Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-02-27
2001-05-15
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S104000
Reexamination Certificate
active
06231159
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording apparatus for recording an image on a sheet and a method for controlling such a recording apparatus, and more particularly, it relates to a technique suitable for a recording apparatus of so-called serial scan type for scanning a recording head in a direction perpendicular to a sheet conveying direction.
2. Related Background Art
In conventional recording apparatuses such as printers, copying machines and facsimiles or conventional recording apparatuses used as composite electronic equipment including a computer or a word processor, or a work station, an image is recorded on a sheet such as a paper sheet or a plastic thin film.
Such recording apparatuses can be divided, according to recording types, into ink jet type, wire dot type, thermal type and laser beam type. In recording apparatuses of serial type using a serial scanning system in which the recording is effected by scanning a recording head in a direction (main scanning direction) perpendicular to a sheet conveying direction (sub scanning direction), an image is recorded by a recording head mounted on a carriage shifted along the sheet. After one-line recording is finished, the sheet is conveyed by a predetermined amount (pitch feed or sub scanning) by means of a convey means, and then, next one-line recording is effected with respect to the stopped sheet. By repeating such operations, the entire sheet is recorded.
On the other hand, in recording apparatuses of line type in which the recording is effected only by the sub scanning in the sheet conveying direction, the sheet is set at a predetermined recording position. And, after one-line recording is effected collectively, the sheet is conveyed by a predetermined amount (pitch feed), and then, next one-line recording is effected collectively. By repeating such operations, the entire sheet is recorded.
Among the above-mentioned recording types, a recording apparatus of ink jet type (in jet recording apparatus) in which the recording is effected by discharging ink from the recording head toward the sheet had advantages that the recording means can easily be made compact, a highly fine image can be recorded at a high speed, the recording can be effected to a normal sheet without special treatment, running cost is cheap, recording noise is small because of non-impact system, and a color image can easily be recorded by using multi color inks.
Particularly, in a recording apparatus of ink jet type in which the ink is discharged by utilizing thermal energy, since a recording head having high density liquid passage arrangement (discharge opening arrangement) can easily be manufactured by forming electrical/thermal converters formed on a substrate, electrodes liquid passage walls and a top wall through semiconductor manufacturing process such as etching, deposition and sputtering, the apparatus can be made more compact.
Now, an example of the conventional recording apparatus of serial scan type will be explained with reference to
FIGS. 9 and 10
. In
FIG. 9
, a pinch roller
102
is urged against a convey roller
101
for conveying a sheet P. A sensor lever
103
rockable around a shaft
103
a
is disposed at an upstream side (in a sheet conveying direction) (referred to merely as “upstream side” hereinafter) of the convey roller
101
. When the sheet P abuts against a flag
103
b
of the sensor lever
103
to rotate the sensor lever
103
around the shaft
103
a,
a tail end detection sensor
104
is operated by a sensor operating portion
103
c
of the sensor lever
103
, thereby detecting passage of the sheet P.
At a downstream side (in the sheet conveying direction) (referred to merely as “downstream side” hereinafter) of the convey roller
101
, a recording head
105
for recording an image in response to image information is mounted on a carriage shiftable in a direction (main scanning direction) perpendicular to the sheet conveying direction, and a platen
106
for supporting a rear surface of the sheet P is opposed to the recording head
105
.
A discharge roller
108
rotated at the same peripheral speed via a transmission roller
107
is disposed at the downstream side of the recording head
105
, and a spurred roller
109
is urged against the discharge roller
108
.
With the arrangement as mentioned above, in a condition that a tail end Pb of the sheet P is conveyed the downstream side of a nip n between the convey roller
101
and the pinch roller
102
, since the sheet P is spaced apart from the convey roller
101
, the sheet is subjected to only a conveying force and pinching and supporting action from the discharge roller
108
and the spurred roller
109
.
Accordingly, in this condition, since the tail end Pb of the sheet P is not held down, an optimum gap between the recording head
105
and the sheet P is not established due to the floating of the sheet P. If the image is recorded by the recording head
105
in this condition, the recording of a high quality image cannot be expected. Further, if the tail end Pb of the sheet P is curved toward the recording head
105
or is curled, the sheet P is contacted with the recording head
105
, thereby contaminating the sheet.
That is to say, generally, in the recording apparatus of serial scan type, after the tail end Pb of the sheet P has passed through the nip n between the convey roller
101
and the pinch roller
102
, it is difficult to ensure the quality of the image.
Nevertheless, when the usage as a recording apparatus such as a facsimile or a copying machine is considered, there is strong request that the image is recorded on the entire recording surface of the sheet P. To this end, as shown in
FIG. 10
, there has been proposed a technique in which there are provided a floating preventing portion
106
a
(provided on the platen
106
) for holding down an upper surface of the sheet at one lateral edge Pr (convey reference side) thereof along the sheet conveying direction to prevent the lateral edge Pr from floating, and a jam preventing rib portion
105
a
(provided on a lower surface of the carriage on which the recording head
105
is mounted) for preventing the sheet jam caused if a floating opposite lateral edge Pl (opposite to the lateral edge Pr) of the sheet abuts against the recording head
105
.
With this arrangement, since the lateral edge Pr of the sheet P is pinched between an upper surface of the platen
106
and the floating preventing portion
106
a,
at least a distance {L
1
−L
2
} shown in
FIG. 10
is maintained to separate the sheet from the nozzle surface of the recording head
105
. Further, if the other lateral edge Pl of the sheet P is floating, since the floating lateral edge Pl is retarded from the recording head
105
by the jam preventing rib portion
105
a
provided on the carriage on which the recording head
105
is mounted, the sheet jam caused by abutting the recording head
105
against the sheet P can be prevented.
Recently, there has been strong request for effecting the recording with respect to various kinds of sheets, and the recording apparatuses has to cope with such request. However, in the above-mentioned conventional example, when a sheet P having very strong rigidity, if a tail end Pb of the sheet P is curved upwardly and the recording is effected up to the vicinity of the tail end Pb of the sheet P, during a return stroke of the recording head
105
after the scanning, there is a danger for abutting the other lateral edge Pl of the sheet P against the jam preventing rib portion
105
a
provided on the carriage to prevent the shifting movement of the carriage on which the recording head
105
is mounted.
SUMMARY OF THE INVENTION
The present invention aims to eliminate above-mentioned conventional drawbacks, and an object of the present invention is to provide a recording apparatus and a method for controlling such a recording apparatus, in which a recording range at a tail end portion of a sheet can be widened without preventing a scanning operation o
Barlow John
Brooke Michael S
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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