Tie plate used in rail fastening structure and its manufacturing method

Abstract

To provide a tie plate with use of a non-metal material which is excellent in electrical insulation and corrosion resistance, and is effective in weight saving.SOLUTION: A tie plate for use in a rail fastening structure to fasten rails with a fastening spring comprises a groove part formed along a laying direction of the rail, in which rails are assembled, and a reinforcement part extending from the groove part to an end in a width direction of the tie plate. The groove part and the reinforcement part are made of a thermoplastic resin.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a tie plate used in a rail fastening structure for fastening a rail to a track slab or a sleeper, and a method for manufacturing the same. [Background technology]

[0002] When fastening rails of railways or the like to track slabs or sleepers, a rail fastening structure is used in which the rails are held in place by metal members such as leaf springs. Various such rail fastening structures are known, and for example, a rail fastening device described in Patent Document 1 is known.

[0003] That is, the rail fastening device described in Patent Document 1 has a tie plate fixed to the roadbed side, and a leaf spring fixed to this tie plate presses down from above to hold the rail. In this case, the end face of the leaf spring is positioned parallel to the longitudinal direction of the rail, and this end face presses directly against the upper surface of the rail bottom. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-123480 Summary of the Invention [Problem to be solved by the invention]

[0005] The tie plates used in conventional rail fastening devices are made of metal, and to prevent corrosion and ensure electrical insulation performance, insulating plates are inserted, the leaf springs are surface-treated, etc. Furthermore, in order to prevent the occurrence of transportation disruptions due to ground faults in return currents that occur due to the electrical insulation between the rail and the rail fastening device, it is desirable to improve the above-mentioned electrical insulation performance.

[0006] However, conventional rail fastening devices have a problem in that because the tie plates are made of metal, the surface treatment of the leaf springs can be damaged, and short circuits can occur due to thinning, breakage, or detachment of the leaf springs, making it difficult to completely prevent the occurrence of the above-mentioned transportation disruptions.

[0007] Furthermore, if the surface treatment of the tie plate is damaged, the damaged part can cause corrosion or electrolytic corrosion, resulting in rail breakage. Therefore, there is a demand to reduce the risk of rail breakage to as close to zero as possible.

[0008] Furthermore, metal tie plates are very heavy, weighing around 10 kg, which makes them difficult to handle when laying or maintaining track.

[0009] The present invention has been made in view of the above problems, and has an object to provide a tie plate using a non-metallic material that has excellent electrical insulation and corrosion resistance and can reduce weight. [Means for solving the problem]

[0010] The tie plate according to the present invention is a tie plate used in a rail fastening structure for fastening rails with fastening springs, the tie plate comprising a groove formed along the laying direction of the rail and into which the rail is assembled, and a reinforcing portion extending from the groove toward the end of the tie plate in the width direction, the groove and the reinforcing portion being: Contains reinforcement made of glass fiber or carbon fiber, and has a tensile breaking stress of 50 MPa or more Made from thermoplastic The tie plate has a step portion formed at a diagonally opposite corner of the reinforcing portion, and a protective plate formed at an end of the step portion in the rail laying direction, and the groove portion, the reinforcing portion and the protective plate are integrally formed. It is characterized by the following.

[0011] In addition, in the tie plate according to the present invention, it is preferable that the reinforcing portions are rib-shaped and extend from both walls constituting the groove portion toward the widthwise ends of the tie plate, that the rib shapes are formed on the front and / or back surfaces of the tie plate, and that the thickness of the rib shapes is in the range of 2 mm or more and less than 10 mm.

[0012] Furthermore, in the tie plate according to the present invention, the reinforcing portion is preferably formed with a locking portion that locks the fastening spring so that it can rotate freely around the laying direction, and the locking portion is preferably erected from the widthwise end of the reinforcing portion.

[0016] In the tie plate according to the present invention, it is preferable that the rib shape includes a plurality of ribs intersecting each other, and that lightening portions are formed between the ribs.

[0017] The method for manufacturing a tie plate according to the present invention is characterized in that the tie plate is manufactured by injection molding.

