Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
  • D21G3/00—Doctors
• • 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
  • D21F7/04—Paper-break control devices
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
  • D21G3/00—Doctors
  • D21G3/005—Doctor knifes

Definitions

• the invention concerns an equipment and a method for passing a paper/board web into a pulper.
• the tendency of passing a web under a doctor blade is increased when the machine speeds become higher and when the basis weight of the web becomes lower.
• needle jets are applied, which jets disrupt the web before it arrives at the doctor blade. Needle-like jets are applied at a high pressure from a jet pipe onto the web face, and in this way the web is disrupted and a layer of water is produced between the roll and the web, in which case separation of the web by means of the doctor blade is facilitated considerably. Further, the needle jet can be oscillating, in which case the effect of disruption is distributed evenly over the roll face, and the needle jets also keep the roll face clean.
• the equipment may comprise jets in themselves known which moisten the web, in which case the disruption of the web by means of the intensive water jets is facilitated.
• the roll face is kept clean by means of needle jets, this further promotes the operation of the doctor blade proper, in which connection the reliability of the operation of said doctor blade is increased.
• the disrupting needle jet it is favourable to use a part of the water entering into the pulper jets in themselves known.
• a sharp air jet is applied across the entire width of the machine. The air jet separates the web from the roll before the blade tip and thereby prevents formation of a situation in which the web passes under the doctor blade. The separation is facilitated by the air cushion formed under the web.
• the nozzle has been arranged near the tip of the blade and connected with an automatic system so that blowing of air is switched on exclusively when the web arrives at the doctor.
• the "upper lip" of the nozzle is resilient and is opened during blowing and closed when the blowing stops. Along with the air, it is also possible to supply water so as to moisten the blade.
• the front face of the blade be coated, for example, with "teflon" so that the friction between the web and the doctor blade of the doctor is reduced, in which case the possibility of the web being wedged between the roll face and the blade is reduced.
• the passing of the web into the pulper can be enhanced further by means of a solution of equipment in which a guide jet, for example an air jet or a water jet, attracts the web along with it by means of a Coanda effect, and said jet is directed down towards the pulper, in which connection guiding of the web into the pulper is promoted by means of a draw produced by said Coanda effect.
• the draw produced in this way together with the jet applied to the tip of the blade, already separates the web before the blade and prevents formation of a situation in which the web passes under the blade. Further, the operation of the doctor can be improved by means of a separate jet placed at the front side of the doctor blade. The jet keeps the roll face and the blade clean.
• Figure 1 is a schematic illustration of a solution of equipment in accordance with the invention.
• Figure 2 illustrates the use of guide jets.
• Figure 3A shows an embodiment of the invention in which a bellows with a resilient cover has been formed in connection with the doctor blade, through which bellows a jet of a medium, for example a jet of air or water, is passed to the vicinity of the forward edge of the doctor blade.
• a medium for example a jet of air or water
• Figure 3B shows a second embodiment of the construction shown in Fig. 3 A, in which the resilient bellows has been formed out of a resilient plate, which has been attached to a pipe through which the medium is introduced.
• Figure 3C shows an embodiment of the invention in which the nozzle pipe for the water jet is connected with the interior of the doctor beam
• Figure 3D shows a construction in which the nozzle pipe for the water jet has been attached to the face of the doctor beam.
• Figure 3E is a sectional view taken along the line I— I in Fig. 3A.
• Figure 4A shows an embodiment of the invention in which the paper web is disrupted by means of needle jets before the web reaches the doctor blade.
• Figure 4B shows a solution in which, before the needle jets, a moistening jet is applied to the face of the web, in which connection, by means of the needle jets, disruption of the web can be accomplished more efficiently and with lower water pressures.
