Patent GB-398579-A (GB)
Title: Improvements in classifiers
IPC: B03B5/58
Filed: 1932-04-25
Abstract: 398,579. Gravity-separation apparatus. DORR CO., Inc., 247, Park Avenue, New York, U.S.A. April 25, 1932, No. 11816. Convention date, May 29, 1931. [Class 46.] In apparatus for classifying particles of different specific gravities comprising a bowl classifier superposed on a secondary compartment which is preferably a rake classifier of the Dorr type, independent passages or conduits are provided, preferably arranged concentrically, for the heavy material passing from the bowl to the secondary compartment and for the liquid carrying fine particles in suspension rising from the secondary compartment into the bowl. A fluid jet is preferably provided to break up any congestion occurring in the communication passages and means are provided for automatic regulation of the supply of washing liquid to the secondary compartment. A bowl classifier 1 with rotating rake arms 3 and overflow weir 5 is superposed on a secondary compartment 2 of the known Dorr type, having a reciprocating rake 7 for removing the heavy constituents. The bowl is formed near the apex with a horizontal floor 32 having a central flared member 33 forming an outlet from the bowl to the secondary compartment. Concentrically arranged within the flared member 33 is a tubular member 16 with a flared lower end 31, the member being made in two parts 19, 20, Fig. 4, joined by a nut 21 so that the length of the member 16 can be varied. The upper part 19 which terminates at about the level of the overflow 5 of the bowl is attached to the hub portion 22 of the bowl rake and is surrounded by a cylindrical ring 23 having apertures 28, also attached to the hub 22. A baffle-plate 24 spaced from the upper end of the member 16 and connected by bolts 25 to the hub 22 is attached to a rotating shaft 26 by which the rake arms 3 and associated parts are driven. A tubular member 30 depends from the baffle-plate 24 and accommodates an upwardly extending pipe 29 through which compressed air may be passed, the supply being controlled by the movements of a float 40 in the secondary compartment 2. Washing liquid is supplied to a T-shaped trough 35 mounted over the compartment 2, the transverse head having perforations to deliver liquid evenly into the compartment. The supply pipe is provided with a valve controlled by the movements of the float 40. Pulp is supplied to the space within the ring 23 and passes out through the apertures 28 into the bowl where the fine particles flow over the weir 5 and the heavier particles are moved to the centre by the rake arms 3 and pass into the compartment 2 through the annular space between the member 33 and the member 16. The heaviest constituents settle and are removed by the rake 7 while intermediates are returned to the bowl by the upward flow of liquid between the member 16 and the tubular member 30 issuing into the space within the ring 23. If congestion occurs the level of liquid in the compartment 2 rises and the movement of the float cuts off the liquid supply and at the same time opens the air valve to allow air to pass to agitate the suspension and remove the congestion.