FI73478B - ANORDNING FOER KONTAKTLOES STABILIZERING UPPBAERING OCH / ELLER TORKNING AV EN ROERLIG BANA. - Google Patents

Description

73478 1 Apparatus for non-experimental stabilization, support and / or drying of a moving track Anordning för contactlös stabilization, uppäräring och / eller torknlng av en rörlig bana 5

The invention relates to a device for non-contact stabilization, support and / or drying of a moving web, in particular a paper web or the like, which device comprises a blast box or boxes extending substantially the entire width of the web, into which blowing air can be introduced and which box comprises a supported web. a support surface fitted against which air jets are blown from said box, by means of which a vacuum contact of the non-contact track is provided, and the support surface of the blowing box has generating sub-beam fields supporting the track, and which blows in opposite directions are arranged in the ejection air from the surface of the surface between the support surfaces to maintain the lower beam area.

Various air nozzles are used in gas blowing devices used in a papermaking and processing machine for non-contact cleaning, drying and stabilization of the web. With these 25 nozzles, the gas to be blown is led to one or both sides of the web to be treated, after which the gas is sucked out for re-use before the next nozzle.

These known nozzles can be divided into two groups, namely over-30 bellows nozzles and under-bellows nozzles. The operation of overpressure nozzles is based on the so-called to the air cushion principle, where the air jet causes a static overpressure in the space between the nozzle and the web.

The sub-nozzle nozzles include the so-called alrfoll nozzles that attract the web 35 and stabilize the web flow. The attraction to Ralna is known to be based on a gas flow field parallel to the web, which due to its flow state forms a static vacuum support surface for the web and the nozzle 73478 2 1, the so-called bearing surface. Both overpressure and vacuum nozzles often use so-called coanda effect to direct air in the desired direction.

Known overpressure nozzles direct sharp jets of air against the web.

Such a local air jet greatly enhances the heat transfer in the jet and web meeting areas, thus causing an uneven distribution of the heat transfer coefficient along the length of the web, which may cause quality damage to the web to be treated. An additional disadvantage of using overpressure nozzles is that they cannot be used for one-to-one side treatment of the web due to overpressure.

With regard to the patent literature related to the present invention, reference is made to the following patent publications: US-3,587,177, DE-AS 2,020,430, FI-42522, SE-393,826 and SE-408,888.

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Em. The construction of the vacuum nozzles known from U.S. Pat. No. 3,587,177 and DE-AS 2,020,430 is characterized in that the nozzle gap opening on the inlet side of the nozzle bearing surface is extended to a curved flow guide surface associated with the front edge of the bearing surface so that the flow follows the bearing surface. The disadvantage of these known nozzles is that the blowing in the direction of the web tends to eject already dried cooling gas from the previous suction space, thus reducing the temperature difference between the web and the drying gas and thus the heat transfer capacity. These nozzles have a very small distance (2-3 mm) from the web to the bearing surface, which places great demands on the evenness and straightness of the drying surface (bearing surface) composed of the nozzles. This places high demands on the construction of wide (> 3 m) overhead nozzles.

Em. FI-pat 42522 discloses a nozzle in which air is blown on one side of the web in jets substantially parallel to it, which cause discontinuities in the width direction of the web, for which reason the heat transfer capacity is uneven. For the same reason, the stability of the track is also poor, and this nozzle cannot handle thin tracks due to the flutter that occurs in them. Also, high blowing speeds 35 cannot be used in this nozzle, and this nozzle is not suitable for double-sided handling of the track.

In addition, reference is made to the applicant's FI-pat. No. 68723, wherein the air dryer 73478 3 1 nozzle shown is characterized in that the nozzle gap is located in the gas flow direction before the plane of the inlet edge of the curved guide surface and that the ratio of the nozzle gap width to the radius of curvature of said guide surface -5 ta of the guide surface substantially before its trailing edge. Em. The facts realized in the FI patent can be used in connection with this invention, as applicable.

