Device for positioning a bending tool

Abstract

Device and method for positioning of a bending tool (1) by means of an electromagnet (2) that can be displaced along a magnetic guide, which bending tool (1) is held on a tool holder (4) by a retaining carriage (3) that can be displaced in a direction of movement along a retaining-carriage guide and which bending tool (1) comprises a magnet holder (5) of a magnetizable material, wherein an adjustable magnetic force acts between the electromagnet and the magnet holder (5).

Claims

1. A method for positioning a bending tool by means of an electromagnet, the method comprising the steps of: providing the bending tool comprising a tool holder, the electromagnet and a magnet holder of a magnetizable material coupled to the electromagnet, wherein the bending tool is held on a retaining-carriage guide, displacing the bending tool, including the tool holder, the electromagnet and the magnet holder along the retaining-carriage guide via a retaining carriage, and thereby displacing the electromagnet along a magnetic guide extending along the retaining-carriage guide, energizing the electromagnet with a nominal voltage for generation of a nominal force as magnetic force, increasing or decreasing the nominal force by a pulse width modulation or by a change of a voltage or by a change of the current capacity in time spans for generation of the necessary magnetic force, depending on: the tool weight and/or the inertial forces acting on the bending tool and/or the friction acting in the retaining-carriage guide and/or the orientation of the magnetic force relative to the movement direction and/or the size of a contact area of respective contact faces of the electromagnet and the magnet holder and/or an extension of the magnetic field into regions having further magnetizable workpieces.

2. The method according to claim 1, further comprising the step of increasing or decreasing the nominal force in levels.

3. The method according to claim 1, further comprising the steps of measuring a tool weight and/or eccentricity with measuring devices and/or retrieving the tool weight and/or eccentricity from a database, and adjusting the magnetic force in dependence on the eccentricity.

4. The method according to claim 1, further comprising the step of increasing or decreasing the nominal force in dependence on a position of the retaining carriage and/or of a passage of time.

5. The method according to claim 1, further comprising the step of partly demagnetizing the bending tool.

6. The method according to claim 1, wherein the bending tool is partly demagnetized in dependence on demagnetization parameters comprising a temporary position of the retaining carriage or of the bending tool.

7. The method according to claim 6, wherein the bending tool is demagnetized at least partly before and/or during and/or after a deposition of the bending tool.

8. The method according to claim 6, further comprising the step of adjusting the demagnetization parameters depending on a movement of the bending tool and/or of a speed of movement of the bending tool.

9. The method according to claim 6, further comprising the step of loading the demagnetization parameters from a database.

Description

(1) FIG. 1 shows a side view of electromagnet and bending tool.

(2) FIG. 2 and FIG. 3 show sectional views of the electromagnet and of the bending tool.

(3) FIG. 4 shows a sectional view of the bending tool and of the retaining carriage.

(4) FIG. 5 comprises a table.

(5) FIG. 6 illustrates a periodic loading of the electromagnet for suppression of an overheating.

(6) FIG. 1 shows a side view of the device according to the invention, wherein the position of the sectional views shown in FIG. 2 and FIG. 3 is indicated by the line A-A in FIG. 1. Furthermore, line B-B shows the position of the sectional view shown in FIG. 4.

(7) FIG. 1 shows an embodiment of the device according to the invention for positioning of the bending tool 1 by means of an electromagnet 2 that can be displaced along a magnetic guide 8. The bending tool 1 comprises a tool holder 4, not visible in FIG. 1, via which tool holder 4 the bending tool 1 is retained by a retaining-carriage guide 10, visible in FIG. 1, via a detachable mechanical connection. A retaining carriage 3 is mounted displaceably in a direction of movement 9 along the a retaining-carriage guide 10.

(8) In the embodiment illustrated in FIG. 1, the retaining-carriage guide 10 and the magnetic guide 8 are formed in one piece. The electromagnet 2 and the retaining carriage 3 are consequently displaceable in parallel directions of movement 9.

(9) The bending tool 1 comprises a magnet holder 5 of a magnetizable material, wherein a magnetic force acts between the electromagnet 2 and the magnet holder 5 upon energization of the electromagnet with a voltage.

(10) FIG. 2 shows a sectional view of the electromagnet 2 and of the bending tool 1 as parts of an embodiment of the device according to the invention for positioning of a bending tool 1 in a bending machine, not illustrated in FIG. 2.

(11) The bending tool 1 comprises bending forms 6, which, for forming of a workpiece, not illustrated in FIG. 2, are pressed onto this workpiece. The bending forms 6 determine the shape of the bent workpiece, among other effects.

(12) The bending tool 1 is retained on a retaining-carriage guide 10 via the tool holder 4. The retention of the bending tool 1 takes place via a detachable mechanical connection, wherein the type of construction of this mechanical connection has no influence on the device according to the invention.

(13) A retaining carriage 3 is mounted displaceably in a manner normal to the plane of the diagram along the retaining-carriage guide 10, illustrated in FIG. 2.

(14) The positioning of the bending tool 1 in a direction normal to the plane of the diagram of FIG. 2 takes place by a displacement of the electromagnet 2 in a direction normal to the plane of the diagram of FIG. 2, wherein a magnetic force is established between the electromagnet 2 and the magnet holder 5. For this purpose, the magnet holder 5 is made of a magnetizable material.

