METHOD FOR PRODUCING A ROTATIONALLY SYMMETRICAL, IN PARTICULAR CYLINDRICAL SCREENING DEVICE
Method for producing a rotationally symmetrical screening device with a plurality of profile bars and screening basket for a pressurized screen. The method includes inserting profile bars parallel to each other into cut-outs open on an interior circumference edge of bar holders and forming the bar holders into rings, thereby narrowing the cut-outs and clamping the profile bars. The forming of rings includes transferring bending forces to at least two locations on sides of the bar holders not provided with the cut-outs. The method further includes connecting abuttable ends of the bar holders to one another.
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The present application claims priority under 35 U.S.C. §119 of German Patent Application No. DE 10 2006 007 660.5, filed on Feb. 22, 2006, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION1. Field of the Invention
The invention relates to a method for producing a rotationally symmetrical, in particular, cylindrical screening device with a plurality of profile bars. Bar holders are provided with cut-outs open at the edge that are shaped to -outs essentially correspond in a complementary manner to bases of the profile bars, and the profile bars are inserted parallel to one another into the cut-outs open at the edge of the bar holders. The bar holders are subsequently formed into rings having an interior circumference on which the cut-outs are located. As a result of forming the rings, the cut-outs narrow and clamp the profile bars.
2. Discussion of Background Information
A known example for the use of screening devices that can be produced according to the method of this type is the screening of fibrous suspensions, as carried out in pressurized screens of the paper-producing industry. The fibers contained in the suspension are thereby to pass through the screen, whereas the undesirable solid components are rejected at the gap and guided out of the screening device again. Since the openings have an essentially oblong shape, i.e., are slots or gaps, fibrous particles are let through more easily than the cubic ones, even if both types should be present in a similar magnitude. A very good elimination effect of non-fibrous contaminants from fibrous suspensions is thus rendered possible with a screening technology of this type. A use for separating different fiber components, the so-called fiber fractionation, is also conceivable. A high precision of the slot shape over the entire screen surface is, however, a prerequisite. With high demands, cylindrical screening devices, so-called screen baskets, are generally used.
DE 39 27 748 A1 shows a possible method for producing screen baskets of this type, in which method the profile bars are clamped by plastic deformation of the support rings provided with recesses for the bars. Profile bars particularly suitable for production methods of this type are used for this. By this method, it was possible to make production considerably cheaper. The method is used with screen baskets where the bars are inserted on the interior edge of the support rings. A bar arrangement of this type is chosen if the suspension is to pass through the slots from the inside outward (centrifugal mode of operation). For the centripetal mode of operation, i.e., with a suspension flow from the outside inward, e.g., screening devices according to DE 44 35 538 A1 can be used.
Screening devices produced by the use of the method according to the invention are preferably used in pressurized screens of the paper-producing industry. It is thereby important that the dimensions of the screen openings are maintained with very low tolerances. In order to keep them unclogged, scrapers are generally necessary, which are moved past the screen surface at a narrow distance and which generate hydraulic impulses. Screening devices for use in pressurized screens must therefore be manufactured very precisely and must withstand high stresses.
SUMMARY OF THE INVENTIONThe invention provides a method with which screening devices can be produced in an even more favorable economical manner. It is also to be usable for different sizes of screening devices without any great expenditure. The screening devices produced are to be of high precision and strength, so that they can be used in pressurized screens.
According to the invention, the bending forces required for forming are transferred at at least two locations on the sides of the bar holders that are not provided with cut-outs and that the bar holders are connected to one another at their two abutting ends after the forming into complete rings.
By the method according to the invention, it is rendered possible to carry out in particular the process of forming in a precise and relatively simple manner. The bending forces required for forming are applied on the circumference of the bar holders. In this stage of the production process, i.e., before the final forming into a closed cylinder is to be carried out, the as yet unfinished screening device is composed of a bent part, the radius of curvature of which is still larger than the radius of curvature of the finished screening device. The bar holders are thus still open at their respective ends, which will be formed into butt joints. The ends mentioned are brought into contact with each other to form the butt joints by the final forming process, or at least brought close enough for a fixing to be possible, e.g., by welding. The shape of the formed component is determined by the bending forces and/or bending moments introduced on the circumference. The counterforce customarily hitherto applied with the aid of a mating shape, e.g., a so-called bending mandrel, acting within the component can be omitted. As is known, a mating shape of this type has a surface that is complementary to the desired shape of the component to be bent. Overall, the bending machine, which is a large, expensive apparatus, is simplified considerably. Furthermore, the bending machine can easily be reset to screening devices of different diameters, since as a rule only the control program needs to be changed.
The present invention is directed to a method for producing a rotationally symmetrical screening device with a plurality of profile bars. The method includes inserting profile bars parallel to each other into cut-outs open on an interior circumference edge of bar holders and forming the bar holders into rings, thereby narrowing the cut-outs and clamping the profile bars. The forming of rings includes transferring bending forces to at least two locations on sides of the bar holders not provided with the cut-outs. The method further includes connecting abuttable ends of the bar holders to one another.
According to a feature of the invention, the rotationally symmetrical screening device can be cylindrical.
In accordance with another feature of the present invention, the profile bars can include base portions insertable into the cut-outs, and the cut-outs may be shaped to essentially correspond in a complementary manner to the base portions of the profile bars.
According to the invention, the location for introducing the bending forces can essentially extend over an axial extension of the screening device. The location can be fixed on the bar holder during forming.
In accordance with still another feature of the invention, the bending forces can act both radially inward and in the circumferential direction.
