Brief Summary

Patents — Infringement and validity — Appeal concerning the validity and alleged infringement of South African Letters Patent No 79/3210 for a low-energy fuse — Appellants, manufacturers and customers of shock tubes, contested the patent's validity on grounds of novelty, inventive step, and clarity — Trial court found in favor of the respondent, the patent proprietor, rejecting the defendants' claims — Appeal court upheld the trial court's decision, affirming the patent's validity and the finding of infringement.

Comprehensive Summary

Summary of Judgment

1. Introduction

The proceedings were an appeal to the Supreme Court of Appeal arising from consolidated patent infringement actions and a counterclaim for revocation. The dispute concerned the validity and alleged infringement of South African Letters Patent No 79/3210, granted for an invention described as a “Low-energy fuse consisting of a plastic tube the inner surface of which is coated with explosive in powder form”, commonly referred to in the evidence as a shock tube.

The appellants were Ensign Bickford (South Africa) (Pty) Ltd (first appellant) and two of its customers, Bulk Mining Explosives (Pty) Ltd and Dantex Explosives (Pty) Ltd (second and third appellants). The respondent, AECI Explosives and Chemicals Ltd, was the plaintiff in the infringement actions and the proprietor of the patent by assignment (acquired on 2 April 1992). The first appellant was linked to a United States corporation (Ensign-Bickford (E-B America)) which manufactured the allegedly infringing shock tubes sold locally.

In the court of first instance, McArthur J sitting as Commissioner of Patents found in favour of the plaintiff on both validity and infringement, dismissed the revocation counterclaim, and granted leave to appeal. The appeal thus required the Supreme Court of Appeal to reconsider (i) the proper construction of the principal claim, (ii) whether the patent was liable to revocation on the grounds pursued, and (iii) whether infringement had been established (to the extent that validity remained intact).

The general subject-matter was the patentability and enforceability of a claimed improvement in shock tube technology, specifically a “sandwich-type” plastic tube structure (two layers) said to reduce loose explosive powder inside the tube and to provide resistance to external damage.

2. Material Facts

Shock tubes were used in mining, quarrying, and construction as a safer initiation system than electrical methods or conventional detonation cord. The tubes were approximately 3 millimetres in outside diameter and had their inner wall coated with a fine explosive powder. A shock wave initiated at one end propagated along the tube by progressive detonation of the coating, and a detonator attached by crimping triggered the intended explosion at the far end. The evidence dealt with products using grades of Surlyn tubing (a Du Pont plastic), and it was accepted that Surlyn grades and explosive powders were commercially available.

The patent in suit was granted under the Patents Act 57 of 1978 on a convention application dated 18 June 1979, claiming a priority date of 8 August 1978 based on a Swedish application by the original patentee (Nobel Nitro AB of Sweden). The plaintiff had initially been a licensee and later acquired the patent, apparently for purposes including litigation. The first appellant’s associated entity (E-B America) had earlier been a licensee under a 1971 pioneer patent in the field, and products manufactured under that earlier technology were known as Nonel mono tubes.

The specification described problems encountered in earlier shock tubes, particularly that the explosive powder did not adhere sufficiently to the tube’s inner surface, could become dislodged during transport or storage, could form blockages terminating the shock wave, or could fall into a detonator causing malfunction. The claimed solution, as expressed in the specification, was to use a sandwich-type tube consisting of an outer part providing resistance to external damage and an inner part with an inner surface having such adhesion that explosive powder was dislodged substantially only by a shock wave.

It was common cause in the appeal that the first appellant’s product alleged to infringe was an over-extruded, two-layer (“sandwich-type”) tube (a Surlyn sub-tube with an outer layer such as polyethylene) manufactured by E-B America and supplied to customers, including the other appellants.

