Marflow Engineering Ltd v Cassellie Ltd

A patent claim is construed by identifying the ordinary meaning of its integers in the context of the specification. A claimed locking member requiring provision in or on a mounting plate must remain attached to, or form part of, that plate. A pipe may comprise interconnected sections, including an intermediary pipe.

For infringement by an equivalent, the variant must achieve substantially the same result in substantially the same way as the inventive concept. The relevant result is assessed by reference to the invention properly understood, rather than an incorrectly identified disadvantage. A patent may therefore be valid and infringed where the accused product uses a different locking mechanism that nevertheless implements the inventive concept.

Marflow Engineering Limited owned a patent for installing a fluid-using appliance, such as a shower, using a plate fixed to a wall. Pipes pass through apertures in the plate and are locked against axial movement before being joined to the appliance.

Marflow alleged that Cassellie Limited’s shower fixing plate infringed claim 1. Cassellie denied infringement and counterclaimed for revocation on the ground of lack of inventive step over two patent disclosures, Krone and Hubbard. The court determined the construction of “fluid pipe” and “locking member”, validity over the cited prior art, and whether Cassellie’s product was an equivalent falling within the scope of claim 1.

1. Construction. The intermediary pipe in Cassellie’s product formed part of the claim 1 “fluid pipe”, although it connected inside the wall to another pipe section. The claim did not require the fluid pipe to be a single uninterrupted pipe.
2. The locking member had to be provided in or on the mounting member. It could be attached within the aperture, attached elsewhere on the plate, or integral with the plate. This requirement applied both before and after locking. The screw thread on Cassellie’s intermediary pipe was therefore not the locking member, and the nuts were not locking elements on a locking member provided on the plate. Normal construction consequently lacked integers (e) and (g).
3. Validity. Claim 1 involved an inventive step over Krone and Hubbard. Krone did not teach use of a mounting plate and presented technical difficulties when used with one. Hubbard disclosed neither the claimed locking member nor locking element, and it was not obvious to modify Hubbard accordingly. The patent was valid.
4. Equivalence. The inventive concept was using a wall-mounted plate, receiving fluid pipes through apertures, and using locking means to secure the pipes to the plate. It did not include any particular type of locking means. Cassellie’s product achieved the three direct results of the concept in substantially the same way: the pipes were secured to the plate, fixed relative to one another, and extended outwardly through the apertures.
5. The relevant accessible joint was the joint between the pipe and the appliance inlet. That joint remained accessible with Cassellie’s product. The answer to Improver Question 1 was therefore yes. No contrary submission was made on Questions 2 or 3. Cassellie’s product was an equivalent falling within claim 1. The patent was valid and infringed.