US2262363A - Furnace closure - Google Patents

Description

yNOV- 11, 1941. "J, G. HOQP 2,262,363 l" FURNACE CLOSURE Filed Nov. 16, 1938 y 2 Sheets-Sheet 2 64 `66 55 INVENTOR ATTORNEY John G. Hao/D.

WITNESSES:

. jected.

y Patented Nev. 11,1941

PATENT LoEFlcE A 2,262,363 FURNAGE cLosUREv John G. Hoop, Pittsburgh, Pa., assignor'to Westinghouse Electric & fManufacturing Company, `East Pittsburgh, Pa., a corporation 'of Penn- Sylvania Application November 16, 1938, Serial No; 240,654 14 claims. t A(o1. 1iorzs My invention relates broadly to `a furnace closure construction of general utility, but of particular application to heat treating furnaces in which a charge `can be. heat-treated While enveloped by an appropriate protective, gaseous-:15

ticular charge being heat-treated, and the procl'o ess of heat treatment to which it is being sub-, Dissociated ammonia, or partially or completely burned hydro-carbon gases, are among the most common of the protective atmospheres u Where protective gases are employed, their entire efficacy may be destroyed if outside air were permitted to leaky into the heating chamber of the furnace. In order to prevent or limit such leakage, the gaseous atmospherewithin the fur- 20 l nace is maintained at a pressure slightly above atmospheric whereby aplenum system obtains in the furnace.` lIhe greater pressure of the `pro-` tective atmosphere now causes the latter to leak out through any cracks or openings in the fur- 11251 furnace. However, leakage is necessarily a source i '30 of continuouswasteand expense, and, therefore, furnace structures of the type described seek `to minimize or decrease `the leakage to as small an `extent as, possible. My invention is directed to' Q improving the sealbetween that part of the fur- 35 nace which requires an opening in a furnace wall,

and the door therefor.

In accordance -with the preferred embodiment of my invention, a furnace door is `provided having an outer shell ofrelatively thin, preferably-140 exible metal, such as sheet metal, and to the edges of lthis shell is secured a door rim, one face of `which serves to abut `a `suitable door frame about a charge entrance or exit opening, as the` case may be, in the furnace wall. The rim and T45 frame are made of heavy material, preferably steel, to resist warping, and their abutting or mating faces are, `in my preferred embodiment,

.ground hat so that, in effect, a tight joint results which prevents `,any appreciable leakage of the 5l) gaseous atmosphere.

As additional precautions to prevent destruction of the efficacy ofthe seal by warpage of the rim and frame, the door frame is protected from the furnacewall some distance from the furnace opening, while the rim of the door is protected by the novel door construction I employ.

It is, accordingly, among the broad objects of my invention to provide a door seated against its door frame so that, in effect, the two comprise a tight seal, and to provide a ldoor construction whereby the possible warpage of the door does not disturb the aforesaid seal.

My inventionincludes also many novel features incorporated into a construction for the furnace doorf. As previously described, the outer shell of thedoor` is of a relatively thin metal to which `is `secured the rim. Also secured to the shell, but

inwardly of the rim, are rigid members associated into a rigid inner frame for the door, the members being. inthe form of steel channels which also support and interlock the'tile of the door, and `a layer of deformable insulation is adjacentl the `side walls. Any warpage of the rigid members, therefore, merely deforms ythe loose insulation, and in extreme cases may deform parts of the shell, but such deformations will not be transmitted to the rim.

Since the component parts of my door can be easily shaped or obtained from standard stock, the door lends itself readily to fabrication and l can be built to any desired size andshape without entailing large expenses that would be incident t0 the casting of the doors in small quantities.

Other objects and novel features of my invention will be apparent from the following descriptionthereof, taken in conjunction with the drawings, in which v Figure 1 `is a fragmentary sectional vertical view of a furnace wall having an opening therefor built in` accordance with the preferred embodiment of my'invention, the closure for the opening being shown diagrammatically,

Fig. 2 is a fragmentary elevational view of the door frame looking at it from outside of the furnace.

Fig. 3 is an elevational view, on a larger scale, of the dooras seen from the furnace side;

Fig. 4 is a horizontal-sectionalview on the line IV'-IVvof Fig. 3; and

Fig. 5 is a vertical sectional view on the line V--V of Fig. `3.

My invention-is applicable to any suitable type of furnace, one wall only of which it is deemed necessary to'show in order to describe the essential features of my invention. The furnace comprises a Wall 2 having an opening 4 through `which a charge may pass. AIhe `furnace Walls are the directheat of the furnace by embedding it in 55 encased in an outer metallic shell 6, impervious to gas, as is customary in the construction of furnaces in which protective gaseous atmospheres are utilized.

