Patent GB-880065-A (GB)
Abstract: 880,065. Apparatus -for aiming weapons. MATHEMA CORPORATION REG. TRUST. Feb. 4, 1958 [Aug. 22, 1957], No. 3581/58. Class 92. Relates to apparatus for aiming weapons to combat moving targets such as aircraft as claimed in Claim 1 of Specification 793,243 and in which computer mechanism operating in dependence upon the bearing angle # and the angle of elevation γ computes the angle of slope # of the flight plane, means being provided for introducing various corrections as indicated below including in particular means for introducing a correction to the estimated bearing angle # initially set in on the approach of the aircraft so that the computed angle of slope # remains constant. Corrections are set in in respect of the following:- (1) the estimated bearing angle # on the approach of the aircraft, (2) alteration in altitude of the target flight path, (3) location of weapon in an inclined plane, and (4) gravity drop of the projectile. In respect of (1), the bearing angle # is taken from a datum line and from the angle # and the angle of elevation γ, the angle of inclination r of the flight plane can be derived. If the datum line and therefore the value for # are correctly chosen, then the angle r will remain constant. If the derived angle # shows any variation, then a correction is necessary until the value # remains constant. The bearing direction #G of the gun barrel is transmitted through a clutch 3, Fig. 1, to the sighting device. An initial estimated value for the bearing angle # is set in by means of a knob 23 and is transmitted to the axis of a pair of curved bodies 11, 12, the curved body 11-having a registering member 39. The curved body 11 is also axially displaced by a slide 9 which is moved by the value γ set in at a coupling 44 by the angle of elevation of the gun barrel. The value r is derived by the rotational value of the registering member 39, the value being registered by an edge 50 in relation to a scale 53. If this value remains constant, the initial adjustment through the knob 23 was a correct one. Should the edge 50 move in one direction or another, a correction is introduced through the knob 23 to the bearing angle #G derived from the weapon until a stationary position of the edge 50 is attained. (2) Correction for alteration in altitude of flight path The correction necessary for a target path of changing altitude can be expressed as a correction angle to the bearing angle #<SP>1</SP> in the flight plane. This correction angle K<SP>1</SP>, Fig. 2, can be derived from the flight plane angle # and the angle of inclination of flight #. The angle v is set in by rotation of a knob 51 and indicator 52 with respect to the scale 53. Rotation of the knob 51 displaces by means of a pulley 74 and cable 59 a registering lever 60 in the axial direction of a curved body 57 which is rotated proportionally to the angle #. The rotational value of the lever 60 is proportional to the correction angle K<SP>1</SP> and this is added or subtracted through a toothed cylinder 61 in a differential gearing 33 to or from the bearing angle #<SP>1</SP> supplied by a curved body 13 and registering member 32. The corrected bearing angle #<SP>1</SP> displaces a disc 34 in the sighting device, the disc being provided with aiming-off curves as described in Specification 793,243, the intersection of a selected curve with a luminous radial line on a disc 31 providing the contact point which is to be aligned with the target. (3) Correction for inclined position of weapon Where the weapon itself is not in a horizontal plane, a further correction is necessary. The correction is calculated in a similar manner as that used for alteration in altitude of the flight path since it is immaterial whether the flight path lies horizontal and the weapon plane is inclined or whether the weapon plane is horizontal and the flight path is inclined. The angle of tilt # is inserted by a knob 63 and the angle # #  that the tilt axis Ov, Fig. 3, makes with the datum line OG is set in at the knob 69. The rotation of the knob 63 is transmitted over a spindle 64 and nut 65 as a displacement to the curved body 66 which is turned in proportion to the bearing angle # #  which is equal to # o  -# # . The registering   number 67 for the curved body 66 transmits a derived value v, which is the angle of inclination of the flight corresponding to the tilt angle # over the cable 59 to the registering lever 60 which in turn transmits the correction value K<SP>1</SP> to the disc 34 having the aiming- off curves. (4) A correction for gravity drop of the projectile is applied by a cam plate 58, Fig. 1, which together with the disc 34 is displaced proportionally to the bearing angle #<SP>1</SP> and in turn displaces a part 45 of the sighting device.