Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-10-24
2004-05-11
Hsieh, Shih-Wen (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C345S029000, C345S030000, C345S032000, C345S033000
Reexamination Certificate
active
06733106
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to ink jet printer maintenance stations, and, more particularly, to maintenance stations for color ink jet printers having printheads arranged radially around a print drum.
2. Description of the Related Art
Ink jet printers are used widely due to their low cost of operation, low energy use and quiet operation. Ink jet printing involves ejection of tiny ink droplets through small nozzles in a controlled manner to create the desired image. Ink is supplied from an ink reservoir to a printing head, which includes various passageways from the reservoir to the nozzle orifices. Energy is applied to the ink from an ink droplet generator near each orifice, which may include the application of electrostatic attraction, the application of oscillating forces from piezo elements, the application of heat from heating elements or the like.
During the printing process, stray droplets and pools of ink can accumulate around the nozzles on the plate surface, and the accumulations thereof can interfere with the trajectory of subsequently ejected ink droplets, thereby affecting print quality. Paper dust, fibers and debris can also accumulate on the nozzle plate, with much the same detrimental effect. To maintain proper and acceptable performance from an ink jet printhead, periodically it is necessary to perform maintenance or cleaning functions on the printhead. It is known to provide a maintenance station at which such maintenance or cleaning functions are performed.
During periods of inactivity, ink forming a meniscus in the nozzles is exposed to air, and can dry or harden, plugging the nozzle. To minimize and delay such “soft plugging” in the nozzles, the printhead is capped, to maintain an appropriate humid environment around the nozzles. However, the cap must appropriately seal to the printhead to maintain the humid environment for an extended period of time. If the cap does not seal properly to the printhead, the sealed humid environment around the nozzles is lost, and ink drying in the nozzles can occur more quickly.
For inkjet printers having one or more printheads mounted more or less in line on a carriage that moves back an forth across the media being printed, to eject ink droplets on the media, arrangement and operation of an appropriate maintenance station is known. However, it also is possible to use a printing drum, with printheads mounted radially around the drum, to eject ink droplets directly on the drum for transfer to the desired media, or to direct ink directly on the media held on the drum. Since the printheads are arranged radially around the drum, the maintenance station must also have a radial orientation to effectively operate upon the printhead nozzle plates. When not in use, the maintenance station must not interfere with carriage movement.
What is needed in the art is a simple maintenance station that provides capping and wiping operations for radially mounted ink jet printheads.
SUMMARY OF THE INVENTION
The present invention provides a radially arranged maintenance station for wiping and capping radially arranged printheads.
The invention comprises, in one form thereof, an ink jet printer with a printer frame; a print drum supported by the frame; and a plurality of printheads arranged radially of the drum. A printhead maintenance station is disposed at an end of the print drum. The station includes a rotatable maintenance cylinder having a periphery, a plurality of caps located at the periphery of the maintenance cylinder; and means for rotating the cylinder and moving the caps radially in the maintenance cylinder between a radially inward position and a radially outward position. A carriage means moves the plurality of the printheads along the print drum and over the maintenance cylinder.
The invention comprises, in another form thereof, a maintenance station for an ink jet printer. A camming spool has first and second camming spool end plates. A core spool has first and second core spool end plates. A capping slide has a carrier, a nozzle plate cap carried on the carrier and mounting means suspending the carrier between the first and second core spool end plates and between the first and second camming spool end plates. The camming spool defines a camming spool guide path for the mounting means between a radially inner position and a radially outer position. The core spool defines a core spool guide path for the mounting means between a radially inner position and a radially outer position. A drive system rotates the core spool and the camming spool both jointly with and independently of each other.
The invention comprises, in a further form thereof, a method for servicing a plurality of printheads arranged radially of a print drum. The method steps include providing a maintenance station at an end of the drum, the maintenance station including a rotatable cylinder and a plurality of radially arranged retractable caps, one of the caps for each of the printheads; moving the printheads axially outward of the drum and in alignment with the maintenance station; rotating the cylinder, and elevating the caps into sealing relationship with the printheads.
An advantage of the present invention is providing a maintenance station for printheads arranged radially around a printing drum in an ink jet printer.
Another advantage is providing a maintenance station for radially arranged printheads that does not interfere with movement of the printheads during non-maintenance operations, and that is easy to align properly with the printheads.
Yet another advantage is providing a maintenance station having nozzle plate caps that can be elevated and retracted.
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Hsieh Shih-Wen
Lexmark International Inc.
Taylor & Aust P.C.
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