US 3818391 A
A tracking assembly for an endless belt assembly of an electrostatograph machine is disclosed comprised of a rotatable yoke assembly having a tracking roller rotatably mounted thereon, and tracking linkage assembly operatively connected to the yoke assembly. Alteration of the linkage setting of the linkage assembly causes the yoke assembly to rotate in either direction on an axis which is in the bisector plane and normal to the roller shaft thereby causing said endless photoconductive belt to be realigned about the belt assembly.
Description (OCR text may contain errors)
[4 June 18, 1974 TRACKING ASSEMBLY FOR AN ENDLESS 3/l972 Baltazzi et al. SSS/l6 BELT ELECTROSTATOGRAPHIC MACHINE Primary ExaminerRobert P. Greiner  Inventors: William E. Jordon, Penfield; Robert Attorney, Agent, 1 Reichen R. Wilson, Rochester, both of NY.
Assignee: Xerox Corporation, Stamford Conn.
 Filed: Dec. 1, 1972  Appl. No.: 311,345
A tracking assembly for'an endless belt assembly of an electrostatograph machine is disclosed comprised of a rotatable yoke assembly having a tracking roller rotat- 355/3 198/202, ably mounted thereon, and tracking linkage assembly operatively connected to the yoke assembly. Alteration of the linkage setting of the linkage assembly causes the yoke assembly to rotate in either direction 199 on an axis which is in the bisector plane and normal to the roller shaft thereby causing said endless photocon- [Sl] Int. G03g 15/00,  Field of Search 355/16, 3;
References Cited ductive belt to be realigned about the belt assembly. UNITED STATES PATENTS l l/ I97] 3,621,987 Sherwood 198/202 4 Claims, 2 Drawing Figures PATENTED JUN I 8 I874 SHEET 1 BF 2 TRACKING ASSEMBLY FOR AN ENDLESS BELT ELECTROSTATOGRAPI-IIC MACHINE BACKGROUND OF THE INVENTION Pat. No. 2,297,691 to Chester F. Carlson, a xerographic surface comprising a layer of photoconductive insulating material affixed to a conductive backing is used to support electrostatic images. In the usual method of carrying out the process, the xerographic plate is electrostatically charged uniformly over its surface and then exposed to a light pattern of the image being reproduced to thereby discharge the charge in the areas where light strikes the layer. The undischarged areas of the layer thus form an electrostatic charge pattern in conformity with the configuration of the original light pattern.
The latent electrostatic image may then be developed .by contacting it with a finely divided electrostatically attractable material, such as a resinous powder. The powder is held in the image areas by the electrostatic fields on the layer. Where the field is greatest, the greatest amount of material is deposited; and where the field is least, little or no material is deposited. Thus, a powder image is produced in conformity with the light image of the copy being reproduced. The powder is subsequently transferred to a sheet of paper or other surface and suitably fixed to thereby form a permanent print.
The latest machine concept for copiers utilizes high speed flash exposure of a document and the arrangement of a moving Photoconductor material in the form of an endless belt including the continuously charging thereof together with provisions for solid coverage.
Photoconductor belts are very delicate, are easily damaged, and the movement thereof through processing stations in the reproduction machine must be accomplished with high precision and with as little irregular movement as possible. Additionally, should the tracking of the photoconductive belt become irregular and uncorrectable, the machine must be placed in an inoperative mode as quickly as possible to prevent irreparable damage to the photoconductive belt as well as the machine.
OBJECTS OF THE INVENTION An object of the present invention is to provide a novel tracking assembly for a photoconductive belt positioned on a belt assembly of an ele'ctrostatographic machine.
Another object of the present invention is to provide a novel tracking assembly for a photoconductive belt positioned on a belt assembly whereby the tracking thereof may be manually adjusted.
Still another object of the present invention is to provide a novel tracking assembly to insure lateral stability of a photoconductive belt positioned on a belt assembly.
SUMMARY OF THE INVENTION These and other objects of the invention are obtained by a tracking assembly for an endless belt assembly of an electrostatograph machine including a rotatable yoke assembly having a tracking roller rotatably mounted thereon, and a tracking linkage assembly operatively connected to the yoke assembly. Alteration of the linkage setting of the linkage assembly causes the yoke assembly to rotate in either direction on an axis which is in the bisector plane and normal to the roller shaft thereby causing said endless photoconductive belt to be re-aligned about the belt assembly.
DESCRIPTION OF THE DRAWINGS A better understanding of the present invention as well as other objects and further features thereof will become apparent upon consideration of the following detailed disclosure thereof, especially when taken with the accompanying drawings, wherein like numerals designate like parts throughout, and wherein.
FIG. 1 is a schematic sectional view of an electrostatic reproduction machine embodying the principles of the invention; and
FIG. 2 is an isometric view of a portion of the belt as- I sembly as seen from the other side of the machine of FIG. 1.
