GB688834A - Improvements in inclination indicators - Google Patents

Abstract

688,834. Levels. ROSENHAGEN, J. Jan. 10, 1950 [Jan. 10, 1949], No. 668/60. Class 97 (ii). [Also in Group XL (b)] In a level having a device for projecting the bubble through a lens system into a projection surface, the whole surface described by the periphery of the level bubble during its movement is a projection object so that the level bubble when in any position is projected into the projection surface which is provided with measuring marks. Two spherical levels, one 17, Fig. 2, having a large curvature and range and the other 13 having a small range, are illuminated by lamp 21 through condenser systems 22, 23, mirrors 24, 25, and heat-absorbing glass 26, 27, respectively. Their images are projected by lenses 14, 18, and mirrors 15, 19, on to the screens 16, 20. A semi-transparent mirror 30 enables an image of level 13 to be projected by mirrors 32, 33, 35 and lens 34 on to a graduated plate 36 whose image is projected to infinity by lens 40 and focused by the object lens 41 of a camera 28 on to the plane 42 where it is photographed. The plate 36 is mounted diametrically opposite to a graduated plate 38 on a circular plate 37. The plate 37 and mirror 32 which is rigid therewith may be rotated through 180 degrees in a bearing 39 to allow the image of level 17 and plate 38 to be photographed. In a modification the plates 36, 38 are marked with a thick cross and four photo-electric recording devices in the focal plane 42 determine the relative position of the level bubble with reference to two co-ordinates. The levels 13, 17 may be tubular and the plates 36, 38 marked with a single thick line. In a further modification a single optical path is provided and several levels fixed on a base-plate may be interchanged by rotating the plate. A number of levels may be used having different setting speeds. Several spherical or tube levels 49, 50, Fig. 5, may be arranged with their bases inclined to increase the range, an optical arrangement such as prisms 51, 52, being used to project the images on to adjacent screens. In a modification, the optical image of a level may be observed by means of a microscope having a circular index mark with crossed lines which is associated with a recording device. Movements of the bubble may be followed on transparent or photographic paper which moves continuously or in steps to mark the time.