DRY FORMING PLANT AND METHOD FOR DRY FORMING A FIBROUS TISSUE USING SUCH DRY FORMING PLANT

Abstract

A dry forming plant is described which comprises at least one distribution unit having a fibre and air inlet. Such distribution unit is placed above a forming wire opposite to at least one vacuum box which is connected to a suction unit. The distribution unit has an open bottom for release of the fibre material onto the forming wire below the distribution unit. More rotating rollers having protruding spikes are provided in the distribution unit for covering the cross sectional area of the open bottom. The vacuum box is divided into at least three longitudinal zones in a direction transversal to the advance direction of the forming wire. Said longitudinal zones have upwardly orientated intakes arranged below the forming wire. The longitudinal zones are connected with the suction unit via an outlet. The outlet comprises first shut-off means for partly or totally closing the outlet. The first shut-off means are independently operable.

Claims

1. A dry forming plant for dry forming of a fibrous tissue from a fibrous material chosen from amongst synthetic fibres and natural fibres, the dry forming plant comprises; a forming wire; at least one distribution unit having a fibre and air inlet, and the at least one distribution unit positioned above the forming wire, a suction unit; at least one vacuum box connected to the suction unit, the at least one vacuum box positioned below the forming wire; wherein the at least one distribution unit includes an open bottom configured and arranged to release the fibre material onto the forming wire which is configured and arranged to be advanced below the distribution unit; and one or more rotating rollers having protruding spikes are provided in the distribution unit, the one or more rotating rollers are configured and arranged to cover the cross sectional area of the open bottom, wherein each of the at least one vacuum box is divided into at least three longitudinal zones in a direction transverse to an advance direction of the forming wire, and wherein the at least three longitudinal zones have upwardly orientated intakes arranged below the forming wire, and wherein each of the at least three longitudinal zones are connected with the suction unit via an outlet, each of the outlets include first shut-off means configured and arranged to partly or totally close the respective outlet independent of the other outlets.

2. The dry forming plant according to claim 1, wherein the at least three longitudinal zones are divided into a number of transverse zones, wherein at least one of the transverse zones includes a second shut-off means, the second shut-off means are configured to partly or totally close the respective intake to that transverse zone independent of the other intakes at least in the advance direction.

3. The dry forming plant according to claim 2, wherein the longitudinal zones and transverse zones are formed by partition plates provided with cut-outs configured and arranged for joining the partition plates.

4. The dry forming plant according to claim 1, wherein the outlet of the longitudinal zones are further connected with the suction unit via suction tubes directed in the advance direction.

5. The dry forming plant according to claim 1, wherein the at least one distribution unit includes two or more independent distribution units arranged side by side in a direction transverse to the advance direction,

6. The dry forming plant according to claim 5, wherein the at least one vacuum box comprises a longitudinal zone in an area where adjacent sides of the two or more independent distribution units are joined, the longitudinal zone is a central zone and at least one side zone is provided on each side of the central zone.

7. The dry forming plant according to claim 1, wherein the at least one vacuum box includes two or more independent vacuum boxes arranged side by side in a direction transverse to the advance direction.

8. The dry forming plant according to claim 1, wherein the at least one vacuum box unit comprises an outermost side zone, the outermost side zone having a local width being smaller than a local width of another longitudinal zone of the at least one vacuum box.

9. The dry forming plant according to claim 1, wherein at least two of the distribution units and/or the vacuum boxes are either identical or symmetrical.

10. The dry forming plant according to claim 1, wherein the first shut-off means for each of the longitudinal zones are slide valves connected with independently operable first operation units.

11. The dry forming plant according to claim 2, wherein the second shut-off means for the at least one transverse zone are rotary dampers mounted on a common pivotally mounted shaft connected with independently operable second operation units.

