US1806027A - smalley - Google Patents

Description

y 9, 1931. E. L. SMALLEY ROTARY .HEARTH FURNACE Filed July 10, 1930 7 Sheets-Sheet I l.:: Q

ATTORNEY May 19, 1931. E. L. SMALLEY ROTAliY HEARTH FURNACE Filed July 10, 1930 7 Sheets-Sheet 2 r I N V EN TOR. (SAM/6w Cw 6mg,

A TTOR I May 19, 1931. SMALLEY 1,806,027

ROTARY HEARTH FURNACE Filed July 10, 1930 7 Sheets-Sheet 3 nvmvrox.

May 19, 1931. E. L. SMALLEY ROTARY HEARTH FURNACE Filed July 10, 1930 7 Sheets-Sheet 4 l INVENTOR. fidw/iw 9, 6M

, ATTORNEY May 19, 1931. E. L. SMALLEY ROTARY HEARTH FURNACE Filed July 10, 1930 7 Sheets-Sheet 5 INVENTOR. a 7

ATTORNEY;

7 May 19, 1931. E SMALLEY 1,806,027

ROTARY HEARTH FURNACE '7 Filed July 10, 1930 7 Sheets-Sheet 6 IN V EN TOR.

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BY 5 d ATTORNEY y 9, 1931. E. 1.. SMALLEY ROTAI QY HEARTH FURNACE Filed July 10, 1930 7 Sheets-Sheet 7 IN VEN TOR.

6M BY 0% dtrfi 447 ATTORNEY.

Patented May 19, 1931 UNITED STATES PATENT OFFICE EDWIN L. SMALLEY, 01 WHITEFISH BAY, WISCONSIN, ASSIGNOR TO HEVI DUTY ELEC- TRIC COMPANY, OF MILWAUKEE, WISCONSIN, A, CORPORATION OF WISCONSIN ROTARY nnmrn 'rommcn Application filed m 10,

My invention relates broadly to rotary hearth furnaces and more particularly to electrically heated rotary hearth furnaces;

One of the objects of my invention is to 5 provide a construction of rotary hearth furnace of the electrically heated type having control circuits so arranged that the time required to saturate articles under heat treatment at a given temperature may be considerably decreased with respect to the time cycle heretofore required for the heat treatment of articles in a rotary hearth furnace.

Another object of my invention is to pro vide a construction of rotary hearth furnace 16 wherein the amount of oxidization formed on articles being heat treated may be considerably reduced over that heretofore experienced by reducing the time required in saturating such articles to a given tempera- 20 ture.

A further object of my invention is to provide a circuit arrangement for electrical heating elements located in the outer and inner side walls of the annular chamber of a 2 rotary hearth furnace in combination with an arrangement of heating elements in the moving hearth of the furnace whereby successive portions of the hearth are progressively transferred from one temperature control circuit to a succeeding temperature control circuit during the cyclic movement of the hearth.

A still further object of my invention is to provide a construction of rotary hearth furnace wherein a swinging bafiie divides the charging and discharging portions of the furnace, the swinging bafiie having heating elements disposed thereon and electrically connected in circuit with the side wall and bottom heating elements in the furnace chamber.

Still another object of my invention is to provide a swinging baflie between the charging and discharging portions of the furnace wherein an electrical circuit may be closed to sound an alarm in the event that articles on the hearth abut against the swinging baflie during the rotary movement of the hearth adjacent the discharge portion of the furnace chamber in order that a warning may 1930. Serial No. 467,078.

be given for the removal of such articles under heat treatment.

Another object of my invention is to provide a system of electrical distribution for energizing successive sections of the heating elements in a rotating hearth,utilizing a minimum number of circuit closing means for simplifying the distribution of energy to the several circuits constituting. the heating means for the furnace.

Another object of my invention is to provide a rotary hearth furnace in which the heating chamber may be fuel fired in combination with an electrically heated rotary hearth for more accurately controlling the temperature of the hearth throughout its rotating cycle.

