US3195725A - Electrically heated screen construction and method - Google Patents

Description

y ,1965 1'.w. HANNON 3,195,725

ELECTRICALLY HEATED SCREEN CONSTRUCTION AND METHOD Filed Aug. 2. 1961' s Sheets-Sheet 1 INVENTOR. Thomas W Hwzzzwn ATTORNEYS July 20, 1965 1-. w. HANNON ELEGTRICALLY HEATED 501mm CONSTRUCTION AND METHOD Filed Aug. 2, 1961 3 Sheets-Sheet 2 ATTORNEYS July 20, 1965 T. w. HANNON ELECTRICALLY HEATED SCREEN CONSTRUCTION AND METHOD Filed Aug. 2, 1961 3 Sheets-Sheet 5 UK I.- 27

\ mmvroze. mom WHwzuwn BY ATTORNEYS United States Patent 0 3,195,725 ELECTRICALLY HEATED SQREEN CGNSTRUCTZSN AND METHGD Thomas W. Hannah, Canton, Ghio, assignor to F. R. talisman & Sons, Inc, Canton, Qhio, a corporation of Filed Aug. 2, 1961, Ser. No. 128,866 14- Claims. (6!. 299-238) My invention relates to improvements in electrically heated screen construction, and the method of supplying electrical energy to screens to be heated. Even more specifically, my invention relates to a new and novel transformer construction and the means for electrically connecting the same with units which have limited movement relative to the transformer during operating and use thereof, such as vibrating electrically heated screens.

Various forms of equipment have been provided for the industrial screening of materials, such as iron ore and other similar types of materials. Most of such equipment has included a platform supporting one or more generally horizontally positioned and usually sloping screens which are vibrated in some manner in order to accomplish the screening operation.

Although various attempts have been made to produce vibratory movement of the screen without greatly affecting the supporting frame members thereof, the most practical and satisfactory method is to vibrate virtually the entire screening unit including not only the screens, but also the supporting frame members thereof. This has usually been accomplished by providing a resilient mounting for the supporting frame members on a supporting surface in such a manner as to retain these supporting members in place, and then provide some form of vibrating means which vibrates the supporting frame members and screens relative to these resilient mountings.

it has also been found that not only is vibration of the screens through which the material must pass required, but heating the screens is some manner during the screening operations will add greatly to the functioning thereof, by causing less blinding or clogging of the screens during this operation. The simplest manner of accomplishing this heating of the screens is to provide the screen cloth which forms the screens of an electrically conducting material and passing a low voltage electrical current therethrough. In this manner, the screen cloth itself provides a resistance heating unit to supply the necessary heat.

Many problems have been involved in the provision of these electrically heating and vibrating screen unts, certain of which have involved the problem of just exactly how to provide an electrical connection to the screen cloth for properly passing the electrical energy therethrough while still maintaining the screen cloth properly tcnsioned to support and vibrate the material being screened. Furthermore the screen cloth must be easily removable and replaceable in view of the relatively short useful life of the screen cloth under the usual abuse and wear encountered.

These electrical connection, support and replacement problems have been extensively solved according to the principles and constructions set forth in my prior Patents Nos. 2,704,155 and 2,812,062, both entitled Electrically Heated Screen Construction, and dated March 15, 1955, and November 5, 1957, respectively.

One of the major problems still remaining in electrically heated screen constructions, which problem is also encountered in various other types of electrical installations where it is necessary to supply electrical energy to a unit which has a limited movement or vibratory movement during the operation thereof, is how to supply this electrical energy to the vibrating or moving unit from a stationary source and still maintain the necessary electrical ice connections intact despite the relative movement between the source and the unit being supplied. Prior to the present invention, the attempts to accomplish this have been through the use of various forms of flexible electrical cables which have usually been connected to the secondary of a transformer and to the moving or vibrating unit so as to attempt to provide the flexibility for the relative movement therebetween.

For instance, in screen heating constructions, the screen cloth serving as the screening medium has been connected to the vibrating frame of the screen heating unit through generally hook-shaped, selectively adjustable skirt boards, which are mounted on and adjustable with respect to side rails or frame members. These skirt boards are provided with electrical conducting means contacting and supporting the side edges of the screen, and flexible electrical cables, usually in the form of braided copper cables, have been connected to the conducting means and to a usual transformer mounted in a stationary location adjacent the vibrating screen unit.

These flexible electrical cables have served the purpose of providing for relative movement between the stationary transformer and the moving or vibrating screen unit, but such cables are relatively expensive and are serviceable for only a relatively short period of time, thereby requiring frequent replacement and further adding to the expense thereof through the additional maintenance costs and lost production time for use of a particular unit. For these reasons, it is desirable to provide some means of supplying electrical energy from a transformer unit to a unit required to have limited movement for operation thereof, such as vibrating screen heating units, which eliminates the high expense and frequent maintenance of the usual flexible electrical cables.

