FI105115B - Heated roller - Google Patents

Description

Heated roller

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The invention relates to a heated roll according to the preamble of claim 1.

In paper and board machines and paper finishing equipment, especially calendars and supercalenders, generally heated rolls are used. Heated rollers are also used, for example, on a press section of a paper machine. The heating of the rolls is generally treated by means of a heat transfer medium such as hot water, oil or steam. There are mainly two types of heated rollers. On the other hand, heating rolls in which the roll shell or the massive roll is provided with substantially axial bores formed near the outer surface of the roll 15 through which the heating medium is passed from one end to the other are known in the art. There are usually several of these bores, which are usually evenly distributed in the circumferential direction. The heating medium may be made to rotate in said bores either once at the end of the roll or two or more times so that in the adjacent bores the heating medium may travel 20 in opposite directions.

. ···. On the other hand, so-called heated rollers are commonly used. double-diaphragm rollers or bypass. rolls having a sealing piece with a displacement cap fitted inside the roll shell, so that there is an annular space between said displacement body and the peripheral surface of the roll shell, where the heating medium is adapted to rotate from the roll end to the end.

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Also known in the art is a heated roll which combines the above types of::: the main types of rolls to be heated, i.e., a roll with axial drill holes · · · V: also provided with internal heating. Such is disclosed in US-A-30 5,072,497.

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A prior art heated roll, wherein the heating medium supply is provided in each of the second passages of the first roller outlet at one end of the roll, and respectively the supply is arranged in every other channel at the second end of the roll and the first roller outlet. U.S. Patent No. 89,087.

FI Patent Publication No. 91,297 discloses a heated roll which is provided with means for increasing the heat transfer coefficient from the flowing heating medium acting on the roll shell or roll material to the roll material in the direction of flow of the heating medium 10. This disclosure also discloses a roll comprising a hollow roll casing with a displacement body inserted therein such that an annular space is provided between the roll casing and the displacement body, in which the heating medium is adapted to rotate from roll to end. The inner surface of the roll shell is provided with an insulating material or similar coating which decreases in the direction of flow or is roughened so that said roughening increases in the direction of flow of the heating medium DE-A-40 02 530 discloses a heated roll with an axial bore in a row such that in the bores closer to the outer surface of the roll: '.: 20, a heating medium is supplied to the end of the roll:' "; up to three times back and forth and in the same radial line: :: there is a return flow.

DE-A-44 07 239 discloses a heated roll, in which the heating medium is steam, which is conducted along axial bores so that heated bores are conducted through the roll in the outer bores and the condensate water is, in turn, returned through the inner bores.

DE-A-43 17 875 describes an application for circulating a heating medium in a heated roll. In this known arrangement, circular currents in opposite directions as well as currents arranged in the center of the roll are used.

3 705775 DE-A-195 38 236 discloses a steam-heated roll in which steam acting as a heating medium is fed through the roll along axial borings and through a hub, and the returned condensate enters the feed end via a circumferential bore and hub.

EP-A-0 597 814 discloses a heated roll having a coating on the outer surface of a roll casing wherein the heating medium is recycled within the roll casing and comprising a ceramic connection or a metal ceramic alloy having lower thermal conductivity and elastic properties than the said roll casing.

[0005] Publication No. 98,940 discloses a method and apparatus for calendering paper comprising an internally heated calender roll for finishing paper with a thermoplastic material having a jacket at least 101.6 mm thick and provided with a conduit for heating heat to the material to be calendered. The roll shell has a thin coating consisting of a cermet or ceramic material.

In prior art thermal roller solutions in which the jacket heating medium channels are in one row close to the surface, a small temperature difference between the outer surface of the roll and the heating oil is achieved with a relatively short heat transfer distance. However, the resulting gradient is relatively large. The resulting heat distribution of the jacket is periodic: / · Depending on the channel distribution and even on the roll surface, there are small periodic »/ ·· temperature variations. Temperature fluctuations cause inhomogeneous thermal expansion of • 1: .v and result in small periodic variations in roll diameter (gingerbread effect). This • · · V 1 25 malfunction may cause eg. periodic oscillation in a rotating nip. The main object of the invention is to solve the problems of uneven heat distribution.

. In addition to the problem described above, in many prior art applications, the heating and cooling of the roller is remarkably slow, since energy can only be transferred to a limited area of the tubing row. when applied to a narrow area on the roll, large temperature differences, and hence stress differences, occur, which can result in 4705775 point-to-point temperature gradients and the plastic may begin to plasticize, which makes the upper limit of the heating rate a limiting factor. The object of the invention 5 is also to provide a solution to the problem.

