Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F3/00—Press section of machines for making continuous webs of paper
  • D21F3/02—Wet presses
  • D21F3/0209—Wet presses with extended press nip
  • D21F3/0218—Shoe presses
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F3/00—Press section of machines for making continuous webs of paper
  • D21F3/02—Wet presses
  • D21F3/0281—Wet presses in combination with a dryer roll

Definitions

• the present invention relates to a press section in a machine for manufacturing a continuous web of fibrous material, comprising one or more presses, at least one of which is a shoe press with extended press nip comprising
• a rotatable counter roll including a cylindrical press body
• a movable heat transfer means for continuous transfer of heat to the web in the extended press nip, and - at least one heat source for continuous heating of the heat transfer means.
• the invention also relates to a press section in a machine for manufacturing a continuous web of fibrous material, comprising one or more presses, at least one of which is a roll press comprising
• a second rotatable press roll defining a press nip with the first press roll, at least the first press roll including a cylindrical press body,
• a clothing running in a loop around a plurality of guide rolls and through the press nip in contact with the web, and being capable of receiving and carrying liquid along with it, - a movable heat transfer means for continuous transfer of heat to the web in the press nip, and - at least one heat source for continuous heating of the heat transfer means .
• the invention also relates to a shoe press with extended press nip for a press section in a machine for manufacturing a continuous web of fibrous material, comprising
• a rotatable counter roll including a cylindrical press body, - a press shoe having a concave surface for pressure-generating cooperation with said press body,
• the invention also relates to a treatment section in a machine for shape and/or surface changing mechanical treatment of a continuous web of fibrous material, comprising at least one roll calender comprising
• a second rotatable roll defining a nip with the first roll, at least the first roll including a cylindrical body
• the invention also relates to a treatment section in a machine for shape and/or surface changing mechanical treatment of a continuous web of fibrous material, comprising at least one shoe calender with extended nip comprising
• a rotatable counter roll including a cylindrical body
• a burner supplies heat to one roll in a press with two rotating rolls.
• the heat is supplied to the envelope surface of the roll immediately before the press nip.
• the roll may have a surface layer with low thermal conductivity, thereby enabling it to maintain a high temperature .
• US-4, 738, 752 describes an extended, heated press nip where the fibrous web encounters a hot surface formed by a rotatable press roll or a metal belt passing in a loop around a plurality of guide rolls.
• the press roll or belt is heated by a heat source.
• the press roll may have a first coaxial layer and a second coaxial layer extending around the first layer and having a coefficient of thermal conductivity that is greater than that of the first layer.
• the first layer may consist of ceramic, whereas the second, outer layer consists of metal and has a thickness of 0.0127-1.27 cm.
• the layers are in intimate contact with each other and, together, form a unitary body.
• the outer layer When a roll of the described known types is heated from the outside, the outer layer will be hotter than the layer or layers disposed inside the outer layer which is rigidly joined to the next inner layer. The outer layer will therefore expand more than the inner layer, thereby causing stresses to arise between the two layers. If the roll is homogenous, the same differences will arise in expansion and stresses between the outer and inner parts where the transition between the parts is without specific bounds. To reduce the risk of damage in the roll as a result of such stress differences, the initial heating of the roll must take place slowly. Another problem is that it is difficult to maintain the geometric shape of the roll across the machine direction, due to difficulties in maintaining the same temperature along the envelope surface of the roll and at the end walls.
• a metal belt as heat-transfer means is that it must be arranged in a loop with at least two rolls, thus constituting a space-consuming configuration.
• a counter roll To allow the surface of the belt to be cleaned with a doctor, a counter roll must be arranged inside the loop of the belt in front of the doctor.
• the belt cannot usually be coated with layers to achieve certain release properties and certain thermal conductivity properties.
• the object of the present invention is to at least essentially reduce the problems discussed above and to provide an improved heat transfer means.
• Said press sections, treatment sections and shoe press according to the invention are characterized in that the said counter roll, first press roll and first roll, respectively, comprise a sleeve that forms said heat transfer means and encloses the cylindrical body.
