GB456681A - Improvements in or connected with devices comprising a cylindrical part which, relative to a mounting, requires to be movable endwise and at one or at more than one position be free to rotate or partially rotate about its axis without movement axially - Google Patents

Abstract

456,681. Optical apparatus. BARR & STROUD, Ltd., STRANG, J. M., and MACGILL, C. D., Caxton Street, Anniesland, Glasgow. July 11, 1935, Nos. 19800/35 and 7296/36. [Class 97 (i)] An optical eyepiece has an eyecap which is axially adjustable on the eyepiece to more than one position relative to the eye lens and has means for retaining it against unintentional axial movement from its selected position of adjustment, release of the eye cap for movement to another position being effected by movement of the eyecap, or of an annular member associated therewith, in a plane normal to the axis of the eyepiece. As shown in Fig. 1 the eyecap B has tongues 2 which engage a three-start screw thread 3, of which each end runs into a circular groove. Thus rotation of the cap with a slight pull causes the tongues to engage the screw thread, thus causing the cap to be moved axially until the tongues engage a second circular groove, when axial movement ceases. Alternatively the grooves may be made slightly deeper than the screw-thread and the cap released by pressure on knurled portions 14, Fig. 7, which causes the tongues 13 to move apart in the direction of the arrows, and allows them to engage the screw thread for axial movement. In a modification shown in Fig. 3, the eyecap comprises two sleeves 5, 6 relatively rotatable to a small extent, a pin 10 on the sleeve 6 engaging an annular groove 12 on the sleeve 5. The sleeves carry. tongues 7, 8 to engage the thread in the barrel A, the tongues being normally held apart by a coiled spring 9 one end of which is connected to the sleeve 5 and the other end to the sleeve 6, so that on rotating the sleeves in opposite directions the tongues 7 and 8 are drawn together as at 7a, 8a, Fig. 5, and register with the screw thread, thus allowing the eyecap to be screwed to the next annular groove 4 where the tongues spring apart and prevent further axial movement. The screwthread may be replaced by a series of axial grooves. Alternatively the tongues may be relatively displaced axially as at 20 and 21, Fig. 12, and may slide in a groove 22 until they reach a slot 23 when they move apart under the action of a spring and by engagement with the slot prevent further axial movement. In a further modification shown in Fig. 8, the eyecap B carries a key 17 which engages a longitudinal keyway 18 at each end of which is a circular groove 19. The outside of the eyecap B engages a screw-thread carried on the inside of a rotatable ring C which also carries a tongue 15 engaging a circular groove 16 in the barrel A. The cap B and eyecap C are rotated until the key 17 engages the keyway 18 when further rotation of the cap C causes the screw-thread to move the eyecap B axially until the key 17 engages the circular groove 19, when axial movement ceases.