Patent GB-843540-A (GB)
Title: Improvements in batch weighers
IPC: G01G19/22
Filed: 1956-09-18
Abstract: 843,540. Batch weighing; selective control. FAIRBANKS, MORSE & CO. Sept. 18, 1956, No. 28510/56. Class 40 (1). A batch weigher in which appropriate quantities of a number of ingredients are fed to a single hopper 20, Fig. 1, is controlled electrically in accordance with a programme coded on a card. Each ingredient is fed at a fast and slow rate and the weighing is effected with the aid of strain gauge cells. Preliminary operations; card reading. When a card has been inserted in a frame (not shown), push button 338, Fig. 2A, is operated momentarily to bring the contact members shown at the. top of Fig. 2 into contact with it. Those encountering perforations make contact with a conducting plate 91. After the release of the button, the contacts remain latched mechanically. Start switch 364, Fig. 5, is then operated and relay 366 pulls up and energizes 368 provided that the card is correctly positioned and in consequence relay 388, but not relay 390, has been energized. Magnet 362 of a sequence switch is thus energized and relay 368 remains energized over the off-normal bank 372. Batch weighing. As soon as the sequence switch moves off normal, magnet 24<SP>1</SP> opens the main valve to admit the first ingredient to hopper 20. The latter is supported by three cells 22, Fig. 3, each comprising a bridge of strain gauges supplied with A.C., having their combined outputs opposed by a voltage from a network 42 to compensate for the weight of the hopper itself, the combined voltages of networks 154, 156, 158, 160 representing the desired weight of the first ingredient as determined by the condition of card-operated relays 70 . . .150 in position 1 of the sequence switch and finally a voltage from a network 314, dependent on cardoperated relays 310, 312 and representing the weight, short of the desired weight, at which it is desired to change from rapid to " dribble " delivery, in the input of an amplifier, Fig. 6, operating a meter and a relay (not shown). When balance is achieved, contacts 382, Fig. 5, are opened and normally energized relay 380 falls and energizes 376 which releases the main valve magnet 24<SP>1</SP>, energizes the sequence switch stepping magnet 362 and then falls back after a delay imposed by capacitor 378. In position 2 of the sequence switch, the " dribble " valve for the first ingredient is opened by magnet 26<SP>1</SP> and network 314 is de-energized. Balance is thus achieved next when the desired weight of the first ingredient has been delivered and the sequence switch is then stepped on as before to initiate the rapid delivery of the second ingredient as determined by the next combination of card relays operated in position 3 of the sequence switch. Delivery of the remaining ingredients takes place in a similar manner in positions 5 to 8. Release. In the remaining positions, relay 384 is energized over the off-normal bank and the switch homes by self-interruption. A push button 344, Fig. 2a, is then operated to energize an unlatching magnet 342 to free the card contacts and at the same time a magnet 346 is operated for a minimum time determined by a shunt capacitor to energize a magnet 348 to release the card.