Sheet feeder

A sheet feeder comprising:

• a support adapted to hold a stack of sheets;
• a straitht guide rail extending from said stack parallel to a transport direction and defining a transport path extending in said direction;
• a generally cylindrical sheet-forwarding roller above said support and vertically engageable with the topmost sheet of said stack, said sheet-forwarding roller being centered on and rotatable about an axis inclined to said direction and rail;
• means for rotating said sheet-forwarding roller about the respective axis while in contact with the topmost sheet of said stack for displacing said topmost sheet in said direction and toward said rail;
• upper and lower pinch feed rollers downstream of said sheet-forwarding roller;
• means for rotating said feed rollers and thereby advancing a sheet engaged thereby along said path in said direction;
• and
• means for vertically displacing said sheet-forwarding roller and urging same periodically down into contact wth the topmost sheet of said stack;
• and
• means for rotating said lower pinch roller continuously in a direction urging a sheet in contact with it back against said transport direction and for rotating said upper pinch roller discontinuously in a direction urging a sheet in contact with it in said transport direction.

A sheet feeder comprising:

• a support adapted to hold a stack of sheets;
• a generally cylindrical sheet-forwarding roller above said support and vertically engageable with the topmost sheet of said stack, said sheet-forwarding roller being centered on and rotatable about an axis inclined to a transport direction defining a transport path extending in said direction;
• means for rotating said sheet-forwarding roller about the respective axis while in contact with the topmost sheet of said stack for displacing said topmost sheet in said direction and toward said rail;
• feed rollers downstream of said sheet-forwarding roller;
• means for rotating said feed rollers and thereby advancing a sheet engaged thereby along said path in said direction;
• a downstream pair of feed rollers flanking said path;
• means for detecting the spacing between said pair of feed rollers;
• and
• means for reverse driving said pair of feed rollers to advance any sheets engaged therebetween back against said direction when the spacing between said pair of rollers exceeds the thickness of a single sheet.