Patent GB-496275-A (GB)
Title: Improvements in and relating to the tuning of radio receivers
IPC: H03J5/16
Filed: 1937-05-26
Abstract: 496,275. Adjusting wireless apparatus. MURPHY RADIO, Ltd., and BOYD, J. D. A. May 26, 1937, No. 14628. [Class 37] In a tuning device of the preselector type, a button is slid along a list of station names so as to register with any one of them and means driven with the tuning means is then adjusted, manually or automatically, e.g. by an electric motor, until arrested by means associated with the button, in the tuning position of the indicated station. The button 8 is slidable in guides 3 on the wall 2 whereby a pointer 5 thereon may be registered with any one of an alphabetical or other list of station names on a face plate 1, correct registration being effected by a spring pressed ball 7 in the button engaging a notched strip 6. The inner end of the button comprises a spring pressed stop 12 which cooperates with a series of projections 16, one for each station, on a drum 14 rotatable with the tuning device. The projections 16 and the stop 12 are rounded as shown, so that during rectilineal adjustment of the button, in which it is moved axially of the drum, the stop 12 may ride over any projections 16 it may encounter, and, during the subsequent rotary movement of the tuning device and drum, the stop will abut against the appropriate projection 16 and stop the tuning device in the required tuning position. The stop 12 is rounded as shown in Fig. 3, so that it will ride over the appropriate projection when the drum is rotated clockwise and will stop the drum only during anticlockwise rotation thereof. When the drum is rotated by a motor, a button, for example, a spring pressed stud 9 mounted in the button 8 is used to make the motor circuit at contacts 19 preferably through a relay, and means are provided for automatically reversing the motor at each end of its travel. The relay remains energized until the drum is stopped in the tuning position by the appropriate projection 16 when the clutch, through which the motor drives the drum, slips and thereby opens contacts to break the relay and motor circuits. Modifications. The drum 14 may be built up of separate discs secured in the appropriate angular relation, and the projections 16 may be replaced by recesses adapted to be engaged by a coned plunger such as 12 preferably carried on one end of a short lever the other end of which is engaged by the stud 9, which, when depressed lifts the plunger from the drum to permit linear adjustment of the button. In another embodiment wherein the motor circuit is controlled by a series of contact discs 31, Fig. 8, (one for each station) which replace the drum 14, a single brush 32 is mounted on the slide 33. Rocking of the slide about its guide rod 34 disengages a boss 35 on the button 38 from the corrugated edge of a guide plate 36. Adjustment of the button along the guide rod 34 then brings the brush 32 on to the appropriate contact disc 31 the insulating boss 37 on which is arranged, in known manner, to break the motor circuit when the receiver is tuned to the station indicated by the button 38. In a modification, the press button 38, Fig. 10, is depressed against the action of a spring 39 to disengage its boss 35 from the corrugated edge of plate 36 and permit a spring 43 to rock a holder 42 to lift the brush 32 off its contact disc. When the button is moved rectilineally to the desired station position and released a disc 41 rigid with the button rocks the holder so that the brush 32 engages the appropriate contact-disc. The corrugations in the plate 36 may be shaped to position the slide exactly on release of the button. The contact-discs 31 may be built to form a solid drum in which case the brush 32 need not be lifted before being slid to another position. The button 8, or 38 may have a position free of stops 16 or 37 for normal tuning of the receiver which is preferably provided with automatic tuning correction, for example, as described in Specification 443,423, [Group XL].