US3023731A - Electrostatic alphanumerical printer with image transfer mechanism - Google Patents

Description

March 6, 1962 F. A. scHWERTZ 3,023,731

ELECTROSTATIC ALPHANUMERICAL PRINTER WITH IMAGE TRANSFER MECHANISM Filed June 6. 1957 2 Sheets-Sheet 1 I N VEN TOR. @me-,Wag A. Sci/M5972.

Sunny @oase March 6, 1962 F A. scHwl-:RTZ

ELECTROSTATIC ALPHANUMERICAL PRINTER WITH IMAGE TRANSFER MECHANISM 2 Sheets-Sheet 2 Filed June 6. 1957 .Lv -F.Lll E @2 z V .M V .U LI an; mw ..n 33 A mw l M m Q y QQQM. IW' 7 United States Patent() 3,023,731 ELECTROSTATIC ALPHANUMERICAL PRINTER WITH IMAGE TRANSFER MECHANISM Frederick A. Schwertz, Pittsford, N.Y., assigner to The Haloid Company, Rochester, N.Y., a corporation of New York n Filed June 6, 1957,Ser. No.'664,138 17 Claims. (Cl. V11S-'625) The present invention relates generally to high-speed recording of computational data'and more particularly to apparatus adapted jto record alphanumerical information electrostatically as "latent images on a continuous insulating medium, which images are thereafter developed and transferred to `an ordinary printing paper.

The written or pr'rnted 'values yielded by the output system of'an electronic computer may assume any one of several forms depending on 'the nature of the data and its eventual use. With vthe recent development of highspeed computer machines and other mechanical and electronic devices which produce data at high rates of speed, there has arisen a concomitant need for high-speed recording devices, for otherwise the printer or other recording mechanism may act to retard the operation of'the entire machine. Where vthe production rate of output data exceeds the 'capacity of the output printer, the usual practice is to store the output information as rapidly as it is produced and to feed it from storage to the printer as rapidly as the printer will accept 'thein'formation In the copending applications entitled Electrostatic Recording of Information, Ser. No. 623,327, filed November 20, 1956 (now abandoned), and High-Speed Electrostatic Alphanumerical Printer, Ser. No. 664,137, tiled June 6, 1957 (now issued as Patent No. 2,919,967), there is described a novel electrostatic image-forming technique for recording alphanumerical information, which technique overcomes many of the drawbacks characteristic of known mechanical and optical printers.

The electrostatic image-forming process as disclosed in said copending applications makes possible the transfer of electrostatic images to a recording medium at eX- tremely high speeds, these images being subsequently rendered visual by methods conventional in the Xerographic art. Digital computer switching circuits co-acting with the electrostatic image-forming apparatus permit the logical spacial ordering of electrostatic images which owe their origin to information pulses received serially in time.

In the art of Xerography in its electrophotographic aspects, an electrostatic charge applied to the surface of a photoconductive insulating layer is selectively dissipated by exposure to a pattern of light and shadow to be recorded, thereby forming on the surface of the insulating layer an electrostatic latent image corresponding to said pattern. An image formed in this fashion may be developed by the deposition of finely divided material in conformity with the charge pattern and thereafter fixed by fusing the powder on the surface of a print to which the powder pattern has been transferred. A detailed description of the Xerographic technique and of the apparatus involved in developing and fixing pictures may be found in the U.S. Patent to Carlson No. 2,297,691.

In the apparatus disclosed in the copending applications as distinguished from Xerography in its electrophotographic aspects, physical symbols or characters rather than light patterns are recorded as electrostatic images. The images are then developed by depositing a finely divided powder or an ink mist, the resulting visible images being made permanent by fusing or drying. The electrostatic images are produced by character faces or symbolshaped electrode elements which are brought in close Mice proximity to an yinsulating surface, Vsuch as a web of dielectric material. The web is electrostically pre'charged by an intense electric field to 'a point somewhat below critical stress value. Alternatively a static bias voltage may be 'applied to bring 'the applied feldto the point of incipient breakdown.

