Screw cap application

On a packaging line, screw caps are inserted onto the bottle and have both a downwards and sideways force applied on different parts of the closure to:

1) make the seal with the bottle
2) enable the cap to be broken and opened as well as resealed
3) enable the closure skirt to stay on the bottle neck once the cap is removed.

During screw cap application, a bottle is picked up off a bottle plate by a sealing head. A cap is added or pushed/dropped onto the bottle if using an automated system. As the sealing head rotates, a plunger/pressure pad is pushed down onto the closure on the bottle and exerts a top pressure on the closure and liner, or the redraw. Thread rollers push the sides of the closure into the free spaces or indents of the screwcap bottle finish thread. Tuck rollers crimp the metal under the screwcap thread or finish locking bead, so that the closure skirt remains on the bottle once the bridges are broken and top part of the cap removed. As the head goes up, the load decreases and the rollers retract. In-line optical inspection using image analysis can identify if caps are too high, if there is insufficient or malformed thread, if there are broken bridges, if rollers have cut through the closure or other non-conformances.