US3689728A

US3689728A - Continuous production dielectric heating apparats

Info

Publication number: US3689728A
Application number: US173043A
Authority: US
Inventors: Aldo M Marini
Original assignee: WILLCOX AND GIBBS Inc
Current assignee: WILLCOX AND GIBBS Inc
Priority date: 1971-08-19
Filing date: 1971-08-19
Publication date: 1972-09-05
Anticipated expiration: 1989-09-05
Also published as: CA925572A

Abstract

A movable support, such as a cart or dolly moves along a continuous production line path, preferably in a closed loop. Each cart carries a pair of spaced essentially parallel plates, between which the structure to be heated dielectrically is to be placed. The plates are connected to a non-contacting electric RF energy coupler, such as a pair of spaced coils, between which another coil is movable, the other coil being connected over a movable arm to an RF generator. As the carts move along the path, the arm carrying the coil connected to the generator is engaged by a cart. Its coil matches with the coils carried by the cart, and is moved synchronously therewith for a predetermined period of time during which energy is transferred from the generator to the plates. To provide for uniform voltage distribution on the plates, tuning stubs or lines, preferably with a movable short circuit, are connected to the plates at suitable locations.

Description

Marini Sept. 5, 1972 [54] CONTINUOUS PRODUCTION DIELECTRIC HEATING APPARATS [72] Inventor: Aldo M. Marini, Woodbury, N.Y.

[73] Assignee: Willcox& Gibbs, Inc., New York,

22 Filed: Aug. 19,1971

21 Appl. No.: 173,043

[52] US. Cl. ..219/10.8l, 156/380, 219/1061, e 219/1069, 264/22 [51] Int. Cl. ..H05b 9/04 [58] Field of Search..2l9/l0.6l, 10.69, 10.73, 10.81; 264/22, 45; 156/272, 380

[56] References Cited UNITED STATES PATENTS 2,504,754 4/1950 Sweeny ..l56/272 x 2,548,093 4/1951 Blewitt ..219/10.69 3,475,522 10/1969 Garibiar et al ..219/l0.8l x

Primary Examiner-J. V. Truhe Assistant Examinerl-lugh D. Jaeger Attorney-Robert D. Flynn et a1.

[57] ABSTRACT A movable support, such as a cart or dolly moves along a continuous production line path, preferably in a closed loop. Each cart carries a pair of spaced essentially parallel plates, between which the structure to be heated dielectrically is to be placed. The plates are connected to a non-contacting electric RF energy coupler, such as a pair of spaced coils, between which another coil is movable, the other coil being connected over a movable arm to an RF generator. As the carts move along the path, the arm carrying the coil connected to the generator is engaged by a cart. lts coil matches with the coils carried by the cart, and is moved synchronously therewith for a predetermined period of time during which energy is transferred from the generator to the plates. To provide for uniform voltage distribution on the plates, tuning stubs or lines, preferably with a movable short circuit, are connected to the plates at suitable locations.

20 Claims, 8 Drawing Figures PATENTEDSEP 51912 SHEET '4 (IF 4 -WATER WETTING AGENT MEASURE QUANTITY FIG.8

CONTINUOUS PRODUCTION DIELECTRIC HEATING APPARATS RELATED APPLICATIONS METHOD OF MANUFACTURING LIGHT- WEIGHT BODIES OF EXPANDED, HEAT SE'I'TA- BLE RESINE, U.S. Ser. No. 173,044 filed Aug. 19,1971

FIELD OF THE INVENTION The present invention relates to a dielectric heating apparatus for use in continuous production of structures of expanded polystyrene, or similar material, for example pallets. During production of such structures, heat has to be generated internally thereof to cure and fuse the expanded polystyrene into a unitary body and to fuse the polystyrene to cover sheets or layers, if used.

Co-pending application U.S. Ser. No. 173,044 filed Aug. 19, 1971, entitled METHOD OF MANUFAC- TURING LIGHT-WEIGHT BODIES OF EXPANDED, HEAT-SETTABLE RESIN, assigned to the assignee of the present application, discloses a method of manufacturing such bodies, and particularly large-area, large-volume light-weight bodies which are structurally strong, capable of carrying substantial weight, and resistant to mechanical damage, and which can be shaped as desired by being molded in a suitable mold. The present invention is directed to an apparatus to efficiently and effectively carry out the method described in the foregoing application and to do so in one continuous production process, with a minimum of equipment and in which all major components of the equipment are practically continuously operating so that the utilization factor of the equipment is high. The disclosure of the aforementioned application is hereby incorporated by reference.

