GB1165472A - Improvements in or relating to Weighing Machines - Google Patents

Abstract

1,165,472. Weighing apparatus. FR. HESSER MASCHINENFABRIK A. G. Jan. 18, 1968, No. 2664/68. Heading G1W. [Also in Division G3] An automatic batch weigher comprises a preliminary weighing unit 1 for measuring out a quantity of material less in weight than a desired weight, a final weighing unit 2 in which, during a final weighing operation, the pre-measured quantity is brought up to the desired weight, a regulating device for controlling the filling of the preliminary weighing unit as a function of the period of time required for a part of the final weighing operation, and an electric signal producing arrangement responsive to deflection of a balance beam 18 of the final weighing unit and connected through an amplifier (38, Fig. 2, not shown) to a compensating magnet 26 which is adapted to urge the balance beam towards its neutral or equilibrium position and to at least one control switch responsive to a pre-selectable amplifier output voltage for controlling the delivery of material from a feed device to a weighing receptacle 20 of the final weighing unit 2. As shown, each weighing unit comprises a pivotally mounted beam on one arm of which is mounted a weighing receptacle 8, 20. The weighing receptacle 8 of the preliminary weighing unit 1 is arranged below a feed hopper 15 provided with a closeable flap 14 which is actuated by an electromagnet 13, the other arm 10 of the beam 4 being provided with a counterweight 9, a switch actuating tab 11 and a holder 12 to which one end of a chain 16 is fastened while its other end is moveable by a motor 17. The weighing receptacle 20 of the final weighing unit 2 is arranged below a feed passage 27 which may be provided with a vibrating device and which is closeable by two flaps 28, 29 connected, respectively, to two electromagnets 30, 31 which are actuated in the final weighing operation to provide a dribble feed before final cut-off of feed. The other arm of the beam 18 which may be provided with hydraulic dampers or eddy current brakes is provided with a weight pan 23 and is operatively connected to a differential transformer 25 and the magnet 26 for urging the beam to its equilibrium position. Operation of batch weigher. With the weighing receptacle 8 charged with a quantity of material to counterbalance the chain weight, a drive is initiated to start the rotation of a shaft 35 by one revolution and the material in the receptacle 8 is directed to the receptacle 20. The differential transformer 25 provides a voltage proportional to the deflection of the beam 18 due to the weight of material in the receptacle 20 while further material is fed to the receptacle 20 from the passage 27. An electronic switch (39) connected to electromagnet 30 is actuated by the output of the amplifier (38) when the quantity of material in the receptacle 20 approaches the desired weight so as to close flap 28 and provide a restricted feed through flap 29. Flap 29 is closed upon actuation of a further electronic switch 40 when the desired weight of material in the receptacle 20 is reached. The switch (39) is so connected to a time switch (45) which is connected to the chain drive motor 27 that if the switch (39) is actuated too soon or too late during the rotation of shaft 35 which is provided with cams actuating further switches in the circuit of the switches (39, 40, 45) the motor 27 suitably adjusts the amount of chain 16 on the beam 10 to decrease or increase the weight of material fed during a subsequent preliminary weighing operation to the receptacle 8. When a cam 48 on the shaft 35 reaches a switch 49, a control unit 47 is actuated to initiate further feed of material to the receptacle 8 to form a further pre-dose therein, which predose is directed to receptacle 20 when emptied of its previous load of pre-determined weight.