INK JET HEAD

Abstract

Disclosed is an ink jet head driven by a drive IC for ejecting an ink droplet having conductivity, comprising a chamber for storing ink, a nozzle plate attached to the chamber, an actuator provided with an electrode electrically contacting ink in the chamber and activated by a current flowing through the electrode from a power supply, a conductive plate including an opening and glued to the nozzle plate such that the nozzle is exposed through the opening, and a current limiter limiting the current when the ink is purged from the nozzle during a period other than that of ink being ejected. Even if the purge is repeatedly carried out, an extraordinarily rising in temperature of the drive IC and resultant breakdown of the IC can be prevented.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of this invention will become apparent and more readily appreciated from the following detailed description of the presently preferred exemplary embodiments of the invention taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view of an ink jet head in an embodiment in the present invention;

FIG. 2 is a plan view of a conductive plate seen from a nozzle side;

FIG. 3 is a partial cross-sectional view of a vicinity of a nozzle of the ink jet head;

FIG. 4 is a partial cross-sectional view of an ink jet head showing a vicinity of a nozzle facing down;

FIG. 5 is an equivalent circuit diagram explaining phenomena occurring when the purge is performed to reduce ink remained adjacent to a nozzle of an ink jet head;

FIG. 6 is a partial cross-sectional view of an ink jet head showing a vicinity of a nozzle in the first embodiment;

FIG. 7 is a partial cross-sectional view of an ink jet head showing a vicinity of a nozzle in the second embodiment;

FIG. 8 is a partial cross-sectional view of an ink jet head showing a vicinity of a nozzle in the third embodiment;

FIG. 9 is a partial cross-sectional view of an ink jet head showing a vicinity of a nozzle in the fourth embodiment; and

FIG. 10 is a partial cross-sectional view showing a vicinity of a nozzle in a conventional ink jet head.

Claims

1. An ink jet head which ejects ink therein having conductivity, comprising: a chamber configured to temporarily store ink;a nozzle plate attached to the chamber, the nozzle plate including a nozzle through which ink is ejected;an actuator configured to actuate ink in the chamber to be ejected, the actuator being provided with an electrode at least a part of which electrically contacts ink in the chamber, the actuator being activated by a current flowing through the electrode from a power supply;a conductive plate including an opening and attached to the nozzle plate such that the nozzle is exposed through the opening; anda current limiter configured to limit the current flowing from the power supply through both the conductive plate and ink in the chamber when ink is purged from the nozzle in a period other than that of ink being ejected.

2. An ink jet head according to claim 1, wherein the current limiter is formed of a resistor provided between the conductive plate and the power supply in an electrical.

3. An ink jet head according to claim 1, wherein the current limiter is formed of a switch cutting off the current when the ink is purged, the switch being provided between the conductive plate and the power supply.

4. An ink jet head according to claim 1, wherein the current limiter is formed of a discharge brush having a prescribed resistance and removing an electrostatic charge on a surface of the conductive plate.

5. An inkjet head according to claim 1, further comprising a control circuit controlling operation of the ink jet head and including the power supply, the control circuit being integrally mounted on the ink jet head.

6. An ink jet head which ejects an ink droplet, comprising: a chamber configured to temporarily store ink;a nozzle plate attached to the chamber, the nozzle plate including a nozzle through which ink is ejected;an actuator configured to actuate ink in the chamber to be ejected, the actuator being provided with an electrode at least a part of which electrically contacts ink in the chamber and activated by a current flowing through the electrode from an power supply; anda plate having a prescribed resistance value, the plate having an opening and being attached to the nozzle plate such that the nozzle is exposed through the opening.

7. An ink jet head according to claim 6, further comprising a control circuit controlling operation of the ink jet head and including the power supply, the control circuit being integrally mounted on the ink jet head.