Patent Publication Number: US-RE39601-E

Title: Method of and a device for transferring running dried web from one device to a subsequent device

Description:
This application is a Reissue of U.S. Ser. No.  08 / 689 , 468  filed on Aug.  9 ,  1996 , now U.S. Pat. No.  5 , 738 , 760 . 
    
    
     FIELD AND BACKGROUND OF THE INVENTION 
     The present invention relates generally to a method of and an apparatus for transferring a fast running ready-dried fibrous web having two longitudinal edges from one device and along a predetermined run to a subsequent device for performing an act or operation on the web. In a typical installation, the apparatus is installed downstream of a drying section of a papermaking machine, or in association with a rewinder or in a converting plant, for example. 
     One embodiment of the invention relates specifically to an apparatus for transferring a fast running ready-dried tissue web having two longitudinal edges from a drying section of a tissue paper making machine and along a predetermined run to a reel-up. 
     In this context, the term “tissue paper” is intended to include any grade of “soft crepe paper” or other paper for sanitary purposes, whether creped or not when used by a consumer. 
     The performance of a tissue machine is often limited by its dry end. Generally, the difference between a tissue machine with high efficiency and one with low efficiency is mainly caused by the performance of the dry end. In the dry end, several causes may result in web breaks, and the produced web may be partially rejected for unsatisfactory quality. However, with good control of the whole paper making process and use of the latest dry end technology it is possible to run a machine at both high speed and high machine efficiency. 
     The main factors affecting dry end machine efficiency are lost time with no paper on the reel, and the amount of paper rejected at paper breaks. On most high speed machines the paper web roll is kicked out at a paper break, because it is difficult to make a turn-up on a half size roll, and if the roll is small, the roll is rejected. Having this in mind, the dry end machine efficiency can be split up as follows. 
     Dry End Machine Efficiency: 
     Creping blade changes 
     Paper breaks including rejected paper in kicked out roll 
     Tail threading failures 
     Turn-up failures 
     Dry end cleaning (to avoid web breaks caused by dirt falling down) 
     Lost process control 
     Roll top waste and roll bottom waste 
     Roll bottom waste is caused by the paper web adjacent the reel spool having to be rejected and, similarly, roll top waste relates to the paper lost at the top of the roll during the kick-out phase, and/or by taking samples for testing and/or roll handling after the tissue machine. 
     In an efficiently operated machine, the threading of a new tail, after creping doctor blade changes and web breaks, does not take more than a few seconds. If the threader is out of adjustment, several minutes can be lost during each attempt to thread. Paper may plug the tail chutes and time consuming cleaning of the whole dry end may be required. The air chute threader is considered the most efficient and safest threader. There, the tail is transferred by compressed air in chutes, substantially as disclosed in U.S. Pat. No. 3,847,390 (Dixon), for example. Pneumatic tail threaders of other than chute type are disclosed in U.S. Pat. Nos. 3,999,696 and 4,014,487 (both Rehn et al.) and 4,923,567 (Liedes et al.). 
     The tail threaders may be mounted outside of any web stabilizers. Web stabilizers or flutter suppressors are disclosed in U.S. Pat. Nos. 4,321,107 (Page) and 3,650,043 (Overly et al.), for example. The design of the leading edge of a flat sheet stabilizer must be such that the boundary layer of air entrained by the web can escape on the top side of the stabilizer when the stabilizer is located above the predetermined run of the web. To maintain web control and prevent wrinkles, breaks and foldovers, the web tension must oppose the forces from disturbing air currents. Such currents originate from the machine room, the boundary layer of air, and the rotating rolls of the paper machine. The heat convection air flows are another source of disturbing air currents in the dry end. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to increase the dry end machine efficiency, primarily by accomplishing a web transfer, which in respect of reliability is comparable to the one obtained with a closed draw, but which also will offer as improved tail threading. 
