GB1192221A - Method and Apparatus for Determining Out-of-Balance Masses in Rotary Bodies. - Google Patents

Abstract

1,192,221. Testing balance. TECALEMIT (ENG.) Ltd. Jan. 19, 1968 [Jan. 19, 1967], No.2984/67. Heading G1X. A method of determining the magnitude and/or position of an out-of-balance mass in a rotary body e.g. a vehicle wheel utilizes the fact that where a rotating body oscillates along a linear path due to an out-of-balance mass, the two points disposed along a line at right angles to this linear oscillation and at a radial distance from the axis of rotation equal to one half of the amplitude of the oscillations, will respectively execute a rectilinear oscillation at right angles to the oscillations of the body for one point and for the other point movement in an ellipse having its major axis in line with the body oscillations this movement being greater than that of any other point at the same distance from the rotational axis of the body, so that by measuring the direction and/or amplitude of the movements of one or both of these two points, the position and magnitude of the out-ofbalance mass can be found. In Fig. 5a is shown a device comprising a shaft 1 mounted for rotation with a vehicle wheel 4, and for pivotal movement about a vertical axis 3 passing through the inner rim 5 of the wheel. A number of equal length pins 6 project from the shaft 1 and are arranged in a helix round the shaft each pin being opposite a pivoted finger 7 movable in associated slot 8 in a plate 9. In operation the vehicle wheel is rotated and then allowed to run down in speed. As it passes through its speed of resonance due the presence of an out-of-balance mass the pins 6 will push the fingers 7 along their slots the maximum displacement being effected by that pin 6 extending in a direction parallel with the major axis of the maximum displacement ellipse as referred to above. By relating this pin 6 to the wheel 4 the position of the out-of-balance mass can be determined, and the magnitude of the mass may be read off from scale lines 12. If desired the pins 6 may be replaced by a continuous helical rib and the fingers 7 may displace a pivoted bar carrying an indicator co-operating with scales marked on a drum, the scales being selected as those appropriate to the balance weights required for wheels of different sizes. Alternatively, the movement of the bar may be indicated by the lighting of one of a row of lamps using suitable electric contacts and the finger 7 which has been moved to the greatest extent may also be indicated electrically. An adapter for holding wheels of different sizes with four or five stud fixing, and employing pivoted fingers carrying screw-threaded pins is described and also an adapter for wire wheels. The wheels may be statically balanced after the dynamic balancing described by attachment of weights to the inside rim of the wheel. A friction damper is also described for damping the oscillations of the shaft 1 and this is designed with a last motion connection so that is only becomes effective for outof-balance masses above a predetermined maximum. In Fig. 15 is shown a device which may be used for determining inbalance of a wheel on a vehicle and this comprises a plate 120 adapted to be fixed to the vehicle wheel and having radial rams of differently coloured spots of different sizes marked thereon. A distinctive central spot is also marked, and the spots in each radial row have the same colour. The wheel is spun and the length of the coloured line traced by the control spot is noted at the resonant speed. At this speed one of the coloured spots will also be executing linear movement at right angles to the line described by the central spot and by noting this colour the position of the out-of-balance mass can be determined. Other visual methods described employ the use of a single spot on a plate and a stepped conically tapering member having differently coloured bands marked thereon. Also described is a method using a number of screw threaded rods disposed parallel to the wheel axis and carrying units which are displaced along the screw threads by a resilient member engaging those nuts at the point of maximum displacement driving wheel oscillations, the length of the movement of the nuts being indicative of the magnitude of the out-of-balance mass and the particular nut which has the greatest displacement being indicative of the effective position of this mass in the vehicle wheel.