EP3150764B1

EP3150764B1 - Acoustic attenuation device for rails

Info

Publication number: EP3150764B1
Application number: EP16190608.6A
Authority: EP
Inventors: Andrea Lancia; Alessandro Lancia
Original assignee: PREGYMIX Srl
Current assignee: PREGYMIX Srl
Priority date: 2015-09-30
Filing date: 2016-09-26
Publication date: 2019-04-10
Anticipated expiration: 2036-09-26
Also published as: EP3150764A1; ITUB20154061A1

Description

The present invention relates to an acoustic attenuation vibration-damping device for railways.
Noise pollution, as it is well known, is a very important problem and it is particular relevant even and above all near railway lines. The framework act on noise pollution N. 447 of 26 October 1995 provides the obligation to file with involved municipalities suitable plans for reducing and abating the noise caused by the passage of trains. The problem is much felt all over the world and many countries provide specific rules for reducing and abating this type of noise.
Upon the passage of a train, a relevant noise component due to the vibrations of rails is added to the noise caused by the train motion. EP0222277A1 and EP1443148B1 disclose acoustic attenuation devices for rails.
The object of the present invention is to intervene onto the latter component with the purpose of removing it or, at least, reducing considerably the level thereof.
Such result is reached by means of an attenuation device as defined in the independent claim n. 1.
Additional features of the present invention are defined in the corresponding depending claims.
The devices for attenuating the vibrations and the noise produced by the passage of trains, applied directly to the rails, have been marketed for some time; but it does not seem they have guaranteed noteworthy results so far.
The invention, which will be described hereinafter, has at least two original features:

it is to be applied exclusively in the lower portion of the rail, in the space interposed between the resting beams, that is in the rail part wherein the vibrations caused by the passage of trains have the maximum values of width and intensity;
it is capable of co-existing, and then of summing the effects thereof, with additional noise-abating systems which are applied exclusively on the sides of the rail.

Other advantageous aspects, together with the structural and functional features of the present invention, will result evident from the following detailed description of preferred embodiments thereof, shown by way of example and not for limitative purpose.
For the description of the invention the figures of the enclosed drawings will be referred to, showing as follows:

Figure 1 is a perspective view of a rail part thereto a device according to a first embodiment of the present invention is applied;
Figure 2 is a section view of the rail part of Figure 1;
Figure 3 is a perspective view of the rail part thereto a device according to a second embodiment of the present invention is applied;
Figure 4 is a section view of the rail part of Figure 3; and
Figure 5 is an exploded view of the rail part of Figure 3.

