FI66948C - SYSTEM FOER TORRFORMNING AV PAPPER ELLER ANNAT ARMMATERIAL AV PARTIKLAR ELLER FIBER - Google Patents

Description

! 66948 A system for dry-forming paper or other sheet material from particles or fibers. - A system for the production of paper or paper having an array of particles or fibers.

The present invention relates to a system for dry forming paper or other sheet materials from particles or fibers, such a system being specified in the preamble of claim 1. Such a system is known from U.S. Pat. No. 4,157,724, in which the dispensing unit is formed by a top-open container having bottom side wall portions forming a screening material, which material gradually passes the fibrous material in the container through these wall portions, after which the exiting material moves through a perforated carried on the upper surface of the forming web by a downward flow of air caused by the suction devices below the forming web. Attached to the distribution tank is a row of fans whose rotating vanes beat the fibrous material in a circulating flow in one direction on one side of the tank and in the opposite direction on the opposite side. The fan blades also provide an outward movement of the material flow toward the inside of the screen or screen walls, with the material flow generally remaining against those walls even though they protrude directly across the forming web, and the same operation generally promotes material passage through the screen walls.

Said circulation of material in the container is very advantageous partly because of the even distribution of material inside the container even when new material is added from only one place and partly because the flow of material generally across the forming web prevents streaks or streaks from forming on the moving forming web. ; in other known systems in which the material in the container is not moved transversely to the forming web, lumps 2 66948 or other local irregularities in the material may cause streaks or streaks as they form local barriers to free fiber exit and settle at fixed points across the formed fibrous web.

Recycling the material on the sides of the tank requires considerable operating power from said fans, although in known systems this is somewhat justified by said whipping blades not only recycling but also whipping the material to keep it that the flow remains of a very limited and defined type of flow without individual fibers spreading throughout the tank and accumulating in all possible places. Nevertheless, the fans must be operated with considerable force or power to achieve the desired results, and it may also be disadvantageous from an operational point of view that one parameter of the speed of the whipping blades determines the various different functions of the dispenser.

The object of the present invention is to provide a dry forming system of the type shown, the simple structure of which differs substantially from the known system and which can be used more flexibly for different purposes.

According to the invention, the outlet wall part forms at least a part of the pipe used to direct the material flow from the corresponding distance or partial distance of the recycling path, the recycling path being preferably located inside a completely closed piping.

The main technical effect of the invention is that the circulating flow of material can only be supported or maintained by passing air through said pipe, since it is no longer necessary to arrange the flow of material to remain individually against the guide wall. The pipes efficiently finance the current and, in principle, the rotational movement as such can be achieved very simply with simple fan devices.

It is still possible to provide special devices inside the tube for keeping the fibrous material air-fluidized and forcing it against the inside of the screen wall part, i.e. the corresponding operating characteristics of the known system are maintained, but this time they do not have to be in any fixed relationship or rotational speed.

However, in a preferred embodiment, a rotating needle cylinder is used which extends axially through straight tube portions, this cylinder both improving circulating flow to perform air fluidization of the fibrous material in the stream and disintegrating the fiber clumps and providing a general ejection effect on the material in the stream. In this case, these functions are naturally related to each other, but it is still possible to adjust the rotational speed independently by changing the supply of additional transport air or arranging a throttle somewhere in the piping.

When the piping system is completely closed, of course, in addition to the holes and the material inlet, the adjustable parameter is the general internal pressure in the piping.

In a very important embodiment of the invention, the screen wall portions of the tubes running across the forming web extend so as to simply form the tubes completely, i.e. completely all around, and these tubes or tube parts are arranged to rotate during use. When the air is drawn down through the horizontal perforated tube, the fibers exit the tube through its lower part and the fibers tend to get stuck in the edge portions of the holes, whereby the free area of the holes may be reduced. However, when the pipe rotates even at a slow speed, the same holes are quickly placed next to the top side of the pipe and the downward air flow penetrates 4,66948 holes in the opposite direction, effectively cleaning the holes whereby the holes and the outside of the pipe are cleaned very efficiently.

