Printing apparatus

Details Printing apparatus Printing apparatus

1998-11-18

2001-10-30

Eickholt, Eugene (Department: 2854)

Incremental printing of symbolic information

Ink jet

Medium and processing means

C346S134000, C271S193000, C271S275000, C198S691000

Reexamination Certificate

active

06309064

ABSTRACT:

This application is based on Patent Application Nos. 319357/1997 filed on Nov. 20, 1997 in Japan, 319988/1997 filed on Nov. 20, 1997 in Japan, and 312889/1998 filed on Nov. 4, 1998 in Japan, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a printing apparatus performing printing of an image by ejecting a printing liquid, such as an ink or the like. More particularly, the invention relates to a suction mechanism for a printing medium at a position where the image is printed using a printing head.
2. Description of the Related Art
In general, an ink-jet printing apparatus is adapted to perform printing by ejecting an ink from a printing head toward a printing medium. The ink-jet printing apparatus is advantageous for easiness of down-sizing of the printing head, capability of printing of high definition image at high speed, low running cost, low noise for non-impact type printing system, easiness of printing of a color image using a plurality of colors of inks. Amongst, a full-line type printing apparatus which employs a line type printing head arranged with a large number of ejection openings in a width direction of a printing sheet, can further speed up printing.
However, in a full-line type color printing apparatus a plurality of line type printing heads provided for respective kinds of inks are aligned in a feeding direction of the printing sheet. In such case, a distance from the printing head located at the most upstream side and the printing head located at the most downstream side becomes significantly long. Therefore, once floating of the printing sheet is caused in the printing region, disturbance can be caused in a printed image. Also, floating of the printing sheet can be a cause of jamming or the like. Therefore, it becomes necessary to downwardly forward bias the printing sheet in order to avoid floating.
As means for biasing the printing sheet, there is a method for sucking the printing sheet utilizing electrostatic force, such as those disclosed in Japanese Patent Application Laid-open No. 133035/1995, Japanese Patent Application Laid-open No. 53081/1995 and Japanese Patent Application Laid-open No. 254460/1997. In such ink-jet printing apparatus, an electrostatic suction plate constituted of a conductive electrode is provided in a platen in the printing region to generate the electrostatic force applying a charge. The printing sheet fed from a feeding apparatus by the electrostatic force is sucked and held on an upper surface of a transporting belt and transported while printing is performed by using the printing head.
As a background art relating to the present invention, an example of the ink-jet printing apparatus will be explained with reference to the drawings.
FIG. 1
is an illustration showing an overall construction of the ink-jet printing apparatus,
FIG. 2
is an enlarged partial view showing the ink-jet printing apparatus shown in
FIG. 1
as viewed from the above, and
FIG. 3A and 3B
are enlarged view of the major part in the ink-jet printing apparatus shown in
FIGS. 1 and 2
.
In an image printing apparatus
70
illustrated in
FIG. 1
, printing sheets P as a printing medium are stacked in a feeding portion
71
and are fed one-by-one from the uppermost one by a feeding roller
72
. The printing sheet P thus fed is guided to a lower transporting guide
73
and is pinched between a transporting belt
74
and a pinching roller
75
. The transporting belt
74
is driven by a driving roller
77
which is, in turn, driven by a not shown driving source, such as a pulse motor or the like, to transport the printing sheet P to a print start position on a platen
76
.
The transporting belt
74
is stretched by the driving roller
77
, a driven roller
78
and a pressure roller
79
. On the other hand, in the platen, a suction force generating means
80
is fixedly mounted by adhering and is located below the transporting belt
74
. It should be noted that the pressure roller
79
is rotatably mounted on one end of an arm which is pivotably mounted on the platen at the other end. The arm
83
is biased by means of a coil spring
84
for applying tension force for the transporting belt
74
.
The printing head
85
is a full-line type having a plurality of printing elements arranged in alignment in a transporting direction over an entire width of the printing region of the printing sheet P. The printing heads of respective colors are arranged in sequential order
85
K (black),
85
C (cyan),
85
M (magenta) and
85
Y (yellow) from the upstream side of the transporting direction of the printing sheet P, with a given interval, and are mounted on a head holder
85
a.
As shown in
FIG. 2
, assuming that an occupied region below the printing head
85
is S
1
, the suction force generating means
80
arranged below the transporting belt
74
has a size S covering the occupied region S
1
. As shown in
FIG. 3A
, the suction force generating means
80
is constituted one set of electrode plate
81
and a grounding plate
82
which are made of conductive metals. These electrode plate
81
and the grounding plate
82
are formed into comb-shape and are of the shapes mutually complement with each other, in which recessed portions of one are penetrated by projecting portions of the other. In a power supply portion
81
a
of the electrode plate
81
, a positive or a negative voltage is applied, and a power supply portion
82
a
of the grounding plate
82
is connected to the ground.
As shown in
FIG. 3B
, in the suction force generating means
80
, the electrode plate
81
and the grounding plate
82
are sandwiched by a base layer
80
a
and a surface layer
80
b
for protection. The transporting belt
72
is placed on the upper side of the surface layer
80
b.
The base layer
80
a
and the surface layer
80
b
are formed of synthetic resin, such as polyethylene, polycarbonate and the like.
In the construction set forth above, the printing sheet P is sucked on the upper surface of the transporting belt
74
by the suction force generating means
80
and is transported by the transporting belt
74
with printing by the printing head
85
.
The printing sheet P, on which the image is printed, is sandwiched and transported by a discharge roller
86
and a wheel
87
contacted under pressure to be discharged and held on a discharged paper receptacle tray
88
. The ejection roller
86
is driven by a rotational force of the driving roller
77
by not shown transmission means. On the other hand, in order to transfer a printing surface, the wheel
87
is in a shape with cone shaped tip ends so as to minimize transfer of the ink of the printed image.
On the other hand, as other construction, with similar construction as the suction force generating means provided in the platen
76
, the electrode plate
81
and the grounding plate
82
are integrally provided with the transporting belt for applying a positive or negative voltage from one of side edges in the width direction of the transporting belt
74
and connecting the other side edge to the ground to form the transporting belt per se as the suction force generating means.
However, in the ink-jet printing apparatus as set forth above, the apparatus having the platen, in which the suction force generating means
80
having one set of comb-shaped electrode plate
81
and the grounding plate
82
, has a region to be sucked in a size S covering the occupied region S
1
of the printing head
85
. Therefore, the driving motor is required a large torque in order to drive the transporting belt
74
. Thus, greater motor is required. Therefore, power consumption becomes large to cause high cost in the apparatus.
On the other hand, the apparatus, in which the suction force generating means
80
is provided integrally with the transporting belt
74
per se, inherently generate a suction force over a region outside of the printing region of the transporting belt
74
immediately below the printing head
85
. Therefore, the printing

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