Device and method for producing a spring wire, device and method for marking a spring wire, device and method for producing springs from a spring wire, and spring wire

Abstract

Device for producing a spring wire (2), comprising: a wire-making device (8) configured such that a spring wire (10) can be produced from a raw material, in particular by drawing; a testing unit (14) configured such that the spring wire (10) can be checked for defects; and a laser marking unit (18) configured such that defective areas of the spring wire (10) can be marked with a laser marking (44) in such a way that a part of the surface of the spring wire (10) can be thermally tempered so that the color of the surface of the spring wire (10) in this part is changed; wherein the wire-making device (8) is configured such that the spring wire (10) can be guided past the testing unit (14) and the laser marking unit (18).

Description

The present invention relates to an apparatus and a method for producing a spring wire, an apparatus and a method for marking a spring wire, an apparatus and a method for producing springs from a spring wire, and a spring wire.At present, spring wires are manufactured with a manufacturing facility in a continuous process. In these methods, errors may occur in or on the spring wire, which are often only insufficiently recognized or identified.In the further course of processing such a spring wire into springs, the production process must frequently be stopped in the event of such wire defects, and the defective region must be cut out with a great deal of time and work.DE 18 03 917 U shows a device for identifying a draw material to be fed to a wire drawing machine, characterized by a fault testing device known per se, by means of which a paint spray valve arranged downstream of the drawing tool and / or a signal transmitter can be acted upon after a fault has been determined.DE 28 53 258 A1 shows an arrangement in which an already produced sheet or tape is passed a checking unit and a laser marking unit.It is therefore an object of the present invention to provide more efficient methods and apparatuses with which a greater spring manufacturing capacity is enabled and processing of faulty spring wire areas can be reliably excluded.This object is achieved by the subject matter of the independent claims. Advantageous further developments are evident from the dependent claims.An apparatus according to the invention for producing a spring wire has the following features: a wire production device which is designed such that a spring wire can be produced from a raw material, in particular by drawing, a testing unit which is designed such that the spring wire can be checked for defects, in particular for material and surface defects, and a laser marking unit which is designed such that defective regions of the spring wire, in particular regions of the spring wire with material and surface defects, can be marked with a laser marking such that a part of the surface of the spring wire can be thermally initiated such that the color of the surface of the spring wire is changed in this part, wherein the wire production device is designed such that, the spring wire can be guided past the test unit and the laser marking unit.An apparatus according to the invention for marking a spring wire has the following features: a feed unit, in particular a feed roller for feeding a spring wire; a checking unit which is designed such that the spring wire can be checked for defects, in particular for material and surface defects; and a laser marking unit which is designed such that defective regions of the spring wire, in particular regions of the spring wire with material and surface defects, can be marked with a laser marking such that a part of the surface of the spring wire can be thermally tempered such that the color of the surface of the spring wire is changed in this part; wherein the feed unit is designed such that the spring wire can be guided past the checking unit and the laser marking unit.According to a basic idea of the present invention, with an apparatus according to the invention for producing a spring wire and with a method according to the invention for producing a spring wire, defective regions of the spring wire can be automatically marked by laser markings, during the ongoing operation of the production process and without interruptions thereof.This spring wire production is efficient and cost-effective because no interruption of the production process is required for marking defective regions.According to a further basic idea of the present invention, with an apparatus according to the invention for marking a spring wire and with a method according to the invention for marking a spring wire, defective regions in already produced spring wires can be automatically marked by laser markings in a continuous method.The defective areas can be reliably characterized for the subsequent processing steps without an additional material being required for this, which reduces waste, especially since defective areas of the spring wire or springs which have been produced from such defective areas of the spring wire can simply be fused in again and processed to form a new spring wire.While with the device and the method according to the invention for producing a spring wire, the spring wire is produced and at the same time defective regions are detected and marked, the device according to the invention and the method according to the invention for marking a spring wire assume that the spring wire has been produced and the defective regions are marked by laser markings in a separate method and on a separate device.The apparatuses and methods largely correspond to one another and differ mainly in that, in the apparatus and the method for producing a spring wire, the spring wire is fed to the test unit and the laser marking unit from the wire production device, whereas, in the apparatus and the method for marking a spring wire according to the invention, the spring wire is fed by a feed unit, in particular a feed roller.Unless stated otherwise, all the advantages and embodiments explained below relate to both aspects of the invention, namely both the device according to the invention and the method according to the invention for producing a spring wire and also the device according to the invention and the method according to the invention for marking a spring wire which has already been produced.There are two variants of the laser markings according to the invention for identifying defective regions of the spring wire. According to a finding on which the invention is based, defective regions of spring wires made of conventional spring steel materials can be labeled by tempering, i.e. characterized by means of a surface region which is changed in color.The laser marking does not have to be arranged exactly at the location at which the defective region is located; it can also be arranged before or after it. It is only important that the spatial relationship between the defective region and the position of the laser marking is known.The laser marking has a color which differs so clearly from the color of the remaining surface of the spring wire that such a laser marking can be detected optically in a simple manner.The material of the spring wire is thereby locally heated to below its melting point. Local changes in structure and the tempering colors associated therewith are produced. Tempering colors are stable to below 200° C., these changes in structure are formed back at higher temperatures and the inscription disappears again.This results in a tempering effect due to changes in the structure of the edge layer. This is a removal-free method which can provide very good contrasts between laser marking and the surrounding region of the spring wire. The material of the spring wire is thereby locally heated only up to a temperature which lies below the melting temperature and below the evaporation temperature. The color change is due to the formation of an oxide layer.The spring wire can be passed in-line through a testing unit followed by a laser marking unit directly after the spring wire is produced or fed, before the spring wire is wound onto a winding roll. This