US1844604A - Heat reclaiming apparatus - Google Patents

Description

Feb. 9, 1932. e. w. SCHWAB HEAT RECLAIMING APPARATUS Filed July 13, 1928 H 4 Sheets-Sheet 1 Feb. 9, 1932. G. w. SCHWAB HEAT RECLAIMING APPARATUS 4 Sheets-Sheet 2 Filed July 1s, 1928 Feb. 9, 1932. G. w. SCHWAB 1,844,604

4 HEAT RECLAIMING APPARATUS Filed July 13, 1928 4 Sheets-Sheet 3 Feb. 9, 1932. G w. scHwAB I HEAT RECLAIMING APPARATUS Filed July 13, 1928 4 Sheets-Sheet 4 I Q Z M 74 V1 Z2 4 F7 7 v 7/ Z7 Z0 70 g 1/2; U J JI Wye/1mm 6 %JM Patented Feb; 9, 1932 UNITED STATES PATENT OFFICE GAS FURNACE 00., F ELIZABETH, NEW'JERSEY, A G ORPORA'IIONOF NEW JERSEY HEAT RECLAIMING APPARATUS Application filed July 13,

' proved economical manner of heating the articles.

Steel carburizing is effected at very high heat, and much fuel has been consumed in the heating up not only the articles but also the carburizing retort as well as the furnace, and much time has been needed, and the output of the apparatus has consequently been relatively low.

One of the main features of the present invention is the reclaiming of a largeshare of the heat from the hot carburized or otherwise heated articles,

andinusing thereclaimed heat for the purpose of heating up cold articles, preparatory to bringing them up second compartment thereof, which is in open to the final stage of high heat. The final stage is effected after the articles are deposlted in the retort in the furnace. The invention isalso useful in normalizing and annealing as well by heat.- There is disclosed a fireless pre heaterfor the cold work, said pre-heater being devoid of a furnace, and havin receptacles in which batches of the articles are deposited in exposed condition.

The batch of carburized or otherwise heated work received from a furnace is'confined in exposed condition in a compartment in the work-pre-heaterwhile the batch of cold articles is confinedin exposed condition in a co'mmunicatiomat top and bottom with the first compartment, to form a-draft on siphon through the hot and cold articles. The heated gas, air or; atmosphere rises tothe top of the first draft compartment, and flows through a porting into the top of the coldarticle draft compartment or flue, and descends to the'bottom thereof, and during its descent imparts much heatto the'cold articles.

The cooled air. or gas then flows through a bottom porting'back into the first compartment or flue, and isagain heated by the exposed articles confined therein, and rises to the top, suchcirculation of air or gas being repeated until the originally cold articles have been heated up toa'point about one-half as otherwise treating metal 1928. Serial No. 292,352.

effects a heat ekchange; the'e ziposed colderticles being heated by reason of theheat so reclaimed from the exposed hot work, through the operation of the draft or current.

In some cases a cold batch may be subjected to heat received from two successive hot batches of work, thus raising; the cold batch more nearly to carburizing temperature.

There is a uniform slow cooling of the carburized work, and also a uniform heating up of the work which is to be carburized, annealed or otherwise heat-treated. The time required for heating up new charges in the carburizing or annealing or other heating retort is materially shortened, thereby correspondingly increasing the productive capreheated charge to the high point required.

In a simple form, the apparatus embodies GUSTAV W. SCHWAIB, OF TOWNLEY, ELIZABETH, NEW JERSEY, ASSIGNOR T0 AMERICAN only two of the communicatingcompartments already mentioned. In another form, the oven may include. four compartments, and

may serve a single carburizing or annealing retort or a battery of four or more retorts, a crane being employed to transfer the work to andfron nthe compartments and the retort.

. In another form of the invention the retort and furnace may be mounted to swlng' up and down,- and; twoor more ovens, each having two communicating compartments, may be mounted on trunnions for swinging upwardly to receive the work from the retort, and downwardly to discharge into the retort; these ovens being mounted upon elevators and the whole being mounted upon a carriage. The carriage may travel along a rowof furnaces, and serve all of them,

Other features and advantages will hereinafter appear. I

In the'. accompanying drawings, or diagrams,

Figure 1 is a sectional elevation, showing a two-compartment oven for pre-heating a charge of work by means of heat reclaimed from carburized work that has been received He or retort. .Figure 4 is a sectional elevation, showing to the cold work. Upon reaching the bottom in hot condition from a carburizing or other upper vent or port 24, and enter compartment retort. 22 containing the cold work.

