Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
  • D21G7/00—Damping devices
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F5/00—Dryer section of machines for making continuous webs of paper
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F5/00—Dryer section of machines for making continuous webs of paper
  • D21F5/001—Drying webs by radiant heating
  • D21F5/002—Drying webs by radiant heating from infrared-emitting elements
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F7/00—Other details of machines for making continuous webs of paper
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F7/00—Other details of machines for making continuous webs of paper
  • D21F7/008—Steam showers
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
  • D21G1/00—Calenders; Smoothing apparatus

Definitions

• the invention concerns a method for controlling the curl of paper, in which method steam treatment and/ or moistening of the paper web and/or equivalent operations are employed in order to control the curl of the paper web.
• the invention concerns a paper or board machine, which comprises at least a headbox, a former, a press, and a dryer section, in which paper or board machine steam boxes and/or moistening devices and/or a one-sided drying impulse and/or equivalent devices for the control of the curl are employed.
• twin- wire draw and/or single-wire draw is/ are employed.
• twin-wire draw the groups of drying cylinders comprise two wires, which press the web one from above and the other one from below against heated cylinder faces. Between the rows of drying cylinders, which are usually horizontal rows, the web has free and unsupported draws, which are susceptible of fluttering, which may cause web breaks, in particular so when the web is still relatively moist and, therefore, of low strength.
• each group of drying cylinders includes just one drying wire, on whose support the web runs through the whole group so that the drying wire presses the web on the drying cylinders against the heated cylinder faces, whereas on the reversing cylinders or rolls between the drying cylinders the web remains at the side of the outside curve.
• the drying cylinders are placed outside the wire loop, and the reversing cylinders or rolls inside said loop.
• the tendency of curling of paper is already affected in connection with the web formation, in particular at the sheet formation stage by means of selection of the difference in speed between the slice jet and the wire and by means of selection of the former and by means of the mode of its running, as well as by means of other running parameters.
• a suitable initial curl form is regulated for the sheet in order that the curling of the paper after one-sided or double-sided copying could be optimized.
• the reactivity of curling i.e. the extent to which curling occurs per unit of change in moisture content, is affected to a greater extent by means of a multi-layer structure of the paper, which is produced in connection with the web formation in the wet end.
• FI Patent Application 963734 (equivalent to US Provisional Patent Application 60/030,693) a method is described for drying a surface-treated paper web or equivalent in an after-dryer of a paper machine as well as an after-dryer for a paper machine for applying the method, wherein, in view of compensating for a tendency of curling of the paper web, in the after-dryer the paper web is dried in a dryer group/groups making use of a normal single-wire draw, and that, in connection with or after the drying, the paper web is treated by means of a device/devices in order to compensate for a tendency of curling of the paper web, said devices being, for example, a steam box, a blow unit, a moistening device, and/ or a soft calender.
• the paper broke is removed from below the dryer groups that are open towards the bottom, substantially by the effect of gravity, onto the broke conveyor placed underneath.
• the paper web which has a tendency of curling because of the asymmetric forward drying, is passed into an after-dryer, in which it is after- treated while, at the same time, moistening and/or plastically working, so that the tendencies of curl that arose in it in the forward drying stage are eliminated.
• the method for drying of paper comprises the following steps: the paper web to be dried is passed from the press section into a forward dryer section, in which the paper web is dried from the side of its bottom face in dryer groups that apply a normal single- wire draw, said forward dryer section comprising exclusively single-wire groups with normal single-wire draw, and from the forward dryer section the paper web is passed into a finishing section, in which the paper web is coated/surface-sized by means of a coating/surface-sizing equipment, dried in an after-dryer section, in which the paper web is dried in at least one dryer group that applies a normal single- wire draw, after which the paper web is calendered in a calender and passed to a reeling station, in which the paper web is reeled into a machine reel, and in the method the curling of the paper web is controlled by means of elements and/or by means of assemblies and combinations formed out of said elements in the area of the forward dryer section and/ or of the finishing section.
