US2520504A - Electric printing - Google Patents

Description

Aug. 29, 1950 Filed Nov. 22, 1944 ZZQ W. J. HOOPER ELECTRIC PRINTING 4 Sheets-Sheet l 9, 1950 w. J. HOOPER 2,520,504

ELECTRIC PRINTING Filed Nov. 22, 1944 4 Sheets-Sheet 2 II I l jzyaivzew Aug. 29, 1950 w. J. HOOPER 2,520,504

ELECTRIC PRINTING Filed Nov. 22, 1944 4 Sheets-Sheet 3 1916 VOL 72765 5001? CE I 9, 1950 w. J. HOOPER 2,520,504

ELECTRIC PRINTING Filed Nov. 22, 1944 4 Sheets-Sheet 4 J97 6 VOL 73 7625 jay/ T1: E

Patented Aug. 29, 1950 ELECTRIC PRINTING William J. Hooper, Elsah, Ill., assignor, by memo assignments, to William O. Huebner, New York,

Application November 22,1944, Serial No. 564,574

18 Claims. (Cl. 101-426) This invention relates to electric printing, and more particularly to printing method and apparatus wherein the ink is transferred from an inked member to the sheet being printed by a field of force rather than by mechanical pressure.

One feature of this invention is that it provides improved methods and apparatus for electric printing; another feature of this invention is that it is adapted to provide controlled uniform transfer of ink; still another feature of this invention is that the field across the air gap at which printing is taking place may be strong enough to have the air in such space at or above the ionization level; a further feature of this invention is that a relatively heavy electron space current is caused to flow to assist in the movement of the ink; still a further feature of this invention is that the flow of space current from each increment of area of the printing surface is controlled in such manner as to prevent formation of arcs; and yet a further feature of this invention is that each increment of area of the printing surface is, for all practical purposes, electrically isolated from adjacent areas and is supplied, prior to the instant of printing, with a. predetermined and carefully controlled quanmy of electricity for effecting optimum results in the transfer of ink to the sheet being printed. Other features and advantages of this invention will be apparent from the following specification and the drawings, in which:

Figure 1 is an elevational view, partly schematic, of one specific embodiment of my invention, an electric printing press of the kind wherein the sheet being printed is passed between two revolving cylindrical members; Figure 2 is an enlarged detail view of the printing gap of the apparatus shown in Figure 1; Figure 3 is an enlarged fragmentary detail view analogous to Figure 2, but of a modified form of apparatus; Figure 4 is a vertical sectional view, partly schematic of another modification of apparatus embodying my invention; and Figure 5 is a vertical sectional view, partly schematic, of another modification of apparatus embodying my invention.

Printing has for centuries been conventionally effected by mechanical pressure between an inked member having a design thereon and the sheet to be printed. Very recently, however, it has been found that ink can be transferred from the inked member to the sheet being printed by the use of a field of force, either magnetic or electrostatic, without actual contact between the inked member and the sheet. Certain arrangements heretofore proposed for electric printing are shown in such patents as Huebner Patent 1,820,194 of August 25, 1931 and Huebner Patent 2,224,39101 December 10, 1940, although these arrangements have never gone into commercial use. A fulldiscussion of this type of printing will not be set forth here, as reference may be made to the above mentioned patents to supplement the present disclosure in regard to the advantages being sought. It is believed sufficient to say that elimination of all. need for mechanical pressure enables very great reductions in the weight and power requirements of a large press, a goal toward which the printing industry has been working for decades.

In view of the newness of electric printing, terminology peculiar to this art has not as yet come into common use, and the words used throughout this specification and claims will be those employed in the conventional printing art wherein ink transfer is effected by mechanical pressure. That is, for example, the term printing" is used to describe the operation of delivering ink from the inked member to the sheet being printed, although it will be understood that the word printing as used herein does not connote any mechanical pressure, but is used in the much broader sense of the word to mean merely transfer of a certain design from one element to another. This is analogous to the use of the term printing in photography, where mechanical pressure is not the cause of transference of a design from the negative to the sensitized paper. It will be also understood that when one of the rolls or printing members is spoken of as having designs formed on the surface thereof, such designs may comprise text, pictures, or anything else desired to be printed. Moreover, the designs may be formed on the surface of the printing member in relief, by intaglio or gravure, or by planographic or lithographic methods. All such methods of forming or preparing a printing surface are well known in the conventional printing art and need not be described here, as is also the case in connection with methods and apparatus for delivering ink to the inked surface in desired quantities. In reading and interpreting this specification and the claims accompanying it, all terminology borrowed from the conventional printing art must be given broad meaning appropriate to this rather special field.

