Patent GB-417595-A (GB)
Title: Improvements in and relating to apparatus for the decantation of liquid and concentration of mud or sludge
IPC: B01D21/00
Filed: 1933-03-06
Abstract: 417,595. Gravity-separation apparatus; governors; valves. COMPAGNIE INDUSTRIELLE FRANCO-AFRICAINE, 3, Rue de Messine, Paris. March 6, 1933, Nos. 6803 and 6804. Convention dates, March 16, 1932 and Aug. 6, 1932. [Class 46.] Mechanism for driving rotating rakes or like stirring devices in apparatus for the decantation of liquid and concentration of mud or sludge comprises a screw and nut or like members with engaging helical surfaces, one of which, when the load becomes excessive, is moved axially and thereby operates means for reducing the load to normal. The invention is described as applied for driving rotary agitators in settling tanks or sand-washing apparatus, the arrangement being such that when the accumulated sediment creates excessive resistance to the movement of the agitators, the device causes the agitators to rise or opens a sediment outlet valve. The rotary shaft 2, Fig. 1, of an agitator 19 in a settling tank 18 is supported by an externally-threaded socket 25 and driven by a motor 22 through epicyclic gearing in a casing 3 which supports the motor and is free to turn on the shaft 2. When the agitator encounters excessive resistance the casing 3 is caused by the reaction to rotate and communicates this motion by means of a connection 27 to the socket 25, which is thus screwed upward in a nut and lifts the shaft 2, so that the agitator is raised to a position in which it encounters less concentrated sediment. The weight of the gearing assisted by counterweights 14 or springs connected to opposite points of the casing 3 by cables 12 resists the upward movement of the shaft and causes it to return to its normal position. The driving gear shown in Fig. 3 is similar to that shown in Fig. 1, but the shaft 21 of the agitator 19 is hollow and the spindle 40 of a sediment valve 10 passes up through the shaft and is supported at its upper end by a nut 26 engaging a screw 25 fixed to the casing 3. The spindle 40 is keyed to turn with the shaft 21. When excessive resistance causes the casing 3 and the screw 25, which are fixed axially, to rotate, the nut 26, which is held against rotation rises and lifts the valve 10 from its seating. Fig. 7 shows a sand-washing vessel to which sand and clean water are supplied through inlets 51, 52 respectively, dirty water passing away through openings 53 to an outlet 54 and clean sand falling to the bottom. The spindle 49 of the sand-discharge valve 10, to which blades 46 are attached, is rotated by a motor 531 through worm gearing 51<1> carrying a nut 26 which engages a screw 25 fixed to the spindle 49. Normally the nut 26 and screw 25 rotate together, the weight of the spindle and attached parts assisted by weights 50 balancing the vertical component of their mutual reaction. When excessive resistance is encountered by the blades 46, the weights are overpowered and the screw 25 rises and opens the valve 10. In a somewhat similar form of apparatus the screw 25 is the driving element and the nut 26 is fixed to and supports the spindle 49. The Specification as open to inspection under Sect. 91 comprises also an arrangement in which a motor 33, Fig. 3 (Cancelled), is fixed on a casing 31, which supports the shaft 2 by means of a ball race 34 and is fixed to a screw 25 engaging in a fixed nut 26. The epicyclic gearing includes a spur wheel 7 loose on the shaft 2 and held against rotation by an arm 27 carrying a roller which travels on a vertical rail 29. A band brake can be applied to the cage 24 by a crank handle 37 supported on the arm 27. The brake application being the equivalent of excessive load resistance will cause the shaft 2 to rise, when desired, for inspection purposes. Fig. 10 (Cancelled) shows a further modification, in which a screw 25 driven by a nut 26 supports a shaft 2 which it rotates by means of epicyclic gearing. This subject-matter does not appear in the Specification as accepted.