GB254319A - Improvements in phonographic sound boxes for talking machines - Google Patents

Abstract

254,319. Enckell, A. June 25, 1925, [Convention date]. Sound-boxes; casings.-Consists in a phonographic sound-box having in combination a casing, an acoustically-insulated needle-carrier, and a damper for acting upon the needle carrier all constructed and arranged substantially as described below. The sound-box is made with a massive casing, a material such as an alloy of heavy metals being used, and the back plate 2, Fig. 2, has a central conical orifice 3. The inner diameter of the rim 5 of the casing may be approximately four times the mean diameter of the orifice 3. Tool-arm mountings; tool-arms, attaching to diaphragms.-The tool-arm or needle-carrier 8 is acoustically insulated by being mounted on two strips of whalebone 11, 12. Fig. 3, which are secured to two projections on a metal plate 13 screwed to the rim of the sound-box casing. The needle-carrying lever is atached to the diaphragm by means of a securing screw 15, Fig. 4, the head of which has exactly the same surface as the end 14 of the lever. Dampers for sound-modifying.-A damper or mute, adapted to act upon the upper end of the tool-arm 8 consists of a block of rubber 16, Fig. 6, mounted in a metal support 18 which is slidably guided in a forked member 22. This has an extension by which it is secured to the soundbox casing. An adjusting screw 24 controls the position of the part 18 carrying the rubber member, which is grooved to engage the tool-arm.