Pipe bending press

Abstract

Method for bending sheet metal during the production of pipes using a pipe bending press, with a bending blade (4) arranged in or on a press upper part (2), to the lower end of which an upper tool (5) is attached and with two lower tools (6a, 6b) arranged in or on a press lower part (3) and spaced apart from one another transversely to the working direction (a), whereby the sheet is bent in several successive forming processes and is moved step by step transversely to the longitudinal direction of the sheet, characterized in that, in order to bend a sheet metal arranged between the upper press part (2) and the lower press part (3), at least one of the lower tools is moved during a working stroke against the upper tool and along the working direction relative to the other lower tool.

Description

[0001] The invention relates to a method for bending sheet metal and a pipe bending press for bending sheet metal in the course of pipe production, with a bending blade arranged in or on an upper press part, to the lower end of which an upper tool is fastened and with two lower tools arranged in or on a lower press part and spaced from one another (transversely to the working direction).

[0002] In the context of the invention, "pipe" refers in particular to a longitudinally welded pipe or open-end pipe. In a pipe bending press of the type described above, which is also referred to as a step-forming press, the sheet metal is bent in several sequential work steps or bending processes. The production of a pipe, and in particular a large pipe, is also referred to as a step-forming process or progressive forming process. The lower tools are generally designed as forming strips running in the longitudinal direction of the sheet and consequently the longitudinal direction of the pipe. During the forming process, the upper tool arranged on the bending blade dips between the spaced-apart lower tools or forming strips, so that the bending force is applied to the sheet metal.

[0003] From DE 18 14 066 A, a pipe bending press of the type described above is known, in which the two lower tools or moldings are moved together against the upper tool during a working stroke with the aid of a pressure stamp.

[0004] Alternatively, DE 102 32 098 B4 discloses a pipe bending press in which the bending blade with the attached upper tool is lowered and pressed down during a working stroke, causing the sheet metal to deform under the influence of the bending blade and the upper forming tool carried by it. The upper tool can be hinged to the lower end of the bending blade. Additionally, the bending blade can be hinged to the upper part of the press at its upper end, creating a two-hinged design. This is intended to prevent moments in the blade during bending.

[0005] A method for bending sheet metal during pipe production is known, for example, from DE 10 2011 053 676 A1. A pipe bending machine is used whose basic tool for defining the curvature contour comprises a segment unit with at least four forming segments that run parallel to one another in the longitudinal direction of the pipe to be produced and are height-adjustable relative to one another. The forming segments, with their shape-defining surfaces, can be adjusted to setting positions on a curve lying in a plane normal to the pipe axis after the curvature correction has been carried out.

[0006] Finally, DE 10 2011 053 676 A1 discloses a sheet metal bending machine and the use of such a machine for producing open-ended tubes, as well as a method for forming a sheet metal into an open-ended tube. The sheet metal bending machine has a bending beam arrangement and / or roller arrangement for forming, with at least one bending beam being provided that can be advanced against the sheet metal, viewed in cross-section relative to the longitudinal extent of the open-ended tube to be formed.

[0007] The existing pipe bending presses have generally proven themselves in practice. However, they do have disadvantages and therefore have potential for further development.

[0008] The invention is based on the object of creating a method and a pipe bending press for bending sheet metal during the production of pipes of the type described above, with which pipes of high quality can be produced in an economical manner with a simple construction of the press.

[0009] This object is achieved according to the invention by a method having the features of patent claim 1 and by a pipe bending press having the features of patent claim 8.

[0010] To bend a sheet metal arranged between the upper and lower press sections, at least one of the lower tools is movable during a working stroke along the working direction against the upper tool and along the working direction relative to the other lower tool. In this context, "movable" does not mean movement transversely to the working direction, for example, to adjust the distance between the two lower tools, but rather movement of the lower tools during a working stroke in the working direction. The working direction is the direction in which the upper and lower tools are moved toward each other, i.e., generally a vertical or approximately vertical working direction.

[0011] The invention is based on the problem that, in known bending processes of the type described above, the sheet metal lifts at least at one end during bending. Starting at one long side, the sheet metal is formed step by step in several bending processes. Then, in known processes, the sheet metal, with its as yet unformed flat area, generally lifts when the lower tools are moved against the upper tool. This lifting impairs the bending process and thus also the quality of the produced tubes. It has already been proposed to provide mechanical support for this lifting in order to prevent negative influences on the forming process. However, this involves complex measures.Based on this problem, the invention has now recognized that the lifting of the sheet during the forming process can be easily avoided if, instead of moving both lower tools together against the upper tool, one of the lower tools is moved against the upper tool and consequently relative to the other lower tool during a working stroke. Assuming that the sheet is bent in several sequential forming processes and is thereby displaced step by step transversely to the longitudinal direction of the sheet, the invention preferably proposes moving the first lower tool located in this feed direction relative to the second lower tool arranged opposite to the feed direction. This is because, by omitting the movement of this second lower tool, the lifting of the sheet in the area not yet bent is prevented.

