Abstract:
The invention relates to a method for re-profiling the running surface of a rail, preferably the convex portion of the rail head cross-profile of a rail, especially a railway rail, by peripheral milling. The aim of the invention is to obtain a profile that meets the requirements and has few corrugations. To this end, for producing the profile in a single peripheral grinding step, more than five, preferably nine milling tracks are produced that are oriented in parallel to the longitudinal direction of the rail. Optionally, the running surface, preferably the convex portion of the rail head cross-profile including the running surface is ground afterwards.

Description:
This application is a continuation of international application number PCT/AT 01/00234 filed Jul. 12, 2001. 
    
    
     The invention relates to a method for re-profiling by peripheral milling at least one running surface of a rail, preferably the convex portion of the rail head cross-profile of a rail, especially a railway rail, which convex portion exhibits the running surface. 
     It is known to re-profile worn rails by peripheral milling, i.e. to provide them with a new profile. For that purpose, the rail head was machined by peripheral milling. In order to somewhat control the costs of a milling cutter, it is known to equip the milling cutter with turning plates mounted to holding devices in turn inserted in recesses in the milling cutter body. In doing so, the turning plates being on a level of the peripheral milling cutter each generate a milling track oriented in the longitudinal direction of the rail. However, for lack of space, the number of turning plates to be attached is limited with peripheral milling cutters of that kind. Therefore, by peripheral milling it was only possible to provide a small number of tracks lying next to each other in the longitudinal direction of the rail and being applied to the rail head by the turning plates. Thereby, a large corrugation is created, and it was necessary to subject the rail head to a smoothing process following upon milling. It is known to equip a peripheral milling cutter for that purpose with a plurality of blades exhibiting the entire desired profile. The plurality of blades is necessary in so far as they ensure that only slight differences in depth occur in the longitudinal direction of the rail. Here, it is disadvantageous that the hollows and points generated by such kind of smoothing extend across the entire cross section that is machined. That causes noise and vibrations when being passed over as well as a decrease in lifetime. 
     The invention aims at avoiding those drawbacks and difficulties and has as its object to provide a method of the initially described kind as well as a rail-profile milling cutter for carrying out the method, by means of which it is possible to achieve a minor corrugation both in the longitudinal direction of the rails and in the cross-profile which complies with the regulations of the railway operators or the railway corporations. The present invention employs a milling operation that—for less stringent regulation requirements, such as for slower speeds of the railway—may suffice alone. To meet more stringent requirements, such as for faster speeds of the railway, an optionally subsequent grinding operation may be employed. 
     In a method of the initially described kind that object is achieved in that, in order to produce the desired profile by a single peripheral milling operation, more than five, preferably nine, milling tracks lying next to each other in the longitudinal direction of the rail are formed and that, in the following, optionally a grinding operation of at least the running surface, preferably the convex portion of the rail head cross-profile, which convex portion exhibits the running surface, is carried out. 
     Preferred variants are characterized in the subordinate claims. 
     As mentioned above, for railways having greater requirements such as, faster traveling speeds, the milling operation, according to the invention, is followed by a grinding operation. Thus, in order to decrease or level the corrugation running in the longitudinal direction of the tracks and, optionally, in order to flatten or level the polygonal line (cross-section), respectively, the milled rail is ground, preferably immediately following upon milling taking place in the same run. The axis of the grinding wheel and a plane perpendicular to the longitudinal direction of the rail includes an angle deviating from 0°. Preferred variants for said grinding are described in the following detailed description of the invention. 
     A rail-profile milling cutter according to the invention is provided for milling at least one running surface of a rail, especially a railway rail, preferably for milling the convex portion of a rail head cross-profile of a rail. The rail-profile milling cutter is a sandwich milling cutter configured with a plurality of wheels each of which is provided with turning plates at the periphery of the wheels. 
