SE464475B - DEVICE FOR MAKING A MATERIAL COAT OF FIBERS - Google Patents

Description

Thus, the hammers are forced to drag or pull around the unsalted carpet, which entails the disadvantage of a high energy consumption.

In addition, the fiber quality is degraded by the recurring * processing.

In a conventional production of a fluff mat, the production takes place in different sub-steps. After cutting or shredding the pulp, the material is fed into a refiner or grinder to expose long, medium and short fibers.

Via pipelines, the material flow is passed on to a portioning device, whereby in some cases a part of the short fibers and undefibrated knots is separated from the material flow on the way to the portioning device. The short fibers separated are returned to the process at a later stage, while the knots are returned to the mill for further processing. From the portioning device, material flows further to form a fibrous layer on endless air-permeable transport paths. A lot of energy is consumed in a conventional system due to long transports in narrow pipelines and inefficient decomposition and defibration of the pulp. The high power consumption in turn creates heat in the process, which adversely affects the exposed fibers which become brittle and gives a poorer quality of the finished fluff mat. Conventional grinders have a design that creates partial overpressure inside the grinder, which leads to particles leaking through openings in the grinder and creating environmental problems. These problems are further exacerbated by the fact that only a part of the total amount of short fibers is recycled to the process, the remaining part getting stuck in necessary filters or polluting the ambient air.

BACKGROUND OF THE INVENTION The object of the present invention is to solve the above problems by means of an apparatus for producing a material web of fiber, which has a low power consumption and gives an end product in the form of a fluff mat of uniform quality, which thus does not need to be reworked, and where 15 20 25 30 35 464 475 3 The thickness or basis weight of the fluff mat can be adjusted with great flexibility. In the process according to the invention, the degree of recycling of the starting material is unusually high, which leads to environmental improvements.

The present invention realizes these objects by means of a device of the kind mentioned in the introduction, which is characterized in that an endless, permeable conveyor belt, on which the web of material is formed, is arranged to connect in a forming opening in the defibration unit, which opening is arranged in the defibration unit directly adjacent to that position. where the defibration ends.

The invention also discloses a method of the kind mentioned in the introduction, which is characterized in that the formation of the material web takes place on the conveyor belt, which connects to the defibration unit in a forming opening, in direct connection with the defibration in the position where the fibers are most exposed.

Further advantageous features appear from the following description of exemplary embodiments and from subordinate claims.

The invention relates to a method for producing fibrous layers, which method has the advantage, compared with the conventional ones, that the production takes place in a single continuous process without intermediate transports and without storage and portioning of intermediate products. The width of the starting material, i.e. the roll mass, is essentially the same as the width of the produced fibrous layer and the different processing steps between the feed of the starting material and the feed of the final product all take place with the same width. No collection of intermediate products takes place in pipes or the like. and no width changes are required during the process, which means that the process uses the material spread that is present in the roll mass from the beginning. This means that you can produce fluff mats with a lower basis weight and also get a better end product and a lower energy consumption. Energy consumption is also reduced by reducing the number of fans needed for the air flow to, in the optimal case, only one fan. The thickness of the fibrous layer is directly proportional to the feed speed of the rolling mat and can thus be controlled very easily by controlling the speed of the feed of the rolling mat. In the manufacture of diapers, for example, there is a need to vary the layer thickness along the longitudinal extent of the diaper, which can be achieved very easily by a pulsating feed of the roll mass.

The device and method according to the invention achieve a high quality of the fluff mat, by maximizing the extraction of high-quality long and medium-length fibers while separating the remaining knots and by forming in immediate connection with the defibration É when the fibers are most exposed.

Brief Description of the accompanying Drawings An embodiment of a device according to the present invention is described in more detail below with reference to the accompanying drawings, in which - Figure 1 shows a vertical sectional view through a device according to the invention, - Figure 2 shows a section along the line II-II in Figure 1 , - Figure 3 shows a section along the line III-III in Figure 1, - Figure 4 shows an enlarged vertical sectional view of a rock hammer according to Figure 1, - Figure 5 shows the rock hammer according to Figure 1 in perspective, - Figure 6 shows an enlarged vertical sectional view of a defibration hammer according to Figure 1, - Figure 7 shows the defibration hammer according to Figure 1 in perspective, - Figure 8 shows a principle sketch of knot separator and formation according to Figure 1. Detailed description of a preferred embodiment of the invention I Figure 1 shows how a starting material in the form of roll mass 1 is fed, cut, defibrated, separated and formed into a final product in the form of a fluff mat 2. Roll mass The width of the fluff can vary, preferably between about 0.1 m up to 1 m, depending on which width of the fluff mat is sought. The roll mass 1 is fed between two feed wheels 3 to an feed opening 4 in a stationary housing 5 for a cutting and defibrating unit. The rolling mass 1 runs along a counter-knife 6 (see also Figure 4), which is arranged at the feed opening 4 on the outside of the housing 5. A cylinder 7 is rotatably arranged in the housing 5, the axial extent of the cylinder being substantially equal to that of the feed opening 4 and 4, respectively. the roll mass 1 width. On the cylinder 7 a number of cutting hammers 8 are arranged and spread over the outer surface of the cylinder, preferably at even distances from each other, along a number of axially directed axes on the outer surface, see Figure 2. During the rotation of the cylinder 7 each cutting hammer 8 cooperates along the cylinder. mantle surface with the counter knife 6, for successive cutting of one mass piece at a time along the entire width of the roll mass. The axial displacement between each rock hammer in the direction of rotation is less than or substantially equal to the maximum width of the rock hammer, e.g.

