Patent GB-1013535-A (GB)
Title: Fine tuning mechanism
IPC: H03J5/30
Filed: 1962-06-04
Abstract: 1,013,535. Adjusting radio apparatus; radio receiving arrangements. STANDARD KOLLSMAN INDUSTRIES Inc. June 4, 1962, No. 21505/62. Heading H3Q. In a multi-channel television tuner comprising a control shaft which can be rotated to any one of a plurality of discrete angular positions in order to select circuitry designed to receive a corresponding television channel, the circuitry associated with each channel comprises a finetuning inductor having an adjustable core which may be moved longitudinally within the inductor by rotation of a gear-wheel secured thereto, fine tuning being effected by rotation of a fine-tuning shaft coaxial with the control shaft and coupled by gearing to a gear-wheel which normally lies adjacent to, but not engaging, the gear-wheel on the core of the fine-tuning coil corresponding to whichever channel is selected, but which, when the finetuning shaft is rotated in either direction is brought into engagement with the gear-wheel on said core. Thus by rotation of the finetuning shaft the appropriate fine-tuning core is adjusted while if the fine-tuning shaft is not moved, none of the gear-wheels on the inductor cores is engaged and the control shaft may be operated to change channel without disturbing the settings of any of the fine-tuning cores. In a first embodiment, a turret tuner, Fig. 1, comprises radio-frequency, interstage, and local-oscillator coil assemblies 21, 22, 23 respectively, mounted to rotate with rotation of shaft 25. A detent disc 24 situated between coil assemblies 21 and 22 serves also as a screen; further screening is provided by an arcuate shield 38 depending from the top plate of the tuner. The individual coils 40 of the local oscillator assembly 23 are provided with respective metal threaded tuning cores 45 having operating gear-wheels 65, Fig. 2, at their outer ends. A fine-tuning shaft 47 surrounding shaft 25 acts through gear-wheels 61, 58, 59 to drive pinion 62 which in the position shown in Fig. 2 does not engage with any of the gearwheels 65. Gear-wheels 58, 59, 62 are mounted on a supporting plate 57 which is so hinged and pivoted that the pinion 62 can be brought into. engagement with an adjacent gear-wheel 65. Plate 57 has a pin 56 extending therefrom; pin 56 carries gear 58 and also passes through an aperture 55, Fig. 3, in an extension 54 on a slipping-clutch device 51 secured by friction to fine-tuning shaft 47. When fine-tuning shaft 47 is rotated in either direction, pin 56 slides along the sloping edges of slot 55 to either the top or bottom of the slot against the action of spring 63. This causes plate 57 to rotate about its pivot point. Figs. 9 and 10 (not shown) thus drawing gears 59 and 62 nearer to the axis of the tuner whereby gears 62 and 65 engage and the tuning of the corresponding coil 40 is adjusted. In a second embodiment a slipping-clutch device 130, Fig. 13, mounted upon fine-tuning shaft 107 is provided with a V-shaped recess 138 shown in face view in Fig. 15. Upon rotation of shaft 107 in either direction, the shaft 121 carrying gears 120, 122 is turned so that its tip lies in one extreme position in the V-shaped recess 138, the shaft 121 then lying parallel with shaft 107 and gears 120, 122 engaging gears 116, 123 respectively. The V-shaped recess 138 is of different depths parallel to shaft 107 at its two extreme positions. This has the result the gear 120 extends further to the right in the Figure when the finetuning shaft is rotated anti-clockwise than when it is rotated clockwise. Hence when rotating anti-clockwise a point will be reached in which gear 116 rides off gear 120 to the left and adjustment ceases; subsequent clockwise rotation, however, permits gear 120 to engage gear 116 until the latter rides off to the right when it can only be re-engaged by an anticlockwise rotation of fine-tuning shaft 107.