| 摘要 |
A device for indicating airtightness of a packing for apparatus which is to be stored under a vacuum and, particularly for protective breathing apparatus, comprises, a packing enclosing a packing space in which the apparatus is stored which has an outer surface with a recessed portion forming a chamber having a cover overlying the chamber enclosing and sealing it. A hollow expansible and retractable member, such as a bellows, is mounted in the chamber and has an opening to its interior extending through the packing into the interior of the packing space so that the pressure inside of the bellows is the same as the packing space. A ball is disposed between the bellows and the cover and it is held by expansion of the bellows against it in a fixed position which indicates an increase of the pressure within the packing beyond a predetermined amount. When the vacuum in the packing is sufficient, the pressure reduces and retracts the bellows so that the ball is freely movable in the space between the bellows and the cover.
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