Note: Descriptions are shown in the official language in which they were submitted.
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SHEET FE~DING APPARATUS
Back~round of the Invention
This in~ention relates to paper feeders for use
on printers having sensors for sensing paper presence,
forward imprinting platen rotation and backward
paper-rejecting platen rotation.
Such a printer is described in U.S.S.N7
204,020, where controls are provided to cause forward
platen ro~ation for first, feeding a sheet of paper from
an upper hopper to a paper load position at the bottom
of the platen and then printing the sheet, and to cause
backwards platen rotation foe ejecting the printed sheet
-! downwardly toward a lower hopper for sequentially
stacking the sheets of paper.
L5 It i6 desirable to provide such printers with a
paper feeder that can dispense unprinted sheets of paper
to the printer.
Summary of the Invention
In one aspect, the invention features a paper
feeder for dispensing sheets of paper, one at a time,
into a printer having sensors for sensing leading and
trailing edges of sheets of paper. The printer has a
platen which rotates in a forward imprinting direction
in response to sensing a leading edge, and rotates in a
25 backward, paper-ejecting direction in response to
sensing a trailing edge. The feeder has a paper
cartridge for holding a stack of paper and at least one
rotatable drive roller to operably contact the topmost
sheet of paper in the cartridge.
A drive train for connecting the platen to the
drive roller is powered and controlled exclusively by
its connection to the platen to cause no rotation of the
;~ drive roller in response to forward platen rotation, and
to cause orward, paper-dispensing rotation of the drive
35 roller in response to backward platen rotationO When
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the platen rotates backwards to eject a sheet of paper
from the printer, the drive train causes the drive
roller to move a sheet of paper from the cartridge into
a paper-loading position on the printer, thus providing
the printer with simultaneous paper ejection and
dispensing. -
The drive train is arranged so that the driveroller delivers sheets of paper to the paper-loading
position not before the platen ejects the peinted sheet
- 10 of paper. In preferred embodiments, the drive roller
rotates at a velocity slower than the rotational
velocity of the platen. In the illustrated embodiment,
the ratio of platen rotation to drive roller rotation is
approximately 2:1. In other embodiments, the drive
train is arranged to cause the feeder to dispense sheets
of paper over a greater distance than the maximum length
of paper being ejected.
Therefore, the printer is provided with
simultaneous paper ejection and dispensing, and the
drive train provides that sheets of paper are not
delivered to the paper-loading position before the
platen ejects the printed sheet of paper.
In other aspects of the invention, the
invention feature a printer having sensors for sensing
leading and trailing edges of sheets of paper, control
means for controlling platen rotation in response to the
sensing, a paper feeder arranged to dispense sheets of
paper, and a drive train for connecting the paper feeder
to a platen. The control means are responsive to
sensing a leading edge and completion of paper ejection,
causing the platen to rotate in a forward imprinting
direction. The control means provide simultaneous paper
ejection from and paper feeding into the printer solely
through sensing a trailing edge and causing the platen
35 to rotate a predetermined amount first in a forward
imprinting direction and second in A backward
paper-ejecting direction. The drive train responds
solely to backward, paper-ejecting p3aten rotation to
dispense a sheet of paper from the feeder, and is
arranged so that ~he paper feeder delivers sheets of
paper to a paper-loading position on the printer not
before the platen ejects the printed sheet of paper.
In still further aspects of the invention, the
~, invention feature a printer having sensors for sensing
the presence of a sheet of paper, a paper feeder, a
drive train, and programmed control means which provide
simultaneous paper ejection frorn and paper feeding into
the printer solel~ through conteolling rotation of the
platen in response to sensing paper presence. The drive
train responds solely to paper-ejecting platen rotation
to dispense a sheet of paper from the feeder, and is
arranged so that the feeder delivers sheets of paper to
a paper-loading position on the printer not before the
platen ejects the printed sheet of paper.
In preferred embodiments, the programmed
control means respond to sensing no paper at start-up of
the printer, by causing the platen to rotate a
predetermined amount in a paper~ejecting direction,
which causes the feeder to dispense a sheet of paper.
