T 0781/96 09-01-1998

Reasons for the Decision

1. The appeal is admissible.

2. Allowability of the amendments

2.1. According to claim 1 in dispute (see the characterising portion), the Coriolis mass flow meter is capable of operating at relatively high temperatures which are in a temperature range having a lower boundary in excess of 260 C and an upper boundary of approximately 426 C and said flow meter is capable of operating without malfunction in said range; the housing enclosing the flow conduit means receiving fluid therethrough whose mass flow rate is to be measured encloses hermetically said flow meter; an inert gas fills said hermetically closed housing; the feed-through means providing a passage for routing signals through said housing means provides a hermetically sealed passage through said housing; the driver means, sensor means, magnet means, coil means and flexure means necessary for the flow meter are all of a high temperature type suitable to operate substantially without malfunction due to thermally caused fatigue within said temperature range; moreover, said housing includes no cooling means utilising an externally supplied flowing cooling medium.

2.2. A first objection of the appellant is that the feature that the housing of the flow meter includes no cooling means utilising an externally supplied flowing cooling medium has no basis in the original application. However, as pointed out by the respondent, the original application (see page 8, lines 12 and 13) specifies that an object of the invention is a Coriolis flow meter that does not utilize a cooling purge. Moreover, the original application (see page 5, line 33 to page 6, line 17, more in particular page 6, lines 10 to 14) specifies that an active gas cooling purge line, typically using nitrogen gas flowing at a sufficient flow rate, is incorporated into the meter of the acknowledged D4 in order to maintain the velocity sensors and drive assembly at a relatively low temperature; further considerations about drawbacks of a system including such purge lines using a cooling purge gas, in particular with an active source of gas being connected to the purge line of the meter, are mentioned in the original application (see page 6, line 19 to page 7, line 15 and page 7, lines 30 to 35). Therefore, the cooling means (to be avoided) is not restricted to those utilising flowing nitrogen gas and, as convincingly argued by the respondent, there is a basis in the original application for a meter wherein the housing of the flow meter includes no cooling means utilising an externally supplied flowing cooling medium. Incidentally, it is to be noted that, for the same reasons, a possible amendment consisting in substituting "cooling purge" for "cooling means", proposed by the respondent in this respect, is not considered as useful and thus is not relevant.

2.3. A second objection of the appellant is that there is no basis in the original application for the feature that the Coriolis mass flow meter is capable of operating in a temperature range from approximately 260 C to approximately 427 C without malfunction, and that, in particular, the driver means, sensor means, magnet means, coil means and flexure means necessary for the flow meter are all of a high temperature type suitable to operate substantially without malfunction due to thermally caused fatigue within said temperature range. In particular, the appellant has stressed that "fatigue" of a material is derivable from the original application only with respect to the ceramic insulation of the wires used in the flow meter.

However, the respondent has convincingly argued as follows in this respect:

Indeed, the original application (see page 4, line 25 to page 5, line 3) mentions drawbacks of prior art meters using eventually fatiguing ceramic insulation of the wires. Yet, the original application (see page 5, lines 22 to 24) stresses that not only the ceramic wiring insulation of known flow meters can result in drawbacks, but also the copper wires: "Copper wires could not be used inasmuch as it exhibits grain growth at temperatures above 400 F which would cause creepage and eventual fatigue". Moreover, it is explicitly mentioned in the original application (see page 8, lines 5 to 10) that an object of the invention is "to provide apparatus for a Coriolis mass flow meter that is capable of reliably operating at relatively high temperatures, such as in excess of 500 F (approximately 260 C) and preferably as high as 800 F (approximately 427 C)". Therefore, in the context of the original application, the objected features are directly and unambiguously derivable.

2.4. It is to be noted that the appellant has also provided arguments concerning the content of the previous application for claiming priority for the patent in suit, or concerning the scope of protection conferred by said previous application for claiming priority or by the application as originally filed. However, since these objections do not relate to the grounds of opposition comprised in the exhaustive and restricted list in Article 100 EPC and in particular to those of Article 100(c) EPC, they are disregarded.

2.5. Therefore, the Board is satisfied that the subject-matter of the patent in suit does not extend beyond the content of the application as filed (Article 100(c) EPC).

3. Sufficiency of disclosure

Only opponent 2, who has not appealed against the impugned decision and who has not provided any comment during the appeal procedure, had based his opposition inter alia on the ground that the invention was not sufficiently disclosed in the European patent. Therefore, since the reasoning in the impugned decision with respect to sufficiency is convincing and since opponent 1, the sole appellant, has not provided any argument in this respect, the Board is satisfied that the European patent discloses the invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art (Article 83 and 100(b) EPC).

4. Novelty

It has not been disputed that D4 represents the closest prior art and that the device known from this document does not comprise all the features of claim 1 in dispute. Therefore, the subject-matter of claim 1 in dispute is new in the sense of Article 54 EPC.

5. Inventive step

5.1. It has not been disputed either that the Coriolis mass flow meter (10) known from D4 (see the abstract; column 3, line 21 to column 5, line 31; column 5, line 60 to column 9, line 3; Figure 1 to 7), i.e. the closest prior art, comprises all the features of the first part of claim 1 in dispute which is shown here above.

