US3128683A

US3128683A - Xerographic apparatus

Info

Publication number: US3128683A
Application number: US103345A
Authority: US
Inventors: Rubin Daniel
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1961-04-17
Filing date: 1961-04-17
Publication date: 1964-04-14
Anticipated expiration: 1981-04-14

Description

April 14-, 1964 D. RUBIN XEROGRAPHIC APPARATUS 2 Sheets-Sheet 1 Filed April 17, 1961 F/Gl INVENTOR- DAN/EL RUB/N BY QAM EQA A A T TOR/V5 Y April 14, 1964 D. RUBIIN XEROGRAPHIC APPARATUS 2 Sheets-Sheet 2 Filed April 17. 1961 N GP INVENTOR. DAN/EL RUB/N 5% 1. QQ Q A Trams/E United States Patent 3,128,683 XERGGRAPHEC APPARATUS Daniel Rubin, Rochester, N.Y., assignor to Xerox Corporation, Rochester, N.Y., a corporation of New York Filed Apr. 17, 1961, Ser. No. 103,345 5 Claims. il. 95-1.7)

This invention relates to xerography and in particular to improved. xerographic method and apparatus for reproduction of images onto a reusable xerographic plate.

In the process of xerography, for example, as disclosed in Carlson Patent 2,897,691, issued October 6, 1942, a xerographic plate comprising a layer of photoconductive insulating material on a conductive backing is given a uniform electric charge over its surface and is then exposed to the subject matter'to be reproduced in the form of activating radiation, as for example, visible light, usually by conventional projection techniques. This exposure discharges the plate areas in accordance with the radiation intensity that reaches them, and thereby creates an electrostatic latent image on or in the photo conductive layer. Development of the latent image is effected with an electrostatically charged, finely divided material such as an electroscopicpowder or marking particles that are brought into surface contact with the photoconductive layer and held thereon electrostatically in a pattern corresponding to the electrostatic latent image. Thereafter, the developed xerographic image is utilized for varied purposes and for example, may be transferred to a support surface to which it may be aflixed by any suitable means.

Development of electrostatic latent images is achieved by placing the developing material within a field range of the electrostatic image whereby to elfect mutual attraction and, as disclosed in the prior art, includes development by means of a dry powder as disclosed in Walkup Patent 2,618,551, or by means of liquid materials in which developer may be suspended. A form of liquid development is disclosed in Mayer Patent, U.S. 2,877,133, in which a latent image bearing plate is brought into surface contact with a liquid of high electrical resistance that contains solid developer particles which are attracted therefrom to the select image portions on the plate. As in dry development, development by liquid techniques may be eiiected on an expendable xerographic plate on which the image remains permanently, or in the instance of a reusable xerographic plate, the developed image may be transferred to a secondary support surface to which it is permanently affixed and the plate cleaned and cycled for reuse as is now conventional in xerography. Still another use of the formed image may be for scanning or projection purposes such as disclosed in copending application Ser. No. 738,520, filed May 28, 195' 8, in the name of Clark et al.

The present. invention is specifically directed to xerographic method and apparatus in which development of electrostatic.latentimages on a xerographic plate utilizes the principles of liquid development and is directed in particular for use in connection with reusable xerographic plates from: which a developed image must be removed before recycling of the plate.

In either instance of reusing a xerographic plate, the plate must be cleaned of developer from previous cycles before recycling. It has been found that plates having been developed by techniques of liquid development are easily cleaned, if cleaning is performed before the developed image has solidified. This may be done by brushing, squeegeeing, or the like, in a developer liquid having a substantial absence of developer or may even be done after the electrostatic charges on the. plate are substantially discharged in a developer liquid containing developer.

In the instance of cleaning a plate from which a developed image has been transferred to a secondary surface, some developer material is consumed from the system that must be replenished in a like amount as that consumed in order to maintain the developer in the liquid at a desired consistency of concentration. In the instance of cleaning a plate where the developed image has not been utilized for forming a permanent image,.it has been discovered that consumption of developer can be reduced and. even substantially eliminated if that which was utilized for development is restored to the system.

Now in accordance with the invention a xerographic apparatus is provided in which a xerographic plate can have an image developed and subsequently be cleaned in a liquid development system, which apparatus by the novelty of its combination is rendered completely automatic and adapted for continuous recyling or" a xerographic plate. When the ingredients utilized in developing are subsequently'restored to the system, substantially no consumption of material occurs and the system is operative indefinitely at a very minimum of cost.

