U.S. patent application number 11/957744 was filed with the patent office on 2009-06-18 for sheet lateral positioning device.
This patent application is currently assigned to XEROX CORPORATION. Invention is credited to Keith A. Buddendeck, Steven R. Moore.
Application Number | 20090152806 11/957744 |
Document ID | / |
Family ID | 40752172 |
Filed Date | 2009-06-18 |
United States Patent
Application |
20090152806 |
Kind Code |
A1 |
Buddendeck; Keith A. ; et
al. |
June 18, 2009 |
SHEET LATERAL POSITIONING DEVICE
Abstract
An apparatus for registering a sheet along a transport path,
including a plurality of spaced apart sheet feeding nip sets of
plural sheet feeding nips in the sheet transport path, the plural
sheet feeding nips of the sheet feeding nip sets comprise plural
drive wheels and plural mating idlers, steerable drive mechanism
for changing the drive wheel to idler alignment to thereby
transport the sheet along the paper path while imparting a lateral
motion to the sheet as it is transported along the paper path.
Inventors: |
Buddendeck; Keith A.;
(Rochester, NY) ; Moore; Steven R.; (Pittsford,
NY) |
Correspondence
Address: |
PATENT DOCUMENTATION CENTER;XEROX CORPORATION
100 CLINTON AVE SOUTH, MAILSTOP: XRX2-020
ROCHESTER
NY
14644
US
|
Assignee: |
XEROX CORPORATION
Norwalk
CT
|
Family ID: |
40752172 |
Appl. No.: |
11/957744 |
Filed: |
December 17, 2007 |
Current U.S.
Class: |
271/228 |
Current CPC
Class: |
B65H 2403/531 20130101;
B65H 9/106 20130101; B65H 9/16 20130101; B65H 2404/132 20130101;
B65H 2404/15212 20130101 |
Class at
Publication: |
271/228 |
International
Class: |
B65H 7/02 20060101
B65H007/02; B65H 9/16 20060101 B65H009/16 |
Claims
1. An apparatus for laterally positioning a sheet along a transport
path, comprising: a plurality of spaced apart sheet feeding nip
sets in said sheet transport path, each one of the sheet feeding
nip sets comprise drive wheels and mating idlers, a steerable drive
mechanism for changing the mating idlers drive wheels alignment to
thereby transport the sheet along the paper path while imparting a
lateral motion to the sheet as the sheet is transported along the
paper path; and an entrance sheet feeding nip and an exit sheet
feeding nip, said entrance sheet feeding nip and said exit sheet
feeding nip having both drive wheels and mating idlers aligned
parallel relative to each other.
2. An apparatus according to claim 1, wherein said drive wheels are
mounted on one of the drive shafts in a fixed position and are
aligned in a position substantially perpendicular to said paper
path transport direction.
3. An apparatus according to claim 2, wherein each of said mating
idlers are mounted on one of the idler shafts wherein each one of
said idler shafts being rotatable about an axis perpendicular to
the transport plane.
4. An apparatus according to claim 3, further comprising an
actuator for rotating said idler drive shafts so that the sheet is
moved both in a direction along the paper path and a lateral
direction to the path.
5. An apparatus according to claim 4, further comprising a sensor
located along an edge of the sheet in the paper path.
6. An apparatus according to claim 5, further comprising a
controller, responsive to a signal from said sensor, for rotating
said idler shafts so that the sheet is moved both in a direction
along the paper path and a lateral direction to the path.
7. An apparatus according to claim 4, wherein said actuator
comprises a rack and pinion system having connecting members
connects each one of said idler shafts for common movement.
8. (canceled)
9. An apparatus according to claim 3, wherein lateral compliance of
said mating idlers is less than or equal to one half the lateral
compliance of said drive wheels.
10. A method of laterally positioning a sheet, consisting of:
feeding said sheet into a first pinch nip having a first
orientation; successively feeding said sheet into successive pinch
nips having a second orientation in which the idlers of each
successive nip are aligned to one another and are aligned
differently than the idlers of the first pinch nip; feeding said
sheet to a final pinch nip having said first orientation.
Description
BACKGROUND AND SUMMARY
[0001] This invention relates generally to a sheet transport
system, and more particularly concerns an apparatus and method for
adjusting sheet position along an axis substantially orthogonal to
the transport direction, referred to herein as the lateral axis, in
a high speed printing machine.
