Sheet alignment using reverse advance roll and stationary pick roll

In a printer system having a printer mechanism and a sheet tray and a sheet feed path extending between the sheet tray and the print mechanism, an active sheet alignment system for feeding and aligning a sheet relative to the printer mechanism, comprising:

• a sheet pick roller mounted for axially rotational movement and for contacting the outside facing sheet in the tray;
• a main sheet advance roller disposed in a sheet feed path between the tray and the print mechanism and arranged so that the distance between the sheet pick roller and the main sheet advance roller is less than the length of the sheet;
• at least one pinch roller disposed adjacent said main roller, said main and pinch rollers being disposed to engagingly receive a sheet in the nip therebetween;
• a motor drive system for selectively driving said main roller in a sheet advancing or in a sheet retracting direction, said system comprising a motor coupled to said main sheet advance roller;
• means for coupling said sheet pick roller to said motor drive system so that said sheet pick roller and said main roller are driven together in the sheet advancing direction to feed a sheet from said tray toward said printer mechanism, and when the main roller is driven in the sheet retracting direction, the sheet pick roller is not driven and remains stationary;
• and
• a controller for controlling said motor drive system to feed sheets seriatum to the printer mechanism in aligned positions, comprising:
• means for controlling said motor to drive said sheet pick and main drive rollers in said sheet advancing direction so that the leading edge of the sheet is fed past the nip of the main and pinch rollers;
• means for reversing the motor, thereby driving the main roller in said other direction while the sheet pick roller is stationary and does not move, thereby forming a buckle in the sheet which tends to align the sheet leading edge with the nip;
• and
• means for changing the motor drive direction to rotate the main sheet advance roller and sheet pick roller to advance the sheet to the print position.

In a printer system having a printer mechanism, a sheet tray for holding a plurality of print media sheets, a sheet pick roller for picking sheets from the tray, a main sheet advance roller and an idler roller disposed adjacent the main sheet advance roller, with the nip between the main and idler roller being disposed less than the length of a sheet from the sheet pick roller, a method for actively aligning the leading edge of the picked sheets with the print mechanism, comprising the steps of:

• rotating the sheet pick roller and main advance roller in an advancing direction so as to pick a sheet from the sheet tray and advance it through the sheet feed path until the leading edge has been advanced past the nip between the main advance roller and the idles roller;
• reversing the main advance roller to rotate in the sheet retracting direction with the sheet pick roller stationary to withdraw the leading edge of the sheet while the trailing portion of the sheet is held fixed by the stationary pick roller, thereby forming a buckle in the sheet which tends to align the sheet leading edge with the nip;
• and
• rotating the main roller and the sheet pick roller in the advancing direction to advance the sheet to the print position.