T 1015/00 07-02-2002

Reasons for the Decision

1. The appeal meets the requirements of Articles 106 to 108 EPC and of Rules 1(1) and 64 EPC and is, therefore, admissible.

2. Main request

Although an opposition cannot be based on the grounds of lack of clarity or support, any amendments made during the opposition and appeal procedure are to be fully examined as to their compatibility with the requirements of the EPC (G 9/91, OJ EPO 1993, 420, point 19 of the reasons) and, therefore, must not give rise to objections under Article 84 EPC (see also T 301/87, OJ EPO 1990, 335).

The Respondent holds that in claims 1 and 3 the feature that Tmax is determined from the temperature increase during the oxidation of the gas mixture gives rise to a clarity problem because a measurement of the varying temperature increase during the oxidation in the process would not lead to this maximum value which is shown by the disclosure in column 4, lines 19 to 35 of the patent to be based on a calculation involving predetermined data, rather than on measurements of the temperature increase. The Board concurs with this objection. In fact, this feature refers to a temperature increase during the (emphasis added) oxidation of the gas mixture which, due to the absence of any other oxidation of the gas mixture, will be understood to refer to the oxidation taking place during the combustion of the gas mixture in the combustion chamber as defined in the precharacterising portion of the claims. As a consequence, the method as defined in claims 1 and 3 requires a measurement of the actual temperature increase in order to determine the maximum permissible temperature increase. It is quite unclear how this could be achieved. Two different possibilities are found in the description: according to column 2, lines 11 to 15 and 38 to 48 of the patent Tmax is determined by the temperature increase during the oxidation of a gas mixture having the maximum permissible concentration, a condition which is normally not met during the actual combustion of the gas mixture, and according to column 4, lines 19 to 35, Tmax is calculated on the basis of a formula and predetermined values. Neither case corresponds to the claimed method of determining Tmax on the basis of measurements of the actual temperature increase made during the oxidation at varying concentrations of the flammable substance.

As a consequence, claims 1 and 3 of the main request are neither clear nor supported by the description as required by Article 84 EPC.

3. First auxiliary request

3.1. Clarity and support (Article 84 EPC)

Since in claims 1 and 3 of the first auxiliary request the method step of determining Tmax from the temperature increase during the oxidation of the gas mixture was removed, the objection of lack of clarity and support does not apply to this request. The further clarity objection of the Respondent to the feature defining the independence of Tmax of the type of the flammable substance is not shared by the Board because the question of whether this feature concerns a discovery or a further limitation of the claim cannot in principle affect the clarity of the claim.

3.2. Basis for the amendments in the original application (Article 123(2) EPC)

As compared with the application as originally filed and with the patent as granted, the independent claims 1 and 3 include the additional features (1) that the confined space is in form of a drying chamber in a drying appliance for drying a printed web, the oxidation taking place in a combustion chamber of the drying appliance, (2) that the maximal permissible temperature increase is determined independent of the flammable substance, and (3) that the safety measures are in form of a switching off of the oxidation and/or a ventilation of the confined space. It is not in dispute that features (1) and (3) are adequately supported by the application as filed, in particular page 3, lines 9 to 13, page 9, last paragraph, page 10, lines 9 to 15 and claim 13 for feature (1) and page 4, lines 5 to 9 for feature (3). Concerning feature (2) the Respondent argues that this feature was an unallowable generalisation of the specific original disclosure of determining the maximal permissible temperature increase in claim 6 and in the text bridging original pages 3 and 4, and no other way of determining Tmax was disclosed. However, this argument is not convincing because a more general information about the maximal permissible temperature increase can be derived from the text bridging pages 2 and 3 and on page 3, last paragraph, relating the temperature increase during the oxidation to the concentration of the flammable substance in the gas mixture whereby Tmax corresponds to the temperature increase during the oxidation of a gas mixture having the maximum permissible concentration of the flammable substance. This information does not rely on a particular formula for determining Tmax, as in original claim 6, and, therefore, provides a sound basis for feature (2).

