Document printer/copier with decoupleable drum-support member

Information

  • Patent Grant
  • 6263177
  • Patent Number
    6,263,177
  • Date Filed
    Friday, May 19, 2000
    24 years ago
  • Date Issued
    Tuesday, July 17, 2001
    23 years ago
Abstract
A document printer/copier comprises a pair of drum-support members for rotatably supporting an image-recording drum and, optionally, an intermediate image-transfer drum. At least one of such drum-support members is adapted to be decoupled from the drum(s) it supports and be moved to a position within the machine frame in which it does interfere with the replacement of the drum(s)'s outer layer. Preferably, such member comprises a selectively energizeable clamp which, when energized, clamps onto an axle bearing of a drum and thereby supports the drum for rotation. When de-energized, the clamp releases the drum bearing, enabling the drum-support member to be slid axially along the drum axis to a position spaced from the drum axle, and thereafter pivoted to a position spaced from the drum axis where it does not interfere with drum servicing and/or replacement.
Description




FIELD OF THE INVENTION




The present invention relates to field of document printing and copying. More particularly, it relates to improvements in methods and apparatus for precisely positioning the various work-stations of a document printer/copier, e.g., an electrophotographic printer, relative to (i) the photosensitive surface of an image-recording, drum on which toner images are formed, and, optionally, (ii) the non-stick (abhesive) surface of an intermediate image-transfer drum to which toner images are transferred from the image-recording, drum before being ultimately transferred to an image-receiver sheet.




BACKGROUND OF THE INVENTION




Automated electrophotographic copiers and printers have been known for nearly fifty years. Copiers and printers differ only from an input standpoint, copiers being adapted to receive hard copy input, whereas printers are adapted to receive an input in electronic form, e.g., from a computer terminal. Both carry out the basic electrophotographic imaging process of uniformly charging a photoconductive layer with electrostatic charge, imagewise exposing the charged layer to radiation adapted to discharge the layer, thereby leaving behind a latent charge image, and applying pigmented electroscopic particles (toner) to the charge image to render it visible. Most often, the toner image so formed is transferred to a receiver sheet whereupon the toner image is permanentized by heat and/or pressure. Optionally, for example, to extend the lifetime of the photoconductive recording element, the toner image formed on the image-recording drum is transferred to an intermediate transfer drum or the like before it is again transferred to the receiver sheet. In the case of full color copying and printing, multiple color-separated toner images (e.g., cyan, magenta, yellow and black) are produced by the above process and transferred in registration to a receiver sheet.




Since the inception of electrophotographic printers/copiers, the “holy grail” for many manufacturers has been to produce images of photographic quality, both monochromatic and full color. As will be appreciated, the quality of a full color image is determined not only by the respective qualities of each of the color-separated toner images formed on the photoconductive recording element(s), but also by the degree with which such images can be transferred from the recording element(s) and brought into perfect registration on the image receiver sheet. Such image quality of the color-separated images and the registration thereof, in turn, depend in large part upon the precision with which the various work-stations or subsystems that carry out the electrophotographic process can be physically placed relative on the surface of the recording element. Thus, various schemes have been proposed and used in the past that address this technical problem.




While focusing on image-quality and registration issues, printer manufacturers are ever mindful of lowering manufacturing and service costs. Thus, substantial efforts have been made to simplify service and maintenance procedures so that the need for service calls by highly trained technicians and specialists can be minimized. Ideally, for example, all of the major work-stations of the printer, e.g. the charging, exposure, development, transfer and cleaning stations, as well as the recording element itself, should be replaceable by the end user or customer with no sacrifice being made to the ultimate image quality. Even where the services of a trained technician are required, the time to implement such replacements should be minimal. The achievement of this goal not only requires that each of the printer work-stations be modularized so as effect a “plug and play” concept, but also requires that a very precise and highly reliable work station-registration scheme be designed so that each work station, upon being removed from the printer frame for servicing and/or replacement, can be returned to within a few microns of its nominal position. In the case of high quality color printing, the respective placements of the printer work-stations is particularly critical and skilled servicing personnel are usually required to make the major sub-system changes. Obviously, the need for service assistance should be minimized.




