US1903909A - Rotary heat treating furnace - Google Patents

Description

April 18, 1933. Fl T COPE ET AL V1,903,909

ROTARY HEAT TREATNG FURNACE Filed April 50,- 1930 4 Sheets-Sheet l 9&1

Apil 18, 193s. F. T. COPE Er AL 1,903,909

ROTARY HEAT TREATING FURNACE Filed April 30, 1930 4 Sheets-Sheet 2 wuenton April 18, 1933. T. COPE ETAL ROTARY HEAT TREATING FURNACE 4 Sheets-Sheet 3 Filed April 50, 1930 gri/vanto@ 17X 00p@ A. b. llfgha/z Y WJw/f/g April 18, 1933. F.. T. coPE ET Al.

ROTARY HEAT TREATING FURNACE Filed April 30, 1930 4 Sheets-Sheet 4 l/ f f grr/vento@ i.' Z aloe Thug/lan ha J. wlw/g dumm@ www@ Patented .Apn 18, 1933 UNITED STATES y PATENT ori-Ica FRANK T. COPE, ARTHUR, H. VAUGHAN, AND WILBUR S. BOWLING, 0F SALEM, VOHIO,

ASSIGNOBS TO THE ELECTRIC FUBNACE COMIANY, OF SALEM, OHIO, A (LOIRIBA- TION OF OHIO Application area April ao,

The invention relates t-o apparatus for heat treating metal articles in the presence of gas, and more particularly to surface hardening of steel in the presence of ammonia, wh1ch 1s commonly known as nitriding, although from the following description it will be evident that other heat treatments, such as gas carburizing, annealing and the like may be advantageously carried on in the furnaces einbodying the invention.

It is usual practice in nitriding to heat the steel objects to be treated, in aclosed container, in the presence of ammo-ma gas, at a temperature usually between 900 F. and 12000 F., for a period depending upon the depth 'of nitrogen penetration desired. A small quantity of ammonia gas is caused to flow continuously into the container, and the spent gas is allowed to escape through a sult-A able outlet. I

Heretofore it has been customary to use a furnace of the so called batch type. However, it is obvious that some form of continuous furnace is more desirable, because of the time necessarily lostin unloading and reloading the container, the inconvenience of moving the container in and out of the furnace, the diliiculty of duplicating temperature. conditions from charge to charge, and the excessive amount of attendance required in the use of a batch type furnace.

An object of the improvement is to provide a furnace for heating objects in containers wherein a plurality of separate charges, each in a container, are at a given time at successive stages of the treatment.

ROTARY naar` HEATING rURNAcE 19ao.` seal No. 448,609.

a convenient position, and with a minimum of `difficulty.` i

Still another object isthe provision of means Vfor conveying the containers from which the entire containers need not be removed at'any stage Aof the heat treatment.

Another object is to provide means for cooling the containers outside of the furnace l arcute portion atall times'extended outside of the heating chamber between said doors; containers, for the objects to be heat treated, being carried upon the hearth, and provided with removable covers adapted to be'removed and replaced for unloading and reloading the material as the containers move to a point outside of the heating chamber.; means being provided ,for continuously circulating gas through the containers while the hearth is in motion; and sealing means being provided for the hearth and for the containers, whereby air is prevented from entering the furnace and containers.

An embodiment of the invention thus briefly described is illustrated in the accompanying drawings, in which Figure 1 is a vertical sectional view of a preferred' form of theimproved furnace, taken substantially on the line 1 1', Fig. 2;

Fig. 2, a plansection taken as on the line 2 2, Fig. l

Fig. 3, a section, similar to Fig. 1, of a modified form of furnace, having a single sealing means for the hearth and containers, talen substantially on the line 3 3, Figy4; an

Fig. 4, a plan section of the modified form of furnace, taken on the line 4--4, Fig. 3.

Similar numerals refer to similar parts throughout the drawings.

