Patent GB-1015105-A (GB)
Title: Centrifuge
IPC: B04B1/20
Filed: 1964-05-21
Abstract: 1,015,105. Centrifugal separators. BIRD MACHINE CO. May 21, 1964 [May 24, 1963; May 8, 1964], No. 21075/64. Heading B2P. In a separator in which solids separated from a liquid are moved, by means of a helical blade conveyer 38, Fig. 1, rotating at a speed different from that of the separator bowl 20, axially along the wall of the bowl and radially inwardly to an axial opening communicating with a solids discharge chamber 12 at one end of the bowl, means are provided whereby, during operation, the level of the separated liquid is maintained radially inwardly of the solids discharge opening so as to provide hydraulic assistance to the movement of the solids within and from the separator bowl. The liquid-solids mixture is fed through a pipe 25 having an outlet portion 29 extending tangentially into a gutter-extension 24 of the bowl in the direction of rotation of the bowl. The mixture flows into the bowl through arcuate openings 27 in a supporting spider 21. The liquid is removed through a pair of radially extending conduits 48, 50 which terminate in scoops 78, 80, Fig. 3 (not shown), having their inlet openings opposed to the direction of rotation of the bowl 20, and which are enclosed by an annular chamber 46 extending from the conveyer hollow shaft 40 and provided with apertures 54, 56 in communication at different levels with the bowl interior, an annular flange 52 being interposed in the chamber 46 between the two conduits 48, 50. This arrangement enables liquids of different specific gravities, when present in the mixture, to be separately discharged. At the beginning of an operation, the liquid level in the bowl must be kept radially outwardly of the solids discharge opening to avoid discharge of the liquid therethrough. When solids have built up on the bowl wall, the conduits 48, 50 are radially adjusted so as to permit operation with the liquid level maintained radially inwardly of the solids discharge opening. To this end, the conduits 48, 50 are carried by hollow fittings 68, 74 communicating with discharge pipes 72, 76 and mounted on eccentrics 64, 70. The pipes 72, 76 are operatively connected through a bolt 94 and associated parts, Fig. 5 (not shown), and held fixed in any desired position by the bolt. Rotation of the bolt will cause the mouth of conduit 50 to move radially inwardly or outwardly. Pipe 72 (and hence pipe 76 which is rotatively fixed thereto by bolt 94) is rotated by means of a worm and worm wheel thereby causing conduits 48, 50 to move radially inwardly or outwardly. Instead of having radially adjustable scoops, the separator may be provided with an annular weir at one end of the bowl, the weir opening being adjustable to provide a change in the level of the liquid during operation. The separated liquid and solids may discharge at opposite ends of the separator. In another embodiment, for treating feed mixtures in which the solids will not form a compact layer between the blade tip and the bowl wall, an artificial layer of a substance such as gypsum or plaster of Paris is built up on the bowl wall before the level of separated liquid is brought radially inwardly of the solids discharge opening. To prevent washing away of this layer by the liquid, a metal ring is provided at the discharge opening, there being no clearance between the ring and the adjacent end portion of the conveyer. The separated solids are washed by liquid supplied at 85 to a pipe 77 from which the liquid discharges at 79 into the hollow shaft 40 and flows through nozzles 83 on to the solids. The washing liquid is removed through the conduit 50. The arrangement shown is particularly suitable to separate solids from liquids tending to foam, since back pressure can be applied to conduits 48, 50 to prevent foaming.