GB513895A - Improvements in telephone instruments - Google Patents

Abstract

513,895. Transmitters and receivers. UNITED STATES INSTRUMENT CORPORATION Jan. 24,1938, No. 2289. Convention date, Dec. 4, 1937. [Class 40 (iv)] In a telephone instrument comprising a pair of pole-pieces and an armature extending therebetween supported for vibratory movement with a diaphragm, one or more permanent magnets are disposed between, and serve to space, the respective pole-pieces of the said pair. As shown in Figs. 1, 2 the armature 28, clamped at one end, is connected by a rod 29 to the diaphragm 15 and oscillates in the gaps between pole-pieces 25, 25<SP>1</SP> spaced apart by permanent magnets 24, 24<SP>1</SP> against which the pole-pieces are held by bolts 26 which are also employed to attach the magnetic unit to a backing plate 16. The lower end of the armature 28 is attached to a downwardly extending projection 30 of a bridge 31 secured to the lower face of the polepieces by screws 33, 33<SP>1</SP> which in conjunction with a screw 34 permit the armature to be adjusted. A ring 17 clamps the diaphragm 15 to the plate 16 which has an annular flange 20 clamped between the casing 21 and a perforated cover plate 22. An insulating plate 35 secured to the upper surface of the pole-piece 25<SP>1</SP> carries terminals 36, 37. In a modification, Figs, 5, 6, 7 (not shown), the lower end of the armature is mounted between spacing members located in the lower gap and in a slot in a resilient bridge having upwardly-directed ends engaging in sockets in the lower face of the coil former. In a further modification, Figs, 8, 9, two pairs of pole-pieces are associated with two magnets 50, 50<SP>1</SP> and the pole-pieces 51, 51<SP>1</SP> are formed with pole-tips 56 and with inwardly-directed portions carrying bridge members 57, 57<SP>1</SP> having slots 59, 59<SP>1</SP> corresponding to the width of the armature 53 which is soldered to the members 57, 57<SP>1</SP>. In a further modification, Fig. 10, the speech-coil 61 which is roughly conical in shape is wound on the armature 60 and a transformer 62 is included in the circuit. In a further modification, Figs, 12, 13, the armature 76 which is supported at its ends and is connected at its centre to the diaphragm 15, is associated with two pairs of pole-pieces 71, 71<SP>1</SP> provided with U-shaped pole-tip members 73, 73<SP>1</SP> and spaced by the magnet 70 and a spacing sleeve 72. The ends of the armature are clamped between a plate 78 and a block 77 formed with projections 81 engaging a fixed member 80, and the block 77 can be adjusted by screws 79, 79'. The armature 76 may be replaced by an armature with a number of radial coplanar arms each vibrating within its coil and air gaps and connected at its centre to the diaphragm.