| 摘要 |
Where track layout needs 2 converging rails to be brought to common point, final sections (12,14) of rails are machined to produce flat vertical surfaces (20,23;22,24), which, when abutted, lie in common plane bisecting angle between rails. Thus juxtaposed, sections are welded together, forming continuous running surface (12D,14D) on top of rail heads (12C,14C), while, if rails are identical in cross-section, flanges (12A,14A) form common base. The central webs (12B,14B) remain separate, leaving a central channel (26). The sections are united by arc welding along the flange join, but, to achieve a high quality running surface, without the addition of material, a laser system is used for the rail head weld. The laser is rated at e.g. 40 kW, the beam being directed vertically on to the meeting of the rails at the head level, and displaced progressively from one end of the meeting line to the other. Gases released during welding into the internal channel (26) are evacuated by lateral apertures (28,30) regularly spaced along one or both webs (12B,14B), or, opt., by slots formed between the flanges. Opt., no vents are provided, but the gases are expelled from the channel (26) by a forced or induced draught fan connected to one end, the flow being oppositely directed to the beam direction of travel. |
