EP3021995A1

EP3021995A1 - Method and device for producing coil springs by spring winding

Info

Publication number: EP3021995A1
Application number: EP14741216.7A
Authority: EP
Inventors: Klaus Reicherter; Andreas Schur; Wolfgang Bäuerle; Uwe-Peter Weigmann
Original assignee: Wafios AG
Current assignee: Wafios AG
Priority date: 2013-07-18
Filing date: 2014-06-26
Publication date: 2016-05-25
Anticipated expiration: 2034-06-26
Also published as: DE102013214161B4; DE102013214161A1; WO2015007496A1; EP3021995B1; CN105377466B; CN105377466A

Abstract

The invention relates to a method for producing coil springs by spring winding by means of a numerically controlled spring winding machine, wherein a wire is fed by a feeding device of a forming device of the spring winding machine under the control of an NC control program and is formed into a coil spring by means of tools of the forming device, and a finished coil spring is then severed from the fed wire by means of a cutting device. Before the finished coil spring is severed, a linear weakening is produced in the region of the surface of the wire at least at two diametrically opposite segments of the wire circumference at a defined severing position along the wire. In one embodiment, two notching tools (152, 154) are used for this purpose, which superficially notch the wire from opposite sides without cutting through the wire. The finished coil spring is then severed from the fed wire at the severing position, e.g., by means of a torsion cut.

Description

description

Method and device for producing coil springs

spring winds

BACKGROUND

The invention relates to a method for producing coil springs by spring winds by means of a numerically controlled spring coiling machine according to the preamble of claim 1 and to a suitable for performing the method spring coiling machine according to the preamble of claim 10.

Coil springs are machine elements that are required in numerous applications in large numbers and different designs. Coil springs, which are also referred to as twisted torsion springs, are usually made of spring wire and designed depending on the load in use as tension springs or compression springs. Compression springs, in particular valve springs, clutch springs or suspension springs are needed, for example, in large quantities in the automotive industry.

Coil springs are nowadays commonly manufactured by spring winches using numerically controlled spring coiling machines. In this case, a wire (spring wire) is supplied under the control of an NC control program by means of a feeder of a forming device of the spring coiling machine and formed by means of tools of the forming device to a coil spring. The tools usually include one or more adjustable in terms of their position wind tools for establishing and possibly changing the diameter of spring coils. Occasionally, one or more pitch tools are also provided by which the local pitch of the spring coils at each stage of the manufacturing process is minimized. determined. Upon completion of a forming operation, a finished coil spring is separated from the supplied wire under the control of the NC control program by a cutter.

In the manufacture of springs often the type of cut is of great importance, as it determines certain properties of the finished coil spring. There are usually three commonly used types of cutting methods, namely the so-called "straight cut", "rotary cut" and "torsion cut." In the straight cut, a cutting tool performs a straight linear cutting motion when cutting the wire During twisting, the wire is mechanically loaded so that it is separated by a torsional stress substantially in a plane perpendicular to the wire axis separating plane.

Although the separation process in torsional cutting is based essentially on breaking or tearing of the wire material by rotation and not on a cutting operation, the usual terms "torsional cut" and "cutting means" are used herein.

The torsion cut is used primarily in wire materials that have high strength and / or prone to brittle fracture. In addition, the winding ratio D / d, ie the ratio between the spring diameter D and the wire diameter d of the spring, should not be too large, since too large winding ratios necessary for the torsional force during pivoting of the spring can no longer be optimally concentrated at the desired separation position , If these conditions are fulfilled sufficiently well, torsion cut a burr-free cut. For other types of cuts, burrs are usually produced at the cut surface.

TASK AND SOLUTION

The invention has for its object to provide a method for producing coil springs by spring winds and a suitable for performing the method spring coiling machine, which allow the separation of a finished coil spring from the supplied wire at a defined location a clean, possibly burr-free cut surface produce. The separation process should be gentle to the spring machines and the environment and not adversely affect the spring geometry. In particular, it should be possible to separate coil springs with relatively high winding ratio by means of torsion cutting from the wire and / or to produce clean cut surfaces even with difficult to cut wire materials.

To solve these problems, the invention proposes a method with the features of claim 1 and a spring coiling machine with the features of claim 10. Advantageous developments are specified in the dependent claims. The wording of all claims is incorporated herein by reference.

