Wheatley & Anor v Drillsafe Ltd & Ors

Patent claims must receive a purposive construction which balances fair protection for the patentee with reasonable certainty for third parties. The claim is read through the eyes of the skilled person and in the context of the specification and drawings. The Improver questions are aids to that unitary exercise, not a substitute for construction.

Where the patent’s inventive concept depends on a centre-less cutter making the first penetration, a retractable central probe which makes a blind hole and centres the cutter may fall outside the claim if the specification shows that strict compliance with “centre-less” was intended. Obviousness must be assessed using the structured Windsurfing approach, distinguishing common general knowledge from information merely known or recorded, and avoiding hindsight.

The appellants were the proprietors and exclusive licensees of a patent for forming threaded holes in tank lids without removing the lid. The patent used a combined tap and rotary centre-less hole cutter in an inert atmosphere.

Ferris J held the patent invalid for obviousness and held that the respondents’ method 2, which used a retractable central probe making a blind hole, would not infringe if the patent were valid. The appellants appealed. The respondents supported the validity decision and relied on additional prior art, including the Veeder Root use and a Japanese patent.

The central issues were whether method 2 fell within the construction of “centre-less hole cutter”, and whether the patent involved an inventive step.

1. Disposition. The appeal was allowed in part. The patent was valid, but method 2 did not infringe claims 1 to 5. There was no order for costs in the appeal, and the claimants were awarded 20% of their costs below.
2. Construction. Under section 125 of the Patents Act 1977 and the Protocol on Interpretation of Article 69, claims must be construed between strict literal interpretation and an approach treating claims merely as guidelines. The court must identify the objective meaning intended by the patentee, through the eyes of the skilled addressee and in the context of the specification as a whole.
3. The Improver questions assist that purposive construction. They require consideration of whether the variant materially affects how the invention works, whether that was obvious to the skilled person at the relevant date, and whether the claim nevertheless shows that strict compliance was intended to be essential.
4. Infringement. The majority, per Mance LJ, held that the patent’s inventive concept was first penetration by an annular cutter without a central guiding device. The specification treated the absence of central guidance as part of the invention and addressed the resulting wandering problem through later claims concerning resilient mounting. Method 2’s retractable probe therefore fell outside the intended scope of “centre-less hole cutter”, notwithstanding that it prevented full penetration of the tank.
5. Validity. The court applied the structured approach in Windsurfing. Evidence that a tool or process was known, used, or recorded did not establish that it formed part of common general knowledge. The claimed combination was not shown to be obvious over common general knowledge, the Veeder Root process, or the Japanese patent. The Japanese patent taught lubricant-assisted drilling with a penetrating pilot drill and did not disclose the claimed centre-less cutter or inert gas.

• Court of Appeal (Civil Division): allowed the appeal on validity but dismissed it on infringement of method 2; the order stated that the appeal was allowed in part.
• Chancery Division: Ferris J, on 23 February 1999, held the patent invalid and held that the alleged acts would not have infringed if the patent had been valid.