US3802834A

US3802834A - Heat transfer plates

Info

Publication number: US3802834A
Application number: US00731529A
Authority: US
Inventors: R Corbett
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-05-23
Filing date: 1968-05-23
Publication date: 1974-04-09
Anticipated expiration: 1991-04-09

Abstract

There is disclosed herein a heat transfer plate adapted to be disposed between coils of metal in an annealing furnace, the plate comprising a plurality of circumferentially spaced bars disposed in two opposing layers, the bars being skewed with respect to true radii of the plate whereby the bars of one layer partially overlap the bars of the other layer.

Description

I Umted States Patent [1 1 [111 3,802,834 Corbett, Jr. 5] Apr. 9, 1974 [54] HEAT TRANSFER PLATES 3,423,079 1/1969 McKeown 263/47 A [76] Inventor: Robert Lee Corbett, Jr., 227 81530 4/196! Menough 263/47 A Westlake Rd., Rocky River, Ohio 441 16 Primary Examiner-John J. Camby Attorney, Agent, or Firm J. H. Slough; Squire, [22] Filed: May 23, 1968 Sanders & Dempsey [211 Appl. No.: 731,529 [57] ABSTRACT [52] U S Cl 432/260 766/5 B There is disclosed herein a heat transfer plate adapted [51] 1 21/04 to be disposed between coils of metal in an annealing [58] Fieid 266/5 B furnace, the plate comprising a plurality of circumfer- 1 432/266 entially spaced bars disposed in two opposing layers, the bars being skewed with respect t0 true radii of the [56] References Cited plate whereby the bars of one layer partially overlap UNITED STATES PATENTS the bars of the other layer. 3,145,982 8/1964 Ludwig 263/47 A 16 Claims, 7 Drawing Figures HEAT TRANSFER PLATES This invention relates to annealing furnaces for treating coils of metal in strip form and relates more particularly to an improved heat transfer plate for transferring heat to and from coils stacked endwise within an annealing furnace.

In known forms of the types of furnaces referred to, the coils of strip material are stacked coaxially upon a suitable base structure having a recirculating fan or blower disposed therein. Each coil defines a central, coaxial opening or eye, and the fan is adapted to circulate a heated, protective atmosphere gas upwardly around the outside of the coils and downwardly through the eyes of said coils. Coil separators or convector plates are provided between adjacent pairs of the stacked coils, said convector plates spacing the coils from each other and affording suitable gas passages thus allowing the heated gas to circulate to the edges of the wraps whereby heat is transferred by convection and conduction to the interior of the coils. The stacked coils are preferably enclosed within a gastight inner cover which is, in turn, disposed within a suitable hood or furnace having radiant tubes, burners, or other suitable heating means for heating the inner cover.

The heat transfer plate of this invention is adapted for use as a coil separtor and convector plate and is further adapted for use as a charge plate for supporting an entire stack of coils and as a top orifice plate for positioning on top of the uppermost coil. In any of the positions mentioned, the heat transfer plate of this invention is adapted to transfer heat in an improved manner from the circulating atmosphere gas to the coils, or from the coils to a cooling atmosphere gas, by both conduction and convection. The heat transfer plae is further constructed in such manner as to provide a controlled turbulence of the atmosphere gas adjacent to the edges of the coil wraps whereby more rapid heating and cooling of the coils is effected resulting in an increase in the overall efficiency of the furnace.

Coil separators or convector plates of the type referred to are subjected to substantial load pressures due to the weight of the coils disposed thereupon and must be constructed in such manner as to withstand these load pressures while at the same time affording adequate gas passages for flow of the heated atmosphere gas to the edges of the coils. The separators must withstand stresses due to extreme temperature changes and provide sufficient supporting area to prevent damage to the edges of the coil wraps. These and many other problems which arise in connection with manufacture and use of coil separators have been solved in an improved manner by the heat transfer plate disclosed herein.

It is, therefore, an object of this invention to provide a heat transfer plate of improved design providing a venturi effect for causing a turbulent flow of atmosphere gas to the edges of coils and discharging the same into the eyes or centers of the coils disposed within an annealing furnace whereby a substantially improved rate of heating and cooling is obtained.

Another object of the invention is to provide a heat transfer plate which affords adequate areas of contact between support bars of the plate and the coils to more effeciently utilize temperature transfer by conduction as well as by convection in the heating and cooling cycles of the furnace.

Another object of this invention is to provide a heat transfer plate as set forth above which is so constructed as to resist distortion due to expansion and contraction of the metal when subjected to extreme temperature changes.

Still another object of this invention is to provide a heat transfer plate having the above features and characteristics wherein the supporting surface areas are proportioned according to the load weight of the coil diameters and are sufficient to support the coils without damage to the edges of the coil wraps, said plate also affording adequate circulation of the atmosphere gas across the edges of the coil wraps.

Yet another object of the invention is to provide a heat transfer plate as characterized above which comprises a plurality of like parts so arranged and itnerconnected as to reinforce each other.

A still further object is to' provide a heat transfer plate as set forth above wherein each of said like parts is secured to at least three other of said like parts.

