Construction and Infringement Flashcards
Catnic Components Ltd.
v
Hill & Smith Ltd.
(1982)
PURPOSIVE CONSTRUCTION
Facts
The Catnic patent called for a lintel (the bar that goes across the top of a window to carry the weight of the bricks laid above it) to have a rear member which should “extend vertically”.
Hill copied the Catnic design, then after receiving a writ from Catnic, changed the design so that the rear member was inclined 6 or 8 degrees from the vertical. This resulted in the Hill lintels being 0.6 or 1.2 per cent weaker in their load bearing capacities. Functionally, this was a negligible difference.
Legal Principle
The House of Lords had to decide whether a claim that specified that the rear support be vertical encompassed a lintel whose rear support was not precisely vertical.
While a literal reading of the claims would have limited the claimant’s patent to lintels at 90 degrees (an thus to a finding of non-infringement), Lord Diplock said that the patent ought to be construed purposively. A purposive interpretation demands that the claims be read through the eyes of the person skilled in the art, and that the purpose or function of the invention be borne in mind when the patent is interpreted.
On reading the patent, it was decided that the person skilled in the art would have understood that the reason why the patent specified that the rear support member was to be “vertical” related to the load-bearing capacity of the lintel. An important factor in the finding that the patent had been infringed was that a 6-degree movement away from 90 degrees only led to a 0.6% reduction in the load-bearing capacity of the lintel. This meant that the defendant’s lintel effectively performed the same purpose or function as the claimant’s lintel.
Purposive interpretation vs. Scope
It is often assumed that purposive construction offers greater protection to patentees than a more literal reading of the claims may provide and, in turn, that the two styles of interpretation are opposites. However, this is not necessarily the case. The reason for this is that while the use of a purposive style of interpretation often means than the scope of the monopoly is broader than that which would arise if the claims were interpreted literally, purposive interpretation does not necessarily require that the claims be read broadly or indeed in the patentee’s favour. All that the purposive approach requires is that the court interpret patents through the eyes of the person skilled in the art, while taking into account the purpose of the invention. Nothing more, nothing less.
Improver Corp
v
Remington Consumer Products Ltd
(1990)
REFORMULATION OF CATNIC: 3 PART TEST
The Catnic Decision
The earlier case of Catnic Components Ltd. v Hill & Smith Ltd., Lord Diplock had established the principle that patents were to be read in a “purposive” manner. The question to be answered in establishing infringement, as formulated by Lord Diplock, was a complex, multi-part enquiry.
The Improver Questions
In the Improver case, Mr Justice Hoffmann (as he then was), on behalf of the Patents Court, reformulated the test as a series of three questions to establish whether a variant (alleged infringing article) infringes the claims of a patent. The variant will not infringe if any of the following are true:
- *(i)** The variant has a material effect on the way the invention works.
- *(ii)** The fact that the variant has no material effect on the way the invention works would not have been obvious to an expert in the field.
- *(iii)** That an expert in the field would have taken from the language used in the patent that strict compliance with the primary meaning was an essential requirement of the invention.
Facts and findings
In the Improver case, the patent covered a depilatory device having a curved “helical spring” driven by a motor. The spring when rotated gripped hairs between its coils and plucked them from the skin. The alleged infringement replaced the spring with a rubber rod having slits in its surface. The question was whether the slitted rubber rod was “a helical spring”. The judge answered the three questions as follows:
(i) the change to a rubber rod had no material effect on the way the invention worked; and
(ii) it would have been obvious to an expert that the rubber rod would work in the same way; but
(iii) the expert would have understood from the patent that the patentee meant to confine his claim to a “helical spring”, in its primary meaning and not in a wide generic sense. For this last reason, the rubber rod did not infringe.