eliminates the need for additional time and also an additional transport path for checking and marking the defective areas of the spring wire.The spring wire can be immediately rolled up after marking its defective region. A drying phase, which might be required, for example, during marking by means of a paint, is dispensed with. The space requirement for the additional test unit to be provided and for the additional laser marking unit to be provided is very small.The inventive material-removing marking of a defective region by a laser ensures that the thickness of the spring wire does not exceed a corresponding tolerance range. This is a great advantage over a conceivable material-applying marking, especially as wire guides and wire inlets during the subsequent production steps are frequently matched exactly to the geometry of the spring wire.An apparatus according to the invention and a method according to the invention for producing a spring wire can also be understood as a development of the apparatus according to the invention and of the method according to the invention for marking a spring wire, wherein the wire production device or the production step of the spring wire takes the place of the first apparatus feature feed unit or the first method step feed. The right to reformulate the first device claim for manufacturing a spring wire and the first method claim for manufacturing a spring wire as dependent claims, respectively, which are related back to the claims of the device and the method for marking a spring wire is expressly reserved at this point.According to one embodiment, the laser marking unit is configured to thermally light a part of the surface of the spring wire in the defective regions of the spring wire such that the color of the surface of the spring wire is changed in this part, direct a laser beam having a temperature of about 200° C. to 660° C. onto the spring wire.In order to apply laser markings with such a color change of the surface of the spring wire, laser beam must impinge on the surface of the spring wire with a corresponding power.The power with which a laser beam is emitted and thus impinges on the surface of the spring wire to achieve the desired color change is dependent on the spot size, the wavelength of the laser, the speed at which the wire is guided past the laser marking unit, and the desired color of the color change. A suitable range for the power of the laser marking unit is in the range 1 to 10 W. Alternatives are of course possible and included.At a tempering temperature of about 200° C., a white yellow tempering color results, at about 220° C., a straw yellow tempering color, at about 230° C., a golden yellow tempering color, at about 240° C., a tan tempering color, at about 250° C., a brown red tempering color, at about 260° C., a red tempering color, at about 270° C., a purple tempering color, at about 280° C., a violet tempering color, at about 290° C., a dark blue tempering color, at about 300° C., a grain flower blue tempering color, at about 32° C., a light blue tempering color, at about 30° C., a blue gray tempering color, and at about 660° C. a gray tempering color. These temperatures are understood to mean a corresponding tolerance range of plus / minus 5 to 10° C.Particularly good contrasts and accordingly particularly good visual recognizability of such laser markings are obtained with a straw-yellow, golden-yellow, yellowish-brown, blue-red, red, purple, violet, dark blue, grain-flower blue and light-blue starting colour, and with a silver-gray colour of the base material.According to a further embodiment, the device further comprises a control unit connected to the test unit and the laser marking unit, which control unit is designed such that, during operation of the device, it receives signals from the test unit about defective regions of the spring wire and controls the laser marking unit such that it introduces at least one laser marking into these defective regions of the spring wire. Such a control unit enables exact synchronization between the detection of a defective region and the marking of the same, independently of the wire feed speed.According to a further embodiment, the apparatus comprises a laser marking unit, wherein the laser marking unit comprises a beam source and / or a scanner optics or a projection mask and / or a focusing device which is / are designed such that they are directed onto the moving spring wire.A laser marking unit, which has a beam source, a scanner optics and a focusing device, is also referred to as a scanner system.With a laser marking unit, which has a beam source, a projection mask and a focusing device, laser markings can be applied by way of the mask projection method. In this case, the laser beam is passed through the projection mask before focusing, which defines the shape of the laser marking to be applied and which in particular represents a negative of the laser marking to be applied. The laser marking is applied in a rapid shot, so to speak. The mask projection method can be used to deposit more complex structures at a high processing speed.Such a laser marking unit is designed such that the laser marking can be introduced along the entire defective region. For this purpose, if a circumferentially wide region and in particular a region of the spring wire which extends around the entire circumference of the spring wire is to be marked, one or more laser marking units with a correspondingly widely projectable laser beam are to be provided.A further embodiment of the invention consists in that the laser marking unit is designed such that the defective regions of the spring wire are marked such that the laser marking forms a machine-readable code, in particular a barcode, a barcode or a data matrix code, or a machine-readable text, and / or wherein the laser marking unit is designed such that each defective region is provided with the same laser marking in each case, or that each defective region is provided with a unambiguously distinguishable laser marking in each case, and / or wherein the laser marking contains additional information about the defective region marked in each case.A machine-readable marking enables reliable machine recognition of such defective regions in a later production step, as a result of which the use of inspection workers can also be minimized.A further embodiment of the invention consists in the laser marking unit being arranged or formed such that the laser marking is applied to the defective region or regions of the spring wire such that it extends at least over a large part of the circumference of the spring wire, in particular over the entire circumference thereof, or wherein the laser marking is applied to the defective region or regions of the spring wire such that it extends only over a partial region of the circumference of the spring wire.By variably applying laser markings to a spring wire, different defects can be identified differently. Laser markings which extend over a large region of the circumference of the spring wire can be detected particularly reliably in a later production step.A further embodiment of the invention consists in that the test unit for checking the spring wire for faults is designed as an optical test unit, as an eddy current test unit or as a leakage flux detection unit. All three options allow reliable and contactless, and therefore non-destructive and non-material-making, checking.A further embodiment of the invention consists in that the test unit and the laser marking unit are arranged next to one another, and wherein in particular the test unit is arranged before or after the laser marking unit, as viewed in the direction of movement of the spring wire. This embodiment makes it possible for the spring wire to be reliably checked and marked during the current process without slowing down, stopping or reversing the production process. The laser marking can be applied, if the test unit is arranged in front of the laser marking unit in the direction of movement of the spring wire, at the location of the spring wire at which a fault is detected, before or after this. If the test unit is arranged after the laser marking unit in the direction of movement of the spring