Burton Parsons v.
copyright 1997 Donald M. Cameron, Aird & Berlis
Burton Parson patented a cream for use on electrocardiogram pads. The cream was conductive because it contained a highly ionizable salt.
Hewlett Packard attacked the patent on the basis of "inutility", arguing that the claim included embodiments which could harm the skin.
At p. 104:
A claim should be given a common sense interpretation that would be given it by a skilled worker in the art, knowing what should or should not be used to achieve the desired purpose.
"With respect, I cannot agree that claim 17 is invalid because the words "compatible with normal skin" are found before "comprising" instead of after so that it would be valid, it seems, if the words were rearranged as follows:
17. An electrocardiograph cream for use with skin contact electrodes comprising a stable aqueous emulsion that is anionic, cationic or non-ionic, containing sufficient highly ionizable salt to provide good electrical conductivity and compatible with normal skin.
In my view, the rights of patentees should not be defeated by such technicalities. While the construction of a patent is for the Court, like that of any legal document, it is however to be done on the basis that the addressee is a man skilled in the art and the knowledge such a man is expected to possess is to be taken into consideration. To such a man it must be obvious that a cream for use with skin contact electrodes is not to be made up with ingredients that are toxic or irritating or are apt to stain or discolour the skin. The man skilled in the art will just as well appreciate this necessity if the cream to be made is described as "compatible with normal skin" as if it is described as containing only ingredients compatible with normal skin. The situation here is completely unlike that in either the Minerals Separation case or in Société des Usines Chimiques Rhône-Poulenc et al. v. Jules R Gilbert Ltd. et al. (1968), 55 C.P.R. 207, 69 D.L.R. (2d) 353,  S.C.R. 950. In those cases the object of the patent was some substances of a definite chemical composition: xanthates in the first, substituted diamines in the second. Unfortunately for the patentees, the claims covered at the same time some xanthates which would not yield the desirable result in one use, and, in the other, some isomers which would not be therapeutically valuable. This is what was held fatal to the validity of the patents."
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