Sheet feeder, image reading apparatus, and image forming apparatus

An image reading apparatus having a sheet feeder, the sheet feeder comprising:

• a sheet stacking unit configured to stack sheets;
• a sheet pickup unit configured to pick up a sheet from one side of the stacked sheets on the sheet stacking unit;
• and
• a sheet separating and feeding unit, formed downstream of the sheet feeding unit in a sheet feeding direction, separately feed sheets one by one to a conveyance path,
• wherein a sheet picked up from the sheet stacking unit by the sheet pickup unit is separately fed from the sheet stacking unit to the conveyance path on the downstream side in the sheet feeding direction via an inclined surface inclining in the sheet feeding direction,
• further comprising an orientation holding unit configured to hold a feed orientation of a sheet currently being separately fed by acting on the sheet is formed between the sheet pickup unit and the sheet separating and feeding unit, and a biasing unit configured to bias the orientation holding unit from the retracted position to the projecting position,
• the orientation holding unit is displaceable between a position where the orientation holding unit projects from the inclined surface and a position where the orientation holding unit is retracted, in the vicinity of an intersection between the sheet stacking unit and the inclined surface, and a projection amount of the orientation holding unit from the inclined surface increases as the number of stacked sheets decreases, and the projection amount from the inclined surface decreases against a biasing force of the biasing unit as the number of stacked sheets increases, and
• the orientation holding unit has a function of holding the feed orientation of a sheet picked up from the sheet stacking unit by the sheet pickup unit, by pushing up the sheet in the projecting position.

An image forming apparatus having a sheet feeder, the sheet feeder comprising:

• a sheet stacking unit configured to stack sheets;
• a sheet pickup unit configured to pick up a sheet from one side of the stacked sheets on the sheet stacking unit;
• and
• a sheet separating and feeding unit, formed downstream of the sheet feeding unit in a sheet feeding direction, separately feed sheets one by one to a conveyance path,
• wherein a sheet picked up from the sheet stacking unit by the sheet pickup unit is separately fed from the sheet stacking unit to the conveyance path on the downstream side in the sheet feeding direction via an inclined surface inclining in the sheet feeding direction,
• further comprising an orientation holding unit configured to hold a feed orientation of a sheet currently being separately fed by acting on the sheet is formed between the sheet pickup unit and the sheet separating and feeding unit, and a biasing unit configured to bias the orientation holding unit from the retracted position to the projecting position,
• the orientation holding unit is displaceable between a position where the orientation holding unit projects from the inclined surface and a position where the orientation holding unit is retracted, in the vicinity of an intersection between the sheet stacking unit and the inclined surface, and a projection amount of the orientation holding unit from the inclined surface increases as the number of stacked sheets decreases, and the projection amount from the inclined surface decreases against a biasing force of the biasing unit as the number of stacked sheets increases, and
• the orientation holding unit has a function of holding the feed orientation of a sheet picked up from the sheet stacking unit by the sheet pickup unit, by pushing up the sheet in the projecting position.