wire, the laser marking is applied after the location of the spring wire at which a fault is detected. It is only important that the local relationship between the fault and the laser marking is known so that the faulty areas are reliably detected during the further processing of the spring wire and an accidental further processing of the faulty areas of the spring wire into springs is precluded.A laser marking applied after the location of the spring wire at which a fault is detected is particularly advantageous if, during further processing of the spring wire into springs, the feed direction of the spring wire is opposite, so that the laser marking can first be detected and only then follows the actual fault location.A further embodiment of the invention consists in that the device further comprises a winding unit, in particular a reel, onto which the spring wire, including the defective region / regions provided with one or more laser markings, can be wound.This ensures that the spring wire produced or marked is rolled up on transportable rollers which can then be transported to machines to be further processed. This represents a simple and practical storage and transport possibility for the spring wire.A further embodiment of the invention consists in that the device has at least one wire guide, in particular a first wire guide arranged upstream of the testing unit and the laser marking unit and a second wire guide arranged downstream of the testing unit and the laser marking unit and upstream of the winding roller.By means of the first wire guide arranged in front of the test unit and the laser marking unit, the spring wire can be guided past the test unit and the laser marking unit reliably and always in the correct position.By means of the second wire guide arranged after the testing unit and the laser marking unit and before the winding roller, the spring wire, in which defective areas have been provided with laser markings, can be wound up well on the winding roller. By moving this wire guide, a desired winding pattern can be achieved.The invention also relates to a method for producing a spring wire, which method comprises the following steps: producing, in particular drawing, a spring wire from a raw material, checking the spring wire for defects, in particular for material and surface defects, and marking the defective regions of the spring wire by means of a laser marking unit, wherein the laser marking unit thermally allows a part of the surface of the spring wire such that it is changed in colour.The invention also relates to a method for marking a spring wire, which method comprises the following steps: feeding a spring wire by means of a feed unit, in particular a feed roller; checking the spring wire for defects, in particular for material and surface defects; and marking the defective regions of the spring wire by means of a laser marking unit, wherein the laser marking unit thermally allows a part of the surface of the spring wire such that it is changed in color.The advantages and embodiments given above with respect to the device for producing a spring wire and with respect to the device for marking a spring wire apply in the same way to the method according to the invention for producing a spring wire or to the method according to the invention for marking a spring wire. These are not listed again in order to avoid repetitions.According to one embodiment of the method, the laser marking unit directs a laser beam at a temperature of about 200° C. to 660° C. onto the spring wire in order to thermally lighten a part of the surface of the spring wire in the faulty regions of the spring wire such that the color of the surface of the spring wire is changed in this part.According to one embodiment of the method, the defective regions of the spring wire are marked by means of a laser marking unit in such a way that the laser marking forms a machine-readable code, in particular a barcode, a barcode or a data matrix code, or a machine-readable text.A machine-readable marking enables reliable machine recognition of such defective regions in a later production step, as a result of which the use of inspection workers can also be minimized.According to one embodiment of the method, the defective regions of the spring wire are marked by means of a laser marking unit in such a way that each defective region is provided with the same laser marking in each case. This represents the simplest marking variant according to the invention. The laser marking reliably identifies each defective region.According to one embodiment of the method, the defective regions of the spring wire are marked by means of a laser marking unit in such a way that each defective region is provided with a clearly distinguishable laser marking. As a result, each laser marking is unambiguously assigned to a defective region.According to one embodiment of the method, the laser marking contains additional information about the respectively marked defective region. In addition to the information that the relevant region of the spring wire is defective, such additional information can also be introduced into the spring wire and provided to a subsequent spring manufacturing machine, for example the information about the type of defect that is the most frequently encountered on the spring wire, the information about the type of defect, for example material or surface defects, further information about the type of material or surface defect, or spring wire dimensions in the defective region.In a further embodiment of the invention, the laser marking is applied to the defective region or regions of the spring wire in such a way that it extends at least over a large part of the circumference of the spring wire, in particular over the entire circumference thereof. Such a laser marking can be recognized particularly reliably in a subsequent method step. For the introduction of such a laser marking, one or more laser marking units with a correspondingly widely projectable laser beam are to be provided.In a further embodiment of the invention, the laser marking is applied to the defective region or regions of the spring wire in such a way that it extends only over a partial region of the circumference of the spring wire. Such a laser marking can be produced particularly easily and cost-effectively, since only one laser marking unit with a laser beam that can be projected to a correspondingly broad width needs to be provided.According to a further embodiment of the method, the method steps of checking the spring wire for defects and marking the defective regions of the spring wire are carried out during a continuous movement of the drawn wire.By this embodiment, it is possible to increase productivity of the spring wire manufacturing. Service lives are reduced or completely avoided.According to a further embodiment of the method, in the case that the laser marking is introduced into the spring wire as a color change, the starting color of the laser marking(s) can be adjusted by changing the power of the laser source.This ensures that the method can also be used with very thin spring wires.In a further embodiment of the invention, the laser marking unit has a beam source and / or a scanner optics or a projection mask and / or a focusing device which is / are designed such that they are directed onto the moving spring wire. Such a laser marking unit is designed such that the laser marking can be introduced along the entire defective region. For this purpose, if a circumferentially wide region and in particular a region of the spring wire which extends around the entire circumference of the spring wire is to be marked, one or more laser marking units with a correspondingly widely projectable laser beam are to be provided.A further embodiment of the method is that the checking of the spring wire for faults is carried out by means of an optical checking method, by means of an eddy current checking method or by means of a leakage flux measurement. All three options allow reliable and contactless, therefore non-destructive and non-material-fatiguing, checking.The invention also relates to an apparatus for producing springs from a spring wire, which apparatus comprises: a spring wire