On the facts relevant to novelty, it was established that E-B America produced a shock tube known as H D Nonel (“heavy duty”), and that various attempts had been made in the mid-to-late 1970s to improve shock tube characteristics such as waterproofing, tensile strength, and abrasion resistance. These attempts included over-braiding (wrapping with polypropylene yarn) and waxing, as well as over-extrusion experiments, including laboratory tests as early as 1976 in which Surlyn tubing was over-extruded with polyurethane. A construction standard document dated 22 September 1979 relating to manufacture of an over-extruded tube (Surlyn sub-tube over-extruded with polyethylene) was proved.

A critical disputed factual question was whether an over-extruded sandwich-type product had been commercially used or sold before the priority date (8 August 1978), such that the invention had been made available to the public by use or otherwise. The defendants sought to prove such prior commercial exploitation primarily through witness testimony and documentation relating to experimentation and marketing material. The trial court found the defendants had failed to prove prior public availability by sale or use before the priority date, emphasising that despite extensive documentation, no invoice, delivery note, or similar record of pre-priority commercial supply was produced. The Supreme Court of Appeal was not persuaded that this factual finding was wrong.

On the issue of inventiveness, the evidence was limited and not strongly directed to the statutory question. The plaintiff led one witness, Dr Viljoen, who explained technical aspects and conceded that co-extrusion was a means of applying an outer layer over an inner layer, and did not suggest that the patent described a synergistic relationship between the layers. The defendants led, among others, Mr Feasler and Mr Spragg (associated with E-B America’s development history) and Mr Hans Lundborg, one of the inventors, whose evidence addressed the development context and perceived solutions to misfires attributed to powder dislodgment and plugging.

3. Legal Issues

The central legal questions were, first, the proper construction of the main claim and whether it should be read narrowly (by importing specific powder loadings from experimental portions of the specification) or broadly (as a claim of wide ambit defining a two-part sandwich tube with functional characteristics). This was a matter of law (construction), informed by evidence only to the extent necessary to explain technical terms.

Second, the court had to determine whether the patent was invalid for lack of patentability under section 25 of the Patents Act 57 of 1978. The invalidity attacks pursued on appeal were grounded principally in obviousness / lack of inventive step, and to a lesser extent in novelty (anticipation by prior use/sale of alleged prior products). These issues involved applying the statutory legal standard to the facts (an application of law to fact), with evaluative judgment concerning what would have been obvious to a person skilled in the art at the priority date.

Third, infringement was in issue, but it became relevant only if validity survived. The defendants accepted that if the claim were construed broadly, infringement was proved. The dispute about infringement therefore turned materially on claim construction and the consequences of validity.

A pleaded ground that the claims were unclear under section 61(1)(f)(i) was so faintly pursued that the appellate court treated it as negligible.

4. Court’s Reasoning

The court began by emphasising that in patent matters the first task is to construe the claims to identify the invention for which monopoly protection is sought. The main claim was analysed as comprising four essential integers: a low-energy fuse with a plastic tube coated internally with explosive powder; the tube being sandwich-type comprising two parts; an outer part resisting external damage; and an inner part whose inner surface has such adhesion that explosive is dislodged substantially only by a shock wave.

The defendants advanced a “narrow construction” argument seeking to confine the claim by importing into it specific powder loadings mentioned in the experimental data in the body of the specification. The court rejected this as impermissible, relying on the principle that the monopoly is defined by the claims, and that it is not permissible to use language elsewhere in the specification to alter the boundaries of the claim so as to convert it into a claim for different subject-matter. The court treated this principle as settled in authority and applicable on the facts, and it accepted that nothing in the specification purported to define or qualify the claim by acting as a “dictionary” for the claim wording. On this basis, the court adopted the “wide construction”.

A significant consequence followed from this construction. The defendants conceded that, on the wide construction, infringement had been proved. The appeal therefore turned primarily on whether, on that same construction, the patent was vulnerable to revocation.

On novelty, the court considered whether alleged prior products anticipated the invention. It agreed with the court below that the over-braided and over-waxed H D Nonel was not, in any practical understanding, a two-part sandwich tube. The core novelty attack depended on proving that an over-extruded sandwich-type product was marketed or publicly used before the priority date. The appellate court endorsed the trial court’s careful analysis and held that the defendants had not discharged the onus of proving such prior commercial use. The absence of documentary proof of sale or supply (such as invoices or delivery notes) was decisive against the defendants’ attempt to establish prior public availability. Accordingly, the novelty attack failed.

