Belt alignment system

An apparatus which controls lateral alignment of a belt arranged to move along a predetermined path. The belt is supported by a pivoted roller. A member having a pair of opposed, spaced flanges extending outwardly therefrom is mounted slidably on a shaft extending outwardly from one end of the roller. A spring, contacting the flanged member, resiliently urges one of the flanges into continuous engagement with one side of the belt. Movement of the belt from the predetermined path slides the flanged member so that one of the flanges frictionally rotates a disc interposed therebetween. Rotation of the disc tilts the roller restoring the belt to the predetermined path of movement.

This invention relates generally to an electrophotographic printing 
machine, and more particularly concerns an improved apparatus for 
controlling the lateral movement of a moving belt. 
In the process of electrophotographic printing, a photoconductive belt is 
charged to a substantially uniform potential so as to sensitize the 
surface thereof. The charged portion of the photoconductive belt is 
exposed to a light image of an original document being reproduced. 
Exposure of the charged photoconductive belt selectively discharges the 
charge thereon in the irradiated areas. This records an electrostatic 
latent image on the photoconductive belt corresponding to the 
informational areas contained within the original document. After the 
electrostatic latent image is recorded on the photoconductive belt, the 
latent image is developed by bringing a developer mixture into contact 
therewith. Generally, the developer mixture 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 belt. The toner powder image is then 
transferred from the photoconductive belt to a copy sheet. Finally, the 
copy sheet is heated to permanently affix the toner particles thereto in 
image configuration. 
As electrophotographic printing machines become increasingly rapid, 
automatic handling of original documents is highly desirable. The document 
handling system must be capable of recirculating either simplex or duplex 
sheets. The document handling unit must operate flawlessly to virtually 
eliminate the risk of damaging the original document and minimizing 
machine shutdowns due to jams or misfeeds. Frequently, this is achieved 
through the utilization of endless belts entrained about rollers for 
advancing the document through at least a portion of its path of travel. 
Since the photoconductive belt in the printing machine passes through many 
processing stations during the printing operation, lateral alignment 
thereof is critical and must be controlled within prescribed tolerances. 
As the photoconductive belt passes through each of these processing 
stations, the location of the latent image must be precisely defined in 
order to optimize the operations relative to one another. If the position 
of the latent image deviates from processing station to processing 
station, copy quality may be significantly degraded. Hence, lateral 
movement of the photoconductive belt must be minimized so that the belt 
moves in a predetermined path. 
Similarly, the belt of the document handling system employed to transport 
original documents to and from the exposure station must move through a 
predetermined path. The lateral movement of the belt used in the document 
handling system must be controlled in order to insure the correct 
positioning of the original document relative to the optical system of the 
exposure station. 
Ideally if the belt were perfectly constructed and entrained about 
perfectly cylindrical rollers secured in an exactly parallel relationship 
with one another, the velocity vector of the belt would be substantially 
normal to the longitudinal axis of the roller and there would be no 
lateral translation of the belt. However, in actual practice, this is not 
feasible. Frequently, the velocity vector of the belt approaches the 
longitudinal axis of the roller at an angle. This produces lateral 
movement of the belt relative to the roller. Thus, the belt must be 
tracked or controlled to regulate its lateral position. Hereinbefore, 
lateral movement of the belt has been controlled by crowned rollers, 
flanged rollers or servo systems. Rollers of this type frequently produce 
high local stresses resulting in damage to the edges of the belt. Servo 
systems using steering rollers to maintain lateral control of the belt 
generally apply less stress to the sides thereof. However, servo systems 
are frequently rather complex and costly. 
Various attempts have been made to develop simple and less costly steering 
systems. The following art appears to disclose relevant devices which 
control the lateral movement of a moving belt: 
U.S. Pat. No. 3,435,693 
Patentee: Wright et al. 
Issued: Apr. 1, 1969 
U.S. Pat. No. 3,500,694 
Patentee: Jones et al. 
