Wednesday, 18 November 2009

T 1276/07 – Rough Ride On A One-Way Street

[…] The patent is concerned with a […] particle filter for the purification of diesel exhaust gases. […] The ceramic members [of the filter are] assembled by interposing a sealing member consisting of inorganic fibers, an inorganic binder, an organic binder and inorganic particles. [2.1]

The document A2 is representative of the closest prior art. […] Claim 1 of the granted patent differs [from A2] in that the sealing member contains an organic binder. [2.2]

[…] Since during regeneration the filter assembly is subjected to high temperatures necessary to remove the particulate material trapped therein a relatively high and uniform thermal conductivity of the sealing member is mandatory in order to afford a high regeneration efficiency and mechanical durability.

[…] it is uncontested that the sealing member fulfils the requirements of adhesiveness and joining durability of the single ceramic members. Furthermore, the [patent proprietor] has demonstrated […] that the presence of an organic binder in the sealing member as defined in Claim 1 leads to a heat transfer between opposite sides of a filter element of a honeycomb filter assembly which is enhanced as compared with a sealing member according to A2 without organic binder. […]

Therefore, the objective technical problem to be solved vis-à-vis A2 is to be seen in the provision of a sealing member joining the ceramic members of a ceramic structural body which provides a high joining durability and adhesiveness as well as an enhanced thermal conductivity of the entire structural body. [2.3]

It could be argued:
(i) that it was obvious that the use of an organic binder together with an inorganic binder would provide enhanced adhesiveness, having regard to [documents] A6 and E9 […] relating to similar cement materials for similar purposes, and
(ii) that some cellulose polymers were known to prevent migration phenomena which lead to inhomogeneities in a ceramic mass, having regard to [document] A28 […]. However, none of the citations comprises any information whatsoever with regard to the influence of organic binders on the thermal conductivity of a composition as specified in present Claim 1. Nor do these citations contain any hint about the influence an organic binder would have on the three-dimensional structure of the organic fibres and the ensuing distribution of the inorganic particles favourable to thermal conductivity.

In the Board’s judgment therefore it is non-obvious to arrive at the claimed solution, irrespective of the fact that the prior art might suggest a partial solution of the underlying technical problem. This conclusion results from the fact that the prior art does not suggest the claimed solution in relation to one essential part of the underlying problem, namely the enhancement of the thermal conductivity. Since the skilled person cannot deduce from the information referred to above with regard to A6/E9 and A28, or any other citation, any link between the properties adhesiveness and/or migration prevention on the one hand, and thermal conductivity on the other hand, any speculation concerning the possible obviousness of the improvement of the last mentioned property by the addition of an organic binder to the cement composition of A2 is based on hindsight.

The reference to decision T 936/96, with the argument that a skilled person intending to improve adhesiveness by adding an organic binder in accordance with E9 would automatically improve the thermal conductivity of the assembled structure of A2, is besides the point. This argument is essentially based on the idea that the improved thermal conductivity is to be regarded as a bonus effect, not able to contribute an inventive step. However, such a conclusion is only justified in the case of a one-way situation, where the distinguishing feature (here: the addition of an organic binder) is the only way to attain the “main” objective (here: improved adhesiveness, migration prevention), a situation that does not apply here.

The subject-matter of Claim 1 as granted therefore involves an inventive step. [2.4]

The Board here construes a technical problem having two aspects (improving durability and enhancing conductivity) and admits that the prior art suggests to solve the first aspect by means of the claimed features.

This appears to be a classical “bonus effect” situation. As stated in T 21/81 already, an additional, possibly unforeseen effect (“bonus effect”; here : enhanced thermal conductivity) does not point towards an invention if the skilled person would already have arrived at the invention because another advantageous effect (here: improved joining durability and adhesiveness) could be achieved by combining prior art documents (here: A6/E9 and A28).

This is what the opponent pointed out, referring to T 936/96, the headnote of which reads: “Once a realistic technical problem is defined and once it is established that a particular solution to such a problem would have been envisaged by a person skilled in the art in the light of the relevant state of the art, then this solution lacks an inventive step, and this assessment cannot be altered by the fact that the claimed invention inherently also solves further technical problems.”

Quite unexpectedly, the present Board refuses to go along this path. It states that “such a conclusion is only justified in the case of a one-way situation, where the distinguishing feature is the only way to attain the “main” objective, a situation that does not apply here”.

I have the impression that this statement is based on a misunderstanding of what is meant by “one-way situation”. This expression does not mean that there is only one single way to attain the objective but that the skilled person, when faced with the objective technical problem, is naturally led to the solution by the prior art.

Leaving aside the “bonus effect”, the Board then establishes that the prior art is silent with respect to the second aspect of the technical problem and concludes that the solution therefore involves an inventive step. In other words, the solution was obvious, but as it solves another unexpected problem, it has to be inventive. Oh dear.

To read the whole decision, click here.