GB688229A - Improvements in or relating to balances - Google Patents

Abstract

688,229. Balances. MINISTER OF SUPPLY. Oct. 10, 1950 [March 17, 1950]. No. 24684/50. Class 143. In a precision balance, convection currents within the casing are minimized by surrounding the beam and load supports with a casing of a material having a high thermal conductivity which provides a direct heat conducting path between the beam and load supports, and between the load supports. The casing is in three parts 18, 18a, 18b; part 18 which has holes 44a for the load supporting loops 32 being rigid with the base and supporting part 18a which, is removable for inspection purposes; and part 18b being vertically movable by a screw jack 37, operable by handles 43, to enable weights and loads to be hung on loops 32 by mechanical loading fingers 57. The balance comprises a quartz, truss construction, beam 14, Fig. 1, suspended on a quartz fibre 15, Fig. 2, which is secured to a rectangular spring 21 and a spindle 23 rotation of which, by a wheel 50a, returns the beam to a neutral position after it has been displaced by the load against the torque exerted by the fibre. A dial 16, indicates the weight of the load, or the difference in weight between the load and the counter-weights. The position of balance is ascertained by an optical unit 17 which, through lenses 55 and a series of prisms produces in an eye piece 54 an image of each end of a horizontal index 29 secured to the beam, these images being aligned at the position of balance.