US1548953A - Electrical heating device - Google Patents

Description

Aug. 11, 1925. 1,548,953

A. A. NIMS ELECTRICAL HEATING DEVICE Filed March l5 1924 may]. 1

15 ATTOR Patented Aug. 11, 1925.

UNITED STATES PATENT OFFICE.

ALBERT A. NIMS, OF BLOOMFIELD, NEW JERSEY, ASSIGNOB TO THE STEIN-DAVIES COMPANY, 01 NEW YORK, N. Y.,

A CORPORATION OF NEW YORK.

ELECTRICAL HEATING DEVICE.

- Application filed March 15; 1924. Serial 1%. 099,452.

To all whom it may concern Be it known that I, ALBERT A. NIMS, a citizen of the United States, and a resident of Bloomfield, Essex County, New Jersey,

have invented an Improvement in Electrical Heating Devices, of which the following is a specification.

This invention relates to an electric heating device of the general type used for heat- 1 ing containers.

The invention makes possible the heating of the surface of the container without the development of hot spots. This uniform heating of the surface of the container is accomplished broadly by making portions of the container closures or short circuits between the terminals of conductors in which a low voltage current has been induced, and making this induction of the current successive in accordance with the cycle progress of an alternating current. The nature and objects of my device will be clear from the following specification and drawings.

In the drawin s, like numbers refer to like parts throw out and shown in:

Fig. 1, an elevation partly in section showing one embodiment of my invention,

Fig. 2 a section 2-2 of Fig. 1 looking in the direction of the arrows.

The preferred form of the invention illustrated includes a metallic shell or container 1 of circular cross-section in this instance and which may be adapted in contour and material to suit any particular case or use. Disposed at intervals about the periphery of the container as shown are transformers; which in. the form illustrated are three in number and spaced around the container.

' These transformers are preferably identical in all ways with each other and each may have laminated cores 3 held in place by suitable means such as clamps or straps 4. Upon two sides of the core 3 are wound the primary coils 5 which, when a current is caused to flow through them, serve to energize the cores 3, Around the primary coils 5 are slats or strips 6 which serve as part of the secondary windings of the transformers. metal having a high conductivity so as to carry a heavy current of relatively low voltage and are insulated from the coils 5 sub- These strips are preferably of stantially as shown. Over these secondaries 6 are retaining elements 7 which may be made rigid with the vessel by any suitable means such as rivets 8', the rivets when used being insulated from the secondary 6 so that no secondary current reaches the shell by way of the connections between the retaining elements and the securing means therefor. These retaining elements 7 not only act to retain the secondary strips 6 in the desired positions, but also support and hold the primaries 5 and the cores 3 in place.

The secondary strips 6 follow generally the contour of the vessel 1 and their ends form an electrical contact in the vessel, in this instance by means of the conducting piece 8 which is interposed between the secondaries and the vessel and firmly fixed to them both. These strips 6 also have a contact with the vessel at 8 which may be made in any approved manner. Except for these contacts at 8 and 8 ,.the secondary strips 6 are insulated from the vessel; this insulation being shown at 9. Therefore the vessel wall between the points 8 and 8 is a part of the secondary circuit; that part of which has a lower conductivity than the strips 6. This arrangement applies to the other side transformers shown and in the preferred form illustrated, the secondary strips for each transformer extend over approximately one third of the circumference of the vessel although it is understood that the number of transformers and. their arrangement may be varied as desired.

Therefore in the scheme shown in the drawings, a substantial portion of the container wall forms a resistance portion between the ends, or contact points, of the secondary strips of each transformer and,

being of lower conductivity than the secondaries, heat will be reduced over these areas and be conducte and distributed to the remainder of the vessel wall. In practice, I prefer to have these side transformers, with their corresponding secondary strips extend from somewhere near the bottom of the container 1 to a point somewhat below the usual level of the material in the vessel, although this need not always be done but will depend upon the circumstances of operation in most cases.

In somewhat. the same manner transformers are associated with the bottom of the shell of the container as shown in section in Fig. l and in plan in Fig. 2.

In the form chosen. 1 show six of these transformers, all having a common laminated core shown as at 10 and 11. This core is built up of laminations which interlace at each crossing point such as 10" and 11 with the result that I obtain an etl'ectivc and rigid structure for the core and one novel and useful. The laminations of the core 10 and 11 are firmly bound together by suitable means such as the clamps 18 so that the core becomes practically a solid unit.

