EP1807226B1 - Method and bending press for bending the boundary edge of a sheet for shaping into an open seam tube - Google Patents

Description

The invention relates to a method for bending a sheet to be formed into a slotted tube according to the preamble of claim. (See, eg DE-A-26 41 573 ). The invention also relates to a clinching press for carrying out the method.

When bending a flat sheet which is to be formed by the well-known UOE method to a slotted tube, the edge strips of the sheet in the U-press and not in the O-press only with very large press pressure in the circular shape of the finished tube to form , Usually, therefore, initially the edge strips are bent in bending presses with different Anbiegewerkzeugen as good as possible to the circular shape, with production reasons, the end portions of the edge strips remain almost undeformed. These so-called roof edges to be detected on the finished pipe should be kept as low as possible or avoided since they can only be corrected with great effort.

Depending on the sheet thickness, the band edges which lie parallel opposite the slot tube are usually provided with a corresponding band edge chamfering (eg double V) for the subsequent longitudinal seam welding.

The known prior art Anbiegepressen for bending the edge strips of flat sheets consist of a fixed fixed in the press frame and contoured according to the radius to be reached contoured upper tool and a vertical opposing lower tool.

Between upper and lower tool of the edge strip of the stationary clamped in the press frame plate is arranged, which can be bent by vertical movement of the lower tool in the direction of the upper tool in the desired edge contour.

Such Anbiegepressen are for example from the DE 26 41 573 A1 , of the DE 43 11 228 A1 or the DE 25 10 488 C known, which address the problem of undeformed end portions in the bending of the edge strips of flat sheets.

A disadvantage of these known presses that the chamfers located on the sheet edges are procedurally deformed during bending plastically, resulting in unacceptable wall thickness underruns can arise. Due to the case-by-case very pronounced deformations, these band edge errors can not be reliably covered by the subsequent welding. This causes time-consuming and costly rework of the faulty tubes.

Extensive investigations on this problem have led to the finding that these deformations in the known presses are caused by the fact that the bending process is initiated by a linear force introduction of the lower tool in the band edges, wherein when the elastic limit of the steel is exceeded plastic deformation, d. H. Deformations of the band edge are caused. This effect increases with increasing sheet thickness and / or higher steel strengths.

Due to the vertical movement of the lower tool in the direction of the upper tool, for example, in convex trained upper and corresponding concave lower tool, especially at the beginning of bending, the risk of deformation of the band edges are particularly large, because in this phase due to the process, a large angular difference between lower tool contour and sheet metal contour occurs , Due to the linear force transmission from the lower tool to the sheet edge, the local voltage peaks are also very large in the initial phase.

The investigations have also shown that these local stress peaks become smaller during the bending process, since the lower tool follows the contour of the edge strip following the upper tool more and more and finally the linear shape merges into a surface contact.

To minimize the roof edge formation is according to DE 23 65 515 A1 Attempts have been made to guide the edge strips by upper and lower Anbiegerollen whose convex or concave peripheral contours correspond to the radius of the edge portions to be angezogen.

Apart from the considerable construction costs of such a two-stage working bending device, a linear force introduction at the strip edge at the beginning of the forming can not be avoided.

Another disadvantage is that the rolling deformation of the edge strips a rolling out of the sheet edges can not be prevented, creating ripples in the edge region.

A further disadvantage is that the bending radius of the edge strip is determined by the circumferential contours of the bending rollers. This means that with changing pipe diameters, a corresponding number of bending rollers with different circumferential contours must be provided.

The object of the invention is therefore to provide a method for bending a flat sheet to be formed into a slot tube in a press brake, wherein plastic deformation or pinching, the prepared for welding strip edges and thus wall thickness underruns in the weld seam on the finished tube can be safely avoided and an application is also possible for different pipe diameters with reduced use of tools.

This object is achieved according to the preamble in conjunction with the characterizing features of claim 1. Advantageous developments are the subject of dependent claims.

According to the teachings of the invention, a method is used to solve this problem, in which already at the beginning of the bending process a surface contact of the working surface of the lower tool with the underside of the edge strip is ensured, which is maintained throughout the bending process. Advantageously, only the end region of the edge strip is contacted in order to keep the area of the undeformed strip edges as small as possible.

