Web tension control system

Claim 1

In a system for controlling operation of a device for feeding a web to a printing machine, wherein said device includes a rotatable reel for supporting an expiring roll from which said web is withdrawn for passage to said printing machine when said expiring roll is in ''''run-off'''' position and at least one replacement roll movable upon rotation of said reel successively through a ''''pasting'''' position and into said ''''run-off'''' position to replace said expiring roll when said web is substantially expired therefrom; a web splicing and severing mechanism for splicing said web passing from said expiring roll to a leading end of a web carried by said replacement roll upon movement of the latter into said ''''pasting'''' position and thereafter severing said web between a resultant splice and said expiring roll; a web tensioning mechanism arranged for surface engagement with said web when withdrawn from said expiring roll; a transition brake associated with said replacement roll for applying transition tension to said web withdrawn therefrom after severing of said web as aforesaid and until said replacement roll is disposed in said ''''run-off'''' position; web tension sensing means movable in response to changes in web tension; and a pneumatic control circuit means responsive to movement of said web tension sensing means for adjustably controlling the pressure of air supplied to said web tensioning mechanism and said transition brake whereby to vary web tension, characterized in that the pressure of air required by said transition brake to maintain a given web tension is substantially less than that required by said web tensioning mechanism to maintain said given web tension, the improvement wherein said control circuit means comprises: first conduit means for connecting said web tensioning mechanism in flow communication with a source of air under a given pressure and incorporating a valve responsive to movements of said web tension sensing means for adjustably controlling pressure of air applied to said web tensioning mechanism; second conduit means for separately connecting said transition brake to said source and incorporating means for reducing pressure of air available for supply to said transition brake to a given value substantially below said given pressure; and a branch conduit connected into said second conduit means intermediate said pressure reducing means and said transition brake, said branch conduit incorporating a dump valve controlling communication of said branch conduit with the atmospheRe for reducing pressure applied to said transition brake to a value below said given value, said dump valve being responsive to said web tension sensing means.

Claim 4

A system for controlling operation of a device for feeding a web to a printing machine, said device comprising in combination: a rotatable reel for supporting an expiring roll from which said web is withdrawn for passage to said printing machine when said expiring roll is in ''''run-off'''' position and at least one replacement roll movable upon rotation of said reel successively through a ''''pasting'''' position and into said ''''run-off'''' position to replace said expiring roll when said web is substantially expired therefrom; web tension sensing means movable in response to changes in web tension; a web splicing and severing mechanism for splicing said web passing from said expiring roll to a leading end of a web carried by said replacement roll upon movement of the latter into said ''''pasting'''' position and thereafter severing said web between a resultant splice and said expiring roll; a web tensioning mechanism arranged for surface engagement with said web when withdrawn from said expiring roll; first circuit means for connecting said web tensioning mechanism to a source of air under a given pressure, said first circuit means including flow control valve means responsive to movements of said web tension sensing means for adjustably varying operation of said web tensioning means; a transition brake associated with said replacement roll for applying transition tension to said web withdrawn therefrom incident to the severing of said web as aforesaid and during transitional movement of said replacement roll into said ''''run-off'''' position; a second circuit means for connecting said transition brake directly to said source incident to severing of said web and during transitional movement of said replacement roll as aforesaid, said second circuit means including means for reducing pressure of air available to said transition brake to a value below said given pressure and second valve means connected into a portion of said second circuit means intermediate said pressure reducing means and said transition brake, said second valve means being responsive to web tension increase sensing movements of said web tension sensing means for connecting said portion of said second circuit means to the atmosphere whereby to further reduce pressure of air supplied to said transition brake; an expiring roll brake; a third circuit means including third valve means operable for connecting said expiring roll brake to said source after the severing of said web and removal of said expiring roll from said ''''run-off'''' position; and fourth circuit means connected into said source and operable in response to a breaking of said web to supply braking air to said portion of said second circuit means and to said third circuit means intermediate said third valve means and said expiring roll brake, whereby rotation of said expiring roll is arrested when said web breaks while said expiring roll is in said ''''run-off'''' position and rotation of said replacement roll is arrested when said web breaks during said transitional movement, said fourth circuit means incorporating check valve means for normally blocking communication of said second and third circuit means with said fourth circuit means and for blocking communication between said second and third circuit means.

Claim 5

A system for controlling operation of a device for feeding a web to a printing machine, said device comprising in combination: a rotatable reel for supporting an expiring roll from which said web is withdrawn for passage to said printing machine when said expiring roll is in ''''run-off'''' position and at least one replacement roll movable upon rotation of said reel successively through a ''''pasting'''' position and into said ''''run-off'''' position to replace said expiring roll when said web is substantially expired therefrom; web tension sensing means movable in response to changes in web tension; a web splicing and severing mechanism for splicing said web passing from said expiring roll to a leading end of a web carried by said replacement roll upon movement of the latter into said ''''pasting'''' position and thereafter severing said web between a resultant splice and said expiring roll; a web tensioning mechanism arranged for surface engagement with said web when withdrawn from said expiring roll; first circuit means for connecting said web tensioning mechanism to a source of air under a given pressure, said first circuit means including flow control valve means responsive to movements of said web tension sensing means for adjustably varying operation of said web tensioning means; a transition brake associated with said replacement roll for applying transition tension to said web withdrawn therefrom incident to the severing of said web as aforesaid and during transitional movement of said replacement roll into said ''''run-off'''' position; a second circuit means for connecting said transition brake directly to said source incident to severing of said web and during transitional movement of said replacement roll as aforesaid, said second circuit means including means for reducing pressure of air available to said transition brake to a value below said given pressure and second valve means connected into a portion of said second circuit means intermediate said pressure reducing means and said transition brake, said second valve means being responsive to web tension increase sensing movements of said web tension sensing means for connecting said portion of said second circuit means to the atmosphere whereby to further reduce pressure of air supplied to said transition brake; an expiring roll brake; a third circuit means including third valve means operable for connecting said expiring roll brake to said source after the severing of said web and removal of said expiring roll from said ''''run-off'''' position; and fourth circuit means connected into said source and operable in response to a breaking of said web to supply braking air to said portion of said second circuit means and to said third circuit means intermediate said third valve means and said expiring roll brake, whereby rotation of said expiring roll is arrested when said web breaks while said expiring roll is in said ''''run-off'''' position and rotation of said replacement roll is arrested when said web breaks during said transitional movement, said fourth circuit means incorporating check valve means for normally blocking communication of said second and third circuit means with said fourth circuit means and for blocking communication between said second and third circuit means.