Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
  • D21G9/00—Other accessories for paper-making machines
  • D21G9/0063—Devices for threading a web tail through a paper-making machine
• • 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
  • D21F3/0272—Wet presses in combination with suction or blowing devices

Definitions

• the invention relates to a device for stabilizing a paper web in a paper machine in the region of a roller, up to which the paper web is guided on a belt, with a box extending in front of the roller along the belt on the side facing away from the paper web, the interior of which is facing the belt is open and in which a vacuum is created to suck the paper web onto the belt.
• the invention further relates to a method for stabilizing a paper web in a paper machine in the region of a roller, up to which the paper web is guided on a belt, in which a negative pressure is generated along the belt, through which the paper web is sucked onto the belt.
• Such a device and such a method for stabilizing a paper web are known in principle (DE-A-44 02 105, DE-A-35 04 820).
• a vacuum is generated in the area before the transfer of the paper web to the roller, through which the paper web is sucked onto the belt, so that the formation of bubbles is counteracted. Furthermore, it is known from the aforementioned DE-A-4402 105 to subject a press felt to negative pressure over a first region of the felt path before entering the press nip and to apply steam in a subsequent region in order to close the press felt drain and thus increase the dryness. In addition, the negative pressure generated counteracts the formation of bubbles.
• the known devices and methods are relatively complex and cannot be used easily in different areas of a paper machine, for example in press sections on the one hand and in dryer sections on the other.
• the object of the invention is therefore to provide a device and a method for stabilizing a paper web in the area of a roller, with which bubble formation is reliably avoided even in the case of high-speed paper webs with low basis weights and reliable web guidance in various areas within cost-effectively a paper machine can be guaranteed.
• the air flow entrained by the paper web or the belt itself is used to generate the negative pressure within the box.
• the air deflector surface is used to deflect the entrained air in order to generate a vacuum inside the box via a suction slit.
• the vacuum required to avoid the bladder is thus generated inside the box generated in a particularly simple manner, since a fan is not required.
• the device according to the invention can be used at numerous points in a paper machine, for example for transferring a paper web from a press felt to a guide roller or suction guide roller or onto a belt which is wound around such a roller, or for transferring one Paper web on a smooth press roller, on a smoothing roller or on a drying cylinder within the dryer section of a paper machine, or for stabilizing the paper web when guided on a screen in the area of a screen drive roller.
• the air deflector surface has a curvature which is directed outward from the band, as a result of which a good suction effect is achieved.
• the suction slit is formed at the end of the deflector surface.
• the paper web is transferred to the roller while the tape is guided over a second roller.
• the device according to the invention is used particularly advantageously in the area of a nip with which the paper web is transferred from the belt to the first roller, the bubble formation which is critical in this area in particular being simple and inexpensive by the device according to the invention is avoided.
• the interior of the box is sealed against the second roller.
• the object of the invention is achieved in an alternative manner in a device according to the aforementioned type in that the box has a first and a second zone, the first zone being designed as a vacuum zone for sucking the paper web onto the belt, and the second Zone seen behind the first zone in the web running direction and is designed as a pressure zone.
• this second alternative enables the paper web to be influenced in a particularly targeted manner in order to avoid the formation of bubbles, while at the same time the transfer of the paper web to the roller is supported by the pressure zone adjoining the vacuum zone and thus a particularly safe transfer to the roller is guaranteed.
• the paper web is thus sucked sufficiently securely onto the belt in the zone of increased pressure occurring in front of the nip and at the same time is transferred to the roller in a particularly advantageous manner through the subsequent pressure zone. In many cases this can lead to an execution due to the pressure support Avoid the roller as a suction roller and use a simple roller instead. This leads to considerable cost savings.
• the air duct inside the box is designed to be particularly simple.
• a second roller can be arranged next to the roller, over which the tape is guided, while the paper web is transferred from the tape to the first roller.
• the box is sealed to the band at its front boundary surface as seen in the direction of web travel.
• the box is sealed against the second roller by a sealing strip.
• the first roller can be designed as a guide roller, for example as a suction guide roller, over which a press felt or a smooth belt is guided
• the second roller can be designed as a felt guide roll, over which the belt, which is also formed as a press felt, is guided from which the paper web is transferred to the other press felt.
• the first roller can also be designed as a press roller, as a wire guide roller, as a smoothing roller or as a drying cylinder, whereupon the paper web is transferred from the belt.
• the object of the invention is further achieved in that, in a method according to the type mentioned at the beginning in the web running direction, an excess pressure directed towards the paper web is generated behind the negative pressure.
• An air flow can be generated along the belt, essentially in the direction of web travel, which is deflected towards the belt.
• the air duct for generating the negative pressure and the excess pressure can be made particularly simple.
• air is blown outwards at the driver's end and at the drive end of the belt and in the direction of web travel.
• the object of the invention is achieved in that, in a method according to the type mentioned at the beginning, an air stream carried along by the belt is deflected and used to generate a lower pressure is used, through which the paper web is sucked onto the belt.
• Figure 1 shows a first embodiment of the invention in a schematic representation in the area of a nip, in which a paper web is transferred from a belt to a first roller while the belt is deflected by a second roller, a compressed air supply being provided to generate a vacuum.
• Figure 2 shows a second embodiment of the invention also with compressed air supply in the area of a nip in a schematic representation.
