US3330190A - Printing apparatus - Google Patents

Description

EARCH ROGM G. P. TAILLIE PRINTING APPARATUS 2 Sheets-Sheet 1 Filed Sept.

A AA A A A AA INVENTOR. GORDON P.

d'AlLLIE 5 ATTORNEYS July 11, 1967 c. P. TAILLIE 3,330,190

PRINTING APPARATUS Filed Sept. 1964 2 Sheets-Sheet J INVENTOR.

. GORDON RTgLIE oifqg g W .q-y

ATTORNE Y5 United States Patent York Filed Sept. 1, 1964, Ser. No. 393,698 1 Claim. (Cl. 954.5)

This invention relates to communication printers and particularly, to printers of the type wherein a photosensitive surface is exposed, in a line by line progression, to light images of alphanumerical characters. More particularly, the invention is concerned with apparatus for conveying selectively illuminated light images of alphanumerical characters from an array of characters to aphotosensitive surface so that the character appears at the photosensitive surface in an in-line arrangement.

Communication printers receive an electrical signal input which must be converted to alphanumerical characters and printed on copy paper. The present invention is intended for use in a printer which translates incoming electrical signals into light images of characters by illuminating areas of a plate containing a series of vertical columns with each of'the various characters to be reproduced and bringing the particular characters illuminated into on-line orientation to thereby expose a photosensitive surface a line at a time.

A device for bringing. optical images into on-line orientation is disclosed in Patent No. 2,725,786, entitled, Optical Card Reading Apparatus, and a printer of the type suitable for use with the present invention is disclosed in copending application Ser. No. 393,699, entitled, Communication Printer, filed Sept. 1, 1964. The device disclosed in Patent No. 2,725,786 visually displays characters corresponding to the punched holes in a data processing card, in a straight line, for ease of reading. The communication printer disclosed in Patent No. 3,149,201 selectively illuminates and prints characters in response to electrical signals. The printer includes a cathode ray tube to illuminate the desired characters and a xerographic reproducing unit to convert the light images into printed copy.

The present invention is an improvement in the means for conveying light images to the photoconductive surface of the xerographic unit. The conveying means shown in copending application No. 393,699, filed Sept. 1, 1964, consists of a pair-of mirrors or a glass block which reflect the light images through a light path from the image source to the photoconductive surface. Though very effective for thepurpo'se intended, the mirrors or glass blocks tend to be long and space consuming. The

present invention reduces the size of the glass blocks by reflecting the light through a tortuous path internally and maintaining the length of the light the same as if the image were directly focused on an image plane.

It is the primary object of this invention to improve communication printers by reducing the size of the light conveying block used to convey light images of oil-center characters to on-line orientation at a photosensitive surface;

It is a further object of this invention to reduce the space used in a communications printer for the optical path by folding and overlapping the light path of characters being reproduced.

It is also an object of this invention to improve the optical system of a communications printer by internally reflecting the light image of the characters to be reproduced within a glass block shaped to fold the light path of the images and to maintain the light path a length equal to the light path necessary to focus the image on a plane coincident with the drum surface.

These and other objects of the invention are attained ice by means of a glass plate positioned between the projection lens and the xerographic drum to receive light images for internal reflection. Some edges of the plate are silvered to reflect the light image through a path, inside the plate, to the xerographic drum.

For a better understanding of the invention as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings wherein:

FIG. 1 is a schematic view of a communication printer suitable for use with the present invention;

FIG. 2 is a perspective of one embodiment of the light conveying element constituting the present invention;

FIG. 3 is a front fragmentary view of a portion of the character plate used in the device shown in FIG. 1;

FIG. 4 is a schematic illustration of the spatial orientation of conventional projection optics;

FIGS. 5 and 6 are alternative embodiments of the light conveying element.

FIGURE 1 shows a schematic representation of one embodiment of a communication printer. The printer con- 'tains a xerographic drum 10 having a photoconductive surface thereon; a flying spot cathode ray tube 12; a relay lens 13 in front of the cathode ray tube; a field lens 15 in front of an opaque plate 14, containing an array of transparent alphanumerical characters, positioned in front of the relay lens 13 and the cathode ray tube 12; a projection lens 18; a character positioning element 16, in the form of a glass plate, adapted to convey light images from the lens 18 to the xerographic drum 10; and an input logic I 20, operatively connected to the cathode ray tube 12 to position the light spot of the cathode ray tube relative to the matrix on the plate 14 in response to an electrical signal.

The apparatus shown herein for translating optical images to printed words on a sheet of paper is a xerographic apparatus which is well known in the art. The same results may be accomplished by using any photosensitive surface in place of the xerographic drum 10, however, a Xerographic apparatus has been shown as illustrative of the type that may be used. The drum 10 containing a photoconductive surface, which is normally an insulating surface in the dark, is driven through a series of process stations by a motor MOT-1. The motor MOT- 1 is adapted to advance the drum a line at a time. That is, after exposure of one line on the drum surface the drum is advanccdone line by the motor MOT-1. The drum is stopped as each line is printed so that thecharacters appear on the drum surface in a straight line. This permits variable character and line printing time. It is also possible to skew the glass plate relative to the drum axis so that a line may be exposed with the drum moving Without producing distortion of the line.