Still another object of my invention is to provide a system of electrical connection for the heating elements in the side walls and hearth of a rotary hearth furnace for automatically cutting off a predetermined sectionof the heaters in the rotary hearth and cutting on another predeterminedsection of the heaters in the rotary hearth in accordance with the progressive movement ofthe hearth during the heat treatment cycle.

Other and further objects of my invention reside in the construction of rotary hearth furnace and electrical control circuits therefor as set forth more fully in the specification hereinafter following, having reference to the accompanying drawings in which:

Figure 1 illustrates in plan view one half of the rotary hearth furnace of my invention; Fig. 1a represents in plan view the other half of the rotary hearth furnace of my invention, plan views beingltaken on different sectional lines at different levels through the furnace, sector A being a top elevationv including part of the door operatingmechanism, sector B being a plan view 0 the fire clay tiles forming part of the arch. of the annular chamber, sector 0 being av plan view of the insulation below the heating elements in the hearth, sector D being a plan view of the under structure below the bottom of the annular hearth, sector E being a plan view of the heating elements and the fire brick composing a recessed portion in the hearth 1 to receive such heating elements,'and sector F being a plan view-of thehearth plates coverlng the heating elements together with a sectional view of the inner and outer side walls of the annular chamber; Fig. 2 shows a half side elevation and sectional view taken substantially along line 22 of Fig. 1a; Fig. 3 is an enlarged cross-sectional view showing the moving hearth and the swinging baffle in the rotary hearth furnace similar to Fig. 2; Fig.4 is a sectional view of the swing ing bafiie together with the control'mechanism for actuating an alarm when the swinging baffle abuts against-material on the rotary hearth during progressivemovement of the hearth; Fig. 5 is a diagrammatic view showing the heating and controlling circuits of a temperature control zone in the rotary hearth furnace showing a plurality of col-' lectorrings for the coils of the rotary hearth and energizing circuits which connect thereto; Fig. 6 is a diagram, showing a modified control circuit whlchmay be employed for progressively energizing different sections of the heatersin the hearthin accordance with 5 p the movement of the furnace; and Fig. 7 is a cross-sectional view of a modified form of irota'ry hearth furnace in which the annular heat treating chamberis provided with fuel heating means therein supplementing the electrically heated rotaryhearth.

The rotary hearth furnace of my invention has proven highly practical in operation. I have found that it requires approxi- '5 mately thirty-five minutes to perform heat treatment work in the same size annular chamber and with the same kilowatts con-- nected as compared to fifty'minutes for the performance of the-same work under similar conditions in rotary hearth furnaces of prior designs. By reducing the heat treatment "time, power consumption is reduced, because radiation'loss of afurnace is a constant per hour. Less oxidization in the heat .treatment of articles occurs because of'the reduction in time during which such articles are subjected to oxidizing temperatures. Heretofore it has been customary to have heating elements only in the side walls of a rotary hearth furnace for high temperature work. This requires that -=the top surfaceof the rotary hearth be elevated in a horizontal plane considerably above the bottom portion of the side wall heating elements. Another method includes theuse of some elevating device to keep the articles above the top of the hearth when the hearth is in the same horizontal plane as the bottom of the side wall elements. In the furnace construction of my invention I do not require that articles be elevated above the bottom portion of the side wall elements, and I'have the succeeding circuits in the hearth automatically connected to the next succeeding temperature control zone with respect to the-side wall elements of the various control zones as will be hereinafter described in detail.

Throughout the drawings I have used the same reference characters to refer to similar parts. Reference character 1 indicates the annular chamber of the rotary hearth furnace formed by side walls 2 and an arch extending therebetween and over the chamber, the walls and arch being of fire brick construction. The side walls 2 are supported by heat insulation material indicated at? all of which is enclosed by a suitable steel outer shell 4, the roof plate 5 and the inner supporting tube 6. The inner and outer side walls 2 of the chamber 1 are maintained in place by angle plates designated at 7. The bottom of the hearth is represented as a steel casting 8 having suitable side retaining plates 9 between which the rotary hearth is built up. I provide an annular sand or fluid seal both at the outside and inside peripheries of the rotary hearth as designated at 10. Sea-ling is effected by means of any suitable materlal in the trough 10 such as sand, oil. or water, etc.

