IMPROVEMENTS IN DREDGING

1277401 Dredgers P C LONDON 22 Aug 1969 [26 Aug 1968] 40724/68 Heading E1F [Also in Division G1] A dredger H having a spoil pick-up cutter head K carried by a pivoted ladder L, and a spud S providing a vertical axis about which the dredger can swing, has apparatus which continuously indicates the position of the cutter relative to a channel to be cut by the cutter. The apparatus comprises a light spot projector 10 which is moved relative to a chart, Fig. 2 (not shown), in dependence upon the operation of Selsyn receivers 64, 112 and 108 by signals received from Selsyn transmitters respectively associated with a cable drum used to move the ladder L and therefore having a rotation proportional to the angle of the ladder, a drive for moving the spud longitudinally of the dredger and therefore having a rotation proportional to the horizontal distance between the ladder pivot P and the spud S, and means driven by a gyro compass and therefore being proportional to the angle of the dredger axis with the longitudinal centre line of the channel, and upon the operation of a motor 82 controlled by manual operation of a knob for compensating for differences in the water level. The dredger may have two spuds used alternatively, and the spuds may be fixed on the dredger or may be movable to extend at an angle to the vertical. Instead of a light spot being moved mechanically to show the position of the cutter it may be shown using conventional analogue computing and electronic display techniques.