Dielectric apparatus for and method of treating traveling paper webs and the like

Abstract

Dielectric apparatus and method for treating traveling paper webs and the like utilizing a high-frequency generator with first and second capacitor plates, the first forming a part of a tank circuit of the generator. A series of generally parallel electrode rods is carried by the second plate and a series of grounded electrode rods are alternately interposed between the rods of the first name series. The first and second capacitor plates are relatively movable with the capacitor plates and the electrode rods being mounted on a vertically adjustable frame thereby to permit variable spacing of the electrodes from the web.

Parent Case Text

The present application is a continuation-in-part of my earlier application Ser. No. 385,130, filed July 27, 1964, now abandoned, and having the same title as the present application.

Description

The present invention relates generally to dielectric treating and more particularly, as indicated, to dielectric apparatus for and a method of heating traveling webs such as paper and the like for drying the same.

In the past webs of paper and the like were commonly heated and dried by passing the same over and in contact with steam heated cylinders, with the drying being effected through heat transfer to the paper web. Although drying by this method has been generally satisfactory, certain inherent operating limitations, such as, e.g., the maximum temperatures obtainable and the non-uniform heating of the web due to contact with only one side of the web, exist where steam is employed. More recently, dielectric heating has been employed to some extent for web heating and drying and offers significant advantages over the use of steam drying cylinders. More heat energy can be provided per square foot of the dielectric material through the use of dielectric heating apparatus as compared with steam, and the material can be more uniformly dried.

An object of the present invention is, accordingly, to provide improved dielectric apparatus for more effectively performing a web drying operation.

A more specific object of the invention is to provide an improved dielectric apparatus in which a series of horizontal electrode rods alternately electrically connected and grounded are provided for heating and thus drying the dielectric material traveling thereover.

Another object of the invention is to provide an improved dielectric apparatus adapted to accommodate webs of dielectric material traveling at relatively high speeds of travel over and adjustably spaced relative to the electrode array.

A further object of the invention is to provide an improved dielectric apparatus wherein the entire unit can be readily vertically adjusted to variably position the same relative to the paper or like webbing, and wherein the source of voltage for the electrically connected electrodes can be similarly vertically adjusted thereby to vary the voltage induced in the electrodes and thus the degree of heating and drying of the paper or other web.

These and other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawings:

FIG. 1 is a top plan view of the dielectric apparatus of the present invention;

FIG. 2 is a front elevational view of the apparatus with the generator for providing the current source being shown schematically;

FIG. 3 is an end elevational view of the apparatus;

FIG. 4 is a perspective, fragmentary view of the capacitor plate which forms part of the apparatus; FIG. 5 is a schematic view of the circuitry employed for applying a high-frequency electric field to the dielectric material;

FIG. 6 is a modified form of the invention, with the electrically connected electrodes in this form being mounted for vertical adjustment;

FIG. 7 is a schematic view similar to FIG. 5, showing the circuitry for the modified form of the invention illustrated in FIG. 6, and

FIG. 8 is a perspective, partially schematic view of a further modified form of the invention.

Referring now in more detail to the drawings, wherein like reference numerals are employed to designate like parts and initially to the form of the invention illustrated in FIGS. 1-5, the dielectric apparatus of the present invention comprises an integral frame construction generally indicated at 10 which includes a plurality of bottom frame members commonly designated 12, a plurality of vertically disposed side and end frame members commonly designated 14 and a plurality of top frame members commonly designated 16. The respective frame members are constructed and arranged to provide a rigid frame assembly.

The entire frame 10 is vertically adjustably supported at each corner thereof by means of helically threaded corner posts commonly designated 18, each of which is vertically fixed and rotatably mounted at its lower end in a base block 20 which firmly engages the surface upon which the apparatus is positioned. The bottom portion of frame 10 has rigidly mounted thereon a plurality of internally threaded sleeve assemblies 22 each of which is vertically aligned with and adapted to receive the associated corner post 18. It will thus be seen that rotation of the vertically fixed corner posts will effect lowering or raising of the entire frame 10 relative to the supporting surface.

