GB843479A - Improvements in or relating to gas-turbine engines - Google Patents

Abstract

843,479. Shafts. ROLLS-ROYCE Ltd. April 2, 1958 [April 8, 1957], No. 11446/57. Class 80 (2). [Also in Group XXVI] In a gas turbine engine comprising a turbine rotor and a coaxial driven member, a reduction in the fuel supply to the engine on failure of the driving shaft and consequent relative rotation of the turbine and driven member is effected by the movement, relative to one end of the shaft, of one of a pair of mechanically interconnected members which are mechanically connected to the rotor assembly at opposite ends, respectively, of the shaft. Preferably the fuel supply is cut off by such movement. A rod 22 (Fig. 1) rigidly secured at one end to the turbine rotor 13a extends coaxially through the shaft 14 and has screw-threaded engagement with a sleeve 24 slidably mounted in a bush 25 and rigidly secured to a tube 26 extending through the compressor rotor 10a. The tube 26 is secured to a cross-member 26a having radial fingers 26b which extend through axial slots 10h in the rotor shaft and are secured to the inner race of a thrust bearing 27. The mechanism 22-27 is normally inoperative, but in the event of a failure in the shaft 14 or rotor 10a the turbine rotor overspeeds and the consequent relative rotation of the rod 22 and the sleeve 24 causes the tube 26 and bearing 27 to move axially and actuate a linkage 28-31 which is connected to the outer race of the bearing 27 and which closes a shut-off cock 20 in the fuel pipe 18. Shut-off also occurs in the event of a failure in the turbine supporting bearing 32, when the turbine and the shaft 14, which is splined to the rotor 10a, move rearwardly and pull the rod 22 and sleeve 24 to actuate the linkage. In an alternative embodiment (Fig. 2) a sleeve 73 in screw-threaded engagement with the turbine stub shaft 72 is splined to a rod 75 secured at its other end to the compressor shaft 40b. Fuel supplied by a pump 52 passes to manifolds 56, 57 through pipes 54a, 54b and 55a, 55b, and a shut-off valve 58 normally held open (as shown) by a spring 65. Valve member 59 is linked by a cable 66 and bell-crank 68 to a plunger 69 biased to the right by a spring 71 serving to keep the cable taut. On failure of the driving shaft the sleeve 73 is displaced to the right by the relative rotation of the turbine stub shaft 72 and depresses the plunger which draws the valve member 59 to the shut-off position in which the land 59b closes the delivery pipe 55a and land 59a is between the pipes 54a, 54b, and diverts fuel from the pipe 54a to a return pipe 62. The pipe 54b then communicates through the space 60 and branch 55c with the pipe 55b, and fuel in both pipes drains out through the space 61 and pipe 63. The shut-off is also actuated by the failure of the turbine supporting bearing 50b. This arrangement may also be used in conjunction with the low-pressure stage of an engine having high- and low-pressure turbines mounted on coaxial shafts.