[0002] In a typical electrophotographic printing process, a
photoconductive member is charged to a substantially uniform
potential so as to sensitize the surface thereof. The charged
portion of the photoconductive member is exposed to a light image
of an original document being reproduced. Exposure of the charged
photoconductive member selectively dissipates the charges thereon
in the irradiated areas. This records an electrostatic latent image
on the photoconductive member corresponding to the informational
areas contained within the original document. After the
electrostatic latent image is recorded on the photoconductive
member, the latent image is developed by bringing a developer
material into contact therewith. Generally, the developer material
comprises toner particles adhering triboelectrically to carrier
granules. The toner particles are attracted from the carrier
granules to the latent image forming a toner powder image on the
photoconductive member. The toner powder image is then transferred
from the photoconductive member to a copy sheet. The toner
particles are heated to permanently affix the powder image to the
copy sheet.
[0003] High quality documents require registration of sheets of
paper or other substrate to the photoreceptor for image transfer.
Accurate registration control locates the image consistently with
respect to the edge of the paper. Typical registration devices
require that incoming sheets arrive within a specific lateral range
in order to be properly registered. Additionally, other devices,
such as compiling trays within an output module, require that
incoming sheets arrive within a specific lateral range in order to
be properly processed. However, as printing systems become larger
and more complex, it becomes increasingly difficult to maintain
control of the lateral position of sheets within the system. This
invention describes a device for adjusting the lateral position of
a sheet in a paper path using relatively inexpensive
components.
[0004] In accordance with one aspect of the present invention there
is provided an apparatus for registering a sheet along a transport
path, including a plurality of spaced apart sheet feeding nip sets
of plural sheet feeding nips in said sheet transport path, said
plural sheet feeding nips of said sheet feeding nip sets comprise
plural drive wheels and plural mating idlers, steerable mechanism
for changing the idler alignment relative to its respective drive
wheel to thereby transport said sheet along the paper path while
imparting a lateral motion to the sheet as it is transported along
the paper path.
[0005] Other features of the present invention will become apparent
as the following description proceeds and upon reference to the
drawings, in which:
[0006] FIG. 1 is a schematic elevational view depicting an
illustrative electrophotographic printing machine incorporating a
sheet registration device of the present invention;
[0007] FIG. 2 is a detailed plan view of the sheet registration
device;
[0008] FIG. 3 is a plan view of the sheet registration device
illustrating the method of operation thereof
[0009] While the present invention will be described in connection
with a preferred embodiment thereof, it will be understood that it
is not intended to limit the invention to that embodiment. On the
contrary, it is intended to cover all alternatives, modifications,
and equivalents as may be included within the spirit and scope of
the invention as defined by the appended claims.
[0010] For a general understanding of the features of the present
invention, reference is made to the drawings. In the drawings, like
reference numerals have been used throughout to identify identical
elements. FIG. 1 schematically depicts an electrophotographic
printing machine incorporating the features of the present
invention therein. It will become evident from the following
discussion that the set transfer device of the present invention
may be employed in a wide variety of machines and is not
specifically limited in its application to the particular
embodiment depicted herein.
[0011] Referring to FIG. 1 of the drawings, the electrophotographic
printing machine employs a photoconductive belt 10. Preferably, the
photoconductive belt 10 is made from a photoconductive material
coated on a ground layer, which, in turn, is coated on an anti-curl
backing layer. The photoconductive material is made from a
transport layer coated on a selenium generator layer. The transport
layer transports positive charges from the generator layer. The
generator layer is coated on an interface layer. The interface
layer is coated on the ground layer made from a titanium coated
MYLAR.RTM.. The interface layer aids in the transfer of electrons
to the ground layer. The ground layer is very thin and allows light
to pass therethrough. Other suitable photoconductive materials,
ground layers, and anti-curl backing layers may also be employed.
Belt 10 moves in the direction of arrow 12 to advance successive
portions sequentially through the various processing stations
disposed about the path of movement thereof. Belt 10 is entrained
about stripping roller 14, tensioning roller 16, idler roll 18 and
drive roller 20. Stripping roller 14 and idler roller 18 are
mounted rotatably so as to rotate with belt 10. Tensioning roller
16 is resiliently urged against belt 10 to maintain belt 10 under
the desired tension. Drive roller 20 is rotated by a motor coupled
thereto by suitable means such as a belt drive. As roller 20
rotates, it advances belt 10 in the direction of arrow 12.
[0012] Initially, a portion of the photoconductive surface passes
through charging station A. At charging station A, two corona
generating devices indicated generally by the reference numerals 22
and 24, charge the photoconductive belt 10 to a relatively high,
substantially uniform potential. Corona generating device 22 places
all of the required charge on photoconductive belt 10. Corona
generating device 24 acts as a leveling device, and fills in any
areas missed by corona generating device 22. Next, the charged
portion of the photoconductive surface is advanced through imaging
station B.