Another object of the invention is to provide a heat transfer plate of the above type which is of simple, sturdy construction, inexpensive to manufacture, and highly durable to use.

Still another object of the invention is to provide a heat transfer plate of sufficiently sturdy construction whereby it can also be used as a load or charge plate directly on top of the diffuser or furnace base thereby causing additional atmosphere gas to come into contact with the bottom edge of the bottom coil directly from the recirculating fan; this additional circulation increases the heating and cooling efficiency of the furnace.

Another object of the invention is to provide a heat transfer plate which allows a crane operator to see through a substantial portion of the plate when manipulating the same into position with respect to a coil.

A further object of the invention is to provide a heat transfer plate which affords increased circulation downwardly through the eyes of the coils and upwardly around the outside of the coils.

FIG. 2 is a fragmentary transverse section taken generally along the line 22 of FIG. 1;

FIG. 3 is an enlarged detail section taken generally along the line 3-3 of FIG. 2;

FIG. 4 is an enlarged plan view of one side of the heat transfer plate of this invention;

FIG. Sis a fragmentary plan view of the opposite side of the heat transfer plate as shown in FIG. 4;

FIG. 6 is a detail section taken along the line 66 of I FIG. 4; and I lindrical body portion 11 is preferably formed of heavy sheet metal and has a downwardly projecting, annular flange portion 14 which projects downwardly into a granular sealing trough 15 of a generally cup-shaped base 16. The base 16 has an upwardly projecting, annular flange 17 having a slightly larger diameter than the flange portion 14 whereby said flange portion is disposed generally within said annular flange 17. The body portion 11 is supported by radially projecting fins 18 the bottom edges of which seat upon the upper edge of the annular flange 17. The base 16 also includes a suitable refractory bottom lining l9 and a central support structure comprising concentric steel rings 20 having refractory material 21 disposed therebetween. An annular plate 22 surrounds the concentric rings 20, and a larger annulus 23 is disposed outwardly therefrom and forms the inner wall of the granular sealing trough l5. Said trough is filled with a suitable granular sealing material 15', such as sand, into which the flange portion 14 projects. The body portion 11 may also be sealed by mechanical seals of other types.

The base 16, as herein illustrated, is securely mounted upon I-beams 24 which are seated in a concrete floor 25 or other suitable supporting means. A

central cavity 26 in the floor 25 affords space for mounting a motor 27 having a shaft 28 which projects upwardly through the central portion of the base 16, the upper end of said shaft carrying a centrifugal blower 29. The blower 29 is disposed within a central opening 30' of a coil support'member or diffuser 30, said support member having upper plate means 31, generally radially disposed spacers 32, lower plate means 33, and circumferentially disposed, angled dcflectors 34. An atmosphere gas inlet 30a and an atmosphere gas outlet 301; project upwardly through the base 16 and the lower plate means 33.

As herein illustrated, the coil support member or diffuser 30 supports four coils of strip sheet steel stacked vertically'and coaxially within the body portion 11 and separated by heat transfer plates 36. Each coil 35 defines a central opening or eye 37, and the uppermost of said coils is provided with a top orifice plate 38 which covers the eye of the upper coil and which may be provided with a central, flow restricting orifice 39.

An inner cover 40 is disposed over the stacked coils 35, the upper end of said cover being closed by an upper end wall 41 having an upwardly projecting lifting bail 41 Said cover has a lower annular base portion 42 which seats upon the annular plate 22 and is sealed thereby by granular sealing means indicated at 42. The inner cover 40 may also be sealed by mechanical seals of other types. In the form shown, heating means for the furnace comprise elongated, gas-fired, radiant tube heaters 43 which are. evenly circumferentially spaced around the outside of the hood 40 within the refractory lining 13;

The heat transfer plates 36 are identical in form and only one of them will be herein described in detail. One of the said plates is detailed in FIGS. 3-7, and it will be seen that said plate is substantially circular and comprises a plurality of identical bars 44. The bars 44 have tapered side edges 44a and 44b and are arranged in layers which for convenience of designation are generally indicated in FIG. 6 as upper layer A and lower layer B. Layer A is superimposed over layer B and as best seen in FIG. 4, the bars 44 of upper layer A are substantially angled or skewed with respect to true radii of the heat transfer plate; that is, their outer ends are circumferentially displaced relative to their inner ends in a counter clockwise direction, whereas the bars of the lower layer B are similarly circumferentially skewed the same amount in the opposite or clockwise direction. The inner edges 45 of the bars in layer B overlap the inner edges of the bars in layer A and define a central opening 46 which is adapted to be disposed coaxially with the eyes 37 of the coils 35 and is somewhat smaller than said eyes. The outer edges 47 of the bars 44 in layer A overlap the outer edges of the bars in layer B and are disposed generally tangent to a circle having a diameter slightly in excess of the diameter of the coils 35. The circumferential spacing and skewing of the bars 44 in each layer is such that each bar of each layer overlaps three of the bars in the other layer. For example; any bar in the layer A has an outer larger end portion 48 overlapping the outer, larger end portion 48 of a bar in the layer B, a medial portion 49 similarly overlapping the medial portion 49 of another bar in layer B, and a tapered inner end portion 50 overlapping the tapered inner end portion 50 of still another bar of the layer B. In a similar manner, each bar in layer B is attached to at least three of said bars in layer A. The outer edges of the bars 44 are rounded as indicated at 44' in FIGS. 6-7 adjacent to the upper and lower coil contacting surfaces of the heat transfer plate 36 to prevent damage to the edges of coil wraps coming in contact therewith. It will be further noted that the outer edges 47 of the bars 44 as seen in plan view (FIGS. 4 and 6) are angled inwardly from rounded apices 47, said apices defining the outer circumference of the plate 36.

