Sheet feeding or delivering – Delivering – With transfer means between conveyor and receiver
Reexamination Certificate
1998-05-08
2001-09-25
Olszewski, Robert P. (Department: 2167)
Sheet feeding or delivering
Delivering
With transfer means between conveyor and receiver
C271S009020, C271S009090, C271S009100, C271S225000, C271S272000, C271S009030, C271S309000, C271S311000, C271S009130
Reexamination Certificate
active
06293541
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet feed unit used in an image forming apparatus or the like, and particularly to a sheet feed unit which stably transports and guides a sheet to be fed while decreasing the noise produced when a trailing edge of a sheet to be fed springs up.
2. Description of the Background Art
By an image forming apparatus, for example, an image forming apparatus using the electrophotographic system, a toner image is formed on a photoreceptor which is a recording medium, and the toner image is transferred onto a sheet such as a plain paper. In order to hold the toner image on the sheet as a permanent image, the sheet is passed through, for example, a heating and fixing unit for fixing the toner, and the sheet is thereafter discharged from the body of the apparatus.
In such an image forming apparatus, a sheet should be transported to an image forming location in order to form a desired image on the sheet. A number of sheets are contained in a paper feed cassette, for example, and a sheet feed unit is provided for transporting the sheets one by one from the cassette to an image forming unit, especially to a transport path which leads to a transfer location where the toner image formed on the photoreceptor is transferred.
According to the invention recited in Japanese Patent Laying-Open No. 5-32341, a body of an image forming unit including a photoreceptor is placed on a paper feed cassette containing a number of sheets as described above in order to entirely reduce an image forming apparatus in size, particularly to decrease an installation area of the apparatus. A plurality of paper feed cassettes housing sheets of different sizes are successively placed on one another under the body of the image forming unit for accommodating various sheet sizes, while the installation area of the image forming apparatus is not changed at all compared with that of a conventional image forming apparatus.
Since the image forming apparatus has such a structure as described above, the transport path where a sheet is fed from the paper feed cassette to the image forming unit as described above is structured such that the path includes a curved reverse section. Therefore, when the trailing edge of the sheet to be fed passes through the reverse section, the edge springs up and noise is produced. On the other hand, when the leading edges of sheets fed from paper feed cassettes of an upper stage and of a lower stage are guided toward the curved reverse section, they are transported at different angles, that is, those sheets touch the guide at different angles. As a result, poor feeding, jam and the like due to different feeding conditions, as well as sound caused by the leading edge hitting against the guide could be produced.
According to Japanese Patent Laying-Open No. 6-92507, a guide mechanism for the sheet feed unit as shown in
FIGS. 1A and 1B
is provided. Specifically, a curved reverse guide section which can be rotated is provided such that the leading edge of a sheet fed from a paper feed cassette of an upper or a lower stage approaches the curved reverse guide section at a constant angle, particularly 45° or less, in order to prevent the poor feeding of a sheet or the like.
Referring to
FIG. 1A
, a sheet fed from a paper feed cassette of an upper stage
50
is guided through a pair of transport rollers
51
to a reverse guide section
52
, and sent toward a resist roller
53
placed at a portion preceding an image forming unit. Referring to
FIG. 1B
, a sheet fed from a paper feed cassette of a lower stage (not shown) placed under the upper stage paper feed cassette
50
is guided through transport rollers (not shown) having the same structure as that of transport rollers
51
, along a vertical guide
54
, to reverse guide section
52
in a direction of the arrow Y.
A sheet transported from the paper feed cassette of the upper or the lower stage is guided to reverse guide section
52
in X or Y direction. The sheets transported from the upper feed cassette and the lower feed cassette approach and touch reverse guide section
52
at different angles. As shown in
FIGS. 1A and 1B
, a part
52
a
of reverse guide section
52
is rotatably supported by an axis and urged by a spring
55
in the clockwise direction. An actuator
57
is attracted to a solenoid
56
placed oppositely to spring
55
, and part
52
a
of reverse guide section
52
is rotated in the counterclockwise direction against the urging force of spring
55
.
When a sheet is transported from upper stage paper feed cassette
50
, solenoid
56
is electrified so that part
52
a
of reverse guide section
52
is set in the state shown in FIG.
1
A. When a sheet is transported from the lower stage paper feed cassette, solenoid
56
is not electrified, and part
52
a
of reverse guide section
52
is set in the state shown in
FIG. 1B
by the urging force of spring
55
.
Accordingly, a sheet Px fed from upper stage paper feed cassette
50
is transported to part
52
a
of reverse guide section
52
positioned as shown in
FIG. 1A
in the X direction. A sheet Py fed from the lower stage paper feed cassette is transported to part
52
a
of reverse guide section
52
as shown in
FIG. 1B
in the Y direction. Consequently, those sheets are guided to part
52
a
of reverse guide section
52
at an approximately same angle (45° or less), so that the sheet can be stably fed.
The angle at which a sheet fed from the upper or the lower paper feed cassette is transported to reverse guide section
52
constituting a reverse path is thus adjusted. At least an angle at which the leading edge of the sheet touches reverse guide section
52
, in other words, an angle, formed by the direction in which a sheet approaches and a guide surface, when the leading edge of the sheet touches reverse guide section
52
, is 45° or less. As a result, a sheet is stably transported and guided. In addition, the noise produced when the trailing edge of a sheet springs up upon passing the reverse section can be reduced.
Using the sheet feed unit having the structure shown in
FIGS. 1A and 1B
provided for a conventional image forming apparatus, the noise produced when the trailing edge of a sheet springs up can be decreased, while the sheet can be stably transported.
However, part
52
a
of reverse guide section
52
should be rotatably placed as shown in
FIGS. 1A and 1B
. Therefore, a space for rotating part
52
a
is required, and the structure of the apparatus becomes complicate. Further, the apparatus is large since solenoid
56
and the like are provided, resulting in increase in cost.
In addition, current should be applied to solenoid
56
, power consumption increases, and power consumption cannot be decreased.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a sheet feed unit by which any noise produced when the trailing edge of a sheet which is transported springs up is eliminated by a simple structure, the sheet can be stably transported and guided, and an image forming apparatus can be entirely reduced in size.
According to one aspect of the invention, a sheet feed unit includes a first transport path along which a first sheet is transported, a second transport path along which a second sheet is transported and guided at a prescribed angle relative to the first transport path, and a protrusion placed at a confluence of the first and second transport paths and having a guide surface placed to allow the second sheet to be transported along the first transport path.
The protrusion is placed at the confluence of the first transport path and the second transport path, and has the guide surface placed to allow the second sheet to be transported along the first transport path. Consequently, the first sheet and the second sheet are guided at the same angle, and those sheets can be stably transported and guided. Further, the protrusion is only provided at the confluence of the first and second transport paths, so that a sheet feed unit can be decreased in size.
The
Horiuchi Takao
Horiuchi Toshihiro
Conlin David G.
Daley, Jr. William J.
Dike, Bronstein, Roberts & Cushman, Intellectual Property Practi
Olszewski Robert P.
Ridley Richard
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