Document sheet conveying device capable of achieving large capacity of sheet feed tray

1. A document sheet conveying device comprising:

a sheet feed tray on which a document sheet is stacked;

a sheet feed mechanism configured to feed, in a predetermined sheet feed direction, the document sheet stacked on the sheet feed tray;

a sheet feed tray lift mechanism configured to lift up and down the sheet feed tray;

a top plate portion which is adjacent to the sheet feed tray at a downstream side, in the sheet feed direction, of the sheet feed tray, is contacted by a lower surface of the document sheet having been fed, and guides the document sheet in the sheet feed direction, a part of the sheet feed mechanism being disposed at the top plate portion;

a fixed wall portion provided to extend downward from an upstream end, in the sheet feed direction, of the top plate portion; and

a lifted wall portion provided to face the fixed wall portion and configured to be lifted up and down along the fixed wall portion together with the sheet feed tray, wherein

the fixed wall portion includes:

a plurality of projection portions that are provided in a width direction crossing the sheet feed direction with intervals therebetween, project toward the sheet feed tray, and respectively have hollow portions whose lower end portions are open; and

a plurality of recessed portions that are arranged alternately with the plurality of projection portions, and

the lifted wall portion includes:

a plurality of projection fitting portions that are respectively fitted in the hollow portions of the plurality of projection portions; and

a plurality of recessed fitting portions that are respectively fitted in the plurality of recessed portions.

2. The document sheet conveying device according to claim 1 , further comprising:

a biasing member configured to bias the lifted wall portion upward, wherein

the lifted wall portion includes: a pair of end portions formed to project outward in the width direction crossing the sheet feed direction; and a pair of projection portions respectively projecting from the pair of end portions outward in the width direction,

the fixed wall portion includes a pair of restriction portions that extend along an up-down direction, and, when the pair of end portions have been inserted therein, guide the pair of end portions to move in the up-down direction, and

the sheet feed tray includes a pair of regulation portions that project from both ends in the width direction toward the lifted wall portion, abut on the pair of projection portions from above, and regulate the lifted wall portion from being lifted up.

3. The document sheet conveying device according to claim 2 , wherein

the pair of restriction portions respectively have upper edge portions and restrict the lifted wall portion from being lifted up when the pair of end portions abut on the upper edge portions, at an upper-limit position where a height of an upper end portion of the lifted wall portion does not exceed a height of an upper end portion of the fixed wall portion.

4. The document sheet conveying device according to claim 3 , wherein

after the lifted wall portion reaches the upper-limit position and stops, the sheet feed tray can be lifted up to a predetermined height that is even higher.