In a generic method, this object is achieved according to the claimed invention in that before the separation at a defined separation position along the wire at least at two diametrically opposite portions of the wire circumference a lienartigen weakening in the region of the surface of the wire is generated. The weakening line, which extends substantially in a plane perpendicular to the wire longitudinal direction, acts as a predetermined breaking point in the subsequent separation process. Therefore, the components intended to produce the attenuation should be included in this Annex. be referred to as components of a predetermined breaking point generating device.

The linear weakening at and near the wire surface may be e.g. be generated by notching, stabbing, rolled, hammered or scratched the wire surface. The weakening will preferably not go very deep in the radial direction, for example, starting from the wire surface only so far that at least 50% of the diameter of the wire in the region of the core (in the center of the wire) remains substantially unaffected by the near-surface weakening. The unaffected inner area may also be larger, e.g. in the range of 60% to 90% of the diameter, possibly even more. What is important is that a significant superficial weakening is created which does not have to extend deep into the wire material.

If a narrow notch or a narrow notch or the like is introduced over a large part of the wire circumference, a predetermined breaking point is created in the longitudinal direction of the wire, in the region of which the cutting forces required for cutting are substantially lower than in the absence of such weakening. The regions of near-surface weakening form preferential regions of the crack initiation during the separation process, with cracks then continuing radially from several sides into the interior of the wire and creating planar fracture surfaces.

By means of these measures, it is possible to reduce the cutting forces or separation forces required during separation in comparison to systems without predetermined breaking point generation. As a result, the cutting device can be designed with lower drive power and less massively designed components. In addition, it is possible to reduce the noise pollution of the environment. By the reduction The required cutting forces can also reduce the mechanical repercussions of the separation process on the spring geometry (eg laying of turns close to the interface) compared to systems without predetermined breaking point generation.

In some embodiments, a linienformige weakening is generated only at two diametrically opposite peripheral regions, wherein the intervening remainder of the surface can remain unharmed. In particular, the wire can be mechanically scored in a curved section by means of numerically controllable scoring tools simultaneously on the inside and on the diametrically opposite outside. It is also possible that line-shaped weakenings are introduced on more than two sides.

In some embodiments, to weaken the wire, a circumferentially uninterrupted circumferential line weakening is created, for example, in the form of an annular notch or annular fusing line.

If a linear weakening is introduced only at two diametrically opposite circumferential regions or over the entire circumference, the predetermined breaking point can have high symmetry (for example mirror symmetry or axis symmetry to a longitudinal center plane or point symmetry (central symmetry) to the wire center), which favors particularly uniform parting surfaces.

In some embodiments, the wire is mechanically notched simultaneously from diametrically opposite sides using numerically controllable notching tools. For example, the wire may be mechanically scored in a curved portion simultaneously on the inside and on the diametrically opposite outside. A corresponding predetermined breaking point generating device has two notching tools movable toward or away from one another with cutting edges lying in a common plane. The notching tools can simultaneously penetrate from the opposite sides superficially into the wire material, wherein one of the notching tools each serves as a counter-tool of the other.

In a variant where the torsion cutting cutter is arranged, the wire is clamped between the notching tools to provide weakening, the notching tools are then held in engagement with the wire, and the coil spring is torsionally separated from the clamped wire. The wire thus remains trapped at the separation point, but is not completely severed by the notching tools. These act rather than clamping tools and hold the wire until it tears by torsional stress or breaks. The torsional fracture is generated by pivoting the spring body, wherein the material separation takes place in the parting line defined by the wedge tools. It can be particularly smooth separation surfaces arise because the supplied wire is fixed by means of the notching tools.

In other embodiments, at least one jet tool is used to create the weakening. Some embodiments of predetermined breaking point generating devices contain a laser system, so that at least one laser beam can be radiated onto the wire surface to produce the weakening. The irradiation can be done from several sides. In order to achieve a radiation from several sides by means of only a single laser beam, in some embodiments, the laser beam is deflected by one or more deflection devices, such as plane mirror, one or more times so that different peripheral portions of Wired can be irradiated with the same laser beam and scored or melted on the surface. As an alternative jet tool and a water jet could be used, possibly also a plasma.

After a predetermined breaking point has been generated on the wire at a defined separating position, the finished coil spring can be separated from the supplied wire by means of a cutting device, whereby due to the predetermined breaking point the cutting forces required for this can be substantially lower than with a wire that is not pre-weakened, ie a wire without predetermined breaking point ,

By generating a predetermined breaking point, for example, the range of application of torsional cutting can be significantly expanded to coil springs with larger winding ratios. So far, the upper limit in the torsion cut was typically at a winding ratio in the range of 3 to 4. In a pre-weakened by means of predetermined breaking wire coil springs with winding ratios greater than 4 can be separated processionally with torsion. The winding ratio may be e.g. between 5 and 10, possibly in the range up to 12 or above. Corresponding embodiments will be explained in detail below.