5.2. However, the Coriolis flow meter known from D4 is indicated as operating at temperatures as high as only 400 F (approximately 204 C), and this is contrary to the relatively high operating temperatures for the Coriolis flow meter in dispute, which are in a temperature range having a lower boundary in excess of 260 C and an upper boundary of approximately 426 C, with said flow meter being capable of operating without malfunction in said range.

Moreover, the Coriolis flow meter known from D4 (see column 8, lines 31 to column 9, line 3; Figure 1 to 3) is indicated as utilising an externally supplied flowing cooling medium for cooling said means, said cooling medium being flowed by a tubing (56) with vents (58) and being withdrawn from the housing (26) through a vent (60). In contrast, in the Coriolis flow meter in dispute, the housing hermetically encloses said flow meter, an inert gas fills said hermetically closed housing, said feed-through means provides a hermetically sealed passage through said housing, said driver means, sensor means, magnet means, coil means and flexure means are all of a high temperature type suitable to operate substantially without malfunction due to thermally caused fatigue within said temperature range, and said housing includes no cooling means utilising an externally supplied flowing cooling medium.

5.3. According to the patent in suit (see column 5, line 37 to column 7, line 21), the Coriolis flow meter of D4 has disadvantages in particular as a result of the provided cooling purge gas means, and an object of the present invention is to provide such a meter operating at temperatures as high as about 426 C and which do not utilize a cooling purge.

5.4. Another flow meter is known from D8 (see in particular the first page, the seven first lines; the second page, the two first paragraphs), which is also a high temperature flow meter because it has an operating range from - 200 C to about 400 C. This flow meter was commercialized and is thus derivable as being capable of operating without malfunction at least up to about 400 C and as comprising technical means also adapted to this range of temperature; in particular, the sensor of said flow meter is in contact with the flowing medium which can have a temperature in the above-mentioned temperature range, said sensor being well protected therefrom. The appellant has argued that the teaching of D8, and in particular the feature that the sensor is protected from the flowing medium to be measured, would lead the skilled person towards the flow meter in dispute. In this respect, he has referred to inter alia the above-mentioned decision T 455/91.

However, the following is to be noted in this respect:

Firstly, among the decisions cited by the appellant, the above-mentioned decision T 455/91 is the only one which, in the statement of grounds of appeal, is commented in detail with respect to the combined consideration of D4 and D8 and, in any case, the other cited decisions are not more relevant in this context.

Moreover, the respondent has convincingly argued as follows:

The flow meter of D8 is not a Coriolis flow meter, but a flow meter based on another principle, wherein a "DSC-SENSOR", i.e. a "differential switched capacitor" is surrounded by the flowing medium to be measured, more in particular in a vortex of said flowing medium; contrary to a Coriolis flow meter, this other known flow meter has no vibrating flow tubes, no magnetic drivers and no magnetic velocity sensors, and is thus not faced with problems associated with such parts. Thus, although Coriolis flow meters and flow meters using a "DSC-SENSOR" both allow the measurements of fluid flows, they belong to different technical fields. Indeed, as mentioned in particular in the above-mentioned decision T 455/91 (cf. the Headnote and points 5.1.3 to 5.1.3.3 of the reasons) indicated by the appellant, the skilled person working in one field would regard a means conveniently adopted in a neighbouring field as being readily usable also in that field. However, according to the end of said paragraph 5.1.3.3. of said decision, he would do so only "if this transfer of technical knowledge involves nothing out of the ordinary". Taking into account the above-mentioned numerous differences in component features between a Coriolis flow meter with cooling by means of an active cooling purge and a flow meter with a protected DSC-sensor, such transfer is to be considered as being "out of the ordinary" and, thus, it would be only the result of hindsight.

5.5. Indeed, a Coriolis flow meter with a housing enclosing the flow conduit means is also known from D9 (see the first page of text, the first column and the first paragraph of the second column; second page, second paragraph of the part "Measuring system" and first paragraph of the part "Principle of operation"; fifth page, the part "Construction"), whereby said housing hermetically encloses said flow meter and said housing includes no cooling means utilising an externally supplied flowing cooling medium. However, the indicated operating temperature range is only up to 150 C, and not about 426 C and, more in particular, no inert gas fills said hermetically closed housing, which is under vacuum, this last feature being indicated as preventing ingress of moisture, i.e. in relation with another purpose.

Incidentally, it is to be noted that the appellant has not provided any argument relating to D9.

5.6. Therefore, since having regard to the state of the art the subject-matter of claim 1 in dispute is not obvious to a person skilled in the art, it involves an inventive step in the sense of Article 56 EPC and it is patentable in accordance with Article 52(1) EPC.

6. Consequently, the grounds for opposition do not prejudice the maintenance of the European patent unamended (Article 102(2) EPC).

7. Therefore, since the Board has considered all the arguments of the appellant filed in writing and since oral proceedings had been requested auxiliarily only by the respondent, it was not necessary to summon the parties to oral proceedings. Moreover, as mentioned here above, opponent 2, a party as of right in accordance with Article 107 EPC, has remained silent during the appeal procedure. Thus, since the parties have had sufficient opportunity to present their comments on the above-mentioned grounds and evidence, a decision may be issued (Article 113(1) EPC).