Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1997-01-14
2001-10-16
Yockey, David F. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S085000
Reexamination Certificate
active
06302516
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to ink supply systems for ink jet printheads.
In many ink jet printheads it is important to maintain a negative pressure at the orifices from which ink is ejected in order to avoid weeping of ink from the orifices when the printhead is not operating. In addition, it is occasionally necessary to purge the printhead by ejecting ink under pressure through the printhead. It is also necessary in many cases to refill the reservoir from which ink is supplied to the printhead from a remote ink supply periodically in order to maintain a desired level of ink in the ink reservoir and to provide a remote ink supply which can be quickly and easily connected to the printhead in an inexpensive manner.
Certain prior art arrangements such as those described in the Robinson U.S. Pat. No. 4,187,511, the Matsumoto U.S. Pat. No. 4,536,777, the Eremity et al. U.S. Pat. No. 4,602,662 and the Mizusawa et al. U.S. Pat. No. 4,677,448 provide a remote ink supply from which ink is drawn to a reservoir for an ink jet head by a vacuum arrangement but these arrangements are complex and expensive. In other prior art arrangements such as described, for example, in the Okamura et al. U.S. Pat. No. 5,485,187, the ink level in the reservoir from which ink is supplied to a printhead is maintained at a desired spacing below the orifices in the printhead so as to produce a desired negative pressure at the orifices in the ink jet head and positive pressure may be applied for purging but the level of ink in a remote ink supply must be the same as the level of ink in the reservoir. The prior art, moreover, does not disclose a simple and inexpensive dual reservoir ink supply system for an ink jet printhead in which the ink in the reservoir can maintained at a desired level while permitting convenient replenishment of the reservoir from a remote ink supply which may be disposed at any level and also providing for purging of the printhead in a convenient manner, nor does it provide a simple and convenient arrangement for connecting and removing a remote ink supply.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a dual reservoir ink supply system for ink jet printheads which overcomes the disadvantages of the prior art.
Another object of the invention is to provide a dual reservoir vacuum ink supply system for an ink jet printhead in which the ink in an ink reservoir supplying ink to the printhead is normally maintained at a desired level while providing for purging of the printhead when necessary and for replenishment of the ink reservoir in a convenient and inexpensive manner.
These and other objects of the invention are attained by providing an ink supply system including an ink reservoir connectable to a remote ink supply and an air pump connected to the ink reservoir by which a vacuum may be applied to draw ink from the remote ink supply through a valve into the ink reservoir. The ink reservoir includes an ink sensor to detect the presence of ink at a desired level in the reservoir and the ink supply system also includes a purge reservoir in which ink is normally maintained at the same level as in the ink reservoir and to which pressure may be applied to purge the printhead when another valve connecting the purge reservoir and the ink reservoir is closed. Preferably, an air pump is provided to apply vacuum to the ink reservoir for replenishment from the remote ink supply and another air pump is provided to apply pressure to the ink in the purge reservoir when purging is required. The valves controlling communication between the reservoirs are preferably solenoid valves. To permit convenient replacement of the remote ink supply, a friction fit luer connection may be used.
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Brooks Jeffrey B
Georgis David G.
BakerBotts LLP
Markem Corporation
Yockey David F.
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