Patent GB-255446-A (GB)
Abstract: 255,446. Naamlooze Vennootschap Nederlandsche Instrumenten - Cie. July 20, 1925, [Convention date]. Gunnery calculators. - In a fire control apparatus for anti-aircraft guns the horizontal speed and direction of the moving target are ascertained by means of two follow-the-pointer devices associated with two speed indicators actuated in accordance with the observed movements of the target in the vertical plane of sight and the plane at right angles thereto. Means are also described for determining the vertical speed component of the target and the displacement during the time of flight plus the lost time. As shown in Fig. 1, a sighting telescope 6 is mounted on pivots 5 in a fork 4 secured to an axis 3 and is rotatable about this axis by means of bevel wheels 9, 10 and a hand operated spindle 7. To the spindle 7 is secured the pivot of a planet wheel 18 of a differential gear 14, 18, 17 the sun wheels of which are in mesh with a bevel wheel 12 on an axis P-P and with a wheel body 22 gearing with a bevel wheel 24 on the axle 5 respectively. This arrangement is so constructed as to maintain the inclination of the telescope constant during the azimuthal movement thereof. The elevation of the telescope in accordance with the varying height of the target as determined by an altimeter is controlled by the bevel wheel 12 by means of a slotted arm 11 integral with the wheel and rotatable about the axis P by means of a nut 27 on a screwed spindle 28 connected by bevel gearing 36 to a spindle 38 coupled to the altimeter. The nut 27 is guided by a rod 30 and the spindle is mounted in bearings 29 formed as nuts on two parallel screwed shafts 31 geared to a hand operated shaft 34. 'The shaft 34 in addition to controlling the distance of the nut from the axis P in accordance with the horizontal range drives through gearing 40 - - 43 a speed indicator 44 indicating the horizontal component of the target velocity in the plane of sight. The component at right angles thereto is indicated on a second speed indicator 47 actuated by a friction disc 57 and roller 58 ; the disc is rotated by gearing 50, 54 connected with the shaft 7 and the roller 58 is adjusted by a screwed portion 62 of the shaft 41. Associated with the speed indicators 44, 47, are follow-the-pointer devices 64, 72 connected to endless bands 67, 75 carrying sliding carriages 69, 77 at right angles. The carriages have slotted arms with which engages a pin 83 on a slide 80 mounted in a pivoted arm 79 carrying a pointer 87 co-operating with a scale 86. If the course of the aircraft is known the arm 79 can be set accordingly and the slide 80 adjusted by rotating the screwed spindle 81 until coincidence of the pointers 64, 72 with the speed indicator pointers is attained; if the course is not known the pointers 64, 72 can be adjusted directly. To determine the vertical displacement of the target during the time of flight and the lost time the device shown in Fig. 5 is provided. The height of the target observed by the altimeter is indicated on a scale 108 and a slide 103 on a screwed spindle 102 is moved along a scale 106 in correspondence with the variation of the altimeter indication by means of a hand wheel 99, the rate of change being shown on a speed indicator 95. A series of displacement curves numbered in accordance with the readings of the speed indicator 95 is provided on a plate 110. An index 113 co-operates with a scale 114 whereby the time of flight plus the lost time is set by rotating the screwed spindle 112. A hand wheel 118 is then rotated to bring an index 115 on to the appropriate velocity curve whereupon the setting i.e. the displacement is conveyed to a differential gear 125 and transmitted to a slide 132 co-operating with a displacement scale 135 to give the total height.