JPH07253112A - Heat-insulating assembly and heat-insulating element - Google Patents

Abstract

PURPOSE: To enhance heat insulating capacity by forming a wall surrounding a hot oil passage into double wall structure, and sealing a cavity between double walls in a vacuum or gas filled state in a heat insulating assembly or element for a hot roll bearing end and a contactless surface area. CONSTITUTION: A heat insulating assembly 15 for reducing heat conduction from at least one heating medium channel 4 extending into a roll shell 1, to a contactless area of the shell 1, and an element 10 for reducing heat conduction from oil channels 6, 7 in a roll shaft 3 to a bearing 5, comprise a first wall 11 disposed concentrically with the center axis of the channels 4, 6, 7 to surround the channels 4, 6, 7, and a second wall 12 concentrically disposed around the first wall 11, and a cavity between these walls 11, 12 is sealed in a vacuum or gas filled state.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention comprises at least one longitudinal channel extending into a roll shell for passing a heating medium through the roll shell, the heating medium channel of the shell to a non-contact region of the shell of the thermoroll. Thermal insulation assembly for reducing heat transfer to the end of the oil channel to prevent heat transfer from the shell end area of the thermoroll and designed to meet the purpose This assembly is carried out by.

The invention further relates to a thermal insulation element for insulating the heating medium channels extending into the shell of the thermoroll.

[0003]

BACKGROUND OF THE INVENTION In papermaking and finishing processes, various heatable rolls are used to remove moisture from the web and, in particular, to modify the quality of the web surface.
Heatable thermo rolls are used in particular in soft calenders. Because the soft calendar is used in an on-machine configuration, it must operate at the same speed as the paper machine itself. Such a calendar has an even number of nips of soft polymer coated rolls and metal coated thermo rolls. The presence of an even number of nips, and thus a pair of soft rolls and metallized rolls, is due to the fact that each polymer coated roll only works with one calendar nip because it cannot absorb the deformations and temperature rises caused by the two nips. To do. Therefore, an even number of nips is required to obtain a glossy web that is symmetrical on both sides. A pair of rolls is sufficient because the cardboard is glossy finished on only one side to a high degree of finish. The temperature of the soft polymer coated roll is accurately monitored and the hot thermo roll surface should not be touched even when the web breaks.

Thermorolls are typically heated with hot oil, although in some cases other suitable heat transfer media such as water may be used. The heated oil flows into the roll from the end of the roll, passes through the longitudinal holes, is distributed to the radial holes formed at the ends of the roll flange, and passes through the longitudinal holes formed in the roll shell.
The circulation of oil in the roll shell first reaches the opposite end of the roll and then returns along parallel holes towards the inlet end into the shell. Return oil is returned to the heating source via the end flange and a second hole in the roll shaft.

[0005]

It is desirable to heat the surface of thermo rolls to higher temperatures to provide a high heating effect to the fast moving web during short dwell times in the nip. . When oil is used to heat the roll, the surface temperature of the roll rises above about 200 ° C. In this case, the temperature of the heating oil passing through the inside of the roll is as high as 280 to 300 ° C., and this high temperature gives an extremely large heat load to the bearing. Due to the high heat load on the roll bearing, it is necessary to provide a large bearing on the roll shaft.
m, and the outer diameter is about 1.0 m. Another load on the bearing is the heat generated by heat conduction from the hot oil passing through the roll shaft.

The length of the thermo roll and the soft roll is
Slightly larger than the width of the web to be finished, leaving areas of non-contact with the web at the ends of the roll. An extremely high-temperature heat transfer flow per unit area is transmitted from the thermo roll to the web, and at the end of the roll, heat is radiated from the roll surface only by radiation, resulting in transfer loss. That is, the surface temperature of the non-contact end region is higher than the temperature of the roll surface portion that contacts the web. Such a temperature difference causes serious problems.

Higher temperatures at the ends of the roll result in greater thermal expansion in the roll end region. At this time, the outer edge of the roll shell swells outward from the roll center axis, and the bending moment generated by thermal expansion tries to push the region adjacent to this swelling region radially inward toward the center axis. To do. This inward shrinkage region exactly coincides with the web edge. As a result, the roll diameter in this contraction region will be smaller than in the roll middle and the web caliper will be thicker at the web edges than at the web middle. Therefore, the caliper contours seen in the cross-machine direction of the web are not uniform, which causes printing problems and reduces web quality. Furthermore, the thick web edges make winding difficult and the winding rolls do not become evenly and tightly wound, resulting in conical narrow roll slits from the ends of the machine rolls. Other hazards also result from damage to the metal thermo roll shell that comes in contact with the soft roll surface,
In this case, the polymer coating on the soft roll is thermally destroyed.