The present invention will be described hereinafter by referring to the above-mentioned figures.
By firstly making reference to figures 1 and 2, they show a perspective and section view, respectively, of a general part of a rail 100, for example a part comprised between two subsequent resting beams (not visible in figure), thereto a device 1 according to the present invention is applied.
The acoustic attenuation device 1, according to a first embodiment of the present invention, comprises a vibration-damping profile 2, having a substantially "C"-shaped cross-section, suitable to be applied under said rail 100 between two subsequent resting beams, with a first contact surface 3 facing a base surface 4 of said rail 100. The device 1 further comprises a closure plate 20 defining a cavity 5 internal to the vibration-damping profile 2.
The device is fixed to the rail by means of anchoring means 30, 31. In particular, according to the present invention, such anchoring means comprises two "C"-shaped locking flanges (30), preferably made of stainless steel, allowing to fix rigidly the device at side edges of the base of the rail 100 by means of suitable self-threading screws (31) which engage into the body of the vibration-damping profile 2.
The upper edges of the locking flanges 30 advantageously can be coated with a gasket made of rubber 32 which has the double function of improving the adherence of the flanges to the base of the rail and to prevent possible vibrations thereof.
All in all, then, the device according to the invention implements a complex box-like structure (see Figure 1), which is to be applied in the lower portion of the rail in the parts comprised between subsequent beams. The main component of the system is constituted by the vibration-damping profile 2 made of recycled polymeric material, with "C"-like section, or made of rubber, preferably of recycled rubber and, said polymeric material comprising non-vulcanized elastomeric granules with varied granulometry.
The rubber that can be used in the production of the vibration-damping profile 2 then can derive from a recycling process and, in turn, it can be recycled; the life cycle of the product is then wholly environmentally friendly. As, according to the invention, the polymeric material comprises granules of different and non-vulcanized elastomers, it has the advantage of absorbing effectively the kinetic energy produced by the rail vibrations.
The closure plate 20 advantageously has a plurality of holes 21.
Preferably, such holes can be made with various diameters, tuned with the different frequencies to be attenuated. For example, the holes can have diameters varying from 0.3 mm and 0.8 mm.
The closure plate 20, by closing the structure of the device, implements an acoustic cavity 5. The plate is capable of breaking the sound wavefront, absorbing and keeping inside the cavity 5 a portion of the sound energy and dissipating the remaining portion thereof outside.
From the operating point of view, the described elements are applied in the space between the beams under the rail, thereto they are fixed rigidly by means of the locking flanges made of steel. The device typically can be produced in elements with length equal to the free space usually existing between two subsequent beams (typically variable between 30 cm and 40 cm) and with width substantially equal to the width of the base surface of a rail (typically equal to about 20 cm). The mechanical features of the polymeric substance give the profile enough stiffness to absorb mechanical energy from the rail and at the same time adequate capability of shaping and adhering perfectly to the lower surface of the rail itself.
The subsequent figures 3 to 5 relate to a second and preferred embodiment of the present invention, by showing a perspective, section and exploded view, respectively, of a part of rail thereto a device 101 according to the present invention is applied.
According to such embodiment, a device 101, apart from what already described in relation to the first embodiment, comprises an intermediate element 6 suitable to absorb at least a portion of the mechanical energy originated by the rail 100, arranged internal to the cavity 5.
According to a possible embodiment, such intermediate element 6 comprises a dampening layer 7, made of a material suitable to absorb vibrations, interposed between a first and a second layer made of metallic material, respectively designated with numbers 8 and 9 in figure.
In particular, the first metallic layer 8 is implemented like a plate made of steel capable of giving more stiffness to the contact surface between rail and vibration-damping profile, so as to improve the capability of absorbing the mechanical energy originated by the rail and to discharge at least a portion thereof, by vibrating.
The dampening layer 7 constitutes a thickness of insulating material, preferably made of rubber, with function of dampening vibrations and partially absorbing the sound energy.
The second metallic layer 9 is implemented as a second metallic layer, analogous, for shape and sizes, to the first plate 8, but with the main function of discharging, by vibrating, the mechanical energy transmitted by the rail.
The thickness of insulating material made of rubber (Figure 1, d), interposed between the two plates of steel, has the function of dampening the vibrations induced onto the two plates made of steel, absorbing a portion of the sound energy and contributing, however, to break the sound wavefront.
According to an additional embodiment, the device 101 further comprises a sound-deadening element 10 placed inside said cavity 5.
The sound-deadening element 10 has the function of receiving the energy transmitted by the vibration of the plate 9. It has a high sound absorption coefficient and then contributes to keep the sound energy inside the cavity 5. To this purpose the sound-deadening element 10 can comprise a layer made of polyester fibre, preferably with a thickness so as to fill-in the cavity 5.
The two metallic plates then perform different functions: the first plate 8 improves the stiffness coefficient of the "C"-like element and it then increases the capability thereof of absorbing mechanical energy from the rail; it further guarantees, by vibrating, the function of partial discharging the sound energy.
The second metallic layer 9, instead, guarantees both a partial discharge of the sound energy and a better transfer of the mechanical energy to the subsequent layer of sound-deadening material.
Once the device is put in place, the above-mentioned components are kept together by the fastening screws 31, which do not prevent the metallic plates from vibrating and absorbing the mechanical energy, which then will be partially absorbed by the dampening and/or sound-deadening elements, and partially transferred outside.
The production process of the system is simple and the materials can be easily found on the market. The vibration-damping structural profile made of rubber, for example, can be produced by moulding with injection press.
The present invention has been sofar described by referring to preferred embodiments thereof. It is to be meant that the technical solutions implemented in the preferred embodiments, herein described by way of example, could advantageously be combined differently therebetween, as defined by the appended claims.

Claims

An acoustic attenuation device (1, 101) suitable to be applied to a part of a rail (100), comprising:
• a vibration-damping profile (2) having a substantially "C"-shaped cross-section suitable to be applied under said rail (100), with a first contact surface (3) facing a base surface (4) of said rail (100);

• means (30, 31) for anchoring the device (1, 101) to said rail (100); and

• a closure plate (20),
characterized in that said closure plate has a plurality of holes (21) and defines a cavity (5) internal to said vibration-damping profile (2);
• wherein a sound-deadening element (10) is placed inside said cavity (5), and
wherein said vibration-damping profile (2) is made of recycled polymeric material, said polymeric material comprising non-vulcanized elastomeric granules with varied granulometry.
The acoustic attenuation device (101) according to claim 1, comprising an intermediate element (6) suitable to absorb at least a portion of the mechanical energy originated by the rail (100), placed inside said cavity (5).
The acoustic attenuation device (101) according to claim 2, wherein said intermediate element (6) comprises a dampening layer (7) made of a material apt to absorb vibrations, interposed between a first and a second layer made of metallic material (8, 9).
The acoustic attenuation device (101) according to claim 3, wherein said dampening layer (7) is made of rubber.
The acoustic attenuation device (101) according to claim 3 or 4, wherein metallic layers (8, 9) are made in the form of stainless steel plates.
The acoustic attenuation device (101) according to one of the preceding claims, wherein said sound-deadening element (10) comprises a polyester-fibre layer having a thickness so as to fill-in said cavity (5).
The acoustic attenuation device (1, 101) according to one of the preceding claims, wherein said holes (21) have varied diameters tuned with corresponding frequencies to be attenuated.
The acoustic attenuation device (1, 101) according to claim 7, wherein said holes (21) have diameters varying between 0.3 mm and 0.8 mm.
The acoustic attenuation device (1, 101) according to one of the preceding claims, wherein said closure plate (20) is made of stainless steel.
The acoustic attenuation device (1, 101) according to one of the preceding claims, wherein said anchoring means (30, 31) comprises a pair of "C"-shaped locking flanges (30), suitable to lock the device at side edges of the base of said rail (100).
The acoustic attenuation device (1, 101) according to claim 10, wherein said anchoring means (30, 31) comprises screw elements (31) for fixing said locking flanges (30) to said vibration-damping profile (2).
The acoustic attenuation device (1, 101) according to one of the preceding claims, having a transversal dimension to be, in use, substantially equal to the transversal dimension of the base surface (4) of the rail (100).