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.

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)