The invention relates to a railroad tie for use in a railroad, which railroad tie is manufactured from at least plastic, and wherein an elongated reinforcing structure is embedded in the plastic. The elongated reinforcing structure is extending with its longitudinal direction in the longitudinal direction of the railroad tie. The invention also relates to a railroad, which comprises at least one such a railroad tie.
A railroad tie, which is manufactured from plastic and which has such a reinforcing structure, is known from WO2006088857A1. This known railroad tie has a good flexural rigidity thanks to its large metal reinforcing structure having high height. However, it is disadvantageous that the large reinforcing structure of high height results into bad damping characteristics of the railroad tie, when railroad carriages riding over the railroad exert, via the rails, dynamic forces onto the railroad tie. These bad damping characteristics usually not only result into excessive noise production, but also unfavourably influence the underground of the railroad. If, for example, the underground is part of a railroad bridge, the railroad bridge in the long run may experience damage. And if the underground is a ballast bed, the ballast bed in the long run may experience damage, whereby the ballast needs replacement within a shorter time period and/or the railway needs re-stabilization and/or needs to be brought at its correct height again.
Another railroad tie, which is manufactured from plastic and which has such a reinforcing structure, is known from US2007187522A1. The purpose of the reinforcing structure of this railroad tie, known from US2007187522A1, is to give this railroad tie an acceptable stiffness/strength at minimized weight of the railroad tie, see paragraphs [0020]-[0022] of US2007187522A1. FIGS. 7-11 of US2007187522A1 show the railroad tie 20, which comprises a reinforcing structure in the form of the shown insert 40. In FIGS. 7-9 of US2007187522A1 it is seen that the insert 40 is situated in-between the two longitudinal tie segments 44, which are situated below the rails 42, that is in-between the two areas 32 where the rails 42 are attached to the railroad tie, also see paragraphs [0064] and [0066]. US2007187522A1 teaches to not situate the insert 40 under the rails 42, for the reason that the soft plastic of the two longitudinal tie segments 44 then permits that these segments 44 can handle the compressive forces exerted on them from the load of a train running directly above them, see paragraph [0064], last sentence. Although the railroad tie known from US2007187522A1 therefore has a better damping behaviour than the railroad tie known from WO2006088857A1, it is disadvantageous that the flexural rigidity and the durability of the railroad tie known from US2007187522A1 are worse than the flexural rigidity and the durability of the railroad tie known from WO2006088857A1.
Yet another railroad tie, which is manufactured from plastic and which has a reinforcing structure, is known from WO2008048095A1. For this railroad tie known from WO2008048095A1, the plastic is Low Density Polyethylene (LDPE), and the reinforcing structure consists of a number of separate steel bars, which are extending parallel and distant relative to one another. Steel bars of the reinforcing structure lying above one another are not connected to one another by the reinforcing structure itself, but by the plastic. This railroad tie known from WO2008048095A1 generally has very good damping properties and its flexural rigidity generally is acceptable for practice. These very good damping properties are explained in that, unlike the railroad tie known from WO2006088857A1, the steel bars of the reinforcing structure which are lying above one another are not connected to one another by the reinforcing structure itself, but by the plastic. Because of this, the damping characteristics are being determined to a more important extent by the plastic, which has a considerably lower lateral stiffness than the reinforcing structure. Said acceptable flexural rigidity is explained in that the bars lying above one another can excellently handle the tensile and compressive stresses, occurring when the railroad tie bends, while the plastic can generally handle the shear stresses, occurring between the bars lying above one another, rather well when the railroad tie bends.
For some railroad tie designs it is, however, desirable to further improve the flexural rigidity obtainable with the technique known from WO2008048095A1. This may for example be the case because in some uses of the railroad ties the desired flexural rigidity is extra high. However, this may for example also be the case because with some designs of railroad ties, for various reasons, various recessed shapes are applied relative to a railroad tie design being designed as a fully straight beam. As an illustration, reference is made to FIGS. 1-3 of WO2008048095A1, in which such a straight beam is shown, as well as to FIGS. 4A-8B of WO2008048095A1, in which some such recessed shapes are shown. In case of some, far-going recessed shapes, it may be that because of the strongly reduced amount of plastic in the railroad tie, the plastic can handle the shear stresses, occurring between the bars lying above one another, less well when the railroad tie bends.
It is an object of the invention to provide a durable railroad tie, which railroad tie combines very good damping properties with a very good flexural rigidity.