In order to achieve the above and later objects, the roll according to the invention is essentially characterized by what is stated in the characterizing part of claim 1.

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According to the invention, the problems caused by uneven even-point temperature gradients are eliminated by dividing the circumferential bores from at least two different radii, i.e., circumferential rows at different distances from the center of the roll, and arranging the bores into a different radial line, i.e. interleaved. In this way, a uniform temperature distribution is achieved because the heat flux is uniformly transferred within the roll casing. In accordance with the invention, instead of heating medium passages disposed in the sheath, the roll itself can be heated from the center, as is known, thereby further stabilizing the temperature in the roll sheath and eliminating the high temperature gradients. In this connection, the temperature of the fluid in the peripheral boreholes vs the center borehole is adjusted to achieve a smooth transition of the thermal path. For central heating, a displacement block may be used to control: * /: heating near the duct edge and to reduce the amount of heating medium • ·> * · required.

In addition, displacement bodies may be used in connection with the arrangement of the invention to provide a temperature equalization in the longitudinal direction of the roll. In addition, heating medium flows in different directions can be used to equalize the temperature in the longitudinal direction of the roll, in which several different combinations, which are generally known per se, can be used. For example, when the channels are in two different rows of 30 radii, the heating medium is introduced from one roll to the other end of the roll along two preferably smaller channels in the upper row and returned along one channel in the lower row. In addition, for example, the direction of adjacent channels may be varied and other arrangements will be apparent to those skilled in the art. The flow of each channel is preferably controlled by its own valve. The flow rate and the temperature of the heating medium are controlled in each channel. The Kes-5 spindle bore can be used as a heating medium channel both as a return channel and as a flow channel with or without a displacement body.

By using the invention, the temperature distribution of the roll to be heated is more uniform and, moreover, the invention can accelerate the transient heating / cooling steps. Heating roller channels are constructed in the roll shell in two or more circumferential rows, and the channels are spaced apart with different rows on a different radial line and the temperatures of the heating medium passing through the channels are suitably arranged to obtain a uniform temperature distribution of the roll shell surfaces. When there are several channels, the diameter of the channels can be reduced accordingly.

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By transferring heat energy through a plurality of regions during the heating / cooling of the roll, the available power is distributed over a larger range. It is possible to heat the roll through a plurality of heating channel rows, and possibly further by induction from the surface. This is how power is distributed over a larger area and not restrictive: '·: 20 large temperature gradients cannot occur. According to the invention, a uniform «·: '': temperature distribution on the surface of the roll and additionally the distribution of the heating duct (heating power) over a larger area allows faster heating of the roll without limiting the thermal tension. ♦ · • · ·. ·. · nee.

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According to one embodiment of the invention, it is also possible to use the center channel duct • · # - · ·. * · 'And the peripheral bores of the diaper in one rational way for different applications.

In normal driving situations, slightly hotter oil is introduced into the center bore, · / ·: compared to the peripheral bore, resulting in a more even temperature distribution of the sheath 30 compared to the use of peripheral ducts alone. This also reduces the amount of periodicity generated on the surface. Also, during the heating and cooling phase of the roll, power is transmitted through both the • • 6 1 ° 5l15 and peripheral channels. When decomposing the total power, the resulting temperature gradients of the transient steps are smaller with the same total power. In other words, this allows for a higher total power output without increasing the temperature gradients. This implies shortened transients in heating and cooling.

The invention is particularly suitable for use with oil-heated rolls.

In the following, the invention will be described in more detail with reference to Figures 10 of the accompanying drawing, however, the details of which are not to be construed as being narrowly limited.

Figure 1 is a schematic representation of temperature equality curves in a roll shell with a prior art solution.

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Fig. 2 schematically illustrates temperature equality curves in a roll shell using an arrangement according to the invention in which the peripheral bores are arranged in two different circumferentially spaced rows.

; ' <(· 20) Figure 3 is a schematic representation of the temperature equality curves when using peripheral

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; "': Hatches and Central Heating. Fig. 1 schematically illustrates a portion of the heater roll casing 11 having, according to the prior art, one row of heating medium channels 12 which are circumferentially oriented. A: 25 in a row near the surface 13 of the sheath 11. The figure illustrates the heat flux acting on the sheath when conducting the heating medium in the ducts. In this embodiment of the prior art • ·: .V, a strong ♦ · · • · · · * Temperature gradient to region 23 resulting in a periodic temperature variation of 22 on the roll surface 14. This may result in minor deformations on the roll surface and cause vibrations and / or deformation of the roll surface.

