Multotec Manufacturing (Pty) Ltd v Screenex Wire Weaving Manufacturers (Pty) Ltd

• Jurisdiction: South Africa
• Judge: Corbett JA, Miller JA, Trengove JA, Viljoen JA and Galgut AJA
• Judgment Date: 09 November 1982
• Citation: 1983 (1) SA 709 (A)
• Hearing Date: 16 September 1982
• Court: Appellate Division

Corbett JA:

Respondent is the registered proprietor of South African patent No 73/5815. The patent covers an invention relating to "improvements in or relating to the separation of particulate material" and in particular to "a screening element, a mould for making a screening element, and a screen A for screening particulate material".

In June 1978 respondent instituted action against appellant in the Court of the Commissioner of Patents alleging that appellant had infringed its patent and claiming an interdict, delivery up of infringing material, an inquiry as to damages and costs. Appellant defended the action. In its plea it denied B infringement and alleged that, in any event, the patent was invalid on the grounds of lack of novelty and obviousness. It counterclaimed for the revocation of the patent. The action was heard by NICHOLAS J. He held that the patent had been infringed, but that it was invalid in that three of the claims in the specification, ie claims 26,27 and 28 (not relied upon by respondent in the infringement action), related to a device C which was obvious. The allegation by appellant that these claims were invalid for lack of novelty was rejected. The Commissioner accordingly (a) granted an interdict restraining appellant from infringing respondent's patent, apart from claims 26,27 and 28; (b) ordered that, if respondent did not within four months of the date of the delivery of the judgment D initiate proceedings for the amendment of the patent so as to cure the invalidity thereof or if, having initiated such proceedings, respondent did not proceed therewith with due diligence and expedition or if such an amendment was refused by the Court, leave was granted to appellant to apply on notice for discharge of the interdict; (c) made an order for the delivery up of all appellant's devices and sales material which E infringed the patent (other than claims 26,27 and 28); (d) postponed the action in so far as it related to an inquiry as to damages and gave directions in regard thereto; (e) ordered the revocation of the patent, but suspended the operation of this order pending the decision of the application for F amendment and directed that the order would lapse in the event of the amendment being granted; and (f) ordered appellant to pay three-quarters of respondent's costs in convention and reconvention, and respondent to pay one-quarter of appellant's costs in convention and reconvention. The judgment of NICHOLAS J has been reported in Burrell's Patent Law Reports (see vol 8 at 53).

G Appellant appealed to the Transvaal Provincial Division ("TPD") against those parts of the order granted by NICHOLAS J listed in (a), (b), (c), (d) and (f) above, ie the whole order, save for the order for revocation of the patent, and also against the Commissioner's dismissal on the ground of invalidity based on lack of novelty. Respondent crossappealed in effect against H the Court's finding of invalidity, against the provisions in the orders consequential thereon and against the order as to costs. The TPD dismissed both the appeal and the cross-appeal with costs, but directed that the four-month period for the commencement of proceedings for the amendment of the patent was to run as from the date of delivery of its (the TPD's) judgment. This judgment has also been reported (see vol 8 Burrell's Patent Reports at 319). Leave to appeal and cross-appeal having been granted by the Court

Corbett JA

a quo, the matter now comes before this Court on the same issues as were canvassed in the two Courts below. It will be convenient to deal with these issues in the logical order in which they arise, viz infringement, invalidity on the ground of A lack of novelty and invalidity on the ground of obviousness, rather than to dissect the case into the appeal and cross-appeal. But before I come to these issues it is necessary to say something about the patent No 73/5815.