[0013] At imaging station B, a raster output scanner (ROS),
indicated generally by the reference numeral 26, discharges
selectively those portions of the charge corresponding to the image
portions of the document to be reproduced. In this way, an
electrostatic latent image is recorded on the photoconductive
surface. An electronic subsystem (ESS), indicated generally by the
reference numerals 28, controls ROS 26. ESS 28 is adapted to
receive signals from a computer and transpose these signals into
suitable signals for controlling ROS 26 so as to record an
electrostatic latent image corresponding to the document to be
reproduced by the printing machine. ROS 26 may include a laser with
a rotating polygon mirror block. The ROS 26 illuminates the charged
portion of the photoconductive surface. In this way, a raster
electrostatic latent image is recorded on the photoconductive
surface which corresponds to the desired information to be printed
on the sheet. Other types of imaging systems may also be used
employing, for example, a pivoting or shiftable LED write bar or
projection LCD (liquid crystal display) or other electro-optic
display as the "write" source.
[0014] Thereafter, belt 10 advances the electrostatic latent image
recorded thereon to development station C. Development station C
has three magnetic brush developer rolls indicated generally by the
reference numerals 34, 36 and 38. A paddle wheel picks up developer
material and delivers it to the developer rolls. When the developer
material reaches rolls 34 and 36, it is magnetically split between
the rolls with half of the developer material being delivered to
each roll. Photoconductive belt 10 is partially wrapped about rolls
34 and 36 to form extended development zones. Developer roll 38 is
a clean-up roll. A magnetic roll, positioned after developer roll
38, in the direction of arrow 12 is a carrier granule removal
device adapted to remove any carrier granules adhering to belt 10.
Thus, rolls 34 and 36 advance developer material into contact with
the electrostatic latent image. The latent image attracts toner
particles from the carrier granules of the developer material to
form a toner powder image on the photoconductive surface of belt
10. Belt 10 then advances the toner powder image to transfer
station D.
[0015] At transfer station D, a copy sheet is moved into contact
with the toner powder image. First, photoconductive belt 10 is
exposed to a pre-transfer light from a lamp (not shown) to reduce
the attraction between photoconductive belt 10 and the toner powder
image. Next, a corona generating device 40 charges the copy sheet
to the proper magnitude and polarity so that the copy sheet is
tacked to photoconductive belt 10 and the toner powder image
attracted from the photoconductive belt to the copy sheet. After
transfer, corona generator 42 charges the copy sheet to the
opposite polarity to detack the copy sheet from belt 10. Conveyor
44 advances the copy sheet to fusing station E.
[0016] Fusing station E includes a fuser assembly indicated
generally by the reference numeral 46 which permanently affixes the
transferred toner powder image to the copy sheet. Preferably, fuser
assembly 46 includes a heated fuser roller 48 and a pressure roller
50 with the powder image on the copy sheet contacting fuser roller
48. The pressure roller is cammed against the fuser roller to
provide the necessary pressure to fix the toner powder image to the
copy sheet. The fuser roll is internally heated by a quartz lamp.
Release agent, stored in a reservoir, is pumped to a metering roll.
A trim blade trims off the excess release agent. The release agent
transfers to a donor roll and then to the fuser roll.
[0017] After fusing, the copy sheets are fed through a decurler 52.
Decurler 52 bends the copy sheet in one direction to put a known
curl in the copy sheet and then bends it in the opposite direction
to remove that curl. Forwarding rollers 54 then advance the sheet
to duplex turn roll 56. Duplex solenoid gate 58 guides the sheet to
the finishing station F, or to duplex tray 60. At finishing station
F, copy sheets are stacked in a compiler tray and attached to one
another to form sets. The sheets can be attached to one another by
either a binder or a stapler. In either case, a plurality of sets
of documents is formed in finishing station F. When duplex solenoid
gate 58 diverts the sheet into duplex tray 60. Duplex tray 60
provides an intermediate or buffer storage for those sheets that
have been printed on one side and on which an image will be
subsequently printed on the second, opposite side thereof, i.e.,
the sheets being duplexed. The sheets are stacked in duplex tray 60
face down on top of one another in the order in which they are
copied.
[0018] In order to complete duplex copying, the simplex sheets in
tray 60 are fed, in seriatim, by bottom feeder 62 from tray 60 back
to transfer station D via conveyor 64 and rollers 66 for transfer
of the toner powder image to the opposed sides of the copy sheets.
Inasmuch as successive bottom sheets are fed from duplex tray 60,
the proper or clean side of the copy sheet is positioned in contact
with belt 10 at transfer station D so that the toner powder image
is transferred thereto. The duplex sheet is then fed through the
same path as the simplex sheet to be advanced to finishing station
F.