[0018] The above summary of the invention does not list all of the necessary features of the present invention, and subcombinations of these features may also constitute inventions. [Effects of the Invention]

[0019] The rail fastening structure according to the present invention has a tie plate made of thermoplastic plastic, which makes it possible to realize a rail fastening structure with excellent electrical insulation and corrosion resistance. Furthermore, because these components are made of thermoplastic plastic, it is possible to reduce the weight. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a perspective view showing an overview of a rail fastening structure according to an embodiment of the present invention; [Figure 2] 1A and 1B are six-view and cross-sectional views of a tie plate used in a rail fastening structure according to an embodiment of the present invention. [Figure 3] 1A and 1B are six-view diagrams and a cross-sectional diagram of a fastening spring used in a rail fastening structure according to an embodiment of the present invention. [Figure 4] 1 is a diagram showing a rail fastening structure according to an embodiment of the present invention, viewed from the rail extension direction; [Figure 5] 10 shows measurement results of fastening spring stress of the rail fastening structure according to the present embodiment. [Figure 6] 10 shows measurement results of tie plate stress in the rail fastening structure according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] Preferred embodiments for carrying out the present invention will be described below with reference to the drawings. Note that the following embodiments do not limit the inventions according to the claims, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0022] FIG. 1 is a perspective view showing an overview of a rail fastening structure according to an embodiment of the present invention, FIG. 2 is a six-sided view and a cross-sectional view of a tie plate used in the rail fastening structure according to an embodiment of the present invention, FIG. 3 is a six-sided view and a cross-sectional view of a fastening spring used in the rail fastening structure according to an embodiment of the present invention, FIG. 4 is a view showing the rail fastening structure according to an embodiment of the present invention from the rail extension direction, FIG. 5 shows the measurement results of fastening spring stress in the rail fastening structure according to this embodiment, and FIG. 6 shows the measurement results of tie plate stress in the rail fastening structure according to this embodiment.

[0023] As shown in Figure 1, the rail fastening structure 1 according to this embodiment is attached to track slabs and sleepers positioned on a roadbed (not shown). The rail fastening structure 1 according to this embodiment includes a tie plate 10 attached to the track slab or sleeper, a rail 2 placed on the tie plate 10 via a rail height adjustment pad 3 and a track pad 4, a fastening spring 20 that holds the lower part of the rail 2 from above, and a fastening bolt 33, a fastening nut 32, and an insulating washer 31 that secure the fastening spring 20.

[0024] 2, the tie plate 10 is made of a non-metallic material, short glass fiber reinforced thermoplastic (FRTP), such as polyamide mixed with short glass fibers. Short glass fiber reinforced thermoplastic has relatively high tensile strength and Young's modulus, and its tensile characteristic curve behaves similarly to that of metallic materials, making it suitable for use.

[0025] The thermoplastic resin can be selected from known plastic materials as long as it does not impair the strength of the tie plate 10 after it is formed. However, engineering plastic resins are preferred for their strength, rigidity, and heat resistance. Preferably, the tensile stress at break measured in accordance with ISO 527-1 and -2 is 50 MPa or greater. The thermoplastic resin may also contain conventional additives, such as reinforcing materials, pigments, dyes, heat stabilizers, weathering agents, lubricants, mold release agents, and antioxidants, as needed. When a reinforcing material is included in the thermoplastic resin, the fiber length is preferably within the range of 10 μm to 10 mm. In this embodiment, the tie plate 10 is formed by injection molding a thermoplastic resin composed of 40 wt. % polyamide 610 resin and 60 wt. % short glass fibers (the total amount of polyamide 610 resin and short glass fibers is taken as 100 wt. %), taking into consideration the balance between rigidity and toughness, low water absorption, and dimensional stability. The weight-average fiber length of the short glass fibers contained in the thermoplastic resin was 239 μm. The thermoplastic plastic had a tensile stress at break of 204 MPa and a compressive stress at break of 252 MPa when bone dry, as measured in accordance with ISO 527-1 and -2, and a tensile stress at break of 169 MPa and a compressive stress at break of 222 MPa when absorbed at atmospheric equilibrium in an environment of 23°C and 50% RH. Injection molding is also suitable as a means of molding thermoplastic plastics because it has a short molding cycle, is excellent for mass production, and provides stable quality, such as the dimensions of molded products.

[0026] The tie plate 10 has a groove 15 formed in the widthwise center along the rail extension direction, and the rail 2 is assembled to this groove 15. The groove 15 also has reinforcing portions 11 extending from the groove 15 toward the widthwise ends of the tie plate 10. The reinforcing portions 11 extend from both ends of the groove 15. The reinforcing portions 11 have locking portions 12 erected from the widthwise ends of the tie plate 10, and step portions 19 formed at diagonally opposing corners of the pair of reinforcing portions 11. Fastening bolt holes 14 are also formed on a diagonal line different from the step portions 19.