If the thermal expansion of the roll end region is excessive,
The radially enlarging end region of the roll widens towards the middle of the roll and reaches the web edge. This allows
The roll diameter decreases towards the middle of the roll, resulting in a wavy web contour. When using a soft calender to finish a large quantity of lightweight grade paper, the web calipers become extremely thin, so even the slightest variations in roll diameter and cross machine contours can result in extremely high cross machine contours of the paper web. There will be large relative fluctuations. For this reason, it is necessary to keep any deformation of the shape of the thermoroll as smooth and small as possible.

Attempts have been made to reduce the heat transfer to the sealing contact end region of the thermoroll by forming a bushing or coating from a material of low thermal conductivity. The coating material used contained zirconium oxide and the insulating bush was formed of polytetrafluoroethylene (PTFE). The insulation bushes and coatings can of course also be formed from various materials, such as ceramics and polymeric materials. The manufacture of such insulating bushes and coatings is relatively easy and easy to fit around the heated oil channels. However, a heat insulating material formed of a solid material cannot exhibit good heat insulating properties like PTFE, and has a thermal conductivity as high as 10 times that of air, for example. Because the insulation used must tolerate temperatures as high as 300 ° C under momentary mechanical loading, normal insulation materials can be used without making the roll shaft too complex. Can not do it.

Finnish Patent No. 72,580 describes a heated roll, in which the formed between the cylindrical outer shell of the roll and an inner shell concentrically surrounded by the outer shell. Hot oil circulates in the cavities that are created. The heating medium is passed into the heating cavity through holes formed in the end of the inner shell. In this roll example, to prevent overheating of the roll end region, the entire inner shell end is surrounded by a heat insulating ring which may be formed from a solid material such as polytetrafluoroethylene. It may be formed as a sealing structure or as a hollow filled metal ring provided with an opening, in which the heat transfer medium is lubricated. The heat insulation assembly as described in this patent publication has a drawback that it can be applied only to the roll described in this publication and has a complicated structure and is difficult to manufacture.

Accordingly, it is an object of the present invention to provide a thermal insulation assembly which has superior thermal insulation capabilities to the prior art and is less susceptible to stresses applied by the operating environment.

The invention is based on the use of a bush-shaped heat insulating element with a gas-tight cavity around the oil channel of the thermoroll.

In the most preferred embodiment of the present invention, the cavity inside the thermal insulation element is evacuated to a high vacuum.

[0014]

SUMMARY OF THE INVENTION To achieve the above objectives, a thermal insulation assembly of the present invention includes a first wall surrounding the longitudinal channel by concentrically arranging about the central axis of the channel and a first wall. A second wall disposed concentrically to the central axis of the channel at a distance greater than the wall, hermetically sealing with the first wall and defining a cavity surrounding the longitudinal channel. Is characterized by.

Further, in order to achieve the above object, the heat insulating element of the present invention comprises a first closed envelope surface, a second closed envelope surface spaced from the first closed envelope surface, and a first closed envelope surface. And an element coupled to the second closed envelope surface to define a hermetically sealed cavity.

[0016]

According to the present invention, there are great advantages. The embodiments according to the invention provide a very high insulation capacity. The highest insulation capacity is obtained by bushes with insulation cavities evacuated to vacuum, but even bushes filled with an inert gas such as air, nitrogen or other gas have better insulation capacity than solid insulation materials. , Meet the requirements. The extraction bush according to the present invention can be easily manufactured using an electron beam welder, and the gas-tight welding bush is maintained during welding by a vacuum equal to the vacuum state in the vacuum chamber of the welder. In contrast, the gas-filled bush can be manufactured in an inert gas atmosphere, for example using laser welding.

The material of the bushing can be steel of the same construction used in the rest of the thermoroll, and the bushing must be of sufficient strength to be insulated or damaged during use. You can When the bush is hermetically sealed, the heat insulation capacity does not decrease during use. If the roll is made of the same material as the roll shell, the coefficients of thermal expansion of all parts of the roll are equal, so that stresses caused by different thermal expansions do not occur between the parts.