It is therefore a primary object of the present invention to provide an electrically heated screen construction and method which solves the foregoing problems, the principles of which are applicable not only to vibrating screen heating units, but which are also applicable to constructions Where electrical energy must be supplied from a stationary source to a unit which must have limited movement for the operation thereof.

It is a further object of the present invention to provide an electrically heated screen construction having a unique form of transformer which is connected to the vibrating screen unit preferably solely by air, yet will properly supply the electrical energy for and to the vibrating screen to be heated.

it is still a further object of the present invention to provide an electrically heated screen construction in which the secondary of the transformer supplying the necessary electrical energy is connected to the transformer primary preferably solely by air, so that the transformer secondary may be secured to the vibrating screen unit and freely vibrate therewith, while the transformer primary may be mounted stationary, thereby solving the problem of a flexible connection between the transformer and vibrating screen unit.

It is an additional object of the present invention to provide an electrically heated screen construction in which the transformer primary is mounted stationary and connected preferably solely by air to a transformer secondary secured for free vibration with the screen supporting and tensioning skirt boards of a vibrating screen unit, yet the transformer secondary is connected to the skirt boards for permitting selective adjustment of the skirt boards relative to the transformer secondary, thereby permitting selective adjustment of the skirt boards to tension and properly support the screen cloth accomplishing the screening function.

Finally, it is an object of the present invention to provide an electrically heated screen construction and method which satisfies the foregoing objects in a simple iprinciples -are set forth in the following description and illustrated in the'accompanying drawings, and which are particularly and distinctly pointed out and set forth in the appended claims forming apart hereof.

The general principle involvedin' theelectrically heated screen construction of the present invention may be broadly stated for application to electrical units generally as including" a transformer primary assembly formed with an opening extending longitudinally therethrough and with said primary assemblybeing adapted for stationary mounting. Further, the unit'may include an electrical power consuming unit having electrical connectors thereon and a closed electrical circuit therethrough between said connectors, with this electrical power consuming unit being mounted for movement within predetermined limits, such as vibrating. Still further, the unit includes transformer secondary means havin'g'ends connected secured to the electrical connectors of the electrical power consuming unit for movement of the secondary means with the electrical power consuming unit and with the secondary means extending through the primary assembly opening. Finally, the transformer secondary means, in

its, extension through the primary assembly is mounted free ofany connection with the primary assembly which would restrict free movement of the secondarymeans longitudinally through and laterally Within the primary assembly opening.

The method involved in the electrically heated screen construction of the present'invention as applied to electrical units generallymay be broadly stated as the method of supplying electrical energy to an electrical power consuming unit which is mounted and adapted. for limited movement and which is provided with electrical connectors and a closed electrical circuit between said connectors. Such method broadly stated includes the steps of providing a transformer primary and positioning a transformer secondary extending longitudinally through the primary while maintaining the secondary free of connection with the primary which would restrict freelongitudina l movement of the secondary relative to the primary andifree lateral movement of the secondary within thejprimary. Still further the method broadly includes the step of'maintaining the secondary secured to the electrical connectors of the electrical power consuming unit to form a closed secondary electricalcircuit through the secondary and through the electrical power consuming unit while the secondary is rigidly maintained movable with the electrical power consuming unit.

As applied more specifically to electrically heated screen constructions, the invention may be stated as includinga screen supporting frame member having vibrating means operab lyfconnected, thereto for vibrating. the framem nbe ith a s r en a r e n ns-d m t e frame member. Further, the construction inclndes electrical connectorsoperably connected to the screen forming ajclosed electricalcircuit through the screen and between said connectors.

Still further, the construction includes a transformer primary having ancpening formed longitudinally therethroug'h. and a'transformer secondary mounted extend-1 ing longitudinally through the primary opening and being securedytothe screen electrical connectcrs for vibrating movement with the screen and screen frame. Finally; the transforrner secondary is mounted free of connection with the primary which would restrict longitudinal movement of the secondary throughthe primary opening and lateral movement of the secondary within the primary opening.