With current large-scale papermaking or further processing machines 10, the equipment consisting of these nozzles becomes large, bulky and expensive. Due to the poor stabilizing ability of the known nozzles, unilateral handling of heavy material webs has previously only been possible only in a horizontal plane with the blowing below the web. This has been able to limit the design of the drying section and increase the size of the machine and the building.

The object of the present invention is to avoid the above drawbacks and to provide a nozzle device based on the vacuum principle, by means of which the stabilizing ability of the device in particular can be improved.

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The free unsupported exports (strokes) of the paper web in the drying section of the paper machine constitute a risk factor, causing the risk of web breaks, because at said free gaps the web tends to flutter when unsupported. Particularly emphasized is the problem in the two-to-25 wire export drying groups of a paper machine, where the paper web passes from one cylinder line to another in free traction. With regard to these problems, reference is made to the applicant's patent US-4,075,768 (issued February 28, 1978), which seeks to eliminate these problems by shortening said free bets. This solution also has its own problems and limitations.

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It is therefore an object of the present invention to provide a non-contact stabilizing device for a paper web which is suitable for use in the drying sections of a paper machine with free web gaps of two-wire export groups for stabilizing the web.

The object of the invention is to provide such a device which is suitable for use in a paper machine other than the above-mentioned object for stabilizing the web. Areas of application of the invention also include fluidized bed dryers, paper web export and processing steps after glue presses and other coating devices.

In this connection, it should be emphasized that the object of the present invention is to further develop continuous track support, drying and / or stabilization devices based specifically on vacuum nozzles.

In order to achieve the above and later objects, the invention is essentially characterized by an intermediate surface between said support surfaces at a considerable perpendicular distance from their plane on the blow box side, at which the length of said vacuum area to be ejected in the track direction is substantially greater than said bearing surfaces.

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

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Figure 1 shows a schematic cross-sectional view of a "short" model of a blowing device according to the invention.

Figure 2 shows (seen from above) the same as Figure 1.

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Figure 3 shows blow molding devices according to the invention applied to a fluidized bed dryer for paper or board.

Figure 4 shows an apparatus according to the invention applied as a free tension stabilizer of a paper web 30 in a multi-cylinder dryer of a paper machine.

Figure 5 shows a modification of the embodiment of Figure 4.

Figure 6 shows a "long" model 35 of a blowing device according to the invention in a schematic cross-sectional view.

5,7478 1 Fig. 7 shows an application of the blowing device according to Fig. 6 in the application corresponding to Fig. 4.

The device shown in Figures 1 and 2 comprises a blow box 10 which is substantially trapezoidal in cross-section. The blow box 10 of Figure 1 represents a "short" model of the invention while Figure 6 represents a "long" model. The blow box 10 is intended for stabilizing, supporting and / or drying a moving web, e.g. a paper or cardboard web W, without mechanical contact. The blow box 10 10 is bounded by side walls 11, 12a and 12b and end walls 17. The active intermediate surface of the blow box 10 opposite the web W to be stabilized, supported and / or dried comprises a wall 14 and folds 14a and 14b at its edges. The support walls 13a and 13b are connected to the side walls 12a and 12b by a sharp fold, as an extension of which are torn wall portions 15R. The extensions of the parts 13R are planar walls 15a and 15b. The wall portions 14a, 15a and 14b, 15b define in pairs two nozzle slots 16a and 16b, the blowing direction of which is at a certain acute angle α with respect to the planes of the support surfaces 13a, 13b. Essential to the invention is that the blowing directions of the nozzle slots 16a and 16b are opposite to the invention, i.e. they have a considerable component extending outwards from the box 10.

An air tube 20 with an adjusting flap 19 for adjusting the pressure level of the box 10 is introduced into the blow box 10. On the inlet side of the web W, there is a curved tongue 18 attached to the second support surface 13b of the blowing box 25, which guides a narrow headband cut from the web.

The operation of the device described above is essentially as follows. The blow air introduced inside the blow box 10 is discharged as air jets Fa and 30 Fb through the nozzle slots 16a and 16b. The air jets Fa and Fb turn the curved surfaces 15R in connection with the nozzle slots 16a and 16b parallel to the support surfaces 13a and 13b by the so-called coanda effect. The air jets Fa and Fb are discharged from the trailing edges of the support surfaces 13a and 13b into the outside air.

