IL31502A - Imaging system - Google Patents

Description

31502/2 n p n y n n s n y n I M A G I N G S Y S RANK XEROX LIMITED C8 29656 This invention relates to imaging systems, and more particularly, to an improved cleaning device.

The formation and development of images on the. surface of photoconductor materials by electrostatic means is well known.' . The basic xerographic process, as taught by C. F. Carlso in U. ,' S. Patent 2,297,691, involves placing a uniform electrostatic, charge -' on a photoconductive insulating layer, exposing the layer to. a light-and-shadow image to dissipate the charge on the areas of the", layer exposed to the light and developing the resulting latent electrostatic image by depositing on the image a finely-divided ·"'··" electroscopic material referred to in the art as "toner". The '.■ toner will normally be attracted to those areas of the layer which, retain a charge, thereby forming a toner image corresponding to , the latent electrostatic image. This powder, image may then be trans- '.'■' ferred to a support surface such as paper. The transferred image may subsequently be permanently affixed to a support surface as by': heat. Instead of latent image formation by uniformly charging the;'-, photoconductive layer and then exposing the layer to a light-and'-- ; '.' shadow image, one may form the latent image by directly charging the layer in image configuration. The powder image may be fixed1 '··'· to the photoconductive layer if elimination of the powder image transfer step is desired.. Other suitable fixing means . such as solvent or overcoating treatment may be substituted for the fore-';1 going heat fixing steps. . -''·· Several methods are known for applying the electroscopic..,; particles to . the latent electrostatic image to be developed." One.-;' development method, as disclosed by E. N. Wise in U. S. Patent ·.""■·.· 2,618,552, is known as "cascade" development.' In this method, a..·."■■ developer material comprising relatively large carrier particles having fine toner articles electrostatically coated thereon is . · is engaged with the electrostatic image-bearing surface and the' toner particles are drawn from the brush to the latent image by ... electrostatic attraction.

Still another technique for developing electrostatic .'·',· latent images is the "powder cloud" process disclosed' by C. F.

Carlson in U. S. Patent 2,221,776. In this method, a developer material comprising electrically charged toner particles, in a gaseous fluid is passed adjacent the surface bearing the latent' electrostatic image. The toner particles are drawn by electrostatic attraction from the gas to the latent image.. This/process is particularly 'useful in continuous tone development. .as disclosed by . W. Gundiach in U. S. Patent 3,166,432 may be used where suitable.

In automatic xerographic equipment, it is conventional to ■employ a xerographic plate in the form of a cylindrical drum which ■·.·. is . continuously rotated ' through a cycle of sequential ope'rations; ; ;.. . including charging, exposing,, developing, transfer and cleaning.

The plate is usually charged with corona or positive polarity by means of a corona generating device of the type disclosed by L.' E.'.' '· Walkup in U. S. Patent 2,777,957 which is connected to a suitable . . ' source of high potential. In forming a powder image on the' electro-;.' static latent image during the development step,' the powder image is .. electrostatically transferred to a support surface by means of a corona generating device such as the corona device mentioned above. ■ In automatic equipment employing a rotating drum, a support surface to which a powder image is to be transferred is moved through the equipment at the same rate as the periphery of the drum and contacts the drum at the transfer position interposed between the drum surface and the corona generating device. Transfer is effected by the corona generating device which imparts an electrostatic charge to attract-~the powder image from the drum to the support surface. The polarity, of charge- required to effect image transfer is dependent upon the visual form of the original' copy relative to the reproduction and the electroscopic characteristics of the developing material employed' to effect development.. For example, where a positive' reproduction is to be made on the positive original, it is conventional to employ a positive polarity corona to effect transfer of a negatively charged toner image to its support surface. When a positive reproduction . from a negative image is desired, it is conventional . to employ , a .' positively charged developing material which is repelled by the charged areas on the plate to the discharged areas thereon to form a In either case, a residual powder image usually remains on the . plate after transfer. Before the plate may be- reused for a subsequent cycle, it is necessary that the residual image be removed " : to prevent "ghost images" from forming on subsequent copies. In the positive-to-positive reproduction process described above, the' residual developer powder is tightly retained on the plate . surface; y a phenomenon that is not fully understood but believed to be caused by an electrical charge that prevents complete transfer of ., the powder to the support surface, particularly in the image .area. Discharge is substantially neutralized by means of a corona . generating device prior to the contact -of the residual powder image with a cleaning device. The neutralization of the charge enhances the cleaning efficiency of the cleaning device. <'■ The residual toner image is removed by electrostato-r graphic cleaning devices such as a "brush" type cleaning apparatus or "web" type cleaning apparatus. The typical brush cleaning j apparatus is disclosed by L. E. Walkup et al in U. S. Patent 2,832,977. The brush-type cleaning means usually comprises one or more rotating brushes which brush residual powder from the plate into a stream' of air which is exhausted through a filtering system. A typical web cleaning device is disclosed by W. P. Graff, Jr. et a in U . S. Patent 3,186,838. As disclosed by Graff, Jr. et al,. ' emoval of the residual powder on the plate is'effected by, passing a web of fibrous material over the plate surface.

While ordinarily capable of satisfactorily cleaning electrostatographic plate surfaces, conventional electrostatographi plate cleaning devices suffer serious deficiencies in certain areas Most of the known cleaning devices are complex and occupy a great deal of space in the electrostatographic copier or duplicator.

Because of the space requirements of the cleaning system, compact It is, therefore, an object of this invention to provide an electrostatographic imaging system which utilizes a cleaning.-. ■.·.'. means which overcomes the above-noted deficiencies.

It is another- object of this invention to provide a '.·' : ('.· '·. improved reusable electrostatographic plate cleaning system occupying reduced space.

It is a further object of this invention to provide an ·..' improved reusable electrostatographic cleaning system adapted to '. " reduce toner, consumption in automatic electrostatographic .imaging ■ . ■ machines . · It is also an object of this invention to provide a plate cleaning system which does not require extensive alignment or adjustment. ·,;■ It is still another object of this invention to provide." ■; a more durable longer lasting reusable electrostatographic plate . : .' ■ ' ' cleaning system.

