US2805054A - Heat treating apparatus - Google Patents

Description

Sept. 3, 1957 R. H. HILL 2,805,054

HEAT TREATING APPARATUS Filed Feb. 2. 1954 FIG! 2 Sheets-Sheet l FIG. 2

FIG.3

INVENTOR. ROBERT H. H ILL ATTORNEYS P 3, 1957 R. H. HILL HEAT TREATING APPARATUS 2 Sheets-Sheet 2 Filed Feb. 2, 1954 INVENTOR. ROBERT H. HILL ATTORNEYS United States Patent HEAT TREATING APPARATUS Robert H. Hill, Elgin, lll., assignor to The Morrison Company, Elgin, ]ll., a corporation of Illinois Application February 2, 1954, Serial No. 407,702

8 Claims. (Cl. 2632) This invention relates to heat treating of steel, and particularly to the prevention of scaling on heat treated articles.

In the past it has been quite common to perform various processes of heat treating by the use of a pit-type furnace in the heating portion of the cycle, followed by the transfer of the heated article to the usual quenching tank. In those articles or structures that are made from steel, and in which the preservation of a non-oxidized or unsealed surface is desirable, it is customary to protect the steel during the heating operation through the use of a protective atmosphere such as nitrogen within the heating furnace. This, of course, prevents oxidation or scaling during the heating operation, but it is well known that during the transfer of the heated metal object from the heating furnace to the quenching tank, there is a short period during which oxidation or scaling may take place. The scale that is thus formed in the transfer period is recognized as being objectionable, and in the past it has been customary to remove such scale as by sand blasting or shot blasting of the finished article. This, of course, is objectionable not only from the standpoint of added cost, but also because it produces a rough or pitted appearance on the finished article.

In view of the foregoing, it is the primary object of the present invention to enable heat treating operations of the aforesaid character to be performed in such a manner that the work does not have an opportunity to oxidize or scale. More specifically, it is an object of the present invention to enable a protective atmosphere to be maintained about the heated work piece during the transfer thereof from the heating furnace to the quenching tank, and a related object is to afford simple and effective means for maintaining the inert or protective atmosphere about the heated work piece during the transfer period, thereby to prevent scaling of the work piece during this period.

Other and more specific objects of the present invention are to afford a mufile in which a work piece may be disposed during the heating, transfer and quenching periods, and which muffle serves to permit and direct proper and efficient circulation of the heating and quenching media during the heating and quenching periods, and which is nevertheless effective during the transfer period to confine a body of the protective atmosphere about the heated work piece.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show preferred embodiments of the present invention and the principles thereof and what I now consider to be the best mode in which I have contemplated applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims.

In the drawings:

Fig. 1 is a vertical sectional view through a mulfled work support embodying the features of the invention, the mufiled work support being illustrated in its operative position in a pit type heating furnace;

Fig. 2 is a vertical sectional view showing the muflled work support of the present invention in the relationship that it assumes during the transfer of the work from the heating furnace to the quenching tank;

Fig. 3 is a vertical sectional view showing the muffled work support in position in a quenching tank;

Fig. 4 is an enlarged vertical sectional view of the muffled work support in the position or relationship shown in Figs. 1 and 3;

Fig. 4A is a fragmental vertical sectional view illustrating the muffle made with a different wall form;

Fig. 5 is a plan sectional view of the structure, taken along the line 55 of Fig. 4; and

Fig. 6 is an enlarged fragmental view similar to view 4, but showing the lid of the muflled work support in its closed relationship.

For purposes of disclosure, the invention is herein illustrated as embodied in a mul'lled work support 20 that embodies a work supporting grid 21 having a plurality of spaced bars 213 from which one or more work supporting hooks or hangers 22 may be suspended for hanging work pieces such as the work piece W beneath the grid 21. The grid 21 has a pair of upwardly extending lifting rods 24 fixed thereto, and in the present instance, these lifting bars 24 are made from strap-like elements disposed in spaced relation as shown in Fig. 4, and having a connecting bar 25 between the strap-like members so that lifting books or other hoisting gear H may be engaged with the cross bars 25 for lifting the grid 21 and any work pieces that may be supported thereon.

