NL8403711A - RAIL INSULATION CUSHIONS. - Google Patents

Description

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RAIL INSULATION CUSHIONS

The present invention relates to rail mounting systems and in particular to rail insulation pads for electrically and dynamically insulating the rail from the sleeper.

Australian Patent 479,377 Writes a commonly used form of rail insulator with a small cross-section and with tapered sides to reduce the occurrence of damage or cracks in the rail cushion.

10 In cases where concrete sleepers are used, it has been found that cracks or cracks in the sleeper may be caused by shocks caused by flattened parts in the circumference of the track wheels or by the track wheel serrations or 15 curves in the rail (eg a weld seam) hits. It has been determined that one way to reduce the occurrence of damage of this nature was to use a rail pad that has both shock absorbing properties and electrically insulating properties. An obvious solution was to apply a thicker rail pad of an elastic material such as rubber.

However, the thickness alone is not the solution. Attempts have been made to provide improved shock absorbing capacity. The (expired) Australian patent application

No. 28158/71 discloses a pad having a row of ribs on top and bottom surfaces which, according to the claims, reduce vibration and noise. Australian Patent 508,353 discloses a high density polyethylene rail cushion (a resilient but inflexible hard material), with a series of radial recesses to prevent cushion rupture due to uneven rails 8403711 - 2 - -Γ ϊ » limit sleeper surfaces.

Although the installation of ribs or recesses in the rail cushions can have some effect in limiting damage to sleepers and to the 5 cushions themselves, damage still occurs frequently, especially in curved sections of the track, where the loads to which the cushions and sleepers exposed on one side of the rail are concentrated.

10 A problem that can occur with thick resilient rail pads is that in curved track sections, the load on the rail places the load to one side of the pad, usually the terrain side or exterior. When the cushion is relatively soft, the rail tilts more easily and under heavy loads it is possible for the rail to be tilted out of the track seat.

The object of the present invention is to improve the force-damping properties of rail insulating pads and also to limit the likelihood of damage to such pads.

To this end, the present invention provides a rail fastening system in which a rail is attached to a sleeper by means of a rail seat 25 consisting of a sleeper, a rail cushion between the sleeper and the rail, a pair of rail clamp supports which are on either side of the rail and against the rail cushion attached, a rail clamp connected to each rail clamp support, each clamp having a portion 30 mounted in the clamp support and pressing a portion onto the rail foot, and a clamp insulator located on the rail foot to electrically isolate the rail foot from the rail clamp and clamp support , the improvement consisting of applying a. rail cushion to electrically and dynamically isolate the sleeper 35 from the rail, which 8403711 4 - 3 - f * cushion is made of a material with a high elastic capacity and where the parts of the cushion on the terrain side which run from the terrain side of the rail extending 20 mm inward, reduced by less than 10% in 5 volume by providing grooves and recesses in both cushion surfaces and the portion of the cushion under the rail being limited by at least 15% in volume by grooving and recesses in both cushion surfaces. This invention also relates to the construction of the cushion itself.

The parts of the cushion on the terrain side, which must be hard enough to prevent deformation and which bear the load of the rail, have a width large enough to bear the load, but too small to stretch the material sideways under load to counteract. Preferably, this applies to both the site side (outside of the rail) and the track side (inside of the rail) of the cushion, so that the cushion need not be laid in a particular way. The cushion material must be able to deform laterally in order to achieve damping of the load. However, where the surface contact is large, frictional resistance prevents such lateral movement. Preferably, the total restriction in volume of the cushion is under the rail. means of the recesses or grooves more than 20%, and preferably more than 30%, and the limitation in volume in the strip of 20mm inward from at least the terrain side of the rail is preferably less than 7.5%, and most preferably less than 3%. Preferably, both sides of the pad extending parallel to the rail are so formed.

In further explaining the problem solved by the present invention, reference is made to Figures 1A, B and C, which show a known »403711 * 9 φ / * - 4 - thick rail pad used for a high force-damping effect. In cases where the cushion is placed on a curved track and the load is applied along the line D as indicated in 5 IA, the cushion will initially bend vertically as shown in 1B, leading to a reduction in the span E-E. This reduction in wingspan means that a greater deflection of the pad occurs, which in turn leads to a further decrease in wingspan on the terrain side as shown in F-F in Figure 1C. This leads to instability of the track seat and excessive wear of the rail cushion.

Figures 2A-2C show a similar situation, with the difference that a harder material is used for the cushion, but a recess in the cushion under the rail offers greater force-damping capacity.

The span G-G on the terrain side of the cushion remains almost constant under a diagonal load D.

In order to achieve optimum resistance to damage by the rail and the highest possible damping of the load, according to the present invention the material of the cushion is resilient and flexible and has an optimal combination of hardness, elasticity without breaking or spring force, cut resistance and high elastic capacity. Preferably, a natural or synthetic rubber should be used which is formulated to have a hardness of between 68 and 90 DURO-A with abrasion and cut resistance and resistant to permanent compression under prolonged heavy load (creep resistance).