Issued: Mar. 17, 1970 
U.S. Pat. No. 3,540,571 
Patentee: Morse 
Issued: Nov. 17, 1970 
U.S. Pat. No. 3,698,540 
Patentee: Jorden 
Issued: Oct. 17, 1972 
U.S. Pat. No. 3,702,131 
Patentee: Stokes et al. 
Issued: Nov. 7, 1972 
U.S. Pat. No. 3,818,391 
Patentee: Jorden et al. 
Issued: June 18, 1974 
Research Disclosure Journal May 9, 1976 
Author: Morse et al. 
No. 14510, Page 29 
U.S. Ser. No. 140,342 
Filed: Apr. 14, 1980 
Applicant: Hamaker 
U.S. Ser. No. 168,938 
Filed: July 11, 1980 
Applicant: Hamaker 
The pertinent portions of the foregoing art may be briefly summarized as 
follows: 
Wright et al. discloses a belt entrained about a plurality of spaced 
rollers. One end of the rollers is journaled in a pivotable frame. A 
sensing member is forced to the right by the lateral movement of the belt. 
The sensing member is connected by a linkage to the frame. If the belt is 
forced against the sensing member, the linkage rotates the frame to a 
position where the belt will track away from the sensing member until 
equilibrium is reached. 
Jones et al. describes a belt tracking system in which a sensing finger 
detects lateral movement of the belt and actuates a control motor. The 
control motor rotates a cam shaft which rotates a camming mechanism to 
pivot a steering roller so as to return the belt to the desired path of 
travel. 
Morse discloses a belt tracking system having a washer journaled loosely on 
a steering roller shaft. A pressure roller contacts the washer. The 
pressure roller is mounted on a pivotable rod and connected pivotably to a 
servo arm. The servo arm is connected pivotably to the frame. Horizontal 
motion of the belt causes the pressure roller to move horizontally. This 
moves the servo arm vertically pivoting the steering roller to restore the 
belt to the desired path. 
Jorden, Stokes et al. and Jorden et al. all describe a belt steering 
apparatus employing a disc mounted loosely on one end of a belt support 
roller. The disc is connected to a linkage which pivots one of the other 
support rollers. Lateral movement of the belt causes the disc to translate 
pivoting the linkage. The linkage pivots the other support roller 
returning the belt to the predetermined path of movement. 
Morse et al. discloses a passive web tracking system. The web is supported 
in a closed loop path by a plurality of supports. The supports include a 
first roller. The first roller is pivotably mounted to align its axis of 
rotation to the normal direction of travel of the web. Fixed flanges 
engage the side edges of the web preventing lateral movement thereof. A 
second roller, spaced from the first roller, is supported at its midpoint 
by a self-aligning radial ball bearing. A yoke supports the second roller 
pivotably. Movement of the roller is limited to rotation about a castering 
axis and a gimble axis by a flecture arm. This permits the web to change 
direction providing uniform tension in the web span. 
Hamaker ('342) describes a belt steering mechanism employing a pivotably 
mounted belt support roller frictionally driven to move in unison with the 
belt. Lateral movement of the belt applies a frictional force on the belt 
roller. The frictional force tilts the roller in a direction so as to 
restore the belt to the predetermined path of movement. 
Hamaker ('938) discloses a belt alignment system in which the belt is 
supported to form an arcuate region. A guide engages the side edge of the 
belt in the arcuate region to prevent lateral movement thereof. 
In accordance with one aspect of the features of the present invention, 
there is provided an apparatus for controlling lateral alignment of a belt 
arranged to move along a predetermined path. The apparatus includes means 
for pivotably supporting the belt. Means sense the lateral movement of the 
belt from the predetermined path and translate relative to the supporting 
means in response thereto. Means, normally spaced from the sensing means 
during belt movement along the predetermined path, tilt the supporting 
means in response to being rotated by the sensing means so as to return 
the belt to the predetermined path of movement. 
