Patent GB-855917-A (GB)
Title: Improvements in or relating to screening, weighing and bagging installations for solid fuel and the like
Inventor: STEWART JOHN
IPC: G01G13/00
Filed: 1957-05-16
Abstract: 855,917. Automatic feed weighers. A.C.E. MACHINERY Ltd. Aug. 18, 1958 [May 16, 1957], No. 15634/57. Class 143 In an automatic feed screening and weighing apparatus for coke and the like wherein the screen feeds directly into the weigh hopper, the screen speed is reduced automatically towards the end of the weighing operation to provide a dribble feed, the screen S being stopped to cut the feed when the correct weight of material has been fed to the weigh hopper WH. As shown the weigh beam B of the weighing apparatus is acted on by a spring SI which operates to move the beam when the quantity of material delivered by the screen S reaches a major portion of the full weight, and thereby effect the change of speed of the screen, and by a spring S2 which serves to overcome the inertia of the beam B until it reaches the point of balance. The material is fed from a hopper SH to the screen S which is reciprocated by either a high or low speed motor HS or LS to feed the material directly into the weigh hopper WH, the unwanted screenings falling into a hopper BH. The weigh hopper WH has a discharge gate D, Fig. 2, pivoted at P and operable to open by levers L1, L2, L3, a rocking arm A and an electro-hydraulic piston motor TH. The weigh beam B is acted upon at one end by a roller R, Fig. 4, on the end of an arm AB centrally pivoted at C, the arm AB being in turn loaded by oppositely acting springs S1, S2 which each tend to raise the beam B. In operation, with the manual/auto switch KSW, Fig. 7, set to auto, the starter ST is operated to energise relays RL1 and RL2, and release the screen brake BR. Relay RL2 starts the high speed motor HS, closes contacts HF, bridging switch SW, and opens contacts AC2. Relay RL1 bridges switch SW, energises a green indicator lamp IL1, sets up a circuit, to the now open contacts AC2, and opens contacts ACI. When the screen S has fed about 90 lbs. of coke to the weigh hopper, the spring S1 moves the beam B until stopped by a stop N1. This movement releases a micro-switch PWC which thereby opens to de-energise relay RL2, thus stopping the high speed motor HS and closing contacts AC2 to energise a relay RL3 which starts the low speed motor LS. When the weigh hopper contains about 3¢ lbs. less than the desired weight in the pan SP, Fig. 1, the beam B is moved by the spring S2 until the latter is stopped by a stop N2, the beam B then being about ¢ lb. from the pointof balance. Thereafter, the beam B leaves the roller R and immediately before the point of balance is reached, a microswitch FWC is released by the beam to de-energise relays RL1 and RL3 and apply the screen brake BR. Release of relay RL1 closes contacts AC1 to set up the circuit of a relay RL5 which can then be energised by a footswitch FPS. Relay RL5 energises a relay RL4, through paralleled switches TC and TS, to start the piston motor TH and a timer T. The motor TH operates to open the discharge gate D and the timer T provides for a sufficient time for complete discharge after which the timer switch TC is opened to release relay RL4, the switch TS having been opened by movement of the motor TH. The piston motor TH returns to rest position wherein it closes the switch TS, and the door D shuts under gravity to close, when fully shut, the switch SW just before the switch TS is closed. The closing of switch SW starts another cycle of operations, but if the door D is prevented from shutting fully, such as because the hopper WH is not completely discharged, then the switch SW is not closed and the closing of switch TS recycles the door opening and timing operation by re-energising relay RL4. A preselection counter PC provides for a desired number of weighings, after which a contact CC is opened to illuminate a red lamp IL2 and shut down the apparatus until the counter is reset.