JP7792595B2 - Synthetic sleepers and their manufacturing method - Google Patents

Description

The present invention relates to a composite sleeper suitable for railway turnout points.

For example, as described in Patent Document 1, synthetic sleepers made of fiber-reinforced plastic (FRP) are known. Furthermore, as described in Patent Document 2, it has also been proposed to place a rail switching device in a recess formed in the sleeper. The synthetic sleepers described in Patent Documents 1 and 2 are made by incorporating a large number of glass fibers into a polyurethane resin matrix resin and solidifying it.

The rail switching device changes the vehicle's path by using an actuator to change the position of the tongue rail, which can move horizontally relative to the base rail. Composite sleepers used at turnout points may be subjected to horizontal loads in addition to the weight of the rail itself and the wheel load of vehicles passing on the rail.

Patent No. 3872884 Japanese Patent Application Laid-Open No. 2020-94326

As described in Patent Documents 1 and 2, fiber-reinforced synthetic sleepers have physical properties and bending strength comparable to those of conventional wooden or concrete sleepers. However, in the case of synthetic sleepers with recesses formed to accommodate rail switching devices, such as those used at turnout points, special consideration was required regarding shear strength and tensile stress around the recesses.

The objective of an embodiment of the present invention is to provide a synthetic sleeper for a turnout point that can accommodate a rail switching device and has high strength against stresses such as shear strength and tension.

In one embodiment, the synthetic sleeper is made of resin reinforced with a large number of electrically insulating fibers, and has upper and lower surfaces, first and second side surfaces, first and second end surfaces, and a recess that opens to the upper surface and accommodates a rail switching device. The recess includes a bottom surface on which the rail switching device is placed, first and second inner surfaces, a first inner end surface that aligns with the first inner surface, and a second inner end surface that aligns with the second inner surface.

The first inner surface is formed at a position corresponding to the first side surface, is inclined in a direction in which the distance from the first side surface increases from the top surface to the bottom surface, and forms a first sidewall portion between the first inner surface and the first side surface. The second inner surface is formed at a position corresponding to the second side surface, is inclined in a direction in which the distance from the second side surface increases from the top surface to the bottom surface, and forms a second sidewall portion between the second inner surface and the second side surface.

Furthermore, the recess includes a first corner portion, a second corner portion, a third corner portion, a fourth corner portion, a first bottom arc portion, and a second bottom arc portion. The first corner portion is formed at a corner between the first inner surface and the first inner end surface. The second corner portion is formed at a corner between the first inner surface and the second inner end surface. The third corner portion is formed at a corner between the second inner surface and the first inner end surface. The fourth corner portion is formed at a corner between the second inner surface and the second inner end surface.

The first bottom arc portion is formed between the first inner surface and the bottom surface, and the radius of curvature of the cross section along the vertical direction is larger than the radius of curvature of the cross section along the horizontal direction of each of the first to fourth corner portions. The second bottom arc portion is formed between the second inner surface and the bottom surface, and the radius of curvature of the cross section along the vertical direction is larger than the radius of curvature of each of the first to fourth corner portions.

The synthetic sleeper of this embodiment has a first rail support portion formed between the first end face and the first inner end face, and a second rail support portion formed between the second end face and the second inner end face. The fiber content per unit volume of the first side wall portion and the second side wall portion may be greater than the fiber content per unit volume of the first rail support portion and the second rail support portion. The radius of curvature of the first bottom arc portion and the radius of curvature of the second bottom arc portion may each be 10 mm or more and 40 mm or less.

The manufacturing method for producing the synthetic sleeper involves placing a core inside an outer mold that has a shape corresponding to the recess of the synthetic sleeper. The resin containing the fiber before hardening is supplied into the cavity formed between the outer mold and the core. After the resin has hardened, the core is removed from the outer mold.

The composite sleeper according to this embodiment has a recess for accommodating a rail switching device to make the turnout point compact, yet it can exhibit great strength against loads such as bending, tension, and buckling, and also has excellent electrical insulation properties.

FIG. 1 is a plan view of a turnout point equipped with a composite sleeper according to one embodiment. 2 is a cross-sectional view of the turnout point portion along the line F2-F2 in FIG. 1. FIG. 2 is a plan view of the composite sleeper shown in FIG. 1 . FIG. 4 is a cross-sectional view of the composite sleeper taken along line F4-F4 in FIG. FIG. FIG. 3 is a cross-sectional view of a portion of the composite sleeper taken along the horizontal direction. FIG. 3 is a cross-sectional view of a portion of the composite sleeper taken along the vertical direction. FIG. 5 is a cross-sectional view of the composite sleeper taken along line F8-F8 in FIG. 4. FIG. 1 is a perspective view showing a synthetic sleeper, a floor plate, and a portion of a rail. FIG. 4 is a diagram showing the relationship between the radius of curvature of the bottom arc portion of the composite sleeper and stress. FIG. 1 is a plan view schematically showing an outer mold and a core used in manufacturing synthetic sleepers. 12 is a cross-sectional view of the core taken along line F12-F12 in FIG. 11 . FIG. 13 is an enlarged cross-sectional view of the core taken along line F13-F13 in FIG. 12 .