' The means of attachment of the bars 44 is preferably by welding along the lateral and end edges of said bars where they cross or overlap as indicated at 51. It will be noted, however, that where the bars cross at the larger end portions 48, the overlapping bars are not welded continuously throughout the length of their overlapping edges, the welds being confined to two spaced areas indicated at 51a and 51b. This enables the bars to expand and contract in response to temperature changes without causing the heat transfer plate to distort.

The spaces between the side edges 44a and 44b of the circumferentially adjacent bars 44 define inwardly tapering passages 55 for the circulation of the heated atmosphere gas to the edges of the coil wraps. Thus, the passage means defined by the spaces between said bars are of substantially changing cross sectional area throughout the length thereof. As will hereinlater become apparent, the direction of circulation with respect to the coil separator 36 is generally radially inwardly through the spaces between the bars, the inward taper of the passages 55 providing a venturi effect adjacent to the central opening 46. Bars in the upper layer A afford passages which are circumferentially skewed with respect to the passages provided by the bars in the layer B, and where any two passages cross, generally indicated at 52, and where they converge at the opening 46, generally indicated at 53, areas of turbulence are created which increase the heating effiency of the flowing atmosphere gas.

Referring again to FIG. 1 of the drawings, the centrifugal blower 29 causes the atmosphere gas to flow radially outwardly below the coils 35 at which point the deflectors 34 direct said gas upwardly along the outer surfaces of said coils within the inner cover 40. At the same time, the blower 29 draws the atmosphere gas downwardly through the concentric eyes 37 of the coils and the openings 46 in the coil separators, the top orifice plate 38 restricting such downward flow whereby a larger portion of the gas is pulled radially inwardly through the passages 55 in the heat transfer plates 36 and contributes to circulation over the edges of the coil wraps.

It will be readily understood that during the heating cycle of the annealing furnace, the heat transfer plates 36, being of smaller mass than the coils 35, will heat or cool more rapidly than said coils. Because the bars 44 are in contact with the edges of the coil wraps, heat is transferred by conduction directly to or from the coils in the area of contact. The heated atmosphere gas passing through the passages 55 between said bars heats the edges of the coil wraps by convection, and it has been found that the turbulence created at 52 (FIG. 4) where the passages cross and at 53 where said passages converge substantially increases the convection heating. However, the turbulence is carefully controlled to take place within the space between the coils and not in the area surrounding the coils where it might, for example, disturb the sand sea] at the lower edge of the inner cover 40 and cause the finer particules of sand to become entrained in the recirculating atmosphere gas.

As best seen in FIG. 4, the increased heating at 52 where the 'flow passages 55 cross is located a substantial distance inwardly from the inner ends of the bars 44 and an even greater distance from the outer ends of said bars. Generally, the turbulent area at 52 is adapted to be disposed substantially one-third of the distance between the inner periphery of the coil to the outer periphery thereof. It is well-known in the art of annealing coils of strip metal that the most difficult portion to heat is located horizontally substantially one-third of the distance between the inner and outer .peripheries of the coil and vertically one-half 'the distance between the edges of the coil wraps. Thus the heat transfer plate of this invention provides for increased heating by convection in the area most closely adjacent to the portion of the coil which is most difficult to heat.

The inwardly tapering shape of the bars 44 insures that a greater supporting surface area is provided radially outwardly of the eye of the coil where the coil wraps are of largest circumference and, therefore, of greatest weight. The outwardly increasing surface area also provides increased heating by conduction at the outer wraps of the coil where the larger portion of the mass is located. In the same manner, the outwardly widening passages 55 between the bars 44 provide a greater flow area for convection heating of the outer wraps of the coil than of 'the inner wraps thereof. Thus the heat transfer plate'of this inventionis proportioned radially to provide outwardly progressively increasing support and heating means which compensate for the outwardly progressively increasing weight and mass of the coil wraps. Performance tests have shownthat with the use of heat'transfer plates of this type in a standard annealing furnace, a given charge can be heated in substantially less time than where prior known types of convector plates or coil separators are used The heat transfer plate 36 of this invention is readily adaptable for use as a charge plate; that is, a top plate for the coil support member or diffuser 30. Support members or diffusers vary in form and construction providing various patterns of ribs, .posts, and the like for supporting thestack of coils 35 to be annealed and diffusing atmosphere gas within the inner cover 40. Diffusers are commonly provided with a solid upper plate disposed upon the ribs or posts for receiving the stack of coils. This construction does not afford means for the atmosphere gas to circulate across the lower edges of the wraps of the lowermost coil, and it is well known that the lower coil is the slowest coil to heat due to the lack of circulation under this coil.

