GB1073991A - Improvements in or relating to chart position indicating apparatus - Google Patents

Abstract

1,073,991. Course recording and Indicating apparatus. DECCA Ltd. Dec. 1, 1965 [Jan. 6, 1965], No. 525/65. Headings G1F and G1J. Chart position indicating apparatus for use with a radio navigation system which provides two sets of signals representing positional data for a mobile craft is provided with a translucent chart 10 movable to and fro in one direction between two spools mounted longitudinally under cover plates 11a, 12a in accordance with one set of signals, and a marking stylus 13 movable to and fro on a housing 23 beneath the chart in a direction transverse to the movement of the chart and in accordance with the other set of signals, the stylus being arranged to strike repeatedly e.g. by solenoid operation to mark the chart, a cursor 42 of rigid transparent material e.g. glass being movable with the stylus across the chart 10 and disposed above the chart so as to constitute an anvil for the stylus. A marking ribbon 15 extends across the chart between the chart and the stylus so that the underside of the chart is marked by the action of the stylus. The cursor 42 moves with the stylus housing 23 on slides 43, 44 moving on guide bars at the sides of the apparatus, and the cursor is marked with a circle 51 so as to give an indication of the instant position of the mobile craft. One side of the chart has a number of tracks of digitally coded opaque markings 35 which are sensed by photo-electric cells 36 illuminated from lamps 38, 39. The cells 36 produce signals representative of the actual longitudinal position of the chart and these are fed to a comparator to be compared with the position of the craft in the corresponding coordinate direction to develop a servo-signal to drive the chart to correct position with respect to the stylus. The position of the stylus is monitered by use of wipers moving along digitally coded conductive tracks, the signals from which are fed to a comparator as before.