In the above-referenced U.S. application Ser. No. 09/474,352, a work station registration scheme for an electrophotographic printer is disclosed in which a plurality of dowel pins on the printer frame serve to locate both a photoconductive drum assembly and an image transfer drum assembly. Each drum assembly comprises a pair of drum-support members, commonly referred to as “spiders,” located at opposite ends of the drum. Each spider contains a centrally located bearing for rotatably supporting a drum axle, and a plurality of outwardly extending mechanical fiducials, e.g. bullet-shaped members, which are adapted to mate with complimentary structure, e.g., V-notched blocks, mounted on each work station to precisely locate and space the work-stations relative to the drum's photoconductive surface. When it comes time to replace the image-recording and/or transfer drums, the work-stations are retracted from their respective positions adjacent the drum surface, thereby providing clearance for drum removal, and the entire drum assembly, including the spider members, are slid axially through an opening in the front wall of the printer frame. The entire drum assembly is then returned to the manufacturer's facility where the assembly is disassembled and a new drum can be substituted for the worn drum. To install a new drum assembly, the reverse process is carried out, the drum assembly being moved axially inward into the printer frame, until the spiders engage and are seated upon the dowel pins. Thereafter, the work-stations are moved toward the drum surface and their respective operative positions. In a similar manner, each of the individual work-stations may be removed from the printer housing, leaving behind, when the drum assembly has been removed, a frame that is totally void of any major components. Only the registration dowel pins remain in the frame, and the entire printer can be reassembled with great precision based on the location of these pins.




While the above-described apparatus fulfills the work station-registration needs for high quality color printing, it may be viewed as a relatively costly and labor intensive solution. For example, to replace the drum surface, the entire drum assembly, which including the relatively costly drum-support members (spiders) and axles, must be replaced. This requires removal of a relatively heavy subsystem from the printer housing and shipment of such subsystem back to the manufacturing for refurbishing. Since most of the drum assembly components do not require replacement, these components undergo unnecessary shipping and handling during which time they may be damaged or have parts misaligned. This disadvantage is exacerbated by the weight of such components. Ideally, only those components of the drum assemblies that actually need replacement (typically the outermost layer of the drum) should be removed from the printer housing and the remaining components should stay in place for the life of the printer.




SUMMARY OF THE INVENTION




In view of the foregoing discussion, an object of this invention is to provide an improved system for precisely and repeatedly positioning the various work-stations of an electrophotographic printer relative to an image-recording and/or image-transfer drum.




Another object of this invention is to provide an improved document printer/copier in which a work station-registration and drum-support member comprising a drum assembly mounted within a printer/copier frame can be selectively de-coupled from the drum assembly and moved within the printer/copier frame to a location providing service access to the outer surface of an image-recording drum and/or image-transfer drum.




According to one aspect of the invention, a document printer comprises (i) a frame including a front frame plate, (ii) at least one reference pin or the like extending from the front frame plate at a predetermined location, (iii) an image-recording drum having an outer photosensitive surface and front and rear axles extending outwardly from opposing ends of the drum along an intended axis of rotation, (iv) a plurality of work-stations for producing transferable visible images on the drum's photosensitive surface, and (v) a front drum-support member mounted on the front frame plate and precisely located thereon by the reference pin extending from the front frame plate, such front drum-support member having a set of mechanical fiducials for locating various work-stations relative to the drum surface. According to the invention, the front drum support member has a selectively energizeable clamping mechanism for selectively engaging a bearing on the front drum axle, whereby the front drum-support member can either rotatably support the front drum axle for rotation, or be decoupled therefrom so that the drum can be removed from the printer frame. Preferably, the front drum-support member is movably mounted on the front frame plate for movement between a first position in which its associated clamping-mechanism is positioned to engage the bearing on the drum's front axle, and a standby position in which the front drum-support member is sufficiently spaced from the drum's front axle to enable servicing of the drum, e.g., to enable replacement of the drum's outer photosensitive layer. Preferably, the printer of the invention further comprises an intermediate image transfer drum having opposing front and rear axles extending outwardly from opposite ends, and the front drum-support member is further provided with a second selectively energizeable clamp for selectively engaging a bearing on the front axle of the transfer drum. Also preferred is that the printer further comprises a rear drum-support member rigidly mounted on a rear frame plate of the printer frame and precisely located thereon by reference pin extending from the rear frame plate. Such rear drum-support member includes (a) a bearing for rotatably supporting the rear axle of the image-recording drum, and (b) a second set of fiducials that cooperate with the fiducials on the front drum-support member for locating the various work-stations of the printer relative to the drum surface. Preferably, the rear drum-support member comprises a selectively energizeable clamp, which serves to releasably and rotatably support the rear axle of the image-transfer drum.




