Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-12-28
2003-02-25
Hsieh, Shih-wen (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S029000, C347S033000
Reexamination Certificate
active
06523930
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention generally relates to ink jet printer apparatus and methods and more particularly relates to an ink jet printer with cleaning mechanism, and method of assembling same.
An ink jet printer produces images on a receiver by ejecting ink droplets onto the receiver in an imagewise fashion. The advantages of non-impact, low-noise, low energy use, and low cost operation in addition to the capability of the printer to print on plain paper are largely responsible for the wide acceptance of ink jet printers in the marketplace.
In this regard, “continuous” ink jet printers utilize electrostatic charging tunnels placed close to the point where ink droplets are being ejected in the form of a stream. Selected ones of the droplets are electrically charged by the charging tunnels. The charged droplets are deflected downstream by the presence of deflector plates that have a predetermined electric potential difference between them. A gutter may be used to intercept the charged droplets, while the uncharged droplets are free to strike the recording medium.
In the case of “on-demand” ink jet printers, at every orifice a pressurization actuator is used to produce the ink jet droplet. In this regard, either one of two types of actuators may be used. These two types of actuators are heat actuators and piezoelectric actuators. With respect to heat actuators, a heater placed at a convenient location heats the ink and a quantity of the ink will phase change into a gaseous steam bubble and raise the internal ink pressure sufficiently for an ink droplet to be expelled to the recording medium. With respect to piezoelectric actuators, a piezoelectric material is used possess piezoelectric properties such that an electric field is produced when a mechanical stress is applied. The converse also holds true, that is, an applied electric field will produce a mechanical stress in the material. Some naturally occurring materials possessing this characteristics are quartz and tourmaline. The most commonly produced piezoelectric ceramics are lead zirconate titanate, lead metaniobate, lead titanate, and barium titanate.
Inks for high speed ink jet printers, whether of the “continuous” or “piezoelectric” type, have a number of special characteristics. For example, the ink should incorporate a nondrying characteristic, so that drying of ink in the ink ejection chamber is hindered or slowed to such a state that by occasional spitting of ink droplets, the cavities and corresponding orifices are kept open. The addition of glycol facilitates free flow of ink through the ink jet chamber.
Of course, the ink jet print head is exposed to the environment where the ink jet printing occurs. Thus, the previously mentioned orifices are exposed to many kinds of air born particulates. Particulate debris may accumulate on surfaces formed around the orifices and may accumulate in the orifices and chambers themselves. That is, the ink may combine with such particulate debris to form an interference burr that blocks the orifice or that alters surface wetting to inhibit proper formation of the ink droplet. Also, the ink may simply dry-out and form hardened deposits on the print head surface and in the ink channels. The particulate debris and deposits should be cleaned from the surface and orifice to restore proper droplet formation. In the prior art, this cleaning is commonly accomplished by brushing, wiping, spraying, vacuum suction or spitting of ink through the orifice.
Thus, inks used in ink jet printers can be said to contribute to the following problems: the inks tend to dry-out in and around the orifices resulting in clogging of the orifices; the wiping of the orifice plate causes wear on the plate and wiper; the wiper itself produces particles that clog the orifice, cleaning cycles are time consuming and slow productivity of ink jet printers. Moreover, printing rate declines in large format printing where frequent cleaning cycles interrupt the printing of an image. Printing rate also declines in the case when a special printing pattern is initiated to compensate for clogged or badly performing orifices.
Ink jet print head cleaners are well known. For example, a wiping system for ink jet print heads is disclosed in U.S. Pat. No. 5,614,930 titled “Orthogonal Rotary Wiping System For Inkjet Printheads” issued Mar. 25, 1997 in the name of William S. Osbome et al. This patent discloses a rotary service station that has a wiper-supporting tumbler. The tumbler rotates to wipe the print head along a length of linearly aligned nozzle. In addition, a wiper scraping system scrapes the wipers to clean them. However, Osborne et al. do not disclose use of an external solvent to assist cleaning and also does not disclose complete removal of the external solvent. U.S. patent application Ser. No. 09/195,727 entitled “Ink Jet Printer With Cleaning Mechanism and Method of Assembling Same” by Charles Faisst, Jr. et al and now U.S. Pat. No. 6,347,858 discloses the use of external solvents to assist in cleaning. The Faisst application, however, requires separate canopies for the solvent delivery and solvent removal processes which complicates the cleaning apparatus and increases costs. In addition, the method of assembly disclosed in the Faisst application is somewhat undesirable in terms of size, cost and complexity.
Therefore, there is a need to provide a suitable ink jet printer with a cheaper, more compact cleaning mechanism, having a simplistic method of assembly, that is capable of cleaning the print head surface.
SUMMARY OF THE INVENTION
As such, an object of the present invention is to provide an ink jet printer with cleaning mechanism and method of assembling same, which cleans the surface of a print head belonging to the printer.
Accordingly, the present invention provides an ink jet printer comprising a print head having a surface thereon and an ink channel therein and a cleaning mechanism associated with the print head and adapted to-clean contaminant from the surface.
According to an exemplary embodiment of the invention, an ink jet printer comprises a print head having a surface thereon surrounding a plurality of ink ejection orifices. The orifices are in communication with respective ones of a plurality of ink channels formed in the print head. A cleaning block assembly is comprised of a manifold body with attached canopy and wiper blade edge. The canopy has a plurality of passageways formed therein, with first and second passageways alignable to the printhead surface. The first passageway delivers a liquid solvent cleaning agent to the surface in the approximate location where the wiper blade is in contact with the printhead surface. As the wiper blade traverses the surface contaminant is loosened from the surface and becomes entrained in the solvent. The second passageway, also alignable to the printhead surface, removes the solvent with entrained contaminant from the surface via an applied vacuum. A piping circuit is provided for supplying liquid cleaning solution filtering the particulate matter from the solvent and for re-circulating clean solvent to the surface of the print head.
A translation mechanism is connected to the manifold body for translating the cleaning block across the print head surface. In this regard, the translation mechanism may comprise a lead-screw engaging the manifold body.
An advantage of the present invention is that solvent supply and removal are accomplished simultaneously through a single, simplistic canopy structure.
These and other objects, features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein therein are shown and described illustrative embodiments of the invention.
REFERENCES:
patent: 5574485 (1996-11-01), Anderson et al.
patent: 5614930 (1997-03-01), Osborne et al.
patent: 5760802 (1998-06-01), Ebinuma et al.
patent: 6158838 (2000-12-01), Capurso
patent: 6164751 (2000-12-01), Griffin et al.
patent: 6241337 (20
Debesis John R.
Green, Jr. Robert J.
Griffin Todd R.
Lapa Larry L.
Mycek Edwin A.
Hsieh Shih-wen
Rushefsky Norman
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