GB814283A - Portable appliance for testing an electric wire fence - Google Patents

Abstract

814,283. Voltage testing. WOLSELEY ENGINEERING Ltd., and DRAKE, R. S. Oct. 17, 1955 [Sept. 9, 1954], No. 26099/54. Class 37. In apparatus for testing an electrified wire fence (Fig. 1) a metal hook 4 is adapted to engage the fence and its shank 3 extends through a rotary insulating knob 7 closing the insulating casing 2, an insulating body 5 fixed therein by radial screws, and an insulating platform 12 carried by insulating pillar 17 into which the shank is screwed and to which cover 19 is fixed by set-screw 18. Within the bore of body 5 the conducting shank is surrounded by metal sleeve 20 affixed at its upper end to knob 7 and carrying at its lower end a cam 21 spring- loaded between boss 11 of body 5 and boss 15 of platform 12 by coil spring 42. An air gap adjustable by rotation of the cam exists between the latter and electrode 13 upstandingly fixed on platform 12, connected in series with high (e.g. 10,000 ohms) resistance 30, neon tube 27 visible through aperture 43 of the casing, flexible lead 32, and earth spike 34 within insulating holder 35. Further rotation of cam 21 beyond the position of minimum gap length brings radial stud 22 thereof in contact with upstanding contact 14 adjacent to contact 13 (Fig. 2, not shown) to short-circuit hook 4 to earth and discharge the test conductor. In operation the presence of voltage is indicated by illumination of the neon lamp and rotation of the knob until the length of spark gap is just sufficient to extinguish, this enables the conductor voltage to be estimated from the knob graduations 8 and index mark 9. The Provisional Specification refers to voltage testing by spark gap adjustment until a predetermined standard of lamp brightness is obtained.