US2875997A - Method of and apparatus for heating coils of metal rod, wire or the like - Google Patents

Description

March 3, 1959 c, c, BLACKMAN 2,875,997

METHOD OF AND APPARATUS FOR HEATING COILS OF METAL ROD, WIRE OR THE LIKE Filed Oct. 24, 1955 5 Sheets-Sheet 1 5 7. IIIIZ.

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METHOD OF AND APPARATUS FOR HEATING COILS OF METAL ROD. WIRE OR THE LIKE Filed Oct. 24, 1955 5 Sheets-Sheet 3 INVENTOR. CALV/N C. BLACK/WAN ATTOENEYS United States Patent METHOD OF AND APPARATUS FOR -HEATING 'COILS OF METAL ROD, WIRE OR THE LIKE :Calvin 1C. .Blackman, Lakewood, Ohio, assignor to Lee Wilson, Rocky River, Ohio Application October 24, 1955, :Serial ,No. 542,190

7 Claims. (Cl. 263-40) This invention relates to an improved method of and apparatus for heat treating coils of metal rod, wire, or the like, andmore-particularly'to the annealing of stacks of such coils in bell-type furnaces;

The heating of coils of metal strip, wire and rod in '-b ell-type Ifurnaces for annealing or other heat treating purposes ,is extensively practiced in the ferrous and nonferrous metal industries. In a widely used and successful embodiment of this type of-furnace the coils are stacked one upon the other on'a furnace-base and an inner cover of relatively thin metal placed thereover with a gas seal between it and the base. The furnace bell carrying the heating elements is then positioned over the inner cover and "the heat generated by the heating elements is transferred' to the coils. 'In the-operation of these furnaces for annealing ferrous .metals the heating chamber within ,the

inner cover is customarily -filled with a non-oxidizing atmosphere before the furnace is heated and a blower is mounted in the furnace base structure for circulating the "atmosphere within the heating chamber to assist in the convection heating of the charge.

It is an object of the present invention to provide a bell-type annealing furnace of the type referred to in which the circulation of the furnace atmosphere within theheating chamber is effective to heat the charge more rapidly and efficiently than with previous furnaces of this type, particularly when the furnace is charged with one or more stacks of coils of rod or wire supported on loading spiders. Other objects of my invention include the provision of an improved method of circulating the atmosphere in .a bell-type furnace whereby transfer of heat to the'charge by convection is-facilitated and a very rapid and efficient heating operation obtained; the provision of an "improved furnace charge support and diffuser together with loading spiders so supported thereon that, in addition to the primary or main circulation of atmosphere 'in the heating chamber, a secondary circulation is induced in the chamber whereby the efficiency of heat transfer is substantially increased and the heating time correspondingly reduced; and the :provision of a bell-type furnace structurewhich is adapted efficiently to heat different numbers of stacks of coils of wire, rod, or the like without change in the furnace structure oroperation and with "increased output for a given size furnace.

L lhe above and other objects of my invention will appear from the following description of several embodiments thereof, reference being had to the accompanying drawings in which:

Figure 1 is a vertical cross-sectional view through a bell-type furnace "in accordance with my invention and charged with three stacks of coils of wire or rod.

Figure 2 is a horizontal cross-sectional view of the furnace shown in Figure 1, taken substantially on line 22 of Figure 1, some of the diffuser vanes being omitted .for the sake of clearness.

Figure 3 is a detached fragmentary vertical cross-sectional view showing the bottom end portion of one of the 2,875,997 Patented Mar. 3, 1959 2 loading spidersshown in Figures 1 and2 with its stripper plate in coil supporting position.

Figure 4 is a plan view of the loading spider of Figure 3, partly in horizontal cross-section andon a somewhat reducedscale from that of Figure 3.

struts and diffuser vanes, some of the struts and part of the grating being omitted for thesake of clearness.

In Figure l-the outer 'bellof the furnace is indicated generally at F. This is ,of usual formand, as illustrated,

includes a pluralityof combustion tubes lmounted. around 'theginner wallt'of the bell and adapted to receive'fuel and air through the inlet pipes 2 and to discharge products of combustiton through the exhaust pipes 3. This bell is adapted tobe lifted from and placed in position on-the furnace base B by means of the lifting eye 4. Alsosupported on the furnace base B is the inner charge cover 5 of relatively thin sheet metal and having annular 'depending sealing flange portions '6 and 7 which, when the inner cover is in position as seen in Figure 1, extend into corresponding troughs 8 and 9 in the base structure B "which-are filled with sand, water, or other suitable sealing material.

