Sheet feeding or delivering – Delivering – With transfer means between conveyor and receiver
Reexamination Certificate
2000-02-24
2002-04-16
Skaggs, H. Grant (Department: 3651)
Sheet feeding or delivering
Delivering
With transfer means between conveyor and receiver
C271S188000, C271S209000, C271S902000
Reexamination Certificate
active
06371479
ABSTRACT:
This application is based on patent application Nos. 11-47740 and 11-47741 filed in Japan, the contents of which are hereby incorporated by references.
BACKGROUND OF THE INVENTION
This invention relates to a switchback device for use in image forming apparatus such as copiers, laser printers, and facsimile machines, and particularly to a switchback device for use in image forming apparatus in the technical field of electrophotography.
FIG. 9
is a diagram of a switchback device of prior art for use in an image forming apparatus. Hereinafter, a conventional switchback device is described referring to FIG.
9
. The conventional switchback device
7
comprises: a tray
73
; a sheet transporting unit
74
including a switchback roller
741
, a switchback roller driver (not shown), a movable arm
742
, an arm shaft
743
, a solenoid
744
, an arm bias member
745
, and a spring
746
; and a sheet slapping unit
75
including a guide member
751
, a guide shaft
752
, a solenoid
753
, a guide bias member
754
, and a spring
755
.
An operation of the switchback device
7
is described. When the switchback device
7
is in a stand-by state, a rotation of the switchback roller
741
is suspended. In this state, the switchback roller
741
is set to a retracted state above the tray
73
, and the guide member
751
is also set to a retracted state (shown by the broken line in FIG.
9
).
When a sheet P is transported from an upstream-located path
24
with respect to a sheet transport direction of the image forming apparatus inside the switchback device
7
, an inlet guide roller pair
241
,
242
is driven to transport the sheet P in a sheet entering direction shown by the solid arrow → on the tray
73
. When the lead end of the sheet P in the entering direction is about to slide under the switchback roller
741
, the switchback roller
741
is pivoted downward to come into contact with the sheet P on the tray
73
and guides the sheet P on the tray
73
further in the entering direction (rightward direction in
FIG. 9
) by transmitting a counterclockwise rotational driving force of the switchback roller
741
in
FIG. 9
to the sheet P which is in contact with the switchback roller
741
. When the entirety of the sheet P is guided inside the switchback device
7
, the solenoid
753
is turned on, and the guide bias member
754
is changed from the broken-line state in
FIG. 9
to the solid-line state shown in
FIG. 9
against the spring force of the spring
755
. When the guide bias member
754
is set to the solid-line state, the guide member
751
is pivoted downward about the axis of the guide shaft
752
due to the weight thereof, thereby slapping a portion of the sheet P, which is certain distance away from a tail end thereof, while the sheet P is guided in the entering direction onto the tray
73
. In this way, the sheet P lands on the tray
73
. Then the guide member
751
is pivoted upward to resume its broken line state.
Subsequently, the switchback roller
741
is rotated in the reverse direction (clockwise direction in
FIG. 9
) to transport the sheet P in exiting direction on the tray
73
(shown by the arrow ← in
FIG. 9
) toward an outlet guide roller pair
251
,
252
disposed on a downstream-located path
25
with respect to the sheet transport direction of the image forming apparatus. Thus, the sheet P exits the switchback device
7
by the outlet guide roller pair
251
,
252
.
In the above conventional switchback device, the following problem is involved due to the fact that the image forming apparatus is loaded with a fixing unit. In the case where the tail end of the sheet P in the entering direction (namely, the lead end of the sheet P in the exiting direction) has a curled or warped portion, it is difficult to transport the sheet P having the curled portion properly into the downstream-located path
25
via the switchback device
7
. A sheet jam or a folded corner end of the sheet P may likely occur when the sheet P is transported in and out of the switchback device
7
.
Further, the sheet slapping operation in which the guide member
751
slaps the portion of the sheet P, which is certain distance away from the tail end thereof, against the tray
73
requires a fine adjustment of the timing to promptly transport the sheet P guided from the upstream-located path
24
toward the downstream-located path
25
. The sheet transporting unit
74
is an essential element in the conventional switchback device
7
in association with the driving mechanism of moving the switchback roller
741
toward and away from the tray
73
in order to guide the sheet P in and out of the switchback device
7
. The conventional switchback device
7
provided with these elements is required to have a complex structure and increases the production cost of the image forming apparatus due to the complex mechanism of accomplishing the sheet slapping operation in combination with driving the switchback roller
741
toward and away from the tray
73
.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a switchback device that enables to accurately transport a sheet downstream with respect to a sheet transport direction while carrying out a switchback operation without a possibility of causing a sheet jam or a folded corner end of the sheet even if the sheet has a curled or warped portion.
According to an aspect of this invention, the switchback device focusing an image forming apparatus comprises: an inverting tray for temporarily holding a sheet guided inside the switchback device thereon; a guide unit for guiding the sheet in pressing contact with the inverting tray when the sheet is transported in an exiting direction on the inverting tray, the exiting direction being opposite to an entering direction of the sheet on the inverting tray; a guide switching unit for selectively changing the guide unit to a sheet guide allow state to allow the sheet to enter the switchback device in the entering direction on the inverting tray and a sheet pressing state to make substantially an end of the sheet in the exiting direction in pressing contact with the inverting tray; and a sheet transporting unit for transporting the sheet out of the switchback device in the exiting direction on the inverting tray.
REFERENCES:
patent: 3900192 (1975-08-01), Gibson
patent: 6244591 (2001-06-01), Paulat
patent: 2-75563 (1990-03-01), None
patent: 2-225256 (1990-09-01), None
patent: 4-246055 (1992-09-01), None
patent: 5-246574 (1993-09-01), None
Kimata Hideaki
Kusumoto Hiroshi
Motobayashi Naoki
Oguma Hiromichi
Osaka Toshiyuki
Jordan and Hamburg LLP
Kyocera Mita Corporation
Skaggs H. Grant
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