The air jets Fa and Fb provide a dynamic vacuum field in connection with the support surfaces 13a and 13b, which attracts the web W to a certain distance, thus stabilizing the passage of the web. The air jets Fa and Fb also eject air from the interface between the support surfaces 13a, 13b in the direction of the arrows Ea and Fb EB so that a vacuum field is created in the area A- at the walls 14 and 14a, 14b, which is also used to support the web W 5. and / or stabilization. The wall 14 may have adjustable openings through which the A-pressure level in the area A can be adjusted, if necessary.

In order for the device described above to function as intended, it must be dimensioned and its process parameters selected in view of the inventive mode of operation of the device.

In Fig. 1, the length of the area between the support surfaces 13a and 13b in the direction of travel of the web W is denoted A: 11a. The corresponding length of the planar portion of the support surfaces 13a and 13b is denoted by B. It should be noted that the device is most suitably symmetrical for 15 minutes with respect to its mean plane K-K. The distance 14 of the vacuum area A wall from the support plane C-C (13a to 13b) is denoted by H. In Figure 2, the transverse width of the device is denoted by Lili and the width W of the web by La. The width of the nozzle openings 16a and 16b is denoted by s. The following are some examples of the above dimensions, their suitable areas and relationships. The width of the vacuum area A = (2-6) x B. The distance H of the wall 14 from the bearing surface C-C Η £ ί B. The width of the nozzle gap s = 2..10 mm, preferably s = 3..5 mm. Dimension B is usually B * 50..100 mm.

From the outlet directions of the blows Fa and Fb as they discharge from the nozzles 16a 25 and 16b, there is a certain angle α with the planes of the support surfaces 13a and 13b. Said angle α is generally in the range α = 20 ° to 60 °, preferably α = 40 ° to 50 °.

As for the process parameters, the overpressure prevailing inside the blow box 10 is of the order of p = 500 Pa. The discharge velocities of the blows Fa, Fb from the nozzle slots 16a, 16b v - 10-50 ms / s, preferably v 25 - 30 m / s. The A-vacuum of the vacuum space is of the order of 10..100 Pa. The dimension H depends on the width s of the nozzle gap, so that the larger s is the larger H must be used.

As shown in Fig. 2, the width of the device in the transverse direction of the web W is slightly larger, e.g. about 5% larger than the width Lq of the web W to be stabilized, supported and / or dried. This allows the web W to "live" slightly in the transverse direction.

It is essential for the operation of the device according to the invention that the effects of the opposite blows Fa and Fb provided by the coanda nozzles 16a, 16b create underlying support surfaces Ka and Kb in connection with the planar bearing surfaces 13a and 13b, between which said blows Fa and Fb -eine region A-, the dimension A of which in the direction of travel of the web W is several 10 times, generally about 2-6 times the corresponding width B of the bearing surfaces 16a and 16b.

The blow box 10 according to the invention with a special nozzle and bearing surface arrangement can be used in different positions for different tasks. Some preferred embodiments of the invention are illustrated in Figures 3, A and 5.

According to Fig. 3, the nozzle boxes 10A, 10B and 10C are arranged to form the support plane C-C of the fluidized bed dryer. The blows Fa, Fb of the blow boxes 10A, 10B, 20 10C discharge (F) from the space T (F) between the blow boxes to be re-dried and used or removed. The non-contact supported and at the same time drying web W of the fluidized bed dryer 11a runs low undulating below the nozzles as the bearing surfaces Ka, Kb and the vacuum areas A- and the gaps Vo vary.

25 The length Vo of the gaps is substantially equal to the length B of the support surfaces. The support surface C-C does not necessarily have to be a plane, but can also be curved. Because the nozzles are located above the web W, soiling of the nozzles does not become a problem, as is the case with devices with double-sided blowing or bottom nozzles.

