Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
  • D21G3/00—Doctors
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H18/00—Winding webs
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F1/00—Wet end of machines for making continuous webs of paper
  • D21F1/36—Guiding mechanisms
  • D21F1/42—Jets
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F1/00—Wet end of machines for making continuous webs of paper
  • D21F1/48—Suction apparatus
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
  • D21F11/14—Making cellulose wadding, filter or blotting paper
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F5/00—Dryer section of machines for making continuous webs of paper
• • 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
  • D21G1/00—Calenders; Smoothing apparatus
  • D21G1/0073—Accessories for calenders
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
  • D21G1/00—Calenders; Smoothing apparatus
  • D21G1/0073—Accessories for calenders
  • D21G1/0086—Web feeding or guiding devices
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
  • D21G3/00—Doctors
  • D21G3/04—Doctors for drying cylinders
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H2406/00—Means using fluid
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H2406/00—Means using fluid
  • B65H2406/30—Suction means
  • B65H2406/36—Means for producing, distributing or controlling suction
  • B65H2406/364—Means for producing, distributing or controlling suction simultaneously blowing and sucking
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H2408/00—Specific machines
  • B65H2408/20—Specific machines for handling web(s)
  • B65H2408/23—Winding machines
  • B65H2408/236—Pope-winders with first winding on an arc of circle and secondary winding along rails
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H2601/00—Problem to be solved or advantage achieved
  • B65H2601/20—Avoiding or preventing undesirable effects
  • B65H2601/26—Damages to handling machine
  • B65H2601/261—Clogging
  • B65H2601/2611—Soiling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H2601/00—Problem to be solved or advantage achieved
  • B65H2601/20—Avoiding or preventing undesirable effects
  • B65H2601/26—Damages to handling machine
  • B65H2601/261—Clogging
  • B65H2601/2612—Pollution
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65H—HANDLING THIN OR FILAMENTARY MATERIAL, e.g. SHEETS, WEBS, CABLES
  • B65H2801/00—Application field
  • B65H2801/84—Paper-making machines

