GB253357A - Improvements in and relating to telephone receivers, loud speaking telephones and the like apparatus - Google Patents

Abstract

253,357. British Thomson-Houston Co., Ltd., Hutt, J., and Bird, G. H. June 8, 1925. Earpieces and attachments ; diaphragms.-The diaphragm of an acoustic device is clamped against the edge of the casing by means which is fitted into or under the instrument cover and arranged to be a press-fit on the outside of the casing. Fig. 1 shows a diaphragm 11 clamped against the end of the casing 12 by an annular lid device 13, the depending rim of which is a close fit against the outside of the casing 12. The depending flange 15 of the cover 14 is arranged to be a tight fit against the co-operating part of the member 13. In the modification, Fig. 2, the flange 15 of the cover 14 rests against an outwardly extending flange 16 on the member 13, the middle portion of which is raised at 17 and terminates in an annular upstanding flange 18 arranged to lie against the co-operating flange 19 on the cover 14. In a further modification, the end of the flange 16 is curled round the end of the flange 15 and the end of the flange 19 is curled round the inner portion of the member 13. Fig. 4 shows a further construction in which the member 13 is initially in the form of a cylinder having V-shaped notches in its upper edge and cuts in its bottom edges, the tongues thus formed at the top end being pressed over flat on to the outer side of the diaphragm as at 25, whilst the material between each pair of cuts in the bottom end is alternately opened up as at 23 against the inner side of the diaphragm 11. leaving a number of tongues 24 to engage against the outside of the casing 12. Instead of forming cuts in the bottom edge of the cylinder, the lower edge thereof may be left intact, incisions being made in the cylinder to form tongues to be pressed flat against the inner side of the diaphragm. A setscrew or pin may be used to prevent accidental displacement of the cover, whilst, in the case of head-attachment gear, the ends of the stirrup may be taken through holes in the rim of the cap into recesses in the side of the casing. The Provisional Specification describes constructions in which the diaphragm is of somewhat larger diameter than the casing or the projecting edge of the diaphragm is rolled over the edge of the casing into a lateral groove therein, or a laterally rounded flange is provided externally on the mouth of the casing and the edge of the diaphragm rolled or pressed over it. In either case the diaphragm may be applied hot so that on contraction it will be taut and firm.