US3636637A

US3636637A - Method and apparatus for drying liquid deposited on liquid receptive material

Info

Publication number: US3636637A
Application number: US35146A
Authority: US
Inventors: Charles N Keith
Original assignee: GRAPHIC POLLUTION CONTROL Inc
Current assignee: GRAPHIC POLLUTION CONTROL Inc
Priority date: 1970-05-06
Filing date: 1970-05-06
Publication date: 1972-01-25
Anticipated expiration: 1989-01-25

Abstract

An electronic dryer for setting ink comprising spaced electrodes of an antenna radiating a high potential radiofrequency electromagnetic field through which is passed a liquid receptive material, such as paper, having wet ink thereon. A shield of dielectric material is positioned to extend between the electrodes to prevent arcing between the electrodes. In addition, ionized air around the electrodes is removed to further minimize the possibility of interelectrode arcing. A static electricity eliminator is employed to generate an electromagnetic field for removing static charges from the paper to prevent arcing between the paper and the electrodes.

Description

United States Patent Keith METHOD AND APPARATUS FOR DRYING LIQUID DEPOSITED ON LIQUID RECEPTIVE MATERIAL Appl. No.: 35,146

Related U.S. Application Data Continuation-in-part of Ser. No. 1,030, Jan. 6, i970, abandoned.

U.S. Cl ..34/l, 2l9/l0.8l Int. Cl ..B0lk 5/00 Field of Search ..34/l; 2l9/l0.8l

[ 51 Jan. 25, 1972 [56] References Cited UNITED STATES PATENTS 3,491,457 1/1970 Schreiber et al ..34/l 3,532,848 10/1970 Loring, Jr. et al. ..2 l9/l0.8l

Primary Examiner-Charles Sukalo Attorney-Richards, Harris & Hubbard [57] ABSTRACT An electronic dryer for setting ink comprising spaced electrodes of an antenna radiating a high potential radiofrequency electromagnetic field through which is passed a liquid receptive material, such as paper, having wet ink thereon. A shield of dielectric material is positioned to extend between the electrodes to prevent arcing between the electrodes. In addition, ionized air around the electrodes is removed to further minimize the possibility of interelectrode arcing. A static electricity eliminator is employed to generate an electromagnetic field for removing static charges from the paper to prevent arcing between the paper and the electrodes.

28 Claims, 32 Drawing Figures alsssl-sa'r PATENTED JAN25 i872 sum 01 gr w FIG. I

v Q a 4 FIG. 2

PATENTEU M25 I972 SHEET 030? 10 FIG. 6

FIG. 5

rATemmJms-m alsasssv INVENTOR:

CHARLES N. KEITH Z'M, mf'zwu ATTORNEYS Pmmmmzsm 3636.637

SHEET [)8 HF 10 lNVENTOR:

CHARLES N. KEITH 332 FIG. 30 QM ATTORNEYS PATENIEDJANZSBYZ SHEET UQUF 10 FIG. 22

METHOD AND APPARATUS FOR DRYING LIQUID DEPOSITED ON LIQUID RECEPTIVE MATERIAL This is a continuation-in-part application of an application filed Jan. 6, 1970, Ser. No. L030, now abandoned.

This invention relates to electronic drying, and more particularly to electronic drying of a liquid on a liquid receptive material by a radiofrequency electromagnetic field. A major problem which has always been present in the printing industry is the offsetting or smudging of wet ink onto the back of printed sheets of paper when they are stacked in the delivery.

station of a printing press.

Two basic types of antioffset devices are presently being utilized by the printing industry. The most common type of antioffset device, used with sheet-fed printing presses, employs spray powder applied between individual sheets, to separate the sheets, to prevent offsetting of wet ink from the face of one sheet to the back of another sheet by holding the sheets in spaced-apart relation until the ink dries. Natural drying of the ink may require several hours, which results in wasted time before sheets can be run through the press for printing on the back of the sheets or for multicolor printing on the same side of the sheet. The spray powder is a direct result of an appreciable portion of the downtime of a printing press because powder adheres to the blanket cylinder which must be cleaned often. On long runs the powder is transferred into the ink train which must be cleaned. Powder is detrimental to the press and adjacent machinery as well as a health hazard.

Large gas-fired heating ovens are the most common type of antioffset device for use with web presses. Ovens are normally very inefiicient and expensive to purchase and install and require an excessive amount of space in the printing shop. Solvents are flashed off and dissipated into the air or must be vented through elaborate systems. After paper has been run through an oven, refrigerated rollers are employed to bring the paper and ink back to room temperature. The ovens, often operating at temperatures as high as 600 F., remove an undesirable amount of moisture from the paper which makes the paper brittle, unstable and causes cracking of the paper in folding and converting operations.

Many different ink compositions have been developed in an effort to provide quick-drying ink to compensate for these problems. varnishes, pigments, solvents, waxes, dyes and driers constitute the major elements of the various compositions of ink. Drying is accomplished primarily by the absorption of the solvents into the paper and the addition of dryers to the ink.

Heretofore attempts have been made to employ highfrequency electrical power to dry ink. However, no electronic dryer heretofore developed has had the capability of generating a useable electric field at a sufficiently high potential, and at optimum frequency, to effectively and economically dry ink in the time limits required in press operations. The long felt but unsolved need for efficient and economical drying apparatus has resulted in excessive printing costs for less than optimum quality.

This invention relates to an electronic dryer which has the capability of drying ink on a printed sheet or web. A high potential radiofrequency field, through which the paper is passed, causes slight dielectric heating of the paper. However, the temperature of the paper is not raised appreciably as it is passed adjacent the dryer and the moisture content of the paper is only slightly reduced.

It is believed that the outermost electrons of certain elements in molecules comprising the ink composition, while having high energy, are loosely bound to their nucleus and perhaps are being shared by other molecules because of their distance from the nucleus and also because of the shielding effect of the innermost electrons. As wet ink is moved through high energy electromagnetic radiation, molecular redistribution of the components of the ink results. Detachment of some of the outermost electrons in the molecules comprising the ink is thought to result in a certain amount of electromagnetically induced ionization. This is believed to cause a molecular rearrangement producing molecular attachments of very high viscosity thereby setting the ink very quickly.

It should be appreciated that, while the detailed description of the preferred embodiment of the invention relates primarily to the drying of ink on paper, the invention has applications for treating materials other than paper and effectively acts upon liquids other than ink.

The term liquid receptive" as used herein means having an affinity for liquid such that liquid is attracted to the receptive material which causes atoms of the liquid to enter into or remain on the surface of the material. The term dry as used herein includes, not only, reduction in moisture, but also, changing from a soft wet state to a relatively solid state by subjectingliquid to electromagnetic energy to form a new internal molecular structure causing the liquid to set or cure. The drying apparatus described herein may be positioned at locations other than at the delivery station of a press. For example, positioning the dryer between printing stations in a multicolor press allows dry trapping wherein one color of ink is printed over another color.

