US2605092A - Heat treat tray - Google Patents

Description

July 29, 1952 M. Bf Hu'rcHlNsoN ET AL 2,605,092

HEAT TREAT TRAY 2 Sl-IEETS-SHEET l Filed Fem 17, 1949 July 29, 1952 M. B. HUTcHlNsoN ET AL 2,605,092

HEAT TREAT TRAY i Filed Feb. 1T, 1949 2 SHEETS- SHEET 2 Patented uly 29, 1952 HEA'r" TREAT t TRAY Martin B. Hutchinson, Grosse Pointe Farms, and.

Raymond J. Shillum, Detroit, Mich.,.assignors. to Brown-Hutchinson IronV Works, Detroit, Mich., ad corporation of Michigan Application February 17 1949, Serial No. 76,864

8, Claims.

Thisv invention relates to the art of heat treatingfand, in particular, refers to trays for carrying-articles to be treated through heat treat furnaces.

In addition to ability to withstandl high'temperatures without excessive sc'aling or -v other forms off chemical deterioration, heat treat trays must also maintain suicientstrength and rigidity While at elevated temperatures to properly support the articles to be--heat treated- The-rst requirement can, ofcourse, Abe met by proper selection of materials, but the second requirement is-a matter of design.' With regard to the design` requirements', the tray must *l have as high a ra'tio of strength to weight vas possible.y The tray'represents a distinct loss in the furnace so farY as absorption of heat and time required to bring the parts up to heat-treating temperatures are concerned, and this lossA is proportional to ther-weight of'tray which must beheated.r Hence, it -istdesired to keep the weight a minimum consistant with satisfactory high temperature strength. The prior art has felt that the maximum ratio of strength to weight is obtained by traydesigns whichv can be embodied into actual trays only by casting or foundry methods.

Hence, the conventional tray, for productionfur'- haces-at least, is acasting.

Heat treat trays, however, are not merely subjected to the dead load-of the parts which they carry through'furnaces. They may also be subject to Yintense internal forces due toexpansin and contraction'-uponi heating and cooling. Unless the designV is just. right and all parts of thtray change ndimension uniformly in response tothe temperature changes,v thesev forces will be present in the tray. They are usually great enough to distortthe tray and very oftensuii'icient-to rupture it. vAs those in theart no w appreciate, it is virtually impossible to produce a cast tray which-is not` subjected to harmful internal forces ofthis nature, and,- to at least this extent, the. castl trays lofthe prior art vare unsatisfactory.`v i N i f The trayl ofthe present invention may be fabricated from wrought metals of `suitable heatresisting-character. -vThe design is such that it proyides a higher strength-weight ratio than heretofore.obtainablewith trays produced by castingv oir-any other method. l-urt hermore,` the present trayis iiexible,V so far asarelative movementor-itsv .componentA parts is concerned, and

internal-forces due to-dimensional changes are either eliminated or, at the' veryleast, reduced to such an extent that they Yare not harmful. Y

Itvwill now v'be lrealized that [an vobject of the invention. is 1130. ncT'f-i. life. of,

hattreat trays.

An additional object is to provide an extremelyv durable general purpose heat treat. tray which may be economically manufactured.

The Vfeatures ofthe invention whereby. these` and other objects are accomplished are illustrated in the accompanying drawings wherein:

Figure 1 shows a typical manner in which the trays are-used;

Fig. 2 is a cross` section taken on line 2-2 of Fig. 1 to showan end elevation ofthe improved tray;

Fig. 3 is a perspective view of the tray;

Fig. 4 is a section taken on line 4-41of Fig.v3;

Fig. 5 is a perspective view-showing the interlock connection betweenframe members;

Fig. Gshowsa modified form of the invention in end elevation; and,l

Figs. 7 and 8 are end and plan views showing a modiedmeans for-connecting the frame work to the riml of the tray.

As best shown in Figs. 3-5, the-improved heattreat tray I comprises basicallyV a rim or marginal member 3 to which is secured a framework 5 consisting of a first'series of spaced parallel strips 1 vrand a second series, normal tothe rst, of spaced.v parallel strips 9.

andthe upper halfof the strips 9 have vertical i slots I5. These slots are at the lines of intersection of the strips and enable the two sets of strips to ttogether orxinterlock without being rigidly interconnected. This connection willbe recog-` nized as the typeA often used between transverszv spacer strips in cardboard boxes. Retail legg boxes in particular are of lthis A construction so thatv hereinafter the present framework 5 will -be referred to asan egg crate framework.

