Patent GB-509020-A (GB)
Title: Improvements in hydraulic classifiers
IPC: B03B5/62
Filed: 1938-01-08
Abstract: 509,020. Fluid-pressure servomotor-control systems ; wet-separating. STOKES, R. O., and THOMAS, W. D. J. Jan. 8, 1938, No. 645. [Class 135] [Also in Group II] In a hydrautic classifier of the hindered settling type having a valve for continuous discharge of the settling solids the degree of opening of which is dependent on the effective head of the settling solids, the control is effected by the provision of a chamber subjected to hydraulic pressure, an operating connection between the valve and part of the wall of the chamber which is movable in response to pressure changes, means for retarding the movement of the part of the wall, and means for varying the hydraulic pressure in the chamber in dependence on the effective head of settling solids. In the form shown in Figs. 1 and 2 the classifier I is supplied with water from a constant level tank by a pipe 7, the water entering the compartment 4 beneath the perforations 3. The heavier solids are discharged continuously through a tube 10, the discharge being controlled by the valve 9. To vary the position of the valve according to the depth of settled solids there is provided a chamber 13 supplied with water under constant head through an inlet 32 connected to the chamber by a constricted helical groove 34. The bottom of the chamber is formed by a diaphragm 14 which is acted on by a spring 23. A tube 27 depends from the diaphragm 14 and terminates in a spherical valve 28 having a passage 29 to allow escape of water from the tube 27, the valve 28 being connected at 31 to the stem 18 of the classifier discharge valve 9. The seating. 25 of the valve 28 is carried by a diaphragm 12, pressed downwards by a spring 21, which forms the top of a chamber 11, which communicates with the classifier by a tube 17 and has an upcast pipe 26 surrounding the tube 27. When the pressure in the classifier increases owing to the increasing depth of settled solids, water rises in the tube 17, the pressure in chamber 11 is increased and the diaphragm 12 rises against its spring thus raising the seating 25 from the valve 28. The flow down the tube 27 is thus increased, the pressure in chamber 13 is reduced, the diaphragm 14 rises and lifts the tube 27, the valve 28, and the valve stem 18, thus opening further the discharge valve 9. The raising of the valve 28 reduces the flow of water from tube 27 and re-establishes equilibrium. Instead of being placed above the classifier as shown in Fig. 1 the control device may be placed to the side of. the classifier, the valve stem 18 being connected to the diaphragm by a double lever arrangement, or a ball valve opening downwardly may be used for the classifier discharge with the stem connected by a single lever to the diaphragm. This last means is shown in Fig. 5 which also shows a modification of the control device in which the pressure on the diaphragm 14 is balanced, instead of by a spring, by the pressure on a smaller diaphragm 55 forming the top of an annular chamber connected directly to the water inlet 32. Fig. 6 shows a modification of the valve mechanism for relieving the pressure in the chamber 13. The diaphragms 55 and 14 are connected by the members 57, 60, the latter being hollow and being connected to the member 59 which carries the tube 27. The interior of the member 60 communicates with the chamber 13 by passages 61, passage of water down the tube 27 being normally substantially prevented by a spring- pressed valve 62. This valve is raised when pressure increases in the chamber 11 by a rod 64 attached to the tube 26 carried by the diaphragm 12. In Fig. 7, the diaphragm closing the top of the chamber 11 is stiffened so that it has two annuli of flexure, one at the periphery and the other at the centre, the central part of the diaphragm being directly connected to the diaphragm 14 by the tube 27. On increase of pressure in 11, the annulus of the diaphragm intermediate the centre and periphery rises, and opens a valve 69 at the bottom of the tube 27 through levers 67, the inner ends of which enter grooves in the valve head. In the form shown in Fig. 8, the diaphragm 14 forms the top of the chamber to which liquid is forced by the increasing pressure in the classifier, the bottom of this chamber being formed by the diaphragm 75. The diaphragms 14 and 75 are forced upwardly by springs 78, 21 respectively, the upward movement of the diaphragm 14 tending to close the classifier valve 9. When diaphragm 75 is forced down by pressure in the chamber between the diaphragms, the opening between valve 83 and its seating 82 closes, pressure increases in chamber 13, causing the diaphragm 14. to move downwardly and open the classifier valve. The valve 83 &c. may be replaced by a valve similar to that shown in Fig. 7.