Transfer of the configuration of the symbol or character from the Vshaped electrode to the insulating web is effected by the use of a relatively low potential triggering pulse which raises the electric field above the critical stress value toiproduce a field discharge in the Vspace between the insulating web and the electrode. The discharge action gives rise to the formation of an electrostatic pattern of the symbol on the insulating surface. Electronic switching circuits'are associated with the electrostatic apparatus to supply trigger pulses thereto in accordance with information received electrically from a digital vcomputer or other signal source. This process is now known as Tesiprinting (Transfer Electro Static Image).

In the copending applications, alphanumerical characters are formed with the aid of raised character-metal elements disposed about the circumference of a cylindrical drum, one column of characters being provided for each column of the printed page. The characters are caused to pass in the vicinity of a paper web by rotating the character drum at a constant angular velocity. Disposed above the paper is an array of electrodes, one for each column tobeprinted. When the selected character passesv beneath a chosen electrode, a high-voltage pulse is applied to effect a field discharge between the selected character and the web at a position corresponding to that of the chosen electrode. y

The field discharge causes the formations of latent electrostatic images on the paper web passing over the character drum. When the web is withdrawn from the electrostatic apparatus, it passes through a development mechanism wherein the invisible electrostatic images are rendered visible by depositing thereon `a finely divided powder which adheres to the charged image areas. To

romote development, the particles are preferably charged by triboelectric or other means. Thereafter the powder images are fused onto the paper to form a permanent print of the information recorded.

Thus in the electrostatic printing devices of the type described in the above-identified copending applications, the paper web must possess characteristics rendering it suitable for supporting an electrostatic image as well as providing a printing surface for a powder image. This requires the use of a carefully dried paper or a paper specially treated to afford a recording surface of high resistivity to sustain an electrostatic charge. This requirement precludes the use of ordinary paper and adds materially to the cost of the operation.

In view of the foregoing it is the principal object of the present invention to provide a non-optical electrostatic printer for recording alphanumerical information wherein the information may be printed on inexpensive paper of ordinary quality. Y

More particularly, it is an object of this invention to provide a high-speed electrostatic printer wherein electrostatic images may be formed on a continuous flexible web of insulating material, which images are then transferred to ordinary paper. A significant feature of the invention is the fact that the continuous web may be reused indefinitely, the image thereon being erased after transfer is effected.

Also, an object of the invention is to provide a character drum for an electrostatic printer, which drum is constituted by a bank of character Vrings insulated from each other, whereby the rings may be separately pulsed. In accordance with an important feature of the invention,

each character ring on the drum is associated with a commutator ring cooperaitng with an electrode spaced therefrom. A field discharge is produced between the character ring and an associated endless metal belt having an insulating layer thereon, the lines of stress extending through a gap between the electrode and the commutator ring.

Also an object of the invention is to provide an electrostatic printer wherein alphanumerical images are simulated by selective activation of an array of electrode pins carried on stationary matrix type recording heads.

Briefly stated, in an electrostatic apparatus for recording and printing alphanumerical information in accordance with the invention, the information received from a computer or other data source is recorded electrostatically on an endless medium having an insulating surface of high resistivity for sustaining electrostatic charges. This endless medium may be constituted by a continuous belt of insulating material or a continuous metal belt having an insulating layer thereon. Alternatively, the endless medium may take the form of a rotary metallic cylinder having an insulating layer coated thereon.

A character-forming station is supported in spaced relation to the insulating surface of the recording medium to define an air gap therebetween. The character station includes character-forming elements adapted to produce latent electrostatic images on said medium when voltages are applied thereto effecting a field discharge in the air gap. The station may be constituted by a rotary drum containing rings of raised-character elements which may be selectively aligned with the medium. Alternatively, the character-forming elements may be constituted by an array of pins which may be selectively actuated by pulses to build up the character by a pattern of dots.

The medium is moved relative to the character station to produce successive lines of characters thereon. A charging station is disposed in advance of the character station to pre-stress the medium to a uniform potential and thereby erase previously made electrostatic latent images. The medium after recording passes through a developer section to form powder images. 'Ihe powder images are transferred by electrostatic attraction to a paper strip and the powder images thereon are fused to provide a permanent print.

For a better understanding of the invention, as well as further objects and features thereof, reference is made to the following detailed description to be read in connection with the accompanying drawing, wherein like components in the several views are identified by like reference numerals.

