Patent GB-781771-A (GB)
Title: Improvements in or relating to axial-flow compressors and turbines
Inventor: MORLEY FREDERICK WILLIAM WALTO
IPC: F01D5/30
Filed: 1954-08-12
Abstract: 781,771. Turbine and compressor blade fixing. ROLLS-ROYCE, Ltd. Aug. 12, 1955 [Aug. 12, 1954], No. 23497/54. Class 110 (3). An axial-flow turbine or compressor has blades of the kind having a root-fixing portion 14, an aerofoil section blade portion proper 13 and an intermediate (or stem) portion 15 therebetween. According to the invention, separate platform members 18 are provided between pairs of adjacent blades to form the boundary of the working fluid passage therebetween and means are provided associated with each platform member to close off the space between the intermediate portions of adjacent blades so as to minimize the leakage of working fluid. The platform members are secured to the associated turbine or compressor structure by interengaging sliding features. In Fig. 1, the blade roots 14 are engaged in axial fir-tree section slots 11 formed in the rotor disc. The disc portions between the slots 11 are formed with T-section projections 17 and the inwardly-turned toes 20 of platform members 18 are engaged therewith. The platform members 18 are locked against axial movement and the spaces through the grooves 19 in the platform members are closed by means of plates 21 which engage grooves 22 in the rotor disc 10 and 23 in the platform members and which are prevented from dropping into the grooves 22 when in the operative position by engaging with the surfaces 24 on the adjacent blade roots. In a second modification, Figs. 5, 8, the platform members 18 have inwardly-turned toes 20 as before but are also formed with integral wall parts 25 which are of such circumferential length as to engage the intermediate portions 15 of the adjacent blades. The wall parts 25 close the passages between the intermediate portions of the blades and also prevent movement of the platform members from left to right, as seen in Fig. 8. Movement of the platform members in the other direction is prevented by means of locking-plates 26 which have central openings 30 which engage undercut lugs 28 formed on the rotor disc between blade root slots. The outer rim portions of the plates 26 engage circumferential grooves 27 formed on the under-surfaces of the platform members 18, while the inner rim portions 31 are bent into the groove 29 formed on the rotor disc, thereby retaining the locking- plate in position. In a third embodiment, Figs. 9, 10, the platform members 18 again have inwardly-turned toes 20 which engage T-shaped projections 17 on the rotor disc between the blade root slots. Each platform member is formed with a slot 50 terminating in a hole 51. A locking tab is engaged within the slot 50 and hole 51 and after assembly the end 53 of the locking tab is bent downwardly to engage the rearward face of the rotor disc 10 so as to prevent disengagement of the platform member in a forward direction. Disengagement in the opposite direction is prevented by means of a wall part 25 formed integrally with the platform member which engages with the forward face of the rotor disc. In a further embodiment, Figs. 11, 13, circumferentially-extending T-section projections 117 are formed on the rotor disc projections between the blade root slots, and the platform members 118 have inwardly-turned toes 120 which engage with the projections 117.