US2564675A - High-frequency power radiating and distributing means for antenna and heating systems - Google Patents

Description

Aug. 21, 1951 L. H. CROOK 2,564,675

HIGH-FREQUENCY POWER RADIATING AND DISTRIBUTING MEANS FOR ANTENNA AND HEATING SYSTEMS Original Filed June 29, 1942 4 Sheets-Sheet 1 2 512 017 ZZZ/75 E [$170k Aug. 21, 1951 L. H. CROOK HIGH-FREQUENCY POWER RADIATING AND DISTRIBUTING MEANS FOR ANTENNA AND HEATING SYSTEMS Original Filed June 29, 1942 4 Sheets-Sheet 2 1951 L. H. CROOK 2,564,675

HIGH-FREQUENCY POWER RADIATING AND DISTRIBUTING MEANS FOR ANTENNA AND HEATING SYSTEMS Original Filed June 29, 1942 4 Sheeqs-Sheet 5 12527231 Z0125 Hfzwafr Aug. 21, 1951 L. H. CROOK HIGH-FREQUENCY POWER RADIATING AND DISTRIBUTING MEANS FOR ANTEN NA AND HEATING SYSTEMS Original Filed June 29, 1942 4 Sheets-Sheet 4 ZZTZ'EZZYEZ" 2:27.075 H [rank system is not Patented Aug. 21, 1951 UNITED STATES PATENT OFFICE HIGH-FREQUENCY POWER RADIATING AND DISTRIBUTING MEANS FOR ANTENNA AND HEATING SYSTEMS LouisHi Crook, Washington, 1). 0. Application April il2, 1946, Serial N0. 661,Z86

and supplants my'copending application entitled fAntenna System,.filed.June 29, 1942,.Serial No.

448,947, now forfeited.

:At the outset, it should be :understood that where the term antenna is used'herein and-in :the appended claims, that term is to be construed iashaving a broad meaning including an electrode :of the character which might be used in a high frequency heating system, andthe termis not tobe construed as limited to its narrow meaning .of. an electrode or the equivalent .usedionly in radio communication.

One of the important objects of this invention is the provision of anantenna system available for use in diathermy or high frequency heating...

,With antenna systems as used for radio communication in .the past, especially as a transmitting system, it was well known that differences in soil, differences in ground contour,- proximity of conductive elements and other and'similar factors adversely affected the systemsand caused erratic field distribution. These formerlyknown systems also were not capable of directing short waves toashigh a degree of accuracy and. efiiciencyas is desirable.

Accordingly, the instant invention to provide an antenna system suitable for the efficient use of energy at very high frequencies in'radio communication, which more than negligiblyaffected by the proximity of conductive objects; or by;varia tions of earth contour.

Another object of the invention is the provision of an antenna system or a high frequency heating system in which the source, ofenergy for exciting a short wave antenna or electrode is housed within a shield which extends from the source to partially envelop the antenna or electrode to cooperate with the antenna or electrode as a wave guide.

.inwhich the. other. pole of the source is connected 20 Claims. (Cl. 219-47) it is also an important object of 2 to a shield for the source and brought to a zone immediately adjacent the antenna.

Electronic or high frequency heating is now recognized as a most useful and advantageous function in many industries. It provides localized heat for cookin surface hardening, annealing, brazing, bonding, drying, preheating, and softening operations as well as performing countless other and specialized functions. Its chief advantage resides in the tremendous rapidity with which an operation may be performed in comparison with prior methods, and in many cases the operations are not only performed faster, but better and more economically.

7 However, with high frequency heating arrangements of the character heretofore'known, the apparatus consisted mainly of electrodes in the form of two plates spaced one above the other, with the material to be heated forming the dielectric of such a flat plate condenser. With suchapparatus, the electric field embraced all surroundingobjects, which resulted in energy absorption and consequent waste of power, besides giving rise to great danger to operators and other persons coming in contact with or adjacent to such an electric condenser system. With these prior systems large and costly safety equipment was an essential, and even that safety equipment did not fully protect the operator. Doors to the rooms housing the equipment had automatic switches which shut off the high voltage power, whenever a door was opened. Such additional apparatus was objectionably expensive, to say nothing of its upkeep and the rooms required for its installation. Further, with these formerly known high frequency heating arrangements,

equipment acting upon the articles to be heated such asqconveyors, presses, etc., interfered with the energy field and absorbed some-of thatenergy. In addition, there was considerable danger at frequent intervals of flash-over occurring.

With the foregoing in mind, it is another important object of the instant invention to provide a high frequency heating arrangement that is substantially completely safe to operators and other persons in the vicinity of the apparatus.

, Another object of the invention is the provision of a high frequency heating arrangement producing intense electric fields by way of an enclosed or substantially ungrounded electric circuit which does notmaterially disturb nor it is materially disturbed by external fields created by other apparatus or any conductive material or persons coming in contact with the external shielding or electrodev of the apparatus, and thus, the ar 3 rangement eliminates the need for the costly safety equipment essential on devices heretofore known.

