Improvements in automatic means for blending materials by weight

Abstract

Abstract 839,626. Electric correspondence control. SIMON Ltd., H., and RICHARDSON SCALE CO. Aug. 13, 1956 [Aug. 23, 1955], No. 24210/55. Class 40 (1). In apparatus as described in Specification 779,356 for blending materials by weight, automatic means are provided to check whether the weight of each material is within a permitted tolerance above and below a predetermined value. As shown, resistors R1 and R2 form two arms of a bridge circuit a third arm of which comprises a potentiometer P responsive to movements of a weigh bucket W, and the fourth arm is formed by a bank of resistors CF1-CP4 and CR1 -CR4 and RU which are pre-set to represent the required weights of the materials to be blended, and which are connected in the bridge in turn by the wiper of bank 2 of a selector switch. When switch S is closed the selector switch wipers move to the second and third positions of terminal banks 1-4 energizing relay 1F to open a gate 1G to deliver the first material to weigh bucket W, which descends, thus increasing the resistance of potentiometer P until it balances resistors CP1 + CR1 + RU whereupon a null-voltage amplifier N operates a relay O to energize O0 which locks and releases 1F to close the gate 1G. OA also is energized to increase the resistance of the arm CP1 + CR 1 + RU by the addition of a resistor RO which if the resistance of P does not exceed an acceptable value, upsets the balance to release O. If, however, there is excessive overweight, the bridge remains balanced and the cycle cannot proceed. On the relapse of O, OB pulls up shunting RU and RO, and thus reducing the resistance of the arm opposing the resistance of P which, if it is not below acceptable value, rebalances the bridge and re-energizes O. If the weight is less than the acceptable minimum the cycle cannot proceed. If O does operate, the wipers of the selector switch move to positions 4 and 5 to initiate the discharge of the second material. When wiper 4 reaches position 3 it energizes a relay X which pulls up sluggishly because of shunting capacitors C1, C2. In due course X energizes Y which locks and interrupts the circuit of X which falls sluggishly away. If, when X falls, the wipers are still in position 3, Y remains locked up and relay A pulls up to give visual and audible alarms and light lamps to indicate " underweight " or " overweight " according to the conditions of OA and OB. Otherwise X releases Y and then pulls up again over the fifth terminal in bank 4 for the next cycle.

Inventors

• 👤 Stanley Godwin Hunter

Bibliographic Details