US 3671118 A
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Description (OCR text may contain errors)
June 20, 1972 J. FANTUZZO ErAL 3,671,118
APPARATUS FOR CREATING DUPLEX REPRODUCTIONS Filed Dec. 24, 1969 INVENTORS JOSEPH FANTUZZQ FRAZER D. PUNNETT BY A 7' TORNE Y United States Patent Oflice 3,671,118 Patented June 20, 1972 US. Cl. 355-3 7 Claims ABSTRACT OF THE DISCLOSURE A duplexing method and apparatus for producing duplicate reproductions of original subject matter on opposite surfaces of a support material. Two oppositely reading latent electrostatic images of subject matter to be reproduced are created on a photosensitive surface and are developed with developer material wherein one of the images comprises a right reading image which is transferred to a storage medium after development. The other image being in wrong reading or mirror form remains on the photosensitive surface to be directly transferred therefrom to one side of a support material whereupon the developed image retained on the storage medium is transferred to the other side of the support material to create a duplex reproduction.
BACKGROUND OF THE INVENTION This invention relates in general to producing reproductions of subject matter and, in particular, to an improved method and apparatus for producing duplicate reproductions on two opposite surfaces of a support material.
More specifically, this invention relates to a duplex method and apparatus wherein a right reading latent electrostatic image of subject matter to be reproduced is formed and developed on a photosensitive surface and is transferred therefrom to a storage medium to be retained thereon. A second wrong reading or mirror latent image is also formed and developed on the photosensitive surface and is transferred directly to one surface of a support material at a transfer station. The other surface of the support material receives through transfer the developed image retained by the storage medium to produce a duplex reproduction of the original.
Although not intended to be so limited, the duplexing method and apparatus of the present invention is described for convenience of illustration in conjunction with the xerographic technique of reproduction. In the process of xerography, a xerographic surface comprising a layer of photoconductive material on a conductive backing is given a uniform electric charge on the surface and then is exposed to the subject matter to be reproduced by various projection techniques. This exposure discharges the surface in accordance with the light intensity reaching it thereby creating a latent electrostatic image on or in the surface. Development of the image is effected by developers which may comprise, in general, a mixture of suitable, pigmented or dyed, resin base powder, hereinafter referred to as toner, which is brought into contact with the surface by various Well-known development techniques. During such development of the image, the toner powder is brought into surface contact with a photoconductive coating and is held there electrostatically in a pattern corresponding to the latent electrostatic image. Thereafter, the developed xerographic image may be transferred to a support material to which it may be afiixed by any suitable means such as heat fusing.
Numerous methods and appaartus have been employed in the prior art to accomplish the aforementioned basic process of xerography, but generally these prior art reproductions have been limited by the fact that only one surface of a support material is utilized to create a duplicate copy. Such an employment of but one surface of a support material to receive developed toner images is uneconomical since a greater amount of support material is required because it requires approximately twice the amount of support material as needed by duplex duplicates. Further, duplex reproductions result in convenient to use duplicates because they may be readily assembled in book form which is especially desirable if an original document includes a large quantity of sheets or the like to be reproduced. Also, since the number of sheets required for duplex reproductions is much less than utilizing only one side of the support material, a great economy of physical volume of the reproductions results to alleviate the problems of storage of the copies for future use. Therefore, it is advantageous in xerography to provide an inexpensive and eflicient method and apparatus for producing duplex reproductions of an original document or the like.
One attempt in the prior art to produce a duplex xerographic reproduction of an original is disclosed in the US. Pat. No. 3,318,212 to Rubin wherein xerographic reproduction is produced on opposite sides of a sheet of support material. Although such a system disclosed in Rubin provides satisfactory duplex reproductions, it suflers from the problem of being comparatively complex and requires the use of a tackified image to produce a duplex duplicate. The provision of a tackified image requires the utilization of a vapor chamber for both surfaces from which the toner image is transferred to the support material. Further, the use of a tackified image does not provide for rapid and high quality production of a duplicate copy as compared to a system utilizing dry tones images for transfer. Therefore, it is desirable in xerography to provide an ef fective system which utilizes a minimum of elements and complexity to provide duplex duplicates when using a dry toner material.
SUMMARY OF THE INVENTION It is, therefore, an object of this invention to improve the method and apparatus for producing reproductions of original subject matter.
.Another object of this invention is to improve the method and apparatus for producing duplex reproductions.
These and other objects are obtained in accordance with the present invention wherein there is provided a duplex method and apparatus that effectively produces reproductions on two sides of a support material. The method and apparatus disclosed herein utilizes a photosensitive surface whereon two electrostatic latent images of opposite reading are created and developed. A right reading latent image is first formed and developed on the surface to be thereupon transferred to an image storage material where it is stored until a developed second wrong reading image on the photoconductor subsequently reaches the transfer station. Then by passing a sheet of support material past both the photoconductor surface and the storage material, each of the respective developed images thereon are transferred to opposite sides of the support material. Thereafter, the transferred image lying on both sides of the support material are transported to a fusing area where a permanent duplex reproduction is produced.
