MXPA97002888A - Ink cartridge with non-affiltered foam and printing method using the mi - Google Patents

Abstract

The present invention relates to an ink cartridge for use in the printing of an ink on a printing medium with an electronic printer, said ink cartridge comprises: a body, a unit of the print head coupled with said body; ink having a netre viscosity of about 1.5 and 10 cetipoises, and a non-felted foam disposed within the body, said foam containing the ink and having a plurability of pores positioned substantially in communication with each other, and with the head unit of printing, said pores having an effective projection which in conjunction with the viscosity of the ink, defines the means for allowing the ink to flow substantially continuously from the foam to the print head unit during operating periods, and is sub-substantially avoided of flowing ink from that unit of the print head during periods of inoperation

Description

INK CARTRIDGE WITH NON-AFFILTERED FOAM AND PRINTING METHOD USING THE SAME BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink cartridge for use in an inkjet printer and, more particularly, to an ink cartridge having a porous foam therein. 2. Description of Related Art An ink cartridge for use in an inkjet printer typically includes a porous member placed therein. The porous member is placed in fluid communication with a print head assembly, and supplies ink to the printhead assembly during periods of operation. Typically, the porous member is in the form of a felted piece of polyurethane foam. The foam is thermally compressed, or felted, until it maintains a compression set at approximately a compression ratio of 3 to 1. That is, the foam is heated almost to its melting point under a compression load and after that is left to cool, resulting thereby in a denser foam with increased effective porosity. When it is felted, the foam achieves an effective porosity of approximately 150 to 200 pores per inch (ppi).

Typically, conventional ink cartridges use a water-soluble, pigment-based ink that is applied to a printing medium. Pigment-based ink spots combine to form characters and graphics on the print medium that is subject to variations in print quality, including blurring, bleeding, diffusion of ink, and lack of optical density. The print quality of the inkjet printer can be greatly improved through the use of a higher, higher viscosity surface tension ink, such as a pigmented ink. The pigments, for example, carbon black pigments or color pigments, are suspended in the water instead of being dissolved in water. After the ink is applied to the paper and the water is dried, the pigments not soluble in water are essentially not affected by the subsequent contact with water. In addition, the increase in viscosity and surface tension allows the ink to be established on the upper part of the reluctant printing medium to diffuse towards other (colored) inks, thus avoiding bleeding of different inks. In addition, the ink of higher surface tension also inhibits the penetration of the ink into the paper, improving the optical density. Finally, the more viscous ink does not tend to travel along the fibers of the paper, creating a cleaner, cleaner print, without blurring. One problem with using a higher viscosity pigmented ink is that the "underfeeding" of the print head assembly occurs when the higher viscosity ink is placed in a conventional felted foam. More particularly, as the ink is injected from the printhead assembly during the operation in a known manner, a suitable supply of the higher viscosity ink must flow from the felted foam towards the head assembly of printing so that the ink can be injected continuously therefrom. However, the felted foam has an effective porosity of between about 150 to 200 ppi which does not allow a suitable proportion of ink flow from the foam to the printhead assembly. The capillary force within the felted foam having such effective porosity contains the highest viscosity ink therein and does not provide sufficient ink flow to the print head assembly. This results in "underfeeding" of the printhead assembly due to inadequate ink flow. A known solution that allows the use of a higher viscosity ink in an ink cartridge is to use a bag spring mechanism within the cartridge. The bag maintains proper back pressure on the ink inside the cartridge and avoids the underfeeding problem as occurs when using a higher viscosity ink with a felted foam. The present inventors have also tried to use a higher viscosity ink with a felted foam having lower effective porosity, but have encountered problems associated with the same. That is, a felted foam having an effective porosity of between about 60 to 80 ppi was used in conjunction with a pigmented ink of higher viscosity. It has been found that to avoid underfeeding of the printhead assembly during operation, the felted foam must have an effective porosity that does not exceed a range of between about 80 and 90 ppi. However, it has also been found that with a felted foam having a porosity of less than about 90 ppi, the print head assembly may drip ink or "wring" during periods of inoperation. Obviously such draining is not desirable. In this way, in order to avoid the underfeeding problem that may occur during dynamic fluid conditions, the problem of runoff results during static fluid conditions.

