Sheet feeding or delivering – Feeding – With means to align sheet
Reexamination Certificate
2000-06-09
2003-06-10
Bollinger, David H. (Department: 3651)
Sheet feeding or delivering
Feeding
With means to align sheet
C271S272000, C271S276000, C271S197000
Reexamination Certificate
active
06575459
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to devices incorporated into an image recording apparatus or the like used to form, e.g., print an image on a sheet of paper or other types of recording media, for transporting a recording medium, and in particular to improvements of such devices driving a belt to transport a recording medium.
2. Conventional Art
Printers and copiers are conventionally known apparatuses for forming, e.g., printing an image on a sheet of paper, film or other types of recording media, as disclosed for example in Japanese Patent Laying-Open No. 6-135613. Generally, such apparatuses employ electro-photography, ink-jetting and the like to form an image.
In electro-photography, a tonered image formed on a photoreceptor drum is transferred onto a recording medium to form an image on the recording medium. In ink-jetting, a printing head jets ink toward a recording medium to form an image on the recording medium.
The above two methods each employ a belt drive device as means for transporting a recording medium. Ink-jet printers using this belt drive device typically have a configuration, as described below:
As shown in
FIG. 4
, a belt drive device of this type includes a drive roller a, a subordinate roller b and a tension roller c, with an endless belt d engaged therearound. Drive roller a, connected to a drive shaft of a motor (not shown), receives the motor's driving force and thus rotates. As drive roller a rotates, belt d in the figure runs in a direction A. Opposite to subordinate roller b, on an upper side in the figure, a pinch roller e is arranged to cooperate with subordinate roller b to pinch belt d. In a vicinity of subordinate roller b, a sheet feed cassette f is arranged, from which a recording medium (a sheet of paper) g is drawn and transported in direction A, pinched together with belt d between subordinate roller b and pinch roller e, as belt d runs.
A printing head h is arranged above belt d between drive roller a and subordinate roller b. The portion of belt d between drive roller a and subordinate roller b will be referred to as a span s. Printing head h is a linear head or a serial head. The linear head has a multitude of jet nozzles depending on the resolution of interest that are arranged across a printing width as required in a direction perpendicular to the plane of
FIG. 4
, e.g., 200 mm for a sheet of the A4 size. The serial head has several tens to hundreds of jet nozzles in direction A as shown in FIG.
4
and prints an image on recording medium g as it moves in a direction perpendicular to the plane of FIG.
4
.
In printing an image, as the belt drive device is driven recording medium g is drawn from sheet feed cassette f, pinched together with belt d between subordinate roller b and pinch roller e and thus transferred in direction A.
For printing head h in the form of the linear head, recording medium g is continuously transferred, while the printing head's nozzles jet ink appropriately to print an image on recording medium g.
For printing head h in the form of the serial head, recording medium g is initially transferred to the position at which printing head h is arranged.
When recording medium g has arrived there, belt d halts. Then printing head h jets ink through its nozzles as it moves in the direction perpendicular to the plane of
FIG. 4
, and it thus prints an image. When printing head h has arrived at one end of recording medium g, belt d again starts to run and then stops after recording medium g has been moved by a predetermined distance. Then printing head h then again moves in the direction perpendicular to the plane of FIG.
4
and thus prints an image. Thus, the print operation by printing head h and the recording-medium transport operation by the belt drive device are alternately provided to print an image on recording medium g.
One exemplary device of this type also includes a platen chamber i arranged on a back side of the belt's span s existing between drive roller a and subordinate roller b. Platen chamber i can aspirate recording medium g on belt d so that recording medium g does not displace and is thus transported satisfactorily. To do so, platen chamber i has an upper surface provided with multiple aspiration holes j. Similarly, belt d is also provided with multiple aspiration holes (not shown). When platen chamber i is driven or a negative pressure is produced, an aspiration force is produced at each aspiration holes of belt d. Thus, belt d aspirates recording medium g to prevent any positional displacement of recording medium g while transporting recording medium g.
The conventional belt drive device configured as above, however, tends to transport recording medium g by a distance larger than a predetermined distance. If such event occurs, a difference would be introduced between the driveability of belt d and the transportability of recording medium g. Thus, recording medium g would slide relative to belt d and thus be positionally displaced from a predetermined position. As a result, recording medium g would be transported with less precision or worse it would come off belt d and contact printing head h or divert from a transporting path and jam up the machine of interest, resulting in an unsatisfactory print operation. As such, recording-medium transport devices using such conventional belt drive device are still disadvantageous in transporting recording medium g.
The present inventors have studied what introduces a difference between the driveability of belt d and the transportability of recording medium g and have found that such difference is introduced by the following event:
More specifically, it has been found that, as shown in
FIG. 5
, when recording medium g is introduced between subordinate roller b and pinch roller e, in a vicinity of the portion pinched by rollers b and e, which will be referred to as a nip hereinafter, belt d has a front surface running at an temporarily increased rate, which introduces the difference between the driveability of belt d and the transportability of recording medium g. More specifically, belt d around subordinate roller b has an expanding front surface and a contracting back surface. Furthermore, as indicated in
FIG. 5
by a broken line, belt d has a layer approximately intermediate as seen in a direction of the belt's thickness that neither expands nor contracts.
The front surface of belt d around subordinate roller b, expanding, runs at a local, higher rate than the belt's back surface and intermediate layer.
For example, if &ohgr; represents a rate at which subordinate roller b revolves, rn represents a distance from the center of subordinate roller b to the intermediate layer of belt d, and &Dgr;r represents a distance from the intermediate layer of belt d to the front surface of belt d, then belt d around subordinate roller b has a front surface running at a rate Vin:
Vin=(
rn+&Dgr;r
)×&ohgr; (1).
Furthermore, the intermediate layer, neither expanding nor contracting, runs at a rate Vn:
Vn=rn×&ohgr;
(2).
As such, the belt's front surface runs faster than the belt's intermediate layer by the difference between the two rates, i.e., &Dgr;r×&ohgr;. While the front surface of belt d around subordinate roller b runs faster than the intermediate layer of belt d therearound, a front surface of belt d not around subordinate roller b, e.g., that of belt d opposite to printing head h, no longer expands and thus runs at a reduced rate and thus the same rate as the belt's intermediate layer.
Thus, belt d has a front surface running faster at subordinate roller b (at a rate V
1
in
FIG. 5
) than at printing head h (at a rate V
2
in FIG.
5
). Because of such difference in rate, in
FIG. 5
at the nip there would work a force which would transport recording medium g on a front surface of belt d at a rate greater than that of the intermediate layer of belt d. That is, recording medium g is transported farther at th
Higuchi Kaoru
Ishikawa Len
Kakiwaki Shigeaki
Bollinger David H.
Conlin David G.
Dike, Bronstein, Roberts & Cushman Intellectual Property Practic
Hartnell, III George W.
Sharp Kabushiki Kaisha
LandOfFree
Recording-medium transport device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Recording-medium transport device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Recording-medium transport device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3088560