Bonded, electrically insulated rail joint system, method for its manufacture, start-up and use

Description

Scope of the Invention

[0001] The present invention relates to the technical field of insulating bonded joints of railway rails (generally trains, subways and the like).

[0002] In particular, the invention refers to a particular joint structured in such a way as to have a longer operating life and a lower acoustic and vibrational impact, offering a higher safety level than existing joints, preventing breakages and potential railway accidents, while also allowing for simple installation and easy maintenance of the railway track.Brief References to the Known Art

[0003] Railway rails are historically jointed by mechanical joints ('couplings') and, more recently, by welds.

[0004] A very common type of joint is the 'bonded insulated joint' (G.I.I.) whose purpose is to mechanically connect the rails while keeping them electrically insulated.

[0005] In this case, there is no continuity offered by welding since there is a discontinuity between the two joints due to the insertion of electrically insulating material.

[0006] It is a well-known fact that, in order to ensure the necessary spacing between trains on the line and avoid collisions at the station, railway tracks are divided into sections of varying lengths, known as 'automatic block sections'. The rails at the ends of these automatic block sections are mechanically connected (jointed) in order to allow trains to pass, but they are also electrically insulated so that a so-called 'track circuit' (or CdB) can be implemented. The two rails of a section are powered at one end by a low-voltage source; this voltage normally drives a relay at the other end of the track. When a train rolls on the section, its (steel) axles short-circuit the rails causing the relay to drop and thus changing the status of the CdB from 'free' to 'occupied'.

[0007] With this system, which has been known for years, information is acquired about the passage of the train at predetermined sections where such information is needed to manage railway traffic.

[0008] That said, G.I.I.'s are widespread throughout the world and find their application in security systems and convoy spacing on the line and at stations.

[0009] In the remainder of this document, G.I.I.'s will also be identified by the internationally known acronym IRJ, from the English "Insulated Rail Joint".

[0010] Although there are numerous types of IRJs, except for the specific cases below, they all fall within the morphology described hereinafter.

[0011] Figure 1A and 1B show an example of a typical IRJ.

[0012] It consists of two identical rail lengths (101, 102), sandblasted and cut at right angles (90° relative to the rail axis) to form a ' butt joint'. The rail lengths are drilled, usually with four or six holes, on the web. The rail lengths are placed end-to-end, thus generating the IRJ's transverse symmetry plane, separating them through a rail-shaped template in electrically insulated nylon (108) of typically 5 mm thickness (end post). The thickness of this template is a compromise between maximum shock reduction (which would require the smallest possible distance) and need to prevent that plastic deformation of the rails, due to the continuous 'hammering' of the wheels, cause mechanical and electrical contact between rail lengths (101), in fact generating an IRJ failure.

[0013] The rail mechanical continuity is restored, at least partially, by means of two lateral jaws (103', 103'') referenced on the rails themselves by means of sloped planes (i.e., 'splint planes'), which ensure their correct positioning.

[0014] Said jaws are secured by means of a screw (105) or irreversible locking nail 105.

[0015] In order to avoid that the jaws short-circuit the rail lengths (101, 102), additional electrically insulating material (102', 102''), commonly made from shaped and perforated fibreglass sheets, is placed between jaws and rail.

[0016] The jaws are then joined to the rails by means of screws or irreversible locking nails (105), provided with washers (106', 106''), by a sleeve made of insulating material (104) and a nut or deformable collar (107) depending on the application.

[0017] The joint is fabricated using high-strength structural adhesives, which play a fundamental function in IRJs, since mere friction would not be sufficient to transmit the vertical forces dependent on the load of the passing vehicles and, above all, the longitudinal forces that arise due to thermal effects (expansion) of the rails.

[0018] Figure 1B shows a top view of the same joint, in which the insulating template (108) as well as the other above-mentioned elements are visible.

[0019] On the plane of vertical symmetry, easily identifiable in the centre of said nylon insulating template (108), the section resistant to vertical loads, which generate bending in the joint, is exclusively provided by the jaws. This results in a flexural stiffness that, in ordinary IRJs, is about one-third of the stiffness of the standard rails with which the IRJ is fabricated. In contrast, the adjacent areas, where the jaws are active, have a stiffness that is about 1 / 3 higher than that of the rails themselves. The two combined effects make the cross-section of symmetry critical, as a passing wheel encounters first a very rigid section (the one with the jaws alongside the rail) followed by a very flexible section (the one with only the jaws and the plastic template), with a stiffness ratio of up to four in ordinary IRJs.

[0020] The cross-section of transverse symmetry, with its abrupt stiffness variation, constitutes, in traditional IRJs, a discontinuity which, given the characteristics of the materials (typically steel), generates impulsive stresses (shocks) whose effects are amplified in the screw passage holes which represent, as is well known, cut-outs capable of generating stress concentrations and therefore fatigue cracks.

[0021] Such cracks, which are quite frequent, are indicated in the catalogue of rail cracks of the Union Internationale des Chemins de Fer (Fiche UIC 712) under the designation 'cracks originating from holes' with code 135 (star cracks). They develop at 45° from the edges of the holes drilled on the web, at the plane of maximum cut. Known art systems such as reaming, chucking, etc. can be used to reduce the possibility of crack emergence and growth.

[0022] The probability of failures increases when, as shown in Figure 1C, the IRJ is mounted in the 'suspended' configuration, i.e., in the centre of the span identified by crossbeams (109) and corresponding rail-traverse couplings (110).

[0023] A very large scientific production is known on performance calculations, numerical and experimental analysis of stresses and strains, and typical damage in IRJs. Suffice it to cite the article by N. K. Mandal e B. Peach, An Engineering Analysis of Insulated Rail Joints: A General Perspective, International Journal of Engineering Science and Technology ISSN: 0975-5462 3964, Vol. 2(8), 2010, 3964-3988 summarizing the whole issue of IRJs of the various types. As a result, IRJs are in fact an unsolved problem for railway line management and safety.

