Dry end web transport system

Abstract

The invention relates to a system for transporting a fibre web ( 47 ) through a dry end of a fibre web processing machine from a drying section ( 1 ) to a reeling section ( 2 ) of the machine. According to the invention, the system comprises one or a plurality of groups of air modules, wherein each group of air modules is arranged for supplying and evacuating air from a predetermined, localized zone along the web run of the dry end, and wherein each group of air modules comprises at least one air supply module ( 9 ) being arranged for supplying air to the localized zone; and at least one air exhaust module ( 10 ) being arranged for evacuating air from the localized zone, wherein the air flow-rate of said at least one air supply module is balanced by the air flow-rate of said at least one air exhaust module such that dust-laden air is prevented from escaping the localized zone by other means than through said at least one air exhaust module.

1 . A system for transporting a fibre web ( 47 ) through a dry end of a fibre web processing machine from a drying section ( 1 ) to a reeling section ( 2 ) of the machine, characterized in that the system comprises one or a plurality of groups of air modules, wherein each group of air modules is arranged for supplying and evacuating air from a predetermined, localized zone along the web run of the dry end, and wherein each group of air modules comprises:
 at least one air supply module ( 9 ,  12 ,  32 ,  39 ) being arranged for supplying air to the localized zone; and   at least one air exhaust module ( 10 ,  57 ) being arranged for evacuating air from the localized zone,   
       wherein the air flow-rate of said at least one air supply module ( 9 ,  12 ,  32 ,  39 ) is balanced by the air flow-rate of said at least one air exhaust module ( 10 ,  57 ) such that dust-laden air is prevented from escaping the localized zone by other means than through said at least one air exhaust module ( 10 ,  57 ). 
     
     
         2 . The system according to  claim 1 , characterized in that the air flow-rate of said at least one air exhaust module ( 10 ) is at least equal to the air flow-rate of said at least one air supply module ( 9 ). 
     
     
         3 . The system according to  claim 1 , characterized in that it comprises an upstream web-supporting foil ( 7   a ) and a downstream web supporting foil ( 7   b ) being arranged one after the other such that a free draw gap is defined between the foils ( 7   a,    7   b ), wherein said at least one air supply module ( 9 ) is positioned at the downstream end of the upstream foil ( 7   a ), and wherein said at least one air exhaust module ( 10 ) is positioned at the upstream end of the downstream foil ( 7   a ). 
     
     
         4 . The system according to  claim 1 , characterized in that it comprises a calendar ( 3 ) comprising two counter-rotating calendar rolls and a calendar lead-in foil ( 71 ) for leading the web ( 47 ) into a nip formed by the calendar rolls, wherein said at least one air supply module ( 12 ) is positioned at the rotating envelope surface of one of the calendar rolls, and wherein said at least one air exhaust module ( 10 ) is positioned at the downstream end of the web supporting foil ( 71 ). 
     
     
         5 . The system according to  claim 1 , characterized in that it comprises a creper lead-out foil ( 13 ) and a second foil ( 68 ) following the lead-out foil ( 13 ), wherein the creper lead-out foil ( 13 ) is arranged for transferring the web ( 47 ) from a creping doctor ( 21 ) being arranged for removing the web ( 47 ) from a Yankee cylinder ( 1 ), and in that said at least one air supply module comprises a seal nozzle ( 64 ) being arranged in the upstream end of the lead-out foil ( 13 ) for removing a boundary air layer from the Yankee cylinder ( 1 ) prior to the web ( 47 ) reaching a creping blade ( 65 ) of the creping doctor ( 21 ), and in that said at least one air exhaust module ( 10 ) is located on the upstream end of the second foil ( 68 ). 
     