[0012] It is fundamentally within the scope of the invention that both lower tools are moved during the bending process, but not simultaneously over the same working stroke; rather, there is always a relative movement between the two lower tools. Preferably, however, only one of the two lower tools is moved, while the other lower tool remains stationary. In order to implement the teaching according to the invention, it is expedient if the two lower tools can be moved independently of one another against the upper tool, namely relative to the respective other lower tool. It is then optionally possible to move both lower tools alternately one after the other relative to the other lower tool.

[0013] Preferably, each of the two lower tools is equipped with at least one separate press drive and is movable. Such a press drive can be designed, for example, as a hydraulic drive, e.g., a hydraulic cylinder. Since sheet metal of a certain length is usually formed to produce tubes of a certain length, a (separate) row of drives, e.g., cylinders, arranged one behind the other in the longitudinal direction of the sheet metal can be provided for each lower tool.

[0014] According to a further proposal of the invention, the bending blade is rotatably or pivotably articulated in or on the upper section of the press and provided with at least one rotary drive. The invention is based on the finding that by rotating the bending blade with the upper tool arranged on it about a rotation axis extending along the longitudinal direction of the sheet, the loads on the bending blade during the forming process can be minimized. This is because when forming by simply moving a lower tool, there is fundamentally the problem that the bending forces are transmitted asymmetrically to the blade. This can lead to high loads. These loads are minimized if the blade is rotated or pivoted in a suitable manner before moving (or possibly even during moving) just one lower tool, namely in relation to the lower tool which is moving up in this case.For this purpose, it may be useful if the pipe bending press is equipped with a control device connected to the lower tools, e.g., the press drives, on the one hand, and to the bending blade, e.g., the rotary drive, on the other. The rotary movement of the bending blade can be controlled depending on the working movement of the lower tools or the lower tool. However, it is generally advisable to move the bending blade into a specific position before each forming process and to hold it there and, if necessary, fix it. For example, it may be sufficient to fix the blade in a specific angular position for a specific sheet metal type.

[0015] The upper tool typically has a circular working surface in cross-section. It is advantageous if the center of this circular working surface coincides with the rotation axis of the bending blade. The bending blade is thus rotated around the center of the circular working surface. This has the advantage that, despite the rotation of the bending blade, the point of contact between the sheet metal and the upper tool always remains in the same position, e.g., in the middle between the two lower tools.

[0016] The invention also relates to the described method for bending sheet metal during the production of pipes using a pipe bending press of the type described. This method is characterized in that, in order to bend the sheet metal, during a working stroke, one of the lower tools is moved against the upper tool and along the working direction relative to the other lower tool.

[0017] It is within the scope of the invention that the sheet metal is bent in several sequential bending processes. The invention optionally proposes that during a bending process only one of the lower tools is moved, while the other lower tool remains stationary. It is always expedient if the bending blade is rotated about an axis of rotation running in the longitudinal direction of the sheet metal or the longitudinal direction of the pipe before one of the lower tools is moved, so that the forces are introduced symmetrically into the bending blade in the manner described. For this purpose, the bending blade can be rotated before one of the lower tools is moved, preferably in the direction of this lower tool.Preferably, the bending blade is rotated into the desired working position before the working stroke of one of the lower tools and with the proviso that the resulting bending force introduced into the sheet by the lower tool runs along or substantially along the longitudinal direction of the blade. Overall, the pipe bending press according to the invention and the working method according to the invention can be used to easily produce high-quality open-slit pipes. A wide range of sheet metal types can be processed. In particular, sheets made of different materials and sheets of different thicknesses can be processed. The press can be used in a variety of ways. In particular, it is also possible to operate the press with the individually movable lower tools in the conventional way, i.e. to raise both lower tools simultaneously. This "classic" working method is suitable, for example, for processing thick sheet metal.With thick sheets, lifting the sheet is less critical, so the lifting may be acceptable. In this case, both lower tools can be raised in the conventional manner. However, since the invention uses separate press cylinders for each lower tool and thus a total of at least two press cylinders or two rows of press cylinders, these two press cylinders or rows can apply twice the pressing force.