As the drum 10 is driven by the motor MOT-1 past a charging station A, a Corotron 22 places a uniform electrostatic charge on the surface of the drum. The drum then rotates to an exposure station B wherein the drum surface is exposed to a light image of the characters to be printed. The light of the images renders the photoconductive surface conductive rather than insulating and discharges-the electrostatic charge in the image areas so that the drum surface contains uncharged areas in image configuration. The drum then rotates to developing station C wherein a developer material containing a triboelectric charge of the same polarity as the charge on the drum surface is cascaded over the surface of the drum. The developer material consists of a finely divided, pigmented, resinous powder herein referred to as toner carried on the surface of glass beads herein referred to as carrier. particles. The developer material is supplied from a reservoir in the bottom of the developer housing 24 to the '1 .J plate surface by means of a conveyor 26 and is cascaded over the drum surface back to the reservoir at the bottom of the developer housing. The carrier particles carry the toner material from the reservoir to the drum surface and upon contact with the non-charged image areas the toner material adheres to the drum surface, while in the non-image or charged areas the toner material is repelled by the charge onthe drum surface and returns with the carrier material to the reservoir. Thus, a powder image of the light image to which the drum was exposed at station B is developed on the drum surface. The drum then rotates past a transfer station D wherein a web of paper or other suitable material 28 is supplied from a supply roll 30 over a pair of guide rollers 32 into contact with the surface of the xerographic drum. A transfer Corotron 34 places an electrostatic charge on the surface of the web of paper while the paper is in contact with the drum surface. The electrostatic charge is of opposite polarity to the charge on the toner material and thus attracts the toner material from the surface of the drum onto the Web of paper. The paper then passes through a heat fuser 35 wherein heat supplied to the paper and the toner material causes the toner to coalesce and bond to the surface of the web. The web then contains a permanent image of the powder image transferred from the drum surface to the paper and is accumulated on a takeup roll 36. After the transfer operation the drum is rotated past a cleaning station E wherein a pair of rotating brushes 38 remove any residual powder from the drum surface prior to recharging and re-exposing the drum. The operation of a xcrographic apparatus is well known in the art and does not require a detailed discussion herein.

FIGURE 2 illustrates a system whereby a cathode ray tube provides a high intensity light spot behind selective characters on a plate. The plate 14 is constructed of opaque material with an array of transparent characters thereon. The character plate 14 may be exposed photographic film with unexposed character areas, or any other suitable material that will give high character resolution. The plate contains vertical columns having all the character symbols required of the printer and contains as many identical columns as are required to form a printed line across the width of the copy being printed. A segment of the character plate 14 is shown in FIG. 3.

As shown herein, the plate 14 is mounted adjacent to the exterior face of the cathode ray tube with a relay lens interposed to focus the light spot on the plate. However,

the plate may be mounted internally in the tube on the.

phosphor surface. Also, when the plate is mounted outside the tube it is sometimes advantageous to eliminate overlap of the light spot on more than one character by conveying the light from the phosphor surface to the particular spot desired by fiber optic bundles running from inside the tube face to the characters.

The projection lens 18 normally would reproduce the spatial orientation of each illuminated character at a focal plane tangent to the drum and perpendicular to the optical projection axis, as shown in FIG. 4. Element 16, shown in FIG. 2, is a glass plate which serves to intercept the light leaving the projection lens in such a manner as to optically displace all characters, disposed vertically in the image plane, to the optical axis while their horizontal positions remain unaffected. Thus a capability is created for a simple optical input with no movingparts and with a I either transmission lines or computer input after being translated by the input logic 20.

For purposes of illustrating the relationship between the character plate, the projection lens and the image plane, FIG. 4 shows a schematic representation whereby the characters on the character plate pass through a projection lens and are focused on an image plane. For simplicity the rays of each character are drawn to represent only the rays from the center of each character that passes through the projection lens. In order to focus all the characters from the plate onto the optical axis at the image plane rather than in the spatial orientation shown, the glass plate 16 is placed between the projection lens and the image plane. The light rays from the characters on the plate then pass through the projection lens and are immediately intercepted by the plate 16. Each of the characters is reflected between the surface of plate 16, through a light path equivalent in length to the original light path from the projection lens to the image plane plus a correction for the index of refraction as the light enters the glass plate. That is the length of the light path within the sheet is determined by takingthe light path from the projection lens to the image plane in air and multiplying it by the index of refraction of the glass. This added length compensates for the changing of the angle of the light path as it enters the glass sheet and thus the angle at which the light rays intercept the surfaces of the glass sheet during reflection toward the image plane.

The spacing or separation of the reflective surfaces is equal to the vertical center to center distance between the characters in the projected image plane. The number of reflections of each character between the surfaces is dependent upon its position above or below the optical axis. It should benoted that the centrally located character in the column does not experience any reflection between the surfaces while each successive character above and below experienced reflections in number equal to their numerical position from tthe central character. Therefore, in order to have the characters all appear upright at the photosensitive surface their orientation in the vertical sense must be alternated on the character plate as shown in FIG. 3. The embodiment of the invention shown in FIG. 2 reduces the overall size of the printer by reducing the size of the light conveying element or glass plate 16.

