METHOD AND DEVICE FOR THE BURR-FREE SEPARATION OF A WIRE AND A CORRESPONDINGLY SEPARATED WIRE PIECE

Abstract

The invention relates to a method for burr-free cutting-off of a wire, an apparatus for burr-free cutting-off of a wire, a wire piece and a hairpin.

Claims

1. A method for burr-free cutting-off of a wire formed with a polygonal cross-section, comprising by the following steps: reshaping of the wire at a longitudinal wire location by moving two reshaping sections of a first reshaping unit, which are opposite one another in a first plane, towards one another along a first axis of movement, wherein the reshaping sections of the first reshaping unit are always spaced apart from one another during the reshaping of the wire, so that the wire cross-section is tapered from two opposite sides during this first reshaping step and a tapered wire cross-section remains, temporally subsequent to the first reshaping, reshaping of the wire at the same longitudinal wire location by moving two reshaping sections of a second reshaping unit, which are opposite one another in a second plane, towards one another along a second axis of movement, wherein the reshaping sections of the second reshaping unit are always spaced apart from one another, so that the already tapered wire cross section is tapered from two further opposite sides during this second reshaping step and the already tapered wire cross section remains in a further tapered shape; and tensile cutting-off of the wire at the same longitudinal wire location with now tapered wire cross-section by applying a tensile force to the wire.

2. The method according to claim 1, characterized in that the first plane and the second plane are congruent.

3. The Method according to claim 1, characterized in that the first axis of movement and the second axis of movement are oriented orthogonally to each other.

4. The method according to claim 1, characterized in that the reshaping sections of the first reshaping unit and/or the reshaping sections of the second reshaping unit are moved in opposite directions at the same absolute speed, during the respective reshaping.

5. The method according to claim 1, characterized in that the reshaping sections of the first reshaping unit and/or the reshaping sections of the second reshaping unit are each moved intermittently or continuously during the reshaping of the wire.

6. The method according to claim 1, characterized in that the wire is supplied to the reshaping units from an input side and is guided along a wire feed direction by means of a wire guide.

7. The method according to claim 1, characterized in that the wire is clamped in a gripper unit for tensile cutting-off, and the gripper unit, preferably gripper unit and reshaping units, is/are moved relative to the wire during the tensile cutting-off.

8. The method according to claim 1, characterized in that the reshaping units do not perform any movement relative to the wire along the longitudinal wire direction during the first reshaping step and/or the second reshaping step from the beginning of the first reshaping step to the end of the second reshaping step.

9. The method according to claim 1, characterized in that the first reshaping step and/or the second reshaping step are effected on the wire moved along the longitudinal wire direction, wherein the reshaping units are moved synchronously with the wire.

10. The method according to claim 1, characterized in that the reshaping sections of the first reshaping unit and/or the second reshaping unit have a greater width than the wire sides respectively reshaped by the reshaping sections.

11. An apparatus for burr-free cutting-off of a wire having a polygonal cross-section, characterized by a first reshaping unit for reshaping the wire with two reshaping sections which are opposite one another in a first plane and can be moved towards one another along a first axis of movement by a tool drive, wherein the reshaping unit is adapted such that the reshaping sections of the first reshaping unit are always spaced apart from one another during the reshaping of the wire, so that during the reshaping by means of the reshaping sections of the first reshaping unit the wire cross section can be tapered from two opposite sides to a tapered wire cross section; a second reshaping unit for reshaping the wire with two reshaping sections which are opposite one another in a second plane and can be moved towards one another along a second axis of movement by the tool drive, wherein the reshaping unit is adapted such that the reshaping sections of the second reshaping unit are always spaced apart from one another during the reshaping of the wire, so that during the reshaping by means of the reshaping sections of the second reshaping unit the already tapered wire cross section can be tapered from two further opposite sides to a further tapered shape; and a gripper unit which can be used to in particular clamp and to tensile cut-off the wire, wherein the apparatus is adapted such that the two reshaping units perform the movement along the respective axis of movement one after the other.

12. The apparatus according to claim 11, characterized in that the first plane and the second plane are congruent.

13. The apparatus according to claim 11, characterized in that the first reshaping unit and the second reshaping unit are arranged such that the first axis of movement and the second axis of movement are oriented orthogonally to each other.

14. The apparatus according to claim 11, characterized in that the first reshaping unit and/or the second reshaping unit, respectively, have/has a threaded shaft which is coupled to the tool drive and has two threaded sections with pitches which are identical in amount but oriented in opposite directions, wherein one reshaping section is respectively coupled to one threaded section.