Figure 2 is a sectional plan of the same. Upon contacting with the cold work, the Figure 3 is a sectional side elevation, to gases heat the same, and therefore part with show the manner of dumping a pre-heated their own heat, and increase correspondingly charge from an oven into a carburizing mufin density and weight, and sink through the cold work, giving off still more of their heat the manner of discharging in hot condition of the compartment or chamber 22, the cooled work from a retort and conveying it to an gases re-enter the compartment 20 through 7 oven, preparatory to reclaiming heat from an opening or port 25 forming a communicatsaid work for use in pie-heating a fresh batch ing passage at the bottom of the oven between of metal articles. the compartments.

Figure 5 illustrates the manner of dis- The gases are reheated by contact with th charging in cooled condition the case-hardstill hot charge 21, and I: crease in I ened or otherwise heat-treated articles from density and and hence rise through the cooling compartment of a a wor t, absorbing still more heat thereoven. from, and still further decreasing in density FigurcG isarseot ollatfrofifelevation, illusand weight, and finally reach the top of the trating-onewform of apparatus, including a compartment 20 (from which they vent) battery of rctorts and also a battery of ovens, through the conduit 24; and the cycle is rcwhich may be used in reclaiming heat and. peated. preheating work by stages. This alternate heating and cooling of the Figure 7 is a sectional elevation, showing gas continues so long as there is substantial a battery of ovens for use in pre-heating the difference in the heat of the articles in the two work by stages. This is a sectional diagram compartments of the oven, and it slows and of the ovens seen imFigure 8. finally ceases when theheat of one batch is Figure 8israplan, and Figure 9 is a secsubstantially the same as the heat of the other tional elevation, of aform of the invention in batch, which would be approximately at a the use of which the work may be carried in heat about half as high as that of the original baskets, which are hoisted out of a pre-he'athot charge received from the retort. ing compartment of an oven and dropped If itis desired to accelerate thereclamation into the common retort, and subsequently of heat, or if it is desired to carry the heating hoisted out of the retort and dropped into aof the fresh batch a little further, there may cooling compartment of an oven. A travelbe employed a fan 26 in the bottom of the ing hoist is shown, the same having a horiheating compartment, which can be mounted zontal swinging adjustment to enable a single upon a vertical shaft 27 extending up from retort to communicate with the two ovens, a motor 28 secured under the bottom of the each oven having a cooling compartment and oven (which may rest upon sills 29) This a heating compartment, the two ovens usefan may be employed to expedite the flow of fully co-operatin'g for two-stage heating. gas through the described fireless heater or At Figures 1 and 2 is shown a heat-reclaimthermo-siphon, thus reducing the time taken ing or work-preheating apparatus in the form for pro-heating the fresh batch, and also carof a cooling compartment 20 within which is rying the heat of the fresh batch up to pracdeposited a charge of incandescent metal artically the same hot point to which the origticles 21 just received from a carburizing reinal hot batch cools. The fan should be tort, or from an annealing or other heatabove port 25. treating retort. There is also shown a heat- The work in the compartment 22' may be ing compartment 22, within which is deposheld upon fixtures, or large work-pieces may ited a fresh charge 23 of cold articles, shown rest upon a grating 30, having the form of a diagrammatically, which it is desired to predome rising from the floor of the compartheat before subjecting them to carburization ment and protecting said fan 26. A similar or other high heat treatment. In most cases grating 31 for the work may be employed in the work-pieces (to be heated) are mounted the compartment 20, and the same may have upon fixtures on which they are charged into a f n- There may be substituted for the sucand removed from th retort, tion-fan 26, shown in compartment 22, a Said compartments taken together forman blowing fan in the lower part of compartment oven, and between them at the top is an open 20, with substantially similar results. communication or gasvent 24, through which To the cooling compartment 20 may be inthe heated gas rising to the top of comparttroduced inert gas through a pipe 32, rising nient 20 is led into the relatively cool comthrough the bottom 33 of the oven and openpartment 22. That is, the atmosphere of ing into the cooling compartment, thus makgases in compartment 20, becoming heated ing atmospheric or gas conditions controllable by contact with the hot work, rise to the top in the heat-reclaiming or exchanging unit; of the compartment and pass out through the said pipe 82 being provided with a valve 34.

ml to retain the heat.

The use of the inert gas minimizes or avoids oxidizing of the heated articles, or other injury thereto, or deteriorationthereof.

