Filta-Matix (Pty) Ltd v Freudenberg and Others

• Jurisdiction: South Africa
• Judge: Harms JA, F H Grosskopf JA, Harms JA, Marais JA, Schutz JA
• Judgment Date: 27 November 1997
• Citation: 1998 (1) SA 606 (SCA)
• Docket Number: 258/96
• Counsel: ABS Franklin for the appellant P Ginsburg (with him C J Van Der Westhuizen) or the respondents
• Court: Supreme Court of Appeal

Harms JA:

This appeal concerns the validity and infringement of patent 76/5566. The patent, entitled 'A Gas Filter Element', belongs to the first respondent, and the second and third I respondents are registered licensees under the patent by virtue of which they could join as plaintiffs in an infringement action. The appellant, the defendant before the Court of the Commissioner of Patents (MacArthur J), admitted that it had copied the commercial product made and sold by the plaintiffs, but denied infringement of the patent. In addition, it counterclaimed for revocation of the patent on several grounds of alleged invalidity. MacArthur J found in favour of the plaintiffs on all aspects of the case, issued an interdict J

Harms JA

and ordered an enquiry into the damages suffered. He granted leave to appeal to this Court. A For the sake of convenience I shall refer to the respondents simply as 'the patentee'.

The patent was granted pursuant to a convention application first filed in Germany on 17 September 1975. That is the effective date of the patent - the date on which its validity has to B be decided. The initial term of the patent was 16 years, which was extended for a further five years. The validity of the patent is to be judged in terms of the repealed Patents Act 37 of 1952. (See s 3(1) of the Patents Act 57 of 1978.) Judgment was given in the Court below on 12 March 1996 and the patent lapsed on 16 September 1996. C

The specification

What follows is a discussion of the more pertinent statements in the specification.

Gas filter elements are employed for separating particles (such as dust) that are in suspension D in a gas (for instance air) from the gas in, for example, ventilating systems.

High surface filter units consisting of sets of filters of mats of fleece material installed in rigid supporting screen structures were known. The mats were in a V-shape, presumably to increase the surface area of the filter because the greater the surface area the better the filtering E properties of the element. These filters were highly effective but had several disadvantages, being uneconomical, difficult to replace and giving problems in controlling the dust proof connection.

Units similar in shape but without rigid supporting screens were also known though not widely F used because of other inadequacies. Their filter pockets were made from glass fibre or textile fibre and sewed, glued or spot welded. These operations are labour intensive and expensive. The individual filter pockets bulge under operational conditions, resulting in uneven flow conditions and allowing the pockets to touch each other, thus impairing their filtering efficiency. Fluttering motions occur causing unsatisfactory performance and damage to the G pockets because of the loosening of fibres. Spacers were used to prevent bulging but the known method of fixing these was time-consuming and caused a reduction of the active filter surface.

Against this background the specification sets out the object of the invention in what can be called the promissory clause: H

'The object of this invention is to provide a pocket filter element which attains the performances of rigid high surface filters as regards the degree of dust separation and dust storage capability while avoiding the aforementioned disadvantages.'

The so-called consistory clause follows:

'This object is achieved according to the invention by a gas filter element comprising a supporting I frame and a plurality of wedge-shaped filter pockets undetachably connected with this frame, and characterised in that the pockets are of a suitable filtering medium and have self-supporting properties provided by a continuous, edge-trimmed weld and spacer elements secured to the filter medium in the air flow direction and, if desired, by additional welded stiffening zones, and that the edges approached by the air flow are continuously and J

Harms JA

undetachably connected with the supporting frame which is made of a hard foamed material and A is connected directly with the filtering medium by a foaming process.'

The specification explains the invention with reference to two drawings and concludes with a more specific promise:

'The advantages achieved by the filter element according to the invention reside especially in the B fact that by its application the filter can be rapidly exchanged, even by untrained labour, while ensuring that break through places of dust are avoided. The filter pockets do not tend to flutter and the filter element achieves the performance of rigid high surface filters as regards its dust separation and storage.'

