DE2352090A1 - METHOD AND DEVICE FOR MANUFACTURING AN AIRLINED FIBER WEB - Google Patents

Description

EiKENBERG & BRÜMMERSTEDT PATENT LAWYERS IN HANOVER

kimberlx-clare: corporation 240/578

Method and device
for the production of an air-laid fiber web

The invention relates to a method according to the preamble of claim 1. At the same time, a device _; to carry out the procedure.

The invention relates particularly to the ^{manufacturer:} position of fibrous webs from wood pulp, especially
on the production of loose wadding or loose fiber webs
of individual cellulosic fibers which are characterized by a high degree of: uniformity and which are essentially none-;

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ne have fiber flakes.

! Techniques for shredding wood pulp and re- Arrangement of the detached fibers to form white fiber webs with relatively independent fibers well known. Usually webs are made of solidified wood pulp fed to a hammer device or a tear roller, which fibers the webs into individual fibers. Afterward the fibers are placed on a receiving surface, for example on an open-pored sieve. This usually shows a suction device on the underside to facilitate the laying of the fibers on the sieve and to support, and usually moves continuously into one. Direction that is roughly transverse to the direction in which the individual fibers are fed.

Although attempts are made by the known method to produce fiber webs in which the fibers in a very are arranged uniformly, in practice, however, conspicuous agglomerations of fibers occur, which usually are referred to as fiber flakes. These fiber flocs are at least the result of an interweaving of the fibers with one another, as they move from the tearing roller, at least to the rope be transported to the receiving area. In addition, the fiber webs produced by the known processes usually a non-uniform basis weight distribution across its width.

It is true that the fiber webs produced by the known processes can be used in many applications find, however, there are some applications where fiber webs which are free of fiber flock and in high quality are desirable Dimensions are uniform across their width. As in

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U.S. Patent Hr. 2692 622 is described particularly useful paper products can be made from such soft paserbanks made of wood pulp, which is a desirable combination of drag, grip and Combine absorbency properties. It is true that fiber webs can also be used for such papermaking processes which are manufactured in the conventional manner, but it would be a part of the goal if webs were available for this purpose that are to a high degree uniformly structured and free from fiber flakes.

It is therefore the object of the present invention to provide a method for producing a uniform Paserbahn to create from individual fibers that is essentially free of fiber flakes.

The invention solves this problem by driving according to the characterizing part of claim 1. By this driving it is made possible to process the individual fibers immediately after the fiberisation of the bonded webs made from pulp after their detachment at the same speed with which they were detached to a recording surface to transport.

A gate direction is used to carry out the method according to the invention for producing an air-laid paserbane with a rotating heating device in a housing with teeth for unraveling a solidified fiber web into individual pasers, with a passage between the housing and the tearing device, with a running open-pored receiving surface on which the pasers are used to form the air laid paserbahn are deposited, with a channel between the tearing device and the running receiving surface,

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by which those leaving the heating device are disconnected th 3? aers are conveyed to the current receiving area, where- "at the channel communicates with the said passage, and with one arranged under the open-pored receiving surface Suction device to support the application of the fibers on the receiving surface, whereby the rotation of the Tear device in the passage between this and the housing, a puncture effect occurs, which generates a process air flow, which conveys the separated 3? aers through the channel to the receiving surface and tends to take part of the process air to re-enter the passage. According to the invention, this door direction is further characterized by that the channel used to deposit the fibers has a "limited cross-section for the transport of the severed Has fibers and the process air to the receiving surface and is at least approximately as wide as the teeth of the ripping device are high, and that a process air duct is seen that connects to the passage between the ripping device and the housing is in communication and means are provided to the process air duct air in such an amount and to be supplied with such a pressure that process air flows back out of the channel used for laying down the fibers is essentially prevented in the passage.