I have made a number of inventions in the field of electrical printing, these inventions being disclosed in certain copending applications to which reference may be had, as applications Serial No. 567,605, filed December 11, 1944 (now abandoned); Serial No. 571,440, filed January 5, 1945 (now abandoned); Serial No. 584,835, filed March 26, 1945; Serial No. 590,704, filed April 27, 1945; Serial No. 604,618, filed July 12, 1945; and Serial No. 617,186, filed September 19, 1945.

Referring now more particularly to specific apparatus illustrated in Figures 1 and 2 of the drawings, the press is here shown as comprising upper and lower portions A and B suspended on a frame member or other carrying means C. The lower portion includes .a main metal cylindrical member or roll I having designs formed on the surface thereof, as text in relief. The cylinder I0 is mounted in conventional manner, not illustrated, to be rotatable about its axis II, and it is electrically grounded throughout. The designs in relief on the surface of the cylinder I0 are inked by means here illustrated as conventional inking means comprising the ink trough I2 and the rolls I3a-d. As will be readily apparent to one familiar with the printing art, rotation of the cylinder I0 results in continually presenting to the printing point (in this case the point directly above the axis of the cylinder) a surface area which has the desired quantity of ink on the raised portions thereof and is devoid of ink on the other portions.

The upper portion of the press is here shown as including a housing I4 having two cylindrical members or rolls I5 and I6 rotatable therewithin about the axes I1 and I8, respectively, the axes II, I1 and I8 all being parallel. All of the cylindrical members I0, I5 and I6 are driven from a single drive means in synchronized relation and at such rotative speeds that the lineal surface speeds are identical and so that adjacent surfaces move in the same direction. The cylinders I0 and I6 may rotate clockwise and the cylinder I5 counter-clockwise, as indicated by arrows on the drawing.

At the bottom of the housing I4 are a pair of gap defining members I9 and 20 of electrical resistance material having high specific resistivity and a relatively low dielectric constant, with high voltage breakdown characteristics, as a high quality plate glass having a dielectric constant of about four. These two members I9 and 20 are wedge shaped, terminating in rather thin apices I'9a and 20a defining the printing gap or air space in the form of a narrow strip extending longitudinally of the cylinders. That is, this gap might be in the neighborhood of an eighth to a half inch wide, and extend longitudinally of the cylinders for their full length and parallel to their axes, preferably on a line between the axes II and I1; and the members I9 and!!! operate to confine substantially the effective part of the electric field of force in this gap. The adjacent or confronting portions of the surfaces of the cylinders I0 and I5 are preferably spaced a matter of a few hundredths of an inch at the printing gap, as two hundredths of an inch. Too close a spacing is mechanically impractical while too wide a spacing may result in loss of clear definition of the printed image due to dispersion of the inked design during its transfer through space. The lower surfaces of the glass members I9 and 20 serve as bearingsurfaces over which pass the sheet to be printed, a paper web 2| being illustrated as fed over the rolls 22a-c; and these lower surfaces are preferably highly polished to minimize static electric effects incident to movement of the web over a stationary bearing surface. To provide one factor of control in connection with design clarity. ionization of the air at the printing gap, and other factors of operation of the press, it is desirable to be able to adjust the spacing between the electrical members II) and I5. This is shown as being accomplished by provision of a vertically adjustable mounting for the entire upper printing section A. This section is here shown as supported from the frame C by bolts Ila-c. The first two of these are mounted in slots, so that when they are loosened the housing It can be moved vertically through a desired range. The bolt 23c is passed through a lug portion projecting from the frame C and is threaded into a portion of the housing I4, that rotation of this bolt (and others like it at other portions of the support) enables raising or lowering of the upper section, the bolts 23a and 231) being tightened during operation of the press to maintain the selected position. A range of adjustment sufficient to enable the space between the cylinders III and I5 to be varied between limits of four or five thousandths of an inch and about fifty thousandths of an inch is desirable.