Further, during the forming, no forces influencing the forming are transferred to the interior circumference surface of the bar holder to be formed into a ring.
According to another feature, no mating shape is used during the forming.
The method can further include applying the bending forces during the connecting of the abuttable ends of the bar holders. Further, complete rings can be formed by the connecting of the abuttable ends of the bar holders.
The method may also include clamping the bar holders during the forming in bending devices applying the bending forces.
According to still another feature, the bending forces can be introduced at a maximum of four locations, and four bending devices can be used to introduce the bending forces at the maximum of four locations. Further, respectively two bending devices may form a bending group which, in interaction, transfers a bending moment to the bar holders.
In accordance with another feature of the invention, the bending forces can be introduced at six locations, and four bending devices and two backing rolls may be arranged to introduce the bending forces at the six locations. Moreover, respectively two bending devices and one backing roll can form a bending group which, in interaction, transfers a bending moment to the bar holders.
According to still another feature of the instant invention, the abuttable ends of the bar holders may be connected to one another by welding.
In accordance with another feature, the forming and the connecting of the abuttable ends of the bar holders can be carried out with a same machine.
According to a further feature of the invention, the bar holders can be assembled from segments before the forming.
Further, the profile bars can be inserted into a bar holder having an open cylinder shape in which the abuttable ends are spaced from each other. Moreover, the forming can include forming a butt joint comprising the abuttable ends. The method can also include welding the butt joint.
In accordance with still yet another feature of the present invention, a screen basket for a pressurized screen usable in the paper-producing industry, is produced by the above-noted method.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWINGSThe present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:
The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.
As shown in somewhat more detail in
It can be expedient to provide one or more nip rolls 14 on the interior contour to support the clamping of bar holders 1 in the bending devices and/or form a counter hold for bending devices 12 and/or 13. They are usually not designed to apply bending forces for forming the bar holders 1.
The subsequent process step, in which a fixed connection of the abuttable ends 6 and 7 is produced, e.g., by welding, is not shown in this representation. Advantageously, the bending forces are only withdrawn after the connection has been made at the butt joints.
A finished screen basket produced according to the invention is shown diagrammatically and in perspective in
As shown in
In a roughly diagrammatic manner,
It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.
Claims
1. A method for producing a rotationally symmetrical screening device with a plurality of profile bars, comprising:
- inserting profile bars parallel to each other into cut-outs open on an interior circumference edge of bar holders;
- forming the bar holders into rings, thereby narrowing the cut-outs and clamping the profile bars, wherein the forming of rings includes transferring bending forces to at least two locations on sides of the bar holders not provided with the cut-outs; and
- connecting abuttable ends of the bar holders to one another.
2. The method in accordance with claim 1, wherein the rotationally symmetrical screening device is cylindrical.
3. The method in accordance with claim 1, wherein the profile bars include base portions insertable into the cut-outs, and the cut-outs are shaped to essentially correspond in a complementary manner to the base portions of the profile bars.
4. The method in accordance with claim 1, wherein the location for introducing the bending forces essentially extends over an axial extension of the screening device.
5. The method in accordance with claim 4, wherein the location is fixed on the bar holder during forming.
6. The method in accordance with claim 1, wherein the bending forces act both radially inward and in the circumferential direction.
7. The method in accordance with claim 1, wherein during the forming, no forces influencing the forming are transferred to the interior circumference surface of the bar holder to be formed into a ring.
8. The method in accordance with claim 1, wherein no mating shape is used during forming.
9. The method in accordance with claim 1, further comprising applying the bending forces during the connecting of the abuttable ends of the bar holders.
10. The method in accordance with claim 9, wherein complete rings are formed by the connecting of the abuttable ends of the bar holders.
11. The method in accordance with claim 1, further comprising clamping the bar holders during the forming in the bending devices applying the bending forces.
12. The method in accordance with claim 1, wherein the bending forces are introduced at a maximum of four locations.
13. The method in accordance with claim 12, wherein four bending devices are used to introduce the bending forces at the maximum of four locations.
14. The method in accordance with claim 12, wherein respectively two bending devices form a bending group which, in interaction, transfers a bending moment to the bar holders.
15. The method in accordance with claim 1, wherein the bending forces are introduced at six locations.
16. The method in accordance with claim 15, wherein four bending devices and two backing rolls are arranged to introduce the bending forces at the six locations.
17. The method in accordance with claim 15, wherein respectively two bending devices and one backing roll form a bending group which, in interaction, transfers a bending moment to the bar holders.
18. The method in accordance with claim 1, wherein the abuttable ends of the bar holders are connected to one another by welding.
19. The method in accordance with claim 1, wherein the forming and the connecting of the abuttable ends of the bar holders are carried out with a same machine.
20. The method in accordance with claim 1, wherein the bar holders are assembled from segments before the forming.
21. The method in accordance with claim 1, wherein, the profile bars are inserted into a bar holder having an open cylinder shape in which the abuttable ends are spaced from each other.
22. The method in accordance with claim 21, wherein the forming comprises forming a butt joint comprising the abuttable ends.
23. The method in accordance with claim 22, further comprising welding the butt joint.
24. A screen basket for a pressurized screen usable in the paper-producing industry, produced by the method of claim 1.
Type: Application
Filed: Feb 21, 2007
Publication Date: Sep 27, 2007
Applicant: VOITH PATENT GMBH (Heidenheim)
Inventor: Werner LANGE (Nattheim)
Application Number: 11/677,394
International Classification: B21D 9/04 (20060101);