Patent GB-470993-A (GB)
Abstract: 470,993. Sighting-apparatus for use on aircraft gun-mountings. STIEGER, H. J. March 31, 1936, Nos. 9536 and 11169. [Classes 92 (i) and 92 (ii)] Machine guns, light guns on aircraft, and the like, which are mounted to be angularly movable about two axes for aiming, are interconnected with the gun sight by a parallel motion which is constrained by an anchorage to move about an axis, so that the gun and sight remain in a common plane which tilts in accordance with the movements imparted to the gun. A machine gun 1, Fig. 1, with casing 1A and hand grip 1B, is mounted on a horizontal pivot in a vertical pillar 3 which turns on a vertical axis in the mounting 4. A fixed arm 5 is ball-jointed at 6 to a member 13 pinned at 12, 12A to links 9, 9A. whose other ends are pinned at 10, 10A to the sight 11, the links 9, 9A being pivoted also on pins 8, 8A on a sleeve 7 which is free to turn on the gun barrel. In a modification, the sight instead of the gun is located intermediately of the ends of the links 9, 9A and the member 13 is ball-jointed to a separate fixture. In a further modification, a bar 20, Fig. 3, curved to clear the magazine &c. 1c of the gun, carries the sight 11 at one end and a slider 18 at the other, the bar being pivoted at 23 to a sleeve 24 free to turn on the gun barrel. The sight is linked also, by a rod 26 to a pin 27 on the sleeve 24, and the slider 18 is guided on a rod 17 carried by a bracket 15 which is pivoted at 4B to the gun-mounting and is normally held stationary by springs 15A engaging opposite ends of a diameter of the bearing 4A. A cam formation 16 on the bracket 15 is adapted to be engaged by a part of the gun to warn when the gun is being aimed in a direction which might be dangerous to local structure. The bracket may be moved by hand or by contact of the sleeve 24, against the resistance of the'springs 15A when the gun is required to be aimed in a direction normally interfered with by the rod 17. To enable a fine adjustment of the linkage to be effected, to make allowance for own and target speeds &c., the link 26 may be coupled to a nut 21B, Fig. 5, on a screw 21c mounted in the sightcarrying frame 22A. A spring may be interposed between the slider 18 and the cam 16 to compensate for variation of wind pressure &c. on the gun when moved to different positions. Protection for the gunner and gun mechanism is provided, such protection being automatically positioned with movement of the gun. In one form, a cowl 60, Fig. 6, accommodates a nosepiece 61 which is carried by, but free to turn on, the rod 17, a radial slit 63 being provided for the passage of the gun barrel and to permit the gun to be aimed without interfering with sighting arrangements. In a further modification, the link 20, Fig. 7, is ball-jointed to a slider 76 guided on a vertical rod 77 and a vertically slitted window 71 is supported by, and rotates in, a bearing 74, about the axis of the column 3 as the gun is traversed. Power may be employed to effect the movements of the gun and cowling. The parallel motion of the gun and sight may be effected by chain and sprocket or other mechanism. According to the second Provisional Specification, the parallel linkage connecting the gun and sight may be anchored by being connected to a fitting strapped to the gunner's head. Further, according to the first Provisional Specification, the sleeve which is rotatable on the barrel, is axially fixed, or has limited axial movement resisted by springs or resilient pads.