US2064937A - Furnace finger - Google Patents

Description

P. s. MENOUGH 2,064,937

FURNACE FINGER Filed June 19, 1936 3 SheQtS- Sheet l Dec. 2 2, 1936. P. s. MENOUGH FURNACE FINGER Filed June 19, 1936 5 Sheets-Sheet 2 P. s. MENOUGH FURNACE FINGER 3 Sheets-Sheet 3 Filed June 19, 1956 Zia/anion- WWW Patented Dec. 22, 1936 UNITED STATES ATENT OFFICE FURNACE FINGER Application June 19, 1936, Serial No. 86,107

Claims.

This invention relates to a conveyor for continuous furnaces and particularly furnaces adapted for heating sheets.

Continuous furnaces for heating sheets, as now constructed, are provided with conveyors comprising a plurality of chains trained around sprockets at opposite ends of the furnace, the upper runs of the chains traversing slots in the furnace hearth and the lower runs extending under the hearth. Carrier blades are attached to the chains at intervals and are adapted to project upwardly through comparatively narrow slots in the hearth to support the sheets above the hearth and carry them through the furnace 15 for progressive heating. The supporting blades generally comprise a web adapted to be secured to the conveyor chain at its lower end and having brackets extending laterally from its upper end to engage the sheets. So far as I am aware, these blades have always been cast of heat resistant alloy, inch or greater in thickness and are usually of one piece. Since they are subjected to the heat of the interior of the furnace and are alternately heated and cooled as they pass through the furnace and then return below it, they soon deteriorate due to the unequal expansion and contraction of the metal on the surface and at the interior of the blades.

The use of cast furnace conveyor blades of the conventional type has revealed numerous objectionable features. In the first place, the cast blade necessarily has a heavy section at the junction between the side brackets and the vertical web. This causes the development of so-called shrinks. As is well known, these result from the fact that the heavier sections cool last, and, due to the shrinkage of the other portions of the casting, molten metal is drawn away from the heavier sections during cooling, producing cracks or depressions. These shrinks are particularly troublesome in alloy steels and are always found under the junction of the side brackets and the web of a cast alloy furnace blade.

Another objection to the cast blade, as conventionally constructed, is that segregations of lower alloys, which solidify after the unsegregated alloy, migrate to the heavier sections of the casting which solidify last. Such segregations are particularly objectionable in castings which are subjected to high temperatures for any substantial period of time because the segregations have a tendency to oxidize and grow. In cast furnace conveyor blades as usually constructed, this tendency is evidenced by the rotting of the joint 55 between the bracket and Web. This action may even continue until the bracket falls off the web. It is accelerated, furthermore, because of the continued repetition of the heating and cooling cycle. The joint between the blade and brackets is, as before stated, of heavier section than the remainder of the blade and, therefore, heats and cools more slowly than the other portions. This produces differences of temperature between various parts of the blade with a consequent unequal expansion and contraction of the parts which hasten early failure.

The present invention seeks to remedy these defects by the provision of conveyor blades that are so constructed that they will more effic'iently withstand the alternate heating and cooling to which they are subjected while in use.

A further object of the invention is the provision of new and improved furnace blades or fingers for conveyor chains for heat treating furnaces that are simple in construction, inexpensive to manufacture and that will resist the deteriorating effects of the alternate heating and cooling to which they are subjected while in use.

Other and further objects and advantages of the invention will appear from the following description taken in connection with the accompanying drawings, in which Fig. 1 is a side elevation of a support according to my invention, ready to be attached to a conveyor chain;

Fig. 2 is an end elevation thereof;

Fig. 3 is a sectional view along the line 3-3 of Fig. 1;

Fig. 4 is a plan view;

Fig. 5 is a sectional view along the line 5-5 of Fig. 1;

Fig. 6 is a partial side elevation of two of the supports mounted on a conveyor chain;

Fig. '7 is a side elevation of a modified form of blade or finger;