The inner and outer side walls or ledges of the annular rotatable hearth are indicated at 11a. Alining of fire clay indicated at llb'extends over the heat insulation designated at 12 for confining the heat in the rotary hearth. Aligning blocks 110 are used; between refractories 16. Upwardly extending fire brickll is located between the fire clay parts 116 and serves to support the cast non-oxidizing members 15 which provide. 100 mounting means for the hearth plate 13'. The hearth plate 13 rests upon the refractory ledges 11a and the non-oxidizing supports 15 as shown. The hearth plate 13 is constructed of any suitable material such as rolled or 5 cast nickel-chromium alloy, the plate being provided with an inner upturned flange 14 which serves the purpose of retaining articles on the hearth. The refractories which support the heating elements 17 are repreno sented at 16 supported on the fire clay parts 11?) and disposedbetween the ledges 11a and fire brick 11. These refractories are shown more fully in my Letters Patent No. 1,762,- 701, dated June 10, 1930, based on applica- H tion Serial No. 373.013, filed June 22, 1929. The electrical .resistor is indicated M17 in the form of a. return bend coil of an alloy.

such as nickel-chromium. Beneath thebot- I tom plate 8 of the rotary hearth there is fixed 1z0 an annular rail 20 which is adapted to roll upon the spaced rollers 21 which are journaled in bearings 21a supported from the foundation of the furnace. The rotary hearth is maintained in alignment during the movement thereof by a plurality of radially positioned horizontally disposed yokes 18, each of which has a roller 18a therein adapted to engage the side of rail 20. The rollers 18a are all radially adjustable by lators 23. Contact brushes 25v are located beneath the rings 22 and are mounted in brush holders 26 having springs 27 for retaining the. brushes in slidable contact on collector rings 22. The insulated support 28 carries the brush holders 26. As the rotary hearth revolves wiping connection is maintained between the contact brushes 25 and the collector rings 22. The steel shell 4 of the furnace is appropriately reinforced by buck stays 29 as shown in Figs-111a and 2. The hearth is rotated by means of driving motor 30 shown in Fig. 1 which is connected through the driving speed reducer 31 to the worm gear speed reducer 32 for driving shaft 32a. On the end of shaft 32a, I provide a pinion 32?; which meshes with the annular rack 32c which is mounted upon suitable brackets 3203 depending from the bottom plate 8. A suitable charging door is shown at '33 while a similar door 34, the position of which is generally indicated in Fig.

1a, is provided at the discharging portion of the furnace. The door operating mechanism for charging door 33 is shown in Fig. 2 as comprising the air hoist 35 which operates segment 36 for elevating or lowering charging door 33. The discharging door 34 is operated by air hoist 35a and segment 34a as shown in Fig. 1a. The loading and unloading shelves are indicated at 38 which are operated by air hoists 37. The heating elements mounted on the inner side walls of the rotary furnace have been designated at 39 while heating elements 40 are arranged on the outer side wall of the annular chamber.

While I have shown and described a furnace chamber heated with electrical heating elements only in the sidewall and hearth, I may, in some cases. prefer to use elements in the arch also, which may be mounted as shown in my Letters Patent No. 1,768,865,

dated July 1st, 1930; MT may prefer to use heating elements in the arch without elements in the side walls. Further, I may Wish to heat the furnacechamber by the combustion fuel method by means of burners extending through the outer side walls to the furnace chamber as shown in Fig. 7; and having in connection therewith, the hearth electrically heated which might be on a three phase connection as shown in Fig. 6.

Fig. 7 illustrates conventional forms of fuel burners 80 extending through the side walls of the furnace chamber and arranged to heat charges within the furnace chamber. I have illustrated a gas connection 81. leading to the burners 80 and controlledthrough adjustable valve 82. The air supply 83 is controlled through adjustable valves 84 leading to the burners 80 whereby the combustion of the gas for heating the furnace chamber may be controlled. The electrically heated rotary hearth construction illustrated in Fig. 7 is identical with the construction heretofore illustrated and described in Figs. 1-6.

