Thermo roll

The present invention relates to thermo rolls of fibrous-web machines and similar types of roll machines. The invention relates to a thermo roll which comprises two end pieces and a shell fastened between them in which flow channels are arranged for heat-transfer medium, whereby onto an end surface of each end piece and/or an end surface of the shell is arranged at least one form for receiving a seal or seals and in these forms corresponding seals are arranged to prevent the leaking of the heat-transfer medium from the flow channels.

The treatment devices of a fibrous web of a paper machine require heat supply into the web in different stages of the process. Heat can be conveyed into the web by means of thermo rolls. A utilised way for conveying heat into the thermo roll is to arrange flow channels inside the shell of the thermo roll along which heat- transfer medium flows from which heat energy transfers to the material of the shell and through that to the web being treated. The heat-transfer medium can be gaseous or liquid or fluidic medium, such as commonly hot water, steam or oil.

The heat-transfer medium can be conveyed into the flow channels located centrally in the shell or on the periphery of the shell via the end pieces of the thermo roll. Generally, the end piece is considered including a shaft journal and a flange part of the roll by means of which the end piece is fastened in the shell e.g. by means of bolts. Known prior art related to the end piece of the thermo roll, to the flow channels of heat-transfer medium and to the heat insulation of the flow channels is disclosed in the applicant's Finnish patent application FI 20041304.

The joint surface between the flange part of the end piece and the shell of the thermo roll, especially for the part of the flow channels, should be sealed to prevent the leaks of heat-transfer medium especially outside the thermo roll.

Nowadays, the joint surface between the end piece and the shell is generally sealed with rubber O rings or laminar graphite seals. As a disadvantage of these sealing ways can be mentioned, on one hand, the poor heat resistance of rubber O rings, because they are not suited for temperatures over 250 ⁰ C. On the other hand, laminar graphite seals cannot resist the micro motion caused by varying loading.

It is also known to seal the joint surfaces between the end piece of the flow channels and the shell of the thermo roll with a seal of two materials the outer shell of which is a soft polytetrafluoroethylene layer and there is a steel spring as an inner support of this shell.

In addition to the above-mentioned problem related to the thermo roll, controlling the temperature and diameter profile in the edge area of the thermo roll of a calender is extremely awkward in both theory and practice. In some cases, the flattening of the thermo roll causes a linear load peak on the edge of the calendering nip. The paper or some other fibrous web travelling through the nip takes power only from the area of the nip, whereby on the edge of the web area of the fibrous web is created a displacement zone in which the temperature changes in a very short area in the longitudinal direction of the thermo roll for several dozens of degrees Celsius. This change in temperature emphasises the linear load peak caused by said flattening but also creates an area beside the linear load peak in which the linear load is lower than elsewhere in the area of the nip.

For compensating the above-mentioned linear load peak of the edge area of the calendering nip have been developed end seals of the thermo rolls which can be arranged e.g. into connection with the flow channels of heat-transfer medium in the edge areas and the end pieces of the shell and also outside the end pieces of the thermo rolls. The effectiveness of such end seals is limited and, even in an optimal situation, they do not provide a straight linear load profile.

In some cases, one has tried to adjust the temperature and diameter profiles in the edge area of the thermo roll by external induction. This has been partially successful but it has not been possible to provide a straight linear load profile with it.

As described above, the thermo rolls are usually heated/cooled by means of the flow channels manufactured in the roll shell. A way for obtaining required heat power in the future is to locate the channels very close to the surface of the thermo roll. Then, the effect of the channels on the peripherical surface temperature and radial displacement profile of the thermo roll (the so-called undulating effect) increases very strongly. The variations of surface temperature can cause problems in paper quality and the variations of radial displacement, again, a barring problem. For minimising these disadvantages, a way would be to strongly increase the number of channels and correspondingly to decrease their size.

The object of the present invention is to provide a novel and inventive thermo roll by means of which above-described problems and disadvantages can be eliminated or at least minimised.

To achieve the above-mentioned objects and those that come out later, the thermo roll according to the invention is mainly characterised by what is presented in the characterising part of claim 1.