The decisive issue became inventive step (obviousness) under the Patents Act 57 of 1978. The court contrasted the earlier position under the 1952 Act (which focused on “common knowledge in the art”) with the current Act, which frames a statutory code. Under section 25(6), the “state of the art” comprises all matter made available to the public anywhere by written or oral description, by use, or in any other way. Under section 25(10), an invention involves an inventive step if it is not obvious to a person skilled in the art having regard to the relevant state of the art immediately before the priority date.

The court held that once novelty survives, the enquiry into inventive step should proceed in a structured way. It adopted, as a convenient sequence for analysis, the four-step approach articulated in Mölnlycke AB and Another v Procter & Gamble Limited and Others (No 5). This required identifying the inventive step asserted; establishing the relevant state of the art; identifying the respects in which the step differed from the state of the art; and assessing whether that difference would have been obvious to the skilled person.

A substantial part of the appellate court’s reasoning concerned the deficiencies in how the issue of inventiveness had been treated at trial and in the judgment below. The trial court had accepted that there were “obvious ways” to address the known problems (such as requesting a different Surlyn grade, reducing core load, or changing particle size) but nevertheless concluded that the invention in its totality was not obvious, warning against the “armchair critic” and noting that problems must be overcome and integrated to produce a product acceptable in the marketplace. The Supreme Court of Appeal held that this was not the correct focus. It stressed that the question is not whether the alleged invention would have been commercially worthwhile, but whether what is claimed as inventive would have been technically obvious to the skilled person, and that the enquiry must be directed to the claim-defined invention rather than to market integration.

In analysing the evidence, the court emphasised that the primary evidence should ordinarily be expert evidence directed to obviousness against the statutory background, and that secondary evidence (such as commercial success and the length of time spent searching for solutions) can assist but must not displace the primary enquiry. On the record, the court found that the technical evidence was not strongly focused on the claim-based obviousness enquiry. Dr Viljoen’s evidence compared “teachings” of documents rather than analysing obviousness of the claim-defined step, and a statement from a 1990 publication describing bi-laminated tubing as an “obvious method” was not treated as a reliable or properly contextualised basis for deciding inventiveness. Lundborg’s evidence indicated that Nobel had identified the powder-displacement issue as marginal, considered solutions such as reducing core load and changing powder fineness, and turned to a tougher outer layer option; on the court’s assessment, this did not indicate that an inventive step was required.

When pressed in argument to identify the inventive step, the plaintiff’s counsel effectively reduced it to the provision of an abrasion-resistant outer part of a sandwich-type tube. The court treated this as posing a simple enquiry. It reasoned that, on the evidence, it was already known that external protection could be improved by outer wrapping or thickening; it was known how to over-extrude plastic tubes; and over-extrusion was known as a protective technique (including in comparable applications such as detonator cords). On that footing, the court held that the step did not go beyond the state of the art, and that in any event the step would have been obvious to the skilled person, particularly given that the claim left the skilled person to choose and combine plastics to achieve the stated characteristics.

The court therefore held that the patent lacked an inventive step and was liable to revocation. It addressed the possibility of permitting an amendment to save the patent, noting that courts commonly afford such an opportunity, but held that no request for such relief was made and, in any event, amendment was inappropriate because the patent had expired and because the specification’s deficiencies (including the lack of instruction on achieving the balance implicit in the claim’s functional integers) could not readily be cured without introducing new matter (which is not permitted).

Finally, the court declined a request by the appellants for an order allowing qualifying fees of expert witnesses, finding no warrant for such a direction on the nature of the evidence. It also criticised both parties’ heads of argument for excessive length and lack of focused reasoning, referring to its earlier guidance on the function and form of heads of argument.