In the particular embodiment of my invention illustrated in Figures 1 and 2, the cylindrical member I5 comprises an inner portion Iia of conducting metal, as cast steel, and an outer surface portion I5b of electrical resistance material having high resistance to current flow therethrough (high specific resistivity, at least ten to the tenth power ohms per cubic centimeter, and preferably ten to the nineteenth power or higher), and a high specific inductive capacity or dielectric constant. The material illustrated is glass, which may have a dielectric constant in the neighborhood of ten, although it will be understood that other materials may be used which meet these qualifications even better, as for example certain ceramics now being used in condensers and having dielectric constants approaching 200, with a specific resistivity in the neighborhood of ten to the sixteenth power ohms per cubic centimeter. It isdesirable that the material of the outer surface have very high resistance to current fiow'therealong, or therethrough (high specific resistivity), in order that the charge on any portion or increment of surface area will not rapidly move to another surface portion when there are potential differentials therebetween, and will not rapidly leak through to the inner conducting metal portion which is grounded. A high dielectric constant is desirable to provide the maximum capacity effect when a quantity of electricity is being delivered to the surface, and to prevent breakdown or rupture of the material at the high voltages used in this electric printing, which may be in the neighborhood of 10,000 volts.

The upper cylindrical member or roll I6 also has an inner portion Ilia of electrically conducting-rigid material, as cast steel, but the outer portion I6b is in this case of electrically conducting but resilient material. A material which I prefer in this regard is electrically conductive rubber,

such material being readily available commercially. The spacing between the axes of the cylindrical members I5 and I6 is preferably such that there is a definite compression of the surface of the rubber portion I6b where it contacts the outer glass surface of the roll I5, so that contact between these surfaces is provided throughout an area rather than as a line contact.

At the top of the upper portion of the press shown is a high voltage source adapted to develop a relatively high direct current potential between ground and its high voltage or "hot" output terminal, this terminal being connected to the inner metal portion of the roll it, as indicated on the drawing. This high voltage source may be of a conventional type which can be secured on the commercial market, taking power from an ordinary commercial alternating current source, as the wires 25 and 26, stepping its voltage up to the desired value, and rectifying and filtering this high voltage power. Manually variable means 21 enables convenient variation of the voltage developed, and the output voltage and current may be read from the meters 28 and 29, respectively. It is quite important that the voltage output be uniform, but this requisite is met by a piece of equipment commercially available which will maintain any desired voltage gradient and deliver currents meeting the requirements of this invention. Voltage control apparatus can be made for almost any power requirement. The current requirements of this electric printing are not heavy in the ordinary sense of the word, but I have found that a very definite electron current or space current flow across the printing gap is requisite to good printing by this method. An electron current of only one or two milliamperes from each square inch of printing area ma be all that is required, but where the roll is several feet in length, as in printing a newspaper web, the a total current flow in the high voltage circuit may approach the neighborhood of 100 milliamperes, even though the width of the printing gap is kept reasonably small.

In the operation of the device disclosed in Figures 1 and 2, the high voltage source develops a potential with respect to ground and applies this to the conducting roll it. The electrically conducting surface of this roll contacts the high resistance and high dielectric constant surface of the roll i5, resulting in the development of a high voltage differential between the surface of the roll ii, at the point of contact, and the inner metal portion ilia, which is grounded. There is thus a capacity or a condenser effect between the surface of the roll it and the inner electrically conducting portion IBa of the roll I5, so that a certain quantity of electricity is delivered to the effective condenser provided by this contact. The capacity involved is a function of the spacing between the metal portion Mia and the adjacent portion of the roll IS, the dielectric constant of the'outer portion Nb, and the areas involved. This effective capacity, the voltage delivered by the high voltage source, and the charging time, determine the quantity of electricity delivered to a given unit or increment of surface area of the roll 15 before it moves out of contact with the roll 16 during the relative rotation of these cooperating members; The primary variables here, once the press has been constructed, are the rate of rotation and the voltage, so that if a normal running speed is chosen the quantity of electricity delivered to a given unit of area of the outer surface of the roll l can be definitely predetermined by adjustment of the voltage by manipulation of the variable means 21.

