Airtight seal/use indicator for a film cartridge

摘要

In a film cartridge, a spool hub has a coaxial cavity in one end portion. A cartridge housing for the spool hub has a hole in one end wall that is aligned with the cavity to permit access to the cavity through the hole. A hermetic plug is sized to fit tightly in the hole to act as an airtight seal for the hole, but is sufficiently compliant to permit it to be forcibly pushed intact from the hole into the cavity to provide a visible indication that the film cartridge has been used.