The invention comprises spaced electrodes for producing a shaped, high potential field of radiofrequency electricity. The shape of the electrodes and the spacing therebetween controls the shape of the field.

A shield of dielectric material having a low dissipation factor and high breakdown voltage, such as Teflon (tetrafluoroethylene polymer,) or silicone rubber, is shaped and positioned to prevent ionization of the air in sufficient magnitude to form a conductive path, thus preventing arcing between the electrodes.

A static eliminator is incorporated into the device for removing staticelectric charges from the material being dried, which result from a number of contacts with dissimilar objects while moving through the press during the printing operation. The static charge is removed by passing the material through an alternating electromagnetic field, leaving the material substantially static charge free. This prevents subsequent arcing between the high potential electrodes and the material.

An object of the present invention is to provide a method and means of quickly drying ink while occupying a minimum amount of space, and without undesirable side effects, which result in downtime of the printing press, in high maintenance costs, substantial reduction in the moisture content of the paper, and reduction of printing quality.

A further object of the invention is to provide a drying device of simple inexpensive construction capable of producing a high potential electromagnetic field positioned so that paper may be moved therethrough without arcing between electrodes.

A further object of the invention is to provide a drying device of simple inexpensive construction capable of producing a high potential electromagneticfield positioned so that paper may be moved therethrough without arcing between electrodes.

A further object of the invention is to provide an electronic drying device having a static eliminator for removing static electricity from paper as it is passed adjacent thereto.

A still further object of the invention is to provide an electronic drying device which may be readily adapted to sheetfed or web-fed lithographic printing presses.

A still further object of the invention is to provide an electronic drying device which produces a high potential radiofrequency electromagnetic field providing high efficiency for drying ink with minimum input power.

A still further object of the invention is to provide an electronic drying device generating an electromagnetic field which is designed to prevent propogation of radio waves outside of the unit.

A still further object of the invention is to provide a method of drying ink comprising the elimination of static charges, and shaping and concentrating electromagnetic energy to efficiently operate primarily on the ink.

Other and further objects of the invention will become apparent from the following description and drawings annexed hereto.

Drawings of suitable embodiments of the invention are annexed hereto so that the invention may be better and more fully understood, in which:

FIG. 1 is a side elevational view of the delivery station of a sheet-fed printing press with the dryer embodying the present invention mounted therein;

FIG. 2 is a cross-sectional view taken substantially along line 2-2 of FIG. 1 and FIG. 3;

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 2;

FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 2;

FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 3;

FIG. 7 is a cross'sectional view taken along line 7-7 of FIG. 3;

FIG. 8 is a schematic wiring diagram of the electrical circuit;

FIG. 9 is an enlarged cross-sectional view taken along line 9-9 of FIG. 6;

FIG. 10 is an enlarged cross-sectional view of an electrode;

FIG. 11 is a fragmentary perspective view of an end portion and mounting of an electrode;

FIG. 12 is a fragmentary cross-sectional view taken along line 12-12 ofFIG. 9;

FIG. 13 is a cross-sectional view of a second embodiment of the dryer taken along line 13-13 of FIG. 14;

FIG. 14 is a cross-sectional view taken along line 14-14 of FIG. 13;

FIG. 15 is a cross-sectional view taken along line 15-15 of FIG. 14;

FIG. 16 is an enlarged cross-sectional view taken along line 16-16 of FIG. 13;

FIG. 17 is a schematic view of a modified form of the inventron;

FIG. 18 is a cross-sectional view taken along line 18-18 of FIG. 17;

FIG. 19 is a schematic view of another modified form of the invention;

FIG. 20 is a schematic view of another modified form of the invention;

FIG. 21 is a fragmentary schematic view of another modified form of the invention;

FIG. 22 is a sectional view showing the rear of an antenna employing circular radiating electrodes;

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIGS. l and 2 of the drawing, the numeral 1 generally designates a housing which contains the component parts of the oscillator section of a dryer including a radiating head or antenna 2 which comprises means for producing a shaped high-frequency, high potential electromagnetic field. Wet, liquid-receptive material, such as printed sheets of paper 4, are moved through the delivery station 12 by gripper bars 6, which are carried by an endless chain 8 on chain rails 10, mounted on the delivery station 12. Sheets 4 are transferred to the delivery station and deposited in a stack 16 after passing through one or more printing stations 14.

Chain rails 10 are grounded by a suitable conductor of highfrequency electricity 3a and the rails 10 are preferably constructed of a highly conductive material, such as brass, to maintain gripper bars 6 at substantially ground potential.

Electrical power, regulated through control station 22, is delivered to the inside of housing 1 through a conductor 18 connected to a conventional direct current power supply 20. Conductor 24 interconnects a conventional source of alternating current (not shown) and power supply 20. A suitable cooling system 26 may be used in conjunction with direct current power supply 20 and oscillator section 1 if it is deemed necessary to do so. An arc suppressor 21 (FIG. 8) is associated with the control station 22 as will be hereinafter more fully explained.

Control station 22 (FIG. 8) comprises suitable electrical components for adjusting the output of power supply 20. Station 22 has start and stop

switches

22a and 22b, plate voltage indicator 22c, plate current indicator 22d, grid current indicator 222, and control 22f connected to a potentiometer for regulating the output power of supply 20. Electrical conduit 22!: contains suitable conductors for connecting control station 22 to the power supply 20.

As best illustrated in FIGS. 3, 4 and 8, an electronic tube, such as triode 30, is mounted in an oscillator circuit 32 enclosed in housing 1. Triode 30 is a conventional electrical component well known to those having ordinary skill in the art. Suitable means, such as blower 30a, is provided for cool ing triode 30.

The cathode or filament 300 of triode tube 30 is connected through

conductors

31 and 33 to a transformer 34 which is connected through

conductors

36 and 37 to power supply (not shown).

FIG. 23 is a cross-sectional view taken along the line 23-23 of FIG. 22; 7

FIG. 24 is a cross-sectional view taken along the line 24-24 of FIG. 22;

FIG. 25 is an enlarged cross-sectional view of three electrodes of the antenna of FIG. 22;

FIG. 26 is a fragmentary perspective view of an end portion and mounting of a circular electrode;

FIG. 27 is a fragmentary cross-sectional view taken along line 27-27 ofFIG. 25;

FIG. 28 is a section of a portion of an electronic dryer taken along the line 28-28 of FIG. 29 where the liquid receptive material passes between opposing set of electrodes;

FIG. 28a is a sectional view taken along the line 28a28a of FIG. 29a showing a modification of the antenna of FIG. 28;

FIG. 29 is a sectional view taken along the line 29-29 of FIG. 28;

FIG. 29a is a sectional view taken along the line 29a-29a of FIG. 28; and

FIG. 30 is an enlarged cross-sectional view of a portion of the antenna of FIG. 29.

