Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-06-02
2002-01-22
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06340223
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a thermal type ink-jet head for recording an image on a recording medium by ejecting ink droplets from an ejection nozzle by the pressure rise occurring when bubbles arise in the ink which is heated by a heating element.
(2) Description of the Prior Art
As the recording head used in a printer for forming an image on a recording medium, thermal type ink-jet heads have been used which eject ink droplets from an ejection nozzle by the pressure rise occurring when bubbles arise in the ink which is heated by a heating element. In a thermal type ink-jet head, a pulse current is supplied to a heating element arranged on the substrate in accordance with the image data, the heating element heats so that the ink being in contact with the heating element is heated giving off bubbles. Generation and expansion of the bubbles causes pressure rise, whereby ink in the ejection nozzle is ejected out as ink droplets. This ink droplet jumps to the recording medium placed in proximity to the ejection nozzle, creating a recording dot in an image as a recording pattern.
In the thermal type ink-jet head, part of the heat generated from the heating element dissipates by way of the substrate. Therefore, in order to eject a sufficient amount of ink for image forming on the recording medium, a large amount of current needs to be supplied to the heating element, giving rise to a drawback of the electric power consumption being increased.
Japanese Patent Application Laid-Open Hei 7 No.227968 discloses a configuration in which a space as a thermally insulating layer is formed between a heating element (heater) and a substrate so that heat arising from the heating element will not transfer to the substrate.
Japanese Patent Application Laid-Open Hei 2 No.3054 discloses a configuration in which a pressure generating means composed of a vibration plate and a heating layer is provided in the form of a cantilever structure or a simple beam supported at both ends and an electric current is supplied to the heating layer so as to cause a heat distortion within the pressure generating means and thereby deform and displace the pressure generating means in the nozzle plate direction, thus causing ink droplets to jump outside.
Registered Japanese Patent publication No.2769447 discloses a configuration in which two layers having different thermal conductivities are formed between a heating element and a substrate so as to inhibit thermal transfer from the heating element to the substrate.
However, since, with the above ink-jet head, heat arising from the heating element is hard to be released to the exterior, the heat generated while the heat element is energized remains in the heating element after removal of the electric supply. Therefore, even if the current is supplied in pulses to the heating element, the heat builds up in the heating element, elevating the temperature of the heating element, thus causing an overheated state. In this way, the ink-jet head has the drawback of overheating which will lower the response of the heating element, resulting in deficiency in the exact control of the ejected amount of ink.
In the configuration disclosed in Japanese Patent Application Laid-Open Hei 2 No.3054, since the pressure generating member is of a cantilever structure or of a beam supported at both ends, the pressure acting on the ink varies depending upon the positions along the beam, presenting poor ink ejection efficiency.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an ink-jet head which can efficiently heat the ink with heat generated from a heating element while the voltage is applied and hence can reduce the electric power consumption and which can reduce the temperature of heating element rapidly while the voltage is not applied, whereby it is possible to exactly control the ejected amount of ink by making the response frequency of the heating element substantially equal to the frequency of the pulse voltage to be applied to the heating element, thus improving the ink ejection response to the print data.
As the means for solving the above drawbacks, the present invention is configured as follows:
In accordance with the first aspect of the present invention, an ink-jet head for ejecting ink by heating and bubbling ink, includes: a heating element to which electric current is supplied so as to heat and bubble the ink; and a head substrate having a void formed between the heating element and the head substrate, and is characterized in that the heating element will buckle into the void by thermal expansion accompanying the temperature rise thereof.
In accordance with the second aspect of the present invention, the ink-jet head having the above first feature is characterized in that the heating element comprises: a heater; a protective film for protecting the heater; and an insulation film for insulating the heater and the above components are formed of materials having approximately equal coefficients of linear expansion to each other.
In accordance with the third aspect of the present invention, the ink-jet head having the above first feature is characterized in that the heating element is arranged with its movement constrained at both ends with respect to the direction of the thickness and the direction perpendicular to the thickness.
In accordance with the fourth aspect of the present invention, the ink-jet head having the above first feature is characterized in that the heating element is configured so as to come into contact with the head substrate when buckled into the void.
In accordance with the fifth aspect of the present invention, the ink-jet head having the above first feature is characterized in that the void is arranged so as to communicate with a cavity that stores ink.
In accordance with the sixth aspect of the present invention, the ink-jet head having the above first feature is characterized in that the head substrate has a communication hole for establishing communication between the void and the exterior.
In accordance with the seventh aspect of the present invention, an ink-jet head for ejecting ink by heating and bubbling ink, includes: a heating element to which electric current is supplied so as to heat and bubble the ink; and a head substrate having a void formed between the heating element and the head substrate, and is characterized in that the heating element is provided in a bimetal configuration made up of multiple kinds of metals so as to cause the heating element to deform into the void by the temperature rise thereof.
In accordance with the eighth aspect of the present invention, an ink-jet head for ejecting ink by heating and bubbling ink, includes: a heating element to which electric current is supplied so as to heat and bubble the ink; and a head substrate having a void formed between the heating element and the head substrate, and is characterized in that the heating element is formed with a shape memory alloy layer which will deform into the void when the heating element exceeds a predetermined temperature.
In accordance with the ninth aspect of the present invention, an ink-jet head for ejecting ink by heating and bubbling ink, includes: a heating element to which electric current is supplied so as to heat and bubble the ink; a head substrate having a void formed between the heating element and the head substrate; and a piezoelectric actuator which pushes and deforms the heating element toward the void.
In accordance with the tenth aspect of the present invention, an ink-jet head for ejecting ink from a nozzle by heating and bubbling ink, includes: a first substrate; a second substrate arranged opposing the first substrate, defining a space to be filled with ink in corporation with the first substrate; and a heating element disposed between the first and second substrates and having a voltage selectively applied thereto so that the ink inside the space is heated and bubbled, and is characterized in that the heating element is arranged between the fi
Brooke Michael S.
Sharp Kabushiki Kaisha
LandOfFree
Ink-jet head and fabrication method of the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ink-jet head and fabrication method of the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ink-jet head and fabrication method of the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2842213