US2640141A - Apparatus for dielectric heating - Google Patents

Description

y 26, 1953 M. P. VORE ETAL 2,640,141

APPARATUS FOR DIELECTRIC HEATING Filed 001;. 12, 1948 2 Sheets-Sheet l Fig.l.

INVENTORS WITNESSES Milton P.Vore and rgbm E.Kirby.' fi :2 a xzagmw ATTORNEY May 26, 1953 M. P. VORE ETAL APPARATUS FOR DIELECTRIC HEATING Filed Oct. 12, 1948 2 SheetsSheet 2 Fig.2.

INVENTORS WITNESSES:

11 1 WWW Q 0' mm W .1 7 m P 2n n H A m x H Y. MM

Fig. 3 is a plan view of the preferred form of our novel dielectric-heating electrode shown in Figs. 1 and 2;

Figs. 4 and 5 are detailed sectional views on the lines IV-IV and V-V of Fig. 3; and

Figs. 6 and 7 are perspective views of two forms of bars used in building the preferred form of our dielectric-heating electrode, to which, however, we are not limited.

The embodiment shown in Fig. 1 comprises a pair of opposed generally horizontal electrodemeans which are indicated in their entireties by the reference numerals 2 and 4, respectively. These electrode-means are vertically spaced to provide a space therebetween which serves as a work-receiving passage. The electrode-means 4 comprises a horizontal metal plate 6 having turned ends 8. An endless conveyor 10 of insulating material has an upper run which rides on the plate 6. The conveyor is wrapped around drums 12, one of which may be driven by any suitable means to move the upper conveyor-run in an assumed direction shown by the arrow in Fig. 1, at the right. The conveyor carries suitable dielectric material l4 through the work-receiving passage between the electrode-means 2 and 4. The plate 6 and the conveyor I0 form a work-supporting means by means of which the material [4 is supported and carried through the apparatus in a linear travel-path. The material is of less height than the extent of the space between the electrode-means 2 and 4, so that an air-gap I5 is present between the top of the material l4 and the bottom of the electrodemeans 2.

The embodiment shown in Fig. 2 comprises generally horizontal opposed electrode-mean 2 and which are vertically spaced to provide a work-receiving passage therebetween. The electrode-means 20 comprises a work-supporting means in the form of metal rollers 22 which are rotated by any suitable means for conveying material 24 thereon through the work-passage in the assumed direction indicated by the arrow at the right of Fig. 2. The material 24 may be the and 32 may be made either of metal or of insulation, depending on whether the electrodemeans 2 is to be grounded or insulated from ground.

Secured to the lower ends of the support-arms and 32 are horizontal stub shafts 34 journalled in suitable fingers 36 which carry a metal frame 38. The frame 38 is part of the electrode-means 2. Accordingly, each point of the electrodemeans 2 can swing back or forth in a vertical plane paralleling the direction shown by the arrows in Figs. 1 and 2, in which the work travels. The parallelogram-like support of the electrodemeans 2 allows the electrode means to remain in a horizontal plane as it swings. Obviously, cables, wires, etc. will allow for an even greater freedom of swinging and other movement.

The electrode-means 2 also comprises a plurality of support-members dependently carried by the frame 38 and a plurality of electrodebars pivotally carried by the lower ends of the depending support-members 40 and subsequently described in greater detail.

The main purpose for showing the two em bodiments of Figs. 1 and 2 is to illustrate the adaptability of the upper electrode-means 2, which constitutes our novel dielectric-heating electrode, with different forms of lower electrode-means of which the electrode-means 4 and 20 serve as illustrations. Thus, for example, a conveyor, such as I0, can be made of metallic material and itselfprovide the lower electrode. The showing of the two modifications is also to illus trate the adaptability of the electrode-means 2 for use in different positions with respect to the travel-path of the material to be heat treated, that is, with respect to direction in which the material is moved by any suitable conveyor means. With such travel-path as a fixed reference, it is apparent that the electrode-means 2 is shown in Fig. l disposed at a right angle with respect to its showing in Fig. 2.