Referring first to the form of the apparatus illustrated in Figs. 1 and 2, the furnace chamber is partially circular and provided with the arcuate outer wall 10 and concentric inner Wall 11, joinedat their upper extremities by the partly annular roof 12, and supported upon a suitable structural frame comprising the base" 13, the uprights 14 and the "beams 15. As shown in Fig. 2, the lower extremities ofthe outer and inner walls are continued'betweenthe charging and discharging'doors C tand D, respectively, as indicated at 10a and 11are spectively. 'l' .I I

A bearing 16, which may be in the form of a ball bearing as shown iny Fig. 1, is mounted upon the base 13, concentric with the furnace chamber, and rotatably supportsthe hub .17, to which are attached the spokes 18 carrying the frame 19, upon'which is mounted an annular casting 20. j.

e A ring gear 21 isv formed around vthe periphery of the casting 20, and .meshes with the pinion 22, mounted upon a vertical shaft 23'-and driven .through the gear reduction 24 which is operativelypconnected to the motor 25 as by the coupling 27, ,the entire driving means being mounted upon a frame 28 carried by the base 13.

The casting 2O carries the refractory hearth 29 Whichis located between the lower ends of theouter andJ innerwalls 1() and 11, respectively, of the furnace chamber. d

For the purpose of sealing thel furnace chamber from the outside atmosphere, spaced annular channels or troughs 30 and 31 are formedlupon the casting 20, and adapted to contain suitable -sealing material, which may be a liquid or a granular material; depending annular flanges 32 and 33 being carried by the inner and outer `walls respectively', and extended into said channels 30 and 31 respectively. j l

Each of the containers fork the objects to be treated includes a bottom plate 34 mount- 'ed upon the hearth 29 and .havinga peripheral sealing trough 35 adapted to contain suitable sealing material.- .n

A depending bearing portion 36 is preferably formed upon each plate 34 and provided with a stulhng box 37, a vertical shaft 38 being journaled therethrough and provided with a fan or propeller 39 at its up-v per end.

This fan shaft'has a pulley 40 on its lower end, operatively connectedas by the belt 41, with a similar pulley 42 upon the sha-ft of a motor 43, suitably -supported upon the rotating frame 19. One of j these 'm'otors may be provided for driving the fan of each of the containers.

The container has therein a hollow cylinder 44, forming a Work supporting receptacle and circulation directing baffle,V open at both ends, and having the reduced neck 45 at its lower end, into the mouth of which -from the sides and upper end of the cylinder 44,. and having its lower open end seated wlithin the sealing channel 35 ofthe bottom p ate.

In order to firmly hold the cover in place around the cylinder during theheat treating operation, ears 50 may beprovided upon the outside thereof, near the lower edge of the cover, for cooperation with the ears 51 upon the outer flange of the sealing channel 3 5, pins 52 being adapted to beV located through suitable registering openings in the The furnace chamber may be heated by i any suitable and well known means, and for the purpose of illustration electric heating elements 53 are shown upon the Walls 10 and 11 thereof.

A central, vertical shaft 54, which may be tubular as shown in the drawings, is carried by `the hub 17, and'extends upward through the tubular casing 55, located through the center of the furnace. The casing55 is attached at its upper end to the beams 15 and at its lower end tothe base plate 15a and serves to support and locate the inner wall 11.

For the purpose of providing a hydraulic sealing chamber, and to permit the use of a slightly elevated pressure Within the container, a cylindric receptacle 56 is fixed to the upper end of the shaft 54 land adapted to contain any suitable liquid. A sealing plate 57 isxed above the receptacle 56, being supported as upon the uprights 58 mounted on the beam ,members 15 andis provided with th'e'inner and outer spaced annular flanges 59 and 60 respectively,` concentric with the shaft 54 and'extending into the-liquid in the re.- ceptacle 56. ,e

