US3879785A

US3879785A - Cleaning apparatus

Info

Publication number: US3879785A
Application number: US354962A
Authority: US
Inventors: Charles F Roth; Gordon C Butler
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1973-04-27
Filing date: 1973-04-27
Publication date: 1975-04-29
Anticipated expiration: 1992-04-29
Also published as: NL7405709A

Abstract

A cleaning device for an electrostatographic imaging surface, is provided with an endless loop cleaner transported in sweeping contact with an electrostatographic imaging surface from which it is desired to remove electrostatically adhering toner. An electrical biasing potential is applied to the endless loop, said biasing potential being of sufficient magnitude and polarity to attract toner from the surface to the cleaning means. A pick-off means is positioned in proximity with the cleaning means and in turn has applied thereto an electrical biasing potential of a magnitude and polarity sufficient to attract toner from the cleaning means to the pick-off means. Toner which is removed from the cleaning means by the pick-off means may then be placed in a convenient receptacle. More specifically, the means for applying the electrical biasing potential is in the form of a corona generating device located within the loop and positioned opposite the area of sweeping contact of the imaging surface with the cleaning means. A cleaning means is provided, preferably in the form of a fiber pile sheet or belt, and the pick-off means includes a pick-off forming device in the form of a roller which is of such a diameter as to cause the fiber pile of the cleaning means to exhibit a spreading or opening effect sufficient to allow a corresponding pick-off roller to remove toner from a deep position within the fiber pile.

Description

United States Patent 11 1 Roth et al.

1 1 CLEANING APPARATUS [75] Inventors: Charles F. Roth, Monroe, N.Y.;

Gordon C. Butler, Welwyn Garden City, England [73] Assignee: Xerox Corporation, Rochester, N.Y.

[22] Filed: Apr. 27, 1973 [21] Appl. No.: 354,962

Primary E.\uminerHarvey C. Hornsby Assistant Examiner-C. K. Moore Attorney, Agent, or FirmJames J. Ralabate; Earl T. Reichert [57] ABSTRACT A cleaning device for an electrostatographic imaging surface, is provided with an endless loop cleaner trans- 1 1 Apr. 29, 1975 ported in sweeping contact with an electrostatographic imaging surface from which it is desired to remove electrostatically adhering toner. An electrical biasing potential is applied to the endless loop, said biasing potential being of sufficient magnitude and polarity to attract toner from the surface to the cleaning means. A pick-off means is positioned in proximity with the cleaning means and in turn has applied thereto an electrical biasing potential of a magnitude and polarity sufficient to attract toner from the cleaning means to the pick-off means. Toner which is removed from the cleaning means by the pick-off means may then be placed in a convenient receptacle. More specifically, the means for applying the electrical biasing potential is in the form of a corona generating device located within the loop and positioned opposite the area of sweeping contact of the imaging surface with the cleaning means. A cleaning means is provided, preferably in the form of a fiber pile sheet or belt, and the pick-off means includes a pick-off forming device in the form of a roller which is of such a diameter as to cause the fiber pile of the cleaning means to exhibit a spreading or opening effect sufficient to allow a corresponding pick-off roller to remove toner from a deep position within the fiber pile.

12 Claims, 4 Drawing Figures CLEANING APPARATUS This invention relates to electrostatographic imaging systems and, more particularly, to an improved apparatus for cleaning electrostatographic imaging surfaces.

The formation and development of images on an imaging surface by electrostatographic means is well known. One basic process, as taught in U.S. Pat. No. 2,297,691, by C. F. Carlson involves placing a uniform electrostatic charge on an imaging surface such as a photoconductive insulating layer, exposing the layer to a light-and-shadow image to dissipate the charge in the areas of the layer exposed to the light and developing the resulting electrostatic latent image by depositing on the image a finely divided electroscopic material referred to in the art as toner. The toner is normally attracted to those areas of the layer which retain a charge, thereby forming a toner image corresponding to the electrostatic latent image. This toner image may then be transferred to a support surface such as paper, and the transferred image may subsequently be permanently affixed to the support surface. After transfer, the residual toner remaining on the layer is removed by a cleaning operation and the layer may then be employed for another imaging cycle.

As is well known in recent years, the steadily increasing size of various industries has required an enormous increase in the amount of paper work that must be accomplished, maintained, and made available for wide circulation. In present day commerical automatic copiers/reproduction machines, the electrostatographic imaging surface, which may be in the form of a drum or belt, moves at high rates in timed unison relative to a plurality of processing stations. This rapid movement of the electrostatographic imaging surface has required vast amounts of toner to be used during development.

Associated with the increased amounts of toner is the difficulty in removing the residual toner image remaining on the imaging surface after transfer. in the reproduction process of Carlson as described above, the residual image is tightly retained on the photoconductive layer by a phenomenon that is not fully understood but believed to be caused by an electrical charge and van der Waalls forces that prevents complete transfer of the toner to the support surface, particularly in the image area. The residual toner image is normally removed by cleaning devices such as a brush type cleaning apparatus or web type cleaning apparatus. A typical brush cleaning apparatus is disclosed in-U.S. Pat. No. 2,832,977 to L. E. Walkup et al. and in U.S. Pat. No. 2,91 1,330 to H. E. Clark. The brush-type cleaning means usually comprises one or more rotating brushes which brush toner from the photoconductive surface into a stream of air which is exhausted through a filtering system. A typical web cleaning device which retains toner is disclosed in U.S. Pat. No. 3,186,838 to W. P. Graff, Jr. et al.

