In modern paper and pulp machines, especially in calenders and presses, are often simultaneously used both so-called thermorolls, the mantle temperature of which is high, and soft-surface rolls associated with the thermorolls, the surface material of the soft-surface rolls, such as a polymer, withstanding less heat than the surface material of an uncoated roll. A problem in the simultaneous use of the thermoroll and soft-surface roll forming a nip is heat transfer (conduction and/or radiation) from the thermoroll onto the surface of the mantle of the soft-surface roll, especially in the edge zone, which the web material passing through the nip does not cover. In such a case the temperature of the edge zone of the roll mantle increases, which results in temperature differences in the transverse direction of the roll mantle surface increasing. This may in turn lead to the roll surface being damaged, especially in the edge zone. A problem is also constituted by the risk of breakage in the unprotected edge zone if subjected to an impact load. For example, when the counter-roll is moved, it may tilt and at the same time hit the surface of the edge zone of a soft-surface roll, thus causing an impact load and damaging it.

To solve the above problems, the patent publication FI/EP 792966 discloses a solution in which insulating tapes are provided around the mantle in the

edge zone of a counter-roll or soft-surface roll. It also comprises a detector, which determines, on the basis of the edges of the web, the width of the insulation tapes in the axial direction of the roll and their location in the roll nip.

The patent publication FI 98390 discloses an apparatus for cooling the edge zone of a roll, in which apparatus water and air are conveyed on the surface of a roll from a nozzle part arranged to be movable. Relating to mobility, the moving of the edge of the web or changes in the width of the web have been taken into account. The structure of such apparatus is, however, complex and expensive.

The aim of the present invention is to provide simple, reliable protection for the edge zone of a roll, which will prevent the edge zone from heating excessively and balances temperature differences of the roll mantle in the axial direction of the roll. In addition to the above, a further aim of the invention is to protect the edge zone against impact loads.

In accordance with the invention, this is achieved by arranging guides in conjunction with the end of the roll and/or the edge zone, by means of which free cooling air can be guided in the edge zone of the roll.

The aim of the present invention is in addition achieved in such a way that in the edge zone of the roll is provided a coating layer of impact load resistant material, and that guides are arranged in conjunction with the end of the roll and/or the edge zone, by means of which free cooling air can be guided in the edge zone of the roll.

According to the invention, as the roll rotates, the air is funnelled by means of the guides from the surroundings of the end of the roll at a reasonable speed in the manner of blasts to the edge zone of the roll. In this case, no separate blowers or corresponding separate devices are required to cool the

edge zone, because the air cooling the roll mantle changes continuously in the edge zone.

The invention is described in the following with reference to the appended drawings, in which: Figure 1 shows a partial sectional view of the end of the polymer-coated roll.

Figure 1A shows another embodiment of the roll shown in Figure 1.

Figure 2 shows a sectional view of Figure 1 along line II-II.

Figure 3 shows an alternative embodiment of the roll of Figure 1.

Figure 4 shows a sectional view of Figure 3 along line IV.

Figure 5 shows a fourth embodiment of a roll according to Figure 1.

Figure 6 shows a sectional view of Figure 5 along line VI-VI.

Figure 1 shows a roll 1, which is fitted with bearings from its shaft 7 at both ends 5 to a bearing block 10. A roll mantle 2 is arranged to rotate around the shaft 7. The roll mantle 2 is supported in a previously known manner on bearings (not shown) provided on the shaft 7. The roll mantle 2 is coated with a material softer than the roll mantle 2 itself, for example, a polymer 3.

The end of the roll mantle 3 is closed solidly or removably by means of an end flange 5'attached to the end 5 of the roll mantle 3. By the end 5 of the roll 1 is here referred to that part of the shaft 7, which is not surrounded by the roll mantle 2.

The roll 1 is in a nip N forming connection with the counter-roll 8. The counter-roll 8 is, for example, a thermoroll. A paper web 9 has been passed through the nip N. The width of the paper web 9 is a distance narrower in the axial direction of the roll 1 than the roll mantle 3, which means that on the roll 1 remains an edge zone 20 free of web material 9.

Heat H is transferred from the thermoroll 8 in connection with the nip contact of the rolls 1 and 8 to the web material 9 passing through the nip N and onto the polymer surface 3 of the roll 1. The heat H transferred to the polymer surface 3 is not harmful to the coating 3 at the point where the web material is between the nip N, because most of the heat is absorbed by the web material and with it away from the roll 1. On the other hand, at the point where there is no web material 9, that is, in the edge zone 20 of the roll 1, the transfer of heat H to the roll 1 is more intensive and may damage it.