It is another object of this invention to provide a-, reusable electrostatographic plate cleaning system which does, not : ;. - require a power source. '.·;.;:. r It is a further object of this invention to provide a: ':··'" . simple inexpensive reusable electrostatographic plate, cleaning :·■ . system.

It is a still further object of this invention to provide a reusable electrostatographic plate cleaning system which is more efficient than known electrostatographic plate cleaning systems..-.

The above objects and others are accomplished, generally speaking, by providing an imaging system employing an improved , ' ■■ : reusable electrostatographic imaging surface cleaning system com- . . prising at least one self-adjusting flexible cleaning blade in ' to form an acute angle of less The cleaning system of this invention is particularly :·· ■ effective in development systems employing two-component type developing materials. In carrying out the developing method of ■ the present invention, any suitable conventional two-component type developing material comprising carrier and toner particles may be used. Representative patents in which these developer compositions, are disclosed include U. S. Patent 2,618,551 to Walkup, U. S. Patent 2,618,552 to Wise, U. S. Patent 2,633,415 to Walkup and Wise, U. S. Patent 2,659,670 to Copley, U. S. Patent 2,788,288 to Rheinfrank . and Jones and U. S. Reissue Patent 25,136 to Carlson. Generally,, the toners have an average particle diameter between about 1 and about 30 microns, and the relatively larger carrier beads have an average particle diameter from about 50 to about 1,000 microns in diameter. Typical toner concentrations include a range from about 0.5 to about 10 percent by weight based on the total weight of the I . - ' · · · Any suitable dry solid lubricant may be employed in the system of this invention. The dry solid lubricant may be; supplied ¾ to the inferface between the cleaning blade and the imaging surface'-. by various techniques. For. example, the dry . solid lubricant may; be ·' in the form of a powder which is intimately mixed with the toner. ■ and supplied to the surface of the imaging, surface during development of the latent electrostatic image. Alternatively, the dry "·..'/'" solid lubricant may be dispersed throughout the photoconductive , ΐ; layer, or suspended in a photdconductor overcoating. As the surface .:; of the overcoating or treated photoconductor gradually wears away,; additional dry lubricant which was originally distributed through .. ·■.... the photoconductive or overcoating layer is exposed and made : available at the interface of the cleaning blade and imaging, surface. In another alternative embodiment, the dry solid lubricant may be .. sprinkled or smeared on the imaging surface at any point during the . imaging cycle prior to the cleaning station. For example, a - " ; ' suitable dispenser such as a plurality of dispensers described in U. S. Patent 3,013,703 may be positioned over a xerographic drum ; between the exposure and development stations and adapted to; continuously or intermittently sprinkle dry solid lubricant particles on the imaging surface. Any suitable dry solid lubricant may be ' employed. Hydrophobic dry solid lubricants are preferred. Further, when the lubricant may ultimately transfer to the receiving sheet, ..'. the lubricant is preferably selected from the' group of materials..· having a color which matches the color of the receiving sheet, j e.g., white lubricant particles would be employed with white receiving · sheets. Obviously, contrasting colors may be employed for novel ■ effects if desired. Typical dry solid hydrophobic lubricants include metal salts of fatty acids such as zinc stearate, barium ' stearate,. lead stearate, iron stearate, nickel stearate, cobalt ' cadmium stearate, magnesium stearate, zinc oleate, manganese oleate, · iron oleate, cobalt oleate, copper oleate, lead oleate, magnesium oleate, zinc palmitate, cobalt palmitate, copper palmitate, magnesium palmitate, aluminum palmitate, calcium palmitate, lead caprylate, ' lead caproate, zinc linoleate, cobalt linoleate, calcium linoleate,/'- ' zinc ricolinoleate and cadmium ricolinpleate; higher aliphatic acids . such as stearic acid and palmitic acid; and colloidal pyrogenic :;·.',..: ··:'..'. silica particles such as Cab-O-Sil available from- the. Cabot .?.

Corporation and mixtures thereof.

Any suitable reusable electrostatographic imaging surface · may be employed in the system of this invention. Well known electrostatographic imaging surfaces include photoconductive materials:.'■.'■.'V''."*, -. such as vitreous selenium, organic or inorganic photoconductors . embedded in a non-photoconductive matrix, organic or inorganic photoconductors embedded in a photoconductive matrix and the like. ': Representative patents in which photoconductive materials are .. -· . disclosed include U. S. Patent 2,803,542 to Ullrich, U. S. Patent; -,,'" 2,970,906 to Bixby, U. S. Patent 3,121,006 to Middleton, U. S.

Patent 3,121,007 to Middleton and U. S. Patent 3,151,982 to Corrsin.' Generally, photpconductive materials are supported by conductive . substrates. Typical conductive substrates include brass, : aluminum, · ; gold, platinum, steel, glass coated with conductive oxides, metallized non-conductive substrates, laminated sheets of metal, and ■: plastic and the like. The conductive substrate may be in the form.: of a flat plate, cylinder, flexible sheet or other suitable con- '. ' figuration. Preferably, the photoconductive surface comprises '.- ; '. vitreous selenium, selenium alloys or mixtures of selenium and other inorganic materials because superior copy quality is . . i, maintained for a greater number of copying or duplicating .cycles.

Fig. 14 is a side view in elevation of still another alternative embodiment of the blade assembly of this invention.: , · ' Fig. 15 is a plan view of the blade assembly and at a right angle with respect to the view of Fig. 14.

Fig. 16 is a view in perspective of a plurality of ■ .. · cleaning blade holding members and blades according to another:.; 'embodiment of this invention.

Fig. 17 is a side view in elevation of an alternative ., .:, ■ embodiment of the. multiple. blade system of Fig. 16. ··' Fig. 18 is a view in perspective of another modified . ... form of the multiple blade embodiment of .Fig. 16.

