Vacuum drum purge method and apparatus

An apparatus for supplying gas to the vacuum ports of a vacuum drum comprising:

• a source of vacuum and a source of gas;
• a vacuum drum, including means for rotating said drum;
• said drum including a plurality of vacuum ports on the surface thereof, said vacuum ports communicating with means for selectively exposing said vacuum ports to said vacuum source and said source of gas as said drum rotates, said exposing means including a manifold having at least a first portion which communicates with said vacuum source and at least a second portion which communicates with said source of gas;
• and
• valve means dividing said first portion of said manifold from said second portion, said valve means comprising a fixed land area separating said first portion of said manifold from said second portion of said manifold.

A method for purging the vacuum ports of a vacuum transfer drum for transferring individual flexible web products from a rotating product drum to a delivery point comprising the steps of:

• rotating said vacuum drum having a plurality of said vacuum ports on the surface thereof;
• exposing said vacuum ports to a source of vacuum from the point at which said individual flexible we products are transferred to said drum to said delivery point;
• and
• continuously exposing said vacuum ports to a source of gas from said delivery point to a point just prior to the transfer of said individual flexible products onto said transfer drum.

A method for purging the vacuum ports of a vacuum product drum for forming individual flexible products from a continuous web of flexible material supplied onto the surface of said drum, said method including the steps of:

• rotating said vacuum drum having a plurality of said vacuum ports on the surface thereof;
• exposing said vacuum ports to a source of vacuum for at least a portion of the rotation of said drum;
• and
• continuously exposing said vacuum ports to a source of gas for the remainder of the rotation of said drum from a point during the transfer of said individual flexible products to a transfer drum to a point after said continuous web has been severed and sealed.

A method for purging the vacuum ports of a vacuum drum which is a transfer drum for transferring individual flexible web products from a rotating product drum to a delivery point comprising the steps of:

• rotating said vacuum drum having a plurality of said vacuum ports on the surface thereof;
• exposing said vacuum ports to a source of vacuum from the point at which said individual flexible web products are transferred to said drum to said delivery point;
• and
• exposing said vacuum ports to a source of gas immediately after said delivery point and just prior to the transfer of said individual flexible products onto said transfer drum.