Continuous web apparatus and method using an air to vacuum seal and accumulator

An apparatus comprising an air to vacuum sealing mechanism comprising:

• a housing configured to contain a sub-atmospheric pressure environment;
• a pair of external nip rollers located outside of the housing and configured to pass a web substrate between them and to provide first sealing surfaces between atmosphere and the sub-atmospheric pressure environment;
• a pair of wiper seals attached to the housing and providing second sealing surfaces between atmosphere and the sub-atmospheric pressure environment between each external nip roller of the pair of external nip rollers and the housing;
• multiple chambers in the housing, the multiple chambers configured to maintain respective sub-atmospheric internal pressures that graduate from atmospheric pressure on a side of the housing facing the pair of external nip rollers to vacuum on an opposite side of the housing, wherein the first sealing surfaces, the pair of external nip rollers, the second sealing surfaces, and the pair of wiper seals separate atmospheric pressure outside of the housing from a first sub-atmospheric internal pressure in an internal volume of the housing which has a set of boundary surfaces that includes surfaces of the pair of external nip rollers;
• at least one conductance limiter configured to pass the web substrate between two parallel plates, wherein each of the two parallel plates is adjoined to a surface of the housing to which one of the pair of wiper seals is mounted,
• an input spool located outside of the housing;
• and
• a welding apparatus located between the input spool and the pair of external nip rollers and configured to weld a trailing edge of the web substrate from a first roll being removed from the input spool to a leading edge of the web substrate from a second roll being mounted on the input spool.