Each of the corner posts 18 is provided with a beveled gear 24 spaced upwardly from the helically threaded portion thereof, the respective bevel gears 24 being adapted to be driven simultaneously for rotating each of the corner posts 18 in either direction. Thus, referring to FIG. 3, a pair of driven shafts commonly designated at 26 are provided, only one of which is visible in FIG. 3, relatively adjacent the lower portion of the frame, the shafts extending parallel to the direction of travel of the paper webbing P. Each of the shafts 26 is rotatably journaled in bearing blocks 28 rigidly mounted on the frame and is provided at opposite ends thereof with beveled gears commonly designated at 30, each of which is adapted to drivingly engage the beveled gears 24 of the corner posts 18. Each of the shafts 26 is provided with a third beveled gear 32 which is adapted to be engaged and driven by a beveled gear 34. As best shown in FIG. 2, the beveled gears 34 are mounted on a longitudinally extending shaft 36 rotatably mounted in bearing blocks commonly designated at 38 mounted on the frame 10. It will thus be seen that rotation of shaft 36 through the described gear arrangement will effect raising or lowering of the frame 10, depending upon the direction of rotation of the shaft 36 to move the top of the apparatus toward or away from the paper web P. The shaft 36 can be driven by any suitable power source (not shown) which forms no part of the present invention.

Rolls R are mounted at opposite ends of the frame for supporting and tensioning the web P, the rolls or the mountings therefor forming no part of the present invention.

Referring now to the electrode arrangement for heating and drying the web P, a plurality of spaced electrodes commonly designated at 40 extend longitudinally of the frame and are secured at opposite ends thereto relatively adjacent the longitudinal ends thereof. The spaced electrodes 40 are thus connected to ground through the frame structure. A capacitor plate 42 is rigidly mounted on the frame 10 relatively adjacent the top thereof, with the capacitor plate 42 being provided with a plurality of transversely spaced, longitudinally extending electrode rods commonly designated at 44. Referring to FIG. 4, each of the electrode rods 44 is laterally offset at each end thereof as indicated at 45 for vertically spacing the main portions of the electrode rods 44 from the plane of the capacitor plate 42. The vertical spacing of the electrode rods 44 is preferably such as to vertically align the same with the grounded electrodes 40 when the fixed capacitor plate 42 is mounted in position on the frame 10, as clearly seen in FIG. 3. It will thus be seen that each of the electrode rods 44 connected to the capacitor plate 42 is disposed between spaced grounded electrode rods 40 thereby to provide a series of alternately electrically connected and grounded electrode rods. The fixed capacitor plate 42, as will be understood, is insulated in the mounting thereof on the frame 10. The capacitor plates 42 and 46 and the electrodes 40 and 44 are preferably aluminum, with the latter being either tubular or solid. If desired, the electrodes can be coated with Teflon or similar material to minimize friction when the web P transverses the electrode rods in contact therewith.

The capacitor plate 42 is capacitively coupled to a movable capacitor plate 46 which is vertically adjustably mounted within the frame 10. As best shown in FIG. 2, one end of the movable capacitor plate 46 is connected to a flexible connector strap 48 the opposite end of which is connected to a tuning stub 50 of conventional construction. The tuned circuit comprising the tuning stub 50, the movable capacitor plate 46 and the electrodes 40 and 44 is excited by a generator unit G shown schematically in FIG. 2, with the preferred circuitry to be hereinafter described when particular reference is made to FIG. 5.

As above noted, the capacitor plate 46 is vertically adjustable within the frame 10, with the purpose of such adjustability being to vary the voltage induced in the fixed capacitor plate 42 and thus the electrodes 40 and 44 thereby correspondingly varying the strength of the electrical field between adjacent electrodes and the amount of heat generated within the dielectric material. Referring to FIG. 3, the movable capacitor plate 46 is supported relatively adjacent each corner thereof by supporting rods commonly designated at 52, the bottoms of which are mounted on transversely extending channel frame members commonly designated at 54. A pair of longitudinally extending channel frame members commonly designated at 56 extend between the channel frame members 54 and are secured thereto to provide a rigid, vertically movable frame for supporting the capacitor plate 46.

