Efforts have been made to reduce the cost and size of ink-jet printers and to reduce the cost per printed page. Some of these efforts have focused on developing printers having small, moving print heads that are connected to larger stationary ink reservoirs by flexible ink tubes. This configuration is commonly referred to as “off-axis” printing.
The development of off-axis printing has created the need to precisely control the pressure of the ink at a variety of locations, including the ink reservoir and the print head. Print cartridges may have an internal pressure regulator for regulating the flow of ink from an external source into an ink chamber within the print cartridge. The internal pressure regulator controls the flow of ink into the print cartridge to maintain a relatively constant back pressure at the print head. A relatively constant back pressure may be necessary to prevent the undesired leakage of ink through the print head. This leakage, or drooling, may degrade the quality of printing produced by the printer and may even cause permanent damage to the printer.
Designs utilizing a separate pressure regulator to address these issues may be relatively complicated. In addition, such pressure regulators often have a low tolerance for ingested air, and hence, require special materials to minimize air transmission. In addition, physical contact between the ink and the parts of the regulator sometimes reduce the operating life of the system, due to the corrosive nature of some inks.
The accompanying drawings illustrate various embodiments of the present apparatus and method and are a part of the specification. The illustrated embodiments are merely examples of the present apparatus and method and do not limit the scope of the disclosure.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.
The present air-driven delivery assembly uses a low pressure source to replenish a small ink tank within a carriage-mounted pen by drawing ink into the pen from an off-axis supply reservoir. The pen contains structure for preventing the ink from being drawn into the low pressure source while allowing the passage of air. This structure allows the pen to be refilled by activating the low pressure source for a predetermined period of time, regardless of the ink level. This allows for a simplified filling and refilling process.
The pen also contains structure for maintaining the ink contained in the pen at relatively low pressure. This low pressure, or back pressure, minimizes the ink that leaks or drools from the print head while the print head is not in use. The air-driven delivery assembly is able to maintain this back pressure over a wide range of temperatures and pressures because, at least in part, the system is opened during periods of non-use.
As used herein and in the appended claims, “on-axis” shall broadly be understood to mean the location of any part, component, or group of components that move with a print head. “Off-axis” shall be broadly understood to mean the location of any part, component, or group of components that do not move with a print head, for example, an off-axis ink reservoir. “Bubble pressure” shall mean the liquid pressure needed to force the liquid through an initially air saturated sample.
As used herein and in the appended claims, a marking material shall be broadly construed as any material suitable for marking a print medium, such as paper. Ink will be used as one example of a suitable marking material, but should not be construed to limit the application of the present system and method to the use of ink. As used herein, a marking material may be, for example, ink, toner, colorant, marking fluid, etc.
In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present method and apparatus. It will be apparent, however, to one skilled in the art, that the present method and apparatus may be practiced without these specific details. Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearance of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
Exemplary Structure
As described below, the on-axis containment chamber (110) may be refilled by a relatively simple low pressure source (140). This operation may be accomplished without drawing ink through the low pressure source (140), which promotes a longer life for the assembly (100). In addition, the air-driven delivery assembly (100) provides for a reduced amount of ink to be stored on-axis in the containment chamber (110). The ink is directly dispensed from the containment chamber (110) through the print head (150), with the containment chamber (110) being refilled from the off-axis reservoir (130). In addition, the reduced size of the on-axis marking material supply in the containment chamber (110) allows for a smaller overall printing device. The use of an off-axis supply reservoir (130) allows for increased supply reservoir volume, which decreases operating expense by reducing the frequency of refilling or replacing the ink supply.
During printing operations, the containment chamber (110) is coupled to atmosphere, such as by opening the vent valve (120), while the low pressure source (140) is turned off. Further, the supply reservoir (130) may be continuously open to the atmosphere, such that ink may be drawn from the supply reservoir (130) without substantially increasing the pressure therein. During printing operations the ink containment chamber (110) acts as an on-axis ink supply.
The print head (150) selectively dispenses material in response to delivery commands, based on a print job. The print job provides motion and dispensing commands that are then used by a printing system to selectively deposit marking material on a print medium to form the desired text or image. The print head (150) described herein may be any marking material dispenser capable of selectively depositing marking material. The print head (150) may be, for example, an inkjet print head capable of performing print on-demand applications including, but in no way limited to, thermally activated inkjet material dispensers, mechanically activated inkjet material dispensers, electrically activated inkjet material dispensers, magnetically activated material dispensers, and/or piezoelectrically activated material dispensers.
