FI78944B - A process and device in a paper machine for collecting and removing dust that comes off the track. - Google Patents

Abstract

A process in a paper machine for collecting and removing dust that comes off the track. In this process, gusts of air are directed at the track (W), which both lifts up the movable paper track (W) without contact and removes dust from it, and addition to at least partially transporting the dust to a collection location (25). The device includes one or more vacuum boxes (30) containing a nozzle box (31) separated by two interstices (34) at whose sides there are coanda nozzles (33) that blow in opposite directions. The interstice (34) is connected to a vacuum space (36) under negative pressure. The nozzle boxes (31) have negative-pressure carrier surfaces (37) that determine the level to which the paper track (W) is raised without direct contact. At the hind side of the vacuum box (30), there is a rear vacuum space (35) that opens onto the passing track (W), and which is joined to the negative-pressure vacuum space (36).<IMAGE>

Description

78944 1 Method and apparatus for collecting and removing loose dust on a paper machine Förfarande och anordning 1 en pappersmaskin för att samla upp och avlägsna Damm som lossnar frän banan 5

The invention relates to a method for collecting and removing dust released from a paper machine.

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The invention further relates to a device for carrying out the method of the invention for simultaneous non-contact support of the web and for collecting and removing dust released therefrom, the device having nozzle boxes with subpalpal bearing surfaces which determine the non-contact support level of the web.

In paper machines, a boundary layer of air is usually formed on both sides of a paper web moving at a fairly high speed, which carries with it dust detached from the web fiber and its fillers. The dust spreads to the environment 20, partly also on the roller coaster. This dust has significant occupational health hazards, especially when it contains various filler wastes.

Particularly pronounced, dust problems have occurred during tissue paper production. Tissue paper of the known type is most commonly made by removing the paper web from the surface of a steam-heated Yankee cylinder with a scraper blade, in which case the web at the same time becomes cramped and creped. During scraping, a particularly large amount of dust is released from the scraper, which the paper web draws in and spreads around it. Thus, the portion between the Yankee cylinder and the winder of the tissue machine is particularly dusty and the dust is ejected from the web and spreads strongly to the environment, especially when the web changes direction with a guide roller or similar guide device such as an air cushion. In practice, tissue grades 35 that contain waste paper, wood chips, and unbleached fibers are the most dusty.

It is an object of the present invention to provide a new method and apparatus by which the dust problems discussed above can be eliminated or at least largely avoided.

It is a further object of the invention to provide such a method and apparatus by which the web can also be reliably guided and, if necessary, changed in its direction.

In order to achieve the above and later objects, the method of the invention is mainly characterized in that in the method blows are applied to the web, which both contactlessly support the moving paper web and remove dust therefrom and at least partially convey the dust to its collection point.

The device according to the invention, in turn, is mainly characterized in that the device comprises one or more dust extraction boxes with two intermediate space-separated nozzle boxes with coanda nozzles blowing in opposite directions or the like, said intermediate space being connected to a vacuum suction space and behind the vacuum cleaner box there is a rear suction space which opens against the passing web and which is connected to a vacuum suction space.

The device according to the invention actively removes and removes dust from the web and, if necessary, also changes the direction of travel of the web. Thus, it is important in the invention that it not only removes the generated dust, but also prevents the dust still trapped in the track from spreading to the environment at a later stage and moving with the rollers to e.g. post-treatment. In the invention, the web is in a way deeply vacuumed.

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A particularly necessary method and device according to the invention is in the area between the scraper and the winder of the tissue machines.

The details of the structure of the device according to the invention can also vary considerably, e.g. because the device according to the invention can bring about very different changes of direction in the course of the track.

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3,78944 in 1 direction. In the past, it was at the points of change of direction that the poly detached from the web particularly strongly and was ejected into its extensive surroundings.

In the following, the invention will be described in detail with reference to the various embodiments of the invention shown in the figures of the accompanying drawing, to the details of which the invention is in no way narrowly limited.

Figure 1 shows a schematic side view of the method and apparatus of the invention applied in a tissue paper machine and the overall dust removal arrangement according to the invention.

Figure 2 shows a first embodiment of a device according to the invention, which is implemented in two sides.

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Figure 3 shows another embodiment of the device according to the invention.

Figure 4 shows a third embodiment of a device according to the invention.

Fig. 5 shows a fourth embodiment of the device according to the invention, in which a remarkably large change of direction is additionally obtained with the dust removal device.

Fig. 1 schematically shows a Yankee cylinder dryer of a tissue paper machine 25 known per se, comprising a Yankee cylinder 10 to which a paper web W is introduced from a forming section by a fabric 12. The fabric 12 passes over press rolls 13 forming a Yankee cylinder 10 with a smooth outer shell the web W is adhered to the surface 11 of the Yankee cylinder 10 and the web W passes through the Yankee-30 hood while drying. The hood consists, for example, of two parts J4a and 14b.

The tissue web W is detached by the blade 18 of the scraper 15 at the detachment point K, whereby the web W at the same time rests and thus crepes. It is at the point K of the detachment-35 that the subsequent run of the web W generates particularly strong dust from the zero fibers detached from the web W, the pieces of fiber and the fillers.