It is also possible to achieve better cutting results in spring coiling machines, which are set up, for example, for a straight cut or a rotary cut, since significantly lower cutting forces are required at a pre-weakened separating position in order to achieve a clean separation of the finished coil springs from the supplied wire. As a result, the components involved in the cutting process are less susceptible to wear and, with moderate dimensioning, can also be used, if required, in relatively difficult to cut wire mesh. materials, such as high-strength spring wires, by means of straight cut or rotary cut separate.

These and other features will become apparent from the claims but also from the description and drawings, wherein the individual features each alone or more in the form of sub-combinations in an embodiment of the invention and in other fields be realized and advantageous and protectable Can represent versions.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a schematic overview of an embodiment of a spring coiling machine;

FIG. 2 shows an enlarged detailed representation of the area of the forming tools with components of a predetermined breaking point generating device; FIG.

Fig. 3 shows in Fig. 3A the spring coiling machine of Figs. 1 and 2 just prior to scoring the wire and in Fig. 3B scoring the wire;

FIG. 4 shows in FIG. 4A an alternative arrangement of the components of the predetermined breaking point generating device, in FIG. 4B the corresponding spring winding machine shortly before the notching of the wire and in FIG. 4C during the notching of the wire;

Fig. 5 shows components of a predetermined breaking point generating device which operates with two jet tools;

6 shows a side view of another spring coiling machine with components of several variants of predetermined breaking points. Generating means capable of generating predetermined breaking points prior to completion of wire feeding; and

7 shows in FIGS. 7A and 7B two variants of predetermined breaking point generating devices which operate by means of a laser and have a movable jet outlet.

DETAILED DESCRIPTION OF THE PREFERRED

EMBODIMENTS

The schematic overview in Fig. 1 shows some structural elements of a CNC spring coiling machine 100 according to an embodiment of the invention. 2 shows an enlarged detailed representation of the area of the forming tools with components of a predetermined breaking point generating device.

The spring coiling machine 100 has a with three pairs of feed rollers 1 12 equipped feeder 1 10, the successive wire sections of a coming from a wire supply and guided by a straightening unit wire 1 15 with numerically controlled feed rate profile in the horizontal direction in the range of a forming device 120 perform. Components of the forming devices are e.g. can be clearly seen in Fig. 2. The wire can be guided on the exit side of the feed rollers through a wire guide device (compare FIG. 6).

The wire is converted into a helical spring F by means of numerically controlled tools of the forming device 120. The tools include two offset by 90 ° angular wind pins 122, 124 which are aligned in the radial direction to the central axis 1 18 and the position of the desired spring axis and are intended to determine the diameter of the coil spring. The position the wind pens may be changed to the basic setting for the spring diameter when setting along oblique directions as well as in the horizontal direction to set up the machine for different spring diameters. A similar adjustment is also possible during the spring coil process to change the diameter as a function of the axial position of a turn along the spring. These movements can be carried out by means of electric drives under the control of numerical control.

A pitch tool 130 has an effective surface oriented substantially perpendicular to the spring axis, which engages adjacent to the turns of the developing helical spring. The pitch tool is movable parallel to the axis 1 18 of the developing coil spring (i.e., perpendicular to the plane of the drawing) by means of a numerically controlled adjusting drive of the corresponding machine axis. The advanced during manufacture of the spring wire is pushed by the pitch tool according to the position of the pitch tool in the direction parallel to the spring axis, wherein the position of the pitch tool, the local slope of the spring is determined in the appropriate section. Gradient changes are effected by axis-parallel process of the pitch tool during spring production. There are also variants without a separate pitch tool, in which the pitch is adjusted via the wind tools.

The machine axes of the CNC machine associated with the tools are controlled by a computer numerical controller 180 which has memory devices in which the control software resides, to which i.a. an NC control program for the working movements of the machine axes heard.