     Advantageous embodiments are described below 
     A device for carrying out the method according to the invention is characterized by 
     a means for generating a relative motion between the rail and the milling cutter as well as the optionally existing grinding wheel, 
     a driving means for the milling cutter as well as a driving means for the grinding wheel in case a grinding wheel is provided, 
     a milling cutter formed of a plurality of wheels provided with turning plates at the periphery, 
     a positioning of the axis of the grinding wheel in a direction deviating from a plane perpendicular to the longitudinal direction of the rail. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, the invention is explained in more detail by way of two exemplary embodiments with reference to the drawings, wherein 
     FIG. 1 shows a side view of a device for carrying out the method according to the invention and 
     FIG. 2 shows a schematic top view along the arrow II of FIG.  1 . 
     FIG. 3 shows a variant of the device for carrying out the method according to the invention. 
     FIG. 4 shows the cross section of a railway rail in various conditions of the rail. 
     FIG. 5 shows the engagement of the grinding wheel on a railway rail seen in cross section, in accordance with the method according to the invention. 
     The rail-profile milling cutter according to the invention is shown in FIGS. 6 to  8 , with FIG. 6 illustrating a partial section through the milling cutter in the assembled state, 
     FIG. 7 illustrating the individual parts of the milling cutter in an exploded view, and 
     FIG. 8 being a side view of a wheel of the milling cutter along the arrow VIII of FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 4, the cross section of a rail  1  is illustrated in various conditions. The rail head  3  situated on the stem of a rail  2  is provided with a convex cross-sectional portion  5  exhibiting the running surface  4  on which the track wheel of a rail vehicle runs, which cross-sectional portion, in its new condition, is illustrated by line A. Due to wear, that convex portion  5  of the cross section of the rail head  3  receives the shape as illustrated by line B. As soon as rail  1  has reached that condition or even earlier, as in accordance with high-speed rails, rail  1  is subjected to finishing so that the convex portion  5  of the rail head  3 , at least, however, the running surface  4 , regains its original condition, i.e. the original cross-sectional shape—as illustrated by line C—with the best possible approximation in accuracy. Thereby, certain tolerances in the range of from 1 to 3 decimillimeters are to be observed according to the regulations of a railway operator or a railway corporation or a supraregional standard such as cen DRAFT pr EN 13674-1. In doing so, it is essential that the guiding surface  6  of the rail  1  and the running surface  4  are finished. 
     As can be seen in FIG. 4, a relatively large amount of material has to be removed according to the wear of the rail, which has to be done as fast and inexpensively as possible in case of laid rails so as to impede the railway traffic as little as possible. 
     FIGS. 1 and 2 illustrate a device according to the invention which is arranged in a stationary position and past which the rail  1  to be machined is moved. FIG. 3 illustrates a device according to the invention which is incorporated in a movable facility such as a locomotive engine so that it is feasible to machine rails which already have been laid by means of said device. In that case, the device according to the invention exists in duplicate so that both the left-hand and the right-hand rails can be finished in one passage. Parts and devices of the stationary facility and the movable device which are mutually identical are marked by identical numerals. 
     Reference numeral  7  denotes a milling unit the rail-profile miffing cutter  8  of which is configured as a peripheral miffing cutter and is described in greater detail hereinafter. The milling cutter  8  can be driven via a driving motor  9  and a gear  10  whereby the direction of rotation is chosen such that the rail  1  is machined by the cut-down milling method. Immediately adjacent to the milling unit  7 , a grinding unit  11  is provided, the grinding wheel  12  of which can be driven by means of a driving gear  13 , preferably also in the direction of rotation of the milling cutter  8  so that down-grinding of the rail  1  is effected. The grinding wheel  12  is equipped with a system for regulating the depth of grinding  14  so that it is feasible to continuously readjust the grinding wheel  12  to the rail  1 , according to its wear. The Said system for regulating the depth of grinding  14  comprises a measuring system for measuring the continuously decreasing diameter of the periphery of the grinding wheel  12 ; it can also make use of measuring data gained from measuring an angular moment of a driving component. 