The described end sealing of the thermo roll is reliable in operation because of the elastic and reversible seal used. An elastic metal seal has the advantages of an elastomer and a traditional metal seal. By the described seal having a core of an elastic metal coil spring or disc spring and the outer shell of a deformable metal material layer, the heat-transfer medium channels of the thermo rolls can be sealed for long life in both occurring temperatures of even more than 350 ⁰ C and occurring temperature variations. Furthermore, an advantage is long life and reliability, inter alia, under varying loads caused by rotation which wear the seal

material of the outer shell of the seal and the elasticity of the core. After opening such a sealing, it is also possible to reuse the described seal, on the contrary to known e.g. rubber O rings which wear to become too thin or the elasticity of which is lost after the use of only a few years.

The other characteristic features and advantages of the present invention are depicted in the following description and dependent claims.

The invention will now be described in more detail by means of exemplifying embodiments with reference to the accompanying schematic drawings.

Fig. 1 shows a partial section of a known flow channel arrangement in connection with an end piece of a thermo roll.

Fig. 2 shows section I-I of Fig. 1.

Fig. 3 shows section II— II of Fig. 1.

Fig. 4 shows partial section A of Fig. 1.

Fig. 5 shows known seal bushings which can be used at the ends of the flow channels of the shell of the thermo roll.

Fig. 6 shows an end sealing of the thermo roll with a composite-structured metal seal.

Fig. 7 shows a thermo roll which is provided with the cooling of the end area of the shell.

Fig. 8 shows an advantageous embodiment of the cooling system of the end area of the shell of the thermo roll.

Fig. 9 shows flow channels of heat-transfer medium arranged in the shell of the thermo roll at least at two distances from the surface of the shell.

Fig. 10 shows sealing arrangements arranged into connection with an end piece fastenable in the shell of the thermo roll for sealing the end piece to the shell of the thermo roll.

An example of a known flow channel arrangement for an end piece of a thermo roll is shown in Figs. 1, 2 and 3. Fig. 1 shows the end piece 2 of one end of the thermo roll 1 which is fastened to a shell 20 which has an outer diameter 20a and an inner diameter 20b. In this example, the flow of heat-transfer medium is conveyed to the end piece 2 of the thermo roll 1 via a forward manifold 17 and, correspondingly, conveyed from the end piece 2 via a return manifold 18, which manifolds 17, 18 are kept in place by a cover 19 joined to the end piece 2.

The flow is guided from flow channels/bores 3, 4 of the end piece 2 of the thermo roll 1 to flow channels 21, 22 of the shell 20 of the thermo roll and vice versa. The end piece 2 and the shell 20 are sealed e.g. in the area of partial section A to prevent the leaking of the heat-transfer medium outside the roll.

In the known example structure, the forward flow channel 3 and the return flow channel 4 of the end piece 2 are paired on the same peripherical cross-section plane, apart from the outer part of the end piece 2. Then, there remains space for bolt holes 5 in the direction of the periphery. The location of the forward flow channel 3 and the return flow channel 4 in the outer part of the end piece 2 i.e. in the area of the outer periphery of the end piece 2 is shown in more detail by means of the sectional drawings of Figs. 2 and 3. The flow of the example structure is such that each forward flow channel 3 has its own return flow channel 4.

Section I-I of Fig. 1 shown in Fig. 2 and section II— II of Fig. 1 shown in Fig. 3 illustrate the location of the flow channels 3, 4; 21, 22 and the bolt holes 5.

By means of partial section A, Fig. 4 shows a schematic example for illustrating a known sealing technique of the end piece 2 of the thermo roll. In an annular groove 30 formed on an end surface 2' of the end piece 2 is installed a rubber O- ring seal 31 which is flattened between the bottom of the groove 30 and an end surface 20' of the shell 20 when the flange part of the end piece is fastened to the shell. In this example, the O-ring seal 31 is located outside the flow channels 3, 4 of the heat-transfer medium in the direction of the radius of the thermo roll. It is also possible to seal each flow channel 3, 4, 21, 22 one by one in a way shown in the lower part of section A of Fig. 4. Then, in a recess surrounding each flow channel or, in the example of the figure, in an annular groove 30.1 is installed an O-ring seal 34. Inside the flow channels in the direction of the radius of the thermo roll, there can also be a sealing to prevent leaking inwards from the flow channels (not shown).