[0024] In order to mitigate the technical problems, a 'smoother' transition between two rail lengths was attempted to reduce the impacts present in the current IRJs by sloping the rail junction line by means of an oblique cut.

[0025] An example of known art is shown in Figure 3, to be found in at least one commercially available IRJ. The small web size of the rails currently used, however, does not allow the rail head to be cut at a significantly small angle (to be understood as the angle between the direction of the cut and the longitudinal axis direction of the rail), with the result that the transition zone is not sufficiently stretched, leading to limited benefits.

[0026] This is demonstrated in Figure 2, which shows an IRJ obtained by machining two standard rails in such a way as to have a sufficiently long transition. This results in an angle of 4.25°, which, however, leads to portions of the rail head unsupported by the web as well as sharp surfaces. This solution, totally technically unacceptable, has in fact never been implemented.

[0027] This problem has been overcome by the known art shown in Figure 4 in which two special rails, with an oversized web, usually used in expansion joints especially at bridges, are shown, which are machined according to this principle.

[0028] This solution is described in the scientific article by R. H. Plaut, H. Lohse-Busch, A. Eckstein, S. Lambrecht and D. A. Dillard, Analysis of tapered, adhesively bonded, insulated rail joints, Journal of Rail and Rapid Transit 2007 221: 195, DOI: 10.1243 / 0954409JRRT107. This solution, as mentioned in the article, requires the rolling of special rails and the creation of special transitions between said special rails and the standard rails, with significant production costs.

[0029] Prototypes of these joints, described in patents US7975933, US8113441, US8302878, US9328464 have been tested in the US but have had no commercial follow-up due to the significant production costs. DE 34 20 712 is also known.Summary of the Invention

[0030] It is therefore an aim of the present invention to provide a new type of bonded insulated rail joint (IRJ) assembly that solves the aforementioned technical drawbacks.

[0031] In particular, it is the aim of the present invention to provide a new IRJ solution that is reliable, low cost and easy to manufacture and install.

[0032] More specifically, it is the aim of the present invention to provide a new type of IRJ that solves the aforementioned technical drawbacks, offers greater safety, less environmental impact (noise and vibrations), is easy to install and allows for simple track maintenance.

[0033] These and other aims are achieved with this bonded insulated rail joint (IRJ) assembly according to claim 1.

[0034] In accordance with the present invention, there is further provided a method for fabricating an insulated rail joint assembly having the features of claim 9, a method for modifying at least on starting switch rail having the features of claim 15 and the use having the features of claim 16.

[0035] Further preferred embodiments are defined by the features of dependent claims 2-8,10-14.

[0036] Such an insulated rail joint (IRJ) (or simply joint as it may be) comprises: At least one first switch rail (1); At least one second switch rail (2); Both said two switch rails (1, 2) having a first portion (1''; 2'') of a predetermined longitudinal length having a standard rail structure which connects to a second portion, lowered with respect to the first portion, and with said second portion comprising, at one of its sides, a conjugate coupling surface (S) preferably of relevant length and of arbitrary shape, and having, on the opposite side, at least a part of conformation of a switch blade or rail structure; Said conjugate coupling surfaces (S) being such that, when said first and second switch rails are coupled together by means of said two arbitrarily shaped conjugate coupling surfaces (S) placed in contact with each other, the structure of a switch blade or rail is restored in the coupling section, said switch blade or rail having a foot, a web and a head; And in which a bolted cover plate (8) is further included, forming a foot to which at least part of said foot of the switch blade or of the rail restored as a result of said coupling is fixed.

[0037] Preferably, advantageously, the two conjugate surfaces, in virtue of their relevant length, hence, form a transition of high longitudinal length.

[0038] In accordance with this solution, all the aforementioned technical drawbacks are solved.

[0039] The use of a starting switch rail allows for the creation of a conjugate coupling surface that is robust since the lowered, unforged part of the starting switch rail has a very thick web section (40 mm). This allows the conjugate coupling surfaces to be obtained while leaving the structure of the switch rail on the opposite side unchanged and with a good amount of material.

[0040] The thus modified switch rail is robust and when coupled with its twin creates a stable and strong solution.

[0041] In addition, the bottom plate having a bolted cover plate function (i.e., the splices) further optimises strengths.

[0042] In fact, said bolted cover plate provides large surfaces for the application of adhesive material and thus substantially contributes to the flexural stiffness and to the longitudinal and structural flexural strength of the IRJ, while providing suitable surfaces for a simple and correct assembly of the IRJ in the current track.

[0043] The adhesive material is inserted in the contact area obviously between bolted cover plate and switch blade foot or restored rail that connects to it.

[0044] The adhesive material used can be any of the known ones and already in use in the industry.

[0045] The use of a switch rail, given the large thickness of the web in the lowered unforged part, therefore, allows the side to be removed, creating a conjugate coupling surface that forms in fact a face that follows a longitudinal development direction at a small angle to the longitudinal axis of the starting switch rail.

[0046] Preferably, but not necessarily, the conjugate coupling surface can be flat.

[0047] However, in further variants, as also clarified below, the conjugate coupling surface structure can take shapes other than simply flat (see examples in Figure 12), thus also allowing for shape coupling and not just friction coupling.

[0048] In all cases, the two surfaces (S) are conjugate in that they mirror each other and are therefore such that they join together to complete the form (i.e., they match each other in mirror-image manner).

[0049] In this way, once the coupling is complete, the head of the restored rail or blade will show a junction curve (L) (also known as a transition line or curve) with high development along the longitudinal axis, solving all the aforementioned technical problems without affecting the structural strength of the obtained assembly or system as it may be.