Fig. 8 is a section on the line 8-8 of Fig. 7;

Fig. 9 is a bottom plan view of the device shown in Fig. 7;

Fig. 10 is a longitudinal vertical section of the furnace shown more or less diagrammatically and disclosing the use of a modified form of the device;

Fig. 11 is a section on the line I l-l I of Fig. 10;

Fig. 12 is a side elevation of one of the blades or fingers;

Fig. 13 is a top plane view of the device shown in Fig. 12;

Fig. 14 is a longitudinal vertical section on the line I4l4 of Fig. 12;

Fig. 15 is a section on the line l5-l5 of Fig. 12;

Fig. 16 is a side elevation of a portion of a modified form of 'a blade or finger;

Fig. 17 is a section on the line I l| 1 of Fig. 18 showing a modified form of blade or finger and bracket; and

Fig. 18 is a section on the line Ill-I8 of Fig. 17.

It has been found that-if the thickness of the carrier blades or fingers for conveyor chains for heat treating furnaces, whether they be cast or fabricated from bars, plates or sheet metal, be reduced to not greater than two-thirds of the conventional thickness, that is, to approximately 2/8 inch or less, the life of the blade may be extended very greatly, in some instances to as much as from three to six times as long. The reason for this surprising result is not clear, but without committing myself to any particular theory relative to this matter, the following is offered as a possible explanation. Heat conductivity of chrome nickel steel is only about onethird that of ordinary steel. The blades or fingers, with their superimposed load of thin steel sheets, pass quickly into a hot furnace'and after .the workhas been raised to the furnace temperature, they exit from the furnace into the outside air while at a red heat. This means that on every heating and cooling of these fingers, there is a sudden surface stress developed due primarily to the poor conductivity of the alloy and to the'fact that the outside fibres of the relatively heavy walled cast fingers are endeavoring to expand or contract against a sluggish interior. As the wall thickness of the finger is decreased, these stresses are so minimized that on thin walled fingers no heat checks develop. With the thinner blades, the metal, on entering the furnace, is exposed on both sides of the blade to the furnace heat and since it is thin, the entire metal throughout the blade will approximately simultaneously become heated and its expansion will be approximately uniform, whereas, in thicker blades, the heating of the imier portion will lag behind that of the surfaces. For instance, in thin blades of channel form made from stock of say 2/8 inch in thickness, there is only inch of metal to heat from each side, whereas, with the conventional blade of inch thickness, there would still remain a central inch to be heated. As a result of this latter non-uniform heating, the unequal expansion of the inner and outer portions will soon cause checking and rapid deterioration of the blade. But with the more nearly simultaneously heating and cooling of the entire metal throughout the exposed surface of the thin blade, the mass of metal expands and contracts substantially uniformly and hence strains and stresses, which would result in checks, cracks and breaks, and distortions of the blade, are eliminated.

It has also been found that with furnace fingers of the conventional thickness, say inch or greater the life of the fingers, whether they be of cast, wrought or sheet metal, may be greatly extended, if they be made in such form or shape that theireifective thickness is greater than-the actual thickness of the material. This may be done by arranging longitudinally extending portions of the fingers in different planes such, for instance, as shown in Figs. 1 to 6, or Figs. 10 to 15, respectively. The reason for this unusual extension of the life of these fingers when thus made is not apparent, and various theories may be advanced, but, without limiting myself to any particular theory, it may be suggested that probably the metal, having portions arranged in different planes, retains the fingers in vertical position under the unusual conditions of excessive heat and load pressure to which the fingers are subjected, thereby reducing to a minimum any unequal skin or surface stresses of the fingers, whereby checking thereof is reduced to a minimum.

By arranging longitudinal portions of the finers exposed to the heat of the furnace in different planes, the life of the fingers of the conventional inch thickness is greatly increased,

in some instances doubled, and by also reducing the thickness of the metal to not greater than 2/8 inch, the life of the fingers may be still further extended to as much as four or five times the life of fiat fingers of the conventional =7 inch thickness.

