Patent ID: 7635125

Claim:
A sheet feeding apparatus comprising: a lifting and lowering tray which supports sheets; an air blowing portion blowing air to an end of the sheets to blow upward the sheets supported on the tray; a sucking and conveying portion sucking and conveying a sheet blown upward by the air blown by the air blowing portion; a sheet detecting mechanism detecting an uppermost sheet of the sheets supported on the tray, a controller configured such that when the uppermost sheet blown upward is lowered to a sucking and conveying position range based on detection of an upper surface of the sheet by the sheet detecting mechanism before starting a sucking and conveying operation of a sheet by the sucking and conveying portion, the tray is lowered until the uppermost sheet reaches the sucking and conveying position while repeating a step operation in which a lowering operation and a stop operation are performed, wherein the sheet detecting mechanism includes: a first sheet surface sensor detecting that the uppermost sheet blown upward has reached a lower limit position of the sucking and conveying range; a second sheet surface sensor detecting that the uppermost sheet blown upward has reached an upper limit position of the sucking and conveying range; and a sensor flag moved along with the uppermost sheet blown upward, and arranged to turn the first sheet surface sensor ON when the sheet has reached the lower limit position of the sucking and conveying range, and to turn the first sheet surface sensor OFF as well as to turn the second sheet surface sensor ON when the sheet exceeds the upper limit position of the sucking and conveying range, and wherein the controller is configured such that the tray is lifted when both the first sheet surface sensor and the second sheet surface sensor are turned OFF, and when the first sheet surface sensor is turned ON and the second sheet surface sensor is turned OFF, the tray is lowered when the first sheet surface sensor is turned OFF and the second sheet surface sensor is turned ON, and the tray is stopped when both the first sheet surface sensor and the second sheet surface sensor are turned ON.