When (and Where) is a Claim ‘Preamble’ Limiting?

A reader of this blog recently asked me about the ‘preamble’ to a patent claim, and in particular whether statements made in the preamble are limiting under Australian law, and whether the position is different under US law.  In other words, can a claim with the same wording nonetheless mean different things in different jurisdictions?

The preamble to a claim is the opening part which generally sets the context for the main features of the claimed invention.  These main features could be the interrelated components of a claim directed to some apparatus, or the series of steps making up a claimed method or process.

The reader in question specifically asked me about the CSIRO WLAN claim, which I analysed in detail about a year ago.  I am only going to talk about the preamble here, so if you are interested in the remainder of the claim you will have to go back and read the earlier article.  That claim opens as follows:

A method for transmitting data in a confined multipath transmission environment of radio frequencies, said data being provided by an input data channel coupled to transmission signal processing means in turn coupled to antenna means, said method comprising the steps of…

This tells us right away that the claim is directed to a method, and we therefore expect that it will define a sequence of steps which together make up the method.  Certainly those steps will be essential to the claimed invention unless there is some very clear indication to the contrary.

But does it make any difference to the scope of the claim that the method is said to be ‘for transmitting data in a confined multipath transmission environment of radio frequencies, said data being provided by an input data channel coupled to transmission signal processing means in turn coupled to antenna means’?  And is the answer to this question likely to depend upon the jurisdiction in which the claim is being interpreted?

The Preamble in Australia

The basic position under the Australian law is substantially the same as under English law, which was perhaps stated most clearly and succinctly by Lord Diplock in Catnic Components Ltd v Hill & Smith Ltd [1982] RPC 183:

My Lords, a patent specification is a unilateral statement by the patentee, in words of his own choosing, addressed to those likely to have a practical interest in the subject matter of his invention (i.e. ‘skilled in the art’), by which he informs them what he claims to be the essential features of the new product or process for which the letters patent grant him a monopoly.

Since the patentee is free to choose the words of his or her own claim, the general principle is that those words should be assumed to have been selected deliberately, and cannot therefore be ignored without good reason.  There is a reasonable amount of case law on the circumstances in which one might treat a feature recited in a claim as ‘inessential’, but such cases are very much the exception rather than the rule.

As said long ago in Nobel’s Explosives Co v Anderson (1894) 11 RPC 115 (at p 128), a claim should not be read so as to ignore clear restrictions, or to capture all that the patentee ‘might have claimed if he had been well advised or bolder’.  More recently, a Full Bench of the Federal Court of Australia (in Australian Mud Company Pty Ltd v Coretell Pty Ltd [2011] FCAFC 121, about which I have written previously) confirmed that:

…there is no warrant for adopting a method of construction that gives a patentee what it might have wished or intended to claim, rather than what the words of the relevant claim actually say. While the Court should read the claims purposively and not with an eye for pedantry, even an appropriately liberal approach to construction should not permit the words of the claims to be stretched beyond their textual limits.

There is no special rule which applies to the ‘preamble’ of a claim – if it can be given effect, it will be.

‘Fields of Use’

Of course, some words present particular questions, wherever they appear in a a claim.  The word ‘for’ is one example – if a method or apparatus is said to be ‘for’ a particular purpose, does this have any limiting effect?

The answer is that, in general, ‘field of use’ terms such as ‘for’, ‘for use’, ‘used to’, ‘used for’ and so forth are limiting under Australian law only to the extent that the claimed invention must be suitable for the stated purpose.  Usually, then, such qualifications have little or no effect, and merely guide the reader as to the intended purpose of the invention.  In most cases, suitability for the purpose will, in any event, be a consequence of the particular combination of features making up the main body of the claim.

So, in the case of the CSIRO WLAN claim, a method ‘for transmitting data in a confined multipath transmission environment of radio frequencies’ is one which (under Australian law) is suitable for that purpose.  It might be suitable for other purposes as well, such as transmitting data in an unconfined space, or in a moving vehicle, or via a copper cable or optical fibre.  The claim is not limited to exclude such other uses of the method merely by the ‘field of use’ statement.

The other elements of the CSIRO claim preamble, however, are different.  The requirements of ‘said data being provided by an input data channel coupled to transmission signal processing means in turn coupled to antenna means’ would, in my opinion, limit the scope of the claimed method, under Australian law, to implementations in which the input data channel, the signal processing means, and the antenna means, are all present and ‘coupled’ as specified.