By way of example, embodiments of the improved electrically heated screen construction and method of the present invention are illustrated in the accompanying drawings forming a part hereof, wherein like numerals indicate similar parts throughout thetseveral views and in which: 7

FIG. '1 is. a perspective view showing an electrically heated screen unit constructed according to the principles of the present invention;

FIG. 2, an enlarged fragmentary end elevation of one 7 of the transformers constructed according to the principles of the present, invention showing the operable connection thereof to the screen supporting unit and looking in the direction of the arrows 22 in FIG. 1;

FIG. 3, a reduced fragmentary top plan view of the transformer of FIG. 2; i a

FIG. 4,' an enlarged fragmentary sectional view, part in elevation, looking in the direction of the arrows 4-4 in FIG. 3; V

FIG. 5, an enlarged horizontal sectional view of the transformer primary with a portion of the secondary being shown extending therethrough in operable position;

FIG. 6, a fragmentary side elevation, with parts broken away, of the transformer primary and looking in the directionof the arrows 6,6 in FIG. 5;

FIG. 7, a fragmentary top plan view, with parts broken away showing the transformer primary with a second embodiment of a portion of a'transf ormer secondary extending therethrough.

Referring to the drawings, an electrically heated screen construction according to. theprinciples of the present invention is shown in FIG. 1 and includes a vibrating screen unit, generally indicated at 10, transformer primaries, generally indicated at 11, and transformer secondaries, generally indicated at 12. The unit illustrated includes two transformer primary and secondary assemblies, but these assemblies are substantially identical so that only one need be considered for an understanding of the principles, of the same.

The vibrating screen unit 10 is basically of a standard construction with certain'changes for adaptation of the same to the principles of the present invention, and includes a screen supporting frame, generally indicated at 13, which is mounted on a supporting surface for vibration relative thereto by the resilient mounting members 14. The screen unit 10 is vibrated, including the total screen supporting frame 13, by a standard vibrating unit, generally indicated at 15, andagain being of usual construction inrunits of this. type. V Y

Further, the screensupportingframe 13is provided with the spaced and opposed side rails- 16, which side rails iii-turn support the usual selectively adjustable generally hook-shaped skirt boards 17. The skirt boardsi l7 in turn engage and tension and support the screen. cloths 18 which perform the screening, function of the unit.

The details, of the constrnctionfof the skirt boards: 17 are set forth in my before mentioned Patent No. 2,812,062 and are, therefore, considered only briefly here.

7 Each skirt board 17 includes a supporting web portionylQ having an upper end 20 pivotally abutting the particular side rail 16 and a lower end 21, uponwhich'is mounted a generally hook-shaped bus bar ZZ. i i 1 V The side edges of the screen cloth lsrpositioned at the skirt board 17 are formed with hook-shaped edge portions 23 which are reversely engaged with the skirt board bus bars 22. Thus, when the skirt boards '17 are pivotally adjusted relative to the side rails 16 by manipulation of the tensioning bolts 24; the screen cloths 18,v may be tensioned and supported between the opposed skirt boards 17 in p roper screening position. V

In the particular unit illustrated'iri FIG. 1, there are four separated screen cloths 18 which are positioned'for forming the closed electrical circuits from the skirt board 17 adjacent one of the sides of a transformer secondary 12, through the particular screen cloth 1%, to the opposed skirt board 17, Within the skirt board to the next adjacent screen cloth l8, and back to the skirt board adjacent the other side of the same transformer secondary 12. With this construction, therefore, the bus bar 22 of the skirt board 17 adjacent the transformer secondary 12 is formed divided between each screen cloth 18, whereas the bus bar 22 on the opposite skirt board 17 is continuous for each set of screen cloths 1S and divided only between the sets.

The bus bars 22 are insulated from the respective skirt boards 17 and are connected to the particular transformer secondary 12 by the generally L-shaped, preferably copper, electrical connectors 25. In order to provide the electrical circuit through the bus bars 22 and screen cloths 13, these bars and cloths also must be electrically conducting materials, with the bus bars preferably being copper and the screen cloths being formed of a selected electrical conducting material depending on the particular material to be screened, that is, the various abrasion and other factors to be considered for providing a maximum operable life.

Each transformer secondary 12 is generally U-shaped and is formed by a pair of generally laterally extending side members 26 connected at their ends, spaced from the particular side rail 155, by a generally longitudinally extending connecting member 27. In the particular embodiment shown, the secondary side member 26 and connecting members 27 are preferably hollow and of generally rectangular crosssection and in this case the transformer secondaries 12 would be adapted for high capacity requirements.

Furthermore, as best seen in FIGS. 3, 4 and 5, the con necting members 27 of these transformer secondaries 12 may also be provided with a series of spaced holes 23 formed therethrough and opening into the hollow interiors of the connecting members, which will even more greatly increase the capacity thereof by providing air circulation for minimizing the temperature build-up therein and thereby minimizing the voltage loss in the secondary 12 which would be caused by such temperature build-ups. In the case Where capacity is not a prob lem and low capacity i sufficicnt, the secondary side and connecting members 26 and 27 may be formed solid and in every case must be formed of an electrical conducting material, preferably copper or aluminum.