As is known to the art, in a system set up as shown, the electrode-means 2 is electrically in sulated from the electrode-means 4 of Fig. 1 and 20 of Fig. 2. Such relatively insulated relation between the respective pairs of electrode-means can be obtained in any suitable way. As an example, Fig. 1 shows the electrode-means 2 grounded. Consequently, the plate 6 of the electrode-means 4 of Fig. 1 should be insulated from ground, and the support-arms 30 and 32 can be of metal. As a second example, Fig. 2 shows the electrode-means 2 insulated from ground. Consequently, the electrode-means 20 can be separately grounded, as shown at 42, and the support-arms 30 and 32 can be insulated, or made of insulating material, or any other suitable expedient used. Obviously other combinations are possible, as for example the electrode-means 2 of Fig. 1 can be insulated from ground and the plate 6 of the electrode-means 4 grounded. Additionally, instead of a grounded circuit-path, a conductor can be substituted.

Assuming, as shown in Fig. 1, that the plate 6 is insulated, a high-frequency electric field is established between the plate and the electrodemeans 2 by electrically connecting power delivering conductors 44 and 46 to the plate 6 and electrode-means 2, respectively. The conductors 44 and 46 receive power, either directly or indirectly, from a high-frequency oscillation-generator 4B. The conductor 46 is shown, for convenience, as grounded at 49. For completing the electric circuit, the electrode-means 2 can be grounded either through the member which support it or through a separate grounding conductor connected through a terminal connector associated with the electrode-means in any suitable manner.

The physical construction of the electrodemeans 2 is more particularly shown in Figs. 3 through '7. The frame 38 of the electrode-means comprises support-bars in the form of two spaced, lengthwise channels 50 and 52 interconnected by a pair of outer channels 54 and 56 and an inner channel 58. The channels 54, 56 and 58 are provided with slots 60, 62 and 64, respectively, the slots extending lengthwise in the base 66 of the channels centrally between the leg 68 of the channels. Each slot receives a plurality of the support-members 40 which carry a plurality of electrode-bars. The electrode-bars :58 'cumprisenarrove stripswor:shapeszsuclnasmhown 6 andi'l. The electrode-beretFigsfi oomprises excomzpzutatively @short strip ml halving anoenter'zhole l2 and a pair of end holesi flk and aflfi whiclrai'e roversize- :or elongated. Q Y-The: othemelectnodeebar, @lshownl ini Fig; 7; comprises a zstiti i vlll sw-hich dis approximately twice as long as-theistrip lll. .fThe v strip? ill-sis vprovided::with I a oen-ter hole: 80; and over-size zor. elongated holes B2 anti- 1M atthe emis 1 or the :strip. The strip 'l8,-.,has"-further h0les186 1 ohm 88; respectively halt -way h-etween the' -v holes 8U' -flIld=-82, end-theholes 80 end ':84. Preferably, the v-electrode-loeus 'have rounded edges to: avoid sharp pohits, and theinoenter end end: holessare -counters-unl: on=thei1= under sides.

As 'shown' in' Fig'; 3;"- the electrode-bars or strips arranged to form a lazy-tong structure. To 'this end; i the strips e.re--arrenged' in- "two :levels emeteries-cross ea'ch otherp' The-*strips*inthei lower level comprise the long parallel *strips 18 end i diagonally opposite sh-ort strips *70. The strips in "the upper level cm'nprise longyparallel strips 18 and diagonally opposite strips 'lfi'. The

bottom surfaces of thestripsin eech levelprefer- 1 can be'moveclto oompressthe spring-l8?! so es-to ahly lie I insingle plane; withiir manuiaeturing end assembly tolerances which in most cases allow considerable leeway.

\ In the arrangement shown; each lower strip +18; rexcept 'the one ettheupper end of. the leizytong arrangement,"crosses three upper -strips *'-'-r-e' at intermediate points-along the length 'of the strip I8, and meets the ends of tWOstripsTB end pointsof the seinestrip'lt. Likewise, an

ripper strip 18 in effecterossesand meetshfive lower strips '78. Accordingly, exceptior'the ,out- --er1nost strips; strip it of the lower level of the lazy tong structure hasfive'junotioir points with th strips 18'"of'theupperlevel, and conversely afsimilar strip "1 8 "10f the upper level of the lazytong has five junction points with the lower strips '78. Three -"ofthe junction points forsuch strips are etthe channels 54-, -56 andSB, and'two are centrallybetweenthefchannels.