While ordinarily capable of cleaning electrostatographic imaging surfaces, conventional cleaning devices have not been entirely satisfactory. Most of the known cleaning devices usually become less efficient as they become contaminated with toner which cannot be removed necessitating frequent replacement of the cleaning device. As a result, valuabletime is lost during down time-while a change is being made. A further problem is that cleaning devices employed in current commerical copier/duplicator machines permanently remove residual toner particles from the system. Since toner is an expensive consumable, permanent removal of the residual toner particles from the system during cleaning is undesirable because it adds to the cost of machine operation. Both the web-type and brush cleaning units normally do not return residual toner particles to be reusable as developer after the cleaning operation due to the collection of lint from the web or brush. Furthermore, the cleaning operation can result in generation of heat resulting in physical and chemical changes in the toner. In addition, an elaborate and noisy vacuum and filtering system is necessary to collect the residual toner particles removed by the brush. Moreover, large amounts of toner particles thrown into the air by the rapidly rotating brush cleaner often drift from the brush cleaning housing and form unwanted deposits on critical machine parts.

While the web-type cleaner has some advantages, it is difficult to align with the surface of the electrostatographic imaging surface, and uneven contact between the web on a takeup roll is often encountered even with complex alignment apparatus. Another problem with the web-type cleaner is that pressure contact between cleaning webs and some imaging surfaces must be kept to a minimum to prevent destruction of the imaging surface.

in U.S. Pat. No. 3,580,673 to F. Y. Yang, there is disclosed another type of cleaning device employing a brush roller contacting the imaging surface, and wherein magnetic beads are intermixed with toner particles and subjected to an attractive bias force which aids in dislodging the residual toner image. However, although the use of magnetic beads accomplishes an cleaning function, it is more desirable to effect and efficient cleaningoperation without the use of additional particulate material. In U.S. Pat. No. 3,572,923 to D. J. Fisher, opposite biasing is employed to attract particles from a brush roller which contacts the imaging surface to remove residual toner. Both of the foregoing systems, although improving toner removal by means of electrostatic forces, require a brush roller engaged in frictional contact with the imaging surface. a

It has been found, however, that the use of brush rollers result in certain difficulties. Specifically, mechanical interference of the fibers forming the interference surface of a brush roller with the imaging surface is greater than is required only for a cleaning action. The extra interference built into the spacing between a roller and an imaging surface is designed to compensate for machine tolerances such as run out and for fiber matting. It is a normal tendency for fibers after repeated interference with an imaging surface to form a mat or a bent-over position which results in reduction of the interference between the brush roller and the imaging surface, thereby changing the mechanical action pick-off roller, the result will be increased matting due to the heavy interference. In addition, as relative humidity and fiber conductivity change, electrostatic conditions of the fibers themselves will change. Electrostatic charge on the fibers will depend to a large degree upon the triboelectric relationship of the fibers and the imaging surface; Conduction from cleaning and toner removal biasing also influencefiber charges and these factors are further influenced by environmental conditions. Since brush cleaning by means of electrostatic biasing requires placement of a charge on the brush at some point prior to its interferring relationship with an imaging surface, the transition between the application of the charge and actual interference will cause a change in the electrostatic charge placed on the fiber due to' variation inthe triboelectric relationship between the' fibers and photoreceptors caused by such environmental conditions. Thus, there is a continuing need for an improved system for cleaning electrostatographic imaging surfaces.

It is therefore, an object of this invention to provide a method and apparatus for cleaning electrostatographic imaging surfaces which overcome the abovenoted' deficiencies.

It is another object of this invention to improve the quality of prints produced by electrostatographic reproduction machines.

his a' further object of this invention to reduce toner consumption in automatic electrostatographic imaging machines.

' apparatus and reproduction equipment which does not require extensive alignment or adjustment.

It is another object of this invention to remove residual toner for immediate reuse in an electrostatographic imaging machine.

It is a further object of this invention to provide a simple, inexpensive and reusable apparatus for cleaning electrostatographic imaging surfaces.

It is still a further object of this invention to provide a cleanin g apparatus for an electrostatographic imaging machine which is more efficient than existing cleaning devices. 7

It is still a further object of this invention to prevent powder cloud formation as a result of a toner particle dispersion at the cleaning station of an electrostatographic imaging machine. I

It is another object of this invention to reduce noise level of an electrostatographic imaging machine. It is another object of this invention to substantially reducethe effects of fiber matting in a cleaning device employed with an electrostatographic imaging machine. v,

It is another object of this invention to provide a cleaning device for an electrostatographic imaging machine employing fiber interference for cleaning an imaging surface with improved removal of toner from the root areas of the fiber.

It is another object of this invention to provide a cleaning device for an electrostatographic imaging machine which will be relatively insensitive to environmental conditions.

