Inkjet printhead having intermittent nozzle clearing

An inkjet printer which expels ink droplets onto a medium from an ink reservoir and which intermittently clears plugged nozzles, comprising:

• a printhead which has a plurality of nozzles disposed in an orifice plate:
• a plurality of ink ejection chambers fluidically coupled to the ink reservoir and each said ink ejection chamber coupled to a respective one nozzle of said plurality of nozzles;
• a plurality of ink ejectors, at least one of said ink ejectors disposed in each of said plurality of ink ejection chambers;
• a microprocessor, coupled to said plurality of ink ejectors, which commands said plurality of ink ejectors in sequence to expel ink in a first time segment from said plurality of nozzles in a first pattern of nozzle expulsions for a first number of nozzle expulsions, said first pattern of nozzle expulsions further including a simultaneous expulsion from each printhead nozzle in repetitive bursts for the duration of said first time segment at a duty cycle of no more than 15 percent of that of said expulsion of ink in a second time segment for a second number of nozzle expulsions;
• pause from ink expulsion for a period of time immediately following said first time segment, said period of time being equal to or less than said first time segment;
• and
• expel ink in a second time segment from said plurality of nozzles in a second pattern of nozzle expulsions for a second number of nozzle expulsions immediately following said pause, each printhead nozzle expelling ink at least once during said second time segment.

An inkjet printer having a printhead with a mechanism for expelling ink from nozzles and an apparatus for clearing blocked nozzles, the printer comprising:

• means for expelling ink in a first time segment from the printhead nozzles in a first pattern of nozzle expulsions for a first number of nozzle expulsions including means for sequentially expelling ink from predetermined nozzles of the printhead nozzles as said first pattern of nozzle expulsions at a duty cycle of no more than 15 percent of that of said expulsion of ink in a second time segment for a second number of nozzle expulsions;
• means for pausing from ink expulsion for a period of time immediately following said first time segment, said period of time being equal to or less than said first time segments;
• and
• means for expelling ink in a second time segment from the printhead nozzles in a second pattern of nozzle expulsions for a second number of nozzle expulsions immediately following said pause each printhead nozzle expelling ink at least once during said second time segment.

A method of clearing blocked nozzles in an inkjet printer printhead having a mechanism for expelling ink from nozzles, the method comprising, without interruption or manual intervention, the steps of:

• (a) expelling ink in a first time segment from the printhead nozzles in a first pattern of nozzle expulsions for a first number of nozzle expulsions, said step of expelling ink in said first time segment including the step of sequentially expelling in from predetermined nozzles of the printhead nozzles as said first pattern of nozzle expulsions at a duty cycle of no more than 15 percent of that of said expulsion of ink in a second time segment for a second number of nozzle expulsions;
• (b) pausing from ink expulsion for a period of time immediately following said first time segment, said period of time being equal to or less than said first time segment;
• and
• (c) expelling ink in a second time segment from the printhead nozzles in a second pattern of nozzle expulsions for a second number of nozzle expulsions immediately following said pausing step, each printhead nozzle expelling ink at least once during said second time segment.

An inkjet printer which expels ink droplets onto a medium from an ink reservoir and which intermittently clears plugged nozzles, comprising:

• a printhead which has a plurality of nozzles disposed in an orifice plate;
• a plurality of ink ejection chambers fluidically coupled to the ink reservoir and each said ink ejection chamber coupled to a respective one nozzle of said plurality of nozzles;
• a plurality of ink ejectors, at least one of said ink ejectors disposed in each of said plurality of ink ejection chambers;
• and
• a microprocessor, coupled to said plurality of ink ejectors, which commands said plurality of ink ejectors in sequence to:
• expel ink in a first time segment from said plurality of nozzles in a first pattern of nozzle expulsions for a first number of nozzle expulsions,
• pause from ink expulsion for a period of time immediately following said first time segment, said period of time being equal to or less than said first time segment;
• and
• expel ink in a second time segment from said plurality of nozzles in a second pattern of nozzle expulsions for a second number of nozzle expulsions immediately following said pause, each printhead nozzle expelling ink at least once during said second time segment, said expulsion of ink in a second time segment including the sequential expulsion of ink from predetermined nozzles of the printhead nozzles as said second pattern of nozzle expulsions at a duty cycle of no more than 15 percent of that of said expulsion of ink in a first time segment for a first number of nozzle expulsions.

An inkjet printer having a printhead with a mechanism for expelling ink from nozzles and an apparatus for clearing blocked nozzles, the printer comprising:

• means for expelling ink in a first time segment from the printhead nozzles in a first pattern of nozzle expulsions for a first number of nozzle expulsions;
• means for pausing from ink expulsion for a period of time immediately following said first time segment, said period of time being equal to or less than said first time segment;
• and
• means for expelling ink in a second time segment from the printhead nozzles in a second pattern of nozzle expulsions for a second number of nozzle expulsions immediately following said pause each printhead nozzle expelling ink at least once during said second time segment, said means for expelling ink in said second time segment further comprising means for sequentially expelling ink from predetermined nozzles of the printhead nozzle as said second pattern of nozzle expulsions at a duty cycle of no more than 15 percent of that of said expulsion of ink in a first time segment for said first number of nozzle expulsions.