Since the material of the outer portion of the roll I! provides highresistance to current flow therealong or therethrough, the quantity of electricit 'delivered to any unit of area of the surface of the roll l5 remains unchanged, for all practical purposes, until that unit or increment of area reaches the printing gap, since the high dielectric nature of the members it and 20 tend to prevent any transfer of charge between the cylinders Hi and I5 until the increment of area under consideration reaches the air gap between these members is and 20. When this point is reached, however, the spacing between the rolls I0 and I5 should be small enough that there is an instantaneous and immediate electron current or space current flow. I have found that it is preferable to so connect the high voltage source that the surface of the cylinder is is given a high charge which is positive with respect to ground. Accordingly, since the cylinder i0 is grounded, electron current will flow, at the instant of printing, from the uppermost surface of the cylinder I0 toward the cylinder I5. It is preferable not only to have a definite space current or electron current flow as a part of the causative effect of ink movement, but it is also highly desirabl to have the electrons move from behind the ink in the sense that they leave the metal conducting surface of the cylinder l0 beneath the layer of ink on the raised portions thereof, with the de-- sired direction of movement of ink articles or droplets coinciding with that of electron movement, as ink pigment particles such as colloidal graphite, for example, have a negative charge in the medium in which they are dispersed.

In order to get the maximum transfer of ink, and to improve uniformity and other desired characteristics in the ink image printed on the web 2|, it is preferable to have the electron current at the printing gap at or above saturation or ionization conditions for electron current movement in air. As is well known, raising the voltage across an air gap causes rapidly increasing electron current flow thereacross until saturation conditions are reached, whereupon substantial increases in voltage effect little or no change in the electron or space current flowing. If the voltage is increased further, however, a stage is reached where the electron current flow again begins to increase, the curve of voltagecurrent curving up rather sharply and then increasing tremendously as there is an insulation breakdown and arcing occurs. By precise control of the quantity of electricity which can be delivered by any increment of area of the surfaces involved, the voltage conditions across the printing gap can be made high enough not only to work in the saturation portion of the curve, but even to exceed this without danger of arcing, since even though the voltage conditions are up in the critical state there is not sufficient current punchavailable to result in the formation of an arc. It will be readily appreciated, of course, that controlling the current output from the high voltage source would not be sufflcient to achieve this result, if the surface of the roll l5 were conducting, since development of arcing conditions at one point could result in the formation of an are, fed by electricity drawn from other areas of the surface of the cylinder [5. Each increment of area involved in this electric printing must be printed independently, as it were, if the conditions mentioned are to be obtained without disruption of the operation by are formation. This control of current flow from each increment of area throughout the whole of the areas involved at the printing gap is very important, and is achieved by an arrangement of the kind just described. By use of a cylinder like the cylinder IS, with, its outer portion of material having very high resistance to current movement and a high dielectric constant, and by proper adjustment of spacing between the cyl- 7 inders It and ii and of the voltage delivered by the high voltage source, the quantity of current on each increment of area given up at the instant of printing can be controlled so that the printing gap is in a state of ionization, with a relatively substantial electron current flow thereacross, yet without danger of arcing. It has been found that arcing not only eventually damages the equipment, but it piles up ink in an unrecognizable blob at and around the arcing point and results in complete or substantially complete lack of ink transfer at other points slightly further removed from the arcing point.

