Patent ID: 6508530
Filing Date: 2003-01-21
Classification: B41J

Abstract:
Aligning method for a multiple ink jet printhead (40) in a dot matrix printer, said printer comprising:a fixed structure (41); a carriage (42) suitable for supporting a multiplicity of ink jet printheads (42) and for moving according to a first direction (x), said printheads (40) being each provided with a plurality of nozzles arranged at a constant pitch in at least one column parallel to a second direction (y), substantially perpendicular to said first direction (x), at least two printheads of said printheads (40) being each provided with integrated optoelectronic means consisting of a plurality (50) of integrated phototransistors (51-i) arranged along a column (50) parallel to said second direction, each integrated phototransistor (51-i) having an open base (52-i), an independent emitter (56-i), and a collector (53-i) connected to a common node (54); an electronic controller suitable for controlling the timing of the ejection of droplets of ink by the nozzles of said printheads (40); and an illuminating device (43) integral with said fixed structure (41) and provided for generating a light beam (66, 70); wherein said method comprises the following steps: moving said carriage (42) according to said first direction (x); illuminating by means of said light beam (66, 70) said integrated phototransistors (51-i), during the movement of said carriage (42), so as to generate a plurality of electric signals corresponding to said integrated phototransistors (51-i); scanning in succession and in a cyclical order said integrated phototransistors (51-i) or detecting said electric signals; calculating a first misalignment of said at least two printheads (40) according to said first direction (x) and a second misalignment of said at least two printheads (40) according to said second direction (y), by processing said electric signals; compensating said first misalignment of said at least two printheads (40) according to said first direction, by altering the timing of the ejection of said droplets of ink; and compensating said second misalignment of said at least two printheads (40) according to said second direction by staggering the commands sent by said electronic controller to said two printheads (40) for the ejection of said droplets of ink.