The spring coiling machine is designed to produce coil springs with a large winding container (eg up to D / d 8). In these Among other things, coil springs demand the provision of a flat end face of the wire, which should be as parallel and central as possible to the spring axis. This surface can serve these requirements as a contact surface for the introduction of forces and moments. Such coil springs are predominantly produced in the wire diameter range of 4 mm to 10 mm, and preferably of chromium-silicon wires (eg wire types FD, TD and VD according to EN 10270-2) or wires for valve springs (eg wire types VD according to EN 10270-2) , They often have a mean winding ratio of 5 to 10, occasionally over it, for example, up to 16.

In principle, various wire materials are suitable for cutting with the torsion cut. However, torsion cutting methods have so far been difficult to perform reliably with winding ratios greater than 4. The spring coiling machine 100 is configured so that a torsion cut can be performed.

Above the spring axis, a numerically controllable cutting and Anritzeinrichtung 150 is arranged, which has at the lower end of a vertically movable tool carrier a first notching tool 152 which can be moved by driving the associated machine axis in the vertical direction downwards towards the workpiece or upwards. The first notching tool 152 has a wedge-shaped cutting edge directed downwards (wedge angle approximately 90 °), which has a sharp first cutting edge SK1 extending parallel to the central axis. After completion of a forming operation, a notch extending transversely to the wire core is produced on the outer side of the spring coil with the aid of the first notching tool at an intended separating position (compare FIG. 3).

As a counter element in this notching operation, a second notching tool 154, which has a corresponding second cutting edge SK2, which is arranged in the interior of the spring coil and upwards in Direction of the first notching tool is directed. The second notching tool 154 is attached to the top of a tool holder in the form of a mandrel 156, which is part of a mandrel unit. The mandrel and the second wedge tool carried thereby is displaceable parallel to the central axis 1 18 by means of a corresponding machine axis and can thus be moved into the interior of the spring or pulled out of this interior. The mandrel as a whole is mounted in a vertically movable mandrel carriage 160 so that the second wedge tool 154 can perform a controlled vertical movement in the direction of the upper notching tool or in the opposite direction.

At least one of the wedge tools, e.g. the inner wedge tool 154 may be provided on the side of the cutting edge facing the front wall of the machine with a nose 154 'projecting beyond the cutting edge (see Fig. 3B) which prevents the wire from deflecting towards the machine wall during the cutting operation. This can prevent the wire from jumping out of the tools.

Below the central axis of a tool unit 170 is arranged, which has a radially to the central axis 1 18 reciprocally movable in the vertical direction tool holder which carries at its upper end a wedge tool 172 which is insertable for initiating the Torsionsschnitts between turns of the coil spring. The wedge tool has at its upper end a flat inclined surface 173, which is inclined starting from the front wall of the spring coiling machine obliquely forward and down. The angle of inclination with respect to the horizontal plane is about 10 ° to 40 °, preferably about 15 °. During the torsion cut, the finished helical spring is pivoted upwards with the aid of the wedge tool 172 moved radially relative to the spring axis and to the central axis, so that the helical spring is twisted at the intended separation point between the notching tools (compare Fig. 3B). The two notching tools 152, 154 and the components of the cutting and pricking unit 150 and the mandrel unit provided for their movement are functional components of a predetermined breaking point generating device, which is adapted to each at a defined separation position of the wire at two diametrically opposite portions of the circumference linear weakening in the form of a transverse to the longitudinal direction of the wire notch in the region of the surface of the wire to introduce. The components of the predetermined breaking point generating device are likewise controlled via the control device 180 on the basis of the NC control program.

The spring coiling machine 100 can operate as follows. At the beginning of the coil spring manufacturing cycle, the upper first notching tool 152 is in a raised position at its upper reversal point and the mandrel with the lower notching tool 154 is retracted so that the lower notching tool is outside the wind plane defined by the wind tools 122, 124 , Then, with continuous wire feed, the helical spring is produced in a manner known per se by spring winds by the advanced wire material being forced through the wind fingers 124, 122 and bent into a circular shape. If the coil spring has reached the desired spring length, the wire feed is stopped so that the intended separation position at which the finished coil spring is to be separated from the supplied wire, in the parting plane 155, by the position of mutually parallel cutting edges SK1, SK2 of each other dressed notching tools 152, 154 is defined.

