Patent GB-1001404-A (GB)
Title: Method and apparatus for pneumatic stratification
IPC: B03B4/00
Filed: 1962-05-18
Abstract: 1,001,404. Separating solid materials. D. B. BINNIX. May 18, 1962, No. 19343/62. Heading B2H. In a method of stratifying a downwardly sloping moving mineral bed, a pulsating pneumatic pressure' is applied upwardly through the bed throughout its length, the pneumatic pressure increasing along the bed to stratify the mineral particles in the bed according to their densities, the stratified layers being separated at the lower end of the bed, and the separation being controlled in accordance with the pulsating pneumatic pressure suspending the particles in the bed at the lower end thereof. The material to be treated, e.g. run-of-mine coal, is fed from a hopper 13 at a rate controlled by a gate which may be adjusted by a handle 15, on to a sloping screen 3. Underneath the screen are disposed a number of separate cells 5, each having a mesh 17 to support a number of glass marbles 16. A valve 18 is fitted to each cell 5 and its position is shown by an indicator 21. The seven cells at the higher end of the screen are fed with air from a chamber 10 and the next five cells from a chamber 11. The last two cells nearest the lower end of the screen are fed from a chamber 12. A fan (not shown) forces air into a chamber 38 and thence through rotary valves 30, 34 to the chambers 10, 11 respectively. The valves 30, 34 are driven by a variable speed motor 31 to pulsate the air supply to the cells 5, and the pulses produced by each valve are arranged to be 180 degrees out of phase. A further fan (not shown) supplies air to the chamber 12 and this supply is pulsated by rotation of a single. bladed valve 44 by a variable speed motor 47. The bed of material on the screen is stratified by the air from the cells 5, and as the material passes down the 'screen the denser waste materials collect closer to the screen. The greater air pressure required to stratify the material bed at the lower end of the screen is provided by utilizing the separate chambers 10, 11, 12, and also the number of marbles 16 in each cell is progressively reduced towards the lower end of the screen. Particles which are very dense and pass quickly to the bottom of the material bed may pass through a screen 24, situated above the last two of the cells 5 above the chamber 10, on to a screen 25 from whence they are removed by a screw conveyer 29. This alleviates the use of air pressures at the lower end of the screen 3 which would be too high for effective separation. A dam 51, held on top of a shoot 51, is provided at the lower end of the screen, the coal passing over the dam and the reject material under the dam. The shoot 50 rests on a cam 54 mounted on a shaft 55 rotatable by a handle 56. The shaft 55 also carries a member 58 which is held in engagement with an adjustable stop 57 by a spring 60. The handle 56 may be depressed to release large pieces of material jammed under the dam 51. The reject material passes to a gate 72 fulcrumed at 71 and it remains there until the pressure built up underneath the screen 3 in the chamber 12 is high enough to actuate a lever 68 also pivoted at 71 to open the 72 against a spring 70. The lever 68 is connected to a lever 65 by a link 67 and the lever 65, pivoted at 66, is connected by a link 64 to a diaphragm 61 in communication with the chamber 12. The position of the fulcrum of the lever 68 and the position of the link 67 are adjustable. A further control over the operation of the gate 72 is provided by a valve 76 held against an opening 75 of a chamber 74, communicating with the chamber under the diaphragm 61, by a weight 80 on a bell crank arm 77. This releases the pressure in the chamber 12 at a pre-set value. The valve 76 may be replaced by a manually operated valve, Fig. 3 (not shown),- or by the automatically operated valve shown in Fig. 4. A pressure responsive means 90 is actuated by the pressure in the chamber 12 and this drives a servomotor 88 to control the valve 84. The sides 73 of the machine may be of clear methylmethacrylate so that the material bed may be viewed.