Patent GB-473024-A (GB)
Title: Improvements in automatic indicators for indicating the position of moving bodies
IPC: G01C21/22
Filed: 1936-03-03
Abstract: 473,024. Maps. NORMAN, H. N. ST. V., and LEVKOVITSCH, P. GOUDIMEMarch 3, 1936, No. 6484. [Class 146 (ii)] An apparatus for indicating on a map or screen the positions of one or more moving bodies, the speeds and directions of which may vary individually, comprise an apparatus for projecting a beam of light on the map or screen and means for continuously displacing the beam of light at a speed and in a direction related to the speed and direction of the moving body. A series of projection units 2, Fig. 1, which may be controlled from a panel 4 by standard push - pull remote controls or synchronous electric motors geared to counters, are arranged to throw independent moving spots of light on a translucent screen 1. Each unit comprises a tube 5, Fig. 2, carrying an adjustable bulb holder 6, a rotatable circular slide 10 on which are representations of aeroplanes, and an adjustable lens system of planoconvex, plano-concave, and plano-convex lenses 7, 8, 9 adapted to throw the focused image of the aeroplane via a mirror 11, Fig. 3, on the screen 1. The mirror 11 is pivoted about its centre line to a casing 12, which may be rotated in bearings 13, carried by gimbals 14 on a standard 15 which is rotatable in bearings 16. By rotating the standard 15 by a pulley 16a, and rocking the casing by a screw knob 18 in the gimbals 14, the image may be set to any desired starting point on the map. The mirror is rocked by an arm 25 pressed by a spring 26 against a cam 24 driven by a synchronous clock 21. The cam is loose on the arbor 24a of the clock and its initial position may be adjusted by a knob. The clock and the cam can be adjusted in slides 22 by a screw 23a; the setting knob 23 of the screw is calibrated in '' ground speed." The direction of motion of the light spot is determined by rotating the casing in the bearings 13 to a position determined by pointer 20 and " track " scale 19. The cam 24 is so proportioned that the light spot moves at approximately the same speed whatever the obliquity of the beam. To facilitate prediction of future positions of the object, an electromagnet 28, carried by an adjustable slide 29 and gradually lifted by the cam 24, may attract the arm 25 to a position the desired interval ahead of the correct present position. In a modification, the mirror 11 is dispensed with and the tube 5 is carried by the casing 12 and rocked by the cam. In this form the knob 18 actuates a cam pressing on the front of the casing. Instead of the cam 24 being adjustable along the length of the rod 25, the cam is made conical in shape and may be longitudinally adjusted on the arbor 24a by the " ground speed " knob, so as to engage the tube 5 with portions of different diameter. In a further modification, the lenses 7, 8, 9 are arranged inside the casing 12 and the light beam is reflected by mirrors into a further mirror 40, Fig. 8, which is rotated through a friction wheel 33 by a disc 32 on the arbor 24a of the clock. The wheel 33 may be adjusted to vary the speed by the ground speed knob 35. The map 1 may be spherically curved and the unit 4 arranged at the centre of curvature, so that great-circle courses or radio bearing may be laid out directly on the surface.