For a general understanding of the illustrated copier reproduction machine in which the invention may be incorporated, reference is had to FIG. 1 in which the various system components for the machine are schematically illustrated. A document to be copied is placed upon a transparent support platen P fixedly arranged in an illumination assembly, generally indicated by the reference numeral 10, positioned at the left end of the machine. Light rays from an illumination system are flashed upon the document to produce image rays corresponding to the informational areas. The image rays are projected by means of an optical system onto the photosensitive surface of a xerographic plate in the form of a flexible photoconductive belt 12 arranged on a belt assembly, generally indicated by the reference numeral 14.
The belt is comprised of a photoconductive layer of selenium which is the light receiving surface and imaging medium for the apparatus formed on a conductive backing. The surface of the photoconductive belt is made photosensitive by a previous step of uniformly charging the same by means of a corona generating device or corotron 13.
The belt is journaled for continuous movement upon three rollers 20, 21 and 22 positioned with their axes in parallel. The photoconductive belt assembly 14 is slidably mounted upon two support shafts 23 and 24 with the roller 22 rotatably supported on the shaft 23 which is secured to the frame of the apparatus and is rotatably driven by a suitable motor and drive assembly (not shown) in the direction of the arrow at a constant rate. During exposure of the belt 12, the portion exposed is that portion of the belt running between rollers 20 and 21. During movement of the belt 12 the reflected light image of the original document positioned on the platen on the surface of the belt to produce an electrostatic latent imagethereon at exposure station A.
As the belt surface continues its movement, the electrostatic image is passed through a developing station B in which there is positioned a developerassembly. generally indicated by the reference numeral 15, and which effects development of the electrostatic image by means of multiple magnetic brushes 16 as the image moves through the development zone.
The developed electrostatic image is transported by the belt to a transfer station C whereat a sheet of copy paper is moved between a transfer roller of transport roller assembly 29 and the belt at a speed in synchronism with the moving belt inorder to accomplish transfer of the developed image by an electrical bias on the transfer roller. There is provided at this station a sheet transport mechanism, generally indicated at 17, adapted to transport sheets of paper from a paper handling mechanism, generally indicated by the reference numeral 18, to the developed image on the belt at the station C.
After the sheet is stripped from the belt 12, it is conveyed into a fuser assembly, generally indicated by 19, wherein the developed and transferred xerographic powder image on the sheet material is permanently fixed thereto. After fusing, the finished copy is discharged from the apparatus at a suitable point for collection externally of the apparatus. The toner particles remaining as residue on the developed image, background particles and those particles otherwise not transferred are carried by the belt 12 to a clearing apparatus 26 positioned on a course of the belt between rollers 20 and 22 adjacent to charge device 25.
Further details regarding the structure of the belt assembly 14 and its relationship with the machine and support therefor may be found in the copending Application Ser. No. 102,312 assigned to the same assignee.
DETAILEDDESCRIPTION OF THE INVENTION Referring now to FIG. 2, there is illustrated a tracking assembly, generally indicated as 30 including the upper roller 20 and the tracking roller 21. The upper roller 20 is rotatably supported on a hollow shaft 32 journaled for rotation in bearings disposed in side plates (not shown) such as described in corresponding application Ser. No. 102,31 1 to David Roth Stokes, et al. entitled BELT TRACKING SYSTEM, assigned to the same assignee now US. Pat. No. 3,702,131. The tracking roller 21 is secured to a shaft 34 journaled for rotation in bearings (not shown) secured to the ends of parallel legs 36 and 38 of a yoke member 40.
At the mid point of the yoke member 40 and extending in an opposite direction relative to the legs 36 and 38, there is provided a shaft, generally indicated as 42, to support the yoke member 40 for limited rotational movement about the axis of the shaft 42 and to permit slight retraction. The shaft 42 is positioned within a cylinder 44 of relatively large diameter disposed within spaced bearings 46 mounted to a frame 48 and having a coaxial reduced portion 50 secured to the lower portion of the cylinder 44 and disposed within a suitable opening, formed in the blight portion of the yoke member 40. A relatively heavy coil spring encircles the portion 50 between the yoke member 40 and the lower surface of the lower bearing 46. The spring 52 imparts a continuous downward force upon the yoke and consequently the roller 21, when the belt 12 is mounted on its supporting rollers thereby placing belt 12 under I a tubular sleeve 52 axially aligned therewith. Suitable openings are formed in the sleeve 52 in diametrically opposed positions for supporting a pin 54 which is pivotally connected to one end of a toggle link 56 to the end of the cylinder. The link 56 is pivotally connected at the other end to one end of another toggle link 58 having its opposite end pivotally connected to the frame structure 48. It will be apparent that the toggle links 56 and 58 and their respective connections form a toggle assembly which when actuated into alignment will cause the cylinder 44 to move downwardly within the bearing 46'and when actuated into a buckled condition will cause the cylinder 44 to be retracted upwardly.