The transformer secondaries 12 are supported on the screen supporting frame 13 by the generally L-shaped shaped support brackets 29, which are secured to the particular side rail 16 and preferably mount the secondary side members as in generally horizontally extending positions through the fastening bolts 30. Bolts 30 are insulated from the support brackets 2d by the insulating washers 31 and furthermore, the side members 26 are also insulated from the support brackets 29, preferably by the insulating sheets 32 positioned thercbetween and formed of an insulating material such as fiber-glass or the like.

A selectively adjustable secondary connector, generally indicated at 33, is provided between each secondary side member 26 and its respective electrical connector 25. These secondary connectors 33 are formed by the slotted, generally T-shapcd plates 34 and the fiat plates 35, as best seen in FIGS. 2, 3 and 4.

The slot-ted plates 34 are provided with the flat, generally horizontally extending side fianges 36 which are bolted flatwise on the electrical connectors 25 and these flanges 36 are connected to a upstanding generally laterally extending portion 37 which has a slot 38 opening toward the particular secondary side member 2%. The fiat plates are mounted in pairs secured to the secondary side members 26 in space upstanding positions for receiving the slotted plates 34 therebetween, and these fiat plates 35 are selectively releasably secured to the slotted plates 34 by a selectively releasable fastening bolt 39*.

Thus, the transformer secondaries 12 are mounted secured on side rail 16 by the support brackets 2? and will vibrate with the remainder of the screen supporting unit, but in order for the skirt boards 17 to be selectively pivotally adjusted with respect to the side rails 16 in order to properly tension the screen cloths 18, these selectively releasable secondary connectors 33 are provided. When the skirt boards l7 have been properly adjusted, the fastening bolts 39 of these secondary connectors 33 are tightened to provided a positive electrical connection from the transformer secondaries 12 through these connectors 33 and through the electrical connectors 25 into the screen cloths 18. In view of the fact that these econdary connectors 33 form an important part of the transformer secondary circuit, they are also formed of an electrical conducting material, preferably copper or aluminum.

The transformer primaries ll are formed preferably generally cylindrical and are provided with preferably generally cylindrical and longitudinally extending openings 49 therethrough. Furthermore, each transfori ier primary ll may be mounted on a stationary supporting surface 41 in usual manner and may be provided with the usual sealed control portion 42 having the selectively movable control knob 43.

The main portion of each transformer primary ll is formed by a hollow, generally cylindrical, preferably steel core which may be formed annular shape merely by tightly wrapping strip steel, as shown, to the desired size. This annular core dd is then transversely Wrapped preferabiy completely around the circular extent thereof by a wire coil 45, which wire coil is separated from core 44 by the usual insulating means 46.

A second wire coil 47 may be wrapped in a similar manner about the first coil 45 and likewise separated therefrom by the usual insulating means 43. Finally, the outer coil 47 is covered completely with further insulating means d? and the entire unit is completely enclosed in a preferably stainless steel case or enclosure 5%, so that the case $9, which is completely insulated from the remainder of the transformer primary 11, forms the exposed hollow generally cylindrical shell.

As shown, the connecting member 27 of the particular transformer secondary 12 is supported extending longitudinally through the particular primary opening it) and is preferably maintained spaced laterally from the case 5t) so that none of the vibratory movement of the secondary 12; is imparted to the primary 11. Thus, the only connection between the transformer primaries 11 and sec ondaries 32 is an air connection and absolutely no wear can take place between these primaries and secondaries. Furthermore, since the secondaries are rigidly secured to the vibrating screen unit 1% for vibration therewith, virtually all possibility of wear is eliminated.

As illustrated in a second embodiment in FIG. 7, in the case Where the particular application permits, the connecting member 27 of the transformer secondary 12 may be a braided cable 51 of copper or aluminum. In this case, the cable 51 may either be supported spaced totally from the transformer primary Ill and extending through the opening it) thereof, or where conditions permit and limited wear can be tolerated, this cable may lay on the case S6) of the primary and extending through the opening.

In view of the fact that case Ell is completely insulated from the electrically conducting portions of the transformer primary it, the construction will still operate satisfactorily even thoughthe cable is laying on the case. There is in this case, however, going to be limited wear of the cable 51 due to the vibratory motion thereof relative to case 59, but in certain cases, this can be tolerated and it would not be of a magnitude to present the problems of a flexible cable soured to a stationary transformer and secured to a vibrating screen unit.

