Patent ID: 6722754
Filing Date: 2004-04-20
Classification: B41J

Abstract:
A method for detecting a carriage jam in a printer having a stepper motor driven carriage, the steps comprising:a) providing a stepper motor having at least a first and a second independent winding for driving the carriage of a printer; b) applying a first, predetermined drive signal comprising a first current and corresponding first voltage waveform to said first winding at a first time; c) applying a second, predetermined drive signal to said second winding at a second, predetermined time, said second, predetermined time being later than said first predetermined time and during a time while said first, predetermined drive signal is still being applied to said first winding; d) defining a reference waveform from the group: voltage waveform and current waveform, for at least a non-jammed operating condition of said stepper motor at approximately said second time; e) observing said first voltage waveform at approximately said second time; f) comparing said first voltage waveform to said reference waveform based upon at least one predetermined feature of said first voltage waveform and said reference waveform; and g) generating a jam detected signal when said at least one predetermined feature of said first voltage waveform differs from said at least one feature of said reference waveform by a predetermined amount.