According to another aspect of the invention, new drum-support members of the above type are provided. Rather than being an integral part of the drum assembly that stay with the drum assembly when it comes time to replace the drum surface, the drum-support members of the invention are adapted to remain in the printer housing while only the outer surfaces of the drum(s) are replaced or serviced. Preferably, the front drum-support member of the invention comprises a selectively energizeable clamp which, when energized, clamps about the outer race of an axle bearing that serves to rotatably mount the image-recording drum. When so clamped, the drum-support members become part of the drum assembly, and a plurality of reference fiducials located at predetermined positions about the periphery of the drum-support member serve to position the various work-stations of the printer. When unclamped, the drum-support members are de-coupled from the drum(s). Mounting structure on the front drum-support member enables such member to be (i) slided axially (relative to the drum's axis of rotation) to suitably displace the member from the drum, and (ii) pivoted to a location laterally spaced from the drum axis. According to a preferred embodiment, the front drum-support member further comprises a bearing for rotatably supporting one end of the image transfer drum in a cantilever fashion and a selectively energizeable clamp which, when energized, clamps about the outer race of an axle bearing serving to rotatably mount an image-transfer drum. Preferably, the rear drum-support member is adapted to be rigidly connected to the rear frame plate of the printer frame.




As indicated above, an advantageous technical effect of the invention is that the most significant technical benefits of the work-station registration scheme disclosed in the above-referenced U.S. application Ser. No. 09/474,352 have been preserved while the cost of implementing such a scheme is minimized by virtue of the fact that the most costly components of the drum assembly (i.e., the drum-support members (“spiders”) and drum axles) are never removed from the printer and can remain with the printer throughout its useful life. Another advantage of the invention is that the end user can gain access to the image-recording and transfer drums for servicing without having to remove and replace relatively heavy sub-assemblies.




The invention and its advantages will be better understood from the ensuing detailed description of preferred embodiments, reference being made to the accompanying drawings in which like reference characters denote like parts.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a side elevation of a portion of an electrophotographic printer embodying the invention;





FIG.2

is a perspective view of a portion of the apparatus shown in

FIG. 1

;





FIGS. 3 and 4

are enlarged perspective views of a movably mounted drum support member in two different positions;





FIG. 5

is a perspective view of a portion of the

FIG. 1

apparatus showing the outer layers of the image-recording and image-transfer drums removed;





FIGS. 6A and 6B

are enlarged side elevations of the front and rear drum supports of the

FIG. 1

apparatus; and





FIGS. 7-10

are front perspective, rear perspective, cross-sectional, and side elevational views, respectively, of portions of the rear drum support shown in FIG.


6


B.











DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS




Referring now to the drawings,

FIG. 1

shows a major portion of an electrophotographic printer


10


embodying the present invention. While the apparatus shown is adapted to produce monochromatic (one color) images, it may be one of several identical printing modules, each being adapted to produce one of the several color-separated images comprising a multicolor print. As shown, printer


10


comprises an image-recording drum


12


having a photoconductive outer surface


14


on which toner images are formed in a conventional manner. As discussed below, surface


14


is part of a replaceable photoconductive tube comprising, for example, an aluminum sleeve, about 8 mm in thickness, having an outer coating of an organic photoconductive material. The photoconductive tube is supported at opposite ends by a pair of circular gudgeons


15


,


15


′ which, in turn, are supported by a drum shaft (shown in FIG.


7


). The forward gudgeon


15


is releasably attached to the drum shaft so that, when the gudgeon is removed from the drum shaft, the photoconductive tube can be slided axially and thereby be removed from the printer frame and, if necessary, be replaced. The printer also comprises an intermediate image-transfer drum


16


with a compliant abhesive (non-stick) sleeve


18


to which toner images formed on the photoconductive outer surface of image-recording drum


12


are transferred prior to being re-transferred to a receiver sheet (not shown). Like the image-recording drum, the image-transfer drum is structured so that its outer layer can be removed and replaced in the field, i.e., at the customer site. Briefly, the drum


16


comprises a cylindrical mandrel


17


(shown in

FIG. 7

) which supports a removable abhesive sleeve. Details of the image-transfer drum are disclosed in the above-referenced U.S. application Ser. No. 09/574,447.




Briefly, toner images are formed on the photoconductive surface of image-recording drum


12


by rotating the drum in a counter-clockwise direction (as viewed in

FIG. 1

) past a series of image processing or work-stations that sequentially operate on a desired portion of the drum's photoconductive outer surface to produce a visible toner image. These image processing stations include a corona charging station


20


for uniformly charging the photoconductive surface


14


with electrostatic charges, a solid-state print head or optical writer


22


for imagewise exposing the charged photoconductive surface, line-by-line, to actinic radiation, thereby selectively dissipating the uniform charge and leaving behind a latent electrostatic charge image, and a toning station


24


for developing the charge image with pigmented electroscopic toner particles. The toner image thus formed is then transferred to the outer surface of the image-transfer drum


16


, and residual toner on the image-recording drum


12


is removed by a pre-clean corona charger


25


an a cleaning station


26


. Upon re-transferring the toner image on the intermediate transfer drum


16


to an image-receiver sheet (not shown), the surface of drum


16


is cleaned by a second cleaning station


28


. Preferably, each work station, with the exception of the optical writer is mounted for slight movement (e.g. about 5 to 7 mm.) towards and away from its respective operative position adjacent the drum surface (shown in

FIG. 1

) to provide adequate clearance for installation and replacement of the processing stations. During such installation, as explained below, these processing stations are moved substantially parallel to drum's respective axis of rotation, through an opening


30


in the front mechanism plate FP of the printer frame F (shown best in FIG.


