EP0438205B1 - Method and apparatus for straightening the ends of elongated workpieces - Google Patents

Description

The invention relates to a device according to the preamble of claim 1 and a method according to the preamble of claim 2. The basis for these preambles is US-A-3869897.

Elongated workpieces. e.g. B. rods or tubes with impermissible deviations in straightness are usually in the manufacturing flow by means of a continuously working straightener, such as. B. roller straightener. In this straightening process, crooked ends are only partially or not at all detected. In the case of workpieces with different cross sections at the ends compared to the rest of the area, such as swaged pipe ends, the previously known continuous process fails completely. For this reason, workpieces that, according to the specification or due to the requirements of further processing, may only have a limited deviation from straightness, must therefore be re-aligned by hand using stamp straightening presses. This process is complex and requires an appropriately trained operator with a good sense of proportion. In addition, a suitable device for having the edge of the sometimes heavy individual pieces must be available for the turning of the workpiece required for straightening. be it a crane or a hoist or something comparable.

From DE 19 01 184 a device for dynamic balancing of workpieces is known, with a driven crankshaft which is adjustable with respect to its eccentricity and which is firmly connected to the workpiece via a crank arm. The workpiece is fixed at its ends and the workpiece axis is deflected all the way around the clamping point of the crank arm beyond the elastic limit of the workpiece. The circumferential deflection takes place without rotating the workpiece about its own axis.

A disadvantage of this device is the disproportionately large design effort for changing the eccentricity of the crankshaft. In addition, the device is not suitable for straightening the ends of elongated workpieces.

A generic device can be found in US-A-3,869,897. By means of this device, the end of a deformed workpiece can be straightened by a circular bending process. The workpiece is loaded beyond the elastic limit. The deflection takes place via an oscillating disc on which four piston-cylinder units are arranged to fix the workpiece. The pin engaging in the oscillating disc is rotated by means of a reversible drive motor and a gear. By means of a pivotable toothed segment, the pin fastened thereon is continuously shifted from its initial position and thus triggers the movement of the oscillating disk. The maximum amplitude for the vibrating disc is reached as soon as the toothed segment strikes the stop element. Then the direction of rotation of the drive motor is changed and the amplitudes continuously decrease again. A disadvantage of this device is the expenditure on equipment and the determination of the maximum amplitude at a fixed value, depending on the design of the meshing gears or the toothed segment. Due to the unfavorable leverage of the pin to the workpiece, the application is limited to thin-walled parts that require only a small straightening force. The maximum amplitude can only be achieved by detouring continuously increasing amplitudes. It is not possible to set an initial load other than zero.

The object of the invention is to provide a structurally simple device with which the ends of different workpieces can also be adjusted with a thick wall.

The object of the invention is to provide a structurally simple device with which the ends of elongated workpieces can also be directed effectively with a thick wall.

This object is achieved with the features specified in claim 1. A method for using the device is part of claim 2.

In the method according to the invention, when the workpiece is stationary, at least one cross section selected in the end region is subjected to an alternating or decreasing bending alternating stress. The bending stress is selected so that the selected cross-section is deformed into the plastic area. An essential feature of the method is that the maximum deflection resulting from the bending stress, which can be predetermined depending on the material used, rotates one or more times (s) around the workpiece axis. The straightening process itself can take place in various ways, depending on whether the maximum deflection is applied briefly or only gradually. In the former case, after centering the workpiece, the maximum deflection is abruptly applied to it, which then rotates once or more (s) around the workpiece axis. Then the sudden relief takes place. In the second case, after centering, the workpiece is subjected to a certain deflection which then rotates in the manner described, the bending stress being increased continuously and continuously during the rotation until the maximum deflection is reached. This is then held over a certain circulation distance, after which the bending stress is continuously reduced until the workpiece is completely relieved. The method according to the invention can be used both for cold and for heated workpieces.

The device consists of at least three, preferably four, plungers arranged symmetrically about a common axis, each of which is connected to a piston-cylinder unit. The piston and cylinder units can be controlled as a function of time and position, and the piston performs a sinusoidal movement over time when straightening. The piston-cylinder units are linked in terms of control so that they can work out of phase with one another.

The advantage of the device or the method lies in the fact that the workpiece stands still during the straightening process and that no rotating tools with a complex construction are required. The process can run automatically and is easy to integrate in a bypass of a production line. By using appropriately dimensioned hydraulic cylinders, the device can be quickly and easily adjusted without having to convert to different workpiece dimensions. The desired maximum deflection can be chosen freely depending on the material used.

In the drawing, a preferred embodiment of the method and the device is explained in more detail.

Figur 1

einen Längsschnitt durch die erfindungsgemäße Vorrichtung

Figur 2

einen Querschnitt entlang der Linie A-A in Figur 1

Figur 3

eine schematische Darstellung der maximalen Durchbiegung f

Figur 4

eine grafische Darstellung des gesamten Richtprozesses

Figur 5

eine grafische Darstellung des Verlaufes der maximalen Durchbiegung f.