• Figure 4C shows an embodiment of the invention in which the nozzle pipe 22 that produces the needle jets L 2 is oscillated in the axial direction of the roll 13 so as to increase the web disrupting efficiency.
• Fig. 1 shows a pick-up roll 10, whose different positions are detected by means of an identifying detector di . From the identifying detector dj there is a signal line ej passing to control units that control the spraying of medium.
• the web arrives from the former F over the pick-up roll 10 in between fabrics H j and H 2 , and it is carried further into a nip N j formed between a lower grooved roll 12' and an upper suction roll 12 and further, along the face of the suction roll 12, along with the fabric H 2 passed on the face 12 of the suction roll onto a centre roll 13, and the web W, which adheres to the face of said centre roll 13, is passed further onto a guide roll 14 in the dryer section K and into the first group R ⁇ of drying cylinders in the dryer section K.
• the web W is passed along with the drying fabric H 3 , and by means of a hold suction produced by suction boxes 15a j and 15a 2 , the web W is kept in contact with the lower face of the fabric H 3 and passed onto the first drying cylinder K j and further from the drying cylinder K j onto the suction cylinder Si (of the VacRoll type).
• the guiding of the fabric H takes place over the guide rolls 16 and 17.
• a doctor blade 19 has been fitted, which services the roll and is in contact with the roll face 13' and which is placed in its blade holder 18, which holder is further mounted on a doctor beam 20.
• the web W when the web W is run into the pulper 25, the web W is disrupted by means of needle-like water jets applied from a needle-nozzle pipe 22.
• the needle-nozzle pipe 22 is placed before the doctor blade 19, and a nozzle pipe 21 that moistens the web, which pipe is in itself known, is placed preferably so that it sprays a jet Li that moistens the web before the needle jets L 2 .
• white water is passed by means of a pump 28 into a trunk line 29, from which trunk line 29 there is a branch line 30a 1.
• the branch line 30a 1 is branched further into the branch lines 30a 2 , 30a 3 , and 30a 4 .
• In the branch line 30a 4 there is a remote controlled control valve 31a j
• In the branch lines 30a 3 and 30a 5 there are remote-controlled control valves 31a 2 and 31a 3 .
• the valves 31a ⁇ , 31a 2 and 31a 3 the flow of water to the water nozzles 50a ⁇ , 50a 2 ,50a 3 provided at the ends of the branch lines is regulated.
• a detector d which detects the position of the pick-up roll and from which a signal line e j passes to the control unit 32a 1 ; and in the first group R j of drying cylinders in the dryer section K, below the suction cylinder Si , there is an identifying detector d 2 , which monitors the web W and from which a signal line e 2 passes to the control unit 32a ⁇ , which controls the main valve 31a of the branch line 30a ⁇ .
• the detectors di and d 2 it is detected in which mode of operation the machine is and whether the web W is placed, for example, in connection with the identifying detector d 2 .
• Fig. 2 shows an embodiment of the invention in which guide jets S j ,S 2 ,S 3 are employed.
• the guide jets St , S 2 and S 3 can be favourably, for example, air jets.
• liquid jets preferably water jets.
• the jets Si and S 2 provide the effect that the web is affixed, by means of a Coanda effect, to the jets, and the web is drawn into the pulper.
• the jets S j and S 2 have been directed from the nozzles 50a, and 50a 2 towards the pulper.
• the jet S 3 applied from the nozzle 50a 3 in connection with the doctor blade 19 is favourably an air jet, and by its means formation of a vacuum is prevented in the gap O at the outlet side between the guided web W and the roll 13 face.
• the jet S 3 replaces the air that has been removed by the web W from the gap O.
• the medium in the jet S 3 is preferably air. However, it is possible to use air or water as a medium in the jets S 1 ; S 2 and S 3 .
• Fig. 3A shows an embodiment of the invention in which the doctor blade 19 is connected with a blade holder 18.
• the blade holder 18 is further connected with a doctor beam 20.
• Loading hoses 33 and 34 pivot the blade holder 18 around an articulated joint 35.
• the front plate 18' of the blade holder 18 is connected with a bellows 37 made of a resilient shield cover, out of whose interior space the medium jet S 3 of the nozzle 50a 3 is applied, favourably an air jet, to the forward tip of the doctor blade 19.