     Just upon their emergence, both the milling chips and the grinding chips as well as the grinding dust are removed via the vacuum means  15  and  16 . 
     Just in front of the milling unit  7  and just behind the grinding unit  11 , guides  17  for the rail  1  are provided in each case, against which guides the rail  1  can be pressed by means of support rolls  18 , whereby it is possible to press at least the running surface  4  of the rail  1 , preferably the crown of the rail head  3 . Furthermore, lateral guiding rolls  19  engaging the rail head  3  on both sides are provided along the device, whereby the lateral guiding rolls  19  fitting closely to the side of the guiding surface  6  of the rail  1  are fixed in their positions. The rail is pressed against the fixed lateral guiding rolls  19  by the lateral guiding rolls  19  fitting closely to the opposite side, whereby the rail  1  assumes an exact position opposite the milling unit and the grinding unit. 
     Between the milling unit  7  and the grinding unit  11 , a further guide  20  is provided, which is equipped with a damping device in order to eliminate any vibrations of the rail  1  caused by the milling cutter. 
     As can be seen in particular in FIG. 2, the axis  21  of the grinding wheel is inclined by an angle α against a plane  22  perpendicular to the longitudinal direction of the rail, which angle is greater than 0, preferably ranging between 1 and 20° C., depending on the respective condition of the rail  1  prior to grinding. If the rail head  3  has a cross section which, due to milling, approaches the ideal cross section, already before grinding, or if the rail  1 , in its new condition, is still provided with a roller skin, the angle α suitably ranges between 5 and 12°, ideally amounting to 8°. However, if the previous state of the cross section has been adjusted to the ideal cross-profile in a less exact manner, f.i., if it has been roughed down only crudely, a smaller angle α, preferably ranging between 1 and 6° C., is suitable for securing an optimal chip removal volume with a long service life of the grinding wheel. 
     In its new condition, the grinding wheel  12  has already been pre-profiled, i.e., it exhibits a profile which roughly mates rail  1 . For an exact manufacture of said counterprofile, it is advantageous to provide a sharpening means  23  with a grinding stone  24  which can be pressed against the periphery of the grinding wheel  12 . Said grinding stone has exactly the desired profile which is to be produced and it also includes angle α together with the grinding wheel. Before grinding of the first rail  1  is started, said grinding stone  24  is pressed against the grinding wheel  12  until the grinding wheel has adopted its profile. While rail  1  is ground, the grinding stone  24  can be lifted from the grinding wheel  12 , since the grinding wheel profiles itself at the pre-profile, i.e., at the milled rail-head area or the rail-head surface still provided with the roller skin, respectively. During machining of a rail head  3 , the grinding stone may optionally be fitted to the grinding wheel  12  for temporary sharpening. 
     Rail  1  may also be used for the adjustment of a profile which exactly mates the grinding wheel  12  provided that it has been milled with sufficient accuracy or still has the roller skin. 
     If, as in the illustrated exemplary embodiment, a milled rail-head surface is ground, the profiled grinding wheel  12  only has the most important task of smoothing the waves generated by the milling cutter  8  and of creating an image of traverse grinding. 
     By inclining the grinding wheel  12  according to the invention, particularly good conditions of engagement as well as a strong smoothing effect occur. The engagement of the inclined grinding wheel  12  is illustrated in FIG.  5 . It is apparent that the inclination creates an advantageous engagement angle, in particular at the point where the convex portion  5  of the rail head  3  meets the side faces  25  of the rail head  3 . Those favourable conditions of engagement allow also in those places a sufficiently extensive removal of material with a very good thermal behaviour being provided so that, on the ground surface, burning cannot occur. Furthermore, a very good service life of the grinding wheel  12  is thereby created. 
