JPH0372758B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heating device for heating a calender roll and a method for heating a calender roll. In particular, the present invention relates to a heating device that heats a calender roll using induction heat and heat supplied from a heat transfer medium.

[Conventional technology]

Various calenders have been used in the past to smooth the surface of dry webs to increase the printability of paper and paperboard produced by paper machines.

Basically, a calender has at least a pair of cooperating rolls that form a calender nip between the rolls, thereby smoothing and finishing the surface of the dried web. Depending on the type of surface required, calender rolls are made of polished metal or
It consists of a combination of polished metal rolls and soft support rolls. Soft rolls include elastomer-covered rolls and so-called filled rolls with a plurality of compressed cotton disks.

When an abrasive metal roll is utilized in combination with a soft roll, the surface of the metal roll is heated in such a way that heat is transferred from the surface of the roll to the surface of the web extending between the metal roll and the soft roll. It has been found that this improves the gloss transferred to the paper surface.

In the past, many proposals have been made in which a heating medium, such as a heating oil, flows through a plurality of channels or ducts extending through the rolls. . Heat from the oil is transferred to the roll and the heat is transferred to the surface of the roll to heat the web passing therethrough.

[Problem to be solved by the invention]

In some applications of the conventional techniques described above, the surface of the roll is heated to over 149°C (300°C), and sometimes to 510°C.
It is desirable to heat it to a temperature as high as ℃ (950〓).
However, in order to heat the surfaces of such calender rolls to these high temperatures, a heat transfer medium such as oil must be supplied at a temperature that significantly exceeds these required surface temperatures. This results in various heat losses and a significant temperature drop in the shell.

Two main problems arise from utilizing heat transfer media operating at such high temperatures. 1st
In addition, the large temperature drop in the shell of the calender roll creates a large temperature gradient in the calender roll, creating excessive stress in the roll. Second, handling heat transfer media such as oil at such high temperatures is extremely dangerous.

U.S. Pat. No. 3,489,344, granted to Mr. Keyes and assigned to Beloit Corporation, presented the problem of controlling the thermal profile of a roll along the cross-machine direction, but did not provide a means to overcome the aforementioned problems. is not shown.

The present invention therefore proposes a calender roll which combines an induction heater which induces heat in the region of the outer surface of the calender roll and heat which is transferred to the calender roll by means of a heat transfer medium flowing through a channel passing through the calender roll. Provides a new heating device for heating.

A suitable device of the present invention overcomes the aforementioned problems associated with conventional calender roll heating devices, yet makes a significant contribution to the art of paper calenders and the like.

Another object of the invention is to provide a plurality of heating devices within the roll extending in its longitudinal direction and spaced equidistantly from the roll surface and arranged around the center of the roll so that heat is transferred from the heat transfer medium to the roll. It is an object of the present invention to provide a heating device for heating a calender roll through which a heat transfer medium flows. Induction heaters generate heat in the area of the outer surface of the roll to supplement the amount of heat transferred from the heating heat transfer medium.

Another object of the invention is to heat the calender roll in such a way that the temperature of the outer surface of the roll is raised by induction to a level that would cause stress in the shell if it were not equipped with an induction heater. An object of the present invention is to provide a heating device for heating.

Another object of the invention is to provide a calender roll such that the outer surface of the calender roll can be heated to a certain temperature level without creating the risks associated with using heat transfer media operating at such high temperature levels. An object of the present invention is to provide a heating device for heating.

Another object of the invention is that the heat transfer medium is
For example, it is supplied to the rolls at a temperature in the range 204-316°C (400-600〓), so as to avoid the various dangers associated with the use of such heat transfer media above the aforementioned temperatures. Another object of the present invention is to provide a heating device for heating a calender roll.

Yet another object of the invention is that the heat transferred by the heat transfer medium to the calender rolls is controlled by the following means: induced heat flows inwardly through the rolls from the area around the outer surface. It is an object of the present invention to provide a heating device for heating a calender roll, which retains the induced heat in a region around the outer surface of the roll within that region by preventing.

