DK151482B - DISTRIBUTOR UNIT FOR DISTRIBUTION OF FIBERS, PREFERRED TO RUBBER PAPER - Google Patents

Description

151482

The present invention relates to a distributor unit for dry laying of fibers on a molding wire, preferably for dry making of paper, and of the kind comprising one or more perforated tubes extending over the molding wire and connected to feed means for an air-fluidized fibrous material. One such device is disclosed in European Patent No. 0032772.

In known units of this kind, the perforated tube, which is preferably kept in rotation, is designed as a perforated plate shell having a large number of perforations, so that the tube acts as a classification network with good withdrawal capacity for the fibers. These are fed to the tube from one end thereof and caused to flow through the tube in a relatively strong air / fiber stream which is recirculated through a corresponding tube disposed adjacent to and parallel to the first tube so that the flow circulates through the two tubes. Below the forming wire is arranged a suction box which creates a downward flow of air which coats and partially flows the perforated pipes across them, whereby fibers throughout the pipes will be conducted through the perforations and the outgoing fibers are fed with the suction air for deposition on the form wire.

Inside the tubes may be provided means such as compressed air nozzles or a rotary brush roll which can affect the fiber / air flow in various ways, namely to agitate the stream to maintain the air suspension of the fibers, influence the flow with an outward force against the tube wall, whereby the withdrawal capacity of the fibers can be substantially increased, and / or influence the flow in its axial direction of movement, namely to support the flow itself through the tube.

During operation, on average, as much fiber material as is discharged through the perforated tubes is fed to the circulating fiber / air stream, and it is thus advantageous that a uniform fiber distribution can be obtained on the mold wire despite any fluctuations in the flow of the feed. fiber material, as well as a reasonably good withdrawal capacity of the fibers.

Exit capacity is very important, ie. it is desirable to work with a large number of perforations in said tubes. However, the tubes should preferably be self-supporting between their opposite ends, as the use of special supports along the tubes can interfere with the desired uniformity of the fiber layer laid on the molding wire, and when the tubes should thus be quite rigid, the degree of perforation is limited. can show up in practice. Of course, the number of perforations can be increased by increasing the pipe diameter, but here too there are practical limits to how far one can go.

The invention provides an increased number of perforations in a manner which proves highly advantageous in several respects in the given context.

The distributor unit according to the invention is characterized in that the perforated tubes are constituted by a circular cylindrical extending sleeve consisting of corrugated plate, the waves extending longitudinally of the tubes. For a given pipe diameter and degree of perforation, the total pipe wall area and thus also the number of perforations will be increased. At the same time, the wavy cross-sectional shape will greatly stabilize the tube against deflection, whereby it may even be permissible to work with an increased degree of perforation, as well as with an increased tube length.

By using a stationary, rotatable brush or card roller embedded in the tube, additional benefits are obtained, as illustrated below.

The invention will now be explained in more detail with reference to the drawing, in which: FIG. 1 is a schematic perspective view of a paper drying plant; FIG. 2 is a perspective view of a portion of a distributor tube used therein formed in accordance with the invention; FIG. 3 is a cross-section of the same tube, and FIG. 4 shows a detailed section of the same cross-section.

The FIG. 1 is described in more detail in said European Patent No. 0032772. It consists of a movable mold wire 2, below which is arranged a suction box 4 and over which is arranged a distributor unit consisting of two parallel, perforated tubes 6, connected at the respective opposite ends through non-perforated tube bends 8 of 180 °. To one of these pipe bends is connected a supply pipe 10, through which a stream of an air-fluidized fiber material can be blown into the pipe system 6.8 from which a stream can circulate.

In the suction action of the suction box 4, an air flow is passed downward and partly through the perforated pipes 6, from which single fibers are fed, which are sucked down for deposition on the forming wire 2. The pipes 6 are rotatably stored, whereby their perforations are successively cleaned of any clogging. by the generally downward flow of air to the suction box 4, as well as rotating, they contribute to increasing the withdrawal capacity of the fibers due to the associated centrifugal action on the fibers present at any moment during withdrawal in the perforations themselves.

