Patent GB-997696-A (GB)
Title: Improvements relating to navigational apparatus
Inventor: VARGO ROBERT EDWARD
IPC: G01C21/12
Filed: 1962-11-30
Abstract: 997,696. Aircraft instruments. COMPUTING DEVICES OF CANADA Ltd. Feb. 19, 1963 [Nov. 30, 1962], No. 45525/62. Heading B7W. Aircraft navigational apparatus comprises a frame 47 fastened to a front panel 11 which carries a screen 10, light projection means 48, a film transport 61 carrying spools 51 and 52 for a film strip 50 and a lens system 53. Referring to Fig. 3, which represents portions of a map area 27, the area 27 is divided into 81 frames in rows of 9, adjoining frames in the rows having no overlap and those in columns having an overlap 42 corresponding in size to a portion of the film strip, represented by a circle 45, which will project on to screen 10 an image that will just fill the screen, so that when the film strip is being moved to change the projected image from one frame to another in the NS direction, by means to be described, just before and just after the change the same image will be shown, one from one frame and one from the other. The front view of the apparatus is shown in Fig. 1 wherein the panel 11, around screen 10, carries an operational mode control knob 12; a knob 23 which switches in an alternative projection lamp should one fail, and a further knob 25 which controls the intensity of the projected light; a scale control knob 24 which selects one of two optical magnifications for the projector; a range knob 17 and counter 20; a course knob 18 and counter 21 and a track indicator scale 16. Operational modes.-The normal mode is the " track " mode in which a circle 14 on screen 10 represents present aircraft position and fixed line 15 represents aircraft track, the projected image moving along line 15 past circle 14 by automatic change of the frames in the film strip, and the track made good being shown on scale 16. In a " leg " mode a destination may be set into the apparatus by a separate push-button unit (not shown) or by using range knob 17 and course knob 18. When the destination has been set in knob 12 can be returned to " track " mode position, the range and course counters 20 and 21 then showing the remaining distance and the course or bearing to the destination. In addition a pointer 22 indicates desired track to the destination, and by displacement from line 15, indicates any track error. In an " ahead " mode, with a destination position set into the apparatus, the screen display automatically advances along the desired track to the destination. If desired knobs 17 and 18 can be rotated to slew the projected map image around to display any particular part. With knob 12 in a " fix " mode, provided to correct positional errors in the display, a separate fix is obtained and knobs 17 and 18 are operated to position the display in accordance with the position given by the fix, knob 12 then being returned to its " track " mode position. Mechanism to move the film strip and adjust the apparatus according to the modes selected is shown in Fig. 5. A turntable 54 carries the film transport 61 which is movable back and forth in the NS direction by a screw and nut mechanism 65, 64 and reversible motor 66, the transport having a fixed guide shaft 62 sliding in bearings 63. The spools 51 and 52 are supported on arms provided with film tensioning devices 68, 70, and drive sprockets 71 are operated through shaft 72 by a reversible motor 73. The turntable 54 is rotated by a motor 74 through gearing 75. Potentiometers 100, 101 are operated through clutches 102, 103 from shafts 65, 72 to record film strip position. Provision is made to disengage the clutches during a frame advance. Two microswitches 86, 87 mounted on table 54 are operated by screw and nut mechanism 88, 90 driven by motor 66 through gearing 91, 92. To initiate NS movement of the film carriage and to advance the film strip by nine frames. If film transport 61 has reached say a northerly limit of movement switch 86 is actuated and a relay 93 is energized to move switches 78 and 83 on to conductors 94 and 95, signals represent ing NS and EW map miles then being stored in memories 76 and 81. Switch 86 operates also a digital frame advancer 96 which provides a discrete predetermined number of pulses over conductors 94 and 95 through switches 78 and 83 to motors 66 and 73 respectively to drive the motors at a substantially faster rate than that imposed by normal aircraft movement to move the film carriage to its south limit and to move the film nine frames.