Page 546 of [1999] 2 All SA 543 (A)
(iv)
A second bag which is made from a reinforced flexible material in which the envelope is located and
(v)
A filler arrangement which is attached to and opens into the first bag and passes through apertures in the envelope
and second bag."
It is integer (iv) that gives rise to the debate.
The respondent's product is very similar to the patented product. It is stated in the answering affidavits that
respondent was engaged in 1989 in development work on, initially, weeping bags but later also on nonweeping
bags. Tests conducted by it established that the pressures applied to the nonweeping bags were of such an order
that the bags were unable to withstand the loading. They required some form of transverse securement. What
respondent's witness says is that respondent then attempted to provide this securement by putting the bag into a
restraining sleeve. It was found that the bag when so reinforced worked well and the sleeve assisted in restraining
the tendency of the folded over flaps of the bag to pull away and open the bag up. This had been a major problem.
What respondent manufactured at relevant times was a bag reinforced in this manner that is by the addition of a
restraining sleeve to provide the necessary resistance or strength. It is common cause that respondent's bag
exhibits the features of all the integers of the main
View Parallel Citation
claim other than integer (iv). It is asserted by respondent that its bag avoids the extra material and labour
required to form a second full bag around the composite inner bag as in the patent. It therefore does not contain
integer (iv) and, accordingly, does not infringe.
The first task of the court is to construe the claim. When the meaning of the claim has been determined the
alleged infringing article is to be compared therewith. What must be shown is that all of the features or limitations
of the claim are present. Appellants' contention is that respondent's bag consists of a "bladder" of an impervious
plastic material (which is said to constitute the first bag of the claim), a "casing" (which is said to constitute the
envelope of the claim) and a "sheath" (which is said to "correspond" to the second bag). The case then turns on a
short point of construction namely whether the sleeve of respondent's bag is a second bag, as that expression is
used in the claims of the patent.
The correct approach to the interpretation of a patent specification is a topic adverted to in almost every
reported decision in patent law. But one need go no further than the careful examination of the problem in
Gentiruco AG v Firestone SA (Pty) Ltd 1972 (1) SA 589 (A) at 613D618G. Appellants' counsel, however, sought to
invoke as an aid to the interpretation of the claim the principle known as "purposive construction". For this reason a
brief word must be said with regard to that proposition. The epithetladen term "purposive construction" derives
from Lord Diplock's speech in Catnic Components Limited and another v Hill and Smith Limited [1982] RPC 183 (HL). It
has been invoked in this Court in the field of patent law inter alia in Multotec Manufacturing (Pty) Ltd v Screenex Wire
Weaving Manufacturers (Pty) Ltd 1 9 8 3 ( 1 ) S A 7 0 9 ( A ) ; Selas Corporation of America v Electric Furnace Co
1983 (1) SA 1043 (A); Stauffer Chemical Co and another v Safsan Marketing and Distribution Co (Pty) Ltd and others
1987 (2) SA 331 (A) and Sappi Fine Papers (Pty) Ltd v ICI Canada Inc 1992 (3) SA 306 (A). The concept of a purposive
construction was used as an interpretive aid in these cases in different ways. In some it is employed as a phrase of
general application in the construction of claims connoting an approach based upon the skilled addressee's
knowledge of the art (as opposed to a purely verbal analysis). In others (as for example in the Multotec case, supra)
it is invoked as an interpretive
Page 547 of [1999] 2 All SA 543 (A)
aid where the alleged infringer was considered to have appropriated what has been called the "pith and marrow"
of the invention and merely substituted a mechanical equivalent for an inessential part. There is in fact no room for
its application in the present case but it is necessary to point out that in all of the above cases the court was
concerned to establish whether the particular features of the claimed invention taken by the alleged infringer
represented all the essential features of the claim.
This, in the final analysis, remains a pure question of construction. In the Catnic case Lord Diplock, after noting
that a patent specification is "a unilateral statement by a patentee in words of his own choosing" addressed to
persons skilled in the art went on to say (at 243):
"A patent specification should be given a purposive construction rather than a purely literal one derived from applying to it
the kind of meticulous verbal
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analysis in which lawyers are too often tempted by their training to indulge. The question in each case is: whether persons
with practical knowledge and experience of the kind of work in which the invention was intended to be used, would
understand that strict compliance with a particular descriptive word or phrase appearing in a claim was intended by the
patentee to be an essential requirement of the invention so that any variant would fall outside the monopoly claimed, even
though it could have no material effect upon the way the invention worked."
How this proposal is implemented is discussed below. What should first be noted is that in the Catnic case too the
ultimate question was one of construction. This is explained in a careful analysis of Lord Diplock's test (in the Catnic
case) by Hoffman J in Improver Corporation and others v Remington Consumer Products Limited and others FSR [1990]