Process to make a screening apparatus having slotted apertures and screening apparatus obtained by this process

The invention relates to a method according to the preamble of claim 1.

A known example of the use of screening apparatus which can be prepared according to the method of this type, is the sorting of fiber suspensions. The fibers contained in the suspension to pass through the screen, while the undesired solid components rejected at the gap and be directed out of the sieve again. Also conceivable is a use for the separation of different fiber ingredients. The fact that the openings have a substantially elongated shape, ie, slots or gaps, fibrous particles to pass through more easily than the cubic, although both species should be similar in magnitude. With such sorting technology therefore a very good elimination effect of seamless fibrous impurities from fiber suspensions is possible. However, this requires a high precision of the slot shape around the screen surface.

A method to prepare such screen baskets, is shown in DE 39 27 748 A1, in which the section bars are clamped by plastically deforming the with depressions provided for the rods retaining rings. To this end, particularly suitable profile rods used for such production process. Using this method it was possible to reduce the cost of production significantly, but caused by the use of such screen baskets were not completely excluded.

Screens or screen baskets with good strength and high surface quality can be produced by a process which is described in DE 42 14 061 A1. Here, a high-temperature soldering process is applied for mounting the rod-like profiles. The results are excellent, the method is, however, complicated and expensive.

German patent document DE 33 27 422 A1 screens or screen baskets are known in which the sorting slots are formed by substantially parallel, rod-like profiles, which are welded to transverse support ribs. Although it has been possible by this manufacturing process, to firmly connect the rods with the retaining ribs, which is at the required precision, if at all, then only feasible at considerable expense. In order to avoid the sticking of fibers during operation of the screening device, all the fabric contacting surfaces must be extremely smooth. The only way to prevent build fibers there and sooner or later lead to constipation. Although it has already been proposals to smooth or cover such welds subsequently. However, these measures were mostly likely to increase the cost of production further.

The invention has for its object to provide an economically advantageous method, the screening devices can be produced which have optimal strength and surface properties.

This object is achieved by the measures mentioned in the characterizing part of claim 1.

In Advantageous embodiments of the method are described and screening devices, which are then manufactured.

The advantages of the invention have an effect especially in Stabsiebvorrichtungen whose sorting slots have a width in the size range below 2 mm. For the pulp sorting or scrubbing slit widths are 0.1 to 0.2 mm is quite common. Such filters must be provided with a very large number of bars in order to obtain a sufficient screen surface with the narrow slots. Therefore, in their preparation to prepare for joining is very elaborate. Although in mass production, it is possible to use special devices, but these are complicated and expensive. In the inventive method, however, the profile bars z. B. be accommodated by simply sliding into position, fixed and remain there until the binder has caused the final grip. It is thus ensured a holding force of the rods in the wells, which is large enough to run the following on the insertion operations of handling without unintentional change of position can. This handling includes eg the transport and how to contact these inters. The binder provides a non-releasable connection at the contact surfaces forth, so as for example during soldering, gluing or welding. When pure contact welding then comes the binder as a melt of the components themselves.

An applicable with advantage in the manufacture of such screening devices is soldering, brazing, at a temperature up to about 900^O C. It is, however, a process at high temperatures of about 1000 up to 1200^O select C, which is performed in a high vacuum. The combination of materials of rods and reinforcing elements takes place by diffusion of the solder into the portions to be joined, causing very high strength with flawless surface. However, the latter soldering initially require major investments.

As expensive compound and the bonding is to be considered, since it is feasible at relatively low temperatures. If for example a technical two-component adhesive is used, the Klemmkräft retained. Thereby, for example, which may lower strength of the adhesive bond can be compensated. If one uses for the bars drawn profiles, such as steel or a steel alloy, including special cross-sectional shapes are commercially available and accurate.

With relatively tight tolerances on grooves and bars after the easy insertion of the rods, a sufficiently tight fit is possible. Then reinforcement elements may be used which have already when inserting the rods their final form. This slightly more expensive processing leads to screening devices with very uniform slots, which can be a decisive advantage particularly for their use for sorting fibrous suspensions for papermaking. However, when larger fit tolerances allowed, which cheapens the process in general, a deformation of the reinforcement elements after the insertion of the rods is necessary to ensure their safe stop. The clamping forces which are generated by this deformation, can during the step in which the binders are effectively become weaker or be lost again. One drawback for finished manufactured screening device is characterized as a rule but not given because the soldering already leads to excellent strength. Here, the already mentioned high-temperature soldering in a vacuum is particularly well suited.

A special case is the widening of the depressions by elastic deformation of the reinforcing members before the bars are inserted or slid. This leads to the discharge, so the rebound to a secure fit and at the same good characteristics of the screening device thus produced. The tolerances must not be as narrow as in working without deformation method. Also, the elastic deformation can be kept low. There are enough relatively small holding forces, as only to be saved in handling the position of the rods.