For that purpose, the invention provides a railroad tie for use in a railroad, which railroad tie is manufactured from at least plastic, and wherein an elongated reinforcing structure is embedded in the plastic, and which railroad tie has a reference condition, being an installed operation condition of the railroad tie, in which reference condition the longitudinal tie direction of the railroad tie and a rail track direction of the railroad, which rail track direction is perpendicular to the longitudinal tie direction, are each extending horizontally, wherein, as seen in said reference condition:
wherein in the two rail supporting longitudinal tie segments the railroad tie has a lower lateral stiffness than in an intermediate longitudinal tie segment, lying in-between the two rail supporting longitudinal tie segments, which lower lateral stiffness is realized at least by change of shape of said reinforcing structure in the longitudinal tie direction and/or by the range within which said reinforcing structure extends in the longitudinal tie direction.
By its nature to serve as reinforcement of the plastic, the material of the reinforcing structure has a higher lateral stiffness than the plastic. Since, according to the invention, the elongated reinforcing structure is extending from and including said one rail supporting longitudinal tie segment, and via the intermediate longitudinal tie segment, up to and including the other rail supporting longitudinal tie segment, this reinforcing structure provides a good resistance against bending of the railroad tie under influence of forces exerted from both rails onto the railroad tie. As a consequence of the locally lower lateral stiffness in the two rail supporting longitudinal tie segments, the dynamic forces exerted from both rails onto the railroad tie are being damped at the most effective locations.
Thanks to the variable damping behaviour, thus being incorporated in the railroad tie itself, the damping measures commonly applied in railroads, such as the application of separate damping material between rails and railroad ties, can be restricted or omitted. The invention thus allows for significant savings regarding installation and maintenance of railroads. Also, thanks to the plastic and to the fact that the reinforcing structure is embedded in the plastic, the railroad tie according to the invention additionally is durable.
All these aspects taken together, the advantages therefore are enormous, also because railroad ties are applied in railroads in very large numbers.
Therefore, the invention is based on the very effective use to the full of reinforcing structures applied in plastic railroad ties for obtaining railroad ties, which in use exhibit an excellent combination of flexural rigidity and damping behaviour. Such a use to the full is extraordinary and the results thereof are surprising, since the requirements of flexural rigidity and damping behaviour of a railroad tie in principle are mutually contradictory.
In a preferable embodiment of the invention, said reinforcing structure in at least one cross-section, as seen perpendicular to the longitudinal tie direction, of the two rail supporting longitudinal tie segments occupies less surface area than in at least one cross-section, as seen perpendicular to the longitudinal tie direction, of said intermediate longitudinal tie segment. Because of this, the plastic, which has a lower lateral stiffness than the reinforcing structure, determines the lateral stiffness of the railroad tie in the rail supporting longitudinal tie segments to a more important extent than in the intermediate longitudinal tie segment.
In another a preferable embodiment of the invention, the railroad tie is free from said reinforcing structure in at least one cross-section, as seen perpendicular to the longitudinal tie direction, of the two rail supporting longitudinal tie segments. Because of this, the two rail supporting longitudinal tie segments have longitudinal sub-segments, in which per unit of length in the longitudinal tie direction there is no presence at all of material of the reinforcing structure. Hence, in the last mentioned longitudinal sub-segments the lateral stiffness of the railroad tie is fully determined by the low lateral stiffness of the plastic.
In a further preferable embodiment of the invention, the railroad tie in at least one cross-section, as seen perpendicular to the longitudinal tie direction, of the two rail supporting longitudinal tie segments has a larger shortest distance between the upper side of the railroad tie and the uppermost part, as seen in said reference condition of the railroad tie, of said reinforcing structure, than in at least one cross-section, as seen perpendicular to the longitudinal tie direction, of said intermediate longitudinal tie segment. Hence, the two rail supporting longitudinal tie segments have longitudinal sub-segments, in which there exists a larger quantity of plastic damping material between the upper side of the railroad tie and the uppermost part of the reinforcing structure.
In a further preferable embodiment of the invention, said lower lateral stiffness of the railroad tie is realized in that in at least one cross-section, as seen perpendicular to the longitudinal tie direction, of the two rail supporting longitudinal tie segments the elongated reinforcing structure, when viewed apart, has a lower lateral stiffness than in at least one cross-section, as seen perpendicular to the longitudinal tie direction, of said intermediate longitudinal tie segment. This may for example be realized in that the reinforcing structure is formed by, for example, two reinforcement bars, lying alongside of one another, which, locally at one or more locations in the longitudinal tie direction, are connected to one another by means of transverse connections of the reinforcing structure. At the location of such a transverse connection, it is more difficult to push the two reinforcement bars transversely towards one another than at locations where such transverse connections are absent.
In a further preferable embodiment of the invention, as seen in said reference condition, the elongated reinforcing structure comprises at least one assembly, which assembly comprises at least two reinforcement bars, which are extending in the longitudinal tie direction, and which are directly and/or via material of the reinforcing structure connected to one another, and of which a first reinforcement bar along at least a part of the longitudinal tie direction is lying higher in the railroad tie than a second reinforcement bar thereof. Because of this, the desired beneficial combination of flexural rigidity and damping behaviour can be obtained with relatively little reinforcing material.