Eacnortheshort end-stripsJfi andfl) crosses ,bzir 7'18 01" 18' at a, point which is'centrallyba "twcenthe innerchannel 58 andgan outer'channel 54 or 56. Each oftheenwstrips 7,0 and I'll) has a" junction point at'iitsend whichis at -the channelfifi; and. a similar point etits end which iset a'channelfMor'SB.

The criss-crossed" arrangement of. the electrode-strips 10, 1,6", "68 andglfilis carried from the channels "54,156, anri'lia by a; plurality of pivot means comprising ;thes upportmembers 40. ,A

support-member "M1 is provided :at each junction point of the bar i8 and iti'that lies at afchennel 'd, 156 or .58. Similar support-members..,are used ateach junction point 'of the bars in and i0 and at the junction points of these bars H! and nrand a bar 18 or-"IB'. In'the preferred embodiment, the support-1nembers-are substantiellye'lilze and are constructed as shown in Fig. 4.

Referring in' particular tol'Fig. A, a support member"Ml-"comprises e-flathea d brass screw 90 having-an end that passes through the slot 64 "inthe chemnel tt. Thelower headend of the screw passes through aligned holes in the strips 711.8 and 758, withithe head of the screw-seating vinn-the; countersunk hole in the lower strip 7-8. ,r-srbrnss washer "is Zlies between the crossing elecatrodeebersr 1 A stop nut 29.4;presses a-isprin rwashrer- 96o qagainstltheqtop. of: thenpperistrip J8? .and

" the -screw '68 iree-lwpasses, pair of: stub aShEtftS 'l' 'si Z emi Mex-tending in opposite directions outdim 1 call contactiwith? the brass we shenhut freeenough xso that they oen twist -erounchthescrew 90.

whe screwullll carries a thrustunut 98- sli-ght1y shove. the stopvnut 1 a compression springl00 above the thrust nut;- em -lower roller meansi lfll' *ebo've the spring lfifl and "below the chennel 58, =ensippe1= ro1ler means Mil: shove I r the I channel, and locking nuts i136 e-nd itt.

Each of the roller meaJ-ns IiJE a-nd "i 34 comprises aplate support ll il having a hole'through which and flScarried rcspectivelywn the "stub shafts l-i'2-and-"i"hl; and suitable retaining '3118811'195501 tsnce of the electrootehars it, "lflQ ltenda'm ebovet-he-lower-electrorie meenst or "it; as the "case-may be;-oan be controlled. -Moreover;:., the

erent'j'unction'pointsof the bars can be inuelly'e justed so as to make the; surface of "the electrode strips as level as convenient-0r desired. After such adjustment;the-thrust nut-'98 determine the force: with which the roller means encl i'fifi presseeainst the bottom and topgof the channel To good el ctrical conduction ,between erchennel and the roller, means, smooth narrow "brezss strips eresecurecl to eachchannel 5 4,

tile-oats along-eschside of the slo'tsj therein, coextensivetherewith. 'il'le'strips l'lg may be "on the upper or-onthelower sidesjofrthecham riels or: on is 0th sides. In, the embodimentsshown, they ere o'hlyyon. the lower sides. The rollers H6 and l 18 "of the :lower roller means 192 ride through the rollers to, the screws'ffiil .land the 1ps'l0",19',l8 and'l'il. :At each of the junction pointsof the, electrode- :st 'ps, between'ithe'channel members, la wpivot "r241 provided for holdingiithe stripstoge'ther, and to. provide go'odgelectrieal,contact therebetween. .A preferred ,form of construction for such pivot means is shown more particularly inFigj. '5; It comprises awshort vbrassscrewJZ-E which seats in the ocountersunkoseatoof" a .lower electrode stripl .enci. passes lthrough the crossin strips;. being, held. by. estop nut 12%.. pressing against a spring washer i3fl. {I'o allowforgreater freedom, of movement .between.,,the crossing strips and for good electricaLcontect, therebetween, a brass, washeri (3210911 beprovided, gthere== between.

