GB380651A - Improvements in sound producers - Google Patents

Abstract

380,651. Sound-producing devices. SUBMARINE SIGNAL CO., 160, State Street, Boston, U.S.A.-(Assignees of Williams, R. L. ; 109, Waban Hill Road, North, Chestnut Hill, Massachusetts, U.S.A.) Nov. 24, 1931, No. 32580. Convention date, Dec. 13, 1930. [Class 40 (iv).] An electrically-operated sound-producer of the type applicable for use as a fog-horn comprises one or a pair of diaphragms 10 mounted in a casing, the diaphragm or diaphragms being adapted to be vibrated by a pair of opposed armatures 11 which are so formed, as shown in Fig. 3, that each has three or more pole faces, of which some are cut at one angle to the direction of motion while the remainder are cut at an equal but opposite angle, the total area of the faces cut at one angle being equal to the total area of the oppositely inclined face or faces. With this arrangement, in the construction shown the two centrally opposed polepieces 14 on the armatures form between them a gap which is equally and oppositely inclined to the gaps formed between two outer pairs of polepieces 13, 15 and each central element has double the cross-sectional area of each of the outer elements. Thus the resultant magnetic pull is wholly in the axial direction of the armatures. The apparatus shown comprises two diaphragms, each of which has one of the armatures 11 secured thereto. A coil 4, to which alternating or intermittent current is supplied, passes through slots 16, 17 formed by the armatures, and is held by clamping arms 5 which are bolted to members 3 extending in wards from the annular body of the casing. Specifications 314,422, [Class 40 (iv), Telephones &c.], 352,957, and 353,089 are referred to.