Conventional methods of molding expanded polystyrene, that is, polystyrene which has a gas occluded therein such as butane, pentane, propane, carbon dioxide, FREON or the like depended on molding the material between mold forms which were heated by applying steam, or other heat sources thereto. Apparatus to carry out such molding processes applied heat from the outside, that is, closest to the mold surface. This results in a smooth outer surface, which may be desired but the interior may remain rather loose and possibly incompletely fused. The resulting structures, while useful as packing material for fragile articles, coffee cups, or for heat insulating structures, have, however, low mechanical strength. To fuse large-area, large-volume bodies of heat-settable resin into one unitary whole requires apparatus capable of producing heat in the inside of the body itself, in spite of the fact that the material, itself, has excellent heat insulating properties.

It is an object of the present invention to provide an apparatus to dielectrically heat large-area structures internally.

' SUBJECT MATTER OF THE PRESENT INVENTION Briefly, movable supports are provided, for example in the form of carts or dollies, moving along a continuous production line path, preferably a closed loop. Each cart or dolly includes a pair of spaced, essentially parallel plates, adapted to have the structure to be heated located therebetween; if the structure is in loose form, such as expanded beads, a mold filled with the beads is placed between the plates. The plates are ener gized by high-frequency energy, as they move along the production path. In a preferred form, the plates are connected to halves of a coil, having a center gap; a coupling coil is placed in the center gap, the coupling coil being electrically connected to an RF generator, and mechanically supported to move along withthe cart or dolly as it moves along the production path for example by mechanically latching on the dolly. Thus,

power can be transferred from the RF generator to the plates on the cart to provide for heating of the material between the plates for a sufficient period of time for fusion of the body, for example for a sufficiently long period to transform moisture within plastic beads to steam, the heat from the steam fusing the beads into a unitary body. The heating effect over the extent of plates should be uniform, and thus uniform voltage distribution is required so that the energy transfer to the substance between the plates will be uniform. To provide for such uniform voltage distribution, the plates are tuned by connecting tuning stubs thereto which can be shorted by a suitable shorting stub.

Parallel to a portion of the production path of the carts is a loading and unloading path having a number of operating stations which operate in synchronism with movement of the carts along the production path. At the operating stations, molded articles are removed from the carts or the molds, if used), and the carts reloaded; if molds are used, the molds are lined, filled with plastic material for example in bead form, with a top cover sheet, and re-introduced between the plates. This apparatus, although independent of the production path, operates in synchronism therewith so that as carts are unloaded by removal of finished articles, empty carts are moved to the loading station for subsequent transport to the heating point at which RF energy can again be coupled to the plates of the moving loaded cart.

As an illustration of an article to be made, a detailed description will be given with respect to the manufacture of pallets.

The invention will be described by way of example with reference to the accompanying drawings, wherein:

FIG. 1 is a fragmentary perspective view of a pallet forming an article to be made by the apparatus of the present invention;

FIG. 2 is a highly schematic, diagrammatic top view of the production paths, and the general arrangement of the apparatus;

FIG. 3 is a fragmentary top view, partly schematic, of the apparatus;

FIG. 4 is a partly schematic circuit diagram of the apparatus;

FIG. 5 is an exploded perspective view of a press cart;

FIG. 6 is a side view of a press cart showing a modified coupling arrangement of RF energy;

FIG. 7 is a perspective partly schematic view of the removal, filling and loading stations forming part of the apparatus; and

FIG. 8 is a schematic view of the apparatus to place expanded polystyrene beads into a mold.

Referring now to the drawings and first to FIG. 1 which partly illustrates a pallet. The pallet comprises a top cover sheet 12, for example of adhesively coated, reinforced paper and bottom liner ll, likewise of reinforced paper, which may be similar to that of the top cover sheet. Facing surfaces of these sheets are adhered together by a thermoplastic adhesive. -A polystyrene fill 5, in expanded, fused form is retained between liner 1! and the top cover sheet 12. It is not necessary that the liner or the top cover sheet completely cover the expanded fused polystyrene; thus, polystyrene material may be exposed, as seen at 15. The edges of the top cover sheet and of the liner are fused together. The finished pallet will have a flat bearing portion 37 fromwhich load supporting projections 25 project downwardly, with spaces therebetween, for example for engagement by the tines of a fork lift truck.