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Fig. 2 schematically shows a portion of the shell of the heated roll 31 having circumferential bores 32 and 33. The peripheral bores are in two circumferential rows R1 and R2 and are spaced, i.e. radially on a different line, as shown in the figure. The figure shows schematically the heat flux as the heating medium is introduced into the peripheral bores. Fig. 2 shows a uniform temperature distribution 24 provided by two peripheral rows R 1, R 2 in accordance with the invention, provided by circumferential bores 32, 33, which are spaced apart on different radial lines to obtain a uniform temperature distribution 24.

Figure 3 schematically shows a portion of a roll shell 41 having peripheral bores 42 and wherein heating is also effected via a hub 45 and the directions of heat flow are indicated by arrows. As shown in the figure, the temperature distribution when heating the hub 45 and the peripheral bores 42 is uniform and the temperature gradients are small. If necessary, a displacement cap (not shown in the figure) known in the art can be used in connection with central heating.

According to the invention, in the application examples shown in Figures 2 and 3, the temperature of the heating medium can be varied in different channels (bores) and thus further equalize the heat distribution and reduce the temperature gradients. In the various channels, the flows can be implemented in the desired directions in different directions, and by using circumferential bores arranged in several rows, they can be interlaced in many different ways and different channels of different sizes may be used to achieve even heat distribution.

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The invention has been described above with reference only to some advantageous embodiments thereof, the details of which, however, are not to be construed as being narrowly limited.

Many modifications and variations are possible within the scope of the inventive idea defined in the following claims • · * · · · *. *. *.

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Claims (11)

A heated roll for a paper machine, paper finishing device or the like, comprising a roll mantle (31) heated by a heating medium, wherein the roll roll (31) is provided with passages (32) extending substantially from the roll surface to the outer surface (34). ) or the like through which the heating medium is rotated to heat the outer surface (34) of the roll mantle (31), characterized in that channels (32, 33) or the like are arranged in at least two circumferential rows (R1) to reduce the temperature gradient of the roll mantle (31). R 2) and that the channels (32, 33) in the two rows (R 1, R 2) or the like are spaced apart so that the channels (32, 33) are on different radial lines. Heatable roll according to Claim 1, characterized in that a channel for recirculating the heating medium is formed in the center of the roll. 15 Heatable roll according to Claim 1 or 2, characterized in that the temperature of the heating medium supplied in the center of the roll is adjustable to reduce the temperature gradient of the roll shell (31) in the channels (32, 33) or the like. 20 A heatable roll for a paper machine, paper finishing apparatus or the like, comprising a roll mantle (41) heated by a heating medium to which: • m: * ·· The roll mantle (41) is formed substantially adjacent the outer surface (34) of the roll mantle (41). End-to-end channels (42) or the like through which the heating medium is rotated to heat the outer surface of the roll shell, and wherein a heating medium is arranged to be rotated through the center of the roll (45), To reduce the temperature gradient of the roll mantle (41) in the passages of the roll mantle (41) • · · '* (42) or the like and the heating medium to be conducted in the roll center (45) •! are individually adjustable. 30 9 105115 Heated roll according to Claim 4, characterized in that, in order to reduce the temperature gradient of the roll mantle (41), the channels (42) or the like are arranged in at least two circumferential rows and that the channels or the like are circumferentially spaced so that the channels (42) are on different radial 5 lines. Heatable roll according to one of Claims 1 to 5, characterized in that the channels (32, 33) in the different rows (R1, R2) of the roll shell (31) or the like have different diameters. Roll according to one of Claims 1 to 6, characterized in that at least two heating media of different temperatures are arranged in the roll (31, 42) channels (32, 33; 42) or the like. Roll according to one of the preceding claims, characterized in that the roll has a valve system for controlling the circulation and temperature of the heating medium. 8 705775 Roll according to one of the preceding claims, characterized in that the roll casing; , 20 (31, 42) channels (32, 33; 42) or the like and / or roll center (45) are provided with a displacement body for adjusting the heating medium flow. * »* (·« • · · Roll according to one of the preceding claims, characterized in that, in the adjacent channels (32) of the first row (Rj) of the roll casing, the heating medium is arranged to be conducted in the same direction and the heating medium is arranged to be returned. along an intermittent channel (33) in a second row (R2). • · * · · · 1 · · • • • «« • · · '• j Roll according to one of the preceding claims, characterized in that the heating medium («'·,' ·!!) Is arranged to flow in adjacent channels (32; 33; 42) in different directions. *:" = 30 «1 · 4« « <I <«t 1« 4 4 «10 7 ° 5775 Patentkrav ^