The present invention relates to inkjet printers, and more particularly to inkjet printers using a continuous ink stream type print head.
Digitally controlled printing is typically accomplished using one of two technologies referred to as “drop-on-demand” and “continuous” inkjet printing. Both printing techniques utilize ink supplies for each color of ink, with the ink being ejected through nozzles formed in a print head.
Drop-on-demand inkjet printing typically uses a thermal or mechanical actuator to provide ink droplets for deposition on a print medium. In continuous ink jet printing technology, ink is typically supplied to an ink reservoir in a print head under pressure so as to produce a jet, or continuous stream of ink from a nozzle in liquid communication with the reservoir. Periodic excitations are imposed on the ink stream to cause the stream to break up into ink droplets.
Some continuous inkjet printers utilize air flow to control the trajectory of ink droplets ejected from a print head, wherein ink droplets can be deflected from their ejection path as they leave the print head to either a print medium or an ink capturing mechanism such as a catcher or gutter. The ink captured by the capturing mechanism can either be recycled back to the ink reservoir for reuse, or disposed of.
Difficulties are often experienced during start-up of continuous stream ink jet printers, when the print head is in an initial dry nozzle plate condition. The ink driving pressure increases from zero but is initially too low to overcome surface tension and drive the ink out of the tiny nozzles in the nozzle plate. A transition period is then reached in which the ink driving pressure overcomes the surface tension effects to force some ink through the nozzles, but the pressure is still insufficient to produce well formed fluid jets of ink. During this transition period from the initial dry nozzle plate condition to fluid jets of ink, ink typically leaks from the print head nozzle and creates a fluid film or beads on the nozzle plate. A similar phenomenon occurs when the printer or print heads are shut down, after which the fluid film or beads can dry on the nozzle plate prior to the next start-up or printing operation of the print head.
A fluid film formed at the nozzle plate increases the probability that fluid leaving the nozzle plate will never overcome the surface tension of the film formed at the nozzles. Fluid beads on the nozzle plate can cause nozzles under the beads to produce a continuous flow of ink that adheres to the nozzle plate. In addition, beads formed adjacent to nozzles can cause misdirection in ink ejected from such nozzles, and inconsistencies in droplet size and shape. The most common solution to clogged jets is to flush the nozzle, or plurality of nozzles with a large amount of ink, however such a method wastes the ink and is not always effective. In addition, this method may not remove the fluid beads from locations adjacent the nozzles, thus misdirected and misshapen drops continue to be ejected from the print head and produce poor quality print images.
A print system according to one aspect of the invention comprises a print head, configured to output a stream of ink from a plurality of nozzles, a cleaning chamber substantially around an ink ejection area of the plurality of nozzles, wherein the cleaning chamber has an outlet for the stream of ink, and a pressurized gas source coupled to the cleaning chamber, whereby the gas is routable through the cleaning chamber at a flow rate sufficient to remove debris and excess ink from a region of the print head.
The print system may further comprise a deflector, positioned on a wall of the chamber so as to deflect the gas to increase an angle of incidence at which gas flow is directed at the plurality of nozzles. An additional aspect of the invention comprises a fluid source coupled to the cleaning chamber, and a deflector positioned on the wall and configured to deflect the fluid so as to effectively cover an area of the plurality of nozzles, wherein the air routed through the cleaning chamber also removes the fluid.
The gas can be air or nitrogen, for example, and the print system may further comprise a negative pressure source coupled to one end of the cleaning chamber.
Another aspect of the of the invention comprises a method of removing unwanted particles from one or more print head nozzles, wherein the method comprises forcing a blast of air into a chamber substantially surrounding the nozzle at a flow rate sufficient to remove unwanted particles from the print head nozzle. The method may further comprise deflecting the gas in the chamber so as to increase an angle of incidence at which the air is directed at the nozzle.
An additional aspect to the method may comprise routing a fluid through the chamber so as to change surface properties of the unwanted particles, and deflecting the fluid in the chamber so as to effectively cover a substantial area of the nozzle for removal of unwanted particles.
