Method for establishing rail fastening, method for increasing vibration resistance of tension springs for restraining track body elements, and rail fastening part

Abstract

A method for establishing a rail fastening, in which a track body element, such as for example a rail bottom 16 of a rail 8, is elastically held down by at least one hold-down part 6, such as for example a restraining arm, of a tension spring 1 in a final assembled position, the tension spring 1 consisting of tempered spring steel, the method comprising mounting the tension spring 1 on a base, the tension spring 1 being brought into a tensioned state by a hold-down device 12, 25, in which the tension spring 1 is brought into a tensioned state starting from a relaxed state by bending the hold-down part 6 along a spring bending path z, wherein during mounting the hold-down part 6 is bent in the direction of the spring bending path z to such an extent that the tension spring 1 is subjected to cold working and then at least partially relaxed.

Description

[Technical Field]

[0001] The present invention relates to a method for establishing a rail fastening, wherein a track body element, such as a rail bottom of a rail, is elastically held down by at least one hold-down, such as a restraining arm of a tension spring in a final assembled position, the tension spring consisting of tempered spring steel, the method comprising mounting the tension spring on a base, the tension spring being tensioned by a hold-down device, the tension spring being tensioned starting from a relaxed state by bending the hold-down along a spring bending path.

[0002] Furthermore, the present invention relates to a rail fastening device comprising a tension spring made of tempered spring steel and a hold-down device that is adjacent to a track body element and can be fastened to a base, in particular to a sleeper, a ribbed plate or an angle guide plate, wherein the tension spring can be or is in a tensioned state relative to the hold-down device in the final assembly position of the tension spring, by bending at least one hold-down part of the tension spring along a spring bending path, so that the hold-down part comes into contact with the track body element, in particular the rail bottom part of the rail, and elastically holds the track body element, starting from a relaxed state and being brought into a tensioned state. [Background technology]

[0003] Typically, the rails of the track body are assembled using a spring element, usually called a tension spring or tension clamp, and a suitable tensioning element or hold-down device to apply tension to the spring element. This tensioning element or hold-down device is usually a screw, so that the spring element is tensioned against the base, applying the required restraining force via its part that rests on the bottom of the rail. Tensioning can be achieved, for example, by connecting the hold-down device directly to the base that supports the rail and fastening system, or by attaching the hold-down device to an additional component, such as a plate, which is then rigidly connected to the corresponding base.

[0004] Widely used tension springs are those of the "e" shape and the "ω" shape. An "e" shape tension spring is described, for example, in EP 313 325 B1. An "ω" shape can be found, for example, in DE 3 243 895 A1.

[0005] Many embodiments of fastening systems with tension springs are known, which can be moved not only to a final assembly position, which is strictly determined relative to the rail bottom and the fastening part, but also to a positionally secured pre-assembly position. To achieve the pre-assembly position, the tension spring is attached in such a way that the part intended to hold down the rail bottom does not rest on the rail. In this way, railway sleepers can already be provided in the factory with a tension spring in the pre-assembly position and in a pre-tensioned state, so that after the rail has been laid at the construction site, the tension spring can be moved and tensioned to the final assembly position by moving it laterally with a certain amount of effort, so that the part intended to hold down the rail bottom rests on the rail bottom and elastically holds it down from above.

[0006] A disadvantage of prior art tension springs is that they are designed for only one installation direction or type. An installation direction is usually understood to be the direction in which a tension spring, already in a pre-tensioned state, is pressed onto the rail bottom. Tension springs that are designed to be installed transversely, i.e., pressed transversely to the longitudinal direction of the rail, are most often found. On the other hand, in longitudinal installation, the tension spring is moved longitudinally to its final installation position. Due to the limited available space, installing a rail longitudinally is advantageous, for example, for fastening rails in the area of ​​a switch. Conventional tension springs are adapted to their specific installation direction, especially for placement in areas of different stiffness. Therefore, they cannot be installed in a direction that deviates from that direction without additional measures, which makes a deviating installation direction completely impossible in most cases, even for geometric reasons alone.

[0007] Another problem with conventional tension springs is the occurrence of breakage and relaxation of the tension spring and the resulting loss of clamping force, particularly with tension springs that are pressed down by a screw.

[0008] Breakage often occurs in tension springs that are overstressed. In conventional rail fastening systems, overload protection is rarely provided. The purpose of overload protection is to limit the load acting on the tension spring, which is particularly useful when the rail is passed over it and is subject to strong up and down or strong tilting movements relative to the sleeper.

[0009] Another reason for tension spring fractures is poor fatigue behavior. In particular, it has been observed that fractures caused by vibration loads are subject to undesirable statistical variability, resulting in tension spring fractures despite being designed to be fatigue-resistant. Finally, vibration loads also lead to a reduction in the clamping force of tension clamps.

[0010] It is already known to subject tension clamps to cold working during the manufacturing process in order to increase their strength and achieve a higher yield point. Cold working is the plastic forming of metals below their recrystallization temperature in order to increase the dislocation density. This is described in relation to tension clamps, for example, in EP 2528702 A1, DE 2411195 A1 and U.S. Pat. No. 9,382,667 (B2). [Prior art documents] [Patent documents]

[0011] [Patent Document 1] EP313325B1 [Patent Document 2] DE3243895A1 [Patent Document 3] EP2528702A1 [Patent Document 4] DE2411195A1 [Patent Document 5] US Patent No. 9382667 (B2) Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention therefore aims to improve the fastening system and the method for establishing rail fastenings in such a way that the above-mentioned drawbacks can be overcome, in particular tension springs are created that have increased fatigue strength and that can reduce the loss of tension. [Means for solving the problem]

[0013] To achieve this object, the present invention provides, according to a first aspect, a method for establishing a rail fastening, in which a track body element, such as a rail bottom of a rail, is elastically held down by at least one hold-down part, such as a restraining arm of a tension spring in a final assembly position, the tension spring consisting of tempered spring steel, the method comprising mounting the tension spring on a base, the tension spring being tensioned by a hold-down device, the tension spring being brought into a tensioned state starting from a relaxed state by bending the hold-down part along a spring bending path, the tension spring being brought into a tensioned state starting from a relaxed state by bending the hold-down part along a spring bending path, the hold-down part being bent in the direction of the spring bending path to such an extent that the tension spring is subjected in places to cold working and then at least partially relaxed.

[0014] Therefore, according to the invention, it is envisaged that the tension spring is made of tempered spring steel, i.e. steel that has been subjected to a combined heat treatment consisting of quenching and subsequent tempering. The tension spring comprises at least one hold-down portion, such as one or two restraining arms, by which the raceway body element is elastically held down in its final assembly position. The spring force is applied by elastically bending the hold-down portion, while the tension spring is held down at the hold-down portion by a hold-down device.

[0015] According to the present invention, work hardening is performed during assembly of the tension spring, e.g., in a pre-assembly position, during movement of the tension spring from the pre-assembly position to the final assembly position, or in the final assembly position, by deforming at least one point of the tension spring beyond its elastic range, i.e., into its plastic range, thereby bending at least one hold-down portion to the extent that it is subjected to cold deformation. It is crucial here that the hold-down portion bends in the direction of the spring bending path that it will also experience during operation, i.e., to hold down the raceway body element. This ensures that cold working is performed at the points of the tension spring that are most heavily loaded during operation, so that the desired hardening occurs precisely at those points that are most susceptible to fracture as a result of sustained vibration loads during continuous operation. The cold working that occurs during assembly of the tension spring creates conditions similar to those experienced during operation, ensuring that the hold-down portion is subjected to bending in exactly the same direction as it is applied during operation. This eliminates the need for time-consuming and usually inaccurate simulations of operational or assembly situations in a manufacturing environment away from the raceway.

[0016] The points of greatest load are usually at the surface of the tension clamp, and as a result, cold working is carried out at least on the surface of the wire forming the tension spring.

[0017] In this context, elastically bending the hold-down portion for cold working refers to moving the hold-down portion relative to the held-down portion of the tension spring, starting from a tensioned state of the tension spring and moving to a tensioned state. Bending can occur by bending the hold-down portion, but the held-down portion is not displaced in the direction of the bending movement, i.e., held in place by a hold-down device. Alternatively, bending can be achieved by bending the held-down portion, but the hold-down portion is not displaced in the direction of the bending movement, i.e., held in place by a base or raceway body element. Thus, bending for cold working can be achieved by changing the distance measured in the direction of the spring bending path between the base or raceway body, on the one hand, and the hold-down device, on the other hand. In this way, cold working can be easily performed during the tension spring assembly process.

