GB499254A - Improvements in and relating to electric fuses - Google Patents

Abstract

499,254. Electric cut - outs. BRITISH THOMSON - HOUSTON CO., Ltd. May 25, 1938, No. 15632. Convention date, May 25, 1937. [Class 38 (i)] An electric fuse consists of a casing 61 containing a number of tubes, 56 to 60, or compartments, through which a fusible conductor 66 is threaded back and forth. The tubes are filled with arc-quenching material and the element passes from one tube to another through holes, such as 67 to 70, at points remote, from one another and from the terminal caps 62 and 63, in order to prevent short-circuiting arcs. Some of the tubes may be filled with gas-producing arc-quenching material and the others with inert arcquenching material. Holes 64 are provided in the terminal caps to allow gases to escape, and porous discs 65 prevent the escape of filling material. Holes 73 are also provided in the tubes to facilitate the escape of gases. In the form shown in Fig. 1, the tubes 17, 18, 19 do not extend the full length of the casing and the holes 67 to 70 of Fig. 5 are in this case unnecessary. A wire 30 is connected in shunt with a portion of the fusible element 24 and is brought out through the wall of the fuse casing, as at 31, into contact with a small body of gunpowder 32 held in place by a label 33 to indicate when the fuse has blown. The portion of the fuse element 24 in shunt with the wire 30 is weakened as at 34 so that fusion starts there. In the modification shown in Fig. 7, the indicator consists of a brightly coloured plunger 100 held down against the action of a spring 103 by a strain wire 101 one end of which is passed, with the fusible element, through a hole 96 in one of the tubes and is anchored to the tube. When the fuse blows, the strain wire is also ruptured, for example by the arc formed, and allows the plunger 100 to be projected.