US1977399A - Heating apparatus - Google Patents

Description

I l l I I I I l I I I I I I I I I I I I II I I Filed Sept. 24, 419.30

2 Sheets-Sheet l Oct. 16, 1934. E. F. NORTHRUP HEATING APPARATUS Filed Sept. 24. 1950 2 Sheets-Sheet 2 M0/magy. Y

UNITED STATES PATENT OFFICE l HEATING APPARATUS Edwin man Nal-tmp, Princeton, N. J., signor to Ahx Eleetrothermic Corporation, Ajax Park,

N. J., a corporation ot New Jersey Appunti september 24, 1930, serial No. 484,121

19 cmnml.L (c1. 21e-13) My invention relates tothe inductive heating of metallic sheets or plates.

One purpose of my invention is to inductively heat a resistorilnullle having a secondary current path passing about more than one mullle A further purpose is to heat interior walls of a resistor muille by induced current conducted from the point of induction through the interior walls. A

A further purpose is to induce electric current in the outside walls of a muille and to pass the current through the partition walls between compartments in the mullle.

. A further purpose is to provide a tortuou or serpentine secondary current path whose convolutions include a plurality of mume compartments within which heating is effected.

A further purpose is to interrupt the edge of an induction furnace resistor secondary in order to require that the induced current travel through a longer path to utilize the additional heating effect secured. Y

A further purpose 'is to provide parallel compartments having walls forming a heating resistor for the compartments, and to induce current in the compartment walls, spacing parts of the separating walls to cause the current to travel on both sides of the spacing in order 'to heat the entire wall.

A further purpose is to longitudinally slit a partition wall between two parallel compartments which are to be heated electrically so that electric current induced in the walls of the compartments may lbe caused to traverse a path about'the slit, increasingthe resistance while avoiding increase in the secondary reactance.

A- further purpose is to utilize not only the sides but the end oi a munie as an electrical resistor in which heat is generated throughv induction of `electric current,

A further purpose is to interrupt the continuity of the enJd of a'resistor mullle in which current is induced so that the end of the mutlle may be heated by l es;

interruption. Y f

A further purpose is to inductively heat a plurality of electrical resistors forming a mule compartment, one resistor being axially above another, and desirably to change the number of resistors used according to the dimensions of the charge. Y

A further purpose is to make up a multiple l compartment muille from separate resistor 66- e on both sides of the tions, each including part of all of the mule walls.

A further purpose isl` to vertically insert a plurality of charges concurrently within a plu-v rality of parallel chambers in a muiiie.

A further purpose is to use a common closure for the charge-inserting ends of a plurality of parallel muffle chambers.

A further purpose is to bell a plurality of mulle compartments so as to vretain gases lighter than air within the compartments and to insert the gas preferably after thel charge has been applied.

Further purposes will appear in the specification and in the claims.

My invention relates to the processes involved as well as to apparatus by which the processes can be carried out.

I have preferred to illustrate one main form only with modifications, selecting a form which is practical, efficient and highly advantageous but which has been selected primarily because it illustrates to the best advantage the principles involved.

Figure 1 is a. broken transverse section partly in elevation, showing the parts of one form of my construction ready for operating assemblage by insertion of the charges. Y

Figure 2 is a broken top plan View of one resistor section used in Figure 1.

Figure 3 is a broken section of Figure 2 taken upon line 3--3.

Figures 4, 4a and 4b are broken top plan views corresponding to Figure 2 but showing modflcations.

Figure 5 is a fragmentary section upon line 5--5 in Figure 4, slightly modified by omission of the dowel, and having added a vview of the next muile section with electrical insulation between the sections.

Figure 6 is a broken bottom plan View or the muille end section shown in Figure 1.

' Figure 7 is a broken section taken upon line l 7-7 of Figure 6.

In the drawings similar numerals'indicate like but adaptation of the .invention to meet thel ing. Unequal heating is likely to cause buckling of the plates.

At the present time the heating of steel sheets for use in automobile bodies requires about 18 hours in one typical installation.

My invention is excellently suited to heating sheets of this character quickly and uniformly;

exacting requirements of this particular work does not mean that the invention is unsuited to other heating applications.

Aside from annealing there are not only numerous other purposes for which relatively broad and thin metal must be heated, as, for example, preliminary to stamping and forming operations, but other objects require heating for the same and for other purposes.