[0018] Carrying out cold working during the assembly process of the tension spring means that it is preferably carried out while the hold-down device is pressing down on the tension spring and before the rail vehicle is driven on the rail for the first time.

[0019] According to the invention, the tension spring is at least partially relaxed after cold working. This ensures that the operating range of the tension spring is in a region that does not lead to plastic deformation during normal operation. This is intended to prevent the tension spring from being subjected to further cold working during operation or to vibration loading up to its plastic limit. Partial relaxation therefore means that the tension spring is used in its final assembly position in a state of less stress than during cold working.

[0020] According to a preferred embodiment of the present invention, this can be achieved by limiting the maximum spring bending path of the hold-down portion in the final installation position of the tension spring with an overload protection portion, and by cold working the hold-down portion by bending the hold-down portion over a spring bending path that is equal to or greater than the maximum spring bending path limited by the overload protection portion. Overload protection can be achieved, for example, by abutting a track body element against a section of the tension spring that forms a stop, or by abutting the hold-down portion against a stop on a hold-down device.

[0021] The invention is based on the realization that the probability of a tension spring breaking under vibration loads can be significantly reduced if the tension spring is initially cold worked as defined by the invention and then loaded at each location only within its elastic deformation range, in particular the scatter of the probability of breaking around the desired value can be significantly reduced.

[0022] In this context, the invention relates according to a second independent aspect to a method for improving the fatigue behavior of a tension spring intended to hold down a track body element, such as a rail bottom of a rail, the tension spring consisting of tempered spring steel and having at least one hold-down element, such as a support arm, bendable along a spring bending path for elastically holding down the track body element, characterized in that the tension spring is provided for assembly into a track in which the maximum spring bending path of the hold-down element is limited by an overload protection element in such a way that no plastic deformation occurs anywhere in the tension spring within the maximum spring bending path, the method determining the maximum spring bending path and subjecting the tension spring to cold working by bending the hold-down element in the direction of the spring bending path beyond or up to the maximum spring bending path.

[0023] In a preferred design, the hold-down portion is bent for cold working to such an extent that the maximum principal normal stress corresponding to the 0.5% yield point, preferably the 1% yield point, is reached or exceeded at the most heavily loaded point of the tension spring. In tests, good results have been achieved when the 0.5% to 1.5% yield point, especially the 1% yield point, is reached. Improvements over the state of the art have also been observed when the 2% yield point is reached.

[0024] In normal operation, it is preferred that the tension spring not exceed said maximum principal normal stress at any point after cold working when the maximum spring bending path is reached, preferably 90% of the maximum principal normal stress, especially 85% of the maximum principal normal stress.

[0025] The principal normal stress can be determined by subjecting a sample of wire material forming the tension spring to a tensile test and constructing a stress-strain diagram from it. The principal normal stress can then be measured at the highest load points by attaching tension sensors within or on the surface of the tension clamp. Alternatively, the principal normal stress can be determined using a suitable simulation program using the finite element method (FEM). To this end, the geometry of the tension clamp, material properties, and boundary conditions (e.g., joints, contact surfaces, etc.) are defined in the simulation program. The force or stress generated by tensioning the clamp is then applied as a load to the model, and the simulation program performs a numerical analysis to calculate the resulting stresses and deformations at various locations on the model. This can then be compared with the stress-strain diagram to determine the degree of bending of the holddown corresponding to the desired yield point.

[0026] As already mentioned, the cold working according to the invention can take place in the final installation position of the tension spring, during the movement of the tension spring from the pre-installation position to the final installation position, or in the pre-installation position, where the pre-installation position is defined as the position of the tension spring where the tension spring is pressed onto the base by the hold-down device, but preferably where the hold-down part of the tension spring does not extend over the track body element.

[0027] Preferably, the cold working occurs in such a way that the tension spring is held under tension by a hold-down device during the movement of the tension spring from the pre-assembly position to the final assembly position by sliding a hold-down part on a sliding surface which is at least partially ascending in the direction of movement, the inclined surface of the sliding surface being dimensioned in such a way that the desired cold working is achieved at the point where the tension spring is most highly loaded.

[0028] In this connection, it is preferable that when the tension spring is moved from the pre-assembly position to the final assembly position, the hold-down portion drops from the sliding surface over the step portion onto the raceway body element to assume the final assembly position, thereby ensuring that the tension spring is at least partially relaxed after cold working, as is done in the present invention. At the same time, the step portion cooperates with the hold-down portion and acts as a rear stop preventing the hold-down portion from moving away from the final assembly position.

[0029] According to an alternative procedure, the hold-down device is formed by a fastening screw, and cold working is performed in the pre-assembly or final assembly position by holding down the tension spring with the fastening screw, and then the tension spring is at least partially relaxed by unwinding the fastening screw or sliding it over a step in the sliding surface.

[0030] Alternatively, the cold working in the pre-assembly or final assembly position can also be carried out using separate tools. Simple embodiments comprise, for example, laterally withdrawable spacers that can be inserted between the raceway body element and the hold-down in the final assembly position when the tension spring is in tension, or a sliding surface for a temporarily adjustable raised hold-down for displacement from the pre-assembly position to the final assembly position.

[0031] In principle, any suitable embodiment of a tension spring comprising at least one resiliently bendable hold-down portion, such as a restraining arm, can be used within the scope of the present invention. In a particularly preferred embodiment, the tension spring comprises a U-shaped main body with a U-bend, a first leg arranged on one side of the U-bend, and a second leg arranged on the other side of the U-bend, wherein a hook-shaped, inwardly bent hold-down portion is formed on the first leg (3) which can be tensioned against the hold-down device (12, 25), and the second leg is formed with a hold-down portion as the end of the second leg which is bent towards or away from the hold-down portion, the U-bend forming a twist so that a hold-down force can be applied to the track body element via the bent end.

[0032] According to a third aspect, the invention relates to a rail fastening device comprising a tension spring made of tempered spring steel and a hold-down device adjacent to a track body element and capable of being fastened to a base, in particular to a sleeper, a ribbed plate or an angle guide plate, wherein the tension spring can be or is in tension with respect to said hold-down device in its final assembled position by bending at least one hold-down part of the tension spring along a spring bending path so that the hold-down part comes into tension starting from a relaxed state and rests against the track body element, in particular the rail bottom of the rail, and elastically holds the track body element, wherein the tension spring is or can be cold worked during assembly by bending the hold-down part in the direction of the spring bending path and is at least partially relaxed in the final assembled position with respect to said bending.

[0033] In particular, the tension springs of the rail fastening system according to the invention are tension springs whose fatigue behavior has been improved before or during assembly by the method according to the second aspect of the invention, and which are therefore adapted so that they never leave the elastic deformation zone in operation, and which have only been previously brought into the plastic zone by overloading once, resulting in cold working.

[0034] In particular, the maximum spring bending path of the holding portion in the final assembly position of the tension spring is limited by the overload protection portion, and the cold working is performed by bending the holding portion over a spring bending path that is longer than the maximum spring bending path limited by the overload protection portion.

[0035] As already described in relation to the method according to the first aspect of the invention, a preferred design is such that the hold-down portion is bent due to cold working to such an extent that the maximum principal normal stress corresponding to the 0.5% yield point, preferably the 1% yield point, is achieved or exceeded at the most highly loaded point of the tension spring.

[0036] Preferably, the tension spring does not exceed the maximum principal normal stress at any point after cold working when the maximum spring bending path is reached, preferably 90% of the maximum principal normal stress, especially 85% of the maximum principal normal stress.

[0037] Cold working is preferably performed at least on the surface of the wire that forms the tension spring.

[0038] Preferably, the hold-down portion can be bent for cold working by pressing a tension spring downwards with a hold-down device.

[0039] Preferably, the tension spring can be attached to the base in a pre-assembly position where the hold-down portion does not overlap the track body element.