[0050] In particular, advantageously, the coupling surface is of considerable length compared to known-art solutions, and therefore considerably longer than known-art transitions.

[0051] For example, it is possible to have longitudinal lengths and thus transitions of 500 mm or more.

[0052] Advantageously, as a result of the coupling of said two arbitrary conjugate coupling surfaces (S), a transition curve (L) is generated that forms, for at least one section of its length or for several sections of its entire length, a predetermined angle with respect to the longitudinal axis of the switch rail on which it is provided.

[0053] Advantageously said angle being less than or equal to 3°.

[0054] Advantageously, said first and second switch rail (1, 2) are standard and said conjugate coupling surface (S) is a surface optionally obtained by: Chip removal, e.g., by milling, of said second portion of the standard switch rail; Forging said second portion of the standard switch rail; A combination of both of the above options.

[0055] Advantageously, in order to electrically insulate the entire IRJ junction system, at least one layer of electrically insulating material (15) inserted between the two conjugate coupling surfaces (S) is further included, and at least one further layer 9) of electrically insulating material is furthermore included inserted between the bolted cover plate and said foot that connects to the bolted cover plate.

[0056] Advantageously, said electrically insulating layers are supported by adhesive material.

[0057] Advantageously, the additional joining elements used for the coupling between said parts are also electrically insulated.

[0058] In this regard, advantageously, first means of connection (3, 4, 5, 6, F) are comprised to connect said first switch rail with said second switch rail via said coupling surfaces.

[0059] Advantageously, said first means of connection, e.g., screws and / or bolts and / or nails in general, are electrically insulated.

[0060] Advantageously, said first means of connection comprise screws and / or bolts and / or nails in general inserted in transverse holes (F) passing through the entire thickness and drilled at the coupling surface (S).

[0061] Advantageously included are second connecting means to connect said second portions to each other coupled to said plate (8).

[0062] Advantageously, said second means of connection, e.g., screws and / or bolts and / or nails in general, are electrically insulated.

[0063] Advantageously, said second means of connection comprise screws and / or bolts and / or nails in general.

[0064] Advantageously, in combination with the foregoing or independently, said second means of connection further comprise one or more blocking elements (10', 10'') shaped in such a way as to overlap for a part thereof the foot of the rail restored by the coupling of said coupling surfaces (S) and, for a part thereof, abutting plate (8) in such a way as to be fixed to said plate by means of nails in general and / or bolts and / or screws in general.

[0065] Advantageously, said first and second switch rail comprising said conjugate coupling surfaces (S) are identical to each other.

[0066] In particular, advantageously, by rotating one with respect to the other by 180° around an axis orthogonal to their support plane and with the switch rails abutting through their feet, they can be coupled by bringing the conjugate coupling surfaces into contact. In such a coupling arrangement, they will result in two complementary elements which, when coupled, complement each other by defining the shape of the rail or blade, in particular the head on which the wheels of the convoy roll.

[0067] Advantageously, therefore, said conjugate coupling surface (S) extends longitudinally for a predetermined length.

[0068] Advantageously, said conjugate coupling surface (S) extends further across the height of said second portion on which it is provided.

[0069] Advantageously, the layer of electrically insulating material can for example be in the form of a fibreglass sheet.

[0070] It is also an object of the present invention to provide a method for creating a bonded, electrically insulated rail joint (IRJ) assembly, which comprises the following steps: Providing at least one first starting standard type switch rail (1) having a first portion (1'') of a predetermined longitudinal length with a standard rail structure that connects to a subsequent second blade portion that is asymmetrical and lowered with respect to the first portion; Providing at least one second starting standard type switch blade bar (2) having a first (2'') portion of a predetermined longitudinal length with a standard rail structure that connects to a subsequent second blade portion that is asymmetrical and lowered with respect to the first portion; Machining of at least part of said second portion for both said first and second starting switch rails in such a manner as to modify said second portion by obtaining on one side of said second portion a conjugate coupling surface (S) preferably of relevant length, and maintaining the original structure on the opposite side; Jointing of said first and second switch rail together by bringing said two conjugate coupling surfaces (S) into contact with each other in such a way as to restore, following said coupling, the structure of a switch blade or rail, said switch blade or rail having a foot, a web and a head; Fastening the foot relative to the said restored switch blade or restored rail with a bolted cover plate (8) arranged underneath said foot.

[0071] Advantageously the conjugate surface is preferably flat but can also be of other arbitrary shapes.

[0072] Preferably, advantageously, the two conjugate surfaces, in virtue of their relevant length, hence, form a transition of high longitudinal length.

[0073] In particular, advantageously, the transition between one rail and the other is completed in a length that can be even more than thirty times the diameter of the typical wheel / rail print (15 mm *30 = 450 mm), while in all other joints the transition is of a length comparable to the size of said print.

[0074] Advantageously, such machining can be: A machining operation on machine tools for chip removal, e.g., milling; Machining by forging; A combination of both.

[0075] Advantageously, as a result of the coupling of said two conjugate coupling surfaces (S), a curve or transition line (L) is generated that forms, for at least one section of its length or for several sections of its entire length, a predetermined angle with respect to the longitudinal axis of the switch rail on which it is provided.

[0076] Advantageously, the angle of the conjugate coupling surface being less than or equal to 3°.

[0077] Advantageously, the jointing of said first and second switch rails takes place by drilling the two conjugate coupling surfaces with one or more holes passing transversally through the entire thickness and the application of first means of connection.

[0078] Advantageously, said conjugate coupling surface (S) extends longitudinally for a predetermined length.

[0079] Advantageously, said conjugate coupling surface (S) extends further over the entire height of said second portion from the head to the foot of said second portion.