In use of the first embodiment construction of the present invention, the screen cloths 18 formed of electrically conducting material are properly positioned with the edge portions 23 thereof engaged with the bus bars 22 of the skirt boards 17, andfor this purpose, these skirt boards may be pivoted away from the respective side rails 16 by loosening the tensioning bolts 24. In order to permit this pivotal movement of the skirt board relative to the side rail 16, however, where the bus bars 22 are connected to the electrical connectors of the transformer secondaries 12, it is necessary to also loosen the fastening bolts 39 of the secondary connectors 33, permitting relative movement between the T-shaped slotted plates 34 and their respective connecting plates 35.

After the cloths 18 have been engaged by the skirt board 17, the tensioning bolts are tightened to properly tension the screen cloths for performing the supporting and screening functions thereof. Once these screen cloths 18 are properly tensioned, the fastening bolts 39 of the transformer secondaries 12 may be tightened to provide virtually a solid connection between plates 34 and of the secondary connectors 33 and, therefore, virtually a rigid or solid connection between the electrical connectors 2S and the secondary side and connecting members 26 and 27.

Again, in the preferred embodiment shown in FIGS. 1 through 6, with the transformer secondaries 12 formed by the rigid side members 26 and connecting members 27, and with side members 26 rigidly supported on the side rails 16 of the screen supporting frame 13, the connecting members 26 will be positioned extending through the longitudinal openings of the transformer primaries 11 spaced laterally from all portions of the primary case Stl. Thus, when the vibrating unit 15 of the screen supporting frame 13 is operated to vibrate the entire screen supporting frame, these vibrations will be carried completely through the transformer secondaries 15, but in view of the fact that the only connection between the transformer primaries 11 and the transformer secondaries 12 is air, these vibrations will not be transmitted to the transformer primaries.

With this first embodiment construction, therefore, the need for a direct flexible connection between the screen supporting frame 13, which is vibrating, and a transformer unit, which is stationary, is completely eliminated. By mounting-the transformer secondary 12 rigidly connected to the screen supporting frame 13 for vibration with this screen supporting frame, and by providing merely an air connection between the transformer secondary and the transformer primary 11, all possibility of wear of the electrical connections for supplying electrical energy through the screen cloths 18 is eliminated.

In the case of the second embodiment construction, where the flexible cable 15 is positioned merely extending through the transformer primary 11 but resting against the case thereof, there will be some slight frictional wear between this cable 51.and the case'50, but under certain conditions this can be tolerated and the wear will still not approach the wear incurred from a direct flexible cable connection as previously used with transformers of standard construction.

The most important broad'principle involved in the present invention is the freedom of movement of the transformer secondary 12 relative to the transformer primary- 11, so that the transformer secondary can be secured directly to the vibrating screen supporting frame 13with the transformer primary being mounted stationary, and no excessive wear will take place between vibrating and stationary members. Furthermore, in the first embodiment construction shown in FIGS. 1 through the entire connection betweentransformerprimary 11 and transformer secondary 12 is air, so that here there can 1 be absolutely no wear.

It should be understood that in the first embodiment formof the present invention shown in FIGS. 1 through 6, wherein the connecting member 27 of the transformer secondary 12 is supported by the side members 26; completely free of any contact with the transformer primary 11, this connecting member 27 could bea braided flexible cable such as indicated at 51 in the second embodiment shown in FIG. 7, or could take on other forms as conditions demand. Furthermore, in the preferred form this connecting member 27 can be solid for relatively low capacities and hollow with the possible addition of the holes 28 for higher capacities as conditions demand. I The important thing for higher capacities is to maintain the temperature at a minimum in order to maintain voltage drops to a minimum.

In the particular construction of vibrating screen unit 19 illustrated and described, merely the usual single phase electrical current is used for energizing the transformer primaries 11. This construction, however, is easily adaptable for the usual three-phase input current,-merely by the provision of two transformer primaries 11 side by side with the single transformer secondary 12, and this will result in single phase electrical current being developed inthe transformer secondary 12.

Thus, according to the principles of the present invention, a broad method is provided of supplying electrical energy to a limited movable electrical power consuming unit by providing a transformer primary 11 with a transformer closed secondary circuit positioned extending longitudinally through the primary in such a manner that the secondary is free of any physical connection with the primary which would restrict free longi tudinal movement through the primary and free lateral movement'within the primary. In the preferred form, the method would include providing only an air connection between the transformer primary and transformer secondary.

In the foregoing description, certain terms have been used for brevity, clearness and understanding but no unnecessary limitations are to be implied therefrom, be-

cause such words are used for descriptive purposes herein and are intended to be broadly construed.

Moreover, the embodiments of the improved. construction and method illustrated and described herein are by way of example and the scope of the present invention is not. limited to the exact details of construction shown.