The foregoing objects of the present invention are achieved by an endless loop cleaning means transported in sweeping contact with an electrostatographic imaging surface from which! it is desired to remove electrostatically adhering toner. An-electrical biasing potential is applied to the endless loop, said biasing potential being of sufficient magnitude and polarity to attract toner from the imaging surface to the cleaning means. A pick-off means is positioned in proximity with the cleaning means and in turn has applied thereto an electrical biasing potential of a magnitude and polarity sufficient to attract toner from the cleaning means to the pick-off means. Toner which is removed from the cleaning means by the pick-off means may then be placed in a convenient receptacle. More specifically, the means for applying the electrical biasing potential is in the form of a corona generating device located within the loop and positioned opposite the area of sweeping contact of the imaging surface with the cleaning means. A cleaning means is preferably in the form of a fiber pile sheet or belt, and the pick-off means includes a pick-off forming device which is of sufficient diameter to cause the fiber pile of the cleaning means to exhibit a spreading or opening effect sufficient to allow a corresponding pick-off roller to remove toner from a deep position within the fiber pile.

The foregoing objects and brief description of the present invention as well as other objects and further features thereof will become more apparent from the following more detailed description and appended drawings wherein:

FIG. 1 is a partial schematic and cross-sectional side elevational view of a cleaning apparatus as employed in conjunction with a form of electrostatographic imaging device employing an endless loop photoreceptor;

FIG. 2 is a detail of the pick-off mechanism of FIG.

FIG. 3 is a perspective illustration of the operation'of the invention employing a fiber pile sheet and recycling device; and,

FIG. 4 shows an alternative embodiment of the present invention employing transversely movable endless belts.

Referring to FIG. 1 there is shown a typical apparatus for reproducing a stationary planar original document supported at an object plane on a transparent platen. For purposes of this explanation, the reproduction medium is illustrated as an imaging surface formed as an endless loop recycling photoreceptor 10 such as an electrostatographic plate formed as an endless belt moving in the direction indicated. For purposes of this invention, the particular form of imaging surface may take the shape of either a drum or endless loop photoreceptor or the like, it being immaterial for purposes of this invention which form is used. The imaging surface 10, which can, for example be a reusable or nonreusable photoreceptor such as selenium or zinc oxide or phthalocyanine in a binder, comprises for the purposes of this embodiment a recycling web of durable flexible and preferably electrically conductive material supporting on its outer surface a thin layer of photoconductive insulating material. Any suitable photoconductive insulating material known in connection with electrostatographic plates may be employed, such as, for example, a thin layer of vacuum deposited vitreous selenium. Selenium, as well as other photoconductor insulating materials coated on a flexible support may be repeatedly bent around a radius of a few inches without cracking or flaking from the support and without removing electrostatographic effectiveness. Cylindrical rollers l2, l4 and 16 support the imaging surface 10 in the form of an endless flexible belt and motor 18 drives the roller 14 about its shaft 20, whereby the imaging surface is continually advanced at a uniform constant rate.

As is well known in electrostatographic processes, the imaging surface 10 in the course of its movement is first charged by means of a corona charging device 22 supported adjacent to the imaging surface to effect a uniform high potential thereon of the order of several hundred volts. After the imaging surface 10 has transversed the charging device 22, it advances planarly between

rollers

12 and 14 to an exposure station illustrated generally as 24 for exposure to a pattern of light and shadow as may be provided in conventional manner. One example of a means or mode of applying a light and shadow pattern is illustrated in U.S. Pat. No. 3,432,231 to J. F. Gardner. The exposure of the imaging surface 10 to the light image discharges the photoconductive layer in the area struck by light so that there remains on the imaging surface an electrostatic latent image configuration corresponding to the light image projected by the device 24. As the imaging surface continues its movement around the roller 14, the latent electrostatic image passes through a developing station 26 at which a suitable mechanism applies developing material to the imaging surface as it passes therethrough. Typical of devices for applying developing material is shown in U.S. Pat. 2,618,552 to Edward N. Wise and U.S. Pat. No. 2,638,416 to Walkup and Wise. Thereafter, the powder image passes through an image transfer station designated generally as 28 at which the powder image is electrostatically transferred to a copy web 30 by means of a second corona charging device 32.

The support surface through which the powder image is transferred may be paper, vellum, cardstock, etc. The web 30 is supported by

rollers

34 and 36, the latter being driven by a suitable motor driving unit 38. The image may then be fixed to the support web by any suitable means such as the heat fuser unit 40, as disclosed, for example in U.S. Pat. No. 2,852,651 to Crumrine and to the aforesaid U.S. Pat. No. 3,432,231. It will be understood that instead of winding onto a pick-up roller 36, the support web 30 may be passed directly to a cutter or the like by which the web is cut into separate lengths, or the web itself may constitute a series or plurality of individual sheets of suitable support surface material such as individual sheets of paper and the like which are periodically provided to the station 28.

The foregoing explanation of the reproduction system employing an endless loop photoreceptor as an imaging surface is provided as exemplary in conjunction with the use of the present invention, it being understood that a drum-type of electrostatographic imaging surface could be used, such as that shown and described in U.S. Pat. No. 3,301,126 to Osborn et a1.

After image transfer, the movement of the imaging surface 10 carries the now residual image pattern to a cleaning station illustrated generally as 42. The heart of the cleaning device 42 is an endless loop cleaning means 44 which is shown in the form of a continuously recycling belt. The belt is composed of a fiber pile 46 which, as shown in FIG. 2, includes a backing member 48 and a plurality of upstanding cleaning fibers 50. The entire cleaning mechanism 42 is secured into a housing, not shown, which is, in turn, secured to the machine frame.

