GB1528042A - Weighing machine - Google Patents

Abstract

1528042 Automatic batch weigher HOWE RICHARDSON SCALE CO Ltd 6 Aug 1976 [19 May 1975] 21121/75 Heading G1N An automatic batch weigher comprises a weigh hopper supported by a lever system connected to a load cell 9, a controlled material feeder, a controlled discharge door in the hopper, a pre-settable weight selector 21 for producing an electrical signal representing a desired material weight and a control unit 30 having digital logic elements and analogue computing elements arrayed in a circuit to receive the electrical signal from the load cell 9 and the electrical signal from the weight selector 21, the control unit 30 comparing the two signals and producing an output signal for the means controlling the feeder to stop the same, as by a cut-off comparator 19 pre-settable by a potentiometer 23, before the delivered weight equals the desired weight to compensate for the weight of material that is delivered to the hopper after the feeder has been signalled to stop and an output signal for the means controlling the hopper door to open the same when the weighing is completed. As described the feeder has a fast and a slow feedrate the slow rate coming into operation on a substantial proportion of the full charge of material having been fed into the hopper. The onset of the slow feedrate is controlled by a dribble feed comparator 18 which is pre-settable by a potentiometer 24. The control logic 30 is also provided with signals representing the tare weight, adjustable by a potentiometer 22 to check whether the hopper has been emptied fully, representing whether the charge of material is under or over the required weight using a comparator 17 pre-set by a potentiometer 25 and representing plant inputs 31 e.g. emergency stop, discharge downstream interlock, bag in place on hopper Figs. 4A, 4C (not shown). The weigher may be checked when required by a proof circuit 34. Automatic taring of the hopper may be introduced by a unit 13 and automatic control of the compensation adjustment by a circuit 15. Signals may be fed to a remote weigh display, printer or data logging equipment 14. The weigher may have a totalizing counter 33 and a batch counter Fig. 3 (not shown). A meter 27 is provided for providing respective readings for adjusting the potentiometers. A means is provided for preventing the opening of the hopper in case of an abnormal condition downstream thereof. The hopper may be fed from a bin in which case a low material level detector may be provided therein. When this detector is operated there is insufficient material for a complete charge and normally the weigher stops. However, the stopping mechanism may be manually over-ridden. The various control buttons, potentiometers, indicators and a mimic display are mounted on a front panel of the batch weigher Fig. 3 (not shown). The circuits are in the form of a plurality of interconnected circuit boards Figs. 4A, 4B, 4C, 4D (not shown).