Having now described the invention, the construction, operation and use of preferred embodiments thereof, and the advantageous new and useful results obtained thereby, the. new and useful construction and'method and reasonable mechanical equivalents thereof obvious to those skilled in the art are set forth in the appended claims. t

I claim: 5 t

1. Electrically heated screen. construction including a transformer primary having an opening formed therethrough, an electrically heated screen unit, spaced electrical connectors on the screen unit electrically connected to a screen thereof and forming a closed electrical circuit through said screen between said connectors, means mounting the electrically heated screen unit for vibratorv movement, rigid'bar like transformer secondary means, means'suspending the secondary means on the electrically heated screen unit, said secondary means extending through the transformer primary opening and with secondary means ends connected and secured rigidly to the electrical connectors of the screen unit for movement of; the secondary means with the vibratory movement of the screen unit, the bar-like transformer secondarymeans being substantially hollow throughout the extent thereof, and the means suspending; the secondary means on the electrically heated screen unitpositioning said secondary means extending through the primary openingfree of any physical contact with the primary.

2. Electrically. heated screen construction including a transformer primary having an opening formed therethrough, an electrically heated screen unit, spaced electrical connectors on. the screen unit electrically connected to a screen thereof and forming a closed electrical circuit through said screen between said connectors, means mounting the electrically heated screen unit for vibratory movement, rigid bar-lilie transformer secondary means, means suspending the secondary means on the electrically heated screen unit extending through the transformer primary opening and with secondary means ends connected and secured rigidly to the electrical con nectors of the screen unit for movement of the secondary means with the vibratory movement of the screen unit, the bar-like transformer secondary means being substantially hollow throughout the extent thereof and having a series of spaced holes formed therein opening into an interior thereof at least in that portion of the secondary means extending through the primary opening, and the means suspending the secondary means on the electrically heated screen unit positioning said secondary means extending through the primary opening free of any physical contact with the primary.

3. Electrically heated screen construction including a transformer primary having an opening formed therethrough, a vibrating electrically heated screen unit having a main supporting frame mounted for vibration, selectively adjustable screen supporting means mounted on the supporting frame and selectively adjustable for positionin and tensioning a screen on the supporting frame, spaced electrical connectors rigidly secured to the selectively adjustable screen supporting means movable with said supporting means in electrical connection with the screen and forming a closed electrical circuit through the screen and between said connectors, rigid bar-like transformer secondary means, secondary support means rigidly suspending the transformer secondary means on the screen unit supporting frame, said seconday means extending through the transformer primary opening tor movement with the vibratory movement of the screen unit, the secondary means being a substantially hollow bar throughout tie extent ticreof and having ends, rigid selectively adjustable connection means between the secondary means ends and the screen unit electrical connectors for selective movement between the screen unit electrical connectors and secondary means, to allow selective adjustment of the screen supporting means during positioning and tensioning of the screen, and the secondary support means rigidly suspending the secondary means on the screen unit supporting frame extending through the primary opening tree of any physical contact with the primary.

Electrically heated screen construction including a transformer primary having an opening formed therethrough, a vibrating electrically heated screen unit having a main supporting frame mounted for vibration, selectively adjustable screen supporting means mounted on the supporting frame and selectively adjustable for positioning and tensioning a screen on the supporting frame, spaced electrical connectors rigidly secured to the selectively adjustable screen supporting means movable with said supporting means in electrical connection with the screen and forming a closed electrical circuit through the screen and between said connectors, rigid bar-like transformer secondary means, secondary support means rigidly suspending the transformer secondary means on the screen unit supporting frame, said secondary means extending through the transformer primary opening for movement with the vibratory movement of the screen unit, the secondary means bein a substantially hollow bar throughout the extent thereof and having ends, the hollow secondany means having a series of spaced holes formed therein opening into the interior thereof at least in that portion of the secondary means extending through the transformer primary opening, rigid selectively adjustable connection means between the secondary means ends and the screen unit electrical connectors for selective movement between the screen unit electrical connectors and secondary means, to allow selective adjustment of the screen supporting means during positioning and tensioning of the screen, and the secondary support means rigidly suspending the secondary means on the screen unit supporting frame extending through the primary opening free of any physical contact with the primary.

