Note: Descriptions are shown in the official language in which they were submitted.
1309~28
This invention relates to a sheet feeder for printer,
particularly to that wherein undesirable plural sheets
feeding is prevented.
Reference is now made to the accompanying drawings in which:
FIG. 1 is the sectional view of the color printer having the
sheet feeder of prior art.
FIGs. 2 to 4 are the sectional views of the color printer
having sheet feeder of the prior art for showing operation
thereof.
FIG. 5 is a sectional view of a color printer having a sheet
feeder embodying the present invention.
FIG. 6 is a sectional view of the paper cartridge in FIG. 5.
FIG. 7 is a circuit diagram of a control circuit of the paper
cartridge of FIG. 5.
FIGs. 8A and 8B are time charts for showing an operation of
the control circuit of FIG. 7.
FIG. 9 is a flow chart for showing feeding operation of the
control clrcul~.
FIG. 1 is a sectional view of sheet feeder of prior art. In
FIG. 1, an ink sheet 8 is conveyed to a take-up reel 10 from
a feeding reel 9. The feeding roller 6 is moved in a
direction shown by an arrow A in FIG. 1 and is made touch to
a top paper 7 of stacked papers in a paper cartridge 5.
Then, by rotation of the feeding roller 6, the paper 7 is
taken out from the paper cartridge 5 and is transferred to a
platen roller 2. Further, the paper 7 is transferred between
the platen roller 2 and a thermal head 1 by pinch rollers 3,
-- 1
13~9428
4, and printing is ma~e with yellow ribbon 8 tsee FIG. 2) by
a thermal head. When the yellow print operation is completed
the paper 7 is transferred to a first paper passage 12.
Next, the paper 7 is transferred to a second paper passage 13
by reversely rotating the platen roller 2 as shown in FIG. 3.
Then, the paper 7 is printed with magenta ribbon by forward
rotation of the platen roller 2 as shown in FIG. 4. Cyan
print operation is carried out in the same manner as the
operation of yellow or magenta print.
The structure of the above-mentioned conventional device
suffers the problem that two or more papers are often taken
out from the paper cartridge 5, thereby resulting in defect
of printing. Therefore, it is necessary to prevent the
problem of plural sheet taking-out.
It is an object of the present invention to solve the above-
mentioned problem.
According to one aspect of the invention there is provided a
sheet feeder comprising: a sheet case, a sheet stopper
provided at rear end of said sheet case, wherein a touching
surface of said sheet stopper is of a material having
friction against a topmost sheet and elasticity, a feeder
roller which, in feeding operation, touches the topmost sheet
of stacked sheets in said sheet case, a feeding roller motor
for driving said feeding roller, and motor driving means for
feeding forward rotation current to said feeding roller motor
for issuing said topmost sheet from said sheet case and a
reverse rotation current to said feeding roller motor for a
short time prior to feeding of said forward rotation current,
thereby making rear end of said topmost sheet touch and push
said sheet stopper, thereby causing separation of said top
sheet.
1309428
In the present invention, the feeding roller rotates in
reverse direction to feeding-out directions for a very short
time, and thus the rear end of sheet in the sheet cartridge
is made contact the sheet stopper provided at the rear end of
the sheet cartridge. Therefore, even when two or more sheets
are sticking each other, the sheets are separated by such
reverse direction rotation of the feed.ing roller.
While the novel features of the invention are set forth
particularly in the appended claims, the invention, both as
to organization and contact, will be better understood and
appreciated, along with other objects and features thereof,
from the following detailed description taken in conjunction
with the drawings.
':;.~
.
1309428
FIG. 5 shows a sectional view of sheet feeder of an
embodiment of the present invention. An ink sheet 8 is
conveyed to a take-up reel 10 from a feeding reel 9. A
feeding roller 6 is moved in direction shown by an arrow A in
FIG. 1 so as to touch a top paper 7 (or other kind of sheet)
of stacked papers in a paper cartridge 5. Then, the feeding
roller 6 is rotated in reverse direction for a small angle as
shown in FIG. 5, so that the rear end of paper is made touch
a sheet stopper 14 provided at the rear end of the cartridge
5. Because the end part of the paper 7 is pushed to the
sheet stopper, the top sheet is bent as shown in FIG. 5.
Therefore, the sheets are separated, even in case of close
sticking of two or more forward direction for taking out the
separated top paper 7 from the paper cartridge 5. The paper
7, thus taken from the paper cartridge 5, is transferred to a
platen
-~'
1 3~2~
roller 2. Further, the paper 7 is trans~erred to a
position which i8 between the platen roller 2 and a
thermal head 1 by means of pinch rollers 3, 4, and is
printed with yellow ribbon (see FIG.2). When the yellow
print operation is completed, the paper 7 i8 transferred
to a first paper passage 12.
Next, the paper 7 is transferred to a second
paper passage 13 by reversely rotating the platen roller 2
as shown in FIG.3. Then, the paper 7 is printed with
magenta ribbon with rotation of the platen roller 2 as
shown in FIG.4. Cyan print operation is carried out
in the same manner as yellow or magenta print operation.
FIG.6 shows a sectional view of the cartridge 5.
At the rear end of the cartridge 5, the paper stopper 14
is provided. On a face of the stopper to be touched by
the paper, a member 14a having elasticity and large
friction in a direction of its surface, such as any one
member of known hook and loop fastener, is provided.
FIG.7 is a block diagram of controi circuit 15.
The control circuit 15 has a driver 22, a controller 20,
an output port 3~, ROM 32, CPU 34, RAM 36 and an input
port 30. The driver 22 is provided for driving a motor 24
for rotating the feeding roller 6. CPU 34 detects the
status of printer by inputting status signals from the
input port 30 and controls the controller 20 and the
positioning circuit 3 for feeding roller 6 by outputting
. .,
1309428
control signals from the OlltpUt port 3~. CPIJ 34 controls
the printer in accordaDce with a computer program stored
in ROM 32.
FIG.9 shows a flow chart of this program. CPU
34 controls the po~itioning circuit 40 through the output
port 3~ to issue a command signal to contact the feeding
roller 6 to the top sheet ~step Sl). Then, in step S2,
CPU 34 outputs control pulses to the input terminal CU of
the controller 20. When the control pulses are inputted
to the input terminal CU of the controller 20t the
controller 20 outputs pulse signals as shown in FIG.8A
from output terminals ~ 2 , ~3 and ~4. The driver 22
outputs signals corre~ponding to the pulse ~ignal~ as
shown in FIG.8A for driving the stepping motor 24.
Therefore, the stepping motor 24 rotates in reverse
direction.
Next, in ~tep S3, CPU 34 outputs control pulses
to the input terminal CD of the controller 20. When the
control pulses are inputted to the input terminal CD of
the controller 20, the controller 2n output~ pul~e ~ignals
as shown in FIG.8B from output terminals ~ 2 ~3 and
. Therefore, the stepping motor 24 rotates in forward
direction.
Although in the embodiment of the invention the
~heet feeder i8 applied for color thermal printer , in
other modified embodiment~ of the invention the ~heet
l~Og428
feeder i9 applied for mono-color thermal printer or dot-
matrix printer (mechanical impact printer).
Although the invention has been described in its
preferred form with a certain degree of particularity, it
iB understood that the present disclosure of the preferred
form has been changed in the details of construction and
the combination and arrangement of parts may be resorted
to without departing from the spirit and th0 scope of the
invention as hereinafter claimed.
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