Gas for the heat treatment is admitted within the center chamber 61v of the gas seal# ing receptacle through the pipe 62 and passes from the chamber 61'into the central pipe 63, carried by the receptacle 56 and then through the radial pas .ige 64 in the bottom of said receptacle to f 'c gas inlet pipey 65 Which eirtends downm l alongside of .the shaft 54 and then outwa.J 1l at an angle, communicating with the cir..n'=iferei1tially disposed inlet charge pipes `gas through any particular container, valves and 7l may be provided inthe pipesk 6 7 and 68 respectively. The spent gas frornthe outlet manifold passes upward throughlthe e discharge pipe 72 and intothe annular chamber 73 ofthe sealingrreceptacle, being discharged through thefpipev 74 which extends through'the stationary'top plate 57 ofthe receptacle. The pipe r'imay extend to a point remote from the furnace it` desired, and may be provided with means for maintaining back pressure and preventing'the entrance of air. Such means may consist of a liquid seal or a throttling valve 81.

The gas su ply pipes'as well as the disfbr the spent gas are thus connected to the hydraulically sealed swivel connection which vpermits relative -movement of Ithe parts without disturbing lthe flow of the gas in either direction.

For the purpose of carrying current to the motors 43 `and the heating elements 53, a plurality of annular conductors? 5 maybe carried upon an insulation ring 76 fixed upon the periphery of therotating receptacle '56, these conductors being connected by any suitable 'wiring whichV may be located through the conduit. 8O and connected to the various motors and heating elements. The conductors Contact with the shoes 77 to which suitable line Wires maybe connected.

In the operation of the apparatus for nitriding or other treatment involving the use of a gas. the hearth may preferably be rotated intermittently in the direction of the ar! row shown on Fig. 2, the doorslC and D being opened at'v intervals to permit the containers to pass in and out of the heating chamber.

As each container passes out of the heating chamber, it may be allowed to cool to a temperature at which it may be opened, gas oonv tinuing to flow meanwhile if desired, after which the container may be opened, unloaded, and filled with new material to. be treated and again passed throughthe furnace chamber. y Y

As above described, it will be obvious that each container is separately sealed from kthe atmosphere, preventing the entrance of air into the container except when desired and suitable gas for the treatment may be continuously circulated through each f container while the same is at a temperature requiring the presence of the'gas.

the as through each container may be independently regulated soi as to "produce the desired results in the heat treating operation.

In Figs. 3 and 4 is illustrated av modified form of furnace in which thencontainers and hearth are sealed by a'single'sea'ling means. Otherwise the general structure 'of 'this furnace is very similar to that above described, as will beevident from an inspection of the drawings and the following detailed description of this modified form'of the invention.

Inpthis form of the furnacev'the furnace chamber is also partially circular and pro-` e ded with the arcuate outer and' inner Walls 10 and 11 respectively, joined at their upper ends by` the partly annularroof 12 and, supported upon the structural frame coinprising the base 13 uprights 1 4" andfbeam members 15. Y j lAs shown inF ig. t, the lower portions of the outer and inner walls are continued i throughout the cut-out portion between opposite 'ends of the furnace chamber,`as shown at 10 and 11, respectively.

`The bearing 416 is mounted uponthe base,' concentric withthe furnace chamber and rotatably supports the hub 17 spokes 18 'and rotatable frame 19 which is mounted the annularcasting 20.

A ring gear 21 maybe formed around the periphery of the casting and engaged by the pinion Q2upon the vertical shaft 23 driven through the gear reduction 24 operatively cennected to the motor 25 as by the coupling 2 l The rotatable casting 20 is provided at its outer and inner edges with the annular sealing channels 30 and 31 respectively, adapted tocontain suitable sealing material and receiving the depending annular ianges 32 and 33 depending from the lower ends of the outer and inner walls respectively.

A plura-litv of circular channels 35, corresponding in number andposition to the containers to be carried upon the hearth, are formed in the casting 20 and communicate with the channels 30 and 31" so as to receive the sealing material beoil in this case.

