Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1999-04-30
2001-11-06
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06312074
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to inkjet printers and, more particularly, to an inkjet printing system that makes use of sensing to determine ink level in the ink supply.
BACKGROUND OF THE INVENTION
Inkjet printers include a drop ejection device and a supply of printing fluid such as ink for replenishing ink to the drop ejection device. In the case of thermal inkjet printing, the drop ejection device is typically referred to as a printhead. Printing is accomplished by the selective actuation of the printhead as the printhead is moved relative to a print media. One common type of previously used inkjet printer uses a replaceable print cartridge that contains a printhead and a supply of ink contained within the print cartridge. This type of print cartridge is not intended to be refillable. When the initial supply of ink is depleted, the print cartridge is disposed of, and a new print cartridge is installed.
Another type of inkjet printer makes use of an ink reservoir that is separately replaceable from the printhead. The replaceable reservoir can be positioned on a scanning carriage with the printhead or positioned off the scanning carriage. In the case where the ink cartridge is mounted off carriage, the ink cartridge is either continuously in fluid communication with the printhead such as being connected by a flexible conduit or intermittently connected by positioning the carriage at a refilling station. The use of a replaceable ink container allows for the replacement of the ink container separately from the printhead, allowing the printhead to be used until end of printhead life, reducing the cost per page of printing.
Regardless of the inkjet printer configuration, it is important that the system have an accurate means of indicating when a low or out of ink condition has occurred to avoid exhausting one or more of the ink supplies in the middle of a printing job. In the case of large format printing, the job or sheet must be scrapped and the job restarted resulting in waste. Moreover, it is important that the printing system stop printing when the ink container is nearly empty. Allowing the inkjet printhead to reach the state of complete ink exhaustion can result in operation of the thermal printhead without ink, which can result in catastrophic damage and failure of the printhead.
There are clear advantages to knowing when the ink container is out of ink as well as having the ability to detect ink levels at numerous positions on the ink container. For example, with large format printers, which use a considerable amount of ink for covering large printing surfaces, the ability to compare ink requirements with the amount of ink remaining in the ink container prior to printing would be invaluable. In addition, providing more comprehensive feedback to the user of ink use allows the user to better anticipate when the ink containers will require replacement.
SUMMARY OF THE INVENTION
The present invention is a fluid level sensing system for determining fluid levels in a fluid container. The system has a resonant member with an attached magnet. The resonant member is disposed in the fluid container. Included is a sensing device for sensing motion of the magnet. The movement of the magnet attached to the resonant member is indicative of fluid level in the fluid container.
In one embodiment of the invention the sensing system includes an exciter driver and a signal receiving device. In this embodiment, the exciter driver invokes the resonant member to resonate and the signal receiving device senses movement of the attached magnet. The resonating signal has an amplitude that is damped according to a level of the fluid remaining in the fluid container. This amplitude is indicative of the fluid level of fluid container.
In yet another embodiment, there is a plurality of fluid containers with each of the fluid containers having a resonant member and a magnet. In this embodiment, the single signal exciter driver and the single signal receiving device are moved relative to the plurality of fluid containers so that the single signal exciter driver applies a resonating signal that selectively resonates each of the resonating members and is received by the single signal receiving device to selectively determine fluid level in each of the fluid containers.
REFERENCES:
patent: 3814146 (1974-06-01), Mesh
patent: 5054318 (1991-10-01), Lew
patent: 5079570 (1992-01-01), Mohr et al.
patent: 5689288 (1997-11-01), Wimmer et al.
patent: 5812156 (1998-09-01), Bullock et al.
Andrews Teri G.
Barlow John
Brooke Michael S.
Hewlett--Packard Company
Sullivan Kevin B.
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