JP2010520811A - Method and bending press for bending edge band of sheet metal formed into open seam tube - Google Patents

Abstract

The invention relates to a method for bending a plane metal sheet to be shaped into an open seam tube, in a bending press (11) comprising an upper tool fixed in the press frame (4) and having a contour corresponding to the bending contour to be achieved, and a vertically mobile lower tool (3) arranged opposite the upper tool (1). The edge strip (3) of the metal sheet fixed in the press frame (4) is bent between said tools in a working step in order to create the desired edge contour. At the beginning of the bending process, the working surface of the lower tool (3), which comes into contact with the lower side of the edge strip (3), takes its bearing in a flat manner in the form of a Hertzian compression. In order to prevent the formation of ridges and plastic deformations or crushing, said flat contacting is to be maintained at a minimal distance from the edge of the metal sheet, at a constant distance therefrom in relation to the point of application of force (P), during the entire bending process, by means of a co-ordinated horizontal and vertical movement of the lower tool (3). The bending press (11) provides a constructive solution for carrying out said method.

Description

  The present invention relates to a method of bending a thin metal sheet formed on an open seam tube according to the preamble of claim 1 and a bending press according to claim 5.

  In the bending of flat sheet metal formed into an open seam tube by the well-known UOE method, the edge of the sheet metal sheet is not formed at all in the U press, whereas in the O press it is extremely Only by applying a high pressure, it is possible to form these marginal bands into a finished round shape. Therefore, in the usual case, the edge band is first bent into a circular shape as efficiently as possible by using various bending tools in a bending press. However, for manufacturing reasons, the edge region of the marginal band will be left almost completely unshaped. These so-called “peaking” that can be found in the finished tube should be as small as possible or avoided altogether. This is because much labor is required to correct these.

  Parallel sheet metal edges located opposite each other in an open seam tube typically have a groove appropriate to the sheet metal thickness (eg, both V grooves) to facilitate subsequent longitudinal seam welding. I have.

  A bending press for bending an edge band of a flat sheet metal known from the prior art comprises an upper tool having a profile corresponding to the bending radius to be achieved when mounted in place in a press frame, and an upper tool And a lower tool movable in the vertical direction.

  The sheet metal edge band is firmly clamped to the press frame between the upper tool and the lower tool and then bent to the desired contour by vertical movement of the lower tool towards the upper tool. ing.

  These types of bending presses are known, for example, from US Pat. These patent documents address the problem of unformed end regions (ie, “(peaking) generation”) associated with the bending of the edge of a flat sheet metal sheet.

  In the case of a bending press known from US Pat. No. 6,057,059, the lower tool can be moved horizontally before bending in order to adapt the press to various sheet metal thicknesses or desired radii of curvature. It is like that. Note that the horizontal displacement of the lower tool under load, that is, during bending, is not described.

  A disadvantage of the known press is that, due to the nature of these methods, the groove located at the edge of the sheet can be plastically deformed during bending, so that the wall thickness can be less than acceptable. These deformations, which can be quite large, make it impossible to ensure that the subsequent welding process can compensate for these edge defects in the sheet metal. As a result, it is necessary to perform time-consuming and expensive finishing operations on defective tubes.

  Due to extensive research on this issue, these deformations associated with known presses are caused by the linear introduction of forces on the edge of the sheet by the lower tool during bending, which forces the steel's elastic limit. When exceeded, it has been recognized that plastic deformation, i.e. deformation of the edge of the sheet metal, occurs. This phenomenon becomes more severe as the thickness of the sheet and / or the strength of the steel increases.

  The size of the unshaped end region is minimized depending on the point of force application, but in some cases the edges of the sheet metal may be unacceptably deformed.

  Since the lower tool moves vertically toward the upper tool, there will be a difference between the contour angle of the lower tool and the contour angle of the sheet metal. This angular difference is greatest at the start of the pressurization operation and decreases continuously toward the end of the pressurization operation, but in practice never becomes zero. Furthermore, the greater the bending angle, the greater the difference between these two angles.

  In particular, in the initial stage of pressing, this large angular difference causes the lower tool to introduce force into the edge of the sheet metal in a linear fashion, so there is a horizontal squeezing effect on the edge of the sheet. Resulting in a high stress peak. In this situation, there is a very high risk that the edges of the thin plate will undergo significant plastic deformation.

  Research also indicates that these local stress peaks decrease as the lower tool approaches the upper tool while following the contour of the marginal band, thus reducing the lower tool profile. However, it has been found that linear contact gradually becomes surface contact under Hertz surface pressure.

  In order to minimize the generation of peaking, in Patent Document 4, an attempt is made to guide the edge band through the upper bending roll and the lower bending roll. The concave or convex peripheral contour of these rolls corresponds to the radius of the edge region to be bent.

