Sheet feeding or delivering – Feeding – By means to convey sheet
Reexamination Certificate
2000-07-14
2002-06-18
Bollinger, David H. (Department: 3651)
Sheet feeding or delivering
Feeding
By means to convey sheet
C271S196000
Reexamination Certificate
active
06406017
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording medium transportation apparatus incorporated in an image recording apparatus that performs image formation such as printing on a recording medium such as a sheet of paper. Particularly, the present invention relates to improvement of an apparatus using a belt drive device and generating suction force by air suction at the belt surface to transport a recording medium held on the belt by the suction force.
2. Description of the Background Art
Conventionally, printers and copy machines are known as the equipment of performing image formation such as printing on a recording medium such as a sheet of paper or film. A belt drive device is employed as the means to transport a recording medium in such equipment.
A general structure of an ink jet type printer transporting a recording medium using a belt drive device will be described hereinafter.
As shown in
FIG. 13
, this type of belt drive device includes a drive roller
101
, a driven roller
102
and a tension roller
103
. An endless belt
104
is extended around rollers
101
,
102
and
103
. Drive roller
101
is connected to a drive shaft of a motor not shown to rotate by the transmission of the drive force of the motor. Belt
104
runs in the direction of arrow A in
FIG. 13
in accordance with the rotation of drive roller
101
. Pinch rollers
105
,
105
sandwiching belt
104
between drive roller
101
and driven roller
102
are provided at the upper area in
FIG. 13
opposite to drive roller
101
and driven roller
102
, respectively. A sheet cassette
106
is arranged in the proximity of driven roller
102
. A recording medium (paper sheet)
107
output from sheet cassette
106
is transported in the direction of arrow A in accordance with the run of belt
104
while being sandwiched with belt
104
between driven roller
102
and pinch roller
105
.
A printer head
108
is provided above the portion of belt
104
located between drive roller
101
and driven roller
102
(this portion of belt
104
is called “span”
104
a
hereinafter). Printer head
108
is configured of the line type head or serial type head. A line type head includes a plurality of spray out nozzles corresponding to the resolution across the required printing width (for example, approximately 200 mm in printing out onto a A4-size paper sheet) in a direction perpendicular to the paper plane of
FIG. 13. A
serial type head includes several ten to several hundred of spray nozzles in the direction of A in
FIG. 13
to effect printing on a recording medium
107
while moving in the direction perpendicular to the paper plane of FIG.
13
.
In a printing operation, recording medium
107
is output from sheet cassette
106
in accordance with the drive of the belt drive device. Recording medium
107
is transported in the direction of arrow A in a status sandwiched with belt
104
between driven roller
102
and pinch roller
105
.
In the case where printer head
108
is of the line type, ink is output appropriately from each spray out nozzle of printer head
108
while recording medium
107
is continuously transported. As a result, printing is effected on recording medium
107
.
In the case where printer head
108
is of the serial type, the travel of belt
104
is temporarily halted when recording medium
107
is transported to the position where printer head
108
is disposed. Ink is output from the spray out nozzle while printer head
108
moves in the direction perpendicular to the paper plane of
FIG. 13
, whereby printing is effected on recording medium
107
. When printer head
108
comes to one side end of recording medium
107
, belt
104
begins to move again. After recording medium
107
is shifted by a predetermined distance, belt
104
stops again. The printing operation is recommenced while printer head
108
moves in the direction perpendicular to the paper plane of FIG.
13
. Thus, the printing operation by printer head
801
and the operation of moving recording medium
107
by the belt drive device are carried out alternately to effect printing onto recording medium
107
.
In this type of device, a configuration of drawing recording medium
107
towards belt
104
is employed to transport recording medium
107
stably on belt
104
. More specifically, a platen chamber
109
is provided at the backside of span
104
a
of belt
104
located between drive roller
101
and driven roller
102
. Platen chamber
109
has suction holes
110
,
110
, . . . formed at the top surface. Air suction is effected through suction holes
110
,
110
, . . . by setting the interior to negative pressure. Also, a plurality of suction holes (not shown) are formed at belt
104
. Recording medium
107
is attracted to belt
104
by the air suction from the suction hole in accordance with the generation of negative pressure within platen chamber
109
. Accordingly, position shifting of recording medium
107
on belt
104
is prevented to allow a stable transportation operation of recording medium
107
.
In the following, the force suppressing recording medium
107
from floating or curling, i.e. the force to draw recording medium
107
is called “suction force” whereas the holding force acting between recording medium
107
and belt
104
is called “attracted force”, and distinction is made therebetween.
When the structure in which recording medium
107
adheres to belt
104
by air suction is employed, the total area of the suction holes covered by recording medium
107
becomes larger if the size of recording medium
107
transported on belt
104
is big enough. In other words, the total area of suction holes not covered by recording medium
107
(suction holes not contributing to attraction) becomes smaller. Therefore, the suction resistance at the suction holes of belt
104
becomes larger, so that a great suction force can be obtained. As a result, recording medium
107
adheres to belt
104
favorably to allow a stable transportation operation.
If recording medium
107
transported on belt
104
is small in size, the total area of suction holes covered by recording medium
107
becomes smaller. In other words, the total area of suction holes not covered by recording medium
107
becomes larger. There is a possibility that a stable transportation operation cannot be performed due to the smaller suction force.
Japanese Patent Laying-Open No. 6-135613 discloses a transportation apparatus directed to solve the above problem. This transportation apparatus is provided with a valve that opens/closes each suction hole of the platen chamber. Open/close control of the valve is provided so that only the suction holes corresponding to the passage of the recording medium are opened. Accordingly, a stable transportation operation of a recording medium can be carried out with a constant high suction force.
The conventional structure of holding the recording medium by air suction has been developed directed to only ensure a high suction force. No consideration was made as to the suction position.
When the suction hole of the belt is located at a position outside the side end of the recording medium, no suction force will be effected on the side end area. There is a possibility of this area will float upwards off the belt. In some cases, this portion may rise to be curled. Generation of such a curl induces the possibility that a printing operation will not be carried out satisfactorily due to the recording medium coming into contact with the printer head to be smudged or causing sheet jamming. This phenomenon is particularly significant in the case where a relatively small recording medium is transported that has the tendency of a lower suction force.
In the case of a serial type printer head, the deliver operation and halt operation of the recording medium are carried out alternately in the transportation operation of an apparatus including this type of head. High accuracy is required in the transportation amount of the recording medium. In order to achieve transportation
Bollinger David H.
Conlin David G.
Dike Bronstein, Roberts & Cushman IP Group, Edwards & Angell, LL
Sharp Kabushiki Kaisha
Tucker David A.
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