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.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is the U.S. National Stage Application of International Application No. PCT-Application PCT/EP2019/066036 filed Jun. 18, 2019, which relates and claims priority to German Application No. 10 2018 114 579.9 filed Jun. 18, 2018, the entire disclosures of each of which are hereby incorporated by reference.

BACKGROUND

The invention relates to a method for burr-free cutting-off of a wire. Furthermore, the invention relates to an apparatus for burr-free cutting-off of a wire having the features of the preamble of the co-ordinate claim. Furthermore, the invention relates to a correspondingly cut-off wire piece and a hairpin.

Methods and apparatuses of the type mentioned above are known to the applicant from practice. Thus, in the production of electric motors for traction drives, individual winding elements (plug-in coils, so-called “hairpins”) are manufactured, which are further processed in the subsequent process to form a complete stator winding. In order to achieve a higher efficiency of electric machines due to a higher filling degree, the hairpin technology transitions from round wires to wires with rectangular cross-section. During the manufacture of the plug-in coils, corresponding wire sections must be cut to length and cut off from continuous material, which are then welded together after being positioned on the stator.

DE 10 2011 116 529 A1 describes a method for cutting a single strand wire.

DE 2 245 771 describes an apparatus and a method for pointing (in German language: “Ankuppen”) of wire pins.

DE 10 2017 205 633 A1 describes an apparatus and method for cutting a wire.

The wire sections are usually cut off by shearing, wherein end faces are formed at the wire ends whose edges are unbroken, i.e. sharp-edged, and have burrs (shear burrs). During the assembly of the plug-in coils, these shear burrs can, if they are not removed in an additional work step, e.g. by hand, enter an insulation (insulating paper) which resides already in the groove of the provided stator of the electric motor. There is therefore a risk that the insulation is destroyed, which can lead to malfunctions of the electric motor.

It is the object of the invention to provide a reliable and, as far as possible, burr-free cutting-off of wires by simple means of construction. Reworking of the wires at the cut-off locations should be avoided.

SUMMARY

The invention achieves this object by a method characterized by a plurality of steps, which are described below.

First, the wire is reshaped (burr-free) at a longitudinal wire location in a first reshaping step 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. In this first reshaping step, the wire cross section is tapered from two opposite sides, e.g. from two narrow sides. During reshaping of the wire, the reshaping sections of the first reshaping unit are always spaced apart from each other so that a tapered wire cross-section remains. Then the wire is reshaped at the same longitudinal wire location in a second reshaping step 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. In this second reshaping step, the already tapered wire cross section is tapered from two further opposite sides, e.g. from two wide sides. During reshaping the wire, the reshaping sections of the second reshaping unit are always spaced apart from each other so that the already tapered wire cross-section remains in a further tapered form. This means that a material web remains at the longitudinal wire location, which is offset inwards compared to the original cross-sectional shape of the wire. In particular, the material web can have the same cross-sectional center as the original cross-section of the wire. In particular, the material web is offset inwardly by the same distance from the original cross-sectional shape on at least two, preferably all, opposite sides. At this point in time, the wire sections arranged before and after the longitudinal wire location, the intended cut-off location, are still connected integrally with each other via the material web. Subsequently, i.e. after the second reshaping step, the wire is tensile cut-off at the same longitudinal wire location by applying a tensile force to the wire (which acts at least proportionally along the longitudinal direction of the wire). Thus the wire is cut-off at the longitudinal wire location.

The advantage of such a cutting-off is that the occurrence of shear burrs can be avoided by the method providing several reshaping steps at a corresponding longitudinal wire location (cut-off location) and a subsequent tensile cutting-off, as described above. By reshaping the wire by means of the reshaping sections, the wire is tapered at the longitudinal wire location so that a defined weak point is created at which the wire is cut off by tensile cutting-off. Since the wire is also tapered before and behind the cut-off location (cut-off plane) by reshaping with the reshaping sections, the wire ends have a tapered, e.g. chamfered or conical shape. Thus, wire sections with wire ends can be provided, which are ideally suited for plug-in coils (hairpins), since these can be easily inserted into the insulation of the grooves of a motor due to their tapered, e.g. conical, wire ends. In other words, an easier insertion of the wire into the stator is possible without damaging the insulation paper, since the “initial cross section” (wire end) is smaller during insertion. The burr-free wire ends contribute to increased safety and reduced scrap. In addition, the process is economically advantageous, as the service life of the reshaping sections is comparatively long, since the reshaping sections only penetrate the wire material (e.g. copper) and only deform it and do not touch each other.