     In accordance with the present invention, this object is achieved by a web transferring method which incorporates the steps of providing a substantially web-wide support surface having an upstream end and a shape conforming to at least a portion of that of the predetermined run, the support surface being located in a position adjacent that of the predetermined run and extending substantially all the way from said one device to the subsequent device, and creating a flow of air in the direction of the web run along the support surface by supplying pressurized air of a first pressure, e.g., from a fan, along a first line across the support surface in a cross machine direction adjacent the upstream end of the support surface and, downstream thereof, along at least one further line across the support surface in a cross machine direction, the flow of air forming between the web and the support surface an air layer of reduced static pressure, so as to stabilize it against flutter. 
     Similarly, in accordance with the present invention the object is achieved by a web transferring apparatus which incorporates the following features: 
     A web support device that has a substantially web-wide support surface, which has an upstream end and a shape conforming to at least a portion of that of the predetermined run. The support surface is located in a position adjacent that of the predetermined run and extends substantially all the way from said one device to the subsequent device. In addition, means are provided for creating a flow of air in the direction of the web run along the support surface. These air flow creating means include means for supplying pressurized air of a first pressure along a first line across the support surface in a cross machine direction adjacent the upstream end of the support surface and, downstream thereof, along at least one further line across the support surface in a cross machine direction. Between the web and the support surface the flow of air forms an air layer of reduced static pressure, so as to stabilize the web against flutter. 
     By the incorporation of the above steps and features, respectively, the number of web breaks downstream of the drying section of the machine (and under unchanged conditions in other respects) will be remarkably reduced and the dry end efficiency will increase. When the number of web breaks at this location sets the limit for the paper production on the machine, the present invention gives an opportunity of increasing the production. 
     In a preferred embodiment of the invention, the web support device includes a series of consecutive substantially web-wide plate members. Each plate member has a leading edge and a trailing edge. The trailing edge of at least one of the plate members is located spaced from and upstream of the leading edge of an adjacent one of the plate members, so as to form a first slot-shaped gap between the plate members for the passage of air therethrough. The pressurized air supplying means include a pipe member extending along and bridging the first slot-shaped gap, and the pipe member has an elongate passage, e.g., a series of equidistantly spaced identical bores or a longitudinal narrow slit, for discharging the flow of air in the direction of the web run. In addition, the pipe member and the two adjacent plate members constitute in combination a plate member assembly . Such a web support device is cost effective in production and reliable in function. 
     The apparatus according to the invention is especially suitable for transferring a fast running ready-dried tissue web having two longitudinal edges from a drying section of a tissue paper-making machine and along a predetermined run to a reel-up. In such an apparatus, the object of the invention stated above is achieved in accordance with the present invention by the incorporation of the following features: 
     A series of consecutive substantially web-wide plate members define a substantially web-wide support surface having an upstream end a shape conforming to at least a portion of that of the predetermined run. The support surface is located in a position adjacent that of the predetermined run and extends substantially all the way from the drying section to the reel-up. Each plate member has a leading edge and a trailing edge. The trailing edge of at least one of the plate members is located spaced from and upstream of the leading edge of an adjacent one of the plate members, so as to form a first slot-shaped gap between the plate members for the passage of air therethrough. Further, means are provided for creating a flow of air in the direction of the web run along the support surface. The air flow creating means include means for supplying pressurized air of a first pressure over the width of the web adjacent the upstream end of the support surface and, downstream thereof, through the first slot-shaped gap formed between the plate members. The pressurized air supplying means include a pipe member that extends along and bridges the first slot-shaped gap, and the pipe member has an elongate passage, such as a series of equidistantly spaced identical bores or a longitudinal narrow slit, for discharging the flow of air in the direction of the web run. The pipe member and the two adjacent plate members constitute in combination a plate member assembly, and the flow of air forms between the web and the support surface an air layer of reduced static pressure, so as to stabilize the web against flutter. 
     By the incorporation of the above features, the number of web breaks in the area between the drying section of the machine and the reel-up (and under unchanged condition in other respects) will be remarkably reduced and the dry end efficiency will increase. When the number of web breaks in this area sets the limit for the paper production on the machine, the present invention gives an opportunity of increasing the production. In addition, the apparatus is cost effective in production and reliable in function. 
