GB357331A - Improvements in or relating to electromagnetic sound warning or signalling apparatus - Google Patents

Abstract

357,331. Sound warning or signalling apparatus. GILL, H. A., 51, Chancery Lane, London.-(E. A. Laboratories, Inc. ; Mytle Avenue, Brooklyn, New York, U.S.A.) July 30, 1930, No. 22999. [Class 13.] The armature of an electro-magnetic sound warning or signalling apparatus for road vehicles, motor boats, signalling stations, &c., of the kind in which an armature 20 carried by a diaphragm 11 is actuated by an electro-magnet 6 and the energizing circuit is made and broken by the armature movement, is provided with a separate projectible and retractible member to change the magnetic flux of the coil and vary the pitch of the note produced. As shown, the device comprises a casing 5 in a recess in which is secured a cap 22 protecting a coil 6. A diaphragm 11 is clamped, by bolts 14, between a clamping ring 13 and a flange on a forward extension 10 to the casing 5, and has riveted to it, by a stud 18, an annular armature 20. A resonator 16 is mounted on the stud 18 by a screw stud and nut 21, as shown, and this screw stud is adjustable in the magnetic field to control the operation of the device to produce sounds of different pitch. A horn 30 or apertured cover plate 31 may be secured to the extension 10 in such a way as not to interfere with the tension on the diaphragm 11. A spring arm 23 carries a contact intermediate its length adapted to contact with a contact 24 on an arm 25 adjustable on a screw bolt against spring action to complete the field circuit and this is broken when a stud 17 carried by the armature moves toward the coil and contacts with and depresses the spring arm 23.