Definitions

• the present invention relates to a system for transporting a fibre web through a dry end of a fibre web processing machine from a drying section to a reeling section of the machine.
• the invention relates to such a system in a tissue paper machine.
• the invention also relates to an air supply module and an air exhaust module for use in such a system.
• the invention also relates to method of preventing dust laden air from escaping a localized zone in a dry end of a fibre web processing machine.
• the conventional methods of controlling the web and containing dust are disappointing.
• the conventional methods are several layers of solutions. Each new successive solution (layer) has been devised without fully re-evaluating what has been previously done.
• the present invention relates to a detailed outline of a dry end design that efficiently integrates the key processes and objectives of the dry end of a tissue or towel grade machine while using new and existing technology.
• Air is not only exhausted at critical locations, it is also supplied at strategic locations.
• Dust leakage is considerable, although much more air is supplied and exhausted than what is really needed. Dust levels are unpredictable and "hit or miss" machine room dust level guarantees must be utilised. ⁇ The intake slots of dust collectors of various types get plugged.
• a common problem associated with conventional systems is the sheet instability which occurs along the edges of the sheet run. This is a result of the incoming air flows.
• the exhaust stream attempts to draw in the web and/or draw air through the web.
• the unit has many internal passages that plug and are difficult to clean.
• the unit does not support the web very well.
• the objective of the present invention is to alleviate these problems.
• the system according to the invention is characterized in that it 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 being arranged for supplying air to the localized zone
• At least one air exhaust module being arranged for evacuating air from the localized zone
• the problems associated with web transportation in a dry end of a conventional tissue machine relate to the following technical areas: the handling of the boundary layer on a moving surface, the handling of flooded nip, the handling of linear free jets, the active airfoils, the passive air foils, sheet tensioning considerations, the spreading of the tissue web, the containment and removal of dust, wet scrubbing and the issue of containment at the pulper.
• Boundary Layer on a Moving Surface A moving surface carries air with it. There are theoretical correlations available for laminar flows and empirical correlations available for turbulent flows. The correlations used originate from those derived for applications involving a stationary plate and a moving airstream and are adopted for use in a given configuration. In a typical application, the vast majority of the boundary layer air is very close to the moving surface.
• Linear Free Jet A linear free jet is a jet of air emerging perpendicularly from a slot in a surface.
• Linear free jets can be used for air curtains.
• a foil comprising a nozzle releasing air along the foil surface in the direction of the travelling web in order to stabilize the web is called an active airfoil.
• a foil lacking such a nozzle is called a passive foil.
• Passive foils are the most common in the industry. They are low cost and adjustable. Flat plates rely upon a slight wrap angle at it's trailing and leading edges to make sure that the web sticks to it.
• Dust accumulation on the leading and trailing edges tends to fall off in large pieces. This usually results in web breaks.
• the dust accumulation on the leading edge is due to the impaction of dust particles that originate from the dust laden boundary layer that is above the web and upstream of the foil .
• the dust particles on the trailing edge originate from the dust-laden air that is drawn into the zone at the trailing edge where the web's boundary layer causes air to be drawn in.
• the dust particles that accumulate on the leading edge will tend to be smaller as there are greater accelerations involved in the airstream and thus increased separation due to impaction.
• the top surface of the web is exposed to allow for pressure relief upstream and downstream of the foil. This results in dust release above the web. In conventional configurations, dust is released between the foils.
• the length of the foil surface in the direction of web travel is limited because air accumulates between the web and foil.
• the web is held to the underside of the foil due to the low pressure that is generated on the foil surface due to the movement of the web. It is also held to the foil due to the sheet tension coupled with the wrap on the leading and trailing edges of the foil. Web permeability contributes to the accumulation of air between the web and the foil.
• the allowable foil length (in the machine direction) increases with: • Increased sheet tension,
• the sheet tension can be predicted through-out the sheet run.
• a sheet handling system must be designed such that the sheet tension varies within an acceptable range through-out the sheet-run.
• the sheet tension varies depending on the location in the dry end.
• the crepe will be pulled out or, worse yet, the web will be torn. If the tension is too low, the web will locally bag or drop off of the foils.
• the start of the sheet run is at the creping doctor.
• the web is pulled at the end of the sheet run by the reel.
• Passive foils drag on the web while active foils push on the web. Consequently, there is a need for strategically locating passive and active foils in the sheet run.
• the consequence of grouping too many passive foils at the start of the sheet run is that the sheet tension will become too high downstream of the passive foils.
• the frictional load on the passive foils can be predicted using experimentally determined friction factors.
• the 'push' provided by active foils can be predicted using experimentally determined correction factors and a simple energy balance.
• active and passive foils are alternately positioned along the sheet run.
• cross-machine variations in sheet stability can be attributed to cross-machine variations in sheet tension.
• sheet tension is not high enough in the center of the machine, the web sags in the center of the machine. This is referred to as 'bagging'.
• 'edge flutter' When the web tension is too loose on the edges, it is referred to as 'edge flutter'.
• Edge flutter is also caused by adverse air currents or cross-machine variations in the web's properties.
• the sheet tension curve is affected by the crepe ratio. Variations in reel speed (crepe ratio) will shift the tension curve vertically.
• the friction load on passive foils is partly a function of sheet tension.
