De Beers Industrial Diamond Division (Pty) Ltd v General Electric Company

• Jurisdiction: South Africa
• Judge: Corbett JA, Hefer JA, Nestadt JA, Kumleben JA and Boshoff AJA
• Judgment Date: 30 August 1988
• Citation: 1988 (4) SA 886 (A)
• Hearing Date: 09 May 1988
• Court: Appellate Division

Corbett JA:

The respondent, the General Electric Company, of Schenectady, State of New York, United States of America, is the patentee of South African patent No 78/7060, a convention patent, entitled 'Composite compact components fabricated with high temperature D filler metal and method of making same'. The patent application was filed with the Registrar of Patents on 18 December 1978 and the patent was granted with 10 January 1978 as the effective date, being the date upon which application for the protection of invention was made in the convention country, viz the United States of America.

E In March 1982 appellant, De Beers Industrial Diamond Division (Pty) Ltd, made application for the revocation of patent No 78/7060 upon the grounds that the invention was not new, that it was obvious, that the claims of the complete specification did not sufficiently and clearly define the subject-matter for which protection was claimed and that the complete specification did not fully describe and ascertain the F invention and the manner in which it was to be performed. Respondent filed a counter-statement to this application in which it, in a special plea, referred to a simultaneously filed application for the amendment in various respects of the complete specification of patent No 78/7060, which amendment, it averred, would have a material effect upon the issues raised in the appellant's a revocation application, and prayed G that the latter application be stayed in terms of s 51(9) of the Patents Act 57 of 1978 ('the 1978 Act').

The application for amendment was opposed by appellant, which filed its answering evidence in the form of an affidavit by Dr R J Caveney, an expert in the scientific field to which the invention claimed in patent H No 78/7060 relates. In his affidavit Dr Caveney averred (and sought to substantiate these averments) that the proposed amendments conflicted with the provisions of s 51(6) and (7) of the 1978 Act and would also not cure either the ground of revocation based upon lack of novelty contending that the claims of the complete specification did not sufficiently and clearly define the subject-matter for which protection was sought. Dr Caveney did not traverse the other grounds of revocation I since (according to him) he had been advised that this would more appropriately be done in the application for revocation itself. In reply respondent filed an affidavit by its expert, Mr H P Bovenkerk. In this affidavit Mr Bovenkerk gave respondent's answers to the averments made by Dr Caveney and, in respect of certain of them, stated that in order J to limit the

Corbett JA

A issues in the application for amendment respondent was prepared, by way of alternative relief, to apply for certain alternative amendments. The original notice of motion was thereafter amended to include these alternative amendments. This provoked a further affidavit from Dr Caveney, criticising the alternative amendments on various grounds and contending that they were in conflict with the provisions of s 51(6) of B the 1978 Act or, alternatively, rendered claim 1 of the specification ambiguous. In answer to these criticisms respondent filed a further affidavit from Mr Bovenkerk.

The application for amendment was heard by Van Zyl J, sitting as Commissioner in the Court of the Commissioner of Patents. At the hearing C respondent abandoned the original application for amendment and pursued only the application for the alternative amendments. The application was opposed by appellant. Van Zyl J granted the application and ordered appellant to pay the costs occasioned by its opposition. An appeal by appellant to the Full Bench of the Transvaal Provincial Division ('the TPD') was dismissed with costs. The judgment of the TPD has been D reported (see De Beers Industrial Diamond Division (Pty) Ltd v General Electric Company 1987 (4) SA 362 (T)). Appellant now appeals to this Court.

The invention disclosed by the complete specification of patent No 78/7060 relates to components consisting of what are termed 'abrasive E compacts', which are used in wire dies, wear surfaces, rock-cutting and drilling equipment and cutting tools for machining. According to the body of the specification, the area of 'primary interest' for the invention is in components useful as cutters for rock-drilling bits and techniques for the fabrication of such components. The specification uses two terms in relation to compacts, viz 'cluster compact' and F 'composite compact'. These are defined. A cluster compact is stated to be

'... a cluster of abrasive particles bonded together either (1) in a self-bonded relationship, (2) by means of a bonding medium disposed between the crystals, or (3) by means of some combination of (1) and (2)'.