The proposed method may be used in a complex process chain. The adjacent methods may be e.g. inserting the insulation into the stator groove, reshaping of hairpins in several steps or stripping the wire ends of a hairpin. The process chain may, for example, be carried out with the sequence stripping—first reshaping step, second reshaping step and tensile cutting-off—reshaping into the hairpin shape. All steps may be performed on one machine having different stations of a preferably clocked in-line system. Individual stand-alone process units are also conceivable.

The term “burr-free cutting-off” is to be understood in the present case such that the cutting-off is effected burr-free with respect to the lateral surfaces of the wire. Thus, after cutting-off, the wire should not have any burrs (shear burrs) that protrude laterally beyond the lateral surfaces of the wire. A certain amount of burr can be formed on the end faces of the wire due to the tensile cutting-off, but this is not important for the further use of the cut-off wire pieces due to the lack of lateral protrusion.

The wire may be a wire of soft material, e.g. copper wire. The wire may be covered by an insulation, e.g. an varnish layer. The wire may have a polygonal, especially tetragonal cross-section, e.g. a rectangular cross-section, wherein a rectangle may be understood as a rectangle with rounded corners and not necessarily as a rectangle in the strict geometric sense. In particular, however, the method uses a wire with a cross-section with two parallel straight sides, or in particular with four straight sides, respective pairs of which are parallel to each other.

The reshaping sections of the reshaping units are movable, in particular along their axis of movement, between an starting position (reshaping sections are located outside the wire) and an end position (reshaping sections have penetrated the wire and are not moved further towards each other). The ends (tool tips) of the reshaping sections facing the wire do not touch each other in the end position.

The reshaping sections form a part of a reshaping tool, which may have a reshaping section (actual machining section) and a shaft section for fastening the reshaping tool, e.g. to a tool carrier or a tool holding plate. The reshaping tool may be mounted in a reshaping unit and may be driven by the reshaping unit, as described later.

As discussed above, the described reshaping steps are carried out one after the other. This prevents any collision of the reshaping sections. In addition, the wire material has the opportunity to “search its way” during reshaping, i.e. to recede from the reshaping sections by plastic deformation. The successive reshaping steps allow the wire material to “recede” in the direction of the respective other process step, wherein a reduced burr formation or a reduced “throw-up” formation can be achieved. The reshaping units may be coordinated by electrically controlled “cams” (cams or eccentrics) or by a CNC system.

The reshaping sections of the first reshaping unit may be arranged in a (first) plane and moved in this plane and/or the reshaping sections of the second reshaping unit may be arranged in a (second) plane and moved in this plane. The arrangement of the respective opposite reshaping sections in one plane contributes to the fact that the wire material is not sheared but deformed (reshaping sections are not offset to each other like scissor blades). The formation of shear burrs can thus be avoided.

The reshaping sections used in the method or present in the apparatus, respectively, are preferably adapted such that they have an extension in a direction transverse to the respective axis of movement which is greater than the extension of the wire in this direction.

When the reshaping sections are arranged opposite one another in one plane, this may mean that the respective tool tips are arranged in a plane in which the respective axis of movement of the reshaping sections is also located. The tool tips of the reshaping sections of the first reshaping unit may therefore be arranged in the first plane and the first axis of movement of the reshaping sections is also located in this plane. Accordingly, the tool tips of the reshaping sections of the second reshaping unit may be arranged in the second plane and the second axis of movement of the reshaping sections is also located in this second plane.

The first plane and second plane may be congruent. Thus, the first plane and the second plane may lie on top of each other. In other words, the reshaping sections of the first reshaping unit and the reshaping sections of the second reshaping unit may all be arranged in a common plane and may be moved in this plane during reshaping. In particular, the tool tips may all be arranged in a common plane and may be moved in this plane during reshaping. This ensures a very precise reshaping of the wire at exactly the same longitudinal wire location, since positioning errors are avoided.

Appropriately, the first axis of movement (along which the reshaping sections of the first reshaping unit are moved) and the second axis of movement (along which the reshaping sections of the second reshaping unit are moved) may be oriented orthogonally to each other. Thereby, the axes of movement may intersect each other. In particular, a polygonal or tetragonal (e.g. rectangular) wire can be processed on the respective opposite side surfaces, wherein good reshaping characteristics can be achieved (wire material can recede in the direction of the other process).

As mentioned above, the reshaping sections do not touch each other during the reshaping of the wire and are always spaced apart from each other along their axis of movement. This ensures that the wire sections abutting each other at the longitudinal wire location (cut-off location) remain connected to each other by a sufficiently strong integral connection in order to achieve the desired contour of the wire ends during tensile cutting-off.