[0018] In principle, it is advisable to bend the sheet metal used in the area of the edges before the described forming process. This bending is usually carried out in a separate bending press, which is not the subject of this invention.

[0019] In the following, the invention is explained with reference to a drawing which merely represents an exemplary embodiment. Fig. 1 a pipe bending press according to the invention in the course of bending a sheet according to a known bending method and Fig. 2 a pipe bending press according to Fig. 1 during the forming of a sheet in the manner according to the invention, Fig. 3 the object after Fig. 2 in a modified, preferred embodiment, Fig. 4 to 8 the object after Fig. 3 in different functional positions.

[0020] The figures show a pipe bending press for bending a sheet metal 1 during the production of a pipe. Such a pipe bending press consists in its basic construction of an upper press part 2 and a lower press part 3. A bending blade 4 is arranged on the upper press part 2, to the lower end of which an upper tool 5 is fastened. Two lower tools 6a, 6b are arranged on the lower press part 3, wherein these lower tools 6a, 6b are spaced from one another transversely to the working direction A. Working direction A is the direction along which the tools are moved towards one another for bending, ie in the exemplary embodiment the vertical direction.

[0021] In order to bend the sheet metal 1 arranged between the upper press part 2 and the lower press part 3, the lower tools 6a, 6b can be moved along the working direction A during a working stroke, namely against the upper tool 5, so that the upper tool 5 dips between the spaced lower tools 6a, 6b.

[0022] Fig. Figure 1 shows the operation of such a pipe bending press in the conventional manner, namely when the two lower tools 6a, 6b are moved together against the upper tool 5. It is evident that in this way the sheet metal can be formed in the desired manner. However, the problem is the fact that the sheet metal with its Fig. 1 Lift the end shown on the left, which has not yet been bent in the desired manner. This is indicated by arrow P.

[0023] To prevent this lifting, the two lower tools in the pipe bending press according to the invention can be moved independently of each other during a working stroke against the upper tool 5 and relative to the other lower tool 6b or 6a. For this purpose, each of the two lower tools 6a, 6b is equipped with its own press drive 7a, 7b. These press drives 7a, 7b are only shown in simplified form in the figures.

[0024] In Fig. 2 it can be seen that by lifting only one of the lower tools, namely the one in Fig. 2 lower tool 6b shown on the right, the lifting of the left sheet end can be prevented.

[0025] The pipe bending press according to the invention is characterized, apart from the separately controllable press drives 7a, 7b for the two lower tools 6a, 6b in the Fig. 3 to 8, is further characterized in that the bending blade 4 is pivotally connected to the press upper part 2. The bending blade 4 is provided with a merely indicated rotary drive 8, with which the bending blade 4 can be rotated about a rotational axis D running along the longitudinal direction of the sheet. This option is in Fig. 3 to 8. This configuration allows the pipe bending process according to the invention to be further optimized. Fig. 3 to 8, the possibility of rotating the bending blade 4 about the rotation axis D before a working stroke and consequently before lifting one of the lower tools 6b, specifically in the direction of the respective lower tool 6b being moved. The rotational movement of the bending blade 4 takes place as a function of the subsequent feed movement of the lower tool 6b, with the proviso that the resulting bending force F introduced into the sheet 1 by the lower tool 6b runs essentially along the longitudinal direction L of the blade. Fig. 3 shows these conditions and makes it clear that in this way an asymmetrical force introduction into the bending blade 4 is avoided.

[0026] In this case, Fig. 4 indicates that the circle center P of the circular working surface 9 of the upper tool 5 coincides with the pivot point D of the bending blade 4. The bending blade is consequently rotated about the circle center P of the working surface 9. This has the advantage that the point of contact between the working surface 9 of the upper tool 5 and the sheet metal 1 to be formed remains in the middle between the two lower tools 6a and 6b, despite the rotation of the bending blade.

[0027] The forming of a sheet 1 in several steps can be explained by a comparative analysis of the Fig. Explain 3 to 8. Fig. 3 shows the arrangement before or at the beginning of the forming in the area of the right side of the sheet 1. The edges of the sheet (right and left) have already been pre-bent or bent in a previous and not shown process step, namely in a separate bending press.

[0028] The sheet is then formed step by step as described and pushed step by step to the right, as shown in Fig. 4 and Fig. 5 is indicated, so that Fig. 5 shows the end of the forming process of the right side of the sheet. Afterwards, according to Fig. 6 to 8 the left side of the sheet is reshaped so that Fig. 8 shows the end of the forming process in the area of the left side. It can be seen that when forming the right side of the sheet, only the right lower tool 6b is operating, while when forming the left side of the sheet, only the left forming tool 6a is operating. The bending blade 4 is also pivoted in different directions in both cases, namely toward the operating lower tool.

