GB783118A - Bearing assemblies for supporting rotary shafts - Google Patents

Abstract

783,118. Stuffing-box substitutes. NAPIER & SON, Ltd., D. March 9, 1956 [March 25, 1955], No. 8861/55. Class 122 (5). [Also in Group XXXIV] A vertical shaft 11 is supported by a ball or roller bearing 21 in a housing 24 and oil supplied to the bearing is prevented from running down the shaft by an air current sealing- arrangement which includes a scavenge pump for drawing off the oil and air mixture. An annular trough 36 is attached to the housing 24 below the bearing 21 and extends inwardly so that its inner side wall, provided with inwardly-directed ridges 40, lies close to a sleeve 34 on the shaft 11 and forms a labyrinth seal therewith. An inverted cup member 35 is attached to the shaft below the bearing and its downwardly-extending side wall overlaps the wall of the trough with clearance. Oil delivered through a conduit 44 and restriction 45 passes through nozzles 47 to the bearing 21. The housing 24 is surrounded by an air-tight casing 48 in which are formed annular passages 49 and 50 communicating with a common chamber 51 to which compressed air is admitted through a passage 52. Compressed air from the passage 50 enters an annular chamber 54 from which it can leak downwardly through a labyrinth seal 41 and upwardly through labyrinth seal 40 to trough space 38. Similarly compressed air from the passage 49 leaks upwardly through a labyrinth seal 42 and downwardly through labyrinth seal 43 to an annular space 55 above the bearing 21. The oil/air mixture in the trough space 38 is drawn off by a scavenge pump through an aperture 56 into a chamber 57 and thence through a pipe 58. The invention is applied to the lower bearing 21 of a shaft 11 of a vertically mounted combustion turbine power unit for a helicopter, the general arrangement of which is shown in Fig. 1. The power unit comprises an axial flow compressor 10, a compressor turbine 12 and a power turbine 14 which drives the helicopter rotor 17. The upper bearing 22, shown in Fig. 3, is a modification of the bearing 21 in which compressed air is supplied to a space 82 between the upper surface of the power turbine disc 14 and a lower wall assembly 83 below the bearing 83. Some air leaks outwardly across the turbine disc for cooling it and escapes through a labyrinth seal 84, and some air leaks upwardly through labyrinth seals 70, 71. To prevent excess pressure building up beneath the bearing a by-pass consisting of a groove 92 in the shaft connects the interior of an inverted cup member 74 with a point above the bearing. Specification 761,442 is referred to in the Provisional Specification.