[0027] The reinforcing portion 11 has a flat upper surface, and the portion that overlaps with the locking portion 12 is formed with an arc-shaped cross section. The fastening bolt hole 14 is formed as a through-hole that penetrates all the way to the back surface of the tie plate 10, and the back surface has a recess into which the head of the fastening bolt 33 can fit.

[0028] The back surface of the tie plate 10 is formed with a plurality of intersecting ribs 17, with lightening holes formed between the ribs 17. The ribs 17 and the lightening holes make it possible to reduce the weight of the tie plate 10, ensure its rigidity, and prevent deformation of the tie plate 10 due to cooling of the material during injection molding. The thickness of the ribs is preferably within the range of 2 mm to 10 mm, and more preferably within the range of 2 mm to 6 mm, as this provides sufficient reinforcement against stresses generated in the tie plate and also suppresses the occurrence of voids, warping, sink marks, etc. during injection molding. The average thickness of the ribs in this embodiment is 4.5 mm.

[0029] The step portion 19 is formed with fixing bolt holes 13 through which fixing bolts (not shown) formed in the track slabs or sleepers can be inserted, and the fixing bolt holes 13 are formed as elongated holes that are long in the width direction so that the position of the tie plate 10 can be adjusted. The upper surface of the step portion 19 is formed flat to ensure a seating surface for the fixing bolt that screws into the fixing bolt. Furthermore, a protective plate 16 is formed on the end of the step portion 19 in the extension direction of the rail. The protective plate 16 acts as a reinforcing rib that suppresses deformation of the groove portion 15 in the width direction, and also maintains the distance between the rail 2 and the fixing bolt, ensuring insulation.

[0030] 3, the fastening spring 20 is a member curved so as to be convex upward in the width direction, and in this embodiment is made of carbon fiber reinforced plastic (CFRP), a non-metallic material, for example, epoxy resin mixed with carbon. Carbon fiber reinforced plastic has a particularly high Young's modulus and is corrosion resistant, making it possible to prevent thinning due to corrosion, breakage, and short circuits due to falling off.

[0031] A through hole 21 extending in the vertical direction is formed in the center of the fastening spring 20. The through hole 21 is formed as an elongated hole that is long in the width direction, and is formed so that the diameter decreases from top to bottom.

[0032] The widthwise end of the fastening spring 20 has an arc-shaped end. The fastening spring 20 is constructed by winding a glass fiber reinforced plastic or carbon fiber reinforced plastic sheet in the widthwise direction, with reinforcing fibers laminated on the cross section, and winding the glass fiber reinforced plastic or carbon fiber reinforced plastic sheet in the widthwise direction makes it possible to form the arc-shaped end.

[0033] As shown in Fig. 4, the rail fastening structure 1 according to this embodiment configured as described above has a tie plate 10 fixed onto a roadbed (not shown), and the rail 2 is held in place by the fastening spring 20 pressing from above with fastening bolts 33 and fastening nuts 32. At this time, the arc end 22 on the base end side of the fastening spring 20 is engaged with the engaging portion 12 so as to be rotatable around the laying direction of the rail 2, and the arc end on the other end side is attached so as to be freely adjustable in height.

[0034] In addition, the through hole 21 of the fastening spring 20 is formed so that its diameter decreases from top to bottom, thereby preventing interference between the fastening bolt 33 and the through hole 21 due to the rotation of the arc end on the other end as described above, and making it possible to reliably apply the elastic force of the fastening spring 20 to the rail 2.

[0035] In addition, in the rail fastening structure 1 according to this embodiment, the tie plate 10 is made of a non-metallic material, so it is possible to eliminate the insulating plate that is used in conventional rail fastening structures and is interposed between the tie plate and the roadbed.

[0036] Next, with reference to Figures 5 and 6, the results of a performance test of the rail fastening structure 1 according to this embodiment will be described. The performance test was a static and dynamic bidirectional load test conducted in accordance with the "Railway Structure Design Standard and Commentary: Track Structure" (hereinafter referred to as the "Track Standard"). The load test was conducted assuming application to a JIS 60kg rail, conventional line (fastening interval 625mm), and track with a curve radius of 600m or more, and the design action loads A and B were determined under a design axle load of 150kN. Measurements were conducted at positions I to IV in Figure 2.