It may be observed that the shell 6 terminates somewhat short of the opening 4, and along the cut-out edges has :secured thereto, as, for eX- ample, by welding, a re-enforcing backing frame 8 which serves as a securing base for the door frame to be subsequently described. The opening 4 is actually formed by a surrounding layer of refractory tile I suitably set to project outward beyond the aperture in the shell 6 for the purpose of protecting a door frame I2 from the direct heat within the furnace. The tile Ill is suitably shaped to provide a seat I4 for the frame I2 which, however, is supported and maintained in position by means of bolts I6 extending through holes spaced at suitable intervals about the frame and secured in re-enforcing plate 8.

Secured to the bottom of the frame by means of the lower bolts I6 is a door rest I8, which serves as a rest for a door 26. Suitable positioning lugs 22 are fastened to the ends of the door rest in order to confine the door to a predetermined position relative to the door frame I2.

The furnace wall 2 is so constructed that the frame I2 in its normal position will be at a slight angle inward of the vertical so that the door 20 resting upon the rest I8 will be forced by its own weight against the door frame I2. It is preferable to have the rest I8 assist this automatic sealing action and, to this end, the rest I8 comprises a protruding side 24 substantially perpendicular to the frame I2.

In accordance with my invention, the door comprises an outer shell 26 formed of sheet metal, which, for the door of the particular embodiment shown, is of a box-like shape with upper and lower sides 28 and 30, respectively, and vertical sides 32. The shell'may be formed of the sheet metal in any suitable manner to any suitable shape, but care should -be taken that the outside periphery 34 conforms substantially to the shape of the bottom of a door rim 36 secured thereto. The door rim 36 conforms in contour to the door frame I2 and is preferably of heavy steel stock. The outersurface of the furnace door therefore comprises the'door rim 36 and the outer shell 26. The shell26 may be formed of a single sheet of m'etal or of a plurality of sheets suitably secured in a gas-tight manner, although I prefer to employ a single sheet shaped by bending or otherwise to the desired conguration. The door rim 36 is also secured to the shell 26, preferably by welding, so that the entire door structure is impervious to gas.

In order to lend a certain amount of rigidity to the door and also to support the refractory and insulating material thereof, suitable frame members are fastened to the shell inwardly of the door rim 36, and may take the form `of channel members with their channels directed toward the center of the door. The channel members are preferably secured to, what may be called for the purposes of identification, the upright bottom 4I) of the shell 26.

A lower channel member 42 is secured to the bottom 46 by means of bolts 44, although any other suitable securing means may obviously be employed, and in such manner that the inside leg 46 and the outside leg 48 of the channel member extend away from the adjacent part of the rim 36. As many additional re-inforcing channels may be added to the door as the weight of the door may require, and in the particular embodiment, an upper channel 50 and side channels 52 and 54 complete a rectangular re-enforcing and supporting frame for the door, being secured substantially gas-tight to the bottom 40 by bolts, such as 44.

The channel members 42, 5I), 52 and 54 are assembled to form the supporting frame which is similar in shape to the door rim 36, but spaced `froml the inner periphery to provide a space that is filled with a deformable insulating material 56 comprising, for example, a mixture of asbestos andan insulating rdiatornaceous substance. Suitable insulating bricks 58 `are placed adjacent the bottom wall 4U inward of the channels, and refractory tiles 66 complete the door structure. From another aspect, my invention may be considered as including a framework comprising the channel members 42, 50, 52 and 54, which `act as rigid side members. In such case, the shell 26 forms a gas-tight connection between the side members and the rim 36.

The lower channel 42 serves as the main support for the refractory and rebrick in 'the door, and to further maintain the rigidty of the channel member, especially when subjected to high temperatures, a plurality of gusset plates '62 may be welded to the channel at suitably spaced in tervals. These gusset plates preferably conform to the cross section of the inside of the channel, exceptthat the upper edge slopes downward substantially from the top of the leg 48 to the middle of the leg 46, as shown more particularly in Fig. 5.

The refractory tile 66 ris suitably formed to rest within the channel frame, being somewhat interlocked in position by the centrally-projecting legs of all of the channel members.

To provide a ready means Ifor raising andvlowering the door and for holding it in position, a plate 64 is tack welded or otherwise secured to the top side `28 of the outer shell, and to this plate at suitably spaced points are secured cable fastening structures' 66 whereby the door may be raised and lowered by means of cables, not shown, secured to pins 68 and'ridingv over pulleys in a customary manner,-suitable guides being provided for the door.