[0040] Preferably, the base has at least some portions with a sliding surface that rises, and when the tension spring is held down under tension by the hold-down device during movement of the tension spring from the pre-assembly position to the final assembly position, the hold-down portion slides on the sliding surface, so that the hold-down portion can be bent and / or partially relaxed for cold working.

[0041] Preferably, the base portion forms a step portion at the end of the sliding surface, and when the tension spring is moved from the pre-assembly position to the final assembly position, the hold-down portion passes over the step portion and falls onto the track body element to assume the final assembly position.

[0042] Preferably, the tension spring comprises a U-shaped main body with a U-bend, a first leg located on one side of the U-bend and a second leg located on the other side of the U-bend, the first leg (3) being formed with a hook-shaped inwardly bent restraining portion which can be tensioned against the hold-down device (12, 25), the second leg being formed with a hold-down portion as the second leg terminal end which is bent towards or away from the restraining portion, the U-bend forming a torsion portion so that a hold-down force can be applied to the track body element via the bent terminal end.

[0043] Preferably, the hold-down device forms or develops a tunnel-shaped recess into which the restraining portion of the tension spring is at least partially inserted.

[0044] Below are described further preferred embodiments of tension springs and rail fasteners that can be used in conjunction with the above-described aspects of the invention.

[0045] As already mentioned, the tension spring preferably comprises a U-shaped main body having a U-bend, a first leg located on one side of the U-bend and a second leg located on the other side of the U-bend, a hook-shaped inwardly bent restraint formed on the first leg which can be tensioned against the hold-down device, and a bent terminal portion formed on the second leg towards or away from the restraint, the U-bend forming a torsion portion so that a hold-down force can be applied to the track body element via the bent terminal portion.

[0046] By starting from a basic "U" shape, the tension spring has a hook-shaped restraining portion on one leg of the U-shape and a terminal portion on the other leg of the U-shape that is bent toward or away from the restraining portion, thereby achieving an asymmetrical shape that is easy to manufacture and allows for both lateral and longitudinal assembly. In both lateral and longitudinal assembly, the bent terminal portion forms the part of the tension spring that is involved when a holding-down force is applied to the track body element or rail bottom.

[0047] The design of the tension spring is similar to the "E" type known from the prior art, with the difference that the "E" type has an additional bend at the end. This bend can be towards or away from the tension spring's restraint. Preferably, the bend extends towards or away from the tension spring's restraint. According to a preferred embodiment, the bend extends at an angle of 80-100°, preferably about 90°, relative to the second leg. This applies both to designs with the bend towards the tension spring's restraint and to designs with the bend away from the tension spring's restraint. The advantages of the bend are evident in both lateral and longitudinal assembly with a restraining device, as will be explained in more detail below.

[0048] In some embodiments of the invention, the U-shaped portion formed by the U-bend, the first leg and the second leg may include a configuration in which the first leg is minimized, so that the U-bend transitions directly into the arresting portion, as it were, whereas in other embodiments the first leg has a constant length, such as a length substantially corresponding to the length of the second leg, and in particular is straight.

[0049] The hook-shaped restraining portion extending from the first leg of the U-shaped portion is used to be restrained in tension by the restraining device when a torsional force is applied from the bent end to the twisted portion formed by the U-shaped bend of the tension spring. In this case, the hook-shaped restraining portion is bent inward, which is understood to mean that the hook-shaped restraining portion is bent into the space between the two legs of the U-shaped portion. Preferably, the hook-shaped restraining portion on the side of the first leg forms the end of the tension spring, i.e., the free end of the portion bent into the hook portion is located between the two legs of the U-shaped portion.

[0050] In this regard, in a preferred embodiment, the restraining portion includes a free end portion connected to the first leg by a hook-shaped bend and disposed between the first leg and the second leg.

[0051] According to a further preferred embodiment of the invention, the hook-shaped bend of the restraining part is a bend of substantially 180°, whereby the free end of the restraining part is substantially parallel to the first leg at least in parts. The expression "substantially 180°" means that the angle is 180°, but can also be between 175° and 185°.

[0052] The hold-down force is provided, at least in part, by torsional loading on the torsion section formed by the U-bend of the tension spring, causing the second leg extending from the U-bend to the bend terminal end to bend resiliently in response. Thus, the second leg forms a bendable spring arm, while the remainder of the tension spring can be as flat as possible to minimize the overall height of the tension spring and the raw material consumption for the tension spring.

[0053] In this regard, in a preferred embodiment, the first leg and the free end of the restraint are adapted to provide a flat bearing surface in an unloaded state, which may serve, for example, as a support for a hold-down device, where the flat state refers to the unloaded state of the tension spring, since the restraint may twist slightly while the tension spring is under tension.

[0054] In the unloaded state, the free ends of the first leg and restraining portion may have their respective central axes lying, preferably throughout their extent, in a central plane that is preferably parallel to the flat receiving surface. For example, in the case of a circular cross section, the centerlines of the corresponding portions are centerlines or axes that pass through the center of the circle.

[0055] However, the free end of the first leg and the restraining portion may lie in the same plane in an unloaded state, with their respective central axes lying in the central plane, which also provides a flat bearing surface and prevents the first leg and the restraining portion, including the hook-shaped bend, from bending out of said plane.

[0056] The design of the U-bend of the tension spring can also contribute to achieving the flattest possible structure, preferably by having the free end of the restraining part at least partially, preferably completely, overlap the U-bend when viewed in the longitudinal direction of the free end.

[0057] However, to ensure sufficient bending of the spring, the bending end of the tension spring may be bent out of said plane when unloaded, in this connection a preferred design is such that the bending end is at a vertical distance from the central plane or flat bearing surface when unloaded.

[0058] If the entire restraint, including the hook bend and first leg, lies in the same plane, this means that the unloaded hook bend and the bend termination define the maximum overall height of the tension spring measured perpendicular to the center plane or flat receiving surface, which allows for a very flat tension spring design.

[0059] In particular, the overall height of the tension spring in an unloaded state may correspond to 1.5 to 3 times the diameter of the wire forming the tension spring in the restraining portion.

[0060] Preferably, in plan view, the bent end portion overlaps the hook-shaped bend in a virtual extension. This means that in a top view of the tension spring, the bent end portion overlaps at least partially with the hook-shaped bend in a virtual extension. For a horizontal assembly of the tension spring, this means that the hook-shaped bend would be above the rail bottom in the final assembly position, thereby forming the overload protection.

[0061] In conventional methods, tension springs consist of spring rods and can therefore be manufactured in one piece from the corresponding original product. This is done by bending an originally straight spring rod several times. If the hook-shaped restraint, U-shaped bend, and bent end are all bent in the same direction, as is preferred, the tension spring can be manufactured in three bending steps. In the first step, the hook-shaped restraint is bent, in the second step, the U-shaped bend is made, and in the third step, the bent end is made. These three bending steps can also be performed in a single circular motion if the three bends are performed in the same direction of rotation. The bends can all be performed in the same plane, or the bending of the individual parts out of a common plane can be performed simultaneously with the bending.

[0062] The tension spring is preferably circular, although oval, elliptical, etc. cross-sectional shapes are also contemplated.

[0063] Due to the relatively simple geometry of the tension spring according to the invention, its mechanical properties can be easily adapted to the respective requirements by changing a few geometric parameters while maintaining the basic shape. For example, the length of the second leg of the U-shaped section, and thus the length of the lever arm acting on the torsion section, determines the stiffness of the tension spring. By selecting the thickness of the spring rod, the tension, pressure force and stiffness can be controlled. The radius of the U-shaped bend also controls the tension and stiffness of the tension spring.

[0064] Preferably, the second leg in its unloaded state has a vertical distance from the central plane or flat receiving surface that continuously increases in the direction of the bent end portion, so that the restraining device can restrain the restraining part and apply the resulting torsional load to the torsion part of the tension spring, thereby applying a restraining force to the bottom of the rail through the bent end portion.

[0065] In particular, this means that in the unloaded state, the second leg is inclined at an acute angle relative to the central plane or flat receiving surface. The acute angle can be between 5° and 20°. When the tension spring is tightened, the acute angle is reduced from the unloaded state, and the tension spring is bent in such a way that, for example, in the tightened state, it is only at an angle of 0° to 5°. This angle may be relaxed to 5° to 10° if the system is fastened with a smaller hold-down force. In this tensioned state, a torsional moment acts on the torsion part of the tension spring, in particular around an axis perpendicular to the axis of the first leg and forming a tangent to the U-bend.

