Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-04-02
2001-11-06
Nguyen, Judy (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06312087
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recorder having a purging device, and more particularly to an ink jet recorder having a purging device which is capable of effectively removing bubbles and foreign objects attached to wall surfaces of ink passages of a recording head.
2. Description of the Related Art
Generally, an ink jet printer, for example, is known as an ink jet recording apparatus for effecting recording such as printing by ejecting ink onto a recording medium such as paper.
In the ink jet printer, as shown in
FIG. 11
, an ink cartridge P
1
in which ink is accommodated is replaceably mounted on a recording head unit P
3
having a recording head P
2
. Ink is supplied from the replaced ink cartridge P
1
to the recording head P
2
, and is ejected through ejection nozzles P
4
so as to effect recording.
Further, such as in the course of using the ink jet printer, a so-called purging operation in which the ink is sucked from distal end sides of the ejection nozzles P
4
, i.e., from nozzle faces P
5
where ejection holes (not shown) are open, is performed by the manual operation of a switch by a user or automatically when a predetermined condition has been met.
The purging operation is an operation in which a suction cap P
6
is applied to the nozzle face P
5
, and negative pressure is applied to the interior of the suction cap P
6
by a suction pump (not shown), thereby sucking the ink from inside the recording head P
2
through the suction cap P
6
and removing the same to outside.
However, there have been cases where very small bubbles and dust remaining inside ink passages cannot be removed sufficiently by only the purging operation based on the suction which makes use of the aforementioned negative pressure.
Namely, there has been a problem in that although very small bubbles and dust are sometimes attached to inner peripheral surfaces (wall surfaces) of unillustrated channels and a manifold for forming ink passages, since the closer to the wall surface, the slower the velocity of flow of the ink, it is difficult to remove the bubbles and dust attached to the wall surfaces even if flow of ink is produced by executing a purge.
If the bubbles and dust remain in the passages of the ink, there have been cases where ejection is hampered during the ejection of the ink, resulting in a decline in the recording quality.
Accordingly, as disclosed in Japanese Patent Application No. 295267/1988 and in its corresponding U.S. Pat. No. 5,298,923, a technique has been proposed in which the printing head is driven in synchronism with the suction of the ink in the purging operation. According to this technique, the ink in the ink passages is vibrated by driving the printing head, and very small dust and bubbles which are attached to the inner wall surfaces of the inner wall surfaces of the ink passages and which could not be removed by suction alone are also exfoliated smoothly and are easily removed by the vibration of the ink.
However, this publication fails to disclose the execution of the operation of the actuators of the print head after the lapse of a predetermined time duration from the start of the purging operation as in the present invention.
When a user has loaded an ink cartridge in a new printer for the first time in the use of the ink jet printer, the ink passages are filled with air. In addition, when the ink cartridge has been replaced, air is present between the ink cartridge and the print head. Further, after making a misjudgment that ejection is impossible when the remaining amount of ink has become small, the user might effect a purging operation to recover the ejecting function. If the user does so, there occurs a state in which the print head is emptied of the ink and the ink passages are filled with air.
If the ink is abruptly sucked by applying a large negative pressure at a stroke when filling the ink passages with the ink by performing a purging operation in the above-described state, the ink and air become mixed and flow into the print head, so that bubbling occurs in the ink, and the bubbles are entrained in the ink inside the print head. In particular, in a case where filter members are provided to prevent dust and the like from moving toward the print head together with the ink, when the ink abruptly passes through the filter members, large-scale bubbling occurs, and bubbles are produced in a large amount.
Thus, in the state in which a mixture of ink and air has abruptly flowed into the print head, if the print head is driven in synchronism with the suction of the ink as in the technique disclosed in the aforementioned publication, the bubbling of the ink is further prompted. As a result, the ejection of the ink is hampered appreciably, and it becomes impossible to effect normal printing.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an ink jet recording apparatus which is capable of effectively removing bubbles and foreign objects attached to wall surfaces of ink passages of a recording head.
Another object of the present invention is to provide an ink jet recording apparatus which is capable of a purging operation which makes it possible to allow ink to be introduced into the recording head while suppressing the bubbling of the ink even in a case where air is present in ink passages of the recording head.
In accordance with a first aspect of the present invention, there is provided an ink jet recorder comprising: a recording head having an ink passage, a nozzle connected thereto, and an actuator for ejecting ink from the nozzle by changing a volume of the ink passage; a purging device for covering the nozzle and sucking the ink inside the recording head; and a control unit for controlling the actuator such that the actuator is operated after the lapse of a predetermined time duration from a start of purge by the purging device.
In the ink jet recorder in accordance with the first aspect of the present invention, the actuator is activated after the lapse of a predetermined time duration after the start of purge, i.e., when the flow of the ink sucked by the purging device is taking place in the ink passage. Very small bubbles and foreign objects which remained attached to the walls of the passages are removed from the walls due to the vibration of the walls of the ink passages or cavitation based on the vibration through the operation of the actuator, and are discharged outside the recording head together with the flowing ink. As a result, it is possible to improve the recording quality.
To remove the bubbles in the ink passage, it has been found that it is effective to perform the operation of the actuator when the ink inside the ink passage has actually started to flow. Namely, by vibrating the ink passage when the ink is flowing at a predetermined flow rate, the separation of the bubbles from the wall is prompted. For this reason, the predetermined time duration can be set to one at least from the start of purge until the flow of the ink inside the ink passage is started.
The ink jet recorder in accordance with the present invention further comprises: an ink cartridge; and a sensor for detecting replacement of the ink cartridge, wherein the control unit is capable of operating the purging device in response to a signal representing detection of the replacement of the ink cartridge by the sensor, and of operating the actuator after the lapse of a predetermined time duration from the start of purge by the purging device. The bubbles in the ink passage are liable to occur due to the replacement of the ink cartridge. Accordingly, in the ink jet recorder of the type in which the ink cartridge is replaced, the replacement of the ink cartridge is automatically detected by the sensor, and the purge is executed on the basis of the signal representing detection of the replacement of the cartridge. At the same time, by driving the recording head after lapse of a predetermined time duration subsequent to the start of purge, it is possible to effectively remov
Imai Koji
Nakamura Hirotake
Brother Kogyo Kabushiki Kaisha
Nguyen Judy
Oliff & Berridg,e PLC
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