The continuously recycling belt 44 is adapted for rotation by means of a plurality of rollers. Thus, motivation is supplied to a tension tracking and drive roller 52 adapted for rotation about a shaft 54 which is journaled for rotation in the housing and is driven in the direction indicated by the arrow by means of a motor 56. The roller 52 is employed for driving since the configuration shown in FIG. 1 permits the belt 44 to exhibit a large degree of wrap about the roller 52, and maximum frictional contact is derived therewith by choosing a frictional coating for roller 52. The tracking featu're is provided by shaping the side of the roller 52 with a crown which will thus provide accurate tracking of the belt 44 during rotation as is well known. The belt is brought into proximity with the imaging surface 10 by means of suitably positioned .forming

roller

56 and 58 each respectively adapted for rotation about their central shafts which are in turn journaled for such rotation into the external machine housing. A corona charging device 60 is positioned between the forming

rollers

56 and 58 for purposes which will be explained in further detail below. A pick-off mechanism, illustrated generally as 62 is provided by a pick-off forming a roller 64 and a main pick-off roller 66, each also adapted for rotation about their respective central shafts, and in turn journaled for rotation into the external machine housing. As the path of the belt 44 continues from the forming roller 58 about the pick-off forming roller 64, it traverses a further corona charging device 68. Another corona charging device is positioned as shown between the roller 52 and the forming roller 56. As shown, the roller 52 is adapted for lateral movement in the schematically illustrated slot 72 by means of a suitable screw or like adjustment. Since the belt 44 is flexible, adjustment of the roller 52 along the slot 72 results in an increase or decrease in tension of the belt 44. Since the forming

rollers

56 and 58 provide an arcuate path for the belt 44 about the imaging surface 10 in accordance with the surface of the roller 12, adjustment of the position of the roller 52 in slot 72 will result in an increase or decrease of tension of the belt 44 against the surface of the imaging surface 10.

For efficient wiping action, it is desirable that the fiber pile 46 of the belt 44 be driven in an opposite direction at the interference formed between the belt 44 and the surface 10 at speeds which may range from about half to about three times the speed of travel of the belt 10. Alternatively, it is noted that the fiber pile of the belt 44 may be driven in the same direction as the imaging surface 10, as long as the relative speeds of the surface 10 and the belt 44 are such that there is sufficient relative motion to obtain the desired wiping action of the cleaning fibers on the surface 10.

Turning now to the operation of the invention, it is noted that for positive to positive reproduction, a negatively charged toner is employed whereas in a negative to positive reproduction a positively charged toner is employed. For purposes of explanation, it will be assumed that positive to positive reproduction is the mode of operation of the device, it being understood that either operation will be usable with the present invention as will be apparent from the following description.

Thus, negatively charged toner forming the residual image left on the imaging surface 10 after emergence from the transfer station 28 passes from the roller 16 towards the roller 12 beneath a corona charging device 74 and a discharge lamp 76. The function ofthe corona charging device 74 which is energized by adc source 74A, is to provide a slightly negative charge to the toner in order to insure that;th e toner retains itsnegative charge characteristicsprior-to entering the cleaning station 42. Activation of the pre-clean lamp 76 serves to place the toner'and surface 10 at approximately the same charge level in order to eliminate any attraction causedby any polarity difference between the toner and surface 10. It should be noted that the corona charging device 74 and discharge lamp 76 are not essential, their elimination being a function of whether the residual toner retains sufficient negative charge to operate in conjunction with the cleaning device 42. After cleariing,a further corona charging device and discharge lamp may be located at a station A in order to neutralize any post cleaning residual charge.

As the negatively charged toner enters into the interference area formed between the belt 44 and the imaging surface 10, toner material is attracted by virtue of the electrostatic andtribo-electric field effects to the fiber pile 46 of the belt 44. To this end, the corona charging device 70, which has been energized by means of the electrical biasing potential applied thereto from the dc biasing source 70A, has resulted in the placement of a positive charge on the fiber material 50. Corona charging device 70 performs a post pick-off charge placement function, neutralizing any prior positive level of the biasing potential applied to the charging device 70 serves to place a positive potential on the fiber material 50. As the belt 44 continues its traverse around the first'forming roller 56 it enters into proximity with the corona charging device 60 which is in turn energized by a dc. source of potential 60A. The source of potential 60A provides a positive voltage level to the coratron unit 60 which in turn provides a positive bias charge to the backing 48 of the fiber pile 46. The resultant positive charge on the fabric pile attracts the negatively charged toner material into the fibers 50 of thebelt 44. It is noted that since the corona charging device 60 is used to supply the cleaning bias to the fiber pile by charging the backing 48, the placement of the corona charging device 60 directly over the area of interference between the cleaning belt 44 and the imaging surface 10, results in an intense cleaning field provided with a relatively small current and little danger from arcing.

Thus, for example, the power supply 60A together with charging unit 60 should bring the backing of the belt to, for example, 4,000 volts relative to ground, the polarity determined by materials used and conditions encountered. This will require the power supply 60A to deliver in the range of 1-3 p. amp/in. and have acoronode potential adequate to avoid cut off. These values will depend on characteristics of the corona charge unit and the power supply system as well as load impedance.