The Patent

The invention which is the subject-matter of patent No 73/5815 B relates, as I have indicated, to improvements in the separation of particulate material (ie material in particle form) and, more particularly, to a screening element, a mould for making a screening element and a screen for screening particulate material. The separation (or "screening") of C particulate material is an important stage in the process known as "ore dressing". Ore, which, for example, is mined underground, is delivered to the surface in a coarse state and the material has to be comminuted (or crushed) in order to be processed. The crushing often takes place in stages and after each crushing the material is conveyed to a screening station, where material of a certain size will be drawn off and only the D oversize material sent through to the following crushing stage. At the screening station the material is passed over a large perforated screen, which is usually designed to vibrate during the screening process. The screen operates like a sieve and separates out the particles which are smaller than aperture size and which, therefore, pass through the screen, from those E which are larger than aperture size and do not. The oversize material is then taken off in one direction, usually for further crushing, and the fine material in another direction for further processing. Apart from ore dressing, such screens are also used in the preparation of furnace burdens, road metal and concrete aggregates.

F Screening machines, as known to the art at the time when respondent patented its invention, are described by the Commissioner in his judgment as follows:

"Screening machines are of various types. The screen with which the patent in suit is concerned is known as a vibrating screen. This type of screen may be set at an angle or horizontally. It consists of a frame to which a reciprocating motion is imparted. Upon the frame is placed a 'screen deck' or 'cloth' G which is normally constructed in sections (also referred to as 'elements', 'panels' or 'modules'). Such sections have apertures, which permit undersized particles to pass through and oversized particles to pass on to a further milling stage. Sections may be constructed of one of a variety of materials, eg grizzly bars, cast steel plates, perforated steel plates, reinforced rubber, and woven wire mesh. In the case of screens H constructed of some of these materials, it is neither necessary nor possible to tension or stretch the screen deck. In the case of screens constructed from other materials (eg where reinforced rubber or woven wire mesh is used) it is necessary that it be tensioned or stretched and attached to the frame by means of clamping plates and tightening bolts. The tensioning devices are primarily concerned with securing the 'cloth' to the frame in such a way that it is laterally tensioned and, more importantly, vertically tensioned, because the forces acting on the cloth act largely in a vertical direction. This vertical component is obtained by arching the screen by the use of so-called bucker-up plates placed under it.

Screening machines with tensioned sections require regular maintenance,

Corbett JA

including regular tightening of the tensioning devices, without which the sections become loose, and 'whipping' results, with a consequent wearing out of the screen deck at an excessive rate."

This summary of the position is fully supported by the evidence. It was quoted, with approval, by the Full Bench of A the TPD and was not challenged before us.

The invention in suit was designed to overcome certain problems encountered in the operation of such screening machines. These problems, as described in the body of the specification, are the following:

(1) Wear and tear

B It is stated in the specification that it is known that screens used for screening ore in mining operations are provided in separate sections (ie panels) secured to a supporting frame. Due to the problem of properly tensioning these sections, they are of relatively large sizes, eg 180 cm x 120 cm. If a part of a section becomes worn or damaged, then, even though the worn C or damaged part may constitute a small area of the entire screen section, the entire section must be replaced. This results in a waste of material and tends to increase the cost of the operation.

(2) Varying sizes of frames

Sizes of vibratory frames tend to vary from customer to D customer, with the result that a manufacturer is forced to manufacture and maintain in stock a range of screen sections of different sizes in order to be able to satisfy his different customers.

(3) Obstruction by securing devices

Some of the known methods of securing the screen sections to E the supporting frame tend to obstruct a relatively large part of the screen section, thereby resulting in a relatively smaller portion of the screen section being available to screen the particulate material. This also necessitates the individual screen sections being relatively large.

The invention seeks to overcome these problems by providing what counsel described as "modular" screen panels of relatively F small size which can be easily affixed to (and removed from) a support frame. The essence of the invention is described in the specification as follows:

"According to the invention there is provided a screening element comprising a panel having screening apertures and G having protrusions spaced along the peripheral region of the panel and being directed transversely to the panel, the panel and the protrusions being of a synthetic plastics material, the protrusions being adapted to engage with a support frame to thereby secure the screening element onto the support frame in a tensioned state. The protrusions may be adapted to clip into corresponding openings provided in the support frame."

Also according to the invention there is provided a mould for H making the screening element according to the invention...