The control means respond to a trailing edge, causing
the platen to rotate a predetermined amount first in a
paper-imprinting direction and second in a
paper-ejecting direction. At the completion of paper
ejection, the control means respond to a leading edge,
causing the platen to rotate in a forward
paper-imprinting direction, and respond to sensing no
paper, causing the printer to deselect.
Also in preferred embodiments, the paper feeder
is releasably attached to the printer and has
3 disengaging means for disengaging, without removing, the
paper feeder from the printer by eliminating operable
contact between the stack of paper and the drive
roller. In the illustrated embodiment, a pusher plate
biase~ against the stack of paper in the cartridge
provides the operable contact, and manipulation of a
select knob, connected to a pusher rod, cause~s the
pusher rod to move the pusher plate away from the s~ack,
thereby eliminating the operable contact.
Other advantages and features of the invention
will be apparent from the following description of the
preferred embodiment thereof, and from the claims.
Descri~tion of the Preferred Embodiment
. _ _
We turn now to the structure and cperation of
the preEerred embodiment first briefly describing the
drawings thereof.
Drawings
Fig. 1 is an exploded view of the preferred
embodiment of the invention, with parts broken away for
clarity.
Fig. 2 is a side view of Fig. 1, with parts
! broken away for clarity.
Fig. 3 is the opposite side view of Fig. 1,
with parts broken away for clarity.
Description
As seen in Figs. 2 and 3, a paper feeder 10 is
attached to one side of printer 50 by spring clip 5~,
and to the opposite side of machine 50 by catch 54.
Components of printer 50 include platen 60
fixedly mounted on platen shaft 61, and paper-loading
guide 56 to guide the unprinted sheet of paper to the
loading position of platen 60 at the edge of the lower
platen feed roll and guide mechanism 57. An optical
q~ sensor 58 mounted on guide S6 is provided to sense the
leading and trailing edges of paper, and platen controls
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63 are provided to control the amount and direction of
platen rotation in response to signals from sensor 58.
Lower platen feed roll and guide mechanism 57
includes an arcuate platen feed guide 66 provided under
platen 60 and arranged to be biased so that the
plurality of platen guide rollers 59 rotatably mounted
on feed guide 66 normally contact platen 60. A printecl
sheet deflection guide 65 is provided to guide printed
paper around platen 60 and between platen 60 and printed
sheet rollers 64 mounted coaxially with ancl normally
contacting platen 60.
To understand the arrangement of the printer to
which the feeder is attached, a short explanation of
paper feeding, printing and ejection follows. As a
leading edge of an unprinted sheet of paper is sensed by
sensor 58, platen controls 63 cause platen 60 to rotate
in a forward direction one quarter of a revolution to
bring the sheet to the loading position of the platen at
the edge of mechanism 57. Platen conteols 63 continue
to cause forward platen rotation so as to print the
sheet of paper, which is pulled around platen 60 by
platen guide rollers 59 which are biased against platen
60. Printed sheet deflection guide 65 guides printed
paper upward around platen 60 and between platen 60 and
printed sheet rollers 64.
When a trailing edge of a sheet of paper is
sensed by sensor 58, controls 63 again cause platen 60
to rotate in a forward direction one ~uarter of a
revolution to bring the sheet out from under platen feed
guide 66. Platen controls 63 then cause platen 60 to
reverse direction to rotate backwards and eject the
printed piece of paper. Printed sheet rollers 64 bear
' against platen 60 to aid in ejecting the printed paper,
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and printed sheet de~lection guide 65 directs the
printed sheet downward toward a lower hopper (not shown)
under the platen~
The paper feeder 10 attached to printer 50 has
5 a removable paper cartridge 12 in which a stack of paper
is held. In the lower two corners of cartridge 12 are
trippers 14 arranged to separate the topmost sheet in
cartridge 12 from the rest of the stack 60 as to allow
feeder 10 to efficiently dispense one sheet of paper at
10 a time.