In the modified form of my invention shown in Figure 3 the paper web 33 is in direct contact with the outer surface of a cylindrical member 34 corresponding to the roll IS, in that this member 34 has an inner cylindrical portion 34a of electrically conducting material such as cast steel, and an outer portion 34b of material having high resistance to current fiow and a high dielectric constant for capacitive purposes, as glass or a special ceramic. In this case the sheet to be printed, as the web 33, is in contact with the outer surface of the cylindrical member 34 at the printing point closest to the cooperating cylindrical member 35. This latter member is of electrically conducting material, as cast steel, with designs formed on the surface thereof, as by putting a plate with relief designs thereon, and is appropriately inked by any conventional method. In the form of-my invention shown in Figures 1 and 2, transfer of ink is limited to a definite and physically defined printing gap, with the space across this gap such that the capacity at the gap between the members Ill and lint is less than that between the members lid and it during the charging period, so that the strain or voltage gradient at the gap is higher than that during charging contact between the rolls l and it. In the modification shown in Figure 3 this increase in voltage strain at the printing portion of revolution also takes place, but no attemptis made to define printing to a narrow arc Of rotation, although as a practical matter the strain between the members is not such as to efiect transfer of ink except where the cylinders are closest, although printing may take place over an inch or more of width at and-about this point of closest spacing. Although it is desirable to feed the web of paper 2| in the printing arrangement shown in Figures 1 and 2 at a lineal speed corresponding to the lineal surface speeds of the rolls ill and I5, physical contact in the first form took place between the moving web and stationary members. In the form shown in Figure 3, however, use of the same lineal speeds enables the paper to be guided.

or carried directly by the surface of the roll 34 at the printing point, with no relative rotation therebetween, so that there is no chance of interference by static electricity transients if a static eliminator has been used in conjunction with the web prior to the printing points.

In the embodiments of my invention illustrated in Figures 4 and 5 the desired quantity of electricity is delivered to the outer surface of the printing roll by controlled conduction through the roll, rather than by contact ofthe surface with a conducting member, as the conducting roll it. In this case the outer portion of the high voltage roll must be of material having what might be termed only moderately high resistance to current flow, (as for example ten to the seventh or eighth power ohms per cubic centimeter) so that the desired quantit of current can flow to a given increment of area, through the roll, be-' time the electrical resistance is high enough to prevent any appreciable transfer of electricity between adjacent increments of area at the instant of printing to prevent formation of arcs.

Referring now more particularly to the embodiment illustrated in Figure 4. a cylindrical member 40 rotates within a. metalhousing 4| having a generally cylindrical inner surface. A pair of members 42 and 43 of material having a high specific resistivity and a relatively low dielectric constant and corresponding to the members II and 2| described in connection with Figures 1 and 2, define the printing gap and provide guide means for the paper web 44 traveling over the rolls 450-0. Ink is delivered from a fountain trough 43, through an intermediate roll 41, to a smooth inked roll 48, the roll 4! serving to ensure uniform distribution of the ink on the roll 48. The roll 43 is of electrically conducting material throughout, preferably comprising a cast metal inner portion and an outer blanket portion of conducting rubber, although th roll may be entirely of metal.

In this case the designs are shown as formed in relief on the exterior surface of the high voltage roll 40. By having the relief portion substantially raised above the remainder of the surface of this roll, and by properly adjusting the spacing between the rolls 40 and 43, ink transfer from the roll 48 to the web 44 will take place at the printing gap only in accordance with the configuration of the raised-portions of the surface of the roll 40. That is, the field strength between the raised portions of the surface of the roll 40 and the surface of the roll 48 is so much greater than that existing with respect 'to the lower or unraised portions of the surface that the desired ink transfer takes place in the designs determined by the raised portions without any noticeable ink transfer taking place elsewhere. One advantage of this arrangement is that all wear and tear on the surface bearing the design, even that incident to repeated reinking, is eliminated. As in all forms of printing apparatus shown in this application, the web 44 is spaced from the inked surface of the roll '48 at the printing point.