[0019] Copy sheets are fed to transfer station D from the secondary
tray 68. The secondary tray 68 includes an elevator driven by a
bidirectional AC motor. Its controller has the ability to drive the
tray up or down. When the tray is in the down position, stacks of
copy sheets are loaded thereon or unloaded therefrom. In the up
position, successive copy sheets may be fed therefrom by sheet
feeder 70. Sheet feeder 70 is a friction retard feeder utilizing a
feed belt and take-away rolls to advance successive copy sheets to
transport 64 which advances the sheets to rolls 98 which feed the
sheets to the registration device of the invention herein,
described in detail below, and then to transfer station D.
[0020] Copy sheets may also be fed to transfer station D from the
auxiliary tray 72. The auxiliary tray 72 includes an elevator
driven by a directional AC motor. Its controller has the ability to
drive the tray up or down. When the tray is in the down position,
stacks of copy sheets are loaded thereon or unloaded therefrom. In
the up position, successive copy sheets may be fed therefrom by
sheet feeder 74. Sheet feeder 74 is a friction retard feeder
utilizing a feed belt and take-away rolls to advance successive
copy sheets to transport 64 which advances the sheets to rolls 98
to the registration device and then to transfer station D.
[0021] Secondary tray 68 and auxiliary tray 72 are secondary
sources of copy sheets. The high capacity sheet feeder, indicated
generally by the reference numeral 76, is the primary source of
copy sheets. Feed belt 81 feeds successive uppermost sheets from
the stack to a take-away drive roll 82 and idler rolls 84. The
drive roll and idler rolls guide the sheet onto transport 86.
Transport 86 advances the sheet to rolls 98 which, in turn, move
the sheet through the registration device to transfer station
D.
[0022] Invariably, after the copy sheet is separated from the
photoconductive belt 10, some residual particles remain adhering
thereto. After transfer, photoconductive belt 10 passes beneath
corona generating device 94 which charges the residual toner
particles to the proper polarity. Thereafter, the pre-charge erase
lamp (not shown), located inside photoconductive belt 10,
discharges the photoconductive belt in preparation for the next
charging cycle. Residual particles are removed from the
photoconductive surface at cleaning station G. Cleaning station G
includes an electrically biased cleaner brush 88 and two de-toning
rolls. The reclaim roll is electrically biased negatively relative
to the cleaner roll so as to remove toner particles therefrom. The
waste roll is electrically biased positively relative to the
reclaim roll so as to remove paper debris and wrong sign toner
particles. The toner particles on the reclaim roll are scraped off
and deposited in a reclaim auger (not shown), where it is
transported out of the rear of cleaning station G.
[0023] The various machine functions are regulated by a controller
29. The controller 29 is preferably a programmable microprocessor
which controls the entire machine functions hereinbefore described.
The controller provides a comparison count of the copy sheets, the
number of documents being recirculated, the number of copy sheets
selected by the operator, time delays, jam corrections, etc. The
control of all of the exemplary systems heretofore described may be
accomplished by conventional control switch inputs from the
printing machine consoles selected by the operator. Conventional
sheet path sensors or switches may be utilized to keep track of the
position of the document and the copy sheets. In addition, the
controller regulates the various positions of the gates depending
upon the mode of operation selected.
[0024] The invention herein has been illustrated in a high speed
black and white printing machine. It is also very suitable for use
in a high speed full color or highlight color printing machine
where accurate sheet registration is critical.
[0025] High quality documents require registration of sheets of
paper to the photoreceptor for image transfer. Accurate
registration control locates the image consistently with respect to
the edge of the paper. In order to provide this accurate
registration control, the registration device accepts incoming
sheets having unknown position and orientation and delivers them to
transfer station D with the sheet edges aligned to predetermined
datums. The registration device performs this function over a
limited range of incoming sheet position and orientation. Notably,
there is a limited range of lateral position that the registration
device can accommodate. In many systems, this condition may be
difficult to guarantee because of the various and potentially long
paths that sheets may take from various sources such as feeders or
duplex paths. Because of manufacturing tolerances and wear effects,
it is typical that the average lateral incoming sheet position from
each of these various sources can vary substantially from one
another. It is therefore desired to have a compact and inexpensive
means to adjust the average lateral incoming position of sheets
from one or more of these sources in order to reduce the total
incoming lateral sheet variation that is delivered to the
registration device.