Along the interior vertical length of cactridge
12 are insert guides (not shown) arranged so that
vertica' cartridge inserts (not shown) can be inserted
into cartridge 12, thus altering the width of cartridge
15 12 so that paper of different widths (i.e. 8, 8 1/4, 8
1/2 inches) may be stacked in cartridge 12.
As seen in Fig. 2, cartridge 12 is supported
within ~eeder 10 by cartridge runners 18 which extend
along the vertical length of paper cartridge 12 and fit
20 over cartridge guide 16 extending along the vertical
interior length of feeder 10. Cartridge guide 16 is
arranged on the interior wall of feeder 10 so that
cartridge 12 is held between drive rollers 20 and pusher
plate 24.
Drive rollers 20 are fixedly mounted on feeder
drive shaft 22, which extends transversely across feeder
10, and pusher plate 24 in the back of feeder 10 is
urged toward drive rollers 20 by spring 26 in order to
provide operable contact between the topmost sheet of
paper in cartridge 12 and drive rollers 20. Pusher rod
30, extending transversely across feeder 10 between
pusher plate 24 and rollers 20 are arranged to move
pusher plate 24 away from cartridge 12 so as to remove
the operable contact between the paper in cartridge 12
and drive rollers 20.
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Select knob 32, mounted to pusher rod 30 on the
exterior of feeder 10, is arranged to move p~sher rod 30
toward and away from pusher plate 24. In Fig. 2, the
extreme pOSitiOlS of pusher plate 24 are shown; first,
in solid lines, as causing operable contact between the
stack of paper and drive rollers 20, and second, in
phanto~, as moved a~ay Erom drive rollers 20, th~ls
removing operable contact and deselecting automatic
- feeding.
As also seen in Fig. 3, eeder drive rollers 20
are connected to platen 60 through through drive tr~in
35, a series of gears and pulleys. Fixedly mounted to
platen shaf~ 61 is platen gear 62 which is mounted
coaxially with and engages plater. gear/pulley 34.
Timing belt 36 is arranged to transfer rotation from
platen gear/pulley 3~ to one-way feeder pulley 38 which
is mounted on the end of drive shaft 22.
One-way feeder pulley 38 is so constructed to
engage with and rotate drive shaft 22 and rollers 20
when timing belt 36 moves counter-clockwise, shown as
"a" in Fig. 3, and to rotate freely without engaging
drive shaft 22 when timing belt 36 moves clockwise, as
shown as "b" in Fig. 3.
Drive train 35 is arranged so that feeder drive
rollers 20 rotate exclusively in response to specific
directional rotation of platen 60, in a direction
opposite to that of platen 60 and at a frequency
proportional to the rotational fre~uency of platen 60.
This arrangement provides that the prede~ermined amount
of backward platen rotation necessary to eject a printed
sheet of paper of maximum length simultaneously causes
; automatic dispensing of an unprinted sheet of paper into
the platen paper-loading position at a time not before
completion of the printed sheet ejection or at least not
before rnost of the printed sheet has been ejected.
s~
In the ill~strated embodi~ent, the rotational
fre~ency of drive rollers 20 is smaller than the
rotatlonal frequency of platen 60; the platen/drive
roller frequency ratio is appriximately 2:1. In other
embodiments, a drive train may be arranqed so that the
platen and drive rollers rotat.e with approximately e~ual
fre~uencies, but that the paper feeder dispenses sheets
of paper to the printer over a greater d.istance than the
maximum length of paper being ejected.
Operation
When sheet feeder l0 is attached to printer 50
and select knob 32 is turned so that pusher rod 30 mQves
pusher plate 24 away from drive roller 20, automatic
sheet feeding is not selected. Automatic sheet feeding
is selected when knob 32 is turned to move pusher rod 30
away from pusher plate 24 so that plate 24, normally
biased by spring 26 toward drive roller 20, presses the
stack of paper within cartridge 12 against drive roller
20, thus providing operable contact between the topmost
sheet of paper and drive rollers 20.