[0066] The hold-down force acting from the bend end portion on the rail bottom and the corresponding reaction force acting from the hold-down device on the restraining portion of the tension spring form a pair of forces that further stress the torsional portion, causing it to bend about an axis perpendicular to the axis of the torsional moment, resulting in a corresponding bending about this axis. This bending causes the bend end portion of the tension spring to have a different angle with respect to the support surface at the rail bottom in the unloaded state than in the loaded state. According to a preferred embodiment of the invention, the bend end portion is provided with a bearing surface for resting on a track body element that extends upward at an acute angle relative to the central plane or flat bearing surface in the unloaded state, so that the bend end portion is oriented substantially horizontally under load to provide a corresponding bearing surface against the rail bottom. The angle between the bend end portion and said plane may preferably be between 2° and 8°, in particular between 5° and 7°. This angle decreases under load due to the above-mentioned bending moment and is preferably between 0° and 1° under loaded conditions.

[0067] When the present invention refers to the angle between two parts of a tension spring or the plane in which the parts lie, this refers to the centerline of the corresponding parts, i.e., in the case of a circular cross section, the centerline or axis passing through the center of the circle.

[0068] The tension spring of the present invention is designed to be usable with various types of hold-down devices.

[0069] In a first assembly variant, the restraining part of the tension spring is inserted into the tunnel-shaped recess of the hold-down device transversely to the longitudinal direction of the rail towards the rail, so that in the final assembly position of the tension spring the hook-shaped bent part preferably extends above the bottom of the rail.

[0070] In a second assembly variant, the restraining part of the tension spring is inserted parallel to the longitudinal direction of the rail into the tunnel-shaped recess of the hold-down device, so that the second leg preferably overlaps the rail bottom.

[0071] From a design point of view, the first and second assembly variants can be realized in that in the longitudinal extension of the free end and in plan view, i.e. in vertical projection onto a central plane or a flat receiving surface, a gap is arranged between the bent end portion and the free end of the restraining part on the side facing the second leg of the free end.

[0072] In a further assembly variant, a free space can be provided between the first leg and the free end of the restraining part, which is penetrated by the threaded shank of the fastening screw forming the hold-down device, and in which the fastening screw can be moved in the longitudinal direction of the first leg, the threaded shank of the fastening screw being larger than the diameter of the wire forming the tension spring of the restraining part, and preferably the inner diameter of the hook-shaped bend is equal to or greater than the radius of the screw shank. Due to this mobility, the tension spring can be moved from a pre-assembly position to a final assembly position when held down by the fastening screw, and vice versa. The maximum amount of movement is achieved when the inner diameter of the hook-shaped bend is equal to or greater than the radius of the screw shank.

[0073] Overall, a compact, flat tension spring is provided that is flexible to use and inexpensive to manufacture due to its low material requirements, preferably in which the tension spring, in plan view, i.e., perpendicular projection onto a central plane or flat receiving surface, lies within a minimally enclosing rectangle with an aspect ratio of 1:1.5 to 1:1, preferably 1:1.1 to 1:1.

[0074] According to a further preferred embodiment, the diameter of the wire forming the tension spring is at least 1 / 7, preferably at least 1 / 6, of the short side of the rectangle that minimally encloses the tension spring in plan view.

[0075] Specifically, the bend termination is located within a corner of a square that is a rectangle that minimally encloses the tension spring in plan view, and that square has a maximum area of ​​1 / 9 of the enclosing rectangle.

[0076] With regard to the rail fastening device, in a further development it comprises a tension spring according to one of the above-mentioned embodiments and a holding-down device adjacent to the track body element which can be fastened to a base, in particular to a sleeper, a ribbed plate or an angle-guiding plate, and in the mounted state of the tension spring, the bent end part is spring-loaded and supported by the holding-down device in such a way that the restraining part can hold down the track body element, in particular the rail bottom part of the rail.

[0077] In this case, when the tension spring is installed, the hold-down device preferably rests not only on the free end region of the restraining part but also at least partly on the first leg.

[0078] The tension spring can be pressed on without a screw or by a screw. To achieve the screw-free alternative, in a preferred design the hold-down device has or forms a tunnel-shaped recess into which the restraining part of the tension spring can be at least partially inserted.

[0079] Depending on whether the tension spring is assembled transversely or longitudinally of the rail, the restraining part of the tension spring can be inserted into a tunnel-shaped recess transversely or parallel to the longitudinal direction of the rail.

[0080] In designs with tension springs that can be inserted transversely to the rail, the tunnel-shaped recess is preferably open on the side facing the track body element, specifically the rail bottom, and the hook-shaped bend protrudes from the tunnel-shaped recess in the tension spring's final installation position and rests on the track body element, specifically the rail bottom. In this way, the hook-shaped bend forms an overload protection element when it protrudes beyond the track body element. For this purpose, the hook-shaped bend is arranged so that there is a vertical gap between the track body element to be held down, specifically the rail bottom, and the hook-shaped bend of the tension spring. Any upward movement of the track body element within this vertical gap is elastically absorbed by the bent end of the tension spring. However, if excessive upward movement occurs, the track body element to be held down hits the hook-shaped bend and thus prevents further lift, ensuring that the tension spring remains within the allowable path and is not overloaded.

[0081] In the variant with a tension spring that can be inserted transversely to the longitudinal direction of the rail, the pre-installation position of the tension spring can be simply achieved by first inserting the tension spring so that it is firmly received in the tunnel-shaped recess, but the hook-shaped bend does not yet protrude from the tunnel-shaped recess facing the track body element to be held down, and the bent end does not yet rest on the track body element. To reach the final installation position, the tension spring is further driven in the direction of the track body element until the bent end presses against the track body element from above.

[0082] In both variants with tension springs that can be inserted transversely to the length of the rail and in variants with tension springs that can be inserted longitudinally of the rail, it is preferred that the hold-down device has a ramp that rises in the insertion direction and on which the bent end section slides during insertion, so that the end section is gradually preloaded during insertion.

[0083] Particularly preferably, the ramp has a first rising ramp section, a second rising ramp section and an intermediate section therebetween on which the bent end portion of the tension spring rests in the pre-installed position, for example the intermediate section may have a recess in which the bent end portion of the tension spring can engage and remain in the pre-installed position.

[0084] In this connection, in a preferred further development, a step is formed at the end of the ramp, through which the bent end portion passes when it reaches the final assembly position where it rests on the track body element, in particular on the rail bottom, and the step forms a rear stop that ensures that the end portion does not leave the final assembly position.

[0085] In variants with tension springs that can be pressed into the longitudinal direction of the rail, overload protection can be achieved by hold-down devices with spaced stops that overlap the bent end when the tension spring is installed, such stops having the effect of limiting the lift of the bent end.

[0086] The fastening system can also be used to fasten a base rail in the area of ​​a switch, in which case the hold-down device can be combined or connected to a sliding seat on the side of the base rail facing the tongue rail, preferably in such a way that the hold-down device forms at least part of the sliding surface for the tongue rail. In this connection, in a preferred embodiment, the fastening system comprises a sliding seat associated with the base rail and having a sliding surface for the tongue rail, the hold-down device having a further sliding surface preferably flush with the aforementioned sliding surface. Alternatively, the upper surface of the hold-down device can be arranged lower than the sliding surface of the sliding seat.

[0087] Preferably, the further sliding surface, like the sliding seat itself, extends in the direction of the base rail so as to overlap the rail bottom of the base rail at a distance.

[0088] Preferably, the hold-down device associated with the sliding seat and the hold-down device arranged on the opposite side of the base rail may be formed integrally with the sliding seat plate.

[0089] As already mentioned, one advantage of tension springs is their wide applicability. Thus, as already mentioned, tension springs can be fastened not only without screws but also with sleeper screws. In this connection, the fastening system according to the invention is preferably such that the hold-down device is formed by a fastening screw that can be screwed into the base, in particular the sleeper or the plate, or by a hook-shaped bolt with a nut that is suspended in the base, in particular the ribbed plate, and both of which are designed with their threaded shanks and / or threads passing through the free space between the first leg of the tension spring and the free end of the restraining part, to hold down the tension spring in the region of the restraining part and, where appropriate, the first leg.

