1341703 Centrifugal separator M S E HOLDINGS Ltd 19 April 1971 [6 April 1970] 16271/ 70 Heading B2P A centrifuge, e.g. for clarifying fluid from machine tools, comprises a centrifuging chamber 34, an inlet, e.g. stationary tube 1, to the chamber, a chamber by-pass 15 communicating with the inlet, and sensing means 25 for sensing flow in the by-pass. The arrangement is such that building up of centrifuged material 40 in the chamber 34 will constrict communication (through inlet passage 41 as shown) between the inlet and the chamber such as to cause a flow from the inlet to the by-pass, which flow will increase with increasing constriction, the sensing means being operable to sense when a predetermined value of flow is reached in the by-pass. A draw bar 2 axially displaceable by a hydraulic actuator extends through the inlet tube 1 and rotatably supports by means of bearings 6 at its lower end a wall member 3 which is also supported by a rubber bearing 7 on the tube 1 and which carries seals 4, 5 at its periphery. The inner conical surface of the member 3 carries vanes 8 which support a tubular member 9 which is splined or keyed at 10 to a tubular portion 11 of a first rotatable structure 12 of the centrifuge. Instead of the splined or keyed coupling the structure 12 may carry pins 23 engaging in apertures 24'in the wall member 3. The structure 12 is mounted by bearings 13, 14 on the tube 1 and is continuously driven from a motor via a belt drive 21. The lower portion of the structure defines with the tube 1 the by-pass passage 15 which communicates with an outlet 16 containing impeller vane 17. The lower end of the structure has a frusto-conical portion 18 having a ring 19 to engage seal 4 and define with member 3 a centrifuging chamber 22 containing one or more separating discs 45. An ultrasonic sensor 25 is mounted in the by-pass passage 15 and emits a signal when appreciable flow exists therein. A second rotatable structure 26 is mounted on the first structure 12 by bearings 27, 28, its lower portion constituting a centrifuge bowl 29 having an aperture 30 at its lower end, an outlet 31 containing diffusion vanes 32 at its upper end, and one or more helical ribs 33 on its inner surface. The bowl 29 defines with the structure 12 a main centrifuging chamber 34 containing vanes 35. The structure 26 is driven from the motor shaft via a controllable, e.g. electromagnetic, clutch and a belt drive 37. A brake disc having braking means 39 is carried by the structure 26. Braking may also be effected in the drive, e.g. by an electromagnetic brake/clutch. Both types of brakes are operable in response to the sensor signal. In normal operation ,the centrifuge is in the condition illustrated at the r.h.s. of the figure with the structures 12, 26 rotating together at the same speed with the seal 5 carried by the member 3 closing the aperture 30 of the bowl 29 Fluid to be cleaned passes from the tube 1 into chamber 34 where sludge 40 separates out on the inner wall of bowl 29 whilst clarified liquid passes through outlet 31. When the build-up of sludge eventualy constricts inlet passage 41 to chamber 34, some fluid will flow through by-pass passage 15 causing the sensor 25 to emit a signal which operates a relay to initiate a discharge operation. The drawbar 2 is first lifted to bring the seal 4 carried by member 3 into contact with ring 19, thereby sealing off chamber 34, l.h.s. of figure. Centrifuging continues in chamber 22, the clarified liquid passing from outlet 16 to outlet 31 and drawing off excess fluid from chamber 34. The clutch is then operated to remove drive from structure 26 and the brake 39 is operated to brake the bowl 29 thereby ejecting sludge downwardly through the now-open aperture 30.