The invention is furthermore embodied in a railroad comprising at least one railroad tie according to any one of the abovementioned embodiments, as well as at least two respective rails, which are extending mutually parallel in the rail track direction, wherein the two rails are attached onto the two respective rail attachment areas.
In the following, the invention is further elucidated with reference to the schematic Figures in the attached drawing.
For the railroad tie 1 shown in
The rail supporting longitudinal tie segments of the railroad tie 1, which segments are situated vertically below the two rail attachment areas 5 and 6, are indicated in
It is remarked that, in the shown example, the railroad tie 1 is substantially symmetrically shaped, both relative to its vertical longitudinal mid-section (perpendicular to the rail track direction S), and relative to its vertical transverse mid-section (perpendicular to the longitudinal tie direction L). In
The reinforcing structure 3, shown in
In
As a consequence of this shown configuration of the reinforcing structure 3 in the railroad tie 1, the railroad tie 1 has in the two rail supporting longitudinal tie segments 15 and 16 a lower lateral stiffness than in the intermediate longitudinal tie segment 17 of the railroad tie. After all, in the longitudinal segments 15 and 16 the lateral stiffness of the railroad tie 1 is determined to a much more important extent by the plastic 2, than in the intermediate longitudinal tie segment 17, while the plastic 2 has a lower lateral stiffness than the reinforcing structure 3.
The reinforcing structure 3 being embedded in this way in the plastic 2 provides a good resistance against bending of the railroad tie 1 under influence of the forces exerted onto the railroad tie, which forces are coming from both rails 7 and 8. As a consequence of the locally lower lateral stiffness in the two rail supporting longitudinal tie segments 15 and 16, the dynamical forces, coming from both rails, exerted onto the railroad tie are effectively damped.
In the example of
In the first place, it can be derived particularly from
In the second place, it can be derived particularly from
In the third place it can be derived particularly from
It is remarked that the abovementioned examples of embodiments of the invention do not limit the invention, and that various alternatives are possible within the scope of the appended claims.
For example, the railroad tie can be manufactured from various kinds of plastic, whether or not being recycled, and whether or not using various kinds of additives thereto. For example, the plastic can be a polyethylene.
Also, the reinforcing structures embedded in the plastic can be of various kinds of materials, such as various metals or metal alloys, steel, etcetera, but also various other kinds of construction materials, such as various construction plastics which have a higher lateral stiffness than the plastic in which the reinforcing structures are embedded. If the reinforcing structures comprise reinforcement bars, these bars can have various kinds of shapes. For example, the bars can have round, oval, polygonal, or many otherwise shaped cross-sections. Also, the reinforcing structures can have various non-flat surfaces for obtaining an improved force transmittal between the reinforcing structures and the plastic in which the reinforcing structures are embedded.
Furthermore, various variations are possible in the shapes and dimensions of the railroad tie. For example, the railroad tie can have various kinds of recessed spaces in all possible sides of the railroad tie, but the railroad tie can also be realized without any such recessed space.
Furthermore it is remarked that in the shown examples the reinforcing structures extend from the intermediate longitudinal tie segment to both sides thereof not farther in the longitudinal tie direction than within the rail supporting longitudinal tie segments. However, it is also possible that the reinforcing structures extend from the intermediate longitudinal tie segment to both sides thereof farther than within the rail supporting longitudinal tie segments, that is to say beyond the rail supporting longitudinal tie segments in the direction of the longitudinal ends of the railroad tie.
However, other variations and/or modifications are also possible. These and similar alternatives are deemed to fall within the scope of the invention as defined in the appended claims.
Number | Date | Country | Kind |
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2010056 | Dec 2012 | NL | national |
Filing Document | Filing Date | Country | Kind |
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PCT/NL2013/050820 | 11/14/2013 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2014/104873 | 7/3/2014 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
7204430 | Barmakian et al. | Apr 2007 | B2 |
8366015 | Van Belkom | Feb 2013 | B2 |
20060180046 | Barmakian | Aug 2006 | A1 |
20070187522 | Kirchmer | Aug 2007 | A1 |
20090308824 | Van Belkom | Dec 2009 | A1 |
20100037795 | Van Belkom | Feb 2010 | A1 |
20160194834 | Van Belkom | Jul 2016 | A1 |
Number | Date | Country |
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2005100691 | Oct 2005 | WO |
2006088857 | Aug 2006 | WO |
2008048095 | Apr 2008 | WO |
Number | Date | Country | |
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20160194834 A1 | Jul 2016 | US |