  Apart from the considerable cost of producing such a two-stage bending device, it is still impossible to avoid introducing forces linearly at the edges of the sheet at the start of the deformation process. It is clear that

  Another disadvantage is that it is impossible to prevent the sheet metal edges from being spread as a result of the rolling deformation of the edge band, so that undulations are formed in the edge region.

  It is also disadvantageous that the bending radius of the edge band is determined by the peripheral contour of the bending roll. This means that an appropriate number of bending rolls with different peripheral contours needs to be stocked to accommodate different tube diameters.

  U.S. Patent No. 6,057,049 describes a method that can minimize the generation of peaking and avoid plastic deformation of the edge of a sheet metal during bending by providing permanent surface contact throughout the bending process. is doing.

  This is realized by combining the movement of the lower tool, which consists of the vertical displacement of the lower tool, with the pivoting around the axis of rotation by the hemispherical bearing that takes place simultaneously.

  While excellent results have been achieved in experiments using this method, this embodiment with hemispherical bearings is complex and expensive. Another drawback of hemispherical bearings is that complex measures must be taken to prevent contamination of the hemispherical shell in order to minimize wear of the lower tool and hemispherical shell.

German Patent Application No. 2641573A1 German Patent Application No. 4311228A1 German Patent Invention No. 2510488C3 German Patent Application Publication No. 2365515A1 German Patent No. 102004050784B3

  Accordingly, an object of the present invention is a method of bending a flat sheet metal formed into an open seam tube, which is simple and inexpensive, minimizes the generation of peaking and is prepared for welding. It is an object of the present invention to provide a method capable of reliably avoiding plastic deformation or squeezing, and thereby preventing the wall thickness from falling below a predetermined value in the seam region of the finished pipe. Another object is to provide a corresponding bending press.

  This object is achieved by combining the preambles and features of claims 1 and 5. Advantageous details are subject to the dependent claims.

  According to the suggestion of the present invention, in order to achieve this purpose, the horizontal and vertical movements of the lower tool are coordinated so that the surface contact is separated from the edge of the sheet by a minimum distance throughout the bending process. A method is used in which the distance is kept constant and the distance is kept constant with respect to the point of force application.

  The great advantage of this method is that, as in the case of the bending press known from DE 102004050784 B1, the generation of peaking is minimized and the plastic deformation of the edge of the sheet is avoided. Nevertheless, these advantages are achieved in this method at low cost by simple horizontal and vertical movement of the lower tool during bending.

  Compared to known bending presses, the lower tool is easily actuated by a standard linear motion press plunger, so the effort required to make the bending press is significantly reduced and the known press There is no need to provide the complex protective equipment necessary to prevent contamination in some cases.

  With regard to the control technique, the sequence of movements to produce the horizontal and vertical displacements of the lower tool is performed so that these movements occur simultaneously, for example, linearly or along the desired curved path Can do. In addition, these movement sequences may be performed in stages, specifically such that horizontal and vertical movements occur alternately.

  In order to limit the generation of peaking to the unavoidable minimum, not only is the point where the lower tool applies force to the edge band as close as possible to the edge of the sheet, but also the surface pressure corresponding to Hertz pressure is It must always be applied to the edge band so that linear pressure on the edge of the sheet is avoided.

  The proper sequence of movements to produce the horizontal and vertical displacements of the lower tool always keeps the point of force exerted on the edge band by the lower tool, so The end region will always be maintained at a certain minimum value.

  This surface contact is maintained throughout the bending process (if there is no surface contact, horizontal stress occurs at the start of bending and a local stress peak occurs at the groove edge of the sheet. However, such horizontal stresses are reliably avoided and plastic deformation caused by excessive local stresses is eliminated.

  For kinematic reasons, as the result of the horizontal and vertical displacement during bending, the lower tool's force action point moves, so the contour of the lower tool's surface in contact with the bottom surface of the edge band is It must be designed so that at least a surface pressure corresponding to Hertz pressure is maintained throughout the bending process.

  This is because, in the region of the force application point at the start of the bending process, the lower tool is provided with a flat contour, for example, connected to the convex contour, or the lower side in contact with the edge band during the bending process. This is realized by providing the entire surface of the tool with a convexly curved shape.

  Advantageously, only one suitable lower tool needs to be stocked to produce various bending radii. Thereby, it is possible to eliminate the setup time for replacing the tool. This can also significantly reduce procurement costs, maintenance costs, and installation costs.

  Additional features, advantages and details of the invention will be derived from the following description of the illustrated exemplary embodiments.

1 is a schematic view of a bending press of the present invention having a lower tool that is movable in the vertical and horizontal directions under load to bend an edge band; FIG. FIG. 2 is a view similar to FIG. 1 a showing the finished bending state.

  FIG. 1 shows the principle of a bending press 11 according to the invention having a lower tool 3 that is movable in the horizontal and vertical directions under load. The state shown in the figure is a state immediately before the edge band (edge piece) 2 of the metal thin plate (metal sheet) is bent.

