METHOD FOR REMOVING DUST IN CONNECTION WITH THE SHEET CUTTER OF A PULP DRYING MACHINE OR EQUIVALENT AND ARRANGEMENT FOR CARRYING OUT THE METHOD

Abstract: The invention concerns a method and an arrangement for removing dust in connection with the sheet cutter (10) of a pulp drying machine or equivalent. In the method, in the sheet cutter (10) of the pulp drying machine, the pulp web (W) is slit in a slitter unit (11) into longitudinal component webs, which longitudinal component webs are further cut in the cutter unit (12) in the cross direction into sheets (W'). In the method, dust that is formed in connection with the slitter unit (11) and/or with the cutter unit (12) in the sheet cutter (10) is removed by means of at least two dust removing devices (31; 32; 33) placed in substantial vicinity of the slitter unit (11) and/or of the cutter unit (12).

Description: Method for removing dust in connection with the sheet cutter of a pulp drying machine or equivalent and arrangement for carrying out the method The invention concerns a method for removing dust in connection with the sheet cutter of a pulp drying machine or equivalent, in which method, in the sheet cutter of the pulp drying machine, the pulp web is slit in a slitter unit into longitudinal component webs, which longitudinal component webs are further cut in the cutter unit in the cross direction into sheets, in which method the cutting is carried out preferably inside an encapsulated space. Further, the invention also concerns an arrangement for carrying out the method for removing dust in connection with the sheet cutter of a pulp drying machine or equivalent, which sheet cutter comprises a slitter unit, a cutter unit, and control units for conveying the pulp web. In a sheet cutter for pulp, in slitting and cutting, a considerable amount of dust is produced. In the sheet cutter and in the following sheet baling press, the dust causes various problems. The dust causes, for example, problems of runnability, such as web breaks, which arise from disturbance in the operation of photocells and of the bale press. Further, clods of dust may cause increased and prolonged servicing and maintenance standstills. Also, dust may cause risk of fire and explosion and, of course, it also causes contamination of the working environment and impurity of the air for breathing. Thus, in a sheet cutter for pulp, dust removing devices are needed to eliminate these problems. As is well known, attempts are made to encapsulate the sheet cutter. The reasons for this encapsulation are a) attenuation of noise, restricting of the dust problems, and c) isolation of the revolving blade part out of reasons of safety at work. Thus, the object of the present invention is to suggest a solution for the problems described above. An object of the invention is to provide an arrangement in which, in the method, the dust is removed at an optimal location and by means of an optimal quantity of air. Further, the construction of the dust removing arrangement is such that it does not cause further problems around the sheet cutter, i.e. it does not cause falling of dust clods onto the web, blocking of the constructions, or disturbance in the operation of the blades in the sheet cutter. In view of achieving the objectives stated above and those that will come out later, the method in accordance with the invention is mainly characterized in that, in the method, dust that is formed in connection with the slitter unit and/or with the cutter unit in the sheet cutter is removed by means of at least two dust removing devices placed in substantial vicinity of the slitter unit and/or of the cutter unit. On the other hand, the arrangement in accordance with the invention for carrying out the method is mainly characterized in that the arrangement comprises at least two dust removing devices, which are placed in substantial vicinity of the slitter unit and/or of the cutter unit. In the direction of progress of the pulp web W, after the slitter unit 11 , the following nip formed by the pair of rolls 14 separates dust from the web and stops the dusty boundary-layer flow. Likewise, the nip formed by the pair of rolls 15 following after the cutter unit 12 separates dust from the web and stops the dusty boundary layer. The outlets 32 and 33 have been fitted below the pair of rolls 14,15 following after the slitting and cutting so that the dust swirling in front of the nip can be removed. By means of the method in accordance with the invention, efficient removal of dust is achieved in connection with the sheet cutter, whereby the problems caused by dust can be eliminated or at least minimized. The dust removing devices used in the arrangement in accordance with the invention extend substantially across the web and are fitted in compliance with the construe- tions and placed at locations at which dust is formed, and their air quantity is optimized so that the removal of dust is efficient. The dust that is formed in slitting