Then the mandrel 156 drives with the second wedge tool 154 forward into the spring body. The vertical position of the mandrel is set so that the cutting edge SK2 of the second wedge tool 154 is only a few tenths of a millimeter from the inside of the spring coil (see FIG. Then, the machine axis of the cutting and pricking device 150 is activated so that the first scoring tool 152 moves from the top to the outside of the wire. The two notching tools 152 and 154 are then slightly moved towards each other, so that the coplanar cutting edges of the notching tools simultaneously penetrate into the surface of the wire material from the outside (first notching tool) and from the inside (second notching tool) at diametrically opposite locations (see Fig. 3B). , In this notching operation, a notch extending perpendicular to the wire longitudinal direction is formed on each side of the wire. These mechanically generated notches act together as a predetermined breaking point. The notching tools penetrate only so deeply into the wire material that a superficial linear weakening of the wire material results, with the interior of the wire remaining "uninjured" or largely undeformed, with typical penetration depths of less than 1 mm, for example in the range between 0, 2 mm and 0.8 mm for typical wire diameters in the range of 4 mm to 10 mm (see Fig. 3B).

The wire is not separated by the notching tools 152, 154. Instead, the notching tools clamp the wire from above and below and thereby hold it in the parting plane 155 at the intended separation position. The actual cutting process, the "torsional cut", is then carried out from below with the aid of the bottom fed wedge tool 172. By a vertical sliding movement, the wedging tool 172 travels from below between the first and second turns of the spring and twists the spring body beyond 3). Thus, the spring is twisted or twisted in the plane of the wedge tools (parting plane 155) and breaks under the torsional stress in the parting plane. Thereafter, the upper wedge tool is retracted upward and the lower notching tool is lowered and retracted by retracting the dome. Thereafter, a corresponding cycle begins for the production of the next coil spring. For left-handed coil springs, the tools and the arrangement are mirror-inverted.

Due to the superficial linear weakening of the wire at two diametrically opposite areas with the help of the notching tools, a predetermined breaking point has arisen. Upon initiation of the torsional stress, crack propagation into the interior of the wire material may occur from opposite sides. The result is a flat, very homogeneous fracture surface, from which ridges protrude neither inwards nor outwards.

In addition, only a small cutting hit is generated. The term "cutting stroke" here generally refers to the noise during the cutting process The cutting stroke is usually lower in the torsion cut than in other types of cutting (eg straight cut, rotary cut) The cutting stroke is lower in the inventive method than in conventional methods, because the required for cutting Forces are smaller due to the pre-induced weakening and the total energy of all parts in the force flow is thus lower The energy in the system relaxes "abruptly" after the spring has been separated at the fracture point and the tools and machine elements are relieved.

In conventional torsional cutting without scoring, there is a practical winding ratio limitation in that the crucial half spring wrap between the engaged position of the wedge tool and the severing position is usually not sufficiently rigid with excessive winding ratios and thus not enough torsional moment could be introduced into the parting plane. In addition, the rotation of the spring body via the wedge tool (FIG. 3B) can also be limited geometrically, so that it is usually desirable when bending back in the direction of the front wall at the latest at an angle range between 70 ° and 100 ° (angle between spring axis and horizontal) comes to break, otherwise the spring body can strike on tools and / or parts of the machine and / or the axis of movement of the wedge tool can not drive sufficient lifting movement more.

These limitations are relaxed by anchoring. By anchoring on diametrically opposite peripheral areas required for the fraction torsional moment is significantly reduced, so that it comes within the geometric limits due to any interference contours or driveways to a severing of the wire. These significant improvements in performing a torsion cut are currently attributed, inter alia, to the fact that the multi-faceted surface indentation promotes cracking or crack propagation at different wire circumference locations. Furthermore, it seems advantageous if the (relatively hard or brittle) wire material in the vicinity of the central axis of the wire remains largely unaffected by the notch or incision. The non-weakened, central material thus represents - figuratively speaking - a torsion axis.

In the embodiment of Figs. 1 to 3, the components of the cutting and Anritzeinheit 150 above the central axis 1 18 and arranged by this defined horizontal plane of the spring coiling machine and the wedge tool 172 engages to initiate the torsional fracture from below between adjacent turns. It is located between the still unbent wire section, which meets the lower wind tool 122, and the separation zone arranged above it, in which the notching tools 152, 154 work, about half a spring wind dung. This forms the first half turn of the next coil spring and remains in the spring coiling machine when the severed coil spring is removed.

If desired, the arrangement shown in Fig. 4 may also be used, in which the components of the cutting and pricking means are located below the central axis 418, the wedge tool 472 being located above the developing coil spring and being inserted from above between adjacent spring coils, to cause the torsional fracture (Figure 4C). The same or corresponding components carry the same reference numerals as in FIGS. 1 to 3, each increased by 300.

