Patent GB-1386950-A (GB)
Title: Checking of a weighing or dosing apparatus
IPC: G01G13/00
Filed: 1971-08-09
Abstract: 1386950 Weighing and dosing apparatus F L SMIDTH & CO AS 7 Aug 1972 [9 Aug 1971] 37375/71 Heading G1W A continuous weighing and dosing apparatus 14 is provided with a feed system which permits the accuracy of the weighing to be checked intermittently by a static weighing. In Fig.1, bulk material is supplied from a silo 1 via valves 5, 6 and 7, a worm conveyor 8 and a shoot 9 to a container 10. A conveyor 11, shoot 12 and worm conveyor 13 supply material to the apparatus 14 at a rate greater than the rate at which apparatus 14 dispenses the material at an outlet 15, and the surplus material passes down a shoot 16 into a weighing container 17 mounted on weighing cells 21. Any material escaping from apparatus 14 is collected by a hopper 18 and enters container 17. Container 17 communicates with container 10 via shoot 16 and valve 20. Level detectors 23, 24 in container 10 close valves 20 and 5, 6, 7, respectively when actuated. Valves 5, 6, 7 are also actuated according to the output of load cells 21 so that they close when the weight of container 17 reaches an upper value, and open again when the weight of container reaches a lower value, apparatus 14 receiving material from container 17 when valves 5, 6, 7 are closed. To check the weighing accuracy of apparatus 14, the reading from apparatus 14 is compared with the decrease in weight of container 17 in a period when valves 5, 6, 7 are closed. A jacket 17" may be filled with water to check the accuracy of cells 21. In a modification Fig.2, (not shown), the weighing cells support and weigh not only container 17 and hopper 18 as in Fig. 1, but also container 10, conveyor 11, shoots 12, 16 and apparatus 14. In Fig.3, a single weighing container may be used to check either of the weighing and dosing apparatuses 14a, 14b. In normal use material passes from silo 1 through valve 5 and along conveyor 8, into container 10' fitted with level controls 23', 24'. Material from container 10 is supplied to apparatuses 14a, 14b, and the surplus material from both falls into a container 17'. The weighing container 17 is mounted on cells 21 and has connected to it a container 10, the container 17 being filled to an upper level H when a check is not being carried out. To check apparatus 14a, switch a is actuated, and this causes valve 32a to close, valves 20 and 35 to open, and valve 30a to change over so that the surplus material from apparatus 14a now passes to container 17. Thus apparatus 14a now receives material from and discharges surplus material to weighing container 17 only, and the rate of loss of weight of container 17 is compared with the weighing readings from apparatus 14a. When the level of the material in container 17 falls to lower level L, an electric contact is made causing valves 20 and 35 to close and valve 32a to open. When the container 17 has been refilled to the upper level H by the surplus material from apparatus 14a, valve 30a changes over so that the surplus again falls into container 17'. A signal is transmitted at the H and L levels during a check to an observer at the read-out of the apparatus 14a or b. (For Figures see next page)