GB945777A - Improvements relating to gear noise measurement and the location of defective gear teeth - Google Patents

Abstract

945,777. Noise-measurement; cathode-ray tube circuits; saw-tooth generating circuits. AUSTIN MOTOR CO. Ltd. Sept. 14, 1962 [Nov. 2, 1961], No. 39207/61. Headings H3P, H4D and H4T. In an arrangement for the quantitative measurement of the noise produced by running a test gear 7 (Figs. 1 and 2), in mesh with a master gear 2 and also for locating any defective gear teeth, the sound emitted by the gear is picked-up by a microphone 13 and, after amplification, displayed on a cathode-ray tube 10 against a linear time-base which is synchronized by a pulse generating device comprising a pick-up coil 17 and a soft-iron slug 15 rotating with the test gear. The overall noise, which is displayed against an arbitary scale (Fig. 4, not shown), is produced by integrating the received amplified sound and for locating defective gear teeth the spikes produced by the (now only partially integrated) received sound are displayed against a scale (Fig. 3, not shown), the divisions of which correspond to those on a scale 22 associated with the test gear 7. Circuit details of the sound amplifier, the time base and the voltage supply arrangement for the cathode-ray tube are shown in Fig. 5. The sound amplifier comprises a pair of amplifying valves V1, V2A, followed by a rectifier circuit MR1, MR2 (including a partial integration circuit C7, R11) which produces a positively going signal with respect to the junction of R19, R20 for driving push-pull stages V3A, V3B D.C. coupled to the " Y " deflection plates SB of cathode-ray tube V7 the " Y " shift of which is controlled by potentiometer P2. In this condition the amplifier is employed for displaying the spikes produced by faulty gear teeth. When, however, the overall noise is to be displayed a large value integrating capacitor C8 is brought into circuit by switch 23. The time-base generator comprises an amplifier V4 (for the pulses induced in coil 17) producing a negatively going pulse which cuts-off a normally conducting valve V2B the resulting positively going pulse output from which is differentiated by C14, R29 and clipped by MR3 to remove the positively going " spike." The remaining negatively going " spike " triggers a Miller transitron V5 the saw-tooth voltage at the anode of which is supplied to push-pull amplifier V6A, V6B, D.C. coupled to the " X " deflection plates TB. The " X " shift is produced by varying the bias on the grid of valve V6B, the tube beam is blanked during fly-back by a negative pulse derived from the screen of V5 and the self-running frequency of the latter is adjusted by P3 to be slightly lower than the rotational frequency of shaft 6. An EHT supply of 610 volts for the cathode-ray tube V7 is produced by combining a - 430 volt supply derived from a voltagedoubler comprising C23 and MR7, MR8 with the + 300 volt supply (via MR5, MR6) employed for the amplifier and time-base circuit. The final anode FA operates at +180 volts and is supplied via equal value resistance R37-R40 from the anodes of the two push-pull amplifiers which arrangement ensures good focus since such voltage is the mean of those applied to the four deflector plates.