SE540798C2

SE540798C2 - Heading device for a chain-welding machine, and chain-welding machine

Info

Publication number: SE540798C2
Application number: SE1550740A
Authority: SE
Inventors: Döderlein Frank
Original assignee: Wafios Ag
Priority date: 2014-06-27
Filing date: 2015-06-05
Publication date: 2018-11-13
Also published as: DE102014212527B3; CN105215259A; CN105215259B; SE1550740A1

Abstract

A heading device (100) for use on a chain-welding machine for flash-butt welding pre-bent chain links comprises a basic element (110) which is mountable in a fixed position on the machine, and a header-die carrier (120) which for performing heading movements is supported with the aid of bearing installations so as to be movable in relation to the basic element and which on a front side has installations for mounting a header die. The bearing installations have a first articulated lever assembly (130) and a second articulated lever assembly (140) which is spaced apart from the former, wherein each of the articulated lever assemblies by way of a first pivot bearing (144A) is articulated on the basic element (110) and by way of a second pivot bearing (146A), which is disposed so as to be axially parallel with the first pivot bearing, is articulated on the header-die carrier (120) in such a manner that a parallelogram-type guide for the headerdie carrier (120) is formed.

Description

Description Heading device for a chain-welding machine, and chainwelding machine TECHNICAL FIELD AND PRIOR ART

[0001] The invention relates to a heading device for use on a chain-welding machine for flash-butt welding pre-bent chain links, according to the preamble of Claim 1, and to a chain-welding machine having a heading device of this type.

[0002] Chains having chain links, which are bent using wire elements, nowadays are widely manufactured with the aid of special automated machine tools which are typically referred to as chain-bending machines. During manufacturing, chain links are bent initially using lineal wire elements of suitable length, so-called pins, and connected to other chain links which likewise may be bent using wire elements or may be manufactured in another way, for example by forging. Since many chains, for example in mining, such as plough chains, for example, have to be designed for significant stress and are exposed to heavy wear, there is an obvious tendency towards ever larger wire diameters of, for example, up to 70 mm or more.

[0003] It is known that pre-bent chain links which, however, are still open at one point and which are initially connected to other chain links to form a chain strand and then welded by way of an electric flash-butt welding method in order to form closed chain links are employed for manufacturing steel chains. The flash-butt welding method may be automated with the aid of special chain-welding machines in order to connect the free ends of a pre-bent chain link in a materially integral manner.

[0004] A chain-welding machine has a heading device which is designed to grip a chain link which is still open, held in a processing position between so-called header dies of the heading device and to head said chain link such that the mutually facing, as yet free end faces of the bent wire are initially brought closer to one another, come into contact with one another, and are then pressed together. Furthermore, a welding electrode is provided for each end portion, which welding electrode, for performing a welding operation, is placeable onto the associated end portion of the chain link in a transverse manner to the heading direction and may bend the end portion in a transverse manner to the heading direction in order to render the chain link in the desired shape.

[0005] In the case of the flash-butt welding method, during the warming-up phase there is always only punctiform contact between the mutually facing end faces of the bent wire. On account of the high current density resulting therefrom, the material of the chain link at these contact points is liquefied and/or evaporated, or ejected in the form of splatters. The end portions partially flash at the point of weld. As a result of the continuous formation and destruction of the contact bridges, even during the warming-up phase an indexing movement of the welding electrodes, including the associated end portions, is provided in order to maintain contact. Pre-heating may be controlled by repeatedly moving elements of the heading device forwards and backwards. After the required temperature has been reached, the current flow is interrupted and, by means of the heading device, a force in the heading direction is abruptly introduced during a heading stroke ("heading blow") by way of which the end portions are headed against one another. An advantage of this method lies in that as a result of flashing, contaminants on the point of weld are also automatically removed and, on account of the evaporating material, an inert gas atmosphere which protects the point of weld is created. On account thereof, a uniform and pure weld connection without inclusions is obtained. Mostly a burr which is mostly removed while still warm is formed at the heading point.

