Thermal bend actuator for a micro electro-mechanical device

Details Thermal bend actuator for a micro electro-mechanical device Thermal bend actuator for a micro electro-mechanical device

2000-05-23

2001-12-11

Barlow, John (Department: 2853)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

C347S044000

Reexamination Certificate

active

06328425

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a thermal bend actuator for a micro electro-mechanical (MEM) device. The invention has application in ejection nozzles of the type that are fabricated by integrating the technologies applicable to micro electro-mechanical systems (MEMS) and complimentary metal-oxide semiconductor (“CMOS”) integrated circuits, and the invention is hereinafter described in the context of that application. However, it will be understood that the invention does have broader application, to thermal bend actuators within other types of MEM devices.
CO-PENDING APPLICATIONS
Various methods, systems and apparatus relating to the present invention are disclosed in the following co-pending applications filed by the applicant or assignee of the present invention simultaneously with the present application:
NPA001US, NPA002US, NPA003US, NPA004US, NPA005US, NPA006US, NPA007US, NPA008US, NPA009US, NPA010US, NPA012US, NPA016US, NPA017US, NPA018US, NPA019US, NPA020US, NPA021US, NPA030US, NPA035US, NPA048US, NPA050US, NPA051US, NPA052US, NPA075US, NPB001US, NPB002US, NPK002US, NPK003US, NPK004US, NPK005US, NPK007US, NPM001US, NPM002US, NPM003US, NPM004US, NPN001US, NPN002US, NPN003US, NPP001US, NPP002US, NPP003US, NPP005US, NPP006US, NPP007US, NPP008US, NPP016US, NPP017US, NPP018US, NPP019US, NPS001US, NPS003US, NPS020US, NPT001US, NPT002US, NPT003US, NPT004US, NPX001US, NPX003US, NPX008US, NPX011US, NPX014US, NPX016US, NPX020US, NPX022US, IJ52US, IJM52US, MJ10US, MJ11US, MJ12US, MJ13US, MJ14US, MJ15US, MJ34US, MJ47US, MJ52US, MJ58US, MJ62US, MJ63US, MJ64US, MJ65US, MJ66US, PAK04US, PAK05US, PAK06US, PAK07US, PAK08US, PEC01US, PEC02US, PP01US, PP02US, PP03US, PP04US, PP07US, PP08US, PP09US, PP10US, PP11US, PP12US, PP13US, PP14US, PP15US, PP16US, PP17US.
The disclosures of these co-pending applications are incorporated herein by cross-reference. Each application is temporarily identified by its docket number. This will be replaced by the corresponding USSN when available.
BACKGROUND OF THE INVENTION
A high speed page width ink jet printer has recently been developed by the present applicant. This typically employs in the order of 51, 200 ink jet nozzles to print on A
4
size paper to provide photographic quality image printing at 1,600 dpi. In order to achieve this nozzle density, the nozzles are fabricated by integrating MEMS-CMOS technology and in this context reference may be made to International Patent Application No.PCT/AU00/00338 lodged by the present Applicant and entitled “Thermal Actuator”.
These high speed page width ink jet printers produce an image on a sheet by causing a thermal bend actuator arm to move relative to a substrate by forming the actuating arm in part from an electrically resistive material and by applying a current to the arm to effect movement of the arm. The arm is connected to a paddle so that upon movement of the arm the paddle is moved to eject a droplet of ink onto the sheet. In order to eject the droplet of ink the paddle extends into a nozzle chamber which has a nozzle aperture, and movement of the paddle causes the droplet to be ejected from the nozzle aperture. The actuating arm is fixed at one end and when current is applied to the arm the arm is caused to bend to, in turn, move the paddle so as to eject the droplet from the nozzle aperture. In order for the paddle to move properly, so as to eject the droplet, the actuating arm is required to bend upwardly and generally pivot around the fixed end of the arm. Bending of the arm is caused by the application of an electrical current to the arm which causes an elongation of part of the arm relative to another part of the arm. To ensure that the actuating arm bends properly it is necessary to control bending modes of the arm which may result in improper movement of the paddle which may effect the ejection of a droplet from the nozzle chamber. For example, the elongation of one part of the arm relative to the other can cause the arm, rather than to bend upwardly as required, to curl up at the sides forming a general dish shaped configuration, or bend into a sinusoidal configuration or other curved configuration. These bending modes may result in improper movement of the paddle which, as noted above, may effect the manner in which a droplet is ejected from the nozzle chamber.
SUMMARY OF THE INVENTION
A first aspect of the invention provides a thermal bend actuator for a micro electro-mechanical device comprising:
a first actuator portion,
a second actuator portion spaced from the first actuator portion, the second actuator portion being conductively heatable to cause bending of the thermal bend actuator,
a first connecting member interconnecting the first and second portions,
a second connecting member interconnecting the first and second portions, and
a torsion member coupled to and interconnecting the first and second connecting members.
Thus, according to this aspect of the invention, the provision of the connecting portions which interconnect the actuator portions and the torsion member which interconnects the connecting portions, reduce the bending modes which are likely to occur upon thermal heating of the thermal bend actuator thereby forcing the actuator to bend according to the desired mode to ensure proper movement of the thermal bend actuator.
The invention may also be said to reside in a micro electro-mechanical device comprising:
a fluid chamber for containing a fluid,
an outlet in the chamber for allowing exit of fluid from the chamber,
a thermal bend actuator for dispensing fluid from the chamber through the outlet aperture, the thermal bend actuator having
a first actuator portion,
a second actuator portion spaced from the first actuator portion and being conductively heatable to cause bending of the thermal bend actuator,
a first connecting member interconnecting the first and second portions,
a second connecting member interconnecting the first and second portions, and
a torsion member coupled to and interconnecting the first and second connecting members.
PREFERRED FEATURES OF THE INVENTION
Preferably each actuator portion has at least two spaced apart fingers, said first connecting member interconnecting first fingers of the first and second actuator portions, and the second connecting member interconnecting second fingers of the first and second actuator portions.
Preferably each finger is provided with a tab and the respective connecting member is coupled to the tab of each finger.
Preferably each finger has a first edge and a second edge and a plurality of tabs are provided on the first edge and second edge of each finger, and the connecting members extend between a respective one of the tabs on the fingers of the first actuator portion and a respective one of the tabs on the fingers of the second actuator portion.
Preferably the connecting members extend through the tabs of one of the actuator portions and have ends which are spaced from the said one of the actuator portions, and a said torsion member interconnects the ends of respective pairs of the connecting members.
Preferably the connecting members comprise connecting rods.
Preferably the torsion members comprise torsion bars.
Preferably the thermal actuator includes a paddle located in the chamber and moveable upon bending of the thermal actuator to eject a droplet of liquid from the chamber through the nozzle aperture.
Preferably the chamber has an upper wall and the torsion member is formed by deposition simultaneously with the upper wall of the chamber.
Preferably the torsion members are formed by deposition by first forming an opening in the tabs provided on one of the actuator portions and depositing material so that the material is deposited through the openings and onto the tabs associated with the other of the first or second actuator portions so as to interconnect the actuator portions, the material being deposited to form the connection members so that the connection members have free ends substantially level with the upper wall of the chamber.
Preferably the connecting members are provided i

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