GB1234239A - - Google Patents

Abstract

1,234,239. Digital weighing systems. ZAKLADY MECHANIKI PRECYZYJNEJ. 23 Dec., 1968 [23 Dec., 1967; 26 Sept., 1968], No. 61201/68. Heading G4H. A weight measuring system comprises a balance beam 1 pivoted on knife edge 1B and carrying a pan on the other edge 1A holding an unknown sample and a number of removable calibrated weights, a coded scale 2 on the other end of the beam, reading means 8 for the scale indicating the deflection of the beam from a datum position which is a measure of the weight of the sample, a cam-and-link mechanism to remove or add selected calibrated weights to restore the balance of the beam under the control of the reading means and means providing a visual read-out of the weight of the sample. The weight of the arm to the right of the edge 1B is exactly balanced by the weight of the arm to the left of the edge plus the weight of all the removable calibrated weights on the pan. The calibrated weights could be the other side of the pivot, the weights then being added instead of removed. The weight of the sample causes displacement of the beam which moves an image of the scale 2, projected by lamp 3, lenses 4, 5 and mirrors 6, 7 over the reading unit 8. The scale, Fig. 2, has ten zones 9 each capable of giving a coded representation of a units digit and a single zone 10 giving the tens digit. The senser unit 8, Fig. 3, has four photocells A-D in slit 13 sensing the four tracks of zone 10 and leading and lagging groups of four photo-cells E-H and I-L in slits 14, 15 for sensing the four tracks of the appropriate zone 9. One or the other of the groups is selected in accordance with the value of the 1 digit A of the tens group. This avoids transition errors when passing from 9 to 10. The two decades are each decoded to give outputs on one of ten leads and display a corresponding decimal number. This number is also recoded in a fourbit binary code for each decade, the bits having weights 1, 1, 2 and 5. These are used to control cam and link apparatus (Fig. 6, not shown) for removing calibrated weights from hangers on the pan so that the weight removed corresponds to the value indicated by the scale 2. The unknown weight should therefore be compensated to within one unit of weight and the beam returns to its balanced position. The pan is then transferred to another beam for a fine indication giving digits valued 0À1 and 0À01. If desired, a still finer indication may be derived from a third beam.