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The invention is explained in more detail below with the aid of examples shown in the drawing. Included is:

! ig. 1 a scheroatic side elevation a device according to the invention with a radial feed of the pulp produced Lanes and with a channel running normal to the receiving surface for depositing of the fibers

Pig. Figure 2 is a schematic side elevation of another device according to the invention with radial feeding of the webs made of pulp and with a channel inclined towards the receiving surface for laying down the fibers ^,

Pig. 3 is a schematic side elevation

a further embodiment of the device according to the invention with a spiral feed of the webs made of pulp and with a perpendicular to the Reception area arranged channel for storing the lasers, and

Pig. 4 is a schematic side elevation of a

further invention. Device with spiral feed of the Pulp-made webs and inclined channel for laying down the fibers.

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The apparatus shown in Fig. 1 comprises an ordinary tear roller 10 with tear teeth 12. Made of pulp Paper webs produced are fed to the tear roller 10 radially, i.e. in the direction of a roller radius via the feed rollers 16. The fangs 12 tear the paper webs 14 into individual fibers 22. Compartment of their separation tone the paper webs, the fibers are passed through a channel 18 conveyed to a running open-pore sieve 20 and deposited thereon.

The tear roller 10 is surrounded by a housing 23, and a passage 25 runs between the two. The tear roller Process air 26 is supplied via channel 24, which flows into passage 25 and in such an amount is fed so that it can convey the fibers 22 through the channel 18 at a speed which is tight at the speed of the fangs. The air can be supplied in a conventional manner, e.g. via a fan 27. At the exit of the channel 18 is below the sieve 20 a suction device 28, which is sufficient is large to accommodate the air flowing out of the duct 18. The suction device supports this Depositing the fibers on the open-pored collecting sieve 20 to form a fiber web 30.

It has been found that, in order to avoid the formation of fiber flakes, the individual fibers are fairly accurate should be passed through the channel 18 at the same speed as they would after being separated from the Paper webs 14 made from pulp leave the fangs 12. More specifically, the fibers should be from that The moment they leave the fangs, maintain their speed in magnitude and direction.

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If it was said here that the speed should be "pretty." exactly "" are retained, then it means that the speed at which the fibers are separated from the paper webs no longer changes in the channel 18 than $ 50, but preferably by no more than $ 20. This is in contrast to conventional means by which fibers are used to form a paserbahn placed on a sieve. In these conventional devices, the fibers move to a limited extent due to the flow randomly from the tear roller to the laying surface, and consequently the fiber speeds change $ 100 or more during transportation to the drop-off area.

In the present invention is achieved by a suitable arrangement and dimensioning of the channel 18, that the fiber speed is maintained fairly accurately. Therefore, the channel 18 is arranged so that his the longitudinal axis runs exactly parallel to the plane that is tangential to the bite teeth at the point, at which the fibers leave the area of action of the fangs. With such an arrangement, the fiber speed becomes not changed by the impact of fibers on the canal wall. So if as in Fig. 1 the Paper webs 14 of the tearing roller are fed radially in a plane parallel to the wire 20, then the Plane tangential to the ripping teeth 12 at the point of contact with the paper webs just perpendicular to the wire 20. Since in the schematic representation in Fig. 1 the point at which the fangs come into contact with the paper webs, coincides with the point at which the severed fibers leave the area of influence of the teeth, runs the longitudinal axis of the channel 18 perpendicular to the screen 20. However, if the fibers after their separation from the Paper webs still forcibly remain in the range of action of the fangs, as for example in Fig. 1 of the US patent

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3268 954 shown, then the axis of the channel is expediently aligned so that it is in the direction of the speed of the axis runs to the point where this compulsion no longer exists.

In order to maintain the parallel relationship of the longitudinal axis of the channel discussed above, its dimensioning is also important. Like in Pig. 1, the channel width is approximately equal to the height of the ripper teeth 12, while the passage between the ripper teeth and the housing of the ripper roller is very narrow. With such a selection of the channel width "the speed of the process air supplied through the supply channel 2 4 remains quite constant on its way with the roller and" from there through the channel 18. Since, as already indicated earlier, the speed of the process air approaches the speed of the fangs, which in turn is approximately equal to the speed of the separated fibers, the process air does not cause any significant changes in the fiber speed when it moves the fibers through channel 18 to the Sieve promoted. In the case of channel widths which approximately correspond to the height of the fangs, for example no more than about 1.5 times the tooth height, speeds in the channel 18 of at least 70 i <> the speed of the fangs are expediently used for the device shown.

