Sheet folding apparatus

A sheet folding apparatus for folding sheets, said sheet folding apparatus comprising:

• a curved conveyance path along which said sheets are moved successively in first and second opposite directions, said curved conveyance path being such that said sheets cannot naturally register to reach a folding position by simple effect of gravity,
• a pair of transport rollers, the pair of transport rollers consisting of a motorized roller and an idler counter-roller, said idler counter-roller positioned across the curved conveyance path from said motorized roller, and
• an adjustable low stop member spaced relative to said transport rollers such that said transport rollers drivingly engage said sheets while said sheets physically engage said adjustable low stop member,
• wherein to register said sheets before folding said sheets, the transport rollers, having loaded said sheets in said first direction, move said sheets back in said second opposite direction to compress said sheets against said adjustable low stop member to generate said elastic deformation of said sheets solely under a force applied by the motorized roller and the idler counter-roller, said elastic deformation sufficient to compensate friction in said curved conveyance path and automatically register said sheets, said idler counter-roller selectively movable to a first position in which said idler counter-roller engages said sheets against said motorized roller to move said sheets in the first direction and to move said sheets in the second direction, and to a second position in which said idler counter-roller releases said sheets from engagement with said motorized roller to allow said sheets to automatically register at said folding position under recovery from said elastic deformation.