Патент USA US3028809код для вставки
April 10, 1962 D. F. KELLER ETAL 3,028,799 APPARATUS FOR ELECTROPHOTOGRAPHIC PRINTING Filed March 8, 1957 2 Sheets-Sheet 1 i5» 1' a 1 42 / 44 \/ 64 Fag. Z April 10, 1962 D} F. KELLER ETAL 3,028,799 APPARATUS FOR ELECTROPHOTOGRAPHIC PRINTING Filed March 8, 1957 2 Sheets-Sheet 2 3.7g. 3 /32 //Z /89 /70 ' i725 United States atent 1 3,028,799 ce 3,028,799 Patented Apr. I 10,’. 1 962 2 wherein a surface means bearing a permanent image is placed against one surface of a transparent electret and ~ APPARATUS FOR ELECTROPHOTOGRAPHIC PRINTING Daniel Franklin Keller, 525 Sheridan Road, Kenilworth, light radiation projected through the surface means and electret wherein a latent image is formed on a photo conductive coating on the opposite surface of the electret. Ill., and Harry E. Gunning, Hazel Crest, Ill., assiguors, The image is rendered visible by applying a dusting pow by mesne assignments, to Daniel Franklin Keller, Ken der and this image is transferred by a surface having an ilworth, Ill. . a?inity for the powder and carried to an electret having Filed Mar. 8, 1957, Ser. No. 644,754 a polarity opposed to the polarity of the ?rst electret 16 Claims. (Cl. 95—1.7) 10 surface whereby the image will be attracted to a paper This application is a continuation-in-part of our co placed‘between the transfer surface and the second elec_ pending application Serial No. 590,621, ?led June 11, tret. 1956, now US. PatentNo. 3,000,735 issued September Another feature of the invention lies in the provision 19, 1961. of a method and apparatus for utilization in a camera This invention relates generally to electrophotography 15 wherein a photoconductive layer is utilized as a surface and electrophotograhic printing and, more particularly, bearing a latent charge image and succeedingly vpassd to improved methods and apparatus for producing latent over ends of an electret or" opposite polarity and there charge images on surface means suitable for use in printing after positioned against a grounding plate and exposed and reproduction procedures, for example, by electropho to radiation from an image and the image is subsequently ?xed on the photoconductive surface by passing it through tographic means. " By exposing photoemissive or photoconductive layers or surfaces to radiation having a desired image or pattern, a dusting chamber. The surface bearing means is sub ‘ sequently passed through a spray chamber wherein the there is produced a corresponding emission of electrons dust is ?xed to the surface in the shape and density varia in the areas receiving the radiation whereupon an elec tions representing the image. trostatic latent image is produced. The electric charge “ A further feature of the invention is the provision of pattern which forms the electrostatic latent image may ‘a printing method and mechanism wherein a surface hear be rendered visible by various developing procedures, for ing an image is placed against a surface of an electret and example, by depositing a suitable material such as ?nely a photosensitive insulating material on thin plastic is divided particles which come under the in?uence of the placed over the surface and exposed to a light and subse 30 charge pattern. quently passed to a dust chamber. The plastic material In following the procedures outlined heretofore, it has been necessary to utilize bulky equipment oftentimes ne with the photoconductive insulating surface is subsequent ly exposed'to another light and carried against a copy cessitating the use of high voltage generating equipment. material held against an electret surface having an outer Artisans in the field have been confronted with serious 35 surface of opposite polarity from the surface beneath the problems with respect to the uniformity of a charging surface bearing the image whereby dust which has been ?eld, the lack of ?exibility with respect to the size of the images reproduced and the safety factors which are present in connection with the high voltage equipment employed. Further, methods heretofore used have not been adapt able to, utilization in an apparatus of a size and weight and having simplicity to be used as a camera or to be _ used in a printing system. In accordance with the prin placed on the surface of the plastic material in accordance with the density of the image is transferred to the copy material producing a printed copy of the image. It is, therefore, an object of the present invention to provide an electrophotographic method and apparatus wherein a strip of supporting material coated with a photoconductive insulator may be fed through a camera ciples of the present invention, it is contemplated to pro to produce a latent charge image by an electrophotographic vide methods and apparatus which may be adapted and 45 process conducted entirely within the camera. utilized in a camera suitable for practical usage for di Another object of the invention is to provide a mecha rectly producing a reproducible, or developed, or per nism wherein a permanent image is produced Within a manent image by electrophotographic means. The present ' camera by drawing a clear plastic ?lm coated with a invention also contemplates the provision of methods and photoconductive insulating material over an electret and apparatus which may be utilized in a relatively uncom- , exposing the ?lm to radiation and subsequently drawing plicated printing arrangement wherein copies or prints are rapidly and directly made from the permanent image with the utilization of electrophotographic processes. to develop and ?x