It is believed by the present inventors that the superposition of underfeeding and runoff problems, which occur when an attempt is made to use a felt foam in conjunction with a higher viscosity ink, are a result of the felting process. When the foam is felted, as described above, the temperature of the foam increases near the melting point and a compressive load is temporarily applied to the foam. Due to the temperature and charge gradients that exist on the foam during the felting process, the pores at the periphery of the foam may be smaller than the pores at the center of the foam. The smaller pores in the periphery of the foam may not allow adequate flow of fluid through them and thus cause the underfeeding problem during the periods of operation, while the larger pores in the center of the foam may not provide sufficient capillary force to prevent runoff from the printhead assembly during periods of inoperation. The use of a felted foam also has other associated problems. For example, during the felting process a chemical residue is created and deposited on the surface of the foam. This residue can react with the ink to modify the ink and create defects in print quality, or it can be carried by the ink towards the printhead assembly where it can clog the nozzles and possibly result in failure of the print assembly. print head. What is needed in the matter is an ink cartridge for use in an inkjet printer that economically and reliably allows the use of a pigmented ink of higher viscosity. SUMMARY OF THE INVENTION The present invention provides an ink cartridge with a non-felted foam having an effective porosity size of between about 60 and 85 pores per inch, which is used in conjunction with a pigmented ink of higher viscosity having a viscosity between about 1.5 and 10 centipoises. The invention comprises, in a form thereof, an ink cartridge for use in printing an ink on a printing medium with an electronic printer. The ink cartridge includes an ink placed therein having a viscosity of between about 1.5 and 10 centipoise. An ink cartridge has a non-felt foam on it. The foam contains the ink and has a plurality of pores positioned substantially in communication with one another. The pores have an effective porosity of between about 60 and 85 pores per inch. The ink cartridge further has an assembly of the print head placed in fluid communication with the foam. The foam has an effective porosity, depending on the viscosity of the ink, where the ink is allowed to flow from the foam to the print head assembly during the periods of operation, and substantially prevents flow from the assembly of the ink. the print head during periods of inoperation. An advantage of the present invention is that a higher viscosity pigmented ink can be used in an ink cartridge during the periods of operation without resulting "underfeeding", and during the periods of inoperation without resultant "runoff". Another advantage is that by eliminating the felting step from the manufacturing process, the cost per piece of the foam is substantially reduced. BRIEF DESCRIPTION OF THE DRAWINGS The above-mentioned and other features and advantages of this invention, and the manner of obtaining them, will become more apparent and the invention will be better understood with reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, where: Figure 1 is a perspective view of an embodiment of an ink jet cartridge that can be used with the method of the present invention; and Figure 2 is a fragmentary, elongated view of the non-felted foam shown in Figure 1, detailing the pores therein. The corresponding reference characters indicate corresponding parts through the various views. The exemplification set forth herein illustrates a preferred embodiment of the invention, in one form, and such exemplification is not construed as limiting the scope of the invention in any way. DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings and particularly to Figure 1, there is shown a perspective view of an embodiment of an ink cartridge 10 that can be used with the method of the present invention.

The ink cartridge 10 is installable in an electronic printer, and is used to print an ink on a printing medium such as paper. The ink cartridge 10 generally includes a body 12, an Automated Tape Joining ( ) circuit 14, an assembly of the print head 16 and porous member or foam 18. The printhead assembly 16 includes a flat (unnumbered) nozzle that is positioned adjacent a semiconductor chip that contains a plurality of thermal elements (not numbered), in a known manner. The nozzles in the flat nozzle of the print head assembly 16 allow ink to be injected onto the printing medium during operation. The printhead assembly 16 is placed in fluid communication with the foam 18. The TAB circuit 14 is electrically connected to the thermal elements of the printhead assembly 16, and provides a mechanical interface for the electrical interconnection with the printhead. Inkjet printer. Referring now to Figure 2, the foam 18 can be seen in greater detail. In the embodiment shown, the foam 18 is a non-felted foam, such as a polyurethane foam based on non-felted polyethylene. The foam 18 includes a plurality of pores 20 that are placed substantially in communication with each other. The pores 20 have an effective porosity of between about 60 and 85 ppi, and preferably between about 70 and 80 ppi. The foam 18 is used to contain an ink, such as a pigmented ink. The ink has a higher viscosity (in relation to pigment-based inks) of between about 1.5 and 10 centipoise (cP), and preferably between about 2.5 and 5 cP. The foam 18 is configured with an effective porosity, depending on the viscosity of the ink, which allows the ink to flow from the foam to the print head assembly during the periods of operation (thereby preventing underfeeding), and substantially prevents the ink from flowing from the assembly of the print head during periods of inoperation (thereby preventing runoff). During operation, the ink cartridge 10 is provided with a non-felted foam thereon, as described above. The printhead assembly 16 is placed in fluid communication with the foam 18, and receives an ink supply therefrom. The ink is contained by the foam, and has a viscosity of between about 1.5 and 10 cP, as indicated above. The foam 18 is configured with a porosity size which, depending on the viscosity of the ink, substantially prevents both the underfeeding during the periods of operation and the runoff during the periods of inoperation. A portion of the ink is injected from the assembly of the print head 16 onto the printing medium during operation. As the ink is ejected onto the printing medium, the ink is allowed to flow from the foam 18 towards the printhead assembly 16 at a sufficient flow rate to avoid underfeeding of the print head assembly. 16. After the ink is no longer injected onto the printing medium, the foam 18 prevents the ink from dripping from the printhead assembly 16. Although this invention has been described with respect to a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. Accordingly, this application attempts to cover any variation, use or adaptation of the invention that; use your general principles. Furthermore, this application attempts to cover such deviations from the present disclosure as long as they fall within the known or customary practice in the matter to which this invention pertains and which fall within the limits of the appended claims.