The heating elements on one side of the swinging baflie 42 are shown at 41. The swinging bafiie 42 is shown more clearly in Fig. 4 and has projecting lugs 43 and 44 as illustrated in Fig. 1a retaining pocket-like electrical refractories 45 which support the return bends of the resistor 41. As shown in Fig. 2, the swinging baflie 42 is mounted upon rockable shaft 46. The shaft 46 extends through the side wall of the furnace and has a lever 47 as shown more clearly in Fig. 4 mounted thereon at the top of which there is, pivotally mounted, lever 48 pivoted to the lever 47 by means of pin 52. Lever 48 has roller 49 rotatably journaled'in one end thereof and the lever is maintained in tension by means of spring 50. The retaining lug 51 keeps the lever 48 in normal position. I While in the drawings I have shown a load ,ing door and a discharge door with the baffle plate approximately midway between the two doors, there are some cases where I may prefer to use only onedoor. Such a case. may be where one operator, due to the time cycle of heating and the character of the work performed. may have sufiicient time to both load and unload the furnace. In that case, the swinging bafilemay be located on the center line of such single door, but the operating characteristics of the baflle plate with its heating elements and the alarm device as hereinbefore described may be utilized.

lVhen any article on the hearth comes in contact with swinging bafile42. which may happen if the operator overlooks the dis-- charging of a piece from the hearth. the bafile plate is thereby swung in the direction indicated by arrow 42a. thereby causing rotation of the swinging bafile. lever 47 and lever 48, until roller 49 comes in contact with the concave face 54 of spring 53, shown mounted at one end by post 55. The deflection of spring 53 thus caused, makes a similar deflection of spring 56 until contact is effected between electrical contact 57 and 58, thus closing circuits 59 as shown, through any alarm device such as a horn, or a light, or a bell as shown; at 60. At the sound of the alarm device, the

operator has the opportunity of removing an article on the hearth which has swung the bafile to an alarm position. In regular practice, however, I provide in conjunction therewith, the motor starting device convenient to the operators position, so that upon the sounding of the alarm he may quickly open the motor circuit; and start the motor again when the overlooked article has been removed.

The electrical connections for the heaters in side walls of the chamber and in the rotary hearth are electrically connected as shown more clearly in Fig. 5. A typical control zone is illustrated in Fig. 5 of which there may be any number in the annular. furnace. The one control zone shown is of 120 length, though I may have the controlling The relationship of spacing between lever- 72 and cams 62 is such that lever 72 is depressed for opening circuit in limit switch 71 before brushes 25 come in contact with electrical separators 61. By such arrangement no current is passing through the circuits while brushes 25 are in contact with separators 61. 1

In the electrical circuits shown, the inner and outer side wall elements 39 and 40 are shown as two phases of a delta connected circuit. The third phase of the same delta circuit is comprised of three. bottom element circuits 17.

When limit switch 71 is open, -it de-energizes relay 64, which in turn opens contactoi' 63. A reverse action takes place when lugs 62 permit lever 72 to assume its normal or closed position.

At 68 I have indicated a customary form of pyrometer control making contact with 69. After the set or normal temperature of the control zone has been reached, it opens the circuit between 68 and 69, thereby de-energizing relay 67 allowing contact to open. When contact is made by pyrometer 68, to contact 69, it closes contactor 65 by means of relay 6'? and current thereby passes through limit switch 71 actuating relay 64 and closing contactors 63a, 63b and 630. The delta connected circuits A, B and C thereby connect all coils in the. control zone.

It may be readily noted that the rotation of the hearth successively picks up the next succeeding coil or one-third of one phase, and automatically connects it to the next succeeding control zone.