There are five claims. Claim 1 conforms with the consistory clause. In the quotation that C follows the numerals in brackets (according to the German tradition of claim drafting) are references to the drawings. The enumeration by way of letters represents the division of the claim into integers proposed by the parties and adopted by the Court a quo. The claim D reads:

'1(a) A gas filter element

(b)

comprising a supporting frame (2) and

(c)

a plurality of wedge-shaped filter pockets (1)

(d)

undetachably connected with the frame, characterised in that

(e)

the pockets are of a suitable filtering medium and E

(f)

have self-supporting properties

(g)

provided by a continuous edge trimmed weld (3) and

(h)

spacer elements (4,6)

(i)

secured to the filter medium in the air flow direction,

(j)

and, if desired, by additional welded stiffening zones (7),

(k)

and that the edges approached by the air flow are continuously and undetachably connected F with the supporting frame

(l)

which is made of a hard foamed material

(m)

and is connected directly with the filtering medium by a foaming process.'

I do not propose to deal with claims 2, 3 and 4 because they are dependent upon and G narrower than claim 1 and therefore do not contribute to the resolution of any issue on appeal. Claim 5 should be mentioned. It is a so-called omnibus claim and claims:

'5. A gas filter element, substantially as described herein with reference to the accompanying drawings.'

The description of the invention with reference to the drawings differs from the description of H the invention in the consistory clause but these differences need not be dealt with at this stage of the judgment.

Reverting to claim 1, the meaning of 'self-supporting' was the subject of much evidence and debate because of its importance for the decision on both infringement and invalidity. It is an ordinary English word with no special or technical meaning. Evidence, expert or otherwise, is I impermissible to explain it. According to The Shorter Oxford English Dictionary it means '(of a physical object) not requiring the usual support'. 'Support' has many shades of meaning but in the context of the invention the following are apposite:

'1. To bear the weight of, especially from below. 2. To hold in position; prevent from falling, sinking or slipping. 3. To be capable of bearing; withstand.' J

Harms JA

(American Heritage Dictionary sv 'support'.) No inconsistencies exist between the wording A of the specification and these definitions and if it be borne in mind that support can be vertical or lateral, more need not be said about the meaning of 'self-supporting'.

Another term in claim 1 that conveniently can be dealt with at this stage is to be found in B integer (j). That integer states that the self-supporting properties may be provided by additional welded stiffening zones 'if desired'. The appellant's case is that because of these words the claim does not sufficiently and clearly define the subject-matter for which protection is claimed and is for that reason invalid. MacArthur J held that the effect of the option given by C the words is to reduce integer (j) to an inessential integer. The result of his finding is that the monopoly covers not only a filter with, but also one without, additional welded stiffening zones. Put differently, the claim can be divided notionally into two claims. Mr Franklin for the appellant attacked the finding and relied upon the reasoning of Van Dijkhorst J in Ian D Fraser-Johnston v G I Marketing CC 1993 BP 461 (CCP) at 477F--G. He held that an integer in a dependent claim which is 'preferably provided' renders the claim unclear because one does not know whether the integer is part of the claim. (This judgment was confirmed on appeal, but the finding on this aspect of invalidity was not in issue: G I Marketing CC v Fraser-Johnston 1996 (1) SA 939 (A) at 942F--G.) E

There is little, if anything, to be gained by comparing the use of similar terms in different contexts to find the meaning or effect of one of them. Nor is there any justification for enquiring whether Van Dijkhorst J's judgment was, in the circumstances of that case, correct or not. The F question remains whether integer (j) renders this claim uncertain or unclear. In my judgment it does not and I fully agree with MacArthur J that the formulation used merely indicates that the integer is inessential in the sense described.

Infringement

To prove infringement, the patentee relied upon the evidence of Mr Reuvers, who said that he G found all the integers of claim 1 in the appellant's product. I have already mentioned that the appellant admitted that it had copied the patentee's commercial product. The appellant sought to establish that neither its product nor that of the patentee fell within the scope of claim 1 H because, so it was said, the self-supporting properties of both filters were derived from the nature of the filtering material and not from the weld (integer (g)) or the spacer elements (integer (h)). To establish the proposition and to gainsay Reuvers' evidence, the appellant relied upon...