[0037] As shown in Figures 5 and 6, the maximum stress generated in the fastening spring 20 of the rail fastening structure 1 according to this embodiment during loading was 57.1 MPa, which was confirmed to be sufficiently small compared to the tensile strength of carbon fiber reinforced plastic, which is 638 MPa.

[0038] Regarding tie plate stress, the maximum tensile stress was 38.6 MPa at measurement point III and the maximum compressive stress was 7.4 MPa at measurement point I when load A was applied, and it was confirmed that these were sufficiently small compared to the tensile breaking stress of 169 MPa and compressive breaking stress of 222 MPa of glass fiber reinforced thermoplastic plastic when it absorbs water at equilibrium in air.

[0039] The dynamic loading test was carried out under the same conditions as the static loading test, with the target number of repetitions being 10. 6 10 times. 6 After the repeated loading, the fastening bolts and nuts did not loosen, and no external abnormalities were found.

[0040] As described above, the results of the static loading test and the dynamic loading test confirmed that the rail fastening structure 1 according to this embodiment has safety in terms of fatigue fracture.

[0041] Next, an electrical insulation resistance test was conducted on the rail fastening structure 1 according to the present embodiment in accordance with the track standard. The electrical insulation resistance test measured the electrical insulation resistance value under three conditions: no spraying (dry condition), spraying of tap water (rainfall condition), and spraying of 0.1% salt water (polluted condition). The results of the electrical insulation resistance test showed that the electrical insulation resistance value exceeded the design reference value of 1.6 kΩ specified in the track standard in all conditions, and was more than 20 times that of conventional rail fastening structures, even in the polluted condition among the test conditions. This confirmed that the rail fastening structure 1 according to the present embodiment has sufficiently high electrical insulation properties compared to conventional rail fastening structures.

[0042] As described above, in the rail fastening structure 1 according to this embodiment, the tie plate 10 is made of thermoplastic plastic, which improves the electrical insulation performance between the rail and the support body, thereby reducing the risk of transportation disruptions such as return current ground faults caused by this electrical insulation.

[0043] Furthermore, in the rail fastening structure 1 according to this embodiment, the tie plate 10 is made of thermoplastic plastic, which makes it possible to reduce its weight compared to conventional tie plates. The tie plate 10 obtained in this embodiment weighs approximately 2 kg, which is significantly lighter than the approximately 10 kg weight of conventional metal tie plates. [Explanation of symbols]

[0044] 1 rail fastening structure, 2 rail, 3 rail height adjustment pad, 4 track pad, 10 tie plate, 11 reinforcement part, 12 locking part, 13 fixing bolt hole, 14 fastening bolt hole, 15 groove part, 16 protective plate, 17 rib, 18 recess, 19 step, 20 fastening spring, 21 through hole, 22 arc end, 31 insulating washer, 32 fastening nut, 33 fastening bolt.

Claims

1. A tie plate used in a rail fastening structure for fastening a rail with a fastening spring, The tie plate includes a groove formed along the direction in which the rail is laid and into which the rail is assembled, and a reinforcing portion extending from the groove toward an end of the tie plate in the width direction, the groove portion and the reinforcing portion are formed of a thermoplastic plastic containing a reinforcing material made of glass fiber or carbon fiber and having a tensile breaking stress of 50 MPa or more; The tie plate has step portions formed at diagonally opposite corners of the reinforcing portion, A protective plate is formed at the end of the step portion in the rail laying direction, The tie plate is characterized in that the groove portion, the reinforcing portion, and the protective plate are integrally formed.

2. 2. The tie plate according to claim 1, the reinforcing portion has a rib shape extending from both walls of the groove portion toward the widthwise ends of the tie plate, The rib shape is formed on the front and / or back surface of the tie plate, A tie plate characterized in that the thickness of the rib shape is in the range of 2 mm or more and less than 10 mm.

3. 2. The tie plate according to claim 1, The reinforcing portion is formed with a locking portion to which the fastening spring is locked so as to be rotatable around the laying direction, The rail fastening structure is characterized in that the locking portion is erected from the width direction end portion of the reinforcing portion.

4. 3. The tie plate according to claim 2, The tie plate is characterized in that the rib shape includes a plurality of ribs that intersect with each other, and a lightening portion is formed between the ribs.

5. A method for manufacturing a tie plate, wherein the tie plate according to any one of claims 1 to 4 is manufactured by injection molding.

Images