When making the spring, the wire is in each case advanced so far that a complete 360 ° turn W1 lies between the supplied wire and the intended separation position. Then the wire feed is stopped and the mandrel 456 is retracted into the spring so that the inner notching tool 454 is at the beginning of the turn following the winding W1. At the same position, the outer notching tool 452 then also engages from the other side of the wire. When the notching tools 454, 452 move together, the wire is notched and clamped at the transition between the winding W1 and the subsequent wire section before the wedge tool 472 engages from above and initiates the torsion. The winding W1 is thus decoupled by means of the notching tools of those forces that lead to torsion. This avoids the bending of the adjacent end / initial turn.

Components of an embodiment in which the predetermined breaking point generating device operates with the aid of jet tools will be explained with reference to FIG. 5. To simplify carry identical or similar components of the spring coiling machine, the same reference numerals as in Figures 1 to 3.

The predetermined breaking point generating device has a first beam outlet device 552 and a second beam outlet device 554, which define a vertical parting plane at the point at which the torsional fracture is to be initiated after completion of the wire feed. The upper, first jet outlet means produces a jet which is directed obliquely to the convexly curved outside of the wire. The lower second jet unit generates a jet which is directed at approximately a diametrically opposite point obliquely on the concavely curved inside of the wire. With the aid of the rays, linear weakenings in the region of the wire surface can be introduced in diametrically opposite regions on the outside and inside of the wire before the wedge tool 172 travels from below between the first winding still hanging on the supplied wire and the second winding and the spring body turns up. Again, a crack initiation of several points of the wire circumference, whereby the required torsional moment is reduced.

In the illustrated variant, the predetermined breaking point generating device operates with the aid of laser beams, wherein the beam outlet devices 552, 554 are designed in the form of beam-guiding exit optics of the laser system.

In another variant, the predetermined breaking point generating device operates with sharply focused water jets, which are blasted under high pressure through outlet nozzles in the jet outlet devices in the direction of the wire surface.

In the variants of Figures 1 to 5, the predetermined breaking point after completion of the wire feed with stopped wire feed on the produced completely curved or finished wound spring, so that the predetermined breaking point between their generation and the initiation of the torsional moment is no longer moved. However, this is not mandatory. Based on Fig. 6 embodiments are explained in which a predetermined breaking point is generated before completion of Federwindeoperation, so that after generation of the predetermined breaking point nor a feed of the predetermined breaking point is up to that position at which the cut takes place.

FIG. 6 shows a front view of parts of a spring coiling machine 600, which has a cutting device 650, which is set up for a straight cut. The wire 615 is conveyed by feed rollers 612 of a feed device in the direction of the forming device 620, which has two wind pins 622, 624 for presetting the spring diameter and a pitch tool 630 for setting the pitch. Above the central axis 618, a cutting device 650 is mounted with a cutting tool 652 which, after completion of a forming operation, separates the manufactured coil spring with a vertical working movement by means of a straight cut from the supplied wire. As a counter element for the cutting tool is a mandrel 655 (cutting mandrel), which is located inside the developing spring and has a vertical cutting edge 656, which cooperates with the cutting tool 652 during separation. The cutting edge 656 defines the parting plane of the straight section.

Immediately behind the feed rollers 612, a wire guiding device 616 is mounted between these and the area of the forming tools, which has an inlet sleeve 616A and a coaxial outlet sleeve 616B spaced apart such that a portion of the inserted wire is externally interposed between the sleeves is freely accessible from several directions. Also in this example coil springs with a relatively high winding ratio (D / d> 8) are to be made, which consist of relatively hard spring steel wire. With the help of a predetermined breaking point generating device, it is possible to significantly reduce the cutting forces required for cutting the wire with respect to wires without predetermined breaking point. As a result, tool wear can be reduced and it is possible to dispense with an otherwise required particularly expensive dimensioning of the components of the cutting device. Also, the cutting stroke and the load on the tools and the machine as a whole are reduced. As a result, a longer service life of the tools can be achieved.

In one of the variants shown here, components of the predetermined breaking point generating device are arranged in the region of the wire guide 616 such that the predetermined breaking point can be generated at that wire section exposed between the inlet sleeve 616A and the outlet sleeve 616B. In the example case, two diametrically opposed jet outlet devices 654A, 654B are attached for this purpose, in order to produce superficial scribing on the wire at two diametrically opposite regions transverse to the wire direction. In the example, the Strahlauslasseinrichtungen are designed as exit optics of a laser system. Alternatively, it could be outlet nozzles of a water jet cutting device.

