Disclosed herein is an improved gas gate for interconnecting regions of
differing gaseous composition and/or pressure, more particularly between
atmosphere and a vacuum. The gas gate includes a cylinder within a housing
situated between the regions of differing gaseous pressure, wherein the
gas gate provides for choke mode transonic flow of air leaks between the
regions. A web of substrate material is adapted to move between the
regions with at least one roller in a first region and at least one roller
in a second region. The rollers are positioned to create sufficient
tension as the web advances over the top peripheral portion of the
cylinder between the two regions or under the bottom peripheral portion of
the cylinder between the two regions.
