Folding machines

Claim 1

A machine for folding sheets comprising a pair of opposed folder rollers supported for rotation in opposite directions on horizontal axes at a folding station and defining a narrow vertically oriented folding bight between which a sheet is inserted for folding, means for in-feeding the sheet in its flat unfolded state along a feed path to a pre-inserting position in a plane spanning the gap between the rollers, the sheet so fed passing a first one of the folder rollers and then the second one, an inserter blade spaced opposite the flat sheet in its preinserting position, means to impart an insertion stroke to the inserter blade during the extent of which the blade engages the sheet in its pre-inserting position to start a fold therein and concurrently inserts the partly folded sheet in the bight between the rollers which are to complete the fold, means to return the inserter blade to its starting position following an insertion stroke, a stop in said feed path located behind said second one of the rollers passed by the in-fed flat sheet, said stop being in position to engage the leading edge of the sheet to be folded and accurately locate the sheet relative to the inserter blade, a reciprocal shuttle presenting a reciprocal sheet support in said feed path for bridging the gap between the folder rollers to lend temporary support to the in-fed sheet as it moves across said gap toward said stop, a fixed sheet support plate in advance of the first folder roller and on which the trailing part of the sheet is disposed when the leading edge engages the stop, means located on opposite sides of the folding bight to apply tension to the leading and trailing portions of the sheet spanning the folding bight, said last-named means including additional sheet feed means located between said stop and said second folder roller and gripping opposite sides of the sheet to feed the sheet toward said stop and said tensioning means further including means pressing the trailing part of the sheet against said sheet support plate with a pre-determined amount of pressure while said additional sheet feed means presents the leading edge of the sheet to said stop whereby said pressing means and said additional sheet feed means cooperate to stretch the sheet taut in its pre-inserting posItion when its leading edge is against the stop as aforesaid, means for withdrawing the shuttle before the inserter blade engages the sheet to be folded, said addition sheet feed means comprising a feed tape and an opposed roller engaging opposite sides of the sheet, and said pressing means comprising a spring biased member and means for regulating the effect of the spring.