[0080] Advantageously, the IRJ is electrically insulated and bonded at least through the insertion of a layer of electrically insulating material and assisted with adhesive material at least between the two conjugate coupling surfaces (S) and between the foot and the bolted cover plate.

[0081] Advantageously, said first portion (1'', 2'') of said standard-type switch rail is obtained by forging.

[0082] Advantageously, said first portion (1'', 2'') of said standard-type switch rail is obtained by forging.

[0083] It is also an object of the present invention to provide a method of modifying at least one starting standard type switch rail (1) having a first portion (1'') of predetermined longitudinal length with a standard rail structure which connects to a subsequent second portion which is asymmetrical and lowered with respect to said first portion; Said method comprising the machining, e.g., by chip removal and / or forging, of at least a portion of said second portion of said starting switch rail in such a manner as to modify a side of said at least a portion of said second portion by obtaining on said side a conjugate coupling surface (S) and maintaining the original structure on the opposite side. Advantageously, said conjugate coupling surface (S), extending longitudinally for a predetermined length; Advantageously, said conjugate coupling surface extending over the full height of said second portion from the head to the foot of said second portion on which it is formed.

[0084] Advantageously, exactly as described above, the conjugate surface forms with respect to the longitudinal axis of the switch rail on which it is cut a small angle, e.g., equal to or less than 3°.

[0085] Also described here is the use of two switch rails modified according to the above method, which are coupled together by bringing the conjugate coupling surfaces (S) into contact with each other to form a bonded insulated rail joint (IRJ) assembly.

[0086] For this purpose, the two switch rails are connected to a bolted cover plate and the entire system obtained is electrically insulated.

[0087] Ultimately, therefore, such an IRJ, which is also fabricated through the use of high-strength structural adhesive, comprises in a possible preferred form of the invention: Two identical switch rail lengths, forged as per railway standard, and therefore having one portion with an unmodified section and one portion taking the form of a standard railway rail, suitably machined to produce a sloped face with a small angle (less than 3°). They are equipped with an arbitrary number (even or odd) of holes for the passage of the blocking devices (first means of connection) in relation to the stresses to which the IRJ is subjected, thus being able to realise 'heavy' and 'light' versions and then coupled through the insertion of a sheet of insulating material of reduced thickness, described in detail below; A series of connection devices (i.e., the so-called first means of connection) with reversible (screws) or irreversible (nails) assembly, suitably sized and applied, adapted to connect said switch rails without deployment of the jaws usually used in current IRJs; A plate 8 acting as a bolted cover plate adapted to further connect the aforementioned switch rails in a portion below the coupling area of the switch rails, thus providing large surfaces for the application of adhesive and thus substantially contributing to the flexural rigidity and to the longitudinal and structural flexural strength of the IRJ, while at the same time providing suitable surfaces for the simple and correct assembly of the IRJ in the current track; A series of connecting elements (called second connecting means), suitably dimensioned and applied, to couple the aforementioned bolted cover plate to the coupled switch rails through the insertion of a sheet of insulating material; A series of ancillary elements (washers, insulating sleeves, etc.) functional to the mechanical connection and simultaneous electrical insulation applied to the IRJ, achieving in particular small thicknesses both for the insulating plate between the two switch rails (by virtue of the 'soft' transition between the switch rails themselves and thus the absence of plastic deformations of the surface in contact with the wheels) and for the insulating nail sleeves (made of advanced materials and by virtue of the fact that the switch rails can be machined in pairs, eliminating the influence of assembly tolerances); The high-strength structural adhesive required to make all surfaces cooperate to resist external mechanical stress.

[0088] Ultimately, the use of two switch rails (e.g., with a 40 mm wide web according to a widely used type of switch rail) makes it easy to obtain a machined surface with low angles to the rail axis while maintaining a robust structure, thus solving all the problems posed.

[0089] The particular combination of thicknesses and types of electrically insulating materials used leads to the short-circuiting of the switch rails when, as a result of the dislodging (failure) of the IRJ, a very small displacement occurs, thus achieving a very high safety condition that prevents the signalling equipment from routing further trains on the track where the IRJ has dislodged.

[0090] In addition, the special structure of the IRJ, and in particular of the bolted cover plate, allows the IRJ to be mounted at a crossbar, reducing stresses (the IRJ is in the "abutted" condition instead of the normal "suspended" condition shown in Figure 1C) and allows the distance between the crossbars to be maintained at the ordinary value of 600 mm (so-called "spacing"), greatly facilitating track tamping operations.

[0091] In this respect, the solution allows, in contrast to ordinary joints, the use of normal machinery for this operation (so-called "tamping machines") since the lower surface of the switch rail head allows the use of rail lifting rollers as in the IRJ subject matter of the present invention the jaws (103', 103'') referred to in Figure 1A of the known art are not provided.

[0092] Further advantages of the above solution are that such a solution allows for coupling tolerances that minimise the play between structural elements and connecting elements and that reduce the thickness of the insulation elements, the latter being made of thin advanced materials, increasing the safety of the IRJ since in the event of a disconnection the switch rails are immediately short-circuited.

[0093] The IRJ, as described above, can be installed on standard railway sleepers using standard rail-to-rail fastening systems.

[0094] In addition, such an IRJ allows to achieve a stiffness in the transverse axis of symmetry of the IRJ that is at least 20 per cent greater than the starting rail stiffness.

[0095] In addition, the IRJ introduced above allows current track maintenance operations (ballast tamping) to be carried out without any limitations.

[0096] In addition, this solution allows for a significant increase in strength through the use of a bolted cover plate provided with a large connection area between switch rails.