Another object of the instantinvention is the provision of a high frequency heating system in which the electrodes are arranged one within the other, the outer electrode being the casing of the heating unit or oven itself, and the entire energy field being confined to the space between the electrodes or the space inside the outer electrode, thus producing an electric field of greater intensity which confined wholly within the outer electrode, resulting not only in more economical operation, but in safety of a high order to the operators and other persons coming within close range of the apparatus.

Also a feature of the instant invention is the provision of a high frequency heating or antenna system in which the operative structure is so arranged as to allow full control of the energy field at all times.

A further object of the invention is the provision of a high frequency heating system in which the work objects or articles to be heated do not adversely affect the energy field.

Another feature of the invention resides in the provision of a high frequency heating assembly so arranged that equipment acting upon the work articles, such as conveyors, presses, and the like, even of massive size, do not for all practical purposes, adversely influence the energy field.

The present invention also provides high frequency heatin apparatus of the character that may be predes-igned by engineers in various shapes and sizes for special work to be done and provides the particular required types and strengths of field for the particular job.

It is also a feature of this invention to provide a high frequency heating system in which one of the electrodes serves as the oven or casing and the work articles are, enclosed thereby.

Still another object of the instant invention is the provision of a high frequency heating or antenna system in which the electrodes and power supply are all part of an enclosed electric circuit.

It is well known that the use of electronic or high frequency heating devices in industry is steadily increasing, and the power requirements and size of the devices are also steadily increasing. Such heating devices of the character heretofore known adversely affect radio broadcasting by setting up disturbances. Consequently, as high frequency radio becomes more and more developed, there will undoubtedly be a considerable problem between the various radio broadcasting stations and the Various users of a high frequency heating device, if such heating devices of the character heretofore known are continued in use.

With this thought in mind, it is a very important object of the instant invention to provide a high frequency heating arrangement, not limited in respect to size or power requirements, which will not adversely afiect or interfere with radio broadcasting.

Briefly, the instant invention may be physically embodied in an antenna or an electronic heating apparatus consisting essentially of a continuous metal casing terminating in a hood-like or housing portion, which is the first electrode, with a second electrode or antenna member disposed therewithin, the energy source or energy transforming means also being disposed within the conductive casing, one terminal of the energy source of transforming means being connected to the second electrode or antenna member by conductive means insulated from the casing itself, and the other terminal of the energy source or transforming means being connected to the inside surface of the casing, which inside casing surface functions as the return conductor.

While some of the more salient features, characteristics and advantages of the instant invention have been above pointed out, others will become apparent from the following disclosures, taken in conjunction with the accompanying drawings, in which:

Figure 1 is a diagrammatic showing in the form of a vertical sectional view of an antenna system embodying principles of the instant invention;

Figure 2 is a diagrammatic showing in perspective, with parts in section, of a somewhat different shape of antenna and shield arrangement embodying principles of this invention;

Figure 3 is a fragmentary part sectional, part elevational view of the upper portion of the structure of Figure 2, taken transversely of the apparatus;

Figure 4 is a fragmentary, part sectional, part end elevational view of the present invention arranged in the form of a high frequency heating device, this view also being of a diagrammatic character;

Figure 5 is a fragmentary side elevational view, with parts in section, of the lower portion of the structure of Figure 4;

Figure 6 is a fragmentary part sectional, part end elevational view of a high frequency heating arrangement embodying principles of the instant invention, illustrating diagrammatically the use of a gasoline engine and generator set as a source of the power supply;

Figure 7 is a fragmentary side elevational view, with parts in section, of the lower portion of the structure of Figure 6;

Figure 8 is a diagrammatic side elevational view, with parts in section, of the instant invention arranged in the form of a cooking or baking oven, including conveying means for carrying the articles to be cooked through the oven;

Figure 9 is a fragmentary end elevational view of the structure of Figure 8;

Figure 10 is a fragmentary part vertical sectional, part elevational view, enlarged, of the oven of Figure 8;

Figure 11 is a fragmentary enlarged end elevational view of the structure of Figure 10;

Figure 12 is a diagrammatic fragmentary part sectional, part elevational view showing a still different arrangement of the instantinvention in the form of an oven or closed unit for heating and cooking various materials; I

Figure 13 is a fragmentary vertical sectional View taken substantially as indicated by the line XIII-XIII of Figure 12, looking in the direction of the arrows; V

Figure 14 is a fragmentary end elevational view of the structure of Figure 12;

Figure 15 is a view similar in character to Figure 12 but illustrating a slightly different disposition of the electrodes;

Figure 16 is a fragmentary vertical sectional view taken substantially as indicated by the line XVI-XVI of Figure 15; and

Figure 17 is a fragmentary end elevational View of the structure of Figure 15.

