Apparatus for driving moving webs in bag making machines

In a machine for heat-forming articles from a running length of plastic, said machine having a die adapted to heat soften and form the plastic, a platen roll positioned adjacent said die for supporting said plastic for engagement with said die, a pair of rolls forming a nip adapted to engage and pull said plastic through the machine, said die located downstream of said nip rolls relative to the direction of movement of said plastic and adjacent the downstream end of said machine, a shuttle mounted to said machine for reciprocation toward and away from said pair of nip rolls, said shuttle adapted to have said plastic trained thereabout, shuttle drive means for reciprocally moving said shuttle to alternately take up said plastic and to pay out said plastic, and an endless looped belt drivingly interconnecting said nip rolls and said shuttle so that a portion of said belt associated with said nip rolls can stop and start interdependently with the take-up and pay-out movements of said shuttle and synchronously with the take-up and pay-out of said plastic, thereby stopping and starting said nip rolls interdependently with said take-up and pay-out movements, the improvement in which:

• said web shuttle comprises a pair of shuttle members, a first said shuttle member positioned upstream and a second said shuttle member positioned downstream relative to the direction of movement of said plastic through said machine, each said shuttle member being independently mounted in said machine for reciprocation, a portion of the loop of said belt extending about each said shuttle member, said shuttle drive means being connected to said shuttle members from outside said portions of the loop of said belt extending about said shuttle members, said drive means synchronously securing said members against said portions of the loop of said belt for reciprocating said shuttle members in unison, thereby stopping and starting said portion of said belt associated with said nip rolls and simultaneously stopping and starting said plastic to stop said plastic while said die is engaged with said plastic and to start said plastic while said die is released therefrom, and said platen roll is synchronously driven by said nip rolls whereby said platen roll assists in the movement of said formed plastic away from said die.

In a machine for discontinuously driving a web moving continuously through the machine, said machine having web pulling means, a web shuttle mounted to said machine for reciprocation toward and away from said web pulling means, said web shuttle adapted to have said web trained thereabout, shuttle drive means for reciprocally moving said web shuttle to alternately take up and pay out said web, and an endless looped belt drivingly interconnecting said web pulling means and said web shuttle so that a portion of said belt associated with said web pulling means can stop and start interdependently with the take-up and pay-out movements of said web shuttle and synchronously with the take-up and pay-out of said web, thereby stopping and starting said web pulling means interdependently with said take-up and pay-out movements, the improvement in which:

• said shuttle comprises a pair of shuttle members, a first said shuttle member positioned upstream and a second said shuttle member positioned downstream relative to the direction of web movement through said machine, each said shuttle member being independently mounted in said machine for reciprocation, a portion of the loop of said belt extending about each said shuttle member, said shuttle drive means being connected to said shuttle members, and said drive means synchronously securing said members against said portions of the loop of said belt for reciprocating said shuttle members in unison, thereby stopping and starting said portion of said belt associated with said web pulling means and simultaneously stopping and starting said web.