US3146100A - Electronic photocopying apparatus and method - Google Patents

Description

Aug. 25, 1964 A. L. KAUFMAN ELECTRONIC PHOTOCOPYING APPARATUS AND METHOD Filed Jan, 26, 1960 I NV EN TOR.

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United States Patent O ce 3,146,100 ELECTRONIC PHOTOCOPYING APPARATUS AND METHOD Arthur L. Kaufman, Westport, Conn., assigner to Bohn Business Machines, Inc., a corporation of New York Filed Jan. 26, 1960, Ser. No. 4,737 3 Claims. (Cl. 96-1) This invention pertains to methods and apparatus for rapidly reproducing duplicates of letters, printed or typed sheets, or sheets having thereon a pattern of any character forming areas of differing light reflectivity.

According to a feature of the invention, reproduction in accordance therewith is effected in a matter of seconds in a continuous, completely dry state process requiring no special skill or training by the operator, in contrast to the many duplicating processes heretofore known involving wet treatments and/or treatments conducted in successive and distinct stages, such as are required in photographic processes and the like, and which are time-consuming and require some considerable degree of special operative knowledge and skill.

According to another feature, the duplicates produced according to the invention are of a permanent character unaffected by exposure to heat, light or passage of time, such as are inherent in duplicates produced by various known means and procedures.

In accordance with the invention, duplicates of a master copy are produced on sheet stock, of paper for example, coated on one side with a light sensitive medium, such as Zinc oxide or the like, by first impressing thereon a substantially uniform electrostatic potential extending throughout the surface area thereof, and thence variably discharging the same in accordance with a light contrasting pattern on the master, by means of light reflected from the master and focused onto the coated sheet stock to produce a latent electrostatic image thereon, following which the so-treated duplicate sheet stock is contacted with a finely divided admixture of iron or other magnetic particles and particles of a thermosetting resin while maintaining the admixture under the influence of a magnetic field.

' As a consequence the resin particles are deposited onto the duplicating sheet stock in accordance with the latent electrostatic image pattern formed thereon as above, the resin deposit being thereafter set by heating to convert the resin to the thermoset condition adherently bonded to the sheet stock. Ordinarily a resin incorporating a pigment, usually black, is employed for such purposes thus to produce a pattern in black on the coated sheet stock. The resin particles are electrically charged by means of the triboelectric effect by contact with the particles of magnetic material, the resin particles being preferably more finely comminuted than the magnetic particles whereby a relatively large number of the former adhere to each magnetic particle.

In duplicates as thus produced, there is in some instances a tendency for an appreciable amount of the resin particles to be retained in background areas, which is objectionable. This results from the fact that the zinc oxide coated surface of the duplicating sheet stock has a rather rough surface microscopically, often causing substantial amounts of the resin dust mechanically to adhere to background areas; and also from the further fact that the charging potential initially impressed on the coated surface may not be completely discharged from the background areas during the reproducing procedure.

In accordance with a feature of my invention, in its preferred embodiment, I eliminate this defect by exposing the duplicate sheet after the resin pattern is formed thereon in the manner aforesaid but prior to heat-setting 3,146,100 Patented Aug. 25, 1964 the same, to a source of light for uniformly exposing all areas of the duplicate sheet stock, thus fully to discharge all residual potentials retained on background areas. The printed or patterned areas are substantially unaffected by this treatment owing to the opacity of the resin content deposited on these areas. Following this uniform light exposure, I contact the sheet with a layer of iron or other magnetic particles maintained in a magnetic tield, whereby the resin particles of the background areas are withdrawn thus leaving a clear background surface. Although some resin content is also thus withdrawn from the patterned or printed areas, the initial deposition layer thereof is sufficiently heavy that the reproduction is substantially unaffected.

Having thus described my invention in general terms,

reference now will be had to the accompanying drawings for a more detailed description of a preferred embodiment of a method and apparatus for practicing the same wherein:

FIG. l is a schematic View in perspective and partially in section of the essential apparatus employed as explained below; while FIG. 2 is a section of a component of the FIG. l apparatus as taken at 2-2 thereof. FIGS. 3, 4 and 5 are, respectively, plan view of, a master sheet embodying a pattern to be reproduced, a view of the duplicate sheet at an intermediate stage of my preferred process, and a view of the nished duplicate sheet.

