Patent GB-1169389-A (GB)
Title: Discharge Mechanism and Fail-Safe for Hydraulic Classifiers.
Inventor: THAMME ERIC PAUL
IPC: B03B5/62
Filed: 1967-05-22
Abstract: 1,169,389. Wet separating. E. P. THAMME. 22 May, 1967, No. 23577/67. Heading B2H. A hydraulic classifier comprises a tank 10, Fig. 1, a float chamber 17 to register liquid level variations in the tank and having a float 16 connected by linkage to a valve 14 for an outlet 13 in the tank bottom, an umbrella 20 extending part way across the tank so that the space 26 below it is inaccessible to freely settling solids, an opening 28 underneath the umbrella providing communication between the space 26 and the float chamber, and a liquid outlet 18 from the float chamber 17. The valve 14 has a stem 15 sealingly supported within a pipe 40 and actuated by the float 16 via a forked lever 50 and a bent rod 54. An alternative form of linkage is described with reference to Fig. 2 (not shown). An auxiliary inlet 30 for the admission of additional water to the float chamber is controlled by a valve 31 actuated by the float 16 through a pivoted lever 33 and a nylon cord 32. The umbrella 20 may have a horizontal or sloping surface and a vertical extension 21 having a lower edge 22. The bottom 29 of the float chamber is inclined to provide a slide for solids carried towards the float chamber and which after settling return by gravity to the tank. An air vent is provided at 27. An auxiliary control or fail-safe mechanism of the gate-type for preventing excessive liquid underflow discharge through the outlet 13 comprises a duct 56 having a sloping bottom and fastened to the bottom of the tank 10. The duct 56 is opened or closed by a gate 63 actuated in the open position by a counterweight 61 and in the closed position by the excessive liquid underflow which trajects beyond the passage 65 for regularly discharged underflow into a hopper 62. A sleeve-type fail-safe mechanism, Figs. 8-10 (not shown) is also described. In operation, water is delivered at first via a chute 11. The fail-safe mechanism closes and opens intermittently until the water level in the tank 10 is high enough to enter the space 26 and the float chamber 17 to elevate the float 16 which thereby seats the valve 14 against the outlet 13. Water overflows into a launder 12 around the top of the tank. Solids to be classified are then introduced in the water via the chute 11 and the fine or light solids are entrained with the overflow in the launder 12. The retained coarse or heavy solids settle and accumulate above the outlet 13 while water drains from the float chamber via the pipe 18. When the accumulated solids reach the lower edge 22 of the umbrella, they form a seal against the opening 28, the solids repeatedly collapsing and building up again thereby causing the level of liquid in the float chamber to vary so that the float 16 alternatively opens and closes the valve 14. Entrained and suspended solids variously settle out or are conveyed into the float chamber. Solids which settle in the float chamber are returned by gravity to the tank and collect directly below the opening 28. Admission of water through the auxiliary inlet 30 is effected when the float falls to a predetermined level due to water being lost into the underflow through the opening 13, the water being admitted until water enters again via the space 26. In a modification, Fig. 5, the umbrella 20 and its extension 21 are annular and the float chamber 17 is extended by an inclined conduit 17<SP>1</SP> having the opening 28 at its lower end.