The apparatus of the present invention provides a continuous production path. Movable supports in the form of dollies, carts, or conveyor units 35 are moved along a production path 49, in the direction of arrow 49', as seen at FIG. 2. The dollies or carts (FIGS. 5 and 6) run on a surface and are carried along by engagement of pins 51 in a chain 50, laid in a U channel along the track 49. Thecarts support a mold press which includes a pair of

parallel plates

41, 42. One of the plates, in FIG. 6 plate 42, is secured to the structure of dolly 35 for example by insulators 80 and ad jistable screw connections 81. The other plate, plate 41, is supported by an inflatable cushion 63, to which pressure fluid, such as compressed air can be applied over a connection nipple 64. A mold 30, (FIG. 7) lined with liner 11, filled with expanded wetted polystyrene pellets or beads, and covered with a top cover sheet 12 is inserted between

press plates

41, 42. To adjust for minor irregularities of the press plates, and to accept molds of different sizes,

plywood sheets

39, 40 are preferably placed between

press plates

41, 42 and the mold 30 proper, as best seen in FIG. 5. These plywood sheets may have a thickness of from one-fourth to 1% inches, and also can actas shims so different sizes of molds can be accommodated without having to re-set the structural attachment of the fixed plate 42, or the support for cushion 63 in the structure of cart 35.

The cart 35 is provided with non-contacting highfrequency energy couplers which project inwardly towards the center X of the loop path. In a preferred form, these couplers are coils 44 (FIGS. 2, 3, 4, 5); they may be capacitative plates 44' (FIG. 6). Mounted at the center X is a swingable arm 52 which carries a matching couplingelement, such as a coil 45, or plates 45 which engage in coupling relationship with the matching coupling members 44 (or 44', respectively) on the cart. The coupling 45 (or plates 45) are connected by a transmission line 46 to terminals 47 where the transmission line connects to a high-frequency generator 48 supplying high-frequency energy, for example in the range of about 27 MHz. A suitable voltage at the plates is about 20,000 V.

Assume that a loaded cart 35, that is, a cart into which a mold 30 has been placed is transported by chain 50 along path 49 (FIG. 2). The U-channel and leading and trailing pins 51 keep the carts on the given path. The cart will be moved through region A. Upon further transport, the cart will reach position B, FIGS.

2, 3. The portion of the path beyond region A is circular with a center point X.

Chain 50 is driven by a motor 65. Frame 52 is normally retained in rest position shown in chain-dotted lines in FIG. 3 by springs 52a and pneumatic checks (not shown). As the cart 35 is moved alongthe path 49, beyond region A to region B, the 'arm 52 will engage the cart 35 over an interengaging locking mechanism 67 and be moved in synchronism with the cart. Any suitable known releasable latch can be used for exam ple a spring-loaded ball, or a catch engaging a matching detent. Upon'engagement of arm 52 and thecart, and as the cart is moving through regions B and C (FIG. 2), the generator 48 is controlled to be energized and to transfer power by the

non-contacting coupling

44, 45 to the

plates

41, 42. When a terminal position D has been reached, for example after about one-fourth to 1 minute or so travel time, an unlatching controller, for example a cam or the like, placed in path 49, unlatches arm 52 so that it can swing back to the starting position for coupling with the coils of a next arriving cart. The return movement efiected by spring 52a and as indicated by arrow 52' (FIG. 3) can be much faster than forward movement synchronized with the speed of the cart is independent therefrom. Energization of the generator 48 and timingcircuits inconnection therewith is itself controlled by switches 58 placed along the track 49. Switches 58 cooperate with suitably arranged actuators on the carts 35; these switches, since they only sense the presence of the carts 35 can be of the contacting type, such as microswitches operated by projecting levers; or they can be non-contacting. Suitable devices are photoelectric sensors in which a light from a stationary switch 58 is projected on a mirror located on the dolly 35 and reflected on a photo cell, photo transistor or the like at switch 58; inductive couplings; capacitative couplings; and other sensing arrangements known in the art. Connection from the various switches 58 to the generator is schematically indicated by control line 68.

The path taken by the carts in region C need not be circular, so long as a path similar to that of coils 44 is followed by coil 45. Thus, the arm 52 may reciprocate, that is, move in a linear path parallel to a linear transport path of the carts 35.

