US3678896A - Conveyor system - Google Patents

Abstract

Apparatus for use in an automatic xerographic reproducing apparatus for cleaning residual toner material from the photoconductive surface after the image has been transferred to a final support material for returning the residual toner to a xerographic developing station via a chain conveyor of improved construction for reuse in the xerographic process.

Description

[ 1 July 25, 1972 United States Patent Hewitt [54] CONVEYOR SYSTEM 198/168 .....l98/l68 ...l18/637 2,756,866 7/1956 Wilde, Jr. 2,738,765 3/1956 Hart.......... 3,590,412 7/1971 [72] lnventor: Robert E. Hewitt, Ontario, N.Y.

Primary Examiner-Mervin Stein Assistant Examiner-Leo Millstein e, Norman E. Schrader and Melvin [21] Appl. No.:

Attorney-James J. Ralabat A. Klein graphic reproducing mu n T x0 C c: A Uli aa m m m m A ar 8 .m nn .i lm MC r-l mm S S mu t a 1 mm .M W 1. A3 sw m 53 5 51 5 3 3 i 50 G5 1 "7 Wm H m 2 "7 m 8 l 1H8 mh In mmm L. 10 W d s a UhF Hum 555 [[1 material from the da n mi km n n O U1 mm MM m c h 8 m photoconductive surface after the im to a final support material for returm References Cited UNITED STATES PATENTS xerographic developing station via a chain conveyor of im- 5/1962 9/1947 proved construction for reuse in the xerographic process.

3,032,009 Magnusson............................l18/637 2,426,998 Hall 198/168 2 Claims, 6 Drawing figures Patented July 25, 1972 4 Sheets-Sheet 1 INVENTOR. ROBERT E. HEWITT BY a ATTORNEY Patented July 25, 1972 $678,896

4 Sheets-Sheet 2 FIG. 2

Patented July 25, 1972 3,678,896

4 Sheets-Sheet 4 CONVEYOR SYSTEM This invention relates to xerographic apparatus and, in particular, to recovering unused toner material from a photoconductive surface after the xerographic image has been transferred and reusing the recovered toner once again in the xerographic development process.

In the art of xerography, as originally disclosed by Carlson in U.S. Pat. No. 2,297,691, a xerographic plate, which is formed of a conductive backing upon which is placed a photoconductive insulating material, is charged uniformly and the surface of the plate exposed to a light image of an original to be reproduced. The photoconductive coating is caused to become conductive under the influence of the light image so as to selectively dissipate the electrostatic charge found thereon thus producing an electrostatic latent image. The latent image is made visible by developing the image with any one of a variety of pigmented resins which have been specifically developed for this purpose. In the xerographic process, the pigmented resin material, or toner, is electrostatically attracted to the latent image on the photoconductive surface in proportion to the amount of charge found thereon. Areas of small charge concentration become areas of low toner density while areas of greater charge concentration become proportionally more dense. The fully developed image is then transferred from the plate surface to a final support material, as for example, paper, and the image fixed thereto to form a permanent record of the original copy.

A preponderance of the toner material is transferred from the photoconductive surface to the final support material during the transfer operation. However, it has been found that the forces bonding some of the toner particles to the photoconductive surface are stronger than the transfer forces involved and therefore some particulate material remains on the photoconductive surface after the xerographic image is transferred. This residual toner, if not cleaned from the xerographic plate in some manner, will have a deleterious effect on subsequent images processed on the plate.

Plate cleaning in automatic xerographic machines in which the plate is continually reused in the xerographic process is accomplished by various devices such as fiber brushes, cleaning webs, wiper blades or the like. The toner material so removed is usually collected and stored in the machine and then periodically removed and discarded. However, most of the commercially accepted methods of cleaning a photoconductive surface in automatic xerographic machines have been found to be dirt producing and wasteful. The fine residual toner material removed from the plate surface is extremely difficult to handle and the material often migrates from the cleaning system into other areas of the machine to contaminate the machine component parts. It has also been found that the residual toner removed from the xerographic plate surface constitutes an extremely high percentage of the total toner used in the xerographic process.

Recently a system of recovering the residual toner for reuse in the development zone has been accomplished effectively by passing a bead chain conveyor between a cleaning station and the development station as described in copending application Ser. No. 838,816, filed on July 3, 1969, and commonly assigned with the instant application. The present invention is an improvement to the bead chain conveyor which must return the residual toner material for reuse in the system.