Numeral references are employed to designate like parts throughout the various figures of the drawing.

Plate terminal 30p of triode 30 is connected through conductor 38 to a variable capacitor 39 in series with a variable inductance 42 which is connected through conductor 40 to mounting bar 42 as will be hereinafter more fully explained.

The grid terminal 30g of triode 30 is connected through conductor 44 to variable capacitor 46 which in turn is connected through conductor 47 to coil 48. Coil 48 is connected through conductor 50 to conductor 38 at node 37, to capacitor 39 and conductor 40 to mounting bar 42.

The triode 30 and the interconnection to the capacitor 46 and the coil 48 comprise an oscillator circuit. This circuit oscillates at a frequency determined by the capacitor 46 and the coil 48 and may be adjusted by means of the capacitor. In operation with the antenna 2, the oscillator continues to operate at the predetermined frequency, since the antenna does not appreciably load the circuit. To minimize the load effect by the antenna, the capacitor 39 and the inductor 42 are adjusted for the material being passed through the electromagnetic field of the antenna.

It should be noted that

conductors

38, 40, 44, 47, and 50 are very short to minimize losses in the electrical circuit.

The remote control station 22 comprises a circuit for controlling the current and voltage to the oscillator circuit 32. Since this is considered to be a conventional circuit, further discussion thereof is not deemed necessary.

A conventional arc suppressor 21 is electrically connected to the oscillator circuit 32 to anticipate and prevent arcing between

electrodes

56 and 58. The are suppressor is a means to detect an increase in the power consumed at the antenna 2 of the dryer. As an arc begins to form between

electrodes

56 and 58, the suppressor 21 detects the formation of the arc and momentarily interrupts the power supplied to the oscillator circuit. The function of the arc suppressor is to prevent damage to the material being dried and to the electrodes.

In the embodiment of the invention illustrated in FIGS. 1-12, mounting

bars

42 and 52, 42a and 52a, and 42b and 52b have upper and lower ends attached through standofi insulators 54 to the top 1a and the bottom lb of housing 1. These mounting bars are disposed in spaced-apart relation with the mounting

bars

42, 42a and 42b connected to support electrodes 56 (see FIG. 4) while mounting

bars

52, 52a and 52b are connected to and support electrodes 58 (see FIG. 5). A plurality of electrodes 56 is provided with electrodes 58 being disposed therebetween in spaced-apart parallel relation thereto.

Tank coils 60a and 60b are connected across mounting bars 42a and 52a and

tank coils

60c and 60d, across mounting

bars

42b and 52b. These

coils

60a and 60b are axially aligned and magnetically coupled such that mutual inductance of each is additive. Two

coils

60a and 60b are employed in parallel to provide low inductance at high voltage.

Mounting bars 52, 52a and 52b, and consequently elec trodes 58, are grounded at 53g through a conductor 53a and choke coil 53.

While mounting

bars

42 and 52 are illustrated as being substantially straight conductive members, it should be appreciated that they may be curved such that

electrodes

56 and 58 would not lie in a common plane.

From the foregoing it will be apparent that

electrodes

56 and 58 constitute a capacitive element in the oscillator circuit 32 while

tank coils

60a, 60b, 60c and 60d constitute inductive elements. The discharge of the

capacitive electrodes

56 and 58 through the

inductive tank coils

60a,

60b

60c and 60d is oscillatory. As explained, since the plate terminal 30p of the triode 30 isconnected through capacitor 46 and the coil 48 to the grid terminal 30g, the circuit is a free-running oscillator. The configuration of the electrodes (hereinafter more fully described), the positioning of mounting bars and the particular manner of mounting the tuning coils all contribute to the provision of an extremely efficient head 2 and the Q or energy-storing effectiveness of the oscillator circuit 32 is quite high for an electronic drying apparatus. The Q of a circuit as illustrated herein ranges from about 700 to over 1,000. Since Q is an amplification factor in such a circuit, the high voltage rise at resonance increases the drying efficiency of the head 2.

The electromagnetic fields between

electrodes

56 and 58 provide energy for drying ink on the sheet or web of paper or other suitable material 4 as the material moves through the fields. Therefore, in one embodiment of the invention, the shape and intensity of the electromagnetic field is controlled, as will be explained.

The electric charge on a conductor is. distributed over the surface of the conductor and the magnetic field around a cylindrical current bearing wire is symmetrical about the wire with the strongest part of the field being near the wire. The electromagnetic field between cylindrical conductors is strongest at points along a line extending between the centers of the conductors. To efficiently cause the field to operate upon ink on a sheet or web, the material should be moved through the strongest part of the field.

Provision of an outwardly projecting surface on a conductor results in a concentration of the electric charge on the curved surface with a corresponding reduction in charge on the surfaces which are not sharply curved. Concentration of charge may rise to an extremely high value if the point is sufficiently sharp.

To this end,

electrodes

56 and 58 are somewhat crescent shaped to concentrate and direct the field outwardly between adjacent bars to allow maximum utilization of the strength of the field without moving gripper bars 6 between electrodes. FIG. 9 illustrates a pair of

conductors

56 and 58 mounted in spaced-apart relation.

Surfaces 57c and 57f (FIG. 10) are preferably symmetrical about axes A and A which intersect at an angle B which is less than I". The outwardly converging convex surfaces 572 and 57f cause electrical charge to move in symmetrically converging paths to the sharply curved points 57. The concave front surface 56" extends between and connects the radiating surfaces 57f.

Points 57 on the edges of substantially crescent-shaped conductor 56 and points 59 on electrode 58 have a radius of curvature r,, for example, of approximately 0.03l inches while the radius r, of the convex back portion 56' and 58' of the respective electrodes has a radius of approximately 0.21 inches. It should be noted that points 57 have surfaces which are more sharply curved than any other surfaces on the electrode 56. Separation between the centers of the bars varies with the strength of the applied field. It should be understood that the dimensions are merely illustrative and not intended to be limiting in nature. However, the specific ratio of r,:r provides good concentration of charge along points 57 and 59 and the symmetrical configuration and inclination of

points

57 and 59 is very efficient for directing the fields in a controlled direction.

It should thus be readily apparent that the crescent-shaped

electrodes

56 and 58 will direct the electromagnetic field outwardly allowing the sheet4 to be moved therethrough.

At high potentials, the air surrounding a conductor becomes partially ionized, resulting in brush or corona discharge which represents a leakage of energy. The corona discharge occurs when the potential gradient exceeds a certain value but is not sufficient to cause arcing.

