Patent GB-838555-A (GB)
Title: Improvements in correctors for use with field artillery
IPC: F41G3/08
Filed: 1957-08-09
Abstract: 838,555. Electric analogue calculating systems. ARENCO A.B. Aug. 9, 1957 [Aug. 10, 1956], No. 25269/57. Class 37. A corrector for use in gun fire control systems operates on the principle of converting the coordinates of the true target point X o  in the desired projectile trajectory into the co-ordinates of a corresponding point X in a trajectory according to the ballistic firing tables and comprises means for setting in the ballistic corrections, e.g. due to wind, density of atmosphere &c. as functions of the co-ordinates of the point X (for which corrections are nil), the relation between the co-ordinates of the target point X o  and the co-ordinates of point X having the following relation where #q represents ballistic deviation in general. The problem is solved by successive approximations for the following two equations : where Al 0  and n 0  are the observed slant range and altitudinal angle of the true target point Xo, and Al and n the slant range and altitudinal angle of the point of impact X according to the ballistic tables. W l  is the windage along the firing plane. The corrector comprises calculating members and hand wheels for setting for Al A o , n and n 0  and a separate zero indicating instrument for each of the A and n circuits, each said instrument being connected to a circuit including a potentiometer set to indicate the voltage proportional to #Al+Al=Al 0  (or # n+n=n0 ) and to parallel branch circuits ore for each ballistic correction and each consisting of potentiometers for the setting in of ballistic corrections and the influence factor for each correction whereby a solution of equation (or of equation 10) can be obtained by obtaining zero deflection on the appropriate instrument. In Fig. 2, the range Al o  of the target point Xo is set on a dial 2 and the wheel 3 is set for the inclined range Al of the point X in the table trajectory. The Al value is transmitted to cams 12-16 via shafts 44-47 and gears 4-11, the influence factors of the various corrections being set into the cams 12 as functions of Al. The number of unit deviations in the muzzle velocity V o  (#V o ) is set in by wheel 17 according to the variations in the muzzle velocity Vo from standard which causes an output from a potentiometer 20 proportional to #V o . The follower 22 of cam 14 moves contact 23 of potentiometer 24 a distance from terminal 25 thereof proportional to C voAl  (influence factor corresponding to Al=#Al/V o .(Al)) so that cam 14 represents C VoAl =P(Al), the actual output of potentiometer 24 being #V o .C voAl , which is the correction of X in the direction of Al, depending on the variation of muzzle velocity. The windage along the firing plane W l = W . cos Vw (Vw=windage angle) is obtained from a mechanical resolver 31 which adjusts potentiometers 32, 33 so that voltages appear in leads 34, 35 proportional to the number of unit deviations in the direction of W l , a voltage being created in lead 38 by cam 13, its follower and potentiometer 37 corresponding to W l C wlAl  (influence factor corresponding to W l =#Al/#W l (Al)). Leads 26 and 28 are connected to the same terminal of instrument 41, the other terminal of which is connected to the slider of potentiometer 43, the sliding contact of which is set to a value corresponding to #Al by screw 48 operated from the output of differential 49, the inputs of which are connected to shafts 45 (Al) and 50 (Al o ) so that Al, the setting of the potentiometer, = Al o  - #Al - 5, the equation (4) above being solved in respect of Al by successive approximations. The wheels are set for #V o , W, V W  and Al o  as described, and the Al wheel 3 turned until there is zero deflection on instrument 41. The voltage ir lead 51 for readings on instrument 41 would normally be the sum of influences in the Al direction so that when the reading is zero, the voltage in lead 42 will be equal to #Al and the wheel 3 will be set for a value of Al corresponding to Al o , the value of the target point Xo in the true trajectory. For the altitudinal angle circuit (n) lead 21 is also connected to potentiometer 52, a voltage being obtained (as described for Alcircuit) in lead 53 proportional to #V o .C vow  (the correction to the n direction caused by #V o ) the correction in n caused by W l  being the sum of two terms, viz. W l C WlN +W l  # N (C WlN ).N where C WlN  is the influence factor in the n direction for n=0 degrees due to windage and #n(C wlN ) is the influence factor for correction of angle n caused by windage along firing plane. The first term is derived from potentiometer 54 (through lead 35) and the second from potentiometer 32 set by rule 30 for W l  as already described in connection with the Al circuit. The slider is connected to one end terminal of potentiometer 95 adjusted from cam 12 in accordance with expression #n.C WlN /Al so that a voltage corresponding to W l .#nC WlN /Al is supplied to potentiometer 58 which will again multiply this last term by Al.n which is set into hand wheel 57 so that the voltage in lead 59 corresponds to the relay 60 ensuring the correct polarity. n o  is set into wheel 70 and potentiometer 73 thereby adjusted to give an output voltage corresponding to no. An instrument 80 is as before included in the circuit, the terminal of which is connected to an input corresponding to - #n+no   and the other to an input corresponding to n, the latter being derived through potentiometers 58 and 83 (output Al.n), cam 85 1 1 (-) and potentiometer 86 (Aln.-=n). The Al Al circuit is operated to solve equation (10) above by setting wheel 70 to the measured value of no and wheel 57 is then turned until instrument 80 is nulled, when the n set in at 57 will be the n value for X in the table trajectory, corresponding to n o  value of the target point in the true trajectory. Instead of earthing the neutral point 29 of the voltage supply 27. 28 for the potentiometer (as shown), the raid-points of the potentiometers may be earthed instead and the other connections changed accordingly. Nomographs are provided on drums 91, 92 which are also rotated by wheel 3 through angles corresponding to the value of Al and the rule 82 is set for the value of Al.n. The nomograph in drum 91 is for fuze setting Tg or the time of flight, and that in drum 92 for U(n)+ #n (where U (n)  represents super elevation according to ballistic tables), the input for both drums being Al and Al.n. The actual values of Tg and U (n) + #n are read off the drums and the quadrant elevation E will be derived from formula E= (U N + #n)+n o .