The upper surface of the furnace base structure B which is within'the inner cover 5 is substantially flat and horizontal and supports the charge support and diffuser unit which is generally'indicated at S. This unit S includes a plurality of diffuser vanes 10 extending spirally out- 'wardly from points adjacent the center of the furnace structure and defining outwardly diverging passages through which the atmosphere within the inner cover'5 is forced by the centrifugal blower 11. At the outer ends of the-vanes 10 a circumferential rim 12 may be provided to ,assist in supporting the vanes and directing the flow of atmosphere upwardly along the side wall of the inner cover 5. At the center portion of the charge support and diffuser unit S, -a blower-inlet plate 13 rests on the top edges of the inner ends of the vanes 10 which, as seen in Figure 1, are preferably notched out so that the top face of plate 13 is flush with the top edges of the vanes 10.

Furnace atmosphere may enter the center inlet of the blower 11 through the inlet opening 14 in the plate 13 while the annular outer part of plate 13 constitutes a walls are maintained at high temperature by the combustion tubes 1, the atmosphere is heated as it moves upwardly to the top wall of the inner cover which directs it inwardly and down through the center area of the furnace and the inlet opening 14 back into the blower 11. The circulation of atmosphere just described is referred to herein as the main flow path and is that usually present in furnaces of this type.

.As will presently appear, due totcertain novel features of my furnace structure, an auxiliary or secondary flow of the furnace atmosphere is induced at locations where it is most effective in improving the rate of heat transfer to the furnace charge.

1'he upper face of the charge support and diffuser un1t S, outwardly from the outer edge of the blower inlet plate 13 is entirely open or exposed to the furnace heating chamber within the inner cover 5. In Figure -1 I have illustrated three loading spiders L symmetrically disposed on and supported by the top edges of the vanes 10 of the charge support unit S. Each of these spiders .L, as best seen in Figures 1, 3, and 4, includes a base ,tion 18 which is preferably ribbed or corrugated as seen in Figure 4 and perforated by a plurality of holes 19 to permit the flow of atmosphere into the interior thereof. Spaced rings 20 serve to reinforce the tubular stem 18, the upper endportion 18 of which preferably tapers inwardly to facilitate placing the coils of wire or the like thereon and carries the top plate 21 which, as illustrated, is centrally apertured at 21'.

As is clearly seen in Figures 1, 3 and 4, the outer edge of the base portion 15 of each spider L projects outward slightly beyond the outer periphery of the stem portion 18 and each spider is provided with a stripping plate 22 having a loose fit on the stem 18 and adapted, as indicated in Figures'l and 5, to support the coils carried on the spider and facilitate removal thereof from the furnace when the annealing operation is finished. Secured to the bottom face of each stripping plate 22 is a plurality of radially extending support bars or ribs 22 which, when the spiders are positioned on the furnace charge support S, rest upon the top edges of the vanes 10 and transmit the load to the vanes.

A plurality of coils of wire, rod, or the like C are stacked on each of the spiders L. These coils are shown in phantom lines, it being understood that they are somewhat irregular in shape and, under the heat applied during the annealing operation, will settle down and .shift their positions to a certain degree but will be maintained in stacked arrangement by the tubular stems 18 of the loading spiders.

When the furnace has been charged as illustrated in Figures 1 and 2 and heat applied by the combustion tubes 1, the blower 14, which is mounted on a vertical shaft 11 and driven by any suitable means such as belt drive 11" from an electric motor (not shown), discharges gas at high velocity outwardly through the passages formed between the diffuser vanes 10. When this gas reaches the side wall of the inner cover it flows upwardly (absorbing heat therefrom), inwardly across the top of the cover 5, and down through the central space between the three loading spiders L and their stacks of coils C. As the gas moves downwardly in the center portion of the heating chamber it passes through the inlet opening 14 in theblower inlet plate 13 and is again picked up by the blower 11, thus maintaining the main or primary flow path of the circulation of the furnace atmosphere.

The gas which moves horizontally through the passages between the vanes is traveling at a very high velocity. As noted above-these passages are open on top to the interior of the heating chamber and the loading spiders merelyrest upon the top edges of the vanes 10. Thus the stacks of coils are in vertically spaced exposed relation to.the top of furnace base structure B. The

rapid flow of gas through the outwardly diverging passages between the vanes 10 induces a secondary or auxiliary circulation of furnace atmosphere around and in direct contact with the convolutions of the coils C into the interior of the spider stem 18 through the holes 19 and then downwardly through theholes 16 and 17 in the spider base portion into the outwardly moving main high-velocity streams between the vanes 10. This auxiliary or secondary induced circulation through and around the coils of rod or wire greatly increases the transfer of heat thereto and thus substantially reduces the time required to bring them up to annealing temperature.