The grid 21 has a cylindrical muflle 28 suspended therefrom by a plurality of relatively narrow vertical connections such as chains 29, and this suspension of the mufile 28 is normally effective to afford an annular passage 30 through which a heat transfer media such as gas or liquid may flow, the upper and lower ends of the mufile 28 being open, as will be evident in Figs. 1 to 4.

Under the present invention, means are associated with the grid and the mulfle whereby the annular passage 30 may be closed, and the closing and opening of the annular passage 30 is, under the present invention, accomplished automatically as an incident to the normal lifting and transporting operations that are performed in respect to the mufiled work support 20.

Thus, as is best shown in Fig. 4 of the drawings, a lid 35 is provided that is mounted on the grid 21, and this lid 35 is made up of two primary elements. Thus, the lid 35 comprises an upper section 35U that has a top wall through which the lifting rods 24 are slidably extended. The upper section 35U also has a downwardly extended side wall 235 which is rested upon and fixed to the upper and outwardly projecting flange 335 of a lower section 35L of the lid 35. The lower section 35L, is in the form of an annular ring of what might be termed Z-shaped cross section in that a cylindrical wall section 435 is extended downwardly from the inner edge of the flange 335, while a second flange 535 extends inwardly from the lower edge of the wall 435. The flange 535 is arranged so as to extend under the ends of the bars 21B of the grid 21, and hence the grid 21 may be supported by the lid section 35L. This support is attained in practice by resting the flange 335 on a fixed supporting means, as will be described hereinafter, and in this connection, it will be observed that the flange 335 extends outwardly beyond the side wall of the muffle 28, and thus the muffle may be lowered through or between the supporting means that are to be engaged until the flange 335 comes to rest upon such a supporting means.

A comparison of Figs. 4 and 6 shows that when the muffled work support is being supported by the flanges 335 of the lid, the lid will be disposed in its upper or open position as shown in Figs. 1, 3 and 4, while in the situation where the muffled work support is being lifted by means of the lifting rods 24, the lid 35 will assume its lower relationship as shown in Fig. 6, thus to effectually close the annular opening 30 above the upper end of the mufile 28, and it will be observed that the top section 35L of the lid 35 in such an instance serves to completely close the upper end of the muffle, and this serves to prevent flow of gas out of the upper end of the rnutfie 28, as will be described in some detail hereinafter.

In Fig. 4 of the drawings, the side wall of the muffle 28 has been shown as being truly cylindrical in form, but this form may be varied and, as shown in Fig. 4A, the side wall is formed from corrugated material as indicated at 128, the corrugations running in horizontal planes about the wall of the muffie. While such a corrugated wall gives a longer useful life, it involves additional cost which may be avoided if desired through the use of the straight wall, as shown in Fig. 4 of the drawings.

In the use of the muffled work support 20 of the present invention, the heating operation that is required in a heat treating operation may be performed in a pit type furnace 50, as shown in Fig. 1 of the drawings, and this pit type furnace embodies bottom and side walls 51 and 52, and inwardly extended stationary work support ring 53 near the upper end of the furnace, and a removable top or cover 54. The space between the support ring 53 and the side wall 52 of the furnace is closed by means of a fixed wall 55, and heat may be applied to the furnace by any suitable means such as radiator pipes 56 disposed along the sides of the furnace and through which a heat transfer liquid may be passed in the usual manner. Such furnaces in most instances include a circulating fan such as the fan 57 shown in Fig. 1, whereby a gaseous heat transfer media such as inert or protective atmosphere may be circulated past the work that is being heated.