In the drawing:

FIG. 1 shows schematically a perspective view of one preferred embodiment of an alphanumerical printer in accordance with the invention;

FIG. 2 shows schematically a perspective view of a second preferred embodiment of an electrostatic printer in accordance with the invention;

FIG. 3 is a separate elevational view of the character drum shown in FIG. 2;

FIG. 4 is a schematic diagram of a third embodiment of the invention;

lFlG. 5 is a detail of FIG. v4;

FIG. 6 is a further embodiment of the invention, shown schematically; and

FIG. 7 is a detail of FIG. 6.

`Referring now to FIG. l, the electrostatic printer comprises an endless web 10 supported between a pair of spaced rollers 11 and 12. Web 10 is composed of a flexible material of high resistivity such as Mylar or Teflon, the material being capable of holding an electrostatic image for a period which permits subsequent utili- Zation thereof by transfer to another surface.

Supported above the upper portion of the web at a position substantially transverse thereto is a character drum, generally designated by numeral 13. Drum 1? is rotatably mounted and driven at a constant angular velocity by a suitable motor. Arranged across the drum is a bank of identical character rings 14, each containing a circumferential assembly of raised-character metallic elements 15. One ring of characters is provided for each column to be printed. The characters in each ring thereof are composed of alphabetical letters, numbers and other symbols, each representative of a different value of the applied information. The drum may be exactly normal to the continuous web, or slightly askew. This factor will be discussed later in the specification. "Ihe character rings are slightly spaced from the web to define an air gap in which a field discharge may occur to effect an image transfer.

Supported below the web in alignment with the drum is an array of stationary electrodes 16, one for each ring in the character drum, the electrodes occupying corresponding positions. By means of an electrode pulsing supply repersented by block 17, the electrodes are sequentially activated such that only one electrode is active at a time to permit electrostatic recording at a corresponding position on the web. In operation, when a character on the ring representative of the input information is angularly aligned with the activated electrode a field discharge is produced to form a charge pattern on the web having the shape of the selected character.

The manner by which the characters are selected and the electrodes are activated is treated in greater detail in said copending application. A disc 18 is attached to one end of the drum, the disc containing magnetic indexing marks 19 in a circumferential arrangement at positions corresponding to the character positions on the rings. As disclosed in said applications, these marks are sensed by a magnetic head (not shown) to produce voltage impulses at time positions reflecting the angular positions of the characters on the rings. A magnetic mark on the other end of the drum cooperating with another pick-up head serves to indicate a full revolution of the drum.

In the electronic control system for the character drum described in the copending application Electrostatic Recording of Information, the logical circuitry requires a synchronous serial input at the specified printing rate, whereas in the system described in the copending application High Speed Electrostatic Alphanumerical Printer, information may be printed as received on a random basis, the operation being asynchronous. Either circuit may be used in conjunction with the character drum in the present invention. By increasing the cornplexity of the logical circuitry and providing a buffer storage system, the printer can be made to record a line for every revolution of the character drum rather than one digit or letter per revolution.

The direction of motion is counter-clockwise whereby the continuous web is iirst subjected to a pre-stressing potential before it arrives at the character drum for recording. This is accomplished by means of a corona charging station 20 positioned in advance of the character drum which pre-stresses the web to a uniform potential below the critical stress value, such that a relatively small pulse at the recording station 13 is sufficient to produce a field discharge effecting image transfer. The corona charging station 2i) also acts to equalize the charged on the web, thereby erasing all previously recorded charges in preparation for the next recording cycle.

The web leaving the character drum and carrying the electrostatic charge pattern enters a development section 2.1 of standard design in which powder is Howed over the latent electrostatic images, the powder adhering only to the charged areas. The powder is caused to fall on the image layer as it turns about roller 12 and to move downwardly thereover by gravity in a continuous stream, the powder being evenly distributed over the image. The operation and structure of the developer section is more fully disclosed in the patent to Schaffert No. 2,576,047, issued November 20, 1951.

t The resultant powder images formed on the web are transferred to a paper strip 22 which is fed from a suitable supply roll 23, the strip travelling lover a transfer roller 24 and being rewound on a take-up roller 25. The characters must be put on the web wrong reading and from right to left so that they are right reading and left to right on the final paper support.

