GB607768A - Improvements in and relating to fusible electric circuit interrupters - Google Patents

Abstract

607,768. Fusible cut-outs. BRITISH THOMSON-HOUSTON CO., Ltd. April 20, 1944, No. 7353. Convention date, April 23, 1943. [Class 38 (i)] The fusible element of an expulsion-type fuse extends into or through a recess or passage in a closed vessel containing a substance which is released when the wall of the passage is burnt through by the heat of the arc, and produces an arc extinguising fluid jet. As shown, the fusible element 18 extends through a passage 24 in a sealed annular vessel 23 -containing a liquid which forms an arc extinguishing vapour. A flexible cable 17 is supported from a fixed terminal 15 by the fuse 18 soldered in position and reinforced, if necessary, by a strain wire 21, the end of the cable preferably being enclosed within an insulating tube 22. The fuse unit, which may be soldered to the liquid container 25, as shown, has its terminal 15 clamped by a screw cap 13 on to a ferrule 12 mounted on an insulating tube 11. The liquid container may be of metal or moulded plastic material and has an air cushion 27 to allow for thermal expansion. In a modified clamping arrangement, Fig. 2 (not shown), in which the fuse and liquid container are separate units, a narrower expulsion tube which may also generate arc-extinguishing gas, encloses the upper part of the cable. In Fig. 3 (also not shown), an open-type pole-mounted cut-out is arranged so that the flexible cable when expelled hangs down as a visual indication, the whole fixture being hingedly removable for fuse replacement. Suitable liquids for arc quenching are mentioned, including that disclosed in Specification 394,776.