[0090] A pre-assembly position is also possible in a simple manner with this type of fastening. This can be achieved by first screwing the tension spring downwards in the pre-assembly position. The rail is then inserted and, with the tension spring screwed downwards, is moved to the final assembly position. For this purpose, it is no longer necessary to loosen the screw after inserting the rail and then tighten it to the final tightening torque after the tension spring has been pressed into the final assembly position, since, even if the screw has been tightened to the final tightening torque in the pre-assembly position, the tension spring can easily be moved from the pre-assembly position to the final assembly position by hand or with a mechanical tool.

[0091] To ensure that the tension spring remains movable between the pre-installation position and the final installation position in the screwed-down state, a preferred embodiment of the invention provides a stop on the base and / or on the hold-down device that limits the screw-in depth of the hold-down device and preferably cooperates with the head or nut of the fastening screw, thereby limiting the hold-down force on the tension spring. The stop thus serves to define the screwed-down or tightened state of the tension spring in such a way that the tension spring remains movable between the pre-installation position and the final installation position. Preferably, the stop defines a minimum vertical distance between the hold-down device and the base, which is equal to or greater than the unloaded diameter of the wire forming the tension spring in the region of the hold-down device, and which preferably does not exceed 1.2 times the wire diameter.

[0092] The final tightening torque or deviations in the clamping force of the screw achieved by the final tightening torque do not have any additional negative effect on the desired tension of the tension spring once it has been tensioned towards the stop, which means that in the final assembly position it is not necessary to check the distance between the tension spring and the rail bottom, as is required for example in some common fastening systems with tension springs.

[0093] The stop portion can preferably offset a predominantly one-sided load on the screw by providing at least one contact point with the screw through which a force acts on the screw that at least partially offsets the one-sided load on the screw when the screw or nut is tightened to a final tightening torque.

[0094] Various variants are possible for moving the tension spring from the pre-assembly position to the final assembly position, in particular the tension spring with the bent end can be rotated or moved transversely to the longitudinal direction of the rail between the pre-assembly position and the final assembly position when the hold-down device is fastened, i.e. in particular when fastened under tension as determined by the above-mentioned stops.

[0095] Preferably, the base is designed in the region of the contact surface passed by the tension spring during movement in such a way that there is no or only a gradual increase in the pretension of the tension spring when the tension spring is moved on the base along its movement path from the pre-assembly position to the final assembly position, so that damaging stresses, especially in shear, are eliminated when the tension spring is moved for all components stressed in the process. For this purpose, possible designs of the base in contact with the contact surface passed by the tension spring on the base during movement do not have grooves and notches transverse to the movement direction of the tension clamp.

[0096] In order to prevent the tension spring from moving automatically or unintentionally from the pre-assembly position to the final assembly position, the base preferably forms a step that slopes in the direction of movement of the tension spring, so that the bent end drops off the step onto the rail bottom when the tension spring moves from the pre-assembly position to the final assembly position, the step thus forming a rear stop for the bent end that prevents it from moving away from the final assembly position.

[0097] In the pre-installation position, the tension springs are advantageously arranged on the base in such a way that the insertion of the rail between the pre-installation tension springs is not hindered. This means that the pre-installation tension springs can be attached to the sleeper before the rail is laid, so that after the rail has been laid, the tension springs only need to be moved to the final installation position using a suitable tool. This is preferably achieved by the base having contact surfaces for the rail bottom and the hold-down device, or by fastening screws arranged in such a way that the tension springs do not protrude beyond the contact surfaces in the pre-installation position.

[0098] In particular, the distance between the screw axis and the contact side may be equal to or greater than the diameter of the wire forming the tension spring.

[0099] For safety reasons, it should be ensured that the fastening screw is not unintentionally loosened when the tension spring is moved from the pre-assembly position to the final assembly position. For this purpose, the situation can be exploited in which the asymmetric tension spring according to the invention is tensioned mainly on one side of the screw towards the screw head or nut in a tensile state, while on the other side of the screw it is supported on a base.

[0100] If the direction of rotation of the screw thread and the assembly position or asymmetry of the tension spring are matched, the screw is loaded in the sense of being tightened when the tension spring moves from the pre-assembly position to the final assembly position. In other words, the nut of the fastening screw or hook bolt mainly presses against the free end of the restraining part of the tension spring and the first leg of the tension spring is supported on the base, and the direction of tightening of the screw thread of the fastening screw or hook bolt is designed in such a way that the free end of the restraining part directly or indirectly applies a torque in the tightening direction to the nut of the fastening screw or hook bolt when the tension spring is moved transversely to the longitudinal direction of the rail from the pre-assembly position to the final assembly position.

[0101] For fastening systems with tension springs that can be rotated between a pre-assembly position and a final assembly position, the rotation from the pre-assembly position to the final assembly position is performed in the direction of tightening of the fastening screw or the nut of the hook bolt, so that in this case the fastening screw or the nut of the hook bolt is directly or indirectly subjected to a torque in a certain rotational direction.

[0102] The invention is explained in more detail below with reference to schematic examples of embodiments shown in the drawings. [Brief explanation of the drawings]

[0103] [Figure 1] 1 is a perspective view of a tension spring that may be used within the scope of the present invention; [Figure 2] FIG. 2 is a top view of the tension spring according to FIG. 1; [Figure 3] FIG. 3 is a diagram based on arrow III in FIG. 2. [Figure 4] 4 is a diagram based on arrow IV in FIG. 2. [Figure 5] 2A and 2B are diagrams of a first design of a rail fastening device using tension springs according to FIG. 1; [Figure 6] FIG. 6 is a detailed view of FIG. 5. [Figure 7] 2A and 2B are diagrams of a second design of a rail fastening device using tension springs according to FIG. 1; [Figure 8] FIG. 8 is a detailed view of FIG. [Figure 9] FIG. 9 is a perspective view of the hold-down device according to FIGS. 7 and 8; [Figure 10] FIG. 10 is a side view of the hold-down device according to FIG. 9; [Figure 11] 1. FIG. 4 shows a third design of the rail fastening device using tension springs according to FIG. [Figure 12] 12A and 12B are diagrams of modified designs of the rail fastener of FIG. 11. [Figure 13] 1. FIG. 4 shows a fourth design of the rail fastening device using tension springs according to FIG. [Figure 14]13 is a diagram of the design according to FIG. 12 with a modified angle-guiding plate. [Figure 15] 15 is a diagram of the angle-guiding plate according to FIG. 14. FIG. [Figure 16] FIG. 15 is a front view of the angle guide plate according to FIG. 14. [Figure 17] 15 is an exploded view of the angle-guiding plate according to FIG. 14 , a bottom view thereof; FIG. [Figure 18] FIG. 13 shows a view of the rail fastening device according to FIG. 12 in a pre-assembly position. [Figure 19] 13 shows a view of the rail fastening device according to FIG. 12 in the final assembled position. [Figure 20] FIG. 19 is a cross-sectional view of the rail fastening device according to FIG. [Figure 21] FIG. 20 is a cross-sectional view of the rail fastening device according to FIG. [Figure 22] 10A and 10B are views of alternative designs of rail fasteners in a pre-assembly position. [Figure 23] 23 shows a view of the rail fastening device according to FIG. 22 in the final assembled position. [Figure 24] FIG. 23 is a cross-sectional view of the rail fastening device according to FIG. 22. [Figure 25] FIG. 24 is a cross-sectional view of the rail fastening device according to FIG. 23. [Figure 26] FIG. 26 is a perspective view of an angle guide plate used in the rail fastening device according to FIGS. 22 to 25. [Figure 27] FIG. 20 is another cross-sectional view of the rail fastening device according to FIG. [Figure 28] Illustrates the cold deformation of a tension spring using a stress-strain diagram. DETAILED DESCRIPTION OF THE INVENTION

[0104] 1 shows a tension spring 1 having a U-shaped main portion with a U-bend 2, a first leg 3 located on one side of the U-bend 2, a second leg 4 located on the other side of the U-bend 2, a stopper 5 formed on the first leg 3 and bent inward into a hook shape so that it can be tensioned against a hold-down device, and a terminal end 6 formed on the second leg 4 and bent toward or away from the stopper. The bent terminal end 6 forms a hold-down portion for holding down the rail bottom of a rail. The stopper 5 has a free end 7.

