Patent GB-660325-A (GB)
Title: Mount for periscopic sextant
IPC: G02B23/08
Filed: 1949-05-17
Abstract: 660,325. Sextants and mountings therefor. KOLLSMAN INSTRUMENT CORPORATION. May 17, 1949 [July 2, 1948], No. 13101/49. Classes 97 (i) and 97 (ii). A periscopic sextant is provided with a mount comprising a stationary mounting portion 4, Fig. 4, a normally stationary datum index line carried by the mount 4 and co-operating with an azimuth ring 34, Fig. 5, freely rotatable relatively to the mount, a rotatable sleeve 19 disposed within the mount and adapted to be indexed with the periscope tube of the sextant and a lubber line connected to the sleeve and rotatable therewith, the arrangement being such that the azimuth indicia on the ring 34 are readable against both the datum line and the lubber line. As shown, the mount comprises a shutter housing 1, and an instrument seat 2. In its upper position the instrument projects through an opening 7 in the top wall 6, the shutter 8 having been opened by levers 12, 13 operated by handle 9. The shutter is guided in its movement between the opened and closed positions by pins 14, 16 engaging slots 15, 17 respectively, and the lever 12 is controlled by an over-centre spring arrangement 18. The tube portion of the sextant is slidably mounted in a sleeve 19, rotatably mounted by bearings 21, 22 in a ring 23 in turn gimballed by trunnions 25 in a ring 24. The ring 24 is mounted by trunnions 27, at 90 degrees to the trunnions 25, in a third ring 26 shock-mounted by cushion washers 28 in the stationary mounting ring 4 so that the sleeve 19 and the sextant mounted thereby has a limited freedom of universal movement. A normally stationary ring 31, adjustable with respect to the mounting by means of bolts 29, carries a datum index line co-operating with a scale borne on an azimuth ring 34 which is freely rotatable with respect to the mounting by means of a spring slip connection 37 between the ring 34 and the clamping ring 33. The ring 34 is connected to a knurled ring 36 by means of which it may be rotated. The sleeve 19 and therewith the sextant may be rotated by means of a ring 38, knurled at 43, and connected to the sleeve by studs 39 and ring 41, the ring 38 being integral with a transparent shield 44 bearing a lubber line and overlying the azimuth scale 31. The ring 38 and sleeve 19 are indexed by a pin- and-slot connection 42. The bottom of the ring 38 is provided with a pair of slots 47, 48, the former communicating with a cut-out portion 49 in turn communicating with an elongated slot 51 in the interior wall of the sleeve 19. A spring-pressed locking-pin 53 projects into a slot 52 in the sleeve 19 above and mating with the slot 48 and a similar pin, or a simple spring-pressed ball 56 projects into the annular cut-out portion 49 adjacent the slot 51. The periscopic tube of the sextant has at its upper end a pin 57 and at its lower end a locking and index plate 58. The upper end of the periscopic tube is inserted in the lower end of the sleeve and the ring 38 rotated so that the pin 57 entering the slot 47 passes round the cut-out portion, over the locking means 56 into the slot 51 where the sextant is locked in its retracted position by the engagement of the pin 57 with the flange 46. With the shutter open it may be raised into its projected position wherein it is locked by the engagement of the spring- urged pin 53 with the locking-plate 58. In its projected position the sextant may be rotated with the sleeve 19 about the vertical axis and tilted through the limited arcs permitted by the gimbal mounting. A handle 59, Fig. 7, operates a threaded stud 61 movable longitudinally to clamp the ring 41 to the ring 23 by means of a slip spring ring 62, thus locking the sleeve 19 and the sextant against rotation about the vertical axis. Specification 660,326 is referred to.