2


).





FIGS. 2 and 5

are a perspective view of the

FIG. 1

apparatus with the work-stations


20


,


22


,


24


,


26


and


28


removed.

FIG. 5

shows a pair of dowel or “reference” pins P


1


,P


2


mounted on the front and rear plates, FP, RP, respectively of the printer frame. As disclosed in the above-referenced U.S. application Ser. No. 09/574,054, these reference pins are engaged by mounting blocks located at opposite ends of the optical writer


22


and thereby serve to control the focus position of the writer relative to the drum's photoconductive surface. As discussed below, pins P


1


-P


4


further serve to precisely locate drums


12


and


16


within the printer frame by precisely positioning a pair of drum-support members used to rotatably support the drums within the printer frame.




Now in accordance with a preferred embodiment of the invention, drums


12


and


16


are rotatably supported by a front and rear drum-support members


32


,


32


′. As best shown in

FIGS. 5 and 7

, the rear drum-support member


32


′ is rigidly connected to the rear frame plate RP of the printer frame and is precisely located thereon by the reference pins P


2


and P


4


. As described in more detail below and in the above-referenced U.S. application Ser. No. 09/574,275, rear member


32


′ serves to rotatably support both drums


12


and


16


by their respective rearwardly-extending axles A


2


and A


4


. Moreover, rear drum-support member supports the image-transfer drum


16


so that it may be moved towards and away from the image-recording drum


12


, the rotational axis of which remains stationary. The front drum-support member


32


, in contrast with the rigidly mounted rear member, is movably mounted on the front frame plate FP of the printer frame for movement between an operative position (shown in

FIG. 2

) in which it is capable of rotatably supporting both of the respective forwardly-extending portions of the axles A


1


and A


3


of drums


12


and


16


, and a standby position (shown in

FIGS. 4 and 5

) in which it is sufficiently spaced from the drum axles to enable, for example, the outer surfaces of the drums to be accessed for service and/or replacement. Each of the drum-support members


32


,


32


′ is provided with a plurality of outwardly extending fiducials


34


which, together with similarly located fiducials on the other drum-support member serve to precisely locate the various work-stations of the printer relative to the respective outer surfaces of the drums. This type of work station registration scheme is disclosed in more detail in the above cross-referenced U.S. application Ser. No. 09/474,352.




Referring additionally to

FIGS. 6A and 6B

, the front drum-support member


32


comprises a housing


35


that is preferably made of aluminum and has, generally speaking, a “figure eight” configuration. A circular hole H


1


and a slot H


3


are provided in housing


35


for receiving pins P


1


and P


3


carried by the printer's front frame plate FP. Each hole or slot is provided with a sleeve S having a tapered forward edge for facilitating the entry of pins P


1


and P


3


. The upper opening


35


A of housing


35


is adapted to receive and rotatably support the front portion of the image-recording drum axle A


1


, while the lower opening


35


B is adapted to receive and rotatably support the front portion of the intermediate transfer drum axle A


3


. Opening


35


A is provided with a pair of reference surfaces


36


,


37


arranged at 90 degrees with respect to each other, thereby defining a V-notch for receiving the front axle bearing B


1


of the image-recording drum


12


. Mounted within housing


35


is a selectively energizeable, double-acting air cylinder AC


1


having a movable actuator


39


extending into opening


35


A. When air is applied through a port


40


of the air cylinder, the actuator moves in a direction towards the apex of reference surfaces


36


,


37


. Thus, when the movably-mounted drum-support member


32


is located in its operative position as shown in

FIG. 2

, the top (free end) of actuator


39


will engage the bottom portion of the outer race of drum bearing B


1


as the actuator moves into opening


35


A. As actuator


39


continues to move towards reference surfaces


36


,


37


, it operates to lift the drum axle A


1


until the axle bearing B


1


contacts the reference surfaces


36


,


37


. At this time, the air cylinder actuator operates collectively with reference surfaces to position the drum axle at a nominal position, that being one that is precisely located with respect to the work station-locating fiducials


34


. A compression spring CS assists in maintaining an upward force on the drum axle. When air is applied to port