the ?lm. Another object of the invention is to provide a camera In accordance with the principles of the present inven tion, it is contemplated to provide as a charging means in an electrophotographic process a layer formed from an electrically stressed substance and providing an eifec~ tive working surface which exhibits a permanent elec trostatic ?eld as high as 30,000 volts per centimeter. A layered member so provided is sometimes referred to in the electrostatic arts as an “electret.” A feature of the present invention is to provide a the ?lm through a dust chamber and a spray chamber wherein a ?lm coated with a photosensitive layer is se quentially drawn over surfaces of opposite polarity on the electret and thereafter placed against a ground plate and exposed to the radiation of an image and substantially drawn through a dust chamber and spray chamber to de velop and ?x the image on the ?lm. Another object of the invention is to provide an im proved photoelectric printing method and apparatus which is simple in construction and operation and wherein copies camera wherein the light radiation passing through the or prints 'may be directly and continuously made by a lens falls upon a photoconductive strip backed by an electret and wherein the strip is subsequently drawn through a dusting chamber and thereafter through a ?xing chamber so that the dust which is gathered upon the sur face in the form of the image will be permanently ?xed photoelectric process obviating the necessity of providing permanent images by 'an electrophotograpln'c process ‘Another object is to provide another form of mecha expensive and complex equipment such as has hereto fore been necessary. Another object of the invention is to provide an elec trophotographic printing process which ?nds utility in a to the strip of material. ‘ printing mechanism wherein a powder deposited in the It is another feature of the invention to provide a 70 form of an image is carried by a transfer blanket to a method and apparatus for the printing of copies from , printing paper. 3,028,799 3 4 nism wherein the powder may be transferred directly to, tem 20 maybe opened for a predetermined period of a printing paper and ?xed thereon. Other objects and advantages will become more ap parent in the teachings of the principles and features of the invention with the disclosure of the preferred embodi ments thereof in the speci?cation, claims and drawings, in which: FIGURE 1 is a somewhat schematic vertical sectional view of one form of a camera employing the principles time to permit the passage of light radiation through the lens in accordance with the re?ective properties of the image to be photographed. At the focal point of the lens is a re?ector plate 22 which is set at a 45° angle with the camera shown in the horizontal position, so that the image is re?ected upward ly against a supporting surface adapted to have a latent charge image formed thereon, sometimes referred to 10 herein as a ?lm ‘24. of the invention; The ?lm may conveniently comprise av backing or FIGURE 2 is another vertical sectional view taken carrying layer with a layer of photo-conductive material through the camera and showing schematically another thereon such as sulfur, anthracene or mercuric sul?de. form of the camera; Means for supplying the ?lm are shown in the form of a FIGURE 3 is a vertical sectional view shown in sche matic form of a printing mechanism for making copies 15 supply roll 26 from which the ?lm is threaded to be posi tioned against the ground plate 28 in the picture taking or prints of images; and location. The end of the ?lm next passes through a FIGURE 4 is avertical sectional view shown in sche dusting chamber 38 and then passes into a spraying matic form of another arrangement of a printing mecha msm. chamber 40. In the embodiments of FIGURES 1 and 2, the inven 20 The spraying chamber is provided with a hinged door 42 which may be swung open about its supporting hinge tion is shown using an electret in a box or similar hand 4+4 to remove the developed and ?xed end of the ?lm camera for purposes of making permanent images. As used herein, the term “electret” denotes a permanent at 46. ' 1y electri?ed substance exhibiting electrical charges of In advancing the ?lm into the camera, the ?lm is ?rst opposite sign at its extremities and of the type disclosed 25 drawn over a scanning bar or roller 48 positioned to be in our acknowledged co-pending application. in engagement with the ?lm. The scanning bar 48 is of Electrets are made from solid substances which are a polarity determined by electret 50. capable of being melted without chemical decomposition The electret member 50 comprises a body 52 with a and which possess a ?nite dipole movement in liquid ?rst lower surace 54 and a second upper surface 56. The state, for example, carnauba wax-beeswax mixtures, mix 30 surfaces 54 and 56 are spaced from each other and paral lel and exhibit a permanent electrical charge with the sur~ tures of carnauba wax with various synthetic, thermo faces 54 and 56 being of opposed polarity in accordance plastic or polar resin such as polyvinyl chloride polymers, with the de?nition of theterm “electret.” etc., soda-lime glass, Pyrex glasses, quartz, and sulfur. As illustrated in FIGURE 1; the electret 50 is pro A, permanent charge is imposed upon the substance of vided on the surface 54 with an electrically conductive the electret by allowing the liquid electret-forming sub layer 58. The surface 56 is provided with an electrically stance to solidify in a strong electric ?eld. For