Fig. 5 shows known teflon tubes 25 or alternatively steel tubes 26 with an oil pocket 26' used as insulation bushings on the edges of the shell of the thermo roll 1. The cylindrical insulation bushings 25; 26 are shown sectioned along their central axis. The purpose of these insulation bushings 25; 26, when installed in the flow channels 21, 22 of the thermo roll 1 in a way shown by Fig. 5, has traditionally been to prevent the increase of the surface temperature of the shell 20 in the area of the shell from which heat power is not conveyed i.e. in the area outside the nip. Fig. 5 shows a schematic example of the location of the fibrous web W in relation to the shell 20 of the thermo roll 1. The insulation bushing 25 ; 26 is shown on the right side of the right edge W of the fibrous web i.e. outside the web area. The insulation bushing 25; 26 is located in the area of the shell 20 from which there is no intent to convey heat power to the fibrous web W.

Fig. 6 shows an end sealing of the thermo roll according to an advantageous

embodiment of the invention by composite-structured metal seals 40. The left side of Fig. 6 shows a cross section of the seal 40 installed in the groove 30 in the end piece 2 of the thermo roll in an uncompressed state and the right side shows a cross section of the seal 40 installed in the recess 30.1 surrounding the flow channel 3, 4 in a compressed state.

According to the invention for securing the operation of the seal 40, the following two basic properties pertain to the seals shown in Fig. 6. First, the seal is able to accommodate to the shapes of the joint surfaces 2'; 20' of the end piece 2 and the shell 20 of the thermo roll. Second, the seal 40 is flexible when the surfaces move in both radial and axial direction and it is able, due to its reversible property, to follow the joint surfaces 2'; 20' of the joint being sealed which surfaces during the varying deflection load of the rotation drive of the thermo roll recede and approach each other in a small scale.

The seals 40 shown in the figure consist of a metal advantageously coil spring 41 and a metal outer shell 42 around the coil spring 41 which is advantageously open from inside the seal 40 and which deforms or gives way when compressing the seal. In some cases, the outer shell 42 can also be closed instead of open and thus considerably totally surrounding the internal reversible spring. The outer shell 42 is soft so that it deforms to the micro shapes of the surface being sealed, such as the end surface 20' of the shell 20 being e.g. of cast iron and the end surface 2' of the flange part of the end piece 2 being e.g. of cast steel. The outer shell 42 can be e.g. of aluminium, silver, copper, iron, nickel, titanium, stainless steel or of an alloy of some of these materials. The deformability of the metal outer shell 42 is advantageously greater than the deformability of the material surfaces being sealed. During compression, the compression pressure directed at the seal 40 by the surfaces 2', 20' being sealed causes the deforming of the metal outer shell 42 of the seal 40, whereby the seal 40 fills poorly sealable points, e.g. cast pores, occurring at the point being sealed, such as the flange or the groove. Thus, the direct contact of the surfaces of the seal 40 to the surfaces being sealed is secured.

The advantageously fine-pitched coil spring 41 arranged inside the metal outer shell 42 has, as the elastic core of the seal, properties which prevent compressibility enabling maximal sealing. The coil spring 41 is advantageously reversible from the compressed state. Thus, the coil spring 41 enables inducing elastic force against the surfaces being sealed at each point between the surfaces being sealed as each spring pitch of the coil spring 41 operates independently as a spring. The elastic reversion property of the coil spring 41 of the seal 40 enables the sealing of the seal 40 even when the joint loosens or is under varying and/or great deflection load. The spring inside the metal outer shell 42 of the seal 40 can also be a metal disc spring which has an annular U form (not shown) which is advantageously open inwards in the direction of the radius of the seal. An advantage of the coil spring 41 is, however, compared with such an open disc spring tightening the outer shell 42 of the seal, its better accommodation even in a short distance from the surface 2'; 20' being sealed to the varying shapes of the surface as each pitch of the coil spring 41 can be easily manufactured better of its reversibility and tensile force than each single discoid tightening spring section possibly correspondingly manufactured narrow of a U-shaped disc spring open on its inner edge.