As the print head (150) operates, the amount of ink remaining in the containment chamber (110) decreases. When the amount of ink decreases below a pre-determined level, or when printing operations are stopped, the containment chamber (110) may be refilled. To refill the containment chamber (110), the containment chamber (110) is decoupled from the atmosphere, such as by closing the vent valve (120). The containment chamber (110) remains connected to the supply reservoir (130) and the low pressure source (140).
Activating the low pressure source (140) initially places the low pressure source (140) at a lower pressure than the containment chamber (110). As a result, air is drawn to the low pressure source (140) from the containment chamber (120). As the air is withdrawn from the containment chamber (110), the containment chamber is placed at a lower pressure than the supply reservoir (130). This pressure differential causes ink to flow from the supply reservoir (130) to the containment chamber (110), thereby refilling the containment chamber (110). As a result, while printing operations are paused, the containment chamber (110) is refilled by the supply reservoir (130), which is off-axis.
As will be discussed in more detail below, in some exemplary embodiments the containment chamber (110) includes structure that allows air to be withdrawn from the containment chamber (110) and that simultaneously prevents ink from being drawn into the low pressure source (140). As a result, the air-driven delivery assembly (100) is configured to use a low pressure source (140) to refill a containment chamber (110), while minimizing the amount of ink that passes through the low pressure source (140).
Exemplary Implementation and Operation
The supply reservoir (210) includes a vent (220) that couples the supply reservoir (210) to the atmosphere. Therefore, the ink contained within the supply reservoir (210) is substantially at atmospheric pressure. A supply tube (225) couples the supply reservoir (210) and the pen (205).
In the illustrated embodiment, the supply tube (225) is coupled to the supply reservoir (210) such that the inlet of the supply tube (225) is near the bottom of the supply reservoir (210). Placement of the inlet of the supply tube (225) near the bottom of the supply reservoir (210) maximizes the amount of ink that can be withdrawn from the supply reservoir (210) while ensuring that ink contained in the supply reservoir (210) is available to the pen (205).
The pen (205) includes a first chamber (230) that is coupled to a print head (150) and a second chamber (235). In the illustrated embodiment, the supply tube (225) extends from near the bottom of the supply reservoir (210) to near the top of the first chamber (230).
The first chamber (230) has a porous medium (240) contained substantially therein. The porous medium (240) may be a hydrophilic material such as polyurethane foam or glass beads. As a result, when ink is contained within the porous medium, pressure may be required to draw the ink from the porous medium into the print head (150). The pressure required to draw ink from the porous medium into the print head (150) may be generally described as a first or foam back pressure. This back pressure may be equivalent to a pressure of approximately two inches of water column.
The first and second chambers (230, 235) are at least partially separated by a barrier (245). A gap (250) is formed near the bottom of the barrier (245) to place the first and second chambers (230, 235) in fluid communication with one another.
As shown in
If the second chamber (235) did not include the second back pressure created by the wetting screen (255), ink contained in the second chamber (235) would possibly flow through the gap (250) and into the porous medium (240). For example, this flow may be due to leakage of air from the pump (215). If this ink flow remained unchecked, ink would flow into the porous medium (240) until the porous medium (240) became saturated. If the porous medium (240) was allowed to become saturated, the first back pressure established above might be lost. This loss of back pressure, in turn, might cause the pen (205) to drool or leak ink.
A wick (265) may be used to ensure contact between the wetting screen (255) and the ink contained in the second chamber (235). The wick (265) extends from the wetting screen (255) into the ink contained within the second chamber (235). The wick (265) fluidly couples the wetting screen (255) to the ink.
Ink is drawn into the second chamber (235) by establishing negative pressure therein, in a similar manner as discussed above with reference to
Closing the vent (275) causes pressure changes in the second chamber (235) to affect pressure in the first chamber (230). The pump (215) then pumps air from the second chamber (235) of the pen (205) though a low-pressure line (270). This reduces the pressure in the second chamber (235) and in the first chamber (230).
Consequently, due to the operation of the pump (215), the lowered pressure in the first chamber (230) causes ink to flow from the supply reservoir (210) to the first chamber (230). The continuing operation of the pump (215) causes the ink to continue to flow from the first chamber (230) into the second chamber (235) and to the wetting screen (255). The hydrophobic membrane (260) then resists the further flow of ink. In some cases, the ink may have a surface tension lower than water. Thus, the membrane (260) would need a lower surface energy that is required to be hydrophobic. In such case, the membrane (260) is oleophobic. In one embodiment, the membrane used is Gore 2432233150-0.