• the dry end of a paper machine comprises a forward dryer section and a finishing section, which finishing section comprises a coating/surface-sizing equipment, an after-dryer, a calender, and a reeling station.
• the dry end of the paper machine comprises elements and/or assemblies and combinations formed out of said elements in view of controlling the curling of the paper web in the area of the forward dryer section and/or of the finishing section.
• the elements for controlling the curling comprise, among other things, blowing of hot moist air through the wire in the forward dryer section, steam boxes employed in the after-dryer, a combination in which steam-treatment by means of a steam box is combined with a cooling cylinder, a lower support belt or support wire in the after-dryer, twin-wire groups employed in the after-dryer, through-drying through the wire in connection with at least one cylinder in the after-dryer, the ratio of cylinder diameter, spraying of water against the web in the after-dryer, infrared boxes before the calender, transfer of moist air from the forward dryer to the after- dryer to be blown against the web, and mechanical working of the web by means of a spreader bar.
• the devices for the regulation of curl and the other, corresponding arrangements are fitted in the dry end of the paper machine before the calender. It has been assumed that, if curl regulation operations are carried out after the calender, they have a detrimental effect on the surface properties of the paper.
• a curl regulation device such as a steam box or a moistening device
• the calendering result is affected to a great extent, i.e. the smoothness of the faces and the bulk of the paper. This quite often prevents full control of the curl.
• the efficiency of a moistening/steam-treatment device suffers from the high temperature of the web.
• the object of the present invention is to approach the problems related to the control of curl from a new point of view and to suggest novel solutions contrary to conventional modes of thinking for said problems.
• An object of the present invention is to provide a method for the control of the curl and a paper or board machine in which the operations necessary for controlling and regulating the curl can be carried out after the calender.
• the method in accordance with the invention is mainly characterized in that, in the method, the operations for controlling the curl of the paper web are carried out after the calendering process carried out in the calender.
• the paper or board machine in accordance with the invention is mainly characterized in that the steam boxes and/or moistening devices and/or equivalent curl control devices for the control of the curl of the paper web are placed after the calender.
• the curl is regulated after the calendering process by means of a steam box or a moistening device or by means of any other, equivalent curl control arrangement in itself known, for example, in connection with a winder, slitter- winder, intermediate calender, Pope-type reel-up, etc.
• the operations necess- ary for controlling the curl can be carried out, for example, as steam blowing carried out in connection with a reel-up, in connection with an unwind stand it is possible to turn the reel around, in which connection the curl regulation effect can be applied to the opposite face of the paper web, by means of steam boxes placed before the reel-up, by means of a steam box fitted in connection with the reel that is being formed, by means of a combination of moistening and steam treatment before the reel-up, by moistening before the reel-up, by fitting, for example, an infra heater or an equivalent device by whose means the web is dried from the opposite side.
• Figure 1 is a schematic illustration of an exemplifying embodiment of the invention for the control of the curl in connection with a reel-up.
• Figure 2 is a schematic illustration of an exemplifying embodiment of the invention for the control of the curl in connection with an unwind stand.
• Figure 3 is a schematic illustration of an exemplifying embodiment of the invention for the control of the curl after the calendering process, in which embodiment, in view of controlling the curl, a steam box has been fitted before the reel-up.
• Figure 4 is a schematic illustration of an exemplifying embodiment of the invention for the control of the curl after the calendering process, in which embodiment, in view of controlling the curl, two steam boxes have been fitted before the reel-up.
• Figure 5 is a schematic illustration of an exemplifying embodiment of the invention, in which, in view of controlling the curl, a steam box has been fitted before the reel- up and in connection with the paper reel that is being formed in the reel-up.
