Sheet-material associating – Associating or disassociating – Sheet associating
Reexamination Certificate
1996-08-07
2001-01-23
Kwon, John T. (Department: 3401)
Sheet-material associating
Associating or disassociating
Sheet associating
C271S258010
Reexamination Certificate
active
06176480
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet stacking apparatus in which sheets discharged from an image forming apparatus such as a copying machine, a laser beam printer and the like are stacked on a sheet stacking plate, and an image forming apparatus having such a sheet stacking apparatus, and more particularly, it relates to control of a position of such a sheet stacking plate.
2. Related Background Art
Among conventional image forming apparatuses such as copying machines, laser beam printers and the like, there is an image forming apparatus having a post-treatment apparatus for effecting a post-treatment such as sheet stapling. In such a post-treatment apparatus, as shown in
FIG. 42
, a tray (sheet stacking plate)
103
on which sheets are stacked is provided on a lift/lower tray shifting stage
102
. On the other hand, an upper rockable guide
88
is provided with a sheet level detection sensor
105
for detecting the fact that a height of a sheet stack S comprised of sheets discharged on the tray
103
reaches a predetermined level. The sheet level detection sensor
105
includes a pivotable sensor lever
106
contacted with the sheet stack S rested on the tray
103
and having an upper end pivotablly supported, and a photo-sensor
107
for emitting a signal representing the fact that the height of the sheet stack S reaches the predetermined level when the sensor lever
106
is rotated by a predetermined angle.
Incidentally, the sensor lever
106
is gradually rocked upwardly as the sheets S are successively stacked on the tray
103
, and, when the height of the sheet stack S reaches the predetermined level, the sensor lever reaches the predetermined angle. With this arrangement, the sheet level detection sensor
105
can detect the fact that the height of the sheet stack S reaches the predetermined level.
When the fact that the height of the sheet stack S reaches the predetermined level is detected by the sheet level detection sensor
105
in this way, a tray lift/lower motor provided on the tray shifting stage
102
is driven, so that the tray
103
is lowered to substantially a position where a first sheet is discharged on the tray. As a result, it is possible to prevent any sheet from jamming at a sheet discharge opening
50
and to increase a maximum stackable amount of sheets on the tray
103
.
Recently, there have been proposed sheet stacking apparatuses each having a plurality of trays. In such sheet stacking apparatuses, for example, when the sheets are successively received one by one in trays from an uppermost one to a lowermost one, after a maximum allowable sheets are stacked on a certain tray, it is necessary that this tray is shifted above the discharge opening and a next (lower) tray is shifted below the discharge opening.
However, when the tray on which the sheets were fully stacked is shifted, as is in the conventional case, if the conventional sheet level detection sensor is provided, since the sensor lever interferes with the movement of the tray, there must be provided for retarding the sensor lever to a position where the sensor lever does not interfere with the movement of the tray whenever the tray is lifted, thereby making the apparatus complicated.
Further, since the conventional sheet level detection sensor cannot detect whether the sheets are stacked on the tray or not, for example, there arises a problem that a different kind of sheet is stacked on the tray on which a certain kind of sheets were already stacked.
SUMMARY OF THE INVENTION
Therefore, the present invention intends to eliminate the above-mentioned conventional drawbacks, and has an object to permit detection of a sheet with a simple construction. Another object of the present invention is to provide a sheet stacking apparatus and an image forming apparatus having such a sheet stacking apparatus, in which, even when a plurality of sheet stacking plates are provided, the positions of the sheet stacking plates can easily be controlled with a simple construction and the presence/absence of sheets on the sheet stacking plates can be detected.
The present invention provides a sheet stacking apparatus for stacking sheets on a sheet stacking plate, comprising a drive device for shifting the sheet stacking plate in an up-and-down direction, a distance sensor disposed above the sheet stacking plate having a light projecting portion for illuminating light toward the sheet stacking plate and a light receiving portion for receiving reflected light, a stacking plate position detection means for detecting a height position of the sheet stacking plate, and a control device for determining the distance between the distance sensor and a sheet stack rested on the sheet stacking plate and for determining the height of the sheet stack on the sheet stacking plate on the basis of the determined distance and the height position detected by the stacking plate position detection means.
Further, the present invention provides the above-mentioned sheet stacking apparatus with a stapling means and the light receiving portion of the distance sensor includes a PSD light receiving element and the illumination portion is designed to emit the light whenever the stapling operation is effected, on the basis of a signal from the control device.
Further, in the present invention, the control device determines that a maximum amount of sheets are stacked on the sheet stacking plate when the height of the sheet stack becomes greater than a first predetermined height and judges that no sheet is stacked on the sheet stacking plate when the height of the sheet stack is smaller than a second predetermined height.
Furthermore, in the sheet stacking apparatus according to the present invention, a through opening for permitting passage of the projected light from the distance sensor is formed in the sheet stacking plate so that, when no sheet is stacked on the sheet stacking plate, the projected light is passed through the through opening to indicate the fact that the height of the sheet stack becomes smaller than the second predetermined height.
The present invention can also be applied to an image forming apparatus comprising an image forming portion and a sheet stacking apparatus for containing sheets on which images were formed in the image forming portion.
With the arrangement as mentioned above, the control device determines the distance between the distance sensor disposed above the sheet stacking plate and an upper surface of the sheet stack rested on the sheet stacking plate. On the basis of the determined distance and the height position detected by the stacking plate position detection means, the height of the sheet stack on the sheet stacking plate is determined. In accordance with the determined result, the drive device is driven to shift the sheet stacking plate.
On the other hand, the present invention provides a sheet stacking apparatus for stacking sheets on a sheet stacking plate, comprising a distance sensor of non-contact type disposed above a sheet stacking plate and having a light illumination portion for projecting light toward the sheet stacking plate and a light receiving portion for receiving reflected light, and a control device for determining the distance between the distance sensor and a sheet stack rested on the sheet stacking plate and for determining a sheet stacking condition of the sheet stacking plate on the basis of the determined distance.
Further, the present invention provides the above-mentioned sheet stacking apparatus further comprising a stapling means and the light receiving portion of the distance sensor includes a PSD light receiving element and the illumination portion is designed to emit the light whenever the stapling operation is effected, on the basis of a signal from the control device.
Further, in the present invention, the control device determines that a predetermined amount of sheets are stacked on the sheet stacking plate when the distance becomes smaller than a first predetermined distance, thereby driving the drive d
Furukawa Hideaki
Nakazawa Noriaki
Yonenuma Masahiro
Canon Aptex Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Kwon John T.
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