T 0099/96 11-01-2000

Reasons for the Decision

1. The appeal is admissible.

2. Since none of the cited prior art documents discloses an extended press nip apparatus having all the features of Claim 1, its subject-matter is considered to be new (Articles 52 and 54 EPC). In the oral proceedings on appeal, this issue was no longer contested.

3. Not disputed is also the fact that the apparatus described in citation E8, which is cited in the introductory part of the description of the patent in suit, represents the prior art closest to the present invention. It describes a two-nip press section of a paper machine, which comprises all the features of the preamble of Claim 1. At least the second nip is an elongate extended press nip comprising a press shoe, which urges the blanket means and the fibrous web against a press roll. Before this nip, heating means, in the form of a steam supply box and considered as the preheater in Claim 1, is disposed adjacent to the web, as said web is moving over a 180 sector of a suction roll surface, towards said extended press nip. According to page 13 of citation E8, the dewatering in the extended press nip is thereby improved.

4. According to the description of the patent in suit, the main object of the invention is to remove greater quantities of water from the fibrous web, in other words to improve the dewatering capacity or drying efficiency of such a known press section, which comprises an extended nip press shoe.

5. This problem is solved by the features of the characterising portion of Claim 1, namely that:

(a) said apparatus comprises further heating means (..) disposed adjacent to said press roll (..) for transferring thermal energy to the web during passage of the web through said pressing section (..),

(b) said thermal energy being transferred to the web either by said press roll (..) or by a thermal transfer means (..) cooperating with said blanket means (..) for defining said pressing section therebetween, and

(c) that when the web (..) passes through the press section between said elongate press shoe (..) and said press roll (..), the web is continuously subjected for an extended period to increased pressure and temperature, so

(d) that water vapor generated within said pressing section (..) during the passage of the web through the pressing section forces the fluid in the liquid phase away from the web.

6. During the discussions in the oral proceedings on appeal, the respondent acknowledged that the reference signs, briefly shown above by the signs (..) when relating to the further heating means, were incomplete (according to Rule 29(7) EPC, such a deficiency has no effect on the scope of the claim) and that the further heating means according to the invention can comprise means heating directly the press roll surface (Figures 2, 3, 9 and 10), or means heating the roll through the web combined with means heating directly the transfer means (Figures 4 and 5), or means heating the roll through the web, possibly associated with the blanket, these means being combined with means heating directly the press roll (Figures 6 and 5), means heating the transfer means through the blanket (Figure 8), or heating means located inside the press roll (Figure 11). In each embodiment, therefore, either the press roll or the transfer heating means directly transfers heat to the web, when said web is passing through the extended nip. This aspect of the invention is emphasized by the above feature (b) in combination with the expression "subjected continuously to increased pressure and temperature" (in the extended press nip) of the following feature (c).

Feature (d) moreover indicates the result which has to be obtained and sets out precisely that, due to the increased pressure and temperature, first water vapor is generated in the pressing section and that further said vapor forces the fluid in the liquid phase away from the web. Such a result implies temperatures inside the pressing section, which are at least at the boiling point of water, and consequently temperatures of the thermal transfer means, namely the press roll or the mentioned particular transfer means, which are well above this point. This interpretation of the above features (b) to (c) is confirmed by the description of the patent as granted, see column 3, lines 46 ff., and line 1 of column 17, which disclose that the basic concept of the invention is the application of high temperatures to the web in order to obtain such an effect, namely that a rapid evolution of water vapor forces the water remaining in the web to flow out of the web in the liquid phase, that is to say under its boiling point. Pressures of up to 107 bar and temperatures of up to 649 C for the press roll are given. According to the description of the patent in suit, it is the combination of high pressures and high temperatures inside the extended nip, which allows such a result to be obtained.

As a consequence, the board of appeal cannot follow the statement of the appellant that features (b) to (c) of the above solution are to be neglected. Claim 1, although it is drafted as an apparatus claim, is in fact to be considered as a mixture of apparatus and process claim, and the solution as claimed does not reside in the feature (a) alone, but in the provision of heating means disposed adjacent to said press roll for transferring thermal energy to the web by means of either the press roll or particular thermal transferring means during the passage of the web through the pressing section, so that said web inside said section is continuously subjected to increased pressure and temperature in order to obtain the result claimed in feature (d). Increased temperatures mean temperatures not only higher than those of the preheated web just before it enters into the pressing section, but higher enough so that the feature (b) is obtained. Therefore, the heating means and their cooperation with the roll or thermal transfer means are to be constructed or arranged so as to obtain this result.

7. In the oral proceedings on appeal the appellants have essentially based their objection of lack of inventive step on the combination of the above mentioned closest prior art with the teaching of the citation E7 .