As shown on the drawings:

It will be appreciated that in all figures or ductive conduit 4, which,

' 9 of the antenna member or housing in effect forms ntatic'allyindicated at I "the metallic casing 2.

the" drawings, the various embodiments of the invention are" shown rather in diagrammatic form, in view of the fact that the invention is not centered primarily in specific details of construction, but more to the broad idea of the two cmay in certain instances function as a part of aradiant energy antenna system, and in other instances, may function as a part of a high frequency heating system, maintaining their gen- "erally related character throughout.

With reference to Figures 1, 2 and 3, there' is shown a two-pole or di-pole arrangement which is suitable for use in an antenna system for radiant energy transmitting purposes. In this arrangement, a source of high frequency energy is generally indicated by numeral I and this source of energy is contained within a metallic, casing 2 of good conductivity. One pole or terminal of the energy source I is connected by way of a conductor 3 to the inside of the casing" 2. Associated with this casing is a coninsofar as the electrical circuit is concerned, is an integral part of the casing. The conduit 4 terminates in a housing or hood portion 5 also of good conductivity, and which housing or hood functions as an electrode or pole in the system.

The other pole or terminal of the energy source I is connected through a conductor 5 to an antenna member or second electrode 1. The conductor 6 extends through the conduit 4, but is insulated therefrom in any suitable manner or by any suitable means. With this arrangement, the casing 2 together with the conduit 4 and hood portion 5 functions as a shield as well asa conductive part of the electrical system.

'In'the illustrated instance, the hood 5 is a. somewhat hemispherical or bowl-shaped concavo-convex electrode disposed substantially concentrically about the antenna member or electrode 1 which is also concavo-convex and substantially in the form of a hemispherical bowl. The forward portion of the hood or housing 5 is preferably reversely curved inwardly as inr dicated at 8 so that its terminal edge is in proximity to but in spaced relationship to the edge 1, so that the hood a shield around the antenna member. This arrangement provides a gap or space It between the confronting edges of the hood 5 and antenna 1, and the width of this gap is, of course, chosen with relation to the potential difference existing between the two electrodes to avoid undue loss of energy.

Likewise, the spacing between the conductor 6 and the conduit 4, the length and diameter "of the conduit, and the spacing, shapes, and

dimensions of the antenna member 1 and the "surrounding hood or shield 5 are suitably chosen with reference to the frequency employed.

The source of energy or transmitter diagrammay be any form of transmitter, oscillator, or other source of energy such as usually comprises batteries, or other 1 sources of current, and suitable electron tubes and associated element for the generation of high frequencies. It is to be understood, however, that the entire transmitter is to be encased within As will more fully appear the antenna system would result 'in' thelater herein, if that source of energy'is atransformer, in turn energized by some outside source, at least the secondary of that transformer must be encased within a conductive casing or housing such as the casing 2.

"From the foregoing that the main circuit ture -'of Figure 1 is a jects, such as transmission lines, lead covered cables in the soil, neighboring objects on the ground, in the ground, or above the ground, do not result in losses or erratic field distribution. In short, the soil or ground does not function as the other pole of this antenna system, whereas with the usual transmitting antenna the ground does so function. Nothing outside the shielding means affects more than negligibly the operation of the antenna system, and this feature is of considerable importance especially where it is desired to project sharply directed waves.

As stated above, the instant invention is not limited to any particular size or shape of electrodes, it only being desirable that the outer electrode effectively enclose the inner electrode. In Figures 2 and 3, I have illustrated anotherarrangement, highly desirable for radio communication purposes, to illustrate that the antenna member and its contiguous shield or outer electrode may be of any form suitable for the projection of radio waves along defined paths. In this instance, there is shown a source of energy generally indicated by numeral H completely housed within a conductive casing l2, with one terminal or pole of the energy source connected to the inside of the casing by a conductor [3. A conductive conduit Id extends from the housing 12 to-a trough-like concavo-convex elongated outer electrode or hood l5 provided with closed ends and having an opening it through which waves may be projected from a trough-like concavo-convex antenna member or electrode I1 disposed inside the hood l5 in substantially concentric relationship, but spaced from the hood. Obviously, the antenna member or electrode I! may be supported in any suitable manner, but is kept electrically insulated from the hood 15. This antenna member I? may be connected by a conductor [8 to the other pole or terminal of the energy source H. While the conductor l8 extends through the conduit [4, it is, of course, insulated by any suitable means from. the conduit.

In connection with the showings in both Figure 1, and in Figures 2 and 3, it will be under- "stood that receiving means may be substituted for the respective transmitters, and the antenna system thus used for receiving signals rather than sending them. In addition, the conduits 4 and I4 may be of flexible tubing, if so desired, so that they may be bent by an operator to position the terminal electrodes 5 and 1 or l5 and I! relatively to an afiiicted portion of the body of a person to direct the emitted waves to that portion'in the application of diathermy, or a similar treatment. The zone'of application of the e'i'n'itted energy may be controlled toa fine degree, since the device or system itself comprises a substantially closed circuit and is therefore practically independent of ground.