The hydrophobic membrane (260) may have a relatively high bubble pressure. The bubble pressure refers to the pressure differential required to draw or force liquid from one side of a membrane to the other. The hydrophobic membrane (260) may have a bubble pressure equivalent to about forty inches of water column. This bubble pressure is substantially larger than the operating pressure of the pump, such that during normal operation, the pump (215) does not draw ink through the hydrophobic membrane (260). In addition, the surface energy of the hydrophobic membrane (260) is lower than the surface energy of the ink. Consequently, the hydrophobic membrane (260) allows air and vapor to pass while preventing ink from passing through at pressures equivalent to less than about forty inches of water column. The pump (215) operates at a pressure substantially lower than forty inches of water column. As a result, the hydrophobic membrane allows air to pass through at the operating pressures of the pump (215), while preventing ink from passing. Accordingly, the pump (215) draws ink into the second chamber (235) without drawing ink through the pump (215). When the level of ink in the second chamber (235) reaches the hydrophobic membrane (260), the pen (205) is refilled and the pump (215) can be turned off. The pump (215) is controlled by a controller (285). The controller (285) can run the pump (215) for a predetermined period of time when the refill operation is initiated. This time period is made sufficient to refill the pen (205). Alternatively, the controller (285) can monitor the pressure or ink level in the pen (205) and control the pump (215) in response to a detected pressure or ink level in the pen (205). The controller (285) may include a mechanical regulator or a sensor that determines when to activate the pump (215) based on ink level or pressure in the pen (205). The controller (285) can also control the vents (275, 200) in coordination with the pump (215). The filling process will be discussed in more detail below with reference to
Once the fill or refill operation is complete, the vent (275) is opened and the pump (215) is deactivated. If the pump (215) does not maintain an air tight seal, air may leak from the pump (215), through the low pressure line (270), and into the second chamber (235). As discussed, if unchecked, air leakage from the low pressure source (270) through the low pressure line (270) may cause the ink within the second chamber (235) to drain into the porous medium (240), thereby saturating the porous medium (240). The wetting screen (255) counters the flow of the ink from the second chamber (235) to the first chamber (230) by establishing a second back pressure, as previously discussed. Accordingly, the second back pressure created by the wetting screen (255) minimizes the effects of air leakage through the low pressure line (270).
During printing, ink is dispensed from the pen (205) though the print head (150) connected to the first chamber (230). As ink is removed from the porous medium (240) in the first chamber (230), the ink saturation level lowers. This allows air to pass through the porous medium (240) and through the gap (250) between the chambers (230, 235). The entering air displaces the ink in the second chamber (235) which ink is then absorbed by the porous medium (240). This continues until the higher ink saturation level in the porous medium (240) causes the air to stop flowing. In this way, ink from the second chamber (235) is moved to the first chamber (230) for use in printing operations.
As shown in
This situation is shown in
Accordingly, the present marking material delivery assembly (200) allows for a simplified on-axis supply to a print head (150) during printing operations, while allowing a simplified refill of the pen (205) to be accomplished by an off-axis supply reservoir (210). Further, the refill is accomplished with a reduced part count and without pumping ink through the low pressure source.
The pen is then coupled to a supply reservoir (step 410) and to a low pressure source (step 420). The supply reservoir and the low pressure source is coupled to the pen in such a manner that removal of air contained in the pen causes ink to flow from the supply reservoir to the pen. Further, the pen includes structure that allows air to be withdrawn, but substantially prevents the withdrawal of ink. The pen also includes a vent that allows the pen to be selectively opened and closed with respect to atmospheric pressure.
Steps 430-450 describe the filling or refilling operation of the pen. To fill the pen, the vent is closed (step 430) such that the pen is not substantially open to the atmosphere. Once the vent has been closed (step 430), the pressure in the pen is dependent, at least in part, on the pressures of the low pressure source and the supply reservoir.
Once the vent has been closed, the low pressure source is activated for a predetermined period of time (step 440) or until a desired pressure or ink level is detected. Activating the low pressure source causes ink to flow from the supply reservoir to the pen. More specifically, the low pressure source draws air from the pen through the wetting structure and a hydrophobic membrane contained within the pen. The hydrophobic membrane permits air to pass, but restricts the movement of ink. As the air is evacuated, the pressure in the pen falls.
As previously discussed, the pen is also coupled to the supply reservoir. The relative pressure in the pen is lower than the relative pressure in the supply reservoir. As a result, ink flows from the supply reservoir to the pen. As the ink flows to the pen, the level of ink contained within the pen rises until the ink level rises to, first, the level of the wetting structure and, subsequently, to the level of the hydrophobic membrane. As ink is further drawn through the wetting structure, the ink level is prevented from rising substantially above the level of the hydrophobic membrane. As previously discussed, this may be due in part to the nature of the membrane, which allows gas or air to pass to the low pressure source while minimizing the amount of ink that passes to the low pressure source.
