GB843449A - Improvements in weighing scale arrangements - Google Patents

Abstract

843,449. Weighing. FAIRBANKS, MORSE & CO. Sept. 21, 1956, No. 28926/56. Class 40 (1). In a weighing system, the voltage from a load cell comprising a bridge of strain gauges 31 and a phase-correcting network 200 supplied with A.C., preferably combined with counterphase voltages from networks 202, 20 representing respectively the dead weight of the weighing arrangement and the tare weight, is balanced automatically by the voltage from a potential divider 22 supplemented as necessary by the voltage from a range-changing potential divider 262. Motor 24 which drives potential divider 22 also drives the pointer 288 of an indicator 286 and the registering element of a printer 29. Motor 210 drives an indicator disc 264 cooperating with holes in the face of indicator 286 to show the range. Potential divider 22 comprises a network 30 with a switch 76 for changing the reading from pounds to kilograms. Coarse and fine balancing arrangement. When the pointer of indicator 288 reaches a given forward position without the achievement of balance, it operates a contact 290, to energize motor 210. The motor then runs in a circuit over a cam-operated contact 346 to a position corresponding to the next range of resistance and this step-by-step action is repeated if necessary until the contact 290 is no longer operated. The converse operation occurs when the balance condition is such that too many sections of the coarse potential divider are connected up. In this case the pointer near the zero mark closes contact 296 to energize 334 which closes a circuit for driving the motor in the opposite direction, 334 remaining locked over 346 until a full step has been made. If 296 is still closed, a further step is made in the same way and so on. At the limit of travel, switch 354 releases the relay 334. Alternative modes of operation. If it is desired that the indicator shall show at all times the weight on the scale platform, switch 78 is operated to supply the two balancing motors continuously when there is unbalance. Alternatively, the scale platform may be loaded with switch 78 open, and the weighing operation initiated by the momentary operation of switch 318. In this case, relay 316 pulls up and locks and supplies the motors in the same way as switch 78, but, when balance is achieved, relay 320 pulls up and unlocks 316 and the indicator remains in the position showing the weight of the platform when last loaded. Making printed record. Push button 118 energizes relay 312 to start the printing motor 101 provided that the weighing operation has been completed, as evidenced by the opening of contact 326 and consequent de-energization of 320. Relay 314 also is energized and holds itself and 312 until the printer has completed its operation whereupon it is unlocked at 332 and motor 101 is de-energized.