US2095565A - Carburizing box - Google Patents

Description

Patented Oct. 12, 1937 UNITED STATES PATENT OFFICE` The Electro-Alloys Co corporation of .Ohio

Application November 18,

mpany, Elyria, Ohio, a

193e, seri-a1 No.7111,465

c claims. (Cl. zes- 4.7)

My invention relates to carburizing boxes and relates more particularly to carburizing boxes'of a type having walls in the vform of plates or sheets of heat resisting material.V I

In the use of carburizing boxes, metal articles to be carburized are placed in the boxes, together with any suitable carburizing agent such as bone dust. The boxes are commonly introduced into a heat treating furnace, with suitable covers, or trays, and when so introduced are subjected to the heat of the furnace. `The heat is directed against the sides and ends of the box, to cause heating ofthe box, the contained articles, and carburizing agent, until the `articles are heated to a desired predetermined temperature, whereupon the metal articles absorb carbon from the carburizing agent. Y

. The effect of the temperature which may reach from1600 to 1800 Fahrenheit isto add tothe carbon content of the surface portions of the iron or'steel articles.. After the carburizing operation, the boxes are then withdrawn from the furnace and cooled, and the accrued heat imposed upon the articles becomes gradually dissipated. Consequently the boxes are subjected to extreme variations in temperature and in former constructions, due tothe expansion and contraction ofthe walls of such boxes, and more particularly the side walls, these walls commonly become permanently warped, fractured, or otherwise damaged. i

Also in prior constructions, there has been difIiculty incurred, `in that some of the metal articles placed in the box `to be carburized become heated 35 to carburizing temperature more rapidly than other articles differently disposed in the box', and the reverse conditiomthat'some of the articles are cooled more rapidly' than other differently :disposed articles, also commonly obtains, with 40 vthe result that the articles are not uniformly carburized. v

It is therefore an object of' my invention to provide an improved carburizing box whereby all of the articles placed therein and subjected to the carburizing temperatures are more uniformly subjected, and for more uniform periods, lto corresponding variations yin temperature, both during the heating andc'ooling periods.

Another object-of .my inventionis to provide van Vimproved carburizing box which will withstand the temperature` conditions incidental to the use of such abox under the conditionsof `practicewith a minimum .of deterioration.

Another object of my invention is to provide Aa box which will not only eiciently withstand the temperature conditions of practice, but at the same time, will withstand the hard mechanical usage imposed upon such al box in practice.

Other objects of the invention will be apparent to those skilled in the art to which my invention -5 Vappertains from reference to the accompanying drawing and from the descriptive specification referring to said drawing, and which disclose a preferred embodiment of my invention.

In the drawing:

Fig. 1 is a top plan View of a carburizing box embodying my invention;

Fig. 2 is a side elevational view of the embodiment of Fig. 1; and

Fig. 3 is a perspective View of a portion of a 15 flexible side wall element separator for the said embodiment.

Referring now to the drawing, and first to Figures 1 and 2, the box'illustrated which is a preferred embodiment of my invention, comprises 20 four cast corner elements, all of which are alike, and which are shown at 2, and intermediate connecting pairs of sheet metal lateralV wall elements 3 and 4, these being Welded at their ends 5 and 6, into longitudinally extending slots 'I '25 of the corner elements 2.

The arrangement of corner elements 2 and sheet metal side wall elements 3 and 4 is such, that each adjacent pair of corner elements are united by the side Wall elements 3 and 4, by the 30 ends 5 and 6 thereof being projected Within the slot 'l of the corner elements. The slot 'l extends for the full length of the elements 2, and the connection is made permanent by securely welding the sidewall ends 5 and B preferably through- 35 out their longitudinal extent to the' portions of the corner elements 2 bordering the slot 1.

Spacer means illustrated in Fig. 3 extending longitudinally of the box and interposed between each pair of wall elements 3 and 4 serve to space .40 the intermediate portions of said walls apart, so that as shown in Fig. 1, the walls 3 and 4 are `necessarily bowed inwardly vand outwardly respectively from their ends to their intermediate portion. y

The spacer means, comprising a flexible hingev Vspacer illustrated in Fig. 3 not only relatively spaces the intermediate portions of said walls but also flexibly secures them against undue separation. The said spacer means comprises pairs 50 vof generally Ushaped loop members comprising the loop members such as 8 `and 9, Fig. 3, which extend in opposite directions with their intermediate portions in overlapping relation, and lhil' ends l and II being out-turned laterally 55 to respectively abut the relatively confronting surfaces of the outer wall element 4, and the inner wall element 3 respectively; to which they are securely welded.

Preferably there will be provided a plurality of pairs of the oppositely extending loop members 8 and 9 which are preferably relatively spaced,v and a connecting rod I2 is inserted longitudinally of the box between the overlapping loops of all of the pairs of loop members of each set of such members.

After the rod I2 has been forced to the position illustrated in the drawing, the ends of the rod which are originally preferably straight, are bent over as shown at I3 and I4, whereby the rod is prevented from thereafter being accidentally removed from its proper position as illustrated, where it maintains the intermediate portions of the side walls 3 and 4 permanently flexibly connected together.

The spacer means of Fig. 3 is generally of the form of a piano hinge joint, the rod I2 forming the hinge pin and the loop members 8 and 9 forming the hinge elements of a hinge connection between said walls.

Preferably the construction ofthe walls, the hinge spacers, and the inter-connecting corners for said walls, is duplicated on all sides and corners of the box, as illustrated.

Preferably the material of all portions of the box above described is of a good quality of heat resisting alloy such as chrome-nickel alloys commonly used in the art for such purposes.

