A typical thermal inkjet has an array of precisely formed nozzles attached to a print head substrate corresponding to an array of firing chambers that receive liquid ink from a reservoir. Each firing chamber may include a thin-film resistor or firing resistor located opposite the nozzle to allow for the presence of ink between the firing resistor and the nozzle. Electric pulses may then be applied to heat the firing resistors to cause a small portion of the ink near the firing resistor to vaporize. The pressure created by this vaporization drives a small amount of ink through the nozzle. The nozzles may be arranged in a matrix array. Properly sequencing the operation of each nozzle in the array causes characters and/or images to form as the print head is moved with respect to a print medium, such as a piece of paper.
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. Print cartridges with an internal pressure regulator often incorporate a diaphragm in the form of a bag. The inside of the bag is open to the atmosphere. The expansion and contraction of the bag controls the flow of ink into the print cartridge to maintain a relatively constant back pressure at the print head.
However, when too much air has accumulated in the body and/or manifold of the print cartridge, the regulator may no longer have the capacity to maintain negative pressure. At that point, air in the print head may render nonfunctional any pressure regulator internal to, or leading to, the print cartridge. As a result, the desired back pressure may be lost (for example, due to variation in the temperature or pressure of the ambient environment), and ink may drool out of the print head. A drooling print head may cause permanent damage to the printer and will likely be unable to print with an acceptable print quality.
Designs utilizing a separate pressure regulator to address these issues may be relatively complicated. In addition, the use of a separate pressure regulator may limit the operating efficiency of the printing device. Accordingly, recent efforts have been directed to providing a less complicated ink supply system that is able to reliably provide back pressure. Some designs utilize foam placed in the ink supply. As the ink supply is drained, the volume of the ink supply tends to decrease. The foam provides small capillary volumes which retain ink; the capillary attraction of the ink to the capillary volumes creates a back pressure. Similarly, other designs utilize a spring placed in an ink bag. However, with these designs, a significant amount of the ink in the supply may be stranded and therefore wasted. Such waste may require more frequent ink re-supply, thereby increasing the operating cost of the system.
An ink delivery regulation apparatus includes a support configured to be positioned within an ink chamber and a resilient deflection member coupled to the support. The resilient deflection member is configured to resiliently deflect from a generally concave shape to a generally convex shape in response to a change in said negative pressure.
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.
An ink delivery apparatus and method of use are described herein. As used herein and in the appended claims, the term “ink” shall refer broadly to any ink, toner, colorant or other liquid marking fluid ejected by a print head. According to one exemplary embodiment described below, an ink delivery regulation apparatus includes a support positioned within an ink chamber and a resilient deflection member coupled to the support. The resilient deflection member is configured to resiliently deflect from a generally concave shape to a generally convex shape in response to a change in said negative pressure.
In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present apparatus and method. It will be apparent, however, to one skilled in the art that the present apparatus and method 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
In
In
In
The deflection of the first, second, and third pressure tuned panels can be tuned to the specific requirements of particular print systems. For example, the overall size, the thickness, the elasticity, and the angles of the pressure tuned panels (210–230) may be varied so as to provide the proper deflection and thus the proper resistance in response to a force due to a negative pressure. Accordingly, the ink delivery regulation apparatus may allow for maintenance of the negative pressure within a determined range.
Exemplary Implementation and Operation
Supplying the ink (step 350) tends to cause the level of the negative pressure in the ink chamber to increase. It is desirable to maintain the pressure within a determined range (step 360). This maintenance of the negative pressure is accomplished through deflection of the pressure tuned panels, and results in a negative pressure range of between about 3–7″ of water column. The pressure tuned panels deflect in response to a force due to the negative pressure. The amount of deflection of the pressure tuned panels is related, at least in part, to the thickness of the pressure tuned panels, as well as their elasticity and the relative angles of the pressure tuned panels with respect to each other and with respect to the support member. As the ink chamber is drained, the pressure tuned panels deflect from a generally concave configuration to a generally convex configuration, thereby resiliently resisting the force and maintaining the negative pressure within the determined range. In the event of a change in the ambient environment, the pressure tuned panels partially return to their undeflected conditions in response to the change in ambient conditions while maintaining the negative pressure within the determined limits.
In addition, a bubble generator may be used to maintain the negative pressure within the determined range. Bubble generators, or “bubblers”, permit ambient air bubbles to enter the ink reservoir when the back pressure within the reservoir exceeds the pressure to which the bubbler is “tuned”. The purpose of the air bubbles delivered by the bubble generator is to keep the reservoir back pressure from increasing to a level that would cause failure of the print head.
Bubble generators typically comprise a small-diameter orifice that provides fluid communication between the pen reservoir and ambient air. The bubble generator orifice is small enough, and the ink surface tension is great enough, to counteract the gravitational and static pressure forces that would otherwise cause ink to leak through the bubble generator orifice. Moreover, because the reservoir ink normally covers the reservoir-end of the bubble generator orifice, ambient air is restricted from entering the reservoir until the back pressure increases to a level great enough for drawing an air bubble through the reservoir ink covering the orifice. Other types of valves that perform an equivalent function are also known in the art.
As the pressure approaches its upper limit, the bubble generator may be activated to provide internal positive pressure. For example, the bubble generator may be tuned to 6″ of water column. As a result, the negative pressure is maintained within the determined limits during the operational cycle of the ink chambers. Accordingly, the configuration of the ink delivery regulation member maintains the negative pressure within determined limits while compensating for variations in the ambient environment.
Once nearly all of the ink has been withdrawn from the ink chamber, the negative pressure increases sharply. This sharp increase in negative pressure indicates that the ink chamber is operationally empty. “Operationally empty” refers to the condition in which there is insufficient ink remaining in the piston to provide a reliable supply for printing. There may still be some ink in the piston. Thus, operationally empty does not mean completely empty. Accordingly, the pressure is monitored for a sharp increase in negative pressure. When such an increase is sensed, a user or the printer is notified that the ink chamber is operationally empty (step 370). As can be seen from the above process, the controlled deflection of the pressure tuned panels facilitates maintenance of a negative pressure within determined pressure limits as ink is withdrawn from the ink chamber. Such control allows for enhanced printer performance
Maintenance of the negative pressure within the ink chamber (130) within determined limits facilitates improved performance of the printing device (400) by reliably supplying ink to the print head (410) while preventing the print head (410) from drooling ink onto the print medium (430) due to such occurrences as temperature or altitude variations. This is accomplished using the ink delivery regulation member (110) described above. Additionally, the ink delivery regulation member (110) allows for smaller printing devices due to the volumetric efficiency of the ink chamber (130,
The ink delivery regulation member (110) may be made of any material that allows it to be configured to at least partially collapse over a predetermined range of negative pressures. Such materials may include, but are in no way limited to, elastomeric materials such as EPDM/Butyl. In the illustrated examples, the pressure tuned panels may be of a constant thickness. This thickness may be, for example, between 0.4–0.8 mm. The ink delivery regulation member may be fabricated by any suitable means, such as, for example, molding.
Alternative Embodiments
Referring again to
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 invention 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 |
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5153612 | Dunn et al. | Oct 1992 | A |
5473354 | Arquilevich et al. | Dec 1995 | A |
5734401 | Clark et al. | Mar 1998 | A |
5745137 | Scheffelin et al. | Apr 1998 | A |
6561635 | Wen | May 2003 | B1 |
Number | Date | Country | |
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20050057619 A1 | Mar 2005 | US |