The dimensioning of the length of the channel and its width, that is its extension in the direction of the axis of the tear roller, is also important to achieve an optimal easerbane. Preferably the length of the channel should be as short be as the overall construction allows. For those in Eig. The device shown schematically in 1 is the shortest

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xpossible channel length through, the size of the radius of the tear roller limited. TJm to obtain a fiber web that is as uniform as possible over its entire width, the width of the channel should be the width of the paper webs made from pulp that are fed to the tear roller, preferably not exceed.

In the case of the tearing roller, goals are generally proportionate high fangs, for example higher than 6 mm, are used. Such tooth heights allow use further channels through which the fibers are deposited on the sieve, and which in turn limit the wide channels the interaction of the pasers with the canal walls to a minimum. ¥ other exemplary embodiments, discussed below show other means of reducing this interaction.

Further features of the present invention are shown with reference to FIG. As in Pig · 1 will be off Paper webs 14 made of pulp are fed to the tear roller 10 with their teeth 12 radially by means of the rollers 16. However, the plane of the paper webs fed to the tear roller does not run parallel to the running wire 20, and consequently, the plane that is at the point of contact between the ripping teeth and the paper webs is also tangential to the ripping roller runs, inclined relative to the solder erected on the sieve. So it goes in line with what has been given above Explanations of the channel 18 so that its longitudinal axis is also opposite to the perpendicular erected on the sieve is inclined. The angle of inclination is approximately the same as the angle of inclination of the tangential plane at the point where the teeth are in contact with the paper webs.

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The use of an inclined channel to deposit the fibers on the screen, as shown in Fig. 2, is "Particularly useful when high tearing capacities are required and the screen 20 is moving at high speed emotional. Fibers that hit the screen from an inclined channel have a velocity component in the direction of movement of the screen, so that breaking of the fibers is reduced to a minimum.

FIG. 2 illustrates yet another feature of the invention, namely with regard to the introduction of the process air through the supply channel 24, which in the example in the doorway guides the process air to a point 32 which is located close to the beginning of the channel 18. In the exemplary embodiment according to FIG. 2, the wall 35 of the channel 18 facing the flow limits the process air channel at the same time. Such an arrangement is particularly suitable when the tear roller is to rotate at high speed and / or when large tooth heights are used. Under these circumstances, the rotating roller produces a pumping action by means of which fibers can pass from the channel 18 into the housing of the tear roller. This could lead to fiber clumps forming in the housing and these fiber clumps being introduced into the channel 18 again by the teeth. However, if the process air is fed to the tear roller near the entrance of the channel 18, then this counteracts the pumping action of the roller and a circulation of the fibers in the housing is prevented. With this arrangement, the process air also serves to strip off fibers adhering to the fangs. The suitable process air flow rate for achieving an optimal fiber web can easily be determined experimentally under the desired working conditions. The suitable flow rate can also be determined visually by opening the inside of the duct through a window (not shown) in the housing.

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observed n than 18. In this pall the flow will be like this set so that the pasers do not collect on the nose 35 of the channel wall 33.

It should also be noted that, as in Pig. 1 the confluence of the process air in the passage a little further away from the entrance of the channel 18, in order to prevent that from the channel 18 pasers and process air withdrawn and passed into the passage 25. However, as in Pig * 2, the confluence is preferred the process air is arranged next to the inlet of the channel 18. This allows the use of lower air pressure, since with a facility according to Pig. in the area of the passage from the entrance of the channel 18 up to the point where the process air is supplied, the pumping action must be overcome.