Current from HF generator 48 is supplied to terminals 47, hence to transmission line 46 and over

coupling elements

45, 44 to the dolly 35 for predetermined periods of time, and at predetermined intensities, depending on the material to be fused, its aging, electrical conductivity, moisture content, size of the mold, and the like. High-frequency energy supplied to

plates

41, 42 causes heating of the moisture within the mold, thus raising the temperature internally thereof so that the moisture will turn to steam. This steam can escape through holes 38 (FIG. 8) formed in the mold, or between the still unfused sides of the top covering sheet 12 and liner 11. The amount of energy supplied can be controlled manually or automatically. FIG. 4 illustrates the electrical arrangement in which a controller controls both the power (current, at a given voltage, and time) of connection of HF generator 48, or of its coupling, as schematically indicated at 60, to the transmission line 46. An instrument, schematically illustrated as a watt meter :62 measures the total power that is the energy distribution over the-area of the.

plates

41, 42 should be as uniform a possible. To provide for such uniformity, tuning

stubs

55, 56, in the form of pipes connected to

plates

41, 42 are provided, connectable by movable short circuit stubs 57. MOre than one set of tuning

stubs

55, 56 may be connected to plates 41, 42 (FIG. 4,) to improve the-voltage distribution of the plates both laterally, as well as horizontally, with respect to the connection of the plates with the coupling element 44 (or 44 respectively). The tuning stubs extend at right angles to the plane of the plates. For ,ease of alignment of the coupling elements on the carts and on arm 52, a pair of spaced, interconnected coils 44 (FIG. 4) are preferred, with which a single loop turn 45, secured to the end of arm 52 can engage. The carts, and the

plates

41, 42 thereon are slightly bigger than the articles to be molded; to make industrial-type pallets, dimensions of about 3 to 4 feet square are suitable. The carts must be strong enough to counteract a compressive force, schematically indicated at C-C' (FIG. 5) and exerted by inflatable cushion 63; the size and weight of the carts, and industrial economyprecludes high-precision guidance of the dollied along the path and some allowance must therefore be made for misalignment between the

coils

44 and 45. Tuning the

individual plates

41, 42 of the dollies, individually, permits slight misalignment of the relatively engaging I-IF energy coupling elements while still providing for uniformity of the field across the plates. It has been found that tuning the plates, with the filled mold located therein to a frequency off, by about 1 MHz with respect to the frequency of the generator improves the voltage distribution and the plates are accordingly tuned to about 28 MHz.

After the applied power has reached a certain level, a timer forming part of controller '53 keeps the power on for about 5-60 seconds, at an average rate .of about 5-20 A times 20,000 V. For a full discussion of the parameters of the method to fuse expanded polystyrene, reference is made to the co-pending crossreferenced application entitled METHOD OF MANUFACTURING LIGHT-WEIGHT BODIES OF EXPANDED HEAT-SETTABLE RESIN, Ser. No. 173,044

Compressed air can be applied at connection 64 at any one of the stages A to C; in a preferred form, compressive force is applied at station A and maintained when the cart leaves the position B until the molded structure is sufficiently cool so that it will not expand further.

Position B, C and D are preferably enclosed within a shielded, protective enclosure 69 to prevent stray radiation. When power is transferred, an ordinary fluorescent light tube 76 unconnected, and suspended in the region of position C will light or glow, as an indicator, and as a safety warning. Compressive force is preferably applied to compressed air inlet 64 beyond the shielding enclosure, and beyond the point at which possible radiation hazards may exist.

The path F beyond section E, up to the ejection station G is selected to be long enough to permit plates 41 42 to cool and the resin to set. For pallets, the length is chosen to provide a running time of the carts 35 from section E to section G of about 6 to 10 minutes.

At the ejection station G, (FIG. 2) or before, air pressure is released from cushion 63, permitting the

plates

41, 42 to separate, for example under spring pressure or by gravity. A hydraulically operated pusher 70, controlled by one of the switches 58 upon sensing of presence of a cart 35 moves a plunger between the released plates to eject the mold 30 from between the plates and place it in a removal position H. The mold 30 (see FIGS. 7 and 8)'is formed with openings 38 therethrough so that the fused pallet can readily be removed by differential air pressure on the pallet. An overhead conveyor 71 (FIG. 2) operating in timed relation with the pusher and equipped with suction cups 6] is lowered on the top sheet 12 and suction is applied, which will lift the pallet out of mold 30, for removal to a suitable inspection, and storage position. If desired, compressed air is applied through openings 38. The conveyor 71 is preferably inclined upwardly to carry the finished article away and over other structures in the apparatus.

