Sheet feeder and image forming apparatus including the same

Abstract

In a sheet feeder that feeds a sheet to an image forming apparatus, a sheet placing table has a placement surface on which a sheet is placed and is inclined downward toward a downstream side in a sheet feeding direction. A sheet detecting unit has an operation piece that presses a leading end of the sheet toward an upstream side in the sheet feeding direction with predetermined pressure. A regulating member is arranged in a vicinity of an end part of the sheet placing table on the upstream side in the sheet feeding direction. The regulating member regulates movement of the sheet to the upstream side in the sheet feeding direction and has regulating portions having different heights from the placement surface of the sheet placing table. The regulating portions are arranged so that the heights are increased toward the upstream side in the sheet feeding direction.

What is claimed is: 
     
         1 . A sheet feeder that feeds a sheet to an image forming apparatus, the sheet feeder comprising:
 a sheet placing table that has a placement surface on which a sheet is placed and that is inclined downward toward a downstream side in a sheet feeding direction in which the sheet is fed to the image forming apparatus;   a sheet detecting unit that has an operation piece which presses an end of the sheet on the downstream side in the sheet feeding direction toward an upstream side in the sheet feeding direction with predetermined pressure and that detects presence or absence of the sheet by an operation of the operation piece; and   at least one regulating member that is arranged in a vicinity of an end part of the sheet placing table on the upstream side in the sheet feeding direction and that regulates movement of the sheet to the upstream side in the sheet feeding direction, wherein   the at least one regulating member has a plurality of regulating portions having different heights from the placement surface of the sheet placing table, and   the plurality of regulating portions are arranged so that the heights are increased toward the upstream side in the sheet feeding direction.   
     
     
         2 . The sheet feeder according to  claim 1 , wherein
 the sheet placing table is a manual tray, and   a plurality of kinds of sheets that have different lengths in the sheet feeding direction are selectively placed on the manual tray.   
     
     
         3 . The sheet feeder according to  claim 1 , wherein
 an extended sheet placing table for a large-sized sheet, which is inclined downward toward the downstream side in the sheet feeding direction, is connected to the end part of the sheet placing table on the upstream side in the sheet feeding direction,   as angle by which the extended sheet placing table is inclined is set to be larger than an angle by which the sheet placing table is inclined, and   the at least one regulating member is arranged at a position in a vicinity of a connection portion of the sheet placing table and the extended sheet placing table.   
     
     
         4 . The sheet feeder according to  claim 1 , wherein
 the at least one regulating member includes two regulating members, and   the two regulating members are arranged within a width of the sheet in a direction orthogonal to the sheet feeding direction on each of right and left sides across a center of the width.   
     
     
         5 . The sheet feeder according to  claim 1 , wherein
 in the plurality of regulating portions, a separation between adjacent regulating portions is set to a length less than a moving amount of the operation piece to the upstream side in the sheet feeding direction.   
     
     
         6 . The sheet feeder according to  claim 1 , wherein
 the plurality of regulating portions are formed in a stepwise shape, a comb shape, or a brush shape.   
     
     
         7 . An image forming apparatus comprising:
 the sheet feeder according to  claim 1 ;   a taking-in unit that takes the sheet, which is placed on the sheet placing table, inside the image forming apparatus; and   an image forming unit that forms an image on the sheet which is taken in by the taking-in unit.