12. A method of dry forming a fibrous tissue from a fibrous material chosen from amongst synthetic fibres and natural fibres, using a dry forming plant according to claim 1, wherein the method includes the steps of: feeding at least one fibrous material into at least one distribution unit, establishing a suction through a forming wire via at least one vacuum box, distributing the at least one fibrous material from the at least one distribution unit onto the forming wire, and advancing the forming wire in an advance direction during the distribution of the fibrous material to form the fibrous tissue.

13. The method according to claim 12, wherein the at least one fibrous material is fed to at least two distribution units arranged side by side in a direction transverse to the advance direction, where a first local suction is provided in a central zone where adjacent sides of the two distribution units are joined, and where the first local suction is independently controlled in relation to a second local suction provided in at least one side zone arranged on each side of the central zone.

14. The method according to claim 12, wherein a first local suction is provided in an outermost side zone arranged at a side edge of the at least one vacuum box, and where the first local suction is independently controlled in relation to a second local suction provided in at least one side zone arranged adjacent to the outermost side zone.

Description

DESCRIPTION OF THE DRAWING

[0086] The invention will now be explained in further detail with reference to the accompanying schematic drawing, wherein

[0087] FIG. 1 is a schematic perspective view of an embodiment of a prior art dry forming plant forming a part of the present invention,

[0088] FIG. 2 is a schematic perspective view of an embodiment of a plant according to the present invention,

[0089] FIG. 3 a partial schematic view of the plant illustrated in FIG. 2,

[0090] FIG. 4 a partial side view of the plant illustrated in FIG. 2,

[0091] FIG. 5 a partial view of a vacuum box of the plant illustrated in FIG. 2,

[0092] FIG. 6 a perspective view of the vacuum box with partition plates mounted for defining a grid of intake openings,

[0093] FIG. 7 a view of the vacuum box provided with suction tubes and rotary dampers arranged in the intakes,

[0094] FIG. 8 a side view of the vacuum box illustrating sliding plates establishing a gap for false drag,

[0095] FIG. 9 a side view seen from the opposite side illustrating the slide plates and the rotary dampers in a vertical position leaving the intakes open,

[0096] FIG. 10 a perspective sketch illustrating the principle of a first modular construction of the plant,

[0097] FIG. 11 a perspective sketch illustrating the principle of a second modular construction of the plant,

[0098] FIG. 12 a perspective sketch illustrating the principle of a second modular construction of the plant,

[0099] FIG. 13 a perspective sketch illustrating the principle of a fourth modular construction of the plant,

[0100] FIG. 14 a perspective sketch illustrating the principle of a construction of the plant, and

[0101] FIG. 15 a schematic view illustrating how a product is built on a forming wire below a distribution unit.

DETAILED DESCRIPTION OF THE INVENTION

[0102] In the explanation of the Figures, identical or corresponding elements will be provided with the same designations in different Figures. Therefore, no explanation of all details will be given in connection with each single Figure/embodiment.

[0103] In the following it is assumed by way of example that a main distribution unit according to the invention comprises four distribution units. This is not limiting the invention. The main distribution unit can comprise from one to a plurality of distributions units.

[0104] In FIG. 1 a main distribution unit 1 according to prior art is shown. The main distribution unit comprises four independent interconnected distribution units 2, 3, 4 and 5 respectively. Fibres are supplied to the first distribution unit 2 via an inlet 6. A vacuum box 7 is positioned beneath a forming wire 8, and the main distribution unit is positioned above the wire. Hereby suction is established through the forming wire and fibres 9 are air laid on the forming wire 8 to form a web 10 in a dry forming process. Only an upper run 22 of the forming wire 8 is illustrated in FIG. 1. The forming wire is an endless wire belt.

[0105] In FIG. 1, the main distribution unit is shown with the interior elements visible in the fourth distribution unit 5. However, it is realized that the housing walls may be made from transparent or opaque materials.

[0106] Inside each distribution unit 2, 3, 4, 5 rotating rollers are provided with protruding spikes 12.