In order to rigidify, reinforce or strengthen the thin blades adjacent to the hearth where the heat has the most destructive effects on the blades, they may be so cast, manufactured or constructed that their effective thickness is much greater than the actual thickness of the metal by forming channels, corrugations or the like in them. As for instance, ifthe blades or fingers are fabricated from fiat bars or the like, they may be bent to'U-form, Z-form or corrugated or bent to any other convenient form having an ef fective increased thickness. If cast, they may have channels, grooves, or corrugations formed therein which will also increase their effective thickness, thus adding rigidity to the blade or finger without increasing the amountor actual thickness of the metal.

Referring now to Figs. 1 to 6,'there is shown a carrier blade or finger, fabricated from a heat resisting alloy, such as, chromium nickel steel, which is commonly used for this purpose. In the drawings, the reference character 9 designates a furnace blade or finger which comprises a pair of vertical supporting standards or members it! and H. The members It] and H may be strengthened or reinforced by increasing their effective thickness without increasing the thickness of the metal as by corrugating or otherwise distorting the metal. These members may be formed from fiat bars by bending the edges thereof to corrugated, channel or other suitable shape to increase their effective thickness. The thickness of the metal from which they are made is substantially 2/8 inch or less. They may also be fabricated from a pair of fiat pieces with spacers between. The members It! and I I are joined by a central cross member I2 welded thereto. Two

such members may be incorporated in each support as shown in Fig. 6, in cases where additional bracing is desired. A bottom cross member 13 and side plates It are Welded to the members l0 and H, as shown at l5 in Fig. 5. The bottom cross member has holes l6 whereby the complete member may be bolted to a clevis l l forming part of a furnace conveyor chain i3 shown in Fig. 6. The hearth line is indicated by the line i811 in this figure.

The upper end of the member In is preferably tapered and rounded to reduce the area of contact with the sheets which are placed thereon as indicated at I 9 in Fig. 6. The flanges of the channel forming the member I! are slit from the bottom or web of the channel, downwardly from the upper. end thereof, as shown in Figs. 2 and 3. A spacer block I la is welded between the flanges. One of the flanges 20 is bent over substantially at right angles to the member i I, while the other fiange 2! is bent outwardly at an angle from the main body of the member. An auxiliary member 22 is welded as shown at 23 and 24 to the ends of the bent-out flanges 20 and 2|. The member 22 is formed from flat bar stock of composition similar to that of the vertical members 10 and H. Since the member 22 overlies both portions of the member I I on which it is carried, the latter affords positive, structural support for the latter so that the weld is not relied on solely to sustain the member 22. Since only the portion of the support above the hearth line is subjected to the heat of the furnace interior, I may make only that portion of wrought metal, and utilize a casting for the lower portion. The upper wrought metal portion, furthermore, may be made removable for renewal or replacement.

As shown in Fig. 4, a support in accordance with my invention engages the sheets at spaced points over a considerable area, the length of which measured by the distance between the members Ill and II and the width by the distance between the upper end of the member I I and the bent-over outwardly projecting end of the member 22. The actual area of contact between the support and sheets, however, is very small, and free access to the bottom surfaces of the sheets is provided for the hot combustion gases. This insures prompt and thorough heating of the sheets. This is particularly important when sheets are being handled in packs, since the packs are heated to uni form temperature throughout. This facilitates the rolling of the packs and improves the quality of the resulting product.

Since the support of my invention is composed of wrought metal members, it is obviously free from the defects of the cast supporting blades previously used, which were peculiar to the method of manufacture thereof. No trouble is experienced with shrinks or segregations and, since the section of my support is substantially the same throughout its entirety, being not substantially greater than 2/8 inch, the support heats and cools to the same extent in all parts. The mass of my support, furthermore, is much less than that of the conventional cast blade so that the amount of heat removed from the furnace by the conveyor supports, when they emerge from the furnace on the return path of the conveyor chain, is minimized.