• the improved heat transfer means enables that the beneficial effects of impulse drying can be utilized more efficiently than has previously been possible.
• Figure 1 is a view in perspective of a shoe press, the counter roll of which having a rigid sleeve the diameter of which being shown greatly exaggerated.
• FIG. 2 is a section through the shoe press in accordance with Figure 1.
• Figure 3 is a section through a part of the counter roll and its sleeve in accordance with Figure 1.
• Figure 4 shows a counter roll with a rigid sleeve in accordance with a second embodiment .
• Figure 5 shows a counter roll with a rigid sleeve in accordance with a third embodiment and a cambered press body .
• Figure 6 shows a part of -a counter roll with a rigid sleeve in accordance with a fourth embodiment.
• Figures 7 and 7a show a counter roll with a rigid sleeve in accordance with a fifth embodiment.
• Figures 8 and 8a show a counter roll with a rigid sleeve in accordance with a sixth embodiment.
• Figure 9 shows a shoe press similar to the one in
• Figure 9a is a detail enlargement of the part ringed in in Figure 9.
• Figure 10 shows a shoe press similar to the one in Figure 9 but with a flexible sleeve in accordance with a further embodiment for geared operation by means of cooperating toothed elements.
• Figure 10a is a detail enlargement of the part ringed in in Figure 10.
• Figure 11 is an end view of a roll press according to the invention.
• Figure 12 is an end view of a roll calender according to the invention.
• Figure 13 is an end view of a shoe calender according to the invention.
• Figures 1 and 2 show schematically parts of a shoe press with extended press nip, included in the press section of a machine for manufacturing a continuous web 1 of cellulosic fibrous material, for instance.
• the invention is particularly applicable, but is not exclusive to paper or board machines for manufacturing paper and board, respectively.
• the paper machine may be designed for manufacturing soft paper or printing paper, e.g. newspaper, or any other grade of paper.
• the shoe press comprises a rotatably journalled counter roll 2, a press shoe 3, an impermeable, flexible belt 4 and a clothing 5, which is in direct contact with the web 1 and is capable of receiving liquid in liquid form and gaseous form from the web, and carrying it out of the press nip.
• the counter roll 2 comprises a stable cylindrical press body 6 having shaft journals 30 for rotary journalling of the counter roll in bearing housings (not shown) .
• the press body 6 rotates about an axis of rotation 11 and has an envelop surface with circular cross section.
• the press shoe 3 has a concave surface 7 for pressure-generating cooperation with the corresponding convex press body 6 in order to obtain the extended press nip.
• the belt 4 runs through the press nip in sliding contact with the concave surface 7 of the press shoe.
• the shoe press is provided with a shoe press roll comprising said press shoe 3 and belt 4 which is rigidly mounted at rotatable peripheral end portions 8.
• the flexible belt may run in a loop around a plurality of rolls, in which loop the press shoe is thus mounted.
• the clothing 5 of the shoe press runs in a loop around a plurality of guide rolls (not shown) and through the extended press nip.
• the web 1 is carried to the press nip by the clothing 5 and is separated from the clothing 5 after the press nip.
• the web runs in an open draw before the press nip.
• the clothing 5 usually consists of a press felt, but a permeable belt with through openings and possible recesses disposed or extending therebetween may be used, or an impermeable belt with recesses of suitable depth, shape and extension.
• Said recesses are situated on the side facing towards the web 1.
• Said openings and recesses are arranged to receive liquid from the web and carry the liquid out of the press nip.
• the openings and recesses also give the web a structured appearance which increases the bulk of the web.
• an open wire or closed wire which has a sealing layer facing away from the web, may be used.
• the shoe press comprises a movable means 9 for continuous transfer of heat to the web 1 when the latter passes through the extended press nip, and a heat source 10 which is arranged at a predetermined point before the press nip, e.g. about 30°-330°, preferably 30°-120° before the press nip for continuous heating of said heat transfer means 9 at start-up to a desired operating temperature and during operation to maintain this operating temperature.
