Method for producing a rail fastening, method for increasing the vibrational resistance of a tension spring for holding down a track body element, and rail fastening

Abstract

The invention relates to a method for producing a rail fastening, wherein a track body element, such as a rail foot (16) of a rail (8) for example, is elastically held down by at least one hold-down section (6), such as a holding arm for example, of a tension spring (1), in the final installation position of the tension spring, said tension spring (1) consisting of a tempered spring steel. The method has the steps of installing the tension spring (1) on a support, wherein a hold-down element (12, 25) is used to bring the tension spring (1) into a tensioned state, in which the tension spring (1) is tensioned from an untensioned state, thereby deflecting the hold-down section (6) along the spring travel (z). According to the invention, the hold-down section (6) is deflected in the direction of the spring travel (z) to such a degree during the installation process that the tension spring (1) undergoes a cold forming process, after which the tension spring (1) is at least partially untensioned. Fig. 1

Description

[0001] Method for producing a rail fastening, method for increasing the vibration strength of a tension spring for holding down a track element, and rail fastening

[0002] The invention relates to a method for producing a rail fastening in which a track body element, such as a rail foot of a rail, is held down resiliently by at least one hold-down section, such as a holding arm, of a tension spring in its final assembly position, wherein the tension spring consists of a tempered spring steel, comprising mounting the tension spring on a base, wherein the tension spring is brought into a tensioned state by means of a hold-down device, in which the tension spring is tensioned starting from a relaxed state with deflection of the hold-down section along a spring path.

[0003] Furthermore, the invention relates to a rail fastening comprising a tension spring made of tempered spring steel and a hold-down device which can be fastened to a base, in particular a sleeper, ribbed plate or angle guide plate, adjacent to a track body element, on which hold-down device the tension spring can be supported or is supported in a final assembly position of the tension spring in such a way that the tension spring, starting from a relaxed state, can be tensioned with the hold-down section against the track body element, in particular a rail foot of a rail, by deflecting at least one hold-down section of the tension spring along a spring path in order to hold it down resiliently.

[0004] The installation of rails on a track bed is usually carried out using a spring element, usually referred to as a tension spring or tension clamp, and a suitable tensioning element or hold-down device to brace the spring element. This tensioning element or hold-down device is usually a screw, by means of which the spring element is braced against the subsurface so that it exerts the necessary holding forces via the section resting on the rail foot. The bracing can be achieved, for example, by connecting the hold-down device directly to the subsurface, which supports the rail and the fastening system, or by attaching the hold-down device to an additional component, such as a plate, which is then firmly coupled to the subsurface.

[0005] Widely used tension springs are those with the "e" shape and those with a "»" shape. A tension spring with the "e" shape is described, for example, in EP 313325 B1. The "o" shape is described, for example, in DE 3243895 A1.

[0006] There are numerous designs of fastening systems with tension springs in which the tension spring can be brought into a precisely defined final assembly position relative to the rail foot and the anchoring components, not only into a precisely defined final assembly position, but also into a secured pre-assembly position. To achieve the pre-assembly position, the tension spring is mounted in such a way that the section intended to hold down the rail foot does not lie on the rail. In this way, railway sleepers can be provided with tension springs arranged in the pre-assembly position and pre-tensioned in the factory. With a certain amount of effort, the tension springs can be brought into the final assembly position and tensioned on the construction site after the rail has been laid in place by shifting them sideways, so that the section intended to hold down the rail foot engages over it and presses it down from above.A disadvantage of prior art tension springs is the fact that they are only designed for a single installation direction or type of installation. The installation direction is understood to be the direction in which the tension spring, which is usually already pre-tensioned, is pushed onto the rail foot. The most common tension springs are those designed for transverse installation, i.e. for sliding the tension spring onto the rail at right angles to the longitudinal direction of the rail. With longitudinal installation, however, the tension spring is brought into its final assembly position in the longitudinal direction of the rail. Due to the limited space, installation in the longitudinal direction of the rail is advantageous, for example, for fastening the rails in the area of ​​switches.Conventional tension springs are adapted to their specified installation direction, particularly with regard to the arrangement of areas of different stiffness, and therefore cannot simply be installed in a different direction, although in most cases a different installation direction is not even possible for geometric reasons.

[0007] Other problems with conventional tension springs include breakage and loosening of the tension springs, resulting in a loss of tension force. This loosening occurs particularly in tension springs that are tensioned with a screw.

[0008] Tension springs often break when they are subjected to excessive loads. Conventional rail fastening systems are, at least in some cases, equipped with an overload protection device. The purpose of an overload protection device is to limit the load acting on the tension spring, which is particularly important when the rail is subject to a strong upward and downward movement or a strong tilting movement relative to the sleeper when passing over it.

[0009] Another cause of tension spring breakage is insufficient fatigue strength. In particular, it has been observed that fractures caused by fatigue loading are subject to undesirable statistical scatter, so that tension spring breakage can occur despite design for fatigue testing. Finally, fatigue loading also leads to a reduction in the tensioning force of the tension clamp.

[0010] To increase strength and yield strength, it has already become known to subject tension clamps to cold forming during the manufacturing process. Cold forming is the plastic deformation of metals below the recrystallization temperature in order to increase the dislocation density. This is described in connection with tension clamps, for example, in EP 2528702 A1, DE 2411195 A1, and US Pat. No. 9382667 B2.

[0011] The present invention therefore aims to improve a fastening system and a method for producing a rail fastening so that the aforementioned disadvantages can be overcome. In particular, a tension spring is to be created that has increased fatigue strength and can reduce the loss of tension force.

[0012] To achieve this object, the invention provides, according to a first aspect, a method for producing a rail fastening, in which a track body element, such as a rail foot of a rail, is held by at least one hold-down section, such as a rail base.a holding arm, a tension spring in the final assembly position of which is held down resiliently, the tension spring being made of a tempered spring steel, comprising mounting the tension spring on a base, the tension spring being brought into a tensioned state by means of a hold-down device, in which the tension spring is tensioned starting from a relaxed state with deflection of the hold-down section along a spring travel, the method being characterized in that the hold-down section is deflected so far in the direction of the spring travel during assembly that the tension spring is subjected to cold forming in places, after which the tension spring is at least partially relaxed.

[0013] According to the invention, therefore, a tension spring made of tempered spring steel is used, i.e., a steel that has been subjected to a combined heat treatment consisting of hardening and subsequent tempering. The tension spring comprises at least one hold-down section, such as one or two holding arms, with which the track body element is resiliently held down in the final assembly position. The spring force is applied by resilient deflection of the hold-down section, while the tension spring is held down at a held-down section by a hold-down device.

[0014] According to the invention, the work hardening takes place in such a way that the at least one hold-down section is deflected during assembly of the tension spring, for example in the pre-assembly position, during movement of the tension spring from the pre-assembly position into the final assembly position or in the final assembly position, to such an extent that the tension spring is deformed at least at one point beyond the elastic range, i.e. into the plastic range, and is thereby subjected to cold forming. What is important here is that the deflection of the hold-down section takes place in the direction of the spring travel that it also experiences during operation, i.e. for holding down the track body element. In this way, the cold forming is effected at the point or points on the tension spring that are subjected to the highest load during operation.are, so that precisely these points are subject to the desired hardening, which is / are susceptible to fracture in continuous operation as a result of continuous vibration loading. Because the cold forming takes place during assembly of the tension spring, a situation similar to actual operation is created, which ensures that the hold-down section deflects in exactly the direction in which it is subjected to stress during operation. The complex and usually inaccurate simulation of the operating or assembly situation in a production environment separate from the track can therefore be omitted.

[0015] The point of highest stress is usually on the surface of the tension clamps, so that the cold forming takes place at least on the surface of the wire forming the tension spring.