[0006] DE 1577 064 describes a header-die guide on an electric flash-butt welding machine. Two guides are disposed in a locationally fixed manner on a frame of the flash-butt welding machine. A housing which in the cross section is configured so as to be U-shaped is guided on rolls in a longitudinally displaceable manner on said guides. A header-die carrier having a header die is disposed on a front end wall of the housing, which faces the chain link to be bent. The stroke movement of the housing is caused by way of a hydraulic cylinder, the cylinder unit of which is disposed so as to be locationally fixed on the machine frame and the piston-rod unit of which is articulated by way of a ball-joint mounting on the front end wall of the housing.

[0007] DE 2317 691 describes a chain-welding machine having two heading levers which are pivotable by way of a control shaft by way of a common drive device and which are coupled with die carriers for header dies which impact on the round features of the chain link to be welded. When the header levers are pivoted in opposite directions, the die carriers move in opposite directions which are at least approximately horizontal. The die carriers are in each case guided in a lineal guide. The lineal guide is to facilitate accurate centring of the header dies on the round features of the chain link to be welded, such that welding the link ends can be performed with constant good quality.

[0008] DE 2457 180 describes a method and a device for electrically butt-welding or flash-butt welding workpieces having rod-shaped ends. A header die of a heading device is rigidly mounted in a horizontal direction on the machine frame and is held so as to be upwardly pivotable only for introducing a chain link to be welded. The other header die is mounted so as to be displaceable in the axial direction in a pivotably mounted pivot sleeve.

[0009] DE 2251 899 describes a method and a device for manufacturing steel chains from C-shaped bent chain links which are unified to form a chain strand. The device has a welding station with a stationary counterbearing for the chain link to be welded, and two header jaws which are disposed on infeed slides. One of the header jaws is infeedable only in the direction of the counterbearing and in the direction counter thereto along a vertical guide. The other header jaw likewise is disposed on an infeed slide and, together therewith, infeedable in the vertical direction in the direction of the counterbearing and the direction counter thereto. The infeed slide is seated on the front side of a header slide which is horizontally displaceable.

[0010] It has been observed in the case of many conventional heading devices that wear becomes apparent already after a comparatively short operating period, which necessitates maintenance works and, if applicable, the replacement of parts. The downtime caused on account thereof is disadvantageous to productivity of the chain-welding machines.

OBJECT AND SOLUTION

[0011] It is an object of the present invention to provide a heading device for a chain-welding machine which enables a long service life without breaks for maintenance and which is distinguished by a comparatively simple construction and high mechanical stability, even when processing chain links having a large wire diameter.

[0012] As a solution to this object the invention provides a heading device for a chain-welding machine having the features of Claim 1. Further, a chainwelding machine having the features of Claim 10 is provided. Advantageous refinements are stated in the dependent claims. By way of reference, the wording of all claims is incorporated in the description.

[0013] The heading device comprises a basic element which is mountable in a fixed position on the machine and which may be fastened on the upper side of a machine frame by means of screws or in another manner, for example. Furthermore, a header-die carrier which for performing heading movements is supported so as to be movable in relation to the basic element is provided. Bearing installations are provided in order for the header-die carrier to be movably mounted on the basic element. Furthermore, installations for mounting a replaceable header die are provided on the header-die carrier. Said installations are located on a front side of the header-die carrier, wherein the front side of the header-die carrier is that side which in the case of a finally mounted heading device faces the chain link to be headed. The term "header die" refers to a die element which is provided for the heading operation to impact on a round feature of the chain link to be headed and to introduce the heading force which acts parallel with a heading direction into the chain link.

[0014] The bearing installations by way of which the header-die carrier is mounted so as to be movable in relation to the basic element comprise a first articulated lever assembly and a second articulated lever assembly which is spaced apart from the first articulated lever assembly. Each of the articulated lever assemblies by way of a first pivot bearing (or pivot joint) is articulated on the basic element and by way of a second pivot bearing (or pivot joint), which is disposed so as to be axially parallel with the first pivot bearing, is articulated on the header-die carrier in such a manner that a parallelogram-type guide for the header-die carrier is formed. Such a parallelogramtype guide for the header-die carrier offers significant practical advantages in comparison with conventional solutions.