By varying the number and the size of bars 44 in a heat transfer plate 36, said plate can be adapted to seat upon any pattern of diffuser ribs or posts thereby adapting it for 'use as a charge support plate directly above the diffuser and allowing combined convection and conduction heating at the lower edges of the lowermost coil wraps. The controlled turbulence action discussed above is thus provided at the bottom of the stack of coils as well as between adjacent coils.

It will be further noted that a heat transfer plate of the type shown at 36 may be used at the top of the stack of coils 35 in place of the top orifice plate 38. This provides for convection heating at the upper edge of the uppermost coil, it being understood that the central opening 46 can be varied in size depending upon the length of the bars 44 to afford the desired restriction at this point.

In the specification and claims of the present application, it will be understood that heat transfer plate or similar terminology refers to the invention as set forth herein whether the same is used as a coil spearator, charge plate, or top orifice plate.

An important advantage of the heat transfer plate of the present invention is that it allows a relatively unrestricted flow 7 of the atmosphere gas downwardly through the aligned eyes 37 of the stacked coils. The central opening 46 is necessarily smaller than the eyes 37 to provide adequate support for the inner coil wraps and prevent said inner wraps from falling or being drawn downwardly through said eyes by the circulating gas. Because only the inner smaller ends of the bars 44 project inwardly of the eyes 37, the gas flows through the spaces between said inner ends and is thereby provided with substantially more unrestricted cross sectional flow area than known coil separators.

It will be further noted that the outer ends of the bars 44 similarly afford a relatively unrestricted flow of the atmosphere gas upwardly around the outside of the coils between said coils and the inner cover 40. The heat transfer plates 36 are usually made for maximum diameter coils but are frequently'used with smaller diameter coils whereby the bars 44 extend radially outwardly beyond the coils 35 a substantial distance. Because of the bar construction of the present invention, only the outer end portions of the bars project into the upward flow of atmosphere gas thereby affording a relatively unrestricted flow path around'the outside of the coils.

Another important advantage of the heat transfer plate of the present invention is its see-through feature. Convector plates now widely used in the annealing art are commonly provided with solid plates either disposed on top of a plurality of radially disposed ribs or sandwiched between layers or ribs. These plates have only a central aperture to allow return flow ofthe atmosphere gas. Manipulation of the convector plates is usually by means of a crane operated by a workman disposed a substantial distance from the furnace. in placing the'convector platesupon the coils of steel, the operator should avoid damaging the coil wraps because bent or damaged wraps present problems at the temper I mill. The construction of the heat transfer plate of the present invention allows the operator to see through a substantial portion of the plate thereby greatly aiding him in th difficult task of accurately placing the plate in position with respect to a coil by use of a crane.

The inner cover 40 is also lowered into position over the stacked coils by means of a crane. This inevitably causes the inner cover to swing as it is lowered whereby it hits the outer peripheral edges of the convector plates. The inner cover also tends to hang up on the edges of the plates when the cover is being removed. The resultcan be considerabledamage to the inner cover. The heat tranfer plate of the present invention greatly reduces damage of the aforesaid type by providing the outer ends of the bars 44 with the rounded apices 47a. Since the apicesdefine the largest diameter of the heat transfer'plate 36, onlyvthese roundedportions actually contact the inner cover thereby reducing friction andeliminating long edges or sharp corners upon which the inner cover can hang up or against which it can swing.

An additional advantage of the present construction is that it provides gas passagesof full height without sacrificing stacking height. As mentioned above, convector plates now commonly used throughout the annealing industry include cover plates or cente plates sandwiched between radial bars which said plates provide an obstruction and frictional loss to the flow of gas between the stacked coils. The result is that in order to provide gas passages of a given height, the total thickness of each convector plate must be increased by the thickness of the cover or center plate. The present invention eliminates this additional plate and thereby reduces the overall thickness of the convector plate.

The significance of the last mentioned feature of the present invention-will become clear from the following example: on a typical annealing floor using 117 stools or bases, approximately 350 convector plates are in use during the annealing of the coils. if the added cover or center plate in each convector plate is a minimal /4 inch thick, there is a total loss in stacking height of 87 b inch per charge or the equivalent of more than two 41 inch wide coils. A 41 inch coil having a diameter of 72 inches weighs approximately 40,000 lbs. whereby the total loss of annealing capacity for each charge would be 80,000 lbs. A conservative estimate is that there could be a saving of at least 8 million lbs. of annealing capacity per year on an annealing floor as set forth above by using the heat transfer plates of the present invention rather than conventional convector plates.

in some instances, coils of substantially greater width than those herein illustrated are annealed in a furnace of the type shown. The result is that fewer coils are stacked in a given furnace whereby fewer convector plates are normally used. However, reducing the number of convector plates also reduces the flow of atmosphere gas between the coils thereby reducing the heating and cooling efficiency. The full circulation capacity of the blower 29 may not be fully utilized if the flow between the coils is thus restricted. This problem can be solved with theheat transfer plates of the present invention by stacking two or more of said plates between adjacent coils to match the flow capacity between the coils with the circulation capacity of the blower. The bars 44 are so angled that when one plate is disposed upon another, the adjacent layers of bars are always disposed at an angle to each other for maximum support.

