Chain link and a method for manufacturing a chain link

Abstract

Chain link (1) for a link chain (2), wherein the chain link (1) has two legs (4, 5) running parallel to each other, which are connected at their ends by radii (6, 7) and the legs (4, 5) and the radii (6, 7) of the chain link (1) are circular in their respective cross-sections (8, 9, 10, 11), wherein the legs (4, 5) have smaller cross-sectional areas (8, 9) compared to the cross-sectional areas (10, 11) of the radii (6, 7) and the chain link (1) is produced by radial forging with axial feed.

Description

The present invention relates to a chain link for a link chain according to the features of claim 1.The present invention further relates to a method for producing a chain link for a link chain according to the features of claim 6.Link chains in question are used in particular in mining and here in particular in underground mining. They require great strength for transferring the kinetic energy to extraction devices, for example as a planing chain or else as a conveyor chain. In such chain drives, the chains run via sprockets, in particular in an upper run and a lower run.For this purpose, the link chain consists of horizontal links which, in the installed state, run substantially horizontally and vertical links which, in the installed state, run substantially vertically. The horizontal and vertical links are each configured in each case as a chain link, in particular a revolving chain link. For this purpose, they each have two parallel legs. The legs are connected at their ends by a respective rounded portion. In the rounded portions, the horizontal and vertical chain links engage in each other. During their use, the chains are exposed to not only the tensile force to be transmitted, but also abrasive wear in particular.A reduction of the leg cross-sectional area with a constant cross-sectional area of the curvatures, for reducing the dead weight and the dimension of a link chain, is known in the prior art and is disclosed, for example, in DE 103 48 491 B3. For this purpose, the relevant chain link is formed by a forging process as a flat chain link with flattened legs.DE 10 2010 013 475 A1 discloses a chain strand which consists of individual horizontal links and vertical links. The horizontal wires are preformed by upsetting a rod.US 1 904 479 A discloses a reinforced anti-slip last chain and a method for its production.Further prior art is formed by DE 198 21 674 C1.The object of the present invention is to provide a chain link which is optimized and improved with respect to its own weight and the tensile force to be transmitted compared to the prior art.The aforementioned object is achieved in a chain link according to the features in claim 1.A further object of the present invention is to provide a production method with which a chain link can be produced with good freedom from forming and an improved material structure.This object is achieved according to the invention by a method for producing a chain link according to the features in claim 6.Advantageous embodiment variants of the present invention are described in the dependent claims.The chain link according to the invention is part of a link chain, which can also be referred to as a conveyor chain or a flat link chain and is used in particular in mining. The chain link has in each case two limbs running parallel to one another, wherein the limbs are connected to one another at the end side in each case via a rounded portion.The legs and the curvature of the chain link are circular in their respective cross sections, wherein the legs have a smaller cross-sectional area than the cross-sectional areas of the curvatures.Due to the reduced cross-sectional area in the legs compared to the rounded portions, it is initially realized that the chain link is lighter compared to a comparable chain link with a circumferentially identical cross-sectional area.The tensile force to be transmitted is not influenced due to the cross-sectional decrease in the legs. Consequently, the full tensile force to be transmitted, which is possible due to the cross-sectional area of the rounded portion, is available. Due to the lower dead weight of the link chain, the wear during operation of the link chain formed from the chain links is reduced. Due to the smaller cross-sectional areas, in particular in the region of the legs, material outlay for producing the link chain can be saved at the same time, which is why the material costs also decrease.According to the invention, the chain link is now characterized in that the chain link is produced by radial forging, also referred to as round forging or longitudinal forging, with axial feed. Radial forging is essentially free-form forging, in which the cross section of the workpiece is reduced in a deformation region using usually 3 or 4 counter-rotating dies or punches, which are arranged radially around the longitudinal axis of the workpiece in a plane perpendicular to the longitudinal axis of a workpiece. The workpiece is rotated between the individual punch strokes about its own longitudinal axis. Compared to the production of a link by a conventional forging process in which the workpiece is forged between a flat upper die and a flat lower die, radial forging has two essential advantages:Ability to forge low ductility and difficult to deform steels and alloys due to the favourable state of tension and elongation of the metal in the deformation zone.avoiding cracks or fractures on the material surface due to the radial arrangement of the punches.Furthermore, the reduction in cross section of the chain link semi-finished product produced by the radial forging, in particular in the region of the limbs, leads to a longitudinal deformation of the chain link semi-finished product in the longitudinal direction of the chain link semi-finished product in the deformation region. This in turn induces a longitudinally directed material structure in the deformation region. It has been shown here that, due to the longitudinally directed material structure, the load capacity of the chain links and in particular of the legs in the chain link longitudinal direction is increased when a tensile force is applied to the link chain. In addition, the rotationally symmetrical shape of the shaped chain link semi-finished product makes it possible to avoid errors during insertion into a bending device.According to the invention, although a circular cross section of the chain link semi-finished product is produced during production, the surface of the chain link semi-finished product has minimal irregularities