A controller controls a floating unit and a conveyor to convey a sheet to a supply destination, and performs a following control of acquiring a detection value of a detector which detects an output signal acquired due to an input to a side of a sheet stack, during floating of sheets floated by the floating unit each time a sheet is conveyed by the conveyor and lifting a stacking tray upon the acquired detection value being less than a threshold value. The controller controls the floating unit and the conveyor to perform a feeding retry upon an occurrence of empty feeding in the conveyor, and determines the threshold value such that a target position for a height position of an upper surface of the sheet stack in the following control is a position where empty feeding is more likely to occur than multiple sheet feeding in the conveyor.

A document conveyance device includes a supply tray, a discharge tray, a conveyance part, a discharge part, and a lifting and lowering part. The lifting and lowering part lifts the supply tray and the discharge part according to a feeding of the document. When the feeding of the document to the document conveyance path is completed and then the supply tray is lifted, in a small number of documents discharge state where the height of the documents stacked on the discharge tray is less than the specified value, the lifting and lowering part positions the supply tray at a taking out position depart upward from the specified value by a predetermined space.

A document conveyance device includes a supply tray, a discharge tray, a conveyance part, a discharge part, and a lifting and lowering part. The lifting and lowering part lifts the supply tray and the discharge part according to a feeding of the document. When the feeding of the document to the document conveyance path is completed and then the supply tray is lifted, in a small number of documents discharge state where the height of the documents stacked on the discharge tray is less than the specified value, the lifting and lowering part positions the supply tray at a taking out position depart upward from the specified value by a predetermined space.

Sheets are set on the top face of a lift plate. A lift mechanism makes a lift plate ascend and descend. A sheet feeding roller and a distance sensor are provided over the lift plate. The distance sensor measures a distance (measured distance) to a measurement target placed below. Based on the measured distance before the lift plate is raised, the controller calculates a remaining quantity value indicating a remaining quantity of sheets. When, after the lift plate starts to rise, the recognized measured distance becomes equal to or smaller than the upper limit distance, the controller makes the lift mechanism stop raising the lift plate.

Sheets are set on the top face of a lift plate. A lift mechanism makes a lift plate ascend and descend. A sheet feeding roller and a distance sensor are provided over the lift plate. The distance sensor measures a distance (measured distance) to a measurement target placed below. Based on the measured distance before the lift plate is raised, the controller calculates a remaining quantity value indicating a remaining quantity of sheets. When, after the lift plate starts to rise, the recognized measured distance becomes equal to or smaller than the upper limit distance, the controller makes the lift mechanism stop raising the lift plate.

A paper stacking apparatus according to an embodiment of the present disclosure includes a stacking table, a first sensor, and a hardware processor. The stacking table includes an upper face on which papers are stacked, the stacking table being capable of being elevated and lowered by a drive mechanism. The first sensor is disposed at a first position and configured to detect the upper face of the stacking table or an upper face of stacked objects stacked on the stacking table. The hardware processor is coupled to the drive mechanism and the first sensor. The hardware processor is configured to determine that the stacking table is excessively elevated when an elapsed time after starting to detect the object by the first sensor is at least a first excessive-elevation determination value of time.

A paper stacking apparatus according to an embodiment of the present disclosure includes a stacking table, a first sensor, and a hardware processor. The stacking table includes an upper face on which papers are stacked, the stacking table being capable of being elevated and lowered by a drive mechanism. The first sensor is disposed at a first position and configured to detect the upper face of the stacking table or an upper face of stacked objects stacked on the stacking table. The hardware processor is coupled to the drive mechanism and the first sensor. The hardware processor is configured to determine that the stacking table is excessively elevated when an elapsed time after starting to detect the object by the first sensor is at least a first excessive-elevation determination value of time.

A sheet feeder includes a sheet stacker, a sheet feed roller, a separation roller pair, and a lifter. Sheets are conveyed and stacked on the sheet stacker. The sheet feed roller feeds the sheets. The separation roller pair separates the sheets fed by the sheet feed roller one by one. The lifter lifts and lowers the sheet stacker depending on a stack amount of the sheets. The sheet stacker includes a first stacking face, a second stacking face, and a bent portion integrally connecting the stacking faces such that the stacking faces form a specified angle. The sheet stacker stacks the sheets such that a center of gravity of the sheets is positioned above the first stacking face and integrally displaces the stacking faces when the lifter operates.

A sheet feeder includes a sheet stacker, a sheet feed roller, a separation roller pair, and a lifter. Sheets are conveyed and stacked on the sheet stacker. The sheet feed roller feeds the sheets. The separation roller pair separates the sheets fed by the sheet feed roller one by one. The lifter lifts and lowers the sheet stacker depending on a stack amount of the sheets. The sheet stacker includes a first stacking face, a second stacking face, and a bent portion integrally connecting the stacking faces such that the stacking faces form a specified angle. The sheet stacker stacks the sheets such that a center of gravity of the sheets is positioned above the first stacking face and integrally displaces the stacking faces when the lifter operates.

A feeding device includes a receptacle, a conveyor, an elastic member, and a load adjuster. The receptacle is vertically movable and holds a stack of sheets. The conveyor feeds an uppermost sheet of the stack of sheets on the receptacle in a feeding direction in which a sheet of the stack of sheets is fed. The elastic member biases the receptacle to press the uppermost sheet of the stack of sheets on the receptacle against the conveyor. At least when a height of the stack of sheets on the receptacle is equal to or greater than a given value, the load adjuster applies a reduced magnitude of load downward to the stack of sheets on the receptacle in response to a decrease in the height of the stack of sheets.