Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Utility Patent
2000-02-23
2001-01-02
Yockey, David F. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Utility Patent
active
06168267
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an improved ink cartridge and to a pressure control system for maintaining ink cartridge pressure.
BACKGROUND
Ink jet technology continues to be improved in order to increase printing speed and print quality or resolution. One means for improving print speed and quality is to increase the number of nozzle holes in an ink jet printhead and to decrease the diameter of the nozzle holes. However, improvements in print speed and quality often result in operational problems not experienced with lower quality slower speed printers.
In an ink jet printer, ink is provided to the printhead from an ink cartridge or supply tank. The ink flows from the tank through a connecting conduit from the ink cartridge through an ink via in a semiconductor chip or around the edges of a semiconductor chip and into ink flow channels and an ink chamber. The ink chamber is situated in axial alignment with a corresponding nozzle hole and a heater resistor defined on the surface of the semiconductor chip. As electrical impulse energy is applied to the heater resistor, the ink adjacent the resistor is heated and a bubble of ink forms which is ejected from the nozzle hole onto a print medium. By selective activation of a plurality of heater resistors on a printhead, a pattern of ink dots are applied to the print medium to form an image.
A critical aspect of the printing process is the controlled supply of ink to the printhead. If the pressure in the ink supply cartridge is too high, ink may run out freely from the printhead onto the print medium before the heater resistor is activated. If the pressure in the ink supply cartridge is too low, the ink channels and chambers on the printhead will not refill fast enough. If the ink chambers and channels are not refilled fast enough there will be missing ink dots or the print speed must be lowered to allow time for ink to refill the ink chambers. Furthermore, as ink is used from the ink cartridge, the pressure in the ink cartridge may decrease to a point which inhibits flow of the remaining ink in the cartridge to the printhead. Accordingly, as the number of nozzles holes on a printhead increases and the diameter of the holes decreases, maintaining a predetermined ink supply pressure in the ink supply system becomes more critical.
There are two primary methods for maintaining ink supply flow to printheads. The first method includes the use of a porous capillary member such as foam which is saturated with ink and provides a controlled flow of ink to the printheads. The second method includes the use of a diaphragm or bellows to provide pressure or back pressure on the ink in the cartridge. Use of a diaphragm or bellows enables the cartridge to be filled with liquid ink as opposed to the use of foam saturated with ink. Accordingly, the ink cartridge may be made smaller for the same volume of ink delivered to the printheads. One disadvantage of smaller ink cartridges which use a diaphragm or bellows for pressure control is that maintaining tolerances during the manufacture of the cartridge body becomes more difficult.
There is a need therefor for an improved pressure controlled ink supply system which maintains a predetermined pressure in an ink supply cartridge so that sufficient ink is provided to a printhead throughout the life of the ink supply cartridge.
SUMMARY OF THE INVENTION
With regard to the above and other objects and advantages, the invention provides an ink cartridge for an ink jet printer, the cartridge including a body portion having a substantially continuous side wall perimeter extending from a substantially planar first side panel portion. A cavity for containing ink is defined by a second side panel portion, the side wall perimeter and the first side panel portion. A lung type pressure regulator is disposed within the cavity and has at least one lung frame wall disposed at an angle within the cavity with respect to a cavity side wall for promoting gas formation in the cavity.
In another aspect the invention provides a method for making an ink supply cartridge for an ink jet printer. The method includes injection molding a substantially rectangular body from a thermoplastic material, the body containing side walls and a first side panel defining an open-ended chamber. A bubble generator and an ink feed port are injection molded integral with a first side wall of the rectangular body, the bubble generator and ink feed port being in fluid flow communication with the chamber. A lung type pressure regulator is also injection molded integral with the body so that the pressure regular is disposed within the chamber of the rectangular body and has at least one lung frame wall adjacent the bubble generator disposed at an angle with respect to the first side wall for promoting gas bubble formation in the chamber. A second side panel is also injection molded from the thermoplastic material, and is fixedly attached the second side panel to the rectangular body to define a closed chamber for containing ink.
In yet another aspect the invention provides an ink jet printer cartridge including a substantially rectangular body having side walls and first and second side panels attached to the side walls defining an ink cavity. Ink is disposed in the ink cavity. A bubble generator is disposed in at least one of the side walls of the rectangular body, and a pressure regulator is disposed in the ink cavity for regulating ink pressure within the cavity. The pressure regulator includes at least one frame wall disposed at an angle with respect to the side wall of the rectangular body containing the bubble generator for promoting gas bubble formation in the ink.
An important feature of the invention is a pressure regulator such as a lung having a lung frame disposed in the body cavity of an ink cartridge wherein the frame of the lung has a surface which promotes gas bubble formation in the cavity. For example, a lung having a lung frame disposed at an angle relative to the body cavity has a number of advantages. One advantage of an angled lung is that the side walls defining the frame of the lung promote gas bubble formation and flow so that the bubbles do not remain closely adjacent to the bubble generator aperture but travel into the main ink cavity. Another advantage is that warpage of the side walls of the body of the ink cartridge may be minimized or reduced because only a small portion of the hot tooling for the lung frame is adjacent the cartridge side walls during molding. Another advantage is that there is increased space within the ink chamber for inserting a ball check valve for the ink feed port. The ink chamber also contains sufficient space for an ink level sensor. Still another advantage is that any ink which may find its way into the lung chamber is urged to drain more readily from the chamber along the angled frame walls.
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Lexmark International Inc.
Luedeka Neely & Graham
Sanderson Michael T.
Yockey David F.
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