GB2416178A

GB2416178A - Railway rail fastening assembly

Info

Publication number: GB2416178A
Application number: GB0415653A
Authority: GB
Inventors: Stephen John Cox; Anbin Wang; Christopher Neil Morison; Andrew Garwood
Original assignee: Pandrol Ltd
Current assignee: Pandrol Ltd
Priority date: 2004-07-12
Filing date: 2004-07-12
Publication date: 2006-01-18
Anticipated expiration: 2024-07-12
Also published as: GB2416178B; CN2789308Y; GB0415653D0

Abstract

A railway rail fastening assembly, for suspending a railway rail 100 at discrete locations along its length above a rail foundation, comprises a pair of elastic members 5 for supporting the head of the rail 100, a pair of brackets 6 for applying a lateral clamping force to respective ones of the elastic members 5, a baseplate 1 having first and second shoulders 3, 4, a resilient rail pad 2 located on the baseplate 1 between the shoulders 3,4, and a pair of wedge members 7, each being inserted between an associated one of the shoulders 3, 4 and an adjacent bracket 6 thereby to maintain the said lateral clamping force. A substantially non-compressible element 50 is provided in a gap between the foot of the rail 100 and the resilient pad 2 so as to limit vertical displacement of the rail.

Description

1 2416178

RAILWAY RAIL FASTENING ASSEMBLY

The present invention relates to a railway rail fastening assembly.

The applicant's Chinese patent application no. 00810625.8 relates to a railway rail fastening assembly in which the head of the rail is suspended at discrete locations along its length above the rail foundation. As shown in Figure l of the accompanying drawings, in one embodiment of such an assembly the rail head lOO is suspended above a rail baseplate l by means of pairs of elastic members 5 to which a clamping load is applied through respective pairs of brackets 6, the pairs of elastic members/brackets being spaced apart along the rail so as to contact the rail only at discrete locations, thereby providing easy access for rail maintenance. The desired clamping load is maintained by means of respective wedges 7 inserted between each bracket 6 and an associated upstand or shoulder 3/4 on the baseplate 1. A resilient rail pad 2 is provided beneath the foot of the rail, so that in the event of overloading of the assembly, or a gradual lessening of the gap under the rail with time, the rail does not come into direct contact with the baseplate l, thereby avoiding sudden shock loading or electrical shorts.

To facilitate easier installation and subsequent maintenance of the assembly, at least one of the shoulders 3/4 may be removable from the baseplate l, being held in position on the baseplate l by the lateral clamping load.

The removable shoulders 3/4 allow the baseplate l to be slid into position under the rail without the need to lift the rail. Similarly, the baseplate l can be removed, if desired, by first removing the or each removable shoulder 3/4. In this way, the time required for track maintenance The low vertical stiffness of such a suspended rail fastening assembly serves to reduce vibration and accordingly is advantageous in an underground railway system, for example. The applicant's suspended rail fastening assembly is also very resilient longitudinally and is therefore also advantageously used on viaducts or bridges where the rail and the underlying structure may expand at different rates, since the low longitudinal stiffness of the applicant's assembly limits the thermal longitudinal force that is transferred between the rail and the structure. The exact longitudinal stiffness and creep force limit values can be varied simply by changing the rail clamping force.

The applicants wish to use a rail fastening assembly on a railway in a city in China on which linear induction motors are to be employed to propel the trains.

It is highly desirable on urban railways to use track which reduces vibration and noise and the applicant's suspended rail fastening assembly, described above, is very suitable for this purpose. As also discussed above, the applicant's assembly is also of benefit on the viaducts and bridges found on urban railways.

However, it has been anticipated that there could possibly be a disadvantage in using a suspended rail fastening system on a track employing linear induction motors, in that the inevitable variation in axle loads which occurs between loaded and unloaded trains, and when rail vehicles are cornering at different speeds, could cause a large variation in vertical displacement between the magnets on the train and on the track. In some circumstances the vertical working range of the linear motor system may be exceeded.

Thus, it seems it may be necessary to be able to limit vertical deflection of the rail in propulsion systems using linear induction motors by providing a rail assembly having moderate vertical stiffness, i. e. a non-suspended rail assembly.

It is desirable to provide a suitable rail fastening assembly for use on track employing linear induction motors which is nevertheless advantageous in urban environments.

According to the present invention, there is provided a railway rail fastening assembly for suspending a railway rail at discrete locations along its length above a rail foundation, the assembly comprising a pair of elastic members for supporting the head of the rail, a pair of brackets for applying a lateral clamping force to respective ones of the elastic members, a baseplate having first and second shoulders, a resilient rail pad located on the baseplate between the shoulders, and a pair of wedge members, each wedge member being inserted between an associated one of the shoulders and an adjacent bracket thereby to maintain the said lateral clamping force, wherein a substantially non- compressible element is provided in a gap between the foot of the rail and the resilient rail pad located on the baseplate, so as to limit vertical displacement of the rail.

