GB1370362A - Sealing arrangement - Google Patents

Abstract

1370362 Shaft seals STAMICARBON NV 30 Nov 1971 [1 Dec 1970 (2)] 55580/71 Heading F2B In a sealing arrangement for a rotary shaft 102, Fig. 1, where it extends through a wall 101 comprising a rotor 103 surrounded by a stator 106, one or more helical grooves 108 provided in the rotor or stator whereby a sealing pressure is created in a fluid contained in the space between the rotor and stator during shaft rotation and means 110 for sealing the shaft when it is at rest, the stator or rotor has at or near at least one end a shoulder 109 extending toward the rotor or stator and the stator is supported from the wall by a flexible sealing member, e.g. O-ring 107. The shaft 102 is the driving shaft of a liquid ring compressor and has the rotor 103 secured thereto; the stator being prevented from rotation by a pin 112. The sealing fluid, which may be the fluid being pumped, is pressurized by the thread 108 to oppose leakage during normal rotation of the shaft. In the embodiment shown in Fig. 2 for the shaft 202 of a viscous material extruder, a sleeve 203 on the shaft has threads 207 and 208 of opposite hand separated by a space 209 and has adjacent each end a groove housing a composite sealing ring 206 formed by an outer P.T.F.E. ring and an inner rubber ring. On each end of the sleeve 203 a shoulder is provided by a thin layer 205, e.g. of molybdenum. A stator sleeve 210 surrounding the sleeve 203 is axially movable on rods 211 having heads secured in a ring 213 abutting a ring 214 and secured by a ring 215 and bolts 216 to the wall 201. The sleeve 201 is sealed to rings 213 and 214 by 0-rings 222 and 221 respectively and biased towards the wall by springs 225 surrounding the bolts 211 and loaded by nuts 227. A space 220 between rings 213 and 214 communicates through bores 224 and a'pressure chamber 223 in the sleeve 210 with the space 209. Sealing liquid, e.g. silicone oil, is supplied through a channel 230 and excess is discharged through a channel 229; 231 is a vent screw. When the shaft rotates, fluid pressure created in space 220 due to the pumping action of threads 207 and 208 moves the sleeve 210 away from the wall to the position shown determined by stop rings 208 on the rods and the shaft is sealed by the sealing fluid. When the shaft stops the pressure in space 220 falls and the sleeve 210 is returned by'the springs 225 towards the wall, leakage then being prevented by the sealing rings 206 engaging the inner surface of sleeve 203. In a further embodiment, Fig. 4, for a pressurized reactor, the agitator drive shaft 402 is rotatably mounted in a housing 403 secured to the vessel wall 401 by a seal housing 403. A stator sleeve 417 surrounds a helically threaded portion 418 of the shaft and is sealed at one end to a spacer 410 by an 0-ring 419 and at its other end to the housing 403 by an 0-ring 420, which latter end also carries a further O- ring 430. Alternatively, the thread may be on the inner surface of sleeve 417. The space between the sleeve 417 and the shaft communicates through passages in spacer 410 with a feed pipe and through a bore 423 with the space 424 between the sleeve and the housing 403, the space 424 connecting with a discharge bore 425 in the housing. A ring 427 rotatable with and slidably sealed to the shaft by an 0-ring 429 carries a metal ring 431 co-operating with another metal ring 432. Pipe 415 and bore 425 are connected to a vessel containing sealing fluid, e.g. silicone oil, and, when the shaft is rotating the pressure of the sealing liquid caused by the thread 418 is controlled by a valve 437 which may be set by a control 441 to be at a constant difference above that of the fluid in the sealed vessel, leakage of the sealing liquid to the vessel being prevented by the face seal rings 431, 432. When the shaft stops the pressure in the vessel moves the ring 427 into sealing contact with the 0-ring 430.