     
         6 . The system according to  claim 1 , characterized in that it comprises a scanner ( 4 ), a scanner lead-in foil ( 77 ) for leading the web ( 47 ) into the scanner ( 4 ) and a scanner lead-out foil ( 78 ) for leading the web ( 47 ) out of the scanner ( 4 ), wherein said at least one air supply module ( 9 ) is 15 positioned at the downstream end of the scanner lead-in foil ( 77 ), and wherein said at least one air exhaust module ( 10 ) is positioned at the upstream end of the scanner lead-out foil ( 78 ). 
     
     
         7 . The system according to  claim 1 , characterized in that the reeling section ( 2 ) comprises a reel drum ( 87 ), which is arranged to form a nip ( 110 ) with a fibre web roll ( 107 ), wherein said at least one air supply module ( 12 ) and said at least one air exhaust module ( 105 ) are positioned above the reel drum ( 87 ), and wherein said at least one air supply module ( 12 ) is arranged to produce an air curtain ( 104 ) directed into the nip ( 110 ). 
     
     
         8 . The system according to  claim 1 , characterized in that said at least one air exhaust module ( 10 ,  57 ) comprises a self-cleaning air exhaust slot ( 48 ). 
     
     
         9 . The system according to  claim 8 , characterized in that said at least one air exhaust module ( 10 ) comprises a rotatable section ( 51 ) having an extending lip ( 53 ), which rotatable section ( 51 ) is arranged to be rotated such that the lip ( 53 ) traverses and clears the exhaust slot ( 48 ). 
     
     
         10 . The system according to  claim 8 , characterized in that said at least one air exhaust module ( 57 ) comprises two slot plates ( 58 ,  59 ) forming an air exhaust slot ( 60 ) there-between, each slot plate ( 58 ,  59 ) displaying a zig-zag pattern having a pitch (E), wherein at least one of the slot plates ( 58 ) is movably arranged in the air exhaust module ( 57 ) such that it can move back and forth in the longitudinal direction of the slot ( 60 ) with a length of stroke equal to or larger than said pitch (P). 
     
     
         11 . The system according to  claim 1 , characterized in that said at least one air supply module ( 32 ,  39 ) comprises a self-cleaning air supply slot ( 34 ,  45 ). 
     
     
         12 . The system according to  claim 11 , characterized in that said at least one air supply module ( 32 ) comprises a cleaning blade ( 33 ) having a toothed edge ( 35 ), the blade ( 33 ) being movably arranged in the air supply slot ( 34 ) in the longitudinal direction of the slot ( 60 ) such that it can be oscillated longitudinally in the air supply slot ( 34 ). 
     
     
         13 . The system according to  claim 11 , characterized in that said at least one air supply module ( 39 ) comprises a cleaning blade ( 40 ) having a linear edge ( 41 ), the blade ( 40 ) being movably arranged in the air supply slot ( 45 ) to follow a V-shaped path such that it can be oscillated longitudinally in the air supply slot ( 34 ) and such that the cleaning blade ( 40 ) is moved in and out of the slot ( 45 ) during the longitudinal oscillation. 
     
     
         14 . The system according to  claim 1 , characterized in that it comprises:
 at least one rotating roll ( 196 ,  203 ,  206 ) over which the web ( 47 ) is wrapped between a web run-in position ( 208 ) and a web run-out position ( 209 ); and   an air exhaust module ( 199 ) having a plenum chamber ( 207 ) which is open towards the rotating roll ( 196 ,  203 ,  206 ) between an upstream sealing device ( 202 ) and a downstream air exhaust slot ( 200 ), the air exhaust slot ( 200 ) being positioned adjacent to the web run-in position ( 208 ).   
     
     
         15 . The system according to  claim 1 , characterized in that it comprises a dry end enclosure ( 61 ) having any combination of air curtains and controlled air flow patterns that envelope the dry end and form barriers preventing dust-laden air from escaping the enclosure ( 61 ). 
     
     
         16 . The system according to  claim 15 , characterized in that it comprises a pulper ( 125 ) which has at least one broke chute opening ( 120 ,  130 ), wherein the at least one broke chute opening ( 120 ,  130 ) comprises an air curtain ( 128 ) arranged to prevent the escape of mist and hot humid air from the pulper ( 125 ) into the dry end enclosure ( 61 ). 
     
