claimed.
What is claimed is then a tube having the characteristics described and identified by the division of the claim into
separate integers made earlier. That, in counsel's terminology is the "wide construction". The distinction between
the narrow and the wide construction for the purposes of this appeal is that defendants' counsel conceded that if
the claim was to be construed in the wide manner set out above infringement had been proved. The defendants'
further contention was however that such a construction rendered the patent open to revocation on the grounds
mentioned above and I turn to consider this question.
The evidence established that in the late 1970's EB America was producing a shock tube known as HD Nonel.
The letters HD stood for "heavy duty" and the word Nonel was an abbreviation for "nonelectric". This product was
the product invented by Nobel in 1971 the Nonel mono tube which was licensed by Nobel to EB America from
1975 to 1977. The defendants called two witnesses, a Mr Feasler and a Mr Spragg, who were in a position to talk of
the events of that time as employees or exemployees of EB America. The characteristics and shortcomings of this
shock tube were explained. The tube was apparently not sufficiently waterproof and lacked tensile strength and
abrasion resistance. This led (as has been stated) to investigations, tests and experiments to improve the product.
One attempt involved the overbraiding of the tube with polypropylene yarn and the application of a wax, which
was a mixture of a polymer and a resin, to the yarn. "Braiding" (as the judgment in the court below explains)
involves the interweaving or plaiting of the yarn over the plastic tube or (as the court below put it) the "wrapping"
of a covering around the plastic tube. The overbraided product did not solve all the problems which it was intended
to eliminate and, indeed, introduced other difficulties. One was that the stretching qualities of the plastic tube were
inhibited. Another was that problems arose with the seal between the tube and the detonator shell. As a result
further modifications were considered. One was a process of overextrusion. As early as 1976 EB America
conducted laboratory tests in which the plastic (Surlyn) tube was overextruded with polyurethane. The immediate
object was to improve the waterproofing of the product. The result was a tube with an inner part and an outer part.
EB does not seem to have been satisfied with the
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product and it concentrated for a while on the production of a "thickwalled" mono tube. After a period during which
its main commercial production was the thickwalled mono tube EB America reverted to the production of an over
extruded product which it then put into commercial production. An EB America Construction Standard (a document
used to control manufacture) dated 22 September 1979 covering the manufacture of an overextruded shock tube
was proved in evidence. The tube was made of a Surlyn sub tube of a certain grade manufactured by Du Pont over
extruded with polyethylene. Thereafter this product or similar overextruded products were produced and widely
sold by EB America. It was common cause that it was this type of a sandwich tube manufactured by EB America
which the plaintiff alleged infringed the patent. EB had, it seems, supplied the defendants.
The defendants' first argument was that the overbraided and overwaxed HD Nonel itself was an anticipation of
the invention. This was rejected in the court below and in my view correctly so as the product, to any practical
understanding, was a single or mono tube. The main contention however was that
Page 460 of [1998] 4 All SA 453 (A)
the overextruded product did so and the defendants sought to establish, through the evidence of Feasler and
Spragg, that EB America had marketed the overextruded product before August 1978. This both witnesses claimed
to be in a position to assert positively (despite the passage of sixteen years). The bulk of the record relates to the
evidence and crossexamination on this issue. The witnesses were able to identify a large number of documents (all
of which seem to have been exhibits in the American litigation) which reflected, in one form or another,
experimentation with or reports related to the overextruded product. It is not necessary for the purposes of this
judgment to particularise the documents or to discuss the efforts of the witnesses to date the commercial
exploitation of the product. Much of the evidence related to an ultimately unsuccessful effort to date an advertising
poster on which an overextruded product was depicted. The problem which the witnesses could not overcome was
the fact that in all this mass of documentation not a single document establishing the sale or commercial use of an
overextruded product, (such as an invoice, delivery note or any similar record) could be found. The evidence in this
regard was carefully analysed in the judgment by the learned judge in the court a quo and he concluded that the
defendants had failed to prove the prior commercial use of the overextruded product. I have not been persuaded
that he erred in this regard. It has not been suggested that the learned judge then erred in holding that the
subject matter of the invention had on this view of the evidence not "been made available to the public (whether in
the Republic or elsewhere) by use or in any other way" before the priority date.
What remains is the issue of obviousness. The objection based on a lack of inventiveness is one of long standing
in our patent law. It was to be found in both the 1916 and 1952 Patents Acts. In terms of section 23(1)(d) of the
1952 Act, it was a ground for revocation of a patent that the invention was "obvious in that it involves no inventive
step having regard to what was common knowledge in the art at the effective date". Under that Act the concept of
common knowledge was fundamental to the
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enquiry (see Gentiruco v Firestone, supra, at 654A and BM Group (Pty) Ltd v Beecham Group Ltd 1980 (4) SA 536 (A)
at 553BF). It is, I think, important to note that the starting point under the present Act is somewhat different. This
has eliminated a number of difficult factual inquires which arose under the earlier legislation, such as the question
as to what degree of general acceptance of knowledge was necessary to constitute common knowledge.