due to the radial forging process. Thus, a chain link produced by radial forging can be clearly distinguished from chain links produced otherwise by its material structure and the surface condition.Preferably, a transition region is formed starting from the cross-sectional areas of the legs to the cross-sectional areas of the rounded portions at the respective end of the legs. The transition region can also be located partially in the region of the legs. In particular, the cross section of the transition region is circular in its longitudinal course.In particular, the diameter of the legs is between 5% and 15%, and preferably between 9% and 11%, smaller than the diameter of the rounded portion. It has been shown here that, at these diameter ratios, the advantageous longitudinal material structure induced by the radial forging is formed over the entire cross section of the legs. In other diameter ratios, the advantageous material structure can be formed, for example, only on the outer edges of the legs. These diameter ratios thus represent an optimum for the load capacity of the chain links or legs in the chain link longitudinal direction.Furthermore, in the side view of the central longitudinal axis plane, the inner contour line and the outer contour line of the chain link preferably have a circumferentially continuous oval shape. The oval shape is characterized by two parallel sides and a semi-circular configuration connecting the respective ends of the sides. This oval shape of the inner and outer contour lines is not interrupted at any point by a constriction, a web, a shoulder, a step shoulder, a slope or the like. It has been shown that this oval embodiment is particularly advantageous for the distribution of tension and the force flow within the chain link.With the method according to the invention, a chain link for a link chain is produced. The chain link has two limbs running parallel to one another, which are connected to one another at the end via rounded portions. The legs and the rounded portions of the chain link are circular in their respective cross sections, wherein the legs have smaller cross-sectional areas than the cross-sectional areas of the rounded portions. The chain link is produced by radial forging with the following method steps:providing a profiled rod, wherein the profiled rod is formed from a steel material,inserting the profiled rod into a radial forging machine and radially forging with a reduction in the diameter of the profiled rod in sections of length, so that the profiled rod is axially extended in the forged section of length, the diameter being reduced in the region of the subsequent legs,removing the radially forged chain link semi-finished product and forming it into a chain link and welding end-face ends of the formed chain link.A significant advantage of the invention is, on the one hand, a better freedom of forming, since both the cross-sectional areas on the curvatures to be produced later and the cross-sectional areas on the legs to be produced later can be produced individually, i.e. with high degrees of forming freedom. Because no material has to be removed at the length sections of the chain link produced with a smaller cross-sectional area, the material use for producing each chain link is smaller.The reduction in cross section of the chain link semi-finished product leads to a longitudinal deformation of the chain link semi-finished product in the deformation region, which in turn induces a longitudinally directed material structure. As has been shown, this is a further advantage essential to the invention, since the longitudinal structural structure increases the load capacity of the chain links and in particular of the legs in the longitudinal direction of the chain link. In addition, the rotationally symmetrical shape of the shaped chain link semi-finished product makes it possible to avoid errors during insertion into a bending device.In radial forging, pressure is repeatedly applied to the workpiece via a plurality of punches arranged around the axis of a workpiece.According to the invention, the workpiece is a profile rod which is formed from a steel material. The profiled rod has a length which is shorter than the circumferential length of the chain link to be produced later. The profiled rod is in particular solid and particularly preferably made of a hardenable steel material. The profiled rod preferably has a round cross section.This provided profile rod is clamped at its two ends or on one side into the radial forging machine, so that the latter can be rotated by the machine along its central longitudinal axis and moved back and forth in the axial direction. The punches arranged radially around the profiled rod then exert pressure on a defined length section of the profiled rod. The profiled rod is then rotated about its own axis and the punches exert a pressure on the profiled rod again. Thus, the cross-sectional area of the profile rod is reduced in the forged length section and the profile rod is axially stretched in the deformation region. This process is repeated until a predefined diameter is reached in the relevant longitudinal section of the profiled rod. According to the invention, at least the cross-sectional area in the region of the later legs is reduced. A reduction in size in the region of the subsequent roundings is also possible.After completion of the radial forging process, a rotationally symmetrical chain link semi-finished product is produced from the profile rod by forming. The length of the chain link semi-finished product corresponds substantially to the circumferential length of the chain link to be produced. The length sections of the chain link semi-finished product in the region of the later curvatures and the length sections of the chain link semi-finished product in the region of the later legs of the chain link are circular.The chain link semi-finished product is then removed from the radial forging machine and formed into a chain link. The two end-face ends are pressed together and welded together in a butt-like manner by the forming process. For this purpose, laser welding, but also resistance welding, can be carried out, for example. Alternatively, a friction welding process can also be carried out.The length sections with the smaller cross-sectional areas form the legs of the chain link and the length sections with cross-sectional areas that are larger in comparison form the rounded sections.The cross-sectional area of at least one rounded portion preferably corresponds to the cross-sectional area of the profiled rod.Preferably, at least