example, conductive layer 60. . _ the substance may be melted while interposed between Attached to the ?rst electrically conductive layer 58 two electrically-independent tinfoil electrodes attached to opposite poles of a high voltage D.C. source furnish 40 is an electrical lead 61 which is electrically connected to the scanning bar 48 so as to place a charge on the sur ing a DC. ?eld of not less than 10,000 volts per centimeter. face of the coated paper in accordance with ‘the electro~ The liquid substance is allowed to remain in the ?uid static charge on the surface 54 of the electret. state within the ?eld for at least one hour and is,‘ there As the ?lm 24 is drawn forwardly to an image-forming afterhprogressively cooled at a slow rate within the ?eld location 62, it passes over the electrically conductive suruntil completely solidi?ed. _ It has been found that electrets so formed are per 45 face 56 which places a charge on the surface of the photo conductive coating in accordance with the electrostatic manently volume~polarized and possess permanent elec charge on the surface 56 of the electret. ' trostatic ?elds of opposite polarities at the extremities or When the ?lm is in the image-forming location 62, it surfaces thereof to which the electrodes were attached. is positioned in juxtaposed relationship to the ground .' In the electrophotographic processes of the prior art, charges in the range of 4500 to 6000 volts per centimeter 50 plate 28. The light-conducting ?lm has been in location to re have been utilized, The permanent electrostatic ?elds ceive light radiations of the image. As the shutter sys possessed by electrets may range from a few hundred volts tem 2.0 is opened, the ?lm 24 is exposed to radiation and per centimeter and may exceed as high as 30,000 volts surface electrons are discharged to the ground plate 28 per centimeter at the working surfaces of the electret and, accordingly, it is contemplated according to the principles 55 in the shape and density of the image. of the present invention that the electret will be provided with surfaces exhibiting a permanent electrostatic ?eld in the order of magnitude of a few hundred volts to an The ?lm 24 is next rolled forward to pass through the dusting chamber 38. The dusting chamber exposes the photoconductive surface to ?ne pigment particles and these particles are picked up in the shape and density upper limit determined by the breakdown potential of of the image. ' 60 the air in contiguity to the charged surface. Guide pins 41 or the like may be provided to guide Although the principles of the present invention ?nd the ?lm as it passes with its surfaces 43 exposed to the speci?c utility in the embodiments illustrated and de dusting chamber 38. The dusting chamber 38 may be scribed, it will be understood that the features and ad provided with seals at its edges to avoid the escape of vantages of the invention may be utilized in other en dust down into the camera chamber 14 or up into the vironments and the speci?c forms shown are for purposes 765 of illustration and for purposes of disclosing the preferred forms. . As illustrated in FIGURE 1, a camera is illustrated spray chamber 40. The dust may be created by agita tion means or may be applied by a brush similar to an iron ?ling brush of the type known to the art. After being developed, the dust coated ?lm is drawn as having ‘a housing shown diagrammatically at 10 with 70 up into the spray chamber 40 where the image is ?xed. ya bellows 12 or similar lightproof enclosure de?ning a camera chamber ‘14. At the front of the camera cham ber is a lens and shutter assembly 16 with lenses 18 and a shutter system 20. The lens and shutter ‘arrangement are the type known to the art whereby the shutter sys The ?xing is accomplished by applying a spray such as by nozzle 64 which sprays over the surface of- the‘ end of the image and causes a permanent adherence of the dust to the ?lm in the density and shape of the image. A plastic solution spray such as F‘Krylon” or any solid 3 6 plastic dissolved in a volatile solvent, which solvent is compatible with the ?lm material, may be applied to ?x which extends the length of the cylinder to provide an equal radiation of the length of the ?lm 122. The light the image. source can be at the axis, but is not limited to being at ' In the form show in FIGURE 2, the camera is pro: vided with a housing 66 having a lightproof bellows 6-8 forming a camera chamber 70. At the front of the cham ber is located a lens and shutter assembly 72 carrying lenses 74 with a shutter system 76. The assembly 72 is arranged so that the shutter may ‘be opened for a pre i that location. A light source can also be placed very near to the inner surface of the electret at a point where the image transfer to the photoconductive surface 116 is to take place. A light shield 128 is provided to restrict the light to the required longitudinal area. As illustrated, the shield determined length of time to permit light radiation corre 10 128 has a break or slit 130 along one side in order that the sponding to the image to pass rearwardly within the light rays may pass therethrough to pass through the trans camera chamber 70. At the back of the camera in an parent holder 124; the negative 122,~and the electret 114. image-forming location 78 is the ?lm 80. The ?lm may A grounding brush 132 is provided supported on a hold be a backing paper with a photoconductive insulating er 134 to be in brushing contact with the outer photo— material ‘thereon and is preferably formed ‘of a roll of 15 conductive layer 116. ' The