The ends of the transversely extending channel frame members 54 extend laterally toward the longitudinal side of the frame and terminate relatively adjacent thereto, with each end thereof being provided with a threaded sleeve 58 to threadedly receive a vertically fixed, rotatably mounted helical screw member 60. Each of the respective helical screws is journaled relatively adjacent the end thereof in bearing blocks 62 mounted on the side frame members 14.

Referring to FIG. 2, each of the helical screw members 60 is provided with a beveled gear 66 at the lower end thereof and each longitudinally aligned pair of gears 66 is adapted to be drivingly engaged by beveled gears 68 driven by longitudinally extending shaft 70. There is thus provided a pair of shafts 70 at opposite sides of the frame which are adapted to be simultaneously driven for raising or lowering the movable capacitor plate 46. The shafts 70 are journaled in longitudinally spaced bearing blocks commonly designated at 72 mounted on the bottom frame members 12.

The shafts 70 are simultaneously driven by means of a common drive shaft 76 the opposite ends of which are provided with beveled gears commonly designated at 78. Each beveled gear 78 is adapted to drivingly engage a third beveled gear 80 mounted rigidly to each of the shafts 70. The drive shaft 76 can be rotated in either direction by any suitable power source, not shown, whereby the capacitor plate 46 can be vertically adjusted relative to the fixed capacitor plate 42.

Referring now to the operation of the apparatus described, the frame 10 is initially vertically adjusted to obtain the desired spacing relative to the paper or like webbing P. For maximum heating the electrodes 40 and 44 will be in contact or nearly in contact with the paper web. The movable capacitor plate 46 is then vertically adjusted to obtain the desired spacing thereof from the fixed capacitor plate 42. The spacing of the electrodes from the web P and the plate 46 from the plate 42 will be dictated by the desired applied voltage, speed of travel of the paper or like webbing, the degree of moisture in the paper, the degree of drying required, etc. When the capacitor plate 46 has been vertically adjusted to the desired position, highfrequency voltage is delivered thereto from the generator unit to be presently described and voltage is thereby induced in the capacitor plate 42 and in the elctrodes 44 electrically connected thereto. By virtue of the difference in potential between the grounded electrodes 40 and the charged electrodes 44, an electrical field will be established between each charged electrode 44 and the adjacently disposed ground electrode 40, with the field being concentrated in the plane of the paper or like webbing P passing thereover, as indicated by dashed lines in FIG. 3. In this manner, through well-understood principles of dielectric heating, heat is created internally of the paper web thereby drying the same.

The degree of heat generated within the paper webbing and thus the degree of drying of the web can thus be simply and effectively regulated by the independent vertical adjustment of the entire frame 10 and/or the capacitor plate 46. The vertical settings for the frame 10 and the movable capacitor plate 46 can be readily determined to provide the optimum heating and thus drying of the web P. To obtain maximum heating, the capacitor plate 46 can be vertically raised to contact the capacitor plate 42 and the entire frame 10 vertically raised so that the electrodes contact the paper webbing P.

Referring to FIG. 5, there is schematically illustrated therein a preferred circuit for providing high voltage to the capacitor plates 42 and 46. A source of high voltage enters the circuit at 90 and passes through a radio frequency choke 92 one end of which is connected through a plate by-pass capacitor 94 to ground. The current passing the choke 92 passes both to the capacitor plate 46 through plate blocking capacitor 96, tuning stub 50 and connector 48 and to the cathode 98. From the cathode, current is directed through grid inductance 100 to radio frequency choke 102, grid bias resistor 104 and grid current meter 106 to ground. Current passing grid inductance 100 is also directed to ground through variable grid capacitor 108.

The tank circuit for the generator thus includes the vertically adjustable plate 46 and the capacitively coupled plate 42, with the former through such adjustment varying the potential gradient between the plates and thus the voltage gradient between adjacent electrodes. The tank circuit includes the capacitor plates 42 and 46 and the electrodes 40 and 44, as well as tuning stub 50, and the voltage across such tank circuit may be controlled by adjusting the connection to such stub (see FIG. 5). The tank circuit thus determines the operating frequency of the generator when employed in the manner shown and described.

