Patent GB-1237101-A (GB)
Title: Automatic batch weigher
IPC: G01G19/30
Filed: 1968-07-25
Abstract: 1,237,101. Batch weighing systems. HOWE RICHARDSON SCALE CO. July 25, 1968 [Aug. 3, 1967], No.35524/68. Heading G1N. In an automatic batch weighing machine, the measuring and control circuitry is so arranged that different functions, such as automatic taring, dribble feeding, allowance for delay in cut-off, over- and under-weight indicator, warning if a selected batch would exceed the maximum load of the scale, and adjustment of batch size while keeping the relative proportions of different ingredients the same, are performed by respective printed circuit modules which can be plugged into and out of a motherboard as required without affecting the remaining parts of the system. Weight sensing. A silicon or resistance strain gauge load cell 101 senses the weight of the weigh hopper 38. The load cell output signal is added to an adjustable zero tare signal and filtered and fed as a positive voltage E1 to all those modules that require it. Automatic taring. An automatic taring module 124 stores in a capacitor 210 a voltage representing the accumulated weight before the start of feeding of a new ingredient and feeds an appropriate negative voltage E2 to all those modules that require it. Weight selection. Voltages representing the desired weight of each ingredient are set on a bank of potentiometers 170, which are sequentially connected into the circuit by a sequencing circuit 156, and fed to a potentiometer 198 which allows adjustment of the batch size without changing the relative proportions of the ingredients. The output signal from potentiometer 198 is fed as a negative voltage E3 to all those modules that require it. Feeding and termination of feeding. As shown in Fig. 1 two ingredients are weighed in turn into a hopper 38 from full flow feeders 24 and 60 respectively and dribble feeders 40 and 62 respectively. The feeders for each ingredient may be arranged side by side to use a common supply hopper. Catch gates 73, 73a, 77, 77a minimize overfeeding. Both feeders for an ingredient are started automatically by the sequencing circuit after the automatic taring module has stored the accumulated weight. A dual circuit comparator module 121 sums the voltages E1, E2 and E3 with an adjustable voltage E4 to determine when the full flow feeder is stopped, subsequent feeding being by the dribble feeder only until the sum of voltages E1, E2, E3 and an adjustable voltage E5 to allow for cut-off delay becomes zero whereupon a relay EP-S is energized to cut-off the dribble feeder. Voltage E5 is set on a bank of potentiometers 170a and may be different for each ingredient if the ingredients have different densities. If dribble feeders are not provided, a comparator module, Fig. 4 (not shown), having only the second summing point (160) may be used. Over- and under-weight indication. A dual comparator module 122 sums the voltages E1, E2 and E3 with an under-weight limit set voltage E7 at junction 140a and with an overweight limit set voltage E8 at junction 160a and stops the automatic operation of the weighing machine if the weight of an ingredient is outside the acceptable range. An alarm light may be provided. Voltages E1, E2 and E3 are also summed in a summing module 123 and their sum is fed to a meter 259. Impossible batch indication. Module 125 sums the selected weight voltage E3 and the automatic taring voltage E2 and operates an alarm 244 if a threshold representing the maximum load of the hopper 38 is exceeded. Resetting and discharge of hopper. When a batch of ingredients has been successfully weighed out a home-stepper relay is energized to cause the system to step through any remaining unused positions in its operation cycle to reset itself ready for the next batch. A discharge relay may be energized at the last step before resetting is finished to open a discharge gate 66.