Single-pass wiping system for inkjet printheads

Details Single-pass wiping system for inkjet printheads Single-pass wiping system for inkjet printheads

1999-10-28

2002-01-22

Le, N. (Department: 2861)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

Reexamination Certificate

active

06340218

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to inkjet printing mechanisms, and more particularly to a single-pass wiper system that removes ink residue from an inkjet printhead in a more time efficient manner than earlier systems, allowing the printhead to more quickly return to printing which increases the throughput rating of the unit (measured in pages per minute).
BACKGROUND OF THE INVENTION
Inkjet printing mechanisms use cartridges, often called “pens,” which eject drops of liquid colorant, referred to generally herein as “ink,” onto a page. Each pen has a printhead formed with very small nozzles through which the ink drops are fired. To print an image, the printhead is propelled back and forth across the page, ejecting drops of ink in a desired pattern as it moves. The particular ink ejection mechanism within the printhead may take on a variety of different forms known to those skilled in the art, such as those using piezo-electric or thermal printhead technology. For instance, two earlier thermal ink ejection mechanisms are shown in U.S. Pat. Nos. 5,278,584 and 4,683,481. In a thermal system, barrier layer containing ink channels and vaporization chambers is located between a nozzle orifice plate and a substrate layer. This substrate layer typically contains linear arrays of heater elements, such as resistors, which are energized to heat ink within the vaporization chambers. Upon heating, an ink droplet is ejected from a nozzle associated with the energized resistor. By selectively energizing the resistors as the printhead moves across the page, the ink is expelled in a pattern on the print media to form a desired image (e.g., picture, chart or text).
To clean and protect the printhead, typically a “service station” mechanism is supported by the printer chassis so the printhead can be moved over the station for maintenance. For storage, or during non-printing periods, the service stations usually include a capping system which substantially seals the printhead nozzles from contaminants and drying. Some caps are also designed to facilitate priming, such as by being connected to a pumping unit that draws a vacuum on the printhead. During operation, clogs in the printhead are periodically cleared by firing a number of drops of ink through each of the nozzles in a process known as “spitting,” with the waste ink being collected in a “spittoon” reservoir portion of the service station. After spitting, uncapping, or occasionally during printing, most service stations have an elastomeric wiper that wipes the printhead surface to remove ink residue, as well as any paper dust or other debris that has collected on the printhead. The wiping action is usually achieved through relative motion of the printhead and wiper, for instance by moving the printhead across the wiper, by moving the wiper across the printhead, or by moving both the printhead and the wiper.
To improve the clarity and contrast of the printed image, recent research has focused on improving the ink itself. To provide quicker, more waterfast printing with darker blacks and more vivid colors, pigment-based inks have been developed. These pigment-based inks have a higher solid content than the earlier dye-based inks, which results in a higher optical density for the new inks. Both types of ink dry quickly, which allows inkjet printing mechanisms to form high quality images on readily available and economical plain paper, as well as on recently developed specialty coated papers, transparencies, fabric and other media. Unfortunately, the combination of small nozzles and quick drying ink leaves the printheads susceptible to clogging, not only from dried ink and minute dust particles or paper fibers, but also from the solids within the new inks themselves. Partially or completely blocked nozzles can lead to either missing or misdirected drops on the print media, either of which degrades the print quality. Thus, keeping the nozzle face plate clean becomes even more important when using pigment based inks, because they tend to accumulate more debris than the earlier dye based inks.
As the inkjet industry investigates new printhead designs, the tendency is toward using permanent or semi-permanent printheads in what is known in the industry as an “off-axis” printer. In an off-axis system, the printheads carry only a small ink supply across the printzone, with this supply being replenished through tubing that delivers ink from an “off-axis” stationary reservoir placed at a remote stationary location within the printer. There are a variety of advantages associated with these off-axis printing systems, but the permanent or semi-permanent nature of the printheads requires special considerations for servicing, particularly when wiping ink residue from the printheads, which must be done without any appreciable wear that could decrease printhead life. To accomplish this objective, an ink solvent has been used in an off-axis printer, specifically the DeskJet® 2000C Professional Series color inkjet printer, sold by the present assignee Hewlett-Packard Company. In this ink solvent system, a polyethylene glycol (“PEG”) compound is stored in a porous medium such as a plastic or foam block that is in intimate contact with a reservoir, with this porous block having an applicator portion exposed so the elastomeric wiper can contact the applicator. This elastomeric wiper moves across the applicator to collect PEG, which is then wiped across the printhead to dissolve accumulated ink residue and to deposit a non-stick coating of PEG on the printhead face to retard farther collection of ink residue. The PEG fluid also acts as a lubricant, so the rubbing action of the wiper does not unnecessarily wear the printhead. Other wiper systems without a solvent have also been sold by the Hewlett-Packard Company in the DeskJet® 850C, 855C, 870C and 890C models of color inkjet printers. These scraper systems used a rotary tumbler to wipe the printheads. Another solventless wiper scraper system has been sold by the present assignee, the Hewlett-Packard Company, in the DeskJet® 720C, 722C, 710C, 712C, 810C, 812C, 830C, 832C, 880C, 882C, 895C and 970C models of inkjet printers, which used a translating pallet to wipe the wipers across the printheads.
All of the Hewlett-Packard Company's DeskJet® printer models mentioned in the paragraph above used wiper assemblies having the cross sectional configuration shown in
FIGS. 4-6
of the drawings.
FIG. 4
is a side view of a wiper assembly W at rest.
FIGS. 5 and 6
show side views of the wiper assembly W making a two-pass wiping stroke, first to the right in
FIG. 5
, then to the left in
FIG. 6
, removing ink residue R from an external surface of an orifice plate of printhead P. The wiper assembly W has a first elastomeric wiper blade W
1
and a second wiper blade W
2
which are mounted to a sled S which moves the blades past the stationary printhead P to wiper the ink residue, Q and other debris from the orifice plate. This earlier dual-blade wiper system is described at length in U.S. Pat. No. 5,614,930, currently assigned to the Hewlett-Packard Company, and was first used in the Hewlett-Packard Company's DeskJet® 850C color inkjet printer. The
DeskJet® model 850C printer employed a revolutionary rotary, orthogonal wiping scheme where the wipers ran along the length of the linear arrays, wicking ink I from one nozzle to the next. This wicked ink I acted as a solvent to break down ink residue accumulated on the nozzle plate. To facilitate this wicking action and subsequent printhead cleaning accomplish this wiping action, the wiper blades W
1
and W
2
have special contours at their tips. The blades W
1
and W
2
are mirror-images of each other, having outboard rounded edges R
1
and R
2
, respectively, and inboard angular wiping edges A
1
and A
2
, respectively. The rounded edges encounter the nozzles first and form a capillary channel between the blade and the orifice plate to wick liquid ink I from the nozzles as the wipers moved orthogonally along the length of the nozzle arra

Affiliated with

Also associated with

Rating

Single-pass wiping system for inkjet printheads does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Single-pass wiping system for inkjet printheads, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Single-pass wiping system for inkjet printheads will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2839749