The transfer roller 24 is supported transversely with respect tothe lower portion of the web intermediate the web rollers 11 and 12 and acts to carry the paper strip into momentary contact with the web; the web and strip moving in like directions at the same speed. The supply roller 23 and take-up roller 25 are mounted below the web rollers l1 and 12, all of the rollers being supported in suitable bearings on a frame. Thus the only point of contact between the paper strip 2-2- and the web 1i) is at the position of the transfer roller.

The transfer roller 24, which may be made of conductive rubber material, is connected to a voltage source 26 which functions to impress a charge across the region of the paper strip 22, engaging web 10. The magnitude of the charge applied to the paper strip and the polarity thereof is such as to overcome the adhesion of the powder particles to the image area on the web and to establish a greater tendency of the particles to adhere to the paper, thereby effecting a transfer o-f the powder image -to the paper strip. The charge applied to the paper strip by the transfer roller is of opposite polarity to the charge on the developer powder, the powder therefore being attracted to and retained by the paper strip.

The powder image transferred to the paper strip is fused thereon by heating elements 27 of any suitable construction disposed in operative relation to the strip between the transfer roller 24 and the take-up roller 25.

To remove residual powder from the web 10 after the transfer operation is completed and before it again enters the charging station for the next recording, a rotary brush 2S is provided which engages the web against its roller 11. The brush acts to remove any powder adhering to the insulating web which has not been previously transferred to the paper strip, thus preparing the web for a fresh supply of powder. The cleaning means may consist of any sui-table wiping or suction device and is preferably of the type disclosed in the patent to Turner et al. No. 2,751,616, issued Iune 26, 1956. After the web has been cleaned of residual toner the charging station 2t) acts uniformly to charge the web 191 to a pre-selected potential by means of corona wires.

In the event'the recording operation is carried out while the web is moving continuously, it is then necessary slightly to skew the character drum 13 relative to the web to compensate for the web motion and thereby insure that the courseof the printed line runs perpendicularly to the edges of the web. Alternatively, the rings on the drum may be staggered relative to each other for the same purpose, in which case the ydrum need not be skewed. But if the web is held stationary during the recording of a line, then the character drum may be supported directly across the web without skewing. In this case, the body of the web and the transfer strip are advanced in a stepwise manner a line at a time by a suitable indexing mechanism actuated upon completion of each line. A common drive maybe provided for said web and said strip to maintain synchronous movement thereof.

Referring now to'FIGS. 2 and 3, there is illustrated another embodiment of the invention which is identical to that -shovvn in FIG. l, save for the structure of the recording web, lthe `character drum and the related electrodes. The web supported between rollers l1 and 12 is constituted -by an endless metal belt 30 having a thin insulating layer 36a of high surface resistivity coated thereon. The metal belt is grounded through the supporting rollers l11 and 12 therefor. Rotatably supported above the upper section of web 30 is a character drum 31 havinga series of character rings 32 thereon similar Y one another.

in nature to the rings on the drum shown in FIG. 1. The rings are, however, electrically insulated from each other by insulating discs 33. Adjacent each ring and electrically connected thereto is a commutator ring 34. Fixedly mounted above the drum is an array of electrodes 35, each electrode being disposed in spaced relation to a respective commutator ring.

The arrangement is such that each character ring may be pulsed separately, as distinguished from. the previously disclosed arrangement in which all of the character rings were electrically interconnected. The character rings on the drum, as best seen in FIG. 3, are in spaced relation to the web layer Sdu, to define a rst air gap 36, andthe electrodes 35 occupy spaced positions relative to the cornmutator rings 34 to define a second air gap 37, The character drum is supported on bearings insulated from the ground.

Thus when a pulse is applied to an electrode 35 relative to ground, a corona discharge will proceed across both air gaps, the gap between the pulsing electrodes and the drum serving as a commutator connection, while the gap between the drum and the web functions as an electrostatic image transfer region. The electronic control circuit responsive to the input information to be recorded acts to apply the pulses to theelectrodes when the selected characters are angularly aligned with the endless dielectriccoated metal belt.

The operation of the printer illustrated in FIGS. 2` and 3 is otherwise identical with that shown in FIG. l. The web is rst pre-stressed at the corona station and after the electrostatic image is recorded it is developed to form a powder image, which image is transferred to a paper strip and fixed thereon. As indicated earlier, it is possible to print a full line in a single rotation of the character drum providing a buffer storage system is employed to handle a line-at-a-time of information.

