Envelope for letters and parcels to protect against theft and interference consists of inner and outer jackets enclosing pressurized monitoring chamber, and tamperproof back pressure valve

摘要

The envelope has an outer jacket (1) of gas-impermeable tear-proof material, which encloses posted goods (2) completely gas-tight. A back pressure valve (4) and a pressure indicator (5) on the outer jacket form a monitoring chamber (3) between goods and jacket, which can be set to a defined internal excess pressure or vacuum. After setting the internal pressure, the valve is secured against removal and/or repeated filling with air. The monitoring chamber may be formed between the outer and an inner jacket (6), which both may be of flexible plastic or metal foil. The insertion aperture for the goods is closed by welding or an adhesive strip. The pressure medium is air or an inert gas. The valve generates an optical signal when tampered with.