It is therefore the principal object of the invention to provide improved xerographic method and apparatus for the reproductionand utilization of processed xerographic images.

his a further object of the invention to improve xerographic method and apparatus for liquid development of electrostatic latent images on a xerographic plate.

It is a further object of the invention to provide xerographic method and apparatus in which electrostatic latent images on a xerographic plate are developed in a liquid development system that has extended utility withoutsubstantial consumption of materials as compared to development systems of the prior art.

It is a further object of the invention to provide improved xerographic method and apparatus for cleaning a xerographic plate after developed image utilization.

These and other objects are attained in one embodiment of the invention in which a flexible and endless xerographic plate is advanced continuously past a charging station and an exposure station after which the plate is immersed in liquid developer to effect image development. The developed image is utilized for protection purposes and the plate thereafter is again immersed in the liquid developer while being brushed for removal'of the previously developed image and restoration of the developer to the liquid.

Embodiments of the invention are disclosed in the accompanying drawings in which:

FIG; 1 is a schematic side sectional view illustrating a continuous automatic apparatus employing the method and apparatus of the invention; and,

FIG. 2 is a schematic side sectional view illustrating an alternative continuous automatic apparatus employing the method and apparatus of the invention.

Reference is now had to FIG. l'in which an apparatus utilizingthe method of the invention isillustrated. The apparatus is housed in a light-tight housing 10 in which an endless flexible xerographic plate 11 comprising a photoconductive layer on a flexible conductive backing suchas conductive paper, foil or the like, is continuously advanced over suitable driven guide rolls. As illustrated, one of the guide rolls is driven by a motor M- l, which may be stopped momentarily where required for exposing an image to the plate. As the plate advances a uniform electrostatic charge is-first applied on its surface by a corona generating device 12 which may be of a'type disclosed in US. Patent 2,836,725 and which is energized from a suitable potential source 13. On further ray tube is projected onto the charged plate surface resulting in an electrostatic latent image that 'is subsequently to be made visible by development. As the plate continues to advance it moves over a skewed guide roll 16 whereon the plate is directed into a developer liquid 17 of high electrical resistance, and which may be of a hydrocarbon such as kerosene, benzene, etc. as disclosed in the abovecited Mayer patent. The liquid is contained in a reservoir 18 wherein development of the electrostatic latent image on the plate is effected. As the plate emerges from reservoir 18 containing the developed image, it again passes over guide roll .16 without overlapping the entering plate portion.

Development may be either direct or reversed, i.e., a positive or negative may be developed in relation to the original exposed image. As for. example, where the source of activating radiation is a cathode-ray tube or the like having a light image on dark background, it may be preferred to effect reversal development i.e., to use developer particles in the liquid that are repelled by the non-image charged areas of the plate to the image uncharged areas thereon resulting in a dark image on a white background.

The plate bearing the developed image then passes a projection station designated 25, whereat the image is suitably illuminated by lamps 26 and 2.7, and the image reflected by a mirror 28 into a lens 2 9, from which it is projected at increased magnification ratio onto a projection screen 30 for viewing by an audience of any convenient size. From the projection station the plate continues to advance and the developed image is thereafter removed from the plate as it re-enters the liquid 17 while being brushed by brushes 31 driven by motor M-2. After. cleaning the plate is recycled. A light shield 32 prevents stray light from reaching the plate surface before development.

Referring to FIG. 2 there is illustrated an alternative embodiment of apparatus utilizing the method of the invention and contained in a light-tight housing 40. Similarly as in FIG. 1, a flexible and endless xerographic plate 11 is advanced continuously past a charging station and an exposure station, after which the plate is immersed in the developer liquid 17 to effect development.

Developer liquid is contained in a reservoir 41. After development the plate passes an exposure station 25 at which the developed image is projected by suitable optics, as above, onto a screen 30. Following projection, the developed image is transferred to a secondary support surface 42 at a transfer station generally designated 43. Any transfer means known in'the art may be employed. In the illustrated embodiment, a web of secondary support material is drawn from a supply reel 44 over guide roll 45 whereafter the Web contacts the xerographic plate 11 in the vicinity of a corona generating device 46, 'which may be similar to corona generator 12 described above and that functions to electrostatically attract the developed image from the plate onto the support material. Thereafter the support material containing the transferred image advances through a suitable fusing device 47 which may, for example, be a heat fuser of the type disclosedin U.S. Patent 2,852,651 and wherein the image is permanently affixed to the surface of the web. After fusing, the web is drawn through an exit slot 48 onto a takeup reel 49 driven by a motor M-S through a slip-clutch 50 whereby web 42 advances at the same lineal rate as the xerographic plate. Alternativelyj the web may be cut into predetermined lengths and stacked in a conventional manner.