moves at the face of the web in the direction of the web, and the dust removing devices used in connection with slitting in the sheet cutter are placed across the web so that the suction takes place at the locations where the concentration of dust is highest and before the dust is spread more widely. In connection with the cutting in the sheet cutter, an abundance of dust is formed, which swirls in the vicinity of the cutter unit, in which case the dust removing devices are placed preferably at both sides of the web in direct vicinity of the cutting blades. In this way, the dust is caught before it can be spread more widely. In the arrangement in accordance with the invention, preferably a suction box is used as the dust removing device, to which suction box a vortex flow has been applied, which prevents adhering of dust on the faces in the suction box. The suction box that is used may include one or several suction slots, through which the air that contains dust is sucked away from the vicinity of the source of dust. The dust suction box can be integrated in the frame or box constructions of the sheet cutter so that the beams that run in the cross direction of the cutter are shaped suitable for the purpose. The vortex suction boxes are also shaped and placed so that the suction flow flushes all the inside faces in the encapsulated area in the cutter and keeps said faces clean, in which case no dead corners or equivalent shapes that gather dust remain in connection with the areas in which dust is formed. In the following, the invention will be described in more detail with reference to the figures in the accompanying drawing, the invention being, however, not supposed to be in any way strictly confined to the details of said illustrations. Figure 1 is a schematic illustration of a sheet cutter of a pulp drying machine and of the dust removing arrangement in said cutter. Figure 2 is a schematic illustration of a vortex suction chamber for use in connection with the dust removing arrangement. As is shown in Fig. 1 , the sheet cutter 10 in the pulp dryer comprises a slitter part 11 and a cutter part 12. The dried pulp web W is passed through the guide roll unit 13 into the slitter 11, in which the pulp web W is slit into longitudinal component webs. After this, the pulp web passes into a drive roll unit 14, from which the pulp web W is passed into the cutter unit 12, in which the component webs are cut off in the cross direction into sheets W of the desired length. The sheets are passed through the guide roll units 15, 16, 17, 18,19 to the bale press unit 20. In the sheet cutter 10 of the pulp dryer, the cutter unit 12 is fitted inside a box construction 25, and the function of said box construction 25 is attenuation of noise and prevention of dust spreading as well as prevention of accidents that may occur to the employees in connection with the revolving blades. In order that the dust formed in the slitter unit 11 and in the cutter unit 12 should not deteriorate the runnability of the sheet cutter 10 or be carried along with the web W, in the interior of the box construction 25 dust removals 31,32 and 33 have been arranged. The encapsulation 25 extends to above the cross-cutter unit 12 and the drive roll unit 14, and in its interior there is a dust removal 31 , and the orifice 31b of its exhaust pipe or equivalent is opened in direct vicinity of the cutter blade 12a of the cross-cutter unit 12, at its inlet side, as viewed in the direction of progress of the web. The dust removal 31,31a extends across the machine width. The dust formed in the slitter unit 11 moves on the web W face in the direction of the web and is carried into the area of the dust removing device 31 , which thus also absorbs dust that has been formed in the slitter unit (arrow Si). Below the pulp web, before the blade beam 50, as viewed in the running direction of the web, the second dust removing device 32 has been fitted to open. Below the cross-cutter unit 12 and below the pulp web W, additionally a third dust removing device 33 has been fitted, by whose means the dust formed in connection with the cutting is absorbed, which dust swirls in the vicinity of the cutter unit 12. The suction beams 32,33 have been fitted below the following pair of rolls, as viewed in the direction of progress. Out of the dust removing devices 32,33 placed below the web W, the air that contains dust is passed along the system of ducts 34,35 to the dust exhaust 37 into its collecting and exhaust duct. The dust removed from the upper dust removing device 31 is also passed to the dust exhaust, through the suction box 31A into the duct 36 and from it further into the dust exhaust duct 37. The air that contains dust is passed along the exhaust duct 37 into an air cleaning device or equivalent. The dust removing devices 31,32,33 comprise one or several suction openings, which extend substantially across the entire width of the web W and remove the dust that is formed