As best illustrated in FIGS. 4, 5, 11 and I2, opposite ends of

electrodes

56 and 58 are bent or deflected to form

loops

56a and 56b and 58a and 58b with the inner ends of the the respective loops being secured to mounting

bars

42a, 42b, 52a and 52b, respectively, and

coils

60a, 60b, 60c, and 60d are mounted as hereinbefore described to minimize voltage built up on the ends of the electrodes. Loops in the end of

electrodes

56 and 58 reduce the energy which is radiated from the ends of the bars to minimize corona discharge and prevent arcing between the ends of the electrodes and between the electrodes and the sides of housing 1.

Referring to FIGS. 4, 5 and 11, it should be noted that each electrode 56 comprises a straight elongated conductive element 56d which has a curved, substantially U-shaped end portion 56a on one end thereof and a curved end portion 56b on the other end. Points or projections 57 constitute elongated conductive surfaces on the electrode 56 to shape or direct the electromagnetic field between adjacent electrodes.

The substantially crescent-shaped cross section of the straight portion of each electrode feathers out at the ends, as illustrated at 56c (FIG. l1), such that the curved end portions 560 and 56b are substantially circular in cross section. Therefore, the end sections 56a and 56b are of circular cross section to minimize the concentration of surface charge and curved in a substantially horizontal plane to minimize corona discharge at the ends of the electrodes.

The inner ends of curved portions 56a and 56b are connected to

straight portions

56c and 56f, respectively, which extend inwardly in substantially parallel spaced-apart relation to sections 56d.

Portions

56c and 56f join through curved segment 56g with outwardly directed terminal 56h which is adapted to be connected through mounting bars 42 to the oscillator 32.

Mounting bars 42, 42a, 42b, 52, 52a and 52b have sockets formed therein to receive outwardly directed

terminals

56h, 58h, respectively. The terminals on the electrodes are secured in the sockets by setscrews 56j and 58], as best illustrated in FIG. 12.

Electrodes 56 are secured to mounting bar 42 by feed terminals 56! which extend outwardly from a portion of each electrode 56 intermediate the curved end portions 56a and 56b thereof. Electrodes 58 are secured to mounting bar 52 by feed terminals 58!.

Positioning terminals 56t and 58: intermediate opposite ends of the electrodes provides more uniform loading over the area adjacent the antenna 2 thereby resulting in a more balanced electromagnetic field across the antenna at high frequencies than would be achieved if feed terminals were on the ends of the electrodes.

Electrodes

56 and 58 are of substantially identical construction. Referring to FIGS. 4 and 5, it should be apparent that portion 56e of each electrode 56 is shorter than portion 56f on the other end of the electrode while portion 58f of each electrode 58 is shorter than portion 58e. This allows spacing of mounting bars without providing electrodes of several different forms and dimensions.

The inner ends of the loops in electrodes 56 terminate adjacent mounting bars 42a and 52b.

The inner ends of

loops

58a and 58b are terminated adjacent to mounting

bars

52a and 52b.

To keep electrical losses low,

electrodes

56 and 58 and the feeder system must have good conductivity and the insulators 54 must have low dielectric loss and low surface leakage. The electrodes may be constructed of copper, aluminum, stainless steel, or other well-known electric conductive materials.

As hereinbefore pointed out, the loss in a given length of transmission line rises with increase in frequency. Therefore, feedlines between triode 30 and mounting bar 42 should be kept as short as possible.

The crescent-shaped electrodes may be constructed with sufficient cross sectional area to provide rigidity for the electrodes, thereby minimizing deflection along the length thereof. This further assures uniformity of the field along the length of the electrodes.

Air is usually a nonconductor of electricity. lts molecules are complete in themselves, and neutral, taking no observable part in electric actions so long as they remain neutral.

When an air molecule is exposed to a high potential electromagnetic field, conditions are created in which disturbances occur of sufficient violence to remove an occasional electron from one of the molecules. When this happens the electron usually attaches itself to a neutral molecule, thus making it into a negatively charged particle or a negative ion. The molecule which released the electron becomes a positive ion. Ions are thus charged molecules carrying with them a quantity of negative or positive charge which does not balance the charges of their nuclei.

A great number of ionized molecules can thus be created with the result that the air becomes a conductor and neutralizes the charges which were creating the electric field.

An electric are results from the sudden breakdown of the insulating strength of the air or other dielectric material separating two electrodes, due to the formation of ions by the intense electric field, accompanied by a rush of electricity through the ionized molecules. The arcing potential between charged bodies is a substantially linear function of the distance between the charged bodies, and for a given distance the arcing potential is a substantially linear function of the potential.

The use of crescent-shaped

electrodes

56 and 58 for directing and concentrating the electromagnetic field between the spaced electrodes sets up a voltage along

points

57 and 59, respectively, which may exceed the arcing potential of static air insulation therebetween. The substitution of other insulating materials for air increases the potential gradient which may be held between

points

57 and 59 on the spaced elec-' trodes.

The ratio of the capacitance with some material other than air between the plates of a capacitor, to the capacitance of the same capacitor with air insulation, is called the dielectric constant of that particular insulating material. When a high voltage is applied to conductors separated by a dielectric, a considerable force is exerted upon the electrons and nuclei of the dielectric. Since the dielectric is an insulator and the electrons do not become detached from their atoms, if the force is great enough the dielectric will break down, resulting in a puncture of the dielectric material which will char and permit current to flow. The breakdown voltage depends upon the com position and thickness of the dielectric material employed.

When conductors on opposite sides of a sheet of dielectric material are oppositely charged a mechanical strain is exerted upon the atoms of the dielectric material. The positively charged particles of the atoms are pulled toward the negatively charged conductor while the negative parts are pulled toward the positively charged conductor. During the extremely short time that the atoms of the dielectric material are being realigned or polarized, there is an apparent current flow of electricity due to the displacement of the charged particles, which is referred to as the displacement current. if the electric field is reversed, the displacement current occurs for an instant in the opposite direction.

The reorientation of molecules results in heating of the dielectric material by molecular friction, the heat being dissipated to the air adjacent thereto. The power loss due to the dielectric heating is the dielectric loss of the material.

Four primary criteria must be met by a dielectric to function effectively to prevent arcing between

electrodes

56 and 58. The dielectric material should have a reasonably high dielectric constant, a low dissipation factor, and a high breakdown voltage so that the material will provide good dielectric qualities over a wide range of operating frequencies and at high voltage. The dielectric material may be fonnable or moldable to provide a configuration similar to that illustrated in FIG. 9 of the drawing.