In this variant, so the predetermined breaking point is generated before the actual forming process of the predetermined breaking point wire section takes place by spring winds. After generating the predetermined breaking point, the wire is advanced so far until the predetermined breaking point is in the separation plane defined by the cutting edge 656. This situation is indicated in Fig. 6 by the score on the outside and inside of the spring in the region of the predetermined breaking point SB. The components of the predetermined breaking point generating device, for example the beam exit devices, can be arranged fixed to the machine so that exactly the required wire length lies between its position and the parting plane. Then the wire feed is possibly briefly interrupted until the predetermined breaking point is generated. In other variants, it is provided that the wire feed for the pre-scoring is not interrupted. For this purpose, mounted in the vicinity of the wire components of the predetermined breaking point generating device are mounted linearly movable parallel to the wire running direction and can be controlled so that it moves synchronously with the advanced wire at the wire speed for the duration of the generation of the predetermined breaking point and then before the next cycle can be moved back again. For this purpose, for example, the wire guiding device with the beam outlet devices attached thereto can be mounted on a carriage in order to be able to move linearly in the direction of wire travel as a whole.

FIG. 6 shows, in conjunction with FIG. 7, an alternative arrangement of components of a predetermined breaking point generating device which generates a predetermined breaking point with the aid of a laser beam at the intended separating position before the separating position provided on the wire moves into the parting plane (defined by cutting edge 656) becomes. The components are arranged here in the space between the wind fingers 622, 624 offset by approximately 90 ° to the parting plane. This arrangement can e.g. be low for reasons of space, if in the area of the parting plane only little space is available.

A beam outlet unit 752 of a laser system is disposed radially outward of the spring and is movable transversely to the direction of travel of the wire 715 by a uniaxial pivotal movement (jet outlet unit 752A in Fig. 7A) or a linear displacement movement (jet outlet unit 752B in Fig. 7B) perpendicular to the wire longitudinal direction. At the inside of the wire winding is diametrically opposite the Strahlauslasseinrichtung a mirror assembly with two V-shaped plan mirrors arranged 761, 762, which are arranged so that at certain positions of the Strahlauslasseinheit the laser beam from a plane mirror or two plane mirrors are reflected at peripheral regions of the continuous wire which can not be reached directly by the laser beam coming from the beam exit means. The angle W between the mirror surfaces may be, for example, in the range of 70 ° to 130 °. In this way, it is possible with a single laser beam, which is moved back and forth in the transverse direction by pivoting or moving, the wire over its entire circumference or the majority of the circumference (more than 180 °) superficially melt along a defined line of weakness or to score. The laser beam can thus be deflected by the deflection mirrors one or more times so that different peripheral sections can be irradiated with the same laser beam, even on the side facing away from the beam exit device.

After the circumferential superficial melting line has been generated at the intended separation position by laser irradiation, the resulting predetermined breaking point is advanced by pressing the wire feed into the parting plane on the mandrel 655, before the finished spring is severed by the cutting tool by straight cut.

The variant explained with reference to FIG. 7 can also be applied elsewhere, e.g. in the field of wire guide, be provided. If space permits it, an arrangement in the parting plane, i. in the area of the cutting edge 656 of the cathedral possible.

This application thus discloses different possibilities, the wire at a defined separation position by scoring or scoring mechanically or by the action of jet tools along a weaken relatively narrow line to create a predetermined breaking point, which allows a clean cut with reduced cutting forces. The cutting force is significantly reduced when indentations or incisions are introduced at least at two diametrically opposite areas or over the entire circumference, as shown here by way of some examples. In particular, thus springs with significantly higher winding ratios can be separated by Torsionsschnitt.

The predetermined breaking point can also be generated by a plunge operation. For this, e.g. in the variant of Fig. 1 to 3 of the mandrel 156 may be provided with a sharp-edged piercing tool which scores a notch in the tangential direction of the wire cross section in the interior of the spring on the inside of the wire during axial feed of the mandrel.

Claims

claims

1. A method for producing coil springs by spring coils by means of a numerically controlled spring coiling machine, wherein a wire under the control of an NC control program supplied by a feeder of a forming device of the spring coiling machine, formed by means of tools of the forming device into a coil spring and then a finished coil spring is separated by means of a cutting device of the supplied wire,

characterized,

a linear weakening in the region of the surface of the wire is produced before the separation at a defined separation position along the wire at least at two diametrically opposite sections of the wire circumference, and the finished helical spring is severed from the supplied wire at the separating position.

