A variable stator vane arrangement for an axial flow compressor

A plurality of stages of variable stator vanes are operated by respective control rings 34, 36, 38, 40, 42. The vanes in each stage are connected to the control rings 34, 36, 38, 40, 42 by operating levers 44, 46, 48, 50, 52. An axially extending member 64 is connected to each control ring 34, 36, 38, 40, 42 by operating links 54, 56, 58, 60, 62. The member 64 is arranged in a plane substantially tangential to each control ring and is movable in the plane substantially tangential to the control rings to change the pitch of the variable stator vanes. Hydraulic rams 66, 68, ball screw actuators or electric stepper motors are provided to move the member 64, and the actuators may be operated to give proportional, or non proportional movement of the variable stator vanes. A controller 94 may use signals from position detectors 78, 80 positioned on the control rings or position detectors 86, 88 positioned on the hydraulic rams together with compressor parameters to control the positions of the vanes. The member 64 may be inclined to axial direction (Fig. 3), formed with steps (Fig. 4) or curved (Fig. 5)