WO2005012641A1

WO2005012641A1 - Rail damper

Info

Publication number: WO2005012641A1
Application number: PCT/GB2004/003294
Authority: WO
Inventors: David Farrington; Les Hodgson; Paul Kitson
Original assignee: Corus Uk Limited
Priority date: 2003-07-29
Filing date: 2004-07-29
Publication date: 2005-02-10
Also published as: GB0317721D0; GB2404942A

Abstract

A rail damper comprises at least one tuned absorber element held in a block of resilient material, in which at least part of the block is held within a rigid encapsulation, the encapsulation being adapted to be held against a rail surface. The encapsulation can be provided with engagement sites for a clip.

Description

RAIL DAMPER

FIELD OF THE INVENTION

The present invention relates to improvements in or relating to damping of rail tracks. It addresses the problem of attaching damping devices to the rail and seeks to improve upon existing methods of doing so.

BACKGROUND ART

Our earlier patent application WO99/15732 described a rail damper in which tuned resonant members are held within a compliant block. This is affixed to a side of the rail, resting in the corner formed by the rail foot and the rail web. Figure 1 shows a damper of this type.

It is necessary to retain the damper in place on the rail. This must be done securely and permanently, as if the damper were to become loose then it could become a hazard to passing rail traffic. Hitherto, this has been achieved by gluing the damper to the rail.

Our copending patent application No. GB0316521.4 describes a damper clip assembly adapted to allow easy attachment and retention of the damper in place on the rail. This invention is a still further development thereof, and is particularly (but not exclusively) applicable to the clips disclosed therein. This application should therefore be read together with GB0316521.4, the contents of which are hereby incorporated by reference.

SUMMARY OF THE INVENTION

The present invention provides a rail damper comprising at least one tuned absorber element held in a block of resilient material, in which at least part of the block is held within a rigid encapsulation, the encapsulation being adapted to be held against a rail surface.

It is convenient for the encapsulation to be in the form of a tubular member in which the block is provided. This tubular member can have one or more closed ends. Where one end is open, the block can project into the encapsulation via that end or can be contained entirely within the encapsulation. A particularly convenient arrangement is for the encapsulation to consist of two such tubular members, with each end of the block projecting into one such member.

The encapsulation can be provided with engagement sites for a clip such as the clip shown in our earlier application GB0316521.4 or other suitable clips. Where the encapsulation is in the form of two tubular members, it is preferred that the clip is arranged to urge the two said members apart. It is preferred that the clip is in frictional contact with the rail as this will enable the assembly to slide along the rail if it should move longitudinally, for example following a breakage.

Such engagement sites can include recesses in the encapsulation which accept free ends of the clip. These recesses can extend into the encapsulation only, or can be deeper allowing the clip to contact the block and/or the absorber elements.

The block and the encapsulation can be made to engage by various means. Examples include casting the block within the encapsulation as a mould, or forming suitable shapes in internal faces of the encapsulation such as dovetails etc. BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way of example, with reference to the accompanying figures in which;

Figure 1 is a side view of an arrangement according to the present invention;

Figure 2 shows the effect on the arrangement of figure 1 of a small longitudinal movement of the rail;

Figures 3 and 4 show the effect of greater movement;

Figure 5 shows a cross section through the damper;

Figure 6 shows the interface between the encapsulation and the rail;

Figure 7 shows an alternative clip in place around the damper; and

Figure 8 shows a section through a modified damper with inter- engagement between the block and the encapsulation.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Figure 1 shows a rail 10 damped according to the present invention. An elongate damper 200 is disposed in the corner between the web of the rail 10 and its foot, and (in brief) comprises a block of resilient material in which is suspended one or more resonant members as set out in WO99/15732. It will be observed from W099/15732 that multiple resonant members are strongly preferred over single resonant members due to their ability to absorb a wider range of resonant frequencies.

Previously, such dampers have been glued to the rail. As discussed in GB0316521.4, this raises difficulties where the rail is re-used in a different context. GB0316521.4 described a clip 202 (shown in figure 1) to allow easy installation and removal of the damper. The present invention allows clipped systems such as those in GB0316521.4 to cope with longitudinal movement of the rail.

Rails move longitudinally when, for example, there is a break at some point. The residual longitudinal stresses in the rail then pull the rail apart at the break point and this results in a length of rail either side sliding through the rail fastenings.

To allow for this, the damper shown in figure 1 is fitted with end caps 204, 206. These each encapsulate one end of the damper and are formed of a suitable rigid material such as plastics. Each end cap is formed with a respective recess 208, 210 into which the end of the clip 202 can fit, and with a downwardly extending abutment shoulder 212, 214 for reasons that will be explained below.

Figure 2 shows the effect of moving the rail slightly. The damper is attached to the rail via the damper and will therefore move with the rail. So long as the movement of the rail is insufficient to bring the damper (etc) into contact with the sleeper 216 or other structures such as the rail fastening 218 then there will be no effect.

Figure 3 shows the effect of still more movement. The abutment shoulder 214 has now been pushed against the sleeper 216 and transmits a longitudinal force 220 to the encapsulation 206. If the shoulder 214 were omitted then the same force could be transmitted by impact between the encapsulation 206 and the rail fastening 218, but contact with the sleeper is likely to be more controllable.