If the web is permitted to move continuously during the recording interval it will move a short distance forward. Since the character images will be formed randomly along the line during this period, the characters will go down in positions slightly staggered with respect to For example, if the character drum is rotating at a frequency of 200 revolutions per second and the web is travelling, say, at a rate of 3 inches per second, the paper will advance 0.0Il5 inch. This then is the maximum 'displacement distance between adjacent characters. For characters 0.1 inch high, that is roughly of typewriter size, such a displacement would probably be noticeable and therefore objectionable. This can be obviated by moving the web intermittently in the manner indicated previously, such that the web is stationary when recording takes place.

It is also possible, as shown in FIG. 4, to use a matrix or a point array type of character presentation which may be selectively pulsed in such a'way as to simulate any alphanumerical character, thus eliminating the need for a moving character drum.

In FIG. 4, in place of the endless web, a rotary metal cylinder 38 is employed which is coated with a layer 39 of material having a high resistivity for holding an electrostatic image. The cylinder moves in a counterclockwise direction and is'pre-stressed at the corona station 20. A stationary character printing station 40 is provided constituted by a bank of recording heads 41 having electrode points or pins 42 which can beselectively pulsed to provide a matrix type of presentation simulating an alphanumerical character. One head is provided at each column position. As shown in the drawing, the characters are each formed by a pattern of dots.

Each recording head 41 consists of a set of five flat faced pins 42 in a row maintained at a fixed distance from the surface of the cylinder layer 39, the pins of the several heads running across the cylinder. The individual characters are built up by seven successive choices of the five aoaavsr pins as the cylinder moves forward. An electronic pulsing circuit is provided for each pin. Thus as the cylinder rotates, the pins in the heads are selectively activated by input information in seven successive steps to construct latent images of the appropriate characters on the cylinder surface.

A magnetic matrix and decoding unit may be used to buffer the pulsing circuits to the pins and the information source. A description of a unit adaptable for this purpose as well as an electronic pulsing circuit for the pins may be found in the article Burroughs Electrographic Printing Technique by Herman Epstein, March 1955- Proceedings of the Western Joint Computer Conference (AIRE-IRE).

The latent images impressed electrostatically on the cylinder are developed at the development section 21, and the resultant powder image is transferred to a paper strip 22 in the manner described hereinabove. After the transfer operation, the cylinder is cleaned of residual toner by the rotary brush 2S, and the surface is pre-stressed in preparation for the next recording.

In FIGS. 4 and 5, the characters are built up of a point array in seven successive. steps as the cylinder advances relative to the single row of pins. Alternatively, each recording head 43, as shown in FIGS. 6 and 7, may consist of seven rows of pins 44, five in each row. This makes possible the formation of the character matrix in one step but involves a more complex pulsing and decoding circuit. It is necessary to use seven coordinated decoding units whereby all seven rows of pins may be selectively pulsed at the same time to form the desired alphanumerical character.

While there have been shown what are at present considered to be preferred embodiments of the invention, it will be obvious that many changes and modifications may be made therein without departing from the essential aspects of the invention. It is intended, therefore, in the appended claims to cover all such changes as fall within the true spirit of the invention.

What is claimed is:

1. An electrostatic apparatus for recording and printing alphanumerical information at high speed, said apparatus comprising a movable endless recording medium having an insulating surface of high resistivity for sustaining electrostatic charges, a character-forming station supported in spaced relation to said insulating surface to define an air gap therebetween and including character-forming conductive elements adapted to produce latent electrostatic images on said medium when voltages are applied thereto having an amplitude raising the electric field across said air gap above the critical stress value and thereby effecting a field discharge in said air gap, means operatively disposed with respect to said medium beyond said station to form powder images of said latent images, and means operatively coupled to said medium to transfer said powder images onto a printing surface by electrostatic attraction.

2. An electrostatic apparatus for recording and printing alphanumerical information at high speed, said apparatus comprising an endless recording medium having an insulating surface of high resistivity for sustaining electrostatic charges, a character-forming station supported in spaced relation to said insulating surface to define an air gap therebetween and including characterforming conductive elements adapted to produce latent electrostatic images on said medium when voltages are applied thereto having an amplitude raising the electric eld across said air gap above the critical stress value and thereby effecting a field discharge in said air gap, means to move said medium relative to said characterforming station to form successive lines of latent images thereon, charging means operatively disposed with respect to said medium in advance of said station to prestress same to a uniform potential and thereby erase previous charges, developer means operatively disposed with respect to said medium beyond said station to form powder images of said latent images, and means operatively coupled to said medium to transfer said powder images onto a paper strip by electrostatic attraction.

