Abstract: The machine comprises a device for shifting the track which is controlled by a device for the detection of its geometrical defects.The detection device comprises three rail feelers to which there are connected a light-ray emitter (17), a screen (18) having two parallel delimiting edges (19, 20) and a receiver (21) having two identical photovoltaic cells (22, 23) arranged in such a manner that the sum of their irradiated surfaces (u+d) is a constant and their difference (u-d) is proportional to the displacements of the screen.The signals produced by the two cells are processed in an electronic circuit comprising a totalizer (28) delivering a signal for the control of the displacement device proportional to the said difference (u-d) and a piloting circuit (30, 41, 42) of the emitter to maintain the irradiation of the two cells constant by comparison of a signal proportional to the said sum (u=d) with a reference signal (S.sub.0).

Abstract: The machine comprises a device for shifting the track which is controlled by a device for the detection of its geometrical defects.The detection device comprises three rail feelers spaced apart from each other and to which there are connected a light-ray emitter (17), a screen (18) having two parallel delimiting edges (19, 20), and a receiver (21) having two identical photovoltaic cells (22, 23) arranged in such a manner that the sum of their irradiated surfaces (u+d) is a constant and their difference (u-d) is proportional to the displacements of the screen respectively.The signals emitted by the two cells are processed in an electronic circuit comprising a calculation unit (30) delivering a signal for the control of the displacement device representative of the quotient (u-d)/(u+d) of the difference divided by the said sum so as to make this signal independent of variations in irradiation of the two cells.

Abstract: The invention is a process and a device for measuring and registering the geometric state of a track in the course of alignment of the track with an aligning machine. The distance between a point on the already aligned track and a straight line defined by two points, one of which is on the already aligned track and one of which is on the part of the track to be aligned, is measured, and the value is registered after each alignment operation.