     Preferably, the apparatus includes a plurality of plate member assemblies, and each assembly has an upstream edge and a downstream edge. The downstream edge of one assembly is located spaced from and upstream of the upstream edge of an adjacent assembly so as to form a second slot-shaped gap between the assemblies for the passage of air therethrough. By permitting some air to pass through the second slot-shaped gap, it will be possible to maintain optimum web transfer conditions by supplying additional air through the pipe member of the subsequent plate member assembly. 
     In a tissue machine, the drying section includes a yankee dryer, from which the web is creped off by means of a creping blade to form a creped web. Then, the substantially web-wide support surface suitably starts at the creping blade to reduce the number of error possibilities. 
     During a creping operation, dust is released from the tissue web, and a major portion of the dust is entrained by the fast running web and the associated boundary layers. Due to the hazards and inconvenience caused by the dust, it is recommendable to provide means for removing a suspension of dust in air passing through the second slot-shaped gap. To make an air flow of a suitable size pass through the second slot-shaped gap, we chose to locate the downstream edge of the plate member assembly at a slightly larger distance from the predetermined run of the web than the distance from the upstream edge of the adjacent plate member assembly to the predetermined run of the web. 
     Preferably, the plate members of each plate member assembly are substantially planar, and a plate member in the assembly forms an angle of at most a few degrees with an adjacent plate member. Thereby, the plate member assemblies are easy to manufacture, and abrupt turns that are error possibilities are avoided. 
     Often, a calender having a nip for calendering the web is provided downstream of the drying section but upstream of the subsequent device. To achieve a safe web transfer through the calender, it is preferred that the web support device has trailing end immediately upstream of the calender nip and a new leading end immediately downstream of the calender nip. 
     As a rule, also scanner equipment for scanning at least one physical property of the web is provided downstream of the drying section but upstream of the subsequent device. Conventional scanner equipment has a frame with a central opening for the passage therethrough of the web, a scanner unit for scanning the physical property, which unit is carried by the frame and is movable back and forth across the web from one longitudinal web edge to the other. However, in order to achieve an equivalent to what might be termed a “closed draw” web transfer through the scanner equipment, we provide a device associated with the scanner unit for forming a surface supporting the web at locations between the scanner unit and the two longitudinal web edges during the passage of the web through the opening, and the web supporting surface of the scanner equipment has an upstream edge and a downstream edge. Further, immediately upstream of the scanner equipment the web support device has a trailing end, which is overlapped by the upstream edge of the scanner equipment the web supporting surface, and immediately downstream of the scanner equipment the web support device has a new leading end, which overlaps the downstream edge of the scanner equipment web supporting surface. The scanner equipment with the web support device is the subject matter of a patent application entitled “Scanning device for scanning a physical property of a fibrous web” filed concurrently herewith by the same applicant. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified schematic side elevational view of the dry end of a tissue paper making machine provided with a preferred embodiment of an apparatus in accordance with the present invention for transferring a tissue paper web from a yankee dryer through a calender and past scanning equipment to a reel-up. 
         FIG. 2  is an enlarged fragmentary side elevational view of a running tissue web supported by two plate member assemblies used in the web transferring apparatus of FIG.  1 . 
         FIG. 3  is a perspective view of the web and the plate member assemblies shown in FIG.  2 . 
         FIG. 4  is an enlarged fragmentary side elevational view of a running tissue web supported by plate member assemblies that are spaced from one another by a slot-shaped gap, one of the assemblies having at its upstream end means for removing a suspension of dust in air passing through the slot-shaped gap. 
         FIG. 5  is an enlarged fragmentary side elevational view of a running tissue web that passes through the calender nip shown in FIG.  1  and is supported by plate members assemblies immediately upstream and downstream of the nip. 
         FIG. 6  is an enlarged fragmentary sectional view of a running tissue web that passes through the scanning equipment shown in FIG.  1  and is supported by plate member assemblies overlapping a web supporting surface provided in the scanning equipment. 