2. The method according to claim 1, characterized in that a linear weakening at and near the wire surface is produced by notching, piercing, rolling, hammering or incising the wire surface.

3. The method according to claim 1 or 2, characterized in that the weakening is generated from the wire surface only so far that at least 50% of the diameter of the wire, in particular between 60% and 90% of the diameter of the wire, in the region of the center The wire remains essentially unaffected by the near-surface weakening.

4. The method according to any one of the preceding claims, characterized in that for weakening the wire at the separating position Only on two diametrically opposite peripheral areas in each case a linear weakening is generated.

5. The method according to claim 4, characterized in that the wire by means of numerically controllable notching tools (152, 154) is mechanically notched simultaneously at diametrically opposite peripheral portions, preferably the wire for generating the weakening between the notching tools (152, 154) clamped is held, the notching tools in engagement with the wire and the coil spring is separated from the jammed wire by torsion.

6. The method according to any one of claims 1 to 3, characterized in that for weakening the wire at the separating position a circumferentially continuous uninterrupted linear weakening is generated.

7. The method according to any one of the preceding claims, characterized in that for generating the weakening at least one jet tool is used.

8. The method according to claim 7, characterized in that for generating the weakening at least one laser beam is irradiated to the wire surface, wherein preferably the laser beam is deflected by at least one deflection simply or repeatedly such that different peripheral portions are irradiated with the same laser beam.

9. The method according to any one of the preceding claims, characterized in that a coil spring (F) with a winding ratio D / d of more than 4, in particular between 5 and 10, generated and separated by means of torsional cut from the supplied wire, wherein the Winding ratio is the ratio between the spring diameter D and the wire diameter d of the coil spring.

10. Spring coiling machine (100) for producing coil springs (F) by spring winds comprising:

a feed device (1 10) for feeding wire (1 15) to a forming device (120), wherein the forming device has at least one winding tool (122, 124),

a cutter for cutting a finished coil spring from the supplied wire after completion of a forming operation;

a control device (180) for controlling the feed device, the forming device and the cutting device on the basis of an NC control program,

marked by,

a predetermined breaking point generating device which is adapted to generate at a defined separation position along the wire at least at two diametrically opposite portions of the wire circumference a linear weakening in the region of the surface of the wire.

1 1. Spring coiling machine according to claim 10, characterized in that the predetermined breaking point generating device comprises two mutually movable or away from each other notching tools (152, 154) lying in a common plane cutting edges (SK1, SK2), wherein the notching tools are preferably so controlled in that the notching tools can simultaneously penetrate superficially into the wire material from opposite sides, one of the notching tools serving as a counter-tool of the other notching tool.

12. Spring coiling machine according to claim 10 or 1 1, characterized in that the cutting device for a separation of the coil spring (F) is arranged by torsion cutting, wherein the spring coiling machine preferably a radially to a central axis (1 18) displaceable tool unit (170) with a wedge tool (172), which can be inserted between turns of the coil spring.

13. Spring coiling machine according to claim 1 1 or 12, characterized in that the spring coiling machine is configured so that the wire (1 15) can be clamped to produce the weakening between the notching tools (152, 154), the notching tools held in engagement with the wire and the coil spring (F) can be separated from the jammed wire by torsion.

14. Spring coiling machine according to claim 10, characterized in that the predetermined breaking point generating device has at least one jet tool with a beam exit device (552, 554, 652, 654, 752) which can be aligned with the wire surface.

15. Spring coiling machine according to claim 14, characterized in that the predetermined breaking point generating means comprises a laser system which is configured such that for generating the amateur weakening at least one laser beam can be irradiated onto the wire surface, wherein preferably at least one deflecting device, in particular a plane mirror (761 A, 761 B) is provided, with which a laser beam is simply or repeatedly deflected so that different peripheral sections of the wire (715) can be irradiated with the same laser beam.

16. Spring coiling machine according to claim 15, characterized in that the laser system has a Strahlauslasseinheit (752), the is transverse to the passage direction of the wire (715) mounted perpendicular to a wire longitudinal direction, wherein diametrically opposite the Strahlauslasseinrichtung a deflection with two V-shaped plan mirrors (761, 762) is arranged, which are oriented so that in certain positions of the Strahlauslasseinheit the laser beam is reflected by one of the plane mirrors or two plane mirrors on peripheral regions of the wire, which are not directly accessible by the laser beam coming from the beam exit device.