The inner portion 40a of the roll 40 is of electrically conducting material, as cast steel, connected to the hot terminal of the high voltage source indicated schematically, which may be like that described in connection with Figure l. The outer portion 40b of this roll is of material of fairly high resistance, but not high enough to prevent appreciable current flow therethrough during the time of one revolution of the roll. Certain waxes, as red sealing wax, can be used for with the outer surface of the inner metal portion 40a. In order to build up the desired charge of electricity on the outer surface of the roll 40, the housing 4| is arranged to have a condenser action in cooperation with the inner metal portion 40a of the high voltage roll, and to increase the effect of this action the interior of the housing-ll is provided with an inner lining or portion 4 Id of material having a high dielectric constant, as glass. Throughout about of its circumference, therefore, there is a capacity relation between th portion 40a and the outer metal portion of the housing ll, providing a condenser which is charged by the high voltage source and discharged at the instant of printing, in so far as any given increment of surface area is concerned. The resistance in ohms at any given section through the outer portion 40b of the high voltage cylinder must be so proportioned that, at the voltage at which the arrangement is being operated, the desired quantity of electricity i delivered to the outer surface during rotation of a given increment of area after it has effected printing and until it again reaches the printing point. This may be determined in accordance with the conventional charging time formula where the time constant t=RC, where t is in seconds, R in ohms and C in farads. The resistance and capacity of a given incremental section through the outer portion 40b ar fixed in the design and construction of the press. and are preferably so proportioned in relation to the time provided at the desired normal running speed that about two-thirds or three-quarters of the eventual maximum charge which could be delivered to an increment of surface area if the roll is stationary is delivered to it during the charging portion of one revolution. As before, adjustment of the space between the rolls 40 and 48, and

adjustment of the voltage delivered by the high.

voltage source, enable the printing gap to be operated at or above the ionization level, yet with control of the current flow such that no arcing takes place.

The form of my invention illustrated in Figure is another form or embodiment of my invention of charging the surface of the high voltage roll, in electric printing, by controlled conduction through the roll. In this form of my invention the roll 50 has an inner portion 50a of conducting material, as cast steel, and an outer portion of moderately high resistance material highly resistant to an electrical breakdown, as glass with a metal salt dispersed therethrough, this outer portion being identified as 5%. An outer metal housing 5| provides an inner cylindrical surface again providing a capacity relationship with the portion 50a, the housing being provided with a lining here identified as 5la, which may be of polystyrene or glass, for example, having a relativelyhigh dielectric constant. Glass members 52 and 53 again serve to define the printing gap and to act as guides for the web 54 moving over the rolls 55a and 55b. As before, the outer surface of the roll 50 is charged from the high voltage source by conduction through the roll, as described in connection with the embodiment of my invention shown in Figure 4.

The design to be printed is in this case formed on the outer surface of the lower rotatable cylinder 58, this cylinder being of conducting material, as a cast steel inner portion with metal type plates thereon, and grounded. Ink in a trough 56 is delivered through the intermediate roll 5] to inking rolls 59a and 59b to continually replenish ink taken from the roll 58 during the printing operation. The operation of this form of press is similar to that more fully described in Figure 4, except that ink is present only on 10 the portions corresponding to the design to be printed, at the printing point.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. Transfer apparatus of the character described, including: a rotating cylindrical member having at least the surface thereof of electrical resistance materialhaving high voltage breakdown characteristics, each increment of area of said member being adapted to retain a quantity of electricity; a source of liquid to be transferred; a sheet spaced therefrom; means for developing a potential differential between said member and sheet; andmeans for delivering a predetermined quantity of electricity to each separate increment of area of the cylindrical member prior to its reaching the transfer zone.

2. Printing apparatus of the character described, including: a first member; a second member spaced from the first member, one of said members having designs formed on the surface thereof and one of said members having the surface thereof and a substantial portion therebeneath of electrical resistance material having a high dielectric constant; means for inking one of said members; means for supporting the sheet to be printed between said members and spaced from the inked member; and means for supplying said resistance surface with an electrical charge of predetermined quantity and having a high voltage differential from said other member.

3. Printing apparatus of the character described, inciuding: a first cylindrical member; a second cylindrical member spaced from the first member, the axes of said members being parallel, one of said members having designs formed on the surface thereof and one of said members having the surface thereof and a substantial portion therebeneath of electrical resistance material having a high dielectric constant; means for inking one of said members; means for supporting the sheet to be printed between said members and spaced from the inked member; and means for supplying said resistance surface with an electrical charge of predetermined quantity and having a high voltage differential from said other member, the inked member being negative with respect to the other member.

4. Printing apparatus of the character described, including: a first cylindrical'member; a

second cylindrical member spaced from the first member, the axes of said members being parallel, one of said members having designs formed on the surface thereof and one of said members having the surface thereof and a substantial portion therebeneath of high resistance material having a high dielectric constant; means for adjusting the spacing between said members; means for inking one of said members; means for supporting the sheet to be printed between said members and spaced from the inked member; and means comprising a power supply for supplying said high resistance surface with an electrical charge of predetermined quantity and having a high voltage differential from said other member, the inked member being negative with r p qi t9 the other member, this power p ly means being variable to enable the space between said members to be maintained at or above the ionization level.