A turnout point equipped with a composite sleeper and a rail switching device according to one embodiment will be described below with reference to Figs. 1 to 10 .
Figure 1 shows an example of a turnout point 10. Figure 2 is a cross-sectional view of the turnout point 10 taken along line F2-F2 in Figure 1. The turnout point 10 includes base rails 11 and 12, horizontally movable tongue rails 13 and 14, a rail switching device 15, a composite sleeper 16, and the like.

The composite sleeper 16 is a flat, approximately rectangular parallelepiped, and has a top surface 20 extending in a substantially horizontal direction, first and second side surfaces 21 and 22 that are parallel to each other, a first and second end surface 23 and 24, a recess 25, and a bottom surface 26 (shown in Figure 2). The recess 25 is open at the top surface 20 of the composite sleeper 16. The first and second side surfaces 21 and 22 of the recess 25 each extend in the longitudinal direction of the composite sleeper 16. The first and second end surfaces 23 and 24 are formed at both ends of the synthetic sleeper 16 in the longitudinal direction. The double-headed arrow X1 in Figure 1 indicates the longitudinal direction of the composite sleeper 16. The double-headed arrow Y1 in Figure 1 indicates the width direction of the composite sleeper 16.

The base rails 11, 12 are fixed to the floor plates 31, 32, which are placed on the upper surface 20 of the composite sleeper 16, by fixing mechanisms 33, 34. The tongue rails 13, 14 are supported via floor plates 35, 36, which are attached to the floor plates 31, 32, so that they can slide in the rail width direction (indicated by the double-headed arrow X2 in Figure 2).

An example of a rail switching device 15 includes a hydraulic cylinder mechanism 40 as an actuator, a hydraulic pump 41, an oil tank 42, an electric motor 43 that drives the hydraulic pump 41, and a control unit 44. The hydraulic cylinder mechanism 40 has a cylinder body 40a and piston rods 40b and 40c. The hydraulic pressure generated by the hydraulic pump 41 drives the piston rods 40b and 40c horizontally, moving the tongue rails 13 and 14 in the rail width direction.

Figure 3 is a plan view of the synthetic sleeper 16. Figure 4 is a cross-sectional view of the synthetic sleeper 16 taken along line F4-F4 in Figure 3, and Figure 5 is a perspective view of the synthetic sleeper 16. The synthetic sleeper 16 is made of electrically insulating resin 51 (for example, a rigid urethane foam matrix resin) reinforced with a large number of electrically insulating fibers 50 (some of which are shown schematically in Figure 5). An example of the fibers 50 is glass fiber, which is mainly continuous along the length of the synthetic sleeper 16. The synthetic sleeper 16 reinforced with fibers 50 has excellent electrical insulation properties and also has great strength against bending loads, tensile loads, and other loads.

The recess 25 of the synthetic sleeper 16 opens to the top surface 20 of the synthetic sleeper 16. That is, the top surface 20 of the synthetic sleeper 16 has an opening 25a. The recess 25 houses part of the rail switching device 15, such as the hydraulic pump 41, oil tank 42, electric motor 43, and control unit 44. A bottom surface 60 on which the rail switching device 15 is placed is formed at the bottom of the recess 25.

As shown in Figures 3 to 5, the recess 25 has a bottom surface 60, a first inner surface 61, a second inner surface 62, a first inner end surface 63, and a second inner end surface 64. The first inner surface 61 is formed at a position corresponding to the first side surface 21 and extends along the first side surface 21 in the longitudinal direction of the composite sleeper 16. The second inner surface 62 is formed at a position corresponding to the second side surface 22 and extends along the second side surface 22 in the longitudinal direction of the composite sleeper 16. The first inner end surface 63 is formed at a position corresponding to the first end surface 23. The second inner end surface 64 is formed at a position corresponding to the second end surface 24.

As shown in Figures 2 and 4, a bottom wall portion 70 is formed between the lower surface 26 of the synthetic sleeper 16 and the bottom surface 60 of the recess 25. As shown in Figure 3, a first side wall portion 71 is formed between the first side surface 21 and the first inner surface 61. A second side wall portion 72 is formed between the second side surface 22 and the second inner surface 62.

