Patent ID: 7681435

Claim:
Arrangement for monitoring the leak-tightness of an evacuated space which is hermetically closed, leak-tight, by means of at least one metallic wall, in which is inserted a device which is connected to the evacuated space and which indicates an inadmissible pressure rise in the evacuated space caused by a leak in the wall, and in which the device comprises: a metallic bellows, which is hermetically connected, leak-tight, to the evacuated space; and an electrical proximity switch to which an evaluation unit is connected, wherein the proximity switch is mounted, in the direction of movement of the bellows, at a distance from the end face of the latter, the size of which is varied as a function of the respective axial length of the bellows, and wherein a tube connected fixedly to the wall is mounted around the bellows, so as to maintain an air gap, surrounds the bellows in a moisture-tight manner and is longer than the bellows in its longest initial position corresponding to the expanded state, and wherein the proximity switch projects into the tube so as to be sealed off with respect to the latter.