• the web massflow is of course constant as a function of location.
• the web acts as a linear tension spring.
• the velocity of the web varies as a function of sheet tension or location. Sheet tension affects product quality and the runnability at the dry end.
• This invention takes web handling and dust control to a new level.
• the supply of air is controlled and the natural airflows due to moving surfaces are favourably manipulated or allowed for.
• the purpose of exhausting air from the pulper is to prevent a large bubble of hot humid air from escaping from the pulper.
• the required pulper exhaust flowrate is not only related to the volumetric flowrate of vapour that is being released by the hot agitated stock.
• buoyancy forces acting on the humid pulper air must be counteracted by the downwards velocity of air at the floor openings. Neglecting localized high air velocities resulting from various forced air currents, buoyancy forces are the dominant factor that must be controlled. Theoretically, if there is no air forced into the pulper and it is completely sealed, no exhaust is required as the air will reach saturation and no more water vapour will be liberated from the stock or showers.
• the flowrate of air into the pulper from other sources such as a trim conveying system Qboundary layer air
• Qboundary layer air The flowrate of air that is carried with the web into the pulper when the web is diverted to the pulper from the Yankee at machine speed.
• Fig. 1 shows a dry end of a tissue paper machine comprising a dry end web transport system according to the invention
• Figs. 2 to 6 show air supply nozzles according to one aspect of the invention
• Figs. 7 and 8 show adjacent air foils according to one aspect of the invention
• Fig. 9 shows an air exhaust module having a self-cleaning air exhaust slot according to one aspect of the invention
• Figs. 10 to 12 show an air exhaust module having a self-cleaning air exhaust slot according to another aspect of the invention
• Fig. 13 shows a dry end enclosure according to one aspect of the invention
• Figs. 14 and 15 show air curtains according to one aspect of the invention
• Fig. 16 shows a creper lead-out foil according to one aspect of the invention
• Figs. 17 and 18 show second foil according to one aspect of the invention
• Fig. 19 shows a calender lead-in according to one aspect of the invention.
• Fig. 20 shows a calender roll dust collector and a calender roll air deflector according to one aspect of the invention
• Fig. 21 shows a scanner passage according to one aspect of the invention
• Fig. 22 shows a reeling station comprising a reel drum according to one aspect of the invention
• Fig. 23 shows web or sheet pressurization at the reel drum according to one aspect of the invention
• Fig. 24 shows a reel shield with a dust collector and a nip flooding air curtain according to one aspect of the invention
• Fig. 25 shows a lower reel drum air curtain according to one aspect of the invention
• Figs. 26 to 28 show a floor flush system according to one aspect of the invention
• Fig. 29 shows a pulper enclosure according to one aspect of the invention
• Figs. 30 and 31 show a pulper module according to another aspect of the invention.
• Fig. 32 shows a pulper door according to one aspect of the invention
• Figs. 33 to 36 show a roll dust collector according to one aspect of the invention.
• air is used for conveying dust.
• the web transport system introduces supply air and evacuates dust-laden air at strategic locations.
• the sheet run is enclosed and the air flows are balanced such that flows into and out of the control volume are accounted for. If deemed beneficial, some of the exhaust air is re-used as supply air; It is re-circulated. This reduces the amount of exhaust air out of the machine room thereby decreasing machine room make-up air requirements.
• Fig. 1 shows an example of a dry end of a tissue paper machine comprising a web transport system according to one embodiment of the invention for leading a web (not shown in Fig. 1 ) from a drying section in the form of a Yankee dryer 1 to a reeling section or station 2.
• the dry end also comprises a plurality of web-processing or web-monitoring apparatus being positioned between the Yankee cylinder 1 and the reeling station 2 along the run of the web.
• the web-processing or web-monitoring apparatus comprise a calender 3, a scanner 4, a slitter 5 and a sheet spreader 6.
• the web transport system according to the invention may be used in dry ends having other configurations.
• This embodiment of the web transport system comprises a plurality of foils or plates 7, 68 being arranged to support the web during the travel from the Yankee cylinder 1 to the reeling station 2.
• the web transport system comprises air supply modules 9, air exhaust modules 10, a dry end enclosure 61 (see Fig. 13), air curtain nozzles 12, a creper lead-out foil 13, airfoil nozzles 14 (optionally), a cut-off doctor 15, a calender air exhaust module 16, a calender air deflector 17, a reel drum air exhaust module 18, a reel drum air deflector 19, a pulper module 20 and a creping doctor 21 .
• the web transport system is comprised of: ⁇ In-machine components (building blocks)
• Air supply modules in the form of nip flooding air jets allow for the control of air flow patterns at a closing nip, whereby the entrance of unwanted materials into a closing nip such as that of a calender or reel can be hindered.
• the top of the web does not need to release dust as it does in a conventional tissue machine dry end. Exposure of the top of the web needlessly results is dust escaping from above the web and forces the building of a big box around the dry end. All conventional efforts at containing the dust above the web are merely inefficient solutions that are costly to implement, operate and maintain while failing to get to the root of the problem.
• the web transport system according to the invention comprises a multitude of sub-systems that can work in unison to efficiently enclose the sheet run from the creping doctor to the reel. Using the web transport system according to the invention, the following objectives are met:
• the sheet run is designed to maintain sheet tension within an acceptable range which results in improved product quality.
• the airflow nozzles and air exhaust modules can be of a self-cleaning design if required.
• Airfoil nozzles 14 are optional in the web transport system according to the invention. They are used when the maximum allowable sheet tension is low.
• active foils are not required. This reduces the complexity of cost of a system. Active type foils usually can be omitted in applications where:
• Air supply modules or nozzles 32 having a self cleaning mechanism according to one aspect of the invention will now be described with reference to Figs. 2 to 6.