Another object of the invention is to heat the calender roll in such a way that the heat transferred from the heat transfer medium to the calender roll prevents induced heat from dissipating inwardly through the roll from the outer surface of the roll. The purpose is to provide a method.

[Means and actions for solving the problem]

The present invention relates to a heating device and a heating method for heating a calender roll using induction heating and heat supplied from a heat transfer medium.

This heating device has a plurality of heating channels extending longitudinally within the calender roll and arranged at equal intervals from the surface of the calender roll. These channels extend longitudinally within the rolls so that the heat transfer medium flows through the channels and heat is transferred from the heat transfer medium to the rolls. The induction heater is located adjacent to the outer surface of the calender roll;
Since it extends over substantially the entire length of the roll, heat is generated in the area of the outer surface of the roll when the induction heater is energized. Rather than a single heater, multiple heaters can also extend along the entire length of the roll. The induction heat replenishes the amount of heat transferred from the heat transfer medium, so that the temperature of the external surface of the roll increases to a level that would otherwise stress the shell. . Furthermore, such temperature levels can be reached without the risks associated with using heat transfer media that operate at such temperature levels.

In particular, a plurality of heating channels extend longitudinally within the calender roll and are arranged around the center of the calender roll at a distance from the roll surface so that the heat transfer medium passes through the heating channels. The heat from the heat transfer medium is transferred by conduction along the entire length and circumference of the roll towards its outer surface, and the heat generated by the induction heater is transferred inward from the outer surface of the calender roll. It is effectively prevented from dissipating into the air. Therefore, the temperature of the outer portion of the calender roll is kept high to prevent a large temperature gradient from occurring within the roll, and the stress generated in the roll, especially the roll shell, is suppressed to a low level.

In a first embodiment of the invention, the heat transfer medium is oil, and in another embodiment superheated water.

The heat transfer medium is supplied to the rolls at a temperature in the range 204-316°C (400-600°), thereby avoiding the risks associated with using heating media above this temperature range.

In addition, the heat transfer medium is 121% higher than the temperature of the roll surface.
Supplied at temperatures in the high range ~177℃ (250-350〓).

Induction heaters generate heat in the area of the outer surface of the roll. The heat transferred to the roll by a heat transfer medium in a plurality of heating channels arranged around the center of said calender roll is such that the heat generated in the induction heater flows inwardly through the roll from such areas. The induced heat is kept in the area by preventing it from dissipating.

The present invention provides a method of heating a calender roll using heat provided by an induction heater and a heat transfer medium. This method extends the entire longitudinal length within the roll and extends around the center of the roll at equal distances from the roll surface in order to transfer heat from a heat transfer medium to the roll so that the roll is heated. passing the heat transfer medium through a plurality of heating channels disposed; and energizing an induction heater disposed outside the roll adjacent to the outer surface thereof and extending along the length of the roll; heat is generated in the area. Additionally, heat transfer from the heat transfer medium to the roll prevents induced heat from dissipating inwardly through the roll from the outer surface of the roll.

〔Example〕

One embodiment of the present invention will be explained with reference to FIGS. 1 to 4. FIG.

FIG. 1 is a side view of a heating device 10 for heating a calender roll 12. This heating device 10 utilizes heat supplied by a heat transfer medium of an induction heater device 14. Figure 1 shows the calendar roll 12.
A paper web W is shown extending through a calender nip 16 formed by a soft calender roll 18 and a soft calender roll 18 cooperating therewith. This induction heating device 14 has a ferromagnetic core 20 with a concave surface 2 of the core.
2 is positioned adjacent to and extending a portion around the outer surface 24 of the calender roll 12.
A wire coil 28 extends around the core 20;
Both ends 30 and 32 of the coil 28 are connected to the AC source 34, so that the coil 28 is connected to the AC source 34.
Heat is generated within the portion of calender roll 12 adjacent outer surface 24 when energized by calender roll 12 .