A first rail support portion 73 is formed between the first end face 23 and the first inner end face 63. A second rail support portion 74 is formed between the second end face 24 and the second inner end face 64. A first floor plate 31 is disposed on the first rail support portion 73. The first floor plate 31 has a pair of extensions 31a, 31b extending toward the first side wall portion 71 and the second side wall portion 72. A second floor plate 32 is disposed on the second rail support portion 74. The second floor plate 32 has a pair of extensions 32a, 32b extending toward the first side wall portion 71 and the second side wall portion 72.

As shown in Figure 3, when viewing the composite sleeper 16 from above, the recess 25 has a first corner portion 81, a second corner portion 82, a third corner portion 83, and a fourth corner portion 84. The first corner portion 81 is formed at the corner between the first inner surface 61 and the first inner end surface 63. Figure 6 shows an enlarged horizontal cross section of the first corner portion 81. The radius of curvature r1 (shown in Figures 3 and 6) of the first corner portion 81 is, for example, less than 10 mm.

The second corner portion 82 is formed at the corner between the first inner surface 61 and the second inner end surface 64. The third corner portion 83 is formed at the corner between the second inner surface 62 and the first inner end surface 63. The fourth corner portion 84 is formed at the corner between the second inner surface 62 and the second inner end surface 64.

The radii of curvature r1, r2, r3, and r4 of the first to fourth corner portions 81, 82, 83, and 84 are, for example, less than 10 mm. If the radii of curvature r1, r2, r3, and r4 exceed 10 mm, the opening area of the recess 25 (area of opening 25a) becomes correspondingly narrower, making it more likely that part of the rail diverting device 15 will come into contact with the corner portions 81, 82, 83, and 84 when inserting the rail diverting device 15. If the corners of the rail diverting device 15 or the like make strong contact with the inner surface of the recess 25, some of the fibers 50 will be cut or damaged, causing a decrease in the strength of the synthetic sleeper 16.

Figure 7 shows a cross section along the vertical direction of a portion of the composite sleeper 16 (near the first inner end surface 63). A lower corner portion 85 extending in the width direction of the composite sleeper 16 is formed between the bottom surface 60 and the first inner end surface 63. As shown in Figure 4, a similar lower corner portion 86 (shown in Figures 4 and 7) is formed between the bottom surface 60 and the second inner end surface 64. The radius of curvature r5 of the cross section along the vertical direction of these lower corner portions 85, 86 may be equal to the radii of curvature r1 to r4 of the corner portions 81 to 84.

Figure 8 is a vertical cross-sectional view of the composite sleeper 16 taken along line F8-F8 in Figure 4. The first side surface 21 and the second side surface 22 are both substantially vertical. The first inner surface 61 of the recess 25 is inclined at an angle θ1 from the top surface 20 toward the bottom surface 60 in a direction in which the distance T1 from the first side surface 21 (i.e., the thickness of the first side wall portion 71) increases. The second inner surface 62 is inclined at an angle θ2 from the top surface 20 toward the bottom surface 60 in a direction in which the distance T2 from the second side surface 22 (i.e., the thickness of the second side wall portion 72) increases.

In this way, the thicknesses T1, T2 of the side wall portions 71, 72 increase at angles θ1, θ2 from the opening 25a of the recess 25 toward the bottom surface 60, which allows the side wall portions 71, 72 to exhibit high bending strength and buckling strength against bending loads (shown in both directions P1 in Figure 8) and compressive loads (shown in both directions P2 in Figure 8), and also makes it easier to remove the core 110 (shown in Figures 11 to 13) used to form the recess 25. A method for manufacturing synthetic sleepers using the core 110 will be described in detail later.

As shown in FIG. 8, a first bottom arc portion 91 is formed between the first inner surface 61 and the bottom surface 60. The radius of curvature R1 of the cross section of the first bottom arc portion 91 along the vertical direction is greater than the radii of curvature r1, r2, r3, and r4 of the horizontal cross sections of the first to fourth corner portions 81, 82, 83, and 84, respectively. The radius of curvature R1 of the first bottom arc portion 91 is 10 mm or more and 40 mm or less (for example, R1 = 20 mm).

A second bottom arc portion 92 is formed between the second inner surface 62 and the bottom surface 60. As shown in FIG. 8, the radius of curvature R2 of the cross section of the second bottom arc portion 92 taken along the vertical direction is greater than the radii of curvature r1, r2, r3, and r4 of the horizontal cross sections of the first to fourth corner portions 81, 82, 83, and 84, respectively. The radius of curvature R2 of the second bottom arc portion 92 is 10 mm or more and 40 mm or less (e.g., R2 = 20 mm).