[0015] Conventional heading devices having movable components typically contain header slides or other bearing installations having linear guides in order to generate a translatory movement of the movable header die in the heading direction. It has been recognized that linear guides in the proximity of the point of weld may be so severely compromised relatively quickly by flashing during welding and by other potential contaminants that wear arises to a degree that components have to be cleaned, repaired or replaced.

[0016] By contrast, a heading device according to the claimed invention may be constructed such that the bearing devices exclusively include pivot bearings and no linear bearings (for example, lineal guides). By contrast to linear bearings, pivot bearings can be sealed against external influences in an excellent manner with low construction complexity. They may be constructed having high mechanical stability at low cost, and during operation are subject to comparatively low wear. The pivot bearings may be configured, for example as pure friction bearings with the aid of sliding bushes and bolts, without rolling elements being employed. By way of dispensing with linear bearings, wear due to contamination may be significantly reduced in comparison with conventional solutions, such that a longer service life of the assembly results without the need for cleaning, repair, and/or replacement of components.

[0017] A parallelogram-type guide for the header-die guide may also offer advantages with a view to mechanical stability. If and when the header-die carrier is constructed in the form of a header slide which is displaceable in a linear manner, precisely in the case of a fully extended slide, a comparatively large free length, that is to say an unsupported length, of the header slide adjacent to the header die may result in the final phase of compression of the chain link and during the so-called header stroke. On account thereof, bending of the header slide may arise in the case of high heading forces. By contrast, however, when a parallelogram-type guide is provided for the header-die carrier, the free length of the header-die carrier between the header die and the pivot bearing of the first articulated lever assembly, which is closest to the header die, may be selected to be comparatively short, such that only a minor protrusion and correspondingly minor deformations may result in this region. Moreover, the free length (between the first articulated lever assembly and the header die) is constant in the case of a parallelogram-type guide, such that this mechanical stability results independently of the pivot position of the header-die carrier.

[0018] In one refinement a first hydraulic cylinder for generating movements of the header-die carrier in relation to the basic element is provided. The first hydraulic cylinder is also referred to as a heading cylinder, since it generates the heading movement. A cylinder unit of the first hydraulic cylinder is coupled in an articulated manner to the basic unit, while a piston-rod unit of the first hydraulic cylinder is coupled in an articulated manner to the header-die carrier. The assembly may also be reversed, such that the cylinder unit is coupled to the header-die carrier and the piston-rod unit is coupled to the basic unit. On account of the first hydraulic cylinder being included between the basic element and the header-die carrier, inter alia a compact construction may be achieved.

[0019] The first pivot bearings assigned to the basic element define first rotation axes which run in parallel with one another and which collectively define or span a first bearing plane. The second pivot bearings assigned to the header-die carrier define second rotation axes which run in parallel with one another and which collectively define or span a second bearing plane. Preferably, a central cylinder axis or cylinder central axis, respectively of the first hydraulic cylinder is disposed between the first and the second bearing plane, on account of which favourable lever ratios for introducing a force into the chain link to be bent result. It may in this way be achieved in a simple manner that the heading cylinder acts in a centric manner on the chain link, such that no unfavourable momentums act on the header-die carrier or other components.

[0020] In order to avoid to the largest extent unfavourable flexural momentums within the heading device even in the case of high heading forces, in preferred embodiments the installations for mounting a header die on an angular outrigger of the header-die carrier are disposed in such a manner that these installations lie in the extension of a central cylinder axis of the first hydraulic cylinder. Typically, it is particularly favourable for the installations for mounting a header die to be disposed on the header-die carrier in such a manner that an impact zone for a chain link on the header die lies in the extension of a central cylinder axis of the first hydraulic cylinder with an accuracy of ± 20 mm. On account thereof, the cylinder axis and the chain-link axis may be largely or exactly congruent, such that forces for bending the chain link may be introduced in an optimal manner. In relation to the abovementioned bearing planes, these installations preferably lie in a region between the first and the second bearing plane.