With this procedure, the surface contact otherwise reliably prevents the local voltage peaks occurring at the chamfered sheet edge occurring at the beginning of the bending, so that plastic deformations due to local voltage exceeding are precluded. This advantageous procedure is achieved by a combined movement of the lower tool, wherein by vertical displacement and simultaneous pivoting about an axis of rotation, the lower tool follows the contour of the upper tool and remains in contact with the surface from the beginning of the bend with the edge strip to be approached.

The axis of rotation can be located according to a first embodiment within the lower tool, the pivoting can be done for example via a rotatably mounted pin arranged in the lower tool.

During the bending, there is kinematic conditional to a relative displacement between edge strip and working surface of the lower tool, resulting in a shift of the force application point of the band edge away. Depending on the strip thickness and the material, the undeformed end area of the marginal strip can thereby be increased slightly in some cases.

If this effect is to be avoided in the design of the Anbiegepresse necessarily, is located in an advantageous development, the axis of rotation in the contact plane between the working surface of the lower tool and the underside of the edge strip.

Here, the lower tool during the entire bending operation, the contour of the upper tool following, pivoted to a defined contact point (axis of rotation) relative to the lower tool.

This pivoting can be realized for example in that the lower tool is pivotally mounted in a dome-shaped receptacle.

The force application point of the lower tool is determined in this storage by the center of the calotte diameter. When the edge strip is bent, the point of force application now shifts slightly outwards in accordance with the bending contour of the edge strip on the sheet edge, with the result that the undeformed area of the edge strip is advantageously further reduced.

In addition to the Kalottenlagerung other types of storage are conceivable, in particular, it is essential that the lower tool is simultaneously formed vertically displaceable and pivotable in such a way that a surface contacting takes place during the entire Anbiegevorganges.

A further significant advantage of the method according to the invention is that only a corresponding lower tool has to be provided to produce different bending radii.

The lower tool according to the invention does not need to be changed since it automatically follows the respective contour of the upper tool corresponding to the pipe diameter. This saves considerable costs in procurement, maintenance and installation.

Further features, advantages and details of the invention will become apparent from the following description of the illustrated embodiments.

Figur 1a

Prinzipskizze eines erfindungsgemäßen Unterwerkzeuges mit einer Drehachse innerhalb des Werkzeuges unmittelbar vor dem Anbiegen eines Randstreifens,

Figur 1b

wie Figur 1a, jedoch im fertig gebogenen Zustand,

Figur 2a

wie Figur 1a, jedoch mit einer Drehachse in der Kontaktebene Unterwerkzeug - Randstreifen,

Figur 2b

wie Figur 2a, jedoch im fertig gebogenen Zustand.

Show it:

FIG. 1a

Schematic diagram of a lower tool according to the invention with an axis of rotation within the tool immediately before the bending of a marginal strip,

FIG. 1b

as FIG. 1a , but in the finished bent state,

FIG. 2a

as FIG. 1a , but with an axis of rotation in the plane of contact lower tool edge strips,

FIG. 2b

as FIG. 2a , but in the finished bent state.

In the FIG. 1a is shown as a schematic diagram of a first embodiment of a lower tool according to the invention with a rotation axis within the tool immediately before the bending of an edge strip.

For bending an edge strip 2, a sheet outside the edge strip area to be applied is fixedly clamped in the press frame 4 of a bending press, not shown, and positioned below a corresponding to the bending radius to be generated contoured upper tool 1.

The end region 8 of the edge strip 2 to be attached is provided with a chamfer 7 for welding the UOE-shaped slot tube.

Below the end region 8 of the edge strip 2, an inventive lower tool 3 is vertically displaceable and at the same time rotatably mounted about an axis of rotation 6, arranged.

With the beginning of the bending process according to the invention, the working surface of the lower tool 3 is in contact with the underside of the edge strip 2, wherein only a portion of the working surface of the lower tool touches the underside of the edge strip 2, since it during the bending, kinematically caused, to a relative displacement of the force application point comes in the contact plane between the lower tool 3 and edge strip 2.