one longitudinal section of a later rounding can also be reduced during radial forging.In particular, the chain link semi-finished product has a transition region between the length sections of the subsequent curvatures and legs. This preferably constitutes between 3% and 10% and particularly preferably between 4% and 7% of the total length of the chain link semi-finished product. It has been shown here that these conditions are particularly advantageous for the force flow and the tension distribution within the chain link.Furthermore, preferably, the welded end-face ends of the unformed chain link lie in the region of the limbs.In particular, the profiled rod is forged radially in the warm or semi-warm state. Particularly preferably, the chain link semi-finished product can also be transformed into the respective chain link in the warm state. It is also conceivable that the radial forging is carried out in the cold state or at room temperature.Optionally, it is further conceivable that the formed and welded chain link is tempered.Further advantages, features and properties of the present invention are the subject matter of the following description. Preferred design variants are shown in the figures. These serve to facilitate understanding of the invention.The following are shown: FIG. 1 shows a part of a link chain with chain links according to the invention in plan view, FIG. 2 shows a chain link according to the invention in plan view, FIG. 3 shows a sectional view through a chain link according to the invention along the section line A-A from FIG. 2, FIG. 4 shows a sectional view through a chain link according to the invention along the section line B-B from FIG. 2, FIG. 5 is a side view of a profiled rod, FIG. 6 is a side view of a chain link semi-finished product, FIG. 7 is a side view of a radial forging machine with a clamped profile rod, FIG. 8 is a sectional view of the radial forging machine taken along the line C--C of FIG. 7; and FIG. 9 is a sectional view of an alternative embodiment of the radial forging machine.In the figures, the same reference numerals are used for the same or similar items, although repeated description is omitted for the sake of simplicity.FIG. 1 shows a chain link 1 according to the invention in plan view, as part of a section of a link chain 2. The vertical links 3 connect the chain links 1, wherein the vertical links 3 are produced in another way. Not shown in detail, further chain links 1 in the form of horizontal links then link to the right and left, with reference to the plane of the drawing, followed by a further vertical link 3 and following.FIG. 2 shows the detailed view of a chain link 1 according to the invention in plan view. The chain link 1 has two parallel limbs 4, 5 which are connected to one another at the end by rounded portions 6, 7. The legs 4, 5 have cross-sectional areas 8, 9, each of which is circular, see FIG. 4 : The rounded portions 6, 7 also have cross-sectional areas 10, 11, each of which is likewise circular, see FIG. 3 : The cross-sectional areas 8, 9 of the legs 4, 5 are smaller than the cross-sectional areas 10, 11 of the rounded portions 6, 7. At the respective end 12, 13 of the legs 4, 5, a transition region 14, 15 extends toward the rounded portions 6, 7. The transition areas 14, 15 are also circular in shape. The transition regions 14, 15 extend from the respective end 12, 13 of the legs 4, 5 at an angle α of greater than 0 degrees to an angle of less than 45 degrees, so that the legs 4, 5 then transition into the rounded portions 6, 7.The inner contour line 16 and the outer contour line 17 of the chain link 1 have a continuous oval shape. The oval shape is not interrupted at any point by a constriction, a web, a shoulder, a step shoulder, a slope or the like.The diameters D 4, D 5 of the legs 4, 5 shown in FIG. 4 are between 4 mm and 6 mm smaller than the diameters D 6, D 7 of the curvatures 6, 7 shown in FIG. 3.FIG. 5 shows a profile rod 18, which is circular and rotationally symmetrical, with the diameter D 18.FIG. 6 shows a chain link semi-finished product 19 which has been produced from the radially forged profile rod 18. The chain link semi-finished product 19 has two length sections 20, the diameter D20 of which corresponds to the diameter D18 of the profiled rod 18, but can also be smaller. The length sections 20 form the region of the later curvatures 6, 7 of the chain link 1.Furthermore, the chain link semi-finished product 19 has the length sections 21 which correspond to the regions of the subsequent legs 4, 5. Thus, the diameters D 21 of the longitudinal sections 21 are equal to the diameters D 4, D 5 of the legs 4, 5.Between the longitudinal sections 20 and 21, a transition region 22 is arranged in each case. This corresponds approximately to the later transition regions 14, 15 of the chain link 1.The chain link semi-finished product 19 is connected at its front ends 23 to form the chain link 1.FIG. 7 shows a simplified illustration of a radial forging machine 24, in which the profiled rod 18 is arranged. The profiled rod 18 is clamped at its two ends by clamping means 25 in the radial forging machine 24. By means of the clamping devices 25, the profiled rod 18 can be rotated about its longitudinal axis and can also be moved back and forth in the axial direction. Arranged radially around the profiled rod 18 are oppositely directed punches 26. This can be seen in particular in FIG. 8. A pressure is applied to the profiled rod 18 by the punches 26, so that the latter is stretched in its axial direction. The cross-sectional area 27 of the profile rod 18 is thus reduced in the region machined by the punches 26. By axially displacing the profiled rod 18 in the left and right direction with respect to the plane of the drawing of FIG. 7, the entire profiled rod 18 can be gripped and forged by the punches 26.FIG. 9 shows an alternative embodiment variant of the radial forging machine 24 with 3 punches 26.Reference Number:1 Chain link 2 link chain 3 vertical links 4 legs 5 legs 6 curvature 7 curvature 8 cross-sectional area of 4 9 cross-sectional area of 5 10 cross-sectional area of 6 11 cross-sectional area of 7 12 end of 4 13 end of 5 14 transition region 15 transition region 16 inner contour line 17 outer contour line 18 profile rod 19 chain link semi-finished product 20 length section 21 length section 22 transition region 23 front ends 24 radial forging machine 25 clamp 26 punch 27 cross-sectional area of 18 D4 diameter of 4 D5 diameter of 5 D6 diameter of 6 D7 diameter of 7 D18 diameter of 18 D20 diameter of 20 D21 diameter of 21 α angle of 14, 15