in connection with the slitting and cutting. In the exemplifying embodiment shown in Fig. 1 , the dust removing devices 32,33 placed below the web W comprise a vortex flow suction box, which is described in more detail in connection with the description related to Fig. 2, and the dust removing device 31 is a general remover, by whose means dust is removed from the area above the web. The quantities of air that are used in the dust removing devices are optimized so that the dust formed in connection with the slitting and cutting can be sucked off effi- ciently from the areas of slitting and cutting and from the interior of the box 25 of the sheet cutter 10. The quantities of air used in each dust removing device may be: Dust remover 31 0.05...1.5 cu.m per second per metre Dust remover 32 0.05...1.5 cu.m per second per metre Dust remover 33 0.05...1.5 cu.m per second per metre. In connection with cross-direction cutting, it is also possible to employ a dust removing device fitted at one side only, for example, to omit the upper dust removing device when most of the dust is passed in the sheet cutter to below the cutter. The dust removing device 32,33 may be composed of a suction box as shown in Fig. 2, into which a vortex flow has been arranged. The vortex flow P produced in the suction box 32,33 prevents adhering and gathering of dust on the faces. Such a vortex suction box 32,33 can be constructed as a unit of its own, or it can be integrated in the frame or box constructions of the cutter 10 so that the beams passing across the cutter are shaped as suitable for the purpose. Also, if necessary, the frame constructions of the cutter can be used as air ducts in the dust exhaust arrangement. The vortex suction boxes 32,33 are shaped and placed so that the air flow flushes all the inside faces in the encapsulated 25 area in the cutter and keeps them clean, such as, for example, in the arrangement as shown in Fig. 1. In the construction shown in Fig. 2, the flow slot E can be regulated across the machine width by means of a screw device R. There are preferably several screws R fitted over the length of the flow gap slot E. In such a case, the dust catching capacity of the suction beam 32,33 can be regulated in any arbitrary way. For example, the catching capacity can be regulated to be invariable, or the suction in the lateral areas can be enhanced. As is shown in the figure, below the pulp web, there is additionally a broke conveyor 55, preferably a belt conveyor. The running direction of the top run M' of the belt M is denoted with the arrow Di . In the vicinity of the end of the belt M, a vertical second end wall N has been fitted, and the wall at the outlet side of the broke fall space T at the belt M is a curtain jet J, which is produced from the nozzle beam 60 through nozzle openings/slots/slot. The curtain jet J extends across the whole machine width and belt width. Thus, the broke fall space T is closed towards the environment and, thus, encapsu- lated. By means of the air jet, i.e. the so-called curtain jet J, passing of impurities and dust into the factory space is prevented. Thus, by means of the dust removing device 33, dust is also removed out of said broke fall space T and, thus, detrimental carriage of dust into the environment is excluded. The curtain jet J at the conveyor 55 efficiently prevents carriage of dust along with the conveyor run into the environ- ment. The wall N and the curtain jet J together make the space T encapsulated. The lower part of the cutter can also be carried into effect without encapsulation and without a related curtain blowing/blowings. Above, the invention has been described with reference to some preferred exemplify - ing embodiments of same only, and the invention is, however, by no means supposed to be strictly confined to the details of said embodiments. Many modifications and variations are possible within the scope of the inventive idea defined in the following patent claims.

Claims: Claims 1. A method for removing dust in connection with the sheet cutter (10) of a pulp drying machine or equivalent, in which method, in the sheet cutter (10) of the pulp drying machine, the pulp web (W) is slit in a slitter unit (11) into longitudinal component webs, which longitudinal component webs are further cut in the cutter unit (12) in the cross direction into sheets (W), characterized in that, in the method, dust that is formed in connection with the slitter unit (11) and/or with the cutter unit (12) in the sheet cutter (10) is removed by means of at least two dust removing devices (31;32;33) placed in substantial vicinity of the slitter unit (11) and/or of the cutter unit (12). 2. A method as claimed in claim 1, characterized in that the lower dust removing device / lower dust removing devices (32,33) absorb(s) dust from below the pair of rolls (14, 15) following after the slitting or cutting. 