• a cleaning plate or blade 33 is oscillated longitudinally in the slot, opening or outlet 34 of the nozzle 32 (see Figs. 2 and 3).
• the plate 33 penetrates the slot 34 with a toothed edge 35. A small portion of the flow is interrupted by each of the teeth, but this is a small sacrifice for maintaining nozzle slot cleanliness.
• the cleaning blade 33 is housed in the plenum area 36 of the nozzle 32.
• the cleaning blade 33 is actuated in a cross-machine direction and it's actuated movement is mechanically constrained to a linear path by stationary pins 37 arranged in linear guide slots 38 in the cleaning blade 33, the pins 37 serving as guides for the cleaning blade 33.
• Figs. 4 to 6 disclose a second embodiment of an air supply module or nozzle 39 having a self cleaning mechanism.
• the nozzle 39 comprises a cleaning plate or blade 40 having a linear edge 41 .
• the nozzle displays a V-shaped guide slot 42 in which a stationary pin 43 is arranged.
• An actuator 44 is arranged to bring the cleaning blade 40 to travel back and forth such that the cleaning blade 40 travels a V-shaped path and such that the edge 41 moves in and out of the air supply slot, opening or outlet 45 of the nozzle 39 when the blade 40 is oscillated longitudinally in the air supply slot 45.
• the type of nozzle disclosed in Fig. 4 to 6 is preferably used only in situations where temporary flow interruptions can be tolerated, e.g. in air curtain nozzles.
• dust is contained by exhausting and supplying air between adjacent foils 7a and 7b, as is shown in Figs. 7 and 8.
• Air is supplied to the zone between the foils 7a and 7b via an air supply module 9 having a downstream facing cross-machine air supply nozzle 46 ejecting fresh air onto the trailing edge of the first, upstream foil 7a.
• This airflow is a uniform laminar flow that has a velocity field with a maximum magnitude that is much lower than the velocity of the web 47.
• the air supply nozzle 46 is adjustable such that the velocity and the volumetric flow of the ejected air can be changed.
• an air exhaust module 10 being arranged to evacuate dust-laden air from the zone between the foils 7a and 7b.
• the air exhaust module 10 comprises an upstream facing cross-machine air exhaust slot 49.
• the air supply module 9 and the air exhaust module 10 are connected to an air duct system (not shown) being arranged for leading fresh air to the air supply module 9 and for leading dust-laden air away from the air exhaust module 10.
• the exhaust flow is slightly greater than the supply flow. This creates a very low under-pressure in the zone between the foils 7a and 7b.
• the air from the supply nozzle 46 combines with bleed-air relieved from the end of the first foil 7a and the induced machine room air from above the foils, as is shown in Fig. 1 1 . All of this air is drawn into the exhaust slot 48. The air is not exhausted through the web 47. Final balance is automatically achieved by bleeding in air from above the web. If there was only the evacuation of the low flow of dust- laden air that bleeds from the trailing edge of the upstream foil 7a, the exhaust slot 47 would have to be very small and, consequently, would be prone to blockage. It would also be very difficult to balance the airflow.
• the gap g (see Fig. 9) of the exhaust slot 48 is in excess of 1 ⁇ 2" (13mm) in order to obtain a low probability of plugging.
• an exhaust slot gap g of 5/8" (16mm) can be used.
• Such an exhaust slot is capable of evacuating 17.4 cfm/inch (19.4 (m3/min)/m) at a web velocity of 4,000 ft/min (20.3 m/s).
• the supply air is primarily re-circulated exhaust air that has been mixed with some fresh air.
• the required flowrate of the supply air is
• the distance between the foils 7a and 7b can vary depending on the application. A distance between the foils 7a and 7b of approximately 3 to 4 inches (76 to 102mm) has proven to be suitable.
• the tending side and drive side ends of the air exhaust module 10 have a round inspection port with a quick release latch. This allows for easy inspection of the interior of the air exhaust module 10.
• the air exhaust module 10 can have a constant profile regardless of the width of the machine. There are semi-tangential outlets 49 located along the width of the module 10 approximately every 2500 mm. Also, the air supply module 9 can have a constant profile regardless of the width of the machine. There are rectangular inlet connections 50 located along the width of the module 9 approximately every 2500 mm.
• the air supply and exhaust modules 9, 10 can be retrofitted to existing foils as required in a rebuild situation.
• At least one, more preferably a majority and most preferably all of the air exhaust modules 10 of the web transfer system comprises a self- cleaning air exhaust slot 48.
• An air exhaust module having such a self-cleaning air exhaust slot 48 will be described in the following with reference to Fig. 9.
• An air exhaust module comprising this type of self-cleaning exhaust slot is suitable for evacuating dust-laden air having a relatively low moisture content.
• the air exhaust module 10 comprises a rotatable section 51 being formed by a cylindrically shaped body 52 and a tangentially extending lip 53, which is fixed to the envelope surface of the body 52.
• the body 52 may be comprised of pipe sections.
• the section 51 is rotatably mounted in a support structure 54 such that when the section 51 is rotated, the lip 53 traverses the exhaust slot 48 of the module 10 and clears the exhaust slot 48.
• a scraper blade 55 removes any material that may be attached to the body 52.
• the lip 53 pushes any material blocking the slot 48 into the module 10 where the loosened material is carried away by the flow of the exhaust air.
• the rotatable section 51 can be rotated more than 180 degrees between a first, idle position and a second position, which is illustrated using broken lines in Fig. 9. When operated, the rotatable section 51 is rotated very quickly from the first position to the second position and then back to the first position.
• a rotary actuator or a pneumatic cylinder with a special linkage assembly preferably arranged on the drive side of the module 10, is used to rotate the rotatable section 51 .
• the support structure 54 comprises equally spaced support struts 56 being arranged along the cross-direction of the module 10.
• the lip 53 and the scraper blade 55 extends continuously along the cross-direction of the module 10 while the body 52 preferably is comprised of several pipe sections, each terminating at a support bearing carried by a support strut 56.
• the pipe sections are linked with a short piece of round bar that passes through each bearing and is fastened to the ends of the pipe sections with pins.
