Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2000-01-27
2002-05-28
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06394574
ABSTRACT:
This application is based on U.S. patent application Ser. No. 11-18984 (1999) filed Jan. 27, 1999 in Japan, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet print head in which ink paths for ejecting ink droplets are formed by joining together a grooved top plate and a heater board by a press member.
2. Description of the Prior Art
An ink jet printing system is recognized as a very effective printing system because it performs non-impact printing that produces virtually no noise during printing, because it is capable of high speed printing and because it requires no special fixing of a printed image on plain paper as a recording medium.
FIG. 14
is a schematic perspective view showing an essential portion of a conventional ink jet print head disclosed in Japanese Patent Application Laid-Open No. 3-101957.
FIG. 15
is a cross section taken along the line Y—Y of FIG.
14
.
In
FIGS. 14 and 15
, reference number
112
represents a heater board having a plurality of electrothermal transducers (not shown) as a heat source. A grooved top plate
113
has integrally formed therein a plurality of ink orifices
101
, grooved ink paths
105
communicating with the ink orifices
101
, wall portions
106
forming ink paths walls, and a recessed portion as a common liquid chamber
107
for supplying ink to the ink paths
105
. Denoted
111
is a base plate to support components. Designated
114
is a spring member that joins together the heater board
112
and the grooved top plate
113
by a pressing force to form the ink paths
105
.
The spring member
114
has a bent end portion
114
A formed at its free end and presses it against a flat upper surface
113
B of the top plate
113
to engage the top plate
113
with the heater board
112
, with a pressing force of the spring member acting through a line contact. It has been a conventional practice to form the spring member
114
with the rigid bent end portion
114
A and press the bent end portion
114
A against the upper surface
113
B of the top plate
113
to join the two members—the top plate
113
and the heater board
112
—with the pressing force.
The ink jet printers of recent years have undergone price and size reductions and there is a corresponding increase in demand for a simplified structure of the ink jet print head. In a print head structure in which the top plate
113
is joined to the heater board
112
fixedly mounted on the base plate
111
, the size of the print head is basically determined by the size of the base plate
111
and thus it is effective in reducing the size of the head to eliminate, or reduce the size of, the base plate
111
. The structure with the base plate
111
eliminated or reduced in size, however, loses a heat dissipating function, one of the functions of the base plate
111
, and thus requires some measures to suppress a temperature rise in the print head.
The official gazette of Japanese Patent Application Laid-Open No. 10-71715 discloses a technology in which the base plate is either eliminated or reduced in size to achieve a size reduction of the print head and also suppress a temperature rise in the print head.
FIG. 16
is an exploded perspective view of a conventional ink jet print head disclosed in the Japanese Patent Application Laid-Open No. 10-71715.
The print head of
FIG. 16
has an orifice plate
202
formed with a plurality of ink orifices
201
, a grooved top plate
200
having ink paths
203
and a common liquid chamber
204
integrally formed therein, a heater board
210
connected with a printed circuit board
205
, and a spring press member
220
. Instead of pressing the upper surface of the top plate
200
as in the preceding conventional art, this print head has the underside of the heater board
210
pressed by the spring press member
220
to bind the grooved top plate
200
and the heater board
210
together. The spring press member
220
is supported like a cantilever on a top plate mount (not shown) integrally formed with the grooved top plate
200
.
In this print head, as shown in
FIG. 17
, the spring press member
220
presses the back of the heater board
210
at a position close to where electrothermal transducers
211
are installed, at a contact angle &thgr; with a pressing force acting through a line contact, to ensure an intimate contact between the top plate
200
and the heater board
210
. Further, in this print head, the spring press member
220
is made of a good thermal conductive material to release heat generated by the electrothermal transducers
211
. The spring press member
220
is assigned a heat dissipating function of the base plate
111
of the prior art shown in FIG.
14
.
(1) In the conventional technology, however, because the spring press member
220
presses, at a contact angle &thgr;, a vicinity of the front edge of the heater board
210
close to where the electrothermal transducers
211
are installed as shown in
FIG. 17
, moments of force B and C as shown in
FIG. 17
are generated. Hence, with this conventional technology the rear end of the heater board
210
tends to float from the grooved top plate
200
. This makes the contact between them unstable.
(2) The grooved top plate
200
is made of a molding resin material and can easily produce warping and bending. As described earlier, the spring press member
220
is supported on the top plate mount formed integral with the grooved top plate
200
, so that when the top plate
200
is warped or bent, the spring press member
220
is shifted from its normal support position and support angle. As a result, the position and angle of the pressing portion of the spring press member
220
are deviated.
Because the heater board
210
of the conventional technology is pressed by a pressing force acting through a line contact despite the fact that the spring press member
220
has variations in its position and attitude caused by warping and bending of the top plate
200
, the pressing force acting through a line contact is directly affected by the variations in position and attitude of the spring press member
220
and is likely to fluctuate or be unevenly distributed. The conventional technology therefore has a problem of not being able to bind the top plate
200
and the heater board
210
together with a uniform contact pressure with respect to the arrangement direction of ink paths
8
.
The present invention has been accomplished to solve the problem described above. It is therefore a primary object of the invention to provide an ink jet print head having a base plate eliminated or reduced in size in which the grooved top plate and the heater board are engaged together with a uniform pressure over their entire contact surface to securely hold them in close contact with each other.
It is another object of the invention to provide an ink jet print head capable of dissipating heat with an improved efficiency.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, the ink jet print head comprises: a grooved top plate having a plurality of groove-like ink paths, a common liquid chamber for supplying ink to the plurality of ink paths and a plurality of orifices for ejecting ink; a heater board having a plurality of heat generating elements for generating an ink ejection pressure arranged at positions on a front surface thereof corresponding to the plurality of ink paths; and a press member for pressing and joining together the grooved top plate and the heater board; wherein the press member presses against a back of the heater board at the vicinity of a joint gravity center of the heater board and the grooved top plate.
With this invention, because the press member presses against the back of the heater board at the vicinity of the joint gravity center of the heater board and the grooved top plate to bring the heater board and the grooved top plate into intimate contact with each other, it is possible to engage the heater board and the grooved top plate with a unif
Kotaki Yasuo
Saito Akio
Takahashi Wataru
Barlow John
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Stephens Juanita
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