• Figure 6 is a schematic illustration of an exemplifying embodiment of the invention, in which, in view of controlling the curl, two steam boxes have been fitted in connection with the paper reel that is being formed in the reel-up.
• Figure 7 is a schematic illustration of an exemplifying embodiment of the invention for the control of the curl after the calendering process, in which embodiment, in view of controlling the curl, both a moistening device and a steam device have been fitted before the reel-up.
• Figure 8 is a schematic illustration of an exemplifying embodiment of the invention in which, in view of controlling the curl, a moistening device has been fitted before the reel-up.
• Figure 9 is a schematic illustration of an exemplifying embodiment of the invention in which, in view of controlling the curl, two moistening devices have been fitted before the reel-up.
• Figure 10 is a schematic illustration of an exemplifying embodiment of the invention in which the curl control devices are fitted in connection with a supercalender.
• Fig. 1 in view of controlling the curl, after the calender, in connection with an online or off-line reel-up, the web W is unwound from the reel 27 over the rolls 22,23,24,25,26 into the reel 21.
• the frame constructions of the reel-up are denoted generally with the reference numeral 28, and the empty reel spools placed in the spool store are denoted with the reference numeral 29.
• Fig. 1 shows possible different alternatives for placing the curl control device in connection with the reel- up 20.
• a steam blow box 22 A or an equivalent device for example, below the reeling nip N between the reel 21 and the reeling drum 22, it is possible to place a steam blow box 22 A or an equivalent device, of which a partial enlarged illustration is shown in the area A, from which it comes out that from the steam blow box 22 A or from an equivalent source, steam blowings can be applied either into the nip N, blowing P2, or towards the reel 21 face, blowing PI .
• a steam blow box or an equivalent device 25A,26A can be fitted in connection with the alignment/guide rolls 25,26.
• the paper web W is unwound in the unwind station 60 from the reel 61, and the web W is passed over the rolls 62,63,64 to the slitter 65, from which it is further passed over the rolls 66,67 to the drum winder 70, in which the web W is wound into the paper roll 71 on support of the winding drums 68 and 69, and in connection with the winding also a rider roll 72 is employed.
• the reference numeral 73 denotes the roll transfer device. In view of controlling the curl, in connection with such an assembly of equipment, various devices can be fitted so as to control the curl.
• a steam box 68 A or the other winding drum 69 can be made into a steam roll, into which a steam blow zone 69A is formed, or a steam pipe 71 A can be fitted in the space between the winding drums 68,69 and the paper roll 71 that is being formed. If necessary, in the unwind stage, the paper roll 61 can be turned around, in which connection the effect of the curl regulation can be applied to the opposite side of the paper web W.
• the last two groups R j ,R2 with single- wire draw in the dry end 30 of the paper machine are seen, over whose group gaps the web W has a closed draw.
• the machine direction i.e. the running direction of the web W is denoted with the arrow S.
• the single-wire groups Ri ,R 2 are so-called normal groups, in which the, for example, steam-heated smoothfaced drying cylinders 10 are placed in the upper horizontal row and the reversing suction cylinders 11 are placed in the lower horizontal row.
• Each dryer group R j ⁇ has a drying wire 15 of its own, which is guided by guide rolls 18.
• the drying wires 15 press the web W to be dried, on the drying cylinders 10, against the smooth heated faces of the cylinders, and on the reversing cylinders 11 the web W remains at the side of the outside curve on the outer face of the wire 15.
• the web W is kept reliably on support of the wire 15 against the effect of centrifugal forces by the effect of a vacuum present in the grooved faces of the reversing cylinders 11 or in the perforated mantle of an equivalent suction roll, by means of which effect cross-direction shrinkage of the web W is also counteracted.
• the reversing suction cylinders 11 that are used are particularly favourably suction cylinders marketed by the applicant with the trade mark VacRoUTM, which have no inside suction boxes and in respect of the details of whose constructions reference is made to the applicant's FI Patent No. 83,680 (equivalent to US Patents Nos. 5, 022, 163 and 5,172,491).
• the support contact between the web W and the drying wire 15 is kept adequate also on the straight runs between the drying cylinders 10 and the reversing cylinders 11 by, at least on the runs from the drying cylinders 10 to the reversing cylinders 11, using blow-suction boxes 17, by whose means formation of pressures induced by the wire 15 is also prevented in the closing wedge-shaped nip spaces between the wire 15 and the cylinder 11 mantles.