15. The apparatus according to claim 11, characterized in that the reshaping units and/or the gripper unit are arranged and fastened on a support plate, wherein the support plate is guided displaceably along the longitudinal wire direction by means of a guide, in particular wherein a motor drive is coupled to the support plate, which can be used to drive the support plate in the longitudinal wire direction.

16. The apparatus according to claim 11, characterized in that the reshaping sections of the first reshaping unit and/or of the second reshaping unit have a greater width than the wire sides respectively reshaped by the reshaping sections.

17. The apparatus according to claim 11, characterized in that the reshaping sections of a reshaping unit, in particular of the first reshaping unit, have a tool tip with a first wedge angle, and in that the reshaping sections of the other reshaping unit have a tool tip with a wedge angle which is, at least directly at the tool tip, smaller than the first wedge angle.

18. The apparatus according to claim 11, characterized in that the reshaping sections of one, in particular the other, reshaping unit, in particular of the second reshaping unit, have a tool tip which has a continuous wedge angle or which has a plurality of sections with different wedge angles, wherein the wedge angle at a free end of the tool tip is smaller than a wedge angle adjacent to the side facing away from the free end.

19. A wire piece with a polygonal cross-section which has been cut-off from a wire (12), wherein the wire piece has a tapered section which is created by plastic reshaping and is offset inwardly in a radial wire direction relative to an original outer surface of the wire and transitions into a fracture surface created by tensile cutting-off, wherein the tapered section has a pair of first radially inwardly sloping surfaces and a pair of second radially inwardly sloping surfaces, wherein the transition of the first sloping surfaces to the fracture surface is formed by a pair of first transition edges and the transition of the second sloping surfaces to the fracture surface is formed by a pair of second transition edges, wherein the first transition edges and the second transition edges are straight and are arranged orthogonally to each other, wherein the distance of the two first transition edges from each other is greater than the distance of the two second transition edges from each other.

20. The wire piece according to claim 19, wherein the tapered section has a first radially inwardly sloping surface and a second radially inwardly sloping surface, wherein the transition of the first sloping surface to the fracture surface is formed by a first transition edge and the transition of the second sloping surface to the fracture surface is formed by a second transition edge, wherein the first transition edge and/or the second transition edge are/is formed as a straight line/as straight lines.

21. The wire piece according to claim 19, wherein the first transition edge and the second transition edge are formed as straight lines and are arranged orthogonally to each other.

22. (canceled)

Description

BRIEF DESCRIPTION OF THE INVENTION

[0063] In the following, the invention is explained in more detail on the basis of the drawing figures, wherein identical or functionally identical elements are provided with reference signs only once, if applicable. The figures show:

[0064] FIG. 1 an apparatus for burr-free cutting-off of a wire in a schematic perspective view;

[0065] FIG. 2 a reshaping unit of the apparatus of FIG. 1 in a solitary position in a perspective view;

[0066] FIG. 3 the reshaping sections of the reshaping units of the apparatus of FIG. 1 on a wire in a schematic perspective view;

[0067] FIG. 4 a section of the wire of FIG. 3 after the first reshaping step and the second reshaping step in a perspective view in a solitary position;

[0068] FIG. 5 the reshaping sections of the second reshaping unit after a tapering of the wire cross section by dipping into the wire (end position) in a sectional view;

[0069] FIG. 6 a reshaping section of the first reshaping unit of the apparatus of FIG. 1 in several views;

[0070] FIG. 7 a reshaping section of the second reshaping unit of the apparatus of FIG. 1 in several views;

[0071] FIG. 8 a cut-off location of a wire after performing the method according to the invention, wherein both resulting wire pieces are shown;

[0072] FIG. 9 a further cut-off location of a wire after performing the method according to the invention, wherein only one wire piece is shown and the wire has a round cross section; and

[0073] FIG. 10 several hairpins.

DETAILED DESCRIPTION

[0074] FIG. 1 shows an apparatus, as a whole designated by reference sign 10, for burr-free cutting-off of a wire 12 having a tetragonal, in this case rectangular, cross-section (but usually with rounded corners). Apparatus 10 comprises a first reshaping unit 14 for reshaping wire 12 from two opposite sides, a second reshaping unit 16 for reshaping wire 12 from two other opposite sides, and a gripper unit 18 which can be used to clamp wire 12 for tensile cutting-off.

[0075] First reshaping unit 14 and second reshaping unit 16 are attached to a frame 20 which is mounted on a support plate 22. Gripper unit 18 is attached to support plate 22 by means of a tool holder 24. Support plate 22 has a plurality of holes (without reference signs) for fastening components. In addition, support plate 22 has recesses 26 for gripping support plate 22.