()n this core 10 and 11 are mounted the primary windings, in this si.\ of them shown at 12, 13, 14, 15, 16 and 17 m Fig, 2. The primary windings as shown are preterably placed symmetrically, so that, in this case, primaries 12, 13 and 14 Will be respectively opposite primaries 17, 15 and 16, all as indicated in Fig. 2. The secondary strips of these bottom transformers are all similar to that shown at (3 on the side transformers in Fig. 1. These secondary strips for-the transformer-on the bottom of the container extend across opposite primaries and form part of the secondary windmgs for both as is illustrated in Fig. 2 by the strips 19 which together with the bottom of the vessel 1, constitute the secondary for the primaries 14 and 16. These strips 19 are secured in place by means such as the straps 20; these straps may have retaining means such as bolts 21 passing through or fixed to the bottom of the container and insulated from the strips 19. The ends of these strips 19 project beyond one edge of the container 1 and are connected thereto in electrical contact by means such as the angle connections '22 having rivets or the like 23. (See Fig. 1.)

As before, the Wall of the containerin this instance, the bottomcomplctcs the secondary windings of the transformers and forms the heated area.

The other pairs of transformers 12 and 17 and 13 and 15 have secondary strips similar to the secondary 19 for the coils 14 and 16, and they have electrical contact with the container wall and also form heated areas as hereinbefore described so that there will be several points of electrical contact between the bottom of the container and the secondaries of the. transformers and a corresponding distribution of heated areas.

From Fig. 2 it is seen that the secondary strips for the three sets of bottom transformers cross each other and it is clear that insulation must be provided between the secondaries themselves and between the bottom of the container and the contiguous secondary strips. I provide such insulation 24 for the bottom of the container and insulations 25 and 26 between the secondaries of the transformers (see Figs. 1 and 2%. As a result of making my invention su istantially as described in the foregoing I obtain extended heated areas of ample capacity to heat the vessel and its contents without the development of hot spots.

To conserve this heat my device may be surrounded by heat insulating material 27 and the whole encased in a supplemental shell or the like 28. Not only does this prevent loss of heat but greater ease and comfort is provided for those who operate my device.

By using the side and bottom walls of the container as integral portions of the transformer secondaries, I secure eti'ect'ive heating areas in direct contact with the material to be heated in the container and by suitable means-one of which might be an arrangement of taps on the rimary windings-I can obtain varying (egrees ot heat and closely regulate this heat to the needs of the occasion.

The preferred form of my invention which I show is adapted for use with a three-phase. system of alternating current although it is obvious that a ditl'erent number of phases may be used with equally good results and I do not restrict myself in all cases to the use of a three-phase system. 1. have chosen this merely by way of example.

It is well known that alternating current is necessary for the operation of transformers and that this current has detinite curve characteristics. tonscqucntly, in a multiple phase system such as I have hosen for illustration, the cores ol the transformers will be energized according to the cycle of the current, each transformer receiving its maximum magnetic intensity in sucwssion so that the secondaries have maximun'l current induced in them accordingly. Consequently, no part of the, vessel forming the resistance portion of the secondaries is held at maximum temperature with the result that an even distribution of heat is secured and hot spots avoided.

It is important to note that the primary coils are so coi'uiected lo the current supply that the currents induced in the common secondaries are in the same direction. This is an essential element in connecting the primaries of opposite transformers to a particular phase.

On the side trans'torn'iers, such as shown in Fig. 1 the heat generated in the shell follows paths normal to the direction of the secondary strips and the heated area corresponds to the surface covered by the strips such as 6 plus whatever tlare of? the heat there may be beyond boundaries of the secondaries.

\Vhile the heat paths are. normal to the direction of the secondary strips and, as before stated, the transforn'iers being energized in succession, I obtain a current sheet which flows in the direction of the circumference of the container. This further explains how I secure an even distribution of heat and an entire absence of hot spots.

The bottom transformers shown in F1g. 1, as before explained, are preferably grouped in pairs each pair having a common secondary with the bottom of the container as the resistance portion and the pr1mar1es connected to the current. supply as heretofore explained. These primaries are therefore energized by opposite pairs in sequence and according to the progress of the cycle of the current so that currents are induced in the secondaries accordingly. I therefore obtain a rotating current sheet so that I again obtain even heating without hot spots on the bottom of the container.

