Preserving inkjet print cartridge reliability while packaged

Details Preserving inkjet print cartridge reliability while packaged Preserving inkjet print cartridge reliability while packaged

2001-12-18

2003-03-18

Nguyen, Judy (Department: 2861)

Incremental printing of symbolic information

Ink jet

Fluid or fluid source handling means

Reexamination Certificate

active

06533405

ABSTRACT:

RELATED APPLICATIONS
(Not applicable)
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
(Not applicable)
FIELD OF THE INVENTION
This invention relates to the storage of inkjet print cartridges and a method for retaining the reliability of the cartridge during the storage of the cartridge.
BACKGROUND OF THE INVENTION
Ink-jet printers have become widely accepted as reliable and inexpensive means of high-quality printing. A typical ink-jet pen has a print head having a plurality of nozzles or orifices through which ink droplets are ejected. Adjacent to the nozzles are ink firing chambers where ink is stored prior to ejection. Ink is delivered to the firing chambers through ink channels in fluid communication with an ink supply. The ink supply may be, for example, contained in a reservoir associated with the printhead. During printing, ink located in the firing chamber is heated or vaporized by a heat transducer, such as a thin film resistor. Formation of the ink vapor bubble is known as nucleation. The rapid expansion of the vaporized ink forces a drop of ink out through the nozzle. The nozzle is constructed to direct the ink droplet upon the media surface to form a “dot” of a printed image.
One type of ink-jet printer includes a carriage that is reciprocated across a sheet of paper that is advanced through the printer. The reciprocating carriage holds a printhead very close to the paper. The printhead is controlled by the printer for selectively ejecting the ink drops from the printhead while the printhead is reciprocated or scanned across the paper, thereby to produce characters or another image on the paper.
In order to print effectively, the firing chambers and nozzles need to be “primed” with ink. Typically, priming includes moving ink into the firing chambers. Ink is moved to and held within the chambers and nozzles by capillary force. Priming does not occur spontaneously as ink is first added to a printhead. Air bubbles lodged in and around the firing chambers may act to prevent spontaneous priming. Priming tends to be even more problematic in printheads that store ink under a slight back pressure. As used herein, the term “back pressure” means a partial vacuum within the printhead. In such systems, the presence of a back pressure ensures ink is expelled only when the print head is activated (i.e., when ink is ejected). However, the slight back pressure is not so high as to impede the movement of ink into the firing chambers and nozzles.
A specific priming operation is usually provided to prime the print head of an ink-jet printer head. Such priming usually takes place in ink-jet printhead factories by inverting the printhead after the ink reservoir has been filled with ink and sucking air and ink through the printer head nozzles. Special low-water-loss packaging is then used to prevent nozzle dry-out in factory-primed printheads. Typically, a factory-primed printhead, once installed in a printer, is not designed for repriming in the event that one or more print head nozzles become de-primed.
Priming devices have been previously used with inkjet print cartridges to remove undesirable air from the ink firing chambers after it has already accumulated. For examples, see U.S. Pat. No. 4,998,115, entitled “Method and Apparatus for Priming an Ink Jet Pen”; U.S. Pat. No. 5,420,619 entitled “OnLine/Off-Line Primer For Ink Jet Cartridge”; and U.S. Pat. No. 5,850,239 entitled “Manual Selecting lnkjet Primer System.” However, because packaged print cartridges sometimes remain in inventory for long periods of time before use, there is a need for preventive techniques which tend to inhibit the accumulation of air during the period after manufacturing and prior to initial use. In addition, many printers in the market do not have priming systems installed.
After priming of a print head there are inevitably small air bubbles in the printhead. Initially, these bubbles are very small and do not interfere with ink flow or otherwise compromise the function of the printhead. However, care must be taken to eliminate the growth of these air bubbles. The growth of air bubbles within the printhead is very undesirable, because the bubbles will grow to an extent that they lead to print quality problems. An air bubble can obstruct ink flow to particular firing chambers from which ink droplets are to be ejected. Air bubbles can cause irregularly shaped ink droplets or cause a print head to deprime resulting in complete failure of the print head. Consequently, ink-jet print heads should be substantially free of such bubbles to function as designed.
There have been attempts to reduce air in the printhead to prevent these bubbles. Measures have been taken to prevent introduction of air into the ink supply or reservoir of the printhead, which often occurs after the printhead has been installed on a printer. These measures have been successful in improved printing quality and print life of the printhead. However, these measures have ignored another avenue in which air is introduced into the printhead, which is through gas transfer through the nozzle-sealing component.
After priming at the factory, the printhead must be packaged so that it can be stored, shipped and otherwise travel through the avenues of commerce to the final user in a functional condition. Since the printhead may be first used several weeks or months after initial priming, it must be protected from air getting into the nozzles or ink supply that could cause bad print quality or cause the printhead to deprime. Any changes, even slow changes, that can lead to the accumulation of air can become a problem. For this reason, the packaging usually includes features to preserve the functionality of the printhead by inhibiting air from getting into the printhead and ink from getting out by the passage of ink through the nozzles. One such feature is a sealing component that usually comprises a flexible polymeric film with an adhesive surface that is adhered to the ink ejection area or orifices of the printhead to close off the nozzles. The function of the sealing component is threefold. First, the sealing component prevents ingestion of air through the nozzles that can occur during shock during transportation and handling. This air ingestion can lead to depriming. Second, the sealing component inhibits drying of ink in the nozzles, which can lead to crusting and full or partial nozzle malfunction. Drying can occur over the extended transportation and storage of the cartridge. Third, the sealing component inhibits unwanted ink ejection or leakage through the nozzles, which can occur from mechanical shock.
After application of the sealing component, the print cartridge, which comprises the printhead with sealing component and its ink supply reservoir, is then enclosed in a container made of a material to inhibit the passage of gas (water vapor) to prevent water loss and drying of the ink.
This system has been generally successful in maintaining printheads in operable condition, even after long periods of storage under varying pressure and temperature conditions. However, there is still a problem of air bubbles growing under the sealing component. Consequently, there is a need to extend the storage life of printheads by eliminating the growth of bubbles to a size that can compromise the functioning of the printhead.
While not being bound to a particularly theory, it is believed that these bubbles grow due to the difference in humidity conditions between the inner and outer surfaces of the sealing tape. While the polymeric materials are generally impervious to the passage of liquid, they do allow for the slow diffusion of gasses through the material, and this passage of gasses can lead to the growth of bubbles.
Reference is now made to
FIG. 1
, which a schematic diagram of an inkjet printhead
100
comprising nozzles
101
with nozzle orifices
102
in a nozzle surface in the form of a nozzle plate
107
, firing chamber
105
, and heat transducers
106
. The firing chamber
105
communicates with an ink reservoir
120
(as shown in
FIG

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