As conventionally cast, these blades are not less than inch in thickness and consequently, the amount of heat necessary to raise this amount of metal from substantially room temperature to that of the interior of the furnace is considerable, taking into consideration that each conveyor is provided with a relatively large number of blades. The sheet furnaces are over-fired, that is, the combustion gases are delivered downwardly from the upper portions thereof and the lower surfaces of the sheets on the conveyor are heated by convection currents of the gases. Anything that tends to prevent the flow of such gases around the edges of the sheet and across the lower surface thereof actually hinders the heating. The webs of the cast blades obviously have this effect since they constitute spaced baflies preventing the flow of hot gases around and under the sheets. The brackets, furthermore, prevent intimate contact of the gases with the sheet over a substantial area. Cast furnace conveyor fingers, therefore, prevent the delivery of heat to certain portions of the sheets and on top of that, actually remove heat from exactly the same portions of the sheets by conduction so that the sheets are not uniformly heated when discharged from the furnace. This introduces complications in the rolling.

The furnace conveyor blades, therefore, are very difficult to repair in case they become bent. The high carbon content necessary to render the alloy fluid when casting, gives rise to a condition known as carbide embrittlement. Under the influence of continued high temperature, the carbide in the alloy comes out of solution and segregates at the grain boundaries, causing brittleness. Almost any effort to straighten a bent blade, therefore, will result in breakage.

Furthermore, since the supports of the present invention have substantially point contact only with the sheets, very little heat is abstracted thereby by the latter and, as before stated, little or no obstruction is offered to the free flow of heating gases over the lower surfaces of the sheets. Since the supports of my invention are formed of rolled bars, bent or shaped to a structure having an apparent thickness that is greater than the actual thickness of the material, they do not require the high carbon content of cast blades which gives fluidity to the alloy when heated to the melting point. The trouble experienced with cast blades from carbide embrittlement is not, therefore, to be expected in the supports of my invention. Since the support of my invention is composed entirely of wrought metal, it may be repaired quite readily, even if it has been severely bent or otherwise deformed.

In Figs. 7 to 9, is shown a modified form of the invention. In this form of construction, the blades or fingers are made from suitable heat resisting stock not over inch in thickness and in order to increase the rigidity of the blades, they are so fabricated that they are hollow. In the form shown, the vertical supporting members 26 and 21 are each made oval or elliptical in cross section in order that they may pass along the slots in the hearth along which they travel. These slots are restricted in width so that heat from the furnace may not pass through them in suiTcient amounts as to adversely affect the operation of the carrier chain and rollers. these slots are narrow, the blades must be comparatively thin also, hence, their elliptical instead of circular form.

Each member comprises an inner channel upright 28 and an outer channel upright 29 having their edges telescoped and secured by welding to form a rigid column. The inner members 28 are turned back to back and are connected together at their lower ends by a bottom cross member 3| which is welded at its ends as at 32 and 33 to the inner uprights as clearly shown in Fig. 9. This cross member is adapted to be attached to the clevis I! of the chain l8 shown in Fig. 6, when the blades are in use. Since the lower end of the blade is below the hearth line and is not subjected to the intense heat of the furnace, it is not necessary to extend the outer members 29 to the lower end of the blade.

The uprights 28 are sectional while the uprights 29 are continuous. The outer uprights 29 are connected together at their intermediate portion by an intermediate cross member 34 which engages the upper ends of the lower sections of the inner uprights 28 and extends into the channels of the outer uprights 29 to which they are secured as by welding. The cross members are U-shaped in cross section as shown in Fig. 8 and are also made from heat resisting stock not over inch in thickness. An upper heat resisting U- shaped cross member 35, made of stock not over Since til) A; inch in thickness extends between the upper. end portions of the outer uprights and is weldedthereto. The upper portions36 of the inner uprights 28. areinterposedbetween the cross members 34 and 35 as shown in Fig. 8. Suitable work supporting. brackets may be provided for the upper ends of the blades, if desired. v

In this form of construction; the blade is oi thin metal and consequently, it is heated substantially simultaneously throughout pansion and contraction is avoided. Blades made from stock inch in thickness substantially in accordance with the construction shown in Figs.