I have discovered that induced current may be applied to great advantage for such heating o'not only fiat sheets and plates but such deformed sheets or plates nested or individually and also to the heating of objects of regular or irregular contours.

however, -that any suitable shape of charge is included within this designation, the muille compartments merely being made to conform to the dimensional requirements of the particular product to be heated.

By my invention I inductively apply current `to a resistor comprising the mume walls. As

` thegdepth of penetration'of the flux is relatively short, and as good coupling is required, substantially all of the induced current will be developed in the periphery of the resistor.

I have therefore provided artiiicial means for conducting the induced current from the peripheral point at which it is developed into the parts of the munie which are not directly accessible to the induction. For this 4purpose I provide an electrically conducting path for diverting the induced current into the interior of the mume, particularly into the partitionwalls between individual munie chambers..

Aside from the resistance heating of the interior parts of the muile, the elongated current path through these interior parts has certain advantages not at ilrst apparent. In the ilrst place, this path increases the resistance of the secondary circuit, thus causing a certain amount of RP heating in the elongated path.

Furthermore, the maximum power will be absorbed by a secondary when the secondary resistance equals the secondary -r'eactan'cel Since in.V my partition walls tlm current on opposite sides of the walls is -ilowing in opposite direction,'the` path through the partition walls is substantially non-inductive and does not tend to increase the secondary reactance. It will however increase the secondary resistance, and as the reactanceis ordinarily more than the resistance, will improve the power consumption.

I ndit convenient to build up my mume of a plurality of inductively heated resistors placed one upon another. Since, when these are properly registered, adjacent parts ofadjacent resistors will be at the same potential, no tion need be placed between resistor sections. When the. dimensions of the charge sheets are increased in'two directions beyond the maximum 80 chamber dimension of the munie section, I will then be obliged to Aemploy new mullle sections.

Sinceinmanycasesthechargewillsuffer from oxidation, I will ordinarily employ a protecting orireatingahnosphereinmymumeto avoid injury to the charge.

Describing the structure of Figurel in illustration and not in limitation v I have showna multiple 'compartment muille 10 made up of sections 11 between which no dif- 90 ference of potential is intended to exist and which are therefore rested one upon another, being quickly and easily alined by means of dowels andY openings 12, 12'.

The mume is shown as bottom-loading at 13 95 and forthis upon aplatform 14having an opening 15. About the munie and upon the platform I placeV an inductor coil 16 supplied with current from any suitable source 17. Conventional power factor correction is shown by condensers 18. At the top the munie is closed by a cover 19.

Electrical insulation for the coil' is shown at 20. Thisatthesametimeactsasaretaining wall, if such be needed, for a nely divided 105 heatA insulator 21 which may be poured into the space and over the combination mullle. Because oftheuseofslitsorcutsinthemullle cover, afterwards discussed at length, I use strips 22 ,to prevent the -nely divided material from passinglntothecompartments 23, 24and25ofthe. mume. ThevariouspartsofFigurelareconventionally, divided at the middle by broken lines 26 to indicate that the number of compartments may be increased if desired.

Thenelydividedmaterialusedmaybeany suitable heat insulator of which Zircon sand is a good example, but of which diatomatious earth-onsaleunderthe nameofsilocel-isthe best example known to me. 120

It is desirable though not necessary to use a heat insulating top above the finely 'divided refractormwhichtoplshowatm. Thisisin- 'Wheremetalsheets29ofsteelorironforexamplearetobeheatedtheyarepreferablybaled andtied at.30 andarerestedupontheiredges onabottomclosure3l whichultimatelyiits into 130 theopeningllntheplatfomsealingtheopcning. 'lhis closure is effected by lifting the bot. tom 31 by means of plungers 32 of hydraulic elevator cylinders 33 whichare shown ashaving inlet and outlet uid Supply and discharge con- Whether the'mume is made up in a single section or is of unit construction as seen in Figure 1, my invention provides for heating not only the outside oi the muille, but also the interior partitions of the muiiie by current induced directly in the outermume walls and conducted through the partition. I secure this highly desirableeffeet in practice by interrupting the e of current through the outer walls at the partitions and directing this current in series though one side of each partition, toward the opposite outer wall, and back through the other side of each partition, the induced current then continuing through the outer wall.

