Ink viscosity measuring device, ink viscosity adjusting method and device therefor, and a printing apparatus

摘要

A cardboard sheet printing apparatus including: a rotating body that freely rotates inside an ink circulation passage through which ink flows, and a rotation-imparting assembly which is magnetically coupled with the rotating body outside the ink circulation passage and imparts rotation to the rotating body. When the rotating body is caused to rotate by the rotation-imparting assembly, the variation in the load current value that occurs upon changes in the viscosity of the ink that contacts the rotating body is detected; and this variation is compared with load current values that correspond to respective changes in the ink viscosity value stored in memory beforehand and is converted into an ink viscosity value and then displayed, so that the viscosity of the ink is adjusted based upon the calculated results.