'7, 8 and 9 have lasted over six times as long as blades cast inch thick from the same composition when used under the same conditions.-.

In Figs. 10 to 16 are shown a modifiedform of construction in which the blades or fingers are cast. In these figures, the reference character 45 designates the furnace having the hearth orfloor '46, shown more or less diagrammatically.

The hearth or fioor 46 is provided with a plurality of slots .41 spaced transversely across the floor and extending longitudinally of the fur-- nace as is usual in such constructions. Extending through these slots are furnace blades or supporting fingers 48 which are attached to and moved by an endless carrier 89 which in turn is operated by sprockets, not shown, in the conventional manner. These blades or fingers are attached at their lower ends to links, stirrups or plates 5|, which, in turn, are supported by rollers 52 as is usual in such constructions.

In the construction shown, the lower end of each finger or blade 48 is provided with a laterally extending lug 53 at one edge and with a lug 54 extending laterally in the opposite direction from the other side of the standard from its opposite edge. The lower ends of the. fingers are also provided with thickened portions or bosses 55 and 56 which have openings 5! and 58 for receiving rivets 59 for connecting the plates 5| to the finger. These plates engage against the shoulders 53 and 54. Lugs 6| and 62, Fig. 15, are provided on the lower ends of.

the fingers as spacers for engaging the plates 5|.

The rollers 52 are mounted on journals 63, Fig. 10, extending through the forward and rear ends of the plates 51. 'The adjacent links 64 of the endless carrier 49 are pivotally connected to the journals 63 for connecting adjacent supporting blades together.

The supporting fingers or blades 48 are cast from a heat resistant alloy, such as chromium, nickel and steel. An alloy of 25 percent chromium, 12 per cent nickel and the remainder steel gives satisfactory results. These proportions may be varied. The fingers or blades are comparatively thin in cross section, approximately 2/8 inch or less in thickness, in order that when it enters the furnace it will be substantially simultaneouslyheated throughout its mass, whereby, checking, breaking and distortion due to unequal expansion throughout the mass are avoided.

Since the fingers or blades are thin in cross section, means must be provided for rigidifying, strengthening or reinforcing the same. In the form of the construction shown, this is accomplished by forming each blade orfinger with an effective thickness greater than the thickness of the metal adjacent to the floor or hearth of the furnacewhere theheat is most destructive to its mass and consequently the evil efiectsof une ualexreceiving the bracket.

by the slot 68 is adapted to support the bracket.

the blade or finger, by providing grooves or corrugations in the same as shown at 65.

Each finger or blade 48 is provided with a plurality of supporting arms 40 and 58 at its upper end. The material of the fingers 48 is preferably of uniform thickness throughout the exposed area. It is common practice to cast the supporting brackets integral with the fingers but this requires thickened portions at the juncture of the bracket and finger and this thickened portion results in unequal expansion and contraction with the attending evils as described above. It has also been proposed to make the brackets separate and to weld the same in place but the reversal of stresses due to the sudden heating and cooling has its deleterious effects on the welds. In the present invention, the brackets 66 are supported in such manner that the welds support no part of the load. As shown, one or more of the upstanding arms, as the arm 48, Figs. 12 and 13, is provided with a slot 60 for The shoulder 70' formed As shown, each bracket 66 is provided with downwardly extending braces 61 and 68, Fig. 14, which are adapted to engage each side of the supporting. finger orblade and is also provided with a tie member 69 which is adapted to engage in the slot 68 in the upwardly extending arm 40 of each blade 48 and be supported by the shoulder 1'9.