Naturally, the seal/seals 40 or part of them can also be installed in the area of the surfaces being sealed in grooves, recesses or some other forms formed in the shell 20 which forms, if required, support setting the seal in its place or keeping the seal in its place. The forms supporting the seal 40 can also be located on both surfaces being sealed.

Fig. 7 shows the thermo roll 1 which is provided with the cooling of the end area of the shell 20.

In Fig. 7, for controlling the temperature and diameter profile in the edge area of the shell 20 of the thermo roll are used insulation bushings installed in the flow

channels at the ends of the shell 20 shown in Fig. 5 which bushings are teflon tubes 25 or alternatively steel tubes 26 with an oil pocket 26'. The purpose of these insulation bushings 25; 26, when installed in the flow channels 21, 22 of the thermo roll 1, is to prevent the increase of the surface temperature of the shell 20 in the area of the shell from which heat power is not conveyed i.e. in the area outside the nip. The insulation bushing 25; 26 is shown on the right side of the right edge W of the fibrous web i.e. outside the web area. The insulation bushing 25; 26 is located in the area of the shell 20 from which there is no intent to convey heat power to the fibrous web W.

Furthermore, for controlling the temperature and diameter profile in the edge area of the shell 20 of the thermo roll can be used cooling of the edge area according to Fig. 7. The edge area of the shell is cooled from inside the roll with either water or some other heat-transfer medium suitable for heat transfer, whereby the cooling medium in addition to cooling the edge of the shell also decreases the diameter of the shell in the edge area. This cooling can be implemented with cooling channels 23, 24, 27 which are located inside the flow channels 21, 22 of the heat-transfer medium seen from the direction of the radius of the thermo roll. Cooling medium, such as water, flows in a way shown by the arrows along the advantageously heat- insulated forward flow channel 23 into the non-heat-insulated cooling channel 27 and out of there along the advantageously heat-insulated return flow channel 24. The length of the non-heat-insulated cooling channels 27 at least in the direction of the corresponding heat insulations of the flow channels 21, 22 of the heat- transfer medium, such as the heat insulation bushings 25, 26, is advantageously about the same length as the heat insulation of the corresponding flow channels 21, 22 and they are located at a corresponding position in the axial direction of the shell 20. In Fig. 7, the forward and return flow channels 23, 24 are advantageously located in a heat-insulating cylindrical material layer 28 arranged inside the shell 20. The shown directions of the forward and return flows are not limiting, also other directions are possible, similarly it is possible to realise the implementation

of the insulation of the forward and return flow channels 23, 24 in a different way, e.g. by arranging the flow channels inside flow tubes of heat-insulating material.

The temperature and diameter profile in the edge areas of the shell 20 of the thermo roll can be adjusted in ways described in the following. The length of the cooling areas arranged on the edges of the shell 20 i.e. in this case the non-heat- insulated cooling channels 27 formed in the material of the inner surface inside the shell 20 can be chosen suitable and thus the profile of the roll adjusted. Another possibility is to choose suitable medium for cooling from available heat- transfer media. Furthermore, it is possible to adjust the temperature and flow of the heat-transfer medium.

The temperature and diameter profile in the edge areas of the shell 20 of the thermo roll can be adjusted based on the quality measurements of the fibrous web W. It is advantageous to use as the measured variable the gloss or thickness profile of the fibrous web W.

Fig. 8 shows an advantageous embodiment of the cooling system of the end area of the shell of the thermo roll.

The left edge of Fig. 8 schematically shows conveying heating medium occurring via a second rotary joint 58 through a second end piece 2.2 of the thermo roll 1 into the shell 20. Hot heating medium flows from a point 59 inside the second rotary joint 58. The flow in the flow channels 21, 22 of the shell 20 takes place in the above-described way and the return flow out of the second rotary joint 58 is designated with reference number 60.