Referring to FIG. 1, the master sheet 10, having indicia 11 thereon, such as typed or printed matter, a drawing or other pattern to be reproduced, is progressively fed horizontally between pairs of pinch rolls 12, past a light and reflector source 13 for brightly illuminating the same. At the same time the duplicating sheet stock 14, is fed at the same lineal speed in the form of continuous strip, from a roll thereof (not shown), thence under a guide roll 15, and thence vertically upward between pairs of spaced electrodes in the form of flamentary pairs of wires 16, 17, disposed respectively on opposite sides of the path of strip travel as shown. The wires 16 are connected together as shown and connected thence over a lead 18 to the positive output terminal of a step-up transformer and rectifier unit 19, having an input plug-in connection 20 for connection to an A C. power source, such as the conventional 60 cycle, 110 volt building power supply. The wires 17 on the opposite side of the strip travel and which face the coated surface 25 of the sheet stock 14, are also connected together as shown and connected thence over a lead 21 to the negative output terminal of unit 19.

In a physical embodiment of the invention which has been operated successfully, the wire pairs 16 and 17 are spaced about 1/2 inch on opposite sides of the path of strip travel, and a direct current voltage of about 6000 volts is impressed between them from unit 19, this voltage being such as to produce a slight corona effect along each of the wires 16, 17. These wire pairs are, respectively, housed in metal shields 22, 23, grounded as at 24, for protective purposes. The sheet stock 14, is coated on the exposed surface shown with a zinc oxide or equivalent electrical insulative, light sensitive coating, as at 25. As a consequence, as the stock is fed between the energized electrode pairs 16, 17, the coated surface is charged throughout to a substantially uniform negative potential with respect to ground.

For purposes of reproducing by electrostatic potential variation on the thus charged stock, the indicia or pattern 11 on the master sheet 10, an optical scanning and focusing system is provided. This comprises a mirror 30, a convex focusing lens 31, and a mask 32, having a narrow, slotted aperture 33 formed therein. The mask is mounted, as shown, adjacent the path of travel of the sheet stock 14 and facing its coated surface 25, with the slotted aperture 33 extending transversely thereof. The mirror and lens are so disposed as shown that light reflected from the surface of the master 10, is picked up by the mirror and reflected thence at right angles through the lens and onto the area of the sheet stock 14 which is covered by the mask 32 except for the slotted aperture 33 therein, the mask being of sufficient height and width to block off all light thus reflected except for the narrow beam 34 which passes through the slotted aperture 33. The lens is so positioned that the beam is brought to a focus on the coated surface of the sheet stock 14, thus forming thereat an optical image corresponding to an exposure area 35 of the master 10.

Accordingly, as the master is fed in the direction of the arrow, the exposure area 35 will in effect sweep along the master in the opposite direction and thus progressively scan the master from end to end. Similarly, the light reected from the master within the exposure area will be reflected and focused by the optical system through the slot of the mask onto the coated surface of the duplicating stock which is being fed at the same lineal speed as the master, and thus progressively reproduce therealong an optical image of the exposure area of the master from instant to instant, thereby variably to discharge the electrostatic potential on the duplicating stock in accordance With said image. In this way the indicia or pattern on the master is reproduced as a latent electrostatic image on the coated surface of the -duplicating stock.

Referring to FIGS. l and 2, the stock is fed past the masking member 32 from a guide roll 39 and thence over a guide roll 40 across a transversely extending slot 41 formed in a tubular member 42 housing a drum 43, and thence under a guide roll 43a, the housing and drum being made of a non-magnetic material, such as polyethylene, or other suitable synthetic resin. Integral with the drum, are oppositely extending shaft portions 44, 45, rotatable in bearings 46, 47, on which are respectively mounted, end plates 49, 50, which close off the opposite ends respectively of the housing 42.

Embedded in the drum are a series of radially extending bar type permanent magnets, as at 51, disposed equiangularly thereabout, as shown in FIG. 1, and equi-spaced therealong, as shown in FIG. 2. The outer ends of the bar magnets are all of like polarity. Disposed about the drum 43 and within the housing 42, is a layer 52 comprising a finely comminuted admixture of iron particles and particles of a thermosetting synthetic resin, such as a phenolformaldehyde or equivalent resin, in the thermosetting stage of cure. The resin preferably incorporates a black pigment, to produce a black on white pattern on the duplicating stock.

Due to the triboelectric effect, the resin particles electrostatically adhere to the iron particles, and the admixture assumes an upstanding tufted or feather duster configuration over each bar magnet, as at 53, under the inuence of the magnetic fields extending radially outward from the respective bar magnets 51. The guide rolls 4f), 43a so space the path of travel of the duplicating stock 14 from the drum 43, that as the duplicating stock is fed over the slot 41 in the housing 42, its coated surface contacts the outer ends of the tufted masses 53, during which time the drum 43 is rotated by shaft 44 in the opposite direction to that of the strip feed. As a result, the positively charged resin particles are withdrawn from the resin-iron admixture, by the negative electrostatic potential on the strip 14, and deposited on the coated surface in amounts varying from point to point in accordance with the corresponding variation in electrical potential thereon.

