Principles of construction
40 There is a tension between two ideas, the force of both of which has been felt in the construction of patent claims: first, there is the idea that a person should not be able to take the 'pith and marrow' or 'substance' of the patented invention and avoid infringement by sidestepping the language of the claims; and, secondly, there is the idea that the language of patent claims has been chosen by the patentee, sets the boundary of the patentee's monopoly, and should not be extended by the Court to catch that which the patentee has left open to be done by others. Both ideas were referred to in, for example, Olin Corporation Ltd v Super Cartridge Co Pty Ltd (1977) 180 CLR 236 at 246 per Gibbs J.
41 This Court is frequently called upon to refer to the principles which govern the construction of patent claims. On each new occasion it seems that the same authorities plus the last preceding one are reviewed. And so the list lengthens.
42 The review frequently commences with reference to the 'purposive' construction of claims, famously advocated by Lord Diplock in delivering the judgment of the House of Lords in Catnic Components Ltd v Hill & Smith Ltd [1982] RPC 183 ('Catnic'), in preference to a 'literal' construction of them. The point of that distinction was clear on the facts of that case. Claim 1 of the specification said 'extend vertically'. The literal, acontextual meaning of this expression was an absolute: a one degree departure from the vertical marks non-verticality. But the skilled addressees would not have read the claim in that way. A 6 degree angle gave a reduction in load bearing capacity of only 0.6 percent, and an 8 degree angle, a reduction of only 1.2 percent. The question was whether the skilled addressee would have understood that a literal meaning was intended by the patentee to be 'an essential requirement of the invention' (at 243). Lord Diplock said that this question of construction does not arise if:
1. the allegedly infringing article's departure from the claim, literally construed, would have a material effect on the way in which the invention worked; and
2. it would have been obvious to the skilled addressee at the date of publication of the specification that it would have that material effect.
If condition 1. is satisfied, but condition 2. is not, the skilled addressee would have been entitled to assume that the patentee thought that he:
'had good reason for limiting his monopoly so strictly and had intended to do so, even though subsequent work by him or others in the field of the invention might show the limitation to have been unnecessary.' (at 243)
43 The subsequent authorities, English and Australian, including 'the Improver questions', formulated in Improver Corporation v Remington Consumer Products Ltd [1990] FSR 181 at 188-189, have been recently reviewed in this Court by Finkelstein J in Root Quality Pty Ltd v Root Control Technologies Pty Ltd (2000) 177 ALR 231, Gyles J in Grove Hill Pty Ltd v Great Western Corporation Pty Ltd (2002) 55 IPR 257; Tamberlin J in Baygol Pty Ltd v Foamex Polystyrene Pty Ltd [2005] FCA 624 ('Baygol'); Bennett J in Sachtler; and a Full Court in Fresenius Medical Care Australia Pty Ltd v Gambro Pty Ltd [2005] FCAFC 220. As well, the English authorities were recently reviewed by the House of Lords in Kirin-Amgen Inc v Hoeschst Marion Roussel Ltd [2005] 1 All ER 667.
44 I am grateful for these reviews of the legal principles but can decide this case by saying that, in my opinion, when proper allowance is made for a purposive construction, the plastic blade (I will call it a 'blade', but in a strictly neutral sense and in order to avoid 'knife', 'rib' and 'vane') of the Cascade Juicer is not, on any reckoning, 'a knife ... having an upwardly directed cutting edge' (and is not, on any reckoning, 'attached to and supported by the tube') within claim 1.
45 The circumstances of this case have little resemblance to a case like Catnic and are rather more akin to those of Baygol, in which claim 1 of the patent said 'concrete spacer' and the allegedly infringing product used plastic spacers. Tamberlin J said (at [28]):
'It is obvious that "concrete", whether used as an adjective or a noun, is not a word which is capable of including "plastic".'
and
'In the present case, there is no such range or spectrum of permissible interpretation which could permit the word "concrete" to mean material other than "concrete".'
46 Baygol is not on all fours with the present case, either, however. Both concrete and plastic were materials known and named as distinct categories independently of, and prior to, the manufacture of the allegedly infringing product. The plastic blade which I am considering is unique in the sense that it did not exist prior to being created as part of the Cascade Juicer, and the question is whether this newly created unique thing falls within the words 'a knife ... having an upwardly directed cutting edge' within the meaning of claim 1. The case is perhaps like Catnic and unlike Baygol in this respect: it may be seen to raise the question how blunt a blade may be, and still be 'a knife ... having an upwardly directed cutting edge' - a question of degree of a kind having no relevance to Baygol's distinction between concrete and plastic.