In addition to its well-knownadvantagesrelative to ease of, manufacture and assembly, the

egg cratevj 'construction has particular virtues When usedina heat treattray. These are in part. asseiadwiih theexpzens'ion and contrae: tion 'of' the stripse 'I and; 9;' Such `eggpgansion 01).

contractionfis appreciablinasmuch as the trays The ends of the' strips Tand 9 may be aixed to the rim 3 by welding, as shown at Il. The rim andstrips asl Vslotsi and I5.

are raised from room temperature to temperatures Whi-ch are not uncommonly as high' as 2000 F., and in some cases even higher, and then lowered back to room temperature. 'Expansion (and the same is true of'contraction) is harmful when resisted. Resistance occurs when there is no room to accommodate expansion and also when all parts are not at the same temperature, Y

i. e., when a temperature gradient exists in the interconnected parts. In the present construction the slots I3 and I5 provide room to accom-` Further- Y 'Y more, they permit a Icertain amount of relative movement or shifting of the strips 'I and 9 as these Y j modate expansion of the strips 'I and 9.V

of the strips E and S and therefore minimizes forces tending to distort or rupture the framework 5 and the tray I.

The egg crate construction also has an advantageous influence upon the load-carrying capacity of the framework 5. When parts to beheat treated are placed on the framework 5, the strips 'I and 9 tend -to bend so that their top edges are shortened and concave in appearance and their bottom edges arelengthened and convex inappearance, i. e.,l their upper halves are in compression and their lower halves in tension. This bending will tend to close the slots i5 Yin the strips 9 and cause the edges thereof toY pinch the strips I and effectuate a somewhat rigid load-transmitting connection so that the weight of the parts being treated may be distributed to some extent throughout the framework. In the event that the slots dornot provide e-nough room for expansion, though the pinching does not prevent expansion of the strips, it may in some cases provide enough resistance to make it desirable to lcontrol vthe temperature at which it occurs by regulation of the Vwidth of slots I5, it is apparent that lateral buckling can take place freely thus providing minimum opportunity for permanent distortion. `It will be recognized that after due consideration kof the loads to be carried, size of the strips 'I and S, and of the temperatures involved, that Vthe slots I5 can be made of surdcient` width so that this pinching occurs at or near al desired temperature. It will be apparent that the strips 9 act as the major load-carrying members and the strips 1 to some extent as spacers due to the relative arrangement of the The-strips 9 by virtue of the pinch lconnection with strips l'l will tend to support the latter strips, which have less resistance to bending, but will also transmit thereto some of the applied load. Y

Vfhile .the tray construction so far ldescribed provides many of the advantages of the invention vand is capable of satisfactory usage, it is desirsupporting the tray inrits travel through a furnace. ,As best recognized from Figures 3 and 4, these members are, in the preferred form, endless straps (which may, of course, be produced by welding two strips together at the ends) loosely disposed around the two side portions of the framework 5. Slots I9 may be provided in the rim-3 to accommodate the straps I'I; andiit may be noted incidentally that the rim 3 need not extend, as shown, above the plane of the framework 5 but such extension provides the obvious advantage of inhibiting the inadvertent sliding or rolling of parts from the tray. The straps I'I arelnot tightly interconnected with the rim 3 or framework and thus may expand and contract independently thereof. Production furnaces often have a series of rolls or the like down the center thereof to locate and facilitate movement of the trays through the furnace. When used in such furnaces, the trays may be provided with a central guide member 2| in which the rollsfit. The guide 2| comprises a downwardly opening .channel 23 which forms one side of an endless strap which, like straps II, is loosely disposed around the framework 5 and rim 3 through slots I9 in the rim and may be formed by bending a suitable strip around the top and sides of the tray and welding the ends to the channel 23.

As indicated in Figs. 1 and 2, the trays I arev lined up in series arrangement with the pusher pads I'I abutting and are forced by suitable pusher rods 24 through the furnace. The trays are supported by the members I'I and 2l, the guide member 2| resting on rolls 25, as just indicated. The lower faces of the members I7 are adapted to slide on the side rails 21 usually provided in furnaces of this type. When the trays are forced through the furnacerin this manner, the pusher y bar load passes from one to the next through the straps I1. There is no pusher load on the frameworks 5 or the rims 3 of the trays due to the fact that the straps are of greater length than the trays and loosely connected thereto. l In order to increase the strength of the straps without transmitting any pusher loads to the framework 5, they are provided with a series of longitudinally spaced transverse stiffening webs 3|. The webs comprise a series of simple plates that are welded to the opposed longitudinal faces of the straps II and ZI. The webs 3| are shorter than the spaces between the strips 9 and are disposed therebetween so that neither interferes with the dimensional changes of the other. The

webs 3I make the members Il and 2| I-beam Y members so far as structural characteristics are or walls 35 in the furnace coact with the sides of the rim 3' to properly position the tray 33 on the rails 271. In this tray the edges of the rim 3 and the straps are shown ush. The egg crate members 'I and 9 are also of the same width as the rim and strap and are therefore provided with cutoutsras shown through which the horizontal Vstrap portions pass.V This tray may be inverted and used `if desired. Infthis case the strips 7,

rather than the-strips 9 as described above, would be the major load-carrying members of such load as may be applied to the framework 5.

