Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-03-06
2003-08-12
Nguyen, Lamson (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06604817
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a print head for a piezoelectric ink jet printer, and more particularly to such a print head including a laminated piezoelectric actuator. The invention also relates to a piezoelectric actuator in the form of a plate for such a print head, and to a process for producing such actuators.
2. Description of the Related Art
U.S. Pat. No. 5,402,159 discloses a print head for a piezoelectric ink jet printer. The print head includes a cavity plate and a piezoelectric actuator in the form of a laminated plate. The cavity plate has nozzles and pressure chambers. The pressure chambers are open on one side of the cavity plate, and each communicate with one of the nozzles. The piezoelectric actuator includes piezoelectric sheets, sets of drive electrodes and some common electrodes. The drive electrodes and common electrodes are interposed between the piezoelectric sheets. Each set of drive electrodes is associated with one of the pressure chambers. The common electrodes are common to all the pressure chambers. The cavity plate lies on the piezoelectric actuator in such a manner that the actuator closes the pressure chambers.
As shown in
FIGS. 11 and 15
of the foregoing patent, the piezoelectric actuator also includes side electrodes formed on side faces of it. Each side electrode is connected electrically to one of the sets of drive electrodes, and can be connected electrically to the outside. The side electrodes may come into contact with the cavity plate, which lies on the piezoelectric actuator. If the cavity plate is metallic, the contact short-circuits the side electrodes.
In order to prevent such short circuits, another conventional art of this type includes a cavity plate made of an alumina ceramic, which is an electrical insulator, or other non-conducting material. However, this cavity plate becomes larger in order to ensure a predetermined strength of the cavity plate. In addition, the material cost for the cavity plate is higher, and the processing steps for it becomes more complicated. As a result, the cost of the cavity plate is considerably higher.
Still another conventional art provides an insulating sheet between a cavity plate and a piezoelectric actuator in order to avoid the short circuit therebetween. The interposition of the insulating sheet allows the cavity plate to be made of metallic. The metallic cavity plate can be smaller and less costly than the cavity plate made of an alumina ceramic or other non-conducting material. However, the interposition of the insulating sheet increases the number of parts for the print head. The increased number of parts prevents the print head from being sufficiently small and inexpensive. In addition, the interposition of the insulating sheet increases the number of places where ink may leak.
In the foregoing patent, the side electrodes are formed on the side faces of the piezoelectric actuator by vacuum metallizing, metal spattering, conductive paste coating, or the like. The side electrodes rise slightly from the side faces. Consequently, while the piezoelectric actuator is produced or assembled, the side electrodes are very liable to be damaged by a handler, a jig or the like coming into contact with them. This causes defectives to be produced at a higher rate while piezoelectric actuators are produced.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an ink jet printer print head including a cavity plate and a piezoelectric actuator which lie on each other, the actuator including side electrodes provided on side faces of it and kept out of contact with the cavity plate without an insulating sheet interposed between the actuator and cavity plate.
It is another object to provide a piezoelectric actuator for an ink jet printer print head, the actuator including side electrodes provided in side faces of it without rising or protruding from them.
It is still another object to provide a process for producing such piezoelectric actuators at a low cost.
In accordance with a first aspect of the present invention, a print head is provided for a piezoelectric ink jet printer. The print head includes a piezoelectric actuator in the form of a plate. The actuator includes a piezoelectric sheet having a first face and a second face which are opposed to each other, and a side face connecting therebetween. The actuator further includes a common electrode lying on the first face of the piezoelectric sheet, a number of drive electrodes lying on the second face of the sheet, and side electrodes formed on the side face of the actuator. The common electrode lies over the drive electrodes. The side electrodes are each connected to one of the drive electrodes or one of the common and drive electrodes. The print head further includes a cavity plate having pressure chambers open on one side of the plate, nozzles each communicating with one of the chambers, and a recess formed on the one side. The actuator lies on the one side of the cavity plate in such a manner that the actuator closes the pressure chambers. The drive electrodes are each aligned with one of the chambers. The side electrodes are aligned with the recess to be kept out of contact with the cavity plate.
Thus, the recess of the cavity plate makes it possible to reliably keep the side electrodes of the piezoelectric actuator out of contact with the plate without interposing an insulating sheet between the plate and actuator. This enables the cavity plate to be metallic. It is consequently possible to reliably make the print head smaller and cheaper without increasing the number of places where ink may leak.
The piezoelectric actuator may further include outer electrodes formed on a surface of the actuator which is opposed to a surface of the actuator covering the one side of the cavity plate. The outer electrodes are each connected to one of the side electrodes. This simple actuator structure makes it possible to connect the outer electrodes reliably to the wiring patterns of a flexible flat cable for connection to external apparatus or equipment by pressing the cable against that surface of the piezoelectric actuator on which the outer electrodes lie.
The piezoelectric actuator may further include a second piezoelectric sheet lying on the first piezoelectric sheet and a third piezoelectric sheet lying on the one side of the cavity plate. The first piezoelectric sheet lies between the second and third piezoelectric sheets. The common electrode lies between the first and second piezoelectric sheets. The drive electrodes lie between the first and third piezoelectric sheets. The outer electrodes lie on the second piezoelectric sheet.
The recess of the cavity plate may be a groove extending along the side surface of the piezoelectric actuator. The groove for all the side electrodes is less costly to form than recesses for the respective side electrodes.
The cavity plate may include a base sheet lying on the one side. The recess may be a slot punched in the base sheet.
In accordance with a second aspect of the present invention, a piezoelectric ink jet printer print head is provided. This print head includes a cavity plate having a plurality of nozzles and pressure chambers each communicating with one of the nozzles, and an actuator lying on one side of the cavity plate. The actuator includes a piezoelectric sheet having a first face and a second face opposed to the first face and a side face connecting the fist and second faces. The side face has recesses formed thereon. The actuator further includes drive electrodes, a common electrode and side electrodes. The drive electrodes lie on the second face of the piezoelectric sheet, and are each exposed in one of the recesses. The drive electrodes are each aligned with one of the pressure chambers. Each side electrode is formed in one of the recesses, and connected to the drive electrode exposed in the associated recess. The common electrode lies on the first face of the piezoelectric sheet over the drive electrodes.
Because the side ele
Hirota Atsushi
Isono Jun
Takagi Atsuhiro
Brother Kogyo Kabushiki Kaisha
Feggins K.
Nguyen Lamson
Oliff & Berridg,e PLC
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