The mold 30 itself comprises a resin impregnated fiberglass body with a wooden support structure, capable of running on slides, or conveyor tracks 72 in a parallel, shunt path, to be re-filled and for subsequent re-loading in the same, or a different cart 35 at a loading station L.

After having been cleared of the finished pallet, the mold 30 is moved to a fill station 1 (FIGS. 2, 8), where expanded wetted polystyrene beads or pellets are introduced therein.

Referring to FIG. 8, polystyrene beads which have gas occluded therein, are introduced into a hopper 20 stored in a storage bin'20a, then expanded by the addition of steam at a steam injection device 21 and transported to a storage container 22, where they are stored upwardly from 2 hours, preferably about 5 to 40 hours. The expanded beads are' transported to a measuring station 18 where a measured amount of pellets are segregated and introduced to an injector 23, where a measured amount of water and wetting agent, mixed together in a mixer 24, are added thereto, and then conducted to a container 26 in which a stirrer 27 is placed. Container 26 hasfill guns 34 attached thereto, and includes a control element which permits the beads to flow through the fill therethrough, when a mold 30 is located therebeneath, transported, for example, by an air blast from compressed air tubes 34a. Empty mold 30, located at injection station I has the liner sheet 11 placed thereover which is, in this form, a flat sheet of reinforced paper having diagonal cuts formed therein. A forming plate 32 is lowered on the liner sheet, and resiliently loaded fingers 33, projecting therethrough, fold the liner 11 between the diagonal cuts into depression 31 formed in the mold. The liner 11 may also be pro-formed, or pre-folded. The bottom of the depression 31 of the mold has small holes 38 therein to permit air to enter from the bottom of the mold, the holes being small enough so beads cannot fall therethrough.

.A fill plate 29 with spacers 28 thereon, together with beneath a doctor blade 73 or the like, to remove excess peaks of beads. Excess beads are placed in a collection shoe l9 and reintroduced into distribution container 26. Top cover 12 is applied at station J (FIG. 2) and the lined filled and covered mold 30 is conveyed past an inspection station K to loading station L to be again introduced between the

open plates

41, 42 of a cart 35 being transported past the loading station I...

The movement of the molds 30 over the shunt path' from station G to station L is synchronzied with move- I ment of the carts 35. The time taken to unload the mold at station E, and line, fill, cover, and inspect the mold at stations I to K will match the travel time of a cart from station G to station L, or be a multiple thereof so that, when a loaded mold is ready for loading at station L, an empty cart will be present thereat.

I claim 1. Continuous production dielectric heating apparatus for structures of expanded resin comprising a movable support, means forming a continuous production line path, and means for moving said support along said continuous production line path;

a pair of spaced, essentially parallel plates on said support adapted to have the structure located therebetween;

an RF generator having an output coupling;

a non-contacting electric RF energy coupling means coupling the RF generator to said plates including a first non-contacting coupling element secured and connected to said plates and a transmission line having one end thereof coupled to the output coupling of the RF generator and having, at the other end, a movable terminal and a second noncontacting coupling element matching, and capable of electrically coupling for power transfer with said first non-contacting coupling element;

means moving said other end of the transmission line and said first coupling element into non-contacting RF energy transfer coupling engagement and moving said coupling means of the RF generator and of said spaced plates in synchronism, for a predetermined time period, during movement of said support along its production line path;

means energizing said RF generator during at least a portion of the time said coupling means are in energy-transmitting coupling relation; and

tuning means connected to each of said plates and tuning said plates for uniform voltage distribution over the area of said plates when the structure is located between said plates.

2. Apparatus according to claim 1, wherein said movable support means comprises a plurality of similar conveyor units travelling in a closed loop path having a portion comprising an essentially circular path, the transmission line 8 being pivoted at the center of the circular portion.

3. Apparatus according to claim 1, wherein said movable support means comprises a plurality of similar conveyor units travelling in a closed loop path;

each of said conveyor units comprising means holding said parallel plates in spaced relation to provide an intermediate space for insertion therebetween of a mold to contain material which is to be dielectrically heated to form the structure;

path

and means moving said plates towards each other, 7

under pressure.