feed unit, in particular a feed roller, for feeding spring wire, in which defective regions, in particular regions with material and surface defects, are marked with a laser marking, a detection unit which is designed to detect laser markings on the spring wire, a spring production unit, in particular an automatic coiling machine, which is designed to produce springs from the spring wire continuously and without interruption, in particular to be coiled and stretchable, and an output unit, in particular an output shaft with switch, which is designed to output springs produced from spring wire without laser marking into a first region, in particular a container with fault-free springs, and dispensing springs made of laser-marked spring wire into a second area, in particular a container with defective springs.According to a basic idea of the present invention, springs can be produced continuously and without interruption by the device according to the invention for producing springs from a spring wire and by the method according to the invention for producing springs from a spring wire, resulting in low machine downtime, high effectiveness and low production costs. Interrupting the spring manufacturing process can be avoided by processing defective spring wire areas equally into springs, which however automatically get into another dispensing container and are thus sorted out and made available for reuse.Defective areas of the spring wire are automatically detected, so that quality problems due to unrecognized defective springs are avoided.With the aid of the spring wire feed unit, a spring wire roller, the defective regions of which are marked with laser markings, can be used and deliver the spring wire required.The recognition unit enables the laser marking to be read in mechanically. Defective areas can be detected more quickly and reliably by a detection unit than is possible for a skilled worker.With the spring manufacturing unit, the device is able to process the spring wire automatically into springs. Such a spring manufacturing unit is also referred to as a spring winch machine and does not need to be explained in more detail here, since it is known to the person skilled in the art.With the aid of the output unit, the produced springs are automatically sorted into springs of fault-free spring wire and into springs of fault-free spring wire. This classification takes place in-line behind the spring production unit in the production process, as a result of which the production does not have to be stopped at any point in time. This results in increased productivity and cost saving.The containers under the dispensing unit can be replaced within a very short time as soon as they are filled. The replacement can take place in the current process when the empty container pushes the filled container out of the device. A more time-effective production sequence is thus ensured.A further embodiment of the device consists in that the containers are equipped with a sensor which is designed to detect the number of springs located in the container.In a further embodiment of the device, the position of the switch is variable between two positions, namely a first position in which springs produced from spring wire without laser marking pass into a container with fault-free springs, and a second position in which springs produced from spring wire with laser marking pass into a container with fault-free springs.With the device according to the invention and the method according to the invention for producing springs from a spring wire, a multiplicity of springs of different spring types can be produced, in particular compression springs, tension springs, torsion springs, torsion springs or spiral springs.According to a further embodiment of the device, it further comprises a control unit connected to the detection unit and the output unit, which control unit is designed to receive signals from the detection unit via defective regions of the spring wire during operation of the device and to actuate the output unit such that those springs which have been produced from the defective region of the spring wire pass into the second region, in particular the container with defective springs.The control unit ensures that the faulty springs automatically enter the container with faulty springs.In a further embodiment of the device, the detection unit is designed as an optical detection unit, as an eddy current detection unit or as a leakage flux detection unit. In the case that the laser markings are designed as color-modified regions of the surface of the spring wire, only one detection unit designed as an optical detection unit can reliably detect the defective spring wire regions provided with laser markings.A further embodiment of the device comprises a spring manufacturing unit with a retraction which is arranged after the detection unit.The invention also relates to a method for producing springs from a spring wire, which method comprises the following steps: feeding spring wire, in which defective regions, in particular regions with material and surface defects, are marked with a laser marking, by means of a spring wire feed unit, detecting laser markings on the spring wire, by means of a detection unit, continuously and uninterruptedly producing, in particular coiling and cutting to length springs from the spring wire, by means of a spring production unit, dispensing those springs which have been produced from spring wire without laser marking into a first region, in particular a container with defect-free springs, and dispensing those springs which have been produced from spring wire with laser marking into a second region, in particular a container with defect springs, by means of an output unit, in particular an output shaft with switch.The advantages and embodiments given above with respect to the device for producing springs from a spring wire apply in the same way to the method according to the invention for producing springs from a spring wire. These are not listed again in order to avoid repetitions.The invention also relates to a spring wire which has the following features: a raw material, in particular made of spring steel, having a substantially constant elongate profile, wherein defective regions of the spring wire, in particular regions of the spring wire having material defects and surface defects, are marked with a laser marking in which the surface of the spring wire is changed in colour with respect to the surface of adjacent regions.In such a spring wire, the defective areas can be automatically and reliably detected directly when producing springs therefrom. If the device for producing springs from a spring wire is suitably set up, defective spring wire regions can likewise be processed to springs, which, however, automatically pass into another dispensing container and are thus sorted out and made available for reuse. Such a spring wire according to the invention can therefore be processed into springs in a particularly effective and cost-effective manner.In one embodiment of the spring wire, in the case that the laser markings are designed as color-modified surface regions of the spring wire, the color of the color-modified surface regions of the spring wire is white yellow, straw yellow, golden yellow, yellow brown, brown red, red, purple, violet, dark blue, corn flower blue, light blue, blue gray or gray, wherein the color of the remaining, color-unchanged surface regions of the spring wire is silvery gray.In a further embodiment of the spring wire, the laser marking forms a machine-readable code, in particular a barcode, a barcode or a data matrix code, or a machine-readable text, and / or wherein each defective region is in each case provided with the same laser marking, or wherein each defective region is in each case provided with a unambiguously distinguishable laser marking, and / or wherein the laser marking contains additional information about the respectively marked defective region.In a further embodiment of the spring wire, the laser marking extends at least over a major part of the circumference of the spring wire, in particular over the entire circumference thereof, or wherein the laser marking extends only over a partial