It will also be understood that either of the arrangements just above described may be utilized for high frequency heating of inanimate objects or materials by locating such objects or materials in proper proximity to the inner electrode 1' or H, as will more fully be apparent from disclosures hereinafter in connection with the other figuresof the drawings. In Figures 4 and 5, I have illustrated an arrangement or system highly desirable for high frequency heating of various objects. The system, however, incorporates the use of a pair of electrodes very similar in character and disposition to the electrodes above described in connection with Figures 1, 2 and 3, and the same general principles of operation govern.

In the instances of Figures 4 and 5, however, I have illustrated the use of a source of energy in the form of a transformer IS. The primary of this transformer may be connected in any well known manner to any suitable source of current supply in a customary grounded circuit arrangement. The secondary 2| of the transformer is completely covered or enclosed within a conductive metal casing 22 corresponding in general to the conductive casings 2 and I2 above described. One end of the secondary transformercoil is connected to the inside of the casing 22 by a conductor 23.

The particular type of transformer illustrated in Figure 4 is more fully set forth, described, and claimed especially as to its association with a completely enclosed or non-grounded circuit in my copending application entitled Electric Distribution' System, filed June 6, 1942, Serial No. 446,149 now Patent Number 2,533,920.

A conductive conduit 24 extends from the casing 22 to the casing 25 of a control element, and the other end of the secondary transformer coil is connected to the mechanism inside that control element by a conductor 26 extending through the conduit 2 but insulated therefrom. The con- .trol element transforms the electrical energy to any desired wattage and frequency that may be required for the particular high frequency heating purpose. Another conductive conduit 21 extends from the casing 25 of the control element to'a box-like outer electrode 28 which functions not only as an electrode, but defines and is the oven. It will be understood that there is complete circuit continuity among the casing 22, the conduit 24, th casing 25, the conduit 21, and the outer electrode or oven 28.

A conductor 30 extends from the apparatus inside the casing 25 through the conduit 21 from which it is insulated to an inner or second domeshaped electrode 3| disposed inside the outer electrode 28. As indicated at 29, the outer electrode has closed end walls covering the end space between itself and the inner electrode 3|, but those end walls are so shaped as to define a substantially arcuate opening 32 at each end of the oven through which material to be heated may be placed in position and removed.

From the showing in Figure 5, it will be noted that the inner electrode 3| is not of th same length-as the outer electrode, but theends of the inner electrode terminatewell short of the ends .of.the outer electrode so that this inner electrode is completely enclosed within th outer elec- .trode. .Inside-the closed ends 29-29 thereof, the

outer electrode is turned upwardly at its lower edge, and between that edge and the corresponding edge of the inner electrode a strip of insulation 33 is disposed on each side of the structure. These insulating strips stabilize the entire construction and effectively insulate the inner elec- It will at once the inner electrode 3| corretrode from the outer electrode. be apparent that sponds to the electrode 1 of Figure 1, and the outer electrode 28 corresponds to the electrode 5 of Figure l.

In Figures 4 and 5, which as stated above are somewhat diagrammatic showings, I have illustrated how two difierent items may be cooked or heat treated, although it will be understood that preferably only one such item is subjected to the field of the electrodes at a time.

In the first instance, I have shown a specimen '34 which may be considered a typical example of a section of a large wooden airplane body,.or wing surface, that has been glued together and is ready for cooking to facilitate the hardening and drying of the glue used. In this particular case, it is preferable to move the oven over the specimen being treated. To that end, it will b understood that the conduit 2? is flexible to enable the operator to move the cooking oven over the relatively large specimen under treatment. As indicated by the dotted lines 3% in Figure 4, there will be a uniform and intense electric cooking .field affecting the specimen 3d as the oven is moved thereover.

A hemispherical arrangement such as shown in Figure l, or the elongated form shown in Figure 2 which has closed ends, is also practical for such ovens as are adapted to be moved over the article to be heat treated or cooked, or in the case of diathermy, the patient to be treated. In all such forms, the operator is protected from the danger of high frequency, high voltage, etc., within the oven. Also, the material to be treated is fully protected from over-burning or over-treating. In the case of diathermy instruments, both the patient and the operator are protected from the dangerous short circuits or flash-overs that ,exist in present day instruments. In fact, the

treated articles are in the electric field of the apparatus and contact only the outer electrode.

To illustrate the use of the oven with the same held stationary and with the object or specimen moved through the oven from end to end thereof, I have selected a specimen 35 which may be plywood in which the laminations are to be effectively glued together by virtue of the developed heat. The electrodes 2-8 and BI are preferably shaped in order to produce a uniform and intense electric cooking held across the material 35 as it is passed in a lengthwise or axial direction through the field between these electrodes. As indicated by the dotted lines 36, a directional field intensity is provided which field is formed by the electric displacement currents of high frequency, in much the same manner as found in the commonly known dielectric of an electric condenser. The shaped electrodes 28 and 3| increase the overall efficiency in the space between them in comparison with the heretofore known flat plate electrodes used in high frequency heating arrangements.