It is a primary `purpose of my invention to provide an effective seal between the door and its frame, and'to this end, the frame' I2, as well as the rim 36, are both of rather substantial stock, suflifciently heavy to resist -warping to a large degree. The frame and rim mayv be annealed, if desired, to remove all internal stresses and their mating faces subsequently ground fiat to' assure adhesive lmating surfaces between them. An effective Vseal is thus obtained'since the ground faces/of the rim and frame -will mate each other soclosely as' to decreaselto va negligible'amount the leakage of anyl gas from inside'the furnace to 'the voutside through the seal.

therefore, the inner rim 36 is Ialso protected'y from the radiant heat' of the furnaceby the tile I0.

Conduction of heat tothe rim 36'froml the `eaeyof the seal between them, remote. .cnnection, it may be observed that the frame #door partsV exposed to` `the interior heat ofV the ,furnace fis reduced to substantially; negligible amounts by the insulation 56 which-compelsthe jconductiorr pathhoff heat from `the exposed legs [of the channels" tovextend to the outer shell `26 vat a point removed from the rim 36,. Anyl conduction heat ,-therefore, is, .thoroughly dissipated `by the outside shell 26 before reaching the rim 35.

It may, therefore, `be seen,` that by my3conV ,struction the amount ofu heat that can reach the `door frame and door rim is substantiallyreduced. In ,addition, the door frame and rim are made, as aforesaid, of heavy stock, and the combination of minimizing the heat flow to the parts, together with their mass exposed vto the cool4 outside, make the possibility of their `warpage, and, therefore, `the destruction of the effi- In this I2 is considerably larger than the rim 36170` the end that both the `rim and the frame will have `a large surfaceareaf for `dispelling to the surroundingA cooling atmosphere whatever heat :reaches thenfi.v i

` Thelchannel members v42, 50, 52 and 54 are, `of course, subjectedto the `heatof the furnace, which, if operated at elevated temperatures, may be quite intense. ',Ihese channels, therefore, may have a tendency .to warp with continued use. To reduce this. tendency the channels sides toward the furnace are slotted atsuitable intervals along their length to an extent approximately .half their width. Such slots 'I0 preferably extend somewhat beyondthe` depth of the refractory `tile 6D, since the latter is only semi-insulating and by making the slots extend beyond them, warpage and distortion due to differential heate ing are decreased.

The slots also prevent excessive permanent distortion of the channels but, nevertheless, it

may be observed that, if the channels should become distorted, whether permanently or not, the flexibility of the outer shell 2E and the de formability of the insulation 56 `will absorb the deformations before they can be transmitted to the rim 36. The` bent `corners between the bottom 40 and the sides `28, 30 and 32 of the sh'ell materially aid thenadaptability of the door to deformations Aof the exposed :parts by being capable of .a change in angle. Additionally the shell 26 is obviously capable of deformation.` If desired` any suitable clamping means may be employed to hold the rim securely against the door frame.` Thus, eccentric cams can be employed for this purpose, as well known to '.thefart, or the door guides (not shown) may be made suiciently close fitting for the purpose.

As an added refinement of my invention, I prefer to have the rim 36 protrude slightly beyond the inner, exposed surface of the remainder of the door, so that the door rim will always bear on the door frame.

It may, therefore, be observed that in accordance with my invention I have `provided a closure for satisfactory use with high temperature furnaces employing a protective gaseous atmosphere, and which may be simply and economically fabricated.

While I have described my invention in apreferr'ed embodiment, it is obvious that changes `may be made and equivalents applied thereto.

I claim as my invention: 1. A furnace door structure comprising a heavy rim, a metallic deformable shell secured .tosaid an inner, substantially `rigid; frame within said shell and secured thereto slightly deformable insulation material between said inner frame` and shell, a layer of insulation mate` rial within the frame and adjacent said shell, and an exposed layer of refractory material in front ofsaid insulation material, and held in position by said frame.

2. A furnace door comprising a metallic box having 'a wide, heavy, open rim and a shell secured to said rim, deformable insulating material adjacent said rim inwardlythereof, said shell having parts madeof deformable material, reenforcing means within said box, insulating and refractory material within said box and substantially completely filling the remaining space therein, said reenforcing means forming a support for the last said' material, and comprising `rigid structural steel members, said steel members `being slotted at spaced intervals along the inner or furnace-facing parts thereof.