It will be seen that the preferred circuit is quite simple and that, in conjunction with the adjustable apparatus, it provides a system wherein the current induced in the dielectric material can be quickly and readily regulated. The entire frame can be moved toward or away from the web of the dielectric material thereby to vary the current induced in the material and thus the degree of heating achieved. Or, the movable capacitor plate 46 can be vertically adjusted to vary the potential gradient between the capacitor plates. A still further alternative is to maintain the plates 42 and 46 and the frame 10 in their adjusted positions and vary the voltage delivered to the tank circuit of the generator. The applicator is thus highly flexible in its capabilities, since all four adjustments including the connections to the tuning stub or any combination thereof may be made as desired.

A self-contained generator may also alternatively be employed with the electrode arrangement shown and described, being coupled inductively or capacitively thereto, but it is much preferred that such electrode arrangement, including plates 42 and 46, comprise an integral part of the tank circuit of the generator as shown in FIG. 5, for example. The latter facilitates rapid tuning and adjustment to accommodate varying operating conditions, especially changes in the web material treated.

Referring to the form of the invention illustrated in FIGS. 6 and 7, the apparatus illustrated therein is generally similar to that previously described and, where appropriate, the same reference numerals have been employed. In this form, however, the electrically connected or hot electrodes 200 are mounted for vertical adjustment on electrode plate 201. The latter is mounted on and insulated from supporting posts commonly designated at 202. The posts 202 are in turn mounted on the channel members 56 which are vertically adjustable in the same manner as described above. The plate 201 is electrically connected to a flexible connector strap 201 as previously described, with the stop being electrically connected at the opposite end thereof to the tuning stub 50.

Referring to FIG. 7, which schematically illustrates the circuit for the FIG. 6 form of the invention, the circuit is the same as that illustrated in FIG. 5 with the exception that in the tank circuit of the generator, voltage is applied directly to the plate 201 and electrodes 200 carried thereby. Owing to the voltage gradient between the charged electrodes 200 and the grounded electrodes 40, an electrical field is developed which passes through the dielectric web material.

The amount of heat generated in the dielectric material in the FIG. 6 form of the invention can be regulated in several ways. The frame 10 can be vertically adjusted to vary the distance of both the electrodes 40 and 200 from the web P, and/or the voltage delivered to the tank circuit of the generator can be varied to vary the intensity of the electric field, in the same manner as described above. Or, the electrodes 200 can be vertically adjusted as described, and as shown in dashed lines in FIG. 6 to vary the voltage gradient between the same and the grounded electrodes 40 and, consequently, the intensity of the electrical field through which the web P passes.

It will be understood by those skilled in the art that means other than grounding the electrode rods 40 may be employed to provide the requisite voltage gradient. For example, the electrode rods 40 and 44 or 200 may both be energized at opposite polarity to provide the voltage gradient which develops the electrical field through which the dielectric material passes. The series of electrodes 40 and 44 or 200 are thus 180.degree. out of phase with each other. The electrode elements, and especially electrodes 44 or 200, may if desired be in the form of elongated plates welded edgewise to their supports, thereby increasing the rigidity of the structure.

As set forth above, one of the ways of regulating the voltage gradient between the energized and grounded electrodes in both the above-described forms of the invention is to vary the voltage delivered to the tank circuit of the generator. As a further alternative to the movable mounting of the hot electrodes themselves or the capacitor plate carrying the same, it is contemplated in accordance with the invention that purely electrical means may be employed to achieve the desired variation in heat generated in the dielectric material. By way of example but not limitation, one such means may be in the form of a variable vacuum capacitor by means of which variable voltage may be delivered to the hot electrodes, thereby varying the voltage gradient between the same and the ground electrodes.

Thus, referring to the form of the invention shown generally schematically in FIG. 8, the hot electrodes 300 are mounted on and extend between fixed frame members 301, only one of which is shown in FIG. 8, which are in turn mounted on and insulated from the machine frame. The members 301 are preferably mounted so as to position the electrodes 300 in the horizontal plane of the ground electrodes 302, shown in dashed lines in FIG. 8. A channel beam 303 extends between the members 301, with the beam mounting a downwardly depending bracket 304 to which is mounted a variable vacuum capacitor 305. The capacitor 305 is commercially available and of the type manufactured and sold, for example, by Jennings Radio Corp., San Jose, California, and may have a variable capacitance of from 100 micromicrofarads to 2000 micromicrofarads. A power driven rotary shaft 306 is operatively connected internally of the capacitor 305 to vary the capacitance of the unit. The capacitor 305 is electrically connected to the electrodes 300 and a supply line 307 electrically connects the capacitor to line 48 of the system circuit, which is essentially the same as the circuits illustrated in FIGS. 5 and 7.