With the muffled work support 20 of the present invention, the work may be supported within the furnace 50 by lowering the muffled work support 20 into the furnace to the position shown in Fig. l, and in this position the flange 335 of the lid rests on the work support ring 53 while the grid 21 rests upon the lower flange 535 of the lid. Thus, the parts of the muifled work support 20 assume the position shown in Figs. 1 and 4 so that the annular opening about the upper end of the muflle 28 is open and operation of the fan 57 may circulate a protective or inert atmosphere through the muffle 28, as indicated by the arrows in Fig. i. This, of course, causes the inert atmosphere to serve as a heat transfer media to increase the heating rate and assure uniformity of heating of the work piece W. The inert atmosphere is, of course, supplied by any conventional means.

After the completion of the heating cycle, the cover 54 of the furnace is removed, and the usual lifting crane is connected to the lifting rods 24. The mufiled work support 20 is then lifted from the furnace 50, and in this removal operation, the first thing that takes place is the lifting of the grid 21 and the muifie 28 from the relationship shown in Fig. 1 to a closed relationship wherein the flange 535 of the lid 35 engages the upper end edge of the muffle 28, as shown in Fig. 6 of the drawings. Further lifting of the grid, of course, results in movement of the lid 35 and the grid and mufile as a unit in the closed relationship shown in Fig. 2 of the drawings. It will be evident that the inert or protective atmosphere that is thus trapped within the lid 35 and the mufl le 28 will, to a large extent, remain within the enclosure that is thus afforded, as shown in Fig. 2 and in the relatively brief time required for transfer of the heated work from the furnace 50 to a quenching tank 60, Fig. 3, the trapped inert atmosphere will serve to protect the heated work W from scaling, as would normally be encountered if air were allowed to circulate freely through the muffle 28 and to pass into contact with the heated work. The mufile 28 and the lid 35 also serve the function of limiting heat loss by radiation or convection during the transfer period.

The quenching chamber or tank 60 has a stationary work support ring 65 therein that is the same as the ring 55, and the muffled work support 20 is lowered through the ring 63 to the relationship shown in Fig. 3. As this takes place, the flange 335 of the lid engages the stationary ring 63 and the parts of the mufiled work support move to the relationship shown in Fig. 3 of the drawings. In this relationship, it will be evident that the annular circulating passage 30 is again open, and a liquid heat transfer media such as oil may be circulated through the muffic 28 and out the top thereof, as indicated by the arrows in Fig. 3. This circulation is attained in the usual manner, and a circulation controlling baffle 64 is preferably disposed about the mufile 28 so that a proper controlled circulation may be attained.

From the foregoing description, it will be evident that the mufiled work support of the present invention serves to properly control and direct the flow of heat transfer media through the muffle and about the work during both the heating and quenching operations, and yet with the muflied work support 20 of the present invention, the inert or protective atmosphere is maintained about the heated work piece during the transfer from the furnace to the quenching tank. This, of course, produces an unscaled heat-treated work piece, and this result is attained economically and makes it unnecessary to perform the costly scale removing operations that have normally been required.

Thus, while I have illustrated and described the preferred embodiments of my invention, it is to be understood that these are capable of variation and modification, and I therefore do not wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall within the purview of the following claims.

I claim:

1. In a heat treating apparatus, a muflie having side walls and an open lower end and an open upper end, a lid adapted to rest on and effectually close the upper end of said muffle, said lid being mounted on and movable up wardly with respect to said muffle to define an annular passage between said upper end of said mufiie and lid, means for mounting a work piece within said muffle, flexible means for suspending said mufile from said lid to thereby open said passage, and means enabling said mufiie to be lifted independently of said lid at a time when said lid is being held to thereby close said passage.

2. In a heat treating apparatus, a work-supporting grid adapted to be rested at its edges on stationary support means within a heat exchange chamber, a muffle having side walls and suspended beneath said grid said muflle having an open lower end, and having an open upper end spaced downwardly from said grid to define an annular passage between said upper end and said grid, a lid having a top wall means and a downwardly extended side wall and mounted on said grid for movement between an upper open position wherein said side wall means is located above said annular passage and a lower closed position wherein said annular passage is closed, lifting means fixed to said grid and extended slidably through said top wall of said lid for attachment to a lifting crane or the like, and means on said lid forming a downwardly facing shoulder for engagement with such a stationary support means of such a heat exchange chamber to shift said lid to its open position as an incident to lowering of the grid into such a chamber.