The backing 48 is itself a resilient high compliance material of relatively high impedance, such as 18 meg ohms, thus providing the high resistivity necessary to limit the current generated by the relatively high volthigh potential enables the degree of interference between the fibers S and the imaging surface to be correspondingly reduced since wiping action no longer becomes as critical as .in prior devices in order to remove toner particles from the surface 10. The use of a continuously recycling belt 44 permits the corona charging device 60 to be placed directly opposite the area of interference within the loop, and thus enables the application of a relatively high charging field to be applied to the belt backing 48 and thus to the fiber 50. It should be noted that the dc. source 60A may be varied and hence the voltage applied to the corona charging device 60 selectively changed to obtain most optimum operating conditions. Furthermore, resistivity of the backing may be selected to accommodate a range.

of voltage supplied from the potential source 60A in accordance with the limitation of current flow necessary in order to prevent any arcing from occurring between the corona charging device 60 and the imaging surface 10. Fibers can support only so much potential longed as well as photoreceptor wear reduced. Desirably, the cleaning fibers of the fiber pile 50 are made from any suitable nonconductive material which will further inhibit the arcing condition noted above. I

Typical cleaning fiber materials are acrylic velvets, orlon, polypropylene, nylon, rayon, acetates, mohair, Arnel, glass, Dynel, Dacron, cotton and other natural and synthetic fibrous or filamentary materials and mixtures thereof. In addition, in order to further enhance the attraction of the toner to the cleaning fibers, the fibersmay be made of or coated with a material having a triboelectric attraction for the toner particles. Typical materials having this relationship are described in US. Pat. No. 2,618,55l to Walkup; US. Pat. No. 2,618,552 to Wise; U.S. Pat. No. 2,638,416 to Walkup and Wise; and US. Pat. No. R25, 1 36 to Carlson. Typical backing materials are fabrics of woven nylon, polypropylene, cotton, etc. of adequate flex, strength and abrasion resistance. The fibers 50 are bonded or otherwise suitably attached to the resilient backing, the base area of the fibers at its junction with the backing being generally designatable as the root structure thereof. It should be noted that the feature of triboelectric attraction with regard to the cleaning fibers further enhances the attraction of toner to the fiber belt, thereby further enhancing the advantages of the present invention. The cleaning fibers may extend any suitable length which may range from l/l6 of an inch to about 5/16 of an inch and preferably about and eighth of an inch to about 3/ l 6 of an inch, for a fiber density ranging from about 10,000 to about 100,000 and more fibers per square inch. Desirably, the interference between the cleaning fibers and the imaging surface will be just brushing contact. It should be noted that the attractive forces created with the intense cleaning bias filed provided by the present invention would be sufficient to attract particles without any contact; however, it has been found that the cleaning bias field in combination with slight brushing contact between the fibers and the imaging surface serve to remove toner with maximum efficiency.

After removal of toner, the belt next passes around the forming roller 58 and approachesthe pick-off station 62 and, in so doing ,.it traverses the corona charging device 68 which is in turn biased by means of elec trical biasing of potential applied for the dc. source 68A. The function of coratron charging device 68 is to provide a pre pick-off charge to the toner particles. To this end, the source 68A applies a negative potential which may be in the range of between 1,000 to 3.000 volts, and more desirably at about 1,500 volts. As a result, toner particles are provided with a negative charge level prior to entering the nip between the pick-off forming the roller 64 and the pick-off roller 66. In accordance with the invention, the pick-off forming roller 64 is coupled to a source of potential 64A which applies an electrical biasing potential of a negative polarity to the pick-off forming roller 64. The pick-off roller 66 is connected to the machine frame through its central shaft which may be journaled to the machine frame housing for rotation. The main pick-off roller which may be of stainless steel or like conductive material is at ground potential relative to the pick-off forming roller 64. Since, in this embodiment the toner particles after emergence from beneath the corona charging device 68 are provided with a negative charge, the additional negative charge provided by the roller 64 acts to repel the particles towards the relatively positive polarity of the main pick-off roller 66.

As a result of the repelling force, the toner particles are dislodged from the fibers 50 and placed on the main pick-off roller 66. As wasnoted in discussion of prior art devices, a great difficulty in removing toner from fiber pile has been the necessity of removing particles from as far down in the pile as possible in order to eliminate toner build-up. As noted in FIG. 2, the present invention provides a pick-off forming roller 64 of relatively small dimension. In this manner, as the belt 44 approaches the nip area between the roller 64 and the roller 50, the small diameter of the roller 64 causes the resilient backing of the roller 48 to deform by making a relatively sharp traverse about the forming roller 64 which causes the fibers of the fiber pile 46 to separate by a distance sufficient to expose the root structure of the fiber pile 46. In this manner, toner particles indicated generally as 78 are thus exposed to the repelling force provided by virtue of the toner particle negative charge and the negative charge placed upon the forming roller 64, causing repelling of the particles to the relatively positively charged pick-off roller 66. Since the spreading of the fibers 50 of the fiber pile 46 by virtue of the small diameter of the roller 64 will result in separation, the effect will be to reduce the shielding of each fiber in the nip by virtue of the surrounding fibers thereby further improving the strength of the electrostatic field of generated between the roller 64 and the roller 66.

The efficiency of removal will be a function of a combination of factors, including the diameter of the pickoff forming roller 64, the depth of the fibers 50 and their density, the angle of wrap of the backing 48 around the perimeter of the roller 64 and the strength of the electrostatic field between the toner, the fiber pile 46, and the pick-off roller 66. These factors can each be adjusted relative to the other to maximize the efficiency of the cleaning operation in each situation.