Since it is necessary that sheet 4, carried by a gripper bar, be moved through the electromagnetic field, it is desirable that the

electrodes

56 and 58 be positioned on the same side of the sheet to allow the gripper bar to pass adjacent thereto. As hereinbefore pointed out, it is desirable that the field between the electrodes be deflected outwardly to facilitate moving the sheet therethrough and the dielectric material must extend across the field between the electrodes without interfering with the movement of the sheet 4 through the field.

Experiments reveal that positioning a flat sheet of dielectric material across

points

57 and 59 of

electrodes

56 and 58, respectively, while it does increase the voltage differential which can be held between the electrodes without arcing, additional benefit can be obtained by using a shaped dielectric sheet. The flat sheet, alone, allows the formation of ionized air, which becomes a conductor, allowing an arc to form between the electrodes.

As best illustrated in FIG. 9 of the drawings, shield 70 in a preferred form comprises a sheet of dielectric material having portions draped and extending between

electrodes

56 and 58 forming a series of troughs 72 which are connected by

portions

76 and 78 which extend across points 57 of electrode 56 and across points 59 of electrode 58, respectively. Provision of trough portion 72 between

electrodes

56 and 58 increases the distance which ionized air must travel to form an arc, by

directing the ions rearvvardly around the trough portion 72. it should be noted that shield 70 extends across the electromagnetic field without interference with the movement of sheet 4 through the field and controls the distance and direction of travel of the ionized air before it is electrically connected to an oppositely charged substance. 7

Selection of a material fro construction of sheet 70, which has a low dissipation factor, is important to minimize dielectric heating of the material with resultant changes in molecular structure, and in some instances melting of the material. Use of material having a low dissipation factor also minimizes ionization of air from the displacement current in the dielectric material, thereby eliminating arcing and minimizing corona discharge.

Various materials may be employed for constructing shield 70. Teflon, a tetrafluoroethylene polymer, has outstanding chemical resistance, excellent electrical properties and good heat stability. Teflon is a thermoplastic which may be readily machined or formed and has a dielectric constant of approximately 2.1, a dissipation factor of less than 0.0002 at one megacycle and a puncture voltage of between 1,000 and 2,000

volts per mil (0.00l inch). Teflon is a noncombustible material and has no true melting point. However, it undergoes a solid-phase transition to a gel at 325 C. with a sharp decrease in strength; and at 400 C. it decomposes slowly to a gaseous monomer and some gaseous, fluoride derivatives.

Shield 70 may be constructed of materials other than Teflon which have a low dissipation factor, high puncture voltage and good formability. One such material is silicone rubber having a dielectric constant of approximately 3.1 and a dissipation factor of 0.0009 at one megacycle. Silicone rubber retains its elasticity at temperatures as high as 300 C. and is unaffected by ozone and corona. Silicone rubber is self-healing since it does not char if arcing occurs. However, silicone rubber is inferior to Teflon in one respect in that since it has a higher dissipation factor the dielectric heating of a silicone rubber shield results in power loss, reducing the efficiency of the dryer.

Housing 1 in which the oscillator circuit and the head 2 are mounted is constructed of brass, copper, aluminum or other materials which are good conductors of radiofrequency electricity. The region occupied by head 2 is completely enclosed by metal, forming an enclosure which is opaque to electromagnetic radiation, thus minimizing the propagation of radio waves into the atmosphere surrounding the housing 1.

Housing 1 is maintained at ground potential by connecting said housing through a conductor 3 connected to ground. Delivery station 12 of the printing press is also maintained at ground potential through grounded conductor 3. Metallic plate 120 of delivery station 12 extends transversely across the front of head 2 in spaced-apart relation therefrom and acts as a front for housing 1. Side frames 12b and 12c of delivery station 12 extend across the ends of

electrodes

56 and 58 in spaced-apart relation therefrom and close the ends of the space between plate 12a and the open front of housing 1. The edges 70e of shield 70 are secured to the housing 1 and are curved to wrap around the ends 56a and 56b of the electrodes as best illustrated in FIG. 4. The upper and lower edges 70f of the shield are secured to the top and bottom of the housing 1 as illustrated in FIG. 3.

Housing 1 has openings 1e, if in opposite ends thereof for circulation of air through the housing to cool tube 30. Screens 1s are disposed across the openings 1e and If to prevent the propagation of electromagnetic waves therethrough.

As best illustrated in FIGS. 3, 4, 6 and 7, means comprising a blower manifold 80 is provided for urging and holding the printed sheet 4 in the radiated field. Manifold 80 comprises vertically disposed spaced hollow tubular members 82 connected by horizontally disposed spaced hollow

tubular members

84 and 85. A suitable source of pressurized air, such as blower 86, is connected to conduit 88 and a suitable coupling 89 to the inside of the hollow tubular members. Passages 90 extend through the walls of

tubular members

82, 84 and 85 such that compressed air passing through conduit 88 into the hollow portion of the tubular members is directed through passages 90 onto the surface of sheet 4, thereby urging the sheet toward

electrodes

56 and 58 to maintain the sheet in the outwardly directed field between the electrodes. Manifold 80 is held in position by supports 92 secured to the side frames of the delivery station.

As the sheet 4 is moved through the printing press, static electricity is generated in the sheet. The amount of charge and the polarity of the charge depends upon many variables such as the type of paper, the type of ink, press speed, humidity and temperature. If sheet 4 carries a high static charge, as it is moved

adjacent electrodes

56 and 58, arcing will result from the sheet to the electrodes, causing severe damage to the sheet making it unuseable.

Means is provided for removing the static charge from sheet 4 before it is moved into close proximity of

electrodes

56 and 58 in head 2.

A suitable embodiment of a static eliminator 95 is illus trated in FIGS. 7 and 8 of the drawing. Conductors 96 are electrically connected through a conductor 98 to a source of either alternating or direct current electricity such as transformer 100. Transformer 100 is connected through conductor 98a to the frame of delivery station 12, which is maintained at ground potential through conductor 3. Conductor 96 extend through hollow portions of

tubular members

82, 84 and 85 such that air directed through .passages in said tubular members is slightly ionized as a result of corona and is effective to reduce the static charge in sheet 4 as it contacts the sheet.

A modified form of a static eliminator is illustrated in FIGS. 17 and 18 of the drawing.

Conductors

97 and 99 may have a cross section identical to that of the

electrodes

56 and 58 such that an outwardly directed electromagnetic field will exist therebetween when the electrodes are connected to

conductors

98 and 98a, which are connected to transformer 100 as hereinbefore explained. Oppositely charged

electrodes

97 and 99 produce an electric field therebetween, which is of lower frequency than that generated between

electrodes

56 and 58, to remove static charge from the sheet before the sheet is moved into the higher frequency field where drying is accomplished.