• the rotatable section 51 can be divided into two part-sections that are actuated independently. This would allow for half of the slot 48 to be functioning while the other half is being cleaned. However, this would require the use of two actuator assemblies instead of one, in which case there would preferably be one actuator on the tending side and one actuator on the drive side of the module 10.
• the design of the air exhaust module 10 disclosed in Fig. 9 allows for materials that may have bridged the exhaust slot 48 to be pushed into the slot 48.
• An optional configuration would allow for bridged materials to be pushed out of the slot 48, in which case the idle position of the lip 53 preferably is inside the air exhaust module 10.
• the actuator or actuators would have to have a reversed configuration in such a configuration.
• the normal exhaust slot of such a dust collector is a long, narrow and semi- rectangular opening running in the cross-machine direction of the module. The opening may be slightly tapered in the direction of the flow of the exhaust air.
• the cross-machine length of the exhaust slot is usually within the range of 10 to 30 feet (3.0 to 9.1 m) and the normal slot gap range is approximately 1 ⁇ 2" to 2" (1 .3 to 5.1 cm).
• Compressed air knock-off shower Manual cleaning is not always practical as the collectors are often located in areas that are difficult to access.
• the compressed air showers are also not effective since there is a high vacuum level at the intake slot which causes difficulties for the wads to become dislodged. If the air showers do dislodge any wads, the wads become airborne in the dry end of the machine and this is not desirable. Large wads that are allowed to fall outside of the collector may cause sheet breaks. Consequently, there is a need for a wet dust collector that allows for the wads to be drawn into the collector so that disturbances outside of the collector are avoided.
• Figs. 10 to 12 schematically disclose a machine-directional view of such an air exhaust module in the form of a dust collector 57.
• the collector 57 comprises an upper slot plate 58 and a lower slot plate 59, each displaying a zig-zag pattern having a pitch P.
• the slot plates 58, 59 define an air exhaust slot 60.
• the lower slot plate 59 is adjustably fixed in the collector 57 as in a
• the upper slot plate 58 is movably arranged in the collector 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 P.
• the open area of the intake slot 60 remains constant and the airflow remains approximately constant as the upper slot plate 58 moves back and forth.
• the oscillation of the upper slot plate 58 can be constant or cycled on and off depending on the rate at which material accumulates on the slot 60.
• the rest position of the upper slot plate 58 is preferably at the mid-point of it's travel, as is shown in Fig. 1 1 .
• a simple pneumatic cylinder with a timer could be used for operating the upper plate 58.
• a limit switch could be used to provide feedback to identify the rest position of the upper slot plate 58.
• both slot plates may be movably arranged in the collector 57 such that they can move back and forth in the longitudinal direction of the slot 60.
• the dry end enclosure of the web transport system is an assembly of physical barriers, air curtains and controlled air flow patterns that effectively envelope the dry end of the machine to prevent the escape of dust.
• the boundaries of this dry end enclosure are shown in Fig. 13 and are described as follows:
• the dry end enclosure 61 is a control volume in which massflows and energy must be balanced.
• Air curtains according to one aspect of the invention will now be described with reference to Figs. 14 and 15.
• Part of the dry end enclosure may be accomplished by of air curtains, as is shown in Figs. 14 and 15, in which case the dry end enclosure comprises air curtain nozzles 62 being positioned along the folis 7 such that vertically downward linear air curtains are created extending from the foils 7 to the floor 63 of the dry end.
• An air curtain is a non-intrusive dynamic barrier between adjoining zones.
• a physical barrier such as a wall or strip curtain is perhaps lower cost but they inhibit the physical and visual access of the operators.
• Air is introduced along the sides of the web or sheet run to stabilize the edges of the web or sheet 47 and contain the dust laden air to the dry end
• the creper lead-out foil 13 is used to transfer the web from the creping doctor.
• a cross-machine seal nozzle 64 in the up-stream end of the lead-out nozzle 13 is used to blow air onto the surface of the Yankee cylinder 1 such that the boundary layer air is removed from the Yankee cylinder 1 before the web 47 reaches the creping blade 65 of the creping doctor 21 .
• This seal nozzle 64 is preferably of the self cleaning type described above in relation to Figs. 2 and 3.
• the foil 13 is a plenum for the nozzle air. In the majority of cases, the dry end toe of the Yankee cylinder 1 will leak air. This leaked air is hot, humid and contaminated with dust and products of combustion from the direct fired heating system of the Yankee Hood. It is important that this air be contained and removed.
• the hood may be pressurized. Every machine has different leakage rates as it depends on the design and balance of the Yankee Hood. This moisture laden air is normally carried with the top surface of the web. It usually results in condensation on the downwards-facing surfaces of the foils. This leads to accumulations of sheet additives or 'stickies' on the foil surfaces.
• the lead-out foil 13 is preferably equipped with side air- curtain nozzles of the type described above in relation to Figs. 14 and 15.
• An exhaust module 10 acting as a dust collector having a cross-machine intake slot is located on the upstream end of the foil 68 that follows the creper lead-out foil 13 (see Fig. 1 ). The zone is balanced.
• the flowrate Q1 of the air that is exhausted by this dust collector is a summation of the following flows:
• Air is drawn in to the area 66 below the web 47 at the creping doctor 21 . This is a result of the movement of the web 47 as it 'pumps out' air with it's boundary layer. In high speed machines, it may be an advantage to introduce low-velocity air below the web 47 at the creping doctor 21 .
• This first foil 13 should not be an active foil because the sheet tension must be relatively low at the creping doctor 21 .
• the lead-out foil 13 is equipped with a knock-down air shower 67. If the web 47 needs to be directed to a pulper 125 (see Figs. 27 to 29) from the creping doctor 21 , compressed air is released through the series of holes in the underside of the foil 13.
• the cross-machine seal nozzle 64 stops the boundary layer air that is carried with the Yankee cylinder 1 . This allows the required wrap angle on this foil 13 to be less than that used on conventional creper lead-out foils. This results in decreased sheet tension downstream of the foil 13.