Referring now to Fig. 1, reference character 10 designates a rotatable xerographic drum having an outer layer 12 of photo- ····.· conductive insulating material such as vitreous selenium. The drum. 10 is mounted to move in the direction indicated by the arrow.

The surface of photoconductive insulating layer 12 is uniformly ; ..charged by conventional cororia charging device 14 and exposed to . a pattern of activating electromagnetic radiation at 16.. The latent electrostatic image formed by the exposure means 16 is developed by rotating drum 10 by means of a conventional driving means, not shown, through a developing apparatus 18 including a developer housing 20 having a lower reservoir or sump portion for accumulating toner, carrier and dry lubricant particles 22. Mounted within the developer housing 20 is a driven bucket-type conveyor 24 used to .carry the developer material from the sump to the upper portion, of th developer housing 20 from where the developer material is cascaded over a hopper chute 28 onto the surface of the photoconductive layer 12. , As the developer material cascades over the drum, toner the. previously . formed electrostatic latent image areas on the surface of the photoconductive layer 12 to form a visible xero-■·' graphic powder image; the remaining developer material falling off the peripheral surface of the drum into the sump of the- developer housing 20. Toner particles consumed dμring the developing operation to form the xerographic powder images are replenished by a toner dispenser 19 such as the dispenser described in U. S. Patent 3,013,703 to Hunt. In the embodiment illustrated i Fig. 1, the dry solid hydrophobic lubricant is employed in finely-divided form and admixed with the toner particles. Thus, the dry solid lubricant particles' are introduced into the machine simultaneously with tjhe toner particles by means of dispense 19. i .

The developed images emerging from' the developing j 'apparatus may be transferred at a transfer station 28 to a moving .. paper web 30. The transferred powder image may be permanently ' fixed to the web 30 by any conventional means such as by hea't fuser 32. The surface of the photoconductor 12 is then cleaned of . residual toner particles by the cleaning apparatus 34 thus, completing the entire charging, exposing, developing, transferring and cleaning cycle.' The cleaning apparatus illustrated in Fig. 1 comprises a. substantially rectangular cleaning blade member 36 pivotaily secured .to a hinged blade holder 38 by means of a shouldered screw 40. The cleaning blade 36 normally rests in pressure contact with the surface of photoconductive layer 12 due to the combined .weight of · ' " the blade itself, the blade holder 38, and cam follower 42 which is secured to blade ^holder 38 by suitable means not shown. The cam follower 42 is located to one side of the drum 10 and extends sufficiently below an extension of the plane of the outer surface of photoconductive layer 12 ' for engagement with cam 44 during by the combined weight of cleaning blade 36, blade holder 38 and cam follower 40 may be supplemented by spring biasing means 46.

Cam 44 is securely attached to an end of and rotates with drum 10. As the cam .44 engages cam follower 42, the cam follower rides upon and follows the curved surface of cam 44 thereby causing blade ; holder 38 and blade 36 to be lifted away from the surface of photo- conductive' layer 12. The raising of the blade 36 permits the ridge . of residual toner particles accumulated by blade 36 to be transported on the moving surface of photoconductive layer 12 into the '.. developing apparatus 18 where it is removed from the surface of photoconductive layer 12 by the cascading developer. Pivotal blade movement should be limited to avoid contact between the blade and the imaging surface while the blade is in the retracted position. This is accomplished in this embodiment by contact between the blade 36 and blade holder 38. Thus, residual toner particles which are' normally wasted by permanent removal from the xerographic machine by conventional cleaning apparatus is immediately reclaimed each 1 cycle for reuse in the embodiment illustrated in Fig. 1. A removable •trough 48 may be positioned subadjacent the nine o'clock position of , the outer periphery of drum 10 to collect any toner particles which may gravitate away from blade 36 along the outer surface of drum 10.

In Fig. 2, another embodiment of the invention is shown ■wherein the outer surface of xerographic drum 50 contains at least one groove which extends longitudinally across the drum surface parallel to the drum axis. The development cycle illustrated in this embodiment is similar to the system described with reference to Fig. 1. However, instead of introducing the dry lubricant with the toner as shown in Fig. 1, the lubricant is supplied to the · surface of photoconductive insulating layer 54 after the photoconductive insulating layer 54 is charged by means of corona charging developing apparatus 60. The dry lubricant, · in particular form, ; is stored in dispenser 62 and controllably released by means of gate 64.

The developing images emerging from the developing apparatus 60 may be transferred at a transfer station 66 to a moving paper web 68. The residual untransferred toner particles. ' adhering . to the surface of photoconductive insulating layer 54 may then be ·'· optionally charged by means of a . conventional corona discharge ·. device 70 such as the device described by L. E. Walkup in' U. S .·'.·. Patent 2,777,957. The polarity of charge imparted to the. residual toner particles by corona charging device 70 depends upon the particular results desired. Where it is desired to eliminate the inconvenience of removing, and discharging the contents of a catch . trough such as trough 48 illustrated in Fig. 1, the corona discharge device should be capable of imparting a . charge polarity which increases the electrostatic charge adhesion between the residual toner particles and the surface of photoconductive insulating layer 54 to prevent the possibility of residual toner gravitating away from the surface of drum 50. Elimination of the trough also permits maximum recovery of residual toner particles for . reuse in the developing apparatus. If desired, the corona discharge device 70 may be used to impart a charge polarity which reduces the electro-', static attraction between the residual toner particles and the surface of photoconductive insulating 54. The reduced attraction reduces the wiper blade pressure required to remove the residual toner particles and therefore extends the life of the photo-conductor and cleaning blade. · Optionally, a light source, not shown, may be employed in conjunction with or substituted for corona discharge device 70 to reduce toner particle adhesion to the photo-conductor, surface. a substantially · rectangular cleaning blade member 72. reinforced by a U-shaped channel member 74 and pivotally secured to a hinged blade holder 76 by means of a shouldered screw 78. The cleaning blade 72 is .biased .by means of leaf spring 80 to bear yieldingly . · ■ against the surface of photoconductive insulating layer 54. As the drum 50 rotates, the residual toner on the surface of photo-/.'" 'conductive insulating layer 54 is dislodged and transported by cleaning blade 72 along the drum surface toward and finally into '.; grooves 52. A screw 82 mounted in a lug 84 serves to limit the lowest position to which the cleaning' blade 72 can be biased by the leaf spring 80. By properly adjusting screw 82, the' cleaning ■■ ί blade 72 can be positioned to bear yieldingly against the surface of photoconductive · insulating layer 54 and yet be prevented from removing accumulated toner from the grooves 52. In addition to serving as a temporary reservoir to accumulate residual toner particles, grooves 52 also are adapted to remove any residual ■ toner particles adhering to the leading face of cleaning blade 72." Removal of the residual toner particles from the leading face of cleaning blade 72 is effected by a wiping action between the leading face of the cleaning blade 72 and faces 86 of grooves 52. As the , drum 50 continues to . rotate, the residual toner particles collected in grooves 52 are transported into the developing apparatus 60 where the collected toner particles are removed by the cascading developer.