The upper edge of the cross member 69 of the brackets may also be provided with a laterally extending flange 15 having a notch 16 for receiving the upper adjacent portion of the blade as clearly shown in Fig. 13. It will thus be seen that when the brackets are in position, they will be supported independently of welds or other securing means. The brackets may be, and preferably are, welded to the blades to prevent their falling olT during the return travel of the conveyor belt. The brackets 66 are each provided with upwardly extending fingers 11 and I8. Preferably, though not necessarily, the supporting arms 48 and 58 of the fingers or blades extend above the level of the fingers Ti and 18 in order that a great portion of the weightof the metal sheets 19 that are being heat treated may be supported directly above thebody of the fingers or blades.

These brackets are also of thin material approximately 2/8 inch or less in thickness Whereby the deteriorating effects of the heat thereon will be reduced to a minimum.

Instead ofproviding the blade or finger with two upwardly extending arms as in Fig. 12, it may be provided with three arms 88, 8| and 82, as shown in Fig. 16. In the event that three arms are employed, the arms 89 and 82 may both be provided with slots for receiving brackets 48.

If desired, the supporting bracket may be interlocked with the blade or finger. This interlocking connection will not only support the load while the finger or blade is traveling through the furnace,'but will also support the bracket upon the return travel of the conveyor. Any suitable means may be employed for this purpose.

' In the form of'the construction shown in Fig. 17, one of the supporting arms 58a of the blade or finger 65a is provided with a recess 83 in its upperedge' and with a laterally extending recess 84 spaced downwardly from the recess 83. The bracket 66a is provided in its central portion with an opening 85 through which the projection 86, formed by the recesses 83 and 84, is

adapted to engage. As shown, the opening is provided at its upper and lower portion with an extension 87 and. 88 for receiving the projection 86. In attaching the bracket 66a, the same is turned at an angle, the projection 86 inserted through the opening 85 and the bracket seated in the recess 83 after which the bracket is turned to vertical position bringing the tie portion 89 into the recess 84. The parts are then welded in position.

It will thus be seen that if the upper tie portion 9| of the bracket engaging the bottom of the recess 83 will support the load as the bracket passes through the furnace and on the return, While the blades or fingers are inverted, the tie portion 89 will be prevented from dropping off by the engagement of the tie portion 89 with the projection 86 should the weld soften or fail.

It will thus be seen that a furnace finger or blade has been provided that is of thin material; that is, it is of such a thickness that the expansion and contraction incident to the use of the same will be substantially uniform throughout the mass exposed, thereby reducing to a minimum the stresses and strains due to the sudden changes of temperature to which it is subjected; and that the blade is rendered sufficiently rigid by forming corrugations thereon or otherwise so constructing it that its effective or overall thickness is materially greater than the metal of the material. Preferably, the metal is not materially above 2/8 inch or below inch, whether the blade be case or fabricated from bars, plates or sheets.

The thickness of the metal may vary somewhat with the different alloys but whatever material is used and whether the fingers or blades be cast or fabricated from plates, bars or sheet metal, their thickness should be such that the metal throughout the mass will be approximately simultaneously heated when the fingers enter the furnace. In any event, the thickness of the material of the blade will be comparatively thin. An alloy of 25 percent chromium, 12 percent nickel and the remainder steel has been found to give excellent results and is preferred although an alloy of 60 percent chromium, 12 percent nickel and the remainder steel has proven successful. These formulas are given by way of examples only and are not intended to be construed as marks of limitation since any heat resistant material suitable for such use may be employed.

The fingers or blades, if reinforced with corrugations may each have its edges provided with only one corrugation as disclosed by the standard to or H in Figs. 1 to 6, or intermediate portions may be provided with a plurality of corrugations as shown at 85 in the cast fingers 48 in Figs. 10 to 16. The number will depend on the weight of the material to be supported, the shape of the fingers, the type of furnace, and the like.

This application is a continuation in part of my application, Serial No. 2,365, filed January 18, 1935, for Furnace conveyer.