brush grounds the outer layer clear plastic with a photoconductive insulating surface. and removes stray charges which would create a false image. '_ , _ The ?lm is supplied from a supply roll 82 housed in ‘ an upper portion‘ 184 of the housing 66 and feeds down As the electret tube 114 rotates in a clockwise direction, wardly to the image-forming location 78 and subsequently as illustrated in FIG. 3, vthe outer photoconductive coat . through a dust chamber 86 and a spray or ?xing cham 20 ing or surface 116 passes through a dusting-box 136. > The ber 88. - In moving to the image-forming location 78, the ?lm 80 passes .a lateral ground brush 91. The ground brush may be moved across the face of the ?lm along the guide dusting box ‘exposes the photoconductivev surface 116, which has had the latent image photoelectrically placed thereon in passing the light exposure of, the slit 130, to a ?ne pigment dust. The dust is attracted to the coating 93 or it may be more feasible to position the ground to 25 118 in the form and density in accordance with the latent contact the ?lm as it comes off the roll 82 as a ground image on the ?lm. on the face of the electret may bring charges to the sur As the coated surface 118 carrying the image, made visible by the attracted powder, leaves the dusting box 136 In the picture-taking location, the ?lm is backed by an it is engaged by transfer cylinder 138 carrying a blanket electret'90 which is shown in the form of a ?at plate 92 30 transfer surface 140. The transfer cylinder is geared to having opposed parallel surfaces 94 and 96, which ex the electret cylinder, in a drive not shown, so that where hibit permanent electrostatic charges of opposing polarity. their surfaces meet at a nip 142 they will have an equal face. ‘ In the picture-taking location, the shutter system is peripheral speed. It should also be understood that the opened whereupon the ?lm 80 is exposed to radiation. A transfer cylinder 13-8 and the electret cylinder 114 can be latent electrostatic image is produced on the ?lm in the 35 conveniently made of the same diameter thereby insuring con?guration and density of the image. equal peripheral speeds. After the image has been formed on the ?lm, it is ' The blanket or transfer surface 140 on the cylinder, is rolled downwardly to pass into the dusting chamber 86. of a nature that will have a greater affinity for the powder In this chamber, the ?lm is exposed to a ?nely separated or dust on the electret cylinder than the surface 118 of pigment or dust which attaches itself to the surface in 40 the electret cylinder. The dust will thus be transferred the con?guration and density of the image and changes to the surface 140 of transfer cylinder remaining in the the latent electrostatic image to a visible image. ‘The ?lm form of the image. The dust or powder, which has been portion 98, which is in the dust chamber 86, is guided by transferred to the blanket surface 140 by contact and spaced horizontally extending guiding bars 160'. affinity, will now be transferred to the surface of a print The leading end 102 of the ?lm is rolled forwardly 45 ing material such as paper 144. ‘The length of paper ‘144 into the spray or ?xing chamber 8-3. At this location a is fed between the transfer roll 138 and a second electret spray nozzle 104 is supplied from a manifold or con 146 at a location 148 where their peripheral surfaces sub tainer 106 and sprays a material such as a clear plastic stantially meet. The paper is rolled from a supply roll coating to ?x the powdered material to the surface of 148 onto a take-up roll 150. the ?lm end 102. The end 102 of the ?lm upon which V51) The electret roll or cylinder 146 has anouter surface the visible image has been ?xed, may be removed by 152 exhibiting a permanent electrostatic charge of a swinging back a door 106 which is hinged to the back of polarity opposite that of the outer surface 118 of the the housing. by a hinge 108. electret tube 114. Thus the powder forming the visible FIGURE 3 illustrates another form of the method of image, which is coated on the surface 140‘ of the transfer the invention for printing copies from a permanent image roll, is attracted to the electret roll 146 and coats on the by an electrophotographic process. A housing is illus trated at 112 wherein a hollow, cylindrically shaped or image-receiving paper 144. The blanket surface 140 of the transfer cylinder 138 tubular electret 114 is located to rotate about a horizontal may be coated with a material such as rubber which has a axis. The tubular electret is made of a transparent mate greater a?inity for the powder image than the insulating rial such as a clear plastic, glass or the like and the outer 60 surface 116 of the electret tube 114. In one form it is surface 118 is coated with a photoconductive insulative advisable to ground the surface‘ 116 of the electret to material. The outer surface 118 of the electret, beneath the coating 116, and the inner surface 120‘ are of op expedite transfer of the image to the blanket 140. This may be accomplished by embedding small particles of cop posite polarity and are permanently electrostatically per or similar substance into the blanket surface .140 of charged in accordance with. the characteristics of the 65 the transfer, cylinder 138. electret. After the image has been transferred to the paper 144, The ?lm 122 is to be placed inside the inner surface it is carried upwardly on the surface of the paper to a 120 of the tubular electret 114. The ?lm 122 is held ?xing element 154 which may be in the form of a spray , against the inner surface of the electret by means of clips or vapor or a heating element.