By placing an effectively incompressible element into the gap under the rail, a large proportion of the vertical load is transferred through the rail and the incompressible element into the resilient pad beneath. This achieves an increase in stiffness of, typically, 5 times, determined mainly by the stiffness of the resilient pad. The effectiveness of the assembly in controlling vibration is diminished, but not eliminated.

Thus, in a rail fastening assembly embodying the present invention it is possible to gain the advantage of low longitudinal stiffness provided by a suspended rail assembly, whilst the vertical stiffness is increased to ensure that linear induction motor propulsion systems can function satisfactorily. In fact, at present the vertical tolerance of the linear induction motor propulsion system in practice is unknown. Accordingly, by providing a suspended rail assembly with a non-compressible element, e.g. a shim, to limit vertical deflection of the rail, should fears over undue deflection of the rail prove to be unfounded the element may be removed to allow the advantages of low vibration and noise to be gained from the suspended rail assembly, whereas if a stiff rail assembly were installed at the outset any subsequently desired reduction in vertical stiffness could only be achieved by replacing the stiff rail assembly with another assembly having reduced stiffness characteristics.

Reference will now be made, by way of example, to the accompanying drawings, in which: Figure l (described above) shows a a partial cross sectional end view of a prior art rail fastening assembly; Figure 2 shows a partial cross-sectional end view of an assembly embodying the present invention; Figure 3 shows a perspective view of the assembly of Fig. 2 (in which the rail is not visible, to allow other parts of the assembly to be seen more clearly); Figure 4 shows a perspective view of a shim for use in an embodiment of the present invention; and Figure 5 shows a perspective view of a baseplate for use with the shim of Fig. 4.

As shown in the Figures a rail fastening assembly embodying the present invention comprises a steel baseplate 1, on which a resilient rail pad 2 (shown in Figure 2 only, in which it is partly visible) is located, above which a rail 100 (not shown in Figure 3) is suspended by means of a pair of elastic members 5 to which a lateral clamping force is applied through respective brackets 6. Each bracket 6 has a base portion 61 which rests on the baseplate 1 and has a hole or slot (not shown) through which a shoulder 3 or 4 extends upwardly. The desired lateral clamping force applied to the elastic members 5 is maintained by means of respective wedges 7 inserted between each bracket 6 and the adjacent shoulder 3 or 4, the wedge 7 being held in place firstly by means of interlocking serrations provided on respective opposing faces of the shoulder 3 or 4 and the wedge 7 and secondly by a securing member 8 which passes through a part 48 of the shoulder 3 or 4. Each of the shoulders 3, 4 is removable from the baseplate 1, each shoulder being installed in the baseplate 1 by inserting a stem of the shoulder vertically into an aperture 10 formed in the baseplate 1 and sliding the shoulder laterally away from the rail area into engagement with the baseplate 1.

The lateral clamping force applied to the elastic members 5 also serves to keep the removable shoulders 3/4 firmly in position against the back of the aperture 10.

The underside of the foot lOOa of the rail 100 contacts a shim 50 provided on the resilient pad 2 located on the baseplate 1. The shim 50 is shaped so as to fit between shoulder regions 3a, 4a of the baseplate 1, two opposing sides of the shim 50 having recesses 50a, 50b, 50c provided so as to locate around the shoulder regions 3a, 4a, which serve to prevent unintentional longitudinal displacement of the shim 50. The shim 50 serves to limit vertical displacement of the suspended rail, in circumstances where greater vertical stiffness of the assembly is required, whilst preserving the low longitudinal stiffness of the assembly. Should lower vertical stiffness be desired subsequently the shim 50 may be removed. The shim 50 may also be made so as to have a slippery surface in circumstances where low longitudinal stiffness is desirable.

Claims

CLAIMS: 1. A railway rail fastening assembly for suspending a railway rail

(lOO) at discrete locations along its length above a rail foundation, the assembly comprising a pair of elastic members (5) for supporting the head of the rail (100), a pair of brackets (6) for applying a lateral clamping force to respective ones of the elastic members (5), a baseplate (l) having first and second shoulders (3, 4), a resilient rail pad (2) located on the baseplate (l) between the shoulders (3,4), and a pair of wedge members (7), each wedge member (7) being inserted between an associated one of the shoulders (3, 4) and an adjacent bracket (6) thereby to maintain the said lateral clamping force, wherein a substantially non-compressible element (50) is provided in a gap between the foot (lOOa) of the rail (100) and the resilient pad (2) located on the baseplate (l), so as to limit vertical displacement of the rail.
2. An assembly as claimed in claim l, wherein the height of the said element is chosen so as to substantially fill the said gap.
3. An assembly as claimed in claim l or 2, wherein either or both the said first and second shoulders (3, 4) is/are removable.