Importance

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Abstract

A direct drive cut-off has a pair of cylinders, each having a helical knife blade. The path of the knife blade around the cylinder defines a synchronous length. A corrugated board is passed in a board path direction between the cylinders at a production rate. The knife blades move in proximity to each other in the board direction to cut the continuous board into sheets. The knife blades enter the board path and engage the continuous board at a beginning of engagement position of a knife blade entering edge and depart the board path at an end of engagement position of a knife blade exiting edge. The sheets are accelerated downstream of the cylinders. The cylinders are controlled by a control unit for accelerating and decelerating the rotational speed of the cylinders so that the knife blades engage the continuous board at the specific length cutting the board into sheets. The control unit is responsive to the production rate, and the sheet length. Therefore, for sheets that are shorter than the synchronous length, when the production rate is above a set speed, the control unit accelerates the cylinders after the knife blades complete the cut but before blade engagement is complete so that the knife blades do not engage the accelerating sheet. For production rates below the set speed and sheets shorter than the synchronous length, the control unit accelerates the cylinders when the knife blades reach the end of engagement position of the knife blade exiting edge.

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First Claim