[0021] For flash-butt welding it is necessary that the end portions of the pre-bent chain link to be welded are incorporated with one another in an electrical circuit for the welding current. To this end, a welding-electrode carrier for carrying at least one welding electrode which, for performing a welding operation, may be placed in a placement direction which is transverse to a heading direction onto an end portion of a chain link, is provided on the heading device. The welding electrodes here do not only serve in electrically contacting the end portions but should additionally also exert a transverse force on the two yet open legs, such that the chain link may also be brought into its desired shape with the aid of the welding electrodes. In one preferred embodiment, the welding-electrode carrier is coupled to the header-die carrier by way of a third articulated lever assembly, wherein the third articulated lever assembly is articulated by way of a first pivot bearing on the header-die carrier and by way of a second pivot bearing on the welding-electrode carrier. On account thereof, it is possible for the welding-electrode carrier to not only pivot in relation to the header-die carrier but also to be displaced as a pivot axle is displaced. On account thereof, simple and accurate positioning of the welding electrodes on the chain link is possible.

[0022] In one refinement, a second hydraulic cylinder is provided for generating movements of the weldingelectrode carrier in relation to the header-die carrier, said second hydraulic cylinder thus also being referred to as a "welding cylinder". Preferably a carrier frame which is fixedly connected to the basic unit and against which the second hydraulic cylinder may be supported in the event of a movement of the welding-electrode carrier is provided. To this end, a cylinder unit of the second hydraulic cylinder may be coupled in an articulated manner to the carrier frame, and a piston-rod unit of the second hydraulic cylinder may be coupled in an articulated manner to the weldingelectrode carrier. A reversed assembly (the cylinder unit being coupled to the welding-electrode carrier, the piston-rod unit being coupled to the carrier frame) is also possible. On account of the attachment to the carrier frame which is fixedly connected to the basic unit, in comparison with conventional solutions, a significant mechanical stress relief on the header-die carrier is achievable. The latter during application of the forces by way of the welding electrodes is not mechanically stressed or is mechanically stressed only in the region of the third articulated lever assembly.

[0023] This deflection of reactive forces of the welding cylinder by way of a discrete carrier frame which is independent of the header-die carrier may be advantageous in a manner which is independent from the other features of the heading device, in particular in a manner which is independent from a parallelogram-type guide for the header-die carrier, also in the case of other heading devices, in particular also in the case of heading devices of the prior art.

[0024] Thus, also a heading device for use on a chainwelding machine for flash-butt welding pre-bent chain links is proposed, which heading device comprises a basic element, which is mountable in a fixed position on the machine, and a header-die carrier which for performing heading movements is supported with the aid of bearing installations so as to be movable in relation to the basic element and which on a front side has installations for mounting a header die, wherein the heading device furthermore has a welding-electrode carrier, which is coupled in an articulated manner to the header-die carrier, for carrying at least one welding electrode which, for performing a welding operation, is placeable in a placement direction which is transverse to a heading direction onto an end portion of a chain link, wherein for generating movements of the welding-electrode carrier in relation to the header-die carrier a hydraulic cylinder (welding cylinder) is provided, and a cylinder unit of this hydraulic cylinder is coupled in an articulated manner to a carrier frame which is fixedly connected to the basic unit, and a piston-rod unit of this hydraulic cylinder is coupled in an articulated manner to the welding-electrode carrier, or vice-versa.

[0025] The invention also relates to a chain-welding machine for flash-butt welding pre-bent chain links, which has a heading device of the type described herein (with a parallelogram-type guide for the header-die carrier).

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Further advantages and aspects of the invention are derived from the claims and from the following description of preferred exemplary embodiments of the invention which are explained hereinbelow by means of the figures.