Electromagnetic eddy currents are generated in the ferromagnetic core 20 by one of the following two methods. AC source 34
When the ferromagnetic core 20 is connected to the copper wire coil 28, a vortex is generated in the ferromagnetic core 20.
A copper wire coil 28 can be wrapped around the . Also, when the AC source 34 is connected to the copper tube, a liquid-cooled copper tube can be run straight along the length of the ferromagnetic core so as to generate vortices in the ferromagnetic core 20. Whichever method is used to generate vortices in the ferromagnetic core 20, the outer surface 2 of the calender roll near the ferromagnetic core 20
A vortex flow is induced in the area No. 4. This area of the outer surface 24 of the calender roll will be heated by the induced swirl.

FIG. 2 is a cross-sectional view taken along line 2--2 of FIG. 1, showing induction heater device 14 disposed along substantially the entire length of calender roll 12. The calender roll 12 is formed with a plurality of elongated channels extending along the entire length of the roll 12. Each of the channels 36-50 includes a central channel 54 extending through the support shaft 56 of the calender roll 12, a radially branched hole 52, as shown in FIGS.
53. For example, the heat transfer medium, such as oil or superheated water, can be connected to a plurality of heating channels 3.
6 to 50 so that the heat transfer medium circulates throughout the length of the calender rolls 12.

FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. Disposed radially inwardly and with each longitudinal channel 36-50 equally spaced from the outer surface 24 of the calender roll 1
It is arranged around the center of 2. When a heat transfer medium such as heating oil circulates through these channels,
Heat is transferred to this calender roll 12 and this heat provided by the heat transfer medium prevents the heat provided by the induction heater device 14 from dissipating inwardly from the outer surface 24 and the area adjacent thereto. . As a result, the heat supplied to the calender roll 12 by the heat transfer medium is supplemented by the heat induced by the induction heater device 14, and the portion near the outer surface of the calender roll 12 is maintained at a high temperature, so that the calender roll 12 The temperature of the outer surface of the calender roll 12 is maintained at a high temperature and large temperature gradients do not occur, so that excessive stress does not occur in the calender roll 12, especially in the shell. Therefore, when the induction heater device 14 is not used, the calender roll 1
It is possible to prevent stress that would be applied to the second region, that is, the shell, and also to prevent various heat losses from occurring. Furthermore, by supplementing the heat provided by the heat transfer medium with the heat from the induction heater 14, the heat transfer medium such as oil
There is no need to heat it above 316℃ (600℃). Therefore, it is possible to prevent dangers that may occur when handling oil or the like at a temperature of 316°C (600°C) or higher.

FIG. 4 shows a calender roll 12, which is a super calender roll, and a support roll, i.e., a soft calender roll 18, through which paper or FIG. 3 is a perspective view showing the paperboard web being stretched;

During operation of the heating device 10, a heat transfer medium passes through heating channels 36-50 formed by the calender rolls 12, and heat is transferred from the heat transfer medium to the calender rolls 12 to heat the rolls 12. The induction heater device 14 is connected to the outer surface 2 of the roll.
4 is energized to be heated. Such induction heaters not only heat the outer surface 24 of the calender roll 12, but also heat the area near the outer surface 24 of the roll 12. Heat transfer from the heat transfer medium to the roll 12 in heating channels 36-50 disposed about the center of the roll prevents induced heat from dissipating inwardly through the roll 12 from the outer surface 24 of the roll 12. can.

Although the present invention has been specifically described above with respect to a calender for calendering a paper web, the present invention is not limited to a calender for paper webs, but rather heats a calender roll used in calendering a web-like material. It should be understood by those skilled in the art that this includes heating devices and methods for heating. Furthermore, although the invention relates to a calender, the invention contemplates an arrangement in which one or more of the calender rolls are replaced by an elongated nip provided by a shoe and a cooperating blanket. It should be understood that it also includes.

Furthermore, the present invention is not limited to the apprentice embodiments described herein, but includes various modifications within the spirit and scope of the invention as defined by the claims. will be understood by those skilled in the art.