DESCRIPTION OF A SECOND EMBODIMENT A second embodiment of the arrangement of the electrodes is illustrated in FIGS. 13-16 of the drawing.

The first embodiment of the invention hereinbefore described and illustrated in FIGS. 1-12 of the drawing may be employed with a web press for drying ink on a web 104. However, since gripper bars are not employed for moving the web 104 through the press,

electrodes

156 and 158 in the modified form may be positioned on opposite sides of the web 104.

Electrodes 156 on one side of the web are connected to mounting bar 142 which in turn connected to the oscillator circuitthrough conductor 40 as hereinbefore explained with respect to the first embodiment. Electrodes 158 are positioned on the opposite side of the web 104 and are supported by mounting bar 152, which is connected through conductor 153a and choke coil 1.53 to ground.

Dielectric shields 170a and 17012 are employed to prevent ionization of the air which would result in arcing between

electrodes

156 and 158.

Tank coils a and 160b are connected to mounting

bars

142a and 152a while

tank coils

160a and 160d are connected to mounting bars 142b and l52b.

Electrodes

156 and 158 are slightly difierent configuration from

electrodes

56 and 58, hereinbefore described. The curved end portions 156a and 158u of

electrodes

156 and 158 do not extend inwardly toward the center of each electrode to facilitate attachment of

tank coils

160a, 160b, 1600 and 160d to mounting bars outwardly of the edges of the web 104.

The crescent-shaped cross section of the electrodes feather into a substantially circular cross section as shown at 1560 and 158c.

A third form of a static eliminator is illustrated in FIG. 14 wherein

electrodes

197 and 199 are positioned on opposite sides of the web 104 and to

conductors

98 and 98a as hereinbefore explained.

Housing 101 extends around radiating heads 102a and has slots 101s in opposite ends thereof through which the web 104 [v passes.

DESCRIPTION OF A THIRD EMBODIMENT As hereinbefore pointed out the primary function of shield 70 is to prevent completion of a circuit of ionized air which would result in arcing between

electrodes

56 and 58. Means other than a shield 70 may be employed to prevent ionization of the air in sufficient quantities to prevent arcing between the electrodes. In the embodiment of the invention illustrated in FIGS. 19 and 20 of the drawing, radiating head or antenna 202 comprises spaced

electrodes

256 and 258, positioned across the open side of housing 201. A blower 230a is mounted inside the housing 201 and draws air from the inside of the housing and exhausts air through an opening in the wall thereof.

If a sufficient quantity of air is drawn between the spaced

electrodes

256 and 258 arcing will not occur across the gap between the electrodes.

While air becomes ionized in the vicinity of each

electrode

256 and 258, it is immediately dispersed rearwardly toward blower 230a, preventing formation of an arc which would damage the sheet and electrodes.

A modified form of a third embodiment of the invention is illustrated in FIG. wherein blowers 230b and 2300 are disposed within housing 201 for drawing air from between electrodes 258' and 256' for use upon a web 204.

The form of the invention illustrated and described as the first and second embodiments employs

shields

70, 170a, 1701: to eliminate arcing as a result of ionization of air

adjacent electrodes

56 and 58 by increasing the distance which the ionized air must travel to form an arc. The third embodiment of the invention illustrated in FIGS. 19 and 20 prevents arcing by drawing ionized air from the vicinity of the electrodes by blower means.

Another modified form is illustrated in FIG. 21 wherein a shield 270 of dielectric material is positioned as hereinbefore described with relation to shields 70 and 170.

However, shield 270 has apertures 272 formed therein to form passages through which air may be circulated by blower of the type designated by numeral 230a in FIG. 19 of the drawing.

DESCRIPTION OF A FOURTH EMBODIMENT Referring to FIGS. 22-27, there is illustrated an embodiment of the invention wherein the antenna radiating the radiofrequency electromagnetic field comprises electrodes having a circular cross section. Previous embodiments of the invention have illustrated the electrodes as having a generally crescent-shaped cross section. The antenna of this embodiment includes electrodes 300 supported on mounting brackets 302 interspersed with electrodes 304 supported on mounting bracket 306. One of the mounting brackets 302 is connected to the oscillator circuit of FIG. 8 through the conductor 40 as hereinbefore explained with respect to an earlier embodiment. Mounting brackets 306 are coupled to ground through the choke coil 53. The complete antenna structure is supported in a housing 308 through standofi" insulators 310. Wet, liquidreceptive material, such as printed sheets of paper, are moved through an electromagnetic field radiating from the antenna by gripper bars 312 in a manner as explained previously. Interconnecting the mounting

brackets

302 and 306 are

inductors

314 and 316. Although the inductors are illustrated as onetum coils, sufficient inductance may be generated to form a tank circuit with the

electrodes

300 and 304 by a straight bar interconnecting the mounting brackets. Where required, the

inductors

314 and 316 may be water cooled.

Where required, a static eliminator 318 is positioned from the antenna to reduce the static charge on a material transv ported past the radiating antenna. This static eliminator comprises conductors in tubular members 320. A similar static eliminator has previously been described.

Referring particularly to FIGS. 25-27, there is shown in detail the cross section of the

electrodes

300 and 304 and the supports for mounting the mounting brackets. Electrodes 300 are attached to the mounting bracket 302 by standoff supports 322 secured to the mounting bracket by a setscrew 324.

Although not specifically illustrated in FIG. 22-27, a dielectric shield may be positioned around and between the

electrodes

300 and 304 to subdue arcing between the electrodes caused by ionization of the surrounding air. Also, as explained previously, the air surrounding the

electrodes

300 and 304 may be displaced by means of a blower. The blower continuously replaces the ionized air thereby minimizing the possibility of arcing between the electrodes.

FIFTH EMBODIMENT OF THE INVENTION Referring to FIGS. 28-30, there is shown an embodiment of the invention wherein electrodes having a circular cross section are mounted such that the liquid-receptive material passes between opposed electrode arrangements. The systems illustrated in FIGS. 28 and 28a both comprise this fifth embodiment with the electrodes of the system of FIG. 28 on opposite sides of the liquid-receptive maten'al displaced as illustrated in FIG. 29. In describing this fifth embodiment, reference numerals followed by a letter identify the system of FIG. 28a.

Electrodes 326 are supported on mounting brackets 328 which are in turn attached to a housing by means of standoff insulators 330. Electrodes 326 comprise the upper half of an antenna; the lower half of the antenna includes electrodes 332. The lower half electrodes 332 are supported on mounting brackets 334 which in turn are attached to the dryer housing through standofi insulators 336. As best illustrated in FIG. 29, the lower set of electrodes of the system of FIG. 28 are displaced from the upper half electrodes. The system of FIG. 28 a, as best illustrated in FIG. 29a, has the lower set ofelectrodes in line with the upper set of electrodes.