It is thought from the foregoing taken in connection with the accompanying drawings that the construction and operation of my device will be apparent to those skilled in the art and that changes in size, shape, proportion and details of construction may be made without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. A support for a conveyor for a heat treating furnace comprising an upwardly extending furnace finger of a heat resisting alloy of thin metal, said finger being so constructed that its intermediate portion has an efiective thickness materially greater than the actual thickness of the material at said portion.

2. In a heat treating furnace having a conveyor traveling beneath said furnace, said furnace having its hearth provided with a slot above and parallel with said conveyor, fingers secured to said conveyor and extending upwardly through said slot for supporting metal material within said furnace for heat-treating the same, each finger of a comparatively thin heat resisting allay and having an effective thickness, adjacent to the hearth, materially greater than the actual thickness of the metal at that point.

3. A furnace finger of a thin heat resisting alloy of metal having its intermediate portion corrugated for rigidifying the structure.

4. A furnace finger for a furnace conveyor comprising an upright member of heat resisting alloy of a thickness not exceeding 2/8 inch but having an intermediate portion so constructed that its effective thickness is materially greater than that amount.

5. A furnace finger made from thin flat metal of a heat resisting alloy, said finger having a corrugated intermediate portion.

6. A furnace finger cast from a heat resisting alloy and comprising a thin upright member having means at its lower end for attaching the same to a furnace conveyor, and having its intermediate portion corrugated for rigidifying the structure.

7. A cast furnace finger of a heat resisting alloy having an intermediate portion not exceeding 2/8 inch in thickness and having said intermediate portion so formed that its overall width is materially greater than the thickness of the material.

8. A cast finger for a furnace conveyor comprising an upstanding relatively thin blade member of heat resisting material, having a plurality of upwardly extending arms of relatively thin material, a vertical slot in one of said arms, a bracket element engaging in said slot, and brace members on said bracket engaging the sides of said blade member for preventing tilting of said bracket while in use.

9. In a conveyor mechanism for heat treating furnaces, comprising an endless flexible element, a blade secured to said element and extending upwardly into said furnace and movable along the same for supporting articles being heat treated in said furnace, said blade being of a heat resisting alloy, the material of said blade being thin and of a uniform thickness throughout all that portion exposed in said furnace but having an overall transverse dimension greater than said thickness for rigidifying said blade.

10. In a heat-treating furnace having a hearth provided with a slot extending lengthwise thereof, a carrier chain beneath said slot, cast fingers on said chain extending through said slot into said furnace, the material of said fingers being of uniform thickness throughout their length above said hearth, each of said fingers having corrugations adjacent to said hearth for increasing the effective thickness of the finger without increasing the thickness of the material.

11. In a heat-treating furnace having a hearth provided with a slot extending lengthwise thereof, a carrier chain beneath said slot, cast fingers on said chain extending through said slot into said furnace, the material of said fingers being of uniform thickness throughout their length above said hearth, and means adjacent to said hearth for increasing the rigidity of said finger without increasing the thickness of the material thereof.

12. A finger for use on a furnace conveyor comprising a supporting member, a supporting bracket, said supporting member and bracket having an interlocking connection for supporting said bracket from said supporting member in both upright and inverted positions.

13. A cast finger for use on a furnace conveyor comprising a body member having a lateral extension provided with a vertical and with a horizontal slot in its top and side edges, respectively, and a bracket element having an opening providing a tie portion beneath said opening, the upper.margina1 edge of said opening being adapted to be seated in said vertical slot while said tie portion is seated in said horizontal slot, said bracket being welded to said body member for preventing relative turning movement thereof.

14. A conveyor finger for heat treating furnaces made of heat resisting alloy of low heat conductivity, thin enough to prevent destructive strains from unequal heating and expansion of the surface and interior of said finger, and having separate longitudinal portions disposed in different planes for retaining said finger in upright position while in use.

15. A conveyor finger for heat treating furnaces made of heat resisting alloy of low heat conductivity, said finger having corrugations extending longitudinally of the portion exposed to heat during the use of the fingers.

PAUL S. MENOUGH.

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