151482 4

Inside each of the tubes 6 is mounted a rapidly rotating brush roll 14 carried in fixed bearings 16 on the tube bends 8. The outer diameter of the brush roll 14 is considerably smaller than the diameter of the tube 6, and the brush roll is positioned so that its brushes 18 stroke tightly. along the inside of the tube 6 at a lower region thereof.

The rotary brush roll will help to keep the fiber material air-fluidized and to influence the flow of fiber material through the tube with a centrifugal outward-facing centrifugal force promoting the fiber exit through the perforated tube wall. In addition, when the brushes 18 on the roller 14 are arranged in a helical row, an advantageous axial transport effect on the fibrous material will be produced by the rotation of the roller.

1 according to the invention, each of the tubes 6 is formed with a wavy cross section, as can be seen in FIG.

2 and in particular of FIG. 3 and 4. This cross-sectional shape of the tube 6 will greatly enhance the stability of the tube in the transverse direction, ie. the tube may be self-supporting over a relatively long length, and at the same time substantially increase the surface area of the tube, so that for a given perforation degree it will exhibit substantially more perforations than a simple circular cylindrical tube and thus an increased fiber exit capacity. Due to the increased stiffness of the pipe, it is even possible to work with an increased degree of perforation, which further increases the capacity.

In order to achieve the desired high capacity, it is essential that the fibers 18 are constantly reorganized. It is not fully understood how this is actually done, but there is reason to believe that the essential effect lies in the fact that the brushes, in their rapid movement, form a vacuum behind them and thereby create a turbulence which affects the fibers vigorously. In the invention, this turbulence as indicated in FIG. 4 could propagate into the profile waves in the tube which lie outside the path of movement of the ends of the brushes, ie. turbulence is also created in the spaces in question so that the fibers are reorganized immediately within the perforations. The turbulence will be increased because the pressure conditions will vary as the brush ends pass the wave peaks and the wave valleys, respectively, and the capacity as a whole will be noticeably increased.

In addition, the present invention preferably uses actual card needles as brushes on the roller 14, i.e. rigid, tapered, pointed needles 18, which, due to their pointedness, prove particularly suitable for disintegrating both short and long fibers.

It will be appreciated that the tangential contact area between the tube 6 and the brushes or needles 18 is of great importance for the withdrawal capacity of the fibers, i.e. it is along this area, the fiber exit of the largest. For the same reason, for the uniformity of the transverse profile of the fibrous web deposited on the forming wire, it is essential that the axial flow of air-fluidized fibrous material in the tube 6 is particularly smooth and unobstructed precisely in or along this region. Using a non-corrugated pipe wall, this area is virtually the only one along which the axial flow cannot flow unimpeded, while the invention provides that an additional axial flow possibility exists in the wave passages outside the brush or needle ends, regardless of the flow. passing through turbulent air. The result is nevertheless that the axial flow in that area is improved, which contributes both to a good capacity and a good uniformity of the fiber exit.

In FIG. 2 only a single brush or needle roller is shown, but it will be seen that there may be room for several such rollers if desired.

In FIG. 4, several different detailed embodiments of the wave profiling of the tube 6 are shown; the invention is not limited to any particular form of profiling.

Claims (2)

151482 PATENT REQUIREMENT ί A distributor unit for drying fibers on a molding wire, preferably for dry-making paper, and of the kind comprising one or more perforated tubes extending over the molding wire and connected end-to-end with means for an air-fluidized fiber material, each tube is preferably rotatably mounted and cooperates with a rotatably brushed rotatable roller inside the tube, characterized in that the perforated tubes are constituted by a circular cylindrical seam consisting of corrugated plate with the waves extending longitudinally of the tubes. Distributor unit according to claim 1, characterized in that the brushes on the brush rolls stored in the tubes consist of rigid, tapered card needles.