Patent ID: 7832720
Filing Date: 2010-11-16
Classification: B65H

Abstract:
1. A sheet feeding device which feeds a sheet, comprising: a tray which supports the sheet and is capable of being lifted and lowered; a sheet feeding portion which feeds a sheet at a topmost position of a sheet stack supported by the tray; an air loosening device which loosens the sheet stack by blowing air to an end portion of the sheet stack supported by the tray; and a sheet detecting device capable of detecting a position of the sheet at the topmost position in the height direction of the sheet stack supported by the tray, wherein a maximum lowering amount when the tray is lowered by a control device is set to a value less than a distance in a height direction from the topmost position of the sheet stack by the sheet detecting device before blowing of air by the air loosening device is started to a lower end position of an air spouting port of the air loosening device, and wherein when feeding of the sheet is started, the control device raises the tray until the topmost position of the sheet stack supported by the tray is detected by the sheet detecting device and stops the tray, when the tray, is stopped, floats the sheet by blowing air against the sheet stack from the air loosening device, and when an upper limit detection sensor of the sheet detecting device is turned ON by a sheet floated by air from the air loosening device, lowers the tray while the air loosening device blows air against sheets, and when the upper limit detection sensor is turned OFF by the time when the lowering amount of the tray reaches the maximum lowering amount, stops the tray at a position in which the upper limit detection sensor is turned OFF, and unless the upper limit detection sensor is turned OFF even when the lowering amount of the tray reaches the maximum lowering amount, stops the tray at the position in which the lowering amount of the tray reaches the limit value and starts the feeding action of the sheet by the sheet feeding portion.