region of the circumference of the spring wire.For the advantages of these embodiments, reference is made to the advantages given above with respect to the apparatus and method for manufacturing a spring wire in order to avoid repetitions.The invention is explained in more detail below on the basis of exemplary embodiments with reference to the appended figures: FIG. 1 is a schematic diagram of a spring wire manufacturing apparatus according to a first embodiment of the present invention; FIG. 2 is a schematic view of a spring wire marking apparatus according to a second embodiment of the present invention; FIG. 3 shows a schematic illustration of the laser marking unit of the spring wire production device from FIG. 1 or of the spring wire marking device from FIG. 2 and of the spring wire guided past it, the defective regions of which are marked by means of the laser marking unit; FIG. 4 shows, on the basis of its two FIGS. 4( a) and 4( d), a longitudinal section and a cross section through exemplary regions of a spring wire, respectively; FIG. 5 is a schematic illustration of a spring wire in each case based on FIG. 5(b), in which four defective regions along the longitudinal extent of the spring wire have been provided with laser markings; FIG. 6 shows, with reference to its partial figures FIGS. 6( a), 6( b) and 6( c), exemplary representations of defective spring wire regions with different laser markings; and FIG. 7 shows a schematic illustration of an apparatus for producing springs from a spring wire, according to a further exemplary embodiment of the invention.FIG. 1 shows a schematic illustration of a spring wire production apparatus 2.The spring wire manufacturing apparatus 2 comprises a wire manufacturing device 8, a first wire guide 12, a checking unit 14, a laser marking unit 18, a control unit 16, a further wire guide 12 and a winding roller 20.The wire production device 8 is designed such that a spring wire 10 can be produced from a raw material, in particular by drawing. This is known to the person skilled in the art and need not be explained in more detail here.The spring wire 10 is continuously produced by the wire production device 8, leaves it in the direction to the right in FIG. 1 and passes successively through the first wire guide 12, the testing unit 14 and the laser marking unit 18, the further wire guide 12 and is finally rolled up on the winding roll 20. The direction of travel of the spring wire 10, which runs from left to right in FIG. 1, is represented by the arrow with the reference numeral 4.The spring wire 10 is guided so precisely by the wire guide 12 arranged in front of the test unit 14 and by the wire guide 12 arranged after the laser marking unit 18 that the test unit 14, which is arranged in particular in a stationary manner, can precisely check the spring wire 10 and the laser marking unit 18, which is arranged in particular in a stationary manner, can precisely mark defective regions of the spring wire 10.The wire guides 12 can thereby be configured in particular as a pair of oppositely directed guide rollers, between which the spring wire 10 runs.The test unit 14 is designed in such a way that it checks the spring wire 10 for defects, in particular for material and surface defects. The test unit 14 can be designed either as an optical test unit or as an eddy current test unit.In operation of the spring wire manufacturing apparatus 2, the spring wire 10 is continuously fed past the inspection unit 14 and laser marking unit 18 which inspect the spring wire during its movement for material and surface defects and, if such defects are detected, laser marking 18 is applied to the corresponding areas of the spring wire 10.If the test unit 14 detects material defects or surface defects of the spring wire 10, it outputs a corresponding signal to the control unit 16, which then controls the laser marking unit 18, which is arranged after the test unit 14 in the running direction of the spring wire 10, in such a way that it provides these defective regions of the spring wire 10 with a suitable laser marking. Exemplary laser markings are illustrated and described below in FIGS. 4, 5 to 6.The laser marking unit 18 is configured such that the defective regions of the spring wire 10 are marked with a laser marking such that a part of the surface of the spring wire 10 is changed in color with respect to the adjoining regions of the surface of the spring wire 10. For this purpose, the laser marking unit 18 directs a laser beam onto the corresponding regions of the surface of the spring wire 10, which causes a tempering temperature between 200 and 660° C. in the surface of the spring wire 10, so that an oxide layer is formed, the color of which depends on the respective tempering temperature and is described elsewhere in this patent application.The laser marking unit 18 is directed towards the moving spring wire 10 for this purpose and, when it is controlled accordingly by the control unit 16, changes the colour in a part of the surface of the spring wire 10 by means of a laser beam directed towards the spring wire 10.For this purpose, the laser marking unit 18 has a beam source and can additionally also have a scanner optical unit or a projection mask and a focusing device, which are illustrated by way of example below with reference to FIG. 3.If the test unit 14 does not detect any material defects or surface defects of the spring wire 10, the laser marking unit 18 is controlled by the control unit 16 in such a way that it does not introduce laser markings into the spring wire 10.Finally, the finished spring wire 10, whose defective areas have been provided with laser markings, is rolled up on the winding roll 20.At the end of the production process, either raw material is no longer replenished into the wire production device 8, so that the production process runs out by itself. Alternatively, the spring wire 10 can also be cut off or cut to length, if appropriate after the production process has been stopped. The winding roll 20 with the spring wire 10 wound thereon can then be completely removed and transported to a spring manufacturing device. Then, a new empty take-up roll may be provided for the next manufacturing process instead of the taken-out take-up roll.At this point, it is again emphasized that the checking of the spring wire 10 and the marking of defective regions of the spring wire 10 by the checking unit 14 and the laser marking unit 18 take place in-line, i.e. during the production process, without the latter having to be slowed down or even stopped. This represents a particularly effective, fast and cost-effective way of producing spring wire 10, in which at the same time the defective regions for the subsequent spring production process can be identified in a simple and direct manner.It goes without saying that the control unit 16 can additionally be connected to the wire production device 8 or the feed roller 22 and to the winding roller 20 or can be connected to a control unit of the wire production device 8, the feed roller 22 and the winding roller 20 or can be formed integrally therewith, such that the actual wire production, the feed speed of the spring wire 10 and the winding of the spring wire 10 on the winding roller 20 can also be controlled.FIG. 2 is a schematic view of a spring wire marking device 21.This spring wire marking device 21 corresponds substantially to the spring wire production device 2 shown in FIG. 1, wherein a feed roller 22 is provided instead of the wire production device 8.Identical elements are provided with the same reference numerals. To avoid repetitions, these elements and their mode of operation are not explained again.The feed roller 22 feeds the spring wire produced in a previously carried out production step, in particular drawn from a raw material, via the wire guide 12 to the checking unit 14 and the laser marking unit 18, where the spring wire 10 is checked and defective regions thereof are marked before the spring wire 10 is guided by the second wire guide 12 to the winding roller 20 and wound up there.The main difference between the spring wire manufacturing apparatus 2 of FIG. 1 and the spring wire marking apparatus 21 of FIG. 2 is that in the spring