[0027] Fig. 1 shows an illustration from an oblique perspective of a heading device according to one embodiment of the invention, in an open position prior to the commencement of a heading and welding operation;

[0028] Fig. 2 shows a side view of the heading device of Fig. 1, including further components of the chainwelding machine;

[0029] Fig. 3 shows a view from an oblique perspective of the heading device of Fig. 1, after termination of a heading and welding operation, having an already closed chain link;

[0030] Fig. 4 shows a side view of the heading device in the configuration of Fig. 3;

[0031] Fig. 5 shows an enlarged detail of the front end of a header-die carrier in an embodiment in which a header die is displaceably mounted on the header-die carrier; and

[0032] Fig. 6 shows a schematic view of the rear side of the rear (second) articulated lever assembly.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0033] Figs. 1 and 2 show an embodiment of a heading device 100 which is provided for use on a chain-welding machine 200 and by way of which pre-bent chain links 300 of a pre-assembled chain strand 310 may be welded in a continuous method to form closed chain links by means of flash-butt welding. After chain bending, that is to say after the chain links have been pre-bent, a chain strand 310 having as yet slightly opened chain links 300 is typically present. These as yet still slightly opened chain links are successively welded by means of flash-butt welding in the chain-welding machine to form completely closed chain links. To this end, each pre-bent and as yet slightly opened chain link 300 is initially positioned in a working position in the chain-welding machine. In the working position, the chain link is supported from below by means of a vertically displaceable counterstop 210 and positioned so as to be lateral on a header die 290 which is mounted in a fixed position on the machine (see Fig. 2).

[0034] Heading strokes are then performed from the opposite direction with the aid of the heading device 100. One heading stroke compresses the chain link in a heading direction A which runs parallel with the longitudinal direction of said chain link and, on account thereof, brings the free ends of the mutually facing end portions of the wire closer together. In a temporally coordinated manner with the heading stroke, a transverse force (transverse to the heading direction, and substantially vertical) is exerted with the aid of welding electrodes 162, 163 on the two as yet open wire legs, and the chain link is thus rendered in the desired shape. During the welding operation which commences then, further heading movements are effected in order to interconnect the ends of the wire by way of flash-butt welding.

[0035] The heading device 100 has a basic element 110 which is mountable in a fixed position on the machine and which in the case of the chain-welding machine 200 is fixedly mounted on the upper side of the machine bed 202. The basic element has a rectangular base plate 112 for mounting onto the machine bed, and on the longitudinal sides of said base plate 112 has vertical side walls 114 for receiving pivot bearings which are to be explained later on. The basic element made of steel may be integrally (monolithically) constructed or be constructed from a plurality of parts.

[0036] An elongated header-die carrier 120 of the heading device is mounted so as to be movable with the aid of bearing installations in relation to the basic element 110, along the longitudinal direction thereof. The header-die carrier 120 substantially has the form of an elongated beam having a rectangular cross section. On the front side facing the chain link an angular outrigger 122 is formed, which is angled downwards in the direction of the basic element. On the front side of the outrigger 122, facing the chain link, mechanical installations for mounting or screwing, respectively, a header die 190 which may impact on a facing curvature of the chain link during heading, are located so as to be about level in height with the locationally fixed header die 290 which lies opposite thereto.

[0037] The header-die carrier 120 is guided so as to be movable by means of a parallelogram-type guide in relation to the basic element 110. To this end, a first articulated lever assembly 130 is provided in the proximity of the front outrigger 122, and a second articulated lever assembly 140 is provided in the proximity of the rear end of the header-die carrier. In principle, the articulated lever assemblies are constructed in an identical manner, such that only the construction of the rear articulated lever assembly 140 (second articulated lever assembly) is to be explained in more detail here (cf. also Fig. 6).

[0038] The second articulated lever assembly has on each side of the header-die carrier one elongate articulated lever 142A, 142B which may also be referred to as a "lug" or a "coupler". The articulated levers couple the header-die carrier 120 in a doublearticulated manner to the basic element 110. The articulated lever 142A is mounted on the side of the basic element 110 by way of a first pivot bearing 144A on the side wall of the basic element, while a second pivot bearing 146A which is axially parallel therewith is located on the side of the header-die carrier 120. Corresponding pivot bearings are located on the opposite side in order to couple the other articulated lever 142B of the pair of articulated levers to the basic element or the header-die carrier, respectively.