The load supporting bars 44 of the present invention preferably provide a total direct contact supporting surface area of about percent of the total area of the heat transfer plate 36. This may be varied somewhat by varying the width of the bars, depending upon the gage of the strip metal comprising the coils 35. Heavier gage metals generally need less supporting surface than the lighter gage metals whereby the bars can be narrower and the spaces therebetween wider. Generally, it is preferred that the bars provide a supporting surface area of from 40 to percent of the total coil area, the higher percentages being preferable for relatively lighter gage metals.

From the foregoing it will be readily seen that the heat transfer plate of this invention comprises, first of all, a sturdy structure capable of supporting almost unlimited weight. This is due to the layered construction in which the bars are disposed flatwise one above the.

other whereby the pressure which the plate can withstand is limited only by the quality or quantity of material from which it is made. By disposing the bars flatwise, and providing the rounded corners 44', adequate supporting surface area is provided for each coil with-' out damage to the edges of the coil wraps. It will be further noted that the spaces between the adjacent bars 44 provide not only adequate flow area for-the atmosphere gas but also a pattern of criss-cross passages which causes a turbulence of the atmosphere gas thereby accelerating the heating arid cooling of the coils. The overlapping construction in which each bar is firmly connected to at least three other bars affords a structure which effectively resists distortion due to the extreme temperature changes and loads to which the bars are subjected. The fact that the entire coil separator is constructed of a multiplicity of like parts effects great savings in cost of construction and, because of its simplicity, provides a coil separator which is highly durable in use. The present construction provides complete through openings between adjacent coils whereby the heated gas flows freely across the edges of the coil wraps. A middle plate of the type found in some prior art devices disposed between the bars is not necessary in this design for connecting the bars together with the result that there is less metal to heat and load or charge piling height is increased within the furnace. it will be further noted that the heat transfer plate disclosed herein is reversible, the relative positions of the bars and passages being the same no matter which side is disposed upwardly, and that said plate may be used either singly or in multiples.

it will be understood that many changes in the details of the invention as herein described and illustrated may be made without, however, departing from the spirit thereof or the scope of the appended claims.

W at Qla mi in at least two layers with one layer being superimposed upon the other layer; at least certain of said bars being circumferentially spaced from each other and providing gas flow passages therebetween; said certain bars being skewed with respect to true radii of said plate and having inner end portions disposed adjacent to the axis of said plate and outer end portions disposed at the outer periphery of said plate; the inner and outer end portions ofieach said certain bar in each layer overlapping and being secured to the inner and outer end portions, respectively, of two other bars in the other said layer.

2. A heat transfer plate as set forth in claim 1: said inner ends of at least some of said bars defining a central opening and the spacing between said certain bars defining passages extending from the outer periphery of said plate to said central opening.

3. A heat transfer plate as set forth in claim 2: said certain bars being substantially flat with the overlapping portions of said certain bars being in flatwise contact with the bars to which they are secured.

4. A heat transfer plate as set forth in claim 2: each said certain bar in each said layer having portions overlapping portions of three bars in said other layer; circumferentially adjacent bars in each said layer defining passages therebetween which cross over and are open to passages of the other said layer whereby a turbulence is produced in the flowing gas at the intersecting passages.

5. A heat transfer plate as set forth in claim 4: said bars and said passages tapering inwardly from the outer edge of said plate to said central opening.

6. A heat transfer plate as set forth in claim 5: each said bar of each said layer having a medial portion overlapping the medial portion of a bar in said other layer.

7. A heat transfer plate for spacing coils of metal stacked coaxially within a furnace, said heat transfer plate comprising two contiguous layers of flat metal bars of substantially uniform length disposed about a vertical axis and circumferentially spaced from each other in each layer; the inner ends of said bars defining a substantially circular central opening about said axis whereby said bars form a flat, annular structure; the bars in one of said layers being skewed with respect to true radii of the plate in one circumferential direction and the bars in the other of said layers being skewed with respect to said radii a like amount in the opposite circumferential direction; each said bar in each said layer having an outer end portion overlapping and welded to the outer end portion of a first bar in said other layer, a medial portion overlapping and welded to a medial portion of a second bar in said other layer, and an inner end portion overlapping and welded to the inner end portion of a third bar of said other layer; circumferentially adjacent bars in each said layer defining passages therebetween, each of which said passages crosses over and is open to passages of the other said layer.

8. A heat transfer plate as set 'forth in claim 7: said outer end portion of each said bar having side edge portions thereof disposed diagonally across said first bar of said other layer; said side edge portions being welded to said first bar only at spaced areas to allow separate expansion and contraction of the bars due to temperature changes.