[0016] The resilient deflection of the hold-down section for the purpose of cold forming refers to a relative movement of the hold-down section relative to the held-down section of the tension spring, starting from the tensioned state of the tension spring into the tensioned state. The deflection can occur in that the hold-down section is deflected while the held-down section is not displaced in the direction of movement of the deflection movement, e.g. is held in place by the hold-down device. Alternatively, the deflection can occur in that the held-down section is deflected while the hold-down section is not displaced in the direction of movement of the deflection movement, e.g. is held in place by the base or the track body element.Deflection for the purpose of cold forming can thus be achieved, for example, by changing the distance, measured in the direction of the spring travel, between the base or track body on the one hand and the hold-down device on the other. This allows cold forming to be carried out easily during the assembly process of the tension spring.

[0017] Carrying out the cold forming during the assembly of the tension spring preferably means that the cold forming takes place in the state in which the hold-down device is clamped down and before the first passage by a rail vehicle.

[0018] According to the invention, the tension spring is at least partially relaxed after cold forming. This ensures that the working range of the tension spring for normal operation is brought below the plastic deformation level. This is intended to prevent the tension spring from undergoing further cold forming during operation or from being subjected to oscillating stress up to the plastic limit. The partial relaxation thus results in the tension spring being used in the final assembly position in a less tense state than during cold forming.

[0019] According to a preferred embodiment of the invention, this can be achieved in that the maximum spring travel of the hold-down section in the final assembly position of the tension spring is limited by an overload protection device, and in that the cold forming takes place by deflecting the hold-down section over a spring travel that is greater than or equal to the maximum spring travel limited by the overload protection device. The overload protection can be achieved, for example, by the track body element abutting against a section of the tension spring that forms a stop, or by the hold-down section abutting against a stop on the hold-down device.

[0020] The invention is based on the finding that the probability of a tension spring breaking due to vibration loading can be significantly reduced if, after an initial cold forming process, as defined by the invention, the tension spring is only loaded at any point within the elastic deformation range. In particular, the scatter of the fracture probability around the expected value can be significantly reduced.

[0021] In this context, according to a second, independent aspect, the invention relates to a method for increasing the vibration strength of a tension spring for holding down a track body element, such as a rail foot of a rail, wherein the tension spring consists of a tempered spring steel and at least one hold-down section, such as a spring spring, which can be deflected resiliently along a spring path.a holding arm for resiliently holding down the track body element, the method being characterized in that the tension spring is provided for installation in a track, in which the maximum spring travel of the hold-down section is limited by an overload protection device in such a way that no plastic deformation takes place at any point on the tension spring within the maximum spring travel, the said maximum spring travel is determined and the hold-down section is deflected in the direction of the spring travel beyond the maximum spring travel or up to the maximum spring travel, so that the tension spring is subjected to cold forming.

[0022] A preferred embodiment further provides that the hold-down section for cold forming is deflected to such an extent that, at the most highly loaded point of the tension spring, a maximum principal normal stress corresponding to the 0.5% yield strength, preferably the 1% yield strength, is reached or exceeded. Tests have shown good results when the 0.5% to 1.5% yield strength, particularly the 1% yield strength, was reached. An improvement over the state of the art was also observed when the 2% yield strength was reached.

[0023] For normal operation, it is preferably provided that the tension spring, after cold forming, when reaching the maximum spring travel, does not exceed the said maximum main normal stress at any point, preferably 90% of the maximum main normal stress, in particular 85% of the maximum main normal stress.

[0024] The principal normal stress can be determined by subjecting a material sample of the wire forming the tension spring to a tensile test and creating a stress-strain diagram from this. By attaching a stress sensor in or on the tension clamp at the point where the highest load will occur, the principal normal stress can then be measured. Alternatively, the principal normal stress can be determined in suitable simulation programs using finite element methods (FEM). For this purpose, the geometry of the

[0025] Tension clamp, the material properties, and the boundary conditions (e.g., connection points, contact surfaces, etc.) are defined in the simulation program. The forces or stresses generated by tightening the clamp are then applied as loads to the model, and the simulation program performs a numerical analysis, calculating the resulting stresses and deformations at each point in the model. By comparing this with the stress-strain diagram, the deflection of the hold-down section that corresponds to the desired yield strength can be determined.

[0026] As already mentioned, the cold forming according to the invention can take place in the final assembly position of the tension spring, during the displacement of the tension spring from a pre-assembly position to the final assembly position, or in a pre-assembly position. The pre-assembly position refers to a position of the tension spring in which the tension spring is held on the base by the hold-down device, but preferably the hold-down section of the tension spring does not overlap the track body element.

[0027] The cold forming preferably takes place during the displacement of the tension spring from the pre-assembly position to the final assembly position, with the tension spring held in the tensioned state by the hold-down device, by the hold-down section sliding on a sliding surface of the base which rises at least in sections in the direction of displacement. The gradient of the sliding surface is dimensioned such that the desired cold forming is effected at the point on the tension spring which is subject to the highest load. In this context, it can further preferably be provided that the hold-down section drops from the sliding surface over a step onto the track body element when the tension spring is moved from the pre-assembly position to the final assembly position in order to assume the final assembly position. This ensures that the tension spring is at least partially relaxed after the cold forming, as provided according to the invention.At the same time, the step acts as a rear stop with which the hold-down section interacts and which prevents the final assembly position from being left.

[0028] According to an alternative procedure, the hold-down device is formed by a fastening screw and the cold forming takes place in the pre-assembly position or the final assembly position by tensioning the tension spring by means of the fastening screw, whereupon the tension spring is at least partially released by turning back the fastening screw or by sliding over the step of a sliding surface.

[0029] Alternatively, cold forming can also be performed in the pre-assembly or final assembly position using a separate tool. A simple design includes a laterally retractable spacer that can be inserted, for example, between the track element and the hold-down section in the final assembly position when the tension spring is lowered. Alternatively, a temporarily provided raised sliding surface for the hold-down section allows for movement from a pre-assembly to a final assembly position.

[0030] In principle, any suitable designs of tension springs which have at least one resiliently deflectable hold-down section, such as, for example, a holding arm, can be used within the scope of the invention. In a particularly preferred embodiment, the tension spring has a U-shaped main section which has 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 on the first leg there is a hook-shaped, inwardly bent holding section which can be supported on a hold-down device, and on the second leg the hold-down section is designed as an end section of the second leg which is bent towards or away from the holding section, wherein the U-bend forms a torsion section, so that a hold-down force can be applied to the track body element via the bent end section.

[0031] According to a third aspect, the invention relates to a rail fastening comprising a tension spring made of tempered spring steel and a hold-down device which can be fastened to a base, in particular a sleeper, ribbed plate or angle guide plate, adjacent to a track body element, on which hold-down device the tension spring can be supported or is supported in a final assembly position of the tension spring in such a way that the tension spring, starting from a relaxed state, can be tensioned by deflecting at least one hold-down section of the tension spring along a spring path with the hold-down section against the track body element, in particular a rail foot of a rail, in order to resiliently hold it down, characterized in that the tension spring is cold-formed by deflecting the hold-down section in the direction of the spring path or is cold-formable during assembly and is at least partially relieved of said deflection in the final assembly position.In particular, the tension spring of the rail fastening system according to the invention is a tension spring whose fatigue strength has been increased before assembly or is increased during assembly by means of a method according to the second aspect of the invention. It is therefore a tension spring that has been tuned such that it does not leave the elastic deformation range in the operating state and has previously been brought into the plastic range only once by overtensioning, whereby cold forming has taken place.

[0032] In particular, the maximum spring travel of the hold-down section in the final assembly position of the tension spring is limited by an overload protection device and the cold forming takes place by deflecting the hold-down section over a spring travel that is greater than or equal to the maximum spring travel limited by the overload protection device.

[0033] As already described in connection with the method according to the first aspect of the invention, a preferred embodiment provides that the hold-down section for the cold forming is deflected to such an extent that a maximum principal normal stress corresponding to the 0.5% yield strength, preferably the 1% yield strength, is reached or exceeded at the most highly loaded point of the tension spring.

