GB836717A - Improvements in apparatus for observing or measuring changes in inclination of a support or for levelling the line of sight of optical instruments by means of a pendulum - Google Patents

Abstract

836,717. Clinometers, optical systems. ZEISS JENA C. VEB. Aug. 9, 1956, No. 24477/56. Classes 97(1) and 97(2) Weights are hung between a suspender or inverted pendulum and a tiltable member so that when the member is tilted the tension in the strings supporting the weights are varied to make the pendulum take up a new non-vertical position of equilibrium. As shown, the tensions in strings 4a, 4b and 5a, 5b due to weights 3a, 3b maintain pendulum 1 in an inverted position of equilibrium and on tilting the member 2 the pendulum takes up a new position of equilibrium. For small angles of inclination cc and #, there is a linear relationship between # and #. The inverted pendulum arrangement may be used in a pendulum level (Figs. 8, not shown, and 9) and in a sighting telescope to maintain the line of sight horizontal (Figs. 12, not shown, and 10). In one form of inverted pendulum the bob is a hollow cylinder 15, Figs. 5 and 7, containing a fixed damping piston 16 and is supported on arms 7 articulated to a fixed frame 6 by crossed band springs 8 or, alternatively, by a torsion wire (not shown). Weights 9, 10 hang between arms extending from the bob and from frame 6. The space 17 may be occupied by an optical component fixed to the pendulum such as, presumably, the two mirror 24, 25 (Fig. 9). Cross-wires 20 are imaged in the focal plane 27 of eyepiece 28 and, on tilting the casing 18, the image is displaced as the mirror carrying member 23 turns about axis Y-Y relatively to the casing and mirror 26. In Fig. 10, mirror 34 is movable to ensure that a horizontal ray in. cident on mirror 32 forms an image in the centre of graticle 31<SP>1</SP> irrespective of the inclination of the telescope casing. Alternatively the movable mirror may be arranged between the objective 30 and eyepiece 31 (Fig. 12, not shown). A suspended pendulum arrangement (Fig. 2, not shown) is used in a further example of a sighting telescope (Fig. 11, not shown).