[0018]

The preferred embodiments of the present invention will now be described with reference to the drawings.

The present invention will be described with respect to a thermal insulation assembly for a shell of a thermoroll using the thermal insulation element of the embodiment according to the invention shown in FIG. However, other insulation assemblies for the shells of thermo rolls using the insulation element of the embodiment according to the invention shown in FIG. 3 are also applications of the invention. Figure 1
As can be seen, thermorolls are advantageously used in combination with both assemblies.

The thermoroll has a body consisting of a shell 1 and two end pieces 2,3. As is conventional, a heating medium, typically oil, is introduced and discharged into the roll from only one end of the roll. The structure shown in FIG. 1 shows the supply end of a roll with oil circulation means. The shell 1 of the thermo roll is a thick hollow cylinder, and an oil channel 4 is provided in the envelope of this hollow cylinder. The end piece has an end flange 2 and a shaft 3. The roll is mounted in the bearing by supporting the shaft 3 of the end piece by the bearing 5. At the center of the shaft 3, a heating oil supply channel 6 is provided, through which the oil flows into a radial channel 8 formed in the end flange 2. The heating oil flows through these radial channels into the longitudinal oil channel 4 of the shell 1, reaches the opposite end of the shell 1, turns at this end and returns via the parallel channel 4. At the feed end of the roll,
Radial channels 9 perforated with heating oil in the radial direction
Collected from and flowed into the return channel 7. The return channel 7 is formed so as to concentrically surround the oil supply channel 6 at the center of the shaft, and causes oil to flow out from the end of the shaft 3 and be sent to the reheating circuit. The oil circulation in the rolls can also be done in different ways, for example by staggering the oil supply flow channels and the return channels in the roll shell, or by each supply flow channel having two
It is also possible to return via individual return channels or to have other configurations. Similarly, the supply of heating oil through the shaft 3 and the end flange 2 can be performed in various ways. Since the present invention is not related to the structure of the oil supply channel system, detailed description of other methods will be omitted. However, the roll structure used in connection with the present invention is such that heated oil or similar medium circulates in individual channels 4 formed in the shell 1 of the roll.

The heat insulating element 15 which penetrates into the oil channel 4 from the end edge of the roll shell 1 and extends to the intermediate portion of the roll, and which reaches the edge of the web 16 slightly downward, is an oil channel formed in the shell 1. Apply around 4 edges. The edges of the paper web 16 divide the surface of the roll shell 1 into two parts when viewed transversely to the device, a non-contact end region and a contact central region in which the web runs.
The heat insulating element 15 comprises an inner cylindrical bush 11 acting as an outer wall of the heating oil channel 4 and an outer bush 12
And the bushes together form a sealed cavity 14 by the end portion 13 of the insulation element. The end portion 13 of the heat insulating element is joined to the ends of the bushes 11, 12 by electron beam welding in a vacuum chamber. At this time, the sealed cavity of the heat insulating element 15 is maintained in a vacuum state equal to the working vacuum of the vacuum chamber of the welding apparatus, typically 10
The order is Pa (1 × 10 ⁻⁴ bar). If this vacuum is set to a relatively high vacuum, the heat insulating capacity of the space sealed by such a vacuum is improved, which is preferable. The insulation capacity of this vacuum level is approximately equal to that of laboratory bleed flasks and higher than that of vacuum bottles for beverage and food storage.

The heat insulating element 15 extends from the edge of the roll shell 1 to slightly below the edge of the web 16 in the middle of the roll. In this way, oil pipe to shell 1
Adequately insulates the heat of the oil flowing to the non-contact areas of the, but does not impair good heat transfer from the shell 1 to the web 16. The required length of the insulating element 15 and the length below the web are based on the roll design and the amount of heat applied.
Of course, thermal insulation elements are attached to the ends on each side of all channels formed in the roll shell.

FIG. 1 shows another embodiment of the heat insulating element according to the present invention, which is suitable for use in the shaft 3 of the roll, and the structure of this heat insulating element will be described below.

