Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1999-01-19
2001-08-14
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S009000, C347S010000, C347S011000, C347S068000, C347S070000
Reexamination Certificate
active
06273539
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for and method of ejecting ink to print images or characters.
2. Description of the Related Art
A typical actuator used for control of ink ejection in the inkjet printer has a plurality of ink chambers and a plurality of piezoelectric elements. This actuator is mounted on a head (printer-head). The piezoelectric elements correspond to the ink chambers, respectively. By expansion and restoring (shrinkage) of the piezoelectric elements, the pressure is applied to the ink in the respective ink chambers. The ink chambers communicate with the corresponding ink ejecting holes, respectively. When the pressure is applied, the ink is ejected from the ink chambers to the outside through the ink ejecting holes. The ink ejecting holes are formed on a nozzle plate, which is attached to the actuator. These ink ejecting holes are arranged in the directions of conveyance of recording papers and movement of the head.
When printing, certain ink chambers are selected from among all of the ink chambers, depending on image data to be printed or resolution. Namely, when printing, the ink chambers that actually eject ink are only selected. Then, the volume of the selected ink chambers is only changed by the expansion and shrinkage of the piezoelectric elements. Therefore, the internal pressure of the selected ink chambers is only controlled. Accordingly, the ink is supplied only into the selected ink chambers, and ejected only from the ink ejecting holes corresponding to the selected ink chambers.
However, the ink is supplied though a common ink channel to the ink chambers, respectively. Therefore, one ink chamber and another ink chamber are connected each other through this ink channel. As a result, when the internal pressure of the selected ink chamber is changed by the distortion of the piezoelectric elements, the change of the pressure is propagated through the ink channel as a pressure wave, and reaches other ink chambers, i.e., non-selected ink chambers. As a result, the ink in the non-selected ink chambers leaks to the outside through the corresponding ink ejecting holes. The leakage of the ink can disturb a shape of a meniscus of the ink in the ink ejecting holes. The disturbance of the meniscus causes undesirable changes of the ejecting direction of the ink or impossibility of the ink ejection.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an apparatus for and method of ejecting ink, which can be prevent leakage of ink from non-selected ink chambers.
To achieve this object, an ink ejecting apparatus according to the present invention has: a plate member in which an ink channel is formed; an ink supplying source for supplying the ink to the ink channel; a plurality of ink chambers formed in the plate member and each communicating with the ink channel to allow the ink to be moved from the ink channel into the plurality of ink chambers; a plurality of ink ejecting holes formed in the plate member and communicating with the plurality of ink chambers, respectively, to eject the ink from the plurality of ink chambers; a selection device for selecting more than one of the plurality of ink chambers that actually ejects the ink; a first control device for reducing a volume of each of the selected ink chambers to actually eject the ink from the selected ink chambers; and a second control device for expanding a volume of each of non-selected ink chambers to absorb a pressure wave which is caused by a change of the volume of each of the selected ink chambers.
When the ink ejection is carried out, the ink is supplied from the ink supplying source to the ink channel. Then, the ink is moved from the ink channel into each ink chamber. Next, the ink chambers that actually eject the ink are selected by the selection device. For example, the selection device selects the ink chambers that actually eject the ink, depending on image data or character data to be printed on the recording medium. Next, the first control device reduces the volume of each selected ink chamber to actually eject the ink. At this time, the pressure wave occurs because of the change of the volume of each selected ink chamber. The pressure wave is transmitted from the selected ink chambers to the non-selected ink chambers. In order to absorb this pressure wave, the second control device expands the volume of each non-selected ink chamber. Therefore, the pressure wave is restrained by the expansion of the volume of each non-selected ink chamber. Accordingly, leakage of the ink from the non-selected ink chambers can be prevented.
The time that the volume of each non-selected ink chamber is expanded is important to improve the capability of the absorption of the pressure wave. According to the present invention, the second control device expands the volume of each non-selected ink chamber at a time that the first control device reduces the volume of each selected ink chamber to actually eject the ink. When the first control device reduces the volume of each selected ink chamber to eject the ink, the amplitude of the pressure wave increases. Therefore, if the volume of each non-selected ink chamber is expanded at this time, it is possible to absorb the pressure wave effectively.
Especially, if the volume of each non-selected ink chamber is expanded at a time that the amplitude of the pressure wave reaches its maximum, it is possible to absorb the pressure wave more effectively.
After the volume of each non-selected ink chamber is expanded, it is necessary to restore this volume. The time that the volume of each non-selected ink chamber is restored is important to improve the performance of the ink ejection. According to the present invention, in order to restore the volume of each non-selected ink chamber, the second control device reduces the volume of each non-selected ink chamber at a time that the amplitude of the pressure wave reaches its minimum. When the amplitude of the pressure is minimum, the internal pressure of the non-selected ink chamber is reduced. Therefore, if the volume of each non-selected ink chamber is restored (reduced) at this time, the internal pressure created by the reduction of the volume of each non-selected ink chamber is absorbed. Accordingly, it is possible to prevent leakage of the ink from the non-selected ink chamber through the corresponding ink ejecting holes.
Furthermore, the second control device may determine the degree of the expansion of the volume of each of the non-selected ink chambers, depending on the number of the selected ink chambers. If the number of the selected ink chambers is large, the amplitude of the pressure wave is large. If the amplitude of the pressure wave is large, the degree of the expansion of the volume of each non-selected ink chamber is large. Therefore, the pressure wave can be effectively absorbed. In contrast, if the number of the selected ink chambers is small, the amplitude of the pressure wave is small. If the amplitude of the pressure wave is small, the degree of the expansion of the volume of each non-selected ink chamber is also small. If the degree of the expansion of the volume of each non-selected ink chamber is small, this volume can be restored quickly. Therefore, it is possible to achieve a rapid ink ejecting action.
Alternatively, the second control device may determine the degree of the expansion of the volume of each non-selected ink chamber, depending on a positional relationship between the selected ink chambers and the non-selected ink chambers.
Furthermore, a plurality of piezoelectric elements may be used to change the volume of each ink chambers. In this case, the plurality of piezoelectric elements may be allocated to the plurality of ink chambers, respectively. Further, in this case, the first control device may include a first driving voltage supplying device for supplying a first driving voltage to the plurality of piezoelectric elements to deflect the plurality of piezoelectric elements, and the second contro
Barlow John
Brother Kogyo Kabushiki Kaisha
Do An H.
Oliff & Berridge PLC.
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