Pursuant to another aspect of the features of the present invention, there 
is provided an electrophotographic printing machine of the type having a 
photoconductive belt arranged to move in a predetermined path through a 
plurality of processing stations disposed therealong. The printing machine 
includes means for pivotably supporting the belt. Means are provided for 
sensing the lateral movement of the belt from the predetermined path and 
translating relative to the supporting means in response thereto. Means, 
normally spaced from the translating means during belt movement along the 
predetermined path, tilt the supporting means in response to being rotated 
by the sensing means so as to return the belt to the predetermined path of 
movement. 
Still another aspect of the features of the present invention is a 
reproducing machine of the type having a document handling system 
comprising a belt arranged to move in a predetermined path to transport a 
document to a processing station. The reproducing machine includes means 
for pivotably supporting the belt. Means are provided for sensing the 
lateral movement of the belt from the predetermined path and translating 
in response thereto. Means, normally spaced from the sensing means during 
belt movement along the predetermined path, tilt the supporting means in 
response to being rotated by the sensing means so as to return the belt to 
the predetermined path of movement.

While the present invention will hereinafter 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. 
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 designate identical elements. FIG. 1 
schematically depicts the various components of an illustrative 
electrophotographic printing machine incorporating the belt control system 
of the present invention therein. As illustrated hereinafter, the belt 
control system is employed in both the document handling unit and the 
photoconductive belt support system. It will become evident from the 
following discussion that the belt control system is equally well suited 
for use in a wide variety of printing machines, and is not necessarily 
limited in its application to the particular printing machine shown 
herein. 
Inasmuch as the art of electrophotographic printing is well known, the 
various processing stations employed in the FIG. 1 printing machine will 
be shown hereinafter schematically and their operation described briefly 
with reference thereto. 
As shown in FIG. 1, the electrophotographic printing machine employs a belt 
10 having a photoconductive surface 12 deposited on a conductive substrate 
14. Preferably, photoconductive surface 12 is made from a selenium alloy 
with conductive substrate 14 being made from an aluminum alloy. Other 
suitable photoconductive materials and conductive substrates may also be 
employed. Belt 10 moves in the direction of arrow 16 to advance successive 
portions of photoconductive surface 12 sequentially through the various 
processing stations disposed about the path of movement thereof. Belt 10 
is entrained about a stripping roller 18, steering roller 20 and drive 
roller 22. Stripping roller 18 is mounted rotatably so as to rotate with 
the movement of belt 10. Steering roller 20 tilts in response to lateral 
movement of belt 10 to restore belt 10 to the desired path of travel. 
Drive roller 22 is rotated by motor 24 coupled thereto by suitable means 
such as a drive belt. As roller 22 rotates, it advances belt 10 in the 
direction of arrow 16. 
Initially, a portion of the photoconductive surface passes through charging 
station A. At charging station A, a corona generating device, indicated 
generally by the reference numeral 26, charges photoconductive surface 12 
to a relatively high, substantially uniform potential. 
Next, the charged portion of photoconductive surface 12 is advanced through 
imaging station B. At imaging station B, a document handling unit, 
indicated generally by the reference numeral 28, is positioned over platen 
30 of the printing machine. Document handling unit 28 sequentially feeds 
documents from a stack 32 of documents placed by the operator facedown in 
a normal forward collated order in a document stacking and holding tray 
34. A document feeder 36 located below tray 34 forwards the bottom 
document in the stack to a pair of takeaway rollers 38. The bottommost 
sheet is then fed by rollers 38 through document guide 40 to feed roll 
pair 42 and belt 44. Belt 44 is entrained about a pair of opposed spaced 
rollers 46 and 48, respectively. Roller 46 is a steering roller which 
tilts to maintain belt 44 in the predetermined path of movement. After 
imaging, the original document is fed from platen 30 by belt 44 into guide 
50 and feed roll pairs 52 and 54. The document then advances into an 
inverter mechanism, indicated generally by the reference numeral 56, or 
back to the document stack through feed roll pair 58. Decision gate 60 is 
provided to divert the document either to the inverter or to feed roll 
pair 58. The inverter comprises a three-roll arrangement and a closed 
inverter pocket. If the document is to be inverted, it is fed through the 
lower two rolls of the three-roll inverter into the pocket. When the trail 
edge of the document clears the nip of the lower two rolls in the 
three-roll inverter, the stiffness of the sheet will cause the trail edge 
to straighten up into the nip of the upper two rollers of the inverter at 
which time it will be fed into roll pair 58 and back onto the document 
stack. Document handling unit 28 is also provided with a sheet separator 
finger to separate the documents to be fed from those documents returned 
to tray 34. Upon removal of the last document from beneath the finger, the 
finger drops through a slot provided in the tray, suitable sensors are 
provided to sense that the last document in the set has been removed from 
the tray, and the finger is rotated in a clockwise direction to again rest 
on the top of the stack of documents prior to subsequent recirculation of 
the document set. Imaging of a document on platen 30 is achieved by lamps 
62 which illuminate the document positioned thereon. Light rays reflected 
from the document are transmitted through lens 64. Lens 64 focuses the 
light image of the original document onto the charged portion of the 
photoconductive surface of belt 10 to selective dissipate the charge 
thereof. This records an electrostatic latent image on the photoconductive 
surface which corresponds to the informational areas contained within the 
original document. Thereafter, belt 10 advances the electrostatic latent 
image recorded on the photoconductive surface to development station C. 