wire manufacturing apparatus 2, the wire manufacturing apparatus 8 forms the first part, so that in one and the same apparatus, the spring wire 10 is manufactured and defective portions thereof are detected and marked. In contrast, in the spring wire marking device 21, an already produced spring wire 10 is provided, which is usually wound on a roll 22, and this spring wire 10 is fed via the wire guide 12 to the testing unit 14 and the laser marking unit 18. The production of the spring wire and the detection of the defective regions thus take place in the spring wire marking device 21 at two different locations.FIG. 3 shows a schematic illustration of the laser marking unit 18 and of the spring wire 10 guided past it, the defective regions of which are marked by means of the laser marking unit 18.The laser marking unit 18 has a beam source 38 for generating a laser beam, a scanner optics 40 or a projection mask and a focusing device 42. The laser marking unit 18 is arranged in such a way that it is directed onto the moving spring wire 10 and is designed such that the laser beam, when directed onto the moving spring wire 10, can change color this surface area by the tempering effect which arises due to changes in structure in the edge layer in order to introduce a laser marking into the spring wire 10. How the beam source 38, the scanner optics 40 or the projection mask and the focusing device 42 must be designed in detail to achieve this is known to the person skilled in the art and need not be explained here in more detail.FIG. 4 shows, on the basis of its FIGS. 4( a) and 4( d), a longitudinal section and a cross section through exemplary regions of a spring wire 10, respectively.In Figs. 4(a) and 4(d), a sectional view is taken along line A-A at 4(a) and line C-C at 4(d), respectively, and the sectional view is taken along line A-A at 4(a) and line C-C at 4(d).According to FIG. 4(a), the region of the spring wire 10 shown has a constant elongate profile and has no material or surface defects, so that this region of the spring wire 10 does not have a laser marking.According to FIG. 4(d), the regions of the spring wire 10 shown here have material defects or surface defects which are not shown here and have therefore each been provided with a laser marking 44 by the laser marking unit 18.As shown in FIG. 4(d), the laser mark 45 is a laser beam-tempered colored surface portion formed on the upper surface of the upper portion of the spring wire 10.This is an elongate marking on the upper side of the spring wire 10, which is perceived as a longitudinal line or longitudinal bar by an optical recognition unit or by a viewer.For example, the surface of the spring wire 10 may be bare and silver gray in color, whereas the laser mark 45 has a brown red color, which has been introduced into the surface of the spring wire 10 by means of a laser beam having a tempering temperature of about 250° C. This results in a contrast that is very easily optically perceptible / detectable. Of course, the base color of the surface of the spring wire 10 may also have a color other than silver gray, and of course, the color of the laser mark 45 may also be other, for example, white yellow, straw yellow, gold yellow, yellow brown, red, purple red, violet, dark blue, grain flower blue, light blue or blue gray. The tempering temperatures required for this are specified elsewhere in this patent application.At this point, it is again emphasized that the laser markings introduced do not have the purpose of marking the spring wire 10 as such, but rather are intended to mark only the defective regions which are intended to be automatically detected in a subsequent spring production process, such that the springs produced therefrom can be automatically discharged.FIG. 5 shows, with reference to FIG. 5(b), a schematic illustration of a spring wire 10 in which four defective regions along the longitudinal extent of the spring wire 10 have been provided with laser markings 47, 49, 51 and 53.In the partial figure 5(b), the laser markings 47, 49, 51 and 53 are designed as removal-free, color-modified surface regions which have been introduced into the surface of the spring wire 10 by means of a laser beam at a defined temperature, for example. The colors of the surface areas caused by different tempering temperatures are explained elsewhere in this patent application. In practice, it is important that an optically well perceptible / detectable contrast is obtained between the color of the surface of the spring wire 10 in the laser markings 47, 49, 51 and 53 and the adjacent regions of the surface of the spring wire 10.The laser marking 47 arranged at the front, i.e. at the far right in FIG. 5(b), comprises a transversely running laser marking on the upper side of the spring wire 10, which is perceived as a transverse line by a recognition device or a viewer.The second laser marking 49, viewed from the front, comprises two mutually separate, transversely running laser markings on the upper side of the spring wire 10, which are perceived as two parallel cross strokes by a recognition device or a viewer.The third laser marking 51 viewed from the front comprises three mutually separate, transversely running laser markings in the upper side of the spring wire 10, which are perceived as three cross strokes by a recognition device or a viewer.The rearmost laser marker 53 comprises four separate transverse laser markers in the top of the spring wire which are perceived as four bars by a detector or viewer.Accordingly, each defective region of the spring wire 10 is provided with a clearly distinguishable laser marking 47, 49, 51, which in the present exemplary embodiment are only exemplary. For example, the first marking 47 can be assigned the meaning "first defective region in the entire spring wire", the second laser marking 49 the meaning "second defective region in the entire spring wire", and so on.FIG. 6 shows, with reference to its partial figures 6(a), 6(b) and 6(c), exemplary representations of defective spring wire regions with different laser markings.All these laser markings have in common that the introduced markings represent areas of the surface of the spring wire 10 which are changed in color.The laser marking 54 forms a pattern introduced into the surface of the spring wire 10, which pattern is perceived by a recognition device or a viewer as "TEST, three cross strokes, TEST", that is to say as a third applied test laser marking which identifies a defective region of the spring wire 10.The laser marking 56 forms a barcode which, like the laser markings described above, extends only over the upper side of the spring wire 10 but around the entire circumference of the spring wire 10. The laser marking 56 thereby forms a pattern of circumferentially colored regions of different width with spring wire regions arranged in each case therebetween, which are unchanged in color.The laser marking 56 thus marked as a barcode can be recognized in particular by a recognition device. By means of such a barcode laser marking 56, in addition to the information that the relevant region of the spring wire 10 is defective, many additional information about the type of defect can be introduced into the spring wire 10 and provided to a subsequent spring manufacturing machine, e.g. the information about the how many defects on the spring wire 10 are in question, the information about the type of defect, e.g. material defects or surface defects, further information about the type of material defects or surface defects, or spring wire dimensions in the defective region.The laser marking 58 forms a so-called data matrix code, which extends only over a region of the circumference of the spring wire 10 and which forms a pattern of color-modified regions that have been introduced into the surface of the spring wire 10.Such a laser marking embodied as a data matrix code can be recognized in particular by a recognition unit. With such a laser marking 58, similar to the laser marking 56 designed as a barcode, a large number of information about the defective region can be introduced into the spring wire 10 and provided for a subsequent spring manufacturing machine.It goes without saying that the laser