‘ As illustrated, the ?xing “or similar holding devices that will retain it against the 70 element 154 provides a heating element 156 which ?xes surface, but which are/not shown. As illustrated, the ?lm the image to the paper 144. is held to the inner surface 120 by a sheet of clear semi In the form shown in FIGURE 4, a hollow electret tube rigid plastic 124 which may be supported between rigid 1’ stops, not shown. The inside of the tube contains a light source 126 75 ' 160 is carried partially exposed in a housing 162 to-rotate ' about a horizontal axis. The electret has an outer surface 163 exhibiting a permanent electrostatic charge. ' ' 3,028,799 In this form of the invention, the ?lm 164 is clamped to an exterior image for a controlled period of time, an the outer surface 163 of the electret cylinder tube 160. The ?lm may be held to the surface by various means but electret within the camera chamber having a surface face may be pulled tightly thereto by a thin outer sheet of plas surfaces each exhibiting permanently charged electro tic material 166. This plastic material may be a material such as “Mylar” polyester ?lm which is available com static ?elds of opposite polarity, means at one side of said electret supplying an area of image-forming ‘material with a photoconductive layer thereon md adapted to be placed mercially. ' ing the lens and including opposed coextensive parallel over the electrostatically charged surface facing the lens, The thin plastic sheet is clamped to the cylinder at a movable grounding element adapted to be moved over one end drawn tightly by appropriate clamps (not shown in detail) at the other end, with the clamped ends being 10 the surface of the image-forming material whereby stray charges on the surface thereof are discharged, and means shown’ generally at 168. for subjecting the image-forming area to contact with The outer thin material 166 is dipped in a thin ‘solution electrostatically attracted material to form a visible image of photoconductive insulating material and is coated on the surface of said image-forming material. thereby. _ 2. An electrophotographic camera combination com The light source is shown at 170 and in this form 15 prising means forming a closed lightproof camera cham is on the outside of the electret tube 160. The light source may be placed within a housing 172 having a nan her, a' lens positioned to expose the interior of the cham row slit 174 across the front to expose‘the photoconduc t-ive layer 166 of the ?lm 1164 to the light across an axially ber to an aerial image, a shutter system for the lens ' extending area. adapted to open the lens for a predetermined period of 20 time wherein light radiation enters the camera chamber, , - A ground brush 176 is provided carried on a holder 177 to neutralize the outer plastic material and remove a plate of permanently electrically pre-stressed substance having parallel surfaces exhibiting permanently charged electrostatic ?elds of opposite polarity ‘with one of said surfaces facing the light radiation which enters the cam When the photoconductive material 166 ‘has been car~ ried past the light source, it next passes through a dust 25 era chamber through the lens, means for movably supply ing an image-forming strip of material having a photo chamber 178. In the dust chamber 178, the surface of ‘conductive layer adjacent a second layer whereby radiation ‘the photoconductive material 166 is exposed to a ?ne dust maybe projected through the lens onto said photoconduc or pigment which is attracted to ‘the surface in the shape tive layer while it is in proximate relationship to the sur and density of the image to be printed. stray electrostatic ?elds therefrom.‘ After the dust chamber, the continued ‘rotation of the electret tube 160 exposes the photoconductive material 166 to alight source 180. This light source brings a charge to the entire surface. . In the form embodied in ‘FIGURE 4, the transfer roll face of the electrically stressed plate, a stationary ground bar located so that the moving image-forming strip will pass in close proximity thereto to remove stray electro static ?elds from the photoconductive surface thereof, and means located adjacent the electrically pre-stressed is omitted and the photoconductive layer 166 is next 35 plate providing an atmosphere of electrostatically at tracted material whereby the surface of said image pressed against a copy material such as a paper 182 fed forming strip is coated with the material in a shape and from a supply roll 184 and rolled onto a take-up roll 186. density varying with the radiation received in accordance The paper passes between the photoconductive layer 166 with the light emitting properties of the image, and means and a paper electretroll 188. The paper electret roll has an outer surface 190 which is opposite in polarity to the 40 for ?xing the layer of electrostatically attracted material on the image-forming strip to render the image permanent. outer vsurface 163 of the electret tube 160. This causes 3. In a mechanism for producing an image by an ‘elec an attraction and a transfer of the visible image formed trophotographic process comprising a closed lightproof by the powder on the 'photoconductive material 166 to camera chamber, an electret plate within said chamber the paper 182. The image, carried on the paper 182, next passes over 45 having opposed parallel spaced surfaces being charged with a permanent strong electrostatic ?eld withropposit‘e