Claydon Yield-O-Meter v Mzuri Ltd & Anor

In a patent action, an alleged prior use anticipates an invention if the invention was made available to the public and a skilled observer could have obtained an enabling understanding of the claimed features. The hypothetical observer is limited to lawful public access and information that could realistically have been acquired in the circumstances. The court must consider whether confidentiality, intervention by those controlling the invention, or practical limits on observation would prevent disclosure. A patent claim is construed purposively, including by reference to the function identified in the claim. Where a claim requires alignment to achieve a stated result, alignment may be assessed in use rather than by strict geometric correspondence outside use. Ordinary words such as “governed by” require a controlling influence, not merely one influence among several.

Claydon Yield-O-Meter Limited claimed that Mzuri Limited and its director infringed claims of two agricultural seed-drill patents. Mzuri counterclaimed for revocation. The dispute concerned construction, infringement, prior use, common general knowledge and inventive step.

The first patent required aligned rows of tines which disturbed spaced strips of soil, with lateral wings placing seed beneath the disturbed soil. The second patent concerned independently adjustable digging and seeding depths. The central issues were whether the first patent had been anticipated by testing a prototype on Claydon’s farm, whether either patent involved an inventive step, and whether Mzuri’s Pro-Til drills fell within the claims.

1. Construction of the 296 Patent. “Frame” did not require a single rigid structure. It could include pivoting sub-frames and a pivotally connected towbar. The requirements that components be carried by the frame were linked to the functional purposes stated in the claim. Alignment was assessed in use, by reference to whether the apparatus left spaced strips of undisturbed soil. Seed had to be delivered sufficiently close to the underside of the seeding tines to achieve the claimed covering function. The disturbed and broken-up soil was soil created by the first tines.
2. Infringement. The Pro-Til’s pivoting assemblies did not prevent it having a frame within the claim. Its pivots allowed the required alignment and soil treatment in use. Even on a strict geometric construction, the tines were aligned when the drill was pulled in a straight line. Subject to validity, claim 16 of the 296 Patent was infringed.
3. Prior use and enablement. Under section 2(2) of the Patents Act 1977, the relevant question was whether the invention had been made available to the public before the priority date. The hypothetical skilled observer was confined to lawful access. The disclosure comprised information which such an observer would have noticed or inferred, at the level of generality appearing in the claim. Confidentiality and the likely conduct of persons controlling the invention had to be considered. Technical equipment could in principle assist observation, but the evidence did not establish that such equipment would reasonably have been available or used. Enablement was therefore assessed by naked-eye observation.
4. The prototype could have been observed from the public footpath. A skilled observer could have seen or inferred the relevant construction, including alignment of the tine rows. The 296 Patent therefore lacked novelty through prior use.
5. Inventive step and the 576 Patent. One-pass strip-tillage formed part of the common general knowledge, but claim 16 of the 296 Patent was not obvious over Handy. The 576 Patent was construed so that the depth wheels had to exercise a controlling influence over seeding depth. The Pro-Til did not satisfy that requirement. Claim 1 of the 576 Patent was nevertheless obvious over the Claydon PCT Application, although not shown to be obvious over Handy.
6. The 296 Patent was invalid, though it would have been infringed if valid. The 576 Patent was invalid and not infringed.