[0107] In the embodiment shown in FIG. 1 the first distribution unit 2 comprises one rotating roller 11, the second distribution unit 3 comprises two rotating rollers 13, 13, the third distribution unit 4 comprises one rotating roller 14, and the forth distribution unit 5 comprises five rotating rollers 15, 16, 17, 18, 19, placed in a substantially horizontal plane parallel to the forming wire 8.

[0108] The five rotating rollers 15, 16, 17, 18, 19, which are placed within the forth distribution unit 5, can be said to make up the bottom of the main distribution unit wherein three rotating rollers 15, 16, 17 are placed by one side wall of the distribution unit and two rotating rollers 18, 19 at the opposite side.

[0109] It will be evident for the person skilled in the art that the number of rotating rollers can be adjusted depending on the desired product and the fibres used.

[0110] Motors 20, arranged with the possibility for a variable rotation rate, drives each rotating roller, ensuring that it is possible to adjust the revolution rate of the engines dependent of choice of rollers, spikes and the product, which is to be formed.

[0111] Each of the rotating rollers 11, 13, 14, 15, 16, 17, 18, 19 has an axle 21, upon which spikes 12 in form of thread-formed elements are protruding. The spikes 12 are established with a size and a mutual distance, which makes it possible to allow for a passage in-between for corresponding spikes 12 on a neighboring rotating roller.

[0112] The rotating spike rollers are in the embodiment shown in FIG. 1 placed so that the outer ends of the spikes describe circles that do not overlap each other but can within the scope of the invention also be meshing like toothed gear or touch each other during the rotation.

[0113] The fibres 9 are supplied to the main distribution unit 1 via inlets 6. Said fibres will comprise agglomerates, lumps and/or shadows and when these comes into contact with the spikes 12, the agglomerates, lumps and/or shadows will be disintegrated or shred in order to ensure an even distribution of fibres 9 in the product 10 formed on the forming wire 8.

[0114] This is due to the fact that the disintegration of agglomerates of a fibrous material are influenced by strokes from spikes on the rotating rollers, and when e.g. an agglomerate is hit by a rotating spike the impact force will ensure that the agglomerate, at least to some extent, will be forced to open and/or disintegrate.

[0115] As this is repeated, not only several times in each distribution unit, but also in the four distribution units, all agglomerates, shadows and/or lumps will be removed in order to ensure an even distribution of fibres 9 in the product 10 formed on the forming wire 8.

[0116] The closer the spikes 12 are placed to each other on the rotating rollers 11, 13, 14, 15, 16, 17, 18, 19, the more efficient will the spikes return agglomerates, lumps and/or shadows to the respective distribution units 2, 3, 4, 5. In this manner the fibre clumps or clusters of fibres are retained by the rotating rollers and separated or disintegrated in a graduated fashion as these retained fibres are returned by the spikes 12 to the distribution unit rather than being sucked down to the forming wire 8 or underlying distribution unit by the vacuum box 7.

[0117] Fibres are supplied in an airflow to the first distribution unit 2 via an inlet 6. The airflow can be created by means of transport blowers, which are linked with pipes that lead to the distribution unit, but other ways of obtaining the airflow known to the person skilled in the art are within the scope of protection.

[0118] In the embodiment shown in FIG. 1 the fibres are primarily led in from each side of the first distribution unit 2, but fibres could also be feed to the distribution unit by means of more inlet pipes on each side of said distribution unit or to several of the distribution units. It is hereby possible to vary the capacity of the main distribution unit by opening and closing the inlet pipes.

[0119] As an alternative to the inlet 6 the fibres can be introduced to the main distribution unit in question by blowing them into said main distribution unit. This will ensure, that the fibres have a substantial velocity upon introduction to the unit, which provides that large concentrations variations throughout the main distribution unit will be reduced or even eliminated, ensuring a more uniform distribution of small fibres in the web. In case the product shall be provided with super absorbents or other powder products a more uniform distribution of such powder products is obtained.