It will thus be seen that the voltage to the hot electrodes 300 may be varied by controlled adjustment of the variable vacuum capacitor 305, thereby varying the voltage gradient between the hot and ground electrodes 300 and 302, respectively, and thus vary the heat created in the dielectric web material.

The new apparatus of this invention is suitable for treating a variety of dielectric materials in addition to the paper material indicated, and may be employed to heat and dry arrays of parallel traveling filaments or yarns, for example, as well as tapes and ribbons of laid or woven materials. A highfrequency generator is employed, ordinarily preferably in the radio frequency range, a frequency on the order of twelve million cycles per second being typical. The number of electrodes employed is a matter of choice, depending upon the requirements of each installation, with the respective electrode series preferably being 180.degree. out of phase with each other for greatest efficiency.

The results obtained through use of the disclosed apparatus have been highly satisfactory. The amount of paper web material dried in a given unit of time is substantially higher than previously, and the dielectric heating has essentially eliminated undesirable tracking and streaking so prevalent with prior art paper drying equipment.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

Claims

1. Apparatus for heating a traveling web of dielectric material comprising a grounded metal frame, means for vertically adjusting said frame, a source of radio frequency energy, a first capacitor plate mounted within said frame intermediate the top and bottom thereof, means independent of said first recited means for vertically adjusting said first capacitor plate relative to said frame, a second capacitor plate fixedly mounted on said movable frame above said first plate, a first series of horizontal electrode rods carried by said second capacitor plate above the latter and in electrical connection therewith, and a second series of parallel electrode rods interposed between and alternating with said first series of electrode rods but carried by and grounded to said frame, whereby when said web of dielectric material is caused to travel closely above said electrodes in a direction transversely of the latter and radio frequency current is applied to said movable capacitor plate, a voltage gradient and current flow will be established in the material in the regions between successive electrodes to heat such material.

2. The combination of claim 1, further including a flexible electrical conductor electrically connected between said first capacitor plate and said source of radio frequency electrical energy, said flexible electrical conductor permitting vertical adjustment of said hot plate relative to said frame.

3. Apparatus for heating a traveling web of dielectric material comprising a grounded metal frame, a first capacitor plate fixedly mounted on said frame, a first series of horizontal electrode rods disposed transversely to the direction of travel of said web and carried by said first capacitor plate above the latter and in electrical connection therewith, a second series of electrode rods interposed between and parallel to said first series of electrode rods and lying in the same horizontal plane, said second series of electrode rods being grounded to said frame, means for vertically adjusting said frame and thus said electrode rods to variably position the same relative to said traveling web, a second capacitor plate mounted on said movable frame below said first capacitor plate, said second capacitor plate being connected to a source of high frequency electrical energy, means for vertically adjusting said second capacitor plate relative to said first capacitor plate thereby to vary the current in said first capacitor plate and in said electrode rods.

4. The combination of claim 3 further including flexible electrically conductive strap means interconnecting said electrical energy source and said second capacitor plate thereby to permit relative vertical movement of the latter relative to said frame.

5. Apparatus for heating a traveling web of dielectric material comprising a grounded metal frame, a first capacitor plate fixedly mounted on said frame, a first series of horizontal electrode rods supported by and electrically connected to said first capacitor plate, a second series of horizontal electrode rods carried by and grounded to said frame, said second series of rods being interposed between the rods of said first series, a radio frequency generator, a second capacitor plate mounted within said frame and electrically connected to said generator, said first and second capacitor plates forming part of the tank circuit of said generator, and means for vertically adjusting said second capacitor plate relative to said first capacitor plate thereby to vary the current in said first capacitor plate and thus in said electrode rods.

