Patent GB-1347565-A (GB)
Title: Apparatus for use in and methods of calibrating pick-up signals in balancing machines
IPC: G01M1/20
Filed: 1971-04-19
Abstract: 1347565 Balancing rotors BALANCE TECHNOLOGY Inc 19 April 1971 [24 Feb 1970] 22220/71 Heading G1N A calibration arrangement for a balancing machine of the type wherein a testpart is set up to be rotated on horizontal spaced-apart carriers, and displacement of the carriers is measured by transducers and wherein weight may be added at two axially-disposed correction planes, such a calibration arrangement provides firstly means for simulating a given unbalance at a correction plane by providing a signal representative of that unbalance and dividing in two components which are applied to vibrators positioned at the carriers, the ratio of the two components being related to the distances of the vibrators from correction planes, and secondly means for associating and combining the outputs of the transducers to give directly the unbalance ( and hence weight to be added or subtracted) at each of the correction planes. As shown a pair of stanchions 10 each support by flexible cables (22) Fig.4 (not shown) carriers 20, 20' having roller bearings rotatably supporting the end of a test rotor 30. Transducers 34, 34' provide signals representative of the displacements of their respective carriers. A vibrator 38, 38' is mounted at the rear of each stanchion 10 to shake its carrier 20, 20' during set up and calibration (as shown in Fig.4), these being electromagnetic vibrators capable of applying precise forces. A motor 60 rotates the rotor 30 by means of a belt 68. As shown in Fig.2 correction enlargements 81, 83 are disposed at planes 80, 82 which indicate axial positions at which weights may be added at a subsequent balancing operation. Reference planes 46, 46' refer to the planes of the bearing carriers, and the distances between these planes are A, B, C, as shown. The arrangement of the planes 46, 80, 82, 46' is also shown on a control panel Fig.5 (not shown). As shown in Fig.5a an oscillator 130 giving a sine wave output of precise frequency and amplitude feeds a plane separation circuit 132 and also one terminal of a stroke sync switch 104. The plane separation circuit 132 operates to provide signals to the vibrators 38, 38', to provide precise forces on the carriers 20, 20', that simulate precise unbalances in the correction planes, for example an unbalance of 0.8 inch ounces. The frequency of oscillator 130 is 12 c.p.s. whilst the rotor rotates at 720 r.p.m. The circuit 132 develops two signals whose ratio is determined by the values A, B, C, set in the circuit by potentiometers RA, RB, RC. Output signals from the transducers are fed to a nodal mixer circuit 140, which is arranged to mix the pick up signals in a particular manner to eliminate the effect in one of the correction planes 80, 82 for unbalance at the other. The output is fed via a phase shifter 150 and filter to a meter drive circuit 144 and thence to a meter 109. Also with switch 104 in the right position Fig.5a the filtered output is fed through a zero-crossing detector and a stroke trigger circuit 156 to power a stroke light 37. The phase shift circuit 150 is set in the factory so that the heavy spot on the rotor will appear at the top of the rotor during strobing operation to indicate where weight must be removed from. A calibration switch has 12 sets of contacts each set having 5 contacts and a wiper in each set, the wipers all being ganged together the first set is designated 1CS1, 2CS1, 3CS1, 4CS1, 5CS1; the twelfth designated 1CS12, 2CS12 etc. When for example, the switch is in position 3, then contacts are made at 3CS1, 3CS2, 3CS3 ---- 3CS12. In position 1, the arrangement is ready for balancing operations after set-up and calibration have been completed. Fig.6 (not shown) discloses the circuit 132 in detail 166 whose output is applied to the control potentiometer RC whose wiper provides a signal for an amplifier 170 in the feedback to the amplifier 166. Two control potentiometers RB, RA, are connected to contacts 2CS1 and 4CS1, and 3CS1 and 5CS1 respectively so that depending on the switch position either the output 176 or that of 174 will be connected to an amplifier 180. The output of amplifier 180 at terminal 182 drives the right vibrator 38'. It is also applied with the input at 160 to an amplifier 188 where a subtraction is effected so that the output at 190 which is applied to the left vibrator 38 is the difference between the input at 160 and the output at 182. The potentiometers RA, RB, RC are calibrated on the control panel 86 directly in inches, since their value relate to the distances A, B, C, referred to above. Assuming the distances A, B, and C are 10, 40 and 50 inches respectively, the operator may set these directly in the potentiometer dials, so that with an input E at 160, the outputs at 182 and 190 will be 1/5E, (or vice-versa depending on the position of CS1). In general when the input at 160 represents an unbalance of 0.8 inchounces, with contacts CS1 at 3CS1 or 5CS1, then the outputs at 190, 182 simulate an unbalance of 0.8 in ounces at plane 80. If the switch is at 2CS1 or 4CS1, this unbalance of 0.8 in ounces is simulated at the right hand plane 82. Fig.8 (not shown) discloses the connection of the circuit 132 to the vibrators 38, 38' through the sets of contacts CS2, CS3, CS4 and CS5, and suitable adjusted amplifiers. Fig.7 (not shown) discloses the nodal mixer 140 and utilizes the sets of contacts CS6 ... CS12, and potentiometers 88, 90, 94, 106, 108. As shown the circuit comprises an upper channel and a lower channel both feeding a common output 204. With the various switches in the positions shown in Fig.7 output from pickup 34' is applied directly across a resistor 210 whilst that from 34 is applied across potentiometer 90. The polarity of the signal 34 may be reversed by operating nodal switch 96. Operation of selector 122 to the L position puts the signal from 34 across fixed resistor 220 and that from 34' across potentiometer 88. Nodal switch 98 may reverse the polarity of this portion. In the upper channel then, the output developed at the wiper of 90, which is a function of the output from pickup 34' mixed with a portion from 34, is applied to the calibration potentiometer 92. A complementary signal is applied to the calibration potentiometer 94 in the lower channel. The position of the wiper in 92 (or 94) calibrates the meter so that a given amplitude corresponds to an unbalance in inch-ounces. The output from 92 is applied to a right correction radius potentiometer 108, as well as to the contacts of CS10. By dialing into this potentiometer 108 the radius in the correction plane that weight must be added, the meter will read directly the amount of this weight in ounces that must be added at this radius. Potentiometers 94 and 106 work similarly for the left correction plane. The output is amplified at 226 and by use of resistors 206 in conjunction with dial 120 Fig.5 (not shown) can give full scale deflections of 100, 10 or 1. Calibration involves movement of the various potentiometers so that the output of the right channel 200 is independent of unbalance in the left correction plane, and vice versa. The outputs of the channels then give the required corrections to be applied to their respective planes. The calibration is effected at stages as the ganged switches are moved through their 2, 3, 4 and 5 positions. After calibration the ganged switches are set to their 1CS positions and the appropriate dimensions A.B.C. are dialed in. The meter readings on 109 give the weights to be added at the selected radius. The angle at which the weight is to be added is determined by the angular position of the reference mark noted during strobing with the switch 104 in the right hand position. This angle may be "remembered" by setting the dial 112. Among alternatives postulated as possible are:- (a) correction planes outside the reference planes, (b) reference planes not at the position of the carriers, (c) weight being removed as well as added, (d) transducers of the seismic or Piezoelectric type.