US3887278A

US3887278A - Multi-section drum assembly

Info

Publication number: US3887278A
Application number: US421219A
Authority: US
Inventors: James Andrew Kolibas
Original assignee: Multigraphics Inc
Current assignee: AB Dick Co
Priority date: 1973-12-03
Filing date: 1973-12-03
Publication date: 1975-06-03
Anticipated expiration: 1992-06-03

Abstract

A multiple image area drum assembly is provided comprising a plurality of photoconductor-carrying frame structures mounted to a common hub independently of each other, whereby each frame structure may be easily removed from the assembly for servicing or replacement without disturbing the other frame structures. Preferably, each frame structure mounting permits axial movement relative to the hub in a convenient manner which significantly reduces the probability of scratching, or otherwise damaging the photoconductor during servicing or installation.

Description

[ 1 June 3,1975

United States Patent 11 1 Kolibas MULTl-SECTION DRUM ASSEMBLY Sept., 1972, Xerographic Drum, Berlier et al.

[75] Inventor: James Andrew Kolibas, Broadview Primary Examiner-Samuel S. Matthews Assistant Examinerl(enneth C. Hutchison Attorney, Agent, or Firm-Harry M. Fleck, Jr.

[22] Filed: Dec. 3, 1973 [21] Appl. No.: 421,219

ABSTRACT 521 [1.8.355/16 A multiple image area drum assembly is Provided 51 int. G03g 5/10; G03g 15/00 mprisin8 a plurality of phmoconducwr-carrying [53] Fidd of 355/3 R, 3 DD 16; frame structures mounted to a common hub indepen- 96 101/132 dently of each other, whereby each frame structure may be easily removed from the assembly for servicing or replacement without disturbing the other frame structures. Preferably, each frame structure mounting permits axial movement relative to the hub in a conve- S T N m MA .IP. a wT A mT S e m n N U M U 3,435,693 4/]969 Wright et al. 355/16 ux niem manner which significantly reduces the womb g'ggg'gig aqa fii 5532 ity of scratching, or otherwise damaging the photocon- I ductor during servicing or installation.

OTHER PUBLICATIONS IBM Technical Disclosure Bulletin, Vol. 15, No. 4,

7 Claims, 2 Drawing Figures M l'LTl-SECTIUN [)Rl" M ASSEMBLY The present invention is generally related to copy machines and. more particularly. to an ll'llPl'U\LLl photocondactor-carrying drum assembly which is easier and less costly to service and repair than conven tional photoconductor drums.

In recent years, various types of electrophotographic reproduction machines have been proposed or manufactured which utilize the well-known principles of photoconductivity to provide an electrostatic image pattern of the original document which is ultimately de veloped and fixed onto a sheet of copy material. Many of these conventional machines include a drum structure with a photoconductive surface. such as selenium. which is exposed to a pattern of shadow and light to provide the electrostatic image.

One of the problems of such conventional drum structures is that there is a gradual build-up of toner film on the surface ofthc photoconductor as copies are made. This build-up requires frequent removal and cleaning of the copy drum in order to maintain copy quality after a predetermined number of copy cycles. In addition. the photoconductor surfaces of such drum structures are susceptible to easy scratching caused by carrier head in the developer composition. or. paper jamming against the drum. Also. damage may occur due to even slight misalignment of the drum during installation or removal. This is due to the fact that the drums tend to drop downward when disengaged from their support shaft mountings. damaging the underside of the photoconductor surface by engagement with the underlying machine frame. If such inadvertent scratching of the photoconductor surface occurs. costly repair or even replacement of the entire drum structure may be necessary.

Other copy machine drum structures have been proposed to overcome the abovemcntioned shortcoming of the photoconductor surfaced drums by providing a supply roll of web-like photoconductor which may be advanced periodically to replace the fatigued image area after a predetermined number of copy cycles. One such arrangement is disclosed by U.S. Pat. No. 3.5 88.242. This drum structure carries a spool of photoconductor which is automatically advanced by a gear mechanism. eliminating the need for cleaning. However. these *drums are as heavy as. if not heavier. than the selenium type of comparable size and. as such. are cumbersome to handle during installation or removal. Also. these drums must be machined within very close tolerances and. as such. are expensive to manufacture. The photoconductor web carried by the drum is readily susceptible to scratching or tearing on sharp edges or protrusions ofthc machine during installation or servicing. lfthe web should become torn. it may be necessary to replace the entire photoconductor roll.

It is an object of the present invention to provide a versatile photoconductor carrying drum assembly which overcomes the above-mentioned disadvantages of the conventional drum constructions.

Another object of the present imention is to provide a unique drum assembly comprised of a plurality of independent photocondactor-carrying frames mounted to a common hub. whereby a single frame may be serviced or replaced without disturbing the others and at a fraction of the cost of replacing the entire drum as scmbly.