[0120] The topmost first distribution unit 2 may or may not have a detachable lid 23 to allow inspection and maintenance of the main distribution unit, and to provide the possibility of admitting false drag so that a negative pressure does not build up in the main distribution unit and obstructs the continuous flow towards the forming wire obtained by means of the vacuum box 7. Preferably, the lid 23 has an air inlet opening 24 for admitting the false drag. The opening may be provided in the lid 23 or any other suitable site on the main distribution unit, e.g. in the axial side of the first 2 and/or subsequent distribution unit, as well as more openings may be provided and favorable. The openings for false drag may also be a gap at the bottom of the main distribution unit, which gap may be adjustable.

[0121] The uniform distribution is furthermore increased as the rotating rollers retain fibres before they are gradually sucked down via the vacuum from the vacuum box to the forming wire. In this way the rotating rollers works as a kind of buffer zone, ensuring, that the fibres do not fall directly onto the forming wire.

[0122] Fibres or other product which are to be part of the final web could also be are added to several of the distribution steps of the main distribution unit according to the invention, increasing the capacity of the main distribution unit.

[0123] In this respect the fibre material comprising the agglomerates, lumps and/or shadows which requires the highest impact force can be feed to the first distribution unit 2, and the fibre material which requires the lowest impact force to the forth distribution unit 5.

[0124] FIG. 2 illustrates a dry forming plant having two distribution units 1 arranged side-by-side in direction transversal to the advance direction 26 for the forming wire 8.

[0125] The distribution unit which may be called a main distributor unit comprises a number of independent distribution units. This is in accordance with the explanation in connection with FIG. 1. However, in the following the mentioning of a distribution unit would correspond to the main distribution unit explained in connection with FIG. 1.

[0126] The two distribution units 1 are identical and are arranged side-by-side in order to increase the width of the product 10 formed on the forming wire 8.

[0127] In the following there is an explanation of one distribution unit 1, however, it is clear that the explanation will be valid for both distribution units 1 illustrated in FIGS. 2-4.

[0128] FIG. 2 illustrates a plant according to the present invention and here it is seen that the former wire 8 has an upper run 22 and a lower run 25. The forming wire 8 has a movement in direction of the arrow 26.

[0129] The vacuum box 7 is arranged in the area between the upper run 22 and the lower run 25 of the forming wire 8. The vacuum box 7 is through funnels 27 (see FIG. 7) connected with suction tubes 28. The suction tubes 28 extend in the advance direction 26 of the upper run 22 of the forming wire 8. The suction tubes 28 (see FIG. 7) have a bend 29 (see FIG. 7) and are connected with further suctions tubes 30 extending transversal to forming wire 8 where the tubes 30 are connected with suction units in form of suction fans 31 arranged at the side of the forming wire 8.

[0130] The suction fans 31 may be connected with the inlets 6 for the distributor unit 1.

[0131] FIGS. 3, 8 and 9 illustrate partial views. A number of elements are not shown for clarity. E.g. only one row of motors 20 for the rotating rollers is illustrated. The distribution unit 1 is disclosed with a fiber cloud box 32 arranged above the distribution unit 1.

[0132] The distribution unit 1 comprises at the inlet side 33 a sliding plate 34 which is used for establishing a gap 35 beneath a lower edge of the sliding plate 34 and the upper run 22 of the forming wire 8. Hereby a possibility for false drag is established. This could be instead of the false drag through an opening 24 and/or be a further possibility for establishing false drag.

[0133] A sliding plate (not illustrated) corresponding to the sliding plate 34 is arranged at the outlet side 37 of the distribution unit 1 in order to adjust a gap (not visible) arranged at the outlet side 37 of the distribution unit 1.

[0134] In FIG. 8 the vacuum box 7 1 is illustrated from one side, and in FIG. 9 the vacuum box 7 is illustrated from the other side, however, with the side plate removed whereby the interior of the vacuum box is visible. Hereby it is possible to see rotary dampers 39 which each are arranged on a common pivotally mounted shaft 40. The pivotally shafts 40 are independently operable by means of second operating units (not shown) associated with each of the shafts 40. The second operating units may be a rotary actuator or any other suitable actuation means, e.g. a handle that is manually operated.

