GB605281A - Devices for the adjustment of electrical circuits - Google Patents

Abstract

605,281. Tuning tools for adjusting radio apparatus. COSSOR, Ltd., A. C., and BELL, D. A. Nov. 27, 1945, No. 31962. [Class 40 (v)] A trimming tool for rotatable tuning elements has a tool-head which is driven both with a continuous movement in either direction and a slight oscillatory movement. Such a tool used in the arrangement shown in the Figure will automatically adjust a circuit to resonance. Radio receiver 1 which is to be lined up has an amplitude modulated signal fed to its input terminals from generator 3. The modulation output is rectifed in circuit 5 and the resulting D.C. potential is connected by means of distributer 7 to the grids of valves 8 and 9 alternately, to control their gain. The grids are also driven in push-pull by a 50 c/s. supply from transformer 10 and since the anodes are connected in parallel an output results which depends in magnitude and sense on the relative gain of the two valves. This output after passing through amplifier 22 is used to drive motor 12 which in turn drives tool-head 11 through epicyclic gear 14 in a direction appropriate to the sense. A second distributer 21 driven synchronously with the first applies power alternately to the solenoid windings 19, 20 to cause core 18 to vibrate springy strip 17. This vibration is communicated to lug 16 carrying the " fixed " element of the gear and thus gives the tool head the oscillating movement. Since the distributers are synchronized, when the tool oscillates to one side the grid of valve 8 is connected to the output of detector 5 and when it oscillates to the other side the output is connected to valve 9. Thus, when the oscillating tool head is engaged with a mistuned trimmer, an unequal bias is applied to these valves, and the resulting 50 c/s. output causes the motor to drive the tool in the correct direction until the " on-tune " point is reached when the differential output of the two valves is zero and the motor stops. In one modification, the oscillatory movement is produced by rocking the intermediate wheel of a differential gear. In another modification, distributer 21 is replaced by a multivibrator and distributer 7 by an electronic switch. Several tools may be used at once and either driven successionally or simultaneously. In the latter case, different vibration speeds could be used to differentiate between the effects of the different tools.