Method and apparatus for stacking paperboard blanks

Apparatus for forming first and second stacks of blanks from vertically displaced, parallel streams of said blanks comprising:

• a first stacking station for stacking the blanks from a first of said streams, said first stacking station including:
• a first conveyor means in alignment with said first stream for advancing, in shingled fashion, the blanks from said first stream;
• first platform means beneath an output end of said first conveyor means for receiving said blanks in stacked formation thereon;
• and
• first gate means adjacent said output end of the first conveyor means for interrupting the advance of said blanks thereon when the height of said
• first stack reaches a predetermined height on said first platform means;
• and
• a second stacking station for stacking the blanks from a second of said streams, said second stacking station including:
• a second conveyor means in alignment with said second stream for advancing, in shingled fashion, the blanks from said second stream;
• second platform means, downstream from said first platform means, beneath an output end of said second conveyor means for receiving said blanks in stacked formation thereon;
• and
• second gate means adjacent said output end of the second conveyor means for interrupting the advance of said blanks thereon when the height of said second stack reaches a predetermined height on said second platform means, said output end of the first conveyor means being upwardly movable in proportion to an increase in height of said first stack for maintaining a substantially constant fall space between said output end and the top of said first stack,
• said second platform means being downwardly movable in proportion to an increase in height of said second stack for maintaining a substantially constant fall space between the output end of said second conveyor means and the top of said second stack;
• and
• switch means for stopping said first and second conveyor means upon respective activation of said first and second gate means,
• each of said conveyor means having an input end movable downwardly relative to said first and second streams for accumulating a storage stack of blanks thereon from said first and second streams respectively while said conveyor means are stopped,
• each of said first and second gate means including:
• first and second roller means between which said blanks pass from the respective conveyor means to the respective platform means, said second roller means movable into engagement with said blanks upon activation of said gate means;
• and
• control means for rotating said second roller means after engagement thereof with said blanks to advance blanks then between said first and second rollers onto said stacks on the respective platform means prior to removal thereof from said stacking stations.