The cutting hammer 8 is shown in more detail in Figures 4 and 5. Figure 4 shows that the cutting hammer 8 is pivotally mounted on the cylinder 7. The peripheral speed of the cylinder 7, which is preferably between 50-150 m / s, produces a centrifugal force on the cutting hammer 8 which is sufficient to the rock hammer during normal operation must assume a radial position. If, on the other hand, foreign particles appear in the path of the rock hammer, the hammer can swing away and thereby damage to the equipment is avoided. The cutting hammer 8 consists of a tool holder 9, in which a cutting edge 10 with the width b1, preferably of cemented carbide, is arranged. The insert 10 cooperates with the counter knife 6 during the rotation of the cylinder to cut off a piece of roll mass. For an efficient cutting, it is essential that the center of rotation of the cutting hammer 8 and the edge of the insert 10 are arranged along the center of gravity axis 27 of the cutting hammer. * On the cylinder 7 there are further, as shown in Figures 1 and 3, a number of defibration hammers. 11 and preferably symmetrically placed around the circumferential surface of the cylinder along axially directed axes. The defibration hammers 11 (see also Figures 6 and 7) cooperate with a tear surface 12 fixedly mounted on the casing 5, which is patterned, preferably toothed, and has an extension on the casing surface of the casing corresponding to about 180 °, for exposing fibers from the cut mass. along the tear surface 12. To increase the friction on the defibration hammer, as shown in Figure 7, the defibration surface is patterned, preferably knurled or toothed.

In the housing 5 a forming opening 13 is arranged, in which a first permeable, endless conveyor belt 14 connects in tangential direction at one end of the opening and bends out from it in the direction of a second permeable, endless conveyor belt 15. The two conveyor belts are movable on a number of rotatable rollers 16 and successively form a forming path for the fluff mat 2. A forming hood 17 connects to the forming opening 13 on the upper side of the first conveyor belt 14 and a first suction box 18 connects to the forming opening 13 on the underside of the belt 14, to create on this side a negative pressure when forming the fluff mat 2 (see also Figure 8) on the conveyor belt 14. The first suction box 18 communicates with a forming hood 19 on the side of the second conveyor belt 15 where the built-up fluff mat runs and on the opposite side of the belt is a second suction box Applied to create a negative pressure for fiber recovery on this side. Figure 1 also shows a fan 21 in connection with the two suction boxes 18, 20 and a simple filter 22 for the outgoing air.

In connection with the forming opening 13, a knot separator 23 is arranged, which has the purpose of first collecting and then leading the undefibrated mass back to the defibration unit for further processing.

The knot separator 23 consists of a passage 24 outside and past the cylindrical housing 5, which passage connects to the housing in the vicinity of the feed opening 4. An ejector 25 with an air inlet 26 creates a pressure drop relative to the forming opening at the passage 24 of the passage 24 to the housing, whereby the air flow with them the knots into a new defibration phase.

The embodiment of the invention described above gives a very good quality of the manufactured fluff mat at a basis weight thereof which is greater than about 75 g / m 2. In dry forming of paper with basis weights between 25 and 75 g / m2, vortex formation between the forming hood 17 and the first conveyor belt 14, which is negligible at higher basis weights, can create irregularities in the fluff mat. A good quality of the fluff mat is achieved in the manufacture of paper with low basis weights in an alternative design of the device according to the invention.

The forming hood 17 at the first conveyor belt 14 is removed so that atmospheric pressure prevails over the belt. Instead, a fan is provided at the air inlet 26 which creates an overpressure in the defibration unit.

Function of the invention The roll mass 1 is fed from a roll between the feed wheels 3 and along the counter knife 6, against whose edge it is cut into suitably large pieces at the meeting with the rotating cutting hammers 8. Each cutting hammer 8 thus cuts a piece smaller than or corresponding to the width of the insert 10. The height of the pulp bit is regulated by the feed speed of the roll mass in combination with the rotational speed of the cylinder 7. The cut piece of pulp is ground, kneaded, rolled, cut and machined between the rotating defibrillation hammer 11 with its toothed or knurled head and the toothed tear surface 12. Large parts of the pulp fibers are exposed during the passage from the feed opening 4 to the forming opening 13. 10 15 20 25 30 35 464 475 After the passage of the pulp pieces through the defibrating unit, these have been converted into exposed short (<1 mm), medium (approx. 1-3 mm) and long fibers (> 3 mm) and undefibrated nodules.