4. Apparatus according to claim 1, wherein said noncontacting coupling means coupling said plates and said RF generator comprises interengaging coupling loops.

5. Apparatus according to claim 4, wherein one of said coupling loops comprises a plurality of groups of interconnected conductors forming one coupling element, said groups of conductors being spaced from each other by a gap;

and the other of said coupling loops comprises at least one loop portion forming the other coupling element and fitting within said gap to permit relative movement, as well as engagement and disengagement of coupling of said loops.

6. Apparatus according to claim 1, wherein said noncontacting coupling means coupling said plates and said RF generator together comprises interengaging plates to provide for capacitative coupling.

7. Apparatus according to claim 1, wherein said tuning means includes tuning stubs connected to said plates and a movable short circuit stub interconnecting the tuning stubs.

8. Apparatus according to claim 7, wherein said tuning stubs comprise at least one tuning stub array having conductors extending at right angles with respect to the plane of said plates.

9. Apparatus according to claim 1, including means shielding said RF generating means, said transmission line, and said movable support at least when said movable support is located such that the coupling means are in coupling engagement, to reduce stray radiation.

10. Apparatus according to claim 1, wherein the means moving said other end of the transmission line in synchronism with the first non-contacting coupling element comprises latching means engaging the movable support and the transmission line.

11. Apparatus according to claim 1, in combination with a mold element of low-dielectric loss material inserted between said plates, said mold element being lined with a liner having a thermoplastic adhesive coating, and filled with wetted expanded thermoplastic and for subsequent cooling of said material in said mold for a period of about 6-l0 minutes.

13. Apparatus according to claim 12, including an unloading and loading station along the closed loop, and located in advance of that portion of the path at which said coupling means can engage in coupling engagement;

said loading and unloading station including means cooperating with said movable plates to permit removal of said mold at the unloading station, insertion of a newly filled mold at the loading station and closing of said plates, towards each other and on the mold, under pressure.

14. Apparatus according to claim 13, wherein the loading and unloading station comprises means removing the mold from between the plates and exposing the finished structure for removal therefrom from the mold;

means forming a filling station for insertion of a liner into the mold and filling the mold with expanded polystyrene beads;

means forming a closing station for placing a top cover sheet over the filled, lined mold;

and means introducing said filled, lined, covered mold between said plates.

15. Apparatus according to claim 14, wherein the means removing the structure from the mold comprises differential air pressure means acting on the structure.

16. Apparatus according to claim 15, wherein the differential pressure means are vacuum cups;

first conveyor means are provided carrying the vacuum cups and lifting the structure from the mold and transporting said structure away from said loading-unloading station;

and second transport means are provided acting on the empty mold and guiding said emptymold, in sequence, in alignment with said filling station, said closing station and said means -to introduce said filled, lined mold between said plates.

17. Apparatus according to claim 1, including positioning switches located along the production line path and controlling the application of power from the RF generator to the energy coupling means.

18. Apparatus according to claim 11, wherein the production path along which the conveyor is movable is a continuous loop line;

and the path along which the mold is guided by said transport means comprises a shunt path extending for a fraction of the length of said loop line along said production line path.

19. Apparatus according to claim 1, including motor means moving said movable supports along said production line path at a predetermined speed;

the speed of the support, and the movement of the mold through said shunt path being synchronized for timed removal of the filled mold from the conveyor, lining the empty mold, filling the mold and covering of the mold, and reintroducing the mold into a conveyor moving along said path.

20. Apparatus according to claim 1, wherein the structures are pallets, having a load bearing surface portion and projecting portions;

and the movable support means comprises dollies having said plates mounted thereon, the plates being slightly larger than the surface portion of the p le and t e tuning means comprises tuning stubs connected to said plates, and a movable short circuit stub interconnecting the tuning stubs.