6. Apparatus for treating a traveling web of dielectric material comprising a grounded metal frame, a first series of electrode rods fixedly mounted on and grounded to said frame, an electrode plate carrying a second series of electrode rods interposed between the rods of said first series, a radio frequency generator, said electrode plate and rods carried thereby being electrically connected to and forming the tank circuit of said generator, means for vertically moving said plate and said electrodes carried thereby relative to said frame to vary the distance and thus the voltage gradient between the latter and the rods grounded to said frame, and means for vertically moving said frame for varying the distance of said grounded and electrically charged rods relative to said web of dielectric material thereby to vary the heat generated in the latter.

7. Apparatus for treating a traveling web of dielectric material comprising a frame, a first series of electrode rods, a second series of electrode rods interposed between the rods of said first series, means for maintaining said rods of said first and second series 180.degree. electrically out of phase with each other to establish a voltage gradient therebetween, means for vertically moving one of said series of electrode rods relative to the other of said series thereby to vary the voltage gradient between the adjacent rods, and means for vertically moving said frame for varying the distance of said grounded and electrically charged rods relative to said web of dielectric material thereby to vary the heat generated in the latter.

8. Apparatus for heating a traveling web of dielectric material comprising a grounded metal frame, means for vertically adjusting said frame, a source of high frequency energy, a first horizontal capacitor plate mounted on said frame, means for vertically adjusting said first capacitor plate relative to said frame, a second capacitor plate fixedly mounted on said frame above said first capacitor plate, a series of horizontal electrode rods carried by said second capacitor plate above the latter and in electrical connection therewith, and a series of parallel electrode rods interposed between and at a different electrical potential than said previously mentioned electrode rods carried by said frame, whereby when said web of dielectric material is caused to travel closely above said electrodes in a direction transversely of the latter and high frequency current is applied to said first capacitor plate, a voltage gradient and current flow will be established in the web in the regions between successive electrodes thereby to heat the web.

9. Apparatus for treating a traveling web of dielectric material, comprising a grounded metal frame, a first planar series of generally horizontal parallel electrode rods carried by and grounded to said frame, second frame means mounted on and insulated from said grounded metal frame, a second series of electrodes carried by said second frame means, individual electrodes of said second series being interposed between and parallel to electrodes of said first series, generator means for establishing a voltage gradient between adjacent charged and grounded electrodes for heating said web, said generator means comprising cathode tube means laterally and remotely spaced from said metal frame, an external tank circuit electrically connected to said cathode tube means, said external tank circuit including said first and second series of electrodes, a tuning stub for tuning said circuit, and a variable vacuum capacitor means mounted on said second frame means in series with said tuning stub and electrically connected to said second series of electrodes, and means for controllably adjusting said variable vacuum capacitor means to vary the voltage gradient between adjacent electrodes thereby varying the heat developed in the dielectric web material passing close by said electrodes.

10. The combination of claim 9 further including means for vertically moving said grounded metal frame to variably position said electrodes from said traveling web thereby to vary the heat generated therein.

11. Apparatus for heating a traveling web of dielectric material, comprising a grounded metal frame, a first plate supported in fixed relation to said frame, a first series of electrode rods supported by and electrically connected to said first plate, a second series of electrode rods supported by and electrically connected to said frame, the rods of said second series of rods being interposed between the rods of said first series, a second plate supported on said frame for adjustment relative to said first plate, said first and second plates forming a capacitor for coupling electrical energy from a source of radio frequency to said series of rods, and means for adjusting said second plate relative to said first plate, thereby to vary the electrical energy applied to said series of electrode rods.

12. A method of drying: comprising

a. providing a high frequency field from a series of spaced electrodes disposed in a predetermined pattern and plane;

b. exposing material to be dried to said high frequency field; and

c. providing relative movement between said field and said material while said material is exposed to said field.

13. The method of drying of claim 12 wherein the material to be dried is in sheet form.

14. A drying apparatus: comprising

a. a series of spaced electrodes;

b. energizing means for energizing said electrodes to provide a high frequency field;

c. support means adapted to position material for exposure to said high frequency electric field; and

d. means for providing relative movement between said high frequency electric field and the material when disposed therewithin.

15. The drying apparatus of claim 14 wherein the high frequency field is moved.