US2089843A - Method and apparatus for annealing - Google Patents

Description

Aug 10,- 1937. L. WILSON ET AL METHOD AND APPARATUS FOR ANNEALING ZSheets-Shet 1 '11. dkwwuka Filed July 2, 1936 INVENTOR3 7 CLZVM Aug. 10, 1937. 1.. WILSON ET AL 2,089,343

METHOD AND APPARATUS FOR 'ANNEALING Filed July 2,1936 2 Sheets-Sheet 2 more eificiently, i. e.,

-ing cover or furnace The function of the' inner cover, of

'atented Au 10, 1937 Lee Wilson and James said Woodson assign'or to said Wilson- Ohio;

Application July- 2, 1936,

PATENT OFFICE 2,089,843 METHOD AND APPARATUS FOR ANNEALING C. Woodson, Cleveland,

Serial No. 88,542

6 Claims. (CL 266-5) This invention relates to the art of annealing and, in particular, to the annealing of sheets in stacks.

The use of cover type furnaces for annealing sheets has become quite general. furnace cover is applied successively to a plurality of charge supporting bases. In order to release the heating cover after heating the charge to annealing temperature, for disposition over successive charges, it has become the practice to employ what are known as inner covers. These are simply open-bottomed boxesof light plate which are placed over bell proper is lowered onto the base.

course, is to prevent access of the atmosphere to the material after removal of the heating cover.

Such inner covers inevitably constitute an obstacle to the transmission of heat from the heating means of the furnacecover to the charge itself The use of inner covers, therefore, slows down the heating process, as compared to the speed of heating which might be obtained in the absence of the covers. In spite of this objection, however, the use of inner covers is an advantage in that it permits the heating cover to be used it operates as a heating hundred per cent of the to protect the charge means substantially one time and is not relied on while it cools.

We have invented a method and apparatus for annealing which retains the advantage of the inner covers, but overcomes the disadvantage to their use. Our invention permits the charge, although enclosed within a protective cover, to be heated as rapidly as if there were no inner cover used in the present practice but, at the same time, we utilize the protective cover to enclose the charge during cooling and release the heating cover so that it may be used in heating other charges. We provide for exposing the charge directly to means suitably mounted in any one of several ways. Radiant tubes may be disposed on or within the inner covers, and may either be sepa-' rately formed or constitute a portion of a wall Fig. 1 is a partial transverse section through a furnace having heat exchange or radiant tubes within the spa'ce enit is lowered into mounted so as to proiect closed by the inner cover when 9 Usually one the charge before the heat-,

the heat radiated by heating Fig. 1a is a diagrammatic view illustrating a detail;

Fig. 2 is a similar view showing a slight modification;

Fig. 3 is a similar view showing heat exchange tubes mounted on and within the inner cover; Fig. 4 shows a modification of this principle;

Fig. 5 is a similar view illustrating heat exchange tubes formedon a wall of the inner cover;

Fig. 6 shows a slight modification of this principle; I

Fig. v'7 is a partial sectional view along the line VII-VII of Fig. 6; and

Fig. 8 isa view similar to Fig. 6 illustrating a further modification.

Fig. 9 is a partial transverse sectional view of a slightly dlfierent construction; and

Fig. 10 shows a further modified construction.

Referring now in detail to the drawings and first to Figure 1, a cover type furnace l comprises a base ii and an insulating cover 12. The base I l includes a pier l3 for supporting a charge H which may be a stack of sheets. A peripheral flange. l extends around the edges of the base H and is adapted to receive the lower edge of the cover I! for supporting the latter. A seal l8 closes the joint between the base and cover.

The base ll is also provided with a low wall I I1 disposedbetween the flange l5 and the pier l3. A sealing channel I8 is carried on top of the wall I! for cooperation with the lower edge of a protective cover l9. Heat exchange tubes 20 are mounted in with burners 2i connected to any suitable fuel source through appropriate control mechanism such as valves. The tubes 20 are of U-shape and the ends of the tubes opposite those in which the burners 2i. are positioned extend outwardly through the wall downwardly to a sub-floor exhaust duct (not shown). This feature of construction is shown clearly in Figure 1a.

In using the apparatus of Figure 1, the covers l2 and Iii-are raised and the charge ll disposed on the pier l3. The burners 2| are then lighted and the covers l9 and l2-lowered in succession. Combustion gases traversing the tubes 20 heat the latter to radiant condition and heat is transmitted directly therefrom to the charge ll. when the charge has been heated to the desired temperature, the burners are extinguished and the cover I2 is moved to the next succeeding base the wall 11 and are provided II to enclose a charge disposed thereon. The

cover l9 protects the charge II from the atmosphere as it cools. .While the construction of Fig.

1 requires separate heating tubes for each base, the additional cost thereof is more than oil'set by the saving in heating. time which is made possible. The permanent mounting of the radiant tubes, however, is a slight inconvenience in placing or removing a charge.

Fig. 2 shows a construction which is not subject to the last mentioned objection. The construction of Fig. 2 includes a base ii, and a cover l2, the base having a pier It for receiving a charge it. Extending around the periphery of the base Ii, removably resting thereon, and adapted removably to support the cover i2, is a ring or frame 22. This element, like the base and cover is composed of refractory bricks assembled 1 within a fabricated enclosure of structural memsealing channel 26 bers and plates. It includes inner and outer sealing flanges nels 24 containing suitable sealing material. The frame 22 is also supplied with a sealing channel 25 adapted to cooperate with a flange depending from the cover i2. It is also provided with 2. adapted to receive the lower edge of a protective coveris. I

Radiant tubes 2t! are mounted in the frame 22 with burners M, in the same manner as in the wall I! of Fig. 1.