The detail of how this diversion of the current path is secured is not important to the broader aspects of my invention, which contemplates the 'artificial extension of the -current path to pass through the partition walls in series with the outer walls. The most convenient way of carrying out the invention is to form a partition dit vided through most.A of .its length parallel to one of its surface planes and electrically connected at the 'ends with the adjoining outer walls, so that the entire partition is in series with the outer wall.

In Figure 2 there is shown one of the resistor sections such as are illustrated in Figure 1. This may be cast integrally whether the divisions are cast in or cut in. 1

The muiiie chambers are separated by parti ` tion walls 44 and 45. Each of the walls 44 and 45 is separated interiorly at 46 or 47, dividing the partition wall 44 into two conductors 48 and I 49 and likewise dividing the partition wall 45 into two conductors 50and 51.

Remembering that the inductor coil surrounds the outer surfacev of the resistor, current will-be induced for `example in the outside conductor 52 and likewise in the short end conductor 53 and will tend to flow around the outside of the resistor. Due, however, to the separation 46, the secondary current will be compelled lto flow through the conductor 48, then across vat 54 and finally back through the conductor 49 on the other side of the partition wall.

60 and 61 atxthe ends of the partition walls are In Figure 4b I illustrate longitudinal partition separations 46z and 463 performing the function of the partition separation 46, and extending from opposite ends toward the interior to the area 54', where the separations cease. In this case 'the induced current will travel in from both sides of the outer wall through the partition wall, across at 54' and back through the opposite partition wall.

The separations 472 and 473 are similar to 46z and 463, and are discontinued at 56 to permit the current to :liow from one side of the partition wall to the opposite sidey of the partition wall.

In Figure 5 I illustrate fragments of two resistor sections 11 placed one above another and separated by electrical insulation 62. In this gure I have omitted the dowel for insuring that the adjoining sections register. 'Ihe insulation will then insure that points of diiferent potential do not come into contact.

6 and 7 illustrate an end section for the munie. For convenience the end section is domed at 63 to provide additional interior capacity for the muille. separations 464 and 47* correspond generally with the partition separations in the interior sections. In addition the centers of the domes contain longitudinal separations 64 to insure that current will flow through the tops of the domes to heat them.

It will be evident that the relation between the resistance and reactance in the secondary circuit will be affected by the frequency, which must'therefore be considered to determine the difference between .the reactance and resistance when this difference is sought to `be made up. The frequency selected will, of course, make a diiference in the depth of penetration, requiring thicker walls for lower` frequency, the walls being preferably not less in thickness than three times the depth of penetration and certainly not I less than twice the depth of penetration. It

must be remembered also that with higher frequency the heating effect is improved at tem- This current and more current there induced'f'vpeltllres bOVe the decalesence point With iron will then flow through the end conductor 55, but

will be again diverted by the separation 47 of vthe partition wall 45, and will take the path through the partition conductor 50, across at 56 and back through the opposite partition conductor 51 to the end conductor 57. The secondary circuit will then be completedthrough the outside condurztors 58 and 59. V

It will beevident that the form of the resistor may be varied in a number of ways immaterial to my invention. I have illustrated'a number of thesevariations in Figures 4, 4a and 4b.`

In Figure 4 the separations 46 and 47 bear the same relation to the other structure as in Figure 2, but the partition wall has been separated at 60 and 61 from the end wall 59. Electrically I consider this change of relatively little importance because it Adoes not vitally alter the current path in the partition, which inany case will be through the partition conductors 48 and 49 or 50 and 51.

In Figure 4a I illustrate the partition separations 46 and 47 yextending from opposite ends of the outside muiile wall. I also show a separation between the outside wall 59'and the partition Wall at 60, but no corresponding separation at the opposite end of the other partition wall. It will thus be seen that the separations outside walls of the muille close to the inductor coil lto build up an appreciable fiow of current and I' then conduct the current thus inductively produced into interior walls of the muffle where I use it advantageously to heat parts in which it would not be possible directly to induce current. Y

I believe that I am the first thus to divert current induced in the walls of a resistor muiile to be used for resistance heating elsewhere.

I believe also that I am the first to assemble an inductively heatedly mufile comprising a plurality of chambers from a series of units built up one against another. I

It will be evident that I have provided not only an adjustable muilie of unusualv adaptability and convenience both in ,manufacture and in use but that I have madeaccessime for direct induction' the interior of: the structures which hitherto have been inaccessible and which .have relied for their heat upon conduction from the exterio'r surface.