Preferably also the plates 3 and 4 are disposed with the grain of the metal affected by the rolling process by which they were originally formed, extending horizontally i. e., in the direction from each one of the corner elements 2 to the next adjacent corner element 2 which are interconnected by said plates.

The box as above described may be employed with any of the usual suitable auxiliary trays, or top and bottom elements, and the carburizing process will be carried out when employing the .box of my invention, preferably in the usual or any other known manner which for sake of brevity will not be described here, being well understood in the art.

In the use of the box of my invention, however, assuming that the box, perhaps with other boxes, is placed in a suitable tray and provided with any suitable top closure, and introduced intoV the carburizing furnace, the side walls of the box are subjected to the heat in theV furnace for a predetermined length of time, 'and at the same time heat is transmitted through the bottom tray and top cover to the carburizing material, and articles to be carburized, in the box.

In single-walled boxes of prior art, it has been found that heat commonly penetrates the side walls and is transmitted to the articles disposed most nearly adjacent to said side walls more rapidly than to articles placed nearer the center of the box, and also that such more nearly adjacent articles are cooled more rapidly than the more centrally disposed articles. This results in a difference in carburizing results imposed upon the said differently disposed articles in the box.

Another difliculty which has been prevalent with single-walled boxes is that heat is transmitted through the lateral wallsV more rapidly than from the tops and bottom and with a resultant difference in carburizing results with respect to lateral surfaces of articles, relative to other surfaces which may be faced towards the top or bottom.

The carburizing agent being a quite efficient form of heat resisting material being so placed as to surround the articles in the box, likewise, adds to the diiliculties such as those above mentioned, which have been previously prevalent.

In my improved double Wall construction, the air space between the outer wall and inner wall elements, retards the flow of heat communicated from the outer wall element tothe articles placed Within the box.

In my improved box having the over-all dimensions commonly employed in the art, it is found that heat vtransmitted to the articles disposed over the major portion of the interior of the box, from the top and bottom, through tray and cover elements, arrives at similar intensity, at the articles within the box, at about the same time as the heat transmitted through the double walls, and communicated laterally to such articles.

Conversely after the carburizing operation, and upon cooling, heat is dissipated in all directions from the articles at approximately the same rate, or in any event, at a more uniform rate in all directions than has been previously attained in boxes of this general character.

In the practical operation of carburizing boxes of the general type to which my invention relates, it is not unusual to advance a plurality such as three boxes through a furnace, in alignment on skids or the like, and with very little space between the successive boxes. In such case the opposing walls of adjacent boxes receive less heat than the other walls. Such variation in temperature communicated to the different walls effects uneven contraction and expansion stresses, which in other constructions has been conducive to undesired deterioration of the boxes. In the carburizing box construction as above described, the walls are susceptible of variations according to the temperatures imposed upon them, individually, and this is also true of the outer and inner wall elements, such as 4 and 3, illustrated in the drawing, and the Walls being more readily yieldable responsive to thermalcontraction and expansion inducive temperatures, increases the life of the boxes.

By the carburizingbox construction herein described, warping and fracturing, which in prior constructions usually results from uneven heating up or cooling-down, which in turn produces uneven expansion and contraction of the box structure, thus causing premature failures, is therefore effectually avoided.

Having thus described my invention in a preferred embodiment, I am aware that numerous and extensive departures may be made from the invention herein illustrated and described, but without departing from the spirit of my invention.

I- claim:

l. A carburizing box comprising a plurality of lateral walls, each wall comprising a pair of metallic plates, said plates secured in close proximity at their ends, and intermediately disposed spacer means interposed between intermediate portions of said plates and flexibly interconnecting said plates.

2. A carburizing box comprising a plurality of lateral walls, each wall comprising a pair of metallic plates, said plates secured in close proximity at their ends, and intermediately spaced spacer means interposed between intermediate portions of said plates and flexibly interconnecting said plates, and corner elements at the junctures of successive pairs of spaced side wall elements, said corner elements and the adjacent ends of said side wall elements being rigidly secured together.

3. A carburizing box comprising a plurality of lateral walls, each wall comprising a pair of metallic plates, said plates secured in close proximity at their ends, and intermediately spaced spacer means interposed between intermediate portions of said plates and flexibly interconnecting said plates, and corner elements at the junctures of successive pairs of spaced side Wall elements, said corner elements and the adjacent ends of said side wall elements being rigidly Welded together, said ends for each associated pair of Wall plates being received within a slot of said corner ele'- ments.

4. A carburizing box comprising a plurality of lateral walls, each wall comprising a pair of metallic plates, said plates secured in close'proximity at their ends, and intermediately spaced spacer means interposed between intermediate portions of said plates, and corner elements at the junctures oi.successive pairs'of spaced side wall elements, said corner elements and the adjacent ends of said side wall elements being rigidly secured together, said spacer means comprising oppositely extending loop elements, and a pin projected between the intermediate portions of said elements, the ends of different said elements being rigidly aixed to different relatively confronting surfaces of said wall elements.

5. A carburizing box comprising a plurality of lateral walls, each wall comprising a pair of metallic plates secured in close proximity at their ends, means rigidly interconnecting each pair of plates, flexible spacer means maintaining intermediate portions of each pair of plates relatively spaced and permitting variation in said spacing responsive to thermal change.

6. A carburizing box comprising aplurality of lateral walls, each wall comprising a pair of metallic plates secured in close proximity at their ends, means rigidly interconnecting each pair of plates at their ends to an adjacent pair of plates, and flexible` spacer means maintaining intermediate portions of each pair of plates relatively HARVEYY H. vLIGHTLE.

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