The pick-off roller 66 is provided with a rotation in I the direction of the arrow in the same relative direction as the movement of the belt 44 in the nip between the

rollers

64 and 66. This rotation may be as a result of the frictional contact between the fiber pile and the roller 66, or it may be the result of an independent drive provided by a separate motor unit coupled to the central shaft of the roller 66, not shown. It may be advantageous from a cleaning viewpoint to provide independent drive to the roller 66 with a slightly higher velocity than the movement of the belt 44, thereby providing relatively clean surfaces of the roller 66 at the moment of removal of toner 78 from the fiber pile 46. In addition, matting forces exerted on the fiber pile 46 as a result of engagement between the

roller

64 and 66 may be reduced by providing a separate drive to the roller 66 and spacing roller 66 from the fiber pile 46 such that only slight engagement of the fibers 50 and the roller 66 occur. If the relative field strength is high enough, there may actually be a gap between the roller 66 and the upper portion of the fiber pile 46.

The rotation of the pick-off roller 66 will be such that toner particles 78 will be carried about the surface of the roller until reaching the position wherein the force of gravity may be sufficient to pull the toner particles 78 from the roller 66. It should be noted that since the roller 66 is preferably at ground potential, and that the particles 78 have a slightly negative charge, the toner particles will not normally adhere to the surface of the roller 66 but will fall as aresult of the gravity attraction upon reaching a non-supported position caused by the rotation of the roller 66. To further insure removal of the toner particles, a scraping assembly 80 may be positioned at an advantageous location relative to the surface of the roller 66 for wiping the particles from the surface of the roller. Particles will then fall into a suitable receptacle 82 which may include a lower portion 84 which will serve to recycle the toner particles falling thereon to the developing station 26 where they may be reutilized in the developing process.

Referring to FIG. 3, the recycling mechanism is shown in some greater detail. With like reference numerals referring to like components relative to FIG. 2, FIG. 3 illustrates an imaging surface 10 which is shown in FIG. 3 is in its alternative form as a photoreceptive layer coated on a drum rather than upon an endless loop as shon in FIG. 1. The operation of the device as shown in FIG. 3 is in all respects as shown in FIG. 1. As shown in FIG. 3, the pick-off roller 66 has coupled thereto a scraper or doctor blade assembly indicated generally as 80 and which comprises a blade member anchored with respect to the roller 66 by any suitable retaining means. As the pick-off roller 66 rotates, toner which is adhering thereto can fall into the receptacle 82 or be scraped therefrom by means of the scraper assembly 80. As the toner is collected in the receptacle 82, it is removed therefrom by means of an auger 86 mounted for rotation on a shaft 88 and driven by suitable driving means not shown. The auger 86 rotates through the toner collected in the receptacle 82 in a direction shown by the arrow towards one or more conduits 90 from which the toner is discharged, as by gravity, and subsequently conveyed as by a belt or the like for reuse at the development station as described above.

In the foregoing embodiment, the cleaning device has been shown as a fiber pile sheet which coacts with the surface of the imaging surface in the manner as described aforesaid. Referring now to FIG. 4, an alterna' tive embodiment is shown wherein the cleaning device is in the form of a belt of relatively narrow dimension.

In this embodiment, the belt moves transversely to the rotation of the moving imaging surface which as shown in FIG. 4 is in the configuration of a drum although it it to be understood that it may also be in the form of a continuous loop photoreceptor such as is shown in FIG. 1. The operational concept pertaining to the device as is described above in connection with the fiber pile sheet is similar to that as described in connection with the transversely moving belt.

As shown in FIG. 4, a belt 92 is constructed as a fiber pile with a flexible backing and cleaning fibers as described in connected with the sheet shown in FIG. 1. The belt isldriven by a series of rollers including first and

second forining rollers

94 and 96, a pick-off forming roller'98, and a driving tension and tracking roller 100. The driving roller 100 includes a motor 102 coupled to the driving roller for supplying the necessary motive force. The belt 92 includes the fiber pile on the surface which will be facing outward against the surface of the drum. The belt is positioned with respect to the drum for an interfering engagement. An elongated corona charging device 106 is shown along the length of the belt 92 directly opposite the drum over the area of interference of the belt and the drum. A corona charging device includes a source of potential 106A for applying the electrical biasing potential to the charging device 106 necessary to form the cleaning bias field as described in connection with the embodiment of FIG. 1. In order: tolmaintain the belt 92 against the surface of theidrumduring its entire period of interference, the coron a"chargi ng device 106 may be adapted to include a pluralityof skids which will apply pressure against the belt during its interference traverse. The additional corona charging devices such as shown in FIG. 1 are applicable to the operation of the device as shown in FIG. 4 but have not been shown for purposes of clarity.