The dependent claims 2 and 4 to 13 correspond to claims 2 and 5 to 14 of the original application and of the granted patent.

Hence, the amended claims of the main request meet the requirements of Article 123(2) EPC.

3.3. Scope of protection (Article 123(3) EPC)

Since the added features (1), (2) and (3) limit the scope of the patent to a specific type of confined space, a specific value of Tmax and specific safety measures, the requirements of Article 123(3) are likewise met.

3.4. Inventive step (Article 56 EPC)

3.4.1. Document V1 relates to a method of controlling a drying process so as to maintain the concentration of organic compounds in the process discharge gas, and thereby in the process itself, below an explosive limit. The organic compounds in the process discharge gas are combusted in a post-combustion chamber and the temperature of the discharge gas is measured before and after the post-combustion. If the measured temperature increase approaches a predetermined upper limit the volume flow rate of the discharge gas is increased, causing an enhanced aspiration of fresh air into the process and a reduction of the concentration of the noxious organic substances in the process (see in particular column 3, line 35 to column 4, line 1 and column 5, line 56 to column 6, line 15).

The upper limit of the temperature increase of the process discharge gas during the post-combustion is set to a value which is below 1300K, preferably 800K or most preferably to somewhere between 300 and 500K (claim 1 and column 3, lines 16 to 20). These limits may depend on the resistance of the materials (column 3, lines 20 to 22), whereas no dependence on the particular type of organic substances in the discharge gas is described. Rather, claims 1 and 2 refer to the specific temperature limits in combination with unspecified organic compounds. It can therefore be concluded that the upper limit is independent not only of the concentration, as argued by the Appellant, but also of the type of organic substance in the process discharge gas.

Since it is the purpose of the control method described in V1 to maintain the concentration of the organic compounds in the process discharge gas below an explosive limit, thereby preventing (in the language of the claims of the patent) the occurrence of an explosive state in a gas mixture, the measures of enhancing the flow rate of the discharge gas to thereby increase the aspiration of fresh air into the process can be considered as "safety measures" in the sense that, by taking these measures, a potentially dangerous situation shall be prevented. The aspiration of fresh air into the process, i.e. the drying chamber or confined space, is described as a consequence of the actual measure of enhancing the discharge gas flow rate, rather than the actual safety measure itself. In any case, it is one of the steps taken directly or indirectly in order to reduce the concentration of the noxious organic compounds, and therefore corresponds to the ventilation of the confined space as a safety measure, as defined in claim 1.

Claim 1 is therefore distinguished from the method disclosed in V1 in that the safety measures of claim 1 are taken when the maximum permissible temperature increase Tmax has been exceeded, whereas in V1 the safety measures are taken when approaching this maximum permissible temperature increase. However, this difference is a mere matter of choice of a suitable value for Tmax in the control method of V1. In fact, it makes no real difference in this control method whether the safety measures of V1 are taken when the measured temperature increase approaches a maximum value of 500K, as specified in column 3, line 20, or exceeds for example a maximum value of 450K. The skilled person will select the appropriate maximum value according to the type of control system so as to prevent the temperature increase from reaching the maximum permissible temperature increase, in this example 500K. The Board cannot see any inventive step in such a selection.

3.4.2. The Appellant argues that disabling the control method of V1 below a certain volume flow rate and the delay and overshoot inherent in such a control method distinguished the disclosure of V1 from a "hard" safety measure as claimed inasfar as the latter was an unconditional, reliable and rapid reaction to a dangerous situation. This argument is not convincing because in both cases the safety measures are taken in the case of a potentially dangerous situation, irrespective of conditions far away from this situation where the safety system may be down, and the control system of V1 responds to the same temperature conditions as in claim 1 and must be as reliable and rapid.