41


, actuator


39


begins to lower (i.e., withdraw into housing


35


) and thereby move away from reference surfaces


36


,


37


. As actuator


39


continues to withdraw into housing


35


(e.g., a distance of about 3 or 4 mm.), it eventually looses contact with bearing B


1


and, at this time, the image-recording drum


12


is totally supported, in a cantilever fashion, by the rear drum-support member


32


′. Owing to a slight play in a rear axle bearing B


2


carried on the rear axle A


2


of drum


12


, the forward, unsupported end of drum


12


sags about 1 mm., causing the upper portion of bearing B


1


to lose contact with reference surfaces


36


,


37


. Owing to this sagging of the forward end the image-recording drum and the resulting lose of contact between the forward bearing B


3


and the V-notch defined by the reference surfaces, drum support


32


is allowed to move axially, as discussed below, unimpeded by any frictional forces between the surfaces that normally support the drum axle for rotation.




Like opening


35


A of housing


35


, opening


35


B is also provided with a pair of reference surfaces


42


,


43


for locating the front axle A


3


of the intermediate image-transfer drum


16


. A second air cylinder AC


3


contained in housing


35


has a selectively movable actuator


45


that is positioned to engage bearing B


3


(best shown in

FIG. 5

) on the forward end of drum axle A


3


when drum-support member is in its operative position. Thus, when actuated by applying air through port


46


, air cylinder AC


3


operates to advance actuator


45


towards the apex of reference surfaces


42


,


43


; in doing so, the actuator engages the lower peripheral portion of the outer race of bearing B


3


and raises the top part of the bearing into engagement with the V-notch defined by reference surfaces


42


and


43


. When so positioned, and when the transfer drum has been raised by the rear drum-support member


32


′ to its operative position (as explained below), the outer surface of the transfer drum engages the photoconductive surface and applies sufficient pressure to establish a desired transfer nip of predetermined width (e.g., 5 mm). When air is applied to the lower port


47


of air cylinder AC


3


, actuator


45


lowers (i.e., withdraws into housing


35


). As actuator


45


lowers, the drum axle it supports moves with it, thereby causing the outer surface of the image-transfer drum to lose contact with the image-transfer drum. Note, at the same time the front end of the image-transfer drum is lowered (or raised) the real end of the drum is moved a corresponding difference via the rear drum-support member


32


′, as explained below. When actuator


45


has been lowered by a distance of about 5 mm., it loses contact with drum bearing B


3


. At this point, the image-transfer drum


16


is totally supported, in a cantilever fashion, by drum-support member


32


′.




Thus, as explained above, the front drum-support member


32


, by virtue of its selectively energizeable clamps, is adapted to either (i) be an integral part of the drum assemblies and function to rotatably support the respect drum axles of drums


12


and


16


, as occurs when the actuators


39


and


45


are in their respective UP positions, or (b) be de-coupled from the drum assemblies, as occurs when the actuators are in their respective DOWN positions. As noted earlier, it is important to the invention that drum-support member


32


not only be able to be decoupled from the drum assemblies, but also be movable to a position within the printer frame where it does not interfere with the servicing of the respective drum surfaces. Thus, in addition to carrying structure for precisely positioning and rotatably supporting the axles of drums


12


and


16


, the front drum support member


32


is provided with structure by which it can be slid in a direction parallel to the respective axes of rotation of the drums, whereby it may be moved forwardly of the respective drum axles A


1


and A


3


, as well as be pivoted about an axis normal to the drum axes, whereby member


32


can be substantially displaced from the drums. As shown in

FIGS. 1-4

and


6


A, housing


35


has an integral yoke portion


50


comprising a pair of spaced arm members


51


,


52


. The arm members of yoke


50


are pivotally mounted on a pair of pivot pins


54


,


55


carried by an end of a movable carriage


58


that is slidably mounted in a track


59


extending between the printer frame plates FP and RP. Pivot pins


54


,


55


share a common axis that is perpendicular to the axes of the drums. Track


59


, on the other hand, extends in a direction parallel to the drum axes. Thus, when the respective air cylinders of drum-support member


32


are de-actuated, in which case the respective actuators


39


and


45


and reference surfaces


36


.


37


and


42


,


43


are spaced from the front axle bearings B


1


and B


3


of the two drums, the drum-support member


32


can be slid forward, off of pins P


1


and P


3


and along track


59


, from its operative position (in which openings


35


A and


35


B surround bearings B


1


and B


3


), to an intermediate standby position in which member


32


is located substantially forward of the plane of front frame plate FP (as shown in FIG.


3


), and substantially spaced from the forward ends of the drums. Thereafter, member


32


can be pivoted 180 degrees about pivot pins


54


,


55


to a final standby position, shown in FIG.