A particularly important application is the use of straight bar-shaped reinforcing elements with the recesses described above. Once the rods have been inserted in a kind of mat formation can be produced by subsequent bending, for example, rounding rollers of the reinforcing elements, the final shape of the screening device. In the same operation the clamping of rods and therefore its necessary for the further manufacturing process fixation occurs. Another cheapening of the process is possible if the depressions are designed in the reinforcing elements so that the rods vertically - can be inserted, so do not need to be pushed from the side - possibly with compressive forces. The fixing of the rods in the reinforcement elements may be up to the conclusion of the manufacturing process, but need not, then be carried out by deformation of the reinforcing elements.

The invention is explained with reference to drawings; in which:<dl id="dl0001" compact="compact"><dt>Fig. 1 a - 1c</dt><dd>diagrammatically some manufacturing steps when applying the method;</dd><dt>FIG. 2</dt><dd>Part of a screening device according to the invention in section;</dd><dt>Fig. 3</dt><dd>a cylindrical screen basket;</dd><dt>FIGS. 4-6</dt><dd>respectively variants of the rods and their arrangement;</dd><dt>Fig. 7</dt><dd>a semi-shells screen average.</dd></dl>

The most important manufacturing steps of the method are shown in Figures 1a - 1 c schematically recorded. In Fig. 1a can be seen part of a reinforcing element 1 with the already introduced depressions 4. A common method for the manufacture of such wells is as laser welding, to achieve higher precision can also electro-erosion be useful. In the preparation of conventional screening apparatus, the reinforcement member includes a large number of such wells. In Fig. 1b three rods 2 are inserted into the recesses, it can be seen that the shape of the recess on the sides of the rod 2 can in each case some air. Thus, the rod can be inserted easily. This air, with the sitting of the rod C in the recess 4 is drawn exaggeratedly, to illustrate the principle better. Very clearly visible is that the rods 2 on its used in the reinforcing member side have thickened, which prevent the falling of the rods reliable. Subsequently, the reinforcing member 1 is deformed so that the rods 2 are clamped. The following is the strength-increasing treatment, such as soldering. When the binder 5, a solder is a fixed non-detachable connection between the parts is achieved (see Fig. 1 c). This representation is only schematic, since such processes, such as soldering under a high vacuum are known in the art.

The cut-out in Fig. 2 shows in perspective a part of the reinforcing element 1, in which the rods 2 are inserted and fixed therein already. It can be seen that a sieve has formed with the columns 3 by this arrangement, through which in the flow direction (arrow S) that can pass to be sorted liquid. In operation, parts, whose size exceeds the free gap, retained and discharged in a conventional manner. A recess 4 for receiving a rod is shown here without the rod. The indicated as fat binder line 5 may have been introduced by soldering, welding or gluing. It forms a firm non-releasable binding of the contact surfaces and thus increases the strength of the screening device decisive. In cases where no optimal for joining cross-section of the bars has been chosen, for example, because the sorting task required specific forms, the strength can be still large enough.

The screening device according to the invention produced can be designed according to FIG. 3 as a cylindrical screen basket, which is held together by a plurality of annular reinforcing elements 1. The illustration shows only part of the existing rods 2, which are used here in the radially inner rings. Of course, this could also have been externally added.

Depending on requirements and manufacturing capabilities, the bars will be 2 more deeply or shallowly inserted into the reinforcing member. 1 Thus almost completely recessed bars are, as shown in Fig. 4, conceivable. This allows a particularly secure connection of rods 2 and reinforcing elements. 1

In many cases it is of advantage, if the the flow facing surfaces of the rods 2 against the direction of movement (arrow 7) of the Räumelementes 8 (only indicated) are inclined so as to form at the trailing edge of the bars paragraphs 6th At this point vortices can be created that improve the eviction action with the help of moving past eviction wing. With spaces is meant that the material-water suspension again sufficiently fluidized and the rejected parts are quickly removed from the screening area, so that the screen surface is offered again for further screening.

In FIG. 5, the recesses 4 are formed in the reinforcing elements 1 as openings. In such cases, the bars must be 2 by inserted at the side, where they have a maintenance without deformation of the reinforcing member, for example, if it is an interference fit or a shrink fit. This is generated as with close fitting tolerances or with different temperatures of the joining partners in the assembly. The profiles used the rods can be freely selected by using criteria (sorting technology) of the screening device. Another suitable for the side through insert molding, FIG. 6.

In Fig. 7 a section is shown through an opening formed as a half shell screening device. In this case, an arrangement is exemplarily selected in which the rods are inserted two at the radially outer part. The fixation may be carried out here, is by the semi-annular reinforcing element 1 together elastically bent and released again after inserting the rods. 2

It is understood that, this insert by choosing the rod cross-section and by the way in the fasteners, the design of the sorting gap a large number of possibilities is given.