Patent GB-594289-A (GB)
Title: Automatic weighing device
IPC: G01G13/02
Filed: 1944-06-05
Abstract: 594,289. Automatic-feed weighers. MARCONI INSTRUMENTS, Ltd., BARTLEY, W. B., and BROCKELSBY, C. F. June 5, 1944, No. 10801. [Class 143] [Also in Groups XXXVIII and XL] Apparatus for weighing out a predetermined mass of a substance comprises means for permitting the substance to flow from a bulk quantity into a container, controlling the intensity of a light beam falling upon a photo-electric cell system in accordance with the mass of the substance in the container so as to control the intensity of an electro-magnetic force which is applied to the container to maintain it in a balanced condition and means for arresting the flow of substance in response to a predetermined intensity of the electro-magnetic force corresponding to said predetermined mass. In the arrangement shown an apen-ended container pc movable vertically under a hopper H has its end closed by a conical member pm carried on a rod pr connected to a core col associated with a winding W1. When switches es1 and es2 are closed a small current flows in the circuit including the photo-electric cell cl resulting in a relatively large voltage on the grid of a valve ev1 so that the maximum current flows in the coil w1 and the core col raises the member pm and container pc to their uppermost positions. A relatively large negative voltage at the anode of the valve evl is applied to the grid of a valve ev2. The members M on the rod pr varies the light falling on the cell c1 and in its uppermost position effects an increase in current in the circuit es1, es2, c1 and consequently a reduction of current in the circuit of the winding W1 which results in an increase in the current flowing in the circuit of the valve ev2 which includes the winding W3. A core Co3 is drawn to the left and brings the opening ha in the plate hc under the hopper H. The mass of substance falling into the container pc gradually depresses the rod pr. The current in the cell circuit is decreased and that in the winding W1 is increased to balance the increased weight of the container. The increased current in the circuit of the winding W1 causes a reduction in the current in the circuit of the valve ev2 and winding W3 so that the plate hc moves to the right and restricts the aperture ha and the flow of substance to the container. The substance is fed at a gradually reduced rate until the current through the winding W3 is reduced so that the aperture ha is closed and a tooth hp on a rod hr connected to the core Co3 rotates ratchet wheel hw to open switch esl. The core CO1 falls, the container pc is arrested by stops pcsl and the closure member pm is withdrawn so that the contents are discharged. The circuit of the winding W3 is opened at contacts sc1 sc2 so that the hopper H is closed until the cycle is restarted by the automatic closure of switch esl which is preferable of the tilted mercury type. The predetermined amount of substance in the container pc is adjusted by variation of the potential of the bias battery eb and the apparatus may be modified for a desired number of operations by a switch in the circuit of the battery ep1, for example by opening switch es2 under control of a counting device driven from the ratchet wheel hw.