Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-09-28
2001-02-06
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S025000, C347S027000, C347S029000
Reexamination Certificate
active
06183058
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention generally relates to ink jet printer apparatus and methods and more particularly relates to a self-cleaning ink jet printer system with reverse fluid flow and method of assembling the printer system.
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 that are placed close to 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 receiver.
On the other hand, 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 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, which piezoelectric material possesses 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 these characteristics are quartz and tourmaline. The most commonly produced piezoelectric ceramics are lead zirconate titanate, barium titanate, lead titanate, and lead metaniobate.
Inks for high speed ink jet printers, whether of the “continuous” or “on demand” type, must 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.
Moreover, the ink jet print head is exposed to the environment where the inkjet printing occurs. Thus, the previously mentioned orifices and print head surface are exposed to many kinds of airborne particulates. Particulate debris may accumulate on the print head surface surrounding the orifices and may accumulate in the orifices and chambers themselves. Also, 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. Of course, the particulate debris 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, and/or the previously mentioned “spitting” of ink through the orifice. However, wiping of the print head surface surrounding the orifice causes wear of the surface and the wiper. In addition, the wiper itself produces particles that clog the orifice.
As indicated hereinabove, ink jet print head cleaners are known. Such an ink jet print head cleaner is disclosed in U.S. Pat. No. 4,970,535 titled “Ink Jet Print Head Face Cleaner” issued Nov. 13, 1990, in the name of James C. Oswald. This patent discloses an ink jet print head face cleaner that provides a controlled air passageway through an enclosure formed against the print head face. Air is directed through an inlet into a cavity in the enclosure. The air that enters the cavity is directed past ink jet apertures on the print head face and then out an outlet. A vacuum source is attached to the outlet to create a subatmospheric pressure in the cavity. A collection chamber and removable drawer are positioned below the outlet to facilitate disposal of removed ink. Although the Oswald patent does not disclose use of brushes or wipers, the Oswald patent also does not reference use of a liquid solvent to remove the ink; rather, the Oswald technique relies on use of heated air to remove the ink. However, use of heated air is less effective for cleaning than use of a liquid solvent. Also, use of heated air may damage fragile electronic circuitry that may be present on the print head face. Moreover, the Oswald patent does not appear to disclose “to-and-fro” movement of air streams or liquid solvent across the head face, which to-and-fro movement might otherwise enhance cleaning effectiveness.
Therefore, there is a need to provide a self-cleaning printer system that addresses the problems of the prior art recited hereinabove.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a self-cleaning printer system that addresses the problems of the prior art recited hereinabove.
With this object in view, the present invention resides in a self-cleaning printer, comprising a print head having a surface thereon and a passageway therethrough in communication with the surface for conducting a flow of cleaning fluid through the passageway and to the surface; a structural member disposed opposite the surface for defining a gap therebetween sized to allow the flow of fluid through the gap, said member accelerating the flow of fluid to induce a shearing force in the flow of fluid, whereby the shearing force acts against the surface while the shearing force is induced in the flow of fluid and whereby the surface is cleaned while the shearing force acts against the surface; and a junction coupled to the gap for changing flow of the fluid through the gap from a first direction to a second direction opposite the first direction.
According to an exemplary embodiment of the present invention, the self-cleaning printer system comprises a print head defining a plurality of ink channels therein, each ink channel terminating in an orifice. The print head also has a surface thereon surrounding all the orifices. The print head is capable of ejecting ink droplets through the orifice, which ink droplets are intercepted by a receiver (e.g., paper or transparency) supported by a platen roller disposed adjacent the print head. However, contaminant such as an oily film-like deposit or particulate matter may reside on the surface and may completely or partially obstruct the orifice. The oily film may, for example, be grease and the particulate matter may be particles of dirt, dust, metal and/or encrustations of dried ink. Presence of the contaminant interferes with proper ejection of the ink droplets from their respective orifices and therefore may give rise to undesirable image artifacts, such as “banding”. It is therefore desirable to clean the contaminant from the surface and orifices.
Therefore, a cleaning assembly belonging to the printer system is disposed relative to the surface and/or orifice for directing a flow of fluid along the surface and/or across the orifice to clean the contaminant from the surface and/or orifice. As described in detail herein, the cleaning assembly is configured by means of a valve system to direct fluid flow in a forward direction across the surface and/or orifice and then in a reverse direction across the surface and/or orifice. This to-and-fro motion enhances cleaning efficiency. In this regard, the cleaning assembly includes a piping circuit having a first piping segment and a second piping segment for carrying the fluid therethrough. The second piping segment is connected to a first fluid flow passageway and the first piping segment is connected to a second fluid flow passageway. The first and
Delametter Christopher N.
Meichle Michael E.
Moghadam Omid A.
Quenin John A.
Sharma Ravi
Eastman Kodak Company
Hsieh Shin-Wen
Le N.
Stevens Walter S.
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