GB546509A - Improved method of and apparatus for determining the out-of-balance of rotors - Google Patents

Abstract

546,509. Testing balance of rotary apparatus. ARNOLD, R. N., and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. March 26, 1941, No. 4041. [Class 106 (ii)] The rotor surface is provided with a dark or light band to contrast with the remainder of the surface and is mounted in a vibrating system so that when the rotor is rotated to produce resonance, an incident beam of light is reflected from the rotor surface through an aperture also synchronously vibrated to produce on the screen an illuminated area which is a measure of the amplitude and a superimposed dark or light band the position and direction of movement of which gives the phase displacement between the reference position and the out of balance force. The rotor 1 to be tested is mounted with its axis vertically in brackets 2, 3 forming part of a frame 4 adjustable vertically in a main frame 5 of U-shape. A torsion bar 6 rigidly attached to one limb of the frame 5 is held at the other end in a bracket 7. By means of a screw release 8 the unsupported length "x" of the bar 6 can be adjusted The other limb of the U-frame 5 is fulcrummed by a leaf-spring fulcrum 9 on the stationary mounting 10. The frame 5 is extended transversely of the bar 6 to form a lever 12 carrying a light shield 13 formed with a horizontal slot 14. The periphery of the rotor has a highly-polished surface all round except for a reference strip of non-polished surface at one place for a reference point. The light and dark surfaces may be arranged oppositely. Light from a source 17 passes through a condenser lens 18 to the rotor surface and is reflected back through a condenser lens 19 and the slot 14 through an objective lens 20 to a screen 22. The incident and reflected beams are arranged to lie substantially in a plane passing through the rotor axis and perpendicular to the torque rod. With the rotor rotating and the torsional system oscillating at or near resonance, an image is produced on the screen 22 in the form of a band the depth "d" of which depends on the amplitude of the torsional vibration, the length of lever 12, and the magnification of lens 20. Superimposed on this is a dark line P indicating the reference band. The depth "d" is utilized as a measure of the amount of out-ofbalance while the position of the line P and its direction of movement are utilized to give the " phase of the out-of-balance.