Actuation of the toggle assembly is produced by a drive link 60 which is pivotally connected at one end to the pivot connection between toggle links 56 and 58 extending transverse of the belt assembly 30 through an outer wall 62 and terminating in a pivotal handle 64 which moves drive link 60 axially to actuate toggle links 56 and 58. In order to remove or to replace a belt photoconductive 12, the handle 64 is suitably moved to cause buckling of the toggle links 56 and 58 which action draws the cylinder 42 upwardly within the bearings 46 to retract the roller 21. Sufficient slack is thereby provided to the belt 12 to permit an operator to move a belt relatively easily over the rollers 20, 21 and 22. After placing a belt over the rollers the handle 64 is moved in an opposite direction to place the toggle links 56 and 58 in an aligned condition thereby forcing the roller 21 against the belt 12 and locking the roller 21 in such position.
A flat sensing ring is mounted for rotation about a bearing 72 disposed on a support plate 74 having a diameter smaller than roller 20 and provided with a curved arm-76. The sensing ring 70 is preferably made of wear-resistant plastic material which will not become damaged when placed in contact with the relatively sharp edge of the photoconductive belt 12, and which will not cause fraying or other damage to the coacting edge of the belt 12. The support plate 74 is provided with a central opening 78 which allows the assembled structure comprising ring 70, bearing 72 and the plate 74 to accommodate and avoid the adjacent end of the shaft 32 and allow the ring 70 to engage the edge of the belt 12.
The curved arm 76 of the support plate 74 is provided with an orifice which fixedly receives the upper portion of an inclined shaft 80 mounted for rotation about its longitudinal axis within a fixed cylindrical casting 82 mounted by a spaced bracket 84 to the frame structure 8, such as by screws (not shown). Suitable bearings (not shown) are utilized within the casting 82 between the same and the shaft 80 in order to facilitate the rotating relationship therebetween. The lower end of the shaft 80 is formed with a reduced portion to which is attached an arm 88 extending perpendicularly relative to the axis of the shaft 80 to swing in either direction upon corresponding rotational movement of the shaft 80.
The arm 88 is pivotally connected to a link member 90 112 including an externally threaded portion 92. Another link member 94 including an externally threaded portion 96 is secured to an arm 97 of ear 98 formed on the upper portion of the yoke member 40. A cylindrically shaped sleeve 100 including a sprocket 102 threadably engages the threaded portions 92 and 96 of each of the link members 90 and 94, respectively, thereby providing a turnbuckle assembly, generally indicated as 99, for altering the distance between the axis of the roller 21 and the axis of the shaft 80 by rotation of the sleeve 100, as more fully hereinafter described.
A spring 101 is provided over the threaded portion 96 of the member 94 between the sleeve 100 and the end of link member 96 to prevent the unintentional rotation of the sleeve 100, such as by vibrations. A support assembly 104 is mounted to the-frame (not shown) and receives for rotation, a shaft 106 disposed within an opening formed in upturned legs 108 of the support assembly 104. A dial 110 is fixedly secured to an end of the shaft 106 extending outwardly from the frame. A sprocket 112 is fixedly secured to to a mid portion of the shaft 106 between the legs 108 thereof.
A shoulder bearing assembly 114 is positioned over a shaft 116 mounted on the support assembly 104. An endless chain 118 is positioned about the sprocket 112 disposed on the shaft 106, the shouldered bearing assembly 114, and about the sprocket 102 formed on the sleeve 100. A tubular member is provided between the shoulder bearing means 114 and the sprocket 102 to guide the chain 118 between the shouldered bearing assembly 114 and the sprocket 102. It will be readily appreciated that rotation of the dial 110 in either direction will cause the sleeve 100 to rotate thereby varying the distance between the center lines of the arms 88 and 97.
Minor variations of the tracking of a photoconductive belt 12 about the belt assembly is corrected in the manner described in the aforementioned application Ser. No. 102,3] 1. Thus, movement of the sensing ring 70 in either direction, as shown'by-the arrows in FIG. 2, will cause the shaft 80 to rotate about its axis since the shaft is fixedly secured to the arm 76 of the support plate assembly 74. The corresponding rotation of the shaft 80 will impart a swinging movement to the turnbuckle assembly 99 thereby rotating yoke member about the shaft portion for producing the same motion on the tracking roller 21. Movement of the sensing ring 70 in either direction will result in the rotation of tracking roller 21 in either direction and thereby causing tracking of the belt 12 in a direction opposite that in which the sensing ring movement occurs when the edge of the belt 12 deviates from a pre-determined portion relative to the guide roller 20.
