GB218783A - Improvements in sound boxes for sound recording and sound reproducing machines - Google Patents

Abstract

218,783. Marks, E. C. R., (Columbia Graphophone Manufacturing Co.). May 1, 1923. Tool-arms and mountings; sound-box cases.- Relates to gramophones and like sound-boxes of the kind having a needle-arm with a crossbar pivotally mounted between upper and lower knife-edge supports. According to the invention, the cross-bar on its upper side pivotally engages the casing by means of knife-edges and grooves, and at its lower side is formed with knife-edges which are supported by adjustable screws carried upon a resilient support. Fig. 1 shows a complete sound box, Fig. 2, show the parts thereof separated, and Fig. 4 is a detailed sectional view. The casing, which is preferably a die casting, has a flange 12 cut away at 13, 14 to provide flat portions; these, together with the part 16 of the back, form a seating for a member 26 - - 28 which carries downwardly-projecting knifeedges 33. The latter engage with grooves in the upper side of the cross-bar 45, to which the needlearm is attached. The underside of the bar 45 has knife-edges 72, Fig. 4, engaging with supporting screws, adjustably mounted in a resilient flange 25 which is integral with a ring 18. The ring is notched to allow the needle-arm 58 to pass through it, and is screwed to the front of the casing, serving to clamp the diaphragm between its gaskets. The socket 54 which receives the needle has triangulated grooves 55, Fig. 7.