[0026] FIG. 2 shows a device suitable for adjusting the lateral
position of the paper. Axles 302-308 are driven by a common direct
drive motor, timing belt drive system or any other suitable drive
method (not shown). The accuracy of this drive is not very
important and thus can be inexpensive. Mounted on axles 302-308 are
drive rollers. Axles 202-208 have mounted thereon idle rollers
which are mounted above respective drive rollers thus forming a
sheet feeding nip set. Axles 302-308 are mounted in a fixed
position and are aligned in a position substantially parallel to
each other and parallel to the lateral axis of the paper path.
Axles 203-207 are connected to each other by a steering mechanism
200 in which axles 203-207 are aligned and pivot in a position
substantially parallel to each other. Steering mechanism 200 is
connected to an actuator which positions the angle of the axles
203-207 thereby changing each idler roller alignment relative to
its respective drive roller. Steering control can be accomplished
by a mechanical actuator such as an adjustment screw or rotary cam,
not shown. It is also possible for the actuator to be a solenoid or
stepper/dc motor with lead screw with stops or home sensors.
[0027] It has been observed that sheets will walk in the lateral
axis along a paper transport depending on the idler roll alignment
to the drive rolls. So long as the first nip and last nip in a
transport are parallel, the net skew induced in the sheet is
substantially zero, but the net lateral walk can be significant.
This behavior has been found to occur when using elastomeric drive
rolls together with thermoplastic idler rolls. The lateral
compliance, or the amount that a roll elastically distorts along
its lateral axis when subjected to a tangential force parallel to
the lateral axis, is a function of the roll material properties. It
has been observed that the lateral compliance of an elastomeric
drive roll is substantially higher than that of a thermoplastic
idler roll. It has further been observed that, under the above
circumstances, the sheet motion will tend to align to the idler
rolls. So deliberately misaligning the idler shafts relative to the
drive shafts in a sheet transport in order to induce lateral walk
in the sheet. This effect can be used to correct for average shifts
in lateral sheet position that may have accumulated in prior
transports. It is possible to simply adjust one or several of the
intermediate idler shafts to a plus, neutral, or minus setting to
achieve varying degrees of lateral walk in the transport. The
present disclosure makes alignment much easier than moving the
whole modules.
[0028] FIG. 3 illustrates the sheet motion achieved by using the
described strategy. Actuator 102 has adjusted the idler axles 203,
204, 205, 206 and 207 to a counterclockwise rotation relative to
the drive roll axles, not shown. As a sheet enters nip formed by
idler axle 203, a small skew angle is formed. As the sheet advances
further, this skew angle is maintained and the sheet moves
laterally according to the idler axle alignment. As the sheet
reaches the nip formed by idler axle 208, an opposite skew is
formed, thus resulting in substantially zero net skew imparted to
the sheet. However, it can be seen that a net lateral shift in the
sheet position has been achieved. The actuator adjustment is made
based upon the average exiting lateral position of sheets, so that
the next downstream transport, such as a registration device,
receives sheets within a predefined lateral position range. The
actuator adjustments can be made manually by an operator or can be
made automatically by a suitable controller. If, for example, a
sensor 134 is provided near the exit of the transport, and if
sensor 134 is placed at the desired lateral exit position of the
transport, then the actuator can automatically vary the idler axle
alignment until the average sheet exit lateral position corresponds
to sensor 134 location.
[0029] In recapitulation, there is provided an apparatus for
laterally positioning a sheet along a transport path, including a
plurality of spaced apart sheet feeding nip sets of plural sheet
feeding nips in said sheet transport path, said plural sheet
feeding nips of said sheet feeding nip sets comprise plural drive
wheels and plural mating idlers, steerable drive mechanism for
changing the idler alignment relative to the respective drive wheel
to thereby transport said sheet along the paper path while
imparting a lateral motion to the sheet as it is transported along
the paper path.
[0030] It is, therefore, apparent that there has been provided in
accordance with the present invention, a sheet registration device
that fully satisfies the aims and advantages hereinbefore set
forth. While this invention has been described in conjunction with
a specific embodiment thereof, it is evident that many
alternatives, modifications, and variations will be apparent to
those skilled in the art. Accordingly, it is intended to embrace
all such alternatives, modifications and variations that fall
within the spirit and broad scope of the appended claims.
[0031] It will be appreciated that various of the above-disclosed
and other features and functions, or alternatives thereof, may be
desirably combined into many other different systems or
applications. Also that various presently unforeseen or
unanticipated alternatives, modifications, variations or
improvements therein may be subsequently made by those skilled in
the art which are also intended to be encompassed by the following
claims. Unless specifically recited in a claim, steps or components
of claims should not be implied or imported from the specification
or any other claims as to any particular order, number, position,
size, shape, angle, color, or material.
* * * * *