A xerographic imaging system incorporating another cleaning embodiment of this invention is illustrated in Fig. 3. . In this imaging system, the cleaning apparatus. 110 is positioned in the development cycle to act on photoconductive insulating layer 112 after charging with corona charging device 114 and exposure at 116. The cleaning apparatus 110 comprises a cleaning blade 117 pivotally 120 by shaft 122. The solenoid 120 is activated periodically,, for ..' example, once every cycle, to permit displacement of: the blade holder 118 and blade 117 away from the surface of photoconductive •insulating layer 112. The raising of blade 117 permits the ridge of residual toner particles accumulated by blade 117 to be trans- ' ported on the moving surface of photoconductive insulating layer .112" into the developing apparatus 124 where it is removed from the ■'. surface of the photoconductive layer by the cascading developer.

Surprisingly good images are obtained even though a coating of ·';,,."... residual toner particles is carried on. the surface of photoconductive insulating layer 112. during the charging and. exposure steps. The solenoid 120 may be energized by any suitable means. For example, ; in Fig. 3, cam 126 may be driven by drum shaft 128 through a direct .':'' drive linkage to close micro-switch 130 once, every imaging cycle.-' · Obviously, other suitable electrically hydraulically or pneumatically activated means may be substituted for the solenoid .' 120. The closing of. micro-switch 130 completes the illustrated ■circuit and permits solenoid 120 to receive electrical energy from '. a suitable source 132.

The developed images emerging from the. developing apparatus 124 may be transferred at a transfer station 134 to a ■ moving paper web 136. The transferred powdered image is permanently fixed to the web 136 by a large high capacity heat fuser 138. Since conventional bulky cleaning systems are eliminated by the employment of the cleaning blade of this invention, and since the toner fusing unit is usually the principal factor in limiting the speed of a ■ xerographic imaging machine, the additional space gained by' employment of the cleaning blade of this invention permits the , ' employment of enlarged- heat fusers such as the heat fuser 138.

Increased exposure time of toner images to heat energy emanating increasing the danger of fire when conventional inflammable', receiving webs such as paper web 136 are employed- The dry solid . lubricant for effecting toner removal with the cleaning blade of . this invention may be supplied to the interface between cleaning blade 117 and surface of photoconductive insulating layer 112 by a . component' of photoconductive insulating layer 112 itself. , For r example, the photoconductive insulating layer may be formed by. '! co-evaporation. of a dry solid lubricant such as zinc stearate and ·' ; selenium onto the drum surface during manufacture. Xerographic plates containing dry solid lubricant dispersed throughout the,''... photoconductive insulating layer are known and described, for '. example, in French Patent No. 1,544 ,44-8 CF/573-D/14-4-7) .

Referring now to Fig. 4, reference character 150 designates a xerographic belt mounted to move in the direction indicated by . the arrow. The surface of the xerographic belt 150 is uniformly ■ charged by conventional corona charging device.152 and exposed to · a' pattern of activating electromagnetic radiation at full frame"', exposure station 154. The latent electrostatic image. formed at the- full frame exposure station 154 is developed by passing xerographic . belt 150 through a developing apparatus 156. The developed surface .'·. of xerographic belt 150 is then passed through a powder cloud of dry solid lubricant in dusting chamber 158. The powder cloud of dry solid lubricant is maintained by a suitable means such as rotating brush 160 positioned within dusting chamber 158. The developed images emerging from dusting chamber 158 are then transferred at a transfer station 162 to a moving receiving sheet or web 164. The residual untransferred toner particles adhering to the surface of xerographic belt 150 may, if desired, then be charged by corona discharge device 166 to neutralize the electrostatic charge attraction graphic belt 150. The charge neutralization treatment permits -a •reduction of the wiper blade pressure required to remove. the residual toner particles. The surface of xerographic belt 150-.is.; finally, cleaned of residual toner particles by the cleaning . apparatus 168 thus completing the entire charging, exposing, developing, lubricant treating and cleaning cycle.

The cleaning apparatus illustrated in Fig. 4 includes a cleaning blade assembly comprising a substantially rectangular ■' .cleaning blade member 170 clamped to a pivoting head 171 by means of plate 172 and a plurality of screws 173. Head 1.71 is pivotally mounted on a single shaft 174 by suitable means not shown. Shaft 174 is in turn secured to a hinged blade holder 176 by a press fit.. The cleaning blade 170 is indirectly biased by means of leaf spring .178 to bear -yieldingly against the surface of xerographic, belt 150.· As the surface of xerographic belt 150 travels past cleaning blade · member 170, the residual toner particles on the surface of the, belt are dislodged and permitted to fall into the trough 180.. The position of the cleaning blade 170 relative to the surface of xerographic belt 150 may- be regulated by a screw and lug assembly 182 As discussed above, the leading edge or face of at least one cleaning blade is preferably positioned to form an acute angle .· of less than about 90° and greater than about 20° with the surface or plane tangent to the surface of the electrostatographic imaging layer at the line of blade contact. The acute angle, designated by the symbol ©]_ in Fig. 5, is normally the angle between' the 'leading edge or face 200 of cleaning blade 202 and the confronting surface 204 of a reusable electrostatographic imaging layer 206.

