The buckle chute is disposed between the first driving mechanism and the second driving mechanism and comprises:
an upper guide and a lower guide for forming a channel having an entry point on the front side of the buckle chute adjacent to the first driving mechanism;
a stop, disposed in the channel between the front side and the back side at a separation length from the entry point, for stopping a leading edge of said at least one sheet or the folded piece entering the channel from advancing further into the channel toward the back side so as to cause said at least one sheet or the folded piece to buckle at a locality thereof outside the entry point of the channel toward the second driving mechanism for forming afolded edge at the buckled locality by the second driving mechanism as the first driving mechanism continues driving said at least one sheet or the folded piece toward the buckle chute; and
an adjustment mechanism, mechanically engaged with the stop, for moving the stop toward the front side or the back side for adjusting the separation length.
According to the present invention, it is possible that the buckle chute further comprises a deflector mechanism, disposed near the entry point of the channel and operable in a first position, for allowing the leading edge of the said at least one sheet or the folded piece to enter into the channel when said at least one sheet or the folded piece is driven by the first driving mechanism toward the entry point