It is therefore an object of this invention to improve xerography, and in particular, automatic xerographic reproducing apparatus.

A further object of this invention is to reduce toner waste in an automatic xerographic reproducing apparatus.

A still further object of this invention is to reclaim residual toner left in a xerographic plate after the transfer operation so that the toner can be reused in the xerographic develop process.

A still further object of the invention is to improve bead chain conveyor for the transport of powder materials.

For a better understanding of the invention as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings, wherein:

FIG. 1 illustrates schematically an automatic xerographic reproducing apparatus employing the toner reclaiming system of the present invention;

FIG. 2 is a side elevation in partial section showing the drum cleaning station, the improved bead chain construction according to the invention and bead chain drive, the xerographic development system, and the associated elements of the toner reclaiming system shown in FIG. 1;

FIG. 3 is a partial top view of the toner reclaiming system shown in FIG. 2;

FIG. 4 is an enlarged sectional view illustrating details of the improved chain construction according to the present invention;

FIG. 5 is an enlarged elevation sectional view of improved chain construction winding around its capstan drive; and

FIG. 6 is an enlarged perspective view of the improved bead chain and tubular conduit having metering means associated therewith to distribute toner material evenly throughout the developer housing.

As shown, the automatic xerographic reproducing apparatus comprises a xerographic plate including a photoconductive layer of a light receiving surface on a conductive backing and formed in the shape of a drum, generally numerically designated 10 which is journaled in the frame of the machine by means of shaft 11. The xerographic plate is rotated in the direction indicated in FIG. I to cause the drum surface to pass sequentially through a plurality of xerographic processing stations.

For the purpose of the present disclosure the several xerographic processing stations in the path of movement of the drum surface may be described functionally as follows:

A charging station A, in which a uniform electrostatic charge is deposited on the photoconductive layer of the xerographic drum;

An exposure station B wherein a light or radiation pattern of an original document to be reproduced is projected onto the drum surface to dissipate the charge found thereon in the exposed areas to form a latent electrostatic image;

A development station C, at which a xerographic developing material having toner particles possessing an electrostatic charge opposite to the charge found on the drum surface in the latent image areas are cascaded over the moving drum surface whereby the toner particles adhere to the electrostatic latent image to make visible the image in the configuration of the original document to be reproduced;

A transfer station D, in which the xerographic powder image is electrostatically transferred from the drum surface to a final support material; and

A drum cleaning and toner collecting station E, wherein the drum surface is first charged and then wiped with a doctor blade to remove residual toner particles remaining thereon after image transfer and wherein the removed toner is col- Iected for reuse in the xerographic process and in which the drum surface is exposed to an incandescent panel to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

The charging station is preferably located at the bottom of the drum in the position indicated by reference character A in FIG. I. The charging arrangement consists of a corona charging device 13 which includes a corona discharge array of one or more corona discharge electrodes that extend transversely across the drum surface and are energized from a high potential source. The corona discharge electrode is substantially enclosed within a shielding member and is adapted to generate a charge confined within this specific area.

Next subsequent thereto in the path of travel of the xerographic drum is an exposure station B wherein a flowing light image of a stationary original is placed on the moving drum surface. Basically, the optical scanning and projecting assembly comprises a stationary transparent copy board l4 adapted to support the original to be copied; an illuminating means LMP-l to illuminate uniformly the original supported on the copy board; a folded optical system including an object mirror 16, a movable lens system 17, and an image mirror 18' arranged in light projecting relationship with the moving drum surface to project successive illuminated incremental areas on the original document onto the drum surface to form a flowing light image thereon. The lens element is positioned beneath the copy board and is arranged to move through a path of travel parallel to the plane of the copy board whereby the subject image of the original is scanned in timed relation to the movement of the light receiving surface on the xerographic drum.

Positioned adjacent to the exposure station is a fade out panel 19 arranged to discharge or expose the drum surface in the areas between copies to a level below that required for xerographic development so that these charged but nonimaged areas will not be developed as the drum moves through the subsequent developing station.

Next adjacent to the exposure station is a developing station C in which is positioned developing apparatus 20 including a housing 28 having a lower sump portion therein capable of supporting a quantity of two component developer material. A bucket type conveyor 27, having any suitable drive means, is employed to carry the developer material from the lower sump area to the upper part of the developer housing where it is deposited in hopper 29. The developer material moves downwardly into contact with the upwardly moving photocon ductive drum surface. Toner particles are deposited in the image areas on the drum surface in relation to the charge pattern found thereon to form a developed xerographic image. The unused developer material passes from the development zone back into the lower portion of the developer housing. Fresh xerographic toner material is supplied to the developer mix in proportion to the amount of toner deposited on the drum surface by means of dispensing apparatus positioned in the lower portion of toner dispensing bottle 21.