These two compartments 20 and 22 are mounted in a common housing 35, and are well insulatedfrom each other and protected against the loss of heat by-means of suitable material 36 betweenthe compartments and the outside steel shell of the housing 35. This insulating material may be Sil-o-cel brick, or any other suitable substance. The loss of heat through the bottom of the oven is minimized by including therein a layer'of slabs of fire-' bricks or heat-retaining, material 37, upon which rest the floors 38, 39 of the compartments 20, 22; said floors having depending flanges 40 keyed in the bricks ,37 to give security and solidity, and also having upturned flanges 41, within which fit steel or other metal shells forming the compartments 20, 22, or the compartments 20 and 22 may beformed only of refractory walls and be devoid of metal linings.

The top of each compartment may be closed by a cover in the form of an inverted metal bowl 42. The cover is made very thick for confining the heat, and is interior'ly channeled around its under side at 43. The compartment has at its top a depending annular vertical flange 44 confined within said chan- The bottom of the cover is in the form of a cup or bowl 45 setting down within the flange 44, and having an out-turned brim 46, the bottom of the cover 42 setting down below said brim 46 to-form the annular channel. Within the cover, a layer of refractory material or brick 48 rests, upon the bottom 45 of the cover. and a layer 49 rests upon the brim 46, said layer 49 surmounted by a ring 50 of refractory material. Bolts 51 secure together the layer 49, the ring 50 and the top 42. There may also be emtheescape of heat.

swinging frame 61, having ployed spacers 52, and the spaces may be filled with Sil-o-cel 53. I

r A constricted vent 54 may be provided in the cover at the top of the heating compartment 22, to permit the displacement of gas and air by inert gas that is let in from time totime through the pipe 32; and said vent 54 may be closed by plug 55 whenever desired, but preferably by a valve or cock.

The lower part of each side wall 47 of each cover sets down within an annular channel 56, one formed at thetop of each compartment, thus further guarding against A single casting may comprise the two annular flanges 57 and 44. The oven 35 may have a cap 58 securedto the outer flanges 57, leaving the channels 56 for movement of the covers. The channels 56 may be filled with suitable finely divided gypsum or other powdered material 59, 60, to form a seal.-

Either cover may be lifted by means Of-&

a jib '62 from.

which depends a swivel 64 in which is mounted a lever 63, having an end hook 65 in which are caught chains 66 rising from the cover 42. The lever may be used for raising the cover, and then the crane can swing the cover off from the oven.

After reclaiming about half of'the heat,

from the cooling charge in compartment20, and the absorption of the recovered heat by the fresh batch in the heating compartment 22, the compartment 20 maybe discharged. 7

Another incandescent charge may be takenfrom the "carburizing or annealing retort,

while the already half-heated new batch is still retained in the heating compartment 22. In this manner the heat of the still-retained charge in compartment 22 may be stepped up or increased, since the circulation of heated gas will begin again, and will con,- tinue as already explained, until the heat of the pre-heating batch in compartment 22 is stepped up to a point about half way between its former heat and the, temperature of the fesh incandescent batch last received from the retort.

In other words, aftera medium pre-heating occurs in compartment 22, the cooling compartment 20 may be discharged and-then refilled with a batch from the carburizing furnace; and as said heated batch in compartment 20 loses its heat, the preheating batch in compartment 22 gains more heat. It is thereupon transferred to the carburizer retort for final heating and carburizing.

It will be understood that after the first incandescent batch from the carburizing retort is deposited in the cooling compartment 20, about half of its heat is reclaimed,

and that then the compartment 20 is discharged andrefilled by a second batch from the carburizing retort, where about onefourth of the heat of the later is reclaimed and absorbed by the preheating batch in compartment 22, which may thereupon be transferred to the carburizing retort. Since the charge so remaining in compartment 20 still retains about three-fourths of its original high heat, it may yet serve to preheat another cool batch of uncarburized articles if the latter is deposited inheating compartment 22. About half of the heat of the partly-cooled charge in compartment 20 may thus be transferred to the cold articles in 22,

whereby the articles in-20 are deprived of about three-eighths of their original heat, and the articles in 22 become heated to about the same point. Then the compartment 20 may be again discharged, and a third batch of incandescent articles may be deposited therein, and heat recovered therefrom and absorbed by the articles in 22, until the heat of the latter is stepped up, so that the heat in each compartment stands at about fiveeighths as high as the original incandescent charge.

near the carburizing temperature, and/only a little fuel therefore needs to be consumed,

' in order to bring them to final carburizing temperature. There is hence a material shortening of the time required in the furnace for carburizing each batch, since only a little time (and little fuel) is required to bring up the hot articles from the preheated point to the carburizing point. This also effects a corresponding increase in the productive capacity of the carburizing furnace. Moreover, the furnace, which may be in continuous operation day and night, would require less forcing during the period of bringing up the fresh articles to carburizing point. This reduced requirementfor forcing is due to the high degree of preheating of the batch of articles to be carburized. Inasmuch as the requirement for forcing is diminished, a longer life may be experted from the retort. Thus in several ways the invention tends to reduce the maintenance cost of the carburizing equipment. as well as the cost of fuel, while increasing its efliciency.