Claims

Chain link (1) for a link chain (2), wherein the chain link (1) has two limbs (4, 5) running parallel to one another, which limbs are connected to one another at the end via rounded portions (6, 7), and the limbs (4, 5) and the rounded portions (6, 7) of the chain link (1) are of circular design in their respective cross sections (8, 9, 10, 11), wherein the limbs (4, 5) have smaller cross-sectional areas (8, 9) compared to the cross-sectional areas (10, 11) of the rounded portions (6, 7) and the chain link (1) is produced by radial forging with axial feed.Chain link (1) according to claim 1, characterised in that a transition region (14, 15) starts from the cross-sectional areas (8, 9) of the legs (4, 5) to the cross-sectional areas (10, 11) of the rounded portions (6, 7) at the respective end (12, 13) of the legs (4, 5).Chain link (1) according to claim 2, characterised in that the cross-section of the transition region (14, 15) is circular in its longitudinal course.Chain link (1) according to one of Claims 1 to 3, characterized in that the diameter (D4, D5) of the limbs (4, 5) is between 5% and 15%, and preferably between 9% and 11%, smaller than the diameter (D6, D7) of the rounded portions (6, 7).Chain link (1) according to one of Claims 1 to 4, characterized in that, in the case of a side view of the central longitudinal axis plane, the inner contour line (16) and the outer contour line (17) of the chain link (1) have a circumferentially continuous oval shape.Method for producing a chain link (1) according to Claim 1, characterized bythe following method steps: - providing a profile rod (18), wherein the profile rod (18) is formed from a steel material, - placing the profile rod (18) in a radial forging machine (24) and radially forging in the case of axial feed with a reduction in the diameter (D18) of the profile rod (18) in portions of the length, such that the profile rod (18) is axially extended in the forged portion of the length, wherein the diameter (D18) is reduced at least in the region of the later legs (4, 5), - removing the radially forged chain link semi-finished product (19) and forming it into a chain link (1) and welding end-face ends (23) of the formed chain link (1).Method according to claim 6, characterised in that the diameter (D18) of the profiled rod (18) corresponds to the diameter (D6, D7) of at least one rounded portion (6, 7).Method according to Claim 6 or 7, characterized in that the diameter (D18) of at least one length section (21) of a subsequent limb (4, 5) is reduced during radial forging.Method according to one of Claims 6 to 8, characterized in that a transition region (22) between the length sections (20, 21) of the subsequent curvatures (6, 7) and legs (4, 5) of the chain link semi-finished product (19) makes up between 3% and 10%, preferably between 4% and 7%, of the total length (L19) of the chain link semi-finished product (19).Method according to one of Claims 6 to 9, characterized in that the welded end-face ends (23) of the shaped chain link (1) are located in the region of the limbs (4, 5).Method according to one of Claims 6 to 10, characterized in that the profiled rod (18) is radially forged in the cold, warm or semi-hot state.Method according to one of Claims 6 to 11, characterized in that the shaped and welded chain link (1) is tempered.

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