9. A heat transfer plate for spacing coils' of metal stacked coaxially within a furnace, said heat transfer plate comprising two contiguous layers-of flat metal bars of substantially uniform length disposed about a vertical axis and circumferentially spaced'from each other in each layer; the inner ends of said bars defining a substantially circular central opening about said axis whereby said bars form a flat, annular structure; the bars in one of said layers being skewed with respectto true radii of the plate in one circumferential direction and the bars in the other of said layers being skewed with respect to said radii a like amount in the opposite circumferential direction; each said bar in each said layer having an outer end portion overlapping and welded to the outer end portion of a first bar in said other layer, a medial portion overlapping and welded to a medial portion of a second bar in said other layer, and an inner end portion overlapping and welded to the inner end portion of a third bar of said other layer; circumferentially adjacent bars in each said layer defining passages therebetween, each of which said passages crosses over and is open to passages of the other said layer; said outer end portion of each said bar having side edge portions thereof disposed diagonally across said first bar of said other layer; said side edge portions being welded to said first bar only at spaced areas to allow separate expansion and contraction of the bars due to temperature changes; the upwardly and downwardly facing, coil contacting surfaces of each said bar being rounded along the perimeter thereof to prevent damage to the edges of the coil wraps.

10. A heat transfer member for transferring heat by both conduction and convection to the coil wrap edges of strip metal coils stacked coaxially within an annealing furnace, said member comprising contiguous layers of flat metal bars of substantially uniform shape disposed about a vertical axis and uniformly circmferentially spaced from each other in each layer; said bars tapering inwardly, the inner ends thereof defining a circular central opening whereby said bars form a generally flat, annular structure; said bars being substantially skewed with respect to the true radii of said member, the bars in one of said layers being skewed in one circumferential direction and the bars in the other of said layers being skewed the same amount in the opposite circumferential direction; each said bar in each said layer having its outer, larger end portion overlapping and secured to the outer end portion of one bar in the other layer and its inner, smaller end portion overlapping and secured to the inner end portion of another bar of said other layer; circumferentially adjacent bars in each layer defining inwardly tapered passages for directing a circulating atmosphere gas across the edges of the coil wraps, each said passage crossing over and being open to a passage of the other said layer whereby a turbulence is produced in the flowing gas at the intersection of said passages adjacent to the edges of the coil wraps when said member is disposed coaxially against an end of a coil, said bars and said passages providing outwardly increasing areas of support, heat conduction, and gas flow whereby said member is radially proportioned with respect to the outwardly increasing larger coil wraps and coil mass.

11. A heat transfer turbulator member as set forth in claim 10: each said bar having a medial portion thereof overlapping and secured to a medial portion of still another bar of said other layer; and each said passage in each layer crossing over and being open to three passages of said other layer.

12. A heat transfer member for transferring heat by both conduction and convection to the coil wrap edges of strip metal coils stacked coaxially within an annealing furnace, said member comprising contiguous layers of flat metal bars of substantially uniform shape disposed about a vertical axis and uniformly circumferentially spaced from each other in each layer; said bars tapering inwardly, the inner ends thereof defining a cir' cular central opening whereby said bars form a generally flat, annular structure; said bars being substantially skewed with respect to the true radii of said member, the bars in one of said layers being skewed in one circumferential direction and the bars in the other of said layers being skewed the same amount in the opposite circumferential direction; each said bar in each said layer having its outer, larger end portion overlapping and secured to the outer end portion of one bar in the other layer and its inner, smaller end portion overlapping and secured to the inner end portion of another bar vof said other layer; circumferentially adjacent bars in each layer defining inwardly tapered passages for dia turbulence is produced in the flowing gas at the interupon the other layer; said bars being circumferentially spaced from each other and providing gas flow passages therebetween; said bars being skewed with 'respect to true radii of said plate and having inner end portions disposed adjacent to the axis of said plate and I outer end portions disposed at the outer periphery of said plate; each said bar in each said layer having porsection of said passages adjacent to the edges of the coil wraps when said member is disposed coaxially against an end of a coil, said bars and said passages providing outwardly increasing areas of support, heat conduction, and gas flow whereby said member is radially proends of the bars in one of said layers extending radially outwardly beyond the outer ends of the bars in the other layer and the inner ends of the bars in said other layer extending radially inwardly beyond the inner ends of the bars in said one layer.

13. A heat. transfer turbulator member as set forth in claim 12: each said bar being welded to the bars it overlaps along overlapping side and end edge portions thereof to provide a unified structure. v

14. A heat transfer plate for transferring heat to coils of metal stacked coaxially within a furnace and directing a flow of atmosphere gas across the edges of the coil wraps, said plate comprising a plurality of horizontal bars disposed about a vertical axis, said bars arranged in at least two layers with one layer being superimposed tions overlapping portions of three bars in said other layer; circumferentially adjacent bars in each said layer defining passages therebetween which cross over and are open to passages of the other said layer whereby a turbulence is produced in the flowing gas at the intersections of said passages; said passages providing a plu rality of cross-over areas circumferentially spaced around said plate inwardly of the inner ends of said bars in such position as to be disposed substantially onethird the distance between the inner and outer peripheries of a coil positioned upon said plate.