[0034] Preferably, after cold forming, the tension spring, upon reaching the maximum spring deflection, does not exceed the maximum principal normal stress at any point, preferably 90% of the maximum principal normal stress, in particular 85% of the maximum principal normal stress. Preferably, the cold forming takes place at least on the surface of the wire forming the tension spring.

[0035] Preferably, the hold-down section can be deflected for cold forming by tensioning the tension spring by means of the hold-down device.

[0036] Preferably, the tension spring can be fastened to the base in a pre-assembly position in which the hold-down section does not overlap the track body element.

[0037] Preferably, the base has a sliding surface which rises at least in sections and on which the hold-down section slides when the tension spring is held in the tensioned state by the hold-down device during the displacement of the tension spring from the pre-assembly position into the final assembly position, whereby the hold-down section can be deflected and / or partially relieved for cold forming.

[0038] Preferably, the base forms a step at the end of the sliding surface, over which the hold-down section drops onto the track body element when the tension spring is moved from the pre-assembly position to the final assembly position in order to assume the final assembly position.

[0039] The tension spring preferably has a U-shaped main section which has 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 on the first leg there is a hook-shaped holding section which is bent inwards and can be supported on a hold-down device, and on the second leg the hold-down section is designed as an end section of the second leg which is bent towards or away from the holding section, wherein the U-bend forms a torsion section so that a hold-down force can be applied to the track body element via the bent end section.

[0040] Preferably, the hold-down device forms or forms a tunnel-shaped recess into which the holding section of the tension spring can be at least partially inserted.

[0041] Further preferred embodiments of the tension spring and the rail fastening which can be used within the framework of the aspects of the invention explained above are described below.

[0042] As already mentioned, the tension spring preferably comprises a U-shaped main section which has 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 holding section which is bent inwards and can be supported on a hold-down device is formed on the first leg and an end section which is bent towards or away from the holding section is formed on the second leg, wherein the U-bend forms a torsion section so that a hold-down force can be applied to the track body element via the bent end section.

[0043] Because the tension spring, starting from the basic shape of a "U", has a hook-shaped holding section on the first leg of the U-shape and an end section bent towards or away from the holding section on the other leg of the U-shape, an asymmetrical shape is achieved which is easy to manufacture and which allows installation in both the transverse and longitudinal directions. In both the longitudinal and transverse installation, the bent end section forms the area of ​​the tension spring via which the hold-down force is applied to the track element or the rail foot.

[0044] This design of the tension spring is similar to the “e” shape known from the prior art, with the difference that the end section of the “e” shape has an additional bend. This bend can be towards or away from the holding section of the tension spring. The bend preferably runs towards the holding section of the tension spring. According to a preferred design, the bent end section runs at an angle of 80-100°, preferably approximately 90°, to the second leg, this applying both to the design with an end section bent towards the holding section of the tension spring and to the design with an end section bent away from the holding section. The advantages of the bent end section become apparent both in longitudinal and transverse installation in conjunction with the hold-down device, as will be explained in more detail below.

[0045] In some embodiments of the invention, the U-shape formed by the U-bend, the first leg, and the second leg also includes configurations in which the first leg is reduced to a minimum, so that the U-bend merges directly into the holding section. In other embodiments, however, the first leg has a certain length, such as a length substantially corresponding to the second leg, and is, in particular, straight.

[0046] The hook-shaped holding section extending from the first leg of the U-shape is used to be held under tension by a hold-down device when a torsional force is exerted by the bent end section on the torsional section formed by the U-bend of the tension spring. The hook-shaped holding section is bent inwards, which means that the hook is bent between the two legs of the U-shape. Preferably, the hook-shaped holding section on the first leg forms the end of the tension spring, i.e. the free end of the area bent into a hook lies between the two legs of the U-shape.

[0047] In this context, a preferred embodiment provides that the holding section has a free end region connected to the first leg via a hook bend, which is arranged between the first leg and the second leg.

[0048] According to a preferred embodiment of the invention, a hook bend of the holding section has a substantially 180° bend, so that a free end region of the holding section runs substantially parallel to the first leg, at least in sections. The expression "substantially 180°" means that the angle is 180°, but can also be between 175° and 185°.

[0049] The hold-down force is provided at least partially by a torsional load on the torsion section formed by the U-bend of the tension spring, resulting in a corresponding resilient deflection of the second leg extending from the U-bend to the bent end section. While the second leg thus forms a deflectable spring arm, the remaining part of the tension spring can be designed as flat as possible to minimize the overall height of the tension spring and the material consumption for the tension spring.

[0050] In this context, a preferred embodiment provides that the first leg and the free end region of the holding section provide a flat support surface in the unloaded state. The flat support surface can serve, for example, as a support for the hold-down device, whereby the flat state refers to the unloaded state of the tension spring, since slight twisting of the holding section may occur when the tension spring is tensioned.

[0051] In the unloaded state, the first leg and the free end region of the holding section can lie with their respective central axes, preferably over their entire extent, in a central plane that preferably runs parallel to the flat support surface. The central axis of the corresponding sections, for example, in the case of a circular cross-section, is understood to mean the center line or axis passing through the center of the circle.

[0052] However, it can also be provided that the first leg and the holding section lie in the same plane in the unloaded state, or with their respective center axes in the center plane. This also provides a flat support surface and prevents parts of the first leg and the holding section, including the hook bend, from being bent out of said plane.

[0053] The design of the U-bend of the tension spring can also contribute to achieving the flattest possible construction in that the free end region of the holding section, seen in the direction of a longitudinal extension of the free end region, preferably covers the U-bend at least partially, preferably completely.

[0054] However, to ensure sufficient spring travel, the bent end section of the tension spring can be deflected from the aforementioned plane in the unloaded state. A preferred embodiment in this context provides that the bent end section has a normal distance from the center plane or the flat support surface in the unloaded state.

[0055] If the entire holding section, including the hook bend, and the first leg lie in the same plane, this means that, with regard to the overall height of the tension spring, the hook bend and the bent end section define the maximum overall height of the tension spring in the unloaded state, measured perpendicular to the center plane or the flat support surface. This enables an extremely flat design of the tension spring.

[0056] In particular, the overall height of the tension spring in the unloaded state can correspond to 1.5 to 3 times the diameter of the wire forming the tension spring in the holding section.

[0057] Preferably, an imaginary extension of the bent end section overlaps the hook bend in a plan view. This means that the imaginary extension of the bent end section at least partially overlaps the hook bend in the plan view of the tension spring. For transverse installation of the tension spring, this means that the hook bend lies above the rail foot in the final assembly position and can form an overload protection feature.

[0058] The tension spring conventionally consists of a spring rod and can therefore be manufactured in one piece from a corresponding starting product. It is manufactured by bending an originally straight spring rod multiple times. If, as is preferably provided, the hook-shaped holding section, the U-bend and the bent end section are all bent in the same direction, the tension spring can be manufactured in three bending steps. The hook-shaped holding section is bent in the first step, the U-bend in the second step and the bent end section in the third step. The three bending steps can also be carried out in one circular operation if all three bends occur in the same direction of rotation. These bends can all occur in the same plane, or individual areas can be deflected from the common plane at the same time as the bends.

[0059] The cross-section of the tension spring is preferably circular, although other cross-sectional shapes are also conceivable, such as oval, elliptical or the like.

[0060] Due to the relatively simple geometry of the tension spring according to the invention, its mechanical properties can be easily adapted to specific requirements by varying certain geometric parameters while maintaining the basic shape. For example, the length of the second leg of the U-shape, and thus the length of the lever arm acting on the torsion section, determines the stiffness of the tension spring. The tension, clamping force, and stiffness can be controlled by selecting the thickness of the spring rod. The radius of the U-bend also controls the tension and stiffness of the tension spring.

