Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-07-10
2001-04-10
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S020000, C347S044000, C347S047000
Reexamination Certificate
active
06213589
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 planar thermoelastic bend actuator 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 of 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 electro-static 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 electro-static 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 el 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 utilises 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. Pat. No. 4,584,590 which discloses a shear 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 that 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
The present invention relates to ink jet printing and in particular, discloses a new form of ink jet printer which utilizes a planar thermoelastic bend actuator to eject ink from a nozzle chamber.
In accordance with a first aspect of the present invention an ink jet nozzle is provided comprising a nozzle chamber having an ink ejection port in one wall of the chamber, an ink supply source interconnected to the nozzle chamber and a thermal actuator activated to eject ink from the nozzle chamber via the ink ejection port. Further, the thermal actuator comprises a lower planar surface constructed from a highly conductive material interconnected to an upper planar material constructed from an electrically resistive material such that upon passing a current between the planar surface, the thermal actuator is caused to bend towards the ink ejection port so as to thereby cause the ejection of ink from the ink ejection port. The actuator is attached to a substrate and further includes a stiff paddle portion which increases the degree of bending of the actuator near the point where it is attached to the substrate. Preferably, the stiff paddle is formed of silicon nitride. Advantageously, the actuator further includes an expansion coating having a high coefficient of thermal expansion on top of the upper planar surface so as to increase the amount of bending of the actuator. The expansion coating can comprise substantially polytetrafluoroethylene. Between the upper and lower planar surfaces there is provided a gap, constructed through the utilization of a sacrificial material which is deposited and subsequently etched away so as to leave the gap. Further, the upper planar surface includes a plurality of etchant holes provided to allow a more rapid etching of the sacrificial layer during construction. Advantageously, the upper planar surface of the actuator comprises substantially Indium Tin Oxide (ITO) whereas the lower planar surface of the actuator comprises substantially a metal layer. Both surfaces are further coated with a passivation material as required. The ink jet nozzle construction can be formed on a silicon wafer utilizing micro-electro mechanical systems construction techniques.
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Barlow John
Do An H.
Silverbrook Research PTY Ltd.
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