It is a further object of the present invention to pro' vide a novel drum assembly comprised of a plurality of photocondactor-carrying frames. each of lightweight. compact construction and relatively simple to install or remove from a copier machine. compared to comentional drum structures.

Still another object ofthe present invention is to provide a versatile drum assembly comprised of a plurality of photoconductor-carrying frames. each of which is mounted for easy installation and removal by axial movement relative to a common hub.

It is a further object of the present invention to provide a novel drum assembly with a plurality of frames. each carrying a photoconductor and being readily removable from the assembly with the photoconductor in generally face-up orientation. whereby the probability of damage to the photoconductor during installation or removal of a frame is significantly reduced.

The foregoing and other objects and advantages of the invention will be apparent from the following more particular description of the preferred embodiment of the invention as illustrated in the accompanying drawings wherein:

FIG. I is a schematic side view of a eleetrophotographic reproduction machine employing the multisection drum assembly of the present invention; and

FIG. 2 is an exploded perspective view of the drum assembly of the present invention with sections removed.

Rcfcrring now. more particularly. to FlG. l of the drawings. a typical electrophotographic reproduction apparatus is generally indicated by the numeral 10 and includes a drum assembly l2 rotatably supported by a pair of framework elements 14. The drum assembly is operatively connected to a drive motor. not illustrated. which effects controlled rotation of the drum assembly in a clockwise direction. as indicated by the arrow at 16. The drum assembly is comprised of four quadrants or sections 18. 20. 22 and 24. each of which carries its own photoconductor element defining a corresponding imaging area. as hereinafter explained. Each quadrant of drum assembly 12 is comprised ofa frame structure including a part-cylindrical surface. upon which the operative portion of the associated photoconductor ele ment resides.

Disposed about the periphery of drum assembly 12. are a number of processing stations which carry out the conventional steps of the xerographic copying process. An initial charging station is defined by a corona discharge unit 26, or equivalent device. which provides a uniform charge on the surface of the photoconductor element prior to exposure. An exposure station. generally indicated by the numeral 28, of the scanning type includes illumination lamps 30 which irradiate a document 32 which passes a scanning slit in face-down orientation. This provides a line image of light and shadow which is projected by a stationary lens 34 onto the underlying photoconductor element of quadrant l8. Various scanning type exposure arrangements are well known to those skilled in the art of clectrophotography and. as such. a detailed description of the scanning ex posure operation is deemed unnecessary for the purposes of this disclosure.

It is emphasized that the drum assembly of the present invention is not limited to use with copy machines having scan type exposure. and may be utilized with flash type exposure by altering each quadrant structure to cause the photoconductor element to assume a planar configuration during exposure. Such a drum structure for flash exposure is disclosed in co-pending application Ser. No. 42l,258. now U.S. Pat. No. 3.826.570, entitled PHOTOCONDUCTOR-CARRYlNG DRUM ASSEMBLY. assigned to the same assignee as that of the present invention.

The next station in the direction of rotation of drum assembly 12 is a de\eloper unit 36, of a conventional type, which applies toner particles to the latent image pattern on the associated photoconductor element to define a developed image. Subsequent to development, the associated drum assembly quadrant is rotated to a transfer station generally indicated by the numeral 38. Here the developed image on the photoconductor ele ment is transferred to a sheet of copy material fed to the transfer station from a supply stack 40. Typically, transfer of the developed image pattern is effected electrostatically and may be aided by the use of a transfer corona, not illustrated. The copy sheet is then separated from the drum quadrant. the toner image is fused at a fusing station 42, and the final copy is transported to an output hopper, such as that indicated at 44. Such transfer and fusing techniques are well known. and a detailed description of such is deemed unnecessary.

Since some residual toner remains on the photoconductor element it is necessary to clean the element prior to re-exposure Typically, this is achieved by providing a pre-clean corona unit 46 which loosens the remaining toner particles and a cleaning unit 48 which brushes the toner particles from the surface of the photoconductor element.

It will be appreciated that the drum assembly of the present invention provides a multiple image area spaced around its circumference, whereby the process stations may be operated concurrently to provide a very high copy production rate. For example, when making multiple copies or consecutive copies, each ex posure operation can be carried out at quadrant 18 while the development operation is taking place at quadrant 20. together with the transfer and cleaning operations at

quadrants

22 and 24, respectively. If flash type exposure is utilized, the drum may be rotated at a higher rate of speed, thus providing an even higher copy production rate.