[0061] In order to be able to exert a holding-down force on the rail foot by tensioning the holding section by means of the hold-down device and the resulting torsional load on the torsional section of the tension spring via the bent end section, it is preferably provided that the second leg, in the unloaded state, has a normal distance from the center plane or from the flat support surface which continuously increases in the direction of the bent end section.

[0062] This means in particular that the second leg, in the unloaded state, runs at an acute angle relative to the central plane or to the flat support surface. The acute angle can be between 5° and 20°. Tightening the tension spring leads to a bending of the tension spring in such a way that the acute angle mentioned decreases from the unloaded state and is, for example, only 0° -5° in the tightened state. This angle can be reduced to 5-10° in the case of fastening systems with a lower hold-down force. In this tightened state, a torsional moment acts on the torsional section of the tension spring, in particular about an axis that runs normal to the axis of the first leg and forms a tangent to the U-bend.The hold-down force acting on the rail foot from the bent end section and the corresponding counterforce acting from the hold-down device on the holding section of the tension spring form a force couple that also forces the torsion section to bend around an axis perpendicular to the axis of the torsional moment, resulting in a corresponding bending around this axis. Due to this bending, the bent end section of the tension spring has a different angle to the support plane at the rail foot in the unloaded state than in the loaded state.So that the bent end section is aligned essentially horizontally in the loaded state in order to ensure a corresponding bearing surface on the rail foot, a preferred embodiment of the invention provides that the bent end section has a bearing surface for bearing on the track body element which, in the unloaded state, runs upwards at an acute angle relative to the central plane or to the flat bearing surface. The angle between the bent end section and the said plane can preferably be 2 ° - 8 °, in particular 5 ° - 7 °. The angle decreases under load due to the said bending moment and is preferably 0 ° - 1 ° in the loaded state.

[0063] When, within the scope of the invention, reference is made to an angle between two sections of the tension spring or to a plane in which the sections lie, this refers to the center line of the corresponding sections, i.e., in the case of a circular cross-section, to the center line or axis passing through the center of the circle. The tension spring according to the invention is designed to be usable with various types of hold-down devices.

[0064] In a first installation variant, the holding section of the tension spring can be inserted transversely to the longitudinal direction of the rail into a tunnel-shaped recess of the hold-down device towards the rail, so that the hook bend preferably overlaps the rail foot in a final assembly position of the tension spring.

[0065] In a second installation variant, the holding section of the tension spring can be inserted parallel to the longitudinal direction of the rail into a tunnel-shaped recess of the hold-down device, so that the second leg preferably overlaps the rail foot.

[0066] From a structural point of view, the first and the second installation variant can preferably be realized in that a gap is arranged between the bent end section and the free end region of the holding section in a longitudinal extension of the free end region and in a plan view, i.e. in a normal projection onto the center plane or the flat support surface, on the side of the free end region facing the second leg.

[0067] In a further installation variant, a free space can be provided between the first leg and the free end region of the holding section, through which space can be passed a screw shaft of a fastening screw forming the hold-down device and in which space the fastening screw can be moved in the longitudinal direction of the first leg, wherein the screw shaft of the fastening screw has a diameter which is greater than the diameter of a wire forming the tension spring in the holding section, and wherein the inner radius of the hook bend is preferably greater than or equal to the radius of the screw shaft. The said displaceability makes it possible to move the tension spring, when held down by the fastening screw, from a pre-assembly position to a final assembly position and back. If the inner radius of the hook bend is greater than or equal to the radius of the screw shaft, a maximum displacement path is provided.

[0068] Overall, a compact, flat, and flexibly usable tension spring is provided, which can also be manufactured cost-effectively due to the low material requirements. Preferably, the tension spring, in a plan view, in particular in a normal projection onto the center plane or the flat support surface, lies within a minimal surrounding rectangle with an aspect ratio of 1:1.5-1:1, preferably 1:1.1-1:1.

[0069] 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 shorter side of a rectangle minimally surrounding the tension spring in a plan view.

[0070] In particular, the bent end section lies within a square corner region of a rectangle minimally surrounding the tension spring in a plan view, which is at most 1 / 9 of the area of ​​the surrounding rectangle.

[0071] With regard to the rail fastening, a further development provides that it has a tension spring according to one of the previously described embodiments and a hold-down device which can be fastened to a base, in particular a sleeper, ribbed plate or angle guide plate, adjacent to a rail, on which hold-down device the holding section is supported in the mounted state of the tension spring in such a way that the bent end section can be arranged to resiliently hold down a track body element, in particular a rail foot of the rail.

[0072] It is preferably provided that the hold-down device, in the assembled state of the tension spring, not only overlaps the free end area of ​​the holding section, but at least partially also the first leg.

[0073] The tension spring can be clamped down screwlessly or with the aid of a screw. For the screwless alternative, a preferred embodiment provides for the hold-down device to have or form a tunnel-shaped recess into which the holding portion of the tension spring can be at least partially inserted.

[0074] Depending on whether the tension spring is to be installed transversely to the longitudinal direction of the rail or in the longitudinal direction of the rail, the holding section of the tension spring can be inserted transversely to the longitudinal direction of the rail into the tunnel-shaped recess towards the rail or inserted parallel to the longitudinal direction of the rail.

[0075] In a design with a tension spring that can be inserted transversely to the longitudinal direction of the rail, the tunnel-shaped recess is preferably open on the side facing the track body element, in particular the rail base, and the hook bend projects out of the tunnel-shaped recess in the finally assembled state of the tension spring and engages over the track body element, in particular the rail base. In this way, the hook bend forms an overload protection device in its state projecting over the track body element. For this purpose, the hook bend is arranged such that there is a vertical distance between the track body element to be held down, in particular the rail base, and the hook bend of the tension spring. Upward movements of the track body element that lie within the vertical distance are resiliently absorbed by the bent end section of the tension spring.However, should an excessive upward movement occur, the track element to be held down will strike the hook bend and will thus be prevented from rising further without overloading the tension spring within its permissible spring travel.

[0076] In the variant with a tension spring that can be inserted transversely to the longitudinal direction of the rail, a pre-assembly position of the tension spring can be achieved in a simple manner by initially only pushing the tension spring in far enough so that it is securely accommodated in the tunnel-shaped recess, but that the hook bend does not yet protrude from the tunnel-shaped recess on the side facing the track element to be held down and the bent end section does not yet come to rest on the track element. Only when the final assembly position is assumed is the tension spring driven further towards the track element until the bent end section presses onto the track element from above.

[0077] Both in the variant with a tension spring that can be inserted transversely to the longitudinal direction of the rail and in the variant with a tension spring that can be inserted in the longitudinal direction of the rail, it can preferably be provided that the hold-down device has a ramp that rises in the insertion direction and on which the bent end section slides during insertion. This results in the bent end section being increasingly pre-tensioned during insertion.

[0078] Particularly preferably, the ramp comprises a first rising ramp section and a second rising ramp section, and an intermediate section located therebetween, on which the bent end section rests in a pre-assembly position of the tension spring. The intermediate section can, for example, have a recess in which the bent end section of the tension spring can engage in order to remain in the pre-assembly position.

[0079] In this context, a preferred further development provides that a step is formed at the end of the ramp, via which the bent end section reaches the final assembly position, in which the end section rests on the track body element, in particular the rail foot, wherein the step forms a rear stop which secures the end section against leaving the final assembly position.

[0080] In the variant with a tension spring that can be inserted in the longitudinal direction of the rail, overload protection can be achieved in that the hold-down device has a stop that overlaps the bent end section at a distance when the tension spring is installed. Such a stop has the effect of limiting the upward movement of the bent end section. The fastening system can also be used in the area of ​​a switch for fixing stock rails, wherein the hold-down device can be combined or connected to a sliding chair on the side of the stock 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 context, a preferred embodiment provides that the fastening system comprises a sliding block associated with the stock rail, said block having a sliding surface for a tongue rail, wherein the hold-down device comprises a further sliding surface that is preferably flush with the sliding surface. Alternatively, the upper surface of the hold-down device can also be arranged lower than the sliding surface of the sliding block.