[0039] The pair of articulated levers 142A, 142B offers a dual-side, double-articulated coupling which is secure in relation to lateral tipping, wherein the pivot bearings on the basic element side rotate about a first pivot axle 145 and on the header-die carrier side rotate about a second pivot axle 147 which runs parallel with the first pivot axle. The articulated levers 132A, 132B of the front, first articulated lever assembly 130 correspondingly rotate about a first pivot axle 135 on the basic element side and a second pivot axle 137 on the header-die carrier side. The spacing between the articulation assemblies 130, 140 in the longitudinal direction is more than double the spacing, in particular about three times the spacing, between the first and the second pivot bearing of an articulated lever.

[0040] Each of the pivot bearings is configured as a pure friction bearing GL (without rolling elements) and has one bearing bush which rotates about a bearing bolt (cf. Fig. 6). The pivot bearings are sealed in relation to the outside by way of suitable seals, seal caps, for example, against ingress of contaminants of all types. In comparison with roller recirculation shoes, for example, the sealed pivot bearings are to the largest extent immune against contaminants and highly wear resistant. Lubrication connectors which serve for flushing out dirt and abrasive wear may be provided.

[0041] On account of the kinematic conditions of the parallelogram-type guide, the operating movement of the header-die carrier 120 is not a purely translatory movement in the longitudinal direction of the headerdie carrier (that is to say parallel with the heading direction), but also contains a comparatively small motion component which runs transversely thereto (in the vertical direction). The movable header tool 190 during the heading stroke bears on a curve of the chain link, pushes the chain link against the locationally fixed header element 290 and brings the pin ends closer to one another. The horizontal orientation of the header-die carrier 120, which is parallel with the horizontal basic element, is maintained here due to the parallelogram-type guide.

[0042] A first hydraulic cylinder 150, which here is also referred to as a "heading cylinder", is provided for generating operating movements of the header-die carrier. A cylinder unit 152 of the heading cylinder is mounted by way of pivot bearings 154 with a horizontal pivot axle in the side walls 114 of the basic element. The piston-rod unit 153, which is axially displaceable within the cylinder unit, with its free end is coupled by way of a pivot bearing 156 with a horizontal pivot axle in an articulated manner so as to be level in height with the installations for mounting the header die on the inner side of the outrigger 122. On account of this assembly, the header die 190 which is carried by the header-die carrier 120 substantially lies in the extension of the central cylinder axis W of the first hydraulic cylinder, such that the force of the latter may be directly transmitted to the header die 190 and thus to the chain link without bending the header-die carrier. The contact point or impact point or impact zone AZ, respectively, between the chain link 300 and the header die 190 in the exemplary case lies at a distance of less than 20 mm or less than 10 mm from the central cylinder axis W (Fig. 5).

[0043] The pivot bearings 154, 156 by way of which the components of the first hydraulic cylinder are coupled to the header-die carrier, on the one hand, and to the basic element, on the other hand, lie between a first bearing plane, which is spanned by the first pivot axles 135, 145, and a second bearing plane, which is spanned by the second pivot axles 137, 147. On account thereof, a compact assembly with only a few components results.

[0044] Movable components of a welding installation are attached in an articulated manner to the header-die carrier 120. A beam-shaped welding-electrode carrier 160 is disposed above the header-die carrier 120, which welding-electrode carrier 160 on its front side carries two pivotable welding electrodes 162A, 162B which for performing a welding operation are placed in a substantially vertical placement direction onto the free end portion of the chain link 300 which faces the heading device 100, in order to establish electrical contact with the chain link, on the one hand, and to also compress the chain link in this direction, on the other hand.

[0045] The beam-shaped welding-electrode carrier 160 with the aid of a third articulated lever assembly 170 is coupled in a double-articulated manner to the rear end of the header-die carrier 120. The doublearticulated coupling permits pivoting about two horizontal pivot axles, on the one hand, and a longitudinal displacement of the welding-electrode carrier in relation to the header-die carrier, on the other hand, in order to be able to precisely set the placement position of the welding electrodes on the chain link.

