METHOD FOR PRODUCING ANNULAR PARTS AND USE OF SAID METHOD

Description

The present invention relates to a method for producing annular or tubular parts according to the preamble of claim 1, particularly a method for cutting, rolling, and welding thin steel strip from a coil, and use of the method.

It is generally known that, in methods for producing tubular, cylindrical, or annular objects from flat or wound starting materials, several complex work steps are necessary, first in order to perform the cutting to the desired starting dimensions, second in order to achieve the desired bending as a sum of several partial bending processes, and third in order to provide the rolled part with a welded longitudinal seam, whereby the finished tubular product is then obtained. An important disadvantage of the known bending methods is that the required shape accuracy often cannot be achieved or can be achieved only with significant mechanical and electronic complexity, even if the entire bending process is divided into several individual bending steps. The known roll bending methods are only conditionally suitable for fully automatic use in production lines, because, particularly in the event of a product change, the machine times, which are already relatively long because of the complex forming processes, are further increased because of tool changes, and thus the economy is further reduced.

Known methods for forming metals sheets are the classic two-roll bending method or the three-roll bending method, also called rolling. A disadvantage of these methods is that different tube diameters require parts of the device—particularly the clamping tools—to be exchanged, whereby the economy of the system also decreases. An invention that avoids the exchange of parts of the device for different tube diameters is described in patent document EP 0 701 878 B1. In this design, flat or tubularly pre-formed metal-sheet blanks are fed to the welding system by means of an additional placement system. The cutting and pre-forming thus occur outside of the described system, which results overall in a greater investment expense and thus has an adverse effect on the investment costs of the entire system.

In patent document DE 10 2008 027 807 B4, a method for producing steel pipes is described, wherein a metal sheet or coil is formed into a tubular body in a bending operation, provided with a longitudinal seam in a subsequent welding operation, and then subjected to a stress-relief treatment.

This method contains complex forming tools having a control device and contains an additional stress-relief treatment for reducing the stresses mechanically produced by the forming of the metal-sheet material. Such a complex method is sensible for thick-walled tubes but is less suitable for thin-walled tubes according to the present invention.

It is apparent that these methods mentioned above are associated with significant complexity. Therefore, the problem addressed by the present invention is that of specifying a method that does not have the disadvantages mentioned above.

This problem is solved by means of the features stated in claim 1. Advantageous embodiment variants are stated in the dependent claims.

The invention presented here describes a method that allows, in a continuous processing process, thin-walled, sheet-shaped starting material to be cut to the desired dimensions in a first sub-process, then to be rolled in a second sub-process, and finally to be provided with a welded longitudinal seam in a third sub-process by means of the same equipment—a combined machine. This results in lower investment costs for machines, and lower variable costs in the operation of such an inventive installation also result, because no tools have to be exchanged during production in the event of changing production batches. Overall, this innovative method results in a favorable cost-benefit ratio for such final products which, on the basis of the tolerances, do not demand very high requirements, for example for drums of washing machines or of dishwashers.

Below, the present invention is explained further on the basis of embodiment examples with reference to drawings.

FIG. 1 shows a schematic illustration of the production of annular parts according to the prior art.

FIG. 2 shows a schematic illustration of the production of annular parts according to the invention.

FIG. 3 shows a first cross-section of a combined machine according to the invention for producing annular parts.

FIG. 4 shows a second cross-section of a combined machine according to the invention for producing annular parts.

FIG. 5 shows a longitudinal section of a combined machine according to the invention for producing annular parts.

FIG. 6 shows a schematic illustration of a coil having the coil starting piece and the coil end piece.

FIG. 7 shows an annular workpiece produced by means of a combined machine according to the invention.

FIG. 1 shows the production of annular parts according to the prior art in a schematic illustration. Thin metal sheet is fed in the form of a coil 7 from a decoiler 1 to the cutting machine 2, where the metal sheet 10 is cut to the required starting dimension. Then a mechanical and/or thermal rolling process is applied to the metal sheet 10 in one or more steps in a rolling machine 3 so that an annular open workpiece 34 having two longitudinal edges 29a, 29b is obtained, which longitudinal edges are then welded together by means of a weld seam 36 in a welding machine 4, whereby an annular part 35 is obtained, which is optionally processed further in an additional processing step by means of an expanding machine 5.

