Amersham Pharmacia Biotech AB v. Amicon Ltd.
Amersham Pharmacia (AP) appealed against a decision holding that its patent for a particular apparatus and method of chromatography had not been infringed by Amicon (A). The object of the invention was to speed up the time taken to remove debris from the inside of chromatography equipment, thereby saving production costs. The apparatus and method patented by AP included a moveable probe, whereas A’s apparatus, which was otherwise very similar, included a stationary probe which had a moveable sleeve.
AP contended that the probe was immaterial to the invention and that a patentee should be protected where the variant was not a material aspect of the invention. A contended that the object of the probe was to break away hardened media from the inside of the apparatus to facilitate reuseability.
Dismissing the appeal, the Court of Appeal held that the moveable probe was material to the invention. The evidence had demonstrated that the different mechanisms of both had the effect of breaking up the hardened media.
The Protocol on the Interpretation of the European Patent Convention 1973 Art.69, incorporated into United Kingdom law by the Patents Act 1977 s.125, did not introduce a doctrine of infringement by equivalent effect. The wording of AP’s patent did not cover the mechanism used by A, and to disregard the wording would contravene the requirement of the Protocol to provide a degree of certainty for third parties. As regards interpretation of patent claims, the Court of Appeal at para 11 observed that-“The court has to take account not only of the words of the claim, but also the description in the specification.”
  EWCA Civ 1042; (2001) 24(12) I.P.D. 24078; Court of Appeal (Civil Division) on 05 July 2001
 (2001) 24(2) I.P.D.24071
 Section 125(1) of the Act states that the invention is that specified in the claims “as interpreted by the description and any drawings contained in that specification, and the extent of protection conferred by a patent or application for a patent shall be determined accordingly.”
 The doctrine of equivalents is a legal rule in most of the world’s patent systems that allows a court to hold a party liable for patent infringement even though the infringing device or process does not fall within the literal scope of a patent claim, but nevertheless is equivalent to the claimed invention.