A vertical bearing 36 is centrally located through the refractory hearth block 29 of each container'and may be provided with a stuiiing box37, a fan shaft 38 being journaled therethrough and provided 'at its upper end with a fan or propeller 39".' vA'motor 43 is carried bv the rotatable frame 19 for uponl driving each fan shaft.,

Each container may havetherein a worksupporting receptacle in the form of a hollow cylinder 44 open at both ends and having the reduced neck 45 at its lower end, the fan 39 being located in the mouth thereof. Legs 46 may be provided for' supporting l each receptacle 44 spaced above the hearth y vIt willalso be seen that the rate of flow of block 29 and the objects to betreated may carrying the which may preferably be placed upon the shelves 47 located in spaced relation within the receptacles upon the-brackets 48. Y,

Each container proper includes, in combination with the cooperating portion of the hearth casting 20', an inverted removable .inner and outer furnace walls, as best shown in Fig. 3.

The furnace chamber may be heated by any suitablemeans such as the electric heating elements 53 locatedl upon the inner and outer walls of the furnace chamber. Refractory blocks of the shape best shown at 51' in Fig. 4 are located upon the casting 20' between the circular hearth blocks 29 which support the containers.

A central vertical shaft 54', which may be tubular as shown in the drawings, is carried by the hub 17' and extends upward through the tubular casing 55' located through the center of the furnace. The casing 55 is attached at its upper end to the beams 15' and at its lower end to the base plate 15a', and serves to support and locate the inner wall 11'.

For the purpose ofeproviding a hydraulic sealing chamber and to permit the usevof a slightly elevated pressure within thev container, a cylindric container 56' is carried by the upper end of the shaft 54 and adapted to contain any suitable liquid. A sealing plate 57 is fixed above the receptacle 56', being supported as upon the uprights 58 mounted on the beam members 15 and is provided with the inner and outer spaced annular flanges 59 and`60', respectively, concentric with the shaft 54' and extending into the liquid in the receptacle 56.

Gas for the heat treatment is admitted within the center'chamber 61' ofthe gas sealing receptacle through the pipe 62 and passes from the chamber 61 into they central pipe 63', carried Vby the receptacle 56' and then through the radial passage 64 in the bottom of said receptacle to the gas inlet pipe 65' which extends downward alongside lof the shaft .54' and then outward at an angle, communicating with the inlet manifold 66'.

Inlet pipes 67' lead from the manifold 66 to the interior of each container, terminating just below the fan 39" of the container so that the gas discharged therefrom is carried upward by the fan, through the container andaround the objects under treatment.

The gas then passes downwardbetween the container proper andthe cover 49 thereof and a portion flows into the correspond-l ing discharge pipei68, these dischar e pipes being connected to the outlet mani old `69'.

For the purpose of controlling the yfiow of gas through any particular. container, valves 70' and 7 y1 may be provided in the pipes' 67 and 68', respectively. The spent gasl from theoutlet manifold passes upward through the discharge pipe 72 and into the annular chamber 73' of the sealing receptacle, being discharged throughthe pipe74 I which extends through. the stationary topk plate 57' of the receptacle. The pipe 74' may extend to a point remote from the furnace, if desired, and may be provided with means for maintaining back pressureand preventing lthe entrance ofair. Such means may consist of a liquid seal or a throttling valve.

For the purpose. of carrying current to the motorsl 43 and the heating elements 53', a plurality of annular conductors 75 ma be carried upon an insulation`ring. 76 xed upon the vperiphery of thek rotating .receptacle 56', these conductors being connected by any suitable wiring which may belocated through the conduit and connected to the various motors and heating elements and contacting with the shoes 77' to which suitable line wires may be connected.

. Although circulating means are shown in the drawings, in the form of fans for continuously circulating gas through the containers during the heat treating operation, it should be understood that such circulating means are not necessary in all cases, and may be omitted within the scope-.of the invention.

