Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-12-04
2004-01-27
Meier, Stephen D. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S048000, C347S063000
Reexamination Certificate
active
06682176
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of inkjet printers and discloses an inkjet printhead chip. In particular, the present invention relates to a printhead chip having nozzle arrangements that incorporate spaced actuating bars.
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 printers have a variety of methods for marking the print media with 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 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 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, by Stemme in U.S. Pat. No. 3,747,120 (1972) which discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 which discloses a piezoelectric push mode actuation of the ink jet stream and by 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 by Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned reference inkjet 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 in communication with the confined space onto a relevant print media. Manufacturers such as Canon and Hewlett Packard manufacture printing devices utilizing the electrothermal actuator.
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.
In the construction of any inkjet printing system, there are a considerable number of important factors which must be traded off against one another especially as large scale printheads are constructed, especially those of a pagewidth type. A number of these factors are outlined in the following paragraphs.
Firstly, inkjet printheads are normally constructed utilizing micro-electromechanical systems (MEMS) techniques. As such, they tend to rely upon the standard integrated circuit construction/fabrication techniques of depositing planar layers on a silicon wafer and etching certain portions of the planar layers. Within silicon circuit fabrication technology, certain techniques are better known than others. For example, the techniques associated with the creation of CMOS circuits are likely to be more readily used than those associated with the creation of exotic circuits including ferroelectrics, gallium arsenide etc. Hence, it is desirable, in any MEMS construction, to utilize well-proven semi-conductor fabrication techniques that do not require the utilization of any “exotic” processes or materials. Of course, a certain degree of trade off will be undertaken in that if the use of the exotic material far outweighs its disadvantages then it may become desirable to utilize the material anyway.
With a large array of ink ejection nozzles, it is desirable to provide for a highly automated form of manufacturing which results in an inexpensive production of multiple printhead devices.
Preferably, the device constructed utilizes a low amount of energy in the ejection of ink. The utilization of a low amount of energy is particularly important when a large pagewidth full color printhead is constructed having a large array of individual print ejection mechanisms with each ejection mechanism, in the worst case, being fired in a rapid sequence.
In the parent application, namely U.S. application Ser. No. 09/113,122 there is disclosed a printhead chip having a plurality of nozzle arrangements. These nozzle arrangements each include an actuator. The actuator has two pairs of actuating arms, each pair comprising an active actuating arm and a passive actuating arm. The active actuating arms are configured so that when heated upon receipt of an electrical signal, they deform and drive an ink displacement mechanism so that ink can be ejected from the respective nozzle chambers. The passive actuating arms serve to provide resilient flexibility and stability to the actuator.
The Applicant has found that it is desirable that the actuator has a certain configuration to avoid buckling of the actuator when the active actuating arms are deformed to displace the actuator. While avoiding buckling, this configuration must also maintain efficiency of the actuator. This configuration is the subject of this invention.
SUMMARY OF THE INVENTION
In general, there is disclosed herein an ink jet nozzle assembly including a nozzle chamber and a nozzle, the chamber including a movable portion and an actuating arm connected to or formed integrally with the movable portion and functioning in use to move said movable portion selectively to eject ink from the chamber via said nozzle, the actuating arm having portions with equivalent thermal expansion characteristics so as to avoid differential thermal expansion in response to changes in ambient temperature.
Preferably the actuating arm is formed of materials having equivalent thermal expansion characteristics and a current is passed through only a portion of the actuating arm to effect said movement.
Preferably said nozzle chamber has an inlet in fluid communication with an ink reservoir. The nozzle chamber may include a fixed portion configured with said movable portion such that relative movement in an ejection phase reduces an effective volume of the chamber, and alternate relative movement in a refill phase enlarges the effective volume of the chamber;
Portions of the actuating arms may be spaced apart and are adapted for selective differential thermal expansion upon heating so as to effect said relative movement.
The inlet may be positioned and dimensioned relative to the nozzle such that ink is ejected preferentially from the chamber throug
Do An H.
Meier Stephen D.
Silverbrook Research Pty Ltd
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