• the heat source may be fixed or movable, e.g. oscillating.
• the counter roll 2 comprises a sleeve forming said heat transfer means 9 and at least enclosing the whole of the axial part of the cylindrical press body 6 active in the press nip, the sleeve being permitted to expand freely in relation to the press body 6 during said heating before the press nip, without unfavourable stresses arising in the sleeve.
• the sleeve 9 has an inner side 17 and an outer side 18, the inner side 17 being arranged to be brought into contact with the press body 6 within the zone of the press nip.
• the sleeve 9 consequently lacks any mechanical or adhering connection or other such permanent, fixing connection which would prevent such free expansion of the sleeve 9 axially and radially in relation to the cylindrical press body 6 outside the press nip where heating occurs, and which would instead give rise to unfavourable stresses in the sleeve.
• the sleeve 9 is thus completely free from permanent, locking connections in all directions so that it is permitted to expand free from stress both axially and radially in relation to the cylindrical press body 6 during heating.
• the press body 6 is arranged to press the sleeve 9 firmly at a contact point
• the sleeve 9 may be homogenous, i.e. made of the same piece of material all the way through without layers, or may consist of two or more coherent layers of different materials, at least one of which acts as at least carrier for the other layer (s) .
• the sleeve 9 may be in the form of a rigid, form-stable sleeve or a flexible sleeve, which is thus not form-stable .
• the sleeve 9 is illustrated schematically as a cylindrical, rigid, form-stable sleeve with an outer side 18 having constant, circular cross section and constituting the envelope surface of the rigid sleeve, and with an inner side 17 having constant, circular cross section and being coaxial with the envelope surface 18.
• the diameter of the rigid sleeve 9, however, is shown as greatly exaggerated in relation to that of the press body 6.
• the sleeve 9 shown in Figures 1-3 thus has constant wall thickness, measured between the inner side 17 and the outer side 18 in all arbitrary cross sections between the parallel end planes of the sleeve.
• the wall thickness of the sleeve 9 is selected depending on each specific use, with varying desires of properties of the sleeve.
• the wall thickness of the sleeve is sufficiently large to ensure that the sleeve is rigid and form-stable, i.e. is at least self-supporting so that, when resting on a flat support, it retains its radius all around and does not collapse to a non-circular form. It should preferably be so rigid and form-stable that it is not noticeably deformed by normal stresses during assembly and operation.
• the rigid sleeve 9 has sufficient wall thickness for it not to be subjected to too great stresses in the press nip that may arise as a result of differences in radius between the various construction elements .
• the rigid sleeve 9 rotates about its own axis of rotation, i.e. its central axis 15, which is situated eccentrically in relation to the axis of rotation or central axis 11 of the press body 6, the eccentric displacement, i.e. the distance between these axes 11, 15, corresponding to half the difference between the outer diameter of the press body 6 and the inner diameter of the sleeve 9, i.e. the radial difference.
• the eccentric displacement i.e. the distance between these axes 11, 15, corresponding to half the difference between the outer diameter of the press body 6 and the inner diameter of the sleeve 9, i.e. the radial difference.
• the concave surface 7 of the press shoe 3 has a radius adapted to the radius of the rigid, cylindrical sleeve 9.
• the sleeve is so rigid and stable that it acquires a pressing function through influence from the press body, i.e. the pressure from the press body at the contact point so shortened is transplanted forwards and backwards, seen in direction of rotation, through the sleeve to the press nip so that the length of the press nip will be approximately the same length as the width of the shoe.
• a slight deformation will arise in the passing section when the rigid sleeve 9 passes the press shoe 3, as a result of differences between the inner radius of the sleeve and the outer radius of the press body.
• the wall of the rigid sleeve can be made so thin that the wall is shaped to the press body, provided the material in the wall can withstand this deformation without it becoming a permanent deformation.