         FIG. 7  is a schematic plan view of a plate member assembly and associated equipment designed to facilitate tail threading along one side of the assembly. 
         FIG. 8  is a schematic plan view of a series of plate member assemblies and associated equipment designed to facilitate the threading of a center tail. 
         FIG. 9  is an enlarged fragmentary side elevational view of a running tissue web supported by an alternative plate member assembly wherein the trailing plate member is extended and stepped. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     Referring now to  FIGS. 1 ,  2  and  3 , one form of apparatus incorporating the teachings of the present invention is illustrated. The apparatus is generally designated by reference numeral  1  and for purposes of illustration is shown as being disposed between a yankee dryer  2  and a reel-up  3  of a conventional tissue papermaking machine. It will be appreciated, however, that the apparatus and method of the present invention may be effectively utilized in any operating environment wherein it is desirable to transfer a fast running ready-dried fibrous web from one device and along a predetermined run to a subsequent device for performing an act or operation on the web, as for example during the processing of the web in rewinder or in a converting plant. In the illustrated operating environment, apparatus  1  transfers the tissue web  4  from yankee dryer  2 , through a nip formed between two rolls  5  and  6  of a calender  7 , and past scanner equipment  8  to reel-up  3 , which in the illustrated embodiment is a drum reel-up having a drum  9  that supports and drives the reel spool, not shown, on which the web is being wound. Of course, neither calender  7  nor scanner equipment  8  form any part of apparatus  1 . 
     In accordance with the present invention, apparatus  1  comprises a web support device  10  that has a substantially web-wide support surface  11 , which has an upstream end  12  and a shape conforming to at least a portion of that of the predetermined run. The support surface  11  is located in a position adjacent that of the predetermined run and extends substantially all the way from one device for performing an act or operation on the web, e.g., the drying section of a papermaking machine, to a subsequent device, e.g., reel-up  3 . In the illustrated embodiment, the drying section is represented by yankee dryer  2 , but a yankee dryer does not have to be included in the drying section. Further, apparatus  1  comprises means  13  for creating a flow of air in the direction of the web run along the support surface  11 . These air flow creating means  13  include means  14  for supplying pressurized air of a first pressure along a first line (at  20 ) across the support surface  11  in a cross machine direction adjacent the upstream end  12  of the support surface  11  and, downstream thereof, along at least one further line across the support surface  11  in a cross machine direction. The means  14  for supplying pressurized air of the first pressure may include any suitable source of pressurized air, such as a fan, blower or other device, not shown, which can deliver air of an absolute pressure in the range of about 120 kilopascals. Between the web  4  and the support surface  11  the flow of air forms an air layer  15  of reduced static pressure, so as to stabilize web  4  against flutter. Although the support surface  11  can be located either above or below the predetermined web run, the handling of possible broke will be facilitated if the support surface is located above the predetermined web run. 
     In a preferred embodiment of the invention, web support device  10  includes a series of consecutive substantially web-wide plate members  16  and  17 . Each plate member has a leading edge and a trailing edge. The trailing edge  18  of at least one of the plate members, in the shown embodiment plate member  16 , is located spaced from and upstream of the leading edge  19  of an adjacent one of the plate members, in the shown embodiment plate member  17 , so as to form a first slot-shaped gap  20  between the plate members for the passage of air therethrough. The pressurized air supplying means  14  additionally include a suitable air duct associated with the source of pressurized air, such as pipe member  21  extending along and bridging the first slot-shaped gap  20 , and the pipe member  21  has an elongated passage  22 , e.g., a series of equidistantly spaced identical bores or a longitudinal narrow slit, for discharging the flow of air in the direction of the web run. In addition, the pipe member  21  and the two adjacent plate members  16  and  17  constitute in combination a plate member assembly  23 . Such a web support device  10  is cost effective in production and reliable in function. 