As in FIG. 1b represented, the lower tool 3 remains during the entire bending operation, due to the combined vertical and rotational movement of the lower tool 3, in permanent surface contact with the underside of the edge strip 2. As a result, linear stresses and resulting stress peaks with plastic deformation in the end portion 8 of the edge strip 2 and in particular on the chamfer 7 safely avoided.

Due to the kinematics of the motion sequence, a displacement of the force application point P → P 'of the lower tool 3 on the underside of the edge strip 2. The force application point shifts slightly according to the current bending radius of the edge of the sheet 2 away.

FIG. 2a also shows in a schematic diagram a further embodiment of a lower tool according to the invention immediately before the bending of an edge strip, but with a rotation axis in the plane of contact lower tool edge strips.

Instead of in FIG. 1 shown lower tool 3 with a rotation axis 6 within the lower tool is now a lower tool 3 'is used, with the axis of rotation 6' as force application point P of the lower tool 3 'in the contact plane between the working surface of the lower tool 3' and the underside of the edge strip 2 is located. Here, the lower tool 3 'during the entire bending operation of the contour of the upper tool 1 following this force application point P or the P' (axis of rotation 6 ') is pivoted.

According to the invention, the lower tool 3 'is pivotally mounted for this purpose in a dome-shaped tool holder 5, wherein the force application point P or P' of the lower tool 3 'is determined in this storage by the center of the dome diameter.

Corresponding FIG. 2b follows the bending of the edge strip 2, the lower tool 3 'while maintaining the surface contacting the contour of the upper tool 1, whereby overstrain or deformation, in particular at the chamfer 7 of the edge strip 2 are also advantageously avoided.

Furthermore, in this type of mounting, the point of application of force P → P 'of the lower tool 3' shifts outwards in accordance with the current bending contour on the underside of the sheet metal.

This shift has the consequence that the undeformed region of the edge strip 2 is advantageously further reduced.

LIST OF REFERENCE NUMBERS

No. description 1 upper tool 2 edge strips 3,3 ' lower tool 4 press frame 5 tool holder 6.6 ' axis of rotation 7 chamfer 8th end P, P ' Force application point

Claims (7)

1. Method for bending a plane sheet for shaping into an open seam tube in a bending press comprising an upper tool (1), shaped to correspond to the bending contour to be achieved and fixedly arranged in the press frame (4), and a vertically displaceable lower tool (3, 3') opposite the upper tool, between which upper and lower tool the edge strip (2) of the sheet, clamped in place in the press frame (4), is bent into the desired edge contour in one work step,
   characterised
   in that, at the beginning of the bending operation, the bottom face of the edge strip (2), which comes into contact with the working surface of the lower tool (3, 3'), comes into planar contact and this planar contacting is maintained during the entire bending operation by means of a combined motion of the lower tool (3, 3') comprising vertical displacement and simultaneous pivoting about a rotational axis.
2. Method according to Claim 1,
   characterised
   in that only the end area (8) of the edge strip (2) is contacted in a planar manner during the entire bending operation.
3. Bending press for bending the edge strip (2) of a plane sheet for shaping into an open seam tube comprising an upper tool (1), shaped to correspond to the bending radius to be achieved and fixedly arranged in the press frame (4), and a vertically displaceable lower tool (3, 3') opposite the upper tool, between which upper and lower tool the edge strip (2) of the sheet, clamped in place in the press frame (4), may be bent into the desired edge contour,
   characterised
   in that the lower tool (3, 3') is provided with a straight working surface and is mounted to pivot about a rotational axis (6, 6'), the pivot range being at least so large that a permanent planar contacting between the working surface of the lower tool (3,3') and the bottom face of the edge strip (2) is made possible during bending.
4. Bending press according to Claim 3,
   characterised
   in that the rotational axis (6) is located within the lower tool (3).
5. Bending press according to Claim 4,
   characterised
   in that the lower tool (3) is provided with a pin mounted in a rotational manner.
6. Bending press according to Claim 3,
   characterised
   in that the rotational axis (6'), in relation to the working surface of the lower tool (3'), is a fixed point of application of force (P, P') on the bottom face of the edge strip (2).
7. Bending press according to Claim 6,
   characterised
   in that the lower tool (3') is mounted to pivot in a dome-shaped tool mount (5).

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