Fig. 8 schematically shows a cooling system suitable for controlling the temperature and diameter profile in the edge area of the shell 20 of the thermo roll 1. The thermo roll 1 is e.g. the thermo roll of Fig. 7. Cooling medium suitable for heat transfer required in cooling, such as water, is guided e.g. from a tank 50 by

means of a pump 52 driven by a motor 51 with suitable adjustable flow volume along an advantageously heat-insulated forward tube system 53 to a first heat exchanger 54 in which the temperature of the cooling medium can be adjusted, e.g. heated with steam S. The temperature and flow of the forward cooling medium are adjusted based on the quality variables of the fibrous web, e.g. gloss and thickness profiles.

After the first heat exchanger 54, the cooling medium, the temperature of which has been adjustable, flows along the forward tube system 53 further via the first rotary joint 55 of the thermo roll 1 and through a first end piece 2.1 of the thermo roll into the cooling medium flow channels 23, 24 and the cooling channels 27 inside the shell 20. The cooling medium cools the edge of the shell 20 of the thermo roll 1 from inside the roll and simultaneously decreases the diameter of the shell 20 in the edge area. The flow channels 23, 24 and the cooling channel 27 of the cooling medium are located inside the flow channels 21, 22 of the heat- transfer medium seen from the direction of the radius of the thermo roll. The cooling medium, such as water, flows at the first end of the roll into the first cooling channel 27 and from there along the forward flow channel 23 to the second cooling channel 27 at the other end of the roll and from the second cooling channel 27 out along the return flow channel 24. From the return flow channel 24, the return flow of the cooling medium comes outside the shell 20 of the thermo roll 1 via the first end piece 2.1 and outside the thermo roll via the first rotary joint 55. From there, the return flow of the cooling medium is guided along a return tube system 56 via a second heat exchanger 57 back to the tank 50. In the second heat exchanger 57, the temperature of the cooling medium can be adjusted e.g. cooled.

Due to the above-described heat-transfer channels 21, 22 of the thermo roll 1 illustrated by means of Figs. 7 and 8, the sealings of their edge areas and further the cooling of the edge areas, the radial displacement profile of the shell 20 of the thermo roll can particularly in the nip area of the fibrous web be arranged as

suitable as possible for calendering the fibrous web. In the described way, it is possible to provide adjustable power for the cooling of the edge area of the shell 20 with which the temperature profile of the thermo roll is not considerably affected in the area of the nip. Thus, the temperature and radial displacement profile in the edge area of the thermo roll can be optimised during run. Furthermore, the described arrangement can complement or replace the profiling means of the edge area of the thermo roll known from prior art.

Fig. 9 shows flow channels 61; 62 of heat-transfer medium arranged in the shell 20 of the thermo roll at least at two distances Dl; D2 from the surface 20a of the shell 20. The figure does not consider in more detail into which direction the heat- transfer medium flows in the flow channels 61; 62. The smaller-diameter flow channels 61 are located closer to the surface 20a of the shell 20 advantageously each at the same distance from the surface of the shell 20 and the larger-diameter flow channels 62 are located farther from the surface 20a of the shell 20 advantageously each at the same distance from the surface of the shell 20.

When aiming at an even temperature and radial displacement profile on the surface of the roll, one has wished to decrease the distance of the flow channels from each other in some cases. From the viewpoint of mechanical durability, the distance of the flow channels from each other has a certain minimum measure the closer the channels cannot be located. Thus as shown in Fig. 9, the flow channels 61, 62 are produced at least at two different depths from the surface 20a of the shell 20, whereby the diameter of the channels which are deeper is larger because the transfer of heat from them onto the surface is more difficult. Furthermore, the flow channels 61; 62 at two distances from the surface 20a of the shell 20 in Fig. 9 are located so that each flow channel 62 deeper from the surface 20a is at the same distance from both adjacent flow channels 61 closer to the surface, in other words, the larger-diameter flow channels 62 are located "between" the smaller- diameter flow channels 61 in Fig. 9. The flow volumes and location of the flow channels in relation to each other and the depths from the surface can be

thermodynamically optimised for minimising the temperature variations of the surface 20a and the radial displacement on the surface 20a of the shell of the thermo roll.