However, when relatively flexible cleaning blades such as the .' cleaning blade .208 illustrated in Fig. 6 are employed, the acute angle between the leading edge or face 210 and electrostatographic ima in surface 212 of electrostato ra hic ima in la er 214 should of contact between the cleaning blade and the confronting electro- statographic imaging . surface or tangent to the. imaging surface to ■ , ' avoid an erroneous reading such as €3 taken at a substantial '. distance from the line of blade contact. I . the embodiments ;■■·.;'■.. illustrated in Fig. 5 and Fig. 6, the cleaning blades are inclined toward the ridge, of collected toner material. It is apparent, however that in the preferred embodiment the overall blade inclination need ' not be toward the ridge collected toner particles, but may in. fact, be inclined away from the collected toner particles as long as there .is a leading edge or face 216 even at a microscopic level to form an acute angle Θ as illustrated in Fig. 7... When the blade angle Q exceeds about 90° with angular knife edged blades, uneven removal of toner particles from the surface of the imaging layer often-. .occurs. Uneven toner removal frequently may be alleviated by increasing blade pressure. However, increased blade pressure tends ■'·.- to increase wear of the contacting surfaces. The configuration of. . the cleaning blade at the point of contact need not be a sharp .corner as illustrated in Figs. 5, 6 and 7, but may be a knife edge ■· or even slightly rounded due to wear or as originally installed. .

Where a rounded or curved contacting surface of a. cleaning blade: surface is 'employed, the radius of curvature should preferably be . less than about-.035 inch because toner will become trapped and . impacted at the shallow angle caused by the rounded edge and the ' ·. · drum interface. The area enclosed by the angle increases as . the radius increases. It is apparent, however, that even the blades of this invention having slightly rounded contacting surfaces are characterized by an overall angular appearance.

It is evident from the embodiments illustrated in the-drawings described above that the principles of the present invention include the use of at least .one self-adjusting or aligning state-graphic imaging surface and a means to directly or indirectly,-.supply dry solid lubricant material to the interface between the; . .cleaning blade and the imaging surface. In the absence of a ■■'.'.''·"''.· means to provide a dry lubricant, repeated exposure of a reusable electrostatographic imaging surface to the abrasive action of a. cleaning blade bearing yieldingly on the moving imaging surface .for. ■ the large number of cycles required in commercial machines causes , .. 'rapid degradation. of both the cleaning blade and imaging surface to the extent that, the cost of equipment replacement and degradation ..- of imaging quality renders the system economically unfeasible. :.It .' ;.is further apparent from the embodiment depicted in the drawings ;· described above, that cleaning blades adapted to rapidly and continuously or intermittently permit the return of the removed residual : toner material to the developer sump for reuse are preferred because greater efficiency and economy of operation are achieved. Because ,of the necessity for uniform and efficient removal of residual toner particles from the surface of reusable electrostatographic. ·'. imaging surfaces in precision high-speed, high-volume copying or duplicating, machines, the self-adjusting feature of the cleaning blade is critical. Non-uniform and incomplete removal of residual- toner particles . contributes to the formation of a toner film on, the' imaging surface with an attendant degradation of image quality, during subsequent imaging cycles. f Ah enlarged fragmentary sectional view of the cleaning blade shown in Fig. 1 is illustrated in. Fig. 8. In this embodiment, the flexible rectangular cleaning blade member 36 is adhesively united to a metal plate 37 which is in turn spaced from blade holder . member 38 by a washer 39. Rectangular blade member 36 is pivotally secured to. lade holder 38 by a single shouldered screw.40 whic is received by a centered threaded hole in metal plate 37. Since is less than the diameter of the opening 43 of blade holder 38; the flexible cleaning blade 36 is free to pivot around the axis of · shouldered screw 40. The ability to freely pivot around the axis of shouldered screw 40 allows the pressure exerted by the cleaning blade 36 along the line of contact with the reusable imaging surface to equalize itself thereby uniformly removing residual' toner particles from the imaging surface without danger of toner build up and film formation.

Another embodiment of. the self-adjusting cleaning blade of this invention is illustrated in Figs. 9, 10 and 11. This, •cleaning blade unit includes a flexible .metal reinforcing plate 210 molded into a rubber cleaning blade 212. The metal reinforcing •plate contains a plurality of punched out sections 214 which permit the portions of the rubber cleaning blade 212 above and below the metal reinforcing plate to adhere to each other during the cleaning., blade molding operation. The flexible metal reinforcing plate 210 is slidably mounted in grooves 216 in the lower support arms 218. Holes 220 are located at each end of flexible metal reinforcing plate 210 to receive a pin 221 or a machine screw 222 and a nut 226. The pi 221 or machine screw 222 and nut 226 are. positioned at the ends of flexible reinforcing plate 210 to limit the distance of . travel of flexible metal reinforcing plate 210 in grooves 216 during the reusable imaging surface cleaning operation. Lower support .'' arms 218 are pivotally mounted with the aid of pins 228 at the ends of upper support arm 230. The upper support arm 230 is pivotally secured by a pin 232 to blade holder 234. Suitable means, not shown, may be attached to' the blade holder 234 to bias the cleaning blade 212 toward the reusable imaging surface. The biasing pressure applied to the blade holder 234 is transmitted to the flexible metal reinforcing plate 210 through upper support arm 230 plate 210 is flexible, in a direction perpendicular to its punched, surface, the biasing pressure imparted to the flexible metal re-...y inforcing plate 210 by lower support arms 218 is substantially, uniformly conveyed to the entire length of rubber cleaning blade Λ .212. If desired, the number of intermediate support arms may be.' .increased or decreased depending upon the length of. the cleaning ": blade employed. It is apparent from the . foregoing discussion that, the cleaning blade of. this embodiment is also self-adjusting and .·' ;·' .would uniformly remove residual- toner particles from the reusable ,'. imaging surface.

