Document transport apparatus

A document transport apparatus for transporting a document sheet to a predetermined position to read the document sheet, comprising:

• a paper feed tray to mount document sheets;
• a document reading portion for reading both sides of each of the document sheets;
• transport means for transporting the document sheets on the paper feed tray to the document reading portion;
• a sheet discharge tray to store the document sheets of which both sides are read;
• a first switchback portion for switching back each of the document sheets of which the front side is read in the document reading portion to transport again to the document reading portion;
• a second switchback portion provided below the first switchback portion to switch back each of the document sheets of which both sides are read in the document reading portion to transport toward the sheet discharge tray;
• a first switchback path provided in the first switchback portion to guide a document sheet that is transported from the first switchback portion to the document reading portion and another document sheet that is transported from the document reading portion to the first switchback path in mutually different directions with the document sheet and the another document sheet overlapping;
• a first switchback roller pair disposed in the first switchback path to switch back the document sheet to transport, while discharging the document sheet to the sheet discharge tray;
• a second switchback path provided in the second switchback portion to guide a prior document sheet that is transported from the second switchback portion to the sheet discharge tray and a subsequent document sheet that is transported from the document reading portion to the second switchback portion in the mutually different directions with the prior document sheet and the subsequent document sheet overlapping;
• and
• control means for controlling transport of the document sheets so that two document sheets are transported to the document reading portion in an order of the front side of the prior document sheet and the front side of the subsequent document sheet, the two document sheets of which front sides are read are switched back by first switchback means, and then re-transported to the document reading portion in an order of the back side of the prior document sheet and the back side of the subsequent document sheet, and that the two document sheets of which both sides are read are switched back sequentially by second switchback means to discharge to the sheet discharge tray,
• wherein the first switchback path guides the document sheet that is transported from the second switchback portion to the first switchback portion and the document sheet that is transported from the document reading portion to the first switchback portion in the same direction with the document sheets overlapping, and
• the first switchback roller pair nips two document sheets to enable the sheets to be transported in the mutually different directions, while transporting two sheets in the same direction while nipping the sheets.