Patent GB-948102-A (GB)
Title: Control circuit for batching systems
Inventor: WILLIAMS ROGER BURTON
IPC: G01G23/365
Filed: 1961-09-23
Abstract: 948,102. Electric batch-weighers. TOLEDO SCALE CORPORATION. Sept. 12, 1961, No. 34141/61. Heading G1N. A control apparatus for a batching system includes means for deriving a voltage proportional to a quantity of incoming material, reference circuits providing a first plurality of reference voltages representing the desired quantity of material, a second plurality of reference voltages representing the amount of material after which the rate of feed is to be reduced, and a third plurality of reference voltages representing the amount of material in suspension when the feed is cut off, a plurality of comparing circuits formed by connecting predetermined combinations of reference circuits to the proportional circuit, and a plurality of output circuits connected sequentially to the comparing circuits. The indicating arm of scale 20 is connected to the slider of a potentiometer 33 to give a voltage of phase #, proportional in amplitude to the weight of material in the hopper. To deliver a predetermined weight of material to the hopper a relay is energized, closing contacts RA1 and RA3 and connecting the arm of potentiometer 33 in series with reference voltage circuit 40, which includes weight setting potentiometer 53, preset to determine the weight of material A to be fed to the hopper, preact potentiometer 62, to allow for material suspended in the air and reaching the hopper after the supply is cut off, and dribble potentiometer 72 to determine the weight at which the rate of feed is to be reduced as the desired weight is approached. The potentiometer supply transformers are wound so that the preact and dribble voltages are of phase #, while the weight setting voltage is of phase #, 180 degrees out of phase with #. The combined outputs are fed to phase-sensitive amplifier or null-detector 111 responsive to phase # and giving a zero output for a signal of phase # or of zero amplitude. Material A is fed to the hopper until the signal reaching amplifier 111 is zero, whereupon relay RDR is de-energized and the supply is slowed down. Meanwhile the outputs from potentiometers 33, 53 and 62 are fed in series to phase-sensitive amplifier 112, and when this output reaches zero relay RF is de-energized and the supply is cut off. The outputs of potentiometers 33 and 53 are then compared with plus and minus tolerance voltages from potentiometers 102, 92 and the outputs are fed to phase-sensitive amplifiers 113,114 which maintain relay ROT energized, and RUT de-energized only if the measured weight is within tolerance. Materials B and C are added similarly. To empty the hopper contacts RD3, RD6 are opened and RD4,RD5 closed to reverse the output phase from potentiometer 33, and contacts RD1,RD2 are closed,whereby a # voltage energizes relays RF, ROT and RUT. Relay RF is de-energized when the hopper is empty. In a modification the weight setting potentiometer for the materials A, B and C are connected in parallel and are preset to correspond to the weight A, A + B, and A + B + C, the preact and dribble potentiometer for the three materials also being connected in parallel. A D.C. supply may be provided instead of A.C.