Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-10-26
2001-08-28
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S029000, C347S033000
Reexamination Certificate
active
06280015
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to inkjet printing and, in particular, to a method and structure for wiping and capping the printhead of an inkjet print cartridge.
2. Related Art
In inkjet printing, one or more print cartridges (pens) are inserted in a moldable print carriage. Each print cartridge includes a reservoir that holds ink. The ink passes from the reservoir through a multiplicity of nozzles to be ejected from a print cartridge printhead onto a print medium. The print carriage is moved laterally back and forth, and the print medium is advanced past the print carriage to enable printing of a desired image or images on the print medium.
Inkjet print cartridge nozzles commonly become plugged with ink blobs or particulate, or otherwise contaminated with internal bubbles that prevent the nozzles from operating properly, resulting in lower print quality. Consequently, printers and facsimile machines that use inkjet printing typically include a service station that provides for spitting, wiping, capping and priming of each printhead in order to keep the nozzles clean and functioning.
During capping, a cap must be properly aligned with the corresponding printhead. Typically, for inkjet print cartridges, cap alignment must be maintained within a fraction of a millimeter of a nominal value. However, tolerances associated with the assembly and operation of an inkjet printing assembly can combine to result in a variation of cap alignment that is too large. Such tolerances may result from, for instance, positioning of the print cartridge in the corresponding stall of the print carriage, attachment of the print carriage to a print carriage movement mechanism (such as a rod) attached to a printer chassis, assembly of the various components of the service station, and attachment of the service station to the printer chassis.
If the cap is misaligned, the cap can contact one or more of the nozzles and absorb ink from the nozzles through capillary action, dirtying the service station with ink and necessitating priming of the nozzles before printing again. Additionally, improper alignment can cause the cap to inadequately seal the area around the nozzles. As a result, air can enter the area around the printhead, causing the ink to dry out and clog the nozzles. Contaminants may also enter the area around the printhead, eventually causing the nozzles to become clogged.
During wiping, interference between the wiper and the print cartridge must be controlled within a specified dimensional tolerance to achieve the proper wiping force. Typically, for inkjet print cartridges, wiper interference must be maintained within a fraction of a millimeter of a nominal value. If the wiper interference is too small, then the wiping force will be too small and the printhead won't be adequately wiped, resulting in poor print quality and shortened print cartridge life. If the wiper interference is too large, debris will be pushed in to the nozzles, clogging one or more nozzles so that ink cannot be ejected from the nozzle or nozzles (“missing dots”), and/or degrading the print quality by partially clogging nozzles or becoming embedded in the ink.
Frequently, the cap and the wiper are mounted on a movable service station sled. For a variety of reasons, there may be a problem with the functionality of the cap, wiper or some other part of the service station sled. For example, because of the frequent contact between the wiper and the print cartridge, the wiper may wear out. Therefore, it is desirable that the service station sled can be replaced without the necessity of replacing the remainder of the service station.
Additionally, printers must include structure for performing various functions, e.g., moving the print carriage, advancing the print medium through a printing path. It is obviously desirable to make the structure for performing these functions as simple, efficient and inexpensive as possible. In particular, it is desirable to use particular components of the printer to perform more than one function, thereby enabling the printer to be made smaller (or, equivalently, perform more functions for the same size), simpler to manufacture and less expensive to manufacture.
SUMMARY OF THE INVENTION
According to the invention, a service station for use in servicing one or more inkjet print cartridges (pens) includes a service station sled assembly movably attached to a service station chassis. The service station chassis is attached to a printer chassis. The one or more inkjet print cartridges are mounted in a print carriage which is, in turn, movably attached to the printer chassis. During printing, ink is ejected through nozzles formed in each print cartridge. At least one wiper and at least one cap are mounted on a sled base of the sled assembly. Lateral movement of the print carriage with respect to the service station causes each wiper to wipe across the corresponding print cartridge printhead to remove ink from the printhead. Vertical movement of the sled assembly with respect to the print carriage causes each cap to enclose the corresponding print cartridge printhead after printing is completed and the print carriage is moved laterally into a capping position. The service station according to the invention can be used with either a facsimile machine that uses thermal inkjet printing, or with a thermal inkjet printer.
In one embodiment, a service station according to the invention includes a cam and cam follower that interact to move a sled assembly on a surface of which at least one wiper and at least one cap are mounted. The cam is formed on a member that is movably attached to a service station chassis and the cam follower is formed on the sled assembly. The cam is shaped so that movement of the cam to a first position causes the cap to contact a printhead of an inkjet print cartridge. Movement of the cam to a second position causes the cap to move away from the printhead. The cam is shaped so that movement of the cam to a particular position, which could be the above-described second position, causes an edge of the wiper to extend beyond the printhead when viewed in a direction parallel to the direction of motion of the print carriage.
In another embodiment, a service station according to the invention for use with a facsimile machine including inkjet printing apparatus includes a motor that is positioned so as to minimize the footprint of the service station. The motor is positioned such that, viewed in a direction perpendicular to the surface of the sled assembly, the sled assembly has a maximum width and the motor has a maximum width, the maximum width of the sled assembly being along an axis that is substantially perpendicular to the axis along which the maximum width of the motor lies.
A method according to the invention includes the steps of: i) positioning a print carriage adjacent to a service station including a sled assembly, and ii) rotating a cam of the service station such that a cam follower of the sled assembly interacts with the cam to cause movement of the sled assembly. In a further embodiment, the step of rotating further comprises the step of positioning the cam at a position so that the cap contacts a printhead of an inkjet print cartridge. In a still further embodiment, the step of rotating further comprises the step of positioning the cam at a second position so that the cap moves away from the printhead. In another further embodiment, the step of rotating further comprises the step of positioning the cam at a position, which can be the second position, so that an edge of the wiper distal from the sled assembly surface extends beyond the printhead of the print cartridge when viewed in a direction parallel to the direction of motion of the print carriage.
Thus, according to the invention, a sled assembly can be moved between capping and wiping positions using a simple mechanism that is easy and inexpensive to assemble and manufacture. Further, the positioning mechanism is driven by a motor that is oriented so
Fujimori Noriyoshi
Kobayashi Atsushi
Nguyen Chan
Shibata Alan
Hewlett--Packard Company
Le N.
Potts Jerry R.
Vo Anh T. N.
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