Sheet feeding or delivering – Feeding – By means to convey sheet
Reexamination Certificate
2002-05-02
2004-05-11
Walsh, Donald P. (Department: 3653)
Sheet feeding or delivering
Feeding
By means to convey sheet
C318S685000, C318S696000
Reexamination Certificate
active
06733009
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus for forming an image on a sheet, which is a recording medium, for use in a printer, a copying machine, a facsimile machine, or the like, and particularly to an image forming apparatus for forming an image on a sheet by moving a recording head, which is image formation means, for scanning while conveying the sheet.
2. Related Background Art
In general, there is widely known an image forming apparatus comprising a recording medium separating and feeding means for separating and feeding a sheaf of sheets one by one, a recording medium conveying means for conveying the separated and fed sheet, an image forming means for forming an image on the sheet under conveyance, and a recording medium discharging means for discharging the sheet on which the image formation has been completed to an outside of the apparatus; it is used as a printer, a copying machine, or a facsimile machine, for example.
Referring to
FIG. 4
, there is shown a perspective diagram illustrating a structure of an ink-jet printer, given as an example of this type of image forming apparatus. Referring to
FIG. 5
, there is shown a cross section of the structure of the ink-jet printer. Referring to
FIG. 6
, there is shown a diagram illustrating a transmission configuration for conveying a sheet in the image forming apparatus.
As shown in FIG.
4
and
FIG. 5
, the ink-jet printer comprises a feeder
1
(i.e. a paper feeding apparatus), a platen
6
, a stepping motor gear
7
(FIG.
5
), a conveying roller
8
, a sensor lever
9
(FIG.
5
), a sheet sensor
10
(FIG.
5
), a pinch roller spring
11
(FIG.
5
), a pinch roller
12
, a recording head
13
as image forming means, a stepping motor
14
, a conveying roller gear
15
, a carriage
16
, a guide shaft
17
, a guide rail
18
(FIG.
5
), a carriage motor
19
, a timing belt
20
, discharging rollers
21
, follower spurs
22
, a frame
23
(FIG.
5
), intermediate gears
24
, and discharging roller gears
25
.
The feeder
1
, which is a recording medium separating and feeding means, comprises a plate
2
, a feeder base
3
, a feeding motor
4
, a feeding roller
5
, and a plate spring
27
. The recording medium conveying means is a conveying roller pair comprising the conveying roller
8
and the pinch roller
12
. The recording medium discharging means is a discharging roller pair comprising the discharging rollers
21
and the follower spurs
22
. A recording medium detecting means comprises the sensor lever
9
and the sheet sensor
10
. The frame
23
is used for mounting the above composing elements.
In addition, as shown in
FIG. 6
, the stepping motor gear
7
arranged at a rotary shaft of the stepping motor
14
is coupled to the conveying roller gear
15
arranged at the conveying roller
8
, two intermediate gears
24
, and two discharging roller gears arranged at the discharging rollers
21
in a sheet conveying direction. Therefore, the conveying roller
8
is driven by the stepping motor
14
, which is a driving source, via the stepping motor gear
7
and the conveying roller gear
15
. The discharging rollers
21
are driven by the stepping motor
14
, which is a driving source, via the stepping motor gear
7
, the conveying roller gear
15
, the intermediate gears
24
, and the discharging roller gears
25
.
As shown in
FIG. 5
, the plate
2
is supported by the feeder base
3
in a condition that it can turn, and the plate
2
is stacked with a sheaf of sheets on its top surface. For sheet feeding, the feeding motor
4
, which is a driving source, rotates the feeding roller
5
and the plate
2
turns toward the feeding roller
5
by means of the plate spring
24
, and the sheaf of sheets are put in contact with the feeding roller
5
with pressure.
Furthermore, when the feeding roller
5
rotates, only the top sheet among the sheets is separated from the sheaf of the sheets and then fed to the downstream. The sheet separated and fed by the feeder
1
is fed to the conveying roller pair by a further rotation of the feeding roller
5
. Then, a leading edge of the sheet pushes the sensor lever
9
arranged between the feeding roller
5
and the conveying roller
8
so as to turn the sensor lever
9
. The sheet sensor
10
detects that the leading edge of the sheet has reached a given position from the sensor lever
9
turning and falling out of the inside of the sheet sensor
10
and detects that a trailing edge of the sheet has reached a given position from the sensor lever
9
entering into the sheet sensor
10
again.
If the sheet sensor
10
detects the leading edge of the sheet, the sheet is conveyed by a given amount by the feeding roller
5
and then abutted against a nip portion
26
between the conveying roller
8
and the pinch roller
12
urged to the conveying roller
8
by means of the pinch roller spring
11
. When the feeding roller
5
further conveys the sheet by a given amount in this condition, the leading edge of the sheet is pushed to the nip portion
26
and the registration is completed.
After the completion of the registration, the sheet is conveyed to the top of the platen
6
by a rotation of the conveying roller
8
and supported by the top surface of the platen
6
at a position where the sheet is opposing to an arrangement surface of an ink discharge nozzle of the recording head
13
.
Subsequently, ink drops are discharged from the recording head
13
mounted on the carriage
16
for scanning the sheet supported by the top surface of the platen, by which an image is formed on the sheet. The carriage
16
is supported by the guide shaft
17
and the guide rail
18
in a condition that scanning is possible and is driven by the carriage motor
19
via the timing belt
20
.
The sheet on which the image formation has completed is discharged to an outside of the apparatus by rotations of the discharging rollers
21
and the follower spurs
22
urged to the discharging rollers
21
by means of spur springs (not shown).
The following summarizes a flow of conveying a sheet in the ink-jet printer with reference to FIG.
7
. As shown in
FIG. 7
, the sheet fed by the feeding roller
5
is conveyed by a rotation of the conveying roller pair comprising the conveying roller
8
and the pinch roller
12
, which is its follower roller, to a position where an image is formed by the recording head
13
. Then, the image is formed on the sheet through a repetition of scanning with the carriage
16
having the recording head
13
and sheet conveyance with the conveying roller pair.
The sheet on which the image formation has completed is discharged to the outside of the image forming apparatus by two discharging roller pairs comprising the discharging rollers
21
and their follower rollers, the follower spurs
22
. As described above, the sheet sensor
10
detects that the leading edge or the trailing edge of the sheet has reached the given position and the stepping motor
14
drives both of the conveying roller pair and the discharging roller pairs.
Conventionally, the image forming apparatus considers a load on the stepping motor
14
or torque characteristics before applying a sine-curved driving current having a fixed peak value as shown in
FIG. 8
or a rectangular-waveform driving current to the stepping motor
14
so as to control the rotation of the stepping motor
14
.
This type of image forming apparatuses include one having a configuration in which the image formation is further continued after the trailing edge of the sheet passes the conveying roller pair. In this image forming apparatus, a sheet conveying state changes from a conveying state with the conveying roller pair or with both of the conveying roller pair and the discharging roller pairs (hereinafter, referred to as a conveying state with the conveying roller pair) to a conveying state with the discharging roller pairs only in the middle of the image formation.
In this image forming apparatus, generally the urging force of the pinch roller
12
at the co
Kohner Matthew J.
Walsh Donald P.
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