Image reading apparatus

An image reading apparatus for reading an image surface of a sheet material while passing the sheet material through an image reading gap formed between a sheet conveying surface of a sheet conveying guide and an image reading surface of an image reading unit, said image reading apparatus comprising:

• a holding member for holding said image reading unit for movement in a direction to change a width of said image reading gap, while keeping a substantial parallelism of said image reading gap;
• an upstream roller pair having a first roller member displaceable in accordance with a thickness of the sheet material, and for nipping and conveying the sheet material into said image reading gap;
• a downstream roller pair having a second roller member displaceable in accordance with the thickness of the sheet material, and for nipping and conveying the sheet material out of said image reading gap;
• an urging member for urging said first roller member toward the other roller member of said upstream roller pair;
• and
• a receiving portion provided on said image reading unit for receiving an upward displacement of said first roller member, to displace said image reading unit upward,
• wherein a displacement of at least one of said first roller member and said second roller member moves the image reading surface of said image reading unit, while the substantial parallelism between the image reading surface and the sheet conveying surface of the sheet conveying guide is kept by said holding member, to change the width of said image reading gap to a widened width, and wherein when a trailing edge of the sheet material has passed through a conveying nip of said upstream roller pair, said first roller member returns to its original position from its displaced position by said urging member independent of said receiving portion while said image reading gap is maintained at the widened width by the displacement of said second roller member.