[0076] By attaching reshaping units 14, 16 and gripper unit 18 to support plate 22, apparatus 10 forms a modular unit 10 which can be handled as such and can be integrated, for example, into a clocked in-line system with processing stations arranged upstream and/or downstream.

[0077] Support plate 22 is movable along the longitudinal direction X of the wire by means of a guide 28. This may be used to move support plate 22 and the components arranged on it with or relative to wire 12 along the longitudinal direction X. The axis of movement of support plate 22 or of modular unit 10 parallel to the longitudinal direction X of the wire has the reference sign X′ (axis of movement X′). Guide 28 is equipped with rails 30 and with corresponding carriages 32 to which support plate 22 is attached. In addition, a motor drive 34 is coupled to support plate 22, which can be used to drive support plate 22 along the longitudinal direction X of the wire or the axis of movement X′.

[0078] Wire 12 is fed along the longitudinal direction X through apparatus 10 (in FIG. 1 from right to left), wherein wire 12 is unwound as a continuous material from a wire coil 36 (coil axis 37) and supplied to apparatus 10 at an input side 38.

[0079] As already indicated, apparatus 10 serves for burr-free cutting-off of a wire 12 having a rectangular cross section and uses reshaping units 14, 16 and gripper unit 18 for this purpose, as described below.

[0080] First reshaping unit 14 is used for reshaping wire 12 with two opposite reshaping sections 40, which can be moved simultaneously towards each other along a first axis of movement Z by a tool drive 42 (see FIGS. 2 and 3). By means of reshaping sections 40, the wire cross-section may be tapered from two opposite sides 44 (narrow sides 44).

[0081] Second reshaping unit 16 is used for reshaping wire 12 with two opposite reshaping sections 46, which can be moved simultaneously towards each other along a second axis of movement Y by a tool drive 48 (see FIGS. 2 and 3). By means of reshaping sections 46, the wire cross section may be tapered from two other opposite sides 50 (wide sides 50).

[0082] Gripper unit 18 is used for tensile cutting-off of wire 12 (see FIG. 1). For this purpose, wire 12 may be clamped using gripper unit 18. Gripper unit 18 has two clamping jaws 52 which can be moved towards each other and have wire clamping sections 54 attached to them.

[0083] Reshaping sections 40 of first reshaping unit 14 and reshaping sections 46 of second reshaping unit 16 are all arranged in a common plane 56 (indicated in FIG. 3). In other words, the tool axes 58, 60 (parallel to the movement axes Z and Y) of reshaping sections 40, 46 (see FIGS. 6 and 7) are arranged in one plane. As reshaping sections 40 of first reshaping unit 14 and reshaping sections 46 of second reshaping unit 16 are not moved relative to cut-off location 62 in the longitudinal wire direction X from the first reshaping step to the second reshaping step, tapering of wire 12 occurs at exactly the same longitudinal wire location 62 (cut-off location 62; see FIG. 4). Plane 56 is orthogonal to the longitudinal direction X of the wire and is arranged vertically in FIG. 1, e.g. perpendicular to support plate 22.

[0084] As can be seen in FIGS. 6 and 7, reshaping sections 40, 46 each form a part of a reshaping tool 41, 47, which may also have a shaft 49, 51 by which the reshaping tool 41, 47 can be attached. The shaft 41, 47 of the reshaping tool 41, 47 may have holes which may be threaded (without reference sign). First reshaping unit 14 and second reshaping unit 16 are arranged such that the first axis of movement Z and the second axis of movement Y are oriented orthogonally to each other. For this purpose, reshaping units 14, 16 are mounted orthogonally to each other on frame 20 (see FIG. 1).

[0085] FIG. 2 shows first reshaping unit 14 with reshaping sections 40 and reshaping tool 41 in solitary position. First reshaping unit 14 has a threaded shaft 64 coupled to tool drive 42, which is designed as ball screw 64. Threaded shaft 64 has two threaded sections 66, 68 with pitches of identical amount but opposite orientation. One reshaping section 40 or reshaping tool 41 is respectively coupled to one threaded section 66, 68.

[0086] Threaded shaft 64 is attached to a base plate 74 of reshaping unit 14 by means of bearing blocks 70, 72. Reshaping sections 40 are each attached to a tool holding plate 78, 80 via shaft 49. Tool holding plates 78, 80 are each connected to a running element 82, 84, in which a nut 86, 88 corresponding to threaded shaft 64 is fastened in each case. Nuts 86, 88 are designed as spindle nuts 86, 88. Tool drive 42, e.g. designed as an electric motor 42, is coupled to threaded shaft 46 by means of a clutch 90.

