Unless otherwise indicated herein, the description in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
As a typical large-capacity sheet feeder, there is known the following sheet feeder.
The sheet feeder feeds a sheet located at an uppermost position of a sheet bundle that is housed in a sheet housing unit and has a plurality of sheets to an image forming apparatus by a sheet feeding unit arranged in a downstream side of a paper feeding direction of the sheet housing unit. The sheets housed in the sheet housing unit are loaded on a lift plate that moves up and down inside the sheet housing unit. The lift plate is suspended by wires and moves up by winding up the wires using a reel located at a motor shaft.
The wires include a pair of upstream-side wires that suspend end portions of the lift plate in an upstream side of the paper feeding direction at both sides of a direction perpendicular to the paper feeding direction and a pair of downstream-side wires that suspend positions of the lift plate in a downstream side of the paper feeding direction with respect to the ends positions in the upstream side at both sides of the direction perpendicular to the paper feeding direction. The pair of upstream-side wires is looped over a pair of upstream-side pulleys arranged vertically above the end portions of the lift plate in the upstream side. The pair of downstream-side wires is looped over a pair of downstream-side pulleys arranged vertically above the end portions in downstream side. Between the upstream-side pulleys and the downstream-side pulleys, side fences are located to position side ends of the sheet bundle along the paper feeding direction.
The sheet housing unit includes a pair of sidewalls opposed to a direction perpendicular to the paper feeding direction. At the downstream side of the paper feeding direction of the pair of sidewalls, a stepped portion having a height lower than an upper end of the pair of sidewalls is formed. A pickup roller of the sheet feeding unit is arranged at the position of the stepped portion. The upstream-side pulleys and the downstream-side pulleys are arranged in the upstream side of the paper feeding direction with respect to a position of the pickup roller of the sheet housing unit and are arranged at a height identical to the pickup roller such that the uppermost sheet loaded on the lift plate can abut on the pickup roller.