GB909132A - Improvements in or relating to weighing machines - Google Patents

Abstract

909,132. Electric weighing systems. MOSSE, R. W. E. July 8, 1959 [April 21, 1958], No. 12625/58. Class 40 (1). [Also in Group XVIII] A machine for weighing out pourable material comprises means for continuously controlling the flow of material to a container in accordance with the difference between the weight of the container and contents and the desired final weight, as measured by a differential transformer. Material flows from a hopper 1 through control blades 3 to a container 2 supported on a beam 4 which carries a counterweight 6. The beam unbalance is measured by the photoelectric transducer shown, or by a differential transformer with a moving core attached to the counterweight 6, and the windings carried by an auxiliary arm 14. A cam 17 is mounted on shaft 18 for rotation with a second cam 21 which controls the magnitude of the opening of the control blades 3. A continuously rotating motor 24 drives a shaft 20 through an electromagnetic clutch 25 which is controlled by the output of the differential transformer. Shaft 20 is constantly engaged by a brake 27 and drives shaft 18. Upon the container 2 being emptied from a previous weighing operation, counterweight 6 drops to its lowest position, and the differential transformer sends a signal to clutch 25. This causes the blades 3 to be opened and the container to be filled. The rotation of shaft 18 to open blades 3 depresses the transducer windings so that the blades no longer move. As the container 2 fills, counterweight 6 rises under the action of spring 7, thus raising the transducer core. Consequently shaft 18 rotates, the blades move in accordance with the profile of cam 21, and the transducer windings follow the core. Any desired rate of flow programme may be obtained by suitable choice of the profiles of cams 17 and 21 and the characteristics of spring 7. Eventually spring 7 acts against a stop 8 so that the transducer core will not move until container 2 is balanced, the full counterweight load then being lifted. The rate of flow is constant during this period. At balance the transducer core suddenly lifts and shaft 18 rotates until the transducer output is again zero, this action causing blades 3 to be shut and flow of material stopped.