15. A convector plate for use between two stacked coils of sheet metal during annealing of the latter, said plate comprising two superimposed rib systems, each composed of a plurality of separate ribs arranged so that the ribs and the passages between the ribs together define an annulus, each rib, being generally wedgeshaped in plan, and having straight edges which extend between the inner and outer peripheries of such annulus and are inclined in the same sense to the radii of the annulus, characterized in that the ribs of each system have their outer ends substantially coinciding with the outer ends of the ribs of the other system, but are inclined to the radii of the annulus in a sense.opposite to the sense in which the ribs of the other system are inclined to the radii of the annulus, and in that the rib systems are constructed so that air drawn inward along the convector plate toward the interior of the coils is separated into two sets of streams, one flowing through the passages between the ribs of one system and the other flowing through the passages between the ribs of the other system, the outer portion of each passage of one rib system, adjacent the periphery of the convector plate, being merged with a passage of the other rib system, and most of the remainder of each passage being separated from the passages of the other rib system to minimize interference between the flow through the remainder of each passage and the flow through the passages of the other rib system.

16; A convector plate according to claim 15 wherein the two rib systems are directly secured to one another, and each rib of one system overlies not more than four ribs of the other system.

UNITED STATES PATENT OFFICE CERTW!(I/\TE OF (IURREC'IION Patent No. 3 802 834 Dated April 1974 Robert L. Corbett, Jr. Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 27, "separtor" should read separator line 35, "plae" should read plate Column 2, line 16,

i "itnercon" should read intercQ filine 49, "spearated" should read separated Column 4, line 64,"effiency" should read efficiency, Column 5, line 65', after. the word "used" insert a period[.). Column 6, line 32 "spearator" should read separator line 66, "or", second occurrence, should read of Column 7, line 9, "th" should read" the line 18, traner" should read transfer line 3 1, "c,ente" should I read center Claim 1, column 9, line 8, delete "in each layer"; Claim 4, column 9, line 22, "delete "in each said layer";

1 Column 10, line 35, "circmferen-" should read circumferen Signed and sealed this 1st day of October 1974.

(SEAL) Attest:

MCCOY i'i. GIBdON JR. C. MaRSkLiL DANN Attesting Officer Commissioner of Patents OQM P04051 (O-69) USCOMM-DC 60376-P69 u.s. GOVERNMENT PRINTING OFFICE: 930

Claims

1. A heat transfer plate for transferring heat to coils of metal stacked coaxially within a furnace and directing a flow of atmosphere gas across the edges of the coil wraps, said plate comprising a plurality of horizontal bars disposed about a vertical axis, said bars arranged in at least two layers with one layer being superimposed upon the other layer; at least certain of said bars being circumferentially spaced from each other and providing gas flow passages therebetween; said certain bars being skewed with respect to true radii of said plate and having inner end portions disposed adjacent to the axis of said plate and outer end portions disposed at the outer periphery of said plate; the inner and outer end portions of each said certain bar in each layer overlapping and being secured to the inner and outer end portions, respectively, of two other bars in the other said layer.

8. A heat transfer plate as set forth in claim 7: said outer end portion of each said bar having side edge portions thereof disposed diagonally across said first bar of said other layer; said side edge portions being welded to said first bar only at spaced areas to allow separate expansion and contraction of the bars due to temperature changes.

9. A heat transfer plate for spacing coils of metal stacked coaxially within a furnace, said heat transfer plate comprising two contiguous layers of flat metal bars of substantially uniform length disposed about a vertical axis and circumferentially spaced from each other in each layer; the inner ends of said bars defining a substantially circular central opening about said axis whereby said bars form a flat, annular structure; the bars in one of said layers being skewed with respect to true radii of the plate in one circumferential direction and the bars in the other of said layers being skewed with respect to said radii a like amount in the opposite circumferential direction; each said bar in each said layer having an outer end portion overlapping and welded to the outer end portion of a first bar in said other layer, a medial portion overlapping and welded to a medial portion of a second bar in said other layer, and an inner end portion overlapping and welded to the inner end portion of a third bar of said other layer; circumferentially adjacent bars in each said layer defining passages therebetween, each of which said passages crosses over and is open to passages of the other said layer; said outer end portion of each said bar having side edge portions thereof disposed diagonally across said first bar of said other layer; said side edge portions being welded to said first bar only at spaced areas to allow separate expansion and contraction of the bars due to temperature changes; the upwardly and downwardly facing, coil contacting surfaces of each said bar being rounded along the perimeter thereof to prevent damage to the edges of the coil wraps.

