Sheet feeding or delivering – Feeding – Separators
Reexamination Certificate
2001-08-14
2003-04-01
Skaggs, H. Grant (Department: 3651)
Sheet feeding or delivering
Feeding
Separators
C271S124000, C271S126000
Reexamination Certificate
active
06540221
ABSTRACT:
FIELD OF THE INVENTION
The present invention is applied to image forming apparatuses such as a printer, a copy machine, and a facsimile which form images on sheets by such processes as printing and transfer, and more specifically relates to a feeder which separates stacked sheets into individual sheets in order and carries sheets to an image forming section.
BACKGROUND OF THE INVENTION
Conventionally, in a feeder of an image forming apparatus, an arrangement in which a feeding cassette storing sheets for image formation is detachably provided with respect to an image forming apparatus body has been mainly used. However, such a structure of a detachable feeding cassette inevitably increases the height of the image forming apparatus.
Recently, in image forming apparatuses such as an ink-jet printer for small volume printing, a fixing type feeding cassette which utilizes a bottom plate of the image forming apparatus body as a bottom plate of the feeding cassette tends to be installed instead of the detachable feeding cassette. Compared with the detachable type, the fixing type can store fewer sheets, but the fixing type has an advantage that the height of the image forming apparatus can be decreased.
However, in the fixing type, because it is fixed, problems which did not occur in the detachable type are brought about. That is, unlike the detachable type feeding cassettes which can classify sheets according to size and type of the sheets to some extent by the feeding cassette and can fix feeding conditions in a predetermined range, the fixing type feeding cassette need to solely cope with various sheets which differ in size, thickness, and surface smoothness, etc. Thus, feeding conditions need to be fixed with respect to every kind of sheet used in the feeder. The feeding conditions include a sheet transport power for feeding and transport sheets out of the feeding cassette, and sheet separating power for separating the sheets into individual sheets.
An arrangement of a conventional feeder using the fixing type feeding cassette is shown in FIG.
7
.
As shown in
FIG. 7
, a bottom plate of a fixing type feeding cassette
50
makes up a bottom
57
of an image forming apparatus body, and a sheet lifting plate
59
which pushes up an end of stacked sheets S stored in the feeding cassette
50
is provided on the bottom plate
57
. The sheet lifting plate
59
rises by switching off a solenoid
58
, so that a front end of the sheets S stacked on the sheet lifting plate
59
is pushed against a feeding roller
51
.
The feeding roller
51
is provided along a body frame
54
, which is also a right side wall of the image forming apparatus, and a roller section of the feeding roller
51
is divided into plural rollers and provided on a shaft
51
a
which stretches from the front side to the rear side (see
FIG. 4
, an explanatory drawing of the present invention in which the feeding roller is indicated by reference number
5
and the roller section is divided into four rollers in FIG.
4
).
Further, a sheet separating section for preventing transport of plural sheets S is provided below the feeding roller
51
, downstream with respect to a position where a front end of the sheets S is pressed against. The sheet separating section is made up of a separating unit
52
which is provided for each of the divided rollers of the feeding roller
51
.
The separating unit
52
includes a separating pad
55
thereon, and the separating pad
55
is pressed against the feeding roller
51
. The separating unit
52
is fixed on the body frame
54
via a mounting fraction
52
a
with a bolt
60
, and pushed along a guide rib
53
provided straight up on the bottom plate
57
of the image forming apparatus in a direction shown by an arrow e by a spring
56
whose end is fixed on the bottom plate
57
. The separating pad
55
above the spring
56
is pressed against the feeding roller
51
by the pushing force of the spring
56
. Here, the guide rib
53
restricts a direction of pressure in pressing the separating pad
55
against the feeding roller
51
.
In this arrangement, in feeding sheets, the sheet lifting plate
59
rises by switching off the solenoid
58
and a front end of the sheets S is pressed against the feeding roller
51
, so that the sheets S in the feeding cassette
50
are pulled out by rotation of the feeding roller
51
and carried between the feeding roller
51
and the separating pad
55
. Here, if plural sheets S are pulled out together one over another, the plural sheets cannot pass between the feeding roller
51
and the separating pad
55
pressed against the feeding roller
51
, and the sheets are separated into individual sheets to prevent transport of plural sheets. A sheet S having passed through between the feeding roller
51
and the separating pads
55
is carried to an image forming section (not shown) in accordance with the rotation of the feeding roller
51
.
However, the arrangement in which a feeder employs a conventional fixing type feeding cassette brings about problems as follows.
1) In the conventional arrangement, since the separating pad
55
is pressed against the feeding roller
51
all the time, a pressed surface of the separating pad
55
tends to wear out easily. Thus, durability of the separating pad
55
is inferior. As a result, steady sheet separating power can not be maintained and steady sheet feeding over extended periods of time can not be realized.
2) In the conventional arrangement, since the separating unit
52
which includes the separating pad
55
is fixed on the body frame
54
with the bolt
60
, it is difficult to displace the separating pad
55
. Besides, the spring
56
for providing enough pressure to press the separating pad
55
against the feeding roller
51
to separate sheets exerts pressure diagonally with respect to a direction normal to the separating pad
55
. Thus, the spring
56
used to press the separating pad
55
against the feeding roller
51
has pushing force greater than it the pressure required to separate sheets. Therefore, even if a thickness of a sheet S passing through between the separating pad
55
and the feeding roller
51
exerts such a force that a space between the separating pad
55
and the feeding roller
51
would be spread, the separating pad
55
is not separated from the feeding roller
51
and the space between them is hardly changed.
As a result, when sheets S are thin sheets of paper, it is easy to separate plural sheets into individual sheets, but when the sheets S are thick sheets of paper such as post cards, the thickness of the sheets S becomes so thick when they are transported together one over another that stronger pressure than needed is given to the sheets S. Thus, while the sheets can be separated into individual sheets, a front end of the separated sheet S is rolled up or is torn. Note that, when pressure of the spring
56
is selected based on thick sheets S such as post cards to prevent the problem which is caused when the thick sheets S are transported together one over another, the pressure required to separate the thin sheets S cannot be obtained, and transport of plural sheets S cannot be prevented.
SUMMARY OF THE INVENTION
The first object of the present invention is to provide a feeder of an image forming apparatus which can feed sheets stably over extended periods of time by improving durability of a separating pad. The second object of the present invention is to provide a feeder of an image forming apparatus which is suitable for a feeder having a fixing type feeding cassette and can prevent transport of plural sheets without fail and without impairing sheets carrying performance regardless of type, size, and surface smoothness etc. of fed sheets.
A feeder of an image forming apparatus of the present invention, to achieve the first object, pressure switching means for pressing a separating pad against a feeding roller only when feeding sheets, wherein, when feeding sheets, said pressure switching means presses the separating pad against the feeding roller, and the feeding rol
Kubo Takashi
Morimoto Yasumasa
Nakashima Akira
Renner Otto Boisselle & Sklar
Sharp Kabushiki Kaisha
Skaggs H. Grant
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