Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-02-08
2002-06-04
Vo, Anh T. N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S072000
Reexamination Certificate
active
06398350
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a liquid jet unit used in an industrial machine, such as a manufacturing machine, a stamping or marking apparatus and a microdispenser, and in an image recording apparatus such as a plotter and a printer. In more detail, this invention relates to a liquid jet device provided with a liquid jet head that can eject a liquid droplet from a nozzle opening, and a piezoelectric vibrator unit used in the liquid jet unit, and in particular, to the liquid jet device and the piezoelectric vibrator unit that are designed to make natural vibration periods of the piezoelectric vibrators uniform.
Industrial machines and image recording apparatuses are available, which employ a liquid jet head for ejecting liquid in the form of liquid droplets. For example, an industrial machine for manufacturing an optical filter is designed to eject color material in the form of liquid droplets onto a filter substrate using an ejection head (a kind of liquid jet head). A stamping or marking apparatus for ejecting color material in the form of liquid droplets from an ejection head onto a fiber product such as a fabric to print figures and patterns on the product, and a microdispenser for ejecting an extremely small amount of liquid from an ejection head to supply the liquid to a predetermined location are also known as the industrial machines. A printer and a plotter are known as the image recording apparatuses, which are designed to eject ink droplets from a recording head (a kind of liquid jet head) onto a printing or recording medium such as paper.
These industrial machines and image recorders require high accuracy for the amount and speed of the ejected liquid droplets. For example, the optical filter manufacturing machine must eject a proper amount (i.e. a proper ejection amount) of an color material droplet onto a proper position with high accuracy since the optical filter manufactured with the industrial machine is used with a liquid crystal display, etc. The image recording apparatus requires high accuracy as to a position onto which an ink droplet is ejected, and an amount of the ejected ink, in order to improve image quality and speed up the recording.
The liquid head used in these industrial machines and image recording apparatuses are designed, for example, such that by applying an electric field to a piezoelectric vibrator provided in the piezoelectric vibrator unit, the piezoelectric vibrator is displaced (expanded and contracted) using its vibration characteristic (natural vibration period) to cause pressure fluctuation in a pressure chamber communicating with a nozzle opening, thereby ejecting a liquid droplet from the nozzle opening.
The piezoelectric vibrator unit is manufactured, for example, according to the following procedure: First, common internal electrodes and segment internal electrodes are laminated alternately with a piezoelectric material interposed between adjacent internal electrodes to manufacture a plate-like laminated substrate, and a common external electrode electrically conducted to the common internal electrodes and a segment external electrodes electrically conducted to the segment internal electrodes are formed on the surface of the laminated substrate to obtain a laminated member. After the base end side portion of the laminated member is fixed to a fixing plate, the leading end side portion of the laminated member is cut into a plurality of segments (piezoelectric vibrators) each having an extremely narrow width of about 50 &mgr;m to 100 &mgr;m using a wire saw, a dicing saw, etc.
Since each of piezoelectric vibrators provided in the piezoelectric vibrator unit are obtained by the mechanical cutting to have an extremely narrow width as described above, slight variations may occur in the widths of the piezoelectric vibrators. The lengths of the free end parts of the piezoelectric vibrators (free lengths) may vary depending on the accuracy in joining the laminated member to the fixing plate. If the natural vibration periods of the piezoelectric vibrators are non-uniform due to these variations, a manufactured liquid jet head suffers from a problem in that the amount of the ejected droplet and the position where the droplet is ejected vary from one nozzle opening to another depending on the variations in the natural vibration periods of the piezoelectric vibrators.
However, hitherto, a method effective for adjusting the natural vibration periods of the piezoelectric vibrators after the laminated member is joined to the fixing plate and divided into the piezoelectric vibrators has been unavailable. Thus, to manufacture a liquid jet head that can eject uniform amounts of droplets from nozzle openings, a piezoelectric vibrator unit having piezoelectric vibrators whose natural vibration periods are uniform needs to be selected among a large number of manufactured piezoelectric vibrator units. This results in the lowering of the manufacturing yield.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a piezoelectric vibrator unit, a liquid jet head, a manufacturing method of the piezoelectric vibrator unit, and a manufacturing method of the liquid jet head, which can make uniform the natural vibration periods of piezoelectric vibrators with high accuracy.
To achieve the object, the present invention provides, as the first aspect thereof, a piezoelectric vibrator unit comprising a plurality of piezoelectric vibrators, each having at least in part, a laminate structure including first and second internal electrodes laminated alternately with a layer of piezoelectric material interposed between adjacent pairs of the first and second internal electrodes to define an active region in a free end part, a first external electrode electrically conducted to the first internal electrodes and a second external electrode electrically conducted to the second internal electrodes, wherein a potential difference is given to the piezoelectric material in the active region through the first and second external electrodes to activate the piezoelectric material, thereby displacing the free end part, wherein:
a partial mass adjusting portion including a partial recess and/or a partial projection is provided to an outer surface of the piezoelectric vibrator in the free endpart to adjust a natural vibration period of the piezoelectric vibrator.
The present invention provide, as a second aspect thereof, a piezoelectric vibrator unit, wherein the outer surface of the piezoelectric vibrator in the free end part is used as a trimming portion where the partial recess is formed by trimming. The second aspect can be effectively used in combination with the first aspect.
The present invention provides, as a third aspect, a piezoelectric vibrator unit, wherein an outermost layer of the piezoelectric material is thicker than another layer of the piezoelectric material. The third aspect can be effectively used in combination with the first or second aspect.
The present invention provide, as a fourth aspect, a piezoelectric vibrator unit, wherein a mass addition portion, formed of material higher in density than the piezoelectric material, is joined to a surface of an outermost layer of the piezoelectric material, and the mass addition portion is used as a trimming portion. The fourth aspect can be effectively used in combination with any one of the first to third aspects.
The present invention provides, as a fifth aspect, a piezoelectric vibrator unit, wherein another mass addition portion is joined to a surface of the piezoelectric vibrator opposite from the outer surface of the piezoelectric material. The fifth aspect can be effectively used in combination with the fourth aspect.
The present invention provides, as a sixth aspect, a piezoelectric vibrator unit, wherein the outer surface of the piezoelectric vibrator, other than surfaces of first and second external electrodes, is used as a trimming portion. The sixth aspect can be effectively used in combination with anyone of first to fifth aspects.
The present invention prov
Seiko Epson Corporation
Vo Anh T. N.
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