the image ?xing element 192. The ?xing element may surface having opposite polarity, a lens for said camera be in ‘the form of a heating element 194, as illustrated, or may spray vapor on the surface to ?x the powder chamber located so that radiation passing through the lens will engage an area adjacent one surface of the elec: The method is well adapted to use in printing or copy 50 tret, a shutter system for the lens adapted to permit pas-' thereto. ing permanent images and employs simple, easily main sage of light radiation for a predetermined time,’means for orienting the charge including means for grounding the surface of an image-forming material adapted to be placed in juxtapositionover the lens facing surface of the ferred to. Thus, it will be seen that we have provided methods 55 electret whereby stray electrostatic ?elds are removed, and apparatus for electrophotographically taking perma means adjacent the electret plate for exposing the image nent images and printing copies embodying principles and, forming material ‘to an atmosphere of electrostatically tained and simply constructed apparatus. Copies can be continuously and rapidly printed with the advantages re features of the invention hereinbefore set forth. The features of invention are well adapted to use with a sensitive pigment particles whereby the particles are coated on the image-forming material with a shape and camera and avoid the necessity of providing the cumber 60 density varying with the latent image on the surface there- " some and complicated devices necessary with methods of in accordance with the radiation received, and means for ?xing the pigment particles on the surface of the We have, in the drawings and speci?cations, presented image-forming material. a detailed disclosure of the preferred embodiments of our 4. A camera for making an image by an electrophoto ‘invention, but it is to be understood that we do not intend 65 graphic process Which comprises a lightproof camera to ‘limit the invention to the speci?c forms disclosed, but chamber, a lens and shutter combination at the front of and apparatus heretofore used. ' intend to cover all modi?cations, changes, and alternative constructions and methods falling within the scope of the ' the chamber adapted‘to open the lens for radiation to the back of the chamber in accordance with an image to be reproduced, an electret plate at the back ‘of the cham-‘ 70 her having a surface with an electrostatic charge of 'a We claim as our invention: 7 1. In combination, a camera means for making an given polarity, a housing for the camera, means within image by an electrophotographic process which comprises the housing for movably supplying a strip of image-form! a lens‘, a closed camera chamber exposed to light only principles taught by our invention. ing material having a photoconductive layer responsive ‘ through the lens, a shutter system for controlling the opening of ‘the lens and ‘exposing the camera chamber to 75 to radiation through the lens to form an image to ‘be 3,028,799" l a - 9 . 4 . . 10 reproduced, a developing chamber having means for pro viding an atmosphere of electrostatic responsive pigment in minute particles which will coat the image-forming ‘conductive insulation layer on the outer surface of the electret element, means for moving and supporting a ?lm strip with a shape and density in accordance with the ra diation received through the lens, and a second ?xing Within the tubular electret whereby light radiation will pass through the ?lm and transparent electret to impress a latent image on the photoconductive insulation layer, means for applying a powdered pigment material to the chamber with means to spray a coating of material over the image-forming strip whereby ‘the visible image is' ?xed on the surface of the image-forming strip. on the inner surface of the electret element, a light source . ' insulation‘ layer on the surface which is attached to the . layer in accordance with the latent image thereon, a trans means having an electret plate having opposing parallel 10 fer cylinder positioned to be rotated about an axis parallel 5. In a photoelectric camera combination, _a charging coextensive surfaces each charged with a permanent elec with the tube and having an outer surface with an a?inity trostatic ?eld with opposite surfaces having opposing for the powdered pigment, a picture material adapted to be rolled in engagement with the transfer cylinder whereby polarity, a camera housing supporting said plate and , the particles are transferred to the surface thereof, and of the chamber located to expose an image forming strip 15 means for ?xing the particles transferred to said picture material. to radiation emitted from an image- externally of the _ 9. A mechanism for reproducing images in accordance camera, a shutter system for the lens adapted to open with claim 8 wherein electrical conductive material is em the lens for a predetermined length of time, means with in the housing supplying a stripv of image-forming ma- ‘ bedded in_ the surface of the transfer cylinder to ground terial of‘a clear plastic with a photoconductive insulating 20 the surface of the electret tube in contact with the trans forming a lightproof camera chamber, a lens at one end surface thereon, said image-forming material being drawn fer cylinder to expedite transfer of the image to the cyl across the surface of the electret plate, a developing inder. chamber ?lled with dust particles of pigment susceptible 10. A mechanism for reproducing images electro photographically comprising a transparent electret ele ment having ?rst and second surfaces permanently ,charged electrostatically with opposed polarity, a photo to electrostatic attraction, whereby the pigment particles are coated on the image-forming strip with a shape and density dependent upon the radiation received by the image-forming strip, and a ?xing chamber adjacent the developing chamber provided with a-coating spray where by the pigment particles are adhered to the surface of the image-forming strip to permanize the image. 