GB848846A - Improvements relating to weighing balances - Google Patents

Abstract

848,846. Weighing balances. GREEN, R. S. Sept. 10, 1958 [Sept. 11, 1957], No. 28663/57. Class 143 A balance of the two-pan, three knife-edge type has a weighing compartment 4 comprising a clear space within the balance case which space is free of the operating mechanism and indicating system, the said compartment being separated by partition means from the rear of the balance case. The partition 3 comprises a rear lower vertical portion 3a, an upwardly and forwardly inclined central portion 3b, and a front vertical portion, the operating mechanism being situated behind the partition or above or beside the weighing compartment 4. In the form shown the rigid sides of the metal case support a bridge 5 of channel cross-section which carries a post 6 with a plane for the central knife edge, the beam carriage 11 being mounted above and within the bridge and being supported on rods or pillars (not shown) situated close to the sides of the case and vertically displaceable by cams (not shown) on the actuating shaft 18. The carriage may alternatively be supported at the centre on bars carried by the bridge and actuated by a cam shaft located in the space between the bridge and the carriage. The pans 25 are suspended from hooks 21 on bars 22 having planes 23 which rest on the outer knife edges 24 of the beam 42, the suspension means comprising the rods 26, 27, 28 and 40. Pan damping is achieved by the engagement of ball 30 and disc 31 actuated by cam 29 on cam shaft 29: beam damping is effected by movement of discs 33 (not shown), carried by arms 32 extending from the beam ends, within cups 34. A ring or like weight may be added to the load on the weight-carrying pan, the ring 36 then being supported on pins 35 projecting from the bar 22 on the appropriate end of the beam: normally the ring is supported free of the pins 35 by the hook 50. The inclination of the beam is indicated by the projection of an image of a graticule 53 onto a screen 39, theoptical path being from a light source 49, through the graticule and a lens 56 and via mirrors 57 to the screen. The graticule carries two scales, one to be read when the ring weight is applied and the other when it is removed. A shutter 38 in the optical path obscures the irrelevant scale, the movement of lever 47 when cam 45 is rotated by shaft 44 serving both to actuate the ring- changing rod 48 and at the same time to move the shutter 38 to the appropriate position.