5. in an electrically heated vibrating screen unit of the type in which a screen is mounted adjustably tensioned on a main supporting frame of the screen unit and is resistance heated by passing electrical energy therethrough including vibrating means operabiy connected to the screen unit inducim substantially continuous vibratory movement or" the main supporting frame and screen during the electrical resistance heating of said screen, selectively a justable screen supporting means mounted on the main supporting frame engaged with said screen for vibration directly with the main supporting frame and screen and selectively adjustable for positioning and tensioning the screen on the supporting frame, spaced electrical connectors secured rigidly with the selectively adjustable screen supporting means movable with said supp rting means in electrical connection with the screen for vibration directly with the screen and the passing of electrical energy through the screen to resistance heat said screen, a transformer secondary, secondary support means rigidly suspending the transformer secondary on the main supporting frame, said secondary receiving vibratory motion from said frame and vibrating directly with said frame and screen, the secondary having ends, selectively adjustable rigid connection means between the secondary ends and the electrical connectors for selective movement between the electrical connectors and secondary, to allow selective adjustment of the screen supporting means during positioning and tensioning of the screen, the secondary and connection means being constructed providing a closed electrical circuit through said secondary and through said screen and back to said secondary, a transformer primary having an opening formed therethrough, means mounting the primary adjacent the screen unit and substantially free of the effect of the vibratory movement of the main supporting frame and screen, said means mounting positioning the primary with the secondary extending through said primary opening free of any physical contact between the primary and secondary and free of the vibratory movement of the secondary relative to the primary, and the primary being electrically connected to the secondary solely by air inducing electrical energy in the secondary upon electrical energization of the primary.

5. Electrically heated screen construction as defined in claim 5 in which the transformer secondary is rigid and bar-like.

'7. Electrically heated screen construction as defined in claim 5 in which the transformer secondary is generally U-shaped, rigid and bar-like.

3. in an electrically heated vibrating screen unit of the type in which a screen is mounted on the screen unit and is resistance heated by passing electrical energy therethrough including vibratin means operably connected to the screen unit inducing substantially continuous vibratory movement of the screen during the electrical resistance heating of said screen, said screen mounted on the screen unit for vibratory movement, a transformer secondary, rigid suspension means for connecting the transformer secondary to the screen unit and receiving vibratory motion and through said rigid suspension means vibrating directly with said screen, means electrically connecting the transformer secondary to the screen and providing an electrical circuit through said secondary and through said screen for the passing of electrical energy through said screen to resistance heat said screen, the transformer secondary having a longitudinal portion extending spaced from the screen unit, a transformer primary having an l 1 opening formed therethrough, means mounting the transformer primary adjacent to but spaced from the screen unit and substantially free of the effect of the vibratory movement of said screenunit, the transformer primary being positioned with thesecondary spaced portion extending through the primary opening with the primary substantially laterally surrounding the secondary spaced portion and being free of any physical connection with the secondary which would restrict free vibratory movement of the secondary relative to the primary, and the primary being constructed electrically connected to the secondary solely by said positioning inducing electrical energy in the secondary upon electrical energization of the primary.

9. Electrically heated screen construction as defined in claim 8 in which the transformer secondary spaced portion extends through the primary opening free of any physical contact with the primary.

10. Electrical-1 y heated screen construction as defined in claim 3 in which the transformer secondary spaced portion extends through the primary opening free of any physical contact with the primary; and in which the transformer secondary is rigid, bar-like and generally U-shaped.

1 1. The method of supplying electrical energy to a substantially continuously vibrating screen of an electrically heated screen unit to resistance heat the screen during said continuous vibration, including the steps of rigidly suspending a transformer secondary on the screen unit for vibration directly with the screen, electrically connecting the transformer secondary with the screen forming an electrical circuit through the secondary and through the screen, positioning the secondary extending with a portion spaced from the screen, positioning a transformer primary spaced from the screen and substantially free of the effect of the vibratory movement of said screen, positioning the primary relative to the secondary substantially laterally surrounding the secondary spaced portion for inducing electrical energy in said secondary upon electrical energization of said primary, and maintaining the relative positioning of the primary and secondary totallyfree of any physical connection which would restrict free vibratory movement of the secondary relative to the primary and which would transmit any appreciable amount of the vibratory movement of the secondary tothe primary.

12. The method of supplying electrical energy to a substantially continuously vibrating screen of an electri cally heated screen unit to resistance heat the screen during said continuous vibration, including the steps of rigidly suspending a transformer secondary on the screen unit for vibration directly with the screen, electrically connecting the transformer secondary with the screen forming 1 an electrical circuit through the secondary and through the screen, positioning the secondary extending with a portion spaced from the screen, positioning a transformer primary spaced from the screen and substantially free of the effect of the vibratory movement of said screen, positioning the primary relative to the secondary substantially laterally surrounding and spacedfrom the secondaryspaced portion for inducing electrical energy in said secondary upon electrical energization of said primary, and maintaining the relative positioning of the primary and secondary substantially free of any physical contact between said primary and secondary during the vibratory movement of the secondary. I