[0105] In Figure 2 it can be seen that a gap x is arranged between the bent end 6 and the free end 7 of the restraining part 5, as seen in plan view, on the side of the free end 7 facing the second leg 4. This gap allows the restraining part of the tension spring 1 to be inserted, hook-shaped bent part first, into the tunnel-shaped recess in the hold-down device (see Figures 5 to 8).

[0106] 3 and 4, it can be seen that the first leg 3 and the restraining part 5, including the free end 7, lie in the same plane, thereby forming a flat bearing surface a. Since the tension spring 1 is made from a bent wire with a circular cross section, this also means that the central axes of said parts lie in a common central plane b. In the unloaded state, the free end 7 of the restraining part 5 is further arranged so that, when viewed in the direction of the longitudinal extension of the free end 7, it completely overlaps the U-bend 2 (FIG. 3). In other words, starting from the first leg 3, the U-bend also lies in the same plane as the first leg 3 and the restraining part 5, including the free end 7, at least up to said overlapping part with the free end 7.

[0107] However, further along the U-bend 2, i.e., towards the second leg 4, the U-bend 2 is bent downwards and out of plane a or b, so that the vertical distance of the second leg 4 from plane a or b increases until it reaches the bend end 6. In FIG. 4, it can be seen that the second leg 4, with its central axis c, encloses an acute angle β with the stopper 5 and the plane a or b of the first leg 3. This results in the spring bending required to elastically hold the track body element or rail bottom against the bend end 6. The direction of the spring bending path is indicated by arrow z in FIG. 4. This is the direction in which the bend end 6 is bent to such an extent that cold working occurs at the point where the tension spring is most highly loaded, thereby increasing the fatigue strength of the tension spring.

[0108] In FIG. 3, the bent end portion 6 has a bearing surface d for resting on the track body element, and when viewed in the direction of arrow III, the bearing surface d is slightly inclined upward in the unloaded state, and an acute angle α exists between the bent end portion 6 or bearing surface d and the plane a or b of the restraining portion 5 and the first leg portion 3.

[0109] FIG. 5 shows a rail 8 with a plate 10 placed on a base plate 9 and fastened to a sleeper 11 in a sandwiched manner. On each side of the rail 8, a tension spring 1, as seen in FIG. 1, is fastened by being inserted into a tunnel-shaped recess 13 in a holding-down device 12. In the final assembled position of the tension spring 1 shown in FIG. 5, the spring presses with its bent end 6 against the rail bottom 16 of the rail 8, optionally with an insulator sandwiched between them. The holding-down device 12 is suitably attached to the plate 10. For example, the plate 10 and the holding-down device 12 are made into one piece and bolted to the sleeper 11. Alternatively, the plate 10 may have a tie-down on its underside that is fixed with concrete into the sleeper 11 when the sleeper 11 is poured from concrete.

[0110] Figure 6 shows an enlarged view of the tension spring 1 inserted into the tunnel-shaped recess 13. It can be seen that the tension spring is inserted at its stop 5 into the tunnel-shaped recess 13 in the direction of the arrow 14, i.e., in the longitudinal direction of the rail, so that the bent end 6 rests on the rail bottom 16. During insertion in the direction of the arrow 14 from a pre-assembly position (not shown) to the final assembly position shown in Figure 6, the bent end 6 slides on a ramp 17 rising in the insertion direction 14 and falls onto the rail bottom 16 over a step formed at the end of the ramp 17. On the side of the hold-down device 12 facing the rail bottom 16, a stop 18 is also formed which overlaps the bent end 6 at a distance and acts together with the end 6 as an overload protection device.

[0111] The ramp 17 is designed so that the bent end 6 is bent at its highest point to such an extent that the tension spring 1 reaches a zone where it is plastically deformed at least at its most highly loaded points and is therefore subjected to cold working. The tension spring 1 is partially relaxed when it falls onto the rail bottom 16. The above-mentioned overload protection limits the spring bending path of the bent end 6 during operation to such an extent that plastic deformation no longer occurs anywhere in the tension spring 1.

[0112] 7 and 8 show a rail fastening device in which the tension spring 1 is inserted into the tunnel-shaped recess 13 (see FIG. 9) of the hold-down device 12 transversely to the longitudinal direction of the rail, i.e., in the direction of arrow 14. When the bent end 6 is pressed in the direction of arrow 14, it also slides along a ramp 17 formed on the outside of the hold-down device 12 and falls onto the rail bottom 16 over a step 19 formed at the end of the ramp 17. An insulator 16 can be arranged between the tension spring 1 and the rail bottom. In the final assembly position shown in FIG. 8, the deterrent 5 projects from the tunnel-shaped recess 13 on the side facing the rail 8 and forms a stop that overlaps the rail bottom 16 with the optional insulator 15 at a distance to form an overload protection.

[0113] The ramp 17 is designed so that the bent end 6 is bent at the highest point of the ramp 17 to such an extent that the tension spring 1 reaches a zone where it is plastically deformed at least at its most highly loaded points and is therefore subjected to cold working. The tension spring 1 is partially relaxed when it falls onto the rail bottom 16. The above-mentioned overload protection limits the spring bending path of the bent end 6 during operation to such an extent that plastic deformation no longer occurs anywhere in the tension spring 1.

[0114] The hold-down device 12 used in Figures 7 and 8 is shown in more detail in Figures 9 and 10, where it can be seen in detail that the ramp 17 consists of three sections adjoining one another in the insertion direction 14. The ramp 17 comprises a first ascending ramp section 20, a second ascending ramp section 22 and a flat intermediate section 21 between them, with the bent end 6 of the tension spring 1 on the intermediate section 21 in the pre-assembly position. Furthermore, Figures 9 and 10 show anchoring parts 31 which can be used when the hold-down device is concrete-fixed or cast-fixed in a concrete sleeper 11 or, for example, a plastic sleeper 11.

[0115] 11 shows a modified design in which the tension spring 1 is tensioned by a hold-down device in the form of a fastening screw 25. The fastening screw 25 is fastened to a rib 24 as a hook-and-bolt or screwed into the sleeper 11 so that its threaded shank or thread passes through the free space between the first leg 3 of the tension spring 1 and the free end 7 of the restraining part 5. The free space between the first leg 3 and the free end 7 of the restraining part 5 is slot-shaped in this case, so that the tension spring 1 can be moved between a pre-assembly position and a final assembly position shown in FIG. 12. In the illustrated embodiment, the rail base 10 is a ribbed plate, the ribs 24 of which determine the position of the rail bottom 16 of the rail 8 on the sleeper 11.

[0116] In a modified design shown in FIG. 12, the fastening system comprises, on each side of the rail 8, an angle guide plate 26 which engages with a groove 27 in the sleeper 11 by means of a rib formed on its underside.

[0117] 13 shows the use of the rail fastening device according to the invention in the area of ​​a switch having a base rail 8 and a tongue rail 28 that can be moved between a remote position and a contact position. In this case, the tongue rail 28 slides with its rail bottom resting on a sliding seat 29, and the holding down devices 12 have further sliding surfaces on their upper sides that are flush with the sliding surfaces of the sliding seat 29. The holding down devices 12, arranged on both sides of the base rail 8, can be formed in one piece with a base plate 30.