[0097] Furthermore, the IRJ makes it easy to optimise the construction solution by producing 'heavy' or 'light' versions of various types depending on the application required.Brief Description of the Drawings

[0098] The invention, in one or more of its embodiments, will be detailed below in accordance with the following drawings: Figures 1A, 1B, 1C, 2, 3 and 4 show solutions in the known art, described above; Figure 5 shows, in order to appreciate the differences in web thickness, the cross-section of a standard rail and the cross-section of a switch rail; The Figure shows the nomenclature normally used in the technical field and highlights how the web of a switch rail is thicker than the web of the standard rail; Figure 6 shows in isometric views the solution indicated here as 'heavy' and therefore preferable in case of high external and thermal loads; In Figure 6 the very low angle of inclination of the coupled surfaces with respect to the rail axis (indicated as the longitudinal axis) through the machining and coupling of two standard forged switch rails ('bars') may be appreciated; In particular, the Figure highlights precisely the small angle formed between the longitudinal axis and the L line joining the two parts; Figure 7 shows isometric views of the adopted solution; Figure 8 shows an exploded view of the adopted solution in which all its components are visible; Figure 9 shows a cross-section at an end nail; Figure 10 shows an isometric view of a track in the section where the IRJs are provided developed according to the 'heavy' solution adopted, which allows to appreciate how it is compatible with ordinary couplings and sleepers, without requiring any modification to the current track; Figure 11 shows a 'light' version, therefore suitable for lower thermal and mechanical loads and therefore preferable for applications such as subways where thermal expansion is lower, for example; Figure 12 shows variants in which the coupling surface formed on the side of the switch blade portion is not necessarily flat but can also have other profiles. Detailed Description of some Invention Configurations

[0099] In accordance with the invention, the proposed solution sees, in fact, the use of the well-known railway switch (turnout) rails however used following their structural modification, to create bonded and electrically insulated rail junction systems (or simply joint as the case may be) to replace those currently known.

[0100] Thus, in an advantageous embodiment of the invention, the solution comprises the arrangement of at least two switch rails which are machined (e.g. milled and / or forged) according to a sloped direction with respect to the longitudinal direction of the switch rails so as to obtain in each switch rail a conjugate coupling surface (S) (also referred to for simplicity in the remainder of this description as coupling surface) which allows the two switch rails to be coupled together, thereby restoring following coupling, a blade or rail structure with a head on which the convoy wheel can normally roll. The foot of the restored blade is fixed to an underlying plate (a bolted cover plate).

[0101] It is well known that switch rails, with a low, asymmetrical cross-section, are partially forged to take the shape of a normal rail at one end, so that they can be jointed to the remaining parts of the track.

[0102] More specifically, it is known that the switch rail is obtained from a rail of a predetermined length whose cross-section, with reference to Figure 5, corresponds entirely to the one on the left indicated as "switch rail section'.

[0103] It is lower than the standard height of a normal rail as well as asymmetrical while the head, which forms the convoy wheel running surface, is the same in both the switch blade and the normal rail.

[0104] In a switch rail production process, starting from a long bar with a section like the one in Figure 5 on the left 'switch rail section', a forging step is carried out on an end portion of the bar in order to shape it like a standard rail and thus according to the sectional shape in Figure 5 on the right 'standard rail section'.

[0105] This provides a transition from the low, asymmetrical, switch blade shape to the standard rail to be jointed with the rest of the rails.

[0106] The standard rail structure is easily achieved by heating this portion in an induction furnace to bring the material to a plastic state and deforming it through passages in special die presses (thus performing a forging process). Through such passes in moulds, the end of the bar takes on the desired normal rail shape (i.e., higher than the remaining blade section and with a thinner web). This means the modified end part is used to create the junction of the switch rail to the normal rail.

[0107] That being said, as introduced above, the present invention sees the use of the well-known switch rail which, however, in its non-forged part (i.e., the lowered asymmetrical part) is instead machined and / or forged.

[0108] In fact, the use of two forged standard switch rails with a 60E1A2 section and suitably shaped (see European standard EN 13674-2), each with a web thickness (d) of 40 mm, makes it possible to achieve a total web of no less than 54 mm after coupling (as better described below), compared to a web thickness (d1) of 16.5 mm of a standard 60E1 rail (see European standard EN 13674-1).

[0109] These switch rail web dimensions allow for an extremely small angle of less than 3° and a correspondingly large coupling length of more than 500 mm.

[0110] This implies, as further explained below and with reference to Figure 6, that the angle formed by the longitudinal axis of the IRJ obtained from the two coupled switch blades and the cut-off line L, which represents the coupling line, is an angle that may be equal to or even less than 3°.

[0111] The thickness of the web therefore allows cuts that extend for a good length (l), therefore equal to or even greater than 500mm, as shown for clarification (but not limitation) in Figure 6, without risking weakening and the creation of sharp bodies.

[0112] The length of the coupling is limited by the need to fit the proposed solution into a current track without any constraints on the type of couplings and spacing of the sleepers.

[0113] More specifically, therefore, the concept of the invention consists mainly in exploiting the standard switch rail, in particular the un-forged part (with reference to Figure 5 the left-hand side "switch rail section") to carry out a machining process which can be, for example, on machine tools, by forging or by other equivalent systems, in order to obtain, on one side of the switch blade, a coupling surface S (also called in the present description face S or flat surface S in an equivalent manner) which couples with a twin.

[0114] The side opposite the S-coupling surface is not machined but is instead retained in its original structure.

[0115] In this way, the coupling restores the switch blade or rail shape.

[0116] The fact that the switch blade is lowered, in accordance with the proposed solution, also allows for a lower counter plate, which makes the entire system structurally stable.

[0117] Briefly, the invention, which shows in Figure 6 a 'heavy' solution with preferably five holes as an example only, consists in using standard switch rails (1, 2), forged as customary, as starting elements for the subsequent switch blade creation to obtain the standard rail shape.