marking unit 18 must be designed such that it can introduce laser markings into the circumferential region of the spring wire 10 in which the laser marking is to be produced.For this purpose, if a circumferentially wide region and in particular a region of the spring wire which extends around the entire circumference of the spring wire 10 is to be marked, one or more laser marking units 18 with a correspondingly widely projectable laser beam are to be provided.In a very simple exemplary embodiment, not represented here by a separate figure, the laser marking unit 18 is designed such that it provides each defective region with a simple, respectively identical laser marking.FIG. 7 shows a schematic illustration of an apparatus 60 for producing springs from a spring wire, according to a further exemplary embodiment of the invention.This spring manufacturing apparatus 60 includes a feed roller 22, a detection unit 24, a spring wire feed unit 28, a spring manufacturing unit 30, a dispensing unit 32 having a defective spring case 34 and a intact spring case 36, and a control unit 26.The feed roller 22 can be the winding roller 20 on which the manufactured spring wire 10 has been wound and the defective regions of which have been provided with corresponding laser markings.This spring wire 10 is guided through a detection unit 24 and via the spring wire feed unit 28 to the actual spring production unit 30, where the spring wire is formed, in particular wound and cut to length into individual springs, which then pass via a discharge shaft, not shown here, to the output unit 32.The detection unit 24 is configured to detect laser markings on the spring wire 10 while the latter is continuously guided through it. The detection unit 24 can be designed as an optical detection unit, as an eddy current detection unit or as a leakage flux detection unit. In the case where the laser markings are formed as color-modified regions of the surface of the spring wire, as in the representations of FIGS. 4(d) and 5(b), only one detection unit formed as an optical detection unit can reliably detect the defective spring wire regions provided with laser markings.The dispensing unit 32 has a switch, which is schematically illustrated in FIG. 7 and can be moved in such a way that springs moving through the dispensing shaft in particular due to their gravity reach in a targeted manner into the container for defective springs 34 or into the container for intact springs 36.If the detection unit 24 now detects a laser marking on the spring wire 10, it outputs a corresponding signal to the control unit 26, which in turn adjusts the switch of the output unit 32 such that those springs which have been produced from the spring wire 10 with laser marking pass into the container for defective springs 34. If the recognition unit 24 does not recognize a laser marking on the spring wire 10, the switch of the output unit 32 remains in the position in which the manufactured springs automatically enter the container for intact springs 36, or is moved into this position if a laser marking has still been recognized by the recognition unit 24 beforehand.In the spring manufacturing device 60 according to the invention, a continuous and uninterrupted manufacturing of springs from a spring wire 10 is possible. Defective areas of the spring wire are automatically detected, but the spring manufacturing apparatus 60 does not need to be stopped, resulting in machine downtime, decreased effectiveness, and higher costs. Rather, the springs produced from such defective regions of the spring wire 10 are automatically moved into another container, namely the container for defective springs 34.List of reference characters2 Spring wire manufacturing apparatus 4 Running direction Wire 8 Wire manufacturing apparatus 10 Spring wire 12 Wire guide 14 Inspection unit 16 Control unit 18 Laser marking unit 20 Winding roller 21 Spring wire marking apparatus 22 Feed roller 24 Detection unit 26 Control unit for output unit 28 Spring wire feed unit 30 Spring manufacturing unit 32 Output unit 34 Defective spring container 36 Intact spring container 38 Beam source 40 Scanner optics 42 Focusing apparatus 44- 58 Laser markings 60 Spring manufacturing apparatus

Claims

Apparatus for producing a spring wire (2), comprising: a wire production device (8) which is designed such that a spring wire (10) can be produced from a raw material, in particular by drawing; a testing unit (14) which is designed such that the spring wire (10) can be checked for defects; and a laser marking unit (18) which is designed such that defective regions of the spring wire (10) can be marked with a laser marking (44) such that a part of the surface of the spring wire (10) can be thermally tempered such that the colour of the surface of the spring wire (10) is changed in this part; wherein the wire production device (8) is designed such that the spring wire (10) can be guided past the testing unit (14) and the laser marking unit (18).Device for marking a spring wire (21), comprising: a feed unit, in particular a feed roller (22) for feeding a spring wire (10); a checking unit (14) which is designed such that the spring wire (10) can be checked for defects; and a laser marking unit (18) which is designed such that defective regions of the spring wire (10) can be marked with a laser marking (44) such that a part of the surface of the spring wire (10) can be thermally tempered such that the color of the surface of the spring wire (10) is changed in this part; wherein the feed unit (22) is designed such that the spring wire (10) can be guided past the checking unit (14) and the laser marking unit (18).The device (2) according to claim 1 or 2, wherein the defects are material and surface defects; and / or wherein defective areas of the spring wire are areas of the spring wire with material and surface defects.The device (2) according to any one of the preceding claims, wherein the laser marking unit (18) is configured to thermally anneal a part of the surface of the spring wire (10) in the defective areas of the spring wire (10) such that the color of the surface of the spring wire (10) is changed in this part, direct a laser beam at a temperature of about 200°C to 660°C onto the spring wire (10).The device (2) according to any one of the preceding claims, further comprising a control unit (16) connected to the test unit (14) and the laser marking unit (18), which control unit is designed such that, during operation of the device (2), it receives signals from the test unit (14) about defective regions of the spring wire (10) and controls the laser marking unit (18) such that it introduces at least one laser marking (44) into these defective regions of the spring wire (10).The apparatus (2) according to any of the preceding claims, wherein the laser marking unit (18) comprises a beam source (38) and / or a scanner optics (40) or a projection mask and / or a focusing device (42) arranged to be directed to the moving spring wire (10).The device (2) according to any one of the preceding claims, wherein the laser marking unit (18) is configured such that the defective areas of the spring wire (10) are marked such that the laser marking (44) forms a machine-readable code or a machine-readable text, and / or wherein the laser marking unit (18) is configured such that each defective area is provided with the same laser marking (44), respectively, or that each defective area is provided with a unambiguously distinguishable laser marking (44), respectively, and / or wherein the laser marking (44) contains additional information about the respectively marked defective area.The apparatus (2) of claim 7, wherein the machine readable code is a barcode (54), a barcode (56), or a data matrix code (58).The device (2) according to any one of the preceding claims, wherein the laser marking unit (18) is arranged or formed such that the laser marking (44) is applied to the defective region or regions of the spring wire (10) such that it extends over at least a major part of the circumference of the spring wire (10), or wherein the laser marking (44) is applied to the defective region or regions of the spring wire (10) such that it extends only over a partial region of