Patent Publication Number: US-2020282487-A1

Title: Welding unit and method for welding rails of a track

Description:
The invention relates to a welding unit for welding rails of a track, having a unit lower edge forming a lower boundary of the welding unit—with regard to a vertical—and a shearing device provided for removing a weld bead, the shearing device being composed of a head part designed to be placed on a rail head, two side parts movable towards one another in each case, and a rail base section provided for being applied to a rail base when in a shearing position. 
     The invention also relates to a method for welding rails of a track and subsequently shearing off a weld bead by means of a shearing device. 
     Welding units of this kind for so-called mobile flash-butt welding have already become known in various embodiments from a multitude of publications, such as from EP 2 315 877 or GB 2 185 703 A, for example. 
     A further welding unit is known from EP 0 132 227 B1, in which two unit components are connected to one another by means of a toggle lever. The displacement cylinders are fastened to a transverse beam on which clamping drives for gripping the rail are provided. 
     In U.S. Pat. No. 3,978,746, a shearing device for removing a weld bead is described in more detail. For shearing, the two side parts are applied to the rail by being pivoted towards one another. 
     It is the object of the present invention to provide a welding unit or method of the type mentioned at the beginning with which an improved welding operation is possible. 
     According to the invention, this object is achieved with a welding unit or method of the specified kind by way of the features cited in the characterizing part of claim  1  or  4 , respectively. 
     Due to the vertical adjustability of the rail base section or of the entire shearing device, it is possible to employ a specially designed welding unit having a unit lower edge which is merely slightly distanced with respect to the rail clamping jaws of the unit. This provides the particular advantage that the two rail ends need to be raised from the sleepers only slightly or not at all for the welding operation, thus avoiding adverse tensions. 
     Since the shearing device is raised above the unit lower edge, with regard to the lower section, there are no problems even if the shearing device by chance comes to lie above a sleeper during the welding operation. For the finalizing shearing operation, merely a slight lifting of the welding unit together with the welded rail is required in order to subsequently be able to lower and pivot the rail base section inward into the shearing position without problems. As a result of the welding process having already been carried out, the rail tensions resulting from the necessary lifting for shearing off the bead are no longer problematic. 
     Additional advantages of the invention become apparent from the dependent claims and the drawing description. 
    
    
     
       The invention will be described in more detail below with reference to embodiments represented in the drawing. 
         FIG. 1  shows a side view of a welding unit having a shearing device for a weld bead, 
         FIGS. 2, 3  each show an enlarged view of the shearing device in a longitudinal direction of the rail, and 
         FIG. 4  shows a schematically simplified variant of the shearing device. 
     
    
    
     A welding unit  1 , already known in manifold embodiments, consists essentially of two unit parts  5  which are movable towards one another with regard to a longitudinal direction  2  of the rail and each have clamping jaws  4  designed to be applied to a rail  3 . Said unit parts  5  have as a lower boundary—with respect to a vertical—a unit lower edge  6  which, in a special design variant shown here, is spaced only slightly from the clamping jaws  4 . Arranged between the two unit parts  5  is a shearing device  7  provided for shearing off a weld bead. 
     As visible in  FIGS. 2 and 3 , the shearing device  7  is composed of a head part  8  designed to be placed on a rail head, two side parts  9  movable towards one another in each case, and a rail base section  11  provided for being applied to a rail base  10  when in a shearing position. The two side parts  9  with the attached rail base sections  11  are pivotable by means of pivot drives  12  about an axis  13  for double-sided application to the rail  3 . The shearing device  7 , mounted together with the pivot drives  12  on a support frame  14 , is designed to be lowered in vertical direction (see arrow  18  in  FIG. 2 ) relative to a carrier body  17  or to the unit parts  5  along an elongated hole guide  16  by means of a drive  15 . 
     The welding operation with formation of the weld bead is carried out with the shearing device  7  in raised position. To that end, the two rails  3  are gripped by the clamping jaws  4  and, after heating of the rail ends, pressed together. Since, as a result of a special design of the welding unit  1 , the unit lower edge  6  is positioned during this approximately at the level of the rail base, the welding operation can be carried out without, or with only minimal, rail lifting while avoiding rail tensions detrimental to the welding quality. 
     As soon as the welding operation is terminated, the welding unit  1  together with the now welded and still clamped rail  3  is lifted so far that the shearing device  7  can be lowered without problems even in the event of a sleeper lying thereunder. As a result of this lowering motion, the two rail base sections  11  of the shearing device  7  move from a rest position situated above the unit lower edge  6  (see  FIG. 2 ) to a shearing position situated below the unit lower edge  6  (see  FIG. 3 ). 
     In further sequence, with actuation of the two pivot drives  12 , each side part  9  together with the rail base section  11  is applied to the rail  3 , and the still glowing weld bead is sheared off by a movement of the shearing device  7  in the longitudinal direction  2  of the rail. 
     In a variant, shown in  FIG. 4 , of the shearing device  7  reduced to the rail base sections  11 , the latter are designed independent of the side parts. For the shearing operation, the two rail base sections  11  can be lowered from a rest position (see right-hand half) into a working position (see left-hand half) and pivoted inward under the rail base  10  into a shearing position. The two side parts, now configured without rail base sections, need to be applied to the rail  3  merely by pivoting.