To compensate for the heat transfer, cooling is arranged in the edge zone 20 of the roll 1, the major part of which is formed by guides 6 formed in the polymer coating 3 of the roll mantle 2. The guides 6 are adjacent spiral-like grooves or corresponding elongated recesses formed on the cylindrical surface of the polymer coating in the edge zone 20, as shown in Figure 1.

They may also be ribs 6'arranged in a corresponding pattern, as shown in Figure 1A. The grooving 6 or ribbing 6'preferably extends in the axial direction of the roll 1 from the outer edge of the polymer coating 3 to that edge of the edge zone 20 on which the edge of the web material 9 is located. The grooving 6 or ribbing 6'preferably extends over the distance of the entire edge zone 20.

As the roll mantle 3 rotates, the guides 6,6'rotate with the roll mantle 2.

This means that they will bring the free air A surrounding the edge zone 20 into a flowing movement so that fresh and cool, that is, cooling air A will flow continuously around the coating 3. The purpose of the grooves 6 or ribs 6'is

thus to change the air A otherwise warming up around the edge zone 20 and to thus cool the polymer coating 3.

Figures 3 and 4 show another embodiment of the invention for protecting the edge zone 20 from excessive heat H. Around the polymer coating 3 of the roll 1 mantle 2 is fitted an end piece 13. It is arranged to rotate with the roll 1 mantle 2 either solidly or removably, for example, by means of bolted joints to the end flange 5'. The outer surface of the end piece 13 is essentially cylindrical. On the outer surface are arranged guides 6,6' diagonally to the axial direction, by means of which free air A is guided, as described in connection with the first embodiment, on the edge zone 20 of the roll 1 to cool the edge zone 20. It is also possible to form a sleeve-like extension comprising the guides 6,6'on the flange 5', which extension can be fitted around the polymer coating 3 of the roll mantle 2. By means of the end piece 13 the guides 6,6'may extend outside the edge of the roll mantle 2, to the end 5 area, which will intensify the flow of cooling air A. The material of the end piece 13 is preferably metal, glass or carbon fibre.

In the vicinity of the ends 5 of the roll 1 are further provided air supply means 11. Their purpose is to bring additional air A intended for cooling to the area of the ends 5 of the roll 1 and thus to ensure a sufficient and fresh supply of cooling air A for the ends 5 of the roll 1 and the edge zone 20. Air supply is realised, for example, by first compressing air A in a compressor 11a and then supplying it through the supply channel 11b to the area of the roll 1 ends 5.

Figures 5 and 6 show a preferred embodiment of the invention, where in the edge zone 20 of the roll 1 mantle 2 is provided a coating layer 4 surrounding the polymer coating 3. The coating layer 4 is of a material which insulates the polymer coating 3 in the edge zone 20 of the roll 1 from the heat H radiated or conducted from the thermoroll 8. In the coating layer 4 are arranged guides 6,6'in the manner taught above for guiding the air A in the

edge zone 20. The coating layer 4 shown in broken line shows an alternative in which the coating layer 4 is arranged to rotate around the roll 1 and the release roll 12. The coating layer 4 is then in contact with the roll 1 in the area of at least one nip N and released over a part of the radial distance of the surface of the roll 1 by means of the release roll 12. In addition to insulation, the heat H transfers effectively away from the roll 1 by means of this arrangement. In addition to the above, the cooling of the polymer coating 3 and the coating layer 4 may be intensified in the edge zone 20 by attaching an end piece 13 according to the previous embodiment to the end 5 of the roll 1, where there are guides 6,6'for guiding the air A.

In some cases, the edge zone 20 may be subjected to mechanical impacts.

For example, when the thermoroll 8 is moved, its end part may hit the edge zone 20 of the roll 1 with impact and bring about an impact load F in the edge zone 20 of the roll 1. For receiving this impact load, the coating layer 4 is of such material, in addition to insulating heat, which will absorb at least a part of the external sudden load F. This arrangement may also be applied to the end piece 13 in connection with the previous embodiment by using material which also withstands impact loads F. The coating layer 4 is of such thin and/or compressible material that it does not affect the nip force exerted on the web material 9 of the nip N in the axial direction of the roll 1. The roll mantle may be a belt or a coating on a polymer roll 1. It is also conceivable to realise the coating layer 4 without the guides 6,6'guiding the air A.