T 0473/15 - CPA from different field

Key points

• In this opposition appeal, the Board is happy to take D5 as the closest prior art, as proposed by the opponents. However, claim 1 is about a filter medium (for removing particles from a fluid stream) whereas D5 is about "chromatographic separation of contaminants".  
• "In other words, D5 relates to a different technical field than that of the patent in suit. However, a closest prior art that is not directed to the same purpose or effect as the invention cannot, according to established case law, lead the skilled person in an obvious way to the claimed invention " 
• " pplied to the present case, this means that the skilled person would not, without hindsight, try to improve the particulate capture efficiency of the medium of D5, which is meant for chromatographic separation. Hence, the skilled person would not, when starting from D5, apply D4's, D10's or any other document's teaching since these documents do not deal with chromatographic separation." 

EPO T 0473/15 -  link

4.2 Closest prior art

In the appellants' [opponents'] view, D5 should be considered as the closest prior art. The board sees no reason to depart from this choice.

4.3 Problem to be solved

According to the patent in suit, one of the problems to be solved is the provision of a filter medium with improved filtration properties (paragraph [39] of the patent).

4.4 Solution

As a solution, the filter medium of claim 1 is proposed, characterised by a layer of fine fibers with a small diameter, spacer particulate and a specific fine fiber solidity, i.e. volume fraction taken by the fibers.

4.5 Success of the solution

It is plausible that fibers with a smaller diameter facilitate the capture of solid particulate matter. [...]

4.6 Obviousness

Although the positive influence of a decrease in the fiber diameter on the particulate capture efficiency is known from D10, as explained above, an inventive step within the meaning of Article 56 EPC is acknowledged:

While the medium of D5 is certainly suitable for capturing particulate from a fluid stream, it actually deals with the chromatographic separation of contaminants. This is illustrated on multiple occasions: see page 10, lines 13 to 31, as well as page 8, line 6, page 13, line 18 and page 14, lines 1 to 10. Consistently, dye is separated from water in the examples in D5 (page 22 lines 21, 22 and 28; Table 2, column "Percent Recovery (Disperse Red 1)").

Admittedly, D5 mentions the term "filtration", e.g. on page 13, line 14 and page 19, line 14). However, on page 10, lines 13 to 31 it is explained that the term "filtering" in D5 is to be understood in the sense of chromatographic separation: "... in which the particles can interact with (for example, chemically or physically react with, or physically contact and modify or to be modified by) a medium or a component thereof to which the particles are exposed".

Apart from page 1, line 12, which refers to the use of fiber fabrics in the prior art only, the term "particle" in D5 refers to the particles enmeshed in the web and not to fine particles to be captured from a fluid stream. page 11, lines 4 to 7 is to be understood in this sense, too.

In other words, D5 relates to a different technical field than that of the patent in suit. However, a closest prior art that is not directed to the same purpose or effect as the invention cannot, according to established case law, lead the skilled person in an obvious way to the claimed invention (see the introductory remarks to Case Law of the Boards of Appeal, 8th ed., I.D.3.2).

Applied to the present case, this means that the skilled person would not, without hindsight, try to improve the particulate capture efficiency of the medium of D5, which is meant for chromatographic separation. Hence, the skilled person would not, when starting from D5, apply D4's, D10's or any other document's teaching, since these documents do not deal with chromatographic separation.

For these reasons, an inventive step within the meaning of Article 56 EPC is acknowledged.