3. In a heat treating apparatus, a muffie having side walls and with open upper and lower ends, a lid having a top wall and a downwardly extended side wall means and mounted for vertical shifting movement with respect to said muffle between an upper open position wherein said side wall means is spaced upwardly from the upper end of said mufiie and cooperates therewith to define an annular passage and a lower closed position wherein said annular passage is closed, lifting means operatively connected to said mufiie and extended slidably through said top wall of said lid for attachment to a lifting crane or the like, and means on said lid forming a downwardly facing shoulder for engagement with the stationary support means of a heat exchange chamber to shift said lid to its open position as an incident to lowering of the lid and the mufile into such a chamber.

4. In a heat treating apparatus, a muflie adapted to receive a work piece and having an open lower end and an open upper end, a lid adapted to rest on and eifectually close the upper end of said muffie, a flexible connection between said lid and mufl'le and said lid being movable with respect to said mufiie to the extent allowed by said flexible connection to define a passage between said upper end of said muflie and the lower side of said lid, and said lid including means adapted to rest on a stationary support and suspend the apparatus therefrom with said mufile suspended below the lid by said flexible connection to afford said passage as aforesaid.

5. In a heat treating apparatus, a mufiie with open upper and lower ends and adapted to receive a work piece, lifting connections on said apparatus enabling said muffle to be lifted and transported, top closure means adapted to close the upper end of said muflie at a time when the mutfie is being transported, a flexible connection between said muffle and said closure means enabling the mufile to be gravity suspended below and from the closure means at a time when the closure means is held stationary independently of the rnufile to thereby open the upper end of the mufiie, and means on said closure means engageable with abutment means in a heat transfer chamber to enable the upper end of said mufile to be opened as aforesaid.

6. In a heat treating apparatus, a mufiie adapted to receive a work piece and having open upper and lower ends, a lid arranged for movement between an upper open position wherein said lid is spaced upwardly from said muflie to define a passage at the upper end of the mufile and a lower closed position wherein said rnufile is closed at its upper end, a flexible connection between said muffle and lid enabling said muffie to be gravity suspended by and below said lid upon holding said lid independently of the mufile to define said passage as aforesaid, means on said lid enabling the lid to be held independently for the purpose as aforesaid, and means on said apparatus enabling a lifting force to be applied to said muffle to take up slack in said fiexible connection and cause said lid while held as aforesaid to close on the upper end of said muffle.

7. In a heat treating apparatus, a mufiie adapted to receive a work piece and having open upper and lower ends, a lid arranged for movement relative to said muflie between an upper open position wherein said lid is spaced upwardly from the upper end of said mufile and cooperates therewith to define a passage and a lower closed position wherein said lid closes oi? the upper end of said muffle, said lid having flange means associated therewith adapted to be held independently of said mufile, a flexible connection between said lid and mufiie enabling the muffle to be suspended by and below said lid at a time when said lid is held as aforesaid to thereby afford said passage as aforesaid, and means for lifting said muffie independently of said lid to enable the lid to close on the upper end of said muffie at a time when said mufile is suspended as aforesaid.

8. In a heat treating apparatus, a muflie having open upper and lower ends, a cover for the mufile movable relative to said muifie to an open position defining an opening between the muflle and cover, means on said cover outwardly of the mufiie for raising said cover to said open position, a flexible connection between said mufiie and cover limiting the extent of opening movement of said cover, and lift means arranged in operative relation with the muffie so that when the lift means is lifted at a time when said cover is in open position slack in said flexible connection is taken up and the cover moves to a closed position wherein said opening is closed.

OTHER REFERENCES Article on Heat Treating Gears, at pages 78 and 79 of Steel' in the issue of September 1, 1941.

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