This force will be transmitted to the clip arm via the engagement 210. As the clip is arranged to urge the end caps 204, 206 apart, this force will therefore tend to counteract that applied by the clip 202. The result is therefore to reverse the action of engagement of the clip. This is shown in figure 4. In its quiescent state, the clip urges the end caps apart, and the damper down onto the rail foot and into the rail web. Under the forces shown in figure 4, the clip will therefore e tend to release these forces. Given the design shown in figure 4 and GB0316521.4, the first such force released is that urging the damper down onto the rail foot. This is effected be a loosening of the contact between the underside of the rail and the clip 202.

The net effect is therefore to reduce the strength of the compression of the damper onto the rail and to allow the damper to slide therealong away from the sleeper 216. Movement of the rail is not therefore problematic.

A direct benefit of this arrangement is that the damper can be designed to occupy a greater proportion of the inter-sleeper gap since there need be no allowance for rail movement. This allows a greater damping effect since a greater proportion of the rail length can be damped. Use of this system can improve the damping effect by several decibels.

Figure 5 shows a section through the rail damper 200. A resilient material 222 holds a plurality of resonant dampers 224a-224d. The encapsulating end cap 206 forms a mould in which the resilient material is formed and has suitably shaped external faces 226 to fit the exterior of the rail.

An aperture 210 is formed as described above, to accept one end of the clip 202. In this example, the end of the clip 202 extends through the end cap 206, through the resilient material 222, and into a suitably shaped recess in the resonant member 224d. This depth of engagement allows a good resistance to removal of the clip 202 during movement of the damper along the rail and hinders vandalism of the damper.

Figure 6 shows the interface between the rail 10 and the end cap 204, 206. A plurality of horizontal grooves 228, 230 etc are formed to accept conformal materials such as epoxy resin. On fitting the damper, these take up the exact shape of the rail and provide a good acoustic conductor between the rail and damper. The rail surface can be provided with a grease or release agent to prevent bonding if desired. The groves need not be especially deep, and shallow depths such as 2mm should suffice. Figure 6 shows the grooves on the face facing the web section of the rail. It is also possible to place these on the face facing the foot of the rail, in addition to or as an alternative to those facing the web. When provided in addition, such further grooves can assist further with the acoustical contact between the rail and the damper.

Figure 7 shows an alternative clip 232. This attaches to the side of the damper 200 and has ends which extend into a horizontal recess therein. It then descends to beneath the rail, traverses the underside, and extends upwards to a corresponding recess on a damper fitted to the other side of the rail. Thus, when subject to a longitudinal force, the clip 232 will tilt and its tension will have a horizontal component, thereby allowing the damper to be moved along the rail.

Figure 8 shows a modified form of damper. The encapsulation 206 around the block of resilient material 200 is formed with a male dovetail 234 extending into the area occupied by the resilient material 200. The resilient material 200 is formed in place around the dovetail 234 or formed with a corresponding female dovetail and fitted in place. With this arrangement, or with other means for securing the resilient material 200 to the encapsulation 206, the encapsulation 206 need not completely surround the resilient material 200.

It will of course be understood that many variations may be made to the above-described embodiment without departing from the scope of the present invention.

Claims

1. A rail damper comprising at least one tuned absorber element held in a block of resilient material, in which at least part of the block is held within a rigid encapsulation, the encapsulation being adapted to be held against a rail surface.

2. A rail damper according to claim 1 in which the encapsulation is in the form of a tubular member in which the block is provided.

3. A rail damper according to claim 2 in which the tubular member has one or more closed ends.

4. A rail damper according to claim 2 or claim 3 in which one end of the tubular member is open and the block projects into the encapsulation via that end.

5. A rail damper according to claim 2 or claim 3 in which the block is contained entirely within the encapsulation.

6. A rail damper according to any one of claims 2 to 4 comprising two such tubular members, with each end of the block projecting into one such member.

7. A rail damper according to any one of the preceding claims in which the encapsulation is provided with engagement sites for a clip adapted to retain the damper on the rail.

8. A rail damper according to claim 6 in which the encapsulation is provided with engagement sites for a clip adapted to retain the damper on the rail, the clip being arranged to urge the two said tubular members apart.

9. A rail damper according to claim 8 in which the clip is in frictional contact with the rail.

10. A rail damper according to any one of claims 7 to 9 in which the engagement sites include recesses in the encapsulation that accept a free end of the clip.

11. A rail damper according to claim 10 in which the recesses extend into the encapsulation only.

12. A rail damper according to claim 10 in which the recesses extend sufficient to allow the clip to contact the block.

13. A rail damper according to claim 10 in which the recesses extend sufficient to allow the clip to contact the absorber elements.

14. A rail damper according to any one of the preceding claims in which the block and the encapsulation engage.

15. A rail damper according to claim 14 in which the block and the encapsulation engage in that the block is cast within the encapsulation as a mould.

16. A rail damper according to claim 14 in which the block and the encapsulation engage via suitable shapes in internal faces of the encapsulation.

17. A rail damper according to claim 16 in which the shape is a dovetail.

18. A clip substantially as described herein with reference to and/or as illustrated in the accompanying figures.