Advantageously, the reshaping sections of the first reshaping unit and/or the reshaping sections of the second reshaping unit can be moved respectively in opposite directions during the respective reshaping, in particular with the same absolute speed. In this way a uniform reshaping of the wire at the opposite sides of the wire can be achieved, wherein undesired deformations of the wire, e.g. bending or buckling, can be avoided. This helps to reduce scrap.

Appropriately, the reshaping sections of the first reshaping unit and/or the reshaping sections of the second reshaping unit may each be moved intermittently or continuously (towards each other) when reshaping the wire. Depending on the characteristics of the wire material and/or the design of the reshaping sections, a desired reshaping can be achieved. With continuous movement of the reshaping sections a short reshaping time can be achieved. With intermittent movement, the wire material can be given time to “find the right way” during reshaping.

Specifically, the wire may be supplied to the reshaping units from an input side and guided along a wire feed direction or longitudinal wire direction by means of a wire guide. This ensures a wire supply with simple means of construction. The wire is stabilized by the guide so that it is held securely, in particular during the reshaping steps and during tensile cutting-off. After a cutting-off, the wire can be discharged at the output side.

Within the scope of a preferred design, the wire may be clamped for tensile cutting-off in a gripper unit. The gripper unit, preferably the gripper unit and the reshaping units (unit formed by gripper unit and reshaping units), may be moved relative to the wire. This allows a constructionally simple tensile cutting-off of the wire at the longitudinal wire location, since this only requires fixing the wire at one location and a relative movement (speed of the gripper unit vgripper-unit is higher than the speed of the wire vwire). For example, the gripper unit may be accelerated, so that by clamping the wire in the gripper unit at the longitudinal wire location (cut-off location) an increasing tensile stress is created by the speed difference (vgripper-unit>vwire) until the wire tears off. A delay of the wire feed along the wire feed direction upstream the gripper unit with a constant speed of the gripper unit would also be a conceivable solution to obtain a speed difference. Also then, vgripper-unit>vwire is valid. The gripper unit may be arranged downstream of the reshaping units in the wire feed direction.

Appropriately, the reshaping units cannot move relative to the wire along the longitudinal wire direction during the first reshaping step and/or during the second reshaping step (relative speed is zero). This allows an exact reshaping at exactly the same longitudinal wire location during the reshaping steps, since positioning errors, which can occur when moving and re-fixing the wire, are avoided. For this purpose, the reshaping units may be moved synchronously with the wire or may be at a standstill together with the wire.

As already indicated above, the first reshaping step and/or the second reshaping step can be performed on the wire moved along the longitudinal wire direction, wherein the reshaping units are moved synchronously with the wire (no relative speed between reshaping units and wire). This allows a fast reshaping and thus a short processing time.

With this method, the wire can be supplied continuously, in particular at a constant rate, from a wire source to the reshaping units. The wire source may be a wire coil. The wire can be moved along a wire feed direction in a section of its transport mostly in a straight line. The reshaping units can be temporarily moved with the wire at the same speed. During this co-movement, the first and second reshaping steps can be carried out without any relative movement between the wire and the reshaping units occurring between the first reshaping step and the second reshaping step. It is appropriate to arrange the reshaping sections of the first reshaping unit and of the second reshaping unit in the same plane. After the second reshaping step, the wire section located downstream of the reshaping units or downstream of the cut-off location can be accelerated, e.g. by means of the gripping device, so that a tensile force can be applied to the wire and the wire is tensile cut-off at the longitudinal wire location having the tapered wire cross section. The speed of the wire section located, in the transport direction, upstream of the reshaping units or upstream of the intended cut-off location, respectively, can thereby preferably remain constant. After the second reshaping step, the reshaping units can be slowed down and moved back against the transport direction so that the process can be carried out again. The moving speed of the reshaping units, the transport speed of the wire and the moving distance of the reshaping units can be adjusted to the desired wire length.

After the tensile cutting-off, the cut-off wire piece may be removed from the gripping device and shaped into a hairpin, for example.

For further development of the method, the measures described below in connection with the apparatus can also be used.

In particular, the implementation of the method by means of an embodiment of the apparatuses described below is in accordance with the invention.

The object mentioned at the beginning is also achieved by an apparatus for burr-free (with respect to the lateral surfaces) cutting-off of a wire having a polygonal, in particular tetragonal (e.g. rectangular), cross-section is characterized by the features described below.