By virtue of the fact that the entire electrical circuit including the two electrodes is a closed circuit, that circuit is not more than negligibly aifected by outside influences whether conductive or not. Likewise, the particular high frequency heating circuit does not materiall affect external adjacent circuits, nor will it create any material or noticeable interference with radio reception and broadcasting in the vicinity. The electronic field through the object being heated is fully controlled at all times by the operator and no expensive tuning equipment to prevent radio interference is necessary. No expensive and cumbersome safety equipment is necessary at all, and it is not necessary even to have switches to open the high voltage, high frequency circuit automatically when the door of the laboratory room containing the heating device is opened.

In Figures 6 and 7, I have illustrated another oven arrangement and in this instance I have shown how any form of the present invention maybe utilized with a gasoline engine-generator, set as a source of energy. In this instance, a gasoline engine is diagrammatically indicated at 3.1, which engine is coupled to drive anelectric generator encased within a conductive housing 38 and a conductive conduit 39 connects the casing 38 with a casing 4.: completely enclosing a transformer 4|. The primary 42 of this transformer is connectedito the inside of the adjacent casing by a conductor 43 at one end, and the other end of the primary is connected by a conductor 44, insulated from the conduit 39, to the generator in the casing 38. The generator is also connected to the inside of the casing 38. The secondary 25 of the transformer is connected at one end by a conductor 46 to the inside of the casing 46.. The other side of the secondary is connected through a conductor 4'! to the apparatus contained within a conductive control box housing .48 and a conductive tube 49 joins the housing 4&3v with the casing 40. The conductor 4-! is, of course, insulated from the tube or conduit 49. As in the previously described embodiments, conductive 1 tube lljoins the casing of the control apparatus and an external electrode 5| which defines the heating oven. A conductor 52 passes through the conduit 50, is insulated therefrom, and is directly connected to a second and inside electrode 53, which corresponds to the inside electrode I described above in connection with Figure 1.

In this instance, I have illustrated how a relatively large hydraulic press or equivalent apparatus may be used in association with the material 54 to be subjected to heat. The press is diagrammatically illustrated and includes a head 55 actuated up and down by suitable mechanism connected to pull screws or posts 56. The

head 55 of the press may for economic reasons be made of plastic material or other non-conductive material, or the pull screws 56 alone may be made of such material. .In the-event it is desired to make the press head of metal, the inner electrode 53 is preferably well insulated from the press head 55 by the use of a strong dielectric element 51 of substantial thickness. A telescopic arrangment is shown at 58 to permit adjustment of theilength of the conductor 52 leading to, the electrode 53 to compensate for various thicknesses of material being heated.

In the system shown in Figures 6 and 7, it will benoted that both coils or windings of the transformer 4| are within separate enclosures. It will also be noted that in the type ofv oven or outer electrode 5| the complete oven is fully enclosed in an equi-potential surface, and this equi-potential surface envelops the entire system, including the source of power as well as between the two electrodes.

the oven and the necessary internal mechanism and connections. The external metal and mechanical portion of the hydraulic press becomes a part of the external surface and has no electrical space short circuits. It shouldbe noted, however, that in any case in which a metal part passes back and forth in the electric oven, the connection with the oven, such as by one of the posts 55, must be a good electrical one and not insulated in any manner from the outer electrode 5|. The external surface of all metal controls, and other apparatus passing through the metal casing 5i must be an electrical part of the outside surface of the external metal casing to insure the external equi-potential surface. Any external metal parts of the entire system may be contacted at any time by the operator without the slightest danger, even though a flash-over may occur within the internal electric system. This is a distinct advantage over any high frequency heating apparatu known or used heretofore.

In Figures 8, 9, l0 and 11, I have illustrated the same general arrangement of electrodes in a high frequency heatin system for purposes of cooking or baking objects carried through the oven portion of the system or a conveyor. It should be noted, however, that the conveyor does not pass through the energy field, except for non-insulated pusher elements/necessary to move the work articles.

In this instance, an outer box-like electrode 59, provided with an opening 60 at each end thereof, forms the oven. A conductive tube 5| is electrically integral with the electrode 59, and aconductor 52 extends through the conduit 6| and is insulated therefrom. This conductor 62. is connected with an inner plate-like electrode 63 which is completely housed and contained within the outer electrode 59. It should be understood that the inner electrode 63 may be held in proper position inside the outer electrode by a dielectric material of very high specific inductive, capacity preferably, such supporting element not being shown in the drawings. It will also be understood that the conduit SI and conductor 62 are connected in the manner above described to ,a control mechanism and in such a manner as to form a substantially closed system.