A tank circuit is formed with the upper set of electrodes 326 and the lower set of electrodes 332 by

inductors

338 and 340 connected to an upper mounting bar 328 and a lower mounting bar 334. As explained previously, the

inductors

338 and 340 may be a straight bar or a bar with a slight curvature, but need not be a coil.

Referring to FIG. 30, there is diagrammatically illustrated an electromagnetic field between the upper electrodes 326 and the lower electrodes 332 for the system of FIG. 28. As the liquid-receptive material 342 passes through the electromagnetic field, there will take place a drying action of the liquid carried by the material.

In the embodiment of FIGS. 28-30, the individual electrodes of the antenna may be mounted as illustrated in FIGS. 25-27. By interconnecting the electrodes at several points along their lengths, and in addition relatively close to the end terminations, a balanced electromagnetic field will be produced. To minimize arcing between the electrodes, a blower may be employed to continuously displace and carry away the ionized air as illustrated in FIG. 20.

While several embodiments of the invention, together with modifications thereof, have been described in detail herein and shown in the accompanying drawings, it will be evident that various other modifications are possible without departing from the scope of the invention.

What is claimed is: 1. In a system for drying a liquid on a liquid-receptive material, comprising:

an antenna positioned along the path of travel of the liquid receptive material, said antenna including a first plurality of spaced electrodes and a second plurality of spaced electrodes with individual electrodes of the second group disposed between adjacent electrodes of pairs of the first group in the spaced-apart parallel relation thereto,

inductance means connected across said first and second plurality of electrodes to form a tank circuit therewith,

generating means having a current output coupled to said antenna,

means for electrically interconnecting the spaced electrodes in groups to produce a substantially balanced electromagnetic field radiating from said antenna through the liquid receptive material, and

means for direct coupling the groups of spaced electrodes to said generating means in a free-running oscillator configuration.

2. In a system for drying a liquid on a liquid-receptive material as set forth in claim 1 including a capacitor in series with an inductance connected between said generating means and said antenna.

3. In a system for drying a liquid on a liquid-receptive material as set forth in claim 1 including means associated with said antenna to subdue arcing between the electrodes.

4. In a system for drying a liquid on a liquid-receptive material as set forth in claim 3 wherein said means to subdue arcing between electrodes includes a blower for directing ionized air away from said antenna.

5. In a system for drying a liquid on a liquid-receptive material as set forth in claim 3 wherein said means associated with said antenna for subduing arcing between electrodes comprises a dielectric shielding material surrounding the spaced electrodes.

6. In a system for drying a liquid on a liquid-receptive material as set forth in claim 1 wherein the spaced electrodes of said antenna have a circular cross section.

7. In a system for drying a liquid on a liquid-receptive material as set forth in claim 1 wherein the spaced electrodes of said antenna have a substantially crescent-shaped cross section.

8. In a system for drying a liquid on a liquid-receptive material as set forth in claim 1 including means for discharging static electric charge on the liquid-receptive material positioned along the path of travel thereof.

9. In a system for drying a liquid on a liquid-receptive material as set forth in claim 8 wherein said means associated with said antenna for subduing arcing between electrodes comprises:

a second plurality of spaced electrodes, and

generating means coupled to said electrodes producing a current output to generate an electromagnetic field through which the liquid-receptive material passes along the path of travel thereof.

10. In a system for drying a liquid on a liquid-receptive material, comprising:

a first plurality of electrodes in spaced-apart relation in an enclosing housing,

a second plurality of spaced electrodes with individual electrodes thereof disposed between adjacent electrodes of pairs of said first plurality of electrodes in spaced-apart parallel relation thereto,

generating means having a current output direct coupled to said plurality of electrodes in a free-running oscillator configuration to produce an electromagnetic field radiating therefrom to the liquid-receptive material,

dielectric shielding materials surrounding said electrodes to subdue arcing therebetween, and

means for moving the liquid-receptive material through the balanced electromagnetic field to effect a drying action of the liquid on the liquid-receptive material.

11. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein said means for moving the material through the balanced electromagnetic field includes gripper bars having opposite ends thereof movable along chain rails, and

grounded conductors extended along the chain rails to maintain said gripper bars at a ground potential.

12. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein the electrodes have a substantially crescent-shaped cross section.

13. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein said electrodes have a substantially circular cross section.

14. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein the dielectric shielding material has a low dissipation factor.

15. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein the dielectric shielding material has a high breakdown voltage.

I6. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein the dielectric shielding material is formed sheet of tetrafluoroethylene polymer extending across the front and between the sides of the electrodes in an undulatory path to provide troughs of shielding material between adjacent electrodes.

17. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein the electrodes are arranged to form first and second heads, the first head and second head being disposed on opposite sides of the liquidreceptive material.

18. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein the housing supporting said electrodes is maintained at a ground potential and constructed of an electrically conducted material.

19. In a system for drying a liquid on a liquid-receptive material as set forth in claim 17 including means for urging the liquid-receptive material into sliding contact with the dielectric shielding material.

20. In a system for drying ink on a ink-receptive material as the material moves through a printing press comprising:

a first plurality of shaped electrodes spaced along and mounted to a first supporting frame,

a second plurality of electrodes spaced along and mounted to a second supporting frame, said second plurality of electrodes having individual elements thereof disposed between adjacent electrodes pairs of said first plurality of electrodes in a spaced-apart parallel relation thereto,

first mounting means for supporting the first plurality of spaced electrodes on said first supporting frame,

second mounting means for supporting the second plurality of spaced electrodes on said second supporting frame,

inductance means electrically connected between said first plurality and said second plurality of electrodes to form a tank circuit therewith,

means for electrically connecting the first supporting frame to ground, and

generating means having a current output direct coupled to the second supporting frame to form a free-running oscillator with said tank circuit and for producing an electromagnetic field radiating from said electrodes through the ink-receptive material.

21. In a system for drying ink on ink-receptive material as set forth in claim 20 including a static eliminator positioned along the path of the material to discharge static charges on the ink-receptive material prior to the material moving through the electromagnetic field produced by said first and second plurality of electrodes.

22. In a system for drying ink on an ink-receptive material as set forth in claim 20 including means associated with the electrodes to prevent ionization of air between electrodes of sufficient magnitude to cause arcing therebetween.

23. In a system for drying ink on a ink-receptive material as set forth in claim 22 wherein said means associated with said electrodes to prevent ionization of air includes;:

a housing extending around the electrodes opposite the path of the moving material, and

a blower arranged to direct air through said housing such that ionization of air adjacent said electrodes is minimized to prevent arcing.