In practice, you might argue, this is not much of a limitation, since it describes any practical Wi-Fi implementation.  However, it does serve to exclude, for example, use of the method for transmission over copper or optic-fibre cabling, which the ‘for transmitting…’ clause does not.

The Preamble in the US

The position in the US on the effect of the claim preamble is somewhat different.  Whereas in the Australian law (and the English tradition) there is a presumption in favour of giving weight to all terms in a claim, in the US there is no such presumption with regard to the preamble.

Section 2111.02 of the USPTO Manual of Patent Examining Procedure (MPEP) is entitled Effect of Preamble, and states:

The determination of whether a preamble limits a claim is made on a case-by-case basis in light of the facts in each case; there is no litmus test defining when a preamble limits the scope of a claim.

The MPEP cites a number of statements from the cases in relation to the effect of the preamble, including:

1. ‘…a claim preamble has the import that the claim as a whole suggests for it’: Bell Communications Research, Inc. v. Vitalink Communications Corp., 55 F.3d 615, 620, 34 USPQ2d 1816, 1820 (Fed. Cir. 1995); and
2. ‘If the claim preamble, when read in the context of the entire claim, recites limitations of the claim, or, if the claim preamble is “necessary to give life, meaning, and vitality” to the claim, then the claim preamble should be construed as if in the balance of the claim’: Pitney Bowes, Inc. v. Hewlett-Packard Co., 182 F.3d 1298, 1305, 51 USPQ2d 1161, 1165-66 (Fed. Cir. 1999).

Generally speaking, a statement in the preamble which creates a structural difference in the claimed invention (or, in the case of a method/process claim, results in a manipulative difference) acts as a limitation on the scope of the claim.

Not surprisingly, therefore, ‘field of use’ statements (e.g. ‘for transmitting data in a confined multipath transmission environment of radio frequencies’ ) are typically not limiting.  Indeed, in many cases such a statement, if it results in no necessary structural or manipulative difference, may not even introduce a limiting requirement that the claimed invention be ‘suitable for’ the stated purpose.

As for the remainder of the preamble in the CSIRO WLAN claim – ‘said data being provided by an input data channel coupled to transmission signal processing means in turn coupled to antenna means’ – it is not entirely clear to me whether this is limiting.  While it recites structure, it does so in the context of a method claim, in which the manipulations recited in the following steps may or may not be dependent upon the structure.

I am inclined to think that the ‘antenna means’ is limiting in this case, because the final step in the claimed method (‘transmitting, by said antenna means, said sub-channel symbols’) expressly requires the use of the antenna means for transmission.  However, the ‘input data channel’ and the ‘transmission signal processing means’ elements of the preamble may not be limiting, because the method steps do not expressly refer to them, and it is not apparent that any ‘manipulative difference’ results from the origin of the data, or the ‘means’ used for performing the processing.

I would be interested in the views of US attorneys on the construction of the preamble in this case.  However, if I were wishing to limit the claimed method to use within a particular structure, I would be inclined to draft the claim to recite the relationship with the structure explicitly within the method steps, rather than relying on the preamble being treated as limiting.

Conclusion

As a general proposition, the effect of the preamble to a claim may vary, depending upon the jurisdiction in which it is interpreted.

The approaches in Australia and the US possibly represent the two extremes in the spectrum.  In Australia, the preamble is generally treated no differently to other parts of a claim, and terms will be limiting unless there is some good reason to interpret them differently.  Even ‘field of use’ statements typically have some effect, even if it is only to exclude from the scope of the claim any products or processes which are not suitable for the stated purpose.

In the US, the preamble is treated differently from the main body of the claim.  Whether statements in the preamble are limiting or not depends upon how they fit within the context of the claim as a whole.  ‘Field of use’ statements will often not have any limiting effect at all – ‘a method for X, comprising…’ might just as well be claimed as ‘a method comprising…’.

Treatment of the preamble is just the tip of the iceberg.  There are numerous reasons why identically-worded claims may have different scope and meaning in different countries.  A good patent attorney can usually draft claims which mean mostly the same thing in most places.  We are, however, still a long way from genuine harmonisation of patent laws, even when it comes to something as basic as how to interpret a claim.

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Tags: Australia, Claim construction, US