The arrangement of the process air supply as in Pig. has the further advantage that the control of the process air in the transverse direction is improved. Although the one in Pig. The device shown is suitable for generating a uniform air pressure across the entire width of the machine, the air supplied must match the pumping action generated by the rotating tear roller, which can be variable, overcome. Accordingly, this requires setup a higher pressure than is theoretically necessary in order to provide a certain safety factor that ensures that neither process air nor Pasern can get back into the passage 25 over the entire width. However, this can lead to an unacceptably high air pressure in some places, which leads to undesirable air pressure Air turbulence in the channel 18 leads to the uniformity of the fiber transport to the open-pored receiving

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disturb area.

These possible difficulties can be avoided if one like in Pig. 2 arranges the supply channel for the process air as close as possible to the channel 18. Then it will be the air is supplied where it is needed and can be supplied in such a quantity and with sufficient pressure, that no process air and no fibers enter the passage 25. There is no need to air to be supplied in excess in order to overcome the suction effect generated by the tear roller, which in the area of the Passage 25 occurs between the opening of the channel 18 and the mouth of the supply channel for the process air, because the distance between the two is very small.

Another feature of the invention is that provision is made for the pressure of the air entering passage 25 to be uniform across its width. To do this is how in Pig. 2, the feed duct 24 for the process air is significantly larger than the confluence of the feed duct into the passage 25 at 32. The feed duct 24 is expediently so much larger than the mouth that the pressure fluctuation over the entire width is less than 1-2 However, S _{9 is} preferably less than 1 f ° . This can be achieved in that the width of the feed channel is about ten times as large as the confluence in the passage 25. Pressure fluctuations of about 3-4 $ are already beginning to disturb the desired uniformity of the laid Easerbahn.

Another feature of the invention is that means are provided to additionally iü the air

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Initiate channel 18. The use of this additional air is particularly desirable when there is a high tear performance are present. With a high tear performance and the correspondingly high fiber concentration in the channel 18, the fiber = material to a greater extent to flake formation. The reasons for this lie in a mechanical interweaving of the fibers and in mutual attraction due to static electricity. The use of additional air allows the use of a channel of greater clear width, so that the fiber concentration through the moderate mixing of the two air currents in the area of their adjacent boundaries is reduced, and results in Desirably to a stronger fiber separation and less interaction of the fibers with one another. As is shown in Fig. 2, the channel 18, the additional air is supplied through an additional air channel 34, the next the entry of the separated fibers and the process air opens into the opening of the channel 18. The speed and the direction of the additional air should match the speed and direction of the process air and the fibers match to turbulence or vigorous mixing which would lead to the formation of fiber flocks. The inner wall 37 of the additional air duct 34 is designed so that it allows a simple flow, and ends just at the point 39, where the additional air and connect the process air to one another.

The use of additional air makes it possible to form the channel 18 for depositing the fibers up to four times as far as the fangs are high. With a tooth height of about 6 mm, the channel width can accordingly be about 25 mm . Any conventional source can be used as the air source, for example a blower 41, it is only

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»4 -r.

lent to ensure that the performance is sufficient, the required To achieve air speed.

FIGS. 3 and 4 show further exemplary embodiments of the present invention. This is where they are made from pulp Paper webs 14 fed to the tear roller in a spiral instead of radially as in the Pig. 1 + 2. The different Features and advantages of a spiral feed are detailed in U.S. Patent Hr. 3606 175 shown. In summary, it can be said that a spiral feed allows high tearing capacities, without fiber breakage and charring or burning phenomena appear. In the examples according to Fig. 3 + 4, the spiral feeding of the paper web accomplished by a guide surface 36, the geometry of which is described in the aforementioned patent and which brings the paper webs 14 into contact with the fangs 12 in a spiral path. At the end 38 of the guide surface 36 there is only a negligibly small distance between the guide surface and the fangs 12.

