Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-09-28
2003-04-22
Hsieh, Shih-wen (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S030000, C347S031000
Reexamination Certificate
active
06550890
ABSTRACT:
This application is based on Patent Application No. 10-276016 filed Sep. 29, 1998 in Japan, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an ink jet printing apparatus and more specifically to an ink jet printing apparatus having an improved recovery device for recovering or keeping in good condition an ink ejection performance of an ink jet print head.
Printing apparatus for printing a print sheet (also referred to simply as “recording paper”), such as paper, cloth, plastic sheet and OHP sheet, are being proposed in a construction capable of mounting print heads of various systems, including, for example, a wire dot system, a thermosensitive system, a heat transfer system and an ink jet system.
Of these printing apparatus, an ink jet printing apparatus (also referred to as an ink jet printer) that ejects ink from ink orifices to print on recording paper is a low-noise, non-impact type printing system and can perform a high-density, high-speed printing operation.
Generally, an ink jet printing apparatus has a means for driving a print head carrier, a means for feeding recording paper, and a means for controlling these means.
There are several types of energy generating elements for generating energy used to eject ink from orifices of the print head. They include an element that uses an electromechanical transducer such as piezoelectric material, an element which radiates electromagnetic waves such as laser to heat ink to eject an ink droplet by the action of heat, and an element that uses an electrothermal transducer having a heating resistor to heat the liquid.
A print head of an ink jet print system that ejects ink droplets by thermal energy is capable of printing at high resolution because the ink orifices can be arranged at high density. In the ink jet print system, a print head using the electrothermal transducer as an energy generating element is advantageous because it can easily be reduced in size and manufactured by fully utilizing the advantages of IC technology and microfabrication technique in the semiconductor field whose technical progress and reliability improvement are remarkable in recent years and because it can easily be increased in integration density and its production cost is low.
As described above, though it is an excellent print system simple in construction, the ink jet print system has problems that need to be solved.
One of the problems is stains formed around ink orifices on that surface (hereinafter referred to as a head face) of the print head which faces the print medium and in which ink orifices are formed. There are mainly two causes for the stains. A first cause for the stains is that when ink ejected for printing strikes the print paper, a part of the ink fails to adhere to the paper and bounces off. Further, when ink is ejected, miniscule ink particles, other than the main ink droplets contributing to the printing, may be formed and float in the air. These ink particles adhere to the head face, forming stains.
A second cause for the stains is ink droplets remaining on the head face during an ejection performance recovery operation, in which a cap is put on the head face to draw ink by suction from within the ink orifices in order to prevent clogging of the ink orifices and then is removed from the head face. When ink is drawn by suction, the cap is filled with ink. When in this condition the cap is removed from the head face, the ink in contact with the head face remains there. To prevent this, the head face may be treated with a liquid repulsive coating but this cannot expel residual ink completely.
Further, to remove ink remaining in the cap when the cap is taken off the head face after the ejection performance recovery operation is performed on the ink orifices, an thin plate-like absorbing body made of porous resin or nonwoven cloth is installed in the cap. If the absorbing body is not provided in the cap, when, with the cap open, the suction is performed to remove ink from the cap, only the ink in the immediate vicinity of the discharge port in the cap is drawn out, leaving the link at the surrounding areas. That is, the use of the absorbing body allows a negative pressure to act slowly so that the ink in the cap is drawn out by suction uniformly.
When unwanted ink droplets adhere to around the ink orifices, troubles occur, such as a so-called “kink” in which the ink ejection direction deviates from the intended direction and an “ejection failures” in which ink cannot be ejected at all, degrading the print quality.
To solve this problem, a method is often adopted which wipes the head face with a blade (or wiper) as a wiping member made of an elastic material such as rubber (this operation is also referred to as “wiping”). The wiping method includes one which scans the print head with respect to a stationary blade to wipe the head face by the blade and one which holds the print head immovable and advances or pivots the blade to bring it into contact with the head face.
To prevent the blade and the print head from contacting each other unnecessarily hard, the former method may support the blade so as to be projectable toward the print head and set the blade in a projected position during the scanning of the print head in one direction only and in a retracted position during the scanning in the opposite direction. The latter method may reciprocally advance or reciprocally pivot the blade extending in a direction perpendicular to the main scan direction and properly advance or retract the print head to and from the blade scanning position. When the wiping is to be performed only during the forward movement for example, the print head is set at the corresponding position and, during the return movement, is retracted from that position.
However, when residual ink remains on the head face in large quantity, a large amount of ink will adhere to the head face wiping blade. As a result, when a means for cleaning the blade (cleaner) is provided, a large quantity of ink will adhere to the cleaner. This raises another problem of disposing of the ink wiped by the blade and of processing an ink receiving member such as cleaner.
Among the technologies that solve these problems and reduce the amount of ink remaining on the head face following the ink ejection performance recovery operation is Japanese patent Application Laying-open No. 11-138855 laid-opened on May 25, 1999.
Although the invention of the Japanese patent Application Laying-open No. 11-138855 (1999) can reduce the amount of ink remaining on the head face after the ejection performance recovery operation, a small amount of grain-like ink is found remaining in a case where there is a relative positional relationship between the cap and the in-cap absorbing body. In such a case it is known that ink often remains when the head engagement portion of the cap and the end portions of that surface of the ink absorbing body in the cap which is parallel to and nearest to the head face are close to each other.
OBJECT OF THE INVENTION
To solve these problems experienced with the conventional systems it is an object of the present invention to provide an ink jet printing apparatus with an ejection performance recovery device which secures a predetermined space between the surface of the in-cap absorbing body facing the head face and the head engagement surface of the cap.
SUMMARY OF THE INVENTION
In the first aspect of the present invention, there is provided an ink jet printing apparatus comprising,
a cap for capping ink orifices provided on a head face of an ink jet print head,
an in-cap absorbing body disposed in the cap, and
a suction means for sucking ink from the ink orifices through the cap,
wherein the cap has a space formed along almost an entire circumference of a head engagement portion of the cap between an end surface of the in-cap absorbing body which is nearest to the head face and the head engagement portion of the cap.
Here, position restriction portions for the in-cap absorbing body may
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