US Patent 7739952 Printing apparatus and method of tension control

A printing apparatus performs printing on a web of printing paper while transporting the printing paper along a transport path. The printing apparatus includes a first transport mechanism located upstream in the transport path, and a second transport mechanism located downstream in the transport path. The transport speed of the printing paper in the first transport mechanism is controlled so that a tension value measured by a first tension sensor provided near the first transport mechanism approaches a predetermined value. The transport speed of the printing paper in the second transport mechanism is controlled so that a tension value measured by a second tension sensor provided near the second transport mechanism approaches the tension value measured by the first tension sensor. Thus, the tension of the printing paper is maintained at the predetermined value in the two locations along the transport path. The printing apparatus presents no hunting problem because the tension control using the predetermined value as a target value is effected only in the first transport mechanism.