The detailed structure of belt steering roller 46 and photoconductive belt 
steering roller 20, both of which are substantially identical, will be 
described hereinafter with reference to FIGS. 2 through 6, inclusive. 
With continued reference to FIG. 1, at development station C, a pair of 
magnetic brush developer rollers, indicated generally by the reference 
numerals 66 and 68, 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. At 
transfer station D, a copy sheet is moved into contact with the toner 
powder image. Transfer station D includes a corona generating device 70 
which sprays ions onto the backside of the copy sheet. This attracts the 
toner powder image from the photoconductive surface of belt 10 to the 
sheet. After transfer, conveyor 72 advances the sheet to fusing station E. 
The copy sheets are fed from a selected one of the trays 74 or 76 to 
transfer station D. After transfer of the toner powder image to the first 
side of the copy sheet, the sheet is advanced by vacuum conveyor 72 to 
fusing station E. 
Fusing station E includes a fuser assembly, indicated generally by the 
reference numeral 78, which permanently affixes the transferred powder 
image to the copy sheet. Preferably, fuser assembly 78 includes a heated 
fuser roller 80 and a backup roller 82. The sheet passes between fuser 
roller 80 and backup roller 82 with the powder image contacting fuser 
roller 80. In this manner, the powder image is permanently affixed to the 
copy sheet. 
After fusing, the copy sheets are fed to gate 84 which functions as an 
inverter selector. Depending upon the position of gate 84, the copy sheets 
will be deflected into a sheet inverter 86 or bypass inverter 86 and be 
fed directly onto a second decision gate 88. The sheets which bypass 
inverter 86 turn a 90.degree. corner in the sheet path before reaching 
gate 88. Gate 88 inverts the sheets into a face up orientation so that the 
image side, which has been transferred or fused, is face up. If inverter 
path 86 is selected, the opposite is true, i.e. the last printed side is 
facedown. The second decision gate 88 either deflects the sheet directly 
into an output tray 90 or deflects the sheets into a transport path which 
carries them on without inversion to a third decision gate 92. Gate 92 
either passes the sheets directly on without inversion into the output 
path of the copier, or deflects the sheets onto a duplex inverter roll 94. 
Roll 94 inverts and stacks sheets to be duplexed in a duplex tray 96 when 
gate 92 so directs. Duplex tray 96 provides intermediate or buffer storage 
for those sheets which have been printed on one side on which an image 
will be subsequently printed on the side opposed thereto, i.e. the sheets 
being duplexed. Due to sheet inverting by roll 94, these buffer sheets are 
stacked in tray 96 facedown. They are stacked in duplex tray 96 on top of 
one another in the order in which they are copied. 