The structure of Fig. 2 may be used in the same manner as that of Fig. 1, the advantage of the construction being that the ring or frame 22 and its tubes 20, may be removed when placing or removing a charge. Fig. 3' shows a modified construction wherein each base is again provided with its own set of radiant tubes, but in this case they are mounted on and in the protective cover which thereby also becomes a Fig. 3, the base it has a peripheral upstanding wall or flange l5 as in Fig. 1 in which burners 2! are disposed. A novel form of protective cover 21 has its lower edge disposed in a sealing channel 28 carried on the base between the pier l3 and the wall i5. The cover 21 is provided with a plurality of heat exchange tubes 29, the lower ends of which extend through suitably shaped openings in the wall of the cover adjacent the lower edge thereof. The upper ends of the tubes project through the top of the cover, but are freely floating relative thereto to permit expansion and contraction. Seals 30 close the spaces between the tubes 29 and openings'in the top of the cover through which they project. The

lower ends of the tubes 29 are in alinement with the burners 2|. 7

When the charge M has been placed and the burners 2| lighted, the covers 2'! and I2 are successively lowered into place. The hot combustion gases flow upwardly through the tubes 29 and heat the latter to radiant condition. The

heat thereof is directly transmitted to the charge which .is disposed closely adjacent the tubes. The base II is provided with a plurality of discharge ports 3| whereby the combustion gases issuing from the upper ends of the tube 29 pass downwardly between the cover 2'! and the cover l2. This has two desirable results; in the first place, the interior surfaces of the walls of the cover l2 are heated thereby; in the second place, a small portion of the burned gases is entrained with the fuel and air burners 2| for combustion in the tubes 29. This reduces the maximum combustion temperature and protects the tubes from excessive heat. The

23 adapted to cooperate with chanheating cover, the outer coverserving merely to insulate against heat loss. In

mixture issuing from the open into a common exhaust duct gases.

a plate 36 overlies adjacent corrugations in the side walls of an inner cover 3'7.

with a pluralwhich are movline position of Fig. 6. The gases produced by combustion of the fuel-air mixture supplied to charge of the gases from the furnace. Fig. 8 shows a construction similar .to that of Fig. 6 except that the burners are mounted on a peripheral wall l5 extending upwardly from the base instead of on the cover itself.

Fig. 9 illustrates a furnace 50 comprising a 5 an upstanding wall 52 extending around the edge thereof. A protective cover 53 and an insulating cover 54 cooperate with the base in the manner already indicated to enclose a charge 55. The cover 53 has heat exchange tubes 56 arranged therein in about the manner shown in Fig. 4.v Burners 51 are retractably mounted-on the cover 54 on brackets 58 and have operating levers 59 for advancing and retracting. them. Burner tubes 60 are posithe cover 54 is thus obtained without the necesthat the heat exchange sity of openings through the base. Fig. 10 shows a similar construction except tubes 56' include the expansion joints 62. The burner structure and mounting of Fig. 10 is similar-to that of Fig. 9 except that the burners 51' and the burner tubes 80' extend through the side walls of the insulating cover 54'.

The upper ends of the tubes 56" are welded to the wall of the cover 53'. The lower ends hang free to embrace short tube sections 63 welded to and extending upwardly from the lower portion of the walls of the cover 63'. Heating gases are exhausted from the space between thecovers 53' and 54' in the manner indicated in Fig. 3, i. e., through ports 64 in the base The several alternative constructions and methods-disclosed are similar in that they all expose the charge directly to the radiations from the ducts through which the heating gases pass. As already pointed out, this accelerates the heating and thereby increases the amount of material which it is possible to anneal with a single set of equipment. This saving in time is reflected in a lower cost of fuel per ton of material treated. Time savings of as much as 15 to 20 per cent can be obtained.

Various changes in the several methods and apparatus disclosed may be made without departing from the spirit of the invention or the scope of the appended claims.

We claim: I

l. The combination. with. a base capable of supporting a charge of material during heat treatment, of a protective cover, a seal on the base cooperatingtherewith whereby said cover is effective when placed over the charge to exclude the atmosphere therefrom while cooling, an insulating cover dimensioned to be placed over the protective cover while heating the charge to confine the heat therein, conduits for heating gases extending along said protective cover, aportion at least of the walls of the conduits being directly exposed to the charge for radiation of heat thereto, and means for delivering hot gases to said conduits.

2. The combination with a base capable of supporting a charge of material during heat treatment, of a protective cover, a seal on the base cooperating therewith whereby said cover is effective when. placed over the charge to exclude the atmosphere therefrom while cooling, an insulating cover of a size to be placed over the protective cover while heating the charge to confine the heat therein, conduits mounted on said protective cover and extending inwardly of the outer boundaries thereof, for conveying hot combustion gases close to the charge, and burners discharging into said conduits. l

3. The apparatus definedby claim 2 characterized by an exhaust said burners, the ends of the conduits adjacent the burners being open to the space adJacent saidport whereby said burners induce recirculation through-the conduits of a portion of the gas which has previously passed therethrough.

4. In a method of heating within inner air excluding and outer heat-insulating covers, the steps including conducting hot gases to the space within the first mentioned cover and confining the gases out of contact with the material.

5'. The method defined by claim 4 characterized by conducting said gases into said space adjacent the bottom of the air-excluding cover and out of said space adjacent the top thereof and thence downwardly along the wall of said heatinsulating cover. p

6. The method defin d by claim 4 character ized by conducting said gases into said space adjacent the bottom of the air-excluding cover and out of said space adjacent the top thereof, and inducing recirculation of a portion of the gases that have previously traversed said space with the gases entering the space for the first time.

. WILSON.

JAMES C. WOODSON.

material enclosed port in said base adjacent

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