A rail cushion of such a material would in itself have insufficient force-damping capacity. According to the present invention, however, use is made of a cushion of a material having a hardness 8403711 f - 5 - f a ·

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ranging from 68 to 85 DURO-A and with abrasion and cut resistance, those portions of the pad that are below the rail are provided with grooves or recesses to effect greater force-damping capability than the edge portions of the pad.

Preferably, no grooves or recesses are provided in the edge parts of the cushion, which would reduce the carrying capacity of the cushion.

This means that the edge parts have a high elastic capacity (equal to that of the selected material). However, the center portion of the cushion must have a high force-damping capacity, and it is essential in the invention that the center section of the cushion has a low load-bearing capacity and a correspondingly low elastic capacity.

This can be achieved by a completely hollow center section without any material. If there is material, it need not come into contact with the rail or crossbar and it may be in the form of a connecting plate.

If surface contact between the cushion and the rail or crossbar is required, the contact area must be small and the structure of the cushion must be such that the elastic capacity is low and a high degree of force damping takes place.

This can be achieved by providing the center part of a corrugated profile with grooves with sloping sides, in order to reduce the carrying capacity of this part of the cushion, because the sloping walls of the corrugations will move together under load and not Being squeezed.

With this construction it is possible to use corrugations * that run parallel to the longitudinal direction of the rail and over the entire cushion. It is also possible to provide the central part of the cushion with a lower elastic capacity by providing wide grooves with a depth of more than 50% of the thickness of the cushion.

When using thicker rail cushions with a high force-damping capacity, a considerable vertical deflection of the cushion will occur. This deflection will of course vary according to the hardness of the cushion material, but also depends on the thickness of the cushion. The thicker the cushion, the stronger the vertical deflection. This vertical deflection under load causes lateral deformation of the cushion from under the railway seat with any load impulse due to the passing of a railway wheel. However, the portion of the pad between the rail and the rail clamp support is completely enclosed by the rail clamp and the rail, and this limits such lateral deformation. Instead, the pad will tend to deform upwardly under the clamp insulator, which lies partly on the rail foot 20 and partly on the rail pad between the foot and the clamp support. This upward force and movement on the clamp insulator results in some cases in early failure of the clamp insulator due to material fatigue.

In order to solve this special problem, according to the present invention, a recess is provided in the rail cushion in the part of the cushion which abuts the clamping support. This recess may be a cavity in the top or bottom surface of the pad, or grooves in the top or bottom face that limit the volume of the pad in that portion of the pad.

Such a recess will provide enough space for the pad to deform under load without exerting pressure on the clamp insulator. Preferably, a cavity is provided in the m ...................

8403711 β <- 7 - top surface that lies below and within the boundary of the clamp insulator. Preferably, the recess represents at least 10%, and most preferably 25%, of the volume of the pad lying between the edge of the clamp support that is parallel to the rail and the rail edge.

The volume of the recess may exceed 50% of the volume of this portion of the pad, but no further advantage is achieved.

The invention will now be described with reference to the drawings, in which figure 3 is a schematic view of a rail seat showing the position of the rail cushion, figures 4a, b and c are a top and two side views of a preferred embodiment of the rail cushion according to the invention, figures 5a, b, c * 5 are corresponding views of a modified embodiment of the cushion from figures 4a, b, c, figures 6a, b, c are corresponding views of another embodiment of the invention, figures 7a, b , c are views of yet another embodiment and Figures 8a, h,, c are views of a modification of the embodiment of Figures 7a, b, c; Figures 9A-9D show another embodiment of the cushion.

The track seat shown in Fig. 3 consists of the rail 7, the cross beam 8 and the rail insulating cushion 9 between them. On either side of the rail 7 and embedded in the cross beam 8 there are two rail clamp supports 10 and a clamp 11 is attached to each of them. foot of rail 7. A clamp-50 insulator 12 isolates both clamps 11 from the feet of the rail 7.

In each of Figures 4 to 8, the edge portions 13 and 14 of the rail pad are adjacent to and below the longitudinal edges of the rail foot, and the edge recesses 15, 35 and 16 are adapted in shape to the portions of the 8403711 * »-8-

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rail clamp supports that rest against that portion of the rail cushion. In all embodiments of the present invention, the edge portions 13 and 14 do not have recesses or grooves spaced 5-20mm inward from the edge of the rail lying on the pad. The edges of the rail are indicated as line 19 in the drawings.

In each of the embodiments, the edge portions 17 and 18 are perpendicular to the longitudinal direction of the rail.

The material of the cushions in each embodiment is preferably a mixture of synthetic or natural rubber with a hardness between 68 and 90 DURO on the Shore-A scale with good creep and cut resistance,

The embodiment according to fig. 4a, b, c in the middle section 20 have no cushion material at all, except for the 20mm strip inward from line 19.