It will be evident `that there is a considerable advantage in coupling in having'the primary coil conform to the shape of the secondary and in spacing it uniformly from the secondary.

I nview of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtainallor part vthe inductor having partition walls carrying current in series with current induced in the outer walls.

2. A resistor forming walls of a-muille adapted to be used with a surrounding primary coil and having interior partition walls electrically in series with its outside walls.

- used with a surrounding inductor coil and having the resistance of its outside walls increased by articially lengthening the circuit path within the interior of the muiile.A

4. A muille secondary resistor adapted to be used with -a surrounding inductor primary and having the length of its'secondary current both artificially and non-inductively -increased at a distance from its outer walls.

5. A secondary muiile' resistor 'adapted to Vbe Iused with a surrounding inductor coil and having the resistance of its outside walls artificially increased byA including in series within their circuit partition walls, the increase being non-- inductive and suiiicient-to make the resistance .of the circuit approach the value of the reactance so that the power consumption is increased.

6. Ina multiple secondary resistor having a plurality of compartments, outer electrically conducting compartment walls, and electrically conducting interior partitionfwalls divided in the planes of the walls, each division being cut through .an outer wall.

7. A resistor muille secondary adapted to be used vwith a surrounding inductor primary and having interruptions in the surface of the resis tor across the induced current path, providing an artificially extended length of secondary conductor path returningupon itself about the interruption.

8. A muille havinga plurality of compartments and a serpentine electrically conducting wall therefor, in combination with an inductor coil surrounding the entire wall and inducing cur` rent through the convolutions of the serpentine wall. Y

9. A resistor mutlle secondary for use with a 4 surrounding inductor primary and having outer side and end walls and partitions between opposite walls to divide the munie into compartments and having the walls from which the partitions spring and the partitions separated for a considerable distance toward the `opposite walls through the lengths of. the partitions, whereby current'- nduced along the outer walls in a di- 3. A secondary muille resistor adapted to be rection across the partitions will follow onepartition part at the separation to a point s up of separate sectionsdivided parallel to the current paths and each apertured perpendicular to the division to form in the aggregate compartments of adjustable height depending upon the number df sections used. 11.. A multiple compartment resistor mums secondary of adiustable height having parallel compartments and comprising independent resistor sections divided transversely across the compartments.` Y

12. A resistor mume secondary section having a plurality of openings transversely to the plane of the section corresponding with compartments to be built up from the sections and having the partitionvwalls between the openings divided in the planes of the partition walls from side to side of the section parallel with the longer Ydimension of the openings and from one terminal QO wall about the `opening nearly to the opposite wall.

1a. A; plurality Yof :nume secondary sections, each having a plurality of openings transversely to the plane of the section correspondingf with 105 compartments to be built up from the sections and having the interior partitio'n walls between the openings divided in the planes of the par' tition walls from side to side of the section parallel with the longer dimension of the openings 110 and from one terminal wall about the opening nearly to the opposite wall and means for ensuring that parts of one section do not engage parts of another section which have a different 14. A resistor mufileV end secondary adapted to closea plurality of 'munie compartments and toreceive induced current from a; primary surrounding the mume,` having the walls of the mume end -separated inwardly from outside edge walls at intervals a substantial distance toward an opposite edge in order-that current induced about the perimeter of the mume end will follow the line ot the separation to a juncture point andbackagaintothesameedgeofthemume. 15. A multiple compartment resistor munie secondary of adjustable height having parallel compartmentsand comprising independent resistor sections divided across the compartmentsopen at the bottom in combina-- tionwithmeansforinsertingcharges from b neathlandaclosurei'orthebottomuponwhich 16. A multiple compartment resistor munie secondary of adjustableheight having parallel compartments and comprising independent resistor sections divided transversely across the compartments open at the bottom in combination l*with means for inserting charges from be- Y neath, a closure for thebottom upon which the 1 charges rest, a closure'icr the top of the muille and means for inserting av vspecial atmosphere within the mume as a bell.

1'1. A redsun munie secondary of non-circular*A i ttons between them separated through to the outer walls to artificially extend the path of the induced current so that the resistance' of the induced current at the frequency selected will approach the reactance of the circuit.

19. A resistor munie secondary adapted for use with a surrounding inductor primary, having a plurality of compartments with interior

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