GB1507580A - Device for optically monitoring the functioning of recording means in a tachograph - Google Patents

Abstract

1507580 Tachographs KIENZLE APPARATE GmbH 17 June 1976 [19 June 1975] 25093/76 Heading G1J To monitor the functioning of the recording pencils 3, 4, 5 in a vehicle tachograph in which the pencils record on the rear face of a diagram disk 6, an image of the pencils is projected on to a screen 12, Fig. 1, or 39, Fig. 4, set in a window 11 or 41 in the dial face 7 at the front of the tachograph. In Fig. 1, a light path is defined by blocks 14, 16, 19 of glass or transparent plastics material mounted on the cover plate 1 of the tachograph housing. Light from a bulb 13 passes through the block 14 which has a matt exit face 15 to provide a uniformly illuminated background to the pencils 3, 4, 5. The entry face of the block 19 incorporates spherical converging lenses 20, 21, 22. To prevent doubleimages, the cover plate 1 carries screens 25, 26, 27, 28, and the blocks 16, 19 have rows of holes 27, 30, 31, 32 with matt bore surfaces. The entry face 17 of the block 16 is not normal to the cover plate 1, Fig. 2, so that the shadows of the pencils on the diagram disk 6 are included in the image on the screen 12. In'Fig. 4, the block 38 forms a condensor lens and the entry surface 36 of a block 35 is partcylindrical to form a converging lens. The block 40 has parallel reflecting surfaces 42, 43 to shift the image inwards from the edge of the dial 7. To provide a clear path for the light between blocks 35, 40, the edge of the diagram disk 6 is bent up by suitable fixed guides, not shown. The bulb 13 can be switched on when the tachograph functioning is to be monitored. Preferably the reflecting surfaces of the transparent blocks are silvered.