The apparatus comprises 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. When reshaping the wire, the reshaping sections of the first reshaping unit are always spaced apart from each other so that the wire cross-section can be tapered to a tapered wire cross-section from two opposite sides by means of the reshaping sections. The apparatus also comprises 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 a tool drive. During reshaping of the wire, the reshaping sections of the first reshaping unit are always spaced apart from each other so that the already tapered wire cross-section can be tapered to a further tapered shape from two further opposite sides by means of the reshaping sections. The apparatus also comprises a gripper unit, preferably arranged downstream of the reshaping units along the longitudinal direction of the wire, for tensile cutting-off of the wire. The wire can be clamped by means of the gripper unit so that tensile cutting-off of the wire can be effected, e.g. by relative movement between the gripper unit and the wire. The apparatus is arranged such that the two reshaping units successively perform the movement along the respective axis of movement (the movement occurs respectively from a starting position along the axis of movement to an end position). It may be provided in particular that the reshaping sections of the first reshaping unit and the reshaping sections of the second reshaping unit are adapted such that they cannot be arranged simultaneously in the end position, in particular since the reshaping sections contact each other during simultaneous movement from the starting position into the end position before reaching the end position.

With regard to the advantages of this apparatus, reference is made to the relevant explanations in connection with the method.

With a preferred design, the reshaping sections of the first reshaping unit can be arranged in a (first) plane together with the first axis of movement and/or the reshaping sections of the second reshaping unit can be arranged in a (second) plane together with the second axis of movement. This contributes to the fact that the wire material is not sheared but deformed, as described above. Shear burrs can thus be avoided. With the reshaping sections being arranged opposite each other in one plane, it may be meant that the respective tool tips are arranged in a plane in which also the respective axis of movement of the reshaping sections is arranged. The tool tips of the reshaping sections of the first reshaping unit may therefore be located in the first plane and the first axis of movement of the reshaping sections is also located in this plane. Accordingly, the tool tips of the reshaping sections of the second reshaping unit may be located in the second plane and the second axis of movement of the reshaping sections is also located in this second plane.

Advantageously, the first and second planes described above may be congruent to each other. In other words, the reshaping sections of the first reshaping unit and the reshaping sections of the second reshaping unit may all be arranged in a common plane. This ensures an accurate reshaping of the wire at exactly the same longitudinal wire location, since positioning errors are avoided, as described above.

Appropriately, the first reshaping unit and the second reshaping unit may be arranged such that the first axis of movement and the second axis of movement are orthogonal to each other. Thereby, the first axis of movement and the second axis of movement may intersect each other. In this way, a polygonal or tetragonal (e.g. rectangular) wire can be processed on the respective opposite side faces, wherein good reshaping characteristics can be achieved. The reshaping units may be mounted on a frame or a housing. The reshaping units mounted in this way can form a reshaping unit.

Specifically, the first reshaping unit and/or the second reshaping unit may each have a threaded shaft coupled to the tool drive, which has two threaded sections with identical but oppositely oriented thread pitches, wherein one respective reshaping section is coupled to a threaded section. This provides a constructionally simple and stable design of a reshaping unit having mutually synchronized reshaping sections (same speed, same travel paths, but opposite directions).

A ball screw can be used as a threaded shaft, which has favorable frictional characteristics. The threaded shaft may be supported by means of bearing blocks and may, for example, be mounted on a base plate of the reshaping unit. The reshaping sections of a reshaping tool may be connected, e.g. in one piece, with a shaft which can be used to attach the reshaping tool to a tool holding plate. The tool holding plates may each be connected to a running body on or in which a nut corresponding to the threaded shaft, e.g. a spindle nut, is inserted. The tool drive, e.g. an electric motor, may preferably be coupled to the threaded shaft by means of a coupling.

With a preferred design, the reshaping units and/or the gripper unit may be arranged and fixed on a (common) support plate. Thereby a modular unit is formed, which can be handled as a unit and can be integrated e.g. into a clocked in-line system.

The support plate may have holes for attaching components and/or recesses for gripping the support plate. The reshaping units may be attached to the support plate by means of a frame or a housing. The gripper unit may be attached to the support plate by means of a tool holder.

Advantageously, the support plate may be guided along the longitudinal direction of the wire by means of a guide, wherein a motor drive may be coupled to the support plate, which can be used to drive the support plate in the longitudinal direction of the wire. This allows the support plate and thus the reshaping units and the gripper unit to be moved with or relative to the wire. Reshaping can thus be performed on the moving wire. By moving the mounting plate or the gripper unit relative to the wire, a tensile cutting-off can be realized. The guide may comprise rails and carriages which correspond to the rails and to which the support plate is attached. The motor drive may have a drive motor, e.g. an electric motor. The drive motor may be controlled with respect to feed, frequency, amplitude, acceleration, speed, position and/or torque.