3. A furnace door adapted to be vertically disposed comprising a wide, heavy, open rim and a shell secured to said rim, deformable insulating material adjacent said rim inwardly thereof, ,said shell having parts made of deformable material, reenforcing means within said box, insulating and refractory material within said box and substantially completely lling the remaining space therein, said reenforcing means comprising a rigid, two-legged steel member rf'ear the lower end ofthe door and having one leg secured to the shell and the other leg extending upwardly to form a supporting means for the last said material. l

4. A furnace dooradapted to be vertically disposed comprising a wide, heavy, open rim and a shell secured to said rim, deformable insulating material adjacent said rim inwardly thereof, said shell having parts made of deformable material, reenforcing means Within said box, insulating andv refractory material within said box andsubstantially completely filling the remaining space therein, said reenforcing means comprising a rigid, two-legged steel member near the lower 'en-d of the door and having one leg secured to the shell and the other leg extending upwardly to form a confining interlock for the last said material, said `other leg being slottedA at intervals. l 5; A furnace door adapted to be vertically disposed comprising a wide, heavy, open rim and a reenforcing means within said box, insulating and refractory material within said box and Asubstantially completely filling the remaining space therein, said reenforcing means comprising a` rigid, two-legged steel member near the lower end of the door and having one leg secured to the shell and the other leg extending upwardly to form a support and vconfining interlock for the last said material, said other leg being slotted- `members within said shell, insulating and refractory material Within said shell and substantially completely filling the remaining space therein, said reenforcing means forming a support forthe last said material, and generally following the contour of said rim, said structural members being substantially the depth of the door, secured to said shell at one end, and having inwardly projecting legs at their other ends. kwhereby to aid in retaining th'e last said material in said shell.

'7. A furnace door comprising a metallic box having a wide, heavy, open rim and a shell secured to said rim, deformable insulating material adjacent said rim inwardly thereof, said shell having at least a part made of flexible sheet metal, re'enforcing means comprising structural members within said shell, insulating and refractory material within said shell and substantially completely lling thel remaining space therein, said reenforcing means forming a support for the last said material, and generally following the contour of said rim, said structural members being substantially the depth of the door, secured to said shell at one end, and having inwardly projecting legs at their other ends, wherebyA to aid in retaining the last said material in said shell, said leg parts of said members being slotted at intervals.

8. A furnace door comprising a metallic box having a wide, heavy, open rim and a shell secured to said rim, deformable insulating material adjacent said rim inwardly thereof, said shell having at least a part made of flexible sheet metal, reenorcing means comprising structural members within said shell, insulating and refractory material within said shell and substantially completely lling the remaining space therein,

said reenforcing means forming a support for the last said material, and generally following the contour of said rim, said structural members being substantially the depth of the door, secured to said shell at one end, and having inwardly projecting legs at their other ends, whereby to aid in retaining the last said material in said shell, said leg parts of said members being slotted at intervals, and gusset means for the bottom of said members.

9'. A` furnace door `comprising a metallic box having a wide, heavy, open rim and a shell secured to said rim, insulating material adjacent said rim inwardly thereof, said shell having at least a part made of iiexible sheet metal, reenforcing means within said box, and insulating and refractory blocks within said box and substantially completely lling the remaining space therein, said reenforcing means forming a support for the said blocks.

10. A furnace door comprising a metallic box having a wide, heavy, open rim and a shell se cured to said rim, insulating material adjacent said rim inwardly thereof, said shell having at least a part made of flexible sheet metal, reenforcing means within said box, and insulating and refractory blocks within said box and substantially completely lling the remaining space therein, said reenforcing means forming a support and interlock for the said blocks and following the contour of said rim.

l1. In combination with a metal-encased furnace having a wall with an opening through which a charge may pass, a door frame about said opening, said wall being constructed to space said frame from said opening, said frame being of metal and having a closure-seating face, a closure for said opening, said closure including refractory tile, and having a rim with a face for mating the said closure-seating face whereby the two will seat together snugly to form a substantially gas-tight seal, means forming part of said closure for insulating said rim from the heat of the furnace, means in said closure for supporting said refractory tile, said last means being inward of said rim, and said closure comprising an outside, iiexible metallic shell whereby warpage of said last means does not aiect said rim.

12. A furnace door structure comprising a framework having relatively rigid side members, a rim about said framework and spaced from said side members, insulating material within said framework, substantially gas-tight means securing said rim to said framework, and insulation between said gas-tight means and said side members.

13. A furnace door structure comprising a framework having relatively rigid side members, a rim about said framework and spaced from said side members, insulating material within said framework, substantially gas-tight means securing said rim to said framework, insulation between said gas-tight means andsaid side members, said gas-tight means being deformable whereby warping, expansion or contraction of said side members will not appreciably affect said rimf.

14. A furnace door structure comprising a framework having relatively rigid side members, a rim about said framework and spaced from said side members, insulating material within said framework, substantially gas-tight means secured to said rim and framework, and insulation between said gas-tight means and said side members, said framework side m'embers being slotted at intervals along the edges facing the furnace. l

JOHN G. HOOP.

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