[0081] Preferably, the further sliding surface, like the sliding chair itself, is extended in the direction of the stock rail in such a way that the further sliding surface overlaps the rail foot of the stock rail at a distance.

[0082] Preferably, the hold-down device assigned to the sliding chair and the hold-down device arranged on the opposite side of the stock rail can be formed in one piece with a sliding chair plate.

[0083] As already mentioned, one advantage of the tension spring is its universal applicability. For example, as already mentioned, the tension spring can be fastened not only without screws, but also with a sleeper screw. In this context, the fastening system according to the invention is preferably designed such that the hold-down device is formed by a fastening screw that can be screwed into the base, in particular a sleeper or plate, or by a hook screw with a nut that is hooked into the base, in particular a ribbed plate, the screw shaft and / or thread of which penetrates a free space between the first leg and the free end region of the holding section of the tension spring in order to hold the tension spring down in the region of the holding section and optionally the first leg.

[0084] With this type of fastening, a pre-assembly position is also easily possible. This can be done by first screwing the tension spring down into the pre-assembly position. The rail is then inserted, whereupon the tension spring, screwed down, is moved into 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 pushing the tension spring into the final assembly position, because the tension spring can be easily moved from the pre-assembly position to the final assembly position using a hand or power tool, even when the screw is tightened to the final tightening torque in the pre-assembly position.

[0085] To ensure that the tension spring remains displaceable between the pre-assembly and final assembly positions when screwed down, a preferred embodiment of the invention provides for a stop to be arranged on the base and / or on the hold-down device, which stops the screw-in depth of the hold-down device and preferably interacts with the screw head or the nut of the fastening screw, so that a hold-down force on the tension spring can be limited. The stop thus serves to define the screwed-down state of the tension spring or the tightened state of the screw in such a way that the tension spring remains displaceable between the pre-assembly and final assembly positions.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, wherein the vertical distance is preferably not more than 1.2 times the wire diameter.

[0086] A deviation from the final tightening torque or the clamping force of the screw achieved with the final tightening torque no longer has a negative effect on the desired tension state of the tension spring once it has been tightened against the stop. This eliminates the need to check the clearances between the tension clamp and the rail base in the final assembly position, as is necessary, for example, with some common fastening systems using tension springs.

[0087] The stop can further preferably enable compensation for a predominantly one-sided load on the screw in that the stop of the screw provides at least one support point via which, by means of the screw or nut tightened with the final tightening torque, a force acts on the screw which at least partially compensates for the one-sided load on the screw.

[0088] Various variants are possible for moving the tension spring from the pre-assembly to the final assembly position. In particular, the tension spring, with its bent end section, can be twistable or displaceable transversely to the longitudinal direction of the rail between the pre-assembly and final assembly positions when the hold-down clamp is tightened, i.e., particularly in the tension state defined by the stop described above.

[0089] Preferably, the support is designed in the region of the contact surface over which the tension spring passes during displacement so that when the tension spring is moved on the support from the pre-assembly position to the final assembly position along the displacement path, there is no increase, or only a gradual increase, in the pre-tension of the tension spring, so that when the tension spring is moved, damaging stress, particularly due to shear, is excluded for all components subjected to stress. For this purpose, one possible design of a support on the contact surfaces over which the tension spring passes on the support during displacement is free of grooves and depressions transversely to the direction of displacement of the tension spring.

[0090] To prevent the tension spring from moving automatically or accidentally from the final assembly position to the pre-assembly position, it is preferably provided that the base forms a step sloping in the direction of displacement of the tension spring, from which the bent end section descends onto the rail foot when the tension spring is moved from the pre-assembly position to the final assembly position. The step thus forms a rear stop for the bent end section, preventing it from leaving the final assembly position.

[0091] In the pre-assembly position, the tension spring is advantageously arranged on the base in such a way that the insertion of a rail between pre-assembled tension springs is not hindered. This means that sleepers can be provided with pre-assembled tension springs before the rails are laid, so that after the rails have been laid, the tension springs only need to be moved into the final assembly position using a suitable tool. This is preferably achieved by the base having a lateral contact surface for the rail foot and the hold-down device or fastening screw being arranged in such a way that the tension spring does not protrude beyond the contact surface in the pre-assembly position.

[0092] In particular, the distance between the screw shaft and the lateral contact surface can be equal to or greater than the diameter of the wire forming the tension spring.

[0093] For safety reasons, it should be ensured that the fastening screw does not become unintentionally loose when moving the tension spring from the pre-assembly position to the final assembly position. For this purpose, the fact that the asymmetrical tension spring according to the invention, when tensioned, is tensioned predominantly on one side of the screw toward the screw head or nut, while resting on the base on the other side of the screw, can be utilized.

[0094] If the direction of rotation of the screw thread and the installation position or asymmetry of the tension spring are coordinated, a displacement of the tension spring from the pre-assembly position to the final assembly position results in the screw being subjected to a load in the sense of tightening the screw. In other words, the fastening screw or the nut of the hook screw predominantly holds down the free end area of ​​the holding section of the tension spring and the first leg of the tension spring is supported on the base and the tightening direction of the thread of the fastening screw or the hook screw is designed in such a way that the free end area of ​​the holding section directly or indirectly applies a torque in the tightening direction to the fastening screw or the nut of the hook screw when the tension spring is moved transversely to the longitudinal direction of the rail from the pre-assembly position to the final assembly position.

[0095] For a fastening system with a tension spring that can be rotated between a pre-assembly position and a final assembly position, it is intended that the rotation from the pre-assembly position to the final assembly position takes place in the tightening direction of rotation of the fastening screw or the nut of the hook screw, so that it is directly or indirectly subjected to a torque in the tightening direction of rotation.

[0096] The invention is explained in more detail below with reference to exemplary embodiments shown schematically in the drawing. In these, Fig. 1 is a perspective view of a tension spring which can be used within the scope of the invention, Fig. 2 is a plan view of the tension spring according to Fig. 1, Fig. 3 is a view according to arrow III in Fig. 2, Fig. 4 is a view according to arrow IV in Fig. 2, Fig. 5 is a first embodiment of a rail fastening using the tension spring according to Fig. 1, Fig. 6 is a detailed view of Fig. 5, Fig. 7 is a second embodiment of a rail fastening using the tension spring according to Fig. 1, Fig. 8 is a detailed view of Fig. 7, Fig. 9 is a hold-down device according to Fig. 7 and 8 in a perspective view, Fig. 10 a side view of the hold-down device according to Fig. 9, Fig. 11 a third embodiment of a rail fastening using the tension spring according to Fig. 1, Fig.12 shows a modified embodiment of the rail fastening of Fig. 11, Fig. 13 shows a fourth embodiment of a rail fastening using the tension spring according to Fig. 1, Fig. 14 shows an embodiment according to Fig.

[0097] 12 with a modified angle guide plate, Fig. 15 is a view of the angle guide plate according to Fig. 14, Fig. 16 is a front view of the angle guide plate according to Fig. 14, Fig. 17 is a bottom view of the angle guide plate according to Fig. 14 in an exploded view, Fig. 19 is the rail fastening according to Fig. 12 in a final assembly position, Fig. 18 is the rail fastening according to Fig. 12 in a pre-assembly position, Fig. 21 is a cross-sectional view of the rail fastening according to Fig.

[0098] 19, Fig. 20 a cross-sectional view of the rail fastening according to Fig. 18, Fig. 22 an alternative embodiment of the rail fastening in a pre-assembly position, Fig. 23 the rail fastening according to Fig. 22 in a final assembly position, Fig. 24 a cross-sectional view of the rail fastening according to Fig.

[0099] 22, Fig. 25 a cross-sectional view of the rail fastening according to Fig. 23, Fig. 26 a perspective view of the angle guide plate used in the rail fastening according to Figs. 22-25, Fig.

