Liquid purification or separation – Filter – Supported – shaped or superimposed formed mediums
Reexamination Certificate
1997-12-18
2001-07-31
Walker, W. L. (Department: 1723)
Liquid purification or separation
Filter
Supported, shaped or superimposed formed mediums
C210S459000, C210S460000, C210S489000, C210S490000, C347S092000, C347S093000
Reexamination Certificate
active
06267251
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a filter for removing contaminants from a fluid and a process for forming same and, more particularly, to a filter adapted for use in an ink jet print cartridge for filtering contaminants from ink prior to the ink flowing to a heater chip.
BACKGROUND OF THE INVENTION
Drop-on-demand ink jet printers use thermal energy to produce a vapor bubble in an ink-filled chamber to expel an ink droplet. A thermal energy generator or heating element, usually a resistor, is located in the chamber on a heater chip near a discharge orifice or nozzle. A plurality of chambers, each provided with a single heating element, are provided in the printer's printhead. The printhead typically comprises the heater chip and a plate having a plurality of the discharge orifices formed therein. The printhead forms part of an ink jet print cartridge which also comprises an ink-filled container.
The print cartridge container includes one or more ink chambers. For a monochrome or single color print cartridge, one chamber is provided. For a three color print cartridge, three chambers are included. The print cartridge container may also include a filter/standpipe assembly for each chamber. The standpipe defines a passageway through which ink flows as it travels from the chamber to the printhead. The filter is attached to the standpipe and functions to remove air bubbles and contaminants from the ink before the ink reaches the printhead. Contaminants, if not removed from the ink, may block orifices in the printhead orifice plate, thereby preventing ink from being ejected from those orifices.
The quality of printed images produced by an ink jet printer depends to a large degree on the resolution of the printer. Higher or finer resolution wherein the dots are more closely spaced provides for higher quality images.
A consideration with increasing the resolution of ink jet printers is that increased resolution results in more printed dots per unit area. For example, doubling print resolution from 600×600 dpi to 1200×1200 dpi results in four times as many dots per unit area. Since the number of dots per unit area increases with increased resolution, the size of each printed dot must decrease in order to avoid saturating the print media. Hence, the size of the orifices in the orifice plate must decrease. In order to prevent the smaller orifices from becoming blocked or obstructed by contaminants contained in ink, finer filters are required.
Conventional filters are typically made from a metal mesh. It is believed that very fine metal mesh filters would be costly to produce. Further, it is believed that ink pressure drop across the metal mesh filter would be large due to the meandering flow path the ink must take as it passes through the metal mesh.
Accordingly, there is a need for an improved filter which is capable of removing particles of varying sizes including very small particles from ink without also effecting a large drop in fluid pressure across the filter.
SUMMARY OF THE INVENTION
With the present invention, an improved filter is provided which is capable of removing particles of varying sizes including very small particles from a fluid without effecting a large drop in fluid pressure across the filter. The filter is adapted for use in an ink jet print cartridge for filtering contaminants from ink prior to the ink flowing to a printhead. It is also contemplated that the filter may be used in other applications where filters capable of removing particles of varying sizes including very small particles are desired.
The filter of the present invention is formed from a silicon substrate. The substrate has first and second etch resistant material layers on its opposing sides. One of the layers includes a plurality of pores, each preferably having an area or size of between about 0.5 &mgr;m
2
and about 25 &mgr;m
2
. The second layer defines a filter layer which filters air bubbles and contaminants from ink passing through the filter. In contrast to conventional metal mesh filters, the silicon filter of the present invention has a direct flow path. Hence, the resistance to ink flow through the silicon filter is reduced. As resistance to ink flow decreases, pressure drop across the filter also decreases.
In one embodiment of the present invention, the second layer includes two or more filter sections, each comprising a plurality of pores. The second layer further includes at least one reinforcement rib positioned between the two filter sections.
In another aspect of the present invention, a print cartridge container/filter assembly is provided. The assembly comprises a print cartridge container having at least one chamber for receiving ink. The container further includes a standpipe which extends into the chamber and defines a passageway for ink to flow from the chamber to a printhead. The assembly further includes a filter, such as the one described above, which is associated with the container.
REFERENCES:
patent: 4095237 (1978-06-01), Amberntsson et al.
patent: 4561789 (1985-12-01), Saito
patent: 4639748 (1987-01-01), Drake et al.
patent: 4771295 (1988-09-01), Baker et al.
patent: 4864329 (1989-09-01), Kneezel et al.
patent: 4931811 (1990-06-01), Cowger et al.
patent: 5124717 (1992-06-01), Campanelli et al.
patent: 5141596 (1992-08-01), Hawkins et al.
patent: 5154815 (1992-10-01), O'Neill
patent: 5201987 (1993-04-01), Hawkins et al.
patent: 5204690 (1993-04-01), Lorenze, Jr. et al.
patent: 5308442 (1994-05-01), Taub et al.
patent: 5443713 (1995-08-01), Hindman
patent: 5537136 (1996-07-01), Brandon et al.
patent: 5560837 (1996-10-01), Trueba
patent: 5576750 (1996-11-01), Brandon et al.
patent: 5610645 (1997-03-01), Moore et al.
patent: 5658471 (1997-08-01), Murthy et al.
patent: 6048051 (2000-04-01), Ahn
patent: 0 518 467 (1992-12-01), None
patent: 0 657 291A (1995-06-01), None
patent: WO 95 13860 (1995-05-01), None
Lewis, Richard J., Sr., Hawley's Condensed Chemical Dictionary, 13th ed.; pp. 40-41 & 1072, 1997.*
Cees Van Rijn, et al., “Deflection and Maximum Load of Microfiltration Membrane Sieves Made with Silicon Micromachining”.
Journal of Microelectromechanical Systems, vol. 6, No. 1, Mar., 1997, pp. 48-54.
Hawley's Condensed Chemical Dictionary, 13th ed (Lewis, Richard, John Wiley & Sons, pp. 231).*
Schnakenberg et al. “THAHW Etchants for Silicon Micromachining”, Jun. 1991, In Proc. Int. Conf. on Solid State Sensors and Actuators (Transducers 1991), pp. 815-818.
Brady John A.
Lexmark International Inc.
Ocampo Marianne
Walker W. L.
LandOfFree
Filter assembly for a print cartridge container for removing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Filter assembly for a print cartridge container for removing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Filter assembly for a print cartridge container for removing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2435011