Patent GB-617149-A (GB)
Title: Improvements in and relating to gun fire control systems and particularly to range finding and correcting apparatus
IPC: F41G3/14
Filed: 1944-07-29
Abstract: 617,149. Calculating-apparatus. SPERRY GYROSCOPE CO., Inc. July 29, 1944, No. 14538. Convention date, July 30, 1943. [Class 106 (i)] Apparatus for automatically computing or controlling range corrections comprises a first means for setting in the range of an object as measured by a range-finder, a second means for determining the length of a projection of the distance between a reference point and the range-finder to a line between the object and the reference point, and a third means actuated by the first and second means for combining the range with said length to determine the range of the object relative to the reference point, the second means comprising means for setting in the horizontal component and separate means for setting in the vertical component of said distance, means for multiplying these components by the respective trigonometrical functions of the azimuth difference and elevation angles relative to the line between the object and the reference point, and means for combining the multiplied quantities to determine the length of the projection. The difference in the range of a target T (Fig. 1) from the range-finder R and a reference point O, respectively, is found, approximately, by projecting the line Ro on to OT. This difference (#D) is given by the expression: d cos (Ao - #A) cos Eo+h sin Eo which can also be expressed as: d/2 cos [(Ao - #A)+Eo] + d/2 cos [(Ao - #A) -Eo]+h sin Eo, where d is 2 the horizontal and h the vertical projection of RO, Eo the angle of elevation and Ao the angle of traverse at O, and #A the angle of azimuth of the range-finder R with respect to the reference point O. A mechanical form of apparatus for solving the equation: Do=DR+#D=DR+d/2 cos f(Ao-#A)+Eo]+- d/2 cos [(Ao - #A) - Eo] + h sin Eo comprises a gear 12 (Fig. 2) rotated to represent DR which movement is added to the movement of a shaft 15 representing #D by a d differential gear 14. The term - cos [(Ao - #A) 2 +Eo] is worked out by the apparatus in the upper portion of Fig. 2. #A, entered on dial 23, is subtracted from Ao.(dial 24) by a differential 31. Eo, entered on a dial 25, is added by a differential 36, and the result: (Ao - #A) +Eo is represented by the position of gear 41 which rotates a disc 42 so as to position a slot 43 therein at this angle. A sliding block 44 carries a pin 45 which is positioned at a distance d/2 from the centre of the disc 42 by means of a second pin 45<1> engaging in a spiral groove 46 of a lower disc 47 which is rotated by the gear 48 of a differential 49. This differential adds the setting d of dial 21 to the movement of the upper disc 42 so that the relative movement between discs 42 and 47 equals d/2. Thus, the movement of a rack 55, rotating a gear 56, d represents the term - cos [(Ao-#A)+Eo], 2 d and this is added to the term - cos [(Ao - #A) - 2 Eo], derived from a similar device (the factor Eo being negatively entered by the interposition of an idler gear 70), by a differential 61. To represent the term: h sin Eo, the Eo shaft 39 rotates a disc 92 having a longer slot 93 (to provide for negative values of h), but operating in a similar manner to the device described above. The factor h from dial 22 is entered into a differential 101 through gears 97 and 98 and the resulting movement of pin 95, representing h sin Eo, is transmitted through a rack 107, gears 108, 111, to a differential 88, the output of which represents #D which is added to DR to give Do as described. An electrical apparatus for solving the equation: Do=DR+#D=DR+d cos (Ao- #A) cos Eo+h sin Eo comprises a transmitter 121, Fig. 3, and receiver 122, which may be of the synchro-transformer or selsyn type, by means of which a signal proportional to the range DR is transmitted. The circuit for the rotor winding 128 of the receiver 122 includes potentiometers 177 and 152, adding voltages proportional to the terms d cos (Ao - #A) cos Eo and h sin Eo, respectively, to control a servo device 123. A hand wheel 131 rotates a rotor 133 in proportion to Eo, and connections 141, 142 to the stator windings 135 supply a voltage proportional to sin Eo, to the potentiometer 152 which is adjustable by a hand wheel 147 to introduce h into the term. A resistor 146 is included in this circuit for initial setting. The conductors 141, 142 are also connected to chokes 153, 154 which, together with a rotary winding 155 of a rotary transformer, form a balanced " Y " connected circuit across the stator windings 135 and cause a voltage across the winding 155 proportional to cos Eo. The output shaft 168 of a differential gear 163 rotates proportionally to (Ao - #A), and the cosine of this value is multiplied into the value cos Eo by the rotary transformer to give a voltage proportional to cos (Ao - #A) cos Eo across the potentiometer 177. The factor d is introduced by a hand wheel 173. In another embodiment, similar to the latter, a two-phase transmission system is employed and the chokes 153, 154 are eliminated.