Methods and apparatus for preventing clogging in ink jet printers

An ink jet printer which comprises:

• at lest one nozzle for ejecting ink droplets in response to a sequence of control signals having controlled amplitude, said sequence comprising firing signals and sub-firing signals;
• and
• control means for generating the sequence of control signals and for controlling the amplitude of the control signals, wherein:
• the control signals are mutually asynchronous and are generated with a frequency which is effective to prevent clogging;
• the firing signals have amplitudes which are effective to both prevent clogging of the nozzle and to eject ink droplets;
• the sub-firing signals have amplitudes which are effective to prevent clogging of the nozzle yet which are ineffective to eject ink droplets;
• and
• generation of the sub-firing signals commences after a predetermined quiescent interval following generation of a firing signal and terminates upon generation of a subsequent firing signal.

An impulse ink jet printer which comprises:

• at least one nozzle for ejecting ink droplets in response to a sequence of control signals having controlled amplitude, said sequence comprising firing signals and sub-firing signals;
• and
• means for controlling the amplitude of the control signals comprising:
• means for generating firing signals having amplitudes which are effective to eject ink droplets;
• means for determining elapsed time following generation of a first firing signal;
• and
• means for generating a plurality of sub-firing signals after a predetermined quiescent interval following generation of the first firing signal and for terminating said generation of sub-firing signals upon generation of a subsequent firing signal, said sub-firing signals having amplitudes which are effective to prevent clogging of the nozzle yet which are ineffective to eject ink droplets.

A method of operating an ink jet printer which comprises at least one nozzle for ejecting ink droplets in response to a sequence of control signals comprising firing signals and sub-firing signals of controlled amplitude, said method comprising the steps of:

• generating a first firing signal which is effective to eject ink droplets;
• determining elapsed time following the generation of the first firing signal;
• generating a plurality of sub-firing signals after a predetermined quiescent interval following generation of the first firing signal, said sub-firing signals having a parameter which is effective to prevent clogging of the nozzle yet which is ineffective to eject ink droplets;
• and
• terminating said generation of sub-firing signals upon generation of a subsequent firing signal.

A method of operating an ink jet printer having at least one nozzle for ejecting ink droplets in response to a sequence of control signals that comprises firing signals and sub-firing signals of controlled amplitude, said method

• generating a sequence of control signals at a frequency which is effective to prevent clogging of the nozzle;
• generating firing signals having amplitudes which are effective to prevent clogging of the nozzle and to eject ink droplets;
• and
• generating sub-firing signals having amplitudes which are effective to prevent clogging of the nozzle yet which are ineffective to eject ink droplets, said generation of sub-firing signals commencing after a predetermined quiescent interval following generation of a sequence of firing signals and terminating upon generation of a subsequent firing signal.

An impulse ink jet printer which comprises:

• at least one nozzle for ejecting ink droplets in response to a sequence of control signals having controlled amplitude, said sequence comprising firing signals and sub-firing signals;
• control means for generating the sequence of control signals and for controlling the amplitude of the control signals, wherein:
• the control means generates a plurality of mutually asynchronous firing signals on demand at varying intervals, said firing signals having amplitudes which are effective to eject droplets of ink from said nozzle;
• and
• the control means generates a plurality of mutually synchronous sub-firing signals after a predetermined quiescent interval following a sequence of said firing signals, said sub-firing signals having amplitudes which are effective to prevent clogging of the nozzle yet which are ineffective to eject droplets of ink therefrom, said quiescent interval exceeding a minimum of said varying intervals between said firing signals, and said generation of sub-firing signals terminating upon generation of a subsequent firing signal.

An impulse ink jet printer which comprises:

• at least one nozzle for ejecting ink droplets in response to a sequence of control signals having controlled amplitude, said sequence comprising firing signals and sub-firing signals;
• and
• means for controlling the amplitude of the control signals comprising:
• means for generating mutually asynchronous firing signals at varying intervals, said firing signals having amplitudes which are effective to eject ink droplets;
• means for determining duration of said varying intervals between said firing signals;
• and
• means for generating a plurality of sub-firing signals after an interval of predetermined duration greater than a minimum of said varying intervals, said sub-firing signals having amplitudes which are effective to prevent clogging of the nozzle yet which are ineffective to eject ink droplets and said generation of sub-firing signals terminating upon generation of a subsequent firing signal.