After transfer the plate passes to a cleaning station 60 a liquid 61 that conveniently may be the same as liquid 17 but without the presence of developer particles, and is contained in a reservoir 62. While immersed, the plate is brushed by suitable brushes 63 driven by motor M-4. The plate thereafter continues to advance and is recycled. The reservoir could conveniently be combined in the manner of FIG. 1, but for practical considerations of design such as degree of physical separation two reservoirs in this instance are preferred.

Because developer particles on transfer are being consumed without being restored to the developing system in the manner of FIG. 1, an amount which is consumed is replenished from a suitable dispensing unit 64 containing developer particles 65 that are dispensed in metered amounts to developer liquid 17. The dispenser is operative in response to a regulatory control (not shown) set to effect dispensing substantially in proportion to the rate of consumption. Setting of the regulatory control may be automatic or manual. Where required for extended operation, make-up liquid can also be made available to the system. Where it is desired to maintain liquid 61 substantially free of developer, separation apparatus may be utilized as disclosed in copending application Ser. No. 103,344, filed concurrently herewith, in the name of Clark et al. Alternatively in the apparatus of FIG. 1, the developed image could be transferred in a like manner as in FIG. 2. and like-wise in FIG. 2, the transfer operation could be efiected without the requirement of previously projecting the developed image. The advantages of any such arrangements would be dependent on the purposes for which the system. were being employed to efiect visible reproduction.

By the apparatus thus described there is disclosed novel xerographic apparatus for the reproduction of images. The apparatus'is comp-act and efliciently arranged while being particularly adapted for continuous image formation. While development is effected in the preferred embodiment by immersing the xerographic plate in the liquid it is not intended to be limited thereby since other means may be utilized for bringing the liquid developer into contact with the plate surface, such as in the Mayer patent cited.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made Without departing from the scope thereof, it is intended that all matter contained in the drawings and specification shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a xerographic process including the steps of forming an electrostatic latent image of copy on a continuously moving xerographic plate, developing the latent image with electroscopic developer particles from a substantially electrically insulating liquid and utilizing the developed image; the improvement comprising a plate cleaning process for removing remaining developer particles from the plate surface after utilization comprising the steps of presenting the plate into contact with an electrically-like liquid as that employed for developing said like liquid having insuflicient developer particle concentration therein to be capable of developing a latent image and concomitantly therewith grazing the plate surface whereby the particles thereon are removed to the like liquid contained therein.

2. In a xerographic process including the steps of forming an electrostatic latent image of copy on a continuously moving xerographic plate, developing the latent image with electroscopic developer particles from a substantially electrically insulating liquid, utilizing the developed image and subjecting the plate to an illumination intensity capable of uniformly electrically discharging all plate areas thereof; the improvement comprising a plate cleaning process for removing remaining developer particles from the plate surface after utilization comprising the steps of presenting the plate into contact with an electrically-like liquid as that employed for developing, and concomitantly therewith grazing the plate surface whereby the particles are removed to the like liquid which at a predetermined developer particle concentration is usable to effect development of a subsequently formed latent image.

3. The improvement according to claim 2 in which grazing is effected by means of a rotating brush.

4. The improvement according to claim 2 in which said like liquid comprises the same developer containing liquid by which development was effected prior to utilization.

5. The method according to claim 4 in which utilization and illumination are combined in the step of optical projection of the developed image and the improvement in- 2,551,582 Carlson May 8, 1951 2,752,833 Jacob July 3, 1956 2,965,756 Vyverberg Dec. 20, 1960 2,987,660 Walkup June 6,1961 3,051,044 McNaney Aug. 28, 1962 3,084,043 Gundlach Apr. 2, 1963 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3 128 683 April I l 1964 Daniel Rubin i i 1 error appears in the above numbered pat- It is hereby certified that I t the said Letters Patent should read as ent requiring correction and the, corrected below.

Column l line 13 for "2 897 9l" read 2 297 69I column 2 line 46 for "protection" read projection column 4 line 64L before "contained". insert to be Signed and sealed this 10th dayof November 1964.,

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents ERNEST W. SWIDER Attesting Officer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N00 3, 128 683 April 14 1964 Daniel Rubin or appears the above numbered pat- It is hereby certified. that err ters Patent should read as ent requiring correction and that the said Let corrected below a Column l line 13 for '"2 897 o9l" read 2 297 69l column 2 line 46 for "protection" read projection column l line 64L before "contained" insert to be --0 Signed and sealed this 10th day of November 1964.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents ERNEST W. SWIDER Attesting Officer