Fig. 12 shows another modification of the self-adjusting- cleaning blade of this invention. In this embodiment, the flexible cleaning, blade 250 is sandwiched between metal plate 25.2.. and metal plate 254. The assembly of plates and wiper blade are; secured together by a plurality of rivets 256. The flexible cleaning blade 250 is divided up into a number of independent blade segments 258 by a plurality of slits 260.. Each of the blade segments 258 may ride over any slight imperfection on the surface ; of the reusable imaging layer without adversely affecting the . position of the adjacent independent blade segments in relation. . to the reusable imaging surface.

Another alternative embodiment of the self-adjusting cleaning blade assembly is illustrated in Fig. 13. A flexible cleaning blade 300 is clamped in the jaws of a blade holder 302. The jaws extend along the entire length of the cleaning blade 300. to prevent undue flexing of the cleaning blade along the direction-, of photoreceptor surface travel. An adjustable plate 304 is sandwiched between the upper jaw of blade holder 302 and cleaning blade 300. V7hen highly flexible cleaning blade materials are employed, the adjustable plate 304 should be selected from relative cleaning blade. Conversely, where stiff cleaning blades are'.' employed,' the adjustable plate may comprise a- soft resilient material such as polyurethane sponge. The blade holder is pivotally mounted in elbow 306 which is '.'in turn pivotally connected to a second elbow 308. " The second .elbow 308 is attached to a- suitable .support by .a hinged means, not shown, which is similar to the hinged support illustrated in Figs. 1, 2 and 4. Elbow 306 comprises two half shells which may be secured together by screws inserted through flanges 310, 312, and 314. As shown in the . partial cut-away view of elbow.306, the split halves of elbow 306 are either molded or machined to form a 'cavity in each shell which conforms to the configuration of the enlarged head 318 of shaft 316..

•.The cavity formed in the elbow 306 should be -s-lightly larger than the enlarged portion of shaft 316 to permit the shaft '316 to freely.. .rotate within the cavity. The other end of the shaft 316 may be rigidly secured by a press-fit to a T-shaped member 320 which is in turn secured by machine screws to blade holder .302. An identical ." arrangement is employed to permit shaft 322 to axially rotate |n . '.·..· elbow 306. The other end of shaft 322 is permanently secured j ·.· it elbow 308 by a press fit, The two pivot points employed in the-cleaning blade shown in Fig, 13 permits automatic alignment of the .cleaning blade 300 relative to the axis of drum 324 as well as .automatic equalization, of pressure along the line of contact between the cleaning bla.de 300 and the reusable surface, of electrostatographi drum .324.

In Figs. 14· and 15, a self-adjusting cleaning blade assembly having one pivot point instead of the two pivot points of the Fig. 13 self-adjusting cleaning blade assembly is shown. A flexible cleaning blade 350 and adjustable stiffener plate 352 are clamped in the jaws of a blade holder 354. The jaws of the 350 to provide sufficient support for the cleaning blade. The blade holder 354 is secured to a T-shaped connecting member 356 by machine screws 358. The T-shaped member 356 is pivotally mounted • on one'end of a shaft 360 in a manner similar to that illustrated ·"· in Fig.. 13. The other end of shaft 360 is permanently secured to .'·.; a hinged member 362. The hinged member 362 is biased toward the " ' reusable electrostatographic drum surface 364 by spring loaded pih:. .366 which is slidably mounted in hollow sleeve 368. The pressure exerted by pin 366 may be adjusted by rotation of the threaded .. . sleeve 368 within a threaded hole in support block 370. The hinged '·. member 362 is hinged at point 372. The' support block 370 and hinge ■ ••half 374 are secured by suitable means, not shown, to a support; arm ;■ 376 which is mounted on a shaft 378. Shaft 378 is permanently secured to the frame of the imaging machine by means not shown. .

.A set screw 380 is threadably received' in the arm 376 to secure ; and ."■...prevent rotation of arm 376 on shaft 378. By loosening the set screw 380, the cleaning blade assembly may be slidably removed from', shaft 378 for repairs or adjustment of the cleaning blade assembly' . . or electrostatographic drum. The set screw 380 may also be used to .'position the arm 367 on shaft 378 thereby permitting adjustment of the cleaning blade angle relative to the surface of the electrostatographic drum. Cam 382 is securely attached to an end of and rotates with drum 364. As the drum 364 rotates in the direction shown by the arrow, cam 382 engages a roller cam follower 384 ' which rotates on a supporting pin 386 which is secured to the lower . ' bifurcated portion of .arm 388 which extends downwardly -from one end of hinged member 362. As the cam 382 engages roller cam followe N . , 384, the roller cam follower rides upon and follows the curved surface of cam 382 thereby causing arm 388 as well as the cleaning blade 350 to be lifted away from the surface of the electrostatographic • residual toner particles accumulated by blade 350 to be trans- portated on the moving surface of electrostatographic drum 364 into the developing apparatus, not shown, where it is removed, from the surface by the cascading developer. Since the blade holder 354 positions the .leading face 390 of cleaning blade 350 at an angle of about 135° with respect to the axis of shaft 360, the ■function of the two pivot points employed in the cleaning blade. - ■ ' assembly of Fig. 13 is accomplished with a single pivot point, thereby permitting automatic alignment of the cleaning blade 350 relative to the axis of drum 364 as well as automatic equalization of pressure between the cleaning blade-- 350 and the reusable surface of . electrostatographic drum 364 along the line of blade-drum contact. In other words, the blade 350 has two adaptations to the imaging surface, one transversely or generally circumferentiall ; '. ' of the imaging surface and one axially across the width thereof: If desired, a plurality of cleaning blades may be -employed to clean the residual toner particles .from the surface of the reusable imaging surface. In the embodiment depicted in Pig. 16, each of the cleaning blade assemblies 400, 402 and 404 extend across the entire axial length of the electrostatographic imaging drum. The blade material employed in each of the cleaning blade assemblies need not be identical to the materials employed in the other cleaning blades. For example, cleaning blade 406 may comprise a flexible but relatively stiff material such as poly-urethane which removes the bulk of the residual toner particles on the surface of, electrostatographic drum 408 whereas the cleaning blades 410 and 412 of cleaning blade assemblies 402 and 404, s_ respectively, may comprise relatively- soft material which removes the residual toner particles, if any, not removed by cleaning blade 406. Where a highly compact multiple cleaning blade system is substituted for the plurality of cleaning. blade assemblies of · Fig. 16. The cleaning blade assembly illustrated in Fig. 17 comprises two cleaning blades 420 and 422 clamped in the jaws of a ... single blade holder 424. The jaws extend along the entire length of the cleaning blades 420 and 422 to prevent undue flexing of the -: cleaning blade. Adjustable stiffener plates 426 and 428 may be ·■ · sandwiched between the upper surface of each blade and the jaws ' of the blade holder. As- discussed above, the stiffening blades provide a-dditional- support .for the cleaning blades , · particularly ,.· . when highly flexible cleaning .blade materials are employed.