Show it:

Figure 1

a longitudinal section through the device according to the invention

Figure 2

a cross section along the line AA in Figure 1

Figure 3

a schematic representation of the maximum deflection f

Figure 4

a graphic representation of the entire straightening process

Figure 5

a graphic representation of the course of the maximum deflection f.

In Figure 1, the device according to the invention is shown in a simplified form in a longitudinal section, wherein the representation of the usually associated system parts has been omitted. The pipe 1 clamped in a device 3, not shown, has an upset end 2, the straightness of which does not correspond to the delivery conditions and should therefore be straightened. For this purpose, as shown in FIG. 2, four plungers 5, 6, 7, 8 are arranged symmetrically about the compressed end 2 of the tube 1 about a common axis 4. The plungers 5 to 8 are each connected to a piston-cylinder unit which is only indicated here and which, because of the graphic representation of the straightening process in FIG. 4, is provided with the Roman characters I to IV. The radial movement of the plunger 5 to 8 is indicated by the arrow 9 shown in each case.

The circumferential maximum deflection f is shown schematically in FIG. The arrow 10 is intended to illustrate the circulation of the deflection f. The position of the plunger 5 to 8 shown in broken lines shows the starting point of the tube 1 after centering. For this example, the offset of the center point 11 characterizes the maximum deflection f, which, calculated from the six o'clock position, has already passed through an angle of 45 degrees. This cycle 10 is generated by the straightening process shown graphically in FIG. In the graphic representation, the stroke of the piston of the respective piston-cylinder unit I to IV is plotted on the ordinate, this stroke corresponding to the radial travel of the associated tappet 5 to 8. As indicated by the arrows, the positive amount should mean a movement of the piston or the plunger toward the center 11 and the negative amount should mean the opposite direction.

The first phase of the straightening process, centering, means a All pistons I to IV are closed in the direction of center 11. The start-up phase then begins, ie the piston I moves in the direction of the center 11 and, correspondingly, the opposite piston III moves away from the center. As soon as the piston I has reached the maximum of the sinusoidal stroke, the tube 1 also has the predetermined maximum deflection f. From here on, the actual straightening begins by running the maximum passage f clockwise or counterclockwise. This is achieved in that the stroke of the piston II and the stroke of the piston IV correspondingly in the opposite direction are used out of phase with the piston I. After one or two revolutions in this example, the stroke movement drops to zero in the run-down phase and by subsequent opening of all four pistons I to IV, ie away from the center 11, the directed end 2 of the tube 1 is released.

In addition to FIG. 4, FIG. 5 graphically shows two different courses of the maximum deflection f. In the sub-picture a are the two determining parameters, i. H. the deflection f and the circumferential angle alpha are entered, for example, for a pipe. In sub-picture b the variant is shown when the maximum deflection f in the shortest time, i. H. is applied with a very steep rise 12 and then the circulation already described takes place. At the end of the cycle, the steep drop 13 takes place until the pipe 1 is completely relieved. In contrast, in the variant shown in partial image c, the cycle begins immediately after the initial deflection f has been applied, with this cycle continuously increasing to the maximum value 14 as the cycle continues . This maximum value 14, comparable to that already shown in partial image b, is maintained for at least one full revolution. This is followed by slowly controlled waste 15 until the pipe 1 is completely relieved.

Claims (4)

1. An apparatus for straightening the ends (2) of elongate workpieces (1), in particular pipes, consisting of a holding element (3) for fixing the workpiece (1) and means for producing a deflection of the axis (11) of the workpiece with at least 3 piston- cylinder units (I-IV) arranged symmetrically about a common axis (4), the tappets (5-8) of which units can be moved in a radial direction towards the axis (4), characterised in that each piston-cylinder unit (I-IV) has a path-dependent and time-dependent control means and these are connected together such that they perform a sinusoidal lifting movement out-of-phase with each other during the straightening operation.
2. A method for straightening the ends (2) of elongate workpieces (1), in particular pipes, in which without rotation of the workpiece (1), about its own axis (11) the workpiece (1) is deflected in revolving manner beyond its elastic limit using an apparatus in accordance with Claim 1, characterised in that the tappets (5-8) during the straightening operation perform a sinusoidal lifting movement out-of-phase and the preset maximum sag (f) is maintained over at least one complete rotation (2π).
3. A method according to Claim 2, characterised in that after centring the workpiece is suddenly stressed until the preset maximum sag is reached and this maximum sag revolves once or several times about the workpiece axis and then the workpiece is briefly relieved of stress.
4. A method according to Claim 2, characterised in that after centring the workpiece is acted upon with a bending stress which is other than zero and the resulting sag rotates about the workpiece axis and the sag is increased continuously during rotation until the preset maximum sag is reached and this is held for a certain amount of rotation and then the sag is continuously reduced until the workpiece is completely relieved of stress.

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