Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C5/00—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work
  • B05C5/005—Curtain coaters
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
  • D21H23/22—Addition to the formed paper
  • D21H23/30—Pretreatment of the paper

Definitions

• the invention relates to a device for applying liquid or pasty application medium by means of an application unit to a running substrate, the substrate being directly applied to the surface of a material web, in particular made of paper or cardboard, and indirectly applied to the surface of a transfer element, preferably a transfer roller, which then transfers the application medium to the surface of the material web, and a device for weakening the air boundary layer carried by the substrate is arranged in the direction of travel of the substrate in front of the application unit.
• a curtain application device i.e. an application device in which the application unit delivers the application medium to the substrate as a curtain or veil that moves essentially due to gravity.
• the application medium is delivered to the substrate in the form of an application medium curtain, which essentially moves from the application unit to the substrate due to gravity.
• the fact that the curtain applicator is at a predetermined distance from the base has the advantage, among other things, that it is exposed to a lower risk of damage, for example, in the event of a web break.
• Curtain applicators differ from other "contactless" applicators, for example free jet nozzle applicators, in which the movement of the application medium from the application unit to the substrate mainly results from the ejection impulse from the delivery nozzle of the application unit, fundamentally, since the shape of the curtain emerging from the delivery unit is only exposed to the interplay between the surface tension of the application medium and gravity.
• the surface tension tries to draw the curtain, which has a very large surface or circumferential length in relation to its volume or its cross-sectional area, in order to reduce its surface. Only gravity, which tries to stretch the curtain, opposes this effect. It is therefore easy to see that the larger this working width, the more difficult it is to obtain an application gas curtain that is uniformly thick over the entire working width.
• the weakening device comprises a blowing device and a suction device
• the blowing device being arranged in the direction of travel of the substrate in front of the application unit and producing an air flow directed against the direction of travel
• the suction device in Direction of the substrate is arranged in front of the blowing device and at least part of the the blowing device generated air flow and sucks at least part of the air boundary layer carried by the substrate.
• blowing device alone and the use of a suction device alone to improve the weakening of the air boundary layer are known per se from the main application DE 100 12 257.
• additional strips, brushes or scraper elements are used which either weaken the air boundary layer before entering the effective range of the suction device or aim to further weaken the residual air boundary layer which has already been weakened by the blowing device.
• These parts touching the material web cause undesirable wear both on the material web and on the weakening device, which on the one hand harbors the risk of a web break and on the other hand entails increased maintenance and an increased use of spare parts.
• Such wear can be prevented according to the invention by the combined use of a blowing device and a suction device arranged upstream of this in the running direction of the material web.
• the blowing device firstly has the task of weakening the air boundary layer carried on the surface of the running subsurface. On the other hand, it supports the action of the blowing device by sucking in the air flow emitted by it and thereby stabilizing its movement along the surface.
• the weakening device according to the invention does not have any weakening elements placed against the surface of the material web, ie, touching it, but is free of such elements. In this sense, the weakening device according to the invention is a weakening device that operates purely or exclusively without contact.
• the blowing device used according to the invention can comprise a blowing box to which air is supplied in the region of both side edges of the substrate. Through this bilateral and preferably symmetrical air supply in the blow box, a substantially uniform air flow can be obtained over the working width of the substrate, which moves in the opposite direction to the air boundary layer carried by the substrate.
• the outlet nozzle of the blowing device can comprise a slot nozzle or a plurality of individual nozzles.
• the suction device used according to the invention can comprise a suction box, from which air is extracted only in the area of one of the side edges of the substrate, preferably in the area of the side edge of the drive.
• the end of the blowing device facing the application mechanism is in the running direction of the substrate a distance of between about 10 from the point of impact of the application medium on the substrate mm and about 50 mm.
• the blowing device has a guide wall which is arranged at a predetermined distance from the running surface, a blowing channel can be formed by this guide wall in cooperation with the background, in which the air expelled by the blowing device flows in the opposite direction to the running direction of the surface.
• the efficiency of the action of the air stream expelled by the blowing device on that from the substrate can be reduced entrained air boundary layer can be improved.
• This effect is particularly effective if the guide wall has a length of between approximately 300 mm and approximately 500 mm in the running direction of the substrate. This corresponds to a wrap angle of approximately 90 °, depending on the roller diameter, if the blowing device is arranged in the region of a support roller around which the material web is at least partially guided.
• the suction device be at a distance of between approximately 0 mm and approximately 50 mm in the running direction of the substrate from the end of the guide wall or the blowing device facing it.
• the blowing device and the suction device can thus connect directly to one another in the running direction of the substrate (distance: 0 mm) and also have a predetermined distance from one another, so that the suction device does not necessarily have to be able to extract all the air expelled by the blowing device.
• the efficiency of the weakening device usually depends on various influences, for example the running speed of the
• the conditioning device By removing the uppermost regions of the air boundary layer, the conditioning device ensures that the dependence on these influences is reduced, if not completely prevented. In addition, the weakening device no longer has to act against the entire air boundary layer, but only against the part let through by the conditioning device. As a result, the weakening device is relieved and can accordingly be designed with less power.