Positioned next and adjacent to the developing station is the image transfer station D. Individual sheets of final support material are fed seriatim into sheet registering and forwarding apparatus 22 from either upper feed tray 35 or lower feed tray 34. The properly registered sheets are then forwarded into moving contact with the moving drum surface and the developed image electrostatically transferred from the drum to the final support material by means of transfer corotron 24. In operation, the electrostatic field created by the corona discharge device electrostatically tacks the transfer material to the drum surface whereby the transfer material moves synchronously with the drum while in contact therewith.

A mechanical stripper finger 25 is pivotally mounted in close proximity to the drum surface immediately adjacent to the transfer corotron. The finger is arranged to move into contact with the drum surface prior to the arrival of the leading edge of the support material. The arcuate shaped stripper finger moves between the drum surface and the leading edge of the final support material to mechanically break the electrostatic bond holding the material to the drum surface. Because of the positioning and the shape of the finger, the leading edge portion of the sheet of final support material is directed upwardly into contact with stationary vacuum transport 26. The trailing edge of the support material, which at this time is still electrostatically tacked to the drum surface, continues to drive the support material forward so that it moves along the bottom surface of the vacuum transport towards fuser assembly 30.

The image bearing support material moving along the stationary vacuum transport moves into the nip between upper fuser roll.3;l and lower fuser roll 32 of fuser assembly 30. The two rolls coact to deliver pressure driving force to the sheet of support material positioned therebetween. A radiant heat source of heat energy 33 extends transverse to the lower roll surface and transfers heat energy to the roll. The roll is specifically coated so that the heat energy transferred thereto is stored on the outer surface of the roll. As the roll rotates in the direction indicated, the heat energy stored there is brought into rubbing contact with the image bearing support material passing through the nip between the two rolls where image fixing is accomplished by delivering a combination of heat and pressure energy to the image bearing support material.

After leaving the fuser assembly, the fixed copy is transported through a circular paper path into a movable guide and drive roll assembly 36. The movable guides can be prepositioned to either feed the paper delivered from the fuser into upper feed tray 35 or into discharge catch tray 37. The apparatus can be programmed by means of the machine control logic system to precondition the paper handling equipment to accept simplex copies in upper feed tray 35. The simplex copy is then once again reprocessed through the xerographic transfer station to form a duplex image and then discharge from the machine as described above.

The next and final station in the automatic xerographic reproducing apparatus is a drum cleaning and toner recovery station E at which cleaning apparatus constructed in accordance with the present invention removes substantially all residual toner particles remaining on the xerographic drum surface after image transfer recovers the residual toner removed for reuse in the automatic reproducing apparatus in a manner to be described below.

A rectangular shaped flexible blade is utilized in the preferred embodiment of the present invention to remove residual toner from the moving dr'um surface. The blade is mounted in blade holder 51 forming one wall of cleaning and collection apparatus 40 (FIG. 1) so that it normally rests transversely in a pressure contact with the photoconductive layer on the drum with the edge of the blade formed by the joinder of upper face surface 47 and front side surface 48 being positioned slightly below the horizontal centerline of the drum. It should be noted that the blade is positioned so that the contacting edge cuts or chissels toner material from the drum surface much like a lathe cutting tool removes material. In fact, it has been found that the forces experienced by the blade are quite similar to the forces encountered by the lathe cutting tool. The blade is best supported in a tool-like fashion having an end relief angle and a slight back rate angle. The end relief angle, that is, the angle between the front side 48 of the blade and a plane tangent to the drum surface at the point of lead edge contact, can be varied for different blade materials to effectively eliminate blade chatter and other undersirable effects associated with improper blade positioning. Although not essential for the practice of the present invention, it is desirable to provide a slight back rack on face surface 47 so that a sharper cutting edge is presented to the drum surface resulting in more efficient drum cleaning.