the circumference of the spring wire (10).The device (2) according to claim 9, wherein the laser marking extends over the entire circumference of the spring wire.Device (2) according to one of the preceding claims, wherein the test unit (14) for checking the spring wire (10) for faults is designed as an optical test unit, as an eddy current test unit or as a leakage flux measurement unit.The device (2) according to any one of the preceding claims, wherein the test unit (14) and the laser marking unit (18) are arranged next to each other, and wherein the test unit (14), viewed in the direction of movement of the spring wire (10), is arranged before or after the laser marking unit (18).The device (2) according to any one of the preceding claims, further comprising a winding unit (20) onto which the spring wire (10), including the defective region / regions provided with one or more laser markings (44), can be wound.The device (2) according to any one of the preceding claims, further comprising at least one wire guide (12).The device (2) according to any one of the preceding claims, further comprising a first wire guide (12) arranged upstream of the testing unit (14) and the laser marking unit (18), and a second wire guide (12) arranged downstream of the testing unit (14) and the laser marking unit (18) and upstream of the winding roller (20).Method for producing a spring wire (10), comprising the following steps: producing a spring wire (10) from a raw material; checking the spring wire (10) for defects; and marking the defective regions of the spring wire by means of a laser marking unit (18), wherein the laser marking unit (18) thermally emits a part of the surface of the spring wire (10) such that it is changed in colour.Method for marking a spring wire (10), comprising the following steps: feeding a spring wire (10) by means of a feeding unit; checking the spring wire (10) for defects; and marking the defective regions of the spring wire by means of a laser marking unit (18), wherein the laser marking unit (18) thermally starts a part of the surface of the spring wire (10) such that it is changed in colour.Method according to claim 16 or 17, wherein the laser marking unit (18) directs a laser beam at a temperature of about 200°C to 660°C onto the spring wire (10) in order to thermally light a part of the surface of the spring wire (10) in the faulty regions of the spring wire (10) such that the color of the surface of the spring wire (10) is changed in this part.Method according to one of claims 16 to 18, wherein the defective regions of the spring wire (10) are marked by means of a laser marking unit (18) such that the laser marking (44) forms a machine-readable code or a machine-readable text.Method according to one of Claims 16 to 19, wherein the defective regions of the spring wire (10) are marked by means of a laser marking unit (18) in such a way that each defective region is provided with the same laser marking (44) in each case.Method according to one of Claims 16 to 20, wherein the defective regions of the spring wire (10) are marked by means of a laser marking unit (18) in such a way that each defective region is in each case provided with a unambiguously distinguishable laser marking (44), and / or wherein the laser marking (44) contains additional information about the respectively marked defective region.Method according to any of claims 16 to 21, wherein the laser marking (44) is applied to the defective region or regions of the spring wire (10) such that it extends over at least a major part of the circumference of the spring wire (10), or wherein the laser marking (44) is applied to the defective region or regions of the spring wire (10) such that it extends only over a minor region of the circumference of the spring wire (10).Method according to any of claims 16 to 22, wherein the method steps of checking the spring wire (10) for defects and marking the defective areas of the spring wire (10) are performed during a continuous movement of the drawn wire.Method according to any of claims 16 to 23, wherein the laser marking unit (18) comprises a beam source (38) and / or a scanner optics (40) or a projection mask and / or a focusing device (42) which is / are designed to be directed onto the moving spring wire (10).Method according to one of Claims 16 to 24, wherein the checking of the spring wire (10) for faults is carried out by means of an optical checking method or by means of an eddy current checking method.Device for producing springs from a spring wire (60), comprising: a spring wire feed unit (28), in particular a feed roller (22), for feeding spring wire (10), in which defective regions are marked with a laser marking (44); a detection unit (24), which is designed to detect laser markings (44) on the spring wire (10); a spring production unit (30), which is designed to produce springs from the spring wire (10) continuously and without interruptions; an output unit (32) which is designed such that it outputs springs which have been produced from spring wire (10) without laser marking into a first region, in particular a container with fault-free springs (36), and outputs springs which have been produced from spring wire (10) with laser marking (44) into a second region, in particular a container with fault-free springs (34).Device (60) according to claim 26, further comprising a control unit (26) connected to the detection unit (24) and the output unit (32), which control unit is designed to receive signals from the detection unit (24) about defective regions of the spring wire (10) during operation of the device (60) and to actuate the output unit (32) such that those springs which have been produced from the defective region of the spring wire (10) pass into the second region, in particular the container with defective springs (34).Device according to claim 26 or 27, wherein the detection unit (24) is designed as an optical detection unit, as an eddy current detection unit or as a leakage flux detection unit.Method for producing springs from a spring wire, comprising the following steps: feeding spring wire (10), in which defective regions are marked with a laser marking (44), by means of a spring wire feeding unit (28); detecting laser markings (44) on the spring wire (10), by means of a detection unit (24); continuously and uninterruptedly producing by means of a spring producing unit (30); dispensing those springs which have been produced from spring wire (10) without laser marking into a first region, in particular a container with fault-free springs (36), and dispensing those springs which have been produced from spring wire (10) with laser marking (44) into a second region by means of a dispensing unit (32).A spring wire (10) comprising: a raw material having a substantially constant elongated profile; wherein defective areas of the spring wire (10) are marked with a laser mark (44) in which the surface of the spring wire (10) is color-modified relative to the surface of adjacent areas.The spring wire (10) according to claim 30, wherein in the case that the laser marking (44) is configured as a color-modified surface region of the spring wire (10), the color of the color-modified surface region of the spring wire (10) is white yellow, straw yellow, gold yellow, yellow brown, brown red, red, purple, violet, dark blue, grain flower blue, light blue, blue gray or gray, wherein the color of the remaining, color-unchanged surface regions of the spring wire (10) is silvery gray.The spring wire (10) according to claim 30 or 31, wherein the laser marking (44) forms a machine-readable code or a machine-readable text, and / or wherein each defective region is respectively provided with the same laser marking (44), or wherein each defective region is respectively provided with a clearly distinguishable laser marking (44), and / or wherein the laser marking (44) contains additional information about the respectively marked defective region; and / or wherein the laser marking (44) extends over at least a major part of the circumference of the spring wire (44), or wherein the laser marking (44) extends only over a minor part of the circumference of the spring wire (10).

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