Yet another aspect of the invention comprises a system for removing unwanted particles from one or more print head nozzles, comprising means for forcing a blast of gas at the print head nozzle and a surrounding area. The system may further comprise means for increasing an angle of incidence at which the gas is directed at the nozzle, and means for applying a fluid to the nozzle and a surrounding area. The system may further comprise means for deflecting the fluid so as to effectively cover a substantial area of the nozzle for removal of unwanted particles. The fluid may be, for example, alcohol.
Another aspect of the invention comprises a printing system, comprising a print head, configured to produce a stream of ink from a plurality of nozzles, a first flow path positioned proximate to an ink ejection area of the plurality of nozzles, wherein gas is routed through the first flow path at a flow rate sufficient to remove debris and excess ink from the plurality of nozzles and a surrounding area, and a second flow path positioned farther away from the ink ejection area of the plurality of nozzles than the first gas flow path, configured to provide a path for gas flow for deflecting at least portions of the stream of ink.
The first flow path may include a deflector configured to increase an angle of incidence at which the gas contacts the plurality of nozzles and surrounding area. The fluid may be routed through the first flow path in addition to the gas.
Embodiments of the invention will now be described with reference to the accompanying Figures, wherein like numerals refer to like elements throughout. The terminology used in the description presented herein is not intended to be interpreted in any limited or restrictive manner, simply because it is being utilized in conjunction with a detailed description of certain specific embodiments of the invention. Furthermore, embodiments of the invention may include several novel features, no single one of which is solely responsible for its desirable attributes or which is essential to practicing the inventions herein described.
Certain embodiments of the invention comprise a method and apparatus for removing debris and excess ink from an ink ejection area of an inkjet print head employing continuous ink jets. In one embodiment of the invention, a burst of gas is routed through a chamber which is proximate to an area of a print head nozzle plate from which ink is ejected. The gas burst advantageously removes debris and unwanted ink from the ejection point nozzle of an ink jet, such that the jet, and the ink droplets produced by the jet, maintain a desired trajectory, shape, and size. In some embodiments, a cover plate is placed over the nozzle location in the print head so as to create a chamber for gas flow.
In an additional embodiment, a fluid is routed through the chamber in addition to the gas, so as to change surface properties of unwanted debris and excess ink located at the nozzle plate, such that the debris and ink are removed more easily and effectively by the flow or burst of gas through the chamber. The use of gas and fluid flow into the chamber can advantageously be applied at startup and/or shut down of the print head so as to remove debris and excess ink collected on the print head during start-up and shut down of the print heads in an inkjet printer. The application of gas and/or fluid may also occur during operation of the print heads, such as between passes of the print head along a print medium.
An exemplary printing system 10 is illustrated in
The printing system 10 comprises a print head 12, at least one ink supply 14, and a controller 16. The print head 12 can be formed from a semiconductor material, such as silicon, using fabrication techniques well known in the field. A plurality of nozzles 18 can be formed on the print head 12, wherein the nozzles 18 are in fluid communication with the ink supply 14 through an ink passage 20, also formed in the print head 12.
In the embodiment of
It will be appreciated that the printing system 10 as shown and described in reference to
The printing system 10 can be implemented in the printer 50 illustrated in FIG. 3. The printer 50 employs a droplet deflector system 51 comprising a gas flow chamber 52 (or substantially contained gas flow path) positioned near the nozzle plate 40 such that ink ejected from the nozzle 18 travels through the gas flow chamber 52 and out an opening 54 substantially aligned with the nozzle 18. Gas flow is provided by a gas source 56 and regulated by a gas flow regulator 58 prior to entry into the gas flow chamber 52.
A stream of large volume ink droplets and small volume ink droplets, formed from the ink filament 42, can be ejected from the nozzle 18 substantially along a path X. In the droplet deflector system 51, gas flow can be provided to the gas flow chamber 52 to apply a force to the stream of ink droplets ejected from the nozzle 18, such that the small volume ink droplets diverge from path X along a printing path Y. The large volume ink droplets may continue along path X and into a gutter 60, which routes the ink from the large volume ink droplets to, for example, an ink recovery system 66. A negative pressure source 68 can provide a negative pressure to the gutter 60 so as to assist in the separation of the small ink droplets from the large ink droplets, and the recovery of the ink droplets traveling substantially along path X.
