Patent GB-634226-A (GB)
Title: Improvements in settling tanks commonly called sand cones
IPC: B01D21/00
Filed: 1947-06-16
Abstract: 634,226. Gravity-separation apparatus. DRIGENKO, C., and PHIPPS, J. D. B. June 16, 1947, No. 15859. [Class 46] A sedimentation tank of the sand cone type, having a sand discharge valve, a water overflow and a control member within the cone having a lower edge to co-operate with the upper surface of deposited sand in forming a variable flow channel for the greater part of the water between the inlet and the overflow, has a tank or like vessel connected to the flow space on the upstream side of the control member so that when the flow is checked by the rise of sand to the lower edge of the control member the water level rises, and means are provided by which the discharge valve is moved in the opening direction by the increased weight of the tank and vice versa. As shown in Fig. 1. the suspension is fed in tangentially at 9 between a cylindrical portion 2 and an inner truncated control cone 5. Sand settles in the lower part of a conical portion 1. while the water rises within the cone 5, overflows into a launder 3 above a division plate 8, and leaves by an outlet 10. When the upper level of sand in the cone 1 reaches the lower edge of the control cone 5, the outflow of clarified water is arrested, and the incoming suspension rises up a flexible hose 21 into a tank 20 attached to one arm of a lever 16, which supports, on the same side of the fulcrum, a sand outlet valve 13, and on the other side a weight-box 22. The weight of liquid in the tank 20 destroys the balance of the lever 16 and causes the valve 12 to open. When the upper level of the sand falls below the lower edge of the cone 5, the apparatus returns to its original condition. Holes 31 having a relatively small combined cross-section are provided in the cone 5 to prevent a sudden inrush of water into the tank 20. A plate 28 prevents the sand from forming a vortex through which water might be discharged from the valve 12, any vacuum under the plate being broken by communication with the atmosphere through a pipe 30. In the modification shown in Fig. 3, clarified water rises inside a control cone 35 or passes inwards through holes 39, 41, to an opening in an upperplate 34 forming the bottom of a launder 36 and is discharged by a pipe 37. The holes 39, which have a total area more than sufficient to pass the maximum quantity of water discharged, may have their effective area reduced by a ring 40 provided with similar holes 41 and sliding within the cone 35. Holes 39, 40 and 31 perform the same function as the holes 31 of Fig. 1. The Provisional Specification describes also an embodiment having an outer cone generally of the form described but with a cylinder, open at the bottom and closed at the top, mounted in the cylindrical upper portion. A flexible hose connects the top of the cylinder to a water tank as previously described. The suspension is fed by a pipe passing through the wall of the conical lower portion and extending axially upwards inside the cylinder, a baffle being provided above the pipe The valve is suspended on two rods on opposite sides of the axis' passing through vertical tubes sealed into the lower conical portion of the cone and extending upwards above the water level. The overflow is discharged into a launder surrounding the upper edge of the cone. In another embodiment there is no space closed at the top and no separate water tank, but the outer cone is of the same form. The valve is normally held closed by a weighted or spring-urged lever pivoted to the lower conical portion. A cylinder coaxially mounted inside the cone is open at the top, to which is attached by a flexible joint a wide funnel which receives the suspension. Straps spanning the funnel are attached to a central vertical rod fixed to the valve disc. When the sand level in the cone reaches the lower end of the cylinder, the level of the suspension in the funnel rises until the excess weight is sufficient to push the valve open.