[0118] The design according to Fig. 14 essentially corresponds to the design according to Fig. 12, but the angle guide plate 26 is a two-part design. As shown in Figs. 15 and 17, the angle guide plate 26 comprises a first part 32 facing away from the rail and a second part 33 facing the rail. The first part 32 is fitted into the groove 27 when assembled and is provided with a rib 34, preferably of trapezoidal cross section, with at least one guide surface 38. The first part 32 and the second part 33 are movable relative to each other along guide surfaces 38, 39 (Fig. 17), which are inclined with respect to the longitudinal direction of the rail, thereby enabling adaptation to the respective track gauge. The second part 33 further comprises a plate-shaped support element 41, on which the tension spring 1 rests, overlapping the upper surface of the first part 32. As can be seen in FIG. 17 , the plate-shaped support element 41 has at least an inclined guide groove 40 on its underside, and a guide pin or the like (not shown) formed on the upper side of the first part 32 engages with the guide groove 40 to hold the two parts 32, 33 together, particularly in the unloaded state. Furthermore, it can be seen that the second part 33, specifically the plate-shaped support element 41, has a through-hole 35 through which the screw 25 passes when the tension spring 1 is installed. The through-hole 35 is formed as an elongated hole perpendicular to the longitudinal direction of the rail. To guide the tension spring 1 laterally, the second part 33, specifically the plate-shaped support element 41, has two walls 37 extending in the insertion direction 14 of the tension spring 1. The tension spring 1 is also guided by a ridge 36 located between the first leg 3 of the tension spring 1 and the free end 7 of the stopper 5.

[0119] The tension spring 1 can be moved between a final assembly position shown in Figure 14 and a pre-assembly position (not shown) in which the tension spring 1 does not overlap the bottom of the rail. The design is such that the screw 25 does not have to be loosened to move the tension spring 1 from the pre-assembly position to the final assembly position. This movement can be performed, for example, by a lever-type tool.

[0120] Figures 18 and 19 show that, based on the design according to Figure 12, the tension spring 1 can be moved between a pre-assembly position (Figure 18) and a final assembly position (Figure 19), in which case the reference numbers from Figures 14 to 17 are also retained as far as corresponding components are concerned. Figures 20 and 21 each show cross-sections of Figures 18 and 19, respectively, along the lines XX and XXI, respectively.

[0121] 20 and 21, the fastening screw 25 has a screw head 42 and a screw shaft 43, and the screw head 42 presses the tension spring downward while sandwiching a washer 44. In this case, the protrusion 36 of the angle guide plate 26 forms a stop 45 with which the screw head 42 or the washer 44 interacts, thereby limiting the screw-in depth of the fastening screw 25. In this case, the stop 45 is used to determine the state in which the tension spring 1 is screwed downward or the tightened state of the fastening screw 25, such that the tension spring 1 remains movable between the pre-assembly position and the final assembly position. In this case, the stop 45 determines the minimum vertical distance h between the washer 44 and the receiving surface of the angle guide plate 26, which is equal to or greater than the unloaded diameter of the wire forming the tension spring in this region.

[0122] FIG. 20 shows that the angle guide plate 26 has a contact side 46 for the rail bottom 16 and the fastening screws 25 are arranged so that the tension spring 1 does not protrude beyond the contact side 46 in the pre-assembly position.

[0123] 18 and 19 further show a ramp 47 formed on the angle guide plate 26, which is positioned so that the bent end portion 6 of the tension spring 1 slides over it as the tension spring 1 is moved from the pre-assembly position to the final assembly position. The ramp is flat or rises in the direction toward the rail bottom 16, and the end of the ramp forms a step that descends toward the rail bottom 16, so that the bent end portion 6 descends over the step and onto the rail bottom 16 when the tension spring 1 is moved from the pre-assembly position to the final assembly position (see FIG. 27).

[0124] 22 and 23 show an alternative design in which the tension spring 1 can be moved from a pre-assembly position (FIG. 22) to a final assembly position (FIG. 23) by rotating it about the screw axis. 24 and 25 are cross-sectional views of FIGS. 22 and 23. To rotate the tension spring 1, a rotatable intermediate piece 48 is provided as a stop 45, which is passed through by the screw axis 43 and engages between the first leg 3 and the free end 7 of the tension spring 1, where it is pressed against the angle-guiding plate 26 by the fastening screw 25. As a result, the intermediate piece 48 in this case forms a rotatable stop 45 that limits and transmits the screw-in depth of the fastening screw 25 and the force that applies tension to the tension spring 1; for this reason, the intermediate piece 48 may also be understood as a component of a hold-down device.

[0125] In contrast to the previously described movable design, the rotatable stop 45 serves to determine the screwed-in state of the tension spring 1 or the tightening state of the fastening screw 25 so that the tension spring 1 remains movable between the pre-assembly position and the final assembly position. The intermediate piece 48 has a portion that overlaps the first leg 3 and the free end 7, thereby tightening the tension spring when the fastening screw 25 is tightened. In this case, the area of ​​the intermediate piece 48 that overlaps the first leg 3 and the free end 7, as the stop 45, determines the minimum vertical distance h between the tension spring's contact surface with the angle-guiding plate 26 and the opposing contact surface of the intermediate piece 48, which is equal to or greater than the unloaded diameter of the wire forming the tension spring in this area. Furthermore, the intermediate piece 48 has an extension 49 that engages behind the end face of the free end 7 of the tension spring 1 or in the free space between the free end 7 and the U-bend 2. The extension 49 acts as a safety element against horizontal movements of the tension spring 1 and as a drive element for transmitting the rotational movement applied to the tension spring 1 by means of an attachment to the intermediate element 48 or the stop 45 .

[0126] The angle guide plate 26 of Figures 22-25 is shown in more detail in Figure 26, where it can be seen that a ridge 50 is formed on the side 46 facing the rail bottom 16, with a contoured edge to provide both a first stop surface 53 for locating the rotatable tension spring 1 in the pre-installation position and a second stop surface 54 for locating the rotatable tension spring 1 in the final installation position. Furthermore, the contact surface 46 forms a stop 52 that extends from the upper edge of the contact surface 46 and descends to the rail bottom. To fully transmit the hold-down force to the rail bottom in the final installation position, the tension spring 1 must have the required vertical movement play between the second leg and the angle guide plate 26. The recess 51 ensures that the upper edge of the contact surface 46 or step 52 is lowered in the appropriate place.

[0127] FIG. 27 shows a cross-section S-S passing through the step portion 52 based on FIG. 19, and the step portion 52 drops at a distance Y from the rail bottom. In order to ensure that plastic deformation of the tension spring 1 does not occur over the entire maximum spring bending path when the bent end portion 6 is bent at the final assembly position, the vertical distance shown in FIG. 21 between the restraining portion 5 acting as an overload protection portion and the rail bottom 16 is below the vertical distance Y between the highest point of the inclined path 47 shown in FIG. 27 and the rail bottom 16.

[0128] FIG. 28 shows the stress applied during cold working and the stress range maintained during normal operation within the spring bending path limited by the overload protection portion, using the stress-strain diagram obtained from the tensile test. The diagram shows the 0.2% proof stress Rp0.2, the 1.0% proof stress Rp1.0, and the 2.0% proof stress Rp2.0. For example, by the stress of Rp2.0, when this stress is reached for the first time, a 2% permanent plastic elongation is achieved. As shown by the thick line, the tension spring is loaded at the maximum stress point by bending the bent end portion 6 in the direction of the spring bending path up to the stress Rp1.0. After the resulting cold working, the tension spring 1 is partially relaxed up to the tension σ u and, that is, through the path y (see FIG. 27), and elastically restrains the rail bottom downward in this state. The overload protection portion restricts the spring bending path above in such a form that the maximum tension σ o = Rp1.0 can occur before it is reached. In the range between σ u and σ o this ensures that the tension spring 1 is loaded only within the elastic deformation range at any point during normal rail operation, preferably at σ o < Rp1.0.

[0129] The following table gives an overview of several test series in which wire for tension springs shown in Figures 1 to 4 was subjected to plastic preloads corresponding to 0.2% yield point Rp0.2 and 2.0% yield point Rp2.0 to induce cold deformation. The mean stress amplitude (MW [MPa]) and standard deviation (Stabw [MPa]) for fatigue strength were then determined using the extended staircase method by Huck to visualize the differences in fatigue strength. The number of tests was increased to allow valid claims to be made, especially for high standard deviations. The results show that more severe cold working, especially at preload Rp2.0, and the subsequent maximum stress σ o When sleeper tensile tests are performed at = (0.85 * Rp2.0), the mean stress amplitude (MW [MPa]) for fatigue strength increases significantly compared to Rp0.2, and the associated standard deviation decreases compared to Rp0.2. [Table 1]

Claims

1. 1. A method for establishing a rail fastening, in which a track body element, such as a rail bottom (16) of a rail (8), is elastically held down by at least one hold-down part (6), such as a restraining arm, of a tension spring (1) in a final assembled position, the tension spring (1) consisting of tempered spring steel, the method comprising mounting the tension spring (1) on a base (11), the tension spring (1) being tensioned by a hold-down device (12, 25), the tension spring (1) being tensioned starting from a relaxed state by bending the hold-down part (6) along a spring bending path (z), characterized in that during mounting the hold-down part (6) is bent in the direction of the spring bending path (z) to such an extent that the tension spring (1) is subjected to cold working and is thereafter at least partially relaxed.