[0046] The operating movements of the weldingelectrode carrier 160 in relation to the header-die carrier 120 are effected with the aid of a second hydraulic cylinder 180 which here is also referred to as a "welding cylinder". A piston-rod unit 184 of the heading cylinder is coupled in the front end region (in the proximity of the chain link) by way of a pivot bearing with a horizontal pivot axle to the upper side of the welding-electrode carrier 160. The cylinder unit 182 of the second hydraulic cylinder is coupled to a horizontal carrier portion of a carrier frame 185 which is fixedly attached to the basic element 110 and reaches across the header-die carrier and the weldingelectrode carrier, which are disposed above one another, in a portal-type manner. The reactive forces which are created when the electrodes are pressed onto the chain link are thus directly transmitted by way of the second hydraulic cylinder 180 and the carrier frame 185 to the basic element 110 and thus do not stress the header-die carrier 120.

[0047] It would also be possible for the movements of the welding-electrode carrier in relation to the header-die carrier to be implemented with the aid of a welding cylinder which is supported in an articulated manner on the header-die carrier, on the one hand, and on the welding-electrode carrier, on the other hand.

[0048] Two welding electrodes 162A, 162B which are to introduce the welding current into the chain link are pivotably attached to the front end of the weldingelectrode carrier 160. The drive for the pivoting movement of the welding electrodes is not illustrated. The welding-electrode carrier may be displaced in relation to the header-die carrier in order to be able to set the positions of the movable header tool and of the welding electrodes in relation to one another, or in order to be able to move the same two post heading and welding back into the correct initial position again, respectively. By way of the welding cylinder the welding-electrode carrier with the welding electrodes is placed onto the chain link and during the further stroke the slightly opened chain-link legs are bent downwards in order to place the pin ends beside one another in a coaxial manner. The welding installation thus also has to be able to exert bending forces on the chain link.

[0049] The heading device may operate as follows. At the start of an operating cycle the heading device is in the initial position shown in Figs. 1 and 2, in which the header-die carrier 120 is retracted into a rearward position and the welding-electrode carrier 160 is upwardly pivoted with the aid of the welding cylinder. By way of indexing the chain strand, a new as yet opened chain link to be welded is moved into the operating position above the vertically displaceable counter-element 210, and the counter-element 210 is lifted in order for the chain link to be welded to be lifted into the correct operating position and to be supported during bending. The two adjacent links are already hooked into the as yet opened chain link (see fig. 2).

[0050] Subsequently the movable components of the heading device 100 are moved with the aid of the heading cylinder (first hydraulic cylinder 150) and of the welding cylinder (second hydraulic cylinder 180) in order for flash-butt welding to be performed. Here, the welding electrodes are placed from above onto the free ends of the chain link which lie opposite, wherein electrical contact is established, on the one hand, and the free ends are also bent into an approximately coaxial configuration, on the other hand.

[0051] With the aid of the heading cylinder the movable header tool 190 is then indexed by way of a forward movement of the header-die carrier 120 substantially in the heading direction A, and the chain link 300, on account thereof, is compressed in the longitudinal direction until punctiform contact between the mutually facing end faces of the wire is established for the first time. The assembly is conceived such that an impact point or an impact zone, respectively, of the chain link on the header tool lies with high precision (with a deviation of at maximum 20mm, for example) in the extension of the cylinder central axis W of the heading cylinder. On account thereof, force can be introduced in an optimal manner with minimum stress by bending momentums on other components.

[0052] On account of high current densities, warmingup takes place rapidly, if applicable right up to punctiform melting at the contact point. In order to achieve sufficient warming-up in the entire region of the end faces to be connected, the movable header tool with the aid of the heading cylinder is, if applicable, repeatedly moved forwards in the heading direction and back so as to be counter to the heading direction, wherein the heading electrodes simultaneously push the free wire ends in the direction of the coaxial orientation. Once sufficient pre-heating has been achieved across the entire cross section, with the aid of the heading device 100 via the heading cylinder a great force is abruptly introduced in a heading stroke ("heading blow") in the heading direction A, on account of which the end portions are headed against one another and are welded together. The components of the chain-welding machine then are located in the welding position shown in Figs. 3 and 4, in which the heading cylinder and the welding cylinder are in each case in their extended positions and the chain link is closed and welded.

