Patent GB-1303191-A (GB)
IPC: G01C15/00
Filed: 1970-01-22
Abstract: 1303191 Track levelling and/or aligning machine F PLASSER 22 Jan 1970 [22 Jan 1969] 3217/70 Heading B7N [Also in Division G1] In an arrangement for determining the position of a railway track for levelling and/or aligning purposes, a laser beam which defines the required position of the track either cooperates directly with the track position correcting apparatus or sets the position of a further reference line which co-operates with the correcting apparatus. The cross-section of the laser beam may extend in a horizontal plane when the arrangement is used with levelling apparatus or in a vertical plane with aligning apparatus or may combine both kinds of beam in the shape of a letter L or a cross for use with both types of apparatus.  In a levelling arrangement, laser beam source 17 is mounted on a remote-controlled, selfpropelled vehicle 19 which is positioned ahead of the correcting machine 1 on uncorrected track. The horizontally extending laser beam from the source 17 is initially directed using sighting means towards a receiver 21 mounted on the machine 1 above corrected track. The receiver includes a light-sensitive portion, e.g. as shown in Fig. 4b, comprising photo-cells 34 above and below a central elongated area 33, which develops signals in response to the beam which automatically control, either directly on lines 26 or via a radio link 25, the laser source positioning mechanism 17<SP>1</SP> whereby the beam is positioned to extend through the receiver area 33. Receiver 20, including upper and lower photo-sensitive elements 27, 28 co-operates with part of the beam and generates signals for controlling unit 11<SP>1</SP> which raises or lowers the receiver until the beam extends between the elements. The unit simultaneously positions light source 11 thus fixing the leading end of a light reference line which co-operates in conventional manner with receiver 13 and shadow board 14 to control the operation of the track position correcting tools, i.e. the lifter 6 and tamper 4. A further receiver 22 mounted to the rear of the correcting position co-operates with the laser beam to provide signals for recording on carrier 30 a comparison between the required position of the track and the actual position after the correction process. The cross level of the track can also be recorded. The apparatus for generating and receiving both the laser beam and the light reference beam are pivotally mounted so that they can be swung over whichever rail is designated the grade rail. In an aligning arrangement, Figs. 5-8 (not shown), the laser beam cross-section extends in a vertical plane and is used to set the position of the leading end of the long chord in the usual two-chord aligning system. All support trolleys for the beam transmit and receive elements and the chord support and measuring elements are urged into contact with the grade rail. Further aligning arrangements in which the laser beam is used either directly or to set the long chord position or to control the final positioning by direct reference to the beam after the track has been roughly set by the chord system are described with reference to Figs. 14-16 A receive element for use with a laser beam 16 having a cross-section in the form of a cross is shown in Fig. 10 and one for use with a beam having a letter L cross-section is shown in Fig. 11. In these figures references 58, 58<SP>1</SP> represent photo-sensitive or thermosensitive elements.