An alternative multiple cleaning blade system is shown in the isometric view in Fig. 18. Each of the cleaning blades '.450 452 and 454 carried by the cleaning blade holders 456, 458 and . 460, respectively, extends across a portion of the axial length of., reusable electrostatographic drum 462. The cleaning blades are. staggered and overlapped to insure that the entire imaging surface '-■of the reusable electrostatographic drum 462 are contacted by the' ,:. blades. The reusable electrostatographic drum 462 contains staggered grooves or/depressions 464, 466 and 468. These grooves or -depressions are positioned to permit each of the cleaning blades, to ride over the grooves rather than into the grooves. For example, cleaning blade 452 is prevented from riding down into the grooves. 464 and 468 by the undepressed surface' of reusable electrostatographic drum 462 located between grooves 464 and 468. Similarily, since the groove 466 is shorter than the length of cleaning blade 452, the undepressed · surface of reusable electrostatographic imaging drum 462 located at each end of groove 466 prevents the cleaning blade 452 from riding down into groove 466. The groove arrangement-shown in Fig. 18 eliminates the need of a means to limit the lowest position of cleaning blade travel since the undepressed portions of cleaning blades from entering the grooves and removing accumulated toner. As the electrostatographic drum 462 continues to rotate, the ■residual toner particles collected in the grooves 464, 466 and 468 are transported into the developing apparatus, not shown, where ■ the collected toner particles are removed by the cascading developer.

Although most of the illustrations discussed above are directed to electrostato'gr-a*¾i.c'-.imaging systems employing a cascade development station, it is apparent that other development techniques such as the magnetic brush, fiber brush, powder cloud and touchdown development systems described above may be used where suitable.

"However, the cascade type development . system · is preferred because of the rapid return of residual . toner particles to the main body of -.developer and uniform mixing of the main' body of developer with . the ■ recovered toner for reuse. The carrier bead trapping and attendant electrostatographic imaging surface bead scratching problems . encountered with the prior art cleaning web systems are completely obviated by^ the cleaning blade systems of the present invention.

Permanent removal of residual toner by conventional web and brush cleaning systems is also eliminated by. employing the preferred cleaning' system of this invention.

Any suitable non-metallic flexible cleaning blade material may be employed In the cleaning, system of this invention.-' Typical non-metallic flexible materials include: polysiloxane rubber, polyurethane rubber, polytetrafluoroethylene resin, poly-trifluorochloroethylene resin, styrene-butadiene rubber, nitrile rubber, nitrile-silicone ' rubber, flexible polyurethane foam, polyethylene resin and' blends, mixtures and copolymers thereof. The blade should be sufficiently soft to minimize abrasion of reusable, imaging surfaces, particularly selenium type' imaging surfaces.

Preferably, the blade material should have a Shore hardness of less permissible. However, the blade should be sufficiently thick to avoid collapse of the blade on the imaging surface under the blade pressure conditions employed. Obviously, greater latitude in •flexibility of the blade material is available when the stiffening .' members described above are employed in the blade holder. The cleaning blade pressure upon the surface of the reusable imaging surface can vary consider&Dly. · Generally, the minimum pressure- necessary for effective removal of the toner particles from the ' •reusable imaging surface is preferred because undue wear of the . '.. reusable imaging surface is avoided. Satisfactory results have ;· been obtained when .the weight of a three pound cleaning blade . ; assembly, such as the cleaning blade assembly illustrated in Fig. 1, was the only source of pressure exerted on the cleaning blade.- The corner between the leading face of the cleaning blade and .the ' blade- end or edge must be sufficiently abrupt to perform an effective scraping action as opposed to a smearing action. However, satisfactory results are obtained when the. angular imaging surface ■ engaging edge of the cleaning blade is slightly rounded due to wear as described above. Thus, effective toner removal is maximized when the surface area of the portion of the blade in contact with .the imaging surface is minimized. A surprisingly large latitude of operating speeds is permissible with the cleaning blade of ' this invention. Extremely high cleaning efficiency is achieved wi cleaning blade to reusable imaging surface relative speeds of up to about 5 feet per second.

The following examples further specifically define and describe the imaging system of the present invention for developing electrostatic latent images with toner, transferring the resulting toner images to a receiving surface and thereafter cleaning the eusable, imaging surface with a flexible self-adjusting cleaning ' indicated. These examples, other than the control examples, are intended to illustrate the- various preferred embodiments of the present invention.

In the following, Examples I through IV, are carried out in a copying machine described in detail in U. S. Patent 3,099,856. A standard Xerox 813 cleaning web is employed in the control example and a self-aligning polyurethane elastomer, Disogrin, cleaning blade is substituted for the cleaning web in the examples illustrating the preferred embodiments of this invention.

