Patent GB-1072257-A (GB)
Title: Control system for classifying apparatus for granular material such as a water scalping tank
Inventor: COCHRAN CLEMENT B
IPC: B03B11/00
Filed: 1964-07-10
Abstract: 1,072,257. Grading solids. EAGLE IRON WORKS. July 10, 1964, No. 28713/64. Heading B2H. A control system for a settling tank having a series of outlet stations 21..27 each having at least a first outlet and an auxiliary outlet with closure means, comprises individual settable measuring means, one for each station, mesuring the discharge of material through the associated first outlet, and connected to closure operating means to divert discharge from the first outlet to the auxiliary outlet when a preset amount has discharged through the first outlet, and an automatic means for resetting all the measuring means when the preset discharge has been made from all of the stations. In Figs. 2 and 4, a sand and water slurry is introduced into a settling tank at 15, and further water at 16. Clear water overflows and is discharged at 28, and sand is deposited in succesively finer fractions from station 21 to station 27. At each station, e.g. 21, Fig. 2, an overhead frame 32, 33, 34, support a motor driven paddle 41 and fluid pressure operated electrically controlled rods 55, 56, 57, connected to closure devices 61, 62, 63, of conduits 65, 66, 67. All conduits 65 lead to a first flume, all conduits 66 to a second flume, and all conduits 67 to a third flume. When the sand level at any one station has built up sufficiently, the paddle 41 at that station is retarded by the sand, and the back-torque on the motor is used to operate a switch and open one or more of the closures 61, 62, 63 until the sand level falls again. The control system comprises devices determining the total period for which each outlet 65 is open, thus predetermining the composition of the total feed to the first flume. Equally, the composition of the total feed to the second flume through the outlets 66 is predetermined. When sand is to be discharged from a station, but no more of that fineness is required in the first or second flumes, the outlet 67 at that station is opened, and sand is discharged into the waste flume. When each outlet 65 has discharged for its predetermined total time, so that sand of a predetermined composition has been delivered to the first flume, the measuring devices associated with those outlets are reset to zero, and further delivery to that predetermined composition can commence, and similarly for the second flume. The first of the outlets 65 to have discharged its predetermined quantity may however be held openable by its paddle 41 by a time delay device, so that that fraction of the sand which is most in excess of nominal requirements is used as much as possible up to the permissible limits specified for the composition in the first flume and similarly for the second flume. In an alternative, each outlet 65, 66 is timed by maximum and minimum devices, so that any outlet may continue to discharge for its maximum time, but the cycle for either flume is terminated and restarted from zero when every outlet of the flume has discharged for its minimum time. Electrical circuits for effecting the various timing operations are described.