The operation of the device shown in FIG. 4 is precisely that as the device shown in FIG. 1 with the exception that a transversely moving belt is employed. In order to prevent saturation of the narrow width belt it is possible to employ a second belt 110 which as shown in FIG. 4 is positioned just above the first belt and driven by means of common shafts coupling complementary rollers at the same locations as the drive, forming and pick-off rollers noted above. In this event, a common pick-off roller 108 may be employed to dislodge toner particles-from the belt 92 and the additional corresponding belt 110. As before, a receptacle 112 receives'the particles which are dislodged from the

belts

92 and 110 as well as the similar scraping mechanism 114 which may be employed to dislodge particles which do not fall thereon of their own accord. To further improve the efficiency of the device, the drive mechanism 102 which intercouples a first driving roller 100 and a second driving roller 116 may be configured such that two rollers are driven in opposite directions, thereby enabling the two belts to move parallel to one another transverse to the drum in opposite directions and thereby further improving the cleaning effect. In this event, it would be necessary to rearrange the'polarity of the corona applied to the

respective belts

110 and 92 at the various positions along its traverse in order to allow the proper polarities to be set up in the fiber pile for attraction and rejection of toner, as well as rearranging the cleaning stations.

The foregoing is thus a description of a new and novel cleaning apparatus capable of removing substantially all of the residual toner on the surface of an electrostatographic imaging member. The use of the endless loop cleaning belt or sheet greatly improves the efficiency of an electrostatographic imaging machine employing fiber rollers or the like. The endless loop cleaning belt with a high compliance support for the fiber pile allows for a combination of machine tolerances with little change in contact pressure. Since the contact pressure is a minimum necessary for proper cleaning action, no more than a minimum matting will occur. Thus, cleaning element life is prolonged and photoreceptor wear is obviously reduced. Additionally, the accummulation of toner in the root area of the fiber pile cleaning material which has heretofore necessitated greater interference by an electrostatic pick-off roller in order to expose toner to the electrostatic attraction of such roller, resulting in increased matting, is avoided by the use of a small roll at the pick-off station to expose the root areas of the fiber, thereby permitting a lower interference profile in order to permit electrostatic attraction of toner from these lower areas of the fiber. Further, variations of environmental conditions resulting in electrostatic changes in the fiber are no longer a problem since the electrostatic charge on the cleaning fibers will no longer depend to a large degree on the triboelectric relationship of the fibers and photoreceptor. The present invention, in the creation of a very high intense cleaning field due to the positioning of a cleaning bias corona charging device opposite the area of interference, permits the direct application of an electrostatic charge far in excess of the normal triboelectric relationship existing with prior art rollers and the like and therefore to a large extent removes environmental conditions as the factor causing a change in the triboelectric effect and therefore in the cleaning action.

Furthermore, the present invention permits accurate removal of toner from the recording surface in such a manner that objectionable filming of toner does not occur and hence the toner is adapted for repeated reuse in the system. In addition, no powder cloud is formed in the cleaning station which undesirably can cause malfunction of the machinery. Furthermore, the cleaning apparatus of the present invention does not require extensive repair, readjustment, replacement of rollers, dispensing of web, and the like. Thus, the apparatus of the present invention not only provides cleaning with greatly improved efficiency but is also inexpensive and reusable and permits toner collected to be used repeatedly.

Although the invention has been described with reference to the structures disclosed herein, it should not be confined to the details set forth since it is apparent that various modifications can be made. Thus, for example, the belt cleaning loops may be adapted to move at different angular relationships with respect to the imaging surface, or additional cleaning stations may be employed at desired locations about the surface of the unit, and the entire operation of the device may be employed for oppositely polarized toner material as in the case of reversal development wherein a positively charged toner is employed. In this event, opposite polarities of coratron charging devices may be employed to place the desired charges on the toner particles for appropriate movement. i

Other variations and changes will be obviously appar ent to those skilled in the art. It will be understood that the examples given in the embodiment shown are done so for purposes of illustration, and, that the invention may be modified and embodied in various other forms without departing from the scope and spirit of the invention as disclosed herein.

What is claimed is:

1. Apparatus for removal of electrostatically adhering toner from an electrostatic imaging surface in an electrostatic imaging device comprising an endless loop cleaning means formed of a fiber structure on a resilient backing transported over an area of interfering contact with said imaging surface, first means for applying an electrical biasing potential to said cleaning means, said biasing potential being of a magnitude and polarity sufficient to provide an intense field across said interfering contact to thereby attract said toner from said surface to said cleaning means with a minimum of said interfering contact, pick-off means positioned in proximity with said cleaning means, second means for applying an electric biasing potential to said pick-off means, said biasing potential being of a magnitude and polarity sufficient to attract said toner from said cleaning means to said pick-off means, and third means'for receiving said toner from said pick-off means, said pick-off means including a pick-off forming roller positioned within said cleaning means, said pick-off forming roller being of a diameter sufficient to cause said resilient backing to deform about said roller until said fibers separate, exposing the root structure thereof, and a pick-off roller coacting with the spread portion of said fiber pile for removing toner from said root structure,

2. The apparatus of claim 1 wherein said cleaning means is an elongated belt of fiber pile material, and said first means includes a corona charging device positioned within said cleaning means opposite said area of interfering contact.

3. The apparatus of claim 1 wherein said pick-off roller is positioned opposite said pick-off forming roller and forming a nip with respect to said forming roller, said cleaning means passing therebetween, means for placing a charge on said toner prior to entry into said nip, and said second means applying said potential to said pick-off forming roller whereby said toner is repelled from said cleaning means to said pick-off roller.

4. The apparatus of claim 3 wherein said apparatus further includes means for applying a charging potential to said cleaning means prior to entrance of said cleaning means into said area of interfering contact, said charge potential being sufficient to neutralize charge applied by said second means.