As a result, if the low pressure source continues to operate after the ink level has reached the hydrophobic membrane, the ink level will not substantially rise beyond the hydrophobic membrane. Consequently, refilling a pen according to the present method may be done by activating the low pressure source for a pre-determined period of time, regardless of the level of the ink contained within the pen. The use of a single time period for refilling simplifies a filling or refilling process, in that a calculation of the time required to fill the pen may be omitted.
Once the pen has been filled or refilled for the predetermined period of time (step 440), the pump is deactivated and the vent is opened (step 450). Printing operations are then performed (step 460). During normal print operations, drop-counter processes may determine whether print operations should be paused while the pen is refilled (determination 470). The pen may be sized such that the pen has sufficient ink to perform most print jobs. If a mid-operation refill is not necessary (NO, step 470), the printing operation is completed (step 480). Once printing operations have stopped, the refilling procedure (steps 430-450) may be restarted, such that the pen will be at maximum capacity when print operations begin again (step 460).
As a result, the present method allows an on-axis containment chamber to be refilled by a relatively simple low pressure source. This operation may be accomplished without drawing ink through the low pressure source, which provides for longer life of the assembly. In addition, the air-driven delivery assembly (200) provides for a reduced amount of ink to be stored on-axis in the pen (205), thereby allowing the marking material to be directly dispensed, while allowing the pen (205) to be refilled using an off-axis reservoir. In addition, the reduced size of the on-axis supply allows for a smaller overall printing device. The use of an off-axis supply reservoir allows for increased supply reservoir volume, which decreases operating expense by reducing the frequency of refilling or replacing the ink supply.
The pen (205) includes both a print head and a refillable ink supply. In such an embodiment, the air-driven delivery assembly (200) provides ink for the print head (150). The print head (150) selectively ejects drops of ink (520) onto a print medium (530), according to print job data, to form desired text and/or images on the print medium (530). The print medium (530) is moved laterally with respect to the print head (150) by a media advancement system that may include, for example, two driven rollers (540, 550). The carriage (510), and hence the print head (150), are moved back and forth across the print medium (530) by a carriage control mechanism that may include, for example, a drive belt (560) or other device.
The print head (150) contains a plurality of firing chambers that are energized on command by selectively firing resistors. Thus, as the print head moves laterally across the print medium (530) and the print medium (530) is moved by the rollers (540, 550), drops of ejected ink (520) form images and/or text on the print medium (530).
The supply reservoir (210) and the pump (215) are located off-axis. By positioning these components off-axis, the size of the printing device (500) may be decreased. Further, the weight carried by the carriage (510) may be minimized, thereby reducing the power required to move the carriage and the precision with which the carriage (510) may be controlled.
Alternative Embodiments
The air-driven delivery assembly (200) discussed with reference to
As shown in
In conclusion, the air-driven delivery assemblies allow for an on-axis containment chamber to be refilled by a relatively simple low pressure source. This operation may be accomplished without drawing ink through a low pressure source, which provides for longer life of a given assembly. In addition, the air-driven delivery assemblies provide for a reduced amount of ink to be stored on-axis in the containment chamber, thereby allowing the marking material to be directly dispensed, while allowing the containment chamber to be refilled using an off-axis reservoir. In addition, the reduced size of an on-axis supply allows for a smaller printing device. The use of an off-axis supply reservoir allows for increased supply reservoir volume, which decreases operating expense by reducing the frequency of refilling or replacing the ink supply.
The preceding description has been presented only to illustrate and describe the present method and apparatus. It is not intended to be exhaustive or to limit the disclosure to any precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the following claims.
Number | Name | Date | Kind |
---|---|---|---|
4484827 | Price, Jr. | Nov 1984 | A |
5116650 | Bowser | May 1992 | A |
5691753 | Hilton | Nov 1997 | A |
6464346 | Otis, Jr. | Oct 2002 | B2 |
6543386 | Boggs | Apr 2003 | B1 |
6612689 | Suenaga et al. | Sep 2003 | B2 |
6637872 | Ara et al. | Oct 2003 | B2 |
6722761 | Asano et al. | Apr 2004 | B2 |
6726313 | Oda et al. | Apr 2004 | B1 |
6783215 | Yoshida et al. | Aug 2004 | B2 |
Number | Date | Country | |
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20060023038 A1 | Feb 2006 | US |