〔Effect of the invention〕

As explained above, the calender roll heating device and heating method of the present invention can have the following effects.

(1) The temperature of the outside surface of the roll is increased by increasing the temperature of the outside surface of the roll with heat generated by an induction heater located outside the calender roll near its outside surface and extending over substantially the entire length of the roll. In comparison, the temperature of the heat transfer medium such as oil supplied to the roll is lowered,
Various dangers that arise when using high temperature heat transfer media can be avoided.

(2) By flowing a heat transfer medium through a plurality of heating channels extending longitudinally inside the roll and arranged around the center of the roll at intervals from the roll, the entire length and circumference of the roll can be heated. The heat from the heat transfer medium is transferred towards the outer surface of the roll over a period of time, and the heat generated by the induction heater is prevented from dissipating towards the inside of the roll, keeping the temperature of the outer part of the roll high and It is possible to prevent a large temperature gradient from occurring within the roll, and to suppress the stress generated in the roll, especially the roll shell.

As described above, the present invention provides a simple device and method that can increase the temperature of the surface of the calender roll by supplying supplementary heat to the surface area of the calender roll, thereby preventing problems such as stress generation in the roll. Moreover, the present invention can solve problems that arise when dealing with internal heat transfer media at high temperatures.

[Brief explanation of drawings]

FIG. 1 is a side view of a heating device according to an embodiment of the present invention, showing a calender roll and an induction heater adjacent thereto. Figure 2 is 2 of Figure 1.
3 is a sectional view taken along line 3-3 in FIG. 2, and FIG. 4 is a perspective view of the device shown in FIGS. 1 to 3. It is. <Symbols in the figure> 10... heating device, 12... calender roll, 14... induction heater device, 16... calender nip, 18... soft calender roll,
20...Ferromagnetic core, 22...Concave surface of core, 24
...Outer surface of calender roll, 28...Wire coil, 34...AC power supply, 36-50...Channel, 52, 53...Radial direction branch holes.

Claims (1)

[Scope of Claims] 1. A heat transfer medium extends longitudinally within the calender roll and flows through it, so that heat is transferred from the heat transfer medium to the calender roll, and the heat transfer medium is arranged to transfer heat from the calender roll surface to the calender roll surface. a plurality of equally spaced heating channels disposed about the center of the calender roll; disposed outside the calender roll near the outer surface of the calender roll and extending substantially the entire length of the calender roll; In order to replenish the amount of heat transferred from the heat transfer medium during heating, heat is generated in the area of the outer surface of the calender roll to increase the temperature of the outer surface of the calender roll to the shell in the absence of the present induction heater. an induction heater for raising the temperature to a level sufficient to cause excessive stress; 2. The heating device according to claim 1, wherein the heat transfer medium is oil. 3. The heating device according to claim 1, wherein the heat transfer medium is superheated water. 4 The heat transfer medium is 204-316℃ (400-600〓)
2. Heating device according to claim 1, characterized in that it is possible to avoid the dangers that arise when using a heat transfer medium that is supplied to the roll at a temperature in the range above the temperature range. 5 The heat transfer medium has a temperature of 121°C or more than the roll temperature.
A heating device according to claim 1, characterized in that the heating device is supplied to the roll at an elevated temperature within the range of 177°C (250° to 350°). 6. Extending the entire longitudinal length within the roll and disposed about the center of the roll at equal distances from the roll surface for transferring heat from the heat transfer medium to the roll and heating said roll. passing a heat transfer medium through a plurality of heating channels; energizing an induction heater disposed outside the roll adjacent to the outer surface of the roll and extending along the length of the roll to a region of the outer surface of the roll; generating heat; wherein the heat transferred from the heat transfer medium to the roll is such that the heat generated by the induction heater is prevented from dissipating inwardly through the roll from the outer surface of the roll; A method of heating a calender roll using heat provided by a heater and a heat transfer medium.