[0118] More specifically, as is evident from Figure 6, a coupling line (L) can be seen which presents a small angle to the switch blade longitudinal axis.

[0119] Figure 8 in fact shows the two separate switch blades in an exploded view and shows that at their end, which is not forged, these switch blades are machined on one side so as to obtain a coupling surface (S).

[0120] The two switch blades are machined in such a way as to obtain mirror-image twins which, when coupled, restore the original head of a rail (which is equivalent (said head) in size and structure to that of an original switch blade) .

[0121] The machining, in fact, affects one side in order to generate the coupling surface S (see also figure 12, for example) while the opposing side remains unchanged (i.e., is not modified).

[0122] Thus, the coupling of said two portions regenerates a rail or switch blade structure in which, in addition to the foot and web, the head on which the convoy wheel rolls is provided.

[0123] The above-mentioned machining is carried out on two switch rails, which are not only a standard component but also a component with a web of increased thickness compared to a standard rail (please note here, with reference to Figure 5, that a switch rail web has a thickness of 40 mm compared to 16.5 mm for the standard rail). This allows the realisation of a coupling surface S that follows a development direction at a small angle to the longitudinal direction (even less than 3°), without the inconveniences that were experienced in the known art when working on a standard rail, thus with too small a web thickness.

[0124] The coupling of the two parts, as then shown in a section of Figure 9, restores an original head size and with a web section that can even be much higher than the known art solutions.

[0125] The coupling surfaces (S) affect one side of the switch blade, for a certain length and small slope in relation to the longitudinal axis of the switch blade being machined.

[0126] This coupling surface (S) also extends across the full height of the switch blade in its un-forged part, from the foot to the head, therefore removing material from the foot to the head or, in case of forging, flattening and modifying the shape from the foot to the head as can be seen clearly from both Figure 8 and Figure 9.

[0127] In a possible variant of the invention, then, the coupling surface (S) can easily be obtained by material removal on machine tools, e.g., by milling.

[0128] For example, two switch blades can be placed side by side as shown in Figure 8 on a milling cutter table and held in position on a work base, e.g., by means of a magnetic system that holds the two switch blades in position.

[0129] The two switch blades, placed next to each other at a certain distance, rest with their foot on the magnetic base and are therefore held in place by the magnetic force. This keeps the area subject to material removal free with a firm hold.

[0130] The milling cutter, preferably of the numerically controlled type, lowers itself and rotating at a certain speed removes material, thus creating the two surfaces (S) in the two switch blades. The two switch blades will be practically twins (therefore identical), so that by inverting one of them relative to the other (i.e., one rotated 180° relative to the other with rotation on an axis orthogonal to the plane of support) the two machined parts can couple to produce the structure of Figure 9 or Figure 6 or 7.

[0131] It is worth noting here that the creation of surface (S) can also be achieved by a method similar to that already in use for the creation of the standard switch rail, i.e., by forging.

[0132] In particular, the unforged end section of the switch blade (i.e., for clarity, the left-hand section in Figure 5 'switch rail section', which in accordance with the first configuration is machined by milling) can also be forged to yield the desired final shape, i.e., surface (S).

[0133] According to this variant, therefore, starting from a switch rail with one forged and one unforged part, the unforged part is now forged. This involves a process in which the part to be modified is heated to a temperature that brings the metal to a condition where it can be machined by plastic deformation and then said deformation is performed using, for example, die presses with one or more passes.

[0134] In all of the above cases, a surface (S) is obtained like the one in Figure 8 or Figure 12 whose line of development in the longitudinal direction (i.e., along the longitudinal length) forms a certain angle to the longitudinal direction of the switch blade.

[0135] The length along the direction of longitudinal development of the surface S, as mentioned, can even exceed 500 mm, and this processing affects the entire height from the foot to the head.

[0136] When the twin parts are thus coupled (see, for example, Figure 6), the joint line (L) has a certain angle to the longitudinal direction of development, the angle being, however, small. This angle can advantageously be less than 4.5 degrees, for example, preferably less than or equal to 3°.

[0137] However, those skilled in the art will be able to assess the most suitable angles according to his or her needs.

[0138] Going further into the structural description of the invention, switch rails (1, 2) are preferably coupled by means of screws or nails (3, 7), (see e.g., Figure 6), although other mechanical connection systems are not excluded.

[0139] The coupling, therefore, requires through holes (F) in the surfaces (S), as shown by the exploded view in Figure 8. Holes F are transverse holes that from surface S pass through the entire thickness of the remaining web.

[0140] In this regard, in order to produce holes that will be precisely aligned with each other, it is preferable to work on switch rails already machined and coupled with each other.

[0141] In this way, it is possible to cancel errors resulting from tolerances otherwise present in the standard solution in which switch rails are machined separately.

[0142] Once the two surfaces (S) have been realised, the two switch blades thus modified are preferably coupled, bringing the two surfaces (S) into alignment as shown in Figure 6 for example, and drilling is carried out on axis, which then allows the connection systems to be inserted.

[0143] This also makes it possible to drill small-diameter holes that cause less weakening of the section and allow the use of thinner insulators. The number and size of nails, screws or other connection systems can be optimised according to the loads to be transmitted; for example, up to at least six of the usual 25.4 mm diameter nails can be used.

[0144] Of course, a drilling solution without necessarily coupling the two switch blades together is not excluded.

[0145] Since the height of the 60E1A2 switch rail is 134 mm compared to 172 mm for a 60E1 rail (see also Figure 5), this difference in height (38 mm) is advantageously exploited by implementing a bolted cover plate 8 with a high coupling surface, which contributes significantly to both the structural strength and the vertical flexural rigidity of the IRJ, the latter being much more uniform than in traditional IRJs.