For accurate alignment and positioning of electrostatic latent images and then corresponding developed images with respect to the processing stations of the printing machine, it is necessary that the photoreceptor belt maintain a constant and predictable path of movement.
In the event the belt deviates from a prescribed path of movement, say in a direction to the right as viewed in FIG. 2, the edge of the belt 12 being in engagement with the surface of the sensing ring 70 will cause corresponding movement thereof about the shaft 80, also to the right. The amount and rate of the movement of the ring is consonant with the amount and rate of deviation of the belt 12. As described above, with the sensing ring being moved in this manner, the tracking roller 21 will be rotated clockwise to cause a counter tracking of the belt to restore the belt 12 to its original path of movement. It is understood that mistracking to the right would be caused by greater forces being exerted on the under surface of the belt 12 by the rollers about the ends thereof on the side of the sensing ring, and that in order to correct such situation a counter force must be applied to the under surface of the belt 12 on the other side thereof.
Deviation of the belt 12 in the other direction will cause the tracking roller 21 to rotate in a direction which will stop the deviation of the belt 12 and to return it to its predetermined path. A light leaf spring 1 20 having one end secured to the arm 76 and its other end maintained under slight tension against the frame 48 provides a slight force upon the ring 70 in a direction toward the sensed edge of the belt in order to overcome the frictional forces in the sensing mechanism and to insure that the ring 70 will follow the end thereof.
The sensing arrangement described above provides for correction of belt deviation in either direction by positively actuating countermeasures in either direction, and to accomplish such correction by sensing only one edge of the belt 12. There is also no need for using two belt sensing mechanisms, one for each belt edge. In addition, the sensing of belt deviation is accomplished at one roller and the actual tracking is produced at another roller, the next roller positioned downstream of belt movement. In this manner, the time lag for correction of belt deviation is almost nil with only a portion of the belt experiencing a deviation. There is no need for a full circumferential movement of the belt before correction is imposed, as is the case wherein sensing and correction occurs at the same roller.
It will be appreciated that a replacement belt may be formed with a minor variation in the circumference thereof as compared with the photoconductive belt being. replaced. Such a variation in circumference would result in mistracking and require excessive trial and error adjustment but may be readily compensated for by adjustment of the turnbuckle assembly 99 of the present invention as more fully hereinafter discussed.
If a new photoconductive belt is placed on the belt assembly 14 which results in a deviation not compensatable by the sensing and control mechanism hereinabove described, the deviation may be corrected by rotation of the dial 110 to adjust the distance between the link members and 94 which results in the slight adjustment rotation of the tracking roller 21. Thus, the photoconductive belt 12 tracked to the right, as seen in FIG. 2, the dial 110 would be rotated thereby moving the chain clockwise about the sprockets 112 and 102 to cause the sleeve to rotate clockwise. Such clockwise rotation of the sleeve will increase the distance between link members 94 and 90 resulting in a slight clockwise rotation of said tracking roller 21 about the shaft 50.
Consequently, with the turnbuckle assembly 99 including the drive assembly therefor of the present invention, variations in the circumference of successive photoconductive belts may be readily corrected to provide for the proper tracking of of such replacement belts.
While the invention has been described in connection with a preferred embodiment thereof, it will be understood that many modifications will be apparent to those of ordinary skill in the art; and that this application is intended to cover any adaptations of variations thereof. Therefore, it is manifestly intended that this invention be only limited by the claims and the equivalents thereof.
What is claimed:
1. An improved electrostatographic machine having a frame, the improvement comprising:
a. a roller assembly disposed on the frame and having a plurality of rollers adapted to support and guide an endless belt having a photosensitive area thereon;
b. means for sensing lateral deviations in the coursing of the belt as the latter is passing over a first of the rollers;
c. means mechanically connecting the sensing means to a second of the rollers so as to cause the second roller to rotate about an axis in response to deviations of the belt; and
d. means for adjusting the mechanical connecting means so as to vary the normal setting of the sec- 0nd roller with respect to said axis.
2. An improved electrostatographic machine having a frame, the improvement comprising:
a. a roller assembly disposed on the frame and having a plurality of rollers adapted to support and guide an endless belt having a photosensitive area thereon; and
b. sensing means disposed at an end of a first of the rollers for sensing lateral deviations of the belt. means connecting the sensing means to a second of the rollers so as to cause the second roller to rotate about an axis in response to deviations of the belt, and means for adjusting the length of the connecting means so as to vary the normal setting of the second roller with respect to said axis.
3. An improved electrostatographic machine according to claim 2 wherein the connecting means is comprised of two threaded sections threadably engaged to opposite ends of a sleeve.
4. An improved electrostatographic machine according to claim 3 which further includes an endless belt means in engagement with the exterior surface of the sleeve, and means for causing the endless belt means to rotate.