[0100] Fig. 27 is a further cross-sectional view of the rail fastening according to Fig. 19 and Fig. 28 shows the cold deformation of the tension spring using a stress-strain diagram.

[0101] Fig. 1 shows the tension spring 1, comprising a U-shaped main section which has 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 a hook-shaped holding section 5 which is bent inwards and can be supported on a hold-down device is formed on the first leg 3 and an end section 6 which is bent towards or away from the holding section 5 is formed on the second leg 4. The bent end section 6 forms a hold-down section for holding down the rail foot of a rail. The holding section 5 comprises a free end region 7.

[0102] In Fig. 2 it can be seen that between the bent end section 6 and the free end region 7 of the holding section 5, as seen in a plan view, a gap x is arranged on the side of the free end region 7 facing the second leg 4. The gap allows the insertion of the holding section of the tension spring 1 with the hook bend first into a tunnel-shaped recess of the hold-down device (see Fig. 5-8).

[0103] 3 and 4 that the first leg 3 and the holding section 5 including the free end region 7 lie in the same plane, so that they form a flat support surface a. Since the tension spring 1 is bent from a wire with a circular cross-section, this also means that the center axis of the said sections lie in a common center plane b. In the unloaded state it is further provided that the free end region 7 of the holding section 5 completely covers the U-bend 2 as seen in the direction of a longitudinal extent of the free end region 7 (Fig. 3). In other words, the U-bend, starting from the first leg 3, at least up to the said overlap with the free end region 7, also lies in the same plane as the first leg 3 and the holding section 5 including the free end region 7.

[0104] However, as the U-bend 2 continues, i.e. in the direction of the second leg 4, the U-bend 2 is bent downwards from plane a or b, so that the normal distance of the second leg 4 to plane a or b increases up to the bent end section 6. In Fig. 4 it can be seen that the second leg 4 with its central axis c forms an acute angle ß with the plane a or b of the holding section 5 and the first leg 3. This gives the bent end section 6 the spring travel required for resiliently holding down the track element or rail foot. The direction of the spring travel is indicated in Fig. 4 by the arrow z. This is the direction in which the bent end section 6 is deflected to such an extent that cold forming takes place at the point of the tension spring with the highest load, which increases the fatigue strength of the tension spring.

[0105] In Fig . 3 it is further shown that the bent end section 6 has a support surface d for resting on the track body element which, in the unloaded state, is slightly inclined upwards in the direction of the arrow III, so that an acute angle a is present between the bent end section 6 or the support surface d and the plane a or b of the holding section 5 and the first leg 3 .

[0106] Fig. 5 shows a rail 8 which is fastened to a sleeper 11 with the interposition of a plate 10 arranged on a base plate 9. The fastening is effected on each side of the rail 8 by means of a tension spring 1 according to Fig. 1, which is inserted into a tunnel-shaped recess 13 of a hold-down device 12. In the final assembly position of the tension spring 1 shown in Fig. 5, the latter presses with its bent end section 6 onto the rail foot 16 of the rail 8, with the optional interposition of an insulator. The hold-down device 12 is fastened to the plate 10 in a suitable manner. For example, the plate 10 and the hold-down device 12 are manufactured in one piece and screwed to the sleeper 11. Alternatively, an anchor can be formed on the underside of the plate 10, which is embedded in the concrete sleeper 11 when it is cast.

[0107] Fig. 6 is an enlarged view of the tension spring 1 inserted into the tunnel-shaped recess 13. It can be seen that the tension spring has been inserted with its holding section 5 in the direction of the arrow 14, i.e. in the longitudinal direction of the rail, into the tunnel-shaped recess 13, so that the bent end section 6 rests on the rail foot 16. When inserted in the direction of the arrow 14 from the pre-assembly position (not shown) into the final assembly position shown in Figure 6, the bent end section 6 slides on a ramp 17 which rises in the insertion direction 14, until it falls over a step formed at the end of the ramp 17 onto the rail foot 16. On the side of the hold-down device 12 facing the rail foot 16, a stop 18 is also formed which overlaps the bent end section 6 at a distance and which, together with the end section 6, acts as an overload protection device.

[0108] The ramp 17 is designed such that the bent end section 6 at the highest point of the ramp 17 is deflected so far that the tension spring 1 reaches the plastically deformed region, at least at its most highly loaded point, and is thus subjected to cold forming. When it falls onto the rail foot 16, the tension spring 1 is partially released. The aforementioned overload protection device limits the spring travel of the bent end section 6 during operation such that no further plastic deformation occurs at any point on the tension spring 1.

[0109] 7 and 8 show an alternative design of the rail fastening, in which the tension spring 1 is inserted transversely to the longitudinal direction of the rail, i.e. in the direction of the arrow 14, into the tunnel-shaped recess 13 (see Fig. 9) of the hold-down device 12. When inserted in the direction of the arrow 14, the bent end section 6 slides again along the ramp 17 formed on the outside of the hold-down device 12 until the bent end section 6 falls down onto the rail foot 16 via a step 19 formed at the end of the ramp 17. An insulator 15 can be arranged between the tension spring 1 and the rail foot. In the embodiment shown in Fig.

[0110] In the final assembly position shown in Fig. 8, the holding section 5 emerges from the tunnel-shaped recess 13 on the side facing the rail 8 and forms a stop which overlaps the rail foot 16 with the optional insulator 15 at a distance and which forms an overload protection device.

[0111] The ramp 17 is designed such that the bent end section 6 at the highest point of the ramp 17 is deflected so far that the tension spring 1 reaches the plastically deformed region, at least at its most highly loaded point, and is thus subjected to cold forming. When it falls onto the rail foot 16, the tension spring 1 is partially released. The aforementioned overload protection device limits the spring travel of the bent end section 6 during operation such that no further plastic deformation occurs at any point on the tension spring 1.

[0112] The hold-down device 12 used in Figs. 7 and 8 is shown in more detail in Figs. 9 and 10, wherein it can be seen in particular that the ramp 17 consists of three sections which follow one another in the insertion direction 14. The ramp 17 comprises a first rising ramp section 20 and a second rising ramp section 22 and an intermediate section 21 lying therebetween which has no gradient and on which the bent end section 6 of the tension spring 1 rests in a pre-assembly position. Furthermore, an anchor 31 can be seen in Figs. 9 and 10, with which the hold-down device can be concreted or cast into a concrete sleeper 11 or, for example, a plastic sleeper 11.

[0113] Fig. 11 shows a modified embodiment in which the tension spring 1 is tensioned by a hold-down device designed as a fastening screw 25. The fastening screw 25 is hooked to the rib 24 as a hook screw or is screwed into the sleeper 11 in such a way that its screw shaft or thread passes through a free space between the first leg 3 and the free end region 7 of the holding section 5 of the tension spring 1. The free space between the first leg 3 and the free end region 7 of the holding section 5 is in this case slot-shaped so that the tension spring 1 can be moved between a pre-assembly position and the final assembly position shown in Fig. 12. In the embodiment shown, the rail base 10 is designed as a ribbed plate whose ribs 24 define the position of the rail foot 16 of the rail 8 on the sleeper 11.

[0114] In the modified embodiment according to Fig. 12, the fastening system comprises an angled guide plate 26 on each side of the rail 8, which engages with a rib formed on the underside in a groove 27 of the sleeper 11.

[0115] Fig. 13 shows the use of a rail fastening according to the invention in the area of ​​a switch, which has a stock rail 8 and a tongue rail 28 that can be moved between a remote and abutting position. The tongue rail 28 slides with its rail foot on a slide chair 29, with the hold-down device 12 having a further sliding surface on its upper side that is flush with the sliding surface of the slide chair 29. The hold-down devices 12 arranged on both sides of the stock rail 8 can be formed integrally with a base plate 30.

