Patent GB-606957-A (GB)
Title: Improvements in and relating to control systems for guns or sights
IPC: F41G5/02
Filed: 1944-11-22
Abstract: 606,957. Gun-fire control systems. SPERRY GYROSCOPE CO., Inc. Nov. 22, 1944, No. 23221. Convention date, Sept. 17, 1941. [Class 92 (ii)] A control system for a gun or gun-sight is provided with means for displacing the gun or sight at a rate proportional to the displacement of a controlling member when this displacement is less than a predetermined limiting amount for normal control purposes, and with means for slewing the gun or sight when the limit is reached. Referring to Fig. 1B, a prism 71 in the optical sighting system is moved in azimuth and elevation by moving a pair of hand grips 3 which are mounted on a shaft 5 passing through a housing 9. Movement of the grips about the horizontal axis of shaft 5 causes a pinion 11 on the shaft to translate a vertical shaft carrying circular racks 13, 19, serving to drive an elevation shaft 29<SP>1</SP>, and movement about a vertical axis produces a rotation of the casing 9 which is geared to a shaft 29. The displacements of the grips about the two axes are proportional to elevational and azimuthal target rates, Er and Ar respectively. Notched discs 30, 301 on shafts 29, 29<SP>1</SP> are engaged by detents which serve by offering slight resistances, to indicate to the operator when the grips are central and when they are approaching their extreme positions. Target following apparatus.-Shaft 29 controls the position of a ball carriage 47 of a variable-speed device whose disc 49 is driven by a constant speed motor 51, and the driven cylinder 53 leads to a differential 41 whose other input is supplied by shaft 29 via another differential 39. The output of differential 41 is connected by shafts to rotate the main body 31 of the sight (see also Fig. 2), causing prism 71 to follow the target in azimuth. Present target azimuthal position Ao thus appears in the shafts 34, 35, between differential 41 and sight body 31. A prism 66 in the sighting system is rotated through twice the angle of the body 31 through gearing as shown, this prism and prism 71 being used in conjunction with a pentagonal prism 91 and an eye-piece 78 through which the target is viewed. Similar mechanism is employed for following the target in elevation, the prism 71<SP>1</SP> being rotated by a worm 75<SP>1</SP> geared to the present elevation Eo shaft 85 via a differential 87. One of the Ao shafts 35 also leads to differential 87 whose function is to prevent change of elevation of the sight as the result of its movements in azimuth. Cams 58, 60 and 58<SP>1</SP>, 60<SP>1</SP> are fitted on the Ar and Er rate shafts 29, 29<SP>1</SP> respectively and serve, when the hand-grips are approaching their maximum displacements, to actuate the switches of motors 57, 57<SP>1</SP> whose functions are to produce rapid rates of change of the orientation of the line of sight. Sight construction.-As shown in Fig. 2, the sight is double-ended, the upper part serving to cover the hemisphere above the horizontal and the lower part, which is of similar construction, serving to cover the lower hemisphere. Only one sight is in operation at a time and to ensure this the prism 91 is caused to pivot about its axis when the line of sight passes through the horizontal. Geared to the Eo shaft 85 of Fig. 1B is a shaft 93, Fig. 2, carrying a cam 95 whose groove 97 is engaged by a pin on a lever 103. The groove has a sharp change 101 at a point corresponding to the horizontal position of the line of sight. When the sight therefore passes through the horizontal the lever 103 turns with its shaft 105 and rotates a shaft 111 carrying cam 113 and a lever 115, which lever is connected to the prism by a spring. The cam inturning releases a latch 121 holding the prism and further rotation of the shaft 111 causes the spring to rotate the prism, to bring the other sight into operation, the latch being subsequently returned to hold the prism in its new position. An indicator 70 with a pointer 80 driven by a shaft 92 connected to the elevation drive of the sight, is used to let the operator know which sight is in use. Range finding.-The range-finding mechanism is of the form disclosed in Specification 606,656 and comprises reticle lines 133, Fig. 1B, between eye-piece 78 and prism 91. The reticle is adjusted by a target dimension knob 135 which translates a cam 139 whose follower is geared to the reticle, and by a foot pedal 140 which serves to rotate the cam. When the reticle lines circumscribe the target image, the shaft 147 between the pedal and cam is displaced through an angle proportional to slant range Do. Azimuth and elevation prediction.-Azimuth rate Ar and slant' range Do data are fed as shown from shafts 29 and 147 respectively to rotate and translate a cam 161, Fig. 1A, whose follower 181 moves in accordance Ar multiplied by time of flight. This data is added via shaft 185, in a differential to Ao data appearing in shaft 193. To this sum is added in a further differential 197 azimuth ballistic correction 8, the output of differential 197 leading to a torque amplifier 203 which in turn actuates a remote position transmitter 204 which transmits data to a gun station or controls the guns. Similar mechanism, including a cam 205 is employed for actuating elevation transmitter 230. Ballistic corrections.-Changes in altitude of the aircraft are considered to produce equivalent changes in wind speed. A fixed scale is therefor provided marked off in convenient altitude steps, and co-operating with this scale is an index on a ring 235, Fig. 1A, which is rotated by an altitude knob 237. Inside ring 235 is an indicated air speed dial 241 rotated by a knob 243, and having markings on its face which are selectively brought opposite the index on ring 235. The markings are so set out that the shaft 249 of knob 243 is displaced by an amount S<SP>1</SP> corresponding to the actual air speed corrected for altitude. Such data together with gun azimuth position from amplifier 203 are conveyed to a resolving mechanism 251 of the type disclosed in Specification 418,670 which yields two outputs in shafts 253, 225, corresponding respectively to S<SP>1</SP> sin Ag and S<SP>1</SP> cos Ag where Ag is the gun orientation in azimuth. These shafts displace cams which are rotated in accordance with gun elevation by a shaft 271 geared to transmitter 230. The cam followers produce axial displacement of further cams which are rotated in accordance with slant range Do, these latter cams being so designed that their followers are lifted to convey the correct ballistic corrections to the torque amplifiers.