Ensign-Bickford (South Africa) (Pty) Ltd and Others v Aeci Explosives and Chemicals Ltd

• Jurisdiction: South Africa
• Judge: van Heerden DCJ, Harms JA, Schutz JA, Scott JA, Plewman JA
• Judgment Date: 21 August 1998
• Counsel: CE Puckrin for the appellants L Bowman for the respondents
• Docket Number: 4/95
• Court: Supreme Court of Appeal

Plewman JA :

This appeal concerns the validity and alleged infringement of South African Letters Patent No 79/3210 in respect of an J

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invention entitled 'Low-energy fuse consisting of a plastic tube the inner surface of which is coated with explosive A in powder form'. The appellants were the defendants in two infringement actions consolidated at the trial stage. The respondent, the plaintiff in the actions, is the proprietor of the patent, having acquired it by assignment on 2 April 1992. MacArthur J, sitting as Commissioner of Patents, decided the case in the plaintiff's favour but granted B leave to appeal to this Court. It will be convenient to refer to the parties as plaintiff and defendant or defendants as the context may require.

The plaintiff is a leading South African company in the explosives field. The original patentee, Nobel Nitro AB of C Sweden (Nobel), is a company of even greater renown in this field. The first defendant is the local subsidiary of a corporation registered in the United States of America, Ensign-Bickford (E-B America), a large manufacturer of products of the type covered by the patent. The other defendants were its customers.

The patent was granted under the Patents Act 57 of 1978 (the Act), on a convention application dated 18 June D 1979, claiming a priority date, based on the original Swedish application by Nobel, of 8 August 1978. The inventors were three persons who were employees of Nobel at the time of the development of the product. The plaintiff was initially a licensee under the patent and seems to have acquired it for the purposes of the litigation. E-B E America, for its part, had been a licensee of Nobel under an earlier 1971 pioneer patent in the field. This was the Pers-Anders Persson US Patent 3590739. The products, produced in accordance with the Pers-Anders Persson patent, became known as the Nonel mono tubes. Nonel was a Nobel trade mark. A number of variations of the F original product appear to have been manufactured from time to time both by Nobel and its licensees. The licence with E-B America included a technical exchange agreement which (though the matter was not investigated at trial in any depth) appears to have involved a mutual obligation to exchange information concerning technical advances on or improvements made with the product. The evidence establishes that both E-B America and Nobel before G and at the time of the application for the patent now in issue were actively pursuing research in order to improve their respective products. Some of the variations will be mentioned below. The plaintiff itself was still manufacturing the mono tube in 1994 and had not, even at that date, undertaken commercial production of the patented tube. H

Fuses of the type covered by the patent are known as shock tubes. A short explanation of the art or science in question must be given. Shock tubes were introduced to the mining, quarrying and construction industries in the early 1970s as a method of initiating explosions which was safer than other then known methods. Shock tubes I became a substitute for electrical initiating methods and for conventional detonation cord. Shock tubes consist of plastic tubes with an outside diameter of approximately three millimetres, the inside wall of which is coated with a fine layer of explosive dust. A detonator is attached to the tube by a process known as crimping. The tube operates by the propagation of a shock wave the initiation of which at one end of the tube causes the J

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progressive detonation of the explosive agent (it being self-propagating) which, at the far end, initiates the main or A intended explosion by means of the detonator. All the shock tubes dealt with in evidence used a make or grade of Surlyn - a plastic tubing, provided by a firm Du Pont. It seems that Surlyns were well known and readily available in a range of grades. Explosive powders were also readily available in the market. B

The trial had some unusual features. Not only had Nobel and E-B America, for the reasons already given, insight into the technical developments of the other but the plaintiff itself also seems to have had some relationship and communication on a technical level with E-B America (though this too was not investigated). E-B, however, was C the manufacturer of the tubes sold locally which were alleged to infringe the patent. What had a large influence on the proceedings was the fact that prior to the South African litigation there had been litigation (on the counterpart American patent) between Nobel, a company known as Ireco and E-B America. As is usually the case with American litigation depositions (an adverse party procedure related to discovery which allows parties to D take evidence on oath of the other party's officers) were taken from a number of persons, including one of the inventors, Mr Hans Lundborg. Both the plaintiff and the defendants made extensive use in cross-examination of the American depositions and of documents discovered in the course of taking such depositions. As far as the E defendants are concerned, it must have been the fact that Lundborg's deposition was available to them that led them to apply, before the trial in South Africa commenced, to take his evidence on commission in Stockholm. In the application for such leave it was stated that the witness would be able to support the counterclaim for revocation of the patent by reason of his knowledge of, inter alia, the details of the development of the patented F shock tube; details of the problems encountered with the prior art products which the patentee sought to overcome; the commercial success of the patented product, and tests conducted on the patented product and the prior art. When Lundborg's evidence was led, not all these promises were fulfilled. It is reasonably clear that the G defendants had not had access to Lundborg for the purposes of consultation before deciding to lead his evidence. An expert summary relating to his evidence was filed but this he himself had not seen at the time of giving evidence. It was presumably prepared by defendants on the basis of his deposition. Since Lundborg is one of the inventors of the patent and an ex-employee of Nobel the procedure would seem to have been a slightly H ambitious attempt by defendants to advance their case. It was, in the end result, not entirely unhelpful to their cause.

The onus of proof on the issue of infringement was on the plaintiff and on the issue of invalidity on the defendants. The plaintiff led the evidence of only one witness, Dr Viljoen - a well qualified scientist in the plaintiff's employ, but I only since January 1992. The defendants thereafter called a number of witnesses (who will be identified later) in support of their contention that the patent was invalid.

At trial three grounds of invalidity were relied on. In the pleadings additional grounds had been advanced but these were not pursued. The objections with which the defendants persisted were a contention that J

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the patent was not patentable in terms of s 25 of the Act as it was not new in the light of the use or sale before the A priority date of two products known as H D Nonel (novelty); a contention that the patent did not involve an inventive step (obviousness), and a contention that the claims were, in terms of s 61(1)(f)(i), not clear (ambiguity). The last of these was so faintly urged in this Court that it can be disregarded. MacArthur J, as has been stated, B found against the defendants on all the grounds for revocation and on the issue of infringement.

I turn then to the specification. The general introduction I have given above in relation to shock tubes is also set out, in a broad sense, in the specification. It must be said, however, that the specification is a very terse document C and, as I will show, in a material sense uninformative. In terms of s 32 of the Act a specification must be framed in what is now a conventional manner and the present specification broadly takes this form. (To the extent that it would seem not to do so, no issue was made thereof in the pleadings and such shortcomings are now D irrelevant.) There is a brief discussion in the specification of the prior art as it has been explained. The plastic material produced by Du Pont (a grade of Surlyn) is identified in the specification as a suitable material for the plastic tube. The document then proceeds to discuss the problems said to have been encountered with the prior art products. The object of the invention and a brief consistory clause follow. It will be of assistance if I quote the E specification. It reads:

'It has been found that explosive in powder form which is applied on the inner surface of the plastic tube does not adhere sufficiently firmly to this surface, the explosive powder often becoming dislodged from the inner surface during transport or storage. During handling the powder may form blockages in the tube or fall down into said detonator. If a F shock wave encounters such a blockage it will terminate at this point. If the explosive powder falls down into the detonator, this may be destroyed without effecting the desired ignition of the explosive substance it is intended to cause to explode.

The object of...