Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-03-21
2002-12-03
Nguyen, Lamson (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S012000, C347S068000
Reexamination Certificate
active
06488355
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet head having a number of nozzles for discharging an ink drop, located with a high density. More specifically, the present invention relates to an ink jet head incorporated in an ink jet printing machine and configured to shoot an ink drop to a recording medium to produce a printed image recording, the ink jet head including a plurality of nozzles, a plurality of chambers located for the plurality of nozzles, respectively, a pressure plate forming one plane of each chamber, and an actuator provided for each pressure plate, so that when the actuator is driven, a corresponding pressure plate is deformed to compress an ink in a corresponding chamber so as to cause an ink drop to be discharged from a corresponding nozzle.
Now, the prior art of the ink jet head will be described with reference to
FIG. 11
, which illustrates one example of the prior art ink jet head disclosed in Japanese Patent Application Pre-examination Publication No. JP-04-148936-A. This prior art ink jet head includes a number of nozzles
101
arranged in a single array to depict a straight line, a number of chambers
102
, each having an elongated plan view shape, staggered at opposite sides of the nozzle array, with one end of each chamber being located on a corresponding nozzle, and the other end of each chamber having a supplying port
103
.
Furthermore, the ink jet head has an ink pool
104
in common to all the chambers, at a layer different from the layer where the chambers are formed. The ink pool
104
is connected to each chamber
102
through the associated supplying port
103
. In addition, an actuator (not shown) is mounted on a pressure plate (not shown) forming one plane of each chamber. The following description will be made on the premise that the actuator is constituted of a piezoelectric actuator.
The ink jet head operates as follows: When the actuator is driven, the pressure plate is flexed to reduce the volume of the chamber
102
, with the result that the ink in the chamber is compressed so that an ink drop is discharged through the nozzle
101
. After the ink drop is discharged, when the pressure plate restores its original form, the ink is re-charged into the chamber through the supplying port from the ink pool
104
The above mentioned prior art ink jet head is advantageous since it is possible to realize a high density location of nozzles by reducing the pitch of the nozzles in the nozzle array and by locating a number of chambers having a narrow witch corresponding to the reduced pitch.
However, since the width of the chamber must be inevitably reduced with increase of the nozzle density, the pressure plate assumes the shape difficult to flex, with the result that it is no longer possible to ensure a necessary amount of volume change in the chamber. For reference, it is said that the amount of volume change of at least 30 pl (picoliter) is required to realize a high speed printing. If only a too small ink drop is discharged, the printing speed unavoidably becomes low.
In this connection, it may be considered to enlarge the longitudinal length of the chamber so as to increase the amount of volume change in the chamber. In this case, however, the occupying area of the chamber becomes large, with the result that the areal density of the nozzles cannot be elevated.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an ink jet head which has overcome the above mentioned problems of the prior art.
Another object of the present invention is to provide an ink jet head including a chamber having a pressure plate of the shape easy to flex, thereby to be able to reduce the occupying area of the chamber while maintaining a necessary volume of discharged ink drop, so as to realize a high density of nozzle location.
Still another object of the present invention is to provide a stably driven, highly reliable, ink jet head capable of maintaining a necessary volume of discharged ink drop even if the nozzles are located with a high density.
A further object of the present invention is to provide an ink jet head which can be manufactured with a simplified fabricating process and with a high working precision.
The above and other objects of the present invention are achieved in accordance with the present invention by an ink jet head comprising:
a plurality of nozzles arranged to constitute a matrix having a plurality of rows inclined at a constant angle to a head main scan direction and a plurality of columns orthogonal to the head main scan direction;
a plurality of chambers provided for the plurality of nozzles, respectively;
a pressure plate formed to constitute one plane of each of the plurality of chambers;
an actuator provided to each pressure plate, for deforming the pressure plate to compress an ink within a corresponding chamber;
a plurality of ink pool branches provided along the plurality of rows or the plurality of columns, for supplying the ink to the plurality of chambers; and
a main ink pool connected to the plurality of ink pool branches,
wherein the pressure plate has a plan view shape fulfilling the relation of 1≦A≦2 where “A” is the ratio of an circumscribed circle diameter of the plan view shape of the pressure plate to an inscribed circle diameter of the plan view shape of the pressure plate.
For example, the pressure plate has the plan view shape of a substantial square, or alternatively the plan view shape of a substantial rhombus having a pair of sides in parallel to the plurality of rows and another pair of sides in parallel to the plurality of columns.
With this arrangement, the pressure plate has the shape easy to be flexed by the actuator when the actuator is driven. Therefore, even if the occupying area of the chamber is reduced, a highly efficient chamber can be realized which can maintain a necessary amount of volume change caused when the actuator is driven. Accordingly, a number of nozzles can be located with a high density without reducing the volume of the discharged ink drop.
When the pressure plate has the plan view shape of a substantial rhombus having a pair of sides in parallel to the plurality of rows and another pair of sides in parallel to the plurality of columns, the actuator preferably has a plan view shape of a substantial rhombus having a pair of sides in parallel to the plurality of rows and another pair of sides in parallel to the plurality of columns.
With this arrangement, the actuators can be formed in bundle by dicing an actuator material sheet in units of row and in units of column. Therefore, the fabricating process can be simplified, and it is possible to elevate the precision in the size and in the position of the actuator.
In addition, each of the plurality of chambers preferably has an ink supply port to form an ink flow in the direction of a long diagonal of the substantial rhombus.
With this arrangement, an ink flow within the chamber is smoothed, so that it is possible to prevent a bubble from staying, thereby to elevate reliability of the ink jet.
When the inclination of each row to the head main scan direction is expressed by “&thgr;” and the interval of the plurality of nozzles in a direction orthogonal to the head main scan direction is expressed by “d” (mm), “&thgr;” and “d” are preferred to have the relation of 0<tan &thgr;≦5d.
With this arrangement, the width of each chamber in the main scan direction can have the size of not less than about 0.2 mm, so that it is possible to obtain the chamber size capable of generating the amount of volume change sufficient to discharge a desired volume of ink drop.
Furthermore, when the number of the nozzles included in each row is expressed by “n”, “n” and “d” are preferred to have the relation of n×d≧0.2.
Also with this arrangement, the width of each chamber in the direction orthogonal to the main scan direction can have the size of not less than about 0.2 mm, so that it is possible to obtain the chamber size capable of generating the amount of volume change suff
Kanda Torahiko
Nakamura Hirofumi
Fuji 'Xerox Co., Ltd.
Nguyen Lamson
LandOfFree
Ink jet head does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ink jet head, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ink jet head will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2981809