• the conditioning device can comprise a strip which extends in the transverse direction of the substrate and which can be formed, for example, by a simple sheet metal strip. However, it is also possible for the conditioning device to take advantage of aerodynamic effects, for example by having a cross section when viewed in the transverse direction, which has the shape of an upside-down airfoil profile.
• the conditioning device can be self-supporting or can also be attached to the weakening device.
• the weakening device according to the invention can be used in particular with an application device which has a curtain application unit, i.e. a commissioned work that delivers the application medium to the underground as a curtain or veil that essentially moves due to gravity.
• a curtain application unit i.e. a commissioned work that delivers the application medium to the underground as a curtain or veil that essentially moves due to gravity.
• air in connection with the present description can be understood to mean any gas or gas mixture which is suitable for influencing the air boundary layer carried along by the substrate in a weakening sense.
• nitrogen gas could also be used instead of air.
• air as the treatment gas is preferred only because compressed air is available in almost every machine hall anyway and therefore without additional infrastructure measures and at low cost.
• the material web in the area of the weakening device preferably in the area or immediately before the air outlet the blowing device takes a curved course.
• the material web can be guided around a support roller and / or around a support belt and / or around a support shoe.
• the air boundary layer is subject to centrifugal forces which attempt to lift the air boundary layer from the material web and thus facilitate the action of the weakening device, in particular the blowing device, on the air boundary layer.
• the radius of curvature of the curved course can be between approximately 300 mm and approximately 500 mm.
• Figure 1 is a rough schematic side views of an application device according to the invention.
• FIGS. 2 and 3 are schematic, taken in the running direction views of the background of a blowing device (Fig. 2) and a suction device (Fig. 3).
• An application device according to the invention is generally designated 10 in FIG. 1. It comprises a curtain application unit 1 2, from the dispensing nozzle 1 4 of which application medium 1 6 is delivered as an application medium curtain 1 8 to a substrate U moving in the running direction L.
• the position of impact of the application medium curtain 18 on the underground U is denoted by P in FIG. 1.
• the substrate U is formed by the surface 20a of a material web 20, to which the application medium 16 is applied as an application layer 22.
• a weakening device 24 is provided in the running direction L in front of the applicator 12 to weaken the air boundary layer G carried on its surface by the substrate U.
• This weakening device 24 comprises, on the one hand, a blower device 26 with a blow box 28 and, on the other hand, a suction device 30 with a suction box 32.
• the blow box 28 is arranged in relation to the running direction L of the substrate U directly upstream of the application unit 12 and in particular of the application medium curtain 1 ⁇ .
• the blowing nozzle 28a is at a distance a from the application medium curtain 18, which is preferably between approximately 10 mm and approximately 50 mm.
• the blowing nozzle 28a ejects an air flow 34 which is directed opposite to the running direction L and moves in a blowing duct 36 formed by a guide wall 28b of the blow box 28 and the substrate U and weakens the influence of the air boundary layer G on the application medium curtain 18.
• This guide wall 28b has a length b of between approximately 300 mm and approximately 500 mm.
• the suction box 32 is arranged at a distance c upstream of the blow box 28 with respect to the running direction L.
• this suction box 32 has the task of weakening the air boundary layer G by sucking it off of the underground U. This is indicated in FIG. 1 by the lines which run obliquely relative to the underground U.
• the Suction box 32 but also the task of stabilizing the air flow 34 expelled from the blow box 28, in particular to keep it on the surface of the subsurface U by also sucking it out of the blow channel 36. This is indicated in Fig. 1 by the small arrows lifting off the underground U.
• a conditioning device in the form of a square bar 38 is arranged upstream of the suction device 30.
• This conditioning strip 38 has the task of lifting off the uppermost layers of the air boundary layer G before the subsurface areas of the air boundary layer are fed to the suction box 32.
• the suction device 30 can be provided with less power and thus at lower cost.
• the thickness of the air boundary layer G no longer varies as much as a function of the operating parameters of the application device 10 after the conditioning bar 38 than is the case without the conditioning bar 38.
• the blowing device 26 supplies the air to the blow box 28 on both sides. That the feed line 28c is divided into two branch lines 28d and 28e, which open into the suction box 28 in relation to the transverse direction or working width direction Q of the substrate U in its drive-side end face 28f or guide-side end face 28g. An air flow 36 which is more uniform in the transverse direction Q can be obtained by this air supply on both sides.
• the air is sucked out of the suction box 32 of the suction device 30 only at one end face 32a of the suction box 32, and although preferably on the drive end of the suction box 32, as shown in Fig. 3.
• the material web 20 is guided around a support roller 40 in the area of the blowing device 26.
• the air boundary layer G is subject to a centrifugal force which it tries to detach from the material web 20, which facilitates the action of the blowing device 26 on the air boundary layer G.
• the material web 20 of the support roller 40 is fed from below in order not to disturb the flow of the application medium curtain 18.

Landscapes

• Coating Apparatus (AREA)
• Paper (AREA)
• Advancing Webs (AREA)
• Auxiliary Devices For And Details Of Packaging Control (AREA)
• Eye Examination Apparatus (AREA)
• Massaging Devices (AREA)
• Iron Core Of Rotating Electric Machines (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

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Family Applications (1)

Country Status (6)

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Family Cites Families (19)

• 2002
  • 2002-05-22 AT AT02771657T patent/ATE463620T1/de active
  • 2002-05-22 DE DE50214344T patent/DE50214344D1/de not_active Expired - Lifetime
  • 2002-05-22 JP JP2002591160A patent/JP4020198B2/ja not_active Expired - Fee Related
  • 2002-05-22 EP EP02771657A patent/EP1432525B1/fr not_active Expired - Lifetime
  • 2002-05-22 WO PCT/EP2002/005621 patent/WO2002094452A2/fr not_active Ceased
• 2003
  • 2003-11-18 US US10/716,303 patent/US7037375B2/en not_active Expired - Fee Related
• 2005
  • 2005-11-17 US US11/281,171 patent/US7326301B2/en not_active Expired - Fee Related

Non-Patent Citations (1)

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