Patent ID: 8419008

Claim:
A sheet-feeding device configured to feed sheets, the sheet feeding device comprising: a tray configured to support a stack of sheets; a lifting and lowering portion configured to lift and lower the tray; a control portion configured to control the lifting and lowering portion; an air blowing portion configured to blow air at an end of the stack of sheets to blow upward the stack of sheets; a suction conveyer configured to draw up and convey a top sheet blown upward by the air blown by the air blowing portion; and a first detection portion configured to detect the upper surface of the top sheet blown upward by the air blown by the air blowing portion, wherein the control portion is configured to control the lifting and lowering portion based on an output of the first detection portion so that the top sheet, blown upward by the air blown by the air blowing portion, of the stack of sheets is positioned in a conveyance range in which the suction conveyer can convey the top sheet; and a second detection portion configured to detect the upper surface of a trailing end portion of the stack of sheets, wherein the second detection portion detects an upper surface of a subsequent sheet, which is conveyed next to the top sheet, after the top sheet is conveyed by the suction conveyer, and when the control portion determines that the subsequent sheet is lower than a predetermined level in which the suction conveyer can convey the subsequent sheet, based on an output of the second detection portion during conveyance of the top sheet by the suction conveyor, the control portion controls the lifting and lowering portion so that the lifting and lowering portion lifts the tray until the upper surface of the subsequent sheet is above the predetermined level, and when the control portion determines that the subsequent sheet is positioned above the predetermined level based on the output of the second detection portion and the control portion determines that the subsequent sheet blown upward by the air blown by the air blowing portion is lower than the conveyance range based on an output of the first detection portion after the top sheet has been conveyed, the control portion controls the lifting and lowering portion so that the lifting and lowering portion lifts the tray until the subsequent sheet is positioned in the conveyance range.