Patent GB-695557-A (GB)
Title: Improvements in or relating to apparatus for controlling axial shaft displacement inrotary machines
IPC: F01D21/08
Filed: 1950-03-03
Abstract: 695,557. Turbines. ASKANIA-WERKE AKT.- GES., and SANNER, W. C. March 3, 1950, No. 5505/50. Class 110(iii) [Also in Group XXIX] In an apparatus for preventing damage due to axial displacement of a rotating shaft in an impeller wheel machine such as a steam turbine, by axial loading thereof, a sensing member 2 is positioned to sense the axial position of the shaft and when the axial displacement of the shaft exceeds a permissible value actuates a device for relieving the shaft of axial load, a pressureoperated power relay being arranged between the sensing member and the load relieving device and being constructed to magnify the displacement of the sensing member. The surface 28 of the sensing member leans against a radial surface on the shaft (not shown) and at its other end bears against a lever 3 mounted on a blade spring 4, the lever bearing against the piston rod 5a of the control piston 5 which slides in the reset sleeve 6. The sleeve 6 has a pin 12 which bears against the inclined surfaces 40, 41 on the reset rod 13 which is attached to the operating piston 9 and piston rod 11, the piston being loaded by a spring 10 and the movement of the piston. being measured by the indicator 24 which is marked in units of shaft displacement. Pressure fluid is led through the conduit 18 to the sleeve 6, and a branch leads to a bore in the sensing pin 2 so that a film of fluid lies between the pin and the shaft to prevent wear. If axial displacement of the shaft causes the pin 2 to move in the direction of the arrow 39, the movement is communicated to the piston rod 5a and piston 5 by the lever 3, and pressure fluid flows through the conduit 20 to beneath the piston 9 which rises against the force of the spring 10, the pressure of the fluid being indicated on the gauge 22a which may also be graduated in terms of shaft displacement. As the piston 9 and reset rod 13 rise, the pin 12, bearing against the inclined surface 40, and the reset sleeve 6 are moved to the right through the force of the spring 8 so that the sleeve follows the movement of the control piston 5, and the control ports to the operating piston 9 close and the piston stops. If the sensing pin 2 has moved so, far that cutting out of axial load is necessary,: the pin 12 is positioned at the junction of the two inclined surfaces 40, 41 so that upon further movement of the sensing pin to the right, the reset sleeve is moved to the left by the upward movement of the surface 41 acting against the pin 12. The flow of fluid to the operating piston 9 is then such that the piston moves rapidly to its upper end position and in so doing, the intermediate element 32 comes into contact with the rod of the second control piston 31 which is moved against its spring so that pressure fluid passes through the pipes 30, 33 to the second operating piston 34 which moves suddenly to its end position and operates the actuator 37 of the overspeed governor. This governor may be tripped independently by the manually operable knob 38. The operation of the apparatus may be tested by means of the adjusting spindle 14, downward movement of which rocks the bell-crank lever 15 about the pivot 16 against the spring 17 which moves the lever 3 and so operates. the control piston 5, the rod 5a lying at the centre of the lever 3 so that a given movement at the upper end of the lever simulates equal movement of the sensing pin 2 and so of the shaft. The device for relieving the shaft of axial load may be activated directly by the operating piston 9 or by the fluid pressure beneath the piston 9. The shaft movement may be recorded.