destroyed without effecting the desired ignition of the explosive substance it is intended to cause to explode.
The object of the present invention is to prevent there being a sufficient quantity of loose explosive powder inside the plastic
tube to enable plugs of explosive agent to be formed. According to the invention this object can be achieved by using a
plastic tube of sandwichtype. The tube consists of two parts, an outer part and an inner part. The outer part endows the
plastic tube with resistance to external damage and the inner part is provided with an inner surface with such adhesion that
explosive agent applied thereon is dislodged substantially only by a shock wave."
The specification then contains some brief paragraphs amplifying the description of the invention and there follow
details of certain tests performed by the patentee giving the experimental data.
As in all patent actions the first task of the court is to construe the claims in order to ascertain what the invention
is which is claimed. I shall deal presently with the submissions of defendants' counsel in this regard but it will assist
if, before so doing, I recite the main claim (which is all that need be considered) divided for convenience into its
essential integers. It is in the following terms:
(a)
Lowenergy fuse consisting of a plastic tube, the inner surface of which is coated with explosive in powder form,
View Parallel Citation
(b)
characterised in that the plastic tube is of sandwichtype comprising two parts,
(c)
an outer part endowing the plastic tube with resistance to external damage, and
(d)
an inner part the inner surface of which has such adhesion that explosive agent applied thereon is dislodged
substantially only by a shock wave.
Page 458 of [1998] 4 All SA 453 (A)
On the face of it, it is therefore a claim of wide ambit in the sense that it is left to the person skilled in the art to
select, according to his skills and wishes, the grade or type of plastic tube or tubes which are to make up the
"sandwichtype" plastic tube. So too, the core loading (that is the amount of the explosive powder used) is not
quantified and is therefore also a matter of choice. What is of particular importance is that no specific relationship
between the requirements of integers (c) and (d) is specified.
It will have been seen that in setting out the objects of the invention it was said in the body of the specification
that "according to the invention this object (namely the prevention of a sufficient quantity of loose explosive powder
collecting inside the plastic tube to permit plugs of explosive to be formed) can be achieved by using a plastic tube
of sandwichtype". This would suggest that a relationship between the sandwichtype tube to be employed and the
difficulty of ensuring powder adherence was or was going to be proposed. However nothing further in the
specification describes any process or means of achieving this balance. (I should add that even if it had, the claims
could not be affected by this for the reasons I give in dealing with defendants' counsel's main submission.)
Defendants' submission was that the claim was to be construed as being limited to certain powder loadings
mentioned in the body of the specification. This was what counsel termed the "narrow construction". It involved
importing into the claim from the body of the specification particularity as to the powder loadings given in the
experiments. The purpose of this argument was, it is clear, to show that the patent had not been infringed because
these loadings had not been found or used in the tubes alleged to infringe. This submission does not bear scrutiny.
It will, I think, suffice to say that nothing contained in the body of the specification in this regard purports to provide
a dictionary for the claims or even (in a more limited sense) to affect the wording of the claims. To construe the
claims in this way would offend against a fundamental principle of patent law, namely that found in the famous
dictum of Lord Russel in the case of Electrical and Musical Industries v Lissen 56 RPC 23 at 39. It is a rule adopted by
this Court in the case of Power Steel Constructions (Pty) Ltd v African Batignolles Construction Pty Ltd 1955 (4) SA 215
(A) at 224DF. The dictum reads:
"... The claims must undoubtedly be read as part of the entire document, and not as a separate document; but the forbidden
field must be found in the language of the claims and not elsewhere. It is not permissible, in my opinion, by reference to
some language used in the earlier part of the specification, to change a claim which by its own language is a claim for one
subjectmatter into
View Parallel Citation
a claim for another and a different subjectmatter, which is what you do when you alter the boundaries of the forbidden
territory ...
... A claim is a portion of the specification which fulfills a separate and distinct function. It, and it alone, defines the
monopoly; and the patentee is under a statutory obligation to state in the claims clearly and distinctly what is the invention
which he desires to protect."
(See also Gentiruco AG v Firestone SA (Pty) Ltd 1972 (1) SA 589 (A) at 613D618G.)
The only evidence relevant to the construction of the specification was that of Dr Viljoen who explained the nature
and functioning of the patent and the meaning of technical words. What is important is that she said that the
process of coextrusion was simply a means of depositing an outer layer over the chosen
Page 459 of [1998] 4 All SA 453 (A)
inner layer. She thus in effect conceded that no synergy between the outer and inner layer was described or