Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-07-10
2001-05-08
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S020000, C347S047000, C347S044000, C347S094000
Reexamination Certificate
active
06227652
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
FIELD OF THE INVENTION
The present invention relates to ink jet printing and in particular discloses a radiant plunger ink jet printer.
The present invention further relates to the field of drop on demand ink jet printing.
BACKGROUND OF THE INVENTION
Many different types of printing have been invented, a large number of which are presently in use. The known forms of print have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.
In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature.
Many different techniques on ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, “Non-Impact Printing: Introduction and Historical Perspective”, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207 to 220 (1988).
Ink Jet printers themselves come in many different types. The utilization of a continuous stream ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electrostatic ink jet printing.
U.S. Pat. No. 3,596,275 by Sweet also discloses a process of a continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electrostatic field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al)
Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. 4,584,590 which discloses a sheer mode type of piezoelectric transducer element.
Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclosed ink jet printing techniques rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.
As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an alternative form of ink jet printing which relies upon an electromechanical activation process for the ejection of ink.
In accordance with a first aspect there is provided an ink jet printing nozzle comprising a nozzle chamber having an ink ejection port at one end; a plunger constructed from soft magnetic material and positioned between the nozzle chamber and an ink chamber, which allows for the supply of ink to the nozzle chamber, and an electric coil located adjacent to the plunger and electrically connected to a nozzle activation signal wherein upon activation the plunger is caused to move from an ink loaded position to an ink ejection position and thereby causes the ejection of ink from the ink chamber through the ejection port. Further, the ink ejection nozzle comprises an armature plate constructed from soft magnetic material and the plunger is attracted to the armature plate on the activation of the coil. A cavity is defined by the plunger in which the electric coil is located, which has its dimensions reduced as a result of movement of the plunger, the plunger further having a series of fluid release slots in fluid communication with the cavity and the ink chamber, allowing for the expulsion of fluid under pressure in the formed cavity. Preferably, the ink jet printing nozzle comprises a resilient means for assisting in the return of the plunger from the ink ejection position to the ink loaded position after the ejection of ink from the ink ejection port. Advantageously, the resilient means comprises a torsional spring of an arcuate construction having a circumferential profile substantially the same as that of the plunger.
In accordance with a second aspect of the present invention, there is provided an ink jet printing nozzle constructed in accordance with the first aspect of the invention wherein the plunger has along one surface a series of slots. This surface forms the inner radial surface defining the cavity between the plunger and the electric coil. Further, the plunger has no fluid release slots in its top surface that defines the top wall of the cavity formed. Upon reduction of the cavity dimensions due to the downward movement of the plunger, induced by the electric coil, an ink flow through the slots into the nozzle chamber occurs assisting in the ejection of ink from the ink ejection port. Preferably, the slots have a substantially constant cross-sectional profile.
REFERENCES:
patent: 4882596 (1989-11-01), Tsuzuki et al.
patent: 405318724 (1993-12-01), None
patent: 406008420 (1994-01-01), None
Barlow John
Do An H.
Silverbrook Research Pty Ltd
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