Scope of Divisional Patent Application

The Case - Memcor Australia Pty Ltd v G.E. Betzdearborn Canada Company [2009] FCA 508.

In my post of 19 March 2009, I presented some basic information concerning the interpretation of the filing date of a divisional patent application.

In this case, GE had filed a divisional application which Memcor opposed on a number of grounds including that the invention defined by the divisional application was not disclosed in the parent application on which the divisional was based (Section 79B(1) of the Patents Act). If that was the case, then the validity of any patent granted on the divisional would be questionable since it would be tested as of the date of filing the divisional as opposed to the earlier filing date of the parent.

The Commissioner of Patents had previously found against Memcor's opposition and this case was an appeal from that decision.

It followed that the question to be tried was whether or not the divisional was an application for a patent for an invention falling within the scope of the claims of the parent application.

Issues of claim construction

In the parent, one of the claims that was considered started with the preamble: "A microfiltration membrane device, for withdrawing permeate substantially continuously from...". The relevant claim in the divisional application read as follows: "A microfiltration membrane device for withdrawing permeate from a multicomponent substrate, said membrane device including a multiplicity of...".

According to Memcor, the claim of the parent application was limited to a microfiltration device in use. In particular, Memcor said that the device of the parent application withdraws permeate "substantially continuously" when the fibres are in a particular condition, which was described in the relevant claim. By contrast, the divisional application covered a microfiltration device not in use, that is, "on the shelf".

In the arguments, GE referred to a useful summary by the Full Court in Kinabalu Investments Pty Ltd v Barron & Rawson Pty Ltd [2008] FCAFC 178. In that case, it was held that "Although the claims are construed in the context of the specification as a whole, it is not legitimate to narrow or expand the boundaries of monopoly as fixed by the words of a claim, by adding to those words glosses drawn from other parts of the specification. If a claim is clear and unambiguous it is not to be varied, qualified or made obscure by statements found in other parts of the document."

A number of other rules of construction are also set out in paragraph 45 of the judgement, which are useful.

Claims that include the word "for" have raised difficulties in the past. However, these days it is well accepted that "for" should be regarded as equivalent to "suitable for". In other words, the relevant invention would not be limited to cover only while "in use". In any event, in this case, the court held that the natural and ordinary meaning of the sentence in question was to define the invention as a device suitable for a purpose rather than as a device only when used for that purpose.


It remains important for practitioners to ensure that claims are clear and unambiguous. One way of achieving this would be to make sure that clients understand the scope of protection defined by the claims, rather than relying on the rather patronising approach of not explaining clearly to clients the implications of claim wording.


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