In this context, the proposed purification has a significant effect on the whole system not only because the screen holes remain open to maintain good system efficiency but also because the described system is capable of handling fibrous material where the fiber length can substantially exceed the fiber lengths considered to be the largest. possible in connection with dry forming processes. In this case, the maximum suitable fiber length is about 3-4 mm, although experiments have shown that the system according to this embodiment of the invention can easily process a material with a fiber length of about 20-25 mm, possibly even more.

Thus, the idea of enclosing the material flow circulating in itself in the piping system, at least in the most important parts of the entire piping, indeed provides important advantages, as can be seen from various aspects of the invention.

In the following, the invention will be explained in more detail with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a system according to the invention.

Figure 2 is a cross-sectional view of the same system.

Figure 3 is a partially sectioned side plan view.

Figure 4 is a cross-sectional view of a modified detail.

5,66948

The system shown in Figures 1-3 comprises a perforated forming web 2 which is continuously moved along a closed path (not shown completely), passing under the distribution unit 4. Attached to this unit and to the web 2 is a suction box 6, the exhaust pipe 8 of which is connected to a suitable vacuum cleaner. The dispensing unit 4 comprises an outer jacket or housing 10 open downwards towards the web 2 and two horizontal tubes 12 extending through the housing across the web and made of spreading screen material, i.e. mesh material or perforated sheet material. The ends of the tubes 12 are supported by rotating bearings 16 mounted on opposite end walls 14 of the housing 10, and outside the walls 14 the ends of the tubes are connected by external, fixed U-tubes 18 and 20, of which the U-tube 20 is provided with a tangential inlet tube 22 extending with tube 12. Arranged at the ends of the tubes 12 are non-perforated sleeves or sleeves 24 which cooperate with the bearings 16 and are located tightly and rotatably at the ends of the U-tubes 18 and 20.

At least at one end of the tubes 12, the sleeves 24 co-operate with a drive for rotating the tubes 12, 24, which in Figure 1, for example, is a belt 26 driven by a motor-driven pulley 28.

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The upper side of the housing 10 is provided with slots 30, the width of which may be adjustable by flap plates 32.

The system described so far can operate by feeding an air-fluidized flow of fibrous material through a flow inlet pipe 22 from a fan (not shown), whereby a circulating material flow is formed in the pipe system 12, 18, 20. From this stream, individual fibers are passed through the screen walls of the tubes together with additional transport air which is fed through the inlet pipe 22. From the suction box 6, air is sucked down through the perforated forming web 2 and 6 66948 down through the housing 10 from the upper slots 30. This substantially vertical air flow passes both across the screen tubes and along its outer sides, thereby promoting fibers leaving the tubes and conveying exiting material down to the forming web 2

The air drawn down from the upper slits 30 has the additional effect of effectively cleaning the outer surface and holes of the screen tubes as the tubes rotate, so that the fibrous material accumulated in and adjacent to the lower outlet holes is removed by the downstream air "countercurrent effect". Any fibrous deposits on the outer surface of the tubes can be blown away as they pass through the upper part of the orbit of the tubes. thereby preventing the formation of lumps which would otherwise form on the outer surface of the sorting screen, for example by the action of static electricity; it is well known that such lumps are disadvantageous because, when grown to a considerable size, they fall off and accumulate on the forming web.

Cleaning of the holes and screen tubes 12 can be substantially enhanced by additional external cleaning devices, such as a rotating brush, or as shown in Figure 2, a nozzle system 44 can be provided in the tube 46 connected to the compressed air source, blowing air jets against the outer surface of the tubes 12 either continuously or intermittently. In this way, a very efficient cleaning is obtained and for this reason it is possible to process considerably long fibers while still maintaining the long-term and high power of the system.

In a large production system, the mere recirculation of material through the tubes by the air supply through the tube 22 may be insufficient to ensure that the material remains properly fluidized. For this reason, each tube 12 is provided with an axially oriented mixing cylinder 34 provided with radial mixing needles 36 along its entire length, the shaft parts 38 of the cylinders 38 being mounted on bearings 40 and at least one end of these shafts extending outwards and provided with pulleys 42 or the like. by means of which the cylinders 34 can be rotated relatively quickly by means of suitable actuators (not shown).

The outer diameters of the needle cylinders 34, 36 are preferably clearly smaller than the inner diameters of the tubes 12, and the cylinders are mounted eccentrically so that the needles 36 accurately wipe the lower interior of the screen tube 12. In this case, the tips of the needles sweep away any fiber accumulations on the inner surface of the tube, and in addition, the needles effectively and vigorously break up the material if there are lumps of fibers.

