Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-01-18
2003-10-14
Nguyen, Lamson (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06631980
ABSTRACT:
FIELD OF THE INVENTION
This invention is related to a liquid jetting head, for example an ink-jetting recording head capable of jetting a drop of ink from a nozzle by means of vibration of a piezoelectric vibrating member in order to record images or characters on a recording medium. This invention is also related to a method of producing such a liquid jetting head.
BACKGROUND OF THE INVENTION
As shown in
FIGS. 24 and 25
, in general, a ink-jetting recording head using longitudinal-vibration type of piezoelectric vibrating members comprises a flowing-path unit
101
provided with a lot of nozzles
108
and a lot of pressure chambers
107
. The flowing-path unit
101
is stuck onto a head case
102
containing the piezoelectric vibrating members
106
.
In detail, the flowing unit
101
consists of a nozzle plate
103
through which the nozzles
108
are formed in two rows, a flowing-path plate
104
through which the pressure chambers
107
respectively communicating with the nozzles
108
are formed and a vibrating plate
105
that seals lower openings of the pressure chambers
107
. The nozzle plate
103
, the flowing-path plate
104
and the vibrating plate
105
are layered one on top of another as shown in
FIGS. 24 and 25
. In the flowing-path plate
104
, ink reservoir spaces
109
are formed for storing ink that is introduced into the respective pressure chambers
107
. In addition, ink-paths
110
are formed in the flowing-path plate
104
for connecting the respective pressure chambers
107
and the ink reservoir spaces
109
.
The head case
102
is made of a synthetic resin. The head case
102
has vertical through spaces
112
. The piezoelectric vibrating members
106
are contained in the spaces
112
. Tail ends of the piezoelectric vibrating members
106
are fixed to a fixing plate
111
, which is attached to the head case
102
. Leading surfaces of the piezoelectric vibrating members
106
are fixed to island portions
105
A (see
FIG. 25
) of the vibrating plate
105
, respectively.
When a driving signal generated in a driving circuit
114
is inputted to a piezoelectric vibrating member
106
through a flexible circuit board
113
, the piezoelectric vibrating member
106
extends and contracts in a longitudinal direction thereof. When the piezoelectric vibrating member
106
extends and contracts, the corresponding island portion
105
A of the vibrating plate
105
vibrates to change a pressure of the ink in the corresponding pressure chamber
107
. Thus, the ink in the pressure chamber
107
may be jetted from the corresponding nozzle
108
as a drop of the ink. In addition, as shown in
FIG. 24
, ink supplying ports
115
for supplying the ink to the ink reservoir spaces
109
are formed through the head case
102
and the vibrating plate
105
.
As the flowing-path plate
104
of the flowing-path unit
101
, conventionally, a plate formed from a silicon mono-crystal substrate by an anisotropic etching process (see Japanese Patent Laid-Open No.9-123448), a plate having a layer made of a photosensitive resin, and an electrocasting plate peeled off from a jig substrate (see Japanese Patent Laid-Open No.6-305142 and Japanese Patent Laid-Open No.9-300635) may be used.
In a case of forming a flowing-path plate
104
from a silicon mono-crystal substrate by an anisotropic etching process, pressure chambers
107
and ink-paths
110
are formed by the etching process. The etched silicon mono-crystal substrate (flowing-path plate
104
) is layered with a metal nozzle plate
103
and a vibrating plate
105
via an adhesive material or the like.
However, in general, a linear expansion coefficient of silicon mono-crystal is different from a linear expansion coefficient of metal. Thus, in the flowing-path unit
101
consisting of the layered plates
103
-
105
, a so-called “warp” may occur. This is not serious in the small-sized recording head, but this may result in difficulty in enlarging the size of the recording head.
In a case of forming a flowing-path plate
104
by layering a photosensitive resin on a substrate, there is a problem that a Young's modulus of the photosensitive resin (flowing-path plate
104
) is lower than that of metal or silicon. That is, the photosensitive resin has only a lower rigidity. Thus, if the pressure chambers
107
are arranged more densely, boundary walls therebetween may deform by means of a pressure in an adjacent pressure chamber
107
, that is, “cross-talk” may occur. Therefore, in the case, it is difficult to densely arrange the nozzles.
In a case of forming a flowing-path plate
104
by pealing off an electrocasting layer formed on a jig substrate, a “warp” of the electrocasting layer may tend to occur during the peeling off from the jig substrate. That is, dimension accuracy of the flowing-path plate
104
may tend to be lower. In addition, the case needs a step of forming the electrocasting layer on the jig substrate and a step of peeling off the electrocasting layer from the jig substrate, which may result in longer time and greater cost.
SUMMARY OF THE INVENTION
The object of this invention is to solve the above problems, that is, to provide a liquid jetting head such as an ink-jet recording head wherein a “warp” of a flowing-path plate is prevented so that the liquid jetting head can be advantageously made more accurate, enlarged and made denser.
In order to achieve the object, a liquid jetting head includes: a flowing-path plate through which a flowing-path space is formed as a flowing-path for a liquid; a nozzle plate provided on one side surface of the flowing-path plate, said nozzle plate having a nozzle that is communicated with the flowing-path space; and a sealing plate provided on the other side surface of the flowing-path plate for sealing the flowing-path space; wherein a portion of the other side of the flowing-path space forms a pressure-chamber space; a portion of the other side of the flowing-path plate including at least a portion of the pressure-chamber space is formed by electrocasting; and a pressure-generating unit is provided at a portion of the other side of the sealing plate corresponding to the pressure-chamber space for changing a pressure of the liquid in the pressure-chamber space.
According to the feature, since the portion of the other side of the flowing-path plate is formed by electrocasting, a “warp” of the flowing-path plate may be prevented. Thus, the flowing-path plate may be formed more accurately. In addition, since the portion formed by electrocasting includes at least the portion of the pressure-chamber space, preferably the whole pressure-chamber space, boundary walls defining the pressure-chamber space may have a relatively higher rigidity. Thus, the pressure-chamber spaces may be arranged more densely. Therefore, the liquid jetting head is advantageous in being made denser, made more accurate, and enlarged.
In addition, since the pressure-chamber space is formed as the portion of the flowing-path space, the pressure-chamber space may be easily positioned relative to the nozzle. Thus, it may be prevented that an air bubble is generated and stays in the flowing-path space. In addition, a step of peeling off the electrocasting portion is unnecessary, which is advantageous in cost.
Preferably, the flowing-path plate has a substrate layer and an electrocasting layer formed on the other side surface of the substrate layer by electrocasting. In the case, the liquid jetting head may be easily produced.
For example, preferably, the pressure-chamber space is formed in the electrocasting layer as a through hole having substantially the same shape in a depth direction thereof, the one side surface of the pressure-chamber space is defined by the substrate layer, the other side surface of the pressure-chamber space is defined by the sealing plate, and lateral side surfaces of the pressure-chamber space are defined by the electrtocasting layer. In the case, a communicating hole may be formed in the substrate layer for connecting the pressure-chamber space and the nozzle. The substrate layer an
Feggins K.
Nguyen Lamson
Seiko Epson Corporation
Sughrue & Mion, PLLC
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