[0135] The distribution unit is not illustrated. It will be arranged over the vacuum box 7 illustrated in FIGS. 8 and 9.

[0136] FIG. 4 illustrates an end view of the dry forming plant illustrated in FIG. 3. FIG. 4 illustrates the sliding plates 34 arranged in an upper respectively a lower position above the forming wire 8. The sliding movement is established as the plate 34 is provided with slits 41 cooperating with screws 42 which may be loosened and tightened for sliding and fixing the sliding plates 34 in any position.

[0137] Instead of using one sliding plate 34 for a distribution unit 1 it is possible to use two or more sliding plates.

[0138] FIG. 5 illustrates a vacuum box 7 used in the dry-forming plant illustrated in FIGS. 2-4.

[0139] The vacuum box 7 is divided into longitudinal zones 43 arranged side-by-side in a direction transversal to the advance direction 26. Accordingly, each of the zones 43 extends in direction of the advance direction 26.

[0140] The longitudinal zones 43 are established by longitudinal partition plates 44 which are provided with cut-outs 45 extending partly over the height of the longitudinal partition plate 44. Hereby transversal partition plates 46 having corresponding cut-outs 47 for engagement with the cut-outs 45 can be arranged perpendicular to the longitudinal partition plates 44 in order to form a grid of individual intakes 48. Only a part of the intakes are illustrated for illustrative purpose.

[0141] The longitudinal partition plates 44 provided with openings 49 for passage of the common pivotally shafts 40 for the rotary dampers 39.

[0142] From FIG. 5 it seen that rotary dampers 39 are provided in the different intakes 48 of the grid formed by the crossing partition plates 44, 46. The intakes 48 are directed upwardly against the forming wire and are arranged below the upper run of the forming wire.

[0143] The longitudinal zones 43 are connected with the suction units 31 via an outlet 36 for each of the longitudinal zones 43. In each of the outlets 36 cut-off means in form of slide valves 50 are arranged. Hereby it is possible partly or totally to close the associated outlet 36. The slide valves 50 are independently operable by means of first operating units (not shown) associated with each of the slide valves 50. The first operating units may be a linear actuator or any other suitable actuation means.

[0144] As it occurs from the above it is possible to adjust the vacuum and thereby the suction established in each of the longitudinal zones 43 with the operation of the slide valves 50. Moreover, it is possible to adjust the vacuum and thereby the suction established in each intake 48 of the grid by operating the rotary dampers 39.

[0145] Accordingly, it is possible to establish a very precise adjustment of the suction force in different areas of the grid formed at the upper side of the vacuum box 7.

[0146] The vacuum box 7 is divided into at least three longitudinal zones 43.

[0147] FIG. 6 illustrates the vacuum box 7 according to FIG. 5 including all longitudinal partition plates 44 and all transversal partition plates 46. For clarity the rotary dampers and the slide valves are not illustrated in FIG. 6.

[0148] The embodiment illustrated in FIG. 6 is divided into seven longitudinal zones 43. The embodiments are divided into six transversal zones 51 by means of the transversal partition plates 46.

[0149] Hereby the grids of intakes 48 are established. One could say that each intake is provided in a crossing area where a longitudinal zone and a transversal zone are crossing.

[0150] The vacuum box illustrated in FIGS. 5 and 6 is intended for being arranged below the two distribution unit 1 arranged side-by-side in direction transversal to the advance direction 21.

[0151] In FIG. 4 it is illustrated that the vacuum box 7 is divided into the seven longitudinal zones 43. Lines 52 illustrate the position of the longitudinal partition plates 44. From FIG. 4 it is seen that a central zone denoted 54 is arranged in the vacuum box in an area 75 where adjacent sides 76 of the two distribution unit 1 are joined.