[0116] The design according to Fig. 14 essentially corresponds to the design according to Fig. 12, although the angled guide plate 26 is constructed in two parts. As can be seen in Figs. 15 and 17, the angled guide plate 26 consists of a first part 32 facing away from the rail and a second part 33 facing the rail. The first part 32 carries a rib 34 which, when installed, engages in the groove 27, wherein the rib 34 preferably has a trapezoidal cross-section and has at least one guide surface 38. The first and second parts 32, 33 are displaceable relative to one another along guide surfaces 38, 39 (Fig. 17) which are inclined to the longitudinal direction of the rail, in order to thereby enable 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 and which engages over the upper surface of the first element 32. As shown in Fig.17, the plate-shaped support element 41 has at least one oblique guide groove 40 on its underside, into which guide pins or the like (not shown) formed on the upper side of the first element 32 engage in order to hold the two parts 32, 33 together, particularly in the unloaded state. Furthermore, it can be seen that the second part 33, in particular the plate-shaped support element 41, has a through-hole 35 through which the screw 25 passes when the tension spring 1 is in the assembled state. The through-hole 35 is designed as an elongated hole perpendicular to the longitudinal direction of the rail. For the lateral guidance of the tension spring 1, the second part 33, in particular the plate-shaped support element 41, has two walls 37 which run in the insertion direction 14 of the tension spring 1.The elevation 36, which is arranged between the first leg 3 and the free end 7 of the holding section 5 of the tension spring 1, also serves to guide the tension spring 1.

[0117] The tension spring 1 can be moved between the final assembly position shown in Fig. 14 and a pre-assembly position (not shown), in which the tension spring 1 does not overlap the rail foot. The design is such that the screw 25 does not have to be loosened in order to move the tension spring 1 from the pre-assembly position to the final assembly position. The movement can be carried out, for example, using a lever-like tool. Figs. 18 and 19 show, based on the design according to Fig. 12, the displaceability of the tension spring 1 between the pre-assembly position (Fig. 18) and the final assembly position (Fig. 19), wherein, where identical components are concerned, reference numerals from Figs. 14-17 have been retained. Figs. 20 and 21 each show a cross-section of Figs. 18 and 19 along the line XX and XX respectively. XXI .

[0118] 20 and 21 that the fastening screw 25 has a screw head 42 and a screw shaft 43, the screw head 42 compressing the tension spring with the interposition of a washer 44. The elevation 36 of the angled guide plate 26 forms a stop 45 with which the screw head 42 or the washer 44 interacts and which thus limits the screw-in depth of the fastening screw 25. The stop 45 serves to define the screwed-down state of the tension spring 1 or the tightened state of the fastening screw 25 such that the tension spring 1 remains displaceable between the pre-assembly and the final assembly position.The stop 45 defines a minimum vertical distance h between the washer 44 and the support 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 area.

[0119] In Fig. 20 it can be seen that the angled guide plate 26 has a lateral contact surface 46 for the rail foot 16 and the fastening screw 25 is arranged such that the tension spring 1 does not protrude beyond the contact surface 46 in the pre-assembly position. Furthermore, in Figs. 18 and 19 a ramp 47 is formed on the angled guide plate 26 which is arranged such that the bent end section 6 of the tension spring 1 slides along this when moved from the pre-assembly position to the final assembly position. The ramp is flat or ascending in the direction of the rail foot 16, with the end of the ramp forming a step sloping down towards the rail foot, over which step the bent end section 6 descends onto the rail foot 16 when the tension spring 1 is moved from the pre-assembly position to the final assembly position (see Fig. 27).

[0120] Figs. 22 and 23 show an alternative embodiment in which the tension spring 1 can be moved from the pre-assembly position (Fig. 22) into the final assembly position (Fig. 23) by rotating it about the screw axis. Figs. 24 and 25 are sectional views of Figs. 22 and 23. For the rotation of the tension spring 1, a rotatable intermediate piece 48 is provided as a stop 45, which is penetrated by the screw shaft 43 and engages between the first leg 3 and the free end region 7 of the tension spring 1 and is pressed there by the fastening screw 25 against the angle guide plate 26, so that the intermediate piece 48 forms a rotatable stop 45, which both limits and transmits the screw-in depth of the fastening screw 25 and its tensioning force to the tension spring 1, which is why the intermediate piece 48 could also be understood as a component of a hold-down device.

[0121] The rotatable stop 45 serves in a similar manner to the previously described movable design to define the screwed-down state of the tension spring 1 or the tightened state of the fastening screw 25 such that the tension spring 1 remains rotatable between the pre-assembly position and the final assembly position. The intermediate piece 48 comprises an area that overlaps the first leg 3 and the free end region 7, whereby the tension spring is tightened when the fastening screw 25 is tightened. The area of ​​the intermediate piece 48 that overlaps the first leg 3 and the free end region 7 defines, as stop 45, a minimum vertical distance h between the bearing surface of the tension spring on the angle guide plate 26 and its opposite contact surface of the intermediate piece

[0122] 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 comprises an extension

[0123] 49, which engages behind the end face of the free end region 7 of the tension spring 1 or engages in the free space between the free end region 7 and the U-bend 2. The extension 49 acts as a safeguard against horizontal displacement of the tension spring 1 and as a driver to support the transmission of the rotational movement applied by the engagement of a tool on the intermediate piece 48 or stop 45 to the tension spring 1.

[0124] The angled guide plate 26 from Figures 22 to 25 is shown in more detail in Figure 26, and it can be seen that a raised portion 50 is formed on the side 46 facing the rail foot 16. The raised portion 50 has a contoured edge to provide both a first holding surface 53 for the pre-assembly position and a second holding surface 54 for the final assembly position of a rotationally displaceable tension spring 1. Furthermore, the contact surface 46 forms a step 52 extending from the upper edge of the contact surface 46 and descending to a rail foot. So that the hold-down force can be fully transmitted to the rail foot in the final assembly position, the required vertical freedom of movement for a tension spring 1 must be present between the second leg and the angled guide plate 26. For this purpose, a recess 51 ensures that the upper edge of the contact surface 46 is lowered at a corresponding point. level 52 .

[0125] Fig. 27 shows the section SS through the step 52 from Fig. 19. This falls away by the distance Y towards the rail foot. In order to ensure that the deflection of the bent end section 6 in the final assembly position over its entire maximum spring travel does not lead to a plastic deformation of the tension spring 1, the vertical distance shown in Fig. 21 between the holding section 5 acting as an overload protection device and the rail foot 16 is less than or equal to the vertical distance y shown in Fig. 27 between the highest point of the ramp 47 and the rail foot 16.

[0126] Fig. 28 shows, based on a stress-strain diagram determined in a tensile test, the stress applied during cold forming and the stress range maintained during normal operation within the spring deflection limited by the overload protection. The diagram shows the 0.2% yield strength Rp0.2, the 1.0% yield strength Rpl.0 and the 2.0% yield strength Rp2.0. With a stress of, for example, Rp2.0, a permanent plastic strain of 2% is reached when this stress is reached for the first time. As shown by the thickened line, the tension spring is loaded at the most highly loaded point by deflecting the bent end section 6 in the direction of the spring deflection up to the stress Rpl.0. After the resulting cold forming, the tension spring 1 is tensioned up to the stress <j upartially relieved, namely over the distance y (see Fig. 27) , and in this state holds the rail foot spring-loaded. The overload protection limits the spring travel upwards in such a way that up to this point, at most the tension <j o = Rpl,0 can occur. In the range between <j u and <j o This ensures that the tension spring 1 is only loaded in the elastic deformation range at any point during normal railway operation, preferably with <j o < Rpl,0.