[0029] In principle, it is possible to use a control device to control the press drives 7a and 7b on the one hand and the rotary drive 8 on the other. However, it will generally be sufficient to bring the bending blade 4 into the desired functional position with the help of the rotary drive 8 at the beginning of a forming process, so that one side of the sheet, e.g. the right side of the sheet according to Fig. 3 to 5 with the same functional position of the bending blade 4. Then the other side of the sheet is processed according to Fig. 6 to 8 with a different but also fixed functional position of the bending blade.

[0030] Overall, the pipe bending press according to the invention and the working method according to the invention allow for the simple production of high-quality open-end pipes. A wide range of sheet metal types can be processed. In particular, sheets made of different materials and sheets of different thicknesses can be processed. The press can be used in a variety of ways. In particular, it is possible to process thick sheets in the conventional manner by lifting both lower tools 6a, 6b simultaneously. This is because lifting the sheet is less critical with thick sheets. If this variant is operated in the conventional manner, the inventive design with two press cylinders allows twice the pressing force to be applied.

Claims

[1] Method for bending sheet metal during the production of pipes using a pipe bending press, with a bending blade (4) arranged in or on a press upper part (2), to the lower end of which an upper tool (5) is fastened and with two lower tools (6a, 6b) arranged in or on a press lower part (3) and spaced from each other transversely to the working direction (a), whereby the sheet is bent in several successive forming processes and is moved step by step transversely to the longitudinal direction of the sheet, characterized by in that, in order to bend a sheet metal arranged between the upper press part (2) and the lower press part (3), at least one of the lower tools is moved during a working stroke against the upper tool and along the working direction relative to the other lower tool. [2] Method according to claim 1, wherein the sheet is bent in several successive bending operations, characterized bythat during a bending process only one of the lower tools is moved, while the other lower tool remains stationary. [3] Method according to claim 1 or 2, characterized by that in several successive bending processes the two lower tools are moved alternately or one after the other. [4] Method according to one of claims 1 to 3, characterized by that the bending blade is rotated around a rotation axis running in the longitudinal direction of the sheet or pipe before one of the lower tools is moved. [5] Method according to claim 4, characterized by that the bending blade is rotated towards one of the lower tools before moving this lower tool. [6] Method according to claim 4 or 5, characterized bythat the bending blade is brought into a position before the working stroke of one of the lower tools in which the resulting bending force introduced into the sheet by the lower tool runs along or substantially along the longitudinal direction of the blade. [7] Method according to one of claims 4 to 6, characterized by that the bending blade is rotated around an axis of rotation which coincides with the center of the circle of the working surface of the upper tool. [8] Pipe bending press for bending sheets (1) in the course of pipe production, according to a method according to one of claims 1 to 7, with a bending blade (4) arranged in or on a press upper part (2), to the lower end of which an upper tool (5) is attached and with two lower tools (6a, 6b) arranged in or on a press base (3) and spaced apart from each other transversely to the working direction A, characterized by , that for bending a sheet metal arranged between the upper press part (2) and the lower press part (3), at least one of the lower tools (6a, 6b) can be moved during a working stroke against the upper tool (5) and along the working direction (A) relative to the other lower tool (6b, 6a), and that the bending blade (4) is rotatably articulated in or on the upper press part (2) and is provided with at least one rotary drive (8). [9] Press according to claim 8, characterized by that the two lower tools (6a, 6b) can be moved independently of one another against the upper tool (5) and along the working direction (A) relative to the respective other lower tool (6b, 6a). [10] Press according to claim 8 or 9, characterized by that each of the two lower tools (6a, 6b) can be moved with at least one of its own press drive (7a, 7b), e.g. at least one hydraulic cylinder or a series of hydraulic cylinders arranged one behind the other in the longitudinal direction of the bleaching machine. [11] Press according to one of claims 8 to 10, characterized by a control device which is connected to the lower tools (6a, 6b) or their press drives (7a, 7b) on the one hand and to the bending blade (4) or its rotary drive (8) on the other hand, wherein the rotary movement of the bending blade (4) or its position can be controlled as a function of the geometry of the pipe to be produced and / or the working movement of the lower tool or tools to be carried out. [12] Press according to one of claims 8 to 11, characterized by that the upper tool has a working surface (9) with a circular cross-section, the center point (P) of which coincides with the axis of rotation (D) of the bending blade (4).

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