GB2421265A

GB2421265A - Railway rail with vibration damper

Info

Publication number: GB2421265A
Application number: GB0427624A
Authority: GB
Inventors: Hugh Thomas Rogers; Tom Giles Wilson Collins; Trevor Reginald Smith
Original assignee: TIFLEX Ltd
Current assignee: TIFLEX Ltd
Priority date: 2004-12-16
Filing date: 2004-12-16
Publication date: 2006-06-21
Also published as: GB0427624D0

Abstract

The rail has the damper (18) disposed on the web (14) or foot (16) upper side or under side of the rail (10). The damper (18) is preferably a constrained layer damper formed from a layer of a metal (22) and a layer of an elastomeric material (20) secured to the rail. Methods of damping rails and manufacturing railway track are also disclosed.

Description

Rail Dampers This application relates to anti-vibration dampers for railway tracks. When trains run on railway tracks that pass around sharp curves of a short radius, a screeching sound may be heard. This sound originates from the rails, which vibrate at their resonant frequency as a train passes over them. This noise is unpleasant for passengers and the vibration can reduce the life of track and rolling stock. According to a first aspect of this invention, there is provided a rail for a railway track comprising a damper disposed on a foot of the rail to reduce vibration, preferably resonant vibration, of the rail. This invention involves the realisation that a significant proportion of the noise originates in the rail flange or foot which generally vibrates at a resonant frequency. Adding a damper attenuates the amplitude of the vibration and may also reduce the resonant frequency thereby reducing the loudness of the noise and also its annoying screeching quality. Preferably the damper is disposed on an upper surface of the foot of the rail. Preferably the damper extends over an edge of the foot of the rail. The damper may comprise a laminar structure, having layers which are stacked in a direction substantially perpendicular to the surface of the rail foot on which the damper is disposed. Preferably the damper is a constrained layer damper. The damper may comprise a layer of damping material, preferably a viscoelastic elastomer, for example an acrylic, and a layer of a relatively inelastic material, such as a metal, conveniently steel, preferably stainless steel. The layer of damping material is preferably applied directly to the rail in use. The damper may cover up to 50%, or up to 90%, preferably substantially 70% of the surface of the foot of the rail on at least one side of the rail web. This may amount to substantially the entire area of rail between adjacent sleepers to which the rail is affixed. According to a second aspect of this invention there is provided a rail comprising a constrained layer damper. According to a third aspect of this invention there is provided a constrained layer damper for a rail, the damper comprising a layer of damping material and a layer of relatively inelastic material and being dimensioned and shaped to conform to a surface of the rail. The damper may be dimensioned and shaped to conform to a surface of the foot of the rail. The second and third aspects of the invention may incorporate any of the features outlined above. According to a fourth aspect of this invention there is provided a method of damping railway track comprising attaching a damper as set forth above to a rail. According to a fifth aspect of this invention there is provided a method of manufacturing railway track comprising attaching a damper as set forth above to a rail. According to a sixth aspect of this invention there is provided a method of manufacturing railway track comprising disposing a damper on a foot of a rail to reduce resonant vibration of the rail. The damper may be disposed on an upper surface of the foot of the rail. Preferably the damper extends over a ledge of the foot of the rail. The damper may comprise a laminar structure, having layers which are stacked in a direction substantially perpendicular to the surface of the rail foot on which the damper is disposed. Preferably the damper is a constrained layer damper. The damper may comprise a layer of damping material and a layer of relatively inelastic material such as metal, conveniently steel, preferably stainless steel. The damper may cover up to 50%, conveniently up to 90%, preferably substantially 70%, of the surface of the rail on at least one side of a rail web. The damper may cover substantially an entire area of rail between adjacent sleepers to which the rail is fixed. An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows schematically a cross section through a rail with a damper attached; and Figure 2 shows schematically a top view of a curved rail track. A section through a typical rail 10 is shown in Figure 1. The rail 10 comprises a head 12, a relatively narrow web 14 and a relatively broad foot flange 16. Disposed on an upper surface of the foot flange 16 and extending to a side surface of the foot flange, is a damper 18. The damper 18 comprises a layer of viscoelastic elastomeric polymer 20 and a layer of stainless steel 22 shaped to conform to the profile of the flange. The layer of stainless steel is approximately 3 mm thick, but the thickness can be varied, commonly being increased, to achieve different levels of vibration reduction. The viscoelastic polymer 20 is an acrylic, and the layer is made as thin as possible, preferably being 1 mm or less in thickness. The layer may have to be thicker if the rail surface is particularly uneven or undulating. The choice of acrylic depends on the climate in which the damper will be used. A suitable acrylic will soften at an appropriate temperature for the climate The acrylic is waterproof. The purer the acrylic the better its function, the presence of fabric scrim in the acrylic noticeably degrades the function of the viscoelastic layer. The acrylic is essentially a pressure sensitive adhesive and fixes the damper 18 to the foot flange 16. When fixed with the viscoelastic layer 20 adjacent to the rail, the damper 18 forms a constrained layer damper. When a train passes over the rail, the curvature causes its wheels to slip slightly on the rail, setting up vibration in the rail which is communicated to the damper, and the elastomeric layer is subjected to an alternating shear stress. The resulting elastic and plastic shear strain dissipates the vibration as heat, and reduces the propensity of the rail to "ring" loudly at its resonant frequency. Noise reductions of up to 6 dB or more can be achieved using this system, depending on the application. Referring to Figure 2, one rail 10 of a length of track is shown fixed conventionally to sleepers 26 by Pandrol or other clips 28. The rail foot 16 is substantially covered on both sides by dampers 18. For a typical track configuration with sleepers at 900mm centres, a single damper approximately 640mm long will substantially fill the inter-sleeper distance and will cover approximately 70% of the length of the rail. Alternatively, on sharply-curved sections shorter lengths of damper can be used to fill the space whilst better accommodating the curve of the rail, as shown in Figure 2. When applying the damper to the rail, it is essential that the rail foot is clean and dry beforehand to ensure a good bond. Once the damper has been positioned on the rail foot, pressure is applied to ensure good and even contact across its area. The damper may be applied to the rail as part of a manufacturing process, or may be retro-fitted when the rail is in place. Generally dampers are applied to both sides of the rail foot, but for cost or access reasons it may be applied to one side only. Once fitted, little or no maintenance is required. The skilled reader will appreciate that other combinations of materials are possible. For example, the metal layer could be aluminium and the elastomeric layer could be other viscoelastic polymers. The viscoelestic polymers must be viscoelastic in the temperature range that the damper is likely to be used in. They are preferably waterproof and self-adhesive. Although the damper is shown as disposed on the top of rail foot it could be used elsewhere, for example on the underside of the rail foot, or anywhere on the rail web. The damper may for example extend wholly or partially over both the flange and the web; in each case the metal backing sheet is preformed so that the damper conforms to the shape of the rail. Each feature disclosed in this specification (which term includes the claims) and/or shown in the drawings may be incorporated in the invention independently of other disclosed and/or illustrated features. Statements in this specification of the "objects of the invention" relate to preferred embodiments of the invention, but not necessarily to all embodiments of the invention falling within the claims. The description of the invention with reference to the drawings is by way of example only. The text of the abstract filed herewith is repeated here as part of the specification. A rail for a railway track comprises a damper disposed on the web or foot of the rail. The damper is preferably a constrained layer damper formed from a layer of a metal and a layer of an elastomeric material. Methods of damping rails and manufacturing railway track are also disclosed.