FIG. 2 shows, again in a schematic illustration, the inventive production of annular parts. Thin metal sheet having a thickness in the range of 0.4 mm to 1 mm is continuously fed in the form of a coil 7 from a decoiler 1 to the combined machine 9 as a starting material, wherein the workpiece, in one and the same combined machine 9, is fed by means of a roller mechanism, clamped, conveyed, cut to the required starting dimension, formed into an annular or cylindrical part on a rotating rolling machine, and welded and thus provided with a longitudinal seam 36.

Then the annular part 35 is automatically or manually removed from the combined machine 9 by means of a mechanism. In this method, further processing can optionally occur in an expanding machine 5 in an additional work step.

Instead of the feeding of the starting material from a coil 7, the feeding of pre-cut plates 8 is also mentioned as an alternative.

FIG. 3 shows a cross-section of the combined machine 9 according to the invention for producing annular parts 35, wherein the workpiece 16 is automatically fed in a conveying direction F of the combined machine 9 and is conveyed by means of the guiding rollers 19a and the

• roller guides 18a, 18b and by means of the
• advancing rollers 19b through the clamping device 22 to beyond the advancing roller 15. The coil starting piece 27 generally has a non-straight edge 30 unsuitable for optimal welding and is therefore fastened by means of the clamping device 22 and cut off by means of the cutting head 24 integrated in the carrier 17 and deposited in a scrap bin 11a, 11b, or conveyed out of the machine by means of a flap 20, wherein a straight welding edge 29a is obtained on the first good piece 31 by means of the cutting. In a next process step, the workpiece 16 is conveyed further onto the rolling tool 21 up to the retaining device 14 at the end of the rotatable magnet bar 13 after the clamping device 22 has been opened, wherein the front end of the workpiece 16 is retained by means of the retaining device 14 by pneumatic and/or magnetic application of force and is conveyed further by means of the rolling tool 21, which rotates in a direction of rotation R.

FIG. 4 shows, in a further cross-section, a combined machine 9 according to the invention, wherein the workpiece 16 has been conveyed further by a half rotation in the

• direction of rotation R in comparison with the position shown in FIG. 3 and has an approximately semicircular cross-section. By continuous conveying of the workpiece 16 in the
• conveying direction F, a further half rotation in the
• direction of rotation R occurs so that the workpiece 16 has the desired periphery and then can be fastened in such a way, by applying a force by means of the clamping device 22, that the rolled, slightly elliptical workpiece 34 can be severed from the coil 7 by means of the cutting head 24, two straight welding edges 29a, 29b thus being formed and a gap B thus being formed. After the can B between the two welding edges 29a, 29b is closed except for a. small remaining gap by means of a further small rotation in the direction of rotation R, wherein the workpiece 34 having a slightly elliptical cross-section is deformed into an annular workpiece 35 having a circular cross-section and then is fixed by means of the clamping device 22, whereupon the application of force at the retaining device 14 can be reduced or eliminated. In the subsequent welding process, the two straight welding edges 29a, 29b are firmly joined by means by means of a longitudinal-seam weld, and the annular workpiece 35 can then be removed from the combined machine 9 by means of a removal mechanism not shown.

FIG. 5 shows the carrier 17 of the combined machine according to the invention, which carrier has an integrated cutting and welding device, in a longitudinal section, wherein the source 23, preferably a laser source, is switchable, so that the source is mechanically and electrically connected either to the cutting head 24, which can be moved in a

• transverse direction Q, or to the welding head 25, which can likewise be moved in the transverse direction Q, and is additionally designed with a feed 26 for filler material for the purpose of filling the remaining gap arising when two edges are joined with filler material if necessary during the welding and thus closing the remaining gap, whereby an optimal weld seam can be produced. The workpiece 16 is guided between the upper and the lower part of the clamping device 22, wherein the mismatch rollers 12 are used to compensate a possible perpendicularly arising mismatch of the two edges of the workpiece 16 to be welded together and thus to enable an additional increase in the welding quality.

FIG. 6 shows, in a schematic illustration, a coil 7, from which the coil starting piece 27, which has a non-straight edge 30, was cut off in a first processing step and from which a first good piece 31 having the straight welding edges 29a, 29b was cut off in a second process step. Furthermore, the coil end piece 28 having the non-straight edge 30, and the last good piece 32 of the coil 7 and the next to last good piece 33 each having the two straight welding edges 29a, 29b, are illustrated.

FIG. 7 shows a slightly elliptical workpiece 34 produced in the combined machine 9 by means of the innovative method, after the cutting and rolling but before the welding, and an annular part 35 after the cutting, rolling, and welding, to which the longitudinally welded weld seam 36 has been applied.