Lubrizol Corporation & Anor v Esso Petroleum Co Ltd & Ors

Patent claims must be construed purposively from their language read in the context of the specification. Preferred processes and examples cannot be used to impose limitations that the claim does not contain, particularly where the claim is to a product rather than a process. The notional skilled addressee is attributed common general knowledge, not every technique known to some practitioners. A claim is sufficiently defined where the specification teaches a recognised measurement method and reasonable conventional techniques can be used. Obviousness is assessed by identifying the inventive concept, the skilled addressee and common general knowledge, the differences from the prior art, and whether those differences required invention. Commercial supply of a product for prospective sale may constitute non-secret prior use even without a concluded contract. Section 64 of the Patents Act 1977 protects only serious and effective preparations sufficiently advanced to result in the infringing act.

Lubrizol, proprietor and exclusive licensee of a patent for lubricant additives, sued Esso Petroleum, Exxon Chemical and Exxon Corporation for infringement. Exxon denied infringement and counterclaimed for revocation.

Jacob J dismissed the action, held the patent invalid and ordered revocation. The principal issues on appeal concerned the construction of the succinic acylating-agent and molecular-weight limitations, ambiguity and fair basis, obviousness over examples in earlier patents, prior use, and the scope of the section 64 defence.

The Court of Appeal had to determine whether the claims were valid and infringed, whether Exxon’s pre-priority dealings constituted prior use, and whether Exxon had made effective and serious preparations to manufacture.

1. Appeal dismissed. Aldous LJ gave the principal judgment. Brooke LJ agreed with the result and added separate reasoning; Roch LJ agreed.
2. Claim 1 was to be construed as a product claim. The words “said acylating agent(s)” referred to PIBSA, not to the mixture of PIBSA and unreacted PIB. The unreacted PIB was a diluent. The specification and examples could not be used to alter the clear language of the claim or convert it into a process or product-by-process claim. This applied the purposive construction principles in British United Shoe Machinery Company Ltd v A Fussell & Sons Ltd (1908) 25 RPC 631 and Rosedale Associated Manufacturers Ltd v Carlton Tyre Saving Coy Ltd (1960) RPC 59.
3. The figure 1.3 was expressed to two significant figures. The specification directed the skilled reader to determine Mn and Mw by GPC using standard techniques. The absence of instructions for RI correction did not make the claim ambiguous because RI correction was not shown to be common general knowledge. Nor was ambiguity established in relation to calibration methods.
4. The claim was fairly based. It claimed the product described as the invention, and its scope was not defined by preferred process details. It was obvious over example 32 of LeSuer and example 5 of Widmer. Applying the structured approach in Windsurfing International Inc v Tabur Marine (GB) Ltd (1985) RPC 59, the only relevant difference was polydispersity, and use of commercially available PIB within the claimed range required no invention.
5. Exxon proved on the balance of probabilities that Batch Zero fell within claim 1. Its supply to Shell and BP for customer testing was ordinary commercial dealing directed towards a sale and was non-secret prior use under section 32 of the Patents Act 1949. A concluded contract was unnecessary. The court therefore did not need to decide whether the use was solely for reasonable trial or experiment.
6. Section 64 of the Patents Act 1977 would not have provided a defence if the patent had been valid. Effective and serious preparations had to be sufficiently advanced, immediately before the priority date, to be about to result in the infringing act. Preliminary planning, technology transfer and site discussions did not satisfy that requirement.

• Court of Appeal (Civil Division): [1998] EWCA Civ 744. Appeal from the decision of Jacob J dismissing the infringement action, holding the patent invalid and ordering revocation. Appeal dismissed.