It may also be readily observed that the hearth section receiving the cold ingoing charge is quickly chilled as is the control zone at the charging door. At the charging door the set'of coils 41 on one face of the swinging bafile 42 may be connected in electrical circharge point, the natural chilling by the opening of. the door is overcome by the combinationof heat source in the side walls, in the hearth and the adjacent face of the swinging baffle. v

In Fig. 6, I have shown in #1 control a. star connected bottom or hearth circuit through only one collector ring with'separators 61, limit switches '71 and 72, together with pyrometer control 68, same as described under Fig. 5. The phase circuits are shown as connected only to the bottom or hearth elements, though it may be readily seen that the side wall elements may be so designed as to form three other equal phases either delta or star connected. With this single form of collector ring covering nine phases, I need use only nine collector brushes compared to the eighteen collector brushes required for three zones, each of three phase as in Fig. 5.

In Fig. 6, I have shown #3 control connected through relays 7 3 and 74,'while #2 control is shown through 7 5 and 76.

For the purpose of clearly explaining the Wiring in the hearth and wall circuits, I have shown fragmentary parts of the circuit diagrams. It will be understood, however, that in Fig. 5 the remaining 180 in the wiring plan are similarly arranged. In Fig. 6 the showing has been simplified by disclosing only the hearth circuit but it will be understood that the hearth circuit is coordinated with the wall circuit in controlling the temperature of the heat treatment cycles which a are carried on in the rotary hearth furnace of my invention.

I have found the rotary hearth furnace as described herein'highly eflicient and successful in o eration and as hereinbefo're noted the time 0 heat treatment and the amount of oxidization of the materi'al'under heat treatment is considerably reduced over the time cycle and the amount of oxidization disposed adjacent said discharging door in impinging alignment with articles on said hearth, and means for electrically heating opposite sides of said swinging bafile.

2. In a rotary hearth furnace, a moving hearth adapted to register with a discharging door, a swinging baflle supported over said hearth in impinging alignment with articles on said hearth and means for sounding an alarm when material on said hearth abuts against said swinging baille during the rotary movement of said hearth.

3. In a rotary hearth furnace, an annular furnace chamber, a movable hearth cooperative with said chamber and adapted to register with a discharging door, a swinging bafile iisposed in impinging alignment with articles on said hearth and means for indicating the abutment of material on said hearth against said swinging baflle during the course of movement of said hearth.

4. In a rotary hearth furnace, a heat treatment chamber, a progressively movable hearth cooperative with said chamber, electric heating elements disposed on the inside walls of said chamber and in the said hearth, and means for automatically and successively energizing selected portions of the heating elements in said hearth.

5. .In a rotary hearth furnace, a heat treatment chamber, a progressively movable hearth cooperative with saidchamber, heating elements on the walls of said chamber, heating elements in said rotary hearth, means connecting said heating elements in delta circuit arrangement, and means for automatically disconnecting certain of the heaters in said hearth from said delta connected circuit and substituting others of the heaters in said hearth in said delta circuit arrangement according to the progressive movement of said hearth.

6. In a rotary hearth furnace, a heat treatment chamber, a movable hearth cooperative with said heat treatment chamber, electric heating elements carried by the walls of said heat treatment chamber, electric heating elements disposed in said hearth, means connecting said heating elements in a heating control circuit, and means for successively disconnecting certain of the heating elements in said hearth and energizing others of said heating elements in said hearth in accordance ,With the progressive movement of said hearth.

7. In a rotary hearth furnace, a furnace chamber, a movable hearth cooperative with said furnace chamber, electric heating elements carried by the walls of said chamber, electric heating elements disposed in said hearth, a control circuit for energizing all of said heating elements, and means in said control circuit for progressively cutting off certain of the heating elements in said hearth and connecting others of the heatlng elements in said hearth in accordance with the pro-'- gressive movement of said hearth.

circuit for selectively disconnecting electrical heaters in certain sectors of said rotary hearth and connecting electrical heaters in other sectors of saidrotary hearth in accordance with the progressive movement of said hear-th.

9. In a rotary hearth furnace, an annular furnace chamber, a movable annularv hearth cooperative with said chamber, electrical heating elements disposed on the interior walls of said annular chamber, electrical heating elements carried by said hearth, an energizing circuit arranged to include all of said heating elements, and means in said energizing circuits for progressively disconnecting the heating elements in a selected sector of said hearth from said energizing circuit and connecting electrical heating elements in another sector of said hearth with said energizing circuit successively in accord ance with the progressive movement of said hearth.

