T 877/06 – The Limits Of Reformulation

[4] Inventive step

The patent in suit relates to a filter arrangement for use in an air cleaner housing, comprising a coiled media construction and a sealing system.

[4.1] Closest prior art

The closest prior art is normally a prior art document disclosing subject-matter conceived for the same purpose or aiming at the same objective as the claimed invention and having the most relevant technical features in common. Document E1 reveals all the features of claim 1 in accordance with the main request except for claim item (b)(i). The parties have identified E1 as the document representing the closest prior art. The board concurs in choosing document E1 as the starting point for assessing inventive step.

[4.2] Technical problem

[4.2.1] The objective of the patent in suit is the removal of particulate material from an air flow upstream of e.g. an engine, a turbine or a furnace.

[4.2.2] The appellant defined the problem underlying the opposed patent as proposing means and methods of filtering air which allowed for an optimal volume of fluted media per available housing volume, protected said media from external forces and allowed the designer of air cleaners more freedom of design […]. The respondent agreed with this formulation of the technical problem.

[4.2.3] Document E1 is concerned with the technical problem of avoiding the bulging of the filter media which is caused by the pressure applied to its periphery by the housing and the seal upon fastening of the cover […]. Compared with this closest prior art, the technical problem of protecting the filter media from external forces, although not explicitly stated in the opposed patent, becomes immediately apparent. Said part of the technical problem is deducible from the application as filed taking into account the features described in the figures and the effects and advantages clearly associated with them. The reformulation of the technical problem is therefore allowed, in line with the principle laid down in decision T 818/93 [5.2, 4th §].

The optimization of the volume of fluted media per available housing volume is, in the board’s view, a technical problem which the skilled person always takes into consideration because of the space restrictions prevailing in the places where such filter arrangements are used (generally engines of vehicles, buses, trucks, boats etc […]). Therefore, said part of the technical problem is taken into account, even if it is not explicitly mentioned as such in the application as filed.

[4.2.4] However, the board observes that the part of the above defined technical problem relating to the “freedom of design” is not addressed in the application documents as filed. In this respect, it was stated in T 13/84 [11] that a reformulation of the technical problem was not precluded by A 123(2) if the problem could be deduced by the skilled person from the application documents as filed when considered in the light of the closest prior art. It follows that reformulation of a problem is prohibited if the problem so modified is neither disclosed in the originally filed application itself nor deducible when the application is considered in the light of the closest prior art. Hence, having regard to the fact that E1 (or, for that matter E3) does not address such a design problem either, the board concludes that the part of the technical problem relating to the “freedom of design” aspect cannot be deduced from a comparison of the opposed patent with the closest prior art. Said part of the technical problem is, therefore, not taken into consideration for the assessment of inventive step.

[4.2.5] Therefore, the board concludes that the problem underlying the patent in suit in the light of document E1 is to protect the filter media from external forces and to optimize the volume of fluted media per available housing volume.

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