     The apparatus  1  preferably includes a plurality of plate member assemblies  23 , and each assembly has an upstream edge and a downstream edge. The downstream edge  24  of one assembly is located spaced from and upstream of the upstream edge  25  of an adjacent assembly so as to form a second slot-shaped gap  26  between the assemblies for the passage of air therethrough. By permitting some air to leave through the second slot-shaped gap  26 , it will be possible to maintain optimum web transfer conditions by supplying additional air through the pipe member  21  of the subsequent plate member assembly  23 . 
     In the embodiment shown in  FIG. 1 , the drying section includes a yankee dryer  2 , from which the web is creped off by means of a creping doctor  27  having a doctor blade  28  to form a creped web  4 . To reduce the number of error possibilities, the substantially web-wide support surface  11  suitably starts at the doctor blade  28 . 
     During a creping operation, dust is released from the tissue web  4 , and a major portion of the dust is entrained by the fast running web  4  and the associated boundary layers. Due to the hazards and inconveniences caused by the dust, it is recommendable to provide means, such as the illustrated round tube  29  for removing a suspension of dust in air leaving through the second slot-shaped gap  26 , as shown in FIG.  4 . To make an air flow of a suitable size leave through the second slot-shaped gap  26 , we chose to locate the downstream edge  24  of the plate member assembly  23  at a slightly larger distance from the predetermined run of the web  4  than the distance from the upstream edge  25  of the adjacent plate member assembly to the predetermined run of the web  4 . In the embodiment shown in  FIG. 4 , the dust removing means include a round tube  29  of comparatively large diameter and having a relatively wide longitudinal slot  30 . As shown, the tube  29  is mounted with one of its slot edges at the upstream edge  25  of one of the plate member assemblies  23 , and with its other slot edge located substantially at the downstream edge  24  of the preceding plate member assembly but spaced outward therefrom, so as to create a gap through which environmental air can be sucked into the tube  29 . Suction in the tube  29  may be created by means of a fan, not shown, and the size of the gap is such that the dust velocity in the tube  29  will exceed a critical minimum, below which dust will settle on the bottom of the tube  29 . 
     As is best shown in  FIG. 2 , the plate members  16  and  17  of each plate member assembly  23  preferably are substantially planar, and a plate member  16  in the assembly  23  forms an angle of at most a few degrees with an adjacent plate member  17 . Thereby, the plate member assemblies  23  are easy to manufacture, and abrupt turns that are error possibilities are avoided. Further, the pipe member  21  is of square cross section, and it is preferred to provide the plate members  16  and  17  with a flange each, not shown, that are secured to the two opposed vertical sides of the square pipe member  21  by means of screws, likewise not shown. The elongate passage  22 , which is formed by a series of equidistantly spaced identical bores or a longitudinal narrow slit for discharging the flow of air in the direction of the web run, is located in the downstream edge  25  of the plate member assembly  23  with a rounded nose flange-like projection, not shown, extending away from the web  4  to guide the air flows so as to reduce the risks of the web  4  hooking on to the upstream edge  25 . 
     When, as illustrated in  FIG. 1 , a calender  7  having two calender rolls  5  and  6  defining a nip for calendering the web  4  is provided between the yankee dryer  2  and the reel-up  3 , a safe web transfer through the calender  7  can be achieved if, as shown in  FIG. 5 , the web support device  10  has a trailing end immediately upstream of the calender nip and a new leading end immediately downstream of the calender nip. 
     As also illustrated in  FIG. 1 , scanner equipment  8  for scanning at least one physical property of the web  4  may be provided between the calender  7  and the reel-up  3 . As shown in  FIG. 6 , conventional scanner equipment includes a frame  31 , which may be a box beam frame of rectangular shape, so that the frame  31  has a central opening for the passage therethrough of the web  4 . Further, conventional scanner equipment includes a scanner unit  32  for scanning the physical property. The scanner unit  32  is carried by the frame  31  and is movable back and forth across the web  4  from one longitudinal web edge to the other. In the illustrated embodiment the scanner unit  32  can be inclined about +/−30° relative to a horizontal plane, so that it can be adjusted to any substantially horizontal web run. The scanner unit  32  includes an upper carriage  33  carrying a first scanner head  34 , and a lower carriage  35  carrying a second scanner head  36 . Each scanner head may be provided with different sensors, not shown, for sensing different properties, such as basis weight, moisture etc. 
