Railways: surface track – Rails – Vignoles
Reexamination Certificate
1998-01-07
2001-01-09
Morano, S. Joseph (Department: 3617)
Railways: surface track
Rails
Vignoles
C238S150000, C238S382000
Reexamination Certificate
active
06170755
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a profiled rail, especially a railway rail, having a reduced total radiated noise level when in use, and comprising a foot section with a bottom surface, a web section, and a head section with a tread surface, and having a rail height and preferably also a rail head width, and in particular a moment of inertia and a section modulus about the axis of the center of gravity, corresponding substantially to those of standard, normally profiled rails having the same load-bearing capacity.
Running rails are profiled, rolled steel bars which are used to build trackways, especially railroad tracks, on which loads can be economically transported. On these tracks, metallic wheels, made preferably from steel or having a steel tire, run on the tread surface of a section of the rail referred to as the rail head. The foot of the rail, which is located opposite to and joined to the head by means of a web, is connected with its bottom surface to a base structure.
In the course of development of railway systems, functionally optimized cross-sectional profiles of rails were appropriately standardized for various loads and applications. In Europe, a frequently used standard profile for railroad rails bears the designation UIC 60; the rail weighs approx. 60 kg/m and tight dimensional tolerances of, for example, ±0.6 mm for the rail height and ±0.5 mm for the width of the rail head are specified. Tight tolerances in the rail profile are important, especially for the purpose of building a geometrically accurate track intended to permit the speed of trains to be increased without any loss in ride comfort and without any major dynamic loads occurring. In order to reduce wear, rails having heads exhibiting increased hardness are already being manufactured and used.
Despite the highest possible dimensional accuracy, a tread or running surface of the best quality, and smoothness of the rails, as railway cars travel along the track, vibrations, and thus radiated noise, occur. This airborne noise can attain high intensity, especially at high transportation speeds, and it can cause considerable environmental pollution. It has been found that the travel noise generated by trains is caused to a considerable extent by airborne noise radiated from the surface of the rail.
Attempts have already been made by sound-insulating surface sections of the rail to reduce the intensity of the radiated noise.
Applying a coating of vibration-damping material, as proposed in DE-A-4225581 or AT-AS 652/90, is only partially successful in achieving this goal; it is also expensive, prevents visual inspection of the rail in the track and, especially if reinforced polymers are used, it can itself be a source of environmental pollution. In addition, there have been several proposals, e.g. in DE-OS 4411833, to use elastic components in the fastening elements to reduce the transmission of vibrations to the base structure and thus to reduce the amount of airborne noise radiated from this source.
All the devices and arrangements so far proposed to reduce the airborne noise radiated from rails or track installations have in common the disadvantage that they are not very effective, and/or are very expensive, and are aimed essentially at reducing the transmission of vibrations from the rail.
SUMMARY OF THE INVENTION
It is therefore a purpose of the invention to reduce or shape the vibration of the rail, when it is travelled on by trains moving especially at high transportation speeds, so that the total level of radiated noise and the noise pollution of the environment are reduced. A particular goal of the invention is thus to reduce the vibrations of the body or the rail itself, which vibrations are responsible for generating the airborne noise, and thereby, in a simple manner, to reduce the radiated noise and the environmental pollution.
Using a profiled rail of the kind mentioned at the beginning, this task or goal is accomplished in that at least one lateral web surface, at least in the lower area between the transition edge at the foot of the rail, namely the edge formed at the transition from the foot into the lateral web surface, on the one hand, and the axis of the center of gravity, on the other hand, is concavely rounded and substantially free of any angularities in the cross section of the rail, and/or the height of the rail foot is larger compared with that of a standard profiled rail.
It has surprisingly been discovered that, contrary to what is assumed by experts in the field, it is not the web between the head and foot of the rail, vibrating like a membrane, that creates most of the radiated noise. Instead, the rail head and in particular the foot of the rail exhibit high solid-borne noise levels and thus contribute greatly to the level of the total sound pressure, and they in turn are chiefly responsible for the noise pollution of the environment. The reasons for the increased wave-like vibration in the longitudinal direction, i.e. the springiness, as a function of the frequency, for example, of one flange of a rail foot have not yet been scientifically fully explained. However, it is assumed that angularities in the surface profile or discontinuous changes in the thickness of the cross section may act as vibration nodes or theoretical clamping points causing or permitting increased vibrations to occur in sections of the rail profile, for example in a flange of the rail foot. In the manner according to the invention, increasing the height of the foot of the rail and/or in particular ensuring the transition, without angularities, from the foot into the lateral surface of the web brings about a change in the vibrations in the area of the rail foot; as a result, the amount of airborne noise radiated by the surfaces of the rail foot into the environment and possibly to a base structure, which reflects this radiated noise, is reduced.
A further reduction in the radiated noise is achieved when the cross-sectional profile is designed symmetrically to the height axis, as a result of which the tendency for local vibration nodes to form in the profiled bar is further reduced.
If, as further advantageously provided, the lower part and the upper part of the lateral surface of the rail web between the transition edge at the foot of the rail and the transition edge at the head of the rail, namely the edge which is formed when the lateral surface of the rail head merges into the upper surface of the web, are designed so as to be concavely rounded and substantially free of angularities in the cross section of the rail, the formation of vibrations, especially in sections of the rail profile which as a result radiate airborne noise, is further reduced.
It may be further advantageous from the point of view of manufacturing or rolling the rail, as well as for the purpose of minimizing the weight, but especially also in order to reduce airborne noise emission, if in the cross section of the rail the lateral surface of the rail web is made up of a circularly and/or an elliptically shaped lower and upper part and possesses preferably a straight middle or intermediate section, merging tangentially with the aforesaid parts, and through this middle section passes the axis of the center of gravity. It may be favorable in this case if the minimum thickness of the rail web is the same as or greater than that of standard rails.
A particularly favorable embodiment, in which the rail possesses a high load-bearing capacity while at the same time radiating a low level of airborne noise, is achieved if the distance between the axis of the center of gravity and the bottom surface at the foot of the rail has a value between (0.5 and 0.38), preferably between (0.47 and 0.41) times the height (A) of the rail.
The vibration sensitivity of the outer sections of the flanks of the rail foot can be largely eliminated or minimized in a simple way if the foot is less wide and/or higher compared with the respective standard rail profile.
If, as advantageously provided, the hardness of the material in th
Morano S. Joseph
Townsend and Townsend / and Crew LLP
Voest-Alpine Schienen GmbH
Wright Andrew
LandOfFree
Reduced radiated-noise rail does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reduced radiated-noise rail, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reduced radiated-noise rail will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2475505