Appropriately, the reshaping sections of the first reshaping unit and/or the reshaping sections of the second reshaping unit may have a greater width than the wire sides respectively reshaped by these reshaping sections. This ensures a uniform reshaping of the wire at the longitudinal wire location (cut-off location). In addition, this enables the processing of wires with different cross-sections, whose side lengths are shorter than the width of the reshaping sections, with only one reshaping section.

In general, the reshaping sections may each have a tool tip that is tapered towards the free end, e.g. conically tapered or chamfered. One may also speak of blade-shaped tool tips.

Specifically, the reshaping sections of a reshaping unit, in particular of the first reshaping unit, may have a tool tip with a first wedge angle and the reshaping sections of the other reshaping unit, in particular of the second reshaping unit, may have a tool tip with a wedge angle which is, at least directly at the tool tip, smaller than the first wedge angle. Thus, reshaping sections corresponding to the desired reshaping can be provided, wherein the remaining material thickness of the wire is greater when reshaping with the first reshaping unit than when reshaping with the second reshaping unit.

Both with the method according to the invention and with the apparatus it may be provided that the remaining material thickness in the respective moving direction is greater in the first reshaping step than in the second reshaping step (remaining material thickness is e.g. less than 0.2 mm).

Thus, the first reshaping unit may be used for reshaping with a lower penetration depth (penetration depth in each case is about 0.5 mm, for example). In this way, the wire may be waisted from its opposite narrow sides, for example. Such reshaping may be called “coining”. The second reshaping unit may be used for reshaping with a higher penetration depth (remaining material thickness between the tool tips 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 material, such a reshaping process may be called “cutting” due to the higher penetration depth of the reshaping sections.

Appropriately, the reshaping sections of the other reshaping unit, in particular of the second reshaping unit, may have a tool tip which has a continuous wedge angle. This allows a cost-effective fabrication of such a reshaping section.

Alternatively, the reshaping sections of the other reshaping unit, in particular of the second reshaping unit, may have a tool tip which has a plurality of sections with different wedge angles, wherein the wedge angle at the free end of the tool tip is smaller than a wedge angle adjacent to the side facing away from the free end. Such a wedge angle at the free end facilitates penetration of the reshaping section into the wire, wherein a larger reshaping may occur due to the subsequent (larger) wedge angle. Between the wedge angle at the free end and the following (larger) wedge angle, the reshaping section may have a straight run. This serves the stability of the reshaping tool, ensures a dimensionally correct opening (specific entry angle) when penetrating the wire material and prevents burr formation.

For further development of the apparatus, also the measures described in connection with the method may be used.

Part of the present invention is also a wire piece which has been cut-off from a wire, in particular by applying a described method and/or by using a described apparatus. Such a wire piece comprises a tapered section created by plastic reshaping, which is offset inwardly in a radial direction of the wire with respect to an original outer surface of the wire. The tapered section transitions into a fracture surface created by tensile cutting-off, which has a surface structure caused by this cutting-off process.

The tapered section has a first surface sloping radially inwards and a second surface sloping radially inwards. 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.

The first transition edge and the second transition edge are formed as straight lines.

The first transition edge and the second transition edge are arranged orthogonally to each other.

The distance between the first two transition edges is greater than the distance between the second two transition edges.

The wire piece may have a rectangular original cross-section.

The wire piece may in particular include copper. In particular, it may include or consist of a copper core with an insulating coating.

Preferably, the tapered section is created in the first and second reshaping steps described above.

The first and second sloping surfaces extend from the original outer surface to the fracture surface. Thereby, it is possible that the first and/or the second sloping surfaces have regions with different gradients. It is therefore possible that the rate at which the surfaces slope radially inwardly varies locally along the longitudinal direction of the wire.

A hairpin formed from one of the wire pieces described above is also part of the invention.

BRIEF DESCRIPTION OF THE INVENTION

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:

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

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

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

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;

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;

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

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

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

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

FIG. 10 several hairpins.

DETAILED DESCRIPTION

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.

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.

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.

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′.

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.

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.

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).

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).

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.

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.

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).

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.

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.

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.

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.

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).

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.

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”.

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

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.

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

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.

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.

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.

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.

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).

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).

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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)