• 3 shows a third embodiment of the invention without compressed air supply in the area of a nip in a schematic representation
• 4 shows a fourth embodiment of the invention without compressed air supply in the area of a nip in a schematic representation
• FIG. 5 shows a fifth embodiment of the invention in a schematic representation, the device according to the invention being arranged in front of a screen drive roller;
• FIG. 6 shows a sixth embodiment of the invention in a schematic representation, the device according to the invention being arranged before the paper web enters a press nip,
• Fig. 8 shows another possible application of the invention in the transfer of the paper web to a drying cylinder in a schematic representation.
• the belt 20 is guided and deflected over a felt guide roller 14 arranged just behind the suction roller 12.
• a device 10 according to the invention for stabilizing the paper web 18 is arranged below the belt 20 and extends essentially parallel to the belt 20 over the entire width of the paper web 18. Due to the high running speed, air layers are inevitably entrained by the belt 20 and the press felt 24, so that there is an air flow 28 in the web running direction 26 above the paper web 18, as well as a parallel air flow 30 below the belt 20, which likewise runs in the web running direction 26.
• the device 10 comprises an outwardly closed box 11, which is arranged below the belt 20 and, while maintaining a certain air gap 37 in the order of about 20 mm to the underside of the belt 20 parallel to the belt 20 to just before the surface of the Roller 14 extends.
• the box 11 At its front boundary surface 41, viewed in the direction of web travel 26, the box 11 is sealed by a sealing strip 40 extending transversely to the web running direction 26 to the band 20, ie to the press felt.
• the box 11 is delimited by a boundary surface 43 which extends in front of the surface of the roller 14 parallel to it.
• the box 11 is sealed against the roller 14 by a further sealing strip 42.
• FIG. 2 A modified embodiment of the invention is shown in Fig. 2.
• the box 11 On the leader and the front side, the box 11 is sealed on the end face to the band 20 and to the roller 14 by an end face plate with a minimally adjusted gap.
• FIG. 4 A modification of the embodiment previously described with reference to FIG. 3 is shown in FIG. 4.
• the air flow 30 is again deflected downwards from the underside of the band 20 through the sealing strip 40 and deflected downwards by means of the deflector surface 48 which is curved downward over the entire web width to create a vacuum in the box 11.
• the suction slot 52 is, however, not arranged at the end of the deflector surface 48, but at the beginning of the deflector surface 48, directly behind the sealing strip 40, through which the box 11 relative to the band 20 on its in The web running direction 26 is sealed at the front end.
• the interior 39 of the box is sealed at its end facing the second roller 14 by a wall 50 with respect to the second roller 14, which can be adjusted relative to the roller 14.
• the box 11 is sealed on the front side on the driver and drive side.
• a particularly good suction effect is achieved by the arrangement of the suction slot 52 at the beginning of the deflector surface 48.
• the suction slot 52 which extends from the air deflector surface 48 to the inside of the box, merges into a boundary surface 55 which initially runs approximately parallel to the band 20 in the interior 49 of the box 11 and finally runs downward at approximately a right angle from the band 20 is angled and is then sealed at its lower end by the wall strip 42 against the second roller 14.
• the air deflector surface 48 and the boundary surface 55 thus create a completely closed volume with an approximately triangular cross section, which reduces the interior 39 of the box 11 and thus considerably increases the negative pressure effect within the interior 39.
• FIG. 5 shows a section of a paper machine in the area of the transfer from a wire section 65 to a subsequent press section 78.
• the paper web 18 is guided in the wire section 65 on the belt 20 designed as a wire via wire drive rollers 60, 61.
• a device 10 according to the invention is arranged in front of the screen drive roller 60 and can be designed similarly to the embodiment according to FIG. 4.
• a suction of the paper web 18 onto the belt 20 is achieved through the box 11, so that the screen drive roller 60 over which the screen is guided does not have to be designed as a suction roller, which leads to corresponding cost savings.
• FIG. 6 Another possible application of the invention is shown in FIG. 6.
• the device 10e according to the invention the structure of which can correspond to the device 10c according to FIG. 4, is arranged on the inlet side of the paper web 18 in a press nip 85, which can be formed, for example, by a free-standing shoe press 12, 14 with a shoe press roller underneath.
• the paper web 18 is removed from a roller 80, which can be the central roller of the press section, by means of a take-off roller 82 and then transferred to the belt 20, which is designed as an underfelt and is guided over felt guide rollers 84, 87. After passing through the press nip 85, the paper web 18 is by means of a removal roller 86 removed from the roller 12 and then transferred to a downstream drying section, not shown.
• the roller 80 and the roller 12 are cleaned in a manner known per se by scrapers 88, 89.
• a press nip is formed by a roller 12 and a counter roller 92, through which, if necessary, a press felt 98 can be guided over felt guide rollers 94, 96.
• the roller 12 can also be a different type of roller, such as a smoothing roller or a drying cylinder.
• a roller 12 designed as a drying cylinder is shown with reference to FIG. 8.
• the paper web is transferred from the belt 20 onto the roller 12, which is designed as a drying cylinder, to a drying section 104, from which the paper web is passed on via a drying wire 100, which is guided over the roller 12 via a deflection roller 102.

Landscapes

• Paper (AREA)
• Unwinding Webs (AREA)
• Registering, Tensioning, Guiding Webs, And Rollers Therefor (AREA)
• Replacement Of Web Rolls (AREA)
• Advancing Webs (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=7790749

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (6)

Family Cites Families (6)

• 1996
  • 1996-04-06 DE DE19613939A patent/DE19613939A1/de not_active Ceased
• 1997
  • 1997-03-29 AT AT97915462T patent/ATE219807T1/de not_active IP Right Cessation
  • 1997-03-29 DE DE59707591T patent/DE59707591D1/de not_active Expired - Fee Related
  • 1997-03-29 JP JP9535803A patent/JPH11508000A/ja active Pending
  • 1997-03-29 WO PCT/EP1997/001604 patent/WO1997038163A1/fr active IP Right Grant
  • 1997-03-29 EP EP97915462A patent/EP0830478B1/fr not_active Expired - Lifetime

Non-Patent Citations (1)

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