When the device consisting of the blow boxes 10 according to the invention is used for drying, the space of the blow air jets Fa and Fb must be suitable for drying.

Figures A and 5 show two examples of the use of the device 35 73478 8 1 according to the invention as a stabilizer for the free web tensions W of a multi-cylinder dryer of a paper machine. According to Figure 4, the blow box 10 according to the invention has been used in a drying rack with a two-wire outlet, which comprises a row of upper cylinders 21 and 22 and a row of lower cylinders 27.

5 The planes T1 and T2 between said rows of cylinders have a constant distance. The web W is supported by upper drying cylinders 25, 26 guided by guide rollers 23, 24 and lower cylinders by drying wire 29 guided by guide rollers 28. In Figure 4, the upper cylinders 21,22 belong to different wire groups (different wires 25 and 26).

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As it moves from one wire group to another and from the upper cylinder 21 to the lower cylinder 27, the web W normally runs as a free unsupported tension W. Figure

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4 is for said free bet V? adapted according to the invention

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a blow box 10, the support areas Ka and Kb of which and the vacuum area A-15 therebetween stabilize the web W so that its flutter and vibrations are reduced. The blow box 10 is arranged substantially halfway between the free draft WP so that the distances VI = V2. In this way, the free space W is halved and the flutter of the web is substantially reduced. It is known that the flutter of the web causes breaks in the web, especially at the beginning of the drying section 20, while the web is still relatively moist. This risk is substantially reduced by the blow box 10 provided according to the invention.

The embodiment shown in Fig. 5 substantially corresponds to that shown in Fig. 4, with the difference that in the wire group to which the cylinder 21 'belongs, the drying cylinders are arranged below the normal plane T1 so that the free pull Wpo is shorter than normal. A blow box 10 according to the invention is arranged for this free draft Wpo, which halves the free draft Wpo so that the distance V10 = V20. In other respects, the stabilization-30 arrangement is as shown in Figure 4.

Fig. 6 shows an example of a "long" model of a blow box according to the invention, in which the length of the active support surface of the box 10 with respect to the cross-sectional area of the blow box is relatively larger than in the "short" design of the blow box 10 shown in Fig. 1. The structure and operation of the blow hose 10 shown in Fig. 6 are essentially the same as those shown in connection with Fig. 1, with the following exceptions. The wall 12a of the blower box 9 73478 1 coincides with the support surface 13a by a substantially rounded part, the curvature of which is marked R: 11a, respectively, the wall 12b joins the support surface 13b with a part having a radius of curvature. Radius of curvature> R ^. The support surfaces 13a and 13b are not in the same plane 5, but have certain small angles with respect to the plane determined by the intermediate surface IA; the first support surface 13a has an angle b1 and the second support surface 13b an angle b. Thus, the support surfaces 13a and 13b guide the web W towards the interface IA, i.e. in the same direction as the vacuum field A- in connection with the interface IA tends to absorb the web W. The dimensions of the "long" model shown in Fig. 10 6 are preferably the following A = (2-6) x B; B = 50 .. 100 mm; H = (0.3 - 1) x B; the width of the nozzle gap 16a, 16b s = 2 .. 10 mm, preferably s = 3 .. 5 mm; b ^ = 5 ° ... 10 °, b ^ = 10 ° ... 20 °.

Fig. 7 shows the use of a "long" model of the blow box according to Fig. 6 in the application described above in connection with Fig. A. Due to the long and narrow design of the blow box 10, most of the free space W of the web W between the cylinders 21 and 27 is stabilized by the bearing surfaces Ka and Kb and the vacuum field A- therebetween. The guide roll 23 of the upper wire 25 20 and the blow box 10 are arranged relative to each other so that the blow box 10 sucks between the web W onto the surface of the drying wire 25. Thus, the web W is left with a very short free space Vq ^ on the inlet side of the blow box 10 from the roll 23, after which the gap V supported by the blow box 10 follows as the web W runs. There is then a relatively short unsupported distance of the web W along the path V1. Otherwise, the implementation of Figure 7 is as described in Figure A.