Any suitable non-metallic flexible cleaning blade material may be employed in the cleaning system of the present invention. Typical non-metallic flexible materials include: polysiloxane rubber, polyurethane rubber, polytetrafluoroethylene resin, polytrifluorochloroethylene resin, styrenebutadiene rubber, nitrile rubber, nitro-silicone rubber, flexinle polyurethane foam, polyethylene resin, and blends, mixtures and copolymers thereof. The blade should be sufficiently soft to minimize plate abrasion and particularly abrasion to a selenium type imaging surface. Preferably, the blade material should have a Shore hardness of less than 65 durometers. Tests have shown that a relatively wide latitude in blade thickness can be employed in the present apparatus with no noticeable change in the cleaning process.

It should be clear that by the doctor blades slightly below the horizontal centerline of the drum surface and providing the blade with a slight back rack, the removed residual toner material will be forced to fall to the backside of the blade, that is to the side away from the photoconductive drum surface. The removed residual toner is thus prevented from recontacting and rebonding itself once again to the drum surface. As illustrated in FIGS. 2'and 3, the removed toner falls into an open side channel 53 adjacent to and running longitudinally along the drum surface. A screw type conveyor 55 mounted upon shaft 54 is journaled for rotation in end plate 56 and cover plate 62. The conveyor is supported in the open side channel in substantially parallel relation to the doctor blade and is arranged to convey the toner particles removed from the drum surface towards toner recovery drive housing 61.

The open side channel 53 is closed at one end by means of end plate 56 while the opposite end of the channel is securely mounted in drive housing 61. The channel communicates with a reservoir or collecting area, generally referred to as 57, in the housing. A top portion of shaft 54 as seen in FIG. 3, extends through end plate 56 and has rigidly affixed thereto driving gear 85. Although not shown, driving gear 85 is driven from the machine main drive system to rotate the auger in a direction whereby the screw conveyor transports toner material laterally behind the blade into reservoir area 57 where the residual toner is collected. The residual toner which is collected in reservoir area 57 of the drive housing 61 is transported back to the developer housing by means of a conveyor system made up of supply and return tubing 66, 67; developer housing connector 70; and toner metering and return loop 71. The various parts making up the conveyor system are mated together so that a continuous substantially closed circuit conduit having a uniform inside diameter runs from reservoir area 57 across the width of the developer housing and returns once again to said reservoir.

An endless chain generally designated 90 according to the invention as will be more fully described hereinafter moves downwardly through the collected toner material in reservoir area 57. The chain beads mechanically force the particulate toner material downwardly into supply tubing 66. The tubing is maintained in operative relation with the drive housing by pressing the tubing firmly into the adapter positioned in the bottom of the drive housing plate 65. The opposite end of tubing 66 is similarly connected in developer housing connector 70. Supply tubing 66 and the return tubing 67 are preferably constructed of a flexible plastic material which, as shown in FIG. 1, is conveniently routed from the toner cleaning and collecting apparatus 40 to the developer housing through the machine so as to avoid the stationary machine components.

New toner is dispensed in the present apparatus by means of a roll dispenser (not shown) positioned in the bottom portion of toner dispensing bottle 75. The bottle is seated between rails 73, 74 extending laterally across the dispensing opening provided in the developer housing. The bottle is adapted to dispense toner at a predetermined rate directly into the developer housing as dispensing roll is rotated in the direction indicated. Developer housing connector 70 is secured to the developer housing by afiixing embossed sections 72 thereon to rails 73, 74 as for example, by screws. The bead chain which has transporting toner material through supply tubing 66, is guided through approximately a 90 turn as the chain passes through connector 70 so that the chain leaves the connector along a path of travel substantially parallel to rail 73. Loop 71, which is also fabricated of a relatively rigid plastic material, is supported in the connector 70 so that the loop is suspended just below the toner dispenser bottle and runs substantially around the outer periphery of the bottle in parallel relation to the support rails. The bead chain entering the dispensing area of the developer housing first passes through a portion of tubing having a series of step-like cutouts 80 formed in the side wall thereof. As illustrated in FIG. 6, the step-like cutouts are progressively lowered in equal increments as the tubing extends across the width of the developer housing from a starting point substantially high on the side wall of the tube to a point whereby the entire side wall of the tube is removed. As the chain transports toner across the width of the developer housing, the toner is incrementally dispensed in substantially equal quantities across the developer housing. The bead chain continues around the loop and once again makes a 90 turn through connector 70 and returns once again to drive housing 61 through return tube 67.

