Railways: surface track – Rail seats – Cushions
Patent
1996-12-05
2000-06-27
Morano, S. Joseph
Railways: surface track
Rail seats
Cushions
238382, E01B 944
Patent
active
060796316
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a rail-fastening assembly.
Railway lines running through cities necessarily pass close to people's homes and offices. Most urban railways run with steel wheels on steel rails, a system which has greater inherent tendency than rubber wheeled road traffic to generate high dynamic forces which can lead to unacceptable levels of noise and vibration. It is, therefore, important that railway track structures are designed to minimize this potential problem. One possible solution would be to resiliently support the track and make the mass of the resiliently supported track structure as large as possible. Another possible solution would be to make the support stiffness as low as possible.
Increasing the track mass tends to be very expensive, because it means that supporting bridges must be made stronger, and that tunnels must have a larger bore to accommodate the extra mass, which is almost always provided as some form of concrete structure or slab.
Reducing the stiffness of a conventional rail support system, in which a resilient pad, or resilient baseplate, or a resiliently mounted sleeper is provided between the foot of the rail and the track foundation, is limited by the need to avoid unacceptable levels of lateral deflection of the rail head when lateral loads are applied thereto. In such systems, the largest vertical deflection which can be safely allowed is generally no greater than 2 or 3 millimetres.
In order to overcome this problem, it has been suggested that the rail could be suspended under its head on continuous rubber supports supported by metal brackets. Such a system allows larger vertical deflections of the rail to be safely accommodated, for example approximately 5 or 10 mm. Correspondingly large lateral rail head deflections do not occur, because the rail is supported much closer to the line of application of forces than on a conventional fastening. The rubber supports are held in position by rigid metal parts. The assembly is held together by the use of bolts passing through the web of the rail and through the brackets and rubber inserts. Such fixing requires the rail to be drilled at regular intervals. In alternative designs, the rail is again suspended on continuous rubber supports, but is located in a continuous concrete trough. The rail no longer needs to be drilled and the assembly is held in place in one design by plastic keys, and in another by clamping plates, which are bolted down into the trough and locate the rail in position.
The track support systems described have been conceived with the primary objective of reducing vibration transmitted through the track to a minimum. This results in two significant features of their design. Firstly, the rail is continuously supported, so that there is no variation in track support stiffness along the length of the rail--this is done with the intention of eliminating harmonic excitation as a wheel traverses the track. Secondly, the fastening is designed so as to have a low vertical stiffness, and for this reason any load applied to the elastic support elements is deliberately minimised, since the stiffness of the elastic elements generally increases as load is applied thereto. In one design, disclosed in EP-A-0620316, the position of the side supporting elements is adjustable laterally, with the aim of achieving correct rail alignment with minimum compression of the continuous elastic elements.
However, there are considerable practical difficulties in the installation and maintenance of the afore-mentioned prior art systems. In the first type of system, in which bolts pass through the rail, the rail must be pre-drilled, and the supporting plates attached thereto before the rail can be installed. On curved track the rail and each of the supports must be bent to the appropriate radius, and the rail drilled at appropriate locations. The opportunity for errors in the calculations required, and in the accurate bending of the components, is large. The continuous support of the rail in both types of system can make it d
REFERENCES:
patent: 3358927 (1967-12-01), Hein et al.
patent: 3387781 (1968-06-01), Moses et al.
patent: 3417922 (1968-12-01), Vaulry
patent: 3525472 (1970-08-01), Sato
patent: 4775103 (1988-10-01), Ortwein
patent: 4793545 (1988-12-01), Raymond
patent: 5165598 (1992-11-01), Ortwein
Brochure titled "Die Flusterchiene. Whisper rail." (4 pages) by Krupp Lonrho GmbH of Essen, Germany (date unknown).
Allen Kenneth George
Brindley Peter William
Conroy Brian George
Cox Stephen John
Garwood Andrew
Holler Norbert P.
Morano S. Joseph
Ortwein Hermann J.
Pandrol Limited
Rubenstein Allen I.
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