Patent GB-888262-A (GB)
Title: Improvements in weighing apparatus
IPC: B07C5/32
Filed: 1960-06-17
Abstract: 888,262. Measuring weight electrically; selective signalling. F.M.C. CORPORATION. June 17, 1960 [June 30, 1959], No. 21294/60. Class 40 (1). [Also in Group XVIII]  A weighing apparatus comprises a platform mounted on a tubular column mounted on a blade spring. The column mounts the core 272 of a transformer 270 whereby movement of the column varies the input signal to an electric circuit which controls a solenoid-operated discharge gate so that either underweight, correct weight or overweight articles selectively discharge down a shoot. A power supply 351 supplies current to a triode 350 of an oscillator 271 which is in circuit with the primary winding 276 of the transformer which has two opposed windings which produce the voltage output signal varying with the weight of the article travelling over the platform. The signal is transmitted to an amplifier in four stages 375 to 378. The amplifier stage 378 supplies an output signal to a circuit containing an A.C. or D.C. current recorder. A portion of the output signal from the stage 377 is fed back to the input stage 375 the remainder is fed to a weight classifying circuit which comprises thyratron tubes 391, 392. A relay timing circuit operated by a phototube 45 has triodes 441, 442 and a relay 450 for operating the discharge gate. The circuit is adjusted by potentiometers 395, 400 so that the signal produced by a correct weight article fires the thyratron tube 391 and the signal produced by an overweight article fires both thyratrons. One of the solenoids 325a to 325a is put in the circuit to operate the gate to discharge down the shoot either an underweight, correct weight or overweight article. If an underweight article is to be discharged down the shoot, the article passing over the weighing platform fires neither thyratron and on discharge it interrupts the light beam to the photo-electric cell and renders the triode 441 conducting and the triode 442 non-conducting, whereby the relay 450 de-energizes and operates solenoid 325a to open the gate. The voltage on the grid of the triode 442 rises and the triode 442 conducts and renders the triode 441 non- conducting and solenoid 450 energizes and the gate closes by spring action. The interval of time for the triode 442 to return to the initial state is controlled by the time constant of a resistor, capacitor operated circuit and is equal to the time an article takes to travel between the beam and the discharge shoot. If the article has the correct weight, the thyratron tube 391 fires, relay 420 energizes and prevents the solenoid 325a operating, the article advances to the discharge conveyer over the discharge gate. The photo-electric cell operates to cause the triode 441 to conduct and the triode 442 not to conduct, relay 450 de-energizes, capacitor 480 charges to plate potential of the tube 391, triode 442 conducts and triode 441 does not conduct, relay 450 energizes, capacitor 480 discharges and the tube 391 discharges. If the article is overweight both thyratron tubes fire, relays 420, 430 energize, the solenoid 325a does not energize and the article discharges passing over the discharge gate. The article interrupts the beam of light, the triode 441 conducts, triode 442 does not conduct, and relay 450 de-energizes. Capacitors 481, 482 charge to plate potential through tubes 391, 392, triode 442 conducts and renders triode 441 non-conducting and relay 450 energizes. Capacitors 481, 482 discharge and the thyratron tubes extinguish, and relays 420, 430 de-energize. In a similar way correct weight or overweight articles are discharged down the shoot by putting into the circuit solenoid 325b or 325c.