5


. In this position, both drums can be accessed for removal of their respective outer layers. An image-recording drum of the type in which the photoconductive sleeve is easily replaceable while the drum shaft is still physically attached to the printer frame is disclosed in the above-referenced U.S. application Ser. No. 09/474,352. An image-transfer drum of the type in which the outer abhesive layer is easily replaceable while the drum mandrel is still physically attached to the printer frame is disclosed in the above-referenced U.S. application Ser. No. 09/574,447.




Referring to

FIG. 6B

, rear drum support member


32


,′ like member


32


, also comprises a “figure eight”-shaped housing


60


. Housing


60


is provided with a pair of holes H


2


and H


4


for receiving the reference pins P


2


and P


4


extending inwardly from the front side of the rear frame plate RP. Hole H


2


is circular and only slightly larger in diameter than pin P


2


, whereas hole H


4


is slightly elongated to facilitate mounting on pin P


4


once pin P


2


has engaged hole H


2


. As noted above, the rear drum-support is rigidly connected to the rear frame plate by bolts or the like. Once in place, the rear drum-support member


32


′ remains stationary. The upper opening


61


of the figure-eight housing


60


serves to rotatably support the rear axle A


2


of the image-recording drum, whereas the lower opening


62


serves to rotatably and releasably support the rear axle A


4


of the image-transfer drum. Upper opening


61


has a small circular through aperture


63


through which the free end of rear axle A


2


projects. Surrounding aperture


63


is a circular recess


64


adapted to receive an inner portion of axle A


2


of somewhat larger diameter than that projecting through aperture


63


. A circular recess


65


with a chamfered edge


65


A surrounds recess


64


and is adapted to receive a ball bearing B


2


mounted on rear axle A


2


. It will be noted that bearing B


2


is the only one of any of the four drum bearings B


1


-B


4


to remain fixed in space within either drum support.




Positioned in the lower opening


62


of housing


60


is a pair of reference surfaces


66


,


67


for precisely locating the rear axle bearing B


4


carried by the rear axle A


4


of the image-transfer drum


16


so that a desired image-transfer nip can be attained between the respective outer surfaces of drums


12


and


16


. Surfaces


66


,


67


cooperate with the movable actuator


68


of a selectively energizeable air cylinder AC


4


to position the rear axle bearing of the transfer drum in the V-notch defined by surfaces


66


,


67


. Bearing B


4


is contained in a carriage


70


that is movably mounted within the lower opening


62


of the rear drum-support member


32


′. Referring to

FIGS. 7-10

, the direction of movement of carriage


70


is controlled by all three pairs of guide rollers


72


,


72


′,


74


,


74


′ and


76


,


76


′, that are rotatably mounted on the carriage. These guide rollers ride atop the front and rear surfaces of member


32


′ and limit movement of drum


16


so as to maintain a parallel relationship between the respective axes of rotation of drums


12


and


16


. An L-shaped bracket


78


mounted on the front side of the drum-support member


32


′ assures that roller pairs


72


,


72


′ and


74


,


74


′ maintain contact with the front surface of member


32


and thereby prevent drum


16


front tipping clockwise, as viewed in the drawings. Note, rollers


72


′ and


74


′ are not shown in the drawings, but are located in positions corresponding to rollers


72


and


74


, but on the opposite side of the drum axle A


4


. Further details of the manner in which member


32


′ supports drum


16


are disclosed in the aforementioned U.S. application Ser. No. 09/574,275.




From the foregoing description of a preferred embodiment, it will be appreciated that an improved apparatus for positioning the various workstations in a document printer/copier has been provided. By virtue of its ability to be selectively de-coupled from and subsequently returned to its operative position with respect to the image-recording and transfer drums, the front drum-support member affords all the advantages of the work station-positioning apparatus disclosed in the aforementioned U.S. application Ser. No. 09/474,352, yet none of the noted disadvantages, in terms of cost and weight.




The invention has been described with reference to a particularly preferred embodiment. It will be apparent, however, that certain modifications can be made without departing from the spirit of the invention, and such modifications are intended to be protected by the following claims.




PARTS LIST






10


—printer






12


—image-recording drum






14


—photoconductive surface






15


,


15


′—gudgeons




DS—drum shaft






16


—image-transfer drum






17


—mandrel






18


—non-stick sleeve






20


—corona charging station






22


—optical writer






24


—development station






25


—pre-clean charger






26


—cleaning brush






28


—image-transfer drum cleaner




P


1


-P


4


—reference pins




H


1


-H


4


—mounting holes




FP—front frame plate




RP—rear frame plate






32


,


32


′—front and rear drum-support members, respectively.