If a spiral feed is used as in FIGS. 2 and 4, then the longitudinal axis of the channel runs for depositing the fibers parallel to the plane that is tangential to the tear roller and touches it where the fangs are closest to the guide surface. Even if the shredding of the paper webs is already happening begins at the beginning of the guide surface 36, the separated fibers leave the effective area of the teeth, however not before they have reached the point of the smallest distance between the teeth and the guide surface. As can be seen from the illustrations, an inclined channel 18 for depositing the fibers, an additional

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additional air supply and a particularly useful one Arrangement of the process air inlet, as described in detail in the previous examples, can be realized.

The device shown can therefore be used to form uniform fiber webs that are completely are free from fiber flakes. The paserbahns formed in this way can be of any weight desired, from single-ply sheets to thick wadding. May this be a Illustrative example clarify: The one in Pig. 1 shown device with a tear roller of 30.5 cm diameter and 33 cm in length, with a tooth height of 9.5 mm can be used to make a combination of four of wood pulp to shred the produced webs, each of which is 0.23 mm thick and a basis weight of 120 g per square meter up / down. To this end, it is expedient to choose a tooth speed of 40 m per second and a width of the channel 18 of 12.5 mm «,

-Patenta Proverbs-

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Claims (6)

Patent to sayings /1. ) A method for producing an air-laid fiber web from individual fibers, in the course of which a solidified fibrous web is frayed into individual fibers using fangs, these individual fibers are conveyed in a gaseous medium to a receiving surface and deposited thereon to form the air-laid fiber web, characterized in , that the fibers are conveyed through an air duct to the receiving surface, the width of which is such that the fibers have essentially the speed with which they are detached from the solidified web. 2. The method according to claim 1, characterized in that the width of the air duct is equal to the height of the fangs. 3. A device for carrying out the method for producing an air-laid fiber web according to claim 2 a tearing direction rotating in a housing with teeth for unraveling a solidified fiber web into individual pieces Fibers, with a passage between the housing and the tearing device, with a running, open-pored receiving surface on which the fibers are laid to form the air Fiber web are deposited, with a channel between the tearing device and the running receiving surface through which the ! the separated fibers leaving the ripping device to the running Receiving surface are conveyed, xvobei the channel is in communication with the said passage, and with a suction device arranged under the open-pored receiving surface to support the laying of the fibers on the receiving surface, whereby by the rotation of the tear device a pumping effect occurs in the passage between this and the housing, which generates a process air flow that removes the separated Fibers through the canal to the 509817/0599 - ¹⁷ - 2252090 Receiving area "and tends to allow part of the process air to re-enter the passage, characterized in that the channel (18) serving to deposit the fibers has a limited cross-section for the transport of the separated fibers and the process air to the receiving area (20) and is at least approximately as large as the teeth (12) of the ripping device (10) are high, and that a process air duct (24) gate is seen, which with the passage (25) between the ripping device (10) and the housing ( 23) is in connection and means are provided to supply the process air duct (24) with air in such an amount and at such a pressure that a return flow of process air from the duct (18) used to deposit the fibers into the passage (25) essentially is prevented. 4. Apparatus according to claim 3, characterized in that the channel (18) intended for depositing the fibers and the process air channel (24) have a common wall (33) and the process air channel (24) is arranged so that it is next to the point ( 35), at which the channel (18) and the passage (25) meet, opens into the passage (25). 5. Apparatus according to claim 3 or 4, characterized in that the longitudinal axis of the channel (18) serving to deposit the fibers is inclined with respect to the solder erected on the open-pored receiving surface (20). ^6th Apparatus according to claims 1 and 3, characterized in that an additional air duct (34) is provided which is connected to the deai duct (18) and is arranged in such a way that additional air is in one place in the duct (18) used to deposit the fibers (39) flows in, which lies next to the entry of the detached fibers into the channel (18), with the additional air flowing in the same direction as the process air B0981T7Ö599 and the channel (18) ″ is up to four times as wide as the teeth (12) of the heating device (10) are high, and that Means (41) are provided for supplying air via the additional air duct (34) into said duct (18), the additional air convey essentially the same speed as the process air has. 5 09 ST Tf 0 5 9 9 Blank page