5. Outcome and Relief

The appeal succeeded. The Supreme Court of Appeal set aside the decision of the Commissioner of Patents and substituted an order dismissing the infringement claim and upholding the counterclaim for revocation.

The court ordered that Patent No 79/3210 is revoked. It further ordered the respondent (plaintiff) to pay the appellants’ costs of appeal, including the costs of two counsel, and in the substituted order similarly awarded costs (including two counsel) in favour of the defendants on the counterclaim.

Cases Cited

Electrical and Musical Industries Limited v Lissen Limited 56 RPC 23.

Power Steel Construction (Pty) Ltd v African Batignilles 1955 (4) SA 215 (A).

Gentiruco AG v Firestone SA (Pty) Ltd 1972 (1) SA 589 (A).

B-M Group (Pty) Ltd v Beecham Group Ltd 1980 (4) SA 536 (A).

Roman Roller CC and Another v Seedmark Holdings (Pty) Ltd [1995] ZASCA 78; 1996 (1) SA 405 (A).

Mölnlycke AB and Another v Procter & Gamble Limited and Others (No 5) [1994] RPC 49 (CA).

Windsurfing International Inc v Tabur Marine (Great Britain) Ltd [1985] RPC 59.

Caterham Car Sales & Coachwork Ltd v Birkin Cars (Pty) Ltd and Another [1998] ZASCA 44; 1998 (3) SA 938 (SCA).

Legislation Cited

Patents Act 57 of 1978, sections 25(1), 25(6), 25(10), 32, 39(6), 51, 61(1)(f)(i), 61(c), and 61(3).

Rules of Court Cited

No rules of court were cited in the judgment.

Held

The principal claim of the patent was construed according to its language and not narrowed by importing experimental limitations from the body of the specification. On that construction, infringement would have been established, but this became immaterial because the patent was held invalid.

The novelty attack based on alleged prior public use or sale of an over-extruded sandwich-type product before the priority date failed on the evidence. The defendants did not prove that such a product had been made available to the public by use or otherwise before 8 August 1978.

The patent was nevertheless revoked because the claimed invention lacked an inventive step under the statutory test. The court held that, having regard to the state of the art, the step relied on as inventive—an outer protective layer conferring resistance to external damage in a sandwich-type shock tube—was obvious to a person skilled in the art at the priority date.

The appeal was upheld with costs (including two counsel), the infringement claim was dismissed, and the counterclaim for revocation succeeded with costs (including two counsel). The patent was revoked, and no opportunity for amendment was afforded, inter alia because the patent had expired and amendment would in any event be problematic.

LEGAL PRINCIPLES

Claim construction is determined by the language of the claims, read as part of the specification, but the boundaries of the monopoly must be found in the claims themselves. It is impermissible to use language in the body of the specification to alter the scope of a claim by importing limitations not expressed in the claim, thereby changing the “forbidden field” defined by the claims.

Under the Patents Act 57 of 1978, the enquiry into inventive step is governed by a statutory framework. The “state of the art” includes all matter made available to the public anywhere by written or oral description, by use, or in any other way, and an invention involves an inventive step only if it is not obvious to a person skilled in the art having regard to that state of the art immediately before the priority date.

A structured approach to obviousness may be adopted by identifying the inventive step said to be involved, identifying the relevant state of the art, determining how the step differs from that state of the art, and then assessing whether the step would have been obvious to the skilled person. The enquiry focuses on the technical obviousness of what is claimed, not on commercial desirability or market acceptance.

Expert evidence is ordinarily central to determining obviousness, while secondary considerations such as commercial success or the length of time taken to arrive at a solution may assist but must remain subordinate to the primary statutory enquiry and should not obscure whether the claimed technical advance was obvious at the priority date.

Ensign Bickford (South Africa) (Pty) Ltd. and Others v AECI Explosives and Chemicals Ltd. (4/95) [1998] ZASCA 73; 1999 (1) SA 70 (SCA); [1998] 4 All SA 453 (A) (21 September 1998)