GB835810A - Improvements in or relating to pendulum devices - Google Patents

Abstract

835,810. Optical systems; levels, theodolites. THOMPSON, E. H. Aug. 14, 1958 [Aug. 23, 1957], No. 26756/57. Classes 97(1) and 97(2) A pendulum device for supporting a graticule or other reference member and/ or for supporting other parts of the optical system of an instrument, such as a level or a theodolite, comprises a tiltable body C, having a portion of constant radius and a bob E disposed beneath the tiltable body and secured thereto by a spring member D, part of which is vertically disposed. In another form, Fig. 1, the tiltable body comprises coaxial cylindrical elements 5, and a cylindrical element 6, which, when the body is viewed in elevation appears to intersect the elements 5 or to be tangential thereto Spring straps 3 connect the elements 5 to one end of a bob 2, and spring straps 4 connect the element 6 to other end of the bob 2. When the body is untilted, the axes of the cylindrical elements lie in a common horizontal plane, and all the spring straps are tangential to their respective elements at a common point of intersection, or at the point of tangency, vertically above the centre of gravity of the bob. The pendulum device may be incorporated in a sighting level, in which case the bob has secured thereto a frame F, Fig. 5, carrying a mirror M2 and a graticule G disposed in the light path through the level, which is provided also with an objective O, a mirror M1 and an eyepiece E, connected, like the'body B, to the instrument so as to tilt therewith. Alternatively, the bob may comprise a pivoted arm A having pointers P1, P2 for reading the vertical circle C of a theodolite, Fig. 6.