Electrically conductive shield for a vacuum switching device

(19)

(11)

EP 0 780 868 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	28.04.1999 Bulletin 1999/17

(43)	Date of publication A2:
	25.06.1997 Bulletin 1997/26

(21)	Application number: 96308893.5

(22)	Date of filing: 06.12.1996

(51)	International Patent Classification (IPC)⁶: H01H 33/66, B23K 1/00

(84)	Designated Contracting States:
	DE FR GB NL

(30)

Priority:

21.12.1995 GB 9526232

(71)	Applicant: GEC ALSTHOM LIMITED
	Rugby, Warwickshire CV21 1TB (GB)

(72)	Inventors:
	Rand, John Rugby, Warwickshire, CV22 7HU (GB) Falkingham,Leslie Thomas Rugby, Warwickshire, CV21 4AB (GB)

(74)	Representative: Hoste, Colin Francis
	The General Electric Company p.l.c. GEC Patent Department Waterhouse Lane Chelmsford, Essex CM1 2QX Chelmsford, Essex CM1 2QX (GB)

(54)	Electrically conductive shield for a vacuum switching device

(57) An electrically conductive shield for a vacuum switching device, e.g. a vacuum interrupter, has a self-centering means for centering the shield within a ceramic insulator surrounding the shield. The self-centering means may comprise three outwardly facing domes (33) formed as "dimples" in the wall of the shield (19; 20). These domes make a clearance fit with the ceramic insulator (8) when cold, however when heated in order to effect brazing of the component parts of the interrupter, the domes (33) make first an interference fit with the ceramic while the shield "floats" relative to the ceramic, then are distorted by a further increase in temperature, the shield being then self-centred within the interrupter. The shield may consist of two shield members (19, 20), the first being as described above, the second having an outwardly turned lip (40) which is a clearance fit when cold, but causes distortion of an end-portion of the second shield member (20) at elevated temperature and acts to centre the second shield member (20).

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