     It can be advantageous if the axis  21  of the grinding wheel  12  is also inclined against the rail&#39;s longitudinal central plane of symmetry  26  by an angle β which may have a size of between 1 and 20°. 
     If different rail profiles are to be machined by means of the device according to the invention, the axis  21  of the grinding wheel  12  may suitably be arranged so as to be adjustable on the device. 
     According to the embodiment illustrated in FIG. 3, the milling unit  7  and the grinding unit  11  are incorporated in a rail-milling line  27 . By means of actuators  28 , the milling cutter  8  and the grinding wheel  12  are moved approximately vertically against the rail  1  until the guides  17  and  20  rest on the rail head  3 . A lateral movement of the grinding unit  11  and the milling unit  7  toward the guiding surface  6  until the lateral guiding rolls  19  rest on the rail head  3  is possible as well. 
     The rail-profile milling cutter  8  according to the invention is constructed as a sandwich milling cutter, i.e., it is comprised of wheels  30  each of which is shaped as a ring wheel. As will be described hereinafter, those ring wheels  30  each support a plurality of turning plates  31 . These are made of hard metals, ceramics or similar materials. As can be seen in FIG. 6, the ring wheels  30  are fastened to a milling cutter core  32  by means of a screw connection  33  and are centered against each other by means of several centering pins  34  and are secured against each other by means of further screws  35 . 
     According to the illustrated exemplary embodiment, nine ring wheels  30  are provided, whereby the two external ring wheels  30  support quadruple turning plates the cutting edges of which are of an arcuated shape and serve for milling, i.e. creating a milling track, close to the guiding surface  6 . At the outer periphery  36 , the ring wheels  30  arranged between the external ring wheels  30  are provided with humps  37  surpassing the outer periphery  36  and manufactured in one piece with the ring wheels  30 . Said humps  37  form seats for the quadruple turning plates  31 , which, however, exhibit straight cutting edges. Due to the humps  37  provided at the ring wheels  30 , spacious chip bags  38  are formed between the turning plates  31 . 
     All turning plates  31  are fastened to the ring wheels  30  preferably by means of screw connections, clamping joints might be used as well. Each of the cutting edges of the turning plates  31  of the ring wheels  30  arranged between the external ring wheels  30  surpasses with its cutting edge the side faces of the ring wheel  30  to which it is fastened. The turning plates  31  of adjacent ring wheels  30 , which turning plates are arranged on the ring wheels  30 , are arranged so as to be peripherally offset so that, with respect to the periphery, the turning plates  31  of the neighbouring ring wheel end up lying between the turning plates  31  of the first ring wheel  30 . 
     By means of the sandwich milling cutter  8  according to the invention, it is possible to mill a great number of milling tracks—even more than nine—extending in the longitudinal direction of the rail  1  onto the rail head  3 , whereby it is feasible to achieve an extremely great accuracy of the milled cross-profile, i.e., an extremely close approximation to the ideal cross-profile of the rail head  3 . For certain requirements, the rail heads  3  re-profiled by means of the milling cutter  8  according to the invention and/or the milling method according to the invention are sufficient without subsequent grinding being necessary, f.i., for travelling speeds which are not too high. For greater requirements, the milled tracks are subjected to a grinding operation such as described above. 
     The essential advantage of the grinding method according to the invention lies in the plurality of adjacent milling tracks which can be milled onto the rail head  3  in a single working process. Particularly advantageously, the milling method according to the invention is combined with the grinding method according to the invention, whereby it is feasible to achieve an extensive removal of material also in case of extremely worn rails as well as a surface which, because of the milling method according to the invention, corresponds to the desired rail profile already to a large extent and which requires only minor grinding, i.e., grinding involving the removal of relatively little material, if any. 
     In doing so, it is possible to combine milling and grinding in a single operating process, thereby manufacturing a running surface or a machined portion of the rail head, respectively, fulfilling the greatest requirements in terms of running qualities, lifetime and avoidance of noise.