EXAMPLE I The ,vitreous selenium drum of a copying machine is corona' charged to a voltage of about.800 volts and exposed to . a light-and-shadow image to form an electrostatic latent image. The selenium drum is then rotated through a cascade development station. A developer comprising a toner comprising a styrene-butyl methacrylate copolymer, polyvinyl butyral, and carbon black prepared by the method disclosed in Example I of U. S. Patent 3,079,342 and carrier beads prepared by the process disclosed in U. S. Patent .2,618,551 is employed in the developer station. After the electrostatic latent images are developed in the developing station, the resulting toner images are transferred to a sheet of paper at a transfer station.

The residual toner powder remaining on the selenium drum afterj passage through the transfer station is removed by a conventional Xerox 813 cleaning web at a cleaning station. A detailed description of this type of imaging system is. set forth in U. S. Patent 3,099,856. The drum is rotated at a constant linear surface speed of approximately 3 inches per second during the imaging cycle. The imaging cycle is repeated for 10,000 cycles. This test serves as a control. Microscopic examination of the selenium surface after 10,000 cycles, reveals considerable wear with a large number of deep scratches blade assembly is found to be about 3 pounds. A cam is securely attached to one end of the selenium drum for contact with a cam follower attached to the blade assembly. Since the cam is securely attached to the selenium drum, the cam causes the blade to lift away from the selenium surface once every imaging cycle to permit; the toner collected by the blade to be transported by the drum surface into the developing housing where it is picked up by the cascading developer. The modified machine is operated for 10,000. cycles and the drum is then removed for examination. .Microscopic surface. No deep scratches can be found anywhere on the selenium, surface. The quantity of toner lost with this cleaning system is-' found to be about 3 . 5 grams.. Thus, the toner lost in this modified ·'.' machine is about 24 times less than the loss in the machine described 'in Example I-. -"'"·:'.'·.'>■ '■:"·■'■ EXAMPLE III The procedure described in Example II is repeated with .':·:. a fresh drum and fresh developer. In addition,- a powder . dispenser,. : : ' is positioned between the cleaning blade assembly and the exposure.'.:; station. The dispenser is regulated to sprinkle a thin powder, film'-, of zinc stearate on the selenium surfa:ce during the imaging cycle'. '·;;,;,':. After 10 , 000 cycles, a microscopic examination of the imaging .·.·.·. ... , ;':: surface reveals substantially the same degree' of wear observed . on'-' '·' ' the imaging surface described in Example II. .'·*:**·*.".·?'*.- EXAMPLE IV ' The test described in Example I is repeated with a.. . modified selenium drum, zinc stearate powder in the developer, and' a self-aligning cleaning blade assembly substituted for the cleaning.' web. The zinc stearate is incorporated into the developer by simply ' tumbling about 100 parts toner particles with about 1 part by weight, based on the total weight of the toner, of zinc stearate i a ,' . sealed horizontal rotating cylinder. The cleaning blade assembly, employed in similar to the cleaning blade assembly illustrated ' ■;.··, in Fig. 2 . The selenium drum is modified to provide two adjacent' ,'.'..' and parallel depressions extending axially along the length of the';.' ; drum. These depressions have a semi-circular cross section with- a.' radius of curvature of about .062 inches.. The blade material is a rectangular strip of natural rubber having a thickness of about ' 1/16 inch. The leading face of the cleaning blade is positioned to form. an acute angle of about 80° with the confronting portion of pressure exerted upon the blade in a direction parallel to the drum- radius at the line of contact is about 3 pounds as determined by a spring scale. A corona discharge electrode is positioned between' . ' the transfer station and the cleaning station to neutralize electric charge carrier by residual toner particles. This neutralization-is accomplished by operating the corona' discharge electrode at a high .voltage alternating potential of about 60 cycles AC and 6/000..'.V peak volts. The-- v-o'l^age- is; i'a-sed at a slightly negative · current, .!; such that.- tftie positive- current is about 10 microamps and the ■' negative' current is about 12 microamps. 'A limit is provided to : .■ permit the cleaning blade to pass over the grooves without sub- .'. stantial penetration, thereby, preventing the cleaning blade from: . scooping out toner particles from the grooves. The toner particles collected in the grooves are picked up by the cascading developer _· in the developing housing. The modified drum is operated for ,000 cycles and the drum is then removed for examination r . Microscopic . studies of the selenium surface indicate, substantially :the- "■.." · same degree of wear observed on the imaging surface described in Example II. The quantity of toner loss in this cleaning system · .' ..· is considerably less than the loss in the machine described in '·.·.· Example I .

While the: in ention' has- been1 particularly shown and ' ^ ' described with1 reference to preferred embodiments thereof, other-, modifications and ramifications of the present invention will. . appear to those s'killed in the art upon a reading of the disclosure. These are intended to be included within the scope of this-invention.

Claims (1)

1. 51502/2 8» An electrostatographic imaging apparatus according to claim 1> wherein said recyclable layer is an annular layer and said cleaning blade aligning means is adapted to permit said cleaning blade to align itself axially along the width of said imaging layer when said cleaning blade is engaged with said imaging ourface* 5* An electrostatpgraphic imaging apparatus accord* ing to Claim 2 in which said cleaning blade yi»g 'meane is adapted to position" the leading face of said cleaning blade at an angle between about 20° and';¾f0° with a tangential plane to said imaging surface at the line of cleaning blade contact when said leaning blade is engaged with imaging surface* 4* An electrostatpgraphic imaging apparatus according to Claim 2 in which said annular recyclable layer is a belt* 5· An electrostatOgraphic imaging apparatus according to Claim 2 in which said annular recyclable layer is a cylinder* 6· An electrostatographic imaging apparatus according to any of claims 1 to 5 further including a corona discharge electrode positioned and disposed to apply electrostatic charge to said imaging surface prior to removal of said residual particles from said imaging surface by said cleaning blade* 7* An electrostatographic imaging apparatus according to any of Claims 1 to 6 in which said fourth of said stations is positioned adjacent said electrostatographic imaging sur ad· between said first of said stations and said seoond of said stations* 8* An electrostatographic imaging apparatus according to any of Olaims 1 to 6 in which said fourth of said stations is positioned adjacent said electrostatographic imaging surface betwee said third of said stations and said first of said stations*