Roll, in particular a roll for a soft calender or supercalender

Abstract: The invention concerns a roll, in particular a roll for a soft calender or supercalender, which roll comprises a metal frame (12), ends (13), and shafts (14), the frame (12) of said roll (10) being coated with a polymer coating (15). In view of equalizing the difference in temperature between the roll (10) ends (13) and the non-coated lateral areas of the metal frame (12), on one hand, and the coated (15) middle area of the roll (10), on the other hand, an arrangement (16;20) for equalizing the difference in temperature has been fitted in connection with the roll (10) ends (13) and with the non-coated lateral areas of the metal frame (12).

Description: The invention concerns a roll, in particular a roll for a soft calender or supercalender, which roll comprises a metal frame, ends, and shafts, the frame of said roll being coated with a polymer coating. Coated rolls are used in paper machines and in paper finishing devices in highly different applications. As examples of such applications can be mentioned soft rolls of soft calenders and of supercalenders, and equivalent. Usually the soft coatings on rolls are made of organic polymers or of their mixtures, which often also include inorganic elements. The soft coatings on rolls are often made of a composite structure, which comprises layers made of different materials. In calenders, such as soft calenders or supercalenders, the roll nips are so-called soft nips, i.e. nips in which a hard roll is fitted as a pair for an elastically resilient roll. Elastically resilient rolls have been so-called paper-filled rolls, i.e. rolls that consist of paper strips fitted as layers one above the other, but at present various types of polymer-coated rolls are used more and more commonly as the resilient rolls. The coating on a polymer-coated roll is an insulator, and when the roll revolves, the polymer coating produces thermal energy as a result of the nip effect and as a result of compression and bending, and this thermal energy is partly conducted into the metal-mantle frame of the roll. The surface temperature of the polymer can be up to 80°C during calendering. The metal mantle of the roll expands because of the thermal energy, which also affects the quality of the paper to be calendered. From the roll mantle heat is also conducted to the roll ends and to the shafts, which are not placed inside the insulating polymer coating, in which connection a difference in temperature arises between the middle portions and the lateral portions of the roll, as a result of which the roll becomes "barrel-shaped". This phenomenon is not desirable in view of the calendering process or of the use of the coatings, in particular in view of their service life. Prior-art publications G 9207957.1 and EP 0554698 disclose solutions to prevent excessive warming of edge zone of a roll coating by means of localized cooling. The object of the present invention is to provide a roll in which the distortion described above and arising from the flow of heat does not occur in the roll frame and with which roll, thus, the quality of calendering remains at the desired level. In view of achieving the objectives stated above and those that will come out later, the roll in accordance with the invention is mainly characterized in that, in view of equalizing the difference in temperature between the roll ends and the non-coated lateral areas of the metal frame, on one hand, and the coated middle area of the roll, on the other hand, by minimizing the conduction of heat to the ends and through the ends into the air, an arrangement for equalizing the difference in temperature has been fitted in connection with the roll ends and with the non-coated lateral areas of the metal frame. According to an exemplifying embodiment of the invention, the end areas of the polymer-coated roll are insulated by means of an insulating material, such as polyurethane or equivalent, in which connection the conduction of heat to the end and through the end to the air is minimized and the difference in temperature between the end areas and the middle areas is equalized, in which case the diameter of the roll remains substantially as desired. According to a second exemplifying embodiment of the invention, in view of minimizing the conduction of heat to the end and through the end to the air and, thus, in view of equalizing the difference in temperature between the end areas and the middle areas, the end areas of the polymer-coated roll have been provided with heating, for example induction heating. In the following, the invention will be described in more detail with reference to the figures in the accompanying drawing, the invention being not supposed to be in any way strictly confined to the details of said illustrations. Figure 1 is a schematic illustration in part of an exemplifying embodiment of a roll in accordance with the present invention and of a backup roll of said roll. Figure 2 is a schematic illustration in part of a second exemplifying embodiment of a roll in accordance with the present invention and of a backup roll of said roll. Figures 3A...3B are schematic illustrations in part of a further exemplifying embodiment of a roll in accordance with the present invention. In Fig. 1 the polymer-coated roll is denoted with the reference numeral 10 and the backup roll with the reference numeral 11. The paper web W runs through the calendering nip between said rolls. The roll 10 comprises a metal mantle 12, ends 13, and shafts 14. The polymer coating on the roll 10 is denoted with the reference numeral 15. The coating 15 consists of coating layers 17,18,19. According to an exemplifying embodiment of the invention, shown in Fig. 1, the roll 10 ends are provided with an insulating material 16. The insulating material 16 covers the roll 10 ends so that the insulating material 16 extends from the edge of the coating 15 to the shoulder 14A of the shaft 14, in which case substantially the entire roll 10 end is insulated, whereby the difference in temperature between the roll 10 ends 14 and the middle areas provided with a coating 15 is equalized and the shape of the roll 10 remains substantially as desired. The insulating material 16 can be polyurethane or any other suitable insulating material. In Fig. 2 the polymer-coated roll is denoted with the reference numeral 10 and the backup roll with the reference numeral 11. The paper web W runs through the calendering nip between said rolls. The roll 10 comprises a metal mantle 12, ends 13, and shafts 14. The polymer coating on the roll 10 is denoted with the reference numeral 15. The coating 15 consists of coating layers 17,18,19. According to a second exemplifying embodiment of the invention, shown in Fig. 2, in the non-coated end areas of the roll 10 provided with a polymer coating 15, heating 20 has been provided, for example induction heating. By means of the heating arrangement 20, the roll 10 ends and the non-coated lateral areas of the metal frame 12 are heated so that the difference in temperature between the roll 10 ends 13 and the coated 15 middle areas is equalized. In Figs. 3A...3B the polymer-coated roll is denoted with the reference numeral 10. The roll 10 comprises a metal mantle 12, ends 13, and shafts 14. The polymer coating on the roll 10 is denoted with the reference numeral 15. According to an exemplifying embodiment of the invention, shown in Figs. 3A...3B, in the non-coated end areas of the roll 10 provided with a polymer coating 15, heating 20 has been arranged as water heating. By means of the water heating arrangement 20, the roll 10 ends and the non-coated lateral areas of the metal frame 12 are heated so that the difference in temperature between the roll 10 ends 13 and the coated 15 middle areas of the roll is equalized. The heating water, which is denoted with the arrows V, is passed to circulate into the bores 21 in the ends 13, for example, through bores 22 that have been made into the shafts 14. A heating arrangement 20 is provided in connection with each end 13 of the roll 10. The heating water V can also be supplied through one end only, in which case the water is passed into the opposite end along an insulated peripheral bore that has been made into the roll 10 frame 12. The temperature of the heating water V is, for example, 10°C hotter than the temperature of the roll. Above, the invention has been described with reference to a preferred exemplifying embodiment of same only, the invention being, however, not supposed to be in any way strictly confined to the details of said embodiment. Many variations and modifications are possible within the scope of the invention defined in the following patent claims.