A composite compact is defined by the specification, in its original G form, as

'a cluster compact bonded to a substrate material such as cemented tungsten carbide. A bond to the substrate can be formed either during or subsequent to the formation of the cluster compact'.

In both these definitions there is, in addition, reference to H disclosures in certain United States patents, which are said to be incorporated by reference in the specification; but more of this anon.

The specification further discloses that conventional rotary drill bits have until now used as cutting elements steel teeth, steel teeth laminated with tungsten carbide, an insert of cemented tungsten carbide or natural diamonds, all of which are set or moulded in a tungsten I carbide crown. Due to the relatively short life and/or high operating cost of these conventional designs, it has recently been proposed to use synthetic diamond composite compacts as the cutting element in such drills.

The specification goes on to explain that in adapting composite compacts to certain drill bit applications, it has been found to be desirable to provide an elongated base or support for the composite J compact to aid

Corbett JA

A attachment in the drill crown. While it is technically feasible to form an integral composite compact of an adequate length directly under high temperature and pressure (and here the specification makes reference to the disclosures in another United States patent), this has not been adopted commercially because of the significantly increased cost of manufacture. One method of avoiding this added cost is to braze an B additional length of cemented carbide to the carbide base of the composite compact (and here again reference is made to what is disclosed in certain United States patents). Where this has been done, field tests have revealed a problem in that the stresses on each cutting element encountered in rock-drilling are severe and some 'disattachment' of the cutters has been experienced because the bond strength of the components C which have been thus brazed together is not strong enough to withstand these stresses.

At this point I should digress to state that in the specification 'brazing' is defined as

'... a group of welding processes wherein coalescense is produced by heating to suitable temperatures above 800 ̊F and by using a brazing D filler metal having a melting point below that of the base metals. The filler metal is distributed between the closely fitted surfaces of the joint by capillary action.'

Reverting to designs whereby additional lengths of cemented carbide are brazed to the carbide base of the composite compact, I note that the specification states that in these designs available attachment E techniques and acceptable brazing filler metals for use with a diamond composite compact - 'made in accordance with the teaching' of United States patent No 3 745 623 - are limited because the diamond layer of such compacts is thermally degraded at temperatures above approximately 700 ̊C. Similarly it has been found that a cubic boron nitride composite F compact - 'made in accordance with the teaching of' United States patent No 3 743 489 - is also thermally degraded at temperatures above approximately 700 ̊C. Because of the thermal degradation problem, it has been necessary to use brazing filler metals with a liquidus (meaning, in lay terms, melting point) below 700 ̊C. Such metals form braze joints generally of lower strength than braze filler metals having a higher G liquidus. Moreover, even when metals having a lower liquidus are used temperatures approaching those at which the diamond layer is degraded are required, resulting in great care having to be exercised to prevent degradation of the compact during brazing.

H With this introduction the specification then proceeds to describe the invention. The objects of the invention are stated as follows:

'Accordingly, it is an object of this invention to provide improved and stronger components comprised of composite compacts.

Another object of this invention is to provide an improved cutter component for drill bits.

I Another object of this invention is to provide an improved fabrication techique for forming high strength bonds to composite compacts without degrading the particulate layer of the composite compact.

Another object of this invention is to provide an improved fabrication technique for forming a high strength bond between a composite compact J and cemented carbide pin in the fabrication of cutters for drill bits.

Corbett JA

A Another object of this invention is to provide improved techniques whereby small composite compacts produced by an expensive high temperature, high pressure process can be dimensionally scaled up to larger sizes permitting easier attachment of the compact to a tool body.'

Under the heading 'Summary of the Invention' the invention itself is thus described: B

'These and other objects of the invention are accomplished by a component comprised of a composite compact bonded to a substrate with a high temperature filler metal which, to...