5. Printing apparatus of the character described, including: a first member; a, second member spaced from the first member, one of said members having designs formed on the surface thereof and one of said members having the surface thereof and a substantial portion therebeneath of high resistance material having a high dielectric constant; means for inking one of said members; means for supporting the sheet to be printed between said members and spaced from the inked member; and means for supplying said high resistance surface with an electrical charge of predetermined quantity and having a high voltage difierential from said other member, this means including a conducting member making moving contact with said high resistance surface.

6. Printing apparatus of the character described, including: a first cylindrical member; a second cylindrical member spaced from the first member, the axes of said members being parallel, one of said members having designs formed on the surface thereof and one of said members having the surface thereof and a substantial portion therebeneath of high resistance material having a high dielectric constant; means for inking one of said members; means for supporting the sheet to be printed between said members and spaced from the inked member; means for rotating said cylindrical members and moving said sheet, this means providing equal surface speeds, in the same direction, of the sheet and at least one of the cylindrical members; and means for supplying said high resistance surface with an electrical charge of predetermined quantity and having a high voltage differential from said other member, this means including a conducting member making moving contact with said high resistance surface.

7. Printing apparatus of the character described, including: a first cylindrical member; a second cylindrical member spaced from the first member, the axes of said members being parallel, one of said members having designs formed on the surface thereof and one of said members having the surface thereof and a substantial portion therebeneath of high resistance material having a high dielectric constant; means for inking one of said members; means for supporting the sheet to be printed between said members and spaced from the inked member; means for rotating said cylindrical members and moving said sheet, this means providing equal surface speeds of said members and sheet in the same direction; and means for supplying said high resistance surface with an electrical charge of predetermined quantity and having a high voltage differential from said other member, this means including a cylindrical member of resilient material of good electrical conductivity making contact with said high resistance surface circumferentially remote from said sheet.

8. Printing apparatus of the character described, including; a first cylindrical member having the surface thereof and a substantial portion therebeneath of high resistance material having a high dielectric constant; a second cylindrical member of material of good electrical conductivity having designs formed on the surface thereof, the axes of said cylindrical members being parallel and the adjacent surfaces being slightly spaced; means for inking said second member; means for supporting the she t to be printed between said members and spaced from the inked member; and power supply means for supplying said high resistance surface with an electrical charge of predetermined quantity and having a high voltage differential from said other member, the inked member being negative with respect to the other member, this power supply means being variable to enable the space between said members to be maintained at or above the ionization level.

9. Printing apparatus of the character described, including: a first cylindrical member having the surface thereof and a substantial portion therebeneath of high resistance material having a high dielectric factor and an inner portion of material of good electrical conductivity; a second cylindrical member spaced from the first member, the axes of said members being parallel, one of said members having designs formed on the surface thereof and one of said members having the surface thereof and a substantial portion therebeneath of high resistance material having a high dielectric constant; means for inking one of said members; means for supporting the sheet to be printed between said members and spaced from the inked member; means for rotating said cylindrical members and moving said sheet, this means providing equal surface speeds of said members and sheet in the same direction; and means for supplying said high resistance surface with an electrical charge of predetermined quantity and having a high voltage differential from said other member, this means including a cylindrical member of resilient material of goodelectrical conductivity making contact with said high resistance surface circumferentially remote from said sheet, the inner portion of the first cylindrical member being at the same potential as said second cylindrical member.

10. Printing apparatus of the character described, including: a first cylindrical member having the surface thereof and a substantial portion therebeneath of material having a high dielectric constant; a second cylindrical member of material of good electrical conductivity having designs formed on the surface thereof, the axes of said cylindrical members being parallel and the adjacent surfaces being slightly spaced; means for inking said second member; means for supporting the sheet to be printed between said members and in contact with a portion of the first cylindrical member; and means for supplying the surface of one of the members with an electrical charge having a high voltage differential from said other member.

