Patent GB-639461-A (GB)
Title: Automatic weighing machine using electronic oscillatory means
IPC: G01G13/295
Filed: 1948-09-20
Abstract: 639,461. Automatic feed weighers. DAMOND, E. Sept. 20, 1948, No. 15513/46 [A Specification was laid open to inspection under Sect. 91 of the Acts, Aug. 26, 1947.] [Class 143] [Also in Group XL(C)] An automatic weighing machine comprises a movable member for indicating the condition of unbalance, this member being associated with the coupled coils of a thermionic valve oscillator circuit to vary the coupling between them thus causing a change in the oscillatory state of the circuit. This change in state controls an associated relay which controls the rate of feed to the machine of the product to be weighed. The figure shows an automatic weighing machine in which the rate of feed of the product to the machine is controlled by the electric motor 108 which vibrates the hopper 107 and by the motor 106 which vibrates the feeding chute 105. A pointer 118 which indicates the degree of unbalance of the machine moves in front of a graduated scale and between two pairs of inductively coupled coils 135, 136 and 120, 121 which are situated on the scale at points corresponding to the predetermined weight to be measured and to a weight slightly less than this. The coupling between the individual coils of each pair is normally sufficient to cause valves 122 and 133 to oscillate, the resultant drop in their anode currents causing relays 116, 117 to release, their contacts 111, 114, and 115 then being in the position shown. When however the pointer 118 moves to a position between say the coils 120, 121 the coupling is reduced, the circuit becomes non-oscillatory and the associated relay is operated. When the weighing operation first commences the pointer 118 is in the position shown between coils 120, 121 in which position it remains until the out-of-balance weight becomes less than some pre-determined amount. In this position valve 133 oscillates relay 117 is released, and its associated contact 115 is in the made position shown, the chute motor 106 being supplied with A.C. from source 109 via contact 115. Valve 122 is non-oscillatory thus relay 116 is operated and contacts 111, 114 made and the hopper motor 108 is supplied with A.C. via contact 111 and rheostat 110 and contact 114 shorting out the end-of-weighing operation rheostat 113 in the chute motor circuit. When the pointer moves into the intermediate position when it is not between either pair of coils, both valves are oscillatory and both relays are in the released position shown thus the hopper motor 108 has its supply disconnected by contact 111 opening, and the rheostat 113 is put in series with rheostat 112 thus reducing the speed of the chute motor 106. When the needle moves into the position between coils 135, 136, valve 122 oscillates and valve 133 is rendered not oscillatory. Relay 116 remaining in the released position i.e. motor 108 being stopped and relay 117 operates breaking contact 115 and thus breaking the supply to the chute motor 106. Thus in this end of weighing position the supply of material to the weigher is stopped and container 103 may be removed.