Sheet stacking apparatus

A method for forming individual stack portions of preselected numbers of sheets from a continuously forming vertical stack formed from a stream of sheets, the method comprising the steps of:

• (1) conveying the sheets at a first speed into a stacking station including a vertical sheet engaging backstop;
• (2) successively slowing the lead sheet in the stream entering the stacking station to a second speed prior to engaging the backstop;
• (3) lowering the stack at a rate approximately equal to the rate of stack height formation;
• (4) creating an upstream offset in the stack of sheets being formed, said offset defined by the trailing edges of a selected number of sheets;
• (5) positioning the end of a stack separating device in the path of the offset to engage said offset during the preceding lowering step;
• (6) moving the separating device horizontally into the stack under said offset to separate the stack into lower and upper stack portions;
• and,
• (7) discharging the lower stack portion from the path of stack formation.

A method for forming a continuous vertical stack of sheets from a stream of sheets, the method comprising the steps of:

• (1) conveying the sheets at a first speed into a stacking station including a vertical sheet engaging backstop;
• (2) successively slowing the lead sheet in the stream entering the stack station to a second speed prior to engaging the backstop by nipping the lead sheet between a nip roll and the next preceding sheet on the stack;
• and,
• (3) positioning the nip roll with respect to the backstop so the leading edge of the next following sheet reaches the nip roll when the leading edge of the lead sheet engages the backstop.