Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-07-10
2001-11-06
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S020000, C347S044000, C347S047000
Reexamination Certificate
active
06312107
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to ink jet printing and in particular discloses a thermoelastic bend actuator using PTFE and corrugated copper 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 207-220 (1988).
Ink Jet printers themselves come in many different types. The utilisation 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 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 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 US 4584590 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 2,007,162 (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 for an alternative form of drop on demand inkjet printing having a number of advantageous features.
In accordance with the first aspect of the present invention there is provided a thermal actuator comprising a heater element encased within a material having a high coefficient of thermal expansion whereby the actuator operates via means of electrically heating the heater element of the thermal actuator wherein the heater element has a corrugated structure so as to improve the thermal distribution of heat from the heater element to the actuation material so as to increase the speed actuation of the thermal actuator. Further the heater element is of a serpentine or concertina form so as to allow substantially unhindered expansion of the actuation material during heating. The thermal actuator is utilised in an ink jet nozzle for the ejection of ink from a nozzle chamber. Advantageously, one surface of the actuator is hydrophobic and the other surface is hydrophilic and the heater material within the actuator comprises substantially copper. The hydrophilic material is formed by means of processing the hydrophobic material.
In accordance with a second aspect of the current invention, there is provided a thermal actuator comprising a heater element having a low coefficient of thermal expansion surrounded by an actuation material having a high coefficient of thermal expansion wherein the thermal actuator includes a first and second layers of actuation material and a third layer of conductive material, at least a portion of which is utilised as a heating element, wherein a portion of the conductor material has a series of slots or holes so as to allow the actuation material to be integrally joined together so as to reduce the likelihood of delamination of the layers. Advantageously, the portion having a series of slots or holes comprises a stiff structural petal at an end of the actuator.
Further the stiff structural petal can include a regularly spaced array of holes defined therein. The thermal vent actuator is attached at one end of a substrate and includes an actuation material having a high coefficient of thermal expansion, and further the actuator comprises a stable clamp on top of the actuator at the end attached to the substrate, which acts to decrease the likelihood of separation of the actuation material from the substrate. Advantageously, the thermal vent actuator is utilised for the ejection of ink from a chamber via an ink nozzle. The stable clamp forms part of a grille structure for the filtering of ink flow into the chamber for subsequent ejection. Preferably the substrate is fabricated from a silicon wafer and the clamp is substantially comprised of silicon-nitride and is formed by means of a sacrificial etching process.
REFERENCES:
patent: 4855567 (1989-08-01), Mueller
patent: 6087638 (2000-07-01), Silverbrook
patent: 2227020 A (1990-07-01), None
Barlow John
Do An H.
Silverbrook Research Pty Ltd
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