Although not shown, seals are provided between the open side channel 53 and the rotating drum surface to prevent residual toner material from escaping from the toner cleaning and collecting apparatus 40. As can be seen, because a close system is thus provided, little or no free toner material is permitted to escape to the surrounding machine areas. The toner cleaning and recovery system as herein disclosed is not only extremely clean to operate but also protects the surrounding machine components from being contaminated by loose or free toner particles. The entire cleaning and collecting apparatus 40 (FIG. 1) is pivotally supported upon pivot arms 58 mounted on tie rod 59 which is locked to the machine frame. To facilitate drum removal, the entire assembly 40 is swung downwardly about rod 59 away from the drum surface. As can be seen, open side channel 53 pivotes downwardly to form a trough capable of containing any loose toner particles which may be in process in the system at this time. When the assembly is moved to the operative position as shown in FIG. 2, a spring biased latch 86 is locked in supporting engagement with latch pan 87 by means of locking mechanism 88 whereby the cleaning edge of the flexible self-adjusting cleaning blade is placed in pressure contact with the rotating drum surface.

A drive sprocket 63 is rotatably mounted on shaft 82 which is journaled for rotation in drive housing 61. The drive sprocket is driven directly from the main machine drive through screw conveyor shaft 54. Driven gear 84, mounted on the bottom end shaft 54, as shown in FIG. 3, turns intermediate gear 83 which in turn drives sprocket drive gear 81 in the desired direction shown in FIG. 2. Passing over the rim of the drive sprocket 63 is endless bead chain generally designated 90. The drive sprocket is arranged to engage and guide the chain to move the chain in the direction indicated. In the past, difficulty has been experienced in bending conventional type bead chain around sprocket 63 due to the fact that residual toner material fills the chain beads causing a stiffness in the chain which may result in a malfunction.

In accordance with the present invention, the chain 90 remains flexible throughout its circuitous path. The chain is formed by hollowed spherically shaped members 93 which have apertures 95 formed therein through which link members 97 are received to form a continuous chain. In the past, it has been found that toner material has entered spherical members 93 through apertures 95 whereby link members 97 have been prevented from moving relative to the spherical members around bends as where the chain passes around drive sprocket 63. As best shown in FIGS. 4 and 5 relatively large openings 100 are formed in the surface of member 93 at right angles to the link members 97. By the arrangement any toner material trapped in the spherical members 93 is discharged through openings 100 due to a pumping action carried out by the belled end portion 101 of link members 97 as spherical members 93 rotate on their axes as best seen in FIG. 5. Now it can be understood that the coaction of the link members 97 on the toner material discharges the material maintaining a flexibility in the chain structure.

Openings 100 should be sufficiently large to adequately expel toner material for chain flexibility but not sufficiently small such that the strength of the chain is not weakened. Under these circumstances, it has been found that the ratio of the area of openings 100 to the surface area of the spherical members 93 may range from about I to 20 to about I to 5.

While this invention has been described with reference to the structure disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the scope of the following claims.

What is claimed is:

1. In apparatus for returning the residual particulate toner remaining on a photoconductive surface after image transfer to a remote developer housing for reuse in the xerographic developing process wherein residual particulate toner is removed from the photoconductive surface and collected and then returned by a tubular conduit connecting said collecting said hollow members being formed with at least one relatively large opening at substantially right angles to said apertures whereby upon bending movement of said chain means around said sprocket residual toner material filling said hollow members may be discharged to enable relative movement between said elongated members and said hollow members.

2. Apparatus according to claim 1 wherein the ratio of the area of said relatively large openings to the surface area of said hollow members ranges from about 1 to 20 to about 1 to 5.

Claims (2)

1. In apparatus for returning the residual particulate toner remaining on a photoconductive surface after image transfer to a remote developer housing for reuse in the xerographic developing process wherein residual particulate toner is removed from the photoconductive surface and collected and then returned by a tubular conduit connecting said collecting means and the developer housing, an endless chain means being arranged to be driven sequentially through said collected toner and then a tubular conduit in communication with the developer housing, the improvement comprising said endless chain means comprising spherically shaped hollow members formed with two small oppositely faced apertures in the surface thereof and elongated members each received through a one of said apertures on adjacent hollow members and formed with belled end portions, drive means to drive the chain means including a drive sprocket to positively engage the hollow members, said hollow members being formed with at least one relatively large opening at substantially right angles to said apertures whereby upon bending movement of said chain means around said sprocket residual toner material filling said hollow members may be discharged to enable relative movement between said elongated members and said hollow members.

2. Apparatus according to claim 1 wherein the ratio of the area of said relatively large openings to the surface area of said hollow members ranges from about 1 to 20 to about 1 to 5.

Images