[0053] On account of the transverse motion components (motion components which are transverse to the heading direction) and of the great forces during the bending operation and heading operation, significant friction forces may be created between the bent portions of the chain link and the faces of the header dies (or header tools, respectively) which are in contact therewith. On account thereof, increased wear and/or unnecessarily great stress on the bearings may arise. In order for the transverse forces to be reduced it is provided in one embodiment that the movable header tool 190 which is carried by the header-tool carrier 120 is attached on the front side of the header-tool carrier so as to be displaceable in a linear manner. Displacement takes place in a more or less vertical manner in the motion plane of the header-die carrier. If and when transverse forces arise, the side of the header die which faces the chain link 300 may remain in adhesive contact with the chain link while the header die 190 is displaced in the transverse direction (upwards or downwards, for instance) in relation to the header-die carrier 120. With the aid of a tension spring the header tool may be pre-tensioned to an initial position into which it is automatically pushed back again by means of the tension spring once the chain link has been released.

Claims

Patent claims

1. Heading device (100) for use on a chain-welding machine for flash-butt welding pre-bent chain links, comprising: - a basic element (110) which is mountable in a fixed position on the machine, - a header-die carrier (120) which for performing heading movements is supported with the aid of bearing installations so as to be movable in relation to the basic element and which on a front side has installations for mounting a header die, characterized in that the bearing installations have a first articulated lever assembly (130) and a second articulated lever assembly (140) which is spaced apart from the former, wherein each of the articulated lever assemblies by way of a first pivot bearing (144A) is articulated on the basic element (110) and by way of a second pivot bearing (146A), which is disposed so as to be axially parallel with the first pivot bearing, is articulated on the header-die carrier (120) in such a manner that a parallelogram-type guide for the header-die carrier (120) is formed.

2. Heading device according to Claim 1, characterized in that the bearing installations exclusively include pivot bearings (134A, 136A, 144A, 146A) and no linear bearings.

3. Heading device according to Claim 1 or 2, characterized in that the pivot bearings (134A, 136A, 144A, 146A) are configured as pure friction bearings, without rolling elements being employed.

4. Heading device according to one of the preceding claims, characterized by a first hydraulic cylinder (150) for generating movements of the header-die carrier (120), wherein a cylinder unit (152) of the first hydraulic cylinder is coupled in an articulated manner to the basic unit (110) and a piston-rod unit (154) of the first hydraulic cylinder is coupled in an articulated manner to the header-die carrier (120), or vice-versa.

5. Heading device according to claim 4, characterized in that the first pivot bearings (134A, 144A) on the basic element (110) define a first bearing plane, that the second pivot bearings (136A, 146A) on the header-die carrier (120) define a second bearing plane, and that a central cylinder axis (W) of the first hydraulic cylinder (150) is disposed between the first and the second bearing plane.

6. Heading device according to claim 4 or 5, characterized in that the installations for mounting a header die on an angular outrigger (122) of the header-die carrier (120) are disposed in such a manner that these installations lie in the extension of a central cylinder axis (W) of the first hydraulic cylinder.

7. Heading device according to any of claims 4-6, characterized in that the installations for mounting a header die are disposed on the header-die carrier (120) in such a manner that an impact zone (AZ) for a chain link on the header die (190) lies in the extension of a central cylinder axis (W) of the first hydraulic cylinder (150) with an accuracy of

8. Heading device according to one of the preceding claims, characterized by a welding-electrode carrier (160) for carrying at least one welding electrode (162A, 162B) which, for performing a welding operation, is placeable in a placement direction which is transverse to a heading direction (A) onto an end portion of a chain link, wherein the welding-electrode carrier is coupled to the headerdie carrier by way of a third articulated lever assembly (170).

9. Heading device according to Claim 8, characterized by a second hydraulic cylinder (180) for generating movements of the welding-electrode carrier (160) in relation to the header-die carrier (120), wherein a cylinder unit (182) of the second hydraulic cylinder is coupled in an articulated manner to a carrier frame (185) which is fixedly connected to the basic unit, and a piston-rod unit (184) of the second hydraulic cylinder is coupled in an articulated manner to the welding-electrode carrier (160), or vice-versa.

10. Chain-welding machine (200) for flash-butt welding pre-bent chain links (300), characterized by a heading device (100) according to one of the preceding claims.