5. The apparatus of claim 1 wherein said cleaning means and said imaging surface are each driven with a relative motion therebetween, and wherein said cleaning means is a first and second elongated belt of fiber pile, and means for driving each of said belts in a direc tion transverse to the direction of movement of said imaging surface across the area to be cleaned.

6. The apparatus of claim 1 wherein said cleaning means and said imaging surface are each driven with a relative motion therebetween, and wherein said cleaning means is a fiber pile sheet, and means for driving said fiber pile sheet in a parallel plane relative to said imaging surface but with a differential surface speed.

' 7. The apparatus-of claim 5 wherein said belts are each driven in opposite directions across said area of interfering contact. g

8. Apparatus for removal of electrostatically adhering toner from an imaging surface in an electrostatographic imaging device comprising an endless loop cleaning means having a resilient backing and a cleaning surface of upstanding cleaning fibers, the cleaning surface being adapted to be transported over an area of interfering contact with said imaging surface, a corona charging device positioned within said cleaning means opposite said area of interfering contact for applying an electrical biasing potential to said cleaning means, said biasing potential applied by said corona charging device being of a magnitude and polarity sufficient to provide a field across said interfering contact to thereby attract said toner from said surface to said cleaning means with a minimum of said interfering contact, pick-off means positioned in proximity to said cleaning means, second means for applying an electric biasing potential to said pick-off means, said biasing potential applied by said second means being of a magnitude and polarity sufficient to attract said toner from said cleaning means to said pick-off means, and third means for receiving said toner from said pick-off means.

9. Apparatus for removal of electrostatically adhering toner from an imaging surface in an electrostatographic imaging device comprising a plurality of endless loop cleaning means each having a resilient backing and a cleaning surface of upstanding cleaning fibers, the cleaning surface of each cleaning means being adapted to be transported over an area of interfering contact with said imaging surface, means for driving said imaging surface in one direction, and means for driving each of said cleaning means in a direction transverse to said one direction, a corona charging device positioned within at least one of said cleaning means opposite said area of interfering contact for applying an electrical biasing potential to said one cleaning means, said biasing potential applied by said corona charging device being of a magnitude and polarity sufficient to provide a field across said interfering contact to thereby attract said toner from said surface to said one cleaning means with a minimum of said interfering contact, pick-off means positioned in proximity to said plurality of cleaning means, second means for applying an electric biasing potential to said pick-off means, said biasing potential applied by said second means being of a magnitude and polarity sufficient to attract said toner from said cleaning means to said pick-off means, and third means for receiving said toner from said pick-off means.

10. The apparatus of claim 8 wherein said pick-off means includes a pick-off forming roller, said pick-off forming roller positioned with respect to said cleaning means whereby the latter wraps around the perimeter of said roller sufficiently to exhibit a deformation of said resilient backing and thereby spreading the fiber of said fiber pile and exposing the root structure thereof.

11. The apparatus of claim 10 wherein said pick-off means includes a pick-off roller positioned opposite said pick-off forming roller and forming a nip with respect to said forming roller, said cleaning means passing therebetween, means for placing a charge on said toner prior to entry into said nip, and said second means applying said potential to said pick-off forming 15 16 roller whereby saidtoner is repelled from said cleaning cleaning means into said area of interfering contact, means to Sam roller i said charge potential being sufficient to neutralize 12. The apparatus of claim 11 wherein said apparatus further includes means for applying a charging potential to said cleaning means prior to entrance of said charge applied by said second means.

Claims

1. Apparatus for removal of electrostatically adhering toner from an electrostatic imaging surface in an electrostatic imaging device comprising an endless loop cleaning means formed of a fiber structure on a resilient backing transported over an area of interfering contact with said imaging surface, first means for applying an electrical biasing potential to said cleaning means, said biasing potential being of a magnitude and polarity sufficient to provide an intense field across said interfering contact to thereby attract said toner from said surface to said cleaning means with a minimum of said interfering contact, pickoff means positioned in proximity with said cleaning means, second means for applying an electric biasing potential to said pick-off means, said biasing potential being of a magnitude and polarity sufficient to attract said toner from said cleaning means to said pick-off means, and third means for receiving said toner from said pick-off means, said pick-off means including a pick-off forming roller positioned within said cleaning means, said pick-off forming roller being of a diameter sufficient to cause said resilient backing to deform about said roller until said fibers separate, exposing the root structure thereof, and a pick-off roller coacting with the spread portion of said fiber pile for removing toner from said root structure.

5. The apparatus of claim 1 wherein said cleaning means and said imaging surface are each driven with a relative motion therebetween, and wherein said cleaning means is a first and second elongated belt of fiber pile, and means for driving each of said belts in a direction transverse to the direction of movement of said imaging surface across the area to be cleaned.

7. The apparatus of claim 5 wherein said belts are each driven in opposite directions across said area of inTerfering contact.

11. The apparatus of claim 10 wherein said pick-off means includes a pick-off roller positioned opposite said pick-off forming roller and forming a nip with respect to said forming roller, said cleaning means passing therebetween, means for placing a charge on said toner prior to entry into said nip, and said second means applying said potential to said pick-off forming roller whereby said toner is repelled from said cleaning means to said pick-off roller.

12. The apparatus of claim 11 wherein said apparatus further includes means for applying a charging potential to said cleaning means prior to entrance of said cleaning means into said area of interfering contact, said charge potential being sufficient to neutralize charge applied by said second means.