GB621032A - Improvements in or relating to sound reproducing and/or amplifying devices - Google Patents

Abstract

621,032. Telephone instruments. DILKS, C. F. Sept. 4, 1945, No. 22728. Convention date, May 28, 1941. [Class 40 (iv)] A sound amplifier comprises a chamber into which air is admitted under pressure and an electromagnetically controlled valve which controls its passage to an outlet. It also comprises a diaphragm which determines the initial setting of the valve under the influence of the air pressure. Air enters the chamber 15, Fig. 1, through a pipe 17 and filter 20 and passes into the outlet 23 through a valve plate 27 adjacent to a seating 25. The valve 27 is supported at one end on a spring strip 30 while its.other end carries an iron armature connected through a flat spring to a rigid support 39. The setting of the spring, and thus of the valve, is determined by a lever 49 to which it is connected and to the outer end of which is linked a flexible diaphragm 64. The air pressure deflects the diaphragm and so lifts the valve slightly off its seating to an extent depending on the pressure. This movement is adjustable by means of a screw 54 engaging a nut 58 which depresses the lever 49 through a spring 57. Polepieces attached to a permanent magnet 81 lie on opposite sides of the armature 32 and are so placed that speech currents passed through a coil 72 cause the armature 32 and valve plate 27 to oscillate. The valve 27 comprises a rectangular block having transverse holes drilled through it parallel to the working face and these allow air to pass to a series of parallel grooves cut in the under face of the block at right angles to the holes. The seating 25 has a similar series of slots arranged in staggered relation to the grooves in the valve so as to prevent a direct flow of air through the valve.