GB791934A - Improvements relating to gas turbine shaft bearing and sealing assemblies - Google Patents

Abstract

791,934. Stuffing-box substitutes. GENERAL MOTORS CORPORATION. May 17, 1956 [May 31, 1955], No. 15394/56. Class 122 (5). A gas turbine shaft bearing and sealing assembly comprises a casing 22 having at its inner periphery a cylindrical cage 30 housing a sleeve 40 supported by the cage for axial movement but prevented from rotation and carrying a seal ring 41 urged by spring means 48 between the sleeve and the cage into sealing contact with a metal seal ring 19 fixed to the shaft 10. The casing 22 comprises inner and outer plates 26 and 27 separated by heat insulating material 28 and the space 37 between the casing and the first turbine wheel 11 is subjected to compressed air derived from the combustion chamber. The sleeve 40 is sealed to the cage by a piston-ring 42 housed in a groove 52 in the sleeve and bevelled, as at 54, Fig. 5, at its outer periphery to reduce the radially outward pressure on the cage due to the compressed air acting behind the ring. Ribs 46 on the interior of the cage engage notches in radial arms 45 on the sleeve 40. The carbon seal ring 41 is recessed at 56 and urged into sealing contact with the ring 19 both by the spring 48 and the air pressure differential across the sleeve which is located between the ring 19 and a flange 51 of a spacer ring 50 secured to the shaft. If relative movement, between the shaft and the cage, due, for example, to expansion when starting the turbine, tends to move the ring 19 away from the ring 41 and, due to the sleeve 40 sticking in the bore 43 of the cage, the rings are no longer in contact, the sleeve is urged towards the ring 19 either by the air pressure build-up between the flange 51 and the end of the sleeve or, if that is insufficient, by direct contact between the flange and the sleeve. The bearing 14 and the seal are lubricated, and the seal is cooled, by oil supplied through a hollow tie-bolt 60 passing through the shaft 10. The oil passes through a spacer 62, a radial passage 63 in the shaft to a groove 64 in the ring 19 whence it is distributed by passages and ports in the ring to the bearing, the face of the carbon ring 41 and the interior of the cage 40.