When automatic sheet feeding is selected and
the printer is first turned on, platen controls 63
within printer 50 rotate platen 60 in a backward
direction so as to cause an unprinted sheet of paper to
be dispensed from feeder l0 onto paper-loading guide
56. As seen as "a" in Fig. 3, drive train 35 transfers
the backward rotation of platen 60 into a
counter-clockwise, paper dispensing rotation of drive
shaft 22 and rollers 20. Specifically, the backward
rotation of platen 60 and platen shaft 61 causes
clockwise rotation of platen gear 62, which engages
gear/pulley 34 and rotates it in a co~lnter-clockwise
direction. Timing belt 36 transfers the
counter clockwise rotation of platen gear/pulley 34 to
~ 3
one-way feeder pulle-~ 3~, which causes drive shaft 22
and rollers ~0 to rotate in a counter-clockwise,
paper-dispensing direction, pushing a piece of paper
do~n onto the printer's paper-loading guide 56.
When the leading edge of the unprinted sheet of
paper is sensed on paper-loading guide 56 by sensor 58,
platen controls 63 cause platen 60 to rotate in a
forward direction one ~uarter of a revolution to bring
the sheet to the loading position of platen 60. Platen
lO controls 63 continue to cause forward platen rotation so
as to print the sheet of paper. Platen g~ide rollers
59, bearing against platen 60, guide paper ~nder and
arcund platen 60, and printed sheet rollers 6~/ bearing
against platen 60, grip printed paper that has passed
15 around platen 60.
During paper printing, drive train 35 does not
transfer the forward rotation of platen 60 to drive
shaft 22 and rollers 20. Specifically, as seen as "b"
in Fig. 3, the forward rota~ion of platen 60 and platen
20 shaft 61 causes counter-clockwise rotation of platen
platen gear 62 and clockwise rotation of gear/pulley
34. Timing belt 36 transfers the clockwise rotation to
one-way feeder pulley 38, which rotates clockwise
without engaging drive shaft 22 and rollers 20.
i 25 Forward paper-imprinting platen rotation
continues until sensor 58 senses the trailing edge oE
the sheet of paper being imprinted. At that time,
platen controls 63 cause platen 60 to rotate in a
forward direction one quarter of a revolution to bring
30 the now-imprinted sheet out from under platen feed guide
66. Platen controls 63 then cause platen 60 to reverse
direc~ion to rotate backwards a predetermined number of
-~ times so as to eject the printed piece of paper in a
downward direction. Printed sheet rollers 64 aid in the
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ejection, bearing against the printed sheet and platen
60. Printed sheet deflec~ioll guide 65 guides the sheet
in its downward path to the :Lower hopper (not shown).
The amount of backwards platen rotation is chosen to
allow thé entire length of a piece of paper having
predetermined maximum length to pass between platen
rollers 64 and platen 60.
As platen 60 is rotating baclcwards to eject the
rinted piece of paper, drive train 35 is transferrinq
the back~ards platen rotation to the drive shaft 22 and
rollers 20 so as to cause the next unprinted sheet of
paper to be dispensed from feeder 10 onto paper-loading
guide 56. The operation of drive train 35 is identical
to its operation described in causing paper Eeed during
printer initiation, i.e., backward, paper-ejecting
rotation of platen 60 and shaft 61 causes
counter-clockwise, paper-dispensing rotation of drive
shaft 22 and rollers 20.
The newly dispensed sheet of paper is fed onto
printer paper-loading guide 56, but sensor 58 does not
sense its presence until the platen has completed the
predetermined number of backward, paper-ejecting
rotations. An insubstantial amount of buckle may appear
in the newly dispensed sheet while it lies on guide 56.
After ejection is completed and sensor 58
senses the newly-dispensed sheet of paper on
paper-loading guide 56, platen controls 63 cause platen
60 to begin the paper loading and imprintiny sequence
described above. If, for some reason, a newly-dispensed
sheet of paper is not sensed by sensor 58, i.e., paper
cartridge 12 was empty, platen controls 63 cause printer
50 to deselect.
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Various modifications of the invention within
the spirit of the invention and scope of the appended
claims will be apparent to those skilled in the printing
apparatus art.