The knots, which are heavy and have a high kinetic energy, strive to continue their movement straight ahead, the knots being separated from the exposed fibers by being thrown in the direction of the tangent into the knot separator 23 and flowing through it by means of the pressure difference between the forming opening and the separator outlet. The knots are then returned to the defibration unit to be re-processed for exposing fibers.

The long, medium and short fibers follow the curved surface of the suction box 18 and the belt 14 due to The Coanda effect and a gradual formation on the conveyor belt begin. The density of the strip is chosen so that long and medium fibers are formed on the fluff mat while short fibers are sucked through the strip by the negative pressure in the suction box 18. After the formation, the fluff mat consists mainly of only long and medium fibers which form a fluff mat with high network strength. The short fibers which do not give any strength to the fluff mat are thus separated during formation.

The short fibers which have passed with the air flow through the first conveyor belt 14 are sucked on to the forming hood 19 in connection with the second conveyor belt 15. Because the short fibers are suitable as absorbent material, they are recycled to the fluff mat, which due to its tightness acts as a disposable filter for the exhaust air. The air stream is sucked through the fluff mat by the negative pressure in the second suction box 20, the short fibers being deposited on, and partly in, the fluff mat. The purified air stream passes the fan 21 and a simple filter 22 to then pass out into the ambient air. The starting material, ie the roll mass, is recycled to more than 99% with this process.

The invention is in no way limited to the embodiments described according to the above, but several modifications of the invention are conceivable within the scope of the claims.

For example, both the tear surface and the defibration surface on the defibration hammers may have different patterned designs, such as, for example, toothed, grooved, wavy or non-uniformly patterned. The radius of the defibration surface of the defibration hammer can vary and the defibration hammers, like the cutting hammers, can for pivotal reasons be pivotally arranged on the cylinder.

The cutting hammer can be provided with an, in relation to the counter-knife, inclined insert instead of a parallel one.

The extent of the tear surface in the described embodiment corresponds to about 180 °, but the area can vary in size between the corresponding just over 0 ° to an extent along the entire surface from the inlet opening to the forming opening. The tear surface or casing can be hinged to the counter knife in order to be able to adjustably vary the distance between the defibration hammer and the tear surface and thereby adapt the device to different types of mass. The conveyor belt can be connected to the forming opening with a transverse edge, a so-called

Set-off, which forms a smaller space under the air flow. In this space a negative pressure is formed which helps to control the air-fiber flow along the conveyor belt.

Claims (4)

464 475 10 15 20 25 30 35 10, Patent claim An apparatus for producing from a pulp a web of material (2) of fiber, said apparatus comprising a cutting unit (3, 6, 8) for cutting the pulp (1), a defibrating unit (5, 7, 11) for exposing fibers from the cut mass, a forming unit (15-20) intended for building up the material web (2), comprising an endless, permeable conveyor belt (14), on one side of which the material web is formed, and a knot separator (23) for removing knots of incompletely fibrous mass from the exposed fibers, the fibrillation unit comprising a cylinder (7) rotatably mounted in a stationary housing (5) with an inlet (4) for the pulp and a forming opening (13) for diverting the exposed fibers. ), which carries a plurality of defibration hammers (II) intended to cooperate with a tear surface (12) located on the inside of the casing in an area extending from the pulp inlet to the forming opening (13), characterized in that the forming opening (13) is en utmatni from the casing (5) of both the exposed fibers and the opening of the incompletely fibrous mass, to which the conveyor belt (14) adjoins at first substantially tangential and then deflected outwardly from the opening (13), while the knot separator (23 ) consists of a knot separator passage (24) first extending tangentially from the forming opening, which then bends in an arcuate inwards and with its other end is connected to the defibrating unit. Device according to claim 1, characterized in that the rotor (7) has, in addition to the defibration hammers (11), a plurality of cutting hammers (8), which are arranged to cooperate with at least one counter knife (6) arranged on the housing (5) for cutting the mass (1) supplied through the pulp inlet (4). 464 475 ll Device according to claim 2, characterized in that each cutting hammer (8) consists of a tool holder (9), in which a cutting insert (10), preferably of hard metal, is arranged, the cutting hammer being pivotally mounted on the rotatable cylinder (7) with its center of rotation and the edge of the insert (10) arranged on the center of gravity axis (27) of the rock hammer. Device according to one of Claims 1 to 3, characterized in that the mass (1) is arranged to be fed along the counter knife (6) through the inlet (4) in the housing (5) in the form of roll mass (1). with a width which is substantially equal to the width of the defibrating unit (5, 7, 11), the width of the forming unit (15-20) and the width of the built-up material web (2).