T 0437/97 06-04-2000

1. The appeal is admissible.

2. Main request

2.1. Article 123(2) and (3) EPC

2.1.1. Claim 1 is supported essentially by original claims 1 to 4. The feature in claim 1 that the vessel is an electric arc melt furnace derives from page 3, last paragraph, of the original description. The substitution of "liquid coolant" for "fluid coolant" in claim 1 derives from the passage bridging pages 2 and 3, from page 3, paragraph 2, from page 4, paragraph 1, and from page 6, paragraph 2, of the original description.

Having regard to the wording "...maintaining a controlled pressure differential..." and "...to minimize the amount of coolant standing in the space" objected to by the respondent in view of the original disclosure, reference is made to the following wording in the passage from page 13, line 24, to page 14, line 15, of the original description:

"Spent coolant should be drained as quickly as possible so that there is a minimum of standing coolant over the lower wall 38...".

"So that the spent coolant may be quickly removed and drained from the interior 23 of roof 10, there is provided a means for establishing and maintaining a pressure differential between the interior of the furnace roof and the coolant outlet. As used herein, this "means for maintaining a pressure differential" refers to and comprises a system wherein a gaseous medium is injected into and pressurizes the space above the sprayed coolant to force the coolant out of the roof drain."

As already outlined in the Board's communication dated 2. July 1998 the above-cited passage discloses that pressure differential means is provided comprising means for injecting a gaseous medium into the space to be cooled for establishing and maintaining a pressure differential between the space and the coolant outlet. It is self-evident that the measure of establishing and maintaining a pressure differential requires an appropriate process step and means to control this differential. On page 14, lines 7 to 15, of the cited passage the context between the maintenance of a controlled pressure differential in the space and its outlet and a quick removal of the spent coolant, that is the achievement of a minimum of coolant standing in the space is outlined.

Thus, the features relating to the maintenance of a controlled pressure differential and a minimisation of the amount of coolant in the space are - contrary to the respondent's statement - clearly supported by the original application.

The remaining independent claims 7, 10 and 13 are supported essentially by original claims 10 and 11 (claim 7), by original claims 14 and 15 (claim 10) and by original claims 19 to 21 (claim 13). Having regard to the terms "liquid coolant" in claims 7, 10 and 13 and to the term "electric arc melt furnace" in claims 2 to 7, 10 and 13, reference is made to the observations appertaining to claim 1.

It follows that the amendments made in the claims comply with the requirement of Article 123(2) EPC.

2.1.2. All the features of claims 1, 7, 10 and 13 added to the respective independent claim as granted lead to a limitation of the scope of protection. This applies also to the issue relating to the substitution of the term "an electric arc melt furnace" for the term "a vessel".

Whilst the respondent is correct in stating that an electric arc melt furnace does not only consist of a vessel and a cover, but comprises additionally a multiplicity of the further parts such as electrodes, electrode holders and supporting beams, exhaust gas ducts, etc., containing partly also water-cooled elements, it is pointed out that the term "vessel for handling a heated substance" comprises any containment which is suitable for handling a heated substance whatever the structure of the vessel may be or whatever additional equipment the vessel may dispose of. The term "electric arc melt furnace for handling a heated substance" relates to a particular containment which besides being suitable for handling a heated substance is defined to comprise all the equipment typical of an electric arc melt furnace. Therefore, the term "electric arc melt furnace" has to be construed more limited than the term "vessel".

Thus, the amendments introduced into the claims comply also with the requirement of Article 123(3) EPC.

2.2. Novelty

2.2.1. In the letter dated 22 October 1997 the respondent set out that the subject-matter of claim 1 and claim 7, respectively, was not novel in view of (D2).

As outlined already in the Board's communication dated 2. July 1998, claim 1 stipulates that the space between the walls of the furnace containment means is maintained at a pressure P enclosed space which is above 101.33 kPa (one atmosphere), and that this pressure is below the value of the pressurised liquid coolant P pressurised coolant and above the pressure of the spent liquid coolant P coolant outlet. Due to the difference between the pressure of the injected liquid coolant and the pressure of the enclosed space it follows that the pressurised liquid coolant and the pressurised gas are injected into the space through separate ducts which applies both to claim 1 and to claim 7.

(D2) describes an apparatus and a method of cooling containment components of a metallurgical furnace, in particular an electric arc furnace. The apparatus comprises spray means in the form of spray nozzles (3) extending into an enclosed space to be cooled for spraying the cooling liquid as droplets against an inner plate (2) of the space. Means (22, 5, 9) for evacuating the spent coolant as saturated vapour and condensed liquid, respectively, are provided, the system operating at normal pressure or at a pressure slightly above one bar. The coolant is led from coolant pressure container (18) through ducts (19) to the spray nozzles (3), no means for injecting a pressurised gas into the space between the inner and outer containment walls being disclosed. It must therefore be concluded that in the case of system operation slightly above one bar this pressure is generated by injection of the pressurised coolant through the spray nozzles (3).