2. 2. The method according to claim 1, characterized in that the maximum spring bending path of the hold-down portion (6) is limited by an overload protection portion (5, 18) in the final assembled position of the tension spring (1), and the cold working is performed by bending the hold-down portion (6) over a spring bending path whose length is equal to or greater than the maximum spring bending path limited by the overload protection portion (5, 18).

3. 3. The method according to claim 1 or 2, characterized in that the holding-down part (6) is bent to such an extent that due to cold working, a maximum principal normal stress corresponding to a 0.5% yield point, preferably a 1% yield point, is reached or exceeded at the most highly loaded point of the tension spring (1).

4. 4. The method according to claim 3, characterized in that the tension spring (1) does not exceed the maximum principal normal stress, preferably 90% of the maximum principal normal stress, in particular 85% of the maximum principal normal stress, anywhere after cold working when the maximum spring bending path is reached.

5. 5. A method according to any one of claims 1 to 4, characterized in that the cold working is carried out at least on the surface of the wire forming the tension spring (1).

6. 6. The method according to claim 1, wherein the step of mounting the tension spring (1) comprises fixing the tension spring (1) in a pre-assembly position in which the hold-down portion (6) does not extend over the track body element.

7. 7. The method according to claim 1, wherein the cold working is performed in the pre-assembly position, during the movement of the tension spring (1) from the pre-assembly position to the final assembly position, or in the final assembly position.

8. 8. The method according to claim 6 or 7, characterized in that the cold working is carried out in such a way that the tension spring (1) is restrained in tension by the hold-down device (12) by sliding the hold-down part (6) on sliding surfaces (17) of the base part which rise in at least parts in the direction of movement of the tension spring (1) from the pre-assembly position to the final assembly position.

9. 9. The method according to claim 6, wherein when the tension spring (1) is moved from the pre-assembly position to the final assembly position, the hold-down portion (6) drops from the sliding surface (17) onto the track body element via a step portion (19, 52) to take up the final assembly position.

10. 8. The method according to claim 1, wherein the hold-down device is formed by a fastening screw (25), and the cold working is performed in the pre-assembly position or in the final assembly position by pressing the tension spring (1) down with the fastening screw (25), and then the tension spring (1) is at least partially relaxed by unwinding the fastening screw (25).

11. 8. A method according to any one of claims 1 to 7, characterized in that the cold working is carried out with the aid of a separate tool in the pre-assembly position or in the final assembly position.

12. 12. The method according to claim 1, wherein the tension spring (1) comprises a U-shaped main body with a U-bend (2), a first leg (3) arranged on one side of the U-bend (2), and a second leg (4) arranged on the other side of the U-bend (2), wherein the first leg (3) is formed with a hook-shaped, inwardly bent restraining portion (5) which can be tensioned against a hold-down device (12, 25), and the second leg (4) is formed with the hold-down portion (6) as an end portion of the second leg (4) which is bent towards or away from the restraining portion (5), and wherein the U-bend (2) forms a torsion portion so that a hold-down force can be applied to the track body element via the bent end portion (6).

13. 1. A method for improving the fatigue behavior of a tension spring (1) for holding down a track body element, such as a rail bottom (16) of a rail (8), the tension spring (1) being made of tempered spring steel and having at least one hold-down element (6), such as a support arm, that is elastically bendable along a spring bending path (z) for elastically holding down the track body element, the method comprising the steps of: providing the tension spring (1) for assembly into a track in which a maximum spring bending path of the hold-down element (6) is limited by an overload protection element (5, 18) in such a way that no plastic deformation occurs anywhere in the tension spring (1) within the maximum spring bending path; determining the maximum spring bending path; and subjecting the tension spring (1) to cold working by bending the hold-down element (6) in the direction of the spring bending path (z) beyond or up to the maximum spring bending path.

14. A rail fastening device manufactured by the method according to any one of claims 1 to 12, comprising a tension spring (1) made of tempered spring steel and a hold-down device (12, 25) adjacent to a track body element (8) and capable of fastening to a base, in particular a sleeper (11), a ribbed plate or an angle guide plate, wherein at least one hold-down portion (6) of the tension spring (1) is bent along a spring bending path (z) so that the hold-down portion (6) comes into contact with a track body element, in particular a rail bottom portion (16) of a rail (8), and elastically fastens the track body element.

1. A rail fastening device, wherein the tension spring (1) can be or is in a tensioned state relative to the hold-down device (12, 25) in the final assembly position of the tension spring (1) so that the tension spring (1) is brought into a tensioned state starting from a relaxed state by holding down the hold-down part (6) in the direction of the spring bending path (z) during assembly, characterized in that the tension spring (1) is or can be cold worked by bending the hold-down part (6) in the direction of the spring bending path (z) during assembly, and is at least partially relaxed in the final assembly position with respect to said bending.

15. 15. The rail fastening device according to claim 14, characterized in that a maximum spring bending path of the holding-down portion (6) in the final assembled position of the tension spring (1) is limited by an overload protection portion (5, 18), and the cold working is performed by bending the holding-down portion (6) over a spring bending path whose length is equal to or greater than the maximum spring bending path limited by the overload protection portion (5, 18).

16. 16. A rail fastening device according to claim 14 or 15, characterized in that the hold-down portion (6) is bent due to cold working to such an extent that a maximum principal normal stress corresponding to a 0.5% yield point, preferably a 1% yield point, is achieved or exceeded at the most highly loaded point of the tension spring (1).

17. 17. The rail fastening device according to claim 16, characterized in that the tension spring (1) does not exceed the maximum principal normal stress, preferably 90% of the maximum principal normal stress, in particular 85% of the maximum principal normal stress, at any point after cold working when the maximum spring bending path has been reached.

18. 18. Rail fastening device according to any one of claims 14 to 17, characterized in that the cold working is carried out at least on the surface of the wire forming the tension spring (1).

19. 19. The rail fastening device according to any one of claims 14 to 18, characterized in that the hold-down part (6) can be bent by applying a downward tension to the tension spring (1) by the hold-down device (12, 25) for cold working.

20. 20. The rail fastening device according to any one of claims 14 to 19, characterized in that the tension spring (1) can be fastened to the base in a pre-assembly position in which the hold-down portion (6) does not extend above the track body element.

21. 21. The rail fastening device according to claim 20, characterized in that the base part has sliding surfaces (17) which rise in at least parts thereof, and when the tension spring (1) is held down in tension by the hold-down device (12) during the movement of the tension spring (1) from the pre-assembly position to the final assembly position, the hold-down part (6) slides on the sliding surfaces (17), so that the hold-down part (6) can be bent and / or partially relaxed due to cold working.

22. 22. The rail fastening device according to claim 20 or 21, characterized in that the base portion forms a step portion (19, 52) at an end of the sliding surface (17), and when the tension spring (1) is moved from the pre-assembly position to the final assembly position, the hold-down portion (6) passes over the step portion (19, 52) and falls onto the track body element to take the final assembly position.

23. 23. The rail fastening device according to claim 14, wherein the tension spring (1) comprises a U-shaped main part with a U-bend (2), a first leg (3) arranged on one side of the U-bend (2), and a second leg (4) arranged on the other side of the U-bend (2), wherein the first leg (3) is formed with a hook-shaped, inwardly bent arresting part (5) which can be tensioned against a holding-down device, and the second leg (4) is formed with the holding-down part (6) as a terminal end of the second leg (4) which is bent towards or away from the arresting part (5), and the U-bend (2) forms a torsion part so that a holding-down force can be applied to the track body element via the bent terminal part (6).

24. 24. The rail fastening device according to any one of claims 14 to 23, characterized in that the hold-down device (12) comprises or forms a tunnel-shaped recess (13) into which the restraining part (5) of the tension spring (1) can be at least partially inserted.

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