3. An electrostatic apparatus for recording and printing alphanumerical information at high speed, said apparatus comprising an endless recording medium having an insulating surface of high resistivity for sustaining electrostatic charges, a character-forming station supported in spaced relation to said insulating surface to define an air gap therebetween and including characterforming conductive elements adapted to produce latent electrostatic images on said medium when voltages are applied thereto having an amplitude raising the electric field across said air gap above the critical stress value and thereby effecting a field discharge in said air gap, means to move said medium relative to said characterforming station to form successive lines, charging means operatively disposed with respect to said medium in advance of said station to pre-stress same to a uniform potential and thereby erase previous charges, developer means operatively disposed with respect to said medium beyond said station to form powder images of said latent images, and means operatively coupled to said medium to transfer said powder images onto a paper strip by electrostatic attraction, said last named means including a paper strip movable in synchronism with said medium, a transfer roller for effecting engagement between said strip and said medium, and means to apply a potential to said transfer roller to attract said powder image to said strip.

4. A high-speed apparatus for recording and printing alphanumerical information, said apparatus comprising a continuous belt of insulating material, a rotary character drum having a bank of like character rings thereon, each ring containing a series of character-shaped raised conductive elements in a circumferential arrangement, the respective characters in the series being representative of different values of incoming information, said drum being disposed across said belt and in spaced relation thereabove to define an air gap, an array of fixed electrodes disposed below said belt at positions corresponding to those of said rings, means responsive to the value of incoming information to apply a voltage pulse between one of said electrodes and said rings when the characters thereon representative of said value are in angular alignment with said belt, said pulse having an amplitude raising the electric eld across said air gap above the critical stress value to effect a field discharge in said gap and thereby forming an electrostatic latent image of the selected character on said belt at a position in accordance with said electrode, means to move said belt relative to said drum to form successive lines of characters thereon, charging means operatively disposed relative to said belt in advance of said drum to prestress said belt to a uniform potential, a developer section operatively disposed relative to said belt at a position beyond said station to form powder images of said latent images, and means operatively coupled to said belt to transfer said powder images onto a paper strip by electrostatic attraction.

5. A high-speed apparatus for recording and printing alphanumerical information, said apparatus comprising a continuous belt of insulating material of high resistivity for sustaining electrostatic charges, a rotary character drum supported substantially transversely relative to the outer surface of said belt and having a bank of like character rings thereon, each ring containing a series of character-shaped raised conductive elements in a circumferential arrangement, the respective characters in the series being representative of different values of incoming information, said drum being disposed in spaced relation to said belt to define an air gap, an array of fixed electrodes disposed transversely relative to the under surface of said belt at positions corresponding to those of said rings, means responsive to the value of incoming information to apply a voltage pulse between one of said electrodes and said rings when the characters thereon representative of said value are in angular alignment with said belt, said pulse having an amplitude raising the electric field across said air gap above ythe critical stress value to effect a field discharge in said gap and thereby `forming an electrostatic latent image of the selected characters on said belt at a position in accordance with said electrode, means to move said belt relative to said drum to form successive lines of characters thereon, charging means operatively disposed relative to said belt in advance of said drum to pre-stress said belt to a uniform potential, a developer section operatively disposed relative to said belt at a position beyond said station to form powder images of said latent images, and means operatively coupled to said belt to transfer said powder images onto a paper strip by electrostatic attraction.