[0127] The following table shows an overview of several test series in which the wire for the tension spring shown in Fig. 1-4 was subjected to a plastic preload corresponding to the 0.2% yield strength Rp0.2 and the 2.0% yield strength Rp2.0 in order to induce cold forming. The mean tolerable stress amplitude for fatigue testing (MW [MPa]) and the standard deviation (Stabw [MPa]) were then determined using the extended step method according to Hück in order to illustrate the differences in fatigue testing. The number of tests was increased, especially for higher standard deviations, in order to be able to make valid statements. According to the results, especially for stronger cold forming with a preload Rp2.0 and subsequent tensile pulsation test with a maximum stress at a distance from it <j o= (0.85*Rp2.0) the mean tolerable stress amplitude for fatigue strength (MW [MPa] ) is significantly increased compared to Rp0.2 and the corresponding standard deviation is reduced compared to Rp0.2.

Claims

Patent claims:

1. A method for producing a rail fastening, in which a track body element, such as a rail foot (16) of a rail (8), is resiliently held down in its final assembly position by at least one hold-down section (6), such as a holding arm, of a tension spring (1), the tension spring (1) being made of tempered spring steel, comprising mounting the tension spring (1) on a base (11), the tension spring (1) being brought into a tensioned state by means of a hold-down device (12, 25), in which the tension spring (1) is tensioned starting from a relaxed state by deflecting the hold-down section (6) along a spring travel (z), characterized in that the hold-down section (6) is deflected in the direction of the spring travel (z) during assembly to such an extent that the tension spring (1) is subjected to cold forming, after which the tension spring (1) is at least partially relaxed.

2. Method according to claim 1, characterized in that the maximum spring travel of the hold-down section (6) in the final assembly position of the tension spring (1) is limited by an overload protection device (5, 18) and that the cold forming takes place by deflecting the hold-down section (6) over a spring travel which is greater than or equal to the maximum spring travel limited by the overload protection device (5, 18).

3. Method according to claim 1 or 2, characterized in that the hold-down section (6) for the cold forming is deflected so far that at the most highly loaded point of the tension spring (1) a maximum Principal normal stress corresponding to the 0.5% proof strength, preferably the 1% proof strength, is reached or exceeded.

4. Method according to claim 3, characterized in that the tension spring (1) after cold forming has been carried out and when the maximum spring travel is reached, at no point does it exceed the said maximum main normal stress, preferably 90% of the maximum main normal stress, in particular 85% of the maximum main normal stress.

5. Method according to one of claims 1 to 4, characterized in that the cold forming takes place at least on the surface of the wire forming the tension spring (1).

6. Method according to one of claims 1 to 5, characterized in that the step of mounting the tension spring (1) comprises fastening the tension spring (1) in a pre-assembly position in which the hold-down section (6) does not overlap the track body element.

7. Method according to one of claims 1 to 6, characterized in that the cold forming in the pre-assembly position, during the displacement of the tension spring (1) from the pre-assembly position to the final assembly position or in the final assembly position.

8. Method according to claim 6 or 7, characterized in that the cold forming is carried out during the displacement of the tension spring (1) from the pre-assembly position into the final assembly position with the hold-down device (12) in the tensioned state held tension spring (1) by sliding of the hold-down section (6) on a sliding surface (17) of the base which rises at least in sections in the direction of displacement.

9. Method according to one of claims 6 to 8, characterized in that the hold-down section (6) drops from a sliding surface (17) over a step (19, 52) onto the track body element during the displacement of the tension spring (1) from the pre-assembly position into the final assembly position in order to assume the final assembly position.

10. Method according to one of claims 1 to 7, characterized in that the hold-down device is formed by a fastening screw (25) and the cold forming takes place in the pre-assembly position or the final assembly position by tensioning the tension spring (1) by means of the fastening screw (25), whereupon the tension spring (1) is at least partially released by turning back the fastening screw (25).

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

12. Method according to one of claims 1 to 11, characterized in that the tension spring (1) has a U-shaped main section which has 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 on the first leg (3) a hook-shaped inwardly bent, on a Holding section (5) which can be supported by a hold-down device (12, 25) and on the second leg (4) the hold-down section (6) is designed as an end section of the second leg (4) which is bent towards or away from the holding section (5), wherein the U-bend (2) forms a torsion section so that a hold-down force can be applied to the track body element via the bent end section (6).

13. Method for increasing the vibration strength of a tension spring (1) for holding down a track body element, such as a rail foot (16) of a rail (8), wherein the tension spring (1) consists of a tempered spring steel and has at least one hold-down section (6) which can be resiliently deflected along a spring travel (z), such as a holding arm, for resiliently holding down the track body element, characterized in that the tension spring (1) is provided for installation in a track, in which the maximum spring travel of the hold-down section (6) is limited by an overload protection device (5, 18) in such a way that no plastic deformation takes place at any point on the tension spring (1) within the maximum spring travel, the said maximum spring travel is determined and the hold-down section (6) is deflected in the direction of the spring travel (z) beyond the maximum spring travel or up to the maximum spring travel, so that the tension spring (1) is subjected to cold forming.

14. Rail fastening, in particular produced by a method according to one of claims 1 to 12, comprising a tension spring (1) made of tempered spring steel and a hold-down device (12, 25) which can be fastened on a base, in particular a sleeper (11), ribbed plate or angle guide plate, adjacent to a track body element (8), on which hold-down device the tension spring (1) in a final assembly position of the tension spring (1) is so can be supported or is supported in that the tension spring (1), starting from a relaxed state, can be tensioned with the hold-down section (6) against the track body element, in particular a rail foot (16) of a rail (8), by deflecting at least one hold-down section (6) of the tension spring (1) along a spring travel (z), in order to resiliently hold it down, characterized in that the tension spring (1) is cold-formed by deflecting the hold-down section (6) in the direction of the spring travel (z) or is cold-formable during assembly and is at least partially relieved of said deflection in the final assembly position.

15. Rail fastening according to claim 14, characterized in that the maximum spring travel of the hold-down section (6) in the final assembly position of the tension spring (1) is limited by an overload protection device (5, 18) and that the cold forming takes place by deflecting the hold-down section (6) over a spring travel which is greater than or equal to the maximum spring travel limited by the overload protection device (5, 18).

16. Rail fastening according to claim 14 or 15, characterized in that the hold-down section (6) for the cold forming is deflected to such an extent that at the most highly loaded point of the tension spring (1) a maximum principal normal stress corresponding to the 0.5% yield strength, preferably the 1% yield strength, is reached or exceeded.

17. Rail fastening according to claim 16, characterized in that the tension spring (1) after cold forming when reaching the maximum spring travel does not at any point have the maximum main normal stress, preferably 90% of the maximum principal normal stress, in particular 85% of the maximum principal normal stress.

18. Rail fastening according to one of claims 14 to 17, characterized in that the cold forming takes place at least on the surface of the wire forming the tension spring (1).

19. Rail fastening according to one of claims 14 to 18, characterized in that the hold-down section (6) can be deflected for cold forming by tensioning the tension spring (1) by means of the hold-down device (12, 25).

20. Rail fastening according to 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 section (6) does not overlap the track body element.

21. Rail fastening according to claim 20, characterized in that the base has a sliding surface (17) which rises at least in sections and on which the holding-down section (6) rests when the tension spring is held in the tensioned state by the holding-down device (12). (1) slides during the displacement of the tension spring (1) from the pre-assembly position into the final assembly position, whereby the hold-down section (6) can be deflected and / or partially relieved for cold forming.

22. Rail fastening according to claim 20 or 21, characterized in that the base forms a step (19, 52) at the end of a sliding surface (17), over which the hold-down section (6) during the displacement of the tension spring (1) falls from the pre-assembly position to the final assembly position onto the track body element in order to assume the final assembly position.

23. Rail fastening according to one of claims 14 to 22, characterized in that the tension spring (1) has a U-shaped main section which has 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 on the first leg (3) there is formed a hook-shaped inwardly bent holding section (5) which can be supported on a hold-down device and on the second leg (4) the hold-down section (6) is formed as an end section of the second leg (4) which is bent towards or away from the holding section (5), wherein the U-bend (2) forms a torsion section such that a hold-down force can be applied to the track body element via the bent end section (6).

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

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