Although I have illustrated three loading spiders and three stacks of coils in the furnace of Figures 1 and 2, it will be understood that a larger number of smaller diameter coils could be supported on spiders on the furnace base. Furthermore, in some instances it may be desirable to anneal only a single large coil in the furnace and I have illustrated a charge support and diffuser arrangement in Figures 5 and 6 which is particularly adapted for practicing my invention when only a single loading spider and a stack'of relatively large diameter coils is centrally located in the heating chamber.

As the furnace bell, inner cover, base structure, blower, diffuser vanes, etc. are substantially the same in the apparatus of Figures 5 and 6 as those described in connection with Figures 1 and 2, the corresponding elements have been identified by similar reference characters. In like manner the loading spider L seen in Figure 5 and the stripping plate 22 associated therewith is the same as that previously illustrated although somewhat larger to accommodate the larger diameter coils.

A blower inlet plate 24, generally similar to plate 13 of Figures 1 and 2, is supported on the top edges of the diffuser vanes 10 and has its central opening 25 centered with the blower 11 to provide an inlet thereto. A plurality of radially extending spacing struts 26 rest upon the top edges of the vanes 10 and extend out from the center opening 25 to the outer rim 12 of the diffuser structure. As seen in Figure 6, each of these struts has a relatively wide bottom flange 27 and a narrow-top flange 28 connected by vertical web member 29. On top of the radial struts 26 is a grating structure G built up of a plurality of concentric rings 30, 31, etc., spaced apart by radial and diagonal webs indicated at 32 and 33 in Figure 6. Thus the grating G comprises an open structure which permits free flow of atmosphere vertically therethrough but possesses sufficient strength and rigidity to support the load of the furnace charge.

The base portion 15 of the spider L rests upon the to; of gating G with its central hole 16 coaxially disposec' relative to the opening 25 in the blower inlet plate 24 but spaced 'thereabove. Also supported on the grating G and carried by the loading spider L is a stripping plat: 22 which carries the stack of coils C.

In the operation of the apparatus of Figures 5 and t the main flow of atmosphere circulated by the blower 1] is outwardly through the outwardly diverging passage: between the diffuser vanes 10, upwardly along the Sidt walls of the inner cover 5 and down through the cente: of the spider L, the opening 16 in the base portion of th spider, the opening 25 in the blower inlet plate, and bacl to the blower 11. Due however to the fact that thl passages between the vanes 10 are open on top and th struts 26 and the grating G do not interfere materiall with vertical downward flow therethrough, the high velo city outward movement of gas in the passages between th vanes 10 induces a secondary or auxiliary circulation 0 atmosphere downwardly through and around the strand of the coils C on the outside of the tubular stem 18 0 loading spider L, through the grating G, and past th struts 26 and back into the main flow path in the passage between the vanes 10. Thus, due to the added flor of atmosphere through and between the c'onvolutions o the coils which is effected by the induced circulation more rapid heating and more efficient overall furnace op eration is obtained than in prior furnaces in which th induced secondary circulation was not present.

Although I have described the illustrated embodiment of my invention in considerable detail it will be under stood that variations and modifications maybe made i the various structural elements of my improved apparatu and in the steps of my-method withoutdeparting fro: the spirit of my invention. I do not -therefore-..wish t be limited to the exact structures and procedures herei '5 described :but claim as my invention .all embodiments thereof coming within the scope of [the appended claims.

I claim: 7

1. In a bell-type furnace, at base structure, a charge support and diffuser-carried by said base structure, a rotary blower supported in said basestructure,'saidcharge support and difiuser-having an opening in Whichfsaid blower is'disposed, a plurality of radially extendingupwardly projecting diifuser vanes having their inner ends forming said opening and an annular blower inlet plate supported on the inner portions of said vanes coaxially with said blower, the passages between adjacent vanes being closed on the bottom, diverging outwardly, and, beyond said blower inlet plate only, being open on top, and a loading spider having a base portion and an upwardly projecting stem portion, said base portion being supported by and resting directly on said vanes of said charge support and diffuser and said stem portion being disposed radially outwardly of said inlet plate and extending upwardly from said base portion and adapted to receive coils of wire or the like.

2. In a bell-type furnace, a base structure, a charge support and diffuser carried by said base structure, a rotary blower supported in said base structure, said charge support and diffuser having an opening in which said blower is disposed, a plurality of radially extending upwardly projecting difiuser vanes having their inner ends forming said opening and an annular blower inlet plate supported on the inner portions of said vanes coaxially with said blower, the passages between adjacent vanes being closed on the bottom, diverging outwardly, and, beyond said blower inlet plate only, being open on top, and a loading spider having an apertured base portion and an upwardly projecting tubular stem portion, said base portion being supported by and resting directly on said vanes of said charge support and diffuser and said tubular stem portion being disposed radially outwardly of said inlet plate and having an apertured wall extending upwardly from said base portion and adapted to receive coils of wire or the like.

