Image forming system and sheet transport apparatus and method

An image forming system comprising:

• an image forming apparatus configured to form images on a plurality of sheets which are sequentially transported with a spacing between the plurality of sheets and that outputs the plurality of sheets;
• and
• a sheet transport apparatus comprising a transport section configured to receive the plurality of sheets sequentially transported and output from the image forming apparatus and transport the plurality of sheets farther downstream in a transport direction and configured to supply a different type of sheet from a different-type-of-sheet supply device, configure to insert the different type of sheet into a spacing provided between the plurality of sheets which are transported in the transport section, and configured to transport the different type of sheet and the plurality of sheets,
• the sheet transport apparatus comprising:
• a transport information obtaining unit configured to obtain information concerning transporting of sheets from the image forming apparatus,
• a timing unit configured to count a time concerning transporting of sheets on the basis of the information concerning transporting of sheets obtained by the transport information obtaining unit,
• a different-type-of-sheet supply unit is configured to start supplying the different type of sheet from the different-type-of-sheet supply device before the spacing into which the different type of sheet will be inserted reaches the transport section, on the basis of the time concerning transporting of sheets counted by the timing unit, and
• a memory configured to store in advance a different-type-of-sheet supply time taken for the different type of sheet supplied from the different-type-of-sheet supply device by the different-type-of-sheet supply unit to reach the transport section,
• wherein:
• the timing unit is configured to count a spacing arrival time taken for the spacing into which the different type of sheet will be inserted to reach the transport section, on the basis of the information concerning transporting of sheets obtained by the transport information obtaining unit;
• and
• the different-type-of-sheet supply unit is configured to start supplying the different type of sheet when the spacing arrival time counted by the timing unit becomes equal to or smaller than the different-type-of-sheet supply time stored in the memory.