This embodiment is different from the embodiment of FIG. 3 described above, and it is preferable that this heat insulating element is manufactured by electron beam line welding, and the inside of the heat insulating element is set to a vacuum level showing a high heat insulating capacity. maintain. In order to make the heat insulating capacity of the extracted heat insulating element higher than that of the gas filled heat insulating element, it is preferable to set the vacuum in the element to 1 kpa or less, particularly 100 Pa or less. Due to the manufacturing advantages mentioned above, it is very easy to make the vacuum inside the thermal insulation element equal to the working vacuum of the vacuum chamber of the welding device.
However, a relatively good thermal insulation capacity is also obtained with the gas-filled thermal insulation element. Such a gas-filled element can be manufactured, for example, by laser welding in an inert gas atmosphere, and the inside of the element is filled with the inert gas. in this case,
The fill gas can be an inert gas such as carbon dioxide, nitrogen or a noble gas. However, the present invention is not limited to products manufactured by a specific manufacturing method.

If the insulating element is intended for use in connection with a perforated oil channel, its shape is preferably cylindrical. However, other shapes are possible.
In fact, it may be partially tapered to lock the insulation element to the inner surface of the perforation channel. The thermal insulation element can be removably attached to surround the oil channel of the shell, or it can be fixed as an integral part of the oil channel by a welded joint.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional side view of an end of a thermo roll incorporating a thermal insulation assembly according to the present invention and adapted to supply a heating medium into the roll.

FIG. 2 is a vertical sectional view of a shell of the thermo roll shown in FIG.

FIG. 3 is a longitudinal sectional view of an embodiment of a thermal insulation element according to the invention for roll channels.

FIG. 4 is a longitudinal sectional view of an embodiment of a thermal insulation element according to the invention for the shaft end of a roll.

[Explanation of symbols]

 1 Shell 2 End Flange (End Piece) 3 Shaft (End Piece) 4 Oil Channel 5 Bearing 6 Supply Channel 8,9 Radial Channel 7 Return Channel 11 Inner Cylindrical Bushing 12 Outer Bushing 13 End Part 14 Sealed Cavity 15 Insulation Element 16 web

Claims (10)

[Claims] 1. A thermo roll from a heating medium channel (4) of a shell (1) comprising at least one longitudinal channel (4) extending into the roll shell (1) for passing a heating medium into the roll shell. A heat insulation assembly for reducing heat transfer to the non-contact area of the shell (1) of the first wall (4) surrounding the longitudinal channel (4) by being arranged concentrically to the central axis of the channel (4). 11) and a larger distance than the first wall (11), and are arranged concentrically with the central axis of the channel (4).
1) a second wall (12) hermetically sealed together and defining a cavity (14) surrounding the longitudinal channel (4). 2. A central region of the surface of the shell (1) intended to finish the web in compressive contact with the web (16) and at the edge of the roll bounded by the edge of the web (16). A thermal insulation assembly as claimed in claim 1 for a thermo roll having a non-contacting end region.
A cavity (14) defined by the first wall (11) and the second wall (12) is defined from the edge of the roll shell (1) to at least the edge of the central contact area, ie the web (16). Insulation assembly that existed to the edge. 3. An insulation assembly according to claim 1 or 2, wherein the cavity (14) defined by the first wall (11) and the second wall (12) is in the form of a cylindrical hollow shell. 4. The first wall (11) constitutes the inner wall of the heating medium channel and the second wall (12) is the roll shell (1).
A channel formed by an inner wall of a perforated channel.
The heat insulation assembly according to any one of claims 1 to 3. 5. A thermal insulation element (10) for insulating a heating medium channel (4) extending into a shell (1) of a thermo roll, comprising a first closed envelope surface (11) and this first envelope surface (11). ), A second closure envelope surface spaced apart from the first closure envelope surface, and an element (13) coupled to the first closure envelope surface (11) and the second closure envelope surface (12) to define a hermetically sealed cavity (14). And a heat insulating element. 6. Thermal insulation element according to claim 5, characterized in that the cavity (14) defined by the closed envelope surface (11, 12) is rotationally symmetrical with respect to the longitudinal axis. 7. The heat insulating element according to claim 5, wherein the absolute pressure in the hermetically sealed cavity (14) is set to 1 kPa, preferably 100 Pa or less. 8. The heat insulating element according to claim 5, wherein the absolute pressure in the hermetically sealed cavity (14) is about 10 Pa. 9. The heat insulating element according to claim 5, wherein the absolute pressure in the hermetically sealed cavity (14) is filled with a gas. 10. The heat insulating element according to claim 5, wherein the absolute pressure in the hermetically sealed cavity (14) is filled with an inert gas.