Claims

1. Continuous production dielectric heating apparatus for structures of expanded resin comprising a movable support, means forming a continuous production line path, and means for moving said support along said continuous production line path; a pair of spaced, essentially parallel plates on said support adapted to have the structure located therebetween; an RF generator having an output coupling; a non-contacting electric RF energy coupling means coupling the RF generator to said plates including a first non-contacting coupling element secured and connected to said plates and a transmission line having one end thereof coupled to the output coupling of the RF generator and having, at the other end, a movable terminal and a second non-contacting coupling element matching, and capable of electrically coupling for power transfer with said first non-contacting coupling element; means moving said other end of the transmission line and said first coupling element into non-contacting RF energy transfer coupling engagement and moving said coupLing means of the RF generator and of said spaced plates in synchronism, for a predetermined time period, during movement of said support along its production line path; means energizing said RF generator during at least a portion of the time said coupling means are in energy-transmitting coupling relation; and tuning means connected to each of said plates and tuning said plates for uniform voltage distribution over the area of said plates when the structure is located between said plates.

2. Apparatus according to claim 1, wherein said movable support means comprises a plurality of similar conveyor units travelling in a closed loop path having a portion comprising an essentially circular path, the transmission line being pivoted at the center of the circular path portion.

3. Apparatus according to claim 1, wherein said movable support means comprises a plurality of similar conveyor units travelling in a closed loop path; each of said conveyor units comprising means holding said parallel plates in spaced relation to provide an intermediate space for insertion therebetween of a mold to contain material which is to be dielectrically heated to form the structure; and means moving said plates towards each other, under pressure.

4. Apparatus according to claim 1, wherein said non-contacting coupling means coupling said plates and said RF generator comprises interengaging coupling loops.

5. Apparatus according to claim 4, wherein one of said coupling loops comprises a plurality of groups of interconnected conductors forming one coupling element, said groups of conductors being spaced from each other by a gap; and the other of said coupling loops comprises at least one loop portion forming the other coupling element and fitting within said gap to permit relative movement, as well as engagement and disengagement of coupling of said loops.

6. Apparatus according to claim 1, wherein said non-contacting coupling means coupling said plates and said RF generator together comprises interengaging plates to provide for capacitative coupling.

11. Apparatus according to claim 1, in combination with a mold element of low-dielectric loss material inserted between said plates, said mold element being lined with a liner having a thermoplastic adhesive coating, and filled with wetted expanded thermoplastic material.

12. Apparatus according to claim 11, wherein said movable support means comprises a plurality of similar conveyor units, and said production line path is a closed loop; and the speed of said conveyor units along said closed loop, with respect to the length of the path is adjusted to provide a time duration of approximately 8-60 seconds for interengagement of the elements of the coupling means to provide for heating, and setting of said thermoplastic material in said mold; and for subsequent cooling of said material in said mold for a period of about 6-10 minutes.

13. Apparatus according to claim 12, including an unloading and loading station along the closed loop, and located in advance of that portion of the path at which said Coupling means can engage in coupling engagement; said loading and unloading station including means cooperating with said movable plates to permit removal of said mold at the unloading station, insertion of a newly filled mold at the loading station and closing of said plates, towards each other and on the mold, under pressure.

14. Apparatus according to claim 13, wherein the loading and unloading station comprises means removing the mold from between the plates and exposing the finished structure for removal therefrom from the mold; means forming a filling station for insertion of a liner into the mold and filling the mold with expanded polystyrene beads; means forming a closing station for placing a top cover sheet over the filled, lined mold; and means introducing said filled, lined, covered mold between said plates.

16. Apparatus according to claim 15, wherein the differential pressure means are vacuum cups; first conveyor means are provided carrying the vacuum cups and lifting the structure from the mold and transporting said structure away from said loading-unloading station; and second transport means are provided acting on the empty mold and guiding said empty mold, in sequence, in alignment with said filling station, said closing station and said means to introduce said filled, lined mold between said plates.

18. Apparatus according to claim 11, wherein the production path along which the conveyor is movable is a continuous loop line; and the path along which the mold is guided by said transport means comprises a shunt path extending for a fraction of the length of said loop line along said production line path.

19. Apparatus according to claim 1, including motor means moving said movable supports along said production line path at a predetermined speed; the speed of the support, and the movement of the mold through said shunt path being synchronized for timed removal of the filled mold from the conveyor, lining the empty mold, filling the mold and covering of the mold, and reintroducing the mold into a conveyor moving along said path.

20. Apparatus according to claim 1, wherein the structures are pallets, having a load bearing surface portion and projecting portions; and the movable support means comprises dollies having said plates mounted thereon, the plates being slightly larger than the surface portion of the pallet; and the tuning means comprises tuning stubs connected to said plates, and a movable short circuit stub interconnecting the tuning stubs.