In order to complete duplex copying, the simplex sheets in tray 96 are fed 
in seriatim by bottom feeder 98 from tray 96 back to transfer station D 
for transfer of the toner powder image to the opposed side of the copy 
sheet. Conveyor 100 and rollers 102 advance the sheet along a path which 
produces an inversion thereof. However, inasmuch as the bottommost sheet 
is fed from duplex tray 96, 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 thereon is transferred thereto. The duplex sheets are then 
fed through the same path as the simplex sheets to be stacked in tray 90 
for subsequent removal by the printing machine operator. 
With continued reference to FIG. 1, invariably after the copy sheet is 
separated from the photoconductive surface of belt 10, some residual 
particles remain adhering thereto. These residual particles are removed 
from the photoconductive surface at cleaning station F. Cleaning station F 
includes a rotatably mounted fibrous brush 104 in contact with the 
photoconductive surface of belt 10. The particles are cleaned from the 
photoconductive surface of belt 10 by the rotation of brush 104 in contact 
therewith. Subsequent to cleaning a discharge lamp (not shown) floods the 
photoconductive surface with light to dissipate any residual electrostatic 
charge remaining thereon prior to the charging thereof for the next 
successive imaging cycle. 
Controller 106 is preferably a programmable microprocessor which controls 
all the machine functions hereinbefore described. The controller provides 
the storage and comparison of counts of the copy sheets, the number of 
documents being recirculated in the document sets, the number of copy 
sheets selected by the operator, time delays, jam correction control, 
etc.. The control of all the exemplary systems heretofore described may be 
accomplished by conventional control switch inputs from the printing 
machine console selected by the operator. These signals activate 
nonelectrical, solenoid or jam control sheet deflector fingers, or drive 
motors, or their clutches in the selected steps or sequences. Conventional 
sheet path sensors or switches may be utilized for counting or keeping 
track of the position of the document and copy sheets. 
It is believed that the foregoing description is sufficient for purposes of 
the present application to illustrate the general operation of an 
electrophotographic printing machine incorporating the features of the 
present invention therein. 
Referring now to the specific subject matter of the present invention, the 
general operation of the belt steering system employed in conjunction with 
steering roller 46 for document handling unit 28 or steering roller 20 for 
photoconductive belt 10, will be described hereinafter with reference to 
FIGS. 2 through 6, inclusive. Both steering roller 46 and steering roller 
20 are substantially identical to one another. 
For purposes of illustration, the belt steering system associated with 
steering roller 46 of document handling unit 28 will be described 
hereinafter. As shown in FIGS. 2 and 3, steering roller 46 is mounted 
rotatably in holder 108. Holder 108 is mounted pivotably on frame 110. In 
this way, any providing of holder 108 will tilt steering roller 46. 
Elongated roller 46 is mounted rotatably in suitable bearings in holder 
108. An elongated shaft 112 extends outwardly from one side of roller 46. 
A pair of opposed spaced flanges 114 and 116 extend outwardly from member 
118 mounted slidably on shaft 112. Disc 120 is interposed between flanges 
114 and 116. The surfaces of flanges 114 and 116 opposed from disc 120 are 
conical. Disc 120 has a rod 122 extending outwardly therefrom. Rod 122 has 
a threaded portion 124 in threaded engagement with holder 108. Free end 
portion 126 of rod 122 engages stop plate 128. In this way, rotation of 
disc 120 causes rod 122 to rotate. As rod 122 rotates, the threaded 
portion, i.e. portion 124 thereof, pivots holder 108 relative to frame 
110. Spring 130 is in engagement with flange 116 to resiliently urge 
flange 114 into contact with belt 10. Pin 132 is located in a slot in 
member 118. In this way, pin 132 secures member 118 to shaft 112 
permitting member 118 to slide relative thereto while rotating therewith. 
In operation, as belt 44 moves in the direction of arrow 134, side edge 136 
of belt 44 engages one side of flange 118. This causes member 112 and 
flanges 114 and 116 to slide in the direction of arrow 134. The resilient 
force applied by spring 130 maintains flange 114 in engagement with edge 
136 of belt 44. The conical surface of flange 114 engages disc 120. As 
flange 114 rotates with roller 46, disc 120 is frictionally rotated about 
its axis. Threaded portion 124 rotates with rod 122 to pivot holder 108 
and tilt roller 46 moving belt 44 in the direction of arrow 138. In this 
way, belt 10 returns to the predetermined path of travel. 