Claims: A roll, in particular a roll for a soft calender or supercalender, which roll comprises a metal frame (12), ends (13), and shafts (14), the frame (12) of said roll (10) being coated with a polymer coating (15), characterized in that , in view of equalizing the difference in temperature between the roll (10) ends (13) and the non-coated lateral areas of the metal frame (12), on one hand, and the coated (15) middle area of the roll (10), on the other hand, by minimizing the conduction of heat to the ends (13) and through the ends (13) into the air, an arrangement (16;20) for equalizing the difference in temperature has been fitted in connection with the roll (10) ends (13) and with the non-coated lateral areas of the metal frame (12). A roll as claimed in claim 1, characterized in that the arrangement for equalizing the difference in temperature in the roll (10) is an insulating material (16), which substantially covers the roll (10) ends (13) and the non-coated lateral areas of the metal frame (12). A roll as claimed in claim 1 or 2, characterized in that the insulating material (16) extends from the axial edge of the coating (15) to the shoulder (14A) on the roll (10) shaft (14) in the radial direction. A roll as claimed in any of the claims 1 to 3, characterized in that the insulating material (16) consists of polyurethane. A roll as claimed in claim 1, characterized in that the arrangement for equalizing the difference in temperature in the roll (10) is a heating arrangement (20) fitted in connection with the roll ends (13) and with the non-coated lateral areas of the metal frame (12) of the roll. A roll as claimed in claim 1 or 5, characterized in that the heating arrangement (20) is an induction heating device. A roll as claimed in claim 1 or 5, characterized in that the heating arrangement (20) is a water heating arrangement. A roll as claimed in claim 7, characterized in that bores (21,22) have been arranged into the roll (10) ends (13) and shafts (14), into which bores the heating water (V) is fitted to be passed.

Inventors: IJAES VESA, KIRVESMAEKI MARKKU, KUOSA HARRI, KYYTSOENEN MARKKU, MERONEN JOUKO, STAPELS ROB, VAINIO RISTO, IJAES, VESA, KIRVESMAEKI, MARKKU, KUOSA, HARRI, KYYTSOENEN, MARKKU, MERONEN, JOUKO, STAPELS, ROB, VAINIO, RISTO, Ijäs, Vesa, Kirvesmäki, Markku, Kyytsönen, Markku
Applicants: METSO PAPER INC, METSO PAPER, INC.
Application year: 1997
Main classification: D21G1
IPC codes: D21G1