- The floor 54 of the outer electrode 59, which fioor is a conductive part of that electrode, tapers upwardly at each end as indicated at 65. so that objects may be smoothly carried through the oven For moving objects, a conveyor 66 may be provided which is of the endless type traveling-over suitable sprocket wheels or the equivalent til-61. This conveyor is provided with pusher elements 68 at periodic intervals therealong. As best seen in Figure 11, there pusher elements are ofsubstantially fanshape, and include a narrow neck portion which travels through a slot 69 extending longitudinally of the floor of the outer electrode. Above the neck portion, each pusher element flares out into a relatively wide body for engaging articles to be baked or cooked within the oven. ,Intthe illustrated instance. loaves of bread-l0 have. been selected as examples ofa work material to beactedupon by the energy field. The uncooked loaves of bread may be placed upontheleftendof the conveyor as viewed inFigure 8, and as the conveyor moves along these loaves .of bread are advanced by the pusher elements 68, travel upwardly over the inclined portion of the oven floor, pass through the energy fielddeveloped by the 11' electrodes, and descend the opposite inclined end of the floor and leaving the oven in the form of baked loaves. The floor construction permits the conveyor, with the sole exception of the noninsulated pusher elements, to travel outside the energy field.

With this arrangement, it will be apparent that the electric displacement currents between the electrodes cook or bake the bread throughout uniformly and in an extremely short period of time. The energy field, as in the previously described embodiments of the invention, is an intense field, and concentrated so that the article being heated gets the full value of the energy field. There is no danger to the operator, and no necessity for expensive safety ap aratus, or need for tuning to prevent radio interference.

In Figures 12, 13 and 14, I have illustrated another oven arrangement, which is highly desirable for heating flu d materials that are forced through the oven under various pressures, for purposes of pressure molding, extrusion processes, and the usual preheating or cooking of plastics justprior to form molding. In this instance, an oven H of tubular shape is provided, and as in the prev ous examples, this oven is also a part of an enclosed electrical circuit. At each end thereof, the oven H is provided with a hollow neck portion 12 for the entrance and exit of material to be heated. It makes no difference which direction the material travels through the oven. In th s instance, however, I have shown an arrangement for the use of spaced or separated inside electrodes 13 and M completely housed within the oven H. A conductor 15 which passes through a conductive conduit l6 leads to the electrode 13, and a similar conductor 11 passing through a conductive conduit l8 leads to the electrode 14. The conduits l6 and 18 are electr cally integral with the oven H. It will, of

course, be understood that the conductors l and 11 lead to the same connection in a control device, and the conduits 16 and 18 are each'connected to the casing of the control device, in the same manner as the sin le conductors andsingle conduits above described. 1

With reference more particularly to Figure 13, it will be seen that the inside electrodes 13 and M are shaped to form a part of the circumference of a circle. Between the electrodes 13 and 14, at eoually spaced distances, are sub-outer electrodes 19 and 8!} also shaped in conformity with portions of the circumference of a circle, the same diameter as the circle partially defined by the electrodes 13 and M. The electrodes '89 and 80 as indcated at 8|8i are conductively connected with the oven 'l I. As indicated at 82 in Figure 13, the space 83 between the conduits l6 and i8 and the respective conductors, and between the oven H and the inside electrodes and sub-electrodes, is preferably filled with an insulation material of high dielectric capacity, which material serves to fix the electrodes in position and to insure the correct paths of electric displacement currents through the material to be heated or cooked. The displacement currents in the electric circuit from electrode 13 to sub-electrode 19 are preferably so arranged as to be in exact phase with those operating in the circuit from electrode M to sub-electrode 8!] to cause a more intense and more uniform electric displacement field in the same direction at the same time.

In Figures 15, 16 and 17, I have illustrated a modification of the structure of Figures 12, 13 and 14, wherein only one substantially semi-cylindrical inside electrode and one substantially semi.-

cylindrical inside sub-electrode are utilized. In" this instance, a conductive oven at having hollow neck openings --85 at opposite ends thereof is provided, and a conductive conduit 85 is electri cally integral with the oven. Inside the oven there is disposed an inner electrode 8'! connected. by a conductor 88 to a suitable control station to the casing of which the conduit as is also connected as above described. The inner electrode 8'! is substantially semi-cylindrical in shape, but is not a full half circle so that space is allowed between it and a similarly shaped and oppositely disposed sub-electrode 59 connected to the oven 84 as indicated at 9%. It will be understood that the space s! between the inner electrode and the oven and between the conductor 88 and the conduit 85 is preferably filled with insulation such as a ceramic lining or other dielectric medium to fix the electrodes in position axially within the oven. This insulation is preferably shaped to insure the best streamiined flow of the material through the oven and insure the best contact of that material with the electrodes.

In connection with the showing in Figures 12 to 17, inclusive, it will be noted that the material passing through the respective ovens actually contacts the two electrode arrangements so as to in eifect short circuit the electrodes. Thus,- the energy field is extremely concentrated inso far asthe material to be heated is concerned.-

From the foregoing, it is apparent that I have provided a novel electrical system which may function as an antenna system or as a high frequency heating system, or as a diathermic treat-- ing device. Two overall types of oven have been described, first, a completelyenclosed oven or radiant energy transmission system totally surrounded by a metal conductor, and second, a radiant energy transmission system in which a portion of the energy field lies outside the metal casing or external antenna in predetermined spaced relations. In the first case all radio interference or danger to the operator is completely eliminated. In the second case we have protection, in as substantial manner as desired, for the commercial radio field, as well as ample pro tection to the operators of the apparatus and the material or patent to be treated. It will further be noted that the invention is economicai to build and operate, and highly durable.