6.v In an electrophotographic apparatus comprising a camera housing de?ning a lightproof camera chamber, a conductive layer on the second surface of the electret ele ment, a light source located adjacent the ?rst surface whereby light vrays may be projected through a ?lm place againstrthe ?rst surface and through the transparent electret to the photoconductive insulation layer,‘ means for applying a powdered material attracted by the charge on the insulated surface whereby a visible image will be lens member at the front of the chamber for admitting produced thereon dependent on the intensity of the ra radiation in accordance with the character of an image, a shutter assembly for the lens, a light~re?ecting surface 35 diated latent image thereon, a transfer blanket means having a greater a?inity for the powdered material than at the back of the camera chamber positioned substan ‘the insulated surface and adapted to remove the pow tially at an ‘angle of 45° with the axis of the lens whereby dered material in the charge pattern in which it has the'light rays will be‘ re?ected vertically upwardly to an ‘formed on the insulated surface, a second electret element image-receiving position'when the camera is positioned horizontally, means for ‘movably' supplying a strip of 40 having a permanently charged electrostatic surface with image-forming material in the‘image-receiving position ' .a polarity opposed to that of said'second surface of the transparent electret, whereby the second electret may be.‘ across the top of the camera chamber, said material having ‘ pressed against the transfer means with an image-receiving ‘a layer of photoconductive material thereon, an electret meansv therebetween and the powdered material will at having a surface located for engagement with the image forming strip as it is drawn into image-receiving position, 45 tract itself to the image-receiving means in the pattern of the image, and means for ?xing the material to said whereby radiation will produce a latent charge image on image-receiving means. said photoconductive layer, and means for developing and. 11. A mechanism for rotary printing of images by an ?xing said latent image into a permanent image by sub electrophotographic process which comprises a hollow jectingthe strip to an electrostatically attracted dust and by adhering the dust to the strip after it is accumulated 50 cylindrically-shaped electret having inner and outer sur faces with a permanent electrostatic charge of opposed “thereon in the shape and density of the latent image, polarity, means on the inner surface of the electret cylin 7. In. an electrophotographic apparatus, an electret member having opposed surfaces permanently charged with electrostatic ?elds of opposite polarity and having coatings of electrically conductive material over each of said surfaces, means for passing an image-forming ma terial in effective electrical engagement with the ?rst layer of electrically conductive material and subsequentlyr in engagement with the second layer of electrically con ductive material, means for placing a grounded plate in coextensive juxtaposed relationship with the image-form ‘ der for supporting a ?lm, a light source positioned within the electret cylinder, a light shield having a narrow light passing strip extending axially across the cylinder and limiting the light passage through the ?lm and the elec~ tret to the narrow strip, a coating of photoconductive in sulation material on the outer surface of the electret, means for applying a material to the outer surface of the cylinder which will a?ix itself thereto in the pattern of the image impressed on it by the light radiation passing through the electret and ?lm, a transfer roll rotatable ing material after it has been passed over the conductive about an axis parallel to the electret cylinder and having layers, a camera lens system exposing the photoconduc an outer blanket surface with an a?inity for the material tive layer on the image-forming material to a radiation in accordance with an image to be reproduced, and de 65 attached to the surface of the electret cylinder to thereby remove said material in the pattern of the image, a veioping and ?xingimeans for permanizing the latent second rotatable electret having an outer permanently image on the photoconductive layer by dusting the layer charged electrostatic surface with a polarity opposite that with an electrostatically attracted powder and adhering of the outer surface of the electret cylinder, means for the powder in its attracted positions in densities and shapes 70 passing a strip of image-receiving material between the varying with the radiation received by the material. '8. A mechanism for reproducing images electrophoto graphically comprising a tubular shaped transparent elec tret element having inner and outer surfaces permanently transfer roll and the second electret whereby the image will ai?x itself to the material, and means for re ceiving the material from the second electret and opera tive to ?x the attracted material to the surface for