Referring now, more particularly, to FlG. 2 of the drawings, the preferred embodiment of the drum assembly of the present invention may be seen in more detail. As mentioned above, each quadrant is defined by an independent frame structure. Preferably. each frame structure is comprised of a rigid support member 50 which defines a part-cylindrical support surface for the imaging portion of a web-like photoconductor element 52. Support member 50 extends axially between a pair of

end plates

54 and 56, which are secured to the associated support member by bolts, or other appropriate fastening means. not illustrated. Each frame structure is provided with a pair of

guide rollers

58 and 60, which are rotatably mounted to support member 50 and extend along the edges thereof parallel to the as semblys axis of rotation. Portions of the photoconductor element are broken away in FIG. 2 to expose corresponding end portions of

rollers

58 and 60.

Each frame structure provided with a supply spool 62 and take-up spool 64 rotatably supported between end plates -4 and 56 and generally disposed within the interior confines of the associated frame structure. A supply roll of the photoconductor is uound around supply spool 62 to provide for replacement of the operative portion of the photoconductor defining the image area when such becomes fatigued or damaged. The end of the photoconductor is appropriately fastened to supply spool 62 in a manner which assures proper grounding of the photoconductor. The photoconductor element comes off of supply spool 62. it wraps partially around roller 60, extends over the curved surface of support element 50. around roller 58 to the take-up spool 64. Preferably, supply spool 62 is keyed to a ratchet gear 66 which is retentively engaged by a spring-loaded pawl 68 carried by end plate 56 of each frame structure. Similarly. each take-up spool 64 is provided with a ratchet 70 which is retentively engaged by a spring loaded pawl 72. Pawls 68 and 72 normally prevent rotation of the supply and take-up spools, thereby assuring that the photoconductor element is held snugly in place in engagement with the curved support surface of element 50 and will not creep during drum rotation. The teeth of each ratchet are arranged to permit clockwise rotation by manual rotation of the take-up spool with sufficient force to overcome the drag of the spring loaded pawls. Preferably. ratchet 70 is provided with a keyway 74 which is adapted to receive a portion or a similarly shaped tool which may be inserted to effect manual advancement of the photoconductor web. Thus. in order to change the operative portion of any one of the photoconductor elements. the take-up spool is merely rotated until the photoconductor element is advanced the desired amount. If desired. this manual advancement may be utilized to replace only a small portion of the image area. in the event of scratching or damage to the photoconductor. or to replace the entire image area when that portion of the photoconductor has become fatigued after a number of copy cycles.

As mentioned above. each frame structure associated with the drum assembly of the present invention can be removed independently of the others. This is achieved by mounting each frame structure to a common hub or rotary member 76 affixed to a main drive shaft 78. Securement of each frame structure to hub 76 is achieved by way of a pair of dovetail elements 80 and 82. or other guide members, mounted at axially opposite ends of the hub. In addition. the overall mounting arrangement includes four

rigid fm members

84, 86, 88 and 90 which are welded. or otherwise affixed, to hub 76 and extend radially outward therefrom. Each fin member is provided with a pair of elongated keys 92 which extend parallel to the hub axis and define guide rails for each frame structure, which aid in the installation and removal operations.

Each

end plate

54 and 56 is provided with a pair of

keyways

96 and 98 which cooperate with keys 92 on the associated fins. In addition, each end plate is pro vided with a dovetail guide or slot 100 which cooperates with guide members 80 and 82 during installation and removal of the frame structure. Preferably. a stop member 102 is fixed to one of hub 76 and extends radially outward beyond guide member 80 to engage end plate 54 when the frame structure is slid fully into position. When the frame structure has been mounted in proper position. it is secured in place against axial movement by way of a lock finger or tab 104, which is pi\ oted to a center position and secured in place by way of a screw threaded to hub 76.

It will be appreciated that installation of each frame structure is a relatively simple procedure which requires a minimum amount of skill and training and which may be accomplished in a minimum amount of time and at a minimum expense. Preferably. both installation and removal of a frame structure is conducted with the structure mounting located at approximately top dead center. such as the position of quadrant 18 illustrated in FIG. 1. With the assembly in this position, the associated photoconductor element is in face-up orientation for mounting or removal of the frame structure, whereby the probability of scratching or damaging the photoconductor is significantly reduced. As mentioned above. with conventional drum structures the removal or mounting thereof exposed the photoconductor element to inadvertent scratching or damage due to the fact that the drum tends to drop downwardly against the machine frame when it is freed from its associated mounting. By providing removal of each quadrant with the photoconductor in face-up orientation. in the event the frame structure drop downwardly somewhat when it becomes freed from its mounting. the photoconductor will not come in engagement with any of the underlying copy machine components. It will also be appreciated that the likelihood of a serviceman losing control over a frame structure during mounting or removal is minimized due to the fact that each frame structure is only a fraction of the weight of the overall assembly. The hub 76 and associated dovetails and mounting fins. which provide rigidity and proper alignment of the frame structures. remain in place further reducing the amount of weight which must be handled. As such. the weight of each structure is considerably less than that of a conventional one piece drum structure of comparable size.