4 78944 1 In connection with the scraper 15 there are dust removal devices comprising nozzle openings 16a, 17a opening on both sides of the scraper blade 18 in connection with the bar of the scraper 15. Said nozzle openings 16a, 17a lead to suction spaces 16, 17 which are connected to a dust separator 5 25 via suction channels 21 and 20. The channels 21 have dampers 19, 22. The suction duct 20 via the suction flow enters in the direction of arrow D, which is obtained by the dust separator 26 via a duct 25 connected to a fan 27.

The dust separator 27 is connected via a suction channel 21 to a first dust extraction box 30A according to the invention, which at the same time non-contact supports the web W without changing its direction. On the opposite side of the web W, after the first dust removal box 30A, there is a second dust removal box 30C, in connection with which the web W changes its direction somewhat. The second dust extraction box 30C is also connected to the suction channel 20 via a suction channel 23 provided with a control damper 24.

In Fig. 1, after the dust extraction boxes 30A and 30C, the web W passes, as is known per se, past the measuring beams 40 to the guide roller 41, through it to the winding cylinder 42, in connection with which a substantially dust roll R is formed due to the method 20 of the invention.

An important feature of the dust extraction boxes 30 according to the invention, of which several different embodiments are shown in Figures 2-5, is that blowing air is introduced into them. 1 according to the first box 25 of Figure 30A of the fan 45 brought to the discharge channel 46 connected to duct 48 through the air blow. Correspondingly, blowing air is introduced from the duct 46 through the duct 47 to the second box 30C. The ducts 47,48 are equipped with control dampers 49.50, by means of which the amount of blowing air can be adjusted. the suction side of the blower 45 with a damper 30 through the channel 43 of the air introduced into the blowing direction of the arrow F direction. The duct 43 can be connected to the outlet duct 28 of the suction fan 27 by a bypass duct 51 with a control damper 52 with which the blowing can be stopped or, if necessary, adjusted. The system takes the exhaust air through the channel 28 in the direction of the arrow FQut.

Various embodiments of the blow box according to the invention will now be described in detail with reference to Figures 2, 3, 4 and 5. It will be appreciated that Figures 2-5 show the devices according to the invention in a machine direction vertical cross-section.

According to Fig. 2, blow boxes 30A and 30B are arranged in succession on both sides of the web W, which are similar in structure. The blow boxes 30 extend over the entire width of the web W and have closed ends which are not shown in the figures for the sake of clarity.

Blowing boxes 30A and 30B comprise nozzle housings 31 having blown channels 32 on opposite sides 10 which open into coanda nozzles 33. On one side, the coanda nozzle 33 abuts a coanda surface 37R having a certain radius of curvature r, the stepless extension of which is planar. a bearing surface 37a which, under the action of the blows and F0, forms a dynamic vacuum field in the region of the bearing surface, which non-contact 15 supports the web W. The nozzles 33 of the nozzle boxes 31 blow in opposite directions F1 and F1. between the nozzle boxes 31 is relatively wide intermediate space 34, through which air is sucked into the space in the direction of the arrow 36, which is a negative pressure because it is one of the suction duct connected to a suction duct as shown in Figure 21 and 23, 20. The blow boxes 31 and 20 in its VAT per se known foil-like nozzles.

Behind the dust extraction boxes 30A and 30B there is a suction space 35 connected to the above-mentioned suction space 36. The suction space 35 opens after the latter bearing surface 37a against the web W and sucks air and with it dust away from the web 25 partly due to the air flow F-. The blows F 1 and F 2 actively remove dust from the web W as well as the air flow F- in the suction space 35. This dust is transported in the direction of arrow D into the dust separator 25.

Thus, the device according to the invention not only collects loose dust already entrained by the track 30 due to boundary layer flows, but also

According to Fig. 2, the direction of the web does not change in the area of the bearing surfaces 37a, 37b of the non-contact dust removal boxes 30A and 30B.

Fig. 3 shows an embodiment of the invention in which, in the area of the dust removal box 30C, at the same time the direction of the web W is changed at a small angle c. This change of direction is effected in such a way that the main directions of the planar or somewhat curved foil support surfaces 37c are at a small angle to each other so that the direction of the web W changes at an angle c. In other respects, the structure of the dust removal box 30C shown in Fig. 3 is as described above in Fig. 2.

Fig. 4 shows an embodiment of the invention in which the dust-10 removal box 30D causes a change of direction of the web W at a relatively large angle d. This is achieved by the mutual arrangement of the curved bearing surfaces 37d of the nozzle boxes 31.

Fig. 5 shows an embodiment of the invention comprising three nozzle boxes, namely edge boxes 31 as described above, with vacuum bearing surfaces 37e, the main direction of which is at a considerable angle to each other. Between the edge boxes 31 there is a third nozzle box 38, which is overpressurized and operates in a so-called float principle. This nozzle box 38 has two opposite blowing channels 39, the coanda nozzles 39a and 39b of which blow in the direction of the arrows Fg opposite each other, forming an overpressure support area for the bearing surface 37e +. The blows particularly effectively separate the dust from the web W. Between the nozzle boxes 31 and 38 there are spaces 34a and 34b connected to the suction space 36 for the above purpose.