10. In a rotary hearth furnace, an annular heat'treatment chamber, a movable annular hearth cooperative with said chamber, electrical heating elements disposed on the interior walls of said heat treatment chamber, electrical heating elements carried by said movable hearth, an electrical energizing circuit for said heating elements, and means for progresslvely energizing and deenergizing selected heating elements in said hearth an annular heat treatment chamber, electrical heating elements disposed on the interior walls of said heat treatment chamber, electrical heating elements on a swinging baflle in said chamber, a rotary hearth cooperative with said chamber, electrical heating elements disposed in said hearth and energizing circuits connected to all of said electrical heating elements, and means in circuit with the electrical heating elements in said hearth for successively cuttting on and cutting off electrical circuits to the heating elements in selected sectors of said hearth from said energizing circuit in accordance with the progressive movement thereof.

12. A rotary hearth furnace comprising a heat treatment chamber having an annular hearth movable and cooperative therewith, electrical heating elements disposed on the interior walls of said chamber, electrical heating elements carried by said rotary hearth, a power control circuit for energizing said electrical heating elements, means segregating electrical heating elements in said hearth into independent sectors, and

means for successively energizing the heating elements in different sectors in accordance with the progressive movement of said hearth. V

13. A rotary hearth furnace comprising an annular heat treating chamber having a discharging door, a rotary hearth movable and cooperative with said chamber, a swinging bafile supported in said chamber and depending to a position adjacent the top of said rotary hearth and adjacent said discharging door, electrical heating elements carried by opposite sides of said swinging baflie, electrical heating elements disposed on the side Walls of said chamber, electrical heating elements supported in and adjacent the top 'of said rotary hearth, a power ,energizing circuit adapted to energize all the said electrical heating elements and adapted to selectively energize the electrical heating elements in a.

predetermined sector of said rotary hearth in accordance with the progressive movement of said hearth.

14. In a rotary hearth furnace, an annular heat treatment chamber, electrical heating elements carried by the interior walls of said chamber, a rotary hearth cooperative with said chamber and having electrical heatin elements in and adjacent the top thereo a power energizing circuit for exciting all of said electrical heating elements, and means in circuit with the electrical heating elements carried by said hearth for selectively connecting predetermined sectors of heating elements in said power energizing circuit progressively in accordance with the movement of said hearth through said furnace.

tions between the heating elements on the inner side walls and the heating elements in the hearth.

17. A rotary hearth furnace comprising an annular heat treatment chamber, electrical heating elements carried by the interior side walls thereof, a rotary hearth cooperative with said chamber, electrical heating elements mounted in the upper portion of said hearth, a commutator member carried by said hearth and having segments connected to the electrical heating elements arranged in groups in said hearth, and slidable connections on said commutator member for progressively energizing said groups of electrical heating elements in said hearth.

18. A rotary hearth furnace comprising an annular heat treating chamber, means for heating said chamber, a rotary hearth cooperatively movable with respect to said chamber and electric heating elements carried by said rotary hearth.

19. A rotary hearth furnace comprising an annular heat treating chamber, fuel heating means for said chamber, a rotary hearth cooperatively movable with respect to said chamber and electric heating elements carried by said hearth.

20. In a rotary hearth furnace an annular heat treating chamber a rotary hearth oooperatively movable with respect to said chamber, fuel burners adapted to heat the interior of said chamber and electric heating elements adapted to heat said rotary hearth.

In testimony whereof I aflix my signature.

EDWIN L. SMALLEY.

15. Arotary hearth furnace comprising I an annular heat treatment chamber a'rotary hearth cooperative with said furnace, electrical heating elements disposed on the interior walls of said annular chamber, electrical heating elements carried by said rotary hearth, the electrical heating elements in said hearth being arranged in independent circuits in sectors of said hearth, a power heating elements disposed therein, heating elements mounted on the interior walls of said chamber, and sliding electrical connec-

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