Claims (15)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and therefore the property described in the following claims is claimed as property. 1. An ink cartridge for use in printing an ink on a printing medium with an electronic printer, said ink cartridge comprising: an ink having a viscosity of between about 1.5 and 10 centipoise; an ink cartridge having a non-felted foam thereon, said foam containing said ink and having a plurality of pores positioned substantially in communication with each other, said pores having an effective porosity of between about 60 and 90 pores per inch, having in addition said ink cartridge an assembly of the print head placed in fluid communication with said foam, said foam having an effective porosity, depending on the viscosity of the ink, wherein the ink is allowed to flow from said foam towards said ink assembly. the print head during the periods of operation, and substantially avoiding flow from said print head assembly during the periods of inoperation. The ink cartridge according to claim 1, characterized in that said effective porosity is between about 70 and 80 pores per inch. 3. The ink cartridge according to claim 1, characterized in that said ink has a viscosity of between about 2.5 and 5 centipoise. 4. The ink cartridge according to the claim 1, characterized in that said ink comprises a pigmented ink. 5. A method for printing an ink on a printing medium using an electronic printer, said method comprising the steps of: providing an ink cartridge having a non-felted foam thereon, said foam having a plurality of substantially positioned pores in communication with one another, said pores having an effective porosity of between about 60 and 90 pores per inch, said ink cartridge further having an assembly of the print head placed in fluid communication with said foam; transporting the ink with said foam, the ink having a viscosity of between about 1.5 and 10 centipoise; configuring said effective porosity of said foam, depending on the viscosity of the ink, in such a way that the ink is allowed to flow from said foam towards said assembly of the print head during the periods of operation, and its flow is substantially prevented from the assembly of the printhead during the periods of inoperation; and injecting ink from said printhead assembly onto the printing medium. The method according to claim 5, characterized in that said effective porosity is between about 70 and 80 pores per inch. The method according to claim 5, characterized in that the ink has a viscosity between about 2.5 and 5 centipoise. The method according to claim 5, characterized in that the ink comprises a pigmented ink. The method according to claim 5, characterized in that said foam comprises a non-felted polyurethane foam. The method according to claim 5, characterized in that it comprises the additional step of allowing a portion of the ink to flow from said foam towards the assembly of the print head during said injection step. 11. A method for printing an ink on a printing medium using an electronic printer, said method comprising the steps of: providing an ink cartridge having a porous member therein, said porous member having a plurality of substantially positioned pores in communication with each other, said pores having an effective porosity of between about 60 and 90 pores per inch, said ink cartridge further having an assembly of the print head placed in fluid communication with said porous member; transporting the ink in said porous member, the ink having a viscosity of between about 1.5 and 10 centipoise; configuring said effective porosity size of said porous member, depending on the viscosity of the ink, such that the ink is allowed to flow from said porous member toward said print head assembly during the periods of operation, and substantially avoids its flow from the assembly of the print head during periods of inoperation; and injecting ink from said printhead assembly onto the printing medium. The method according to claim 11, characterized in that said effective porosity is between about 70 and 80 pores per inch. The method according to claim 11, characterized in that said ink has a viscosity of between about 2.5 and 5 centipoise. The method according to claim 11, characterized in that said ink comprises a pigmented ink. 15. The method according to claim 11, characterized in that said foam comprises a non-felted polyurethane foam.