With the nozzle box 30E shown in Fig. 5, a change of direction is obtained in the web W, which is particularly large so that the angle of change e is of the order of 90 ° or more. At the same time, a particularly efficient dust removal is achieved.

The suction flow F- of the dust extraction and support blows to the suction space on the discharge side of the web provides efficient dust removal and at the same time non-contact support of the web, which may be based on vacuum foil nozzles, as shown in Figures 2, 3 and 4, or foil nozzles. in addition to the overpressure bearing surface connected to the bearing surface 37e + of the float nozzles. According to the invention

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7 78944 Ί Due to non-contact support, even the holes in the track do not cause track breaks.

The air velocities in the front and rear nozzles 33, i.e. the velocities of the blowers Fj and? 2 5, are preferably equal to each other and the air velocity v is of the order of v = 10-30 m / s. In the rear suction mode 35, the air flow speed is of the order of 5 m / s or less. The widths of the nozzle slots of the Coanda nozzles 33 and 39a, 39b are of the order of s = 1-5 mm, preferably about 2 mm. Most preferably, the width of the intermediate space 34 is generally in the range 1 ^ * = 50-150 mm and the width of the rear space 10 35 = 50-100 mm.

The dust extraction boxes 30 according to the invention can be moved out of the path of the track W, e.g. in track break situations. An example of this is the lower dust extraction box 30A shown in Figure 1, which is pivoted about the articulation shaft 55 on the arms 54 in the lower position 30 'in the event of a track break.

In the following, the claims are set forth within the scope of the inventive idea defined by which the various details of the invention may vary and differ from those set forth above by way of example only.

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Claims (10)

1. A method in a paper machine for collecting and removing danu that is released from the web, characterized in that during the process, blows are directed at the web (W), which blows carried the movable paper web (W) without contact and detach dust from this and in addition at least partially transport the dust to the collection site (25) for this. 10 Method according to claim 1, characterized in that the vacuum cleaning treatment according to the method is directed to the two opposite sides of the web (W). 3. A method according to claim 1 or 2, characterized in that the method uses blows which are directed in connection with the support surfaces (37), between themselves in opposite directions, which blows form a negative pressure field in connection with the support surfaces, which supports the web. (W) and providing a rear suction space (35) in communication with the web (W) which is joined to a source of pressure as well as the intermediate space (34) of said carrier blisters 1, F 2 (Fj, F2) is led into the suction compartment (36). Method according to any of claims 1-3, characterized in that the direction of the web (W) is changed in the method on the same thread as the support and vacuum suction blades are directed towards it (Figures 3,4 and 5). Method according to any one of claims 1-3, wherein one or more dust removal trays (30), characterized in that said dust removal trays (30) are connected to a dust separator (25) by means of a suction channel (20), which separator is connected to the suction side of the suction blower (27) and that blowing air is introduced into said dust removal trays (30) by means of a blower (45). 35 Method according to claims 1-3, used in connection with a tissue paper machine in the area between its yankee cylinder (10) and the wheelchair device (42), characterized in that it is connected to the shaver (15) which operates against the yankee cylinder, which is most conveniently a creping blade, has provided suction blades (16,17), the suction openings (16a, 17a) of which open into contact with the blades blade (18) and that said suction blades (16,17) are connected to the vacuum suction system. A dust separator (25) and with a suction blower (27). Device for carrying out the method according to any of claims 1-6, for simultaneous contactless support of the web (W) and the collection and removal of dust discharging therefrom, in which device nozzle slides (31) are provided. , where there are suppressed support surfaces (37), which determine the contact-free support level of the web (W), characterized in that the device comprises one or more vacuum suction drawers (30), where there are two of said nozzle drawers (31) separated by an intermediate space (34), on whose sides there are coanda nozzles (33) or equivalent blowing in opposite directions, that said intermediate space (34) is joined by a suction space (36) under vacuum and that on the rear of the vacuum suction drawer (30) there is a rear suction compartment (35) which opens to the bypass path (W) and which Mr is joined to the suppressed suction compartment (36). 8. Apparatus according to claim 7, characterized in that the support surfaces (37c, 37d, 37e) of the nozzle drawers (31,38) of the vacuum suction drawers (30C, 30D, 30E) are thus positioned between them and designed so that the web (W) Changes its direction at a given angle (c; d; e) at the pass past the vacuum cleaner drawer and over it (Figures 3,4 and 5). 9. Device according to claim 7 or 8, characterized in that the device includes, apart from said outermost nozzle case (31), a third nozzle case (38) placed between them, which limits the intermediate spaces (34a, 34b) with the outermost nozzle case. (31), which interstices (34a, 34b) Mr joined by a suction space (36), such as Mr joined by a suction channel (20). 35 io. Device according to claim 9, characterized in that said middle third nozzle case (38) comprises two nozzles blowing in opposite directions, most preferably