Sheet feeding or delivering – Feeding – By means to convey sheet
Reexamination Certificate
2000-06-16
2001-12-25
Ellis, Christopher P. (Department: 3651)
Sheet feeding or delivering
Feeding
By means to convey sheet
C198S472100
Reexamination Certificate
active
06332612
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a sheet conveying apparatus having a plurality of electrodes disposed to attract and convey a sheet by an electrostatic force, and an image recording apparatus provided with the same.
2. Related Background Art
An ink jet recording apparatus having a sheet conveying apparatus of a conventional electrostatic attraction type will hereinafter be described with reference to the accompanying drawings.
FIG. 7
is a schematic cross-sectional view of an image recording apparatus according to the conventional art, and
FIGS. 8A and 8B
are a plan view and an enlarged cross-sectional view, respectively, of a sheet conveying apparatus. The image recording apparatus
50
shown in
FIG. 7
has a recording head
51
for effecting image recording, and a conveying belt
52
which is a sheet conveying apparatus of an electrostatic attraction type. The recording head
51
is of a line type in which discharge openings are arranged over a width substantially equal to the width of a sheet conveyed, and is capable of effecting high-speed image formation as compared with a serial type in which a recording head is carried on a carriage and is caused to scan.
However, because of the high speed, discharged ink is unfixed immediately after recording, and there is the undesirable possibility of an image being disturbed if a recording surface is contacted with a sheet conveying apparatus for holding the sheet. So, in such an apparatus, design is made such that the back side of the recording surface of the sheet is attracted to the conveying belt
52
provided with electrostatic attracting means and the sheet is conveyed without the conveying belt contacting with the recording surface.
The conveying belt
52
is a circular ring-shaped belt member passed over a driving roller
58
and a plurality of supporting rollers
59
,
60
and
61
, and is rotatively driven to thereby convey the sheet which is a recording medium such as paper or a plastic sheet. As the electrostatic attracting means in this conveying belt
52
, there is, for example, one as shown in
FIG. 8A
wherein a group of electrodes (hereinafter referred to as the comb-teeth electrodes
53
and
54
) comprising strip-like electrodes of different polarities alternately disposed are formed and as shown in
FIG. 8B
, electrically conductive brushes
55
as electricity supplying means are provided on the opposite ends of the conveying belt
52
. In such a construction, when one of the comb-teeth electrodes
53
and
54
is connected to earth potential and a predetermined voltage is applied to the other to thereby produce a potential difference, an attracting force can be provided by an electrostatic force.
However, the comb-teeth electrodes
53
and
54
are embedded in the conveying belt
52
and therefore, the thickness of the conveying belt
52
and the hardness of the material thereof vary in the electrode portions and these factors appear as the irregularity of speed in the driving roller
58
portion or the like, and the accuracy of sheet conveyance is reduced. Also, generally the electrode portion is worked by printing or the welding of the electrode materials, but it is difficult to effect such working on an endless belt and therefore, the conveying belt is formed by working it into a band-like belt, and thereafter joining the ends of the belt into an endless shape.
Therefore, the conveying belt
52
does not become a seamless belt of good mechanical accuracy and particularly, the joining portion adversely affects an image in the application thereof to a recording apparatus for the reason that the degree of smoothness thereof is lowered, or causes an inconvenience such as jam or rubbing by the floating of a sheet. Therefore, usually it is necessary to detect the joining portion of the conveying belt, and control the belt so that no sheet may be placed on the joining portion, and a marker
56
has been printed on the conveying belt
52
or a reflecting member has been attached to the conveying belt
52
to thereby effect detection by the use of an optical sensor
57
. However, it has required much labor and cost in the manufacture to print the marker
56
on a surface discrete from the electrode pattern or stick it in the form of a seal. Also, the position at which the marker is stuck on the conveying belt has been limited.
SUMMARY OF THE INVENTION
So, the present invention has as its object to provide a sheet conveying apparatus and an image recording apparatus in which an electrode at a particular position on a conveying belt is formed in a particular aspect, whereby the position can be recognized without a marker or the like being discretely required.
To solve the above-noted problems, in the typical construction of a sheet conveying apparatus and an image recording apparatus according to the present invention, the sheet conveying apparatus has a conveying belt for conveying a sheet, a first group of electrodes comprising a plurality of electrodes installed in the conveying direction of the conveying belt, and a second group of electrodes comprising electrodes installed between adjacent ones of the first group of electrodes, the sheet is attracted and conveyed by an electrostatic force produced with a potential difference provided between the first group of electrodes and the second group of electrodes, an electrode of the first or second group of electrodes on the conveying belt which is at a particular position is formed in a particular aspect, and detecting means for detecting the aspect of the electrode is provided on the circumference of the conveying belt so that the operation of the apparatus may be controlled on the basis of the information by the detecting means.
REFERENCES:
patent: 4244465 (1981-01-01), Hishikawa et al.
patent: 5003325 (1991-03-01), Bibl
patent: 5531436 (1996-07-01), Ohyama et al.
Bower Kenneth W
Canon Kabushiki Kaisha
Ellis Christopher P.
Fitzpatrick ,Cella, Harper & Scinto
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