• the blow-suction boxes 17 are understood as blow boxes whose blowing of air produces a vacuum, and said boxes 17 do not communicate with sources of vacuum.
• blow box constructions of other types in themselves known are also included in the scope of the overall concept of the present invention.
• blow boxes 16 are also used, by whose means said intermediate spaces are air-conditioned and evaporation taking place from the web W is promoted.
• the faces of drying cylinders 10 are kept clean by doctors 14.
• the finishing section includes a machine reel-up 50, such as a Pope-type reel-up.
• the machine reel that is being made by means of the reel-up 50 is denoted with the reference MR Q , and one complete machine reel with the reference MR.
• the web W is brought to the machine reel-up 50 through the calender 40 from the after-dryer 30 over the guide and alignment rolls 35,45,46,47. After the last guide/alignment roll 47 a measure- ment device 48 is fitted for measurement of the properties of the web W before reeling.
• the calender 40 may be favourably a so-called soft calender, in which one roll can be heated and the other roll has a soft coating.
• the calender may also consist of two hard rolls. There may also be several calender nips.
• a steam box 81 has been fitted on the run of the web W between the guide/alignment rolls 46,47, in which case, thus, the curl is affected after the calendering process before the reel-up 50. If it is desired to control the tendency of curling efficiently in both directions, a steam box 81 A or equivalent can also be fitted above the web.
• a steam box 82 has been fitted between the alignment/ guide rolls 45 and 46, and a steam box 81 has been fitted on the run of the web between the alignment/guide rolls 46,47, the control of curl being affected by means of both of said steam boxes on the run of the web W between the calender 40 and the reel-up 50.
• a steam box 83 has been fitted in connection with the paper reel MR Q that is being formed, in which case, besides in connection with the run of the web between the calender 40 and the reel-up 50, the control of the curl is also affected in connection with the making of the reel MR Q that is being formed.
• a displaceable steam box 83 has been fitted, which is illustrated by the arrow S 83 . The box 83 is shifted as the reel size becomes larger when the reeling proceeds.
• a web W moistening device 85 has been fitted on the run of the web W between the alignment/guide rolls 45,46, in which case the curl of the web W is controlled after the calender 40 and before the reel-up 50 both by means of a moistening treatment and by means of a steam treatment.
• a moistening device 86 in view of controlling the curl after the calender 40, on the run of the web W between the alignment/guide rolls 46,47, a moistening device 86 has been fitted.
• the figure also shows an IR dryer 87, by whose means an impulse of thermal energy can be applied to the top face of the web so as to affect the tendency of curling of the ultimate product.
• IR drying it is also possible to use some other dryer device.
• said devices can be fitted at both sides of the web. Regulation of curl by means of one-sided additional drying can be employed either alone or in combination with steam- treatment and/or moistening devices.
• moistening devices 85,86 have been fitted on the runs of the web W between the alignment/guide rolls 45,46 and
• the regulation of curl is carried out in connection with a supercalender 110.
• the web W runs from the unwind stand 100 to the top portion of the supercalender 110 and from the bottom portion of the supercalender 110 further to the reel-up 120.
• the supercalender 110 consists of a vertical stack of rolls, in which the web W glazing nips consist of a hard-faced and a soft-faced roll.
• a few possible positions are indicated in which it is possible to employ steam boxes and/or moistening devices and/or devices that heat the web face intensively.
• the devices can be placed on the run (91,92) of the web W between the unwind stand 100 and the supercalender 110 and/or in connection with the take-out leading rolls 111 in the supercalender 110 (93,94) and/or on the run of the web W between the supercalender 110 and the reel- up 120 (95,96).

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Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Cited By (3)

Families Citing this family (3)

Citations (1)

• 1997
  • 1997-05-15 FI FI972080A patent/FI106271B/fi not_active IP Right Cessation
• 1998
  • 1998-05-08 CA CA002289475A patent/CA2289475A1/en not_active Abandoned
  • 1998-05-08 WO PCT/FI1998/000395 patent/WO1998051857A1/en not_active Application Discontinuation
  • 1998-05-08 AU AU74331/98A patent/AU7433198A/en not_active Abandoned
  • 1998-05-08 EP EP98921505A patent/EP1009876A1/en not_active Withdrawn

Patent Citations (1)

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