Only residual amounts of resin particles will be deposited on the background areas of the duplicating stock corresponding to the background areas of the master, since the potential in those areas will have been substantially discharged by the light reflected from the master onto such areas. On the other hand, the resin particles will be deposited in relatively heavy layers throughout areas of the duplicating stock corresponding to the pattern i areas of the master, since little light will have been reflected therefrom to discharge the potential of corresponding areas of the duplicate. The thickness of resin layer deposits on these pattern areas will of course vary from point to point with the amount of light reflected from the master at corresponding points.

As above stated, duplicating stock is fed past slot 41 from the guide roll and thence under the guide roll 43a. At this stage there has been reproduced on its coated surface, a pattern composed of the deposited resin particles corresponding to that of the master with some sprinkling of resin particles also deposited in the nonpatterned or background areas. Thus referring to FIGS. 3 and 4, if we assume the master 56 comprises the large block letter T printed in solid black on white paper, the reproduction thereof on the duplicating stock 14 as it passes under the guide roll 55, would be about as shown in FIG. 3. That is, the block letter T of the master 56 will be faithfully reproduced in black on the duplicating stock as at 57, but the background area 58 of the duplicate, will not in general be pure white, as at 59 of the master, but will ordinarily have the somewhat mottled appearance shown at 58, owing to adhering resin particles or small masses thereof, as at 60. These are deposited as above stated as a result of the rather coarse coated surface of the duplicating stock and also by residual amounts of electrical potential retained on discrete areas thereof.

In order to remove these background resin deposits, the stock 14 is fed from guide roll 43a, past a lamp and reflector element 65 of sufficient intensity completely to discharge residual background area potentials, the patterned or printed areas, however, remaining substantially unaffected by the opacity of the resin deposit thereon. The strip is fed thence across the slot 66 in a housing 67, enclosing a permanent magnet bearing drum 68 constructed like that above described, but which is enveloped in a layer of finely divided iron particles 69, which assumes the tufted configuration shown owing to the magnetic fields above discussed. This drum is likewise oppositely driven to the direction of the strip feed, contact between the paper stock and the tufts of iron filings serving to withdraw the resin particles from the background areas of the duplicating stock.

The strop is fed beyond the drum 63, under a guide roll 70. At this stage the pattern on the duplicating stock has the appearance shown in FIG. 5, with both the block letter T and the background area being faithfully reproduced as in FIG. 1, the resin particles of FIG. 4 having been removed in the manner aforesaid.

At this stage the resin deposit on the pattern areas is held against the stock only by electrostatic attraction and can be rubbed olf. In order permanently to bond the deposited resin pattern to the stock, it is fed over an electrical heating coil 71, which fuses the resin into a solid, fully cured thermoset state, adherently bonded to the sheet stock.

What is claimed is:

l. The method of reproducing on a duplicating sheet of material coated with a photoconductive insulating medium, a contrasting pattern formed on a master sheet by areas having different degrees of light absorption, which comprises: progressively feeding said duplicating sheet between spaced electrodes having a high direct current voltage impressed therebetween for charging all so-coated areas of said duplicating sheet to a substantially uniform electrostatic potential, concurrently therewith progressively feeding said master sheet past a source of illumination, while focusing a beam of rays reflected from said master onto said duplicating sheet thereby to discharge the potential from areas thereof in accordance with the pattern on said master, feeding said duplicating sheet thence in progressive contact with a magnetically suspended rotating substantially cylindrical mass composed of an intimate admixture of particles of magnetic material and particles of a substantially opaque thermosetting synthetic resin in a ine state of sub-division, said mass being suspended in a magnetic field extending radially from the surface thereof and directed substantially normal to the path of travel of said duplicating sheet, whereby said resin particles are deposited on said sheet in accordance with the electrostatic potential pattern thereon, thus to reproduce thereon the pattern on said master sheet, feeding said duplicating sheet thence past a light source having suicient intensity to discharge therefrom residual potentials retained on background areas thereof, but prevented by the opaqueness of said resin particle from substantially discharging the residual potentials retained on the image areas thereof, and thence in contact with a magnetically suspended substantially cylindrical mass composed of particles of a magnetic material in a fine state of sub-division, said mass being suspended in a magnetic field extending radially outward from the surface thereof and directed substantially normal to the path of travel of said duplicating sheet, thereby to Withdraw therefrom resin particles adhering to said background areas, and feeding said duplicating sheet thence past a source of heat for converting the resin pattern thereon to the thermoset condition adherently bonded to said sheet.