At Figure 7 is shown diagrammatically a double heat reclaiming unit. The descrip-' tion of the cooling and heating compartments 20 and 22 is applicable to Figure 7, in which the heat of the fresh cool batch in 22 is raised very nearly to the point to which the hot batch is cooled. The fresh batch may, however, be made much hotter than the cooling batch in the compartment 20, and this is done by removing the cooled batch from 20 and depositing in 20 another heated batch from the carbonizing or annealing retort. The above-explained circulation of the heated gas or atmosphere to the top of compartment 20 and through the topport 24: into the compartment 22 and out through the bottom port 25 into compartment 20 is kept up, until the heat of the fresh batch in the compartment 22 is stepped up to a degree that is about half way between the temperature of the incandescent articles received from the retort and deposited in compartment 20. The above-explained circulation of heated gas or atmosphere also applies to compartments 7 0 and 71.

This four-compartment or two-step heating reclaiming unit permits quicker and even more nearly complete heating reclaiming or exchange than the two-compartment unit seen at Figures 1 and 2.

At Figures 8 and 9 is shown a two-unit heat exchanger in connection with one carbonizing furnace retort of the vertical type. The compartments are arranged in an arcuate row, and the carbonizing retort is placed at the center of the arc. This two-unit heat exchangeris serviced with a radial crane 80, which may swing upon a'vertical pivot 81, its free end being provided with a horizontal, curved track-way 82. Along the rail 80 travels a carrier 83, having a pulley 84 and chain 85 to lift the cover 86 of any compartment. It will be understood that the covers of all compartments are closed during the heat-reclaiming or exchanging operations. The chain 85 may raise the work as well as the cover.

The apparatus seen in Figures 8 and 9 is preferable where the parts to be carburized are delicate, or where they are promiscous or miscellaneous in character and need to be handled carefully. fork of this kind may be charged into a number of annular baskets .87, placed one upon another to form 2. tier,

which rests upon an annulai' )latform 88 supported by a central rod 89. aid rod extends from the platform up through the centers of the baskets and hangs from a hook 90, which is connected by a link 90 to cover 86, so that when the cover is raised by the chain, the work may be brought up with it. In this manner a charge maybe brought from thevertical retort 91 to either cooling chamber 20 or 70, or a preheated charge may be transported from'either chamber 22 or 71 to the retort. The drawings show diagrammatically a series of nine baskets assembled in one column and locked together to form a single unit with a bottom platform. The latter forms a distributor or deflector for the hot gases, and may be in'the form of an iron casting. The central lifting rod locks the baskets and-platform together to form the unit, which is therefore chargeable or dischargeable at onehoisting and lowering operation.

\Vhile the multiple basket method shown at said figures is adapted for carburizing delicate parts and also miscellaneous parts, a different method can be used for other kinds of work. However, for certain work the number of baskets could be reduced to only one ortwo. Simple rod-fixtures can be used for certain classes of work, such as ring-gears and also other gears.

It will be understood that the heat-reqaiming compartments could belplace d in a straight row, as 'at'Figure 7, and that the track 82 could be straight, or, at least, that a traveling crane could be employed which would move instraight paths one at right angles to the other, one path running along the row of heat-containing compartments and the other path going to the retort 91, employing for this service a tram-rail-crane.

At Figure 9 is illustrated a bell in the form of a tube 92, having an annular cover 93 affixed thereto and engageable by the lifting cover 86, so that by means of the chain there may be raised first the charge into the bell 92, and then the charge. and bell may both be raised for transportation to a compartment, or to the retort 91. Then the bell may be lowered to rest on top of the furnace, and the charge being lowered into the retort. The bell is closed by the cover 86, and an advantage of its use is that it prevents excessive loss of heat from the hot articles. vThis bell may be of insulated material employed for charging and discharging, and within which the charge is transported from the carbonizing retort-to any cooling chamber, while it also may be usedfor transporting a fresh charge from a pre-heating chamber to the carbonizing ietort.

A small jib crane is shown at 61, 62, Fig ure 1, to service any cover. a

Referring to Figure 2, the heat exchange chambers 20 and 22 would be about 24 inches in diameter by 48 inches available depth, in

order to correspond to a standard size vertical' retort furnace. Including fixtures, it is conservatively assumed that one charge weighs about 2,000 lbs. In the low pre-heat there would be a cooling charge which just had passed through the high cycle and cooled say from 1700 degrees F. to 1100 degrees F., exposed to a freshly Charged charge, say at degrees F. A heat exchange would est-ablish a balance between cooling and pre-heating chargetheoretically at 580 degrees ,F.

