Apparatus for weighing out a predetermined weight of material

1,129,046. Weighing apparatus. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. July 25, 1967 [Aug. 4, 1966], No.34933/66. Heading G1W. [Also in Division G3] In an automatic feed weigher comprising a weigh pan 1 which is fed with material from a hopper 27 and which is suspended from a pistion 3 movable within a tapered cylinder 4 to provide a variable leak between the piston and cylinder, the cylinder 4 has an inlet port 7 for admitting gas under pressure which opposes the weight of the pan and its contents, and a pneumatically operated switch 14 is arranged to be operated by the gas pressure within the cylinder when such pressure is at least of a predetermined value, the switch when operated being arranged to interrupt supply of material to the pan. The pan 1 which is fed with material from the hopper 27 by a vibratory conveyer 26 is arranged to be tilted by a ram actuated pivoted lever 35 when the pan has received a predetermined weight of material so as to tip the material from the pan. The vibratory conveyer 26, pneumatically operated switch 14 and ram 38 are arranged in such a way that batches of material are weighed successively at regular time intervals, the feed to the pan being cut-off when a predetermined load is on the pan and before such load is discharged by tilting the pan. The switch 14 is so arranged in an electric circuit comprising transistors, relays, cam actuated switches and an electric motor driving the cams that any departure from a required feedrate of material from the hopper during one weighing operation is corrected for the following weighing operation by automatic adjustment of the operation of the conveyer 26. The pneumatically operated switch 14 comprises a pair of contacts 22, 23 arranged at different levels in a tube 16 up which mercury 15 rises by an amount proportional to the pressure below the piston 3 in the cylinder 4, the mercury on reaching contact 23 causing a current to flow via a contact 46 thereby to cause the vibratory conveyer 26 to effect a dribble feed to the pan, the feed being completely stopped when the mercury 15 short circuits contacts 22, 46. A counter may be arranged to count the batches weighed by the apparatus.