Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-01-18
2004-06-01
Hsieh, Shih-wen (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06742860
ABSTRACT:
BACKGROUND AND SUMMARY
The present invention relates to printing devices. More particularly, the present invention relates to an apparatus and method for capping one or more printheads in a printing device.
Printing devices, such as inkjet printers and laser printers, use printing composition (e.g., ink or toner) to print images (text, graphics, etc.) onto a print medium advanced through a printzone of the printing device by a print medium transport mechanism. Inkjet printers may use print cartridges, also known as “pens”, which deposit printing composition, referred to generally herein as “ink”, onto a print medium, such as paper, labels, forms, transparencies, or fabric, as the print medium is advanced through the printzone of the printing device. Each pen has a printhead that includes a plurality of nozzles. Each nozzle has an orifice through which printing composition is ejected. To print an image, the printhead is propelled back and forth across the print medium by, for example, a carriage while ejecting printing composition in a desired pattern as the printhead moves. The particular ink ejection mechanism within the printhead may take a variety of different forms known to those skilled in the art, such as thermal printhead technology. For thermal printheads, the ink may be a liquid, with dissolved colorants or pigments dispersed in a solvent.
During periods of nonuse, the printheads of the pens are capped to minimize evaporation of ink to the ambient through the nozzles. Capping also helps protect the printheads from damage. During capping, each of the caps pushes against the pens until a seal around the pen is achieved. The seal is made to discourage evaporation of printing composition from the nozzles to the ambient. When this seal is made, it may force air into the printhead which can cause one or more of the printhead nozzles to become deprimed. This seal also creates a volume of air in the cap. This volume fluctuates with pressure as temperature changes, or with altitude excursions and can also lead to depriming the nozzles. Depriming in-turn degrades output print quality of the printing device, potentially wastes print media, and can permanently damage the printheads.
A diffusion path may be used to help prevent depriming of the nozzles. The diffusion path creates an avenue for pressure equilibration with the ambient by allowing escape of air between the cap and the environment. The diffusion path also helps prevent depriming of the nozzles during capping by allowing compressed air to escape to the ambient. The diffusion path, however, can cause printing composition evaporation while a printhead is capped if too much printing composition is allowed to vent through the diffusion path to ambient over time. This leads to a loss of printing composition as well as possible clogging of one or more printhead nozzles, both of which are undesirable. Clogging can degrade output print quality, require replacement of a printhead if the nozzles cannot be unclogged, necessitate user intervention and potentially waste print media.
Alleviation of these above-described problems would be a welcome improvement. The present invention is directed to solving them with the goals of helping maintain optimal printing device output print quality, helping prevent printhead nozzle depriming, helping prevent loss of printing composition, helping prevent printhead nozzle clogging, helping prevent premature printhead replacement caused by damage, helping prevent waste of print media, and helping minimize necessary user intervention.
An embodiment of an apparatus in accordance with the present invention for use with a printhead includes a cap configured to define a first opening and to have a sealing member that abuts the printhead. The apparatus also includes a vent coupled to the first opening. The apparatus further includes a reservoir coupled to the cap via the vent and configured to be isolated from ambient as the sealing member abuts the printhead.
The above-described embodiment of an apparatus in accordance with the present invention may be modified and include at least the following characteristics, as described below. The reservoir may be configured to retain vapor from the printhead. The vent may be configured to have a length and a cross-sectional area. In such cases, the length of the vent is greater than the cross-sectional area of the vent. The reservoir may have a fixed volume.
The apparatus may further include a humectant in the reservoir. The apparatus may be used in a printing device.
An alternative embodiment of an apparatus in accordance with the present invention for capping a printhead includes a diffusion path and a first cavity having a first opening coupled to the diffusion path. The apparatus also includes a second cavity having a second opening coupled to the diffusion path and configured to communicate with the first cavity via the diffusion path. The diffusion path, first cavity, and second cavity are sealed from ambient during capping of the printhead.
The above-described alternative embodiment of an apparatus in accordance with the present invention may be modified and include at least the following characteristics, as described below. The second cavity may be configured to store vapor from the printhead. In such cases, the diffusion path may be sized to help minimize loss of vapor from the second cavity to ambient when the printhead is uncapped. The second cavity may have a fixed volume.
The apparatus may further include a humectant in the second cavity. The apparatus may be used in a printing device.
An embodiment of a method in accordance with the present invention for use in a printing device having a printhead includes capping the printhead and diffusing pressure variations caused by capping into a fixed volume. The method also includes sealing the printhead and fixed volume from ambient during capping.
The above-described embodiment of a method in accordance with the present invention may be modified and include at least the following characteristics, as described below. The printing device may include a plurality of printheads and the method may further include isolating each of the printheads from communication with one another. The method may additionally include retaining vapor from the printhead in the fixed volume. The method may further include limiting loss of vapor from the fixed volume.
An embodiment of an apparatus in accordance with the present invention for use in a service station includes a plurality of caps each including an opening and each configured to engage a printhead during nonuse. The apparatus also includes a plurality of separate chambers each of which is coupled to a different cap via a different opening, each of which is isolated to receive vapor from a single printhead, and each of which is sealed from ambient during cap and printhead engagement.
The above-described embodiment of an apparatus in accordance with the present invention may be modified and include at least the following characteristics, as described below. Each chamber may be configured to accommodate pressure variations occurring during cap and printhead engagement.
The apparatus may further include a plurality of conduits configured to couple the chambers to the caps. In such cases, the conduits may be configured to minimize loss of vapor during periods of printhead use. Also in such cases, the conduits may be the same length.
The apparatus may further include a humectant in each chamber. The apparatus may be used in a printing device.
Another alternative embodiment of an apparatus in accordance with the present invention for use in a printing device having a printhead with a plurality of nozzles includes structure for protecting the printhead during periods of nonuse. The apparatus also includes structure for diffusing pressure variations occurring during engagement between the structure for protecting and the printhead to help prevent nozzle deprimes. The apparatus further includes structure for isolating the printhead from ambient during engagement between the st
Anderson Erik A.
Hewlett--Packard Development Company, L.P.
Hsieh Shih-wen
LandOfFree
Apparatus and method for capping one or more printheads in a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for capping one or more printheads in a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for capping one or more printheads in a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3301709