• Pressurized air is used to induce an airflow from the edges of the Yankee cylinder and direct it into the pulper opening.
• the misting showers are used to ensure that the trim or Yankee fuzz is knocked down into the pulper.
• a second foil 68 according to one aspect of the invention will now be described with reference to Figs. 17 and 18.
• This foil 68 is an important variable to be used in the design of a dry end.
• the geometry of this foil 68 is adjusted to suit the specific requirements of the machine.
• the leading edge of this foil is equipped with an exhaust module 10 that has a self-cleaning exhaust slot similar to the type described above in relation to Figs. 7 to 9.
• the air that enters this exhaust slot is a mixture of air from above and below the creper lead-out foil 13, as has been discussed above.
• a cross-machine knockdown air shower pipe 69 is located on the strong-back of the cut-off doctor 15. Favourable air currents are generated to draw the web 47 downwards when needed.
• Fixed curtain panels 70 hang from the dry end toe of the Yankee Hood are close to the top end of the second foil 68 when the foil is retracted. This seals the area 70 next to the Yankee cylinder 1 to help contain dust while the web 47 is directed down to the pulper 125 (see Figs. 27 to 29) from the cut-off doctor 15.
• a calender lead-in according to one aspect of the invention will now be described with reference to Fig. 19.
• the majority of machines do not use a calender.
• special transition zones are incorporated in the foils to allow for transfer of the web into and out of the calender rolls while enclosing the web from above.
• a calender lead-in foil 71 leads the web 47 into the gap formed between the counter-rotating calender rolls 72, 76 of the calender 3.
• At the entrance to the calender there is a wrap on the lower calender roll 72.
• An air supply module in the form of an air curtain nozzle 12 producing a nip-flooding air jet is used to accomplish two main tasks. ⁇ It prevents dust laden air from entering the closing nip.
• An optional sheet spreading airfoil on the calender lead-in foil 71 may be used.
• a dust collector 10 with a self-cleaning intake slot is strategically located at the downstream end of the web supporting foil 71 and removes dust laden air from the trailing edge of the foil 71 .
• a calender roll dust collector 16 and a calender roll air deflector 17 will now be described with reference to Fig. 20.
• the deflector 17 and the dust collector 16 are used on the wet end side of the lower calender roll 72. This is similar in design to the unit used at the reel drum (to be described below).
• Boundary layer dust-laden air is normally pumped into the zone 73 between the moving calender roll 72 and the underside of the web 47.
• the minimum required flowrate of air from this collector 16 for relief of the over-pressure in this zone 73 can be predicted with the following equation.
• B1 the volumetric flowrate rate of the boundary layer on the underside of the web 47.
• B2 the volumetric flowrate rate of the boundary layer on the rotating lower calender roll 72.
• the boundary layer airflows can be approximated using CFD analysis tools.
• the dust laden air is effectively contained above the web while it passes through the scanner 4.
• the concept employed here is similar to the foil to foil transfer as described above in relation to Figs. 7 and 8.
• the web 47 is supported by a scanner lead-in foil 77 at the entrance of the scanner 4.
• the trailing edge of this foil 77 is close to a scanner head 80 as shown in Fig. 21 .
• An air supply module 9 having a low pressure supply nozzle 46 is located above this trailing edge and it releases air in the direction of the sheet travel and towards an air exhaust module 10 acting as a dust collector having an air intake or exhaust slot 48.
• the velocity of the air is of relatively lower magnitude than that of the web 47.
• a scanner lead-out foil 78 is positioned downstream of the scanner 4.
• the foil 78 is sloped such that approximately 2 degrees of wrap is achieved to ensure good transfer.
• the leading edge of this foil 78 has a smooth leading edge.
• the exhaust slot 48 is located directly above this edge.
• the exhaust slot 48 is self-cleaning.
• the volumetric flow rate of the exhaust air is slightly higher than the volumetric flow rate of the air supply module 9. The web is not drawn in as the zone is balanced.
• An enclosure panel 79 is oriented cross-machine and extends from the top of the dust collector 10 to the upper dry end face of the scanner frame.
• Adequate clearance to the moving scanner head is provided.
• a reeling station 2 comprising a reel drum 87 according to one aspect of the invention will now be described with reference to Fig. 22.
• the area on the wet end side of the reel drum is a zone that is naturally pressurized due to the incoming boundary layer air that moves with the underside of the web 47 and the outer surface of the reel drum 87.
• the boundary layer air on the underside of the web 47 has a relatively high concentration of dust.
• a deflector 19 is oriented cross-machine and is located on the wet end side of the reel drum 87. It is equipped with a wiper blade 88. The wiper blade 88 cuts off the boundary layer air that moves with the reel drum 87 and helps prevent the web 47 from 'ballooning' above the reel drum.
• a reel drum air exhaust module 18 in the form of a dust collector is used to evacuate air from the area. If this air is not evacuated directly from this zone, the zone would be pressurized and it would squeeze the dust laden air out the sides of the machine. It would also cause the web 47 to 'balloon' as it is transferred to the reel drum 87.
• the dust collector 18 is sized to suit the flowrate of boundary layer air that comes with the web 47 and the rotation of the reel drum 87.
• the intake of the collector 18 may be the self-cleaning type described above in relation to Fig. 9.
• the minimum required flowrate of air from this collector 18 for relief of the over-pressure in this zone can be predicted with the following equation.
• B1 the volumetric flowrate rate of the boundary layer on the underside of the web 47.
• B2 the volumetric flowrate rate of the boundary layer on the rotating reel drum 87.
• the boundary layer airflows can be approximated using CFD analysis tools.
• a sheet spreader 6 is located directly before the reel drum area. Air is introduced above the web 47 directly after the sheet spreader 6 and before a reel shield 101 . This zone is covered by an enclosure 102 and is pressurized to help keep the web 47 tight to the surface of the reel drum 87. To transfer the web from the sheet spreader 6 to the reel drum 87 while preventing 'ballooning' of the web, air is released at the trailing edge of the spreader 6.