• the resilient shield cover 37 is provided with a nozzle opening 38, which is opened by the effect of pressure, in which connection, when pressure is applied to the interior of the resilient shield cover 37, the medium jet S 3 , preferably an air jet, is passed through the nozzle opening 38 to the tip of the blade 19.
• the medium jet S 3 preferably an air jet
• the flow duct formed between the resilient shield cover 37 and the front plate 18' is favourably formed so that a throttle is formed in the duct before the nozzle opening.
• This has an effect that stabilizes the opening of the nozzle opening in the cross direction of the machine.
• the pressure in the duct is reduced, which attempts to make the opening smaller.
• the pressure in the duct is increased, which attempts to open the nozzle opening.
• the stabilizing is enhanced by making the flow in the cross direction of the machine more difficult, for example, by providing the throttle area in the duct with grooves fitted in the machine direction or with a corresponding set of ducts 37'.
• Fig. 3B shows an embodiment in which the pipe 40 comprises a flexible plate 34 in its connection, in which case, when pressure is passed through a flow opening 42 provided in the pipe 40 into connection with the plate 34, the plate is displaced, and the space between the plate 34 and the blade holder is opened so as to spray a medium to the tip of the blade 19.
• Fig. 3C shows an embodiment in which the nozzle pipe 43 is placed inside the doctor beam 20, in which case a medium jet S 3 is passed through an opening provided in the doctor beam towards the blade 19 tip and into connection with the face 13' of the centre roll 13.
• Fig. 3D shows an embodiment in which a nozzle pipe 43 has been fitted onto the face of the doctor beam 20, through which pipe 43 a medium jet S 3 is passed in a way similar to that in the embodiment illustrated in Fig. 3C.
• Fig. 3E is a sectional view taken along the line I— I in Fig. 3 A.
• Fig. 4 A shows an embodiment of the invention in which a jet pipe 22 produces needle jets L 2 so as to disrupt the web W on the face 13' of the centre roll 13.
• a jet pipe 21 by whose means moistening jets L j are passed into connection with the web W, in which connection, by means of the needle jets L 2 , the web, which has already been moistened, can be disrupted readily by means of the needle jets passed at a high pressure out of the nozzles 22a j ,22a 2 ....
• the jet pipe 22 can be oscillated in the cross direction of the web by means of a separate actuator, in which way the effect of the needle jets L 2 is enhanced.
• Fig. 4B is an axonometric view illustrating the equipment of disrupting the web W.
• a high-pressure needle jet L 2 is produced from each nozzle 22a 1 ,22a 2 ,22a 3 ... of the jet pipe 22.
• a jet Li which moistens and softens the web W is sprayed out of the nozzle pipe 21.
• the pipe 22 can be favourably fitted in connection with a conventional pipe 21, as is shown in the figure, or it can be arranged as a separate pipe. In both solutions, as the medium jet, it is possible to use water that has been derived as retention from the wire.
• Fig. 4C shows an embodiment of the invention in which the nozzle pipe 22 which produces the needle jets L 2 is oscillated in the axial direction of the roll 13 in the way indicated by the arrow J, .
• the disruption of the web W produced by means of the needle jets is enhanced further.
• the web when the web is passed into the pulper 25, it is first passed in the ordinary way from the doctor blade 19 of the doctor, and, additionally, medium jets S ⁇ ,S 2 ,S 3 are used as an aid, of which jets the jet S 3 is preferably an air jet.
• the operation of the jets Si ,S 2 , S 3 is stopped, and the web W to be passed into the pulper is disrupted by means of the needle jets L 2 , and to the forward side of the point of impingement of said needle jets a jet L j that moistens the web W is passed.
• the jets Li moisten the web W before the needle jets L 2 , in which case the needle jets L 2 do not require an equally high spraying pressure.
• the jet L 2 together with the jet L, or without said jet as soon as the web arrives at the doctor blade. It is also possible to use the medium jets S-t , S 2 and S 3 alone or as different combinations.
• the front face of the doctor blade 19 can be coated with "teflon" or with a fluoropolymer or with any other material that reduces the friction.

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Cited By (6)

Citations (5)

• 1998
  • 1998-07-03 FI FI981541A patent/FI104646B/fi active
• 1999
  • 1999-06-24 WO PCT/FI1999/000560 patent/WO2000001884A1/en active Application Filing
  • 1999-06-24 AU AU47881/99A patent/AU4788199A/en not_active Abandoned

Patent Citations (5)

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