34


—reference fiducials






35


—front drum-support housing






35


A,


35


B—openings in housing


35






A


4


-A


4


—drum axles




B


1


-B


4


—axle bearings






36


,


37


—reference surfaces




AC


1


, AC


3


, AC


4


—air cylinders






39


—actuator




CS—spring






42


,


43


—reference surfaces






45


—actuator






46


,


47


—air ports






50


—yoke portion






51


,


52


—arms






54


,


55


—pivot pins






58


—carriage






59


—track






60


—housing of rear drum support


32









61


,


62


—openings in housing


60








63


—aperture






64


—recess






65


—recess






65


A—chamfered edge






66


,


67


—reference surfaces






68


—actuator






70


—carriage






72


,


72





74


,


74


′,


76


,


76


′—guide rollers






78


—bracket



Claims
  • 1. A document printer comprising:(i) a frame including a front frame plate, (ii) a reference pin extending from said front frame plate at predetermined location, (iii) an image-recording drum having a photo-sensitive outer surface and having opposing and outwardly extending front and rear axles disposed on an intended axis of drum rotation, each of said front and rear axles supporting a bearing by which said drum is rotatably supportable; (iv) a plurality of work-stations for producing transferable images on the drum's photo-sensitive outer surface; and (v) a front drum-support member mounted on said front frame plate and precisely located thereon by said reference pin, said front drum support member having (a) a set of mechanical fiducials for locating at least one of said work-stations relative to the drum surface, and (b) a selectively energizeable clamping mechanism for selectively engaging the bearing on said front drum axle, whereby said front drum-support member can either rotatably support said image-recording drum, or be decoupled therefrom so that the drum can be removed from the printer frame independent of said drum-support member.
  • 2. The apparatus as defined by claim 1 wherein said front drum-support member is movably mounted on said front frame plate for movement between a first position in which said clamping mechanism is positioned to engage the bearing on the drum's front axle, and a standby position in which the front drum-support member is sufficiently spaced from said front axle to enable servicing of the drum.
  • 3. The apparatus as defined by claim 1 wherein said frame comprises a rear frame plate spaced from said front frame plate and having a pair of reference pins extending therefrom at predetermined locations, and wherein said apparatus further comprises a rear drum-support member mounted on said rear frame plate and precisely located thereon by said reference pins extending from said rear frame plate, said rear drum-support member including (a) a bearing for rotatably supporting said rear axle of the photosensitive drum, and (b) a second set of reference fiducials that cooperate with the reference fiducials on said front drum-support member for locating said at least one work station relative to said photosensitive drum surface.
  • 4. The apparatus as defined by claim 3 wherein said front and rear drum-support members are also provided with selectively actuatable clamps for releasably and rotatably supporting a pair of axles extending from opposite ends of an image-transfer drum.
  • 5. The apparatus as defined by claim 1 wherein said front drum support member is slidably mounted on said frame for movement in a direction substantially parallel to said axis of drum rotation.
  • 6. The apparatus as defined by claim 1 wherein said front drum support member is pivotally on said frame for movement about a pivot axis substantially normal to said axis of drum rotation.
  • 7. The apparatus as defined by claim 1 wherein said front drum support member is slidably mounted on said frame for (i) movement in a direction substantially parallel to said axis of drum rotation, and (ii) for movement about a pivot axis substantially normal to said axis of drum rotation.
  • 8. The apparatus as defined by claim 1 wherein said clamp is pneumatically operated.
  • 9. A document printer comprising:(i) a frame including a front and rear frame plates; (ii) a plurality of reference pins extending from said front and rear frame plates at predetermined locations on each plate; (iii) an image-recording drum having a photo-sensitive outer surface and having opposing and outwardly extending front and rear axles disposed on an intended axis of drum rotation, each of said front and rear axles supporting a bearing by which said drum is rotatably supportable; (iv) a plurality of work-stations for producing transferable images on the drum's photo-sensitive outer surface; (v) a front drum-support member mounted on said front frame plate and precisely located thereon by at least one reference pin extending from said front frame plate, said front drum support member having (a) a selectively actuatable clamping mechanism for selectively engaging the bearing on said front drum axle, whereby said image-recording drum is either supported by said front drum-support member for rotation, or decoupled from said front drum-support member and (b) a set of reference fiducials for locating at least one of said work-stations relative to the drum surface; and (vi) a rear drum-support member mounted on said rear frame plate and precisely located thereon by at least one of said reference pins extending from said rear frame plate, said rear drum-support member including (a) a bearing for rotatably supporting said rear axle of the photosensitive drum, and (b) a second set of reference fiducials that cooperate with the reference fiducials on said front drum-support member for locating said at least one work station relative to said photosensitive drum surface.
  • 10. The apparatus as defined by claim 9 wherein said front drum-support member is movably mounted on said front frame plate for movement between a first position in which said clamping mechanism is positioned to engage the bearing on the drum's front axle, and a standby position in which the front drum-support member is sufficiently spaced from said front axle to enable servicing of the drum.
  • 11. The apparatus as defined by claim 9 wherein said front and rear drum-support members are also provided with selectively actuatable clamps for releasably and rotatably supporting a pair of axles extending from opposite ends of an image-transfer drum.
  • 12. The apparatus as defined by claim 9 wherein said front drum support member is slidably mounted on said frame for movement in a direction substantially parallel to said axis of drum rotation.
  • 13. The apparatus as defined by claim 9 wherein said front drum support member is pivotally on said frame for movement about a pivot axis substantially normal to said axis of drum rotation.
  • 14. The apparatus as defined by claim 9 wherein said front drum support member is slidably mounted on said frame for (i) movement in a direction substantially parallel to said axis of drum rotation, and (ii) for movement about a pivot axis substantially normal to said axis of drum rotation.
  • 15. The apparatus as defined by claim 9 wherein said clamp is pneumatically operated.
  • 16. For use in a document printer having (i) a frame including a front frame plate;(ii) a reference pin extending from said front frame plate at predetermined location, (iii) an image-recording drum having a photo-sensitive outer surface and having opposing and outwardly extending front and rear axles disposed on an intended axis of drum rotation, each of said front and rear axles supporting a bearing by which said drum is rotatably supportable, and a (iv) a plurality of work-stations for producing transferable images on the drum's photo-sensitive outer surface; and a front drum-support member adapted to be mounted on said front frame plate and precisely located thereon by said reference pin, said front drum support member having (a) a set of mechanical fiducials for locating at least one of said work-stations relative to the drum surface, and (b) a selectively energizeable clamping mechanism for selectively engaging the bearing on said front drum axle, whereby said front drum-support member can either rotatably support said image-recording drum, or be decoupled therefrom so that the drum can be removed from the printer frame independent of said drum-support member.
  • 17. The apparatus as defined by claim 16 wherein said front drum-support member comprises an integral yoke adapted to be connected to a carriage slidably mounted in a track mounted on the printer frame, whereby said front drum-support member can be slidably mounted on said front frame plate for movement between a first position in which said clamping mechanism is positioned to engage the bearing on the drum's front axle, and a standby position in which the front drum-support member is spaced forward of said front axle.
  • 18. The apparatus as defined by claim 17 wherein said yoke is adapted to be pivotally mounted on said carriage for movement about a pivot axis substantially normal to said axis of drum rotation.
  • 19. The apparatus as defined by claim 16 wherein said clamp is pneumatically operated.
  • 20. The apparatus as defined by claim 16 wherein said front drum-support member comprises a selectively energizeable clamp for selectively engaging a bearing carried on the axle of an image-transfer drum comprising said printer.
CROSS-REFERENCE TO RELATED APPLICATIONS