It will, of course, be understood that various details of construction may be varied through a wide range without departing from the princig ples of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. A dipole antenna system comprising an antenna having a peripheral edge and forming one pole of the system, a metallic shielding casing having a terminal portion disposed about said antenna and extending forwardly of said edge and forming the other pole of the system, a source of energy within said casing, a conductor within said casing and connecting one terminal of said source to said antenna, the other terminal of said source being connected to said casing.

2. A dipole antenna system comprising an antenna formed of a curved metallic member and forming one pole of the system, a source of en-' ergy, a metallic casing housing said source, a conductor within said casing and connecting one terminal of said source to said antenna, the other terminal of said source being connected to said eas est sa eas ha i g a. curved terminal po tion thereof forming the other pole of the system and disposed about said antenna in shielding relation thereto;

35A dipole antenna system comprising a metallic casing, a source of energy housed within said casing and having one terminal connected tosaid casing, said casing having a tubular extension terminating in a curved shielding mem ber: forming onepole oi the system and shaped toypresent a from opening, a curved'metallio antenna member forming the other pole of the system and placed within said curvedshielding member and rearwardly' of said opening, and'a lead Within said casing connecting said antenna with the other terminal ofsaid source.

4. A dipole antenna system comprising'a conductive metallic casing closed'at one end and having its other end curved and formingone pole of the system and provided with an opening; a curved antenna member forming theother pole of the system entered in said casing and ad jacent said opening, a source of energy in said casinga conductive lead in said casing connecting one terminal of said source to said member, the other terminal of said source being connected tosaid casing to conduotively bring said other terminal into proximity to said antenna member.

5. A dipole. wave emitter comprising a metallic casing having a portion shaped to define a hollow first electrode, a second electrode entered in said first electrode, energy transforming means within said casing, a conductor within and insulated from said casing and connecting one pole of said transforming means with said second electrode,

the other pole of said transforming means being connected to said firstielectrode.

6. A transmitter comprising an elongated metallic casing closed at one end and terminating at the other end in a boWl-shapedportion; a

source of power contained within said casing and disposed adjacent the closed, end thereof,.a bowlshaped member disposed within the bowlrshaped terminalportion of said casing and in spaced and insulated. relation thereto, conductor means in said casing connecting said bowl-shaped member and oneterminal of said source and ininsulated relation to said casing, theother terminal of said source. being conductivelyi connected to. said casing,

'7. A transmitter comprising an elongatedi metallic casing closed at. one end and terminating, at, the other endin an elongated curved trough-shaped portion, a sourceof power in said casinganddisposed therein remote from said terminal portion, an elongatedcurved troughshaped member disposedcwithin said terminal portion and in spaced and insulated relation thereto, a conductor within said casing connecting said trough-shaped member to oneterminal of said source and being in insulated relation to and shielded by said casing, the other terminal of said source being conductively connected to said casing.

8. A transmitter comprising an elongated metallic casing closed at one end and terminating at the other end in a bowl-shaped portion having a free peripheral edge, a source of power in said casing and disposed therein remote from said terminal portion, a bowl-shaped member disposed within said terminal portion and in spaced and insulated relation thereto, said bowl-shaped member having a free peripheral edge disposed in the terminal portion inwardly of the free peripheral edge of said terminal portion, a conductor connecting said bowl-shaped member with one terminal or said source,.-said' conductorbeing disposed within said casing in insulated relation toand-shielded-by said casing, the other terminal of said source being condu'ctively con+ nectedto said casing. I

93A dipole antenna r assembly comprising a curvedmetallic hood having a front opening and forming the terminal of an elongated casing and one pole of the antenna, an elongated metallic casing closed at one end and having said hood as its terminal at the other" end, a source of power within said casingand remote from said hood, a curved metallic member in said hood and in spaced and insulated relation thereto and formingtheother pole of the dipole antenna, a conductorwithin said casing connecting said curved member-to one; terminal of said source, said conductor being disposed in insulated relation to and shielded by said casing-the other terminal of said source being connected to said casing.

10. A dipole.antennaassembly comprising an elongated metallic casing closed at one end and terminating at its other end in a hood having a front opening, said hood being one pole of the dipole antenna, asource of energy in said casing and remotev from said hood and having one terminal conductively connected to said casing, a curved metallic member entered in said hood and in spaced and insulated relation thereto,.said member being the other pole of said dipolean- 'tenna, a conductor within said casingconnecting said member with the other ,terminalof said source, said conductor being disposed ininsulated relation toand shielded by said, casing.

11. A, dipole antenna. assembly comprising an elongated, metallic, casing closed at one ,end and terminatingatits other end, in a curved hood havinga front opening, said hood beingone pole of the dipole assembly, a source of energy in said casing and remote fromsaid hood; conductor means in said casing and in spaced and insulated relation thereto, one, end. ofsaid conductor means being, connected .to, one terminal of said source and the other end of said conductor means, terminating in said hood to, provide the other pole of theldipole assembly, the other terminal of said, source. being conductively connected to said casing.