• the free space 16 inside the sleeve 9 minimises to the free space 16 inside the sleeve 9, only slight amounts of heat will be consumed by the press body. During operation this space 16 containing air is in the shape of a crescent. Transfer of heat from the sleeve 9 to the press body 6 only occurs within the contact point 14 in the press nip. However, the amounts of heat consumed here are in any case small since the contact surface here constitutes a very small proportion of the circumference and the fact that the heat is transported from one surface to another.
• the temperature in the hot surface of the sleeve at the beginning of the press nip may generally be within the range of 150°C-400°C.
• Figure 4 shows another embodiment of a rigid sleeve 9, the inner side 17 of which is provided with a plurality of endless grooves 19 which are axially uniformly distributed and extend round the circumference to form corresponding cams 31, the cylindrical surfaces of which form the inner side 17 of the sleeve that determines the wall thickness of the sleeve.
• the contact surface with the press body 6 is decreased by about 50% in the shown embodiment, and the amount of heat transferred to the press body is thus also reduced.
• Such a sleeve provided with grooves is therefore advantageous from the energy aspect and also from the heating aspect during start-up, since the heating takes place more quickly without the press body 6 being negatively affected.
• the sleeve 9 is retained against the press body by means of rings 12 forming stops, as described in the embodiment according to Figure 3.
• Figure 5 shows a further embodiment of a rigid sleeve 9 having a cylindrical envelope surface 18 and a cambered inner side 17, the press body 6 having a correspondingly cambered outer side so that the space 16 remains constant, seen in one and the same longitudinal section.
• Axial guidance of the sleeve is thus achieved in relation to the press body without the need for any mechanical stop.
• the thickness of the sleeve thus varies over its entire length and is narrowest in the middle. The variations in thickness lie within the thickness values and intervals specified in this patent application.
• Figure 6 shows an additional embodiment of a rigid sleeve 9, one end of which is provided with or designed with a radially inwardly directed flange 20.
• a circular ring 12 is then mounted at one end surface of the press body 6, the ring 12 having a peripheral recess 21 for receipt of the sleeve flange 20 and to form an axial, outer stop 22 to retain the sleeve 9 on the press body 6 while still allowing it to expand freely in relation to the press body 6 towards its other end which is entirely free.
• a small gap exists between the flange 20 and stop 22 or between the flange 20 and press body 6 to allow a movement of the sleeve 9 circumferentially in relation to the press body 6.
• Figures 7 and 7a show a further embodiment of a rigid sleeve the inner side of which being provided with a recess 23 running around the inner side, in which a flat ring 24 is received to function as axial stop for the sleeve.
• the ring 24 is rigidly mounted on the press body 6.
• Figures 8 and 8a show an additional embodiment of a rigid sleeve 9, both ends of which carry a flat ring 25 rigidly mounted on the sleeve 9.
• the ring 25 is suitably inserted into recesses 26 in the ends of the sleeve 9 and has an inner diameter less than the inner diameter of the sleeve so that a stop 27 is obtained to retain the sleeve 9 on the press body 6, the sleeve 9 being somewhat longer than the press body 6 so that a small space 28 is obtained between each stop ring 25 and the opposing end surface of the press body 6.
• Figures 9 and 9a show a further embodiment of the press body 6 and rigid sleeve 9 of the counter roll.
• the press body 6 is provided at its ends with a toothed ring 32 having external teeth, the sleeve 9 being provided on its inner side 17 with a toothed ring 33 having internal teeth in order to obtain a toothed engagement within the area of the press nip.
• the teeth do not engage with each other after the press nip.
• the sleeve 9 is thus caused to rotate by means of gear transmission, whereas the sleeves described previously here are driven by means of friction engagement between the surfaces meeting in the press nip.
• the toothed rings of the sleeve are mounted on the end surfaces of the sleeve, in which case the toothed ring of the press body are also mounted on its end surfaces (not shown) .
• the sleeve is provided at one end with a toothed ring which is in engagement with tooth elements of an external drive member, in which case a similar drive arrangement is provided at the other end of the sleeve.
• the toothed ring 33 has the same, or substantially the same coefficient of linear expansion as the sleeve in order to avoid undesired stresses in the sleeve upon heating.