11. Printing apparatus of the character described, including: a first cylindrical member having the surface thereof and a substantial portion therebeneath of electrical resistance material having a high dielectric constant; a second cylindrical member of material of good electrical conductivity having designs formed on the to enable the space between said members to be maintained at or above the ionization level.

12. Printing apparatus of the character described, including: a first member; a second member spaced from the first member, one of said members having designs formed on the surface thereof and one of said members having the surface thereof and a substantial portion therebeneath of high resistance material having a high dielectric constant; means for inking one of said members; means for supporting the sheet to be printed between said members and spaced from the inked member; and means for supplying said high resistance surface with an electrical charge of predetermined quantity and having a high voltage differential from said other member, this means including a conducting member in good capacitive relationship with the member having the high resistance surface.

13. Printing apparatus of the character described, including: a first cylindrical member; a second cylindrical member spaced from the first member, the axes of said members being parallel, one of said members having designs formed on the surface thereof and on of said members having the surface thereof and a substantial portion therebeneath of high resistance material having a high dielectric constant; means for inking one of said members; means for supporting the sheet to be printed between said members and spaced from the inked member; and means for supplying said high resistance surface with an electrical charge of predetermined quantity and having a high voltage differential from said other member, the inked member being negative with respect to the other member, this means including a conducting member at least partly surrounding and in good capacitive relationship with the cylindrical member having the high resistance surface.

14. Printing apparatus of the character described, including: a first cylindrical member; a second cylindrical member spaced from the first member, the axes of said members being parallel, one of said members having designs formed on the surface thereof and one of said members having the surface thereof and a substantial portion therebeneath of high resistance material having a high dielectric constant; means for inking one of said members; means for supporting the sheet to be printed between said members and spaced from the inked member; and means for supplying said high resistance surface with an electrical charge of predetermined quantity and having a high voltage differential from said other member, the inked member being negative with respect to the other member, this means including capacity means at least partly surrounding and in good capacitive relationship with the cylindrical member having the high resistance surface, this capacity means having an inner portion of material having a high dielectric constant and an outer portion of conducting material at the same potential as the other cylindrical member.

15. A method of printing by use of two spaced members, at least one of the members being a rotating cylindrical member having a surface of high resistance material having a, high dielectrio constant, one of the members having designs formed on the surface thereof and one of the members providing a source of ink for transfer to a sheet to be printed, comprising: supporting the sheet to be printed between said members and spaced from the ink; and developing a potential differential between said members and controlling the current flow between said members at the instant of printing by bringing each increment of area of the cylindrical member in contact with a charged conducting member prior to the instant of printing by such increment of area to deliver a predetermined quantity of electricity thereto.

16. A rotary capacitor comprising a cylindrical member having an inner cylindrical plate portion of electrically conducting material and an outer surface dielectric portion of material having a high dielectric constant.

17. Current controlling apparatus, including: a rotary capacitor having at least a surface portion of material having a high dielectric constant; means associated with said capacitor for charging increments of area of said surface portion as they come in operative relation thereto; and means associated with said capacitor for discharging charged increments of area of said surfac portion as they come in operative relation to this latter means.

18. Apparatus of the character described for controlling high voltage, low amperage current flow throughout a substantial area, including: a rotary capacitor comprising a cylindrical member having an inner cylindrical portion of electrically conducting material and an outer surface portion of material having a high dielectric constant; means associated with said capacitor for charging increments of area of said surface portion as they come in operative relation thereto; and means associated with said capacitor for discharging charged increments of area of said surface portion as they come in operative relation to this latter means.

WILLIAM J. HOOPER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,600,842 Philips Sept. 21, 1926 1,820,194 Huebner Aug. 25, 1931 1,838,218 Durham Dec. 29, 1931 2,042,003 Huebner May 26, 1936 2,065,136 Huebner Dec. 22, 1936 2,152,077 Meston Mar. 28, 1939 2,173,032 Wintermute Sept. 12, 1939 2,224,391 Huebner Dec. 10, 1940 2,451,288 Huebner Oct. 12 1948 FOREIGN PATENTS Number Country Date 301,508 Germany Feb. 2, 1917 176,469 Switzerland June 17, 1935

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