The inventors conducted tests on the maximum tensile stress of the synthetic sleeper 16. In the tests, as shown in Figure 9, rails 11 and 12 were placed on the synthetic sleeper 16 via floor plates 31 and 32. A load equivalent to the wheel load of a vehicle was then applied to the synthetic sleeper 16 via the rails 11 and 12. The dimensions of the synthetic sleeper 16 used in the tests were 2100 mm in length, 400 mm in width, and 140 mm in thickness. The recess 25 was 850 mm in length, 220 mm in width, and 110 mm in depth.

As a result of the test, maximum tensile stress occurred in the first side wall portion 71 and the second side wall portion 72. In particular, large stress occurred in the areas indicated by arrows A1, A2, A3, A4, and A5 in Figure 5, i.e., near the tips of the extensions 31a and 31b of the first floor plate 31 and near the tips of the extensions 32a and 32b of the second floor plate 32. In contrast, the tensile stress in the first rail support portion 73 and the second rail support portion 74 was lower than in the side walls 71 and 72. Therefore, to increase the strength of the synthetic sleeper 16, it is desirable to increase the fiber content (fiber 50 content per unit volume) of the first side wall portion 71 and the second side wall portion 72, including the areas indicated by arrows A1, A2, A3, A4, and A5 in Figure 5, greater than the fiber content of the first rail support portion 73 and the second rail support portion 74.

Figure 10 shows the relationship between the stress generated in the bottom arcuate portions 91, 92 and the radius of curvature when a bending load is applied to the side wall portions 71, 72. If the radii of curvature R1, R2 are smaller than 10 mm, the stress increases sharply, so it is preferable to set the radii of curvature R1, R2 to 10 mm or more. However, if the radii of curvature R1, R2 are larger than 40 mm, the width W1 (shown in Figure 8) of the substantially flat portion of the bottom surface 60 on which the rail switching device 15 is placed decreases, so it is preferable to set the radii of curvature R1, R2 to 40 mm or less.

It goes without saying that the matrix resin and fiber materials that make up the synthetic sleepers can be changed as needed. Specifications such as the shape and size of the synthetic sleepers are not limited to those described in the embodiments, and can be selected appropriately depending on the situation at the turnout point. Furthermore, the technical concept of the present invention can also be applied to track other than at turnout points.

The manufacturing method of the synthetic sleeper 16 will be described below.
Fig. 11 is a plan view schematically showing an outer mold 100 and a core 110 (also referred to as a middle mold) used in manufacturing a synthetic sleeper 16. Fig. 12 is a cross-sectional view of the core 110 taken along line F12-F12 in Fig. 11. Fig. 13 is an enlarged cross-sectional view of the core 110 taken along line F13-F13 in Fig. 12.

The synthetic sleeper 16 is manufactured using a molding device that includes at least an outer mold 100 and a core 110. The outer mold 100 has an inner surface 101 that corresponds in shape to the outer surface of the synthetic sleeper 16. The core 110 has an outer surface 111 that corresponds in shape to the recess 25 of the synthetic sleeper 16.

That is, the core 110 has a surface 120 (shown in Figures 12 and 13) corresponding to the bottom surface 60 of the recess 25 of the composite sleeper 16, a first inclined surface 121 at an angle θ1' (shown in Figure 13) corresponding to the first inner surface 61 of the recess 25, a second inclined surface 122 at an angle θ2' corresponding to the second inner surface 62, a first end surface 123 (shown in Figure 12) corresponding to the first inner end surface 63, and a second end surface 124 corresponding to the second inner end surface 64. It also has a curved surface portion 125 with an arc-shaped cross section corresponding to one lower corner portion 85 (shown in Figure 4) of the recess 25, and a curved surface portion 126 with an arc-shaped cross section corresponding to the other lower corner portion 86 (shown in Figure 4).

As shown in FIG. 11, the core 110 of this embodiment has a first curved surface 131 with a radius of curvature r1' corresponding to the first corner portion 81 of the composite sleeper 16, a second curved surface 132 with a radius of curvature r2' corresponding to the second corner portion 82, a third curved surface 133 with a radius of curvature r3' corresponding to the third corner portion 83, and a fourth curved surface 134 with a radius of curvature r4' corresponding to the fourth corner portion 84. Furthermore, the core 110 has a first arcuate surface 141 (shown in FIG. 13) with a radius of curvature R1' corresponding to the first bottom arcuate portion 91, and a second arcuate surface 142 with a radius of curvature R2' corresponding to the second bottom arcuate portion 92.