13; The method of supplying electrical energy to a substantially continuously vibrating screen of an electrically heated screen unit to resistance heat the screen during said continuous vibration, including the steps of rigidly securing a generally U-shaped bar-like transformer secondary having spaced leg portions and a connecting portion on the screen unit for vibration directly with the screen, electrically connecting the secondary leg portions with the screen forming a closed electrical circuit through the secondary and through the screen, positioning the secondary with the secondary connecting portion spaced from the screen, positioning a transformer primary having an opening formed therethrough spaced from the screen and substantially free of the effect of the vibratory movement of said screen, positioning the primary relative to the secondary'with the secondary connecting portion extending through the primary opening and spaced from the primary for inducing electrical energy in said secondary upon electrical energization of said primary, and maintaining the relative positioning of the primary and secondary so that the primary and secondary are substantially totally free of any physicial contact during the vibratory movement of the secondary.

14. The method of supplying electrical energy to a substantially continuously vibrating screen supported on a vibrating main supporting frame of an electrically heated screen unit to resistance heat the screen during said continuous vibration, including the steps of supporting a screen on the vibrating main supporting frame tensioned in operable position with selectively adjustable screen supporting means of said main supporting frame, rigidly suspending a bar-like transformer secondary having ends on the vibrating main supporting frame for vibration with the main supporting frame and screen, selectively adjustably and electrically connecting the secondary ends to the adjustable screen supporting means of the main supporting frame in electrical contact with the screen supported by said screen supporting means forming a closed electrical circuit through the secondary and through the screen, positioning the secondary supported on the main supporting frame extending spaced from the screen, positioning atransformer primary having an opening formed therethrough spaced from the screen and substantially free of the effect of the vibratory movement of said screen, positioning the primary relative to the secondary with the secondary extending through the primary opening andspaced from the primary for inducing electrical energy in said secondary upon electrical energization of said primary, and maintaining the relative positioning of the primary and secondary so that the primary and secondary are substantially totally free of any physical contact during the vibratory movement of the secondary.

References fitted by the Examiner UNITED STATES PATENTS 743,331 11/03 Ries. 962,828 6/10 Gin. 1,413,053 4/22 Onstad 219-221 1,515,593 11/24 Elsdon-Dew 219-1049 1,626,295 4/27 Patschieder 219-50 1,733,250 10/29 Davis 219-300 2,621,704 12/52 Langer. 2,703,392 3/55 Rex 338- 2,752,578 6/56 Vt/inkel 338-130 2,850,163 9/58 Scanlonet a1. 209-238 2,868,378 1/59 Burstlein 209-238 2,989,182 6/61 Burstlein 209-238 3,080,055 3/63 Riesbeck 209-238 HARRY B. THORNTON Primary Examiner.

HERBERT L. MARTIN, MAX L. LE Y, Examiners.

Claims (1)

11. THE METHOD OF SUPPLYING ELECTRICAL ENERGY TO A SUBSTANTIALLY CONTINUOUSLY VIBRATING SCREEN OF AN ELECTRICALLY HEATED SCREEN UNIT TO RESISTANCE HEAT THE SCREEN DURING SAID CONTINUOUS VIBRATION, INCLUDING THE STEPS OF RIGIDLY SUSPENDING A TRANSFORMER SECONDARY ON THE SCEEN UNIT FOR VIBRATION DIRECTLY WITH THE SCREEN, ELECTRICALLY CONNECTING THE TRANSFORMER SECONDARY WITH THE SCREEN FORMING AN ELECTRICAL CIRCUIT THROUGH THE SECONDARY AND THROUGH THE SCREEN, POSITIONING THE SECONDARY EXTENDING WITH A PORTION SPACED FROM THE SCREEN, POSITIONING A TRANSFORMER PRIMARY SPACED FROM THE SCREEN AND SUBSTANTIALLY FREE OF THE EFFECT OF THE VIBRATORY MOVEMENT OF SAID SCREEN, POSITIONING THE PRIMARY RELATIVE TOTHE SECONDARY SUBSTANTIALLY LATERALLY SURROUNDING THE SECONDARY SPACED PORTION FOR INDUCING ELECTRICAL ENERGY IN SAID SECONDARY UPON ELECTRICAL ENERGIZATION OF SAID PRIMARY, AND MAINTAINING THE RELATIVE POSITIONING OF THE PRIMARY AND SECONDARY TOTALLY FREE OF ANY PHYSICAL CONNECTION WHICH WOULD RESTRICT FREE VIBRATORY MOVEMENT OF THE SECONDARY RELATIVE TO THE PRIMARY AND WHICH WOULD TRANSMIT ANY APPRECIABLE AMOUNT OF THE VIBRATORY MOVEMENT OF THE SECONDARY TO THE PRIMARY.

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