• Figures 10 and 10a show an embodiment of a sleeve 9 which is flexible.
• the end portions of the flexible sleeve 9 are provided with axial slots 34 to form a circumferential engagement portion 35, with which toothed rings 36 arranged on the press body 6 are brought into engagement within the area of the press nip.
• the wall thickness of the rigid sleeve 9 is generally within the interval 5-100 mm, preferably 15-40 mm.
• the difference between the internal diameter of the rigid sleeve 9 and the external diameter of the press body 6 is generally within the interval 0.01-100 mm, preferably 0.5-10 mm, measured at room temperature. During operation, when the rigid sleeve is hot, this difference in diameter is naturally considerably greater.
• the surface of the sleeve in contact with the web can be treated as a conventional press roll surface to be cleaned by a doctor, for example.
• the rigid sleeve 9 When the rigid sleeve 9 consists of several layers, one of the layers is a carrier layer, mainly functioning as a stabilizing carrier, with sufficient wall thickness for the carrier layer to be provided with a surface layer, for instance, having the desired property or properties.
• a carrier layer mainly functioning as a stabilizing carrier, with sufficient wall thickness for the carrier layer to be provided with a surface layer, for instance, having the desired property or properties.
• the carrier layer may be provided on its outer side with a surface layer of a suitable material to obtain desired release property and/or a desired thermal conductivity of the surface of the cylindrical sleeve 9.
• a particular thermal conductivity may be desirable in order to control the supply of heat to the web and thus prevent delamination of the web. Delamination is the phenomenon when the web bursts as it leaves the press nip due to the vapour pressure in the web being greater than the forces holding the web together can withstand.
• the cylindrical press body 6 may on its outer side be provided with a surface layer of one or more suitable materials in order to increase its resistance to wear and/or resistance to corrosion, and/or to provide insulation so that the amount of heat transferred from the sleeve 9 to the cylindrical press body 6 is further reduced within the press nip.
• the sleeve 9 may be provided on its inner side with such a surface layer.
• Materials suitable to provide a surface layer with the desired release property and desired thermal conductivity are aluminium oxide, chromium oxide and zirconium oxide based ceramics.
• Suitable materials to increase the wear resistance are tungsten and chromium carbides and chromium steel.
• Suitable materials to increase the corrosion resistance are nickel, chromium, and cobalt based alloys.
• Suitable insulating materials are zirconium oxide based ceramics.
• Suitable materials for a homogenous sleeve (i.e. one without layers) and for the carrier layer of a sleeve consisting of at least two layers include nodular iron, cast steel and weldable high-strength structural steel.
• a sleeve that is flexible has a wall thickness generally within the interval 0.4-5.0 mm, preferably 0.8-2.3 mm.
• the difference between the internal circumference of the flexible sleeve and the external circumference of the press body is generally within the interval 0-100 ⁇ mm, preferably O.l ⁇ -lO ⁇ mm, measured at room temperature.
• the flexible sleeve 9 may consist of two or more layers .
• Any suitable heat source 10 may be used, although an induction heater is currently preferred. Examples of other heat sources are electric heaters, infrared heaters, laser heaters and gas burners.
• the press may suitably comprise a second shoe press provided with a sleeve of the type described or another structure but inverted, so that the sleeve is disposed in under-position in order to transfer heat to the other side of the fibrous web.
• the press body of the shoe press may be a roll called solid roll, modified in accordance with the invention, but it is also possible to use a curvature-compensated roll. Since the contact area between the hot sleeve and the shell body of the curvature-compensated roll is small, little heat is transferred to the roll. Sufficient heat can be conducted away with the oil in the roll to maintain a reasonable temperature and thus sufficient viscosity in the oil to achieve satisfactory functioning of the roll.
• the temperature of the web may be increased before the press nip by arranging one or more steam boxes in the felt loop and/or close to the free side of the web.
• FIG 11 shows schematically parts of a roll press included in the press section of a machine for manufacturing a continuous web 101 of cellulosic fibrous material, for instance.