The novel method and apparatus of the present invention produces satisfactory duplex reproductions with a minimum of elements. The original copy may comprise, for example, a two sided original document, two separate sides from two originals, or a side by side microfilm document and the like. The invention requires only one storage medium and a single photosensitive surface to effect a duplex reproduction of the original copy wherein merely one image transfer is necessary besides the actual transfers to the support material. Further, the duplex method and device of the present invention utilizes a dry toner image to be transferred electrostatically to a support material in a manner not heretofore possible because the prior duplex systems require use of tackified images to effect a duplex reproduction. The present system disclosed herein results in a faster and more economical device which readily produces high quality duplex reproductions with less complexity than prior art duplex systems.
DESCRIPTION OF THE DRAWING [Further objects of the invention together with additional features contributing thereto and advantages accruing therefrom will be apparent from the following description of one embodiment of the invention when read in conjunction with the accompanying drawings where- FIG. 1 is a schematic illustration of a duplex xerographic reproduction device of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, there is shown a schematic view of a drum type automatic xerographic reproducing machine for producing duplex reproductions according to the present invention. The central element of the apparatus is a drum I mounted for rotation and drivable in a clockwise direction by motor M. The drum comprises an outer surface with a layer of photoconductive insulating material such as, for example, vitreous selenium, or any other suitable surface. A uniform electrostatic charge is placed on the photoconductor surface of the drum by means of a conventional corona charging device 2. The uniformly charged surface of the drum is then moved to an exposure means 3 which exposes the charged surface to copy to be reproduced to thereby form a latent electrostatic image of the copy on the photoconductor drum surface. The exposure means may comprise, for example, a device which wil alternately reverse the image of the copy or document to be reproduced. Such a reversing image optical system may be any conventional type as, for example, disclosed in the aforementioned US. Pat. No. 3,318,212 to Rubin wherein microfilm originals are being duplicated. Other exposure means also may be utilized in conjunction with the present invention to expose the drum to alternately reading images of two sided original documents, one side from two documents and the like. The optical means exposes the charged surface to copy to be reproduced and forms a first right reading latent electrostatic image on the photoconductor drum. Following the formation of a right reading electrostatic image, the image moves past a conventional development device 4 to bring the latent image into contact with developer material, such as toner powder or other electroscopic material, for development thereof.
After development, the visible first right reading image moves to a transfer station -5 which includes a corotron 6 mounted adjacent a storage medium 7 of suitable material such as, for example, a dielectric belt of Mylar. It is within the scope of the invention to use other forms and materials for the storage medium such as a drum and the like or other materials capable of storing a visible toner image. The belt 7 is mounted on rollers 8 to allow the surface of the storage medium to be driven by a suitable motor means (not shown) in direct confrontation to the surface of the drum 1. A conventional corona device 6 is mounted on the opposite side of the dielectric belt 7 to transfer the developed right reading image from the drum to the belt by applying an electrical field to the back thereof.
As is apparent from the foregoing, the visible right reading image transferred from the drum thereupon is reversed in reading when placed upon the dielectric material. The length of the dielectric belt may be of any convenient size, such as, for example, one-half the circumference of the photoconductor drum. Further, it is desirable to drive the belt at a speed equal to the surface speed of the drum although other speeds of the belt may be selected if desired.
Subsequent to the formation of the first right reading image upon the drum 1, another area of the surface thereof is uniformly charged by the corona charging device 2. The uniformly charged surface of the drum then moves past the exposure means 3 to expose the surface to additional subject matter to be reproduced to form thereon a latent electrostatic image of opposite reading than the previously formed image which in this instance is a mirror or wrong reading image. The latent wrong reading image on the drum surface thereupon moves to the development device 3 to bring the charged image into contact with developer material to create a visible wrong reading image.
The time sequence of the charging, exposure and development of the two oppositely reading images in the machine disclosed herein is effected by the machine control circuit (not shown). The particular selected time sequence of operation depends on such factors as the location of various stations around the drum, the length of and velocity of the storage belt relative to the size and surface speed of the drum and the like. For convenience of illustration the area of the surface of the drum to receive the first right reading image is located diametrically opposite to the area of the drum supporting the wrong reading image. Therefore, when the first right reading image reaches the transfer station 5 for transfer to the storage belt 7 the center of the first image is situated one-half of the circumference of the drum from the second wrong reading image. Then by selecting a length of the storage belt 7 of one-half the circumference of the drum 1 and moving the belt at the speed of drum surface, the image transferred will move on the belt and return to confront the transfer station 5 at the instant the visible wrong reading latent image on the drum moves to the transfer station. Accordingly, the two images lying respectively on the storage belt and the drum confront each other at the same time.