     In order to achieve an equivalent to what might be termed a “closed draw” web transfer through the scanner equipment  8 , we provide a device  37  associated with the scanner unit  32  for forming a surface  38  supporting the web  4  at locations between the scanner unit  32  and the two longitudinal web edges during the passage of the web  4  through the opening. The web supporting surface  38  of the scanner equipment  8  has an upstream edge and a downstream edge. Further, immediately upstream of the scanner equipment  8  the web support device  10  (or the adjacent plate member assembly  23 ) has a trailing end, which is overlapped by the upstream edge of the scanner equipment web supporting surface  38 , and immediately downstream of the scanner equipment  8  the web support device  10  (or the adjacent plate member assembly  23 ) has a new leading end, which overlaps the downstream edge of the scanner equipment web supporting surface  38 . The scanner equipment  8  with the web support device  37  is the subject matter of a patent application entitled “Scanning device for scanning a physical property of a fibrous web” filed concurrently herewith and assigned to the assignee of the present application. 
     As an illustrative, but not shown, example of the device  37  forming the web support surface  38  we can mention an extensible and retractable arrangement of lamellae or plates mounted to cover both of the two areas bounded laterally by the laterally reciprocating scanner unit and the frame and longitudinally by the plate member assemblies that are located immediately upstream and downstream of the scanning equipment. Another possibility would be a belt fixed to the scanner unit and having its ends fixed to and coiled upon two rolls carried by the frame laterally outside of the web. This is the embodiment illustrated in FIG.  6 . When the scanner unit moves laterally, the belt is uncoiled from one of the rolls and coiled on the other one. A third possibility would be to fix the ends of the belt to the frame and to provide belt guide rolls at the scanner unit to temporarily deflect the run of the belt above, or below, the scanner unit. Further possibilities are described in the simultaneously filed patent application mentioned above. 
     With reference to  FIGS. 7 and 8 , in addition to the means  14  for supplying pressurized air of the first pressure for the forming of the web flutter suppressing air layer  15  between the web  4  and the web support surface  11 , the air flow creating means  13  suitably further includes means  39  for supplying pressurized air of a second pressure, higher than the first pressure, at a plurality of locations along the web support surface  11 , so as to pneumatically convey a paper tail, formed by slitting of the web, from the yankee dryer  2  to the reel-up  3 . The means  39  for supplying pressurized air of the second pressure may include a compressor, not shown, which can supply air of an absolute pressure in the range of about 150 to about 200 kilopascals. In a tissue machine having a yankee dryer, the tail cutter mostly is placed on the tender side of the machine and includes a nozzle, which usually is activated outside the tissue web and moved in over the web to create a free tail having a wedge-shaped leading end. However, when the present invention is applied in small width tissue paper machines it is, as a rule, possible to dispense with the tail cutting and to carry out the “tail” threading with a full width tissue web. Therefore, in the present context, the term “tail” is to be interpreted as including also a full width tissue paper web, provided that the web width is no more than at most three meters, preferably no more than about two and a half meters. 
       FIG. 7  shows a plate member assembly  23 , in which the square pipe member  21  has a first partition  40  that divides it lengthwise into a first portion  41  and a second portion  42 . The means  14  for supplying pressurized air of the first pressure is shown as including a first manifold pipe  43 , which is connected to the first portion  41  of square pipe member  21  by means of a first branch pipe  44  having a first valve  45 . The means  39  for supplying pressurized air of the second pressure is shown as including a second manifold pipe  46 , which is connected to the second portion  42  of the square pipe member  21  by means of a second branch pipe  47  having a second valve  48 . A conduit  49  having a check valve  50  provides fluid communication between the first portion  41  and the second portion  42  of the square pipe member  21  and permits air of the low first pressure to pass from the first portion  41  into the second portion  42  but prevents flow of air of the high second pressure in the opposite direction. The conduit  49  with the check valve  50  are shown as separate components but they may, of course, be integrated with the first partition  40 . 