[0152] Turning to FIG. 6 it is visible that the vacuum box 7 comprises a first side zone 55 on each side of the central zone 54. Moreover, it is seen that a second side zone 56 is also arranged in a more outwardly position compared to the central zone 54. Finally, it is also seen that an outermost side zone 57 is arranged at each side of the vacuum box 7.

[0153] As already explained above the dry-forming plant may be provided in modular form. Accordingly, modular distribution units 1 may be used.

[0154] These modular distribution units 1 can be used together with one single vacuum box 7 or together with a number of modular vacuum boxes 7 arranged side-by-side in a direction transversal to the advance direction 26.

[0155] FIG. 10-14 illustrate different embodiment for a dry-forming plant manufactured of a modular set of distribution units 1 and vacuum boxes 7. Other combinations than the illustrated combinations are possible. The partitions plates in the vacuum boxes 7 are not illustrated. However the partition plates will be arranged according to the principles described above.

[0156] FIG. 15 illustrate a different embodiment for a dry-forming plant manufactured of only one distribution unit 1 and one vacuum box 7.

[0157] In FIGS. 10-14—and also in FIG. 15 only the distribution units 1 and the vacuum boxes 7 are illustrated for clarity.

[0158] FIG. 10 illustrates two identical distribution units 1 arranged in a position above one vacuum box 7. The vacuum box is divided into three longitudinal zones 43 and comprises a central zone 54 arranged below the area 75 where sidewalls 76 for the distribution units are combined. On each side of the central zone 54 a side zone 56 is arranged. Furthermore, outermost side zones (not illustrated here) are provided at the outermost sides of the vacuum box 7.

[0159] FIG. 11 illustrates a different embodiment having three identical distribution units 1 arranged side-by-side in a position above to two identical vacuum boxes 7 which are also arranged side-by-side. Instead, the two vacuum boxes 7 may be symmetrically arranged around the adjoining sides. Here the longitudinal zones are not illustrated.

[0160] FIG. 12 illustrates a further embodiment which also has three identical distribution units 1 arranged side-by-side in a position above four identical vacuum boxes 7 which are also arranged side-by-side.

[0161] FIG. 13 illustrates a further embodiment where three identical distribution units 1 are arranged side-by-side. Below the distribution unit five identical vacuum boxes 7 are arranged.

[0162] When using more than two vacuum boxes 7 arranged side-by-side, then the outermost side zone 57 needs only to be provided at the two outermost sides of the vacuum boxes arranged side-by-side. Such outermost side zone 57 is intended for overcoming problems with “elephant foot” in the outermost edge area of the product 10 formed closest to the outermost side of the distribution unit.

[0163] However, all vacuum boxes 7 can be identical, seeing that the control of the vacuum established in each of the longitudinal zones 43 can be adjusted. The adjustment may be effected in such a way that an outermost side zone 57 of a vacuum box 7 arranged in an intermediate position in the row of side-by-side arranged vacuum boxes 7 may be controlled in the same manner as a neighboring longitudinal zone 43.

[0164] FIG. 14 illustrates one distribution unit 1 arranged in a position above one vacuum box 7. The vacuum box 7 comprises a central zone 54 and on each side of the central zone 54 a side zone 55 is arranged. Furthermore, outermost side zones 57 are provided at the outermost sides of the vacuum box 7. The outermost zones 57 have a smaller local width than the local width of the side zones 55. Further, the central zone 54 has a smaller local width than the local width of the side zones 55.

[0165] FIG. 15 illustrates the formation of the product 10 formed on the forming wire 8. It is seen that the product has very low height at the inlet side 33 of the distribution unit 1 and have a larger height at the outlet side 37 of the distribution unit 1. In order to establish a uniform suction force over the length of the product arranged below the distribution unit 1 the rotary dampers 39 are arranged under different angles.

[0166] In FIG. 15 a smoothening roller 58 is illustrated. This smoothening roller 58 may be provided for establishing a smoothening of the surface of the product 10.