In the event belt 10 moves in the direction of arrow 138, spring 130 
resiliently urges flange 114 against side edge 136 thereof. Member 118 
slides on shaft 112 until the conical surface of flange 116 engages disc 
120. As roller 46 rotates, member 118 and flanges 114 and 116 rotate 
therewith. In this way, flange 116 frictionally rotates disc 120 in a 
direction opposite to that of flange 114. Thus, threaded portion 124 
pivots holder 108 in the opposite direction to that produced by the 
rotation of disc 120 by flange 114. Rotation of disc 120 pivots holder 108 
to tilt roller 46 such that belt 10 moves in the direction of arrow 134 
toward the predetermined path of travel. 
If the tilting of roller 46 in the proper direction does not provide 
sufficient force to stop the belt from moving laterally, member 118 will 
move unit it hits a stop, i.e. pin 132 acts as a stop. At this point, belt 
44 becomes edge guided with some of the restraining force being provided 
by surface friction. The conical surfaces of flanges 114 and 116 
automatically disengage from disc 120 preventing abuse and wear thereof. 
Referring now to FIG. 4, there is shown a side view of the belt control 
system depicted in FIGS. 2 and 3. As illustrated thereat, belt 44 is 
entrained about roller 46. The conical surfaces of flanges 114 and 116 are 
adapted to engage and frictionally rotate disc 120 which, in turn, rotates 
rod 122. Rod 122 has a threaded portion 124 in threaded engagement with 
holder 108. Holder 108 is pivoted about pin 140. Stop plate 128 engages 
free end portion 126 of rod 122 to prevent translation thereof. Threaded 
portion 124 of rod 122 rotates with disc 120 to pivot holder 108 about pin 
140. As holder 108 pivots, roller 46 tilts in a direction such that belt 
44 returns to the predetermined path of travel. 
Referring now to FIG. 5, there is shown one embodiment of disc 120 with rod 
122 having threaded portion 124 thereof in threaded engagement with 
threaded portion 142 of holder 108. As shown thereat, threaded portion 142 
extends only over a portion of holder 108 with the remaining portion 144 
thereof being a counterbored hole to provide clearance for rod 122. Thus, 
threaded portion 124 of rod 122 is in threaded engagement with the 
threaded portion 142 of holder 108. Free end portion 126 of rod 122 
engages stop plate 128. Rotation of disc 120 causes corresponding rotation 
of rod 122 and threaded portion 124 in threaded portion 142 of holder 108. 
This causes holder 108 to pivot tilting roller 46 so that belt 44 returns 
to the predetermined path of travel. 
Turning now to FIG. 6, there is shown another embodiment of disc 120 having 
rod 122 extending therefrom with portion 124 in threaded engagement with 
portion 142 of holder 108. Ball bearings 146 are mounted in a countersunk 
portion of hole 144 to align and provide rotation of rod 122 relative to 
holder 108. This minimizes friction between holder 108 and rod 122 during 
the rotation of disc 120. As disc 120 rotates, rod 122 rotates in 
conjunction therewith. Rotation of rod 122 causes threaded portion 124 to 
rotate in threaded portion 142 of holder 108. Holder 108 pivots about pin 
140 (FIG. 4) to tilt roller 46 so as to return belt 44 to the 
predetermined path of travel. 
In recapitulation, it is evident that the apparatus of the present 
invention controls lateral movement of a belt and provides a support 
therefore. Any lateral movement of the belt induces tilting in a roller 
support to restore the belt to the predetermined path of travel. 
It is, therefore, evident that there has been provided in accordance with 
the present invention, an apparatus for supporting and controlling the 
lateral movement of a belt so that the belt moves in a preselected path of 
travel. This apparatus fully satisfies the aims and advantages 
hereinbefore set forth. While this invention has been described in 
conjunction with a specific embodiment thereof, it will be 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 as fall within the spirit and 
broad scope of the appended claims.