In the manufacturing method of this embodiment, the core 110 is used to form the recess 25 of the synthetic sleeper 16. The core 110 is placed inside the outer mold 100. This forms a cavity 150 (shown in Figure 11) for the synthetic sleeper 16 between the inner surface 101 of the outer mold 100 and the outer surface 111 of the core 110. Uncured resin 51 containing fiber 50 is supplied into this cavity 150. After the resin 51 in the cavity 150 has cured, the core 110 is removed from the outer mold 100. In this way, the synthetic sleeper 16 having the recess 25 is integrally molded.

The manufacturing method using the core 110 of this embodiment makes it easy to remove the synthetic sleeper 16 that is integrally molded between the outer mold 100 and the core 110. Furthermore, compared to conventional manufacturing methods in which the recesses 25 are formed by cutting, there is no waste of material, and manufacturing costs can be reduced compared to when cutting is performed.

10...Turret point, 11, 12...Base rail, 13, 14...Tongue rail, 15...Rail switching device, 16...Synthetic sleeper, 20...Top surface, 21...First side surface, 22...Second side surface, 23...First end surface, 24...Second end surface, 25...Recess, 26...Bottom surface, 31, 32...Deck, 50...Fiber, 60...Bottom surface, 61...First inner surface, 62...Second inner surface, 63...First inner end surface, 64...Second inner end surface, 70... Bottom wall portion, 71...first side wall portion, 72...second side wall portion, 73...first rail support portion, 74...second rail support portion, 81...first corner portion, 82...second corner portion, 83...third corner portion, 84...fourth corner portion, 91...first bottom arc portion, R1...radius of curvature, 92...second bottom arc portion, R2...radius of curvature, 100...outer mold, 110...core, 111...outer surface of core, 150...cavity.

Claims (5)

A synthetic sleeper made of resin reinforced with electrically insulating fibers, the synthetic sleeper having an upper surface and a lower surface, a first side surface and a second side surface, a first end surface and a second end surface, and a recessed portion that opens in the upper surface and accommodates a rail switching device,
The recessed portion is
a bottom surface on which the rail switching device is placed;
a first inner surface formed at a position corresponding to the first side surface, inclined in a direction in which a distance between the first side surface and the first inner surface increases from the top surface to the bottom surface, and defining a first sidewall portion between the first side surface and the first inner surface;
a second inner surface formed at a position corresponding to the second side surface, inclined from the top surface toward the bottom surface in a direction in which the distance between the second side surface and the second inner surface increases, and defining a second sidewall portion between the second inner surface and the second side surface;
a first inner end surface along the first end surface;
a second inner end surface along the second end surface;
a first corner portion formed at a corner between the first inner surface and the first inner end surface;
a second corner portion formed at a corner between the first inner surface and the second inner end surface;
a third corner portion formed at a corner between the second inner surface and the first inner end surface;
a fourth corner portion formed at a corner portion between the second inner surface and the second inner end surface;
a first bottom surface arc portion formed between the first inner surface and the bottom surface, the first bottom surface arc portion having a curvature radius of a cross section along a vertical direction that is larger than the curvature radius of a cross section along a horizontal direction of each of the first to fourth corner portions;
a second bottom surface arc portion formed between the second inner surface and the bottom surface, the second bottom surface arc portion having a cross section along the vertical direction with a radius of curvature larger than the radii of curvature of each of the first to fourth corner portions;
A synthetic sleeper characterized by comprising: The synthetic sleeper according to claim 1,
a first rail support portion formed between the first end surface and the first inner end surface;
a second rail support portion formed between the second end surface and the second inner end surface;
Synthetic sleeper with The synthetic sleeper according to claim 2,
A synthetic sleeper in which the fiber content per unit volume of the first side wall portion and the second side wall portion is greater than the fiber content per unit volume of the first rail support portion and the second rail support portion. The synthetic sleeper according to any one of claims 1 to 3,
A composite sleeper, wherein the radius of curvature of the first bottom arc portion and the radius of curvature of the second bottom arc portion are each 10 mm or more and 40 mm or less. A manufacturing method for manufacturing the synthetic sleeper according to claim 1,
a core having a shape corresponding to the recess of the synthetic sleeper is placed inside the outer form,
supplying the resin containing the fibers before hardening into a cavity formed between the outer mold and the core;
a resin curing step for curing the resin, the resin curing step being performed by removing the core from the outer mold, and the synthetic sleeper being molded as a single unit;