The glass plat eprlight conveying element 16 is conso that the light rays are uniformly reflected regardless of the direction in which they are traveling. The light rays intercept the top and bottom surfaces of the element 16 at an angle less than the critical angle and are refiected internally along the paths shown in dotted lines in FIGS. 2, 5 and 6. The plate 16 is shaped so that the light rays as illustrated by the dotted lines in FIG. 2 pass through a tortuous path within the glass plate so that thelength of the light path from the lens 18 to the xerographic drum 10 is equal in length to the light path through a straightlight conducting element such as that shown in FIG. 1. The light rays passing through len sglfi are intercepted by edge 40 of the glass block and die refiected between the parallel top and bottom surfaces of the glass block to the point where they intercept the opposite edge 42. The edge surface 42 is silvered to reflect the light rays back into the glass block along the path illustrated by the dotted lines to a third edge surface 44 which is also silvered to reflect the light rays towards the xerographic drum 10. The light rays then continue to be reflected between the parallel surfaces of the glass plate until they intercept the edge 46 which is clear rather than silvered, and'whereat the light rays leave the glass plate and expose the photosensitive surface of the drum. As pointed out above the total length of the light path, as indicated by the doted lines, is equivalent to the length of light path in a straight light conducting element as shown in FIG. 1. The angle of edge surfaces 42 and 44 are constructed to reflect the light rays along the path desired to ultimately reach the xerographic drum.

The plate 16 .is a relatively thin plate and when extended longitudinally as illustrated in FIG. 1 the length of the plate is large and space consuming. The length to thickness ratio is particularly large in the straight longitudinal plate and creates problems in obtaining the re quired degree of flatness on the exterior surfaces. By folding the optical system as shown in FIG. 2 the overall size of the glass plate 16 is considerably reduced and the size of the length to thickness ratio is also reduced. Thus there is a savings in construction of the element itself and in the overall size and construction of the printer.

Two alternative embodiments are shown in FIGURES I 5 and 6 wherein the light conducting element 16 has silvered edges at 48 and 50 in FIG. 5 and at 52 in FIG. 6.

In operation, a plate of the type shown in FIG; 3, containing a font of characters, arranged in vertical columns containing each of the characters to he used in the printing process and horizontal rows of identical characters, is placed on the face of the cathods ray tube or adjacent to the tube with a relay lens interposed between the tube and the plate. A signalis received from a remote source,

such as a communications transmiter or a computer output and, through the input logic 20, is used to control the orientation of. the light spot of the cathode ray tube. lf :1 character is to be printed in a given position then the spot of the cathode ray tube illuminates a character in the corresponding column on the plate in response to the input signal. The light passing through the plate is focused by the projection lens and intercepted by the transmitting element 16 and internally reflected to the photosensitive surface 10. After the photosensitive surface has been exposed to a full line of print the drum is stepped by one line and the spot in the cathode ray tube'again starts to scan the character plate for the printing of the next line.

While the invention has been describedwith reference to the structure disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claim.

I claim:

In an optical system for a communication printer of the type wherein a photosensitive drum surface is exposed in a line by line sequence to light images from a matrix of transparent characters which are selectively illuminated and placed along a predetermined axis on the drum surface, the optical system including:

a lens positioned to receive light rays of selected illuminated characters and being capable of imaging the received light rays in a plane perpendicular and tangent to the predetermined axis on the photosensitive drum,

an optical element having two parallel surfaces joined by a plurality of spaces, each space being perpendicular to the parallel surfaces such that the faces cut the individual planes described by each of the parallel surfaces into irregular polygons having at least four sides,

said optical element having a light my entry face in juxtaposition to said lens, said entry face being. perpendicular to the geometrical center line of said lens, the parallel surfaces being positioned so they are equidistant from the geometrical center line of said lens such that the imaging light rays directed from said lens are reflected therebetwccn for off axis characters,

said optical element having an exist face angularly disposed from said entry face, the exist face being in a plane parallel to the image plane and positioned adjacent said drum along the predetermined axis thereon, and at. least two other reflecting spaces arranged to redirect the imaging light rays entering said element at the entry face towards the exit face.

References Cited UNITED STATES PATENTS 2,388,961 11/1945 Elliott -45 2,682,194 6/1954 Roscnburgh 88-24 2,725,786 12/1955 McCarthy 954.5 X I 2,887,935 5/1959 Scot 95-4.5 2,946,268 7/1960 Moyroud 9.5-4.5 2,979,026 4/1961 Reuter 88-24 3,006,259 10/1961 Blakely 95--4.5

JOHN M. HORAN, Primary Exar'nincr.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,330 ,190 July 11 1967 Gordon P. Taillie It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6, line 12, for "spaces, each space" read faces, each face Signed and sealed this 22nd day of April 1969.

(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

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