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
  • D21F3/04—Arrangements thereof
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F2/00—Transferring continuous webs from wet ends to press sections

Definitions

• the invention relates to a method of controlling the vacuum level in a suction roll/rolls in a paper/board machine.
• This application proposes using a vacuum pump the speed of rotation of which can be controlled and which is connected through a water separator to a suction roll, such as a pick-up roll.
• the use of the vacuum pump according to the invention becomes advantageous specifically because of the quick controllability of the capacity of the pump and its wide control range and low energy costs.
• the pump is advantageously placed in the vicinity of the site of operation and each unit to be operated is equipped with a vacuum pump of its own the speed of rotation of which can be adjusted.
• the structural size of the pump is small, with the result that the vibrations caused by it are minimal.
• piping arrange- ments are not needed to the extent corresponding to that of the prior art constructions having pumps placed far from their sites of application.
• the vacuum level of the pumps is controlled according to the running situation.
• the vacuum level of the pick-up roll is controlled by adjusting the speed of rotation of the vacuum pump connected thereto.
• the vacuum level of the pick-up roll is raised by increasing the speed of rotation of the pump and, when the web has passed over the pick-up roll, the speed of rotation of the pump is reduced, respectively, thereby lowering the vacuum level produced by it in the pick-up roll to a desired level of vacuum during continuous ramiing.
• the same principle is followed in the felt suction rolls and transfer suction rolls situated after the pick-up roll as well as in the Vac rolls of a dryer section.
• Control of the vacuum pumps is carried out through the central processing unit of the paper or board machine such that the pumps operate in a preprogrammed manner according to a control logic which receives its control, for example, from sensors or other observation means which observe the travel and presence of the web at any given observation point.
• Figure 1A shows the transfer of a paper web from a wire section to a press section at the stage at which a pick-up roll has not yet been moved into connection with a wet wire H 0 of the wire section and, at this stage, the web is passed down into a pulper or equivalent.
• Figure IB shows the lowering stage of the pick-up roll where the pick-up roll has been lowered into connection with the wet wire H 0 of the wire section, in which connection the web W can be picked up by means of the pick-up roll to a press section.
• Figure 2 is a graphic illustration of a pick-up roll according to the invention and the figure shows a water separator placed in connection with the pick-up roll and a vacuum pump which has been connected to the water separator and the speed of rotation of which can be controlled according to the invention.
• Fig. 1A shows the transfer of a paper web from a wire section to a press section.
• the web W is passed into a pulper from a wet wire H 0 in the stage of Fig. 1A.
• the press section 100 comprises a so-called pick-up roll 11, which is a roll provided with an inside suction box and suction zone, a given inside sector of which roll can be supplied with a vacuum producing desired adherence to the web W, and which suction zone can be brought, together with a felt passed over the roll 11 , into contact with the web W on the wet wire H 0 at the stage at which it is desired to pick the web W to the press section 100 and further to a dryer section 200.
• pick-up roll 11 is a roll provided with an inside suction box and suction zone, a given inside sector of which roll can be supplied with a vacuum producing desired adherence to the web W, and which suction zone can be brought, together with a felt passed over the roll 11 , into contact with the web W on the wet wire
• the press section 100 includes a press unit 101 which comprises an upper press roll lOla j and its backing roll 101a 2 , in which connection felts H j and H 2 are passed through a nip N, between the press rolls 101a 1 , 101a 2 -
• a felt suction roll 12 is disposed in connection with the felt H 2 after the nip Ni and its function is to guide the web W from the press 101 and keep it apart from the felt Hi and further cause it to run with the lower felt H 2 when the web W is transferred to a transfer suction roll 13.
• the transfer suction roll 13 is situated inside a felt loop H 3 and said transfer suction roll 13 comprises an inside suction box and a suction zone, the web W being transferred by means of the transfer suction roll 13 out of connection with the felt H 2 into connection with the felt H 3 of a second press 103.
• the felt H 3 and a transfer belt or felt H are passed through a nip N 2 between press rolls 103a ⁇ ,103a 2 of the second press.
• the web W is passed from the nip N 2 between the press rolls 103a j , 103a 2 on the surface of the transfer belt or felt H onwards and picked up further via a transfer suction roll 14 to the dryer section 200 and further into connection with a drying wire H 5 .
• a felt is used instead of the transfer belt H , there is after the second press nip N 2 most advantageously a felt suction roll inside the felt loop H 4 , as after the first press nip N j , to guide and keep the web W on the surface of the felt H 4 .
• the web is carried over a first drying cylinder Ki further into connection with a Vac roll, or a suction cylinder S j , and onwards in a conventional manner in the group of drying cylinders.
• the Vac roll Si is a conventional suction cylinder which is provided with a non-inside suction box and by means of which the web W is kept in contact with the surface of the drying wire in connection with the Vac roll S 1 ,S 2 ...
• the Vac roll, or the suction cylinder Si comprises perforations extending through the shell of the roll and an inside free space without a suction box into which vacuum is sucked through the end of the shaft of the roll Sj by means of a pump 10a 5 having a high speed of rotation in accordance with the invention.