It is well known that it is difficult to evenly heat a circular surface by making that surface the resistance in a circuit for it must necessarily bethat parts of that sur face will receive less current than others with the resultant uneven heating. By disposing my transformers as I have and so connecting them as to secure a rotating current sheet, I avoid these disadvantages and provide even and effective heating over the bottom surface of the container. This is important and is not found elsewhere.

Furthermore, in all cases, I reduce the space enclosed by the secondaries to a minimum with the result that any magnetic leakage between the primaries and the sec ondaries is practically eliminated which is an important operating advantage. I

From the foregoing description and as shown in the drawings, it is apparent that my invention embodies new and useful prop erties and has advantages and benefits not found in devices of a similar class.

While 1 illustrate my device in a preferred form to show the principles involved and the method of their application, it is ob vious that many changes and variations may be made without departing from the spirit of my invention and I desire that my claims be interpreted in this light. I

Also I desire to bring out that one of the prime objects of my invention is to produce evenly heated areas and for that reason the shell or container should have a substantially uniform thickness of wall. That is, there should be no sudden or abrupt reductions in thickness such as would develop hot spots or tend to create a higher temerature in one part of the heated area than in another. it IS possible that the containers have a wall or walls of difierent thicknesssuch as the bottoms and side or sides and still be heated uniformly so long as the path of resistance in the secondary part of the shell is of substantially even thickness. My use of the terms uniformcross section,

uniform thickness, etc. is meant in the light of the foregoing.

What I claim is:

1. An electric heating device including a metallic shell, of uniform cross section of metal, a plurality of electrical conductors 'in the circuit with said shell and means for inducing current in said conductors.

2. An electric heating device having a metallic shell of uniform cross section of metal to form part of a plurality of secondary circuits and means for inducing low voltage'currents in said secondaries.

3. Anelectric heating device including a vessel and a plurality of transformers disposed about the surface thereof, said vessel forming part of the secondaries of said transformers to generate heat in said vessel.

ondaries at the same time to give an even heating eil'ect to said shell.

6. An electric heating device including a metallic container of uniform thickness, a plurality of secondary circuits including the container, a series of magnetic cores adapted to produce currents in said secondaries in phase sequence.

7. An electric heating device including a metallic container, a plurality of transformers, the secondaries of said transformers including the shell of the said container and the cores of the transformers being magnetized in sequence to effect a rotative heating edect of the container.

8. An electric heating device including a metallic container, a plurality of magnetic cores having primary and secondar windings, the secondary windings inclu ing the said container to form heated areas therein and a rot-ative area of magnetic intensity created in said cores according to the progress of the cycle of the primary current.

9. An electric heating device'including a shell, a plurality of magnetic cores having primary and secondary windings thereon, said secondaries being partly composed of narrow conducting strips in close proximity, each strip forming a closed secondary with the shell to create rotative heating effects according to the cycle progression of the current in each secondary.

10. In an electric heater, a metallic container for material to be heated, a plurality adapted to energize sald cores, secondary windings on said primaries composed of parallel strips, each strip forming a closed secondary with said container to form paths of increased resistance to cause heat to be generated in said container, a heat insulating material surrounding said container and cores and windin s, and a supplementary container surroun ing the whole.

11. An electric heating device including a plurality of transformers with a common magnetic core and a metallic shell of substantially uniform cross section said shell being a part of the secondaries of said transformers, and a heat insulating substance surroundin the whole.

12. An e ectric heating device including a vessel, a plurality of transformers disposed upon vthe surfaces of said vessel, said vessel forming a portion of the secondaries of said transformers to form evenly heated areas thereon.

13. An electric heating device including a metallic container, a plurality formers disposed upon the vertical surfaces of said container, a plurality of transformers disposed upon the under surfaces of said vessel; portions of the container forming portions of the secondaries of all transform ers to produce heated areas in the container.

14. An electric heating device includin a vessel, a plurality of transformers disposed upon a surface of said vessel, said transformers having a common core and portions of said vessel forming a part of the secondary windings of said transformers.

15. A heating device including a container, means to induce low voltage currents in portions of the wall of said container to produce heated areas therein, said currents being in the phase sequence of an alternating current. i

In testimony whereof, I have signed my name to this specification this 8th day of 45 March, 1924.

ALBERT A. NIMS.

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