Said smaller-diameter 61 and larger-diameter 62 flow channels can be located advantageously symmetrically and at even distances in relation to each other, but also some other location is possible. The symmetry of the location of the flow channels is also advantageous from the viewpoint of manufacturing and the balance of the thermo roll.

A possible manufacturing technique for manufacturing the thermo roll shown in Fig. 9 more easily and cost-effectively than today is the hot isostatic pressing (HIP) technique.

The advantage of the arrangement shown in Fig. 9 is that the heating channels can be located, when large heat power is required, close to the surface 20a of the thermo roll, whereby the heat power conveyable via the heating channels 61 close to the surface and the flow channels 62 farther from the surface can be increased.

Fig. 10 shows sealing arrangements arranged into connection with the end piece 2 of the thermo roll 1 for sealing the end piece 2 to the shell 20 of the thermo roll 1.

Fig. 10 shows the end surface of the end piece 2 of the thermo roll 1 which is sealed to the shell 20 of the thermo roll 1 of Fig. 9 to prevent the leaking of the heat-transfer medium. Flow channels 61'; 62' of heat-transfer medium are located in the end piece 2 at least at two distances Dl; D2 from the surface 20a of the shell 20 of Fig. 9, in other words, they are located at radial distances corresponding the ones of the flow channels 61, 62 of the shell 20 from the central axis of the thermo roll 1. The smaller-diameter flow channels 61 ' are located closer to the outer diameter of the end piece 2 advantageously each at the same distance from the surface of the end piece and the larger-diameter flow channels

62' are located farther from the outer diameter of the end piece 2 advantageously each at the same distance from the surface of the end piece 2.

To prevent the leaking of the heat-transfer medium, from the flow channels of the thermo roll 1 , which can be used for heating the thermo roll 1 or even for cooling the edge areas of the shell 20 e.g. in a way shown by Fig. 7, to the end piece 2 can be arranged first forms 30 to receive seals and, if required, second forms 30.1 and, if required, third forms 30.2. These forms 30, 30.1, 30.2 can also be formed on the end surface 20' of the shell 20 of the thermo roll 1, as depicted above in connection with the description of Fig. 6.

The first form 30 or, if required, several first forms is/are located outside the flow channels 61 ', 62' seen from the direction of the radius of the end piece 2. Its (their) purpose is to form a receiving space, such as a groove, for realising the end sealing with the composite-structured metal seal 40 shown in Fig. 6 and to prevent the potential leaking of heating or cooling medium from said flow channels 61 ', 62' and possible forward and return flow channels 23, 24 of the cooling medium directed outside the thermo roll.

The second forms 30.1, if one wishes to use them, can be located around each outer smaller-diameter flow channel 61 ' and/or inner larger-diameter flow channel 62' forming in a way described in Fig. 6 a recess 30.1 or a groove 30.1 around the flow channel 61 '; 62' in which recess or groove the corresponding composite- structured metal seal 40 can be set. Its purpose is to prevent the leaking of the heating or cooling medium flowing in the flow channels 61 '; 62'. Naturally, the forward and return flow channels 23, 24 shown in Fig. 7 in connection with the joint of the shell 20 and the end piece 2 can also be sealed with composite- structured seals 40 arranged in the corresponding second forms 30.1 (not shown in Fig. 10).

The third form 30.2 or, if required, several third forms is/are located inside the flow channels 61 ', 62' seen from the direction of the radius of the end piece 2. Its (their) purpose is to form a receiving space, such as a groove, for realising the end sealing with the composite-structured metal seal 40 shown in Fig. 6 and to prevent the potential leaking of heating or cooling medium from said flow channels 61 ', 62' and possible forward and return flow channels 23, 24 of the cooling medium directed outside the thermo roll.

The invention was described above by way of examples with reference to the figures of enclosed drawings. The invention is not, however, limited to what is presented in the figures, but different embodiments of the invention can vary within the scope of the inventive idea defined in the enclosed claims.