The object of this last document is to improve the dewatering action of the press section of a paper machine running at high speeds. According to this document, it was already known to boost the dewatering by raising the temperature of the felt, web or press roll, however only small improvements were obtained, since on the one hand, the heating temperatures were to be kept relatively low to avoid deteriorations of the felt, which moves with the web, and, on the other hand, the time available for heat transfer was limited because of the high velocities. The solution proposed by this document consists, in a press section comprising three linear press nips, in having first heating means between the first and second press nips for one side of the web and second heating means between the second and third nips for the other side of the web, the thermal energy of these two heating effects being such that the temperature of the web rises before the last nip at least above 50 C but remains preferably below 95 C, since one basic idea of the solution is to create strengthening bonds of hemicellulose (a kind of fibres of the web) contained within the web, while taking care not to heat the web past the softening points of other kinds of fibres of the web, for example lignite and cellulose. The first heating means consists of a hood supplying hot steam onto the web during its passage over a section of the suction roll, which is one of the two rolls defining the second nip, the web passing over the surface of the other roll after said nip. The second heating means in the form of infra-red radiators extends over the largest possible sector of this other roll between the second and third nips, said roll being a smooth-surface stone roll. This particular kind of heating means is used, since it provides heat deeply enough in the web in order to reach the wished bond effect which strengthens the web simultaneously with the increase of dryness of the web and, thus, permits higher speeds. It is moreover disclosed in this citation E7 that it is possible in both heat treatment steps to extend the heat treatment very close up to the nips so that the thermal energy directed to the web is efficiently used in the nips (column 4, last lines). In the last part of the description, see column 12, lines 4 to 12, a short sentence at the end of the paragraph indicates that, because of the second heating means, the stone roll fairly soon acquires a certain constant temperature and, thus, heats the web in the second nip and thereafter (column 12, lines 4 to 12).

8. It is first pointed out that this prior art does not deal with extended press nips, thus even less with press shoe nip, so that, having regard to the problem underlying the present invention, it is already doubtful whether the person skilled in the art would have considered this document.

Should he nevertheless have done so because of the broad aim of improving the dewatering of a web in a press section, he would not have found a teaching which substantially brings much more than that which was already known from the closest prior art according to E8. As mentioned above in Point 3, it was known from this closest prior art that the dewatering effect in the extended nip was improved by the heat provided by the steam pre-heater. What can be further suggested by the citation E7 is eventually to bring the heating means very close up to a nip for the same object, since otherwise this prior art only teaches to provide heating means between each pair of nips and nothing more, and that for a different purpose, namely for alternate heating of both sides of the web. Contrary to the opinion of the appellants, no clear suggestion appears in this prior art to provide further heating means for the same nip additionally to first heating means, such as the pre-heater according to E7. The only possible step for improving the dewatering effect, which could be deduced from E7, would therefore have been to bring the pre-heater closer to the pressing section in the arrangement according to E8.

9. The heating means in the disclosure of E7 can only heat the rolls through the web, since the web is the element of the press section, which is heated first. There is no direct heating of the roll or of thermal transfer means, so that, inside the nip, the temperatures which could be obtained are lower than or equivalent to those of the web given by the upstream located heating means. Therefore, there is no suggestion in E7 to provide further heating means, which constitutes means for subjecting the preheated web continuously and simultaneously to an increased pressure and temperature inside the pressing zone, that is to say for an extended period. By locating the heating means between the nips, E7 rather teaches a successive application of heat and pressure. Moreover, the limited temperature range given in E7, even if it is only disclosed as preferable, at least cannot suggest the result according to feature (d) of the claimed solution.

For all these reasons, the combination of the prior art according to E8 with the teaching of the citation E7 does not lead to the subject-matter of Claim 1 of the patent in suit.

10. In his written submissions, the appellant has further combined E8 with the citation E1. This last citation concerns a quite particular apparatus comprising hose rolls, whose first object is to improve the elasticity of the paper web. In the drying section of a paper machine, these hose rolls are located between and pressed by drying cylinders of larger diameters. Consequently, between the drying cylinders and the hose rolls extended nips are formed, in which the paper web travels. The appellant has assimilated these extended nips to the extended nip obtained between a press shoe and a press roll, although a press shoe forms a solid surface. Already for this reason, the production of this document appears to be the result of a search a posteriori.

Moreover, this document does not relate to the press section of a paper machine. It is clearly indicated on page 1 of this citation that the therein disclosed invention concerns an apparatus for pressing a web against a movable counter-surface, and as far as a paper machine is given as example, it is the drying section of this machine which is mentioned. As a consequence, a dewatering process by pressing is not disclosed, nor an extended press. Moreover, this document does not teach to remove water in the liquid phase from a web by a simultaneous application of heat and pressure over a long period, so that an important concept of the present invention as claimed is missing. Thus, this citation E1 cannot suggest the solution of the present invention according to Claim 1.

11. It follows that the apparatus according to present Claim 1 of the patent in suit involves an inventive step. Since the method according to Claim 14 comprises all the same features, however presented in the form of process steps, the same conclusion applies for this claim.