12,, A dipole. antenna .assembly comprising an elongated ,metalliccasing closed atone end and tern'linatingv at. itsother end in a curved hood having a frontopening, said hood being one pole oithedipole assembly, asource of energy within said/casing, a conductor in said casing and in spaced-and insulated relation thereto and shielded thereby,said conductorohavingone end .connected to one terminal of said source and having its other end entered within said hood to provide the other pole of said dipole assembly, the other terminal of said source being conductively connected to said casing.

13. In an antenna assembly, an ungrounded arrangement including an antenna member, a conductive casing terminating in a hood about but spaced from said antenna member, a source of energy in said casing, means connecting one terminal of said source to the casing, and a conductor insulated from said casing but disposed therewithin and connecting the other terminal of said source to said antenna member.

14. A self-contained ungrounded antenna assembly, including a hollow conductive casing terminating at one end in a hood-like portion, an antenna member disposed in said hood-like por- 7 tion with its terminal edge spaced from but in 15 proximity to the edge ofsaid hood-like portion, a sourceof energy in said casing, means con-'- necting a terminal of said source to said casing, and a conductor running through said casing but insulated therefrom and connecting the other terminal of said source to said antenna member, whereby the energy field is internal and the inside surface of said casing serves as a return conductor.

15. In a closed radiant energy transmission system, a pair of electrodes one within the other but spaced apart, hollow conductive means electrically integral with one of said electrodes, a source of energy in said hollow conductive means, a conductor connecting one terminal of the source to the inside of said hollow conductive means, and a conductive means extending through said hollow conductive means but insulated therefrom connecting the other terminal of the source to the other of said electrodes.

, 16. In a closed radiant energy transmission system, an outer electrode in the form of a housing, an inner electrode completely contained within the outer electrode but spaced and insulated therefrom, hollow conductive means electrically integral with the outer electrode, a source of energy in said means, one terminal of said source being connected to the inside of said means, and means extending within said hollow conductive means but insulated therefrom connectini, the other terminal of said source with the inner electrode.

17.'In an encosed radiant energy heating system, an outer electrode in the form of a housing,

an inner electrode completely contained within the outer electrode but spaced and insulated therefrom, hollow conductive means electrically integral with the outer electrode, a source of energy in said means,'one terminal of said source being connected to the inside of said means, and

means extending within said hollow conductive means but insulated therefrom connecting the other terminal of said source with the inner electrode, said electrodes being arranged to define a path for work material which material directly contacts both electrodes.

18. In a wave transmitter of the character described, an ungrounded arrangement including an electrode, a conductive casing terminating in a hood forming a second electrode about but spaced and insulated from the first electrode, a source of energy in the casing, means connecting one side of said source to the casing, a conductor in the casing and insulated therefrom connecting the other side of said source to the first electrode, said second electrode having closed ends except for work passage openings, and the first electrode being disposed above the work path through said openings.

19. In a wave transmitter of the character described, an ungrounded arrangement including an electrode, a conductive casing terminating in a hood forming a second electrode about but spaced and insulated from the first electrode, a source of energy in the casing, means connecting one side of said source to the casing, a conductorin the casing and insulated therefrom connecting the other side of said source to the first electrode, said second electrode having closed ends except for work passage openings, and the first electrode being of transversely arcuate shape and defining a Work material path between said openings.

20. In a closed radiant energy transmission system, a pair of electrodes one Within the other but spaced apart, hollow conductive means electrically integral with one of said electrodes, a source of energy in said hollow conductive means, a conductor connecting one terminal of the source to the inside of said hollow conductive means, a conductive means extending through said hollow conductive means but insulated therefrom connecting the other terminal of the source to the other of said electrodes, the outer electrode being in the form of a housing with the ends closed except for opposed openings through which work material may enter and leave, the inner electrode being adjacent the path of material, and conveying means to carry material through the outer electrode from end to end thereof.

LOUIS H. CROOK.

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

UNITED STATES PATENTS Number Name Date 1,522,188 Hull Jan. 6, 1925 1,951,731 Kassner Mar. 20, 1934 1,972,050 Davis Aug. 28, 1934 2,177,272 Zottu Oct. 24, 1939 2,181,870 Carter Dec. 5, 1939 2,226,871 Nicholas Dec. 31, 1940 2,231,457 Stephen Feb. 11, 1941 2,231,602 Southworth Feb. 11, 1941 2,235,506 Schelkunoif Mar. 18, 1941 2,239,069 Worden et a1 Apr. 22, 1941 2,259,318 Mouromtseff Oct. 14, 1941 2,307,011 Barrow Jan. 5, 1943 2,341,617 Hull Feb. 14, 1944 2,368,663 Kandoi'an Feb. 6, 1945 2,398,318 MacMillin et a1 Apr. 9, 1946

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