[0146] Figure 5, for the sake of clarity, shows with 'delta of height' the difference in height between the forged portion of the right 'standard rail' and the left 'switch rail' showing precisely how the section of the un-forged switch blade is lowered compared to the forged portion.

[0147] This difference in height (delta of height which is approximately 38mm as mentioned) is used to install, as clearly shown in Figure 9, the bolted cover plate, which is nothing more than a plate, preferably metal, with flat surfaces on which the foot resulting from the coupling of the two surfaces (S) abuts and is fixed. Figure 9, reproduced below, clearly shows a cross-section of the coupling between bolted cover plate 8 and the two switch blades machined as described and placed on the bolted cover plate.

[0148] The bolted cover plate 8 can be secured with normal screws 12, bolts in general or similar.

[0149] Screws or bolts generally penetrate through the cover plate and intercept the foot, completing the connection.

[0150] If necessary, additional elements (10', 10'', 11', 11'', 14) cooperating with the screws or bolts in general may be provided.

[0151] For example, Figure 8 shows in the exploded view that screws 12 penetrate through blocks (10', 10'') that overlie the foot.

[0152] More specifically, a larger detail is shown by the exploded view in Figure 8 in which, assuming that all connections are obtained with the help of the usual high-strength adhesives, all the elements required to realise the proposed solution are observed:

[0153] First of all, switch rail 1 with profile '60E1A2' is highlighted, which is commercially available with a forged transition 1' and ending with a rail profile (1'') 60E1 also concurrently obtained by forging. The originally unforged portion involves processing to create the above-described sloped surface (S), which can be obtained, as mentioned, by machining (on machine tools, e.g., with a milling machine) or by forging.

[0154] Holes (F) on the web (in particular through-holes through the surface (S)) for subsequent assembly are highlighted.

[0155] Figure 8 also shows an additional hole (F') for connection to the bolted cover plate (8).

[0156] Figure 8 shows, of course, an entirely identical second switch rail 2 (i.e., the twin) for which what has already been described applies;

[0157] A template 15 is then provided made of electrically insulating material, preferably GRP, shaped to mimic surface (S) and with holes matching holes (F).

[0158] Given the particular length and 'smoothness' of the coupling that develops longitudinally (preferably for more than 500 mm), which drastically reduce shocks and the associated plastic deformations of the rail head, said template can be made particularly thin compared to conventional IRJ head templates, virtually eliminating surface damage to the rails and guaranteeing a particularly durable geometry.

[0159] Figure 8 then shows irreversible locking nails 3, including steel shimming washers 4 and insulators 6.

[0160] Locking collar 7 and insulating sleeve 5, which are used to lock the elements (1, 2, 15) just described together, are then highlighted.

[0161] Again, the exploded view in Figure 8 shows bolted cover plate 8, which is provided with suitably machined surfaces (8') to allow easy mounting on standard cross beams and with a series of threaded holes required for subsequent locking.

[0162] Also shown is a corresponding insulating template 9 which is intended to isolate bolted cover plate 8 from switch rails (1, 2).

[0163] One or more screws 12, including steel shimming washers (12') and insulating washers (12'') are additionally fitted with an insulating sleeve 13. They are designed to connect switch rails (1, 2) with bolted cover plate (8) with insulating template (9) therebetween.

[0164] A number of additional elements may further be provided, specific to 'heavy' solutions, also referred to in this description as 'sleepers' (10', 10''). They are provided with appropriate insulating templates (11', 11'') and further bind, by means of screws 14, bolted cover plate 8 with switch rails (1, 2) while maintaining the electrical insulation. Preferably, so called sleepers can be implemented in those joints that are particularly mechanically stressed.

[0165] Figure 9 allows viewing the insulating elements between nail and switch rails 5, between lock washers and switch rail 6, between sleepers and switch rails and between bolted cover plate 8 and bars 9. Of particular interest is the fact that both insulators 15 and 5 can be manufactured in much smaller thicknesses than standard solutions, the former due to the 'softness' in the wheel-rail contact that avoids plasticisation and the latter due to the possible simultaneous machining of the bars.

[0166] They can therefore be fabricated below the aforementioned 5mm thickness of known art, so having thicknesses in the order of 1.5mm, for example.

[0167] The 'light' solution, shown as an example with only three nails in Figure 11, is essentially identical to the previous one but is obtained by eliminating the crosspieces and simplifying the bolted cover plate. This results in a version optimised for rigid rails, low loads, low temperature ranges, and small rail cross-sections.

[0168] With reference to the coupling surface obtained in the switch blade portion, as mentioned above, this is preferably flat as the flat shape is obviously the easiest to fabricate.

[0169] However, as also sketched in Figure 12, nothing precludes that the coupling surface be conveniently fabricated in any shape (obviously either by forging or milling).

[0170] By way of example, therefore, four possible variants of the coupling surface are shown in Figure 12, from right to left: A flat surface; A surface fabricated with a split profile (preferably with 10 mm fittings); A surface fabricated with a split profile (preferably with 40 mm fittings); A surface fabricated of circular arcs (preferably 500 mm in radius);

[0171] It can be seen that in the last three conditions, a self-centring shape coupling (so-called 'positive') is advantageously obtained, which locks the IRJ by binding its surfaces mechanically and not by friction, greatly increasing the resistance of the IRJ.

[0172] It can also be seen that while in the flat solution transition (L) is obviously a straight line in the last three conditions of the cases in Figure 12 (i.e., broken profile or with circular arcs), transition sections are determined.

[0173] Each transition section preferably has small angles, i.e., angles that are preferably less than or equal to 10° and even more preferably less than or equal to 3°.