The printing path Y leads the small ink droplets to a print medium 70 supported on a print drum 72, and a catcher 74 is positioned at or near the opening 54 such that ink droplets straying from the printing path Y are prevented from contacting the print medium 70. An additional negative pressure source 76 can be provided at an outlet 78 of the gas flow chamber 52 so as to apply a negative pressure to the gas flow chamber and assist in the separation of the small ink droplets and the large ink droplets. Also, the negative pressure source 76 can assist in the removal of ink, collected at the catcher 74, from the gas flow chamber 52. The outlet 78 of the gas flow chamber 52 may also have fluid communication with the ink recovery system 66.
In the embodiment of
As shown in
The debris and excessive ink cleared by the gas flow can be deflected to a catcher 132 located on an edge of the slit 122 opposite the inlet 130, or it can flow out of the cleaning chamber 120, along with the gas, through an outlet 134 located at an end of the cleaning chamber 120 opposite the inlet 130. The catcher 132 can be, for example, a porous frit or foam material, a mesh screen, or a gutter so as to prevent fluid, debris, excessive ink, etc., from leaving the cleaning chamber 120 via the slit 122. The outlet 134 from the cleaning chamber 120 can be in fluid communication with an additional ink recovery system 138 along with the outlet 78 from the gas flow chamber 52, so as to route ink, gas, and fluid to a recovery or recycling system.
In the event fluid is also routed into the cleaning chamber 120 from the fluid supply 104, it can also exit the cleaning chamber 120 via the outlet 134. In one embodiment, the outlet 134 can also have communication with the negative pressure source 76 in addition to the outlet 78, so as to increase the force and rate with which debris and excess ink can be removed from the cleaning chamber 120. Also, a gas flow valve 140 can be positioned in the flow path 124 between the gas supply 106 and the cleaning chamber 120 so as to control the amount and pressure of gas flow into the cleaning chamber 120.
In one embodiment, the cleaning chamber 120 is formed by the nozzle plate 113 and a cover 142, wherein the cover 142 is positioned substantially parallel to the nozzle plate 113. In one advantageous embodiment, the cover 142 also comprises a deflector 144 located on the gas inlet 130 side of the slit 122, such that gas or fluid entering the cleaning chamber 120 is deflected by the deflector 144 to the nozzle opening 114 at an increased angle of incidence. It will be appreciated by those skilled in the art that the placement of the deflector 144 in
As described and shown herein, the gas flow chamber 52 of the drop deflector system 51 is positioned adjacent to the cleaning chamber 120, however the invention is not limited to such a structure. In one embodiment, the gas flow chamber 52 is more particularly a substantially contained gas flow path positioned approximately parallel to the cleaning chamber 120, such that a stream of ink leaving the cleaning chamber passes through a gas flow path of the drop deflector system 51. In addition, the droplet deflector system 51 can be implemented in a number of configurations in combination with the cleaning chamber 120 so as to effectively direct the appropriate ink droplets to the print media 70 in a desirable manner.
A method of operation of one embodiment of the print head cleaning system will now be described with reference to
Multiple cover embodiments are illustrated in
Although a cleaning system and method is shown and described as implemented in a printer using air flow to direct a continuous stream of ink droplets, the systems and method described herein are not limited to such a printing system. The systems and methods described herein may be implemented in printing systems wherein, for example, electrostatic charge is used to direct ink droplets, or alternate configurations of air flow deflection of ink droplets are used. In such environments, the systems and methods of the described invention may be modified so as to effectively perform their intended functions.
The foregoing description details certain embodiments of the invention. It will be appreciated, however, that no matter how detailed the foregoing appears in text, the invention can be practiced in many ways. As is also stated above, it should be noted that the use of particular terminology when describing certain features or aspects of the invention should not be taken to imply that the terminology is being re-defined herein to be restricted to including any specific characteristics of the features or aspects of the invention with which that terminology is associated. The scope of the invention should therefore be construed in accordance with the appended claims and any equivalents thereof.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
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Number | Date | Country | |
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20040070645 A1 | Apr 2004 | US |