     In normal operation, air of the low first pressure, usually about 120 kilopascals, is supplied from the first manifold pipe  43  through the first branch pipe  44  with the first valve  45  to the first portion  41  of the square pipe member  21 , and from there through the conduit  49  with the check valve  50  to the second portion  42  of the square pipe member  21  while the second valve  48  is closed. For tail threading, air of the high second pressure, usually about 150 to 200 kilopascals, is admitted to the second portion  42  of the square pipe member  21  by opening the second valve  48 . When air of the high second pressure starts flowing through the check valve  50  it will cause the check valve to close, so that the high second pressure will be confined to the second portion  42  of the square pipe member  21 . At the high second pressure mentioned above, the flow of air discharged through the elongate passage  22  in the square pipe member  21  will have an exit velocity on the order of 50 meters per second. When tail threading is carried out on a narrow full width web, the first partition  40 , the conduit  49  and the check valve  50  may be dispensed with, but if desired the first valve  45  may be a check valve. 
       FIG. 8  shows a series of four plate member assemblies  23  and associated means for supplying air of a first and a second pressure. The first one and the last one of the shown assemblies differ from the one shown in  FIG. 7  only in that the square pipe member  21  has also a second partition  51 , so that the square pipe member  21  is divided lengthwise into a first portion  41  at one web edge, a central second portion  42 , and a third portion  52  at the other web edge. The first branch pipe  44  with the first valve  45  is connected to both of the first portion  41  and the third portion  52  of the square pipe member  21 , while the second branch pipe  47  with the second valve  48  and the conduit  49  with the check valve  50  are connected to the second portion  42  as before. Of the four plate member assemblies shown, the two middle ones are not connected to the first manifold pipe  43 , which supplies air of the low first pressure to create the flutter suppressing air layer  15 , they are connected only to the second manifold pipe  46 , which supplies air of the high second pressure to be used for tail threading. In the embodiment illustrated in  FIG. 8 , air of the high second pressure is supplied to the central second portion  42  of all of the square pipe members  21  during tail threading, while during ordinary operation air of the low first pressure is supplied only to every third square pipe member  21 . Naturally, the number of middle plate member assemblies may vary dependent on the circumstances in the specific installation, but during ordinary operation it is not necessary to supply air for flutter suppression as frequently along the predetermined run of the web as air for tail threading has to be supplied. 
     When the reel-up  3  has a support drum  9  like in the embodiment illustrated in  FIG. 1 , it is suitable to mount the most downstream ones of the plate member assemblies arcuately along a top portion of the cylinder surface of the drum  9  and to make them of a reduced size in the cross machine direction, so as to dispense with substantially all flutter suppression capability (which actually is not needed in this position) while retaining the tail threading capability. Then, the reduced size plate member assemblies preferably are mounted on a support member  54  having an upstream end, which member is mounted to be pivotable around at its upstream end, so that the reduced size plate member assemblies can be swung away in order not to prevent a new reel spool, not shown, from being lowered onto the drum  9 . 
     As illustrated in  FIG. 9 , to reduce the air consumption at least one of the plate members  16  and  17  may have at least one transverse step  53  of a height of about a few millimeters, so as to cause a sudden increase in a distance from the predetermined run of the web  4  to the plate member as the web  4  runs from the drying section  2  to the subsequent equipment  3 . Of course, if desired, it is also possible to provide a series of equidistantly spaced identical bores, not shown, like those forming the elongate passage  22  in the square pipe member  21 , in the vertical portion of said at least one transverse step  53 . 
     While the present invention above has been described with reference to the drawings, several obvious modifications thereof are possible within the scope of the appended claims. As an illustrative example, it would be possible to use plate members  16  and  17  which, instead of being planar, are slightly curved in the running direction of the web  4  and thereby would be more rigid. It would also be possible to substitute another type of dust remover for the round tube  29 , e.g., a suitable one of those disclosed in U.S. Pat. No. 4,906,333 (Myren).