2. The method of duplicating on a photoconductive surface, a light contrasting pattern from the surface of a master, said method comprising: impressing a uniform electrostatic potential on and throughout said photoconductive insulating surface, focusing thereon an image from the surface of said master by light projected therefrom, thereby to produce on said photoconductive-insulating surface an electrostatic image of the pattern on the master surface, thereafter contacting the electrostatically imaged photoconductive insulating surface with finely comminuted particles of a substantially opaque resin to deposit such particles thereon in accordance with said electrostatic image, uniformly illuminating the so treated photoconductive insulating surface with an illuminating intensity sucient to discharge residual electrostatic potentials throughout the background areas of said pattern but substantially insuicient to discharge the electrostatic potential throughout the image areas of said pattern, and brushing evenly across the entire photoconductive insulating surface bearing said deposited resin particles to remove residual resin particle deposits from said background areas.

3. The method of reproducing on a duplicating sheet of material coated with a photoconductive insulating medium, a light contrasting pattern formed on a master sheet by areas having different degrees of light reflection which comprises: progressively feeding said duplicating sheet between spaced electrodes having a high direct current voltage impressed therebetween for charging all so-coated areas of said duplicating sheet to a substantially uniform electrostatic potential, concurrently therewith progressively feeding said mastersheet past a source of illumination while focusing a beam of rays reected from said master onto said duplicating sheet thereby to discharge the electrostatic potential from areas thereof in accordance with the pattern on said`\master, feeding said duplicating sheet thence in progressive contact with a mass of particles of a substantially opaque thermosetting resin in a fine state of subdivision, whereby the resin particles are deposited on the sheet in accordance with the electrostatic potential thereon, thus to produce thereon the pattern on said master sheet, feeding said duplicating sheet past a light source having sufficient intensity to discharge therefrom residual potentials retained on background areas thereof, but prevented by the opaqueness of said resin particles from substantially discharging the potentials retained on the image areas thereof, and thence brushing evenly across the entire surface of fsaid duplicating sheet so as to withdraw therefrom resin particles adhering to said background areas.

References Cited in the le of this patent UNITED STATES PATENTS 2,297,691 Carlson Oct. 6, 1942 2,357,809 Carlson Sept. l2, 1944 2,756,676 Steinhilper July 31, 1956 2,815,449 Giaimo Dec. 3, 1957 2,817,765 Hayford Dec. 24, 1957 2,832,977 Walkup et al. May 6, 1958 2,885,556 Gundlach May 5, 1959 2,887,023 Young May 19, 1959 2,889,758 Bolton June 9, 1959 2,890,968 Giaimo lune 16, 1959 2,904,000 Fisher et al. Sept. l5', 1959 2,911,330 Clark Nov. 3, 1959 2,914,403 Sugarman et al Nov. 24, 1959 2,924,519 Bertelsen Feb. 9, 1960 2,939,787 Giaimo June 7, 1960 2,970,299 Epstein et al. Ian. 31, 1961 3,005,388 Limberger Oct. 24, 1961 3,057,720 Hayford et al. Oct. 9, 1962

Claims (1)

1. THE METHOD OF REPRODUCING ON A DUPLICATING SHEET OF MATERIAL COATED WITH A PHOTOCONDUCTIVE INSULATING MEDIUM, A CONTRASTING PATTERN FORMED ON A MASTER SHEET BY AREAS HAVING DIFFERENT DEGREES OF LIGHT ABSORPTION, WHICH COMPRISES: PROGRESSIVELY FEEDING SAID DUPLICATING SHEET BETWEEN SPACED ELECTRODES HAVING A HIGH DIRECT CURRENT VOLTAGE IMPRESSED THEREBETWEEN FOR CHARGING ALL SO-COATED AREAS OF SAID DULPLICATING SHEET TO A SUBSTANTIALLY UNIFORM ELECTROSTATIC POTENTIAL, CONCURRENTLY THEREWITH PROGRESSIVELY FEEDING SAID MASTER SHEET PAST A SOURCE OF ILLUMINATION, WHILE FOCUSING A BEAM OF RAYS REFLECTED FROM SAID MASTER ONTO SAID DUPLICATING SHEET THEREBY TO DISCHARGE THE POTENTIAL FROM AREAS THEREOF IN ACCORDANCE WITH THE PATTERN ON SAID MASTER, FEEDING SAID DUPLICATING SHEET THENCE IN PROGRESSIVE CONTACT WITH A MAGNETICALLY SUSPENDED ROTATING SUBSTANTIALLY CYLINDRICAL MASS COMPOSED OF AN INTIMATE ADMIXTURE OF PARTICLES OF MAGNETIC MATERIAL AND PARTICLES OF A SUBSTANTIALLY OPAQUE THERMOSETTING SYNTHETIC RESIN IN A FINE STATE OF SUB-DIVISION, SAID MASS BEING SUSPENDED IN A MAGNETIC FIELD EXTENDING RADIALLY FROM THE SURFACE THEREOF AND DIRECTED SUBSTANTIALLY NORMAL TO THE PATH OF TRAVEL OF SAID DUPLICATING SHEET,

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