Patent GB-213947-A (GB)
Title: Improvements in and relating to apparatus for directing the fire of guns at rapidly moving targets
IPC: F41G5/08
Filed: 1922-12-09
Abstract: 213,947. Bergh, S. J. van den. Dec. 9, 1922. Gunnery calculators.-A method of and apparatus for controlling the fire of anti-aircraft guns are described based on the assumption that the target is moving at a constant speed in a straight path and on the principle that the time taken to determine the predicted position (measuring time) is always in constant ratio to the sum of the " measuring time," the time taken to transmit the data to the guns (i.e. the " service time " which is assumed constant), and the time of flight of the projectile to reach the predicted position. The apparatus as shown comprises a telemeter and associated mechanism one member of which is caused to move, during the " measuring time," when the telemeter is in coincidence proportionally to the displacement of the target but at a speed which is the inverse of the said constant ratio (in the example illustrated 1:4) so that the position of the member at the end of the " measuring time " corresponds to the predicted position. Pointers actuated by the mechanism co-operate with scales and charts to indicate the azimuth, elevation, and trajectory chart particulars which are to be communicated to the guns. The apparatus is supported by a tripod 1, Fig. 3, having a flanged disc 2 and clamping screw 3 for fixing a hollow shaft 4 around which the apparatus is adapted to rotate. The casing 6 carries a. telemeter adjusted in elevation and azimuth by hand wheels 35, 82 respectively; the shaft of the wheel 35 carries a long pinion 30 with which engages a pinion 28 adapted to rotate a screw 14 provided with a nut 13 having a pin 12 engaging a slotted arm 10 that is mounted on a spindle 9 connected to the horizontal axis of the telemeter. The shaft of the wheel 82 carries a pinion 79 that engages with a wheel 78 fixed to the shaft 4. A second pinion 80 engaging the wheel 78 is connected to a wheel 69, Figs. 1 and 4, so that the wheel 69 always remains with a point on its periphery in the same azimuthal direction. When the telemeter is brought to coincidence and the height of target read off, a screwed shaft 19, by means of a hand wheel 22, Fig. 1, is rotated according to the height and imparts movement through screws 19, 20 to a slide 16 carrying the screw 14. The pin 12, by the above described manipulations, is positioned according to the horizontal range and the height of the target, and these positions are communicated to a pointer d, Fig. 6, carried by a member 86 movable in slotted rods 87, 89. The rod 87 receives movement in accordance with the height from a bevel wheel 102 on the shaft 19 through gearing connected to the screws 90, 91. The rod 88 is attached to a rack 104 with which engages a pinion 108 mounted on a shaft 109. The other end of the shaft 109, Fig. 3, carries a bevel wheel 124 engaging a similar wheel 123 mounted on the spindle 122 of the planet wheel of a differential gear 125, 127; the wheel 127 is fixed to a bushing which carries a pinion 59 engaging a rack 54 articulated at (c) to a rack 52 connected by means of pinions 53, 48 to a rack 49 pivoted at (a) to a rod 50. The pinions 48, 53 are mounted at a point (b) on a rod 47 which, with a second rod 46, is mounted on screws 40, 41, actuated through gearing in accordance with the horizontal range by means of shaft 31 of the hand-wheel 35. A known spring device 61 is provided as a means to ensure that in the normal position, the line (a) (c) of the rack mechanism 49, 52 shall be parallel to the line of the axles 60, 62. The point (c) is always in alignment with the points (a) and (b) and at a distance from the point (a) four times as great as the distance between (a) and (b), that is, according to the constant ratio. The rod 50 slides in a plate 63 and has a slot 51 through which passes a vertical shaft 64 pressed down by means of a spring 66 engaging the lower end of the shaft and a square disc 67 covering a hollow pivot 68 on which is rotatably mounted the wheel 69. A round disc 71 grooved to engage an aperture in the disc 67 is provided with a spring 72 which co-operates with a notch in the pivot 68 and carries a cam 74 adapted to co-operate with a hand-operated arm 75. When the arm 75 is turned anticlockwise the shaft 64 is lowered and the disc 67 is raised so as to prevent the sliding movement of the rod 50 through the plate 63 and to permit it to partake of the rotation of the plate. The pointer d, Fig. 6, is arranged above a chart 110 representing the vertical plane of site and bearing indications 111, 112, 113 representing respectively elevations, fuze setting, and drift and time of flight. The indications 111, 112 are obtained by a pointer 117 (e) integral with the pointer d. The bevel wheel 126 of the differential gear 125, 127, is secured to a bevel wheel 129 which through a wheel 130 co-operates with a similar wheel 131 connected to a strip 56 having a projecting rib engaging a groove in the rack 54 and carrying a pointer 57 co-operating with a scale 58. The zero of this scale 58 is adapted to remain in the same azimuthal direction by means of a differential gear 140 . . 143 and a toothed wheel 157, Fig. 3, which engages a toothed ring 156 on a downward projection of the scale plate. The planet wheels of the differential gear carry a worm wheel 145 which engages a worm 146 on a shaft 147 operated by a hand wheel 148 to give the corrections for drift, wind and other atmospheric conditions. The arm 75 referred to above is operated at the beginning of the " measuring time " to fix the rod 50 with respect to the plate 63 so that during this time the point (b) will represent the position of the target and the point (c) the position of the predicted point. At the beginning of the measuring time after the telemeter has been brought into coincidence the provisional data are read off from the chart 110 and communicated to the gun-crews and at the end of the time the final data are read off the guns being fired at the end of the service time. A chronometer for use in co-operation with the apparatus and for firing the guns automatically is shown in Fig. 9, and comprises a dial 170, a pointer 166, and a rotatable lever 167. The pointer is normally in a position of rest opposite an index 169 and the dial has a scale the zero point of which is at such a distance from the index 169 that the pointer travels this distance in one-third of the service time. The dial indications correspond with times of flight and the pointer travels the distance between adjacent graduations in one-third of the time represented by them. The lever 167 has an arm 171 with two contacts 172, 173 arranged so that the pointer travels the distance in the service time and the lever carries a pointer 174 which is set to the time of flight read off from the chart 110. At the start of the measuring time the pointer 166 is released and by the above described setting it will reach the contact 172 at the end of the measuring time and close the circuit through a battery 175 and audible signal 176. At the end of the service time the contact 173 is closed and operates a device 177 for discharging the guns automatically or for giving a signal for firing by hand. In a modification, Fig. 11 and 13, the predictor (c) is formed as a pointer and a rack 54<1> is hinged to a fourth member (c<1>) adapted to form a predicting line with respect to an axis 198 in the prolongation of the bar 47. Means are provided for positioning the line in a direction corresponding with that of the movement of the target and in the same azimuthal direction when the casing is turned, and for placing the member (c') at a distance from the axis 198 proportional to the product of the resultant target velocity and the sum of the " service time " and " time of flight."