Thermal bend actuator

Details Thermal bend actuator Thermal bend actuator

2000-02-15

2002-05-21

Barlow, John (Department: 2853)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

Reexamination Certificate

active

06390605

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of micro electromechanical devices such as ink jet printers. The present invention will be described herein with reference to Micro Electro Mechanical Inkjet technology. However, it will be appreciated that the invention does have broader appications to other micro electro-mechanical devices, e.g. micro electro-mechanical pumps or micro electromechanical movers.
BACKGROUND OF THE INVENTION
Micro electro-mechanical devices are becoming increasingly popular and normally involve the creation of devices on the &mgr;m (micron) scale utilizing semi-conductor fabrication techniques. For a recent review on micro-mechanical devices, reference is made to the article “The Broad Sweep of Integrated Micro Systems” by S. Tom Picraux and Paul J. McWhorter published December 1998 in IEEE Spectrum at pages 24 to 33.
One form of micro electro-mechanical devices in popular use are ink jet printing devices in which ink is ejected from an ink ejection nozzle chamber. Many forms of ink jet devices are known.
Many different techniques on ink jet printing and associated devices 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).
Recently, a new form of ink jet printing has been developed by the present applicant, which is referred to as Micro Electro Mechanical Inkjet (MEMJET) technology. in one form of the MEMJET technology, ink is ejected from an ink ejection nozzle chamber utilising an electro mechanical actuator connected to a paddle or plunger which moves towards the ejection nozzle of the chamber for ejection of drops of ink from the ejection nozzle chamber.
The present invention concerns improvements to a thermal bend actuator for use in the MEMJET technology or other micro electro-mechanical devices.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the present invention, there is provided a thermal actuator for micro electro-mechanical devices, the actuator comprising a supporting substrate, an actuation portion, a first arm attached at a first end thereof to the substrate and at a second end to the actuation portion, the first arm being arranged, in use, to be conductively heatable, a second arm attached at a first end to the supporting substrate and at a second end to the actuation portion, the second arm being spaced apart from the first arm, whereby the first and second arm define a gap between them; and wherein, in use, the first arm is arranged to undergo thermal expansion when conductively heated, thereby causing a force to be applied to the actuation portion.
Accordingly, the operational characteristics of the actuator such as e.g. its operation temperature can be less dependent on a material of the actuation portion when compared with conventional thermal actuators. In conventional thermal actuators, the actuation portion is typically located, in part, between the arms of a thermal actuator (tri-layer actuator). Furthermore, if the actuation portion is located, in part, between the arms, shear stresses are, in use, induced in that part of the actuation portion, which can reduce the efficiency of the actuator.
The actuator may be arranged in a manner such that a heating current can be applied to the first arm through the supporting substrate. The first and second arms are preferably formed from substantially the same material. The actuator can be manufactured by the steps of: depositing and etching a first layer to form the first arm; depositing and etching a second layer to form a sacrificial layer supporting structure over the first arm; and depositing and etching a third layer to form the second arm, and etching the second layer to form the gap between the first and second arms.
The first arm can comprise two elongated flexible strips conductively interconnected at the second end. The second arm can comprise two elongated flexible strips.
The actuation portion can comprise a paddle structure. Accordingly, the actuator may be used inside a liquid ejection chamber, the paddle structure being movable for the ejection of liquid from the chamber.
The first arm can be formed from titanium nitride and the second arm can also be formed from titanium nitride.
In accordance with another aspect of the present invention there is disclosed a novel form of manufacture of an ink jet printing system.


REFERENCES:
patent: 5058856 (1991-10-01), Gordon et al.
patent: 5889541 (1999-03-01), Bobrow et al.
patent: 5897789 (1999-04-01), Weber
patent: 6180427 (2001-01-01), Silverbrook
patent: WO 99/03681 (1999-01-01), None

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