within the valve body. It referred to the evidence of Illinois’ expert witnesses, Dr Wallace, who agreed in cross-examination that the fuel metering chamber “could not be much further away from the closure”, which Airco argued supported its contention that the closure was not in “close proximity” to the closure.

However, the Full Court agreed with the primary judge that the phrase “close proximity” is used to describe the disposition of the fuel metering chamber relative to the closure in the context of the fuel cell as a whole. In reaching this conclusion, the Full Court observed that the “closure” is not a part of the fuel metering valve, but forms part of the housing which includes within it a separate fuel container and the fuel metering valve. Thus, the Court rejected Airco’s submission that the primary judge ought to have considered the question of proximity in the context of the fuel metering chamber being in the fuel metering valve. The Full Court agreed with the primary judge’s finding that the fuel metering chamber does not need to be positioned adjacent to, or as close as possible to, the closure for the internal valve fuel cell of the invention to operate more efficiently and effectively than those described in the prior art. Rather, the requirement of “close proximity” ensures that the fuel metering chamber is sufficiently proximate for the fuel metering valve and fuel cell to function effectively.

In relation to the second end opposite integer, Airco submitted that the primary judge erred in construing “opposite” as meaning “facing” or “across from”, with two components “having a co-axial relationship with each other”. It argued that the primary judge ought to have construed this integer as requiring the fuel metering chamber to be located at the other end of the valve body to the “second end” of the valve body, outside the fuel container. Airco argued that the term “opposite” is used consistently throughout the specification to identify two ends of various objects, and that there was no reason why the term “opposite” in the claim should have a different meaning. Again, Airco placed some reliance upon the oral evidence of Dr Wallace, which it said supported its construction of “opposite”.

The Full Court upheld the primary judge’s construction. It observed that the word “opposite” as used in claim 1 is broader than the language used in the passages of the specification identified by Airco in its submissions, and that the word “opposite” is sensitive to context. The Full Court rejected Airco’s argument that the primary judge’s construction rendered the word “opposite” redundant, because it served to distinguish the arrangement of the invention from that of the prior art.

The authors note the following interesting features of the Full Court’s decision.

First, the Full Court observed that the construction of the close proximity integer adopted by the primary judge was supported by dependent claims 3 and 7 of the Patent, confirming that dependent claims can be used to assist in construing independent claims.

Secondly, the Full Court rejected the criticisms advanced by Airco that the primary judge erred insofar as her construction was contrary to the evidence of both experts. In doing so, the Court noted that expert opinion does not supplant the judicial role, reiterating that it is for the Court to determine the meaning of the language of the claims, aided by the evidence of experts to assist in understanding unfamiliar terms and the technical context, and that the judge is under no obligation to adopt a particular construction of the claim based on the evidence of one or other of the expert witnesses. The authors consider that this supports the proposition that the Court may arrive at a construction not adopted by any of the experts and that a party is not bound by its own expert’s view or acceptance as to a particular construction.