A sheet of support material 9 is delivered to end 7a of the storage belt 7 of a conventional sheet feeding mechanism (not shown). Paper tacking corotrons 10 are mounted adjacent end 7a of the belt on the opposite side of the roller 7 wherein the sheet of support material is fed between the belt and the corotrons 10 and a charge is applied by the corotrons to the support material to cause the sheet to adhere to the storage belt directly over the toner image retained thereon. Thereafter, the storage belt carries the sheet to the transfer station 5 and the corotron 6 applies an electric field to the back of the sheet to transfer the developed image lying on the drum to one surface of the support material.
The sheet of support material thereupon retains on one surface the developed image transferred from the drum 1 and the opposite surface of the sheet is in contact with the developed image lying on the storage belt. A second transfer corotron 11 is positioned at end 7b of the storage belt to apply an electric field to the sheet material as it is carried by the adherence of the sheet to the belt. The electric field produced by the second transfer corotron 11 transfers the image stored on the belt 7 therefrom to the surface of the sheet 9 of support material. A conveying means 12 thereafter carries the sheet retaining an image on each surface to a suitable conventional fusing means 13 to afiix the developed image on each surface to the sheet to produce a permanent duplex copy. It should be apparent that the first developed image stored on the belt creates a right reading toner image on one side of the support material when transferred thereto. Similarly, the mirror toner image transfered from the drum to the other side of the support material likewise creates a right reading toner image and a suitable reading duplex is produced.
In the above description there has been disclosed an improved method and apparatus for effectively creating a duplex reproduction of desired subject matter. For convenience of illustration, the exposure means creating the alternately reversed images was illustrated as a single alternately reversing exposure device. However, it should be apparent that two separate exposure devices may be utilized to optically create each of the opposite reading images upon the photoconductive drum sequentially or simultaneously. Further, the two images may be formed on different areas of the drum other than diametrically opposite ones as disclosed herein. Moreover, the photoconductive surface was described for convenience of illustration as that being of a xerographic drum but the invention may also employ other photosensitive members such as plates, webs and the like. Also the relative speed and length of the dielectric material and the photosensitive surface may be selected to be any desired magnitude other than as disclosed which would insure the images on each member to effectively transfer on both sides of the support material. It is further within the scope of the invention to store the first developed image on a stationary belt or surface while the second image is developed if so desired.
While the invention has been described with reference to a preferred embodiment it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention and, in addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential teachings.
What is claimed is:
1. Apparatus for obtaining right reading xerographic toner images on opposite sides of the support member comprising a continuous reusable photosensitive surface supported for movement relative to charging, exposing and developing means for creating right and reverse reading toner images on the photosensitive surface,
first electrostatic transfer means adjacent the photo sensitive surface for electrostatically transferring both right and reverse reading images from the photosensitive surface,
a single continuous, reusable storage surface adjacent said photosensitive surface for receiving only right reading images electrostatically transferred directly from the photosensitive surface by the first transfer 6 means and for storing the received image and recycling it past the first transfer means simultaneously with the passage of a reverse reading image on the photosensitive surface past the first transfer means, feed means for transporting a support member between the photosensitive and storage surfaces to receive only reverse reading images electrostatically transferred directly from the photosensitive surface by the first transfer means and for preventing transfer of the reverse images to the storage surface by the first transfer means,
second electrostatic transfer means adjacent the storage surface and support member receiving a reverse image at the first transfer means for electrostatically transferring an image on the storage surface to the free side of said support member,
whereby right reading toner images are obtained for opposite sides of a support member.
2. The apparatus of claim 1 wherein the storage surface includes a dielectric material.
3. The apparatus of claim 1 wherein the storage surface includes a belt.
4. The apparatus of claim 1 wherein the right and reverse reading toner images are formed on two areas on the photosensitive surface a predetermined distance apart.
5. The apparatus of claim 4 wherein the storage surface includes a belt of a length equal to said predetermined distance and adapted to be moved at the selected speed of the photosensitive surface whereby the stored image lying on the belt returns to the first transfer means at the same time a reverse reading image on the photosensitive surface moves past the first transfer means.
6. The apparatus of claim 1 further comprises fusing means to affix the toner images transferred to the two surfaces of the support members to produce a permanent duplex copy.
7. The apparatus of claim 1 wherein said photosensitive surface is on a rigid cylindrical drum and said storage surface is on a flexible dielectric belt.
References Cited UNITED STATES PATENTS JOHN M. HORAN, Primary Examiner US. Cl. X.R. 355---26