3. A method as claimed in claim 1 , characterized in that, in the method, dust is removed by means of two dust removing devices (31,33) from substantial vicinity of the cutter unit (12) from below and above the web (W). 4. A method as claimed in claim 1 , characterized in that, in the method, dust is removed by means of three dust removing devices (31,32,33) so that one dust removing device (31) removes dust from above the slitter unit (11) and from above the cutter unit (12) from substantial vicinity of the dust formation area, and dust is removed from below the web (W) by means of two dust removing devices (32,33) from below the slitter unit (11) and from below the cutter unit (12). 5. A method as claimed in any of the claims 1 to 4, characterized in that, in the method, as a dust removing device, a vortex suction box (32,33) is used, in which vortex suction box a vortex is produced in the air that contains dust, by means of which vortex adhering of dust to the face of the suction box is prevented (FIG. 2) and absorption of the dust from the interior of the encapsulation box (25) into the dust removing box is promoted. 6. A method as claimed in any of the claims 1 to 5, characterized in that, in the method, the total air quantity that is used in the dust removing devices is 0.1...3.0 cubic metres per second per metre, preferably 0.5...1.0 cu.m per second per metre. 7. A method as claimed in any of the preceding claims 1 to 6, characterized in that, in the method, dust is removed from below the pulp web by means of a dust removing device (33), which absorbs dust also from above the broke conveyor (55), in which connection, in the solution of equipment, the space (T) above the conveyor belt (H) of the broke conveyor (55) has been encapsulated by, as one wall of the encapsulation, employing a curtain jet (J) in the vicinity of the belt (M) of the broke conveyor (55). 8. An arrangement for carrying out the method as claimed in any of the claims 1 to 7 for removing dust in connection with the sheet cutter of a pulp drying machine or equivalent, which sheet cutter (10) comprises a slitter unit (11), a cutter unit (12), and control units (13, 14, 15, 16, 17,18, 19) for conveying the pulp web (W), charac- terized in that the arrangement comprises at least two dust removing devices (31;32;33), which are placed in substantial vicinity of the slitter unit (11) and/or of the cutter unit (12). 9. An arrangement as claimed in claim 8, characterized in that the arrangement comprises two dust removing devices (31,33), which are placed in substantial vicinity of the cutter unit (12) and one of which is placed above the web (W) and the other one below the web (W). 10. An arrangement as claimed in claim 8 or 9, characterized in that the arrange- ment comprises three dust removing devices (31,32,33), of which two (32,33) are placed below the pulp web (W) to be slit and cut, one (32) of them in substantial vicinity of the slitter unit (11) and the other one in substantial vicinity of the cutter unit (12), whereas one device (31) is placed above the pulp web (W) to be slit and cut. 11. An arrangement as claimed in any of the claims 8 to 10, characterized in that the dust removing devices (32,33) (FIG. 2) are vortex suction boxes, and that the vortex suction box comprises screws (R), by whose means the flow slot (E) can be regulated across the machine width. 12. An arrangement as claimed in any of the claims 8 to 11 , characterized in that the dust removing devices (31,32,33) communicate with the dust exhaust system (37) through suction ducts (34,35,36). 13. An arrangement as claimed in any of the claims 8 to 12, characterized in that the arrangement comprises an encapsulated (25) space above the cutter unit (12). 14. An arrangement as claimed in any of the preceding claims 8 to 13, characterized in that, below the pulp web (W), the arrangement comprises a broke conveyor (55), whose broke fall space (T), out of which the broke is removed further, is closed towards the environment by means of a curtain jet (J), and which broke fall space (T) further comprises a wall (N), by whose means the space (T) is encapsulated, in which connection, by means of the dust removing device (33), dust and impurities are removed out of said space (T) placed below the pulp web (W) . 15. An arrangement as claimed in any of the preceding claims 8 to 14, character- ized in that the dust removing device/devices (32,33) placed below the pulp web (W) has/have been fitted below the pair of rolls (14, 15) that follows after the slitter/cutter unit (11, 12).

Inventors: AALTONEN RAMI, ENKVIST JENS PETTER, HANNUS LARS HAAKAN MIKAEL, LEIMU JUHA, LINDSTROEM JAN, AALTONEN, RAMI, ENKVIST, JENS, PETTER, HANNUS, LARS, HAAKAN, MIKAEL, LEIMU, JUHA, LINDSTROEM, JAN
Applicants: AALTONEN RAMI, ENKVIST JENS PETTER, HANNUS LARS HAAKAN MIKAEL, LEIMU JUHA, LINDSTROEM JAN, VALMET CORP, AALTONEN, RAMI, ENKVIST, JENS, PETTER, HANNUS, LARS, HAAKAN, MIKAEL, LEIMU, JUHA, LINDSTROEM, JAN, VALMET CORPORATION
Application year: 1997
Main classification: B26D7
IPC codes: B26D7