3.4.3. However, even in the case that the safety measures defined in claim 1 could be distinguished from the control method described in V1 as defining emergency measures to be taken if a maximum permissible temperature increase has been exceeded, despite any control of the process, no inventive step could be recognised. The requirement for safety measures, as emergency measures, for example in the case of a failure of a control system, is a typical requirement in systems such as drying appliances where the concentration of flammable substances may reach an explosive level. This is clearly shown by V2, chapter 4.2.8.3. The question arises whether, as argued by the Appellant, the skilled person implementing such an emergency system would base it on measurements of the gas concentration with special sensors. The Board cannot follow this argument. In fact, since V1 teaches (for example in column 3, lines 7 to 15 and 37 to 39) the relationship or "equivalence" between the temperature increase and the concentration of flammable substances and, based on this relationship, to utilise the temperature increase for the purpose of controlling the process so as to avoid an explosive state, the skilled person would be aware that utilising the same temperature increase, representing the concentration of the flammable gases, also as a basis for the safety or emergency measures which are necessary in the case of failure of the control would require no additional sensors and, therefore, would be much more economic than the conventional solution employing gas sensors. Switching off the oxidation, together with the entire process, would be a standard emergency measure but ventilation would also be taken into consideration because it is proposed in V1 in connection with the control for diluting the solvents, which effect is likewise desirable in the case of an emergency situation.

3.4.4. The Board therefore concludes that claim 1 of the first auxiliary request does not meet the requirement of inventive step. Since a decision can be made only on a request as a whole, no further consideration of the other independent claim 3 is required.

4. Second auxiliary request

4.1. Amendments

Claims 1 and 3 of the second auxiliary request include, as compared with the corresponding claims of the first auxiliary request, the further feature that Tmax is determined according to the equation Tmax = k*dT*CLEL, wherein Tmax is the maximal permissible temperature increase in C, k is a factor which depends on the safety standard, dT is the specific temperature increase in C/(g/Nm3) and CLEL ist the concentration of the flammable substance at the lower explosive limit in g/Nm3. This equation was disclosed in original claim 6, which via claim 4 referred back to original claims 1 and 3, and likewise in the description from page 5, line 36 to page 6, line 6, as a preferred embodiment. No objection under Article 123 EPC therefore arises.

4.2. Inventive step

The added feature defines an equation for calculating, on the basis of a safety factor and material data found in handbooks, the maximum permissible temperature increase without having to rely on measurements or experiments.

In document V1 the maximum temperature increase is set to a preferred value of 300 to 500K, which is below the limit of 1300K. Thus, the maximum temperature increase can be expressed in the form of a fraction of the limit, i.e. Tmax = k * Tlimit, whereby the fraction k is is a "safety factor" which depends on the resistance of the materials (see column 3, lines 20 to 22) which is a material property found in handbooks, and Tlimit = 1300K. Considering that for the reasons set out in connection with the first auxiliary request, it would be obvious to base any required emergency measures in V1 on a measurement of the temperature increase, rather than of the concentration, a limit for the temperature increase relevant for safety or emergency measures, if at all distinguished from the control measures of V1, would be determined in the same manner as a fraction k of Tlimit, possible with a slightly higher value of k. It is true that, as argued by the Appellant, V1 does not say how the value of 1300K for Tlimit is determined. In the Board's view, however, this is a matter of obvious considerations for a skilled person. In fact, based on the relation of the temperature increase and the concentration of the flammable substances as set out in column 3, lines 7 to 9 and 37 to 39 of V1, the skilled person will determine Tlimit so that this is the temperature increase at the maximum permissible concentration. This concentration is CLEL, i.e. the concentration at the lower explosive limit of the substance under consideration, because the purpose of preventing explosive concentrations, as set out in column 3, lines 10 to 12 of V1, can only be achieved when maintaining the concentration below this limit. Since the factor relating the concentration to the temperature increase is the specific temperature increase dT C/(g/Nm3) , the maximum temperature increase at the lower explosive limit Tlimit is dT*CLEL. Thus, the selection of 300 to 500K in V1 corresponds to k*dT*CLEL with dT*CLEL = Tlimit being 1300K. The equation specified in claims 1 and 3 of the second auxiliary request therefore reflects the obvious considerations of the skilled person determining the permissible temperature increase as specified in V1.

4.3. Since the subject-matter of at least claim 1 does not meet the requirement of inventive step, the second auxiliary request is likewise not allowable.