Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-09-27
2003-06-10
Nguyen, Judy (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06575565
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the piezo-electric actuator of the print head of an ink jet printer and a method for producing such an actuator.
2. Description of Related Art
The print head of a known ink jet printer has ink channels and piezo-electric elements provided adjacently to them. The ink jet printer performs printing a print by applying a voltage to the piezo-electric elements to reduce the volume of one or more of the ink channels, ejecting ink from this channel or these channels through an orifice or orifices.
FIG. 11
of the accompanying drawings shows the print head of a conventional ink jet printer, which is disclosed in the Assignee's U.S. Pat. No. 5,402,159, for example. This print head includes a piezo-electric actuator
103
, which is provided over ink ejectors
90
a
,
90
b
and
90
c
. The piezo-electric actuator
103
includes five piezo-electric ceramic sheets or layers
40
laminated or stacked together. An internal negative electrode
42
lies on the upper side of each of the top, middle and bottom ceramic sheets
40
. Separate internal positive electrodes
44
a
,
44
b
and
44
c
lie on the upper side of each of the other two ceramic sheets
40
. The positive electrodes
44
a
,
44
b
and
44
c
are provided over or above the ink ejectors
90
a
,
90
b
and
90
c
, respectively. The ink ejectors
90
a
,
90
b
and
90
c
have ink channels
32
a
,
32
b
and
32
c
, respectively, and orifices
37
a
,
37
b
and
37
c
, respectively. This print head consists of a small number of parts and is simple in structure. It is easy to make the resolution of the print head higher by varying the electrode pattern. The use of the laminated piezo-electric actuator
103
results in lower drive voltage.
A deformation restraining member
80
is bonded to restrain the piezo-electric actuator
103
from deforming away from the ink channels
32
a-
32
c
. This makes it possible to deform the piezo-electric actuator
103
effectively toward the ink channels
32
a-
32
c
and consequently drive the ink ejectors
90
a-
90
c
at lower voltage. This also makes it possible to reduce the cross talk at each ink channel
32
a
,
32
b
or
32
c
which is caused by the deformation of the adjacent ink channel or channels due to irregular deformation of the piezo-electric actuator
103
. The cross talk reduction improves the SN ratio (S/N).
The process for producing this print head includes alternately stacking, pressing and calcining the piezo-electric ceramic sheets
40
and the internal electrodes
42
and
44
a-
44
c
, and thereafter bonding the deformation restraining member
80
with an adhesive or the like. This complicates the process, increases the number of steps of the process, and raises the production cost.
SUMMARY OF THE INVENTION
In view of the foregoing problems, it is an object of the present invention to provide a piezo-electric actuator for an ink jet printer head which makes it possible to reduce cross talk, restrain the laminated piezo-electric element of the print head from deforming away from the ink channels of the head, and which can be assembled simply and produced at a low cost. It is another object to provide a method for producing such an actuator.
In accordance with a first aspect of the present invention, a piezo-electric actuator is provided for an ink jet printer head which has an ink channel and an orifice, and which ejects ink from the channel through the orifice by changing the volume of the channel. The actuator includes an active layer and a restraining layer. One side of the active layer faces the ink channel. The active layer includes at least one sheet formed out of piezo-electric material and provided with an electrode thereon. The restraining layer is positioned on the other side of the active layer, and restrains the active layer from deforming. The restraining layer includes at least one sheet. The active and restraining layers are sintered to be integral with each other.
The active layer is interposed between the ink channel and the restraining layer, which is formed integrally with the active layer. The restraining layer restrains the active layer from deforming. This makes it possible to efficiently utilize the deformation of the active layer to change the volume of the ink channel. It is therefore possible to improve the ink ejecting performance of the print head and reduce power consumption. This also makes it possible to prevent deformation in parallel to the layers to restrain the volume change of the ink channel or channels adjacent to a driven ink channel. It is therefore possible to prevent cross talk.
The active and restraining layers are formed by being integrally sintered. Consequently, in comparison with the case where a deformation restraining member is bonded with an adhesive or the like, it is possible to reduce the number of steps of the process for producing the piezo-electric actuator. This simplifies the producing process and lowers the production cost. It is also possible to increases the strength of the actuator.
The sheets of the active and restraining layers may be formed out of the same material. In this case, members for forming the active layer can be used as they are for the restraining layer. This makes it possible to produce the piezo-electric actuator simply at a lower cost. The same material makes the layers fit together, and prevents them from being warped, distorted or deformed, when they are integrally sintered. This results in high accuracy or precision.
The sheet of the restraining layer may be provided with a dummy electrode, which does not contribute to the deformation for driving the ink channel. In this case, when the active and restraining layers are integrally sintered, it is possible to equalize the differences in shrinking percentage in the directions perpendicular to the layers to prevent warps and/or waves due to the difference in shrinking percentage between the layers. This can made the piezo-electric actuator very flat. Consequently, the actuator can be bonded closely to the cavity layer in which the ink channel is formed. This results in high accuracy or precision.
The dummy electrode of the restraining layer may be connected to the electrode of the active layer, and face this electrode through a ceramic, which is a dielectric. In this case, there is no potential difference between the dummy electrode and the electrode of the active layer, producing no electric capacity between them. As a result, no electric power is wasted.
The dummy electrode of the restraining layer and the electrode of the active layer may be positioned in substantial symmetry in the piezo-electric actuator. In this case, when the active and restraining layers are integrally sintered, it is possible to roughly equalize the differences in shrinking percentage in the directions perpendicular to the layers to prevent warps and/or waves due to the difference in shrinking percentage between the layers. This can make the piezo-electric actuator even flatter. Consequently, the actuator can be bonded closely to the cavity layer. This results in high accuracy or precision.
In accordance with a second aspect of the present invention, a piezo-electric actuator is provided for an ink jet printer head. The actuator includes a laminate including a plurality of piezo-electric sheets stacked and sintered at the same time. The actuator also includes an electrode formed on at least one of the sheets which is positioned on one side of the laminate. Only said at least one sheet on the one side is adapted for activation with a drive voltage. At least one of the sheets which is positioned on the other side of the laminate is not adapted for activation (deactivated). This actuator is simple in structure and therefore very easy to produce.
In accordance with a third aspect of the present invention, a print head is provided for an ink jet printer. This print head includes an ink ejector having an ink channel formed therein and an orifice through which ink can be ejected from the chann
Isono Jun
Kojima Masatomo
Takagi Atsuhiro
Brother Kogyo Kabushiki Kaisha
Nguyen Judy
LandOfFree
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