Print head carriage homing system

摘要

A printer has a bi-directional stepper motor that drives an endless toothed belt which is secured to a print head carriage for driving the carriage back and forth across the printer along a line of printing. A timing strip is molded integral with the frame of the printer and positioned under the print head carriage. An optical sensor of the light emitting diode and phototransistor type is secured to the underside of the carriage and positioned to straddle the timing strip as the carriage is driven back and forth across the printer. The printer controller uses timing strip/sensor signals to place the print head in a home position when the printer is turned on and also when the print head has been moved from an operating position, e.g. in the case of changing a ribbon. The timing strip/sensor signals are also used to detect a carriage jam condition.