Reference is made to the commonly assigned U.S. patent applications, the respective disclosures of which being incorporated herein by reference: (1) U.S. application Ser. No. 09/474,352, filed on Dec. 29, 1999 and entitled “Apparatus for Positioning Work Stations in a Document Printer/Copier”. (2) U.S. application Ser. No. 09/574,054, filed concurrently herewith and entitled “Pin Mount for Optical Writer/Recording Element in a Document Printer/Copier”. (3) U.S. application Ser. No. 09/574,275, filed concurrently herewith and entitled “Cantilever Drum Mount for Document Printer/Copier”. (4) U.S. application Ser. No. 09/574,447, filed concurrently herewith and entitled “Image Transfer Drum for Document Printer/Copier”.

US Referenced Citations (5)
Number Name Date Kind
4888620 Fujino et al. Dec 1989
5218405 Wong Jun 1993
5630197 Nishino et al. May 1997
5758243 Haneda et al. May 1998
5999771 Wakihara Dec 1999
Foreign Referenced Citations (3)
Number Date Country
55-88090 Jul 1980 JP
1-232378 Sep 1989 JP
2-123377 May 1990 JP
Non-Patent Literature Citations (4)
Entry
U.S. application No. 09/474,352, filed Dec. 29, 1999, entitled Apparatus for Positioning Work Stations in a Document Printer Copier.
U.S. application No. 09/574,054, filed May 18, 2000, entitled Pin Mount for Optical Writer/Image-Recording Element in a Document Printer/Copier.
U.S. application No. 09/574,275, filed May 19, 2000, entitled Cantilever Drum Mount for Document Printer/Copier.
U.S. application No. 09/574,447, filed May 19, 2000, entitled Image Transfer Drum for Document Printer/Copier.