Optimum phase determination based on the detected jet current

An ink jet recording apparatus of the continuous jet type, comprising:

• jet forming means including a nozzle for pressurizing ink to form a jet of such ink;
• oscillating means for providing a drive signal having an oscillation frequency at or around a spontaneous droplet breakoff frequency of an ink jet;
• a vibrating element mounted on said nozzle and responsive to said drive signal to cause an ink jet to separate into discrete ink drops in synchronism with the drive signal;
• a charging electrode for charging ink drops in response to a charging voltage applied responsive to a digital charge signal;
• means responsive to said drive signal for generating a plurality of digital charge signals, each of said digital charge signals differing in phase from one another;
• an electrically isolated conductive drop catcher connected to said electrically isolated conductive drop catcher for catching drops and for providing a drop-charge signal representative of the charge level of the drops caught;
• a current detector connected to said electrically isolated conductive drop catcher for detecting a jet current;
• and
• processor means connected to said jet forming means and said current detector for successively selecting each of said plural digital charge signals and applying the selected digital charge signal to said vibrating element, storing the detected charge associated with each of said plural digital charge signals, and determining that digital charge signal providing optimal charging of the ink drops.

An ink jet recording apparatus of the continuous jet type, comprising:

• means for forming a stream of discrete ink drops and projecting the so-formed ink drops along a path, said means for forming including means for generating a plurality of digital pulse signals in response to an excitation signal, each of said digital pulse signals having a different respective phase relationship and including means for selecting one of the plural digital pulse signals as the selected digital pulse signal;
• means responsive to said excitation signal for electrically charging the ink drops projected along the path;
• an electrically isolated conductive drop catcher for catching ink drops projected along the path;
• means connected to said conductive drop catcher for detecting the electrical charge associated with the ink drops caught by said drop catcher and providing an electrical signal indicated of that charge;
• and
• processor means connect to said means for forming and connected to said means for detection for successively selecting each of said plural digital pulse signals as the selected pulse signal and storing the charge-indicating signal associated with each of said plural digital pulse signals, and determining that digital pulse signal providing optimal charging of the ink drops.

An ink jet recording apparatus of the continuous jet type, comprising:

• ink jet forming means including a nozzle for pressurizing ink to form a jet of such ink an having a vibrating element mounted on said nozzle for breaking the ink jet into discrete ink drops in response to a digital excitation signal;
• oscillating means having an oscillation frequency at or around a spontaneous droplet breakoff frequency of an ink jet and providing a recurring trigger signal therefrom;
• means connected to said oscillating means and responsive to the recurring trigger signal for providing a plurality of digital excitation signals at the oscillation frequency and phase-displaced from one another;
• charging means responsive to the recurring trigger signal for selectively charging an ink drop in synchronism therewith;
• an electrically isolated conductive drop catcher for receiving charged ink drops;
• a current detector connected to said electrically isolated conductive drop catcher for detecting a jet current that is a function of the charged ink drops received by said drop catcher;
• and
• processor means connected to said ink jet forming means and said current detector for successively applying each of the plural digital excitations signals to the ink jet forming means and storing the detected jet current associated with each digital excitation signal, and determining that digital excitation signal of the plural digital excitation signals providing optimal charging of the ink drops.