The device according to the invention can be used in all different positions, regardless of the track width, for non-contact web stabilization, support and / or drying.

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)

Apparatus for contactless stabilization, support and / or drying of a movable web, in particular a paper web or the like, comprising: a blister drawer (10) or drawers (10A, 10B, 10C) extending substantially over the entire width ( Lq) of the web (W) to be supported, in which / which air ducts can be introduced blowing air, and which drawer (10) comprises a support surface arranged against the web (W) to be supported, in connection with which support surface one blows air jets (Fa , Fb) from said drawer, by means of which the contactless support of the web (W) is provided with vacuum, with the air nozzles (16a, 16b) blowing in mutually opposite directions on the supporting surface of the blowing drawer (10). with which nozzles there are generally planar support surfaces (13a, 13b) extending to the opposite edge regions of the blowing tray (10), to which surfaces by means of said blisters form suppressing fields (Ka, Kb) which support the web (W), and which opposite blisters (Fa, Fb) are arranged to eject (Ea, Eb) air from the site at the surface (14,14a, 14b) between the support surfaces (13a, 13b) to maintain said suppression region (A-), characterized therein; that between said support surfaces (13a, 13b) there is an intermediate surface (14,14a, 14b) at a noticeable vertical distance (H) from their side on the side of the blowing drawer (10), at which intermediate surface length (A) of the suppression region (A) -) to be ejected is substantially greater in the running direction of the web (W) than the corresponding width (B) of said support surfaces (13a, 13b). 25 1 Patent claim 2. Device according to claim 1, characterized in that the width of the negative pressure area (A-) between said air nozzles (16a, 16b) in the running direction of the web (W) is 2-6 times the corresponding width (A = (2-6) x B ) of said opposite support surfaces (13a, 13b) under vacuum. 30 Device according to claim 1 or 2, characterized in that the air nozzles (16a, 16b) of the device are directed in opposite directions such that the direction of the starting directions of their blisters is at a certain angle (a) at a relative direction of the support surfaces 35 (13a). , 13b), the magnitude of which angle (a) is in the range a = 20 ° -60 °, most preferably a = 40 ° -50 °. 13 73478 Device according to any one of claims 1-3, characterized in that the length (B) of the planks of said supporting surfaces (13a, 13b) in the running direction of the web (W) is less than or substantially equal to the distance (H) of the boundary wall ( 14) of said suppressor region (A-) from the support plane (CC), most preferably H = »(0.3 - 1) x B. Device according to any one of claims 1-4, characterized in that the width (s) of the nozzle openings of said air nozzles (16a, 16b) is in the range = 2-10 mm, most preferably in the range s = 3-5 mm. 10 Device according to any one of claims 1-5, characterized in that the width (s) on the nozzle heel of said air nozzles (16a, 16b) and the overpressure (p) traveling within said blowing carriage (10) are so chosen that the air velocity (v) in said air jets (Fa and Fb), in the range v = 10-50 m / s, most preferably v = 20-40 m / s. 7. Apparatus according to any one of claims 1-6, characterized in that said blowing carriage (10) is so dimensioned and the blowings are arranged that the negative pressure which occurs at said suppression area (A-): 20 is of the class 10-100 Pa. 8. Apparatus according to any one of claims 1-6, characterized in that the planes of said support surfaces (13a, 13b) are located between each other in the same plane, which is in the direction of the main direction of the web (W) to be stabilized (Figure 1 ), or that said support surfaces (13a, 13b) have small angles (b 2, b 2) facing their intermediate surface (14), which angles are most preferably between 0 ° -20 ° (Figure 6). The use of the device according to any of claims 1-8 in one: a papermaker's multi-cylinder dryer to stabilize the free web (Wp) of the paper web (Wp) from one dryer cylinder row to another (Figures 4.5 and 7). The use of the device according to any of claims 1-8 in a contactless float dryer of a paper web or any other corresponding continuous blank web, the float dryer having in the running direction of the web (W) several blowers (10A, 10B, 10C ..) after each other, most preferably at regular intervals (Vo), which air jets (Fa, Fb) blown from these have no support.