Rotary die-cut apparatus and gearing arrangement therein

Abstract

A rotary die-cut apparatus, in which a die roll cooperates with a resiliently covered anvil roll for die-cutting carton blanks passed therebetween, incorporates a constant mesh gear train between the die roll and the anvil roll for providing an infinite hunting ratio between the rolls. This provides more uniform wear of the anvil roll cover and prolongs its effective life. Preferably, this gear train includes a harmonic drive having a wave generator cam rotatable by a trim motor. An arrangement for sensing changes in diameter of the anvil roll due to wear of its cover may provide an input for determining the speed of the trim motor. A resurfacing mechanism for removing the outer surface of the cover when worn may provide this input. A pulse generator is preferably incorporated in a controller of the trim motor for periodically making random changes in the speed of the trim motor. The gear train, with or without the trim motor, preferably has a gear ratio through multiple pairs of gears which itself provides an infinite hunting ratio. A gear on the anvil roll concentric therewith may mesh inside an internally toothed ring gear, these gears remaining in mesh when the anvil roll is moved about an eccentric axis towards or away from the die roll. An electric register for registering the die roll may be interconnected with the trim motor for rotation of the anvil roll with the die roll when the apparatus is stopped.