[0087] Second reshaping unit 16 is designed in the same way as first reshaping unit 14, but has reshaping sections 46 or reshaping tools 47 instead of reshaping sections 40 or reshaping tools 41.

[0088] Reshaping sections 40 of first reshaping unit 14 may have a larger width than wire sides 44 (narrow sides 44; see FIG. 3) reshaped by these reshaping sections 40. Reshaping sections 46 of second reshaping unit 16 may have a larger width than wire sides 50 (wide sides 50) reshaped by these reshaping sections 46. At this point, it should be noted that the illustration in FIG. 3 is schematic and shows reshaping sections 40, 46 in their respective end positions in wire 12, wherein reshaping sections 40, 46 do not enter wire 12 simultaneously, but one after the other for reshaping reasons, especially since reshaping sections 40, 46 would otherwise collide with each other as described above.

[0089] In general, reshaping sections 40, 46 each have a respective tool tip 92, 94 which tapers towards the free end, e.g. a conically tapered or chamfered tool tip 92, 94 (see FIGS. 6 and 7).

[0090] Reshaping sections 40 of first reshaping unit 14 have a tool tip 92 with a first wedge angle 96, and reshaping sections 46 of second reshaping unit 16 have a tool tip 94 with a wedge angle 98 which directly at the tool tip 94 is smaller than first wedge angle 96. Reshaping section 40 may have an end face 93 which is orthogonal to tool axis 58. Wedge angle 96 may be 30°, for example.

[0091] First reshaping unit 14 may be used for reshaping wire 12 with a smaller penetration depth (penetration depth is e.g. about 0.5 mm each). In this way, wire 12 may be waisted from opposite narrow sides 44, for example. Such a reshaping may be called “coining”. Second reshaping unit 16 may be used for reshaping with a greater penetration depth (remaining material thickness between the tool tips 94 in the end position is about 0.2 mm, for example). Although this reshaping process does not involve cutting-off, but only deformation of the wire material, such a reshaping process may be called “cutting” because of the higher penetration depth compared to “coining”.

[0092] Reshaping sections 46 of second reshaping unit 16 may have a tool tip 94 which has a continuous wedge angle 98 (not shown).

[0093] Alternatively, reshaping sections 46 of second reshaping unit 16 may have a tool tip 94 which has a plurality of sections with different wedge angles. The wedge angle 98 at the free end of tool tip 94 may be smaller than a wedge angle 100 adjacent to the side facing away from the free end. Between wedge angle 98 at the free end and wedge angle 100, the reshaping section 46 may have a straight run 102. Wedge angle 98 may be 15°, for example. Wedge angle 100 may be 30°, for example. Reshaping section 46 may have an end face 103 orthogonal with respect to tool axis 60.

[0094] The method for burr-free cutting-off of wire 12 having a rectangular cross-section is performed as follows:

[0095] First, a burr-free reshaping of wire 12 is effected at a longitudinal wire location 62 (see FIG. 4) by simultaneously moving two opposite reshaping sections 40 of first reshaping unit 14 towards one another along the first axis of movement Z. During this first reshaping step, the wire cross section is tapered from two opposite sides 44 and a tapered wire cross section remains.

[0096] Subsequently, a reshaping of wire 12 is effected at the same longitudinal wire location 62 by simultaneous moving two opposite reshaping sections 46 towards one another along a second axis of movement Y. During this second reshaping step, the already tapered wire cross section is tapered from two other opposite sides 50 and the already tapered wire cross section remains in further tapered form. FIG. 3 shows this schematic view after performing both reshaping steps before a tensile cutting-off.

[0097] Reshaping units 14, 16 do not move along the longitudinal direction X of the wire relative to wire 12 during the first reshaping step and the second reshaping step. In other words, the relative speed between reshaping units 14, 16 and wire 12 is zero.

[0098] The first reshaping step and the second reshaping step are effected on wire 12 moved along the longitudinal wire direction X, wherein reshaping units 14, 16 are moved synchronously with wire 12 during the reshaping steps.

[0099] Subsequently, a tensile cutting-off of wire 12 is effected at the same longitudinal wire location 62 by applying a tensile force to wire 12 which acts at least partly along the longitudinal wire direction X. Reshaping sections 40 of first reshaping unit 14 and reshaping sections 46 of second reshaping unit 16 are all arranged in a common plane 50 and are moved in this plane (see FIG. 3). The first axis of movement Z and the second axis of movement Y are oriented orthogonally to each other (see FIGS. 1 and 3).

