Improvements in and relating to means for avoiding errors due to parallax in taking readings from scales and pointers

摘要

349,787. Weighing-apparatus. INTERNATIONAL BUSINESS MACHINES CO., Ltd. and MILES, J. W., Beavor Lane, Hammersmith, London. June 4, 1930, No. 17171. [Class 143.] Indicating mechanism.-In order to minimize errors due to parallax in t a k i n g readings from scales and pointers of indicating apparatus more particularly weighing-apparatus a sighting device is provided comprising a hood-like s ructure extending to a distance from the pointer or other reference body and having an aperture of slit-like proportion whereby the index is viewed between planes of observation approximating closely to the true plane. As shown applied to a weighing machine of the movable indicator drum type, Fig. 1, a horizontally arranged wire 4 is situated between the graduated drum 1 and a magnifying lens 5 in a frame 6. At each end of the drum is mounted a bracket 7, Fig. 2, with convergent channels 9, 10, into which are slid rectangular slats 11, 12, forming a hood of translucent material with their surfaces treated to avoid internal reflection.