3. In a bell-type furnace, a base structure, a charge support and diffuser carried by said base structure, a

rotary blower supported in said base structure, said charge support and difiuser having an opening in which said blower is disposed and a plurality of radially extending upwardly projecting diffuser vanes having their inner ends forming said opening, a blower inlet plate supported on the inner ends of said vanes, the passages between adjacent vanes being closed on the bottom, diverging outwardly and being closed on top at their inner end portions and open on top at their outer end portions, and a loading spider having an apertured base portion and an upwardly projecting tubular stem portion, said base portion being supported by and resting on said vanes and said stem portion being disposed above said open topportion of the passages therebetween, said tubular stem having an apertured wall extending upwardly from said base portion and adapted to receive coils of Wire or the like.

4. In a bell-type furnace, a base structure, a charge support and diffuser carried by said base structure, a rotary blower supported in said base structure, said charge support and diifuser having an opening in which said blower is disposed and a plurality of radially extending diffuser vanes having their inner ends forming said opening, the passages between adjacent vanes diverging outwardly and being open on top at their outer portions only, a loading spider having an apertured base portion and an upwardly projecting tubular stem portion, said base portion being supported by and resting on said vanes of said charge support and diffuser and said tubular stem having an apertured wall extending upwardly from said base portion and adapted to receive coils of wire or the like, a blower inlet plate on said charge support and diffuser disposed above said blower and having a central into said passages between said vanes adjacent said loading spider and radially outwardly of said blower inlet plate.

5. In a bell-type furnace, a base structure having a substantially flat upper surface, a charge support and diffuser carried by said base structure,- a centrifugal blower supported in said base structure, said charge support and diffuser having an opening in which said blower is disposed and a plurality of radially extending upwardly projecting difiuser vanes having their inner ends forming said opening, the passages between adjacent vanes being completely closed on the bottom and open on top at their outerportions only, a plurality of loading spiders each having an apertured base portion and an upwardly projecting tubular stem portion, said base portions being supported by and resting on said vanes of said charge support and diffuser in spaced relation to said opening therein, said tubular stem portions each having an apertured wall extending upwardly from the base portion and being adapted to receive a stack of coils of wire or the like, a blower inlet plate on said charge support and diffuser disposed above said blower and having a central blower inlet opening and an outer baflle portion disposed to close the top of the inner end portions of said passages between said vanes, said stem portions of said loading spiders being disposed above said open outer end portions of said passages, and a charge cover mounted on said furnace base structure and forming a heating chamber thereon, said blower being adapted to draw atmosphere in said chamber down through said blower inlet opening in said bafile plate and discharge same outwardly through said passages between said diffuser vanes whereby atmosphere is drawn down into said passages between said vanes adjacent said loading spiders and radially outwardly of said blower inlet plate.

6. The method of circulating the atmosphere in a belltype furnace having a heating chamber, a base structure, and a blower supported by said base, which includes the steps of discharging atmosphere in a main flow path horizontally outwardly from said blower across said furnace base with decreasing velocity and increasing static pressure, directing said atmosphere upwardly around the peripheral wall of said furnace heating chamber, drawing said atmosphere downwardly in the central portion of said heating chamber into the blower inlet, supporting a stack of coils of wire or the like in radially outwardly spaced relation to said blower inlet and in' vertically spaced exposed relation to said furnace base structure whereby said atmosphere discharged horizontally outwardly from said blower passes through the space between said base structure and the bottom of said stack of coils, and maintaining the velocity of flow of said outwardly discharged atmosphere at a rate which will induce a secondary downward flow of atmosphere adjacent said stack of coils into said main horizontal flow path.

7, In a bell-type furnace, a base structure, a charge support and diffuser carried by said base structure, a rotary blower supported in said base structure, said charge support and diffuser having a central opening in which said blower is disposed, a plurality of radially extending upwardly projecting diffuser vanes having their inner ends forming said opening, and an annular blower inlet plate supported on the inner portions of said vanes coaxially with said blower, the passages between adjacent 7 vanes being closed onthe bottom, diverging outwardly and, beyond said blower inlet plate only, being open on top, a loading spider having a'base portion'and an upwardly projecting stem portion,- and grating means for supporting said base portion above and in spaced rela- 'tion to the top edges of said vanes of said charge support and diflfuser, 'said stern extending upwardly from said base portion and being adapted to receive coils of wire or the like. g

References Cited in the file of this patent UNITED STATES PATENTS Pierce Feb. 16, 1943 Wilson Ian. 14, 1947 Straub Aug. 19, 1952 Tauber et a1. Aug. 17, 1954 Campbell et a1. Ian. 17, 1956 Berquist Apr. 24, 1956

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