     
         17 . The system according to  claim 16 , characterized in that it comprises an air exhaust module ( 131 ) which is positioned at said at least one broke chute opening ( 130 ) for evacuating air from within the pulper ( 125 ). 
     
     
         18 . The system according to  claim 17 , characterized in that the air exhaust module ( 131 ) for evacuating air from within the pulper ( 125 ) comprises an array of vertically oriented intake or pick-up tubes ( 132 ) which extend into the top of the pulper ( 125 ) adjacent to said at least one broke chute opening ( 130 ), wherein each of the intake tubes ( 132 ) comprise a tapered section located at the bottom end of the tube ( 132 ), which tapered section has a diameter which is smaller than the diameter of the main section of the tube ( 132 ) so that the tapered section serves as a venturi throat. 
     
     
         19 . The system according to  claim 18 , characterized in that water is introduced into each of the intake tubes ( 132 ) via a water pipe ( 133 ) which is semi-tangential to the intake tube ( 132 ). 
     
     
         20 . A dry end of a fibre web processing machine for transporting a fibre web ( 47 ) from a drying section ( 1 ) to a reeling section ( 2 ) of the machine, characterized in that it comprises a system according to  claim 1 . 
     
     
         21 . An air exhaust module ( 10 ,  57 ) for use in a group of air modules according to  claim 1 , characterized in that it comprises a self-cleaning air exhaust slot ( 48 ). 
     
     
         22 . The air exhaust module ( 10 ) according to  claim 21 , characterized in that it comprises a rotatable section ( 51 ) having an extending lip ( 53 ), which rotatable section ( 51 ) is arranged to be rotated such that the lip ( 53 ) traverses and clears the exhaust slot ( 48 ). 
     
     
         23 . The air exhaust module ( 57 ) according to  claim 21 , characterized in that it comprises two slot plates ( 58 ,  59 ) forming an air exhaust slot ( 60 ) there-between, each slot plate ( 58 ,  59 ) displaying a zig-zag pattern having a pitch (P), wherein at least one of the slot plates ( 58 ) is movably arranged in the air exhaust module ( 57 ) such that it can move back and forth in the longitudinal direction of the slot ( 60 ) with a length of stroke equal to or larger than said pitch (P). 
     
     
         24 . An air supply module ( 32 ,  39 ) for use in a group of air modules according to  claim 1 , characterized in that it comprises a self-cleaning air supply slot ( 34 ,  45 ). 
     
     
         25 . The air supply module ( 32 ) according to  claim 24 , characterized in that it comprises a cleaning blade ( 33 ) having a toothed edge ( 35 ), the blade ( 33 ) being movably arranged in the air supply slot ( 34 ) in the longitudinal direction of the slot ( 60 ) such that it can be oscillated longitudinally in the air supply slot ( 34 ). 
     
     
         26 . The air supply module ( 39 ) according to  claim 24 , characterized in that it comprises a cleaning blade ( 40 ) having a linear edge ( 41 ), the blade ( 40 ) being movably arranged in the air supply slot ( 45 ) to follow a V-shaped path such that it can be oscillated longitudinally in the air supply slot ( 34 ) and such that the cleaning blade ( 40 ) is moved in and out of the slot ( 45 ) during the longitudinal oscillation. 
     
     
         27 . A method of preventing dust laden air from escaping a localized zone in a dry end of a fibre web processing machine, characterized by the steps of:
 placing at least one air supply module ( 9 ) within the localized zone;   placing at least one air exhaust module ( 10 ) within the localized zone; and   balancing the air flow-rates of said at least one air supply module ( 9 ) and said at least one air exhaust module ( 10 ) such that the air flow-rate of said at least one air exhaust module ( 10 ) is at least equal to the air flow-rate of said at least one air supply module ( 9 ).