Eugen Seitz AG v KHS Corpoplast GmbH & Anor

In a patent validity and infringement action, a prior disclosure is anticipatory only if made available to a person free in law and equity to use it and if it enables the skilled person to reach the invention without undue burden. Obviousness remains a single statutory question. Structured approaches assist that inquiry, but must not become a rigid checklist or permit hindsight. A prior machine showing only partial use of plastics did not make an entirely plastic high-pressure valve piston obvious where the skilled person would regard metal as necessary because of pressure and repeated impact. A claim is construed purposively in context. A technically divided version of the claimed piston may infringe where it performs the same function in substantially the same way. A dependent claim directed to a particular plastic may lack independent validity if the claimed all-plastic piston is obvious, but a dimensional claim remained valid where the prior art used a materially different sealing arrangement.

Seitz sought revocation of a patent jointly owned by KHS and Norgren concerning pneumatic valves in the blowing stations of rotary stretch blow moulding machines. The patent claimed, principally, a control piston made from plastic for high-pressure blowing air, with further claims concerning a shaft cap, PETP and the relative dimensions of the piston shaft and flow path.

Seitz relied on a confidential 1992 fax for novelty and on four linear-machine systems supplied in 2001 for obviousness. It also sought declarations concerning infringement of its proposed valve. The central issues were whether the alleged prior disclosures were available to the public, whether the claims were obvious, how claim 1 should be construed, and whether the proposed valve infringed.

The court rejected the challenges to amended claim 1 on novelty and obviousness, held it valid, and found that the proposed Seitz product infringed. Claim 18 was also valid and infringement was admitted. The court’s conclusions were as follows:

1. Novelty. A disclosure must be made to at least one person free in law and equity to use it, and must disclose the invention so that the skilled person, possessing the common general knowledge, can reach it without undue burden. The 1992 fax was imparted in circumstances importing an obligation of confidence and therefore could not anticipate the patent.
2. Obviousness. The statutory question is whether the invention was obvious to the skilled person. The structured approach in Pozzoli SpA v BDMO SA [2007] FSR 37, as approved in MedImmune v Novartis [2012] EWCA Civ 1234, is useful but does not require slavish application. The ALS 1-4 machines disclosed partial use of plastic in a linear-machine exhaust valve, while leaving the piston shaft and other high-pressure valves substantially metal. In the context of the skilled person’s prejudice that metal was required for the relevant stresses, that disclosure did not make an entirely plastic piston in a rotary machine obvious. The challenge therefore failed.
3. Construction and infringement. Applying the purposive approach under article 69 of the EPC and its Protocol, claim 1 was preferably construed as directed to a directly sealing piston rather than a piston-and-ball valve. Nevertheless, the proposed valve infringed because its separate plastic control piston and check valve operated as a unitary piston and could not avoid the claim merely by dividing the structure into two parts.
4. Other claims. Claim 3 was not infringed because the alleged shaft cap was not a separate cap. Claim 15 would not be independently valid if claim 1 were obvious, since using PET was then not inventive. Claim 18 was valid: the prior art’s piston-and-ball sealing method was materially different, and did not make the claimed dimensional relationship obvious.