(D2) does not, therefore, disclose the injection both of pressurised liquid coolant and of pressurised gas into the space between the inner and outer containment walls, let alone the injection of coolant and gas through separate ducts and under the pressure relations indicated in claim 1. This conclusion applies also to claim 7 which likewise incorporates the above-cited features relating to the injection of pressurised liquid coolant and gas.

2.2.2. (D1) describes a method of and an apparatus for liquid phase cooling of a vessel, a furnace or a component thereof having an outer plate and an inner plate which define an enclosed space therebetween wherein a liquid coolant in the form of droplets is sprayed against the inner plate to be cooled and the coolant is removed while still substantially in its liquid form thereby preventing undesired build-up of coolant on the inner plate. The liquid coolant is removed from the enclosed space by pump means positioned downstream of the enclosed space which creates a low pressure in the enclosed space whereby the chance of coolant leaking into the furnace is reduced.

Similar to the disclosure of (D2), the furnace cooling system known from (D1) does not describe the feature that pressure differential means is provided comprising means for injecting a pressurised gas into the enclosed space for maintaining the space at a pressure above one atmosphere and below that of the pressurized liquid coolant.

2.2.3. Claims 1 and 7, respectively, are therefore novel (Article 54 EPC).

2.3. Inventive step

2.3.1. The respondent argues that with regard to the disclosure of (D1) the subject-matter of claim 1 and claim 7, respectively, does not involve an inventive step.

As already set out in section 2.2.2 above, in the system described in (D1) liquid coolant sprayed against the plate to be cooled is removed from the enclosed space by pump means located downstream of the enclosed space creating a low pressure in the enclosed space.

As explained repeatedly in (D1)(see e.g. claim 1; column 2, line 55 to column 3, line 2, column 3, lines 19 to 26) a spray of liquid coolant in the form of droplets is directed against the plate to be cooled. Contrary to the respondent's opinion there is no hint in (D1) of injecting a pressurised gas into the enclosed space as required by claims 1 and 7, respectively, of the patent in suit.

The following is pointed out in column 10, lines 4 to 15. of (D1):

"The pump in the test facility comprises a venturi through which waste water from another area of the furnace is caused to flow, producing a low pressure in the scavenger system to evacuate the cooling fluid from the coolant space. Operation of the pump is essential to successful operation of the invention, since in the absence of the pump the volume of water in the cooling space becomes unmanageable."

From the above passage it derives clearly that generation of a low pressure in the scavenger system of the space to be cooled is indispensable to the known system.

The suggestion of the respondent that it is clear for the skilled person that instead of a suction pump at the chamber outlet a pressure pump at the chamber inlet can be applied, cannot be followed by the Board. In a suction pump scavenger system the outlet pipe downstream of the enclosed space is an essential component, failure of which for example caused by leaks will impair the operation of the system. Furthermore, the arrangement of means for injecting a pressurised gas into the enclosed space enables an appropriate positioning of the gas injection means in the sense of achieving the sought-after pushing effect. In contrast to this concept, the operation of a suction pump in the outlet duct of the enclosed space leads to uniform pressure reduction in this space without the possibility of achieving such a locally enhanced pushing effect.

It follows that (D1) teaches in a direction which leads away from the subject-matter of claims 1 and 7, respectively.

2.3.2. The respondent states that it is known from (D2) to operate the cooling chamber with a pressure above one bar and that this pressure is generated by supplying gas and leads to an ejection of the coolant from the bottom of the cooling chamber.

As pointed out already in section 2.2.1 above, in the system known from (D2) the coolant is led from coolant pressure container (18) to the spray nozzles (3) and - contrary to the respondent's statement - no means for injecting a pressurised gas into the space between the inner and outer containment walls for the purpose of forcing out spent liquid coolant are disclosed. Such means do also not appear to be required in this system which operates according to the principle of evaporation cooling in which mainly saturated vapour is generated and drawn off by means of the suction pump (5).

Since (D2) does not teach the injection of pressurised gas into the space to be cooled for maintaining a controlled pressure differential between the space and the coolant outlet sufficient to force the spent liquid coolant out of the space, it cannot lead - similar to the circumstances of (D1) - in an obvious manner to the subject-matter of claim 1 and claim 7, respectively.

2.3.3. To summarize, the Board considers that the solution to the technical problem underlying the invention as defined in independent claims 1 and 7, respectively, involves an inventive step and that therefore these claims as well as dependent claims 2 to 6, 8 and 9 relating to particular embodiments of the invention in accordance with Rule 29(3) EPC are to be maintained.

2.4. Independent claims 10 and 13 and claims 11, 12 and 14 to 16 dependent thereon have not been attacked by the respondent. The Board, after examination of these claims in the light of the prior art discussed in the opposition and appeal proceedings, sees no reason to dispute patentability of these claims. Claims 10 to 16 according to the main request are therefore likewise to be maintained.

3. The grounds of opposition do not prejudice maintenance of the patent in amended form in accordance with the appellant's main request and it is therefore not necessary to consider the appellant's auxiliary requests.