We claim l. A furnace having a discontinuous, an-

'nular chamber, a continuous, annular, rotatable hearth located concentric with said chamber and forming the bottom thereof, a

the container, and means' for admitting.

gas to the lower end of said work-supporting receptacle and withdrawing gas from the container at a point outside of the work-supporting receptacle.

2. A furnace having a discontinuous, annular chamber, a continuous, annular, rotatable hearth located concentric with' said chamber and forming the bottom thereof, a

.closed container supported by said hearth, a

hollow work-supporting receptacle within theV container open at its'upper end and spaced from the sides andtop of the container, and means for circulating gas in'one' direction through said hollow work-support and in the opposite direction between'the work-support and the sides of the container.

3. A furnace having a discontinuous, annular chamber, a continuous, annular, rotatable hearth located concentric with said chamber and forming the bottom thereof, a closed, work-carrying container supported by said hearth, a pipe for supplying gas to said container, a second pipe for carrying away spent gas from said container, said pipes rotating with the hearth, a sealed swivel connection associated with said pipes, xed pipes connected with said swivel connection, and means for maintaining a positive gas pressure within said container, said means being associated with the pipe for carrying away spent gas and being located beyond said swivel connection.

4. Avfurnace having a discontinuous, annular chamber, a continuous, annular, rotatable hearth located concentric with said chamber and forming the bottom thereof, a plurality of spaced, separately closed, workcarrying containers supported by said hearth, a pipe for supplying gas to each container, a second pipe for carrying away spent gas from each container, said pipes rotating with the hearth, a hydraulically sealed swivel connection associated with said pipes, pipes connected with said swivel connection, and means for maintaining a positive gas pressure within said container.

5. A furnace having a discontinuous, annular chamber, acontmuous, annular, rotatable hearth located concentric with said chamber and forming the bottom thereof, a plurality of spaced, separately closed, workcarrying containers supported by said hearth, a pipe for supplying gas to each container, a second pipe for carrying away spent gas from each container, said pipes rotating with the hearth, a hydraulically sealed swivel connection associated with said pipes, pipes connected with said swivel connection, and means for maintaining a positive gas pressure within said container, said means being associated with the pipe for carrying away spent gas and being located beyond said swivel connection.

6. A furnace having a discontinuous, annular chamber, a continuous annular rotatable hearth located concentric with said chamber and forming the bottom thereof, a closed container supported by said hearth, a hollow work-supporting receptacle within the container, open at its upper end and spaced from the sides and top of the container, and means for admitting gas to said work-supporting receptacle and withdrawing gas from the container.

7. A furnace having a discontinuous, annular chamber, a continuous, annular, rotatable hearth located concentric with said chamber an'd forming the bottom thereof, a plurality of spaced separately closed workcarrying containers supported by said hearth, a circumferentially disposed inlet pipe rotating with said hearth, and a separate connection between the inlet pipe and each container.

8. A furnace having a discontinuous, annular chamber, a continuous, annular, rotatable -hearth located concentric with said chamber and forming the bottom thereof, a plurality of spaced separately closed workcarrying containers supported by ksaid hearth, a circumferentially disposed inlet pipe rotating with said hearth, a circumferentially disposed outlet pipe rotating with said hearth,.and separateconnections between the inlet and outlet pipes and eachcontainer.

9. A furnace having a discontinuous, annular chamber, a continuous, annular, rotatable hearth located concentric with said chamber and forming the bottom thereof, a plurality of spaced separately closed workcarrying containers supported by said hearth, an inlet pipe rotating with said hearth and having a circumferentially disposed portion, an outlet pipe rotating with said hearth and having a circumferentially disposed'portion, separate connections between the circumferentially disposed portions of the inlet and outlet pipes and each container, a sealed swivel connection associated with the inlet and outlet pipes, and fixed pipes connected with the swivel connection.

In testimony that we claim the above, we have hereunto subscribed our names.

FRANK T. COPE. ARTHUR H.v VAUGHAN. WILBUR S. BOWLING.

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