• the roll press comprises a first or upper rotatably journalled press roll 102, a second or lower rotatably journalled press roll 103 and a clothing 105, which is in direct contact with the web 101 and is capable of receiving liquid in liquid form and gaseous form from the web, and carrying it out of the press nip that is defined by the two press rolls.
• the upper press roll 102 comprises a stable cylindrical press body 106 having shaft journals (not shown) for rotary journalling of the press roll 102 in bearing housings.
• the press body 106 is arranged and designed in the same way as described above in connection with the shoe press.
• the clothing 105 is arranged and designed in the same way as described above.
• the roll press has a movable sleeve-formed heat transfer means 109 and a heat source 110 which are arranged and designed in the same way as described above in connection with the shoe press.
• Figure 12 shows schematically parts of a roll calender included in the treatment section of a machine in which a continuous web 201, e.g. a paper or board web, is subjected to a form and/or surface changing mechanical treatment in one or more nips .
• the web may be coated or uncoated.
• the machine may be included as a part of a paper machine, for instance, upstream of the reel-up.
• the roll calender comprises a first or upper rotatably journalled roll 202 and a second or lower rotatably journalled roll 203, said rolls defining a roll nip with each other.
• the upper roll 202 comprises a stable cylindrical body 206 having shaft journals (not shown) for rotary journalling of the upper roll 202 in bearing housings. As for the rest, the cylindrical body 206 is arranged and designed in the same way as described above in connection with the shoe press.
• the roll calender has a movable sleeve- formed heat transfer means 209 and a heat source 210 which are arranged and designed in the same way as described above in connection with the shoe press.
• Figure 13 shows schematically parts of a shoe calender with extended nip included in the treatment section of a machine in which a continuous web 301, e.g. a paper or board web, is subjected to a form and/or surface changing mechanical treatment in one or more nips .
• the web may be coated or uncoated.
• the machine may be included as a part of a paper machine, for instance, upstream of the reel-up.
• the shoe calender comprises a rotatably journalled counter roll 302, a shoe 303 and an impermeable, flexible belt 304.
• the counter roll 302 comprises a stable cylindrical body 306 having shaft journals (not shown) for rotary journalling of the counter roll 302 in bearing housings.
• the cylindrical body 306 is arranged and designed in the same way as described above in connection with the shoe press.
• the shoe 303 has a concave surface 307 for cooperation with the corresponding convex body 306 of the counter roll 302 in order to obtain the extended nip.
• the flexible belt 304 runs through the nip in sliding contact with the concave surface 307 of the shoe.
• the shoe calender is provided with a roll including said shoe 303 and belt 304 which is rigidly mounted at rotatable peripheral end portions (not shown) .
• the flexible belt may run in a loop around a plurality of rolls, in which loop the shoe is thus mounted.
• the shoe calender has a movable sleeve-formed heat transfer means 309 and a heat source 310 which are arranged and designed in the same way as described above in connection with the shoe press.
• the web-contacting elements 203, 209 and 304, 309 and their surfaces of the roll calender and shoe calender are constructed and designed in accordance with the basic conceptions described above in connection with the shoe press and simultaneously taking into consideration each specific type of calendering that is to be carried out under supply of heat for each specific continuous web running through the nip, said considerations being well known for the expert in the technique of calendering, e.g. those being basis of shoe calenders of the type OptiDwellTM which is sold by Valmet Corporation, Finland.

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• Treatment Of Fiber Materials (AREA)

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• 1998
  • 1998-09-22 SE SE9803201A patent/SE512799C2/sv not_active IP Right Cessation
• 1999
  • 1999-09-07 WO PCT/SE1999/001550 patent/WO2000017445A1/en not_active Application Discontinuation
  • 1999-09-07 EP EP99951305A patent/EP1121485A1/en not_active Withdrawn
  • 1999-09-07 CA CA002344928A patent/CA2344928A1/en not_active Abandoned
  • 1999-09-07 JP JP2000574340A patent/JP2002526677A/ja active Pending

Non-Patent Citations (1)

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