181. At 189 the learned Judge stated:
"In the end, therefore, the question is always whether the alleged infringement is covered by the language of the claim.
This, I think, is what Lord Diplock meant in Catnic when he said that there was no dichotomy between 'textual infringement'
and infringement of the 'pith and marrow' of the patent and why I respectfully think that Fox LJ put the question with great
precision in Anchor Building Products Ltd v Redland Roof Tiles Ltd when he said the question was whether the absence of a
feature mentioned in the claim was 'an immaterial variant which a person skilled in the trade would have regarded as being
within the ambit of the language" (the emphasis is that of Hoffman J).
But there is another facet of Lord Diplock's test to which attention must be directed. This is the role of section 125
of the English Patents Act of 1977 and article 69 of the European Patent Convention. The convention was concluded
in Munich in 1973.
England has adhered to it. Article 69 was an attempt to ensure a measure of uniformity in the construction of
patent specifications within the European community by stipulating permissible readings of patent claims (the
Protocol). The reason, in brief, lies in the difference between the traditional approach to claim interpretation in
United Kingdom and the continental approach which rests largely on the views of persons skilled in the particular
art. An article by B Sherman in [1991] 54 Modern Law Review page 499 "Patent Claim Interpretation: The Impact of
the Protocol on Interpretation" is instructive in this regard. It seems as if the aim has not been wholly achieved.
What Hoffmann J's analysis showed is that Lord Diplock's proposed test was influenced by the Protocol (see
Hoffman J in the Improver case, supra, at 190 and Southco Inc and another v Dzus
Page 548 of [1999] 2 All SA 543 (A)
Fastner Europe Ltd [1990] RPC 587 at 603 and 604). Lord Diplock's proposal is that the court should ask itself three
questions. Two of these are questions of fact dependent on extrinsic evidence. To the extent to which this could be
understood to suggest that extrinsic evidence on interpretation be led in all cases it would not be in accordance
with our law. It is contrary to the judgment of this Court in the Gentiruco case (see the judgment of Trollip JA at
617A618G). In the cases in this Court in which the concept of a purposive construction has been invoked this has
always been in a context which in no way detracted from the firmly established principles of claim construction.
Generally, evidence on record for other reasons, such as evidence to explain the art and science in question to
enable the court to view the patent "through the eyes of
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the addressee", allowed the court to adopt a purposive approach. In the Multotec case, for example, the claim in
question was ambiguous and the invocation of an aid to interpretation was appropriate.
What I have said has been prompted only by the need to point out that it is not always open to a court to resort
to evidence as an aid to construction. None of the South African authorities to which I have referred (nor indeed the
English cases other than the Improver Corporation case and the Southco case) have directed attention to the effect
of the Protocol in the Catnic case or to the factual nature of part of the test. In most cases a test which necessitates
extrinsic evidence will be inappropriate. The caution sounded by Trollip JA in the Gentiruco case at 613DE about the
use of English and American decisions remains valid and apposite. (I should add that Lord Diplock's approach has
also been invoked in cases not concerning patents. An example is Public Carriers Association and others v Toll Road
Concessionaries (Pty) Ltd and others 1990 (1) SA 925 (A) at 943CH again a case where ambiguity was a problem.
But it is beyond the scope of this judgment to discuss the application of the Catnic test in decisions other than
patent cases.) What can be said is that in patent cases the need for a practical construction is obviously desirable.
But care is called for in the manner in which recourse may be had to Lord Diplock's test.
As I have said, the present case is a good example of circumstances where it would be singularly inappropriate
to attempt to apply the Catnic procedure. Counsel sought to do so both in the main argument and in an alternative
argument. In his main argument he addressed an argument, without evidence on the point, as to what the "true"
invention was. In the alternative argument he sought to raise a "pith and marrow" contention, again without any
appropriate evidence having been adduced. The present patent in fact involves no technical complexities and uses
no esoteric phraseology. The words of the claim are ordinary English words clearly used in their ordinary
connotation and the claim is unambiguous. There is therefore nothing which would justify a reference either to
phraseology in the body of the specification or to extrinsic evidence relating to the art. The claim in issue must
simply be read in its own terms.
No aid to interpretation (going any further than the need to read the document as a whole) is called for. In the
consistory clause itself there is discussion of the first bag being made of an unseamed tube with ends sealed to
provide a closed bag. This statement is followed by a description of the envelope being in the form of an open
ended tube. The openended member is thus accurately described as a tube in contrast to a bag. With that
background one turns to the claim where one encounters the word "bag" not only used in its ordinary sense but
also used in juxtaposition to the word "envelope". There is also a reference to a first bag and a second bag. The
ordinary meaning of the word "bag" according to the Shorter Oxford English Dictionary is "a receptacle of flexible
Page 549 of [1999] 2 All SA 543 (A)
material open only at the top (where it can be closed)". The word is unambiguous. The patentee must therefore be
understood to have intended the limitation to the claim which follows from the use of the
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