Method of measuring the printing pressure in a printing machine

摘要

A force or movement sensor is disposed on or proximate to an impression cylinder of a sheet-fed printing machine in order to sense the printing pressure. The sensor is sampled in synchronism with the rotation of the impression cylinder and the feeding of the sheets in order to detect a first pressure signal when pressure is applied to the fed sheets, and to detect a second pressure signal when the impression cylinder is relieved of the printing pressure. The differential value of the first and second pressure signals is displayed as an output or is evaluated by a pressure control system. As a result, static and quasi-static disturbances are suppressed. The mesurement is not affected by wear of the cylinder bearings or journals, variations in machine speed, and zero-point shift in the sensor and its associated electronics. These disturbances are further suppressed by averaging or accumulating samples over sample intervals and over a number of revolutions of the impression cylinder. Also, by proper synchronization of the sampling intervals with the feeding of sheets to the impression cylinder, the method can be used in a two-color rotary press for separately determining and independently controlling the pressures from the top and bottom ink transfer cylinders in response to a single sensor at the impression cylinder.