• the geometry of the enclosure 102 helps create a pressurized zone or volume 103 above the web 47. Initially, the air has a low velocity and a positive static pressure. The air travels with the web 47 and passes through the restriction between the shield 101 and the reel drum 87. The air is released to the area above the reel drum 87. The static gauge pressure is zero where it is released and the dynamic pressure is positive.
• Creating an over-pressure on top of the web 47 is the same as creating an under-pressure below the web 47.
• the pressure differential is easily adjustable by changing the air flowrate into the zone 103 or adjusting the gap between the shield 101 and the reel drum 87. The air is introduced at low velocity thus avoiding web stability issues.
• the reel shield 101 extends across the machine and is oriented vertically above the reel drum 87.
• An air exhaust module in the form of an area dust collector 105 is attached to the top of the reel shield 101 .
• the dust collector 105 comprises a self-cleaning slot as described in connection with Fig. 9.
• the nip flooding air jet concept is employed in a similar fashion as used with the entrance to the calender.
• An air supply module in the form of a nip flooding or air curtain nozzle 12 is located above the reel drum 87. This linear free jet is oriented cross-machine and is directed at the roll 107.
• the nip flooding air nozzle 12 is preferably fitted with a self cleaning mechanism as described above in relation to Figs. 4 to 6.
• the supply air duct 109 has a diver damper (not shown) to temporarily halt the nozzle air flow during threading.
• the air curtain nozzle 12 air floods the nip 1 10 across the full width of the web.
• the majority of the air that enters the nip originates from the nozzle 12 and the boundary layer air of the jumbo roll 107.
• this air enters the converging nip 1 10, it is rejected opposite the direction of the web as it passes over the reel drum 87. Particulate and small pieces of broke that may be carried with the top of the web over the reel drum 87 are rejected by the strong air currents that exit the closing nip 1 10.
• An intense rotational flow field is generated in the zone bounded by the air curtain 104, the top of the reel drum 87, and the reel shield 101 .
• the boundary layer airflows can be approximated using CFD analysis tools.
• the reel collector 105 has a relatively large exhaust volumetric flowrate and it has a large intake slot gap of 3 inches (76mm). It is capable of drawing in large amounts of broke. A broke trap is used downstream of this collector to separate the large pieces of broke and deliver them to the pulper.
• a lower reel drum air curtain nozzle 1 17 is used to contain dust that would otherwise get carried out with the boundary layer air of the roll 107. This nozzle 1 17 can also clean the web immediately after it has been rolled up. It blows air against the roll 107 immediately after it touches the reel drum 87.
• the nozzle 1 17 is a fixed cross-machine nozzle and preferably comprises a self cleaning mechanism as described above in relation to Figs. 4 to 6.
• a soft curtain 1 18 extends down from the nozzle plenum to the floor.
• This curtain is made of former fabric or similar material. It allows for the passage of broke which is normally pushed into the pulper opening. If there is no pulper opening below the reel, then rigid panels are used for the curtain below the nozzle 1 17.
• this nozzle 1 17 can be actuated if deemed necessary. It could be actuated such that it follows the varying jumbo roll 107 diameter as it is wound. With the nozzle 1 17 close to the surface of the roll 107 at all times, the web is cleaned. This is the best time to clean the sheet.
• a floor flush system according to one aspect of the invention will now be described with reference to Figs. 26 to 28. After knocking the sheet into the pulper 125 at the cut-off doctor 15 or creping doctor 21 , and prior to re-establishing the sheet to the reel, a clean-up is required.
• the web transport system according to the invention is designed such that there are very few locations where broke can hang-up or accumulate below the sheet run.
• Compressed-air blow-pipes (not shown) can be installed to help ensure that all broke goes to the floor.
• the floor 1 19 is sloped towards the pulper opening(s) 120.
• the floor area is curbed along the sides of the machine near the sole plates.
• a cross-machine spray header pipe 121 is located on the floor 1 19 and oriented cross-machine. Water is released from this pipe 121 with a low velocity and hits a curved plate 122. The water 'fans-out' and produces a uniform flow of water on the floor 1 19 in the machine direction. This shower can wash across the entire machine width of the floor. The water flowrate is sufficient to wash the broke down into the pulper 125 (see Figs. 27 to 29).
• the spray pipe 121 is designed such that it does not cause atomization of the water which could cause humidity problems within the enclosure zone. This header 121 requires low pressure and high flow for a short duration (perhaps 30 seconds).
• the floor 1 19 can be sloped to one or more other broke chute openings 120. It is a function of existing machine geometries. Fig. 27 shows how it is applied to a machine that has three openings 120.
• Fig. 28 shows how it is applied to a machine that has only one broke chute opening 120.
• a pulper enclosure 127 according to one aspect of the invention will now be described with reference to Fig. 29.
• This aspect of the innovation allows for the containment of the 'bubble' of hot humid air and mist in the pulper 125.
• the exhaust, to be directed outside of the building, is much less than that of a conventional system.
• the pulper 125 has up to three broke chute openings 120. One is located below the creping doctor 21 and optional openings 120 are under the calender 3 and under the reeling station 2. Sometimes, an additional opening (not shown) is included beside the machine for manual disposal of broke.
• a pulper module 20 is positioned at the floor opening below the creping doctor 21 .
• pulper doors 124 are arranged on all broke chute openings 120 with the exception of the opening below the Yankee cylinder 1 , where an air- curtain 128 (see Fig. 30) is used to prevent the escape of mist and vapour into the enclosed zone below the web.
• This system allows for complete control of the pulper's mist and vapour.
• a pulper module 20 according to another aspect of the invention will now be described with reference to Figs. 30 and 31 .
• the pulper module 20 seals the pulper 125 at the operating floor below the creping doctor 21 while allowing for the occasional passage of broke.
• a cross-machine air curtain 128 is used at the pulper floor opening.
• the air curtain nozzle 129 is directed slightly downward from horizontal. During production, the air curtain nozzle 129 is in operation. It accomplishes two tasks:
• Adverse airflows such as those due to trim discharge into the pulper are controlled while needing only a minimal exhaust flowrate.