In FIG. 5a ,. b, c, a connecting plate 21 with raised ribs 22 in the form of a cross forms the connection between the four sides 13, 14, 17 and 18.

It should be noted that the connecting plate 21 and the ribs 22 do not form a load-bearing support.

In the embodiment according to FIG. 6a, b, c, lateral undulations 24 extend between the sides 17 and 18. These undulations have contact surfaces 25 and connecting walls 26 which extend obliquely to the perpendicular. This ensures a low load-bearing capacity of these undulations.

Fig. 7a, b, c show an embodiment in which the corrugations 27 extend parallel to the longitudinal direction of the rail and to near the edges 17 and 18 of the cushion. As in the version according to 35. 4a, b, c, the ends of the undulations are curved so that they form a closed loop. 8403711 * a. .............—- w <* - 9 - φ%

A variant of the embodiment according to Fig. 7a, b, c is shown in FIG. 8a, b, c, in which the undulations extend parallel to the longitudinal direction of the rail up to the edges 17 and 18 and do not form closed loops 5.

Fig. 9A shows a top view of the top surface of the pad and FIG. 9B is a top view of the bottom surface. Fig. 9C is a sectional view taken along line A-A in FIG. 9A and FIG. 9D is a sectional view 10 taken along line B-B in FIG. 9A. The recesses 31 and 32 in the top surface of the pad next to the respective edge recesses 15 and 16 reduce the volume of the pad between the edge of the clamp support 10 parallel to the rail 7 and the edge of the rail 7 by 25%. The grooves 33 in both faces of the pad are 7mm deep and are arranged in a chevron shape, the grooves alternately located in the top and bottom surfaces.

Each of the aforementioned embodiments 20 provides an increase in damping capability over existing rail pads, while at the same time providing greater resistance to rail damage in curved track sections. Some embodiments, in particular those in FIG. 4a, b, c and 5a, b, 25 c, use less material and are therefore cheaper to produce.

8403711

Claims (14)

1. Rail mounting system in which a rail is attached to a crossbar by means of a rail seat, consisting of a crossbar, a rail cushion "between the crossbar and the rail, a pair of 5 rail clamp supports attached to the crossbar on either side of the rail and abutting the rail cushion a rail clamp connected to each rail clamp support, each clamp having a portion secured in the clamp support and a portion resting on the rail foot, and a clamp insulator located on the rail foot to electrically isolate the rail foot from the rail clamp and clamp support, the improvement being the provision of a rail cushion to electrically and dynamically isolate the sleeper from the rail, the cushion being made of a material having a high elastic capacity and the portions of the cushion on the terrain side 20mm inward from the site side of the rail, reduced by less than 10% in volume by applying grooves and onion recesses in both cushion surfaces and the portion of the cushion under the rail is reduced by at least 15% in volume by providing grooves and recesses in both cushion surfaces. Improvement according to claim 1, wherein the rail cushion consists of a resilient, flexible material with a hardness between 68 and 90 DURO on the Shore-A scale. The improvement according to claim 1 or 2, wherein the volume of the pad lying under the rail 30 is reduced by at least 20%. 8403711. a »^ i ί» ψ - 11 - The improvement of claim 1 or 2, wherein the volume of the pad extending 20mm inward from the terrain side of the rail is reduced by less than 7.5%. 5. The improvement of claim 1, wherein the portion of the rail pad that abuts the rail gland support has recesses or grooves in the top or bottom surface of the pad to reduce the volume of the pad in that portion. 6. Improvement according to claim 5, wherein the top surface of the part of the cushion lying against the clamping support has recesses such that the volume of the cushion lying between the edge of the clamping support parallel to the rail and the rail edge by at least 10% is reduced. Rail cushion according to claim 1. Rail cushion according to claim 7, wherein the rail cushion is formed from a resilient / flexible material with a hardness between 68 and 90 20 DURO on the Shore-A scale. Rail cushion according to claim 7 or 8, wherein the volume of the cushion lying under the rail is reduced by at least 20%. Rail cushion according to claim 7 or 8, wherein the volume of the cushion extending 20 mm inward from the terrain side of the rail is reduced by less than 7.5%. 8403711 T - 12 -. / f · 1 'i w The rail cushion of claim 7, wherein the portion of the rail cushion that abuts the rail clamp support has recesses or grooves in the top or bottom surface of the rail cushion to reduce the volume of the cushion in that section. Rail cushion according to claim 11, wherein the upper surface of the part of the cushion lying against the clamping support has recesses such that the volume of the cushion between the edge of the clamping support is parallel to the rail and the rail edge by at least 10% is reduced. Rail cushion according to claim 8, wherein the recesses or grooves have a depth of at least 50% of the thickness of the cushion. Rail cushion according to claim 8, wherein grooves are provided · in both surfaces of the cushion with a depth of more than 50% of the thickness of the cushion, the grooves alternately on one and the other surface and at a distance from each other are provided. 8403711