From the foregoing description. it will also be appreciated that the drum assembly of the present invention provides a plurality of independent photoconductor elements which may be selectively advanced. replaced. or serviced independently of each of the other photoconductor elements. Thus. if one of the photoconductors becomes fatigued or damaged. appropriate action may be taken to correct the condition without effecting the other photoconductor elements. The operative portion of each photoconductor element defines a separate image area. Preferably. the photoconductor element comprises a layer of an organic photoconductor. such as polyvinyl benzocarbazole. on aluminized Mylar of 3 to 5 mils thickness. With Mylar ofS mils thickness, the supply roll may be of sufficicnt size to accommodate approximately 40 feet of photoconductor when mounted in a frame structure with a 8% X l4 inch image area.

lt is not intended that the drum assembly of the present invention be limited to the embodiment of the copy machine illustrated in FIG. 1. Also. it is not intended that the assembly be limited to four frame structures and image areas. as a greater or lesser number may be utilized if it is practical and desirable to do so. Also. the drum assembly is not to be limited to the exact mounting arrangement illustrated in the drawings. as other appropriate mounting means may be utilized which permit removal of each frame structure independently of the others. It is foreseeable that the photoconductor element of each frame structure may be advanced automatically by an appropriate mechanism. rather than the manual means disclosed above What is claimed is:

l. A photoconductor drum assembly for an electrophotographic reproduction apparatus. said assembly comprising;

a stationary support.

a rotary member mounted to said support for rotation about an axis.

a plurality of frame structures mounted to said rotary member. each frame structure including a support surface.

a photoconductor element carried by each of said plurality of frame structures. each photoconductor element comprising a web which extends between a supply location and a take-up location of the associated frame structure with an intermediate portion of the web engaging said support surface. and

releasable fastening means associated with each of said frame structures normally fastening such to said rotary member independently of the other frame structures and for selectively releasing such for movement relative to said rotary member independently of the other frame structures. said fastening means upon release permitting the associated frame structure to be displaced axially of said rotary member for convenient servicing or the like.

2. The assembly set forth in claim I wherein the intermediate portion of each photoconductor element defines a separate imaging area and said assembly includes a means associated with each frame structure for selectively advancing said photoconductor between said storage location and said take-up location whereby the photoconductor element defining any one image area may be changed independently of the other photoconductor elements.

3. The assembly set forth in claim 1 wherein each of said support surfaces is of generally part cylindrical configuration. said support surfaces normally being disposed on a common circumference about said axis of rotation.

4. The assembly set forth in claim 3 wherein said support surfaces together define a generally cylindrical surface about said axis of rotation.

5. The assembly set forth in claim 1 wherein said plurality of frame structures are mounted adjacent to each other circumferencially around said rotary member to define a plurality of imaging areas spaced around said rotary member.

6.The assembly set forth in claim 1 wherein said releasible fastening means includes means for guiding the associated frame along a path substantially parallel to said rotary member axis when the frame is selectively released and displaced from said normal position.

7. The assembly set forth in claim 6 wherein said guide means slidably supports said frame structure during displacement.

Claims

1. A photoconductor drum assembly for an electrophotographic reproduction apparatus, said assembly comprising; a stationary support, a rotary member mounted to said support for rotation about an axis, a plurality of frame structures mounted to said rotary member, each frame structure including a support surface, a photoconductor element carried by each of said plurality of frame structures, each photoconductor element comprising a web which extends between a supply location and a take-up location of the associated frame structure with an intermediate portion of the web engaging said support surface, and releasable fastening means associated with each of said frame structures normally fastening such to said rotary member independently of the other frame structures and for selectively releasing such for movement relative to said rotary member independently of the other frame structures, said fastening means upon release permitting the associated frame structure to be displaced axially of said rotary member for convenient servicing or the like.

2. The assembly set forth in claim 1 wherein the intermediate portion of each photoconductor element defines a separate imaging area and said assembly includes a means associated with each frame structure for selectively advancing said photoconductor between said storage location and said take-up location whereby the photoconductor element defining any one image area may be changed independently of the other photoconductor elements.

3. The assembly set forth in claim 1 wherein each of said support surfaceS is of generally part-cylindrical configuration, said support surfaces normally being disposed on a common circumference about said axis of rotation.

5. The assembly set forth in claim 1 wherein said plurality of frame structures are mounted adjacent to each other circumferencially around said rotary member to define a plurality of imaging areas spaced around said rotary member. 6.The assembly set forth in claim 1 wherein said releasible fastening means includes means for guiding the associated frame along a path substantially parallel to said rotary member axis when the frame is selectively released and displaced from said normal position.