Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-07-10
2001-07-03
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S020000, C347S044000, C347S047000
Reexamination Certificate
active
06254220
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to ink jet printing and in particular discloses a Shutter Based Ink Jet Printer.
The present invention further relates to the field of drop on demand ink jet printing.
CROSS REFERENCES TO RELATED APPLICATIONS
The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, U.S. patent applications, identified by their U.S. patent application serial numbers (USSN) are listed alongside the Australian applications from which the US patent applications claim the right of priority.
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 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 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)
Piezo-electric ink jet printers are also one form of commonly utilized ink jet printing device. Piezo-electric 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 piezo electric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezo-electric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a Piezo electric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. no. 4,584,590 which discloses a sheer mode type of piezo-electric 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 overcomes some of the aforementioned difficulties of the prior art through the use of a shutter based ink jet nozzle.
In accordance with a first aspect of the present invention, there is provided an ink jet printing device comprising an ink chamber having an oscillating ink pressure, a plurality of nozzle apparatuses in fluid communication with the ink chamber which include a grilled shutter having a first open state permitting the expulsion of ink from the nozzle apparatus and a second closed state substantially restricting the expulsion of ink from the nozzle chamber, and a shutter activation means adapted to drive, on demand, the grilled shutter from a first to a second of these states. Further, the nozzle apparatus includes a locking means adapted to lock the grilled shutter in an open or closed state as required. The method of operating the ink jet printing device of the type in accordance with the present invention comprises the following steps:
opening the grilled shutter during a first high pressure period in the ink chamber;
utilising the high pressure period and a following low pressure period for the expulsion of ink from the nozzle apparatus;
utilising a subsequent high pressure period for the refilling of the nozzle apparatus; and
closing the grilled shutter until such time as further ink is required to be expelled from the nozzle apparatus.
Preferably, the ink jet printing device has a shutter activation means that comprises a thermocouple device. The thermocouple device consists of two arms, one arm having a thermal jacket of low thermal conductivity. Advantageously, the arm having no thermal jacket includes a thinned portion adapted to increase the travel of the thermocouple upon activation.
In the ink jet printing device constructed in accordance with the present invention, both the magnitude and frequency of the oscillating ink pressure in the ink chamber can be altered. Preferably, the size and period of each cycle can be scaled in accordance with such pre-calculated factors such as the number of nozzles ejecting ink and the pressure requirements for nozzle refill with different inks.
REFERENCES:
patent: 5612723 (1997-03-01), Shimura et al.
patent: 403153359 (1991-07-01), None
Barlow John
Do An H.
Silverbrook Research Pty Ltd
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