[0028] The rail shown in FIGS. 1-3 is an ordinary rail used for trams and trains and having a foot portion 11, a web portion 12 and a head portion 13. In the first embodiment of the invention shown in FIGS. 1 and 2, a separate saddle profile structure 14 is added onto the top of the railhead 13 to extend in its longitudinal direction. This separate structure substantially has the section of an inverted U having a web portion 15 and two leg portions 16a, 16b. The separate structure is suitably an extruded or continuously cast profile of aluminium or a forged or hot rolled profile of wrought steel.

[0029] As seen particularly in FIG. 1, the curvature of the surface of the separate structure 14 facing the railhead is adapted to the curvature of the railhead 13 such that these curvatures are substantially uniform. A supporting layer 17 of a resilient material, such as rubber, is interposed between the top surface of the rail head and the separate structure, thus keeping the latter at a substantially uniform distance a from the rail head. A typical thickness of the layer 17 is 1-6 mm, preferably 2-3 mm, in a squeal suppression embodiment, and 1-8 mm, preferably 2-5 mm, in a roar noise reduction embodiment. It is designed to resist vertical loads and to ensure lateral flexibility of the separate structure. To achieve this, the material shall have a high bulk modulus to avoid “polymer crushing” (less than 30% compression of the rubber material), and a low modulus of shear to give the important lateral flexibility. Further, its material properties shall not change significantly with temperature changes. It is advantageous that the rubber material exhibits a high material loss factor, typically ηm =0.3-0.9 or more in a squeal suppression embodiment, and 0.3-0.8 in a roar noise reduction embodiment. A useful material would be butyl rubber.

[0030] Between the opposed inner sides of the legs 16a, 16b of the saddle profile structure and the respective sides of the rail head there may be provided lateral cushions 18a, 18b of a flexible material soft enough to enable lateral movement of the separate structure relative to the rail head.

[0031] In order to firmly hold the separate structure 14 in place, its leg portions 16a, 16b are provided with flanges 19a, 19badapted to be located in a common, substantially horizontal plane when the separate structure is mounted onto a rail. Angle irons 20, 21 having substantially perpendicular legs 20a, 20b and 21a, 21b, respectively, are firmly attached to the web portion 12 of the rail by means of horizontally spaced bolts 22 extending through the legs 20b, 21b and the web portion 12 and having nuts 22a and bolt heads 22b. The legs 20a, 21a are substantially horizontally aligned and spaced a small distance b from the flanges 19a, 19b, respectively. Resilient layers 23a, 23b are interposed between the respective facing flanges 19a, 19b and legs 20a, 21a to ensure lateral flexibility of the separate structure relative to the rail head. Bolts 24, 25 having nuts 24a, 25a and bolt heads 24b, 25b, respectively, vertically extend through the respective opposed flanges 19a, 19b and legs 20a, 21a to connect the separate structure 14 to the angle irons.

[0032] Besides keeping the separate structure to the rail, the bolts 24, 25 serve to reinstate the galvanic connection between the wheel of a train and the rail that has been lost by the interposition of the layer 17 between the mass structure and the railhead. It is imperative, thus, that the heads and nuts of the bolts 24, 25 have good electrical contact with the flanges 19a, 19b and the legs 20a, 21a to ensure galvanic contact to the angle irons and further into the rail web by means of the bolts 21.

[0033] In order to attenuate vibrations propagating along the web portion, layers 26a, 26b of a visco-elastic material, such as polyurethane, may be applied between the web portion 12 and the legs 20b, 21b, respectively.

[0034] The arrangement shown in FIG. 3 differs from the one according to FIGS. 1 and 2 only in that the separate structure 14′ is asymmetrical as concerns the thickness of its web portion 15′. It will be seen thus, that in order to better withstand the load of a wheel, the web portion 15′ has a thickened portion 15′a which is the portion of the rail on which a wheel is to roll. It will further be seen, that the adjoining leg portion 16′a is also somewhat thickened in relation to the opposed leg portion 16′b.

[0035] Although the embodiment according to FIGS. 1-3 will provide a solution to the noise problem, it involves the drawback that at least one of a pair of rails will have to be laterally displaced since adding a structure to a normal rail will influence the track width.

[0036] The second embodiment of the present invention shown in FIGS. 4a and 4b sets this drawback aside.

[0037] FIG. 4a shows a section through a railhead 13 of a normal rail and the upper portion of its web portion 12. A cross-hatched portion 13′ defined by a dash-dotted line indicates portions of the railhead to be removed in order to reduce the railhead section to an extent enabling a saddle profile structure having substantially the exterior dimensions of the original railhead to be mounted onto the reduced railhead 13″ as shown in FIG. 4b.

[0038] Thus, the second embodiment of the present invention shown in FIG. 4b does not involve a change of the cross section of a normal rail. As mentioned, this has been accomplished by machining a normal railhead 13 so as to remove material 13′ from the top and at least one side of the railhead (the one against which the flange of a railcar wheel bears, although FIGS. 4a and b show both sides being reduced) leaving a reduced railhead 13″, and in that the removed material has been replaced by a saddle profile structure 14′ resembling that shown in FIG. 1, and an interposed elastic layer 17, substantially according to FIG. 1, although the saddle profile structure 14′ has exterior dimensions corresponding to those of the non-machined railhead shown in FIG. 4a.

[0039] The saddle profile structure 14′ is kept attached to the remaining rail by equal means as shown in FIG. 1, including flanges 19a, 19b, angle irons 20, 21, bolts 22, 24, 25, and interposed resilient layers 23a, 23b. Supplementary lateral cushions 18a, 18b may be interposed between the flanges 16a, 16b of the saddle profile structure and the lateral sides of the reduced railhead 13″.

[0040] The third embodiment of the present invention shown in FIG. 5 utilises a rail section particularly manufactured for the purpose of enabling mounting thereon of a saddle profile structure.

[0041] Thus, the portion of the rail section where its web portion 12 merges with the railhead has been widened to provide two opposed shoulders 30a, 30b having flat upper surfaces 31a, 31b, respectively, corresponding to those of the legs 20a, 20b, respectively, of the angle irons 20, 21 of FIG. 1. The shoulders 30a, 30b merge with a reduced railhead 13a having substantially the shape of the remaining railhead 13″ of

[0042] FIG. 4b. A saddle profile structure 14″, shaped and imensioned substantially as the one according to FIG. 4b, is mounted onto the railhead 13a by means of bolts 24, 25 extending through flanges 19a, 19b of the saddle profile structure 14″ and the shoulders 30a, 30b, respectively. As before, a resilient layer 17 is interposed between the saddle profile structure 14″ and the diminished railhead 13a, and supplementary lateral cushions 18a, 18b may be interposed between the flanges 16a, 16b of the saddle profile structure and the lateral sides of the reduced railhead 13a.

[0043] As can be seen in the Figures, the web portion 15 of the separate structures is substantially thicker than its flange portions. This is to make the web portion stiff enough not to cause polymer crushing. The ultimate stress limit for useful polymers is at about 30% compression. In operation, thus, a limit of about 20% compression should not be exceeded. Under such circumstances, it is preferred to make the web portion not less than about twice as thick as the flange portions. This, in turn, means a reduced deflection of the web portion and, consequently, that only a portion of the wheel load is absorbed by the resilient layers 23a, 23b so as not to risk causing detrimental polymer crushing, whereas a remaining portion of the load is transferred from the web portion through the flange portions to the rail by means of the angle irons 20, 21 and its attachment bolts 22 in the embodiments of FIGS. 1-4b, and straight into the shoulders 30a, 3b in the embodiment of FIG. 5.