Impulse ink jet system

An impulse ink jet print head comprising:

• a plurality of operating plates held together in a superposed relationship including at least:
• a first plate including at least one nozzle therein for ejecting droplets of ink therethrough;
• a second plate defining at least one elongated ink chamber therein having relatively long sidewalls and relatively short endwalls, said chamber being connected to an ink supply and having an outlet for directing ink toward said nozzle in said first plate;
• said nozzle having a central axis extending transversely of the planes of said plates and intersecting said second plate at an extremity of said chamber;
• said plates having passage means connecting said nozzle with said outlet;
• a third plate contiguous with said second plate and including piezoelectric transducer means adapted, upon application of a voltage thereto, for displacing ink in said chamber thereby causing the ejection of ink droplets from said nozzle;
• a fourth plate contiguous with said second plate having a restrictor therein positioned intermediate the ink supply and said pressure chamber and an exit orifice in mutual communication with said pressure chamber and with said nozzle;
• a fifth plate contiguous with said fourth plate having a manifold therein connected to an ink supply and an exit orifice in mutual communication with said pressure chamber and with said nozzle;
• and
• a sixth plate intermediate said fifth plate and said first plate and contiguous therewith to form a compliant exterior to said manifold in said fifth plate, said sixth plate having an exit orifice therein in mutual communication with said pressure chamber and with said nozzle;
• said first plate having a compliance relief slot positioned in generally coextensive relationship with said manifold to permit motion of said sixth plate in response to pressure waves developed in said manifold.

An impulse ink jet print head comprising:

• a plurality of operating plates held together in a superposed relationship including at least:
• a first plate including at least one nozzle therein for ejecting droplets of ink therethrough, said nozzle having a diameter in the range of 50 to 85 micrometers and a length to diameter ratio in the range of approximately 1.0 to 2.0;
• a second plate defining at least one elongated ink chamber therein having dimensions lying in the range of 2 mm to 20 mm for length, 1.0 mm to 1.5 mm for width, and at least 0.15 mm for depth, said chamber being connected to an ink supply and having an outlet for directing ink toward said nozzle in said first plate;
• said nozzle having a central axis extending transversely of the planes of said plates and intersecting said second plates at an extremity of said chamber;
• said plates having passage means connecting said nozzle with said outlet;
• a third plate contiguous with said second plate including piezoelectric transducer means mounted thereon so as to overlie said pressure chamber and adapted, upon application of a voltage thereto, for displacing ink in said chamber thereby causing the ejection of ink droplets from said nozzle, said transducer means being substantially coextensive with its associated said pressure chamber, said third plate including said transducer means having a compliance in the range of 2 to 10.times.10.sup.-18 m.sup.3 /Pa;
• and
• a fourth plate contiguous with said second plate having a restrictor therein, positioned intermediate the ink supply and said pressure chamber;
• wherein ejection of droplets having a diameter of at least 80 micrometers occurs at frequencies up to 7 KHz without substantial variation in droplet diameter and speed.

A method of operating an ink jet print head defining an ink chamber therein having an inlet for filling the chamber and a nozzle and including piezoelectric driver means for displacing ink in the chamber movable about a de-energized position in the absence of an applied voltage and an energized position in the presence of an applied voltage for imparting a sequence of pressure waves to the ink in the chamber thereby causing the ejection from the nozzle of successive discrete ink droplets having a diameter of at least 70 micrometers at droplet ejection rates up to 7 KHz without substantial variation in droplet diameter and speed while avoiding interference from fluid oscillations caused by a previous droplet ejection comprising the steps of:

• imparting a voltage pulse for a first variable period of time to move the driver means to the energized position;
• reducing the voltage applied to the driver means for a fixed period of time chosen such that the velocity of a droplet ejected from the nozzle is substantially equal to the median of a series of velocities possible as a function of pulse width and resulting from the pressure waves present in the fluid;
• imparting a voltage pulse for a second variable period of time to again move the driver means to the energized position;
• and
• again reducing the voltage applied to the driver means for the fixed period of time.

A method of operating an ink jet print head of the construction including a plurality of operating plates held together in a contiguous superposed relationship and comprising a first plate having a nozzle therein for ejecting droplets of ink therethrough, a second plate defining an ink chamber therein overlying said nozzle, and a third plate including piezoelectric driver means for displacing ink in the chamber thereby causing the ejection of ink droplets from said nozzle, the piezoelectric driver means being movable about a de-energized position in the absence of an applied voltage and an energized position in the presence of an applied voltage, the method comprising the steps of:

• imparting a voltage pulse for a first fixed period of time to move the driver means to the energized position;
• reducing the voltage imparted to the driver means for a variable period of time;
• imparting a voltage pulse for a second fixed period of time to again move the driver means to the energized position;
• and
• again reducing the voltage imparted to the driver means for a variable period of time;
• thereby imparting a sequence of pressure waves to the ink in the chamber and causing the ejection from the nozzle of discrete ink droplets having a diameter of at least 80 micrometers at droplet ejection rates up to 3.5 KHz without substantial variation in droplet diameter and speed.

A method of operating an ink jet print head of the construction including a plurality of operating plates held together in a contiguous superposed relationship and comprising a first plate having a nozzle therein for ejecting droplets of ink therethrough, a second plate defining an ink chamber therein overlying said nozzle, and a third plate including piezoelectric driver means for displacing ink in the chamber thereby causing the ejection of ink droplets from said nozzle, the piezoelectric driver means being movable about a de-energized position in the absence of an applied voltage and an energized position in the pressure of an applied voltage, the method comprising the steps of:

• imparting a voltage pulse for a first fixed period of time to move the driver means to the energized position;
• reducing the voltage imparted to the driver means for a variable period of time;
• imparting a voltage pulse for a second fixed period of time to again move the driver means to the energized position;
• and
• again reducing the voltage imparted to the driver means for a variable period of time;
• wherein the duration of the fixed periods of time is approximately in the range of 10 to 30 microseconds;
• thereby imparting a sequence of pressure waves to the ink in the chamber and causing the ejection from the nozzle of discrete ink droplets having a diameter of at least 80 micrometers at droplet ejection rates up to 5 KHz without substantial variation in droplet diameter and speed.