  In order to bend the edge band 2, the sheet metal is tightly clamped to the press frame 4 of the bending press 11 outside the area of the edge band to be bent, directly below the upper tool 1 having a profile corresponding to the resulting bending radius. It is positioned.

  In the end region 8 of the edge band 2 to be bent, a groove 7 is provided in order to facilitate the welding of a UOE molded open seam tube.

  A lower tool 3 according to the invention, supported so as to be movable in the vertical and horizontal directions under load, is arranged directly under the end region 8 of the edge band 2. The direction in which the lower tool can be moved is indicated by a vertical arrow 9 and a horizontal arrow 10.

  In order to make the undeformed end region as small as possible, according to the invention, the point of action P of the lower tool 3 is separated from the metal edge by a minimum distance in the end region 8 of the edge band 2. Is located.

  According to the invention, the lower tool 3 is designed such that permanent surface contact with the bendable edge band 2 can occur at least under Hertz pressure, so that the deformation of the edge of the sheet is almost completely Will be avoided.

  The surface profile of the lower tool 3 is provided with a flat area 5 in the plane in contact with the edge band 2. This area continues to the convex area 6 in the operating area of the lower tool 3.

  At the start of the bending process, according to the invention, the flat area 5 of the working surface of the lower tool 3 comes into surface contact with the bottom surface of the edge band 2. In this case, only a partial region of the working surface of the lower tool 3 comes into contact with the bottom surface of the edge band 2.

  As the bending proceeds, the force application point is relatively displaced at the contact surface between the lower tool 3 and the edge band 2 for kinematic reasons.

  As shown in FIG. 2, the lower tool 3 moves vertically and horizontally as it proceeds to the end position during the bending process, more specifically, this movement occurs during the bending process. The force application point P will be carried out so as to remain at the original position of the end region in the marginal band 2 while moving along the working surface towards the convex area 6 in the lower tool 3. The lower tool 3 is adapted to move such that both horizontal and vertical movements occur, for example, simultaneously in a linear fashion or in stages.

  Permanent surface contact with the bottom surface of the edge band 2 ensures that linear stresses on the end region 8 of the edge band 2, in particular the groove 7, and stress peaks resulting in plastic deformation as a result are avoided. it can.

DESCRIPTION OF SYMBOLS 1 Upper tool 2 Edge zone 3 Lower tool 4 Press frame 5 Flat area of action surface 6 Convex area of action surface 7 Groove 8 Terminal area 9 Vertical movement of lower tool 10 Horizontal movement of lower tool 11 Bending Press P Force acting point

Claims (9)

  Formed into an open seam tube by a bending press having a fixed upper tool having a contour corresponding to the bending contour to be achieved and a lower tool arranged facing the upper tool and movable vertically. A method of bending a flat sheet metal sheet, wherein the edge band of the sheet metal sheet firmly clamped to a press frame between the upper tool and the lower tool is formed into a desired edge profile by a single work process. Wherein the working surface of the lower tool that is bent into contact with the bottom surface of the edge band provides surface contact at least under Hertz pressure at the very start of bending. The coordinated horizontal and vertical movements of the lower tool are positioned at a minimum distance from the edge of the sheet metal throughout the bending process. , The position of the predetermined distance from the force application point, and wherein the maintained.   The method of claim 1, wherein the horizontal movement and the vertical movement occur simultaneously.   The method according to claim 2, wherein the horizontal movement and the vertical movement are performed linearly.   The method according to claim 1, wherein the horizontal movement and the vertical movement are alternately performed step by step.   A flat metal formed into an open seam tube by means of a fixed upper tool having a contour corresponding to the bending contour to be achieved and a vertically movable lower tool arranged facing said upper tool A bending press for bending an edge band of a thin plate, wherein the edge band of the metal thin plate firmly clamped to a press frame between the upper tool and the lower tool is formed into a desired edge by a single work process. In a bending press adapted to be bent into a contour, the lower tool (3) comprises a surface contour capable of being in surface contact with the edge band (2) at least at the contact surface during the bending process; It is supported so as to be movable in both the vertical direction (9) and the horizontal direction (10) under load, and the range of movement in the horizontal direction and the vertical direction is the same as that of the thin metal plate. At least a sufficient distance to be positioned relative to the force application point (P) of the lower tool (3) throughout the bending process. Bending press characterized by that.   Bending press according to claim 5, characterized in that the surface contour of the working surface of the lower tool (3) consists of a convex area (6).   Bending press according to claim 5, characterized in that the surface contour of the working surface of the lower tool (3) consists of a flat area (5) and a convex area (6).   The bending press according to any one of claims 1 to 7, wherein the mobility of the lower tool (3) in the horizontal direction and the vertical direction is realized by using a movable press plunger. .   The bending press according to any one of claims 1 to 8, wherein the press plunger is configured to be fluid-driven.

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