Patent GB-510835-A (GB)
Title: Improvements in or relating to a machine for separating liquid from solids
IPC: B04B11/08
Filed: 1938-10-14
Abstract: 510,835. Centrifugal separators. SHARPLES CORPORATION. Oct. 14, 1938, No. 29805. Convention date, Oct. 21, 1937. [Class 23] A mixture of solids and liquid is supplied to a centrifugal strainer separator over a weir extending axially along the bowl, and the circumferential uniformity of the solids deposited on the bowl is maintained by a spreader extending substantially throughout the axial extent of the bowl and bearing on the solids with a yielding pressure; the solids are removed by means of a scraper which can be moved into very close proximity to the screen. The frame 10 supports bearings 11, 12 in which the separator shaft 13 is mounted. The bowl 16, Fig. 4, carried by the shaft has a wall 17 with continuous circumferential grooves 31 from which a number of radial holes 32 pass through the wall. The filter screen 35, Fig. 13, has a number of widely-spaced axial strands 37 which are formed to curve about the closely-spaced circumferential strands 36. A piece of woven screen is formed to the desired shape and adjacent ends of strands 36 are welded to form continuous circumferential bands of such size that the screen fits snugly in the bowl. With this construction, a solid particle which is small' enough to be caught in the mesh can readily escape to the inner surface of the bowl so the screen is self clearing. The back of the screen forms a series of axial channels which conduct the liquid to the grooves 31 and the holes 32 for discharge into the casing 24. The mixture is fed to the bowl through a conduit 42 and the rate of feed is controlled by a pneumatically operated valve 43, Figs. I, 17. From the conduit 42 the mixture passes to the feed tube 44, Figs. 6, 8, which extends axially into the bowl and is provided along its under side with a slot 46. The sides of the slot consist of walls 47, 48 which form weirs over which the material is supplied along the full length of the bowl. A drain hole 45, Fig. 6, is provided in the feed tube 44 at a position outside the bowl, so that when the valve 43 is closed to stop the supply of material, the feeding of the charge into the bowl stops abruptly as the level in the feed tube drops below the level of the slot walls 47, 48; the material then drains from the tube through the hole 45 to the casing 24. Rinsing liquid can be supplied through the conduit 52, Fig. 1, subject to control by a solenoid operated valve 54. A spreader plate 55, which has a boss 58, Figs. 5, 11, secured to a shaft 56 by set screws and a key, has at its free edge a plate 61 preferably serrated. This plate is inclined to the bowl wall and extends the full length of the wall to assist in distributing and levelling the solid particles deposited. The spreader is held in contact with the cake of solids under light pressure by a pressure fluid device. The shaft 56 is connected by a linkage to the horizontal shaft section 72 of a bell crank lever 71, Fig. 9, which has a roller 77 engaging an abutment 78 on the upper side of the piston 69 in a cylinder 66. Pressure fluid is supplied to the cylinder through a port 84, and its discharge from the lower part of the cylinder is controlled by a needle valve 86. As the cake of solids builds up and the spreader 55 moves away from the bowl wall the bell crank lever moves the piston 69 downwards; the rate of this movement is determined by the needle valve 86 which can be set to maintain the spreader in contact with the cake. A pressure relief valve 82 is mounted in a passage 81 through the piston and the outlet 79 from the cylinder is arranged above the piston. The rod 93, Fig. 17, is linked to the spreader 55 through a lost motion connection and this rod opens the valve 185 to cause the feed valve 43 to close and thereby stop the supply of material to the bowl. The discharge scraper 96, Figs. 5, 16, has a cutting edge 97 arranged above a shoot 98 which conducts the solids outside the casing. The scraper is carried by arms 112, 113 on a non-rotatable shaft 114 which can be longitudinally adjusted in a boss 115. The boss itself can be moved to adjust the radial position of the scraper 96 by means of the fluid pressure cylinder and piston 119, 120. The extreme cutting position of the scraper and boss is controlled by a limit switch 123. When the scraper is withdrawn from its cutting position, the ends of the scraper fit against the ends of the shoot so that the apparatus is vapour-tight. The various steps in the operation of the machine are controlled by a rotary drum 130, Fig. 17, having contacts 156, 177, 188, 195. The closing of the main switch 153 energizes the solenoid 151 which operates the toggle levers 148 to lift the spindle 134 of the rotary drum 130 thereby throwing in the clutch 147 so that the drum can be rotated by the time control motor 135 the circuit of which is completed by the engagement of contacts 156, 157. The feeding valve 43 is held open by the pneumatic motor 165 as long as the contacts 177, 178 are in engagement. When the cake of solids reaches the desired thickness, the valve 185 is opened by the linkage associated with the spreader 55 and this permits the spring 173 to close the valve 43. Alternatively this closure is obtained when the contact 177 leaves the contact finger 178. The engagement of the contacts 188, 189 next occurs, and this causes the operation of the valve 54 for the supply of rinsing water while the engagement lasts. The engagement of the last pair of contacts 195, 196 causes the operation of the scraper mechanism so that the scraper 96 is fed towards the bowl wall until its movement opens the limit switch 123. The scraper returns under gravity to its inactive position and the cycle of operations is thus completed. While the limit switch is open the solenoid 151 is de-energized, the clutch 147 is disengaged and a spring returns the control drum 130 to its initial position.