a charged electrostatically with opposed polarity, a photo 75 permanent print. a, 028,799 12 11 jected into said photoconductive layer when said lens 12. A mechanism for reproducing images electro photographically (comprising a tubular-shaped transparent is opened, and a developing chamber into which said strip material is moved away from said electret and having an electret element having inner and‘outer surfaces perma atmosphere of charge-responsive material coating the nently charged electrostatically with opposed polarity, a image-forming material non~uniformly with a shape and density varying with the radiation received from the photoconductive insulation layer on the outer surface of the electret element, means for supporting an image a bearing means on the. inner surface on the electret ele image. ' I Y 15. An electrophotographic reproduction apparatus ment, a light source within the tubular electret whereby - which includes, an electret,.means passing. a layer'of light radiation will pass through the image and trans parent electret to impress a latent image on the photo-j 10 image-forming material having a photoconductive layer through the permanent electrostatic ?eld adjacent the conductive insulation layer, means for applying a pow surface of the electret, means forming a grounded sur dered pigment material to the insulation layer on the face in close proximity to the image-forming material, surface which is attached to the layer in accordance camera lens means for exposing the photoconductive lay with the latent image thereon, a transfer cylinder posi tioned to be rotated about an axis parallel with the tube 15 er of image-forming material to a radiation in an image to be reproduced to form a latent electrostatic image in and having an outer surface with an affinity for the pow the image-forming material, and means for developing dered pigment, a grounding brush positioned in contact the image to render it visible. with the insulation layer after contact with the transfer cylindena copy material adapted to be rolled in engag ment’with the transfer cylinder whereby the particles are 16. An electrophotographic reproduction apparatus in 20 cluding an electret, means passing an image-forming ma transferred to the surface thereof, and means for ?x ing the particles transferred to said copy material. 13. A mechanism for reproducing images electro terial having a photoconductive layer attached thereto ‘ through the "permanent electrostatic ?eld adjacent the surface of an electret, means passing the image-forming material in electrical contact with a layer of electrically an electret with the inner and outer surfaces of opposing 25 conductive material on a ?rst surface of said electret, and subsequently with a second layer of electrically conduc polarity, means for attaching a thin plastic material with tive material on another surface of said electret, means a photoconductive insulating surface thereon to the outer pho'tographically comprising a rotating cylinder forming placing ‘a coextensive ground adjacent the image-forming peripheral surface of the cylinder wherein an image-bear material, a camera lens system for exposing the image ing ?lm may be held between the plastic material and cylinder, a light source exteriorly of the cylinder adapted 30 ‘forming material to a radiation in accordance with an image to be reproduced to formulate an electrostatic to apply light radiation to the photoconductive surf-ace of image on the photoconductive layer, and means for de the thin plastic material, a dust chamber for applying a veloping and ?xing the image on the image-forming ma- ' ' .pigment dust to the outer surface of the plastic material whereby the latent image is rendered visible, and a second electret cylinder having an outer surface permanently 35 terial. electrostaticall-y charged and being of a polarity opposing V ders, said paper receiving'the image in its visible form from the layer of thin plastic material as attracted by 40 the surface of the second electret. 14. In combination in a camera for making an image ‘by electrophotography comprising a closed light-proof ‘camera chamber, a lens located at one end of the cham 45 ber, a shutter device to be opened to expose the interior of the closed chamber through the lens to an image to be photographed, an electret in said camera having a flat sur face facing said lens and possessing a permanently pre charged electric ?eldof a given polarity, ?lm advancing 50 and guide means movably positioning strip form image forming material having a layer of photoconductive ma terial in adjacent coextensive relationship across said flat surface of said electret, whereby radiation may be pro g V . References Cited in the ?le of ‘this patent the polarity of the outer surface of the ?rst electret cylin der, means for passing a copy paper between said cylin V ‘UNITED STATES PATENTS 2,221,776 I Carlson _____________ __ Nov. 16, 1940 2,297,691 2,543,051 2,551,582 2,693,416 ,Carlson ..__ ____________ __ Oct. 6, Oughton et a1 __________ .._ Feb. 27, Carlson ______________ _.. May 8, Butter?eld __________ __ Nov. 2, 2,695,363 1942 1951 1951 1954 ' Marvin _____________ .._ Nov. 23, 1954 2,732,775 - Young et al. _________ __ Jan. 31, 1956 2,781,704 2,831,409 2,843,084 Mayo et al. ___________ __ Feb. 19, 1957 Bixby et al. __________ __ Apr. 22, 1958 vI-Iayford _____________ __ July 15, 1958 "OTHER REFERENCES 'Review of Modern Physics, \vol. 20, No. 3, July 1948, _ page 470. - Electrical Engineering, October 1953, pages 869-872. V‘ I Radio Electronics, January 1950, pages 8-82.