10. A heat transfer member for transferring heat by both conduction and convection to the coil wrap edges of strip metal coils stacked coaxially within an annealing furnace, said member comprising contiguous layers of flat metal bars of substantially uniform shape disposed about a vertical axis and uniformly circumferentially spaced from each other in each layer; said bars tapering inwardly, the inner ends thereof defining a circular central opening whereby said bars form a generally flat, annular structure; said bars being substantially skewed with respect to the true radii of said member, the bars in one of said layers being skewed in one circumferential direction and the bars in the other of said layers being skewed the same amount in the opposite circumferential direction; each said bar in each said layer having its outer, larger end portion overlapping and secured to the outer end portion of one bar in the other layer and its inner, smaller end portion overlapping and secured to the inner end portion of another bar of said other layer; circumferentially adjacent bars in each layer defining inwardly tapered passages for directing a circulating atmosphere gas across the edges of the coil wraps, each said passage crossing over and being open to a passage of the other said layer whereby a turbulence is produced in the flowing gas at the intersection of said passages adjacent to the edges of the coil wraps when said member is disposed coaxially against an end of a coil, said bars and said passages providing outwardly increasing areas of support, heat conduction, and gas flow whereby said member is radially proportioned with respect to the outwardly increasing larger coil wraps and coil mass.

12. A heat transfer member for transferring Heat by both conduction and convection to the coil wrap edges of strip metal coils stacked coaxially within an annealing furnace, said member comprising contiguous layers of flat metal bars of substantially uniform shape disposed about a vertical axis and uniformly circumferentially spaced from each other in each layer; said bars tapering inwardly, the inner ends thereof defining a circular central opening whereby said bars form a generally flat, annular structure; said bars being substantially skewed with respect to the true radii of said member, the bars in one of said layers being skewed in one circumferential direction and the bars in the other of said layers being skewed the same amount in the opposite circumferential direction; each said bar in each said layer having its outer, larger end portion overlapping and secured to the outer end portion of one bar in the other layer and its inner, smaller end portion overlapping and secured to the inner end portion of another bar of said other layer; circumferentially adjacent bars in each layer defining inwardly tapered passages for directing a circulating atmosphere gas across the edges of the coil wraps, each said passage crossing over and being open to a passage of the other said layer whereby a turbulence is produced in the flowing gas at the intersection of said passages adjacent to the edges of the coil wraps when said member is disposed coaxially against an end of a coil, said bars and said passages providing outwardly increasing areas of support, heat conduction, and gas flow whereby said member is radially proportioned with respect to the outwardly increasing larger coil wraps and coil mass; each said bar having a medial portion thereof overlapping and secured to a medial portion of still another bar of said other layer; each said passage in each layer crossing over and being open to three passages of said other layer; the outer ends of the bars in one of said layers extending radially outwardly beyond the outer ends of the bars in the other layer and the inner ends of the bars in said other layer extending radially inwardly beyond the inner ends of the bars in said one layer.

13. A heat transfer turbulator member as set forth in claim 12: each said bar being welded to the bars it overlaps along overlapping side and end edge portions thereof to provide a unified structure.

14. A heat transfer plate for transferring heat to coils of metal stacked coaxially within a furnace and directing a flow of atmosphere gas across the edges of the coil wraps, said plate comprising a plurality of horizontal bars disposed about a vertical axis, said bars arranged in at least two layers with one layer being superimposed upon the other layer; said bars being circumferentially spaced from each other and providing gas flow passages therebetween; said bars being skewed with respect to true radii of said plate and having inner end portions disposed adjacent to the axis of said plate and outer end portions disposed at the outer periphery of said plate; each said bar in each said layer having portions overlapping portions of three bars in said other layer; circumferentially adjacent bars in each said layer defining passages therebetween which cross over and are open to passages of the other said layer whereby a turbulence is produced in the flowing gas at the intersections of said passages; said passages providing a plurality of cross-over areas circumferentially spaced around said plate inwardly of the inner ends of said bars in such position as to be disposed substantially one-third the distance between the inner and outer peripheries of a coil positioned upon said plate.

15. A convector plate for use between two stacked coils of sheet metal during annealing of the latter, said plate comprising two superimposed rib systems, each composed of a plurality of separate ribs arranged so that the ribs and the passages between the ribs together define an annulus, each rib being generally wedge-shaped in plan, and having straight edges whiCh extend between the inner and outer peripheries of such annulus and are inclined in the same sense to the radii of the annulus, characterized in that the ribs of each system have their outer ends substantially coinciding with the outer ends of the ribs of the other system, but are inclined to the radii of the annulus in a sense opposite to the sense in which the ribs of the other system are inclined to the radii of the annulus, and in that the rib systems are constructed so that air drawn inward along the convector plate toward the interior of the coils is separated into two sets of streams, one flowing through the passages between the ribs of one system and the other flowing through the passages between the ribs of the other system, the outer portion of each passage of one rib system, adjacent the periphery of the convector plate, being merged with a passage of the other rib system, and most of the remainder of each passage being separated from the passages of the other rib system to minimize interference between the flow through the remainder of each passage and the flow through the passages of the other rib system.

16. A convector plate according to claim 15 wherein the two rib systems are directly secured to one another, and each rib of one system overlies not more than four ribs of the other system.