Fig. 3 shows the. l lazy-tong 4, arrangement ,of veleetrod.e.,b2n's slightly-i extended. Thev upper strips-T181 are allparallel and equally; spacedmavin dtheireends at theslotsin the outer. cha-nnels Mandffrfi. These stripsareoblique to thesecham .nels but. deviate only slightly from 2 perpendicu- 1a]: "thereto. The lower stri s r 181 obliquely i cross the. ,upper strips 18? and elso,,.have their end points atthei slotsiin the outer-channels Blend 56. ".The inneriuchannel 5,8 serVes as-a, further supporting .pointjfor each. strip. 1-" The intermediate Kpivot p0ints"I2G,he1p.t0 prevent sag inthe strips at the (junction points :between channels. l The-crossing strips provide .a, perforated electrode-means, having, splurality oftdiamondmshaped openings. {The openings tarerarrensed in rows with the Qnenings ,m a rowbeins staggered withzresp ct athepe ringstin. the. edj,acent-.;r.0w ,.=;,theastesser n rbein vtimes, the two-strips :18 land118'-t,-intoagood;.electrig ..,such that no strai ht-linemanibedrasvnzacrqssthe electrode-means without cutting across an opening. It is also to be noted that each opening provided by the criss-crossed strips has nonuniform lengths at different parts thereof, measured in parallel directions.

Preferably, a large number of strips are provided in order to produce the electrical effect of an electrode-means consisting of a solid metallic sheet. It is known that a perforated metallic sheet can provide the effect of a solid piece of metal for bounding an electric field if the openings in the structure are not too large. In a typical lazy-tong structure, such effect was obtained by using long aluminum strips of close to 60 inches in length, and short aluminum strips slightly more than half that long. The number of strips used correspond to the number shown in Fig. 3, in a frame having dimensions that were approximately 56 inches by 46 inches, the shorter dimensions being that in which the lazy-tong structure could be expanded and contracted. With the arrangement of the electrode-strips in the manner shown, with their flat faces facing the opposed electrode- means 4 or 20 and their narrow edges upstanding, the strips as a whole can be said to lie on the same level when they are spaced far enough from the opposed electrode- means 4 or 20 and they are sufficiently thin. In the specific embodiment described, the strips were 3% inch thick, and the work-receiving passage 1 to 3 inches high.

Obviously, by loosening the thrust nuts 98, the lazy-tong structure can readily be spread out or collapsed for increasing or decreasing the crisscrossed area encompassed by the structure. The nuts can then be retightened. Loosening the nuts I05 and I08 also permits the lazy-tong structure to be extended or contracted, but may require more caution in order not to change the vertical spacing between the electrode-means.

The holes 74, I6, 80, 82 and 84 in the electrodebars or strips are sufficiently oversize or elongated to allow the lazy-tong electrode-means 2 to be adjusted so as to occupy any desired portion of the area of the frame 38, from a maximum determined by the length of the slots 60, 62 and 64 to a minimum determined by the width of the strips. By adjusting the angle which the strips make with each other, and corresponding with the angle which each strip makes with the channel members of the frame, the effective area for the electrostatic field of the electrode-means 2 is correspondingly changed.

If the electrode-means 2 is arranged as shown in Fig. 1, the overall length of the electrostatic heating field can be changed in the direction of movement of the material I4. Such an arrangement is more likely to be used where the width of the material being heat treated remains fairly constant. If the electrode-means 2 is disposed as shown in Fig. 2, the overall width of the electrostatic heating field can be changed in a direction transverse to that in which the material 24 moves. Such an arrangement is more likely to be used where the width of the material being dielectrically heated will vary from time to time and it is desirable to adjust the electrode-means to a corresponding width. In this latter arrangement, should an arc strike from the material to one of the electrode-strips, it will ultimately reach an opening formed in the criss-cross arrangement of the strips. As the point of origin of the arc moves into the opening, the arc elongates and becomes extinguished. In the meantime, the spot of glue or other material which caused the arc to strike has .a chance to become burned out.- For such 76 arc-extinguishing operation, it is desirable to provide a minimum spacing between electrode-strips on the same level,'the spacing being such that an opening will always be encountered by an are moving with the material.

Oblique strips in a single layer only also provide an open space for elongating any are occurring in the air-gap I6.