24. In a system for drying ink on an ink-receptive material as set forth in claim 20 wherein said electrodes have a substantially crescent-shaped cross section.

25. In a system for drying ink on an ink-receptive material as set forth in claim 24 wherein the said substantially crescentshaped cross section of the electrodes feathers into a substantially circular cross section at opposite ends of each electrode.

26. In a system for drying ink on an ink-receptive material as set forth in claim 20 including means mounted in spacedapart relation from the electrodes for directing the ink-receptive material into the balanced electromagnetic field.

27. In a system for drying ink on an ink-receptive material as set forth in claim 26 wherein the means for directing material into the balanced electromagnetic field is a perforated manifold, and

a source of pressurized air communicating with the manifold to direct air through the perforation against the material.

28. In a system for drying ink on an ink-receptive material as set forth in claim wherein the electrodes of said first and 5 second plurality are arranged to form first and second heads, the first head and second head being disposed on opposite sides of the ink-receptive material.

Claims

2. In a system for drying a liquid on a liquid-receptive material as set forth in claim 1 including a capacitor in series with an inductance connected between said generating means and said antenna.
3. In a system for drying a liquid on a liquid-receptive material as set forth in claim 1 including means associated with said antenna to subdue arcing between the electrodes.
4. In a system for drying a liquid on a liquid-receptive material as set forth in claim 3 wherein said means to subdue arcing between electrodes includes a blower for directing ionized air away from said antenna.
5. In a system for drying a liquid on a liquid-receptive material as set forth in claim 3 wherein said means associated with said antenna for subduing arcing between electrodes comprises a dielectric shielding material surrounding the spaced electrodes.
6. In a system for drying a liquid on a liquid-receptive material as set forth in claim 1 wherein the spaced electrodes of said antenna have a circular cross section.
7. In a system for drying a liquid on a liquid-receptive material as set forth in claim 1 wherein the spaced electrodes of said antenna have a substantially crescent-shaped cross section.
8. In a system for drying a liquid on a liquid-receptive material as set forth in claim 1 including means for discharging static electric charge on the liquid-receptive material positioned along the path of travel thereof.
9. In a system for drying a liquid on a liquid-receptive material as set forth in claim 8 wherein said means associated with said antenna for subduing arcing between electrodes comprises: a second plurality of spaced electrodes, and generating means coupled to said electrodes producing a current output to generate an electromagnetic field through which tHe liquid-receptive material passes along the path of travel thereof.
10. In a system for drying a liquid on a liquid-receptive material, comprising: a first plurality of electrodes in spaced-apart relation in an enclosing housing, a second plurality of spaced electrodes with individual electrodes thereof disposed between adjacent electrodes of pairs of said first plurality of electrodes in spaced-apart parallel relation thereto, inductance means connected across said first and second plurality of electrodes to form a tank circuit therewith, generating means having a current output direct coupled to said plurality of electrodes in a free-running oscillator configuration to produce an electromagnetic field radiating therefrom to the liquid-receptive material, dielectric shielding materials surrounding said electrodes to subdue arcing therebetween, and means for moving the liquid-receptive material through the balanced electromagnetic field to effect a drying action of the liquid on the liquid-receptive material.
11. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein said means for moving the material through the balanced electromagnetic field includes gripper bars having opposite ends thereof movable along chain rails, and grounded conductors extended along the chain rails to maintain said gripper bars at a ground potential.
12. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein the electrodes have a substantially crescent-shaped cross section.
13. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein said electrodes have a substantially circular cross section.
14. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein the dielectric shielding material has a low dissipation factor.
15. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein the dielectric shielding material has a high breakdown voltage.
16. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein the dielectric shielding material is formed sheet of tetrafluoroethylene polymer extending across the front and between the sides of the electrodes in an undulatory path to provide troughs of shielding material between adjacent electrodes.
17. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein the electrodes are arranged to form first and second heads, the first head and second head being disposed on opposite sides of the liquid-receptive material.
18. In a system for drying a liquid on a liquid-receptive material as set forth in claim 10 wherein the housing supporting said electrodes is maintained at a ground potential and constructed of an electrically conducted material.
19. In a system for drying a liquid on a liquid-receptive material as set forth in claim 17 including means for urging the liquid-receptive material into sliding contact with the dielectric shielding material.
20. In a system for drying ink on a ink-receptive material as the material moves through a printing press comprising: a first plurality of shaped electrodes spaced along and mounted to a first supporting frame, a second plurality of electrodes spaced along and mounted to a second supporting frame, said second plurality of electrodes having individual elements thereof disposed between adjacent electrodes pairs of said first plurality of electrodes in a spaced-apart parallel relation thereto, first mounting means for supporting the first plurality of spaced electrodes on said first supporting frame, second mounting means for supporting the second plurality of spaced electrodes on said second supporting frame, inductance means electrically connected between said first plurality and said second plurality of electrodes to form a tank circuit therewitH, means for electrically connecting the first supporting frame to ground, and generating means having a current output direct coupled to the second supporting frame to form a free-running oscillator with said tank circuit and for producing an electromagnetic field radiating from said electrodes through the ink-receptive material.
21. In a system for drying ink on ink-receptive material as set forth in claim 20 including a static eliminator positioned along the path of the material to discharge static charges on the ink-receptive material prior to the material moving through the electromagnetic field produced by said first and second plurality of electrodes.
22. In a system for drying ink on an ink-receptive material as set forth in claim 20 including means associated with the electrodes to prevent ionization of air between electrodes of sufficient magnitude to cause arcing therebetween.
23. In a system for drying ink on a ink-receptive material as set forth in claim 22 wherein said means associated with said electrodes to prevent ionization of air includes;: a housing extending around the electrodes opposite the path of the moving material, and a blower arranged to direct air through said housing such that ionization of air adjacent said electrodes is minimized to prevent arcing.
24. In a system for drying ink on an ink-receptive material as set forth in claim 20 wherein said electrodes have a substantially crescent-shaped cross section.
25. In a system for drying ink on an ink-receptive material as set forth in claim 24 wherein the said substantially crescent-shaped cross section of the electrodes feathers into a substantially circular cross section at opposite ends of each electrode.
26. In a system for drying ink on an ink-receptive material as set forth in claim 20 including means mounted in spaced-apart relation from the electrodes for directing the ink-receptive material into the balanced electromagnetic field.
27. In a system for drying ink on an ink-receptive material as set forth in claim 26 wherein the means for directing material into the balanced electromagnetic field is a perforated manifold, and a source of pressurized air communicating with the manifold to direct air through the perforation against the material.
28. In a system for drying ink on an ink-receptive material as set forth in claim 20 wherein the electrodes of said first and second plurality are arranged to form first and second heads, the first head and second head being disposed on opposite sides of the ink-receptive material.