Claims

1. An insulated rail joint (IRJ) assembly comprising: - At least one first switch rail (1); - At least one second switch rail (2); - Both said two switch rails (1, 2) having a first forged portion (1''; 2'') of a predetermined longitudinal length having a standard rail structure so that an end of said first portion can be joined, in use, to a rail of a track, and with the opposite end of this first portion that connects to a second portion, with height lower than the first portion, and with said second portion comprising, at one of its sides, a coupling surface (S) and having, on the opposite side, at least one portion of a switch blade structure; - And wherein said coupling surfaces (S) are such that, when said first and second switch rails are coupled together by means of said two coupling surfaces (S) placed in contact with each other, a structure of a switch blade or a rail is restored in the coupling section, said switch blade or said rail having a foot, a web and a head; - And in which a bolted cover plate (8) is further included, forming a foot to which at least part of said foot of the switch blade or of the rail restored as a result of said coupling is fixed; - And wherein said bolted cover plate (8) is a metal plate with flat surfaces on which the foot resulting from the coupling of the two surfaces (S) abuts and is fixed.

2. The joint assembly, according to claim 1, wherein following their coupling said two coupling surfaces (S) generate a transition line (L) which forms, for at least a section of its length or for several sections of its entire length or for its entire length, a predetermined small angle with respect to the longitudinal axis of the switch rail on which it is provided.

3. The joint assembly, according to one or more of the preceding claims, wherein at least one layer of electrically insulating material (15) inserted between the two coupling surfaces (S) which couple together is further included, and at least one further layer (9) of electrically insulating material inserted between the bolted cover plate and said foot which connects to the bolted cover plate (8) is furthermore included.

4. The joint assembly, according to one or more of the preceding claims, wherein first connecting means (3, 4, 5, 6, F) for connecting said first switch rail with said second switch rail through said coupling surfaces are comprised.

5. The joint assembly, according to one or more of the preceding claims, wherein second connecting means for connecting said second portions to each other coupled to said bolted cover plate (8) are comprised.

6. The joint assembly, according to claim 5, wherein said second connecting means further comprise one or more blocking elements (10', 10'') shaped so as to overlap for a part thereof with the foot of the rail restored by the coupling of said coupling surfaces (S) and, for another part thereof, abutting the bolted cover plate (8) so as to be fixed to said bolted cover plate by bolts or screws in general.

7. The joint assembly, according to one or more of the preceding claims, in which said first and second switch rails comprising said coupling surfaces (S) are arbitrary and mutually identical.

8. The joint assembly, according to one or more of the preceding claims, wherein said coupling surface (S) extends longitudinally for a predetermined length so as to form, following coupling, a transition (L) of high longitudinal length.

9. A method for fabricating an insulated rail joint (IRJ) assembly comprising: - Providing at least one first starting switch rail (1) having a first forged portion (1'') of a predetermined longitudinal length having a standard rail structure so that an end of said first portion can be joined, in use, to a rail of a track, and with the opposite end of this first portion that connects to a subsequent second portion that is asymmetrical and with height lower than the first portion; - Providing at least one second starting switch rail (2) having a first (2'') forged portion of a predetermined longitudinal length having a standard rail structure so that an end of said first portion can be joined, in use, to the rail of the track, and with the opposite end of this first portion that connects to a subsequent second portion that is asymmetrical and with height lower than the first portion; - Machining of at least part of said second portion for both said first and second starting switch rails (1, 2) in such a way as to modify said second portion by obtaining on one side of said second portion a coupling surface (S) and maintaining an original structure on the opposite side; - Joining of said first and second switch rails together by bringing said two coupling surfaces (S) into contact with each other in such a way as to restore, following said joining, a structure of a switch blade or a rail, said switch blade or said rail having a foot, a web and a head; - Fastening the foot relative to the said restored switch blade or restored rail with a bolted cover plate (8) arranged underneath said foot; - Wherein said bolted cover plate (8) is a metal plate with flat surfaces on which the foot resulting from the joining of the two surfaces (S) abuts and is fixed.

10. The method, according to claim 9, in which said machining is: - A machining operation on machine tools for chip removal, e.g., milling; - Machining by forging; - A combination of both.

11. The method, according to one or more of the preceding claims 9 or 10, wherein as a result of joining said two coupling surfaces (S), a transition line (L) is generated which forms, for at least a section of its length or for several sections of its entire length or for its entire length, a predetermined small angle with respect to the longitudinal axis of the switch rails on which it is provided.

12. The method, according to one or more of the preceding claims 9 to 11, wherein the joining of said first and second switch rails is performed by drilling the two coupling surfaces with one or more holes passing transversely through the entire thickness and applying first connecting means.

13. The method, according to one or more of the preceding claims 9 to 12, wherein said coupling surface (S) extends longitudinally for a predetermined length so as to form, following joining, a transition of high longitudinal length.

14. The method according to one or more of the preceding claims 9 to 13, wherein the said insulated rail joint (IRJ) assembly is electrically insulated and bonded at least by the insertion of a layer of electrically insulating material and assisted with adhesive material at least between the two coupling surfaces (S) and between the foot and the bolted cover plate.

15. A method of modifying at least one starting switch rail (1) having a first forged portion (1'') of a predetermined longitudinal length having a standard rail structure so that an end of said first portion can be joined, in use, to a rail of a track, and with the opposite end of this first portion which connects to a subsequent second portion asymmetrical and with height lower than the first portion; - Said method comprising the machining, e.g., by chip removal and / or forging, of at least a portion of said second portion of said starting switch rail in such a manner as to modify a side of said at least a portion of said second portion by obtaining on said side a coupling surface (S) and maintaining the original structure on the opposite side.

16. The use of two switch rails modified in accordance with the method according to claim 15, which are coupled together by bringing the coupling surfaces (S) into contact with each other to form an insulated rail joint (IRJ) assembly.