• the nozzle 129 is a good destination for the supply air. Air that is supplied back into the machine from a recirculation system is air that does not need to be discharged to the atmosphere.
• Fig. 30 shows a pulper module 20 that would be used on a machine that has a single pulper opening below the creping doctor.
• a cross-machine opening 130 on the dry end side of the pulper module 20 allows for the passage of broke from the floor flush system as described above in relation to Fig. 28.
• This opening 130 on the dry end side of the pulper module 20 is only needed in applications where there is only one broke-chute floor opening below the creping doctor. In applications where there are more than one broke-chute openings, the floor flush system would direct the water and broke to the other openings 120 (see Figs. 27).
• the air curtain nozzle 129 could have water mist introduced internally to ensure that it remains clean in situations where the supply air is not very clean.
• a mechanical self-cleaning nozzle design e.g. of the type shown above in relation to Figs. 4 to 6, is another acceptable option.
• An air exhaust module in the form of a cross-machine pulper exhaust header or collector 131 is located above the operating floor.
• An array of vertically oriented intake or pick-up tubes 132 extend from the header 131 and into the top of the pulper 125 adjacent the floor opening 130.
• Each of the intake tubes 132 have a concentric tapered section at it's intake 134 located at the bottom end of the tube 132 (see Fig. 31 ).
• the intake diameter is smaller than the diameter of the main section of the tube 132.
• the intake 134 serves as a venturi throat. Water is introduced to each of the pickup tubes 132 via a semi-tangential water pipe 133.
• Inspection ports are included in the main cross-machine header 131 . They are located on top of the header concentrically above each tube 132.
• a gravity operated pulper door 135 is preferably used.
• the hinged door 135 is made of light-weight stainless steel sheet metal. It is held closed by gravity but it easily opens to allow for the passage of wetted broke 136. It functions like a check-valve.
• a flushing shower 137 preferably having a manual valve is needed to wet the broke and ensure that it moves through the door.
• a manual button and a controls system timer can be used to give a few minutes of flushing with a control valve. Alternatively, water from a floor flush system would suffice.
• the axis of rotation for the door is preferably oriented cross- machine.
• a sloped panel 138 may be added as shown in Fig. 32 or an existing portion of a sloped broke chute wall may serve the same purpose.
• a moving web carries air with it.
• a web is wrapped around a roll (such as a turning roll or a spreading roll)
• some of the boundary layer air gets trapped between the web and the roll. This phenomena reduces traction.
• Fig. 33 shows a roll 196 in the dry end of a tissue machine. Dust-laden air travels over the roll 196.
• a high-pressure zone 197 is formed at the web run- in position 208 and a low-pressure zone 198 is formed at the web run-out positing 209. The high-pressure zone 197 pushes the web 47 away from the roll 196 and the low-pressure zone 198 makes the web adhere to the roll 196.
• the roll dust collector according to the invention has been devised to capture dust at it's source.
• the roll dust collector improves traction while removing the dust laden boundary layer air.
• the roll dust collector 199 (see Fig. 34) can be integrated to a new or existing roll.
• the dust collector 199 comprises a plenum chamber 206 which is open towards the rotating roll 196 such that the roll 196 forms part of the dust collector housing.
• the roll On the upstream side of the interface, the roll is sealed to the roll dust collector.
• the roll dust collector At the downstream side of the interface, adjacent to the web run-in position, the roll dust collector comprises an air intake or exhaust slot 200 running in the cross-machine direction of the dust collector 199.
• the intake slot 200 has an out-going nip. Broke which may land on the intake slot, is dislodged due to the movement of the roll 196. If the exhaust flow is temporarily halted with a divert damper, the air will flow out of the slot due to the pumping action of the rotating roll.
• the roll dust collector housing 201 is sealed to the roll with a sealing device in the form of a doctor blade 202.
• the doctor blade is a light-weight cleaning doctor comprised of plastic or composite material. It is lightly loaded against the roll.
• the sealing device can be made with an airknife.
• an internal vortex airflow pattern is generated because of the internal moving surface of the roll 196. As with conventional dry type dust collectors, the internal vortex serves to help maintain internal cleanliness.
• the volumetric flowrate is determined by predicting the volumetric flowrate of air carried with the boundary layer of the moving web plus any supplemental airflows introduced to the zone upstream of the roll.
• the roll dust collector according to the invention can be applied to almost any in-going nip where a web wraps a roll. It improves traction and contains dust.
• Fig. 35 shows a tissue machine spreader roll 203 equipped with a roll dust collector 199.
• the spreader roll 203 is positioned immediately downstream a slitter 204 comprising saw blades 205 which are adjustable in the cross-machine direction.
• the roll dust collector 199 forms a slitter dust collector in this case.
• an air supply module 9 of the type previously described is used to introduce supplemental air to the zone.
• Fig. 36 shows an example of the dry end of such a machine.
• the dry end comprises four rolls 206, each being equipped with a roll dust collector 199.
• Airflows to the roll dust collector intakes can be primarily boundary layer air or it can be supplemented with low velocity air supply modules that serve as containment curtains. External blowing nozzles can be added to maintain cleanliness of the roll dust collector doctor blades.

Landscapes

• Paper (AREA)
• Woven Fabrics (AREA)

Priority Applications (5)

Applications Claiming Priority (1)

Publications (1)

Family

ID=43598344

Family Applications (1)

Country Status (5)

Cited By (3)

Families Citing this family (13)

Citations (6)

Family Cites Families (1)

• 2009
  • 2009-12-22 US US12/674,643 patent/US20120145347A1/en not_active Abandoned
  • 2009-12-22 EP EP09803763.3A patent/EP2516738B1/en active Active
  • 2009-12-22 BR BR112012015314A patent/BR112012015314B1/pt active IP Right Grant
  • 2009-12-22 WO PCT/EP2009/067794 patent/WO2011076268A1/en active Application Filing
  • 2009-12-22 CN CN200980163154.XA patent/CN102666982B/zh active Active

Patent Citations (6)

Also Published As

Similar Documents

Legal Events