6. A high-speed apparatus for recording and printing alphanumerical information, said apparatus comprising a continuous belt of insulating material of high resistivity for sustaining electrostatic charges, a rotary character drum supported substantially transversely relative to the outer surface of said belt and having a bank of like character rings thereon, each ring containing a series of character-shaped raised conductive elements in a circumferential arrangement, the respective characters in the series being representative of different values of incoming information, said drum being disposed in spaced relation to said belt to deline an air gap, an array of fixed electrodes disposed transversely relative to the under surface of said belt at positions corresponding to those of said rings, means responsive to the value of incoming information to apply a voltage pulse between one of said electrodes and said rings when the characters thereon representative of said value are in angular alignment with said belt, said pulse Having an amplitude raising the electric ield across said air gap above the critical stress value to effect a eld discharge in said gap and thereby `forming an electrostatic latent image of the selected characters on said belt at a position in accordance with said electrode, means to move said belt relative to said drum to form successive lines of characters thereon, charging means operatively disposed relative to said belt in advance of said drum to pre-stress said belt to a uniform potential, a developer section operatively disposed relative to said belt at a position beyond said station to form powder images of said latent images, means operatively coupled to said belt to transfer said powder images onto a paper strip by electrostatic attraction, said last-named means including a paper strip movable in synchronism with said belt, a transfer roller for eecting engagement between said strip and said belt, and means to apply a potential to said transfer roller attracting said powder image to said strip.

7. Apparatus, as set forth in claim 6, further including means to fuse said powder image onto said strip.

8. A high-speed apparatus for recording alphanumerical information, said apparatus comprising a continuous metal belt having an outer layer of insulating material thereon for sustaining electrostatic charges, a rotary character drum supported substantially transversely relative to said belt in spaced relation thereto to dene an electrostatic air gap, said drum having a bank of like character rings thereon insulated from each other and a bank of commutator rings each adjacent to and in electrical contact with a respective character ring, each ring containing a series of character-shaped conductive elcments in a circumferential arrangement, the respective characters in the series being representative of different values of incoming information, an array of Xed electrodes aligned with said commutator rings and spaced therefrom to form a commutating air gap, and means responsive to the value of incoming information to apply a voltage pulse to a selected electrode relative to said metal belt when the characters on said drum representative of said value are in angular alignment with said belt, said pulse having a magnitude raising the electric eld above the critical stress value and effecting a eld discharge between said characters and said insulating layer to form an electrostatic latent image thereon.

9. A high-speed apparatus for recording and printing alphanumerical information, said apparatus comprising a continuous metal belt having an outer layer of insulating material thereon for sustaining electrostatic charges, a rotary character drum supported substantially transversely relative to said belt in spaced relation thereto to dene an electrostatic air gap, said drum having a bank of like character rings thereon insulated from each other and a bank of commutator rings each adjacent to and in electrical contact with a respective character ring, each ring containing a series of character-shaped conductive elements in a circumferential arrangement, the respective characters in the series being representative of different values of incoming information, an array of xed electrodes aligned with said commutator rings and spaced therefrom to form a commutating air gap, means responsive to the value of incoming information to apply a voltage pulse to a selected electrode relative to said metal belt when the characters on said drum representative of said value are in angular alignment with said belt, said pulse having a magnitude raising the electric eld above the critical stress value and effecting a eld discharge between said characters and said insulating layer to form an electrostatic latent image thereon, and means to form a powder image of said latent image and to transfer same to a paper strip.

l0. High-speed apparatus for recording and printing alphanumerical information comprising a rotary metal cylinder having a dielectric layer coated thereon for sustaining electrostatic charges, a character recording station including a bank of stationary character heads extending across said cylinder, each head including a row of conductive point electrodes disposed in spaced relation to said dielectric layer to deine an air gap, means to rotate said cylinder relative to said recording station, means selectively to pulse said point electrodes during movement of said cylinder in accordance with the value of applied information to be recorded, said pulse having an amplitude raising the electric field across said air gap above the critical stress value to eifect a field discharge across the gap thereby to form an electrostatic point charge pattern on said layer simulating a character representative of said value, developer means to form powder images of said charge patterns, means to transfer said powder images to a paper strip by electrostatic attraction, and prestressing means Ato return said layer at a uniform potential after said transfer operation.

ll. High-speed apparatus for recording and printing alphanumerical information comprising a rotary metal cylinder having a dielectric layer coated thereon for sustaining electrostatic charges, a character recording station including a bank of stationary character heads extending across said cylinder, each head including a row of conductive point electrodes disposed in spaced relation to said dielectric layer to dene an air gap, means to rotate said cylinder relative to said recording station, means selectively to pulse said point electrodes during movement of said cylinder in accordance with the value of applied information to be recorded, said pulse having an amplitude raising the electric eld across said air gap above the critical stress value to effect a eld discharge across the gap thereby to form an electrostatic point charge pattern on said layer simulating a character representative of said value, developer means operatively disposed relative to said cylinder beyond said station to form powder images of said charge patterns, means including a charged transfer roller to transfer said powder images to a paper strip by electrostatic attraction, prestressing means in advance of said station to return said layer at a uniform potential after said transfer operation, and rotary brush means in advance of said pre-stressing means to clean said cylinder of residual powder.