Claims

1. A rail for a railway track comprising a damper disposed on a foot of the rail to reduce vibration, preferably resonant vibration, of the rail.

2. A rail according to Claim 1 in which the damper is disposed on an upper surface of the foot of the rail.

3. A rail according to Claim 2 in which the damper extends over an edge of the foot of the rail.

4. A rail according to any preceding claim in which the damper comprises a laminar structure, having layers which are stacked in a direction substantially perpendicular to the surface of the rail foot on which the damper is disposed.

5. A rail according to any Claim 4 in which the damper is a constrained layer damper.

6. A rail according to Claim 4 or Claim 5 in which the damper comprises a layer of damping material, and a layer of relatively inelastic material, such as a metal, conveniently steel, preferably stainless steel.

7. A rail according to any preceding claim in which the damper covers up to 50%, conveniently, up to 90%, preferably substantially 70%, of the surface of the foot of the rail on at least one side of a rail web.

8. A rail according to Claim 7 in which the damper covers substantially an entire area of rail between adjacent sleepers to which the rail is affixed.

9. A rail comprising a constrained layer damper.

10. A constrained layer damper for a rail, the damper comprising a layer of damping material and a layer of relatively inelastic material, and being dimensioned and shaped to conform to a surface of the rail.

11. A damper according to Claim 10, being dimensioned and shaped to conform to a surface of a foot of the rail.

12. A method of damping railway track comprising attaching a damper according to any of Claim 10 or claim 11 to a rail.

13. A method of manufacturing railway track comprising attaching a damper according to any of Claim 10 or Claim 11 to a rail.

14. A method of manufacturing railway track comprising disposing a damper on a foot of a rail to reduce resonant vibration of the rail.

15. A method according to Claim 14 in which the damper is disposed on an upper surface of the foot of the rail.

16. A method according to Claim 15 in which the damper extends over an edge of the foot of the rail.

17. A method according to any of claims 14 to 16 in which the damper comprises a laminar structure, having layers which are stacked in a direction substantially perpendicular to a surface of the rail foot on which the damper is disposed.

18. A method according to Claim 17 in which the damper is a constrained layer damper.

19. A method according to Claim 17 or Claim 18 in which the damper comprises a layer of damping material and a layer of relatively inelastic material, such as a metal, conveniently steel, preferably stainless steel.

20. A method according to any of claims 14 to 19 in which the damper covers up to 50%, conveniently up to 90%, preferably substantially 70% of the surface of the foot of the rail on at least one side of a rail web.

21. A method according to Claim 20 in which the damper covers substantially an entire area of rail between adjacent sleepers to which the rail is affixed.

22. A rail substantially as described above and shown in the accompanying drawings.

23. A damper substantially as described above and shown in the accompanying drawings.

24. A method of damping railway track substantially as described above.

25. A method of manufacturing railway track substantially as described above.