Sheet feeding or delivering – Feeding – Separator and conveyor
Reexamination Certificate
1998-11-04
2003-06-17
Walsh, Donald P. (Department: 3653)
Sheet feeding or delivering
Feeding
Separator and conveyor
C271S010010, C271S010080
Reexamination Certificate
active
06578840
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a sheet conveying apparatus for conveying sheet materials which is applied to an image forming apparatus such as an electrophotographic apparatus, an electrostatic recording apparatus or a laser beam printer.
2. Related Background Art
As image forming apparatus of this kind, there are, for example, electrophotographic apparatuses, electrostatic recording apparatuses, laser beam printers, etc. As a first example of the prior art, an image forming apparatus using an electrophotographic process will hereinafter be described with reference to
FIGS. 22 and 23
of the accompanying drawings.
In
FIGS. 22 and 23
, the reference numeral
201
designates an image forming apparatus, and the reference numeral
202
denotes a feeding cassette containing sheet materials S therein. The feeding cassette
202
has the sheet materials S stacked therein, and is mounted on the image forming apparatus
201
from the direction of arrow A.
A feeding roller
203
is adapted to be rotated about the center of rotation
203
a
to thereby feed the sheet materials S into the image forming apparatus
201
. A conveying roller
204
is rotatably installed in the image forming apparatus
201
. A pinch roller
205
is rotatably installed in the image forming apparatus
201
. This pinch roller
205
is pressed by pressing means (not shown) in order to form a nip with the conveying roller
204
.
The reference numerals
206
,
220
and
210
respectively denote a drive input gear, an idler gear, and a conveying roller driving gear. These gears are all rotatably installed in the image forming apparatus
201
and are connected together so as to be capable of transmitting drive. The conveying roller driving gear
210
is fixed in the direction of rotation with the conveying roller
204
, and by the conveying roller driving gear
210
being rotated, the conveying roller
204
can be driven.
When the drive input gear
206
is rotated in the direction of arrow E by a main motor (not shown), the conveying roller
204
is rotated in the direction of arrow H through the idler gear
220
and the conveying roller driving gear
210
. By this operation, the conveying roller
204
and the pinch roller
205
function to feed the sheet material S fed by the feeding roller
203
into the image forming apparatus
201
.
Register rollers
211
convey the sheet material S at predetermined timing, and a process cartridge
212
contains a photosensitive drum
212
a,
a primary charger, a developing device, a cleaning device (not shown), etc. therein. The reference numeral
213
designates a transfer roller, and the reference numeral
214
denotes a fixating device containing a fixating roller
214
a,
a pressing roller
214
b,
etc. therein. The references numeral
215
,
216
and
217
respectively designate first discharge rollers, second discharge rollers, and a discharge tray on which printed sheet materials S are to be stacked. A scanner unit
218
scans a laser beam L, and a mirror
219
directs the laser beam L to the photosensitive drum
212
a.
In the construction as described above, when the image forming apparatus
201
is instructed to effect printing by a host computer (not shown) connected thereto, the feeding roller
203
is rotated, whereby a sheet material S in the feeding cassette
202
is fed, and the fed sheet material S is conveyed into the image forming apparatus
201
by the conveying roller
214
and the pinch roller
215
. The sheet material S is further directed to the process cartridge by the register rollers
211
, and an image is printed on the surface of the sheet material S by a known printing process.
The sheet material S after transfer is further conveyed to the fixating device
214
, where the image thereon is fixated, and then the sheet material S is discharged onto the discharge tray
217
by the first discharge rollers
215
and the second discharge rollers
216
.
The prior art as described above, however, has suffered from the following problem.
In the first example of the prior art, there is a case where due to paper jam (hereinafter referred to as the “jam”) or other trouble, the image forming apparatus
201
is stopped with a sheet material nipped between the conveying roller
204
and the pinch roller
205
(the position of the sheet material S
1
in FIG.
22
).
In such case, in the construction of the prior art, a pressing force for forming the nip is acting between the conveying roller
204
and the pinch roller
205
, and the conveying roller driving gear
210
is always connected to the main motor or other driving system, so that when the sheet material S
1
is to be pulled out for the treatment of the jam, it has been necessary to rotate the main motor or other driving system.
Therefore, due to the load of the main motor or other driving system, a great force has become necessary to pull out the sheet material S
1
, and the treatability of the jam has been bad. Also, the sheet material S
1
might be broken by the operation of pulling out the sheet material S
1
, and the broken sheet material S
1
might remain in the image forming apparatus
201
to hinder the conveyance of the sheet materials S.
(Second Example of the Prior Art)
FIGS. 24 and 25
of the accompanying drawings show a second example of the prior art.
In
FIGS. 24 and 25
, portions common to those in the first example of the prior art are designated by reference numerals corresponding to those in the first example.
A feed roller
325
and a retard roller
326
form the nip therebetween, and the feed roller
325
is rotated in the direction of arrow V by driving means (not shown). The retard roller
326
is connected to a retard roller driving gear
328
through a torque limiter
327
. The retard roller driving gear
328
is connected to an idler gear
320
so as to be capable of transmitting drive.
Accordingly, when the idler gear
320
is rotated in the direction of arrow F, the retard roller driving gear
328
is rotated in the direction of arrow R, whereby the drive force in the direction of arrow R is given to the retard roller
326
through the torque limiter
327
. When predetermined or greater torque in the direction of arrow W is given to the retard roller
326
, slip occurs in the interior of the torque limiter
327
, so that the retard roller
326
is rotated in the direction of arrow W against the driving force of the retard roller driving gear
328
in the direction of arrow R.
By such construction, when a plurality of sheet materials S come into the nip portion between the feed roller
325
and the retard roller
326
, only the uppermost sheet material S is conveyed.
During image formation, when the image forming apparatus
301
is instructed to effect printing by a host computer (not shown) connected thereto, a paper feeding roller
303
is rotated, to feed a sheet material S in a paper feeding cassette
302
. When a plurality of sheet materials S are fed, only the uppermost sheet material S is conveyed into the image forming apparatus
301
by the feed roller
325
and the retard roller
326
. An image is formed on the conveyed sheet material S, which is then discharged onto a discharge tray
317
.
Again in the second example of the prior art, there is a case where when the image forming apparatus
301
is stopped due to jam or other trouble, a sheet material S
1
is at the nip between the conveying roller
304
and the pinch roller
305
and at the nip between the feed roller
325
and the retard roller
326
, as shown in
FIGS. 24 and 25
.
However, when the sheet material S
1
is to be pulled out in the direction of arrow J when the jam has occurred, a pressing force for forming the nip is acting between the conveying roller
304
and the pinch roller
305
, and between the feed roller
325
and the retard roller
326
. Therefore, by the force with which the sheet material S
1
is pulled out, drive force in the direction of arrow H acts on the conveying roller driving gear
310
, so that a driving force in the direction of arrow F
Rodriguez Joseph C
Walsh Donald P.
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