Patent GB-471733-A (GB)
Title: Tuning dial for radio receiving apparatus
IPC: H03J1/04
Filed: 1935-12-06
Abstract: 471,733. Loud-speakers. DREYFUS, J. A. Dec. 6, 1935, Nos. 33922, 33923, 33924, 33925, and 33926. Convention dates, Jan. 16, March 16, April 25, May 22, and Aug. 27. Addition to 438,631, [Group XL]. [A Specification was laid open to inspection under Sect. 91 of the Acts, June 8, 1936.] [Class 40 (iv)] [Also in Groups XL and XXXVI] In a receiver in which a sound-pervious tuning dial covers part or the whole of the loudspeaker opening as in the parent Specification, the dial consists of celluloid or similar plastic material, or of glass, provided with narrow sound-transmitting slits between which the tuning indicia are located ; alternatively, the dial may consist of fabric such as silk. In a modification the loudspeaker diaphragm may itself constitute the tuning dial. Figs. 1 and 2 show part of a receiver in which the tuning dial 27 of celluloid is mounted in the sound opening of the loudspeaker 19, the core 26 of which is drilled to form a bearing for the spindle 25 operated by the tuning spindle and carrying a pointer comprising three lamps 31, 32, 33 co-operating with concentric scales on the dial, the appropriate lamp being switched in for each waverange by the wave-change switch. The dial is generally illuminated from the rear by a lamp 29 and reflectors 30. The part of spindle 25 within the core 26 may be of chrome steel. The dial 27 may be covered by a veil 37 of fabric, rendering the dial invisible when the lamps 29, 31, 32, 33 are not alight. These lamps may be controlled by a switch actuated by push-pull movement of the tuning knob. A construction of celluloid dial is shown in Figs. 3 and 4. Long radial slits 57, 58 render the dial soundpervious and may be used as linear tuning indicia; other symbols such as figures or letters may be formed by other perforations. Such a dial tends to disperse the central pencil of sound rays characteristic of the higher audiofrequencies and the dial thus serves as a tone filter ; to this end also the central opening may be varied in size. The whole of the rectangle may be illuminated, coloured wavelength indicator lamps being located in the corners. The dial may also be of pongee silk on which the tuning indicia are printed, preferably on both sides. If a fabric veil is placed in front of such a dial a moirÚ effect is obtained ; the veil may also be of metallic fabric, which, in a further modification, may also constitute the dial. Also, the dial may be built up from one or more parallel plates, the slots in one plate corresponding with the solid portions of the other. The pulley transmitting the drive from the tuning element to the dial pointer may be located within the loud-speaker cone and may be of conical shape to diffuse the central soundbeam ; in such case the pulley is moulded from transparent material. In further modification shown in Figs. 14 and 15, the diaphragm 85 of the loud-speaker constitutes the tuning dial, three concentric scales being provided if three wavebands are employed. The cone is illuminated by reflected light from a lamp 91 and reflector 92, the pointer 84 being parallel to the cone. A veil 93 of silk or metal fabric covers the loud-speaker opening. The loudspeaker cone may be of transparent material.