If a more direct contact for an electrical circuit to the electrode-means 2 is desired, one or more of the electrode supporting-members 40 can be provided with a terminal connector I34, as shown in Fig. 4. The connector is held in place on a screw by a holding nut I36. The terminal connector I34 receives a conductor I38 which may be insulated or grounded so as to correspond to the conductor 46 of Fig. 1. In order to carry the electricity readilyfrom the connector to the various electrode-strips, the parts of the electrode supporting members 40 that may be called up to carry current are preferably made of brass, and for economy the channels of the frame 38, and the various electrode strips Ill, 10', 18 and 18 can be of aluminum.

There is a distinct advantage in providing a plurality of support-members 40 for carrying the criss-crossed strips. The relatively elongated screw 90 of each support-member allows for limited vertical adjustment of the levels of the strips 10, 10', 18 and 18, through raising or lowering the holding nuts I06 and I08. The nut 98 can be adjusted for a suitable compression of the spring I00.

A swinging support for the lazy-tong, such as provided for Fig. 2, and obviously also applicable to Fig. 1, also has a distinct advantage in case any material being dielectrically heated should buckle. The electrode-means 2 can swing when a piece of buckled board should hit it, a may sometimes occur in edge gluing where a plurality of elongated narrow veneers or boards are placed lengthwise on the conveyor means with their upright edges to be glued together. A safety switch such as I40 can stop the conveyor motor through a motor controlling relay I42, when the electrodemeans swings. The buckled boards can then be removed, or the electrode-means swing out of the way to permit the boards to pass.

While we have described our invention in fairly particular detail, it is obvious that these details are subject to wide variations and that many modifications can be made thereof.

We claim as our invention:

1. Dielectric heating apparatus, comprising, in combination, a pair of parallel, generally horizontal, relatively insulated electrode-means vertically spaced to form a work-receiving passage, the upper one of said electrode-means comprising a plurality of elongated obliquely crisscrossed strips having faces lying substantially in a plane, the strips being carried with said faces adapted to bound a high-frequency electric field, fastening means for securing said strips together, and conductor means for applying high-frequency power between said pair of electrode-means.

2. Dielectric heating apparatus adapted for the continuous gluing of veneers of wood, comprising, in combination, a lower work-supporting conveyor means compri ing a lower electrode-means, said conveyor means being adapted to move wood in a predetermined linear travel-path therealong, a plurality of metallic strips having narrow edges and flat faces, supporting means supporting said strips along the top of said travel-path with the strip-edges upstanding and the strip-faces lying in a-substantially flat surface paralleling "said said supporting means -oomprising adjustable *mech-anisnr for changing thespacing between said strips" lor raisinga-nd lowering "them,

and means for relativelyinsulating said lower "electrode-means and said strips.

3. Dielectric heating apparatus adapted for the continuous gluing of veneers 'of-wood comprising, in combination, a lower work-supporting conveyormeans comprising alower electrode-means "said conveyor means being adapted to move wood in a travel-path therealong; aflirame above said conveyor means, .said iramecornprising. a plurality of spaced elongated support-bars a plurality of metallic electrode-strips having flat surfaces, and pivot means associated with said supportbars and said electrode-strips, and carrying said electrode-strips from said support-bars in a lazy tong arrangement, with the flat surfaces of the strips facing said conveyor means.

4. An invention including that of claim 3 but further characterized by supporting means swingingly carrying said frame above said lower electrade-means.

5. Dielectric heating apparatus adapted for the continuous gluing of veneers of wood comprising, in combination, a lower work-supporting conveyor means comprising a lower electrode-means, said conveyor means being adapted to move wood in a travel-path. therealong, a frame above said conveyor means, said frame comprising a plurality of spaced elongated support-bars, each of said support-bars having a central elongated slot therein, a plurality of spaced pivot means ineluding pivots in each of said slots, said pivots being slidable in the slots, said pivot means including means for fixing said pivots in selected positions in said slots, a plurality of electrodcbars carried by said pivots in a lazy-tong ar-- rangement. said lower electrode-means and said electrode-bars being relatively insulated, and means comprising a terminal connection for the supply of high-frequency power to said electrode-- bars.

6. A dielectric-heating electrode comprising a supporting-bar, a plurality of strips, supportmeans for supporting said strips from said supporting bar with the strips in spaced parallel relation to each other but oblique to said supporting bar, said strips having faces directed in the same general direction and adapted to be the boundary of a highdrequency electric field, said support-means being adjustable to vary the spacing between said strips.

