GB1409800A - Precision balance having a device for raising weights - Google Patents

Abstract

1409800 Precision balance LIBRA ROTOGET SRL 4 Oct 1972 [5 Oct 1971] 45667/72 Heading G1W A precision balance comprises a beam 3 pivoted at 4, a counterweight 6, a set of balance weights 8 which normally load beam 3 so that the beam is balanced with no load on the pan 2, and a mechanism for selectively raising the weights to balance the beam when a load is placed on pan 2. The weights 8 are in the form of horizontal concentric annular rings supported from the beam 3 by rods 9 and slotted arms 15, a member 10 connected to the rods 9 resting on a pivot 11 of the arm Fig. 2. The mechanism for selectively raising the weights to balance the beam comprises four rotatable annular plates 30, 31, 32, 33 which have camming profiles 34 on their upper surfaces, and vertically slidable pins 28, 29 carried by cross-members 26 and co-operating with the profiles 34 whereby, according to the angular positions of the plates 30, 31, 32, 33, selected pins are displaced vertically upwards to raise-selected weights 8 off the arms 15 and to hold the raised weights against crosspieces 25. Each plate 30, 31, 32, 33 is supported by three gear-wheels 36 meshing with gear teeth 35 formed on the underside of the plate, and one of the three gear-wheels 36 is linked to a weight setting control knob 12, 12a, 13 or 13a on the front of the balance Fig. 3. Each control knob is provided with a detent device 55, 56 for locating it in the correct weight raising position. Each weight is raised by two diametrically opposed pins 28 which co-operate with a single or a pair of camming profiles 34, and each pin is spring-loaded Fig. 7 (not shown). A device for locking the annular plates 30, 31, 32, 33 in a desired position Fig. 8 consists of a plate 59 provided with pins which engage holes in the plates, the plate being normally biased to the non-locked position by springs 68, but actuation of a lever 70 Fig. 1 causing beam 69 to fall and move the plate 59 upwardly into its locking position by means of lever 63. The beam 3 is also provided with a damping device 7, and with an optical projection vernier read-out device.