Furthermore, the needles 36 throw the material directly through the screen so that a very high removal power is achieved.

According to Fig. 3, the needles 36 are screwed to the cylinder at short distances by a screw to the surface of the cylinder, and during their rapid rotation the needles then act as a conveying screw which promotes the flow of material through the tube 12. The circulating current can well be generated by a conventional fan. for example, with axial fan blades attached directly to the cylinders near their ends. Another possibility is to spray the exhaust air into the system through nozzles placed inside the U-tubes 18 and / or 20. However, it appears entirely sufficient to use the cylinders 34 for this purpose when the needles 36 are arranged to extend along the helical line. Of course, the needles or part of them can be shaped slightly propeller-like to further enhance the main current.

Inside the tubes 12, in the vicinity of their upper surface, a fixed protective plate 48 can be provided, which are supported at the ends inside the U-tubes 18 and 20 by brackets (not shown).

This plate restricts the direct downflow of air through the screen tubes to the forming web 2, as it may be advantageous to increase the air flow downwards along the outer surfaces of the screen tubes. However, air from above can still penetrate the screen tubes through these side portions.

The needle cylinder 35, 36 disintegrates the fiber clumps very efficiently due to possibly the eccentric position of the cylinder in the tube 12, and in extreme cases it may be possible to feed the material into the piping only as a fiber clump material, for example by spraying through one of the top or inner openings. In this case, the supply pipe 22 can be omitted or it can be used exclusively for the supply of excess air.

Figure 4 shows that instead of a needle cylinder, one or more through tubes 50 connected to a compressed air source and provided with nozzles 52 can be used in the screen tubes to direct an air jet to the inner surface of the screen tube, thereby achieving an ejection and mixing effect on the fibrous material. On the discharge side of the pipe, the showers may have a speed component.

The flow and pressure conditions inside the tube 12 may vary somewhat along the length of the tube and, if necessary, may cause some differentiation of these conditions, for example by arranging the top shield 48 axially obliquely or forming a shield of different widths at different points in the tube. The helical line of the needles 36 on the cylinder 34 may have a non-constant pitch and the degree of perforation of the screen tubes may be staggered.

It would also be possible to use only one screen tube 12 when the U-tube system is non-perforated; however, considerable movement of material within the tube may tend to form a different outlet power along the tube and in order to achieve an even fiber distribution in the web, it is normally recommended to use screen tubes 12 in pairs, as return flow through another screen tube may compensate for non-uniform capacity. On the other hand, the recycling system may well have more than two sieve tubes 12, for example four such tubes.

Rotation of the screen tubes is very important for cleaning the holes and can occur at such a rate that the associated centrifugal forces further increase the ejection effect on the fibers in the holes in the vicinity of the lice.

The invention also relates to a described method for producing a web material by directing the material flow through the distribution tubes 12 and preferably by rotating the tubes during operation and cleaning them successively during rotation.

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Claims (7)

1. A system for dry forming paper or other web material of particles or fibers, including a movable, perforated molding strip (2) and a distribution unit (4) located above this, which is provided with a perforated outlet wall part, through which the particle or fiber material introduced into the container may gradually depart from the container, whereby a suction device (6) for sucking air down through this belt is arranged under the perforated belt (2) to transport the material emitted from the belt, the dispensing unit to the type On the other hand, there are means for controlling the material introduced therein in an air stream through a recirculation path, at least part of which extends over the perforated band (2) along the inner surface of the container's outlet wall part, characterized in that the outlet wall part is at least part of it. of the pipe (12) used to control the flow of material along the present stretch of recycle or part thereof, the recirculation path preferably Mr. belt enclosed in a closed pipe system (12, 18, 20). 2. A system according to claim 1, characterized in that said pipe (12) is rotatably arranged and that substantially fixed screen cleaning parts are arranged, such as air nozzles (44) for cleaning the heel from the outer side of the pipe. 3. A system according to claim 2, characterized in that the sieve tube (12) is made entirely of the sieve screening material and arranged to rotate in a single direction continuously or periodically. System according to claim 1, 2 or 3, characterized in that separate or inside the sieve tube (12) is arranged.