7. A dielectric-heating electrode comprising a plurality of obliquely criss-crossed strips electrically interconnected, said oriss-crossed strips being adjustable to vary the angle of oblique crossing of the strips and to vary the spacing between said strips, and a terminal on said dielectric-heating electrode.

8. A dielectric-heating electrode comprising a plurality of layers of spaced parallel metallic strips, the strips of each layer having faces adapted to bound an electric field and lying substantially in a plane, the strips of a first layer crossing the strips of a second layer, and clamping pivot means at the crossing points of said strips, said strips being electrically interconnected.

9. A dielectric-heating electrode comprising a plurality of layers of spaced parallel strips, the strips of each layer having laces adapted to 10 bound anflelectric" field and-lying substantially ina=plane, the strips of a-"first:layer crcssing the strips ofasecond layer,- andfastening-means securing the strips together, said "fastening means comprising loosenablesupport-members for changing theanglebetween crossing strips.

1 0. A dielectric'heatingelectrode comprising a framehaving a plurality of'parallel elongated spaced support-bars, a plurality of elongated electrode bars, support=members adjustably securinga firstenrl-of-each of said electrode-bars to a first of said support-bars. andthe opposite .end to a 4 secondof" said "support-bars; with the" electrode-bars remainingzparallel and'equally spaced with respect to each other inall of the adjusted .positionsthereof, said electrode-bars havingiaces lying substantially in a plane, and being oblique to said support-bars.

11. A. dielectric-heating electrode comprising a frame having a pair of outer support-bars and an inner support-bar therebetween, said supportbars being spaced and parallel on the same general level, a plurality of first electrode-bars extending from and between said outer supportbars, a plurality of second electrode-bars from and between said inner support-bar and said outer Support-bars, said electrode-bars being crossed, said. electrode-bars being in electrically linked relation.

12. A dielectric-heating electrode comprising a frame having a pair of outer support-bars and an inner support-bar therebetween, said supportbars being spaced and parallel on the same general level, said support-bars having slots along their lengths, pivot means adjustably positionable in said slots, and extending below said support-bars, said pivot means comprising roller means rollable on the support-bars, a plurality of metallic strips carried by said pivot means below said rollers with the strips in lazy-tong arrangement, certain of said strips extending from and between said outer support-bars, and means for passing electricity to said strips.

13. A dielectric-heating electrode comprising a frame having a pair of outer support-bars and an inner support-bar therebetween, said supportbars being spaced and parallel on the same general level, said support-bars having slots along their lengths, pivot means adjustably positionable in said slots, and extending below said supportbars, a plurality of metallic strips carried by said pivot means below said support-bars, said pivot means comprising electricity conducting members electrically roller connected to said strips, and comprising means for vertically adjusting said strips.

14. An adjustable dielectric-heating electrode comprising a supporting bar having an elongated slot, pivot means adjustably positionable in said slot, and extending below said supporting bar, said pivot means comprising roller means rollable on said supporting bar, a plurality of metallic strips carried by said pivot means in lazy-tong arrangement below said roller means, said supporting bar comprising a high-conductivity memher on which said roller means can roll.

15. An invention including that of claim 12 but further characterized by said pivot means comprising a plurality of vertical members carrymg said strips, and means for vertically adjustlinng said members with respect to said supporting 16. A dielectric heating-electrode comprising a plurality of spaced elongated obliquely crisscrossed electrode-bars arranged in a plurality of superimposed levels, conducting junction means at the crossing points of said bars, and supporting means movably supporting said bars for lim ited movement in a general direction maintaining the associated bars in their common level, the movement raising said levels.

17. An invention including that of claim 15 but characterized further by said bars being crisscrossed.

MILTON P. VORE. ROBERT E. KIRBY.

References Cited in the file of this patent UNITED STATES PATENTS Number Number Number Name Date Crandell June 30, 1942 Rouy Dec. 15, 1942 Walton et al. June 11, 1946 Grell et a1 Jan. 28, 1947 Brown Oct. 7, 1947 Graham et a1 Dec. 28, 1948 Nutt Dec. 20, 1949 Stanton et a1 Feb, 20, 1951 Wood Feb. 27, 1951 FOREIGN PATENTS Country Date Germany June 3, 1931 OTHER REFERENCES Modern Plastics, June 1944, page 118.

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