12. High-speed apparatus `for recording and printing alphanumerical information comprising a rotary metal cylinder having a dielectric layer coated thereon for sustaining electrostatic charges, a character recording station including a bank of stationary character heads eX- tending across said cylinder, each head including a rectangular array of conductive point electrodes in spaced relation to said dielectric layer to define an air gap, said array being formed by parallel rows of pins, means to rotate said cylinder relative to said recording station, means selectively to pulse said pins in accordance with the value of applied information to be recorded, said pulse having an amplitude raising the electric field across said air gap above the critical stress value to effect a field discharge across the gap thereby to form an electrostatic point charge pattern on said layer simulating a character representative of said value, developer means to form a powder image of said charge pattern, means to transfer said powder images by electrostatic attrac tion to a paper strip, and means to erase said charge pattern before said cylinder reaches said station.

13. An electrostatic apparatus for recording and printing alphanumerical information at high speed, said apparatus comprising a movable endless recording medium having an insulating surface of high resistivity for sustaining electrostatic charges, a character forming station including a set of conductive character forming elements supported relative to one side of said surface, a set of conductive backing elements supported relative to the other side of said surface, one of said sets being spaced from said surface to form an air gap therebetween, electrostatic images of said character forming elements being produced on said surface when voltages are applied to said character forming elements relative to said backing elements effecting a field discharge in said air gap, means operatively disposed with respect to said medium beyond said station to form powder images of said latent images, and means operatively coupled to said medium to transfer said powder images onto a printing surface by electrostatic attraction.

14. An electrostatic apparatus for recording and printinc' alphanumerical information at high speed, said apparatus comprising a movable endless recording medium having an insulating surface of high resistivity for sustaining electrostatic charges, a character forming station including a set of conductive character forming elements supported relative to one side of said surface, a set of conductive backing elements supported relative to the other side of said surface, one of said sets being spaced from said surface to form an air gap therebetween, electrostatic images of said character forming elements being produced on said surface when voltages are applied to said character forming elements relative to said backing elements effecting a field discharge in said air gap, means operatively disposed with respect to said medium beyond said station to form powder images of said latent images, and means operatively coupled to said medium to transfer said powder images onto a printing surface by electrostatic attraction, said printing surface being formed of a material having a resistivity which is low relative to that of said recording medium.

15. An electrostatic apparatus, as set forth in claim 14, wherein said recording medium has a surface formed by a flexible plastic and said printing surface is formed of paper.

16. An electrostatic apparatus, as set forth in claim 14, wherein said recording medium is formed of a coated paper, which coating imparts high resistivity thereto, and said printing surface is formed of uncoated paper.

17. An electrostatic apparatus for recording and printing alphanumerical information at high speed, said apparatus comprising a movable endless recording medium having an insulating surface of high resistivity for sustaining electrostatic charges, a character forming station including a conductive character forming element supported relative to one side of said surface, a conductive backing element supported relative to the other side of said surface, one of said elements being spaced from said surface to form an air gap therebetween, electrostatic images of said character forming element being produced on said surface when a voltage is applied thereto relative to said backing element effecting a field discharge in said air gap, means operatively disposed with respect to said medium beyond said station to form powder images of said latent images, and means operatively coupled to said medium to transfer said powder images onto a printing surface by electrostatic attraction.

References Cited in the file of this patent UNITED STATES PATENTS 1,865,610 Blair July 5, 1932 2,715,360 Brown Aug. 16, 1955 2,726,940 Buhler Dec. 13, 1955 2,777,745 McNaney Jan. 15, 1957 2,825,814 Walkup Mar. 4, 1958 FOREIGN PATENTS 1,112,180 France Nov. 9, 1955 734,909 Great Britain W Aug. 10, 1955 OTHER REFERENCES General Electric Review, July '1952, pp. 20, 2l, 22 and 61.

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