• the speed of rotation of the pump 10a 5 can be controlled and, thus, the vacuum prevailing inside the Vac roll, i.e. the suction cylinder Si , is controlled by adjusting the speed of rotation of the pump 10a 5 .
• high-speed pumps 10a ⁇ , 10a 2 ,10a 3 , 10a 4 , and 10a 5 are used as devices which produce a vacuum in the rolls/cylinders.
• the suction side of the pumps 10a 1 , 10a 2 ... is connected to through a water separator 51 to the rolls/cylinders 11,12,13,14,8 ! in order to produce a vacuum inside them.
• the pumps 10a 1 , 10a 2 , 10a , 10a , and 10a 5 may also be called vacuum pumps.
• the speed of rotation of the vacuum pump lOa j is accelerated to a vacuum level desired to be produced in the pick-up roll 11 before the paper web W is transferred from the wet wire H Q onto the pick-up felt H ⁇
• the pick-up roll 11 is lowered into connection with the wire H 0 and the web W carried on it, and when the paper/board web W has been transferred onto the pick-up felt Ht , the vacuum in the roll 11 is made constant so as to be at a desired predetermined level by reducing the speed of rotation of the vacuum pump 10a j .
• the speed of rotation of the vacuum pumps 10a 7 , 10a 3 , 10a of the other transfer and felt suction rolls 12, 13, 14 is also accelerated by means of a preprogrammed system or possibly by making use of a measurement of vacuum in the transfer and felt suction rolls 12,13, 14 so as to achieve a desired vacuum level.
• the paper/board web W is not causing any flow resistance in the area of the suction sector of the transfer suction roll 12,13, 14, so that the permeability of only the wet press felt or drying wire is high and the capacity demand of the vacuum pump 10a 2 , 10a 3 , 10a 4 is also high.
• the corresponding vacuum control of the Vac roll S ⁇ ,S 2 ... is carried out either in a preprogrammed manner or based on data received from a sensor.
• the vacuum level of the Vac roll is raised and, when the web W is present, the vacuum is lowered by adjusting the speed of rotation of the pump 10a 5 to a given preset level.
• Fig. IB shows the lowering stage of the pick-up roll 11, in which connection the web W has already been passed through the press 100.
• the speed of rotation of the vacuum pump 10a ⁇ is lowered quickly in order to reduce the vacuum in the pick-up roll 11 and, in addition, in order to speed up the operation, a valve 120 (in Fig. 2) in a pipe system 50 leading to the roll 11 may also be quickly opened into the ambient atmosphere synchronized with the lifting movement of the pick-up roll 11.
• the speed of rotation of the vacuum pump 10a j or pumps 10a 2 , 10a 3 , 10a ,10a 5 is lowered so as to achieve a desired vacuum level.
• the paper web producing a high flow resistance covers the suction zone of the transfer or felt suction roll and the Vac roll S j and the capacity demand of the vacuum pump 10a ⁇ , 10a , 10a3, 10a 4 , 10a 5 is lower.
• the vacuum pumps 10a ⁇ , 10a 2 , 10a 3 , 10a 4 , 10a 5 are connected to the suction sites, i.e. rolls and cylinders, in accordance with the invention such that the suction side of the vacuum pump is connected to a water separator 51 of its own, which water separator 51 is further connected from its upper suction space through a pipe system to a roll or cylinder.
• the vacuum of the transfer and felt suction rolls can also be increased in a programmed manner and quickly, thereby assuring the run of the web W to a desired path of travel if it is found by means of sensors observing the travel of the web that the web tends to pass or has already passed to an undesirable path of travel.
• New fabrics in a paper/board machine such as wires and felts, which have not clogged, require a suction capacity and a vacuum level different from those of old fabrics and fabrics that have become less permeable.
• the vacuum levels are changed in connection with each unit, such as Vac roll, transfer suction roll, pick-up roll, etc. Otherwise it is possible to apply constant vacuum levels, which may be preprogrammed for each ranning situation.
• Fig. 2 illustrates a pick-up roll 11 according to the invention.
• a pipe system 50 leading to a water separator 51, into which is also opened a duct for a vacuum pump 10a j whose speed of rotation can be controlled.
• a water outlet duct 53 of the water separator 51 comprises a control valve V.
• Vacuum is passed from the water separator 51 into the duct 50 which is connected to a hollow shaft f inside the roll shell of the pick-up roll 11 , which shaft f opens into a space D j between partition walls E j and E ⁇ inside the roll 11 for applying the vacuum to a given sector over the length of the roll 11.
• the duct 50 comprises a quick opening valve 120, and by adjusting this valve, the vacuum level can be quickly lowered, when needed, in the space D j inside the roll 11.
• Vacuum is produced first in a pipe system 52 on the suction side of the pump 10a j whose speed of rotation can be controlled, and therefrom into the water separator container 51, into which the pipe 50 opens from the suction sector Di of the pick-up roll 11.
• the suction sector Di is defined by the partition walls E ⁇ E ⁇ of a suction box 40 inside the roll 11.
• the vacuum is sucked into the sector D j and the adherence suction is passed further to the web W carried on the wet wire H 0 .
• the vacuum and the suction are applied via perforations C j ,C 2 ... of the shell of the roll 11 through the felt Hi to the web W.
• the reference numeral 60 designates an actuator used for moving, i.e. lifting and lowering of the pick-up roll 11.
• the pump equipment with high speed of rotation is constituted by a combination of an electric motor and a pump 70, 10a ⁇ .
• the maximum speed of rotation is about 10000—35000 r/min.
• the electric motor rotating the pump 10a t is designated by the reference numeral 70 in the figures.

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Publications (1)

Family

ID=8554401

Family Applications (1)

Country Status (4)

Citations (2)

• 1999
  • 1999-04-13 FI FI990806A patent/FI990806A/fi unknown
• 2000
  • 2000-04-11 DE DE10084416T patent/DE10084416T1/de not_active Withdrawn
  • 2000-04-11 AU AU39676/00A patent/AU3967600A/en not_active Abandoned
  • 2000-04-11 WO PCT/FI2000/000301 patent/WO2000061862A1/en active Application Filing

Patent Citations (2)

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