Dot matrix printer with printing head spacing adjustment - uses sheet thickness sensor to control stepper motor stating cog attached to eccentric setting axis

摘要

The printer has a printing head mounted on a carriage adjusted by rotation of an eccentric axis. The printing head carriage is displaced along a guide rail parallel to the eccentric axis and is freely adjustable in the setting direction. The eccentric axis has a cog segment rotated by a setting motor (9) under control of an analogue signal provided by a sheet thickness detection roller. Respective magnetic circuits contain an indicator attached to the printing head and a sensor attached to the carriage, with a Hall element (26) for compensation of the two magnetic circuits, the DC voltage variation provided by the Hall element controlling the stepping motor via a microcontroller (34) contg. a ROM memory (36). ADVANTAGE - Simple measurement and accurate setting of printing head to match sheet thickness.