Ink-jet printing machine and printing method

An ink-jet printing method providing a printing sheet on a transfer path formed by an orbital transfer belt, transferring the printing sheet along the transfer path, performing ink ejection from an ink-jet head disposed above the transfer path on the printing sheet transferred on the transfer path, the method comprising:

• pressing a central region of the printing sheet transferred on the transfer path by a sheet pressing roller disposed across the transfer path between a sheet feeding unit and the ink-jet head;
• detecting a deformation of the printing sheet exceeding a predetermined distance by contact of a deformed part of the printing sheet and a detecting unit, which is disposed between the sheet pressing roller and the ink-jet head and away from an upper surface of the transfer belt by the predetermined distance;
• and
• pressing the printing sheet transferred on the transfer path by a guide roller disposed across the transfer path and between the detecting unit and the ink-jet head;
• wherein a ratio of a distance between the sheet pressing roller and the detecting unit to a distance between the upper surface of the transfer belt and the detecting unit is set approximately equal to a ratio of a distance between the guide roller and the ink-jet head to a distance between the upper surface of the transfer belt and the ink-jet head.

An ink-jet printing machine comprising:

• a transfer belt unit including an orbital transfer belt which serves as a transfer path of a printing sheet;
• a sheet feeding unit configured to feed the printing sheet onto the transfer path;
• an ink-jet head disposed above the transfer path and configured to perform ink ejection on the printing sheet transferred on the transfer path;
• a sheet pressing roller disposed across the transfer path between the sheet feeding unit and the ink-jet head and configured to press a central region of the printing sheet transferred on the transfer path;
• and
• a detecting unit disposed between the sheet pressing roller and the ink-jet head and away from an upper surface of the transfer belt by a predetermined distance and configured to detect a deformation of the printing sheet that exceeds the predetermined distance by contacting with a deformed part of the printing sheet,
• wherein the detecting unit comprises:
• a swing part supported to swing in a transfer direction of the printing sheet with one end extending toward the surface of the transfer belt;
• and
• a swing sensor part configured to detect that the other end of the swing part is disengaged from the swing sensor part.