[0100] During the reshaping of wire 12, reshaping sections 40 of first reshaping unit 14 and reshaping sections 46 of second reshaping unit 16, respectively, are always spaced apart from each other. For reshaping sections 40, this can be seen in FIG. 3, which shows reshaping sections 40, 46 in their maximum approximated end position. For reshaping sections 46, this can be seen in FIG. 5 where reshaping sections 46 are shown in their end position (remaining material web between reshaping sections 46 can be seen).

[0101] Reshaping sections 40 of first reshaping unit 14 and reshaping sections 46 of second reshaping unit 16, respectively, have the same travel distance and are moved in opposite directions with the same absolute speed. During reshaping of wire 12, reshaping sections 40 of first reshaping unit 14 and reshaping sections 46 of second reshaping unit 16 may each be moved intermittently or continuously.

[0102] Wire 12 is supplied to reshaping units 14, 16 from an input side 38 and is guided by a wire guide (not shown) along the wire longitudinal direction or wire feed direction X. On an output side 39, wire 12 is guided by gripper unit 18 and may be supplied to a further processing unit after cutting-off. Gripper unit 18 is arranged downstream of reshaping units 14, 16 in the longitudinal wire direction or wire feed direction X.

[0103] For a tensile cutting-off, wire 12 is clamped in gripper unit 18 and gripper unit 18 is moved relative to wire 12 by driving support plate 22 together with reshaping units 14, 16. Since the speed of gripper unit 18 or support plate 22 is higher than the speed of wire 12 (relative speed), an increasing tensile stress is created until wire 12 is torn off at longitudinal wire location 62 (cut-off location 62).

[0104] After the wire section (wire rod) has been torn off, the separated part of wire 12 is held by gripper unit 18. The cut-off wire section is then removed from gripper unit 18 and supplied to the next processing station, e.g. to reshaping.

[0105] After the tensile cutting-off, apparatus 10, designed as a unit 10, moves back towards wire coil 36 and synchronizes again to the feeding speed of wire 12 until the following wire is positioned in gripper unit 18 and is clamped there. Subsequently the first reshaping step and the second reshaping step are effected analogously as described above.

[0106] The return speed or the return distance of unit 10 towards wire coil 36 are set according to the desired length of the wire rod.

[0107] The above cut-off wire piece forms a wire piece 104 which has been cut-off by the method according to the invention. Wire pieces 104 on both sides of a cut-off location 62 created by the method according to the invention are shown in FIG. 8, wherein the corresponding wire 12 has a rectangular cross-section. FIG. 9 shows a single wire piece 104 with a circular cross section which has been cut-off by the method according to the invention.

[0108] Wire pieces 104 shown in FIGS. 8 and 9 each extend along a longitudinal direction L of the wire. A radial wire direction R extends orthogonally to the longitudinal wire direction L and forms together with a wire circumferential direction U a cylindrical coordinate system related to wire 12 or the respective wire pieces 104. Wire pieces 104 shown in FIG. 8 have a rectangular cross-section. In other words, an original outer surface 107 of wire pieces 104 is rectangular when considering a cross-section orthogonal to the longitudinal direction L. Wire piece 104 in FIG. 9 or its original outer surface 107, respectively, has however a round cross-section.

[0109] Wire pieces 104 each have a tapered section 106 which is offset inwardly in the radial direction R from the original outer surface 107 of wire 12 or wire piece 104. Tapered section 106 has been created in the first and second reshaping steps described above.

[0110] The respective tapered section 106 transitions inwardly in the radial wire direction R into a fracture surface 108. Fracture surface 108 is created by the tensile cutting-off described above.

[0111] Since tapered section 106 in this case has been created in the first and second reshaping steps described above, it has a pair of first radially inwardly sloping surfaces 110 created by the first reshaping step and a pair of second radially inwardly sloping surfaces 112 created by the second reshaping step.

[0112] First sloping surfaces 110 extend from original outer surface 107 to fracture surface 108. The transition of first sloping surfaces 110 into fracture surface 108 is formed by a pair of first transition edges 114, which in the present case are straight. Second sloping surfaces 112 also extend from original outer surface 107 to fracture surface 108. The transition of second sloping surfaces 112 to fracture surface 108 is formed by a pair of second transition edges 116, which in the present case are also straight.

[0113] First transition edges 114 and second transition edges 116 extend orthogonally to each other. This orthogonal arrangement of first transition edges 114 and second transition edges 116 is induced by the reshaping steps performed in the present example and the first and second reshaping units 14, 16 with straight-edged reshaping sections 40, 46 and first and second movement axes Z, Y extending orthogonally to each other.

[0114] FIG. 10 shows two hairpins, each made from a wire piece 104 by reshaping, wherein the wire piece has a cut-off location 62 at both ends, as illustrated in FIG. 8.