It wil1' be recognized that in some cases the weld connections II may'possibly set up resistance to changes in length of the strips Y'I and :9. 1

to an extent that is not compensated by the egg crate interconnection of the strips. To avoid this possibility, the strips may be slidably mounted in suitable slots 37 in the rim. These slots may, for example, be cut from the top or the bottom edge of the rim 3 and the strips inserted and then the slots closed by weld beads 35. Though not essential, the ends of the strips may be bent into engagement with the outside of the rim, as shown at 4l With this mode of attachment of the framework 5 to the rim 3, relative movement of the strips 7 and 9 and rim can occur freely and no distortive forces will be created by resistance to expansion and contraction.

From the foregoing description, it is evident that the present heat treat tray provides man37 improved features, particularly when compared with the conventional cast trays. One of these is a maximum strength-weight ratio. Prior trays have been rigid and thus unable to withstand internal stresses due to expansion and contraction. The present tray, on the other hand, is not rigid; the component parts are independently movable. Nevertheless, the present construction maintains the structural integrity of the tray and there is no chance of disassembly. Preferably, of course, the component parts of the present tray are made of uniform section, i. e., the same gauge metal. However, the non-rigid interconnection of the parts makes this unnecessary since variations in length changes due to temperature gradients resulting from sectional non-uniformities may occur without resistance.

Other advantages, such as the ease of fabrican tion and assembly, will be apparent to those in the art as will be certain modifications that can be made without departing from the spirit of the invention.

What is claimed is:

1. A fabricated wrought iron heat treat tray comprising an egg crate framework defining a load-supporting surface, said frame work including a first setof spaced parallel strips and a second set of spaced parallel strips extending -at substantially right angles to said first set of strips, the strips of each set being slotted at the lines of intersection with the strips of the other set so that the two sets of strips are interlocked without being rigidly connected and a rim member connected to the framework and defining the periphery of said surface, said rim member being of a material having substantially the same expansion and contraction characteristics as said frame work.

2. A heat treat tray comprising an egg crate rim, an egg crate framework within the rim,

said frame work including a first set of spaced parallel strips and a second set of spaced parallel strips extending at substantially right angles to said first set of strips, the strips of each set being slotted at the lines of intersection with the strips of the other set, so thatthe two sets are interlocked without being rigidly connected, and means providing slots in the rim for receiving the ends of the frame members whereby said framework is supported by the rim but the ends of the members are movable relative thereto.

5. In a heat treat tray, the combination of an endless upright strap-,like member comprising a rim, an egg crate framework secured within and to the rim and defining a load-supporting surface, said rim extending above the surface to provide a marginal border therefor, laterally spaced longitudinally aligned Vpairs of slots in the marginal border, straps loosely disposed around the rim and framework in said slots having webs in openings of the framework but capable of force transmitting engagement with only the rim.

6. In a heat 'treat tray, the combination of rim means and a grid defining a load-carrying surface supported by the means, said grid including certain intersecting members with slots atr the lines of intersection to provide mouths for receiving the other members.`

7. The invention as claimed in claim 6 wherein each of the intersecting members has slots at the lines of intersection to provide mouths in which each of the members receives another.

8. In a heat treat tray, an egg crate framework defining a load-supporting surface, said frame work including a first set of spaced parallel strips and a second set of spaced parallel strips extending at substantially right angles to said first set of strips, the strips of each set being slotted at the lines of intersection with the strips of the other set so that the two sets of strips are interlocked without being rigidly connected and pusher pad means comprising a longitudinal beam member having web sections disposed in certain of the openings of the framework and spaced from the framework members.

framework defining a load-supporting surface,

said frame work including a first set of spaced parallel strips and a second set of spaced parallel strips extending at substantially right angles to said first set of strips, the strips of each set being slotted at the lines of intersection with the strips of the other set so that the two sets of strips are interlocked without being rigidly connected a rim member connected to the framework and defining the periphery of said surface, and an endless strap loosely disposed around said framework and rim.

3. A heat treat tray comprising an egg crate framework defining a load-supporting surface, said frame work including a first set of spaced parallel strips and a second set of spaced parallel strips extending at substantially right angles to said first set of strips, the strips of each set being slotted at the lines of intersection with the strips of the other set so that the two sets of strips are MARTIN B. HUTCHINSON. RAYMOND J. SHILLUM.

REFERENCES CTED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,145,708 Blaney Jan. 31, 1939 2,168,333 Harris Aug. 8, 1939 2,241,952 Jachman May 13, '1942 2,287,740 Klouman June 23, 1942 2,303,882 Johnson Dec. 1, 1942 2,417,083 Menough Mar. 1l, 1947 2,453,845 Jackson Nov. 16, 1948 OTHER REFERENCES Pages 189, 190, Heating of Steel, by M. I-I. Mawhinney, 1945. Published by Reinhold Publishing Corporation, 330 West 42nd Street, New York, N. Y.

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