(15) The electromagnet 2 is designed as a hollow member, wherein the magnet holder 5 is introduced into the inner region of the hollow member. The electromagnet 2 and the magnet holder 5 have—as is visible in the sectional diagram of FIG. 2—congruent polygonal shapes.

(16) In particular, the magnet holder 5 has a star-like cross-sectional shape. The electromagnet 2 has, in cross section, a negative shape congruent to this.

(17) A contact face 7 of the electromagnet 2 and a contact face of the magnet holder 5 are spaced apart from one another. Accordingly, these contact faces are of different sizes.

(18) The shaping, according to the invention, of electromagnet 2 and magnet holder 5 may permit the magnetic field generated by the electromagnet 2 to be adjusted to such a weak value that it does not extend into sub-regions of the tool holder 4. The magnetic field may be limited substantially to sub-regions of the bending forms 6 directly adjacent to the electromagnet 2.

(19) FIG. 3 shows a side view of the electromagnet 2 and of the bending tool 1 as parts of a further embodiment of the device according to the invention for positioning of a bending tool 1 in a bending machine, not illustrated in FIG. 3.

(20) The bending tool 1 comprises bending forms 6, which, for forming of a workpiece, not illustrated in FIG. 3, are pressed onto this workpiece. The bending forms 6 determine the shape of the bent workpiece, among other effects.

(21) The bending tool 1 is retained on a tool holder 4 on a retaining-carriage guide 10. The retention of the bending tool 1 takes place via a detachable mechanical connection, wherein the type of construction of this mechanical connection has no influence on the device according to the invention.

(22) A retaining carriage, not illustrated in FIG. 3, is mounted displaceably in a manner normal to the plane of the diagram along a retaining-carriage guide 10.

(23) The positioning of the bending tool 1 in a direction normal to the plane of the diagram of FIG. 3 takes place by a displacement of the electromagnet 2 in a direction normal to the plane of the diagram of FIG. 3, wherein a magnetic force is established between the electromagnet 2 and the magnet holder 5. For this purpose, the magnet holder 5 is made of a magnetizable material.

(24) The electromagnet 2 is designed as a round hollow member, wherein the magnet holder 5 is introduced into the inner region of the hollow member. The electromagnet 2 and the magnet holder 5 have—as is visible in the sectional diagram of FIG. 2—congruent polygonal shapes.

(25) In particular, the magnet holder 5 has a circular cross-sectional shape. The electromagnet 2 has an annular cross-section shape as a congruent shape.

(26) FIG. 4 shows the sectional view B-B indicated in FIG. 1, wherein a bending tool 1 different from the bending tools illustrated in FIG. 2 and FIG. 3 is illustrated in FIG. 4. Bending tool 1, comprising a bending form 6, has a shape having a center of gravity P eccentric relative to the retaining-carriage guide 10. Because of the eccentric position of the center of gravity P, at which center of gravity P the dead weight of the bending tool 1 acts, the forces F1, F2 and F3 are developed, which forces F1, F2 and F3 act on the detachable mechanical connection between tool holder 4 and retaining-carriage guide 10.

(27) The inertial forces, not indicated in FIG. 4, acting on the bending tool, likewise act at the center of gravity P.

(28) FIG. 5 comprises a table, in which the voltage [V] with which the electromagnet is energized is entered in the first column from left to right. In the fourth column, the attainable power [W] is entered that can be maintained over a duration in seconds [s], entered in column 11, in order to suppress an overheating of the electromagnet. The table contained in FIG. 5 relates to a 12-V electromagnet.

(29) As follows from FIG. 5, a 12-V electromagnet can be energized for only 74 seconds with 24 volt and consequently with an elevated voltage for generation of an elevated magnetic force.

(30) FIG. 6 symbolically shows a diagram, wherein the time t is plotted on the abscissa and the voltage V on the ordinate, with which voltage V the electromagnet 2 is energized. It is expressly pointed out that no magnitudes of the voltage and/or no time values can be inferred from the diagram.

(31) A working cycle 12 takes place following an idle time 15. During the working cycle 12, the electromagnet 2 is energized at least partly with a voltage, so that a magnetic force is generated.

(32) The method according to the invention may—as illustrated in FIG. 6—be executed such that a second time span 14 of the working cycle 12 follows a first time span 13 of the working cycle 12, wherein the electromagnet 2 is energized with a first nominal voltage in the first time span 13, whereas the electromagnet 2 is energized with a second nominal voltage in the second time span 14. In FIG. 6, for reasons of clarity, only a first time span 13 and a second time span 14 respectively of a working cycle 12 are denoted by reference numerals.

(33) The first nominal voltage and the second nominal voltage are different. Due to the alternating nominal voltages, it results that the electromagnet 2 is energized, during a working cycle 12, for a shorter time in total with the higher first nominal voltage than during an energization with a high nominal voltage over the entire time period of the working cycle 12. Due to the inertia of the electromagnet 2, the magnetic force generated by the alternating energization with the first nominal voltage and the second nominal voltage remains substantially constant. Since the electromagnet 2 is energized with a high first voltage only over short first time periods 13, no overheating of the electromagnet takes place. The problem of the overheating of the electromagnet occurs—as is evident from the table in FIG. 5—upon an energization with voltages higher than the nominal voltage.