The cooling charge would then be discharged and. replaced with a new change (just discharged from the. retort of the carbonizing furnace) so that the charge previously pres heated to 580" degrees F. would be exposed 'to an incandescent charge at"'-1-700:-,fdegrees F. A complete heat exchange would establish in this case a balance of 1140 degrees F. for each side, at which temperature the pro-heated charge would be chargedjnto the retort of the carbonizing machine 1 There wouldthus be regained 2,000 lbs. times (1140 degrees F. less 60 degrees F.) times .14average specific heat, or 302,400 B. t. u. net, which at 15% general furnace efiiciency, would have required 2,016,000 B. t. u. to accomplish. This shows an economy (figuring with 500 B. t. u. fuel gas-at $1 per 1,000 cu. ft.) of 4,032 cu. ft. or $4.03

for one heat exchange. Simultaneously, 'of course, the required heating-up time in the carbonizing retort for the charge would have been reduced from three hours to less than one and one-half hours, thus correspondingly increasing the production capacity of the carbonizing furnace,

Figuring with an average carbonpenetra- 2,000 pounds,

tion required for the work of inch, the heat exchanger 'ould make possible about six charges per ay of 24 hours, or a fuel economy alone of 6 $4.14, that is, $24.84 per 24-hour day.

Assuming that a plant operates four vertical retort furnaces, each having a retort ;24 inches inside diameter by 48 inches available height, and obtains four charges perday per furnace,-and that one-heating cycle includes three hours heating up time and three hours carburizing time, it would make 16 charges-per 24 hours for the four furnaces, or for every one and a half hours there would be one charge. A two-unit heat exchanger, or a four-chamber unit,-Would for such conditions, do the work of three hours cooling and three hours pre-heating. Assuming the time of three hours would prove ample. As-

suming a charge, including fixtures, to weigh a complete heat exchange as above explained, would theoretically regain 302,400 B. t. n. An efficiency of would reduce this to 272,160 B. ther 10% for radiation losses, would'leave a net gain of say 244,944 B. t. u. At 15% furnace efficiency, it would have. required 1,670,000 B. t. u. or 3,340 cubic feet of 500 B. t. u. gas for an equal amount of heating.

90 v t. u. Deducing fur- 244,944 net B. t. u. would raise the tempera t'ure of 2,000 pounds of work to be pre-heated about 880 degrees F. Nearly one-half of the heatilng-up time, or about 1 hours, would be save The figures given are estimated. The prevailing operating conditions will determine thedegree of efficiency of any unit.

When equipped with accelerating fan, one

7 double unit heat exchanger may serve two or more carbonizing furnaces or machines, correspondingly multiplying the economies to be obtained from such heat exchanger.

At Figures 3 to 6 is illustrated a battery of.

carburizingfurnaces 100, of the rotary type V illustrated in patent to A. W. Machlet No.

1,337,244, each furnace containing a revolving retort 101 protruding from the ends of the furnace. The forward end 1020f the retort is for receiving and discharging the work. The rear endhas a driving gear 103,

- as set forth in said patent; the retort revolv-.

furnace up or down is effected by means of a hand-wheel 106 and a worm 107 meshing with a worm-wheel or sector 108 fixed upon the furnace body.

When it is desired to charge aretort, the

f cover 109 (Figure 4) is detached'therefrom,

and the-furnace is tilted upby means of the hand-wheel 106 to the position seen at Figure 3. A pre-heating oven 110, in many respects resembling 35 (Figure 1), is arranged at a suitable elevation (Figure 3), and is tilted rearwardly upon trunnions 111; and a chute 112 is placed in position to carry the preheated batchfrom compartment 22, down to the uptilted retort 101. The retort, the chute and the compartment are given such as inclination that the work will slide down into the retort gently, without injury to the articles. After the chute is placed, the cover 113 is swung open by means of hand-wheel 114 (Figure 6) which revolves a worm 115 that meshes with a worm-sector 116 provided upon a pintle 117, which serves as a hinge for the cover or door.

When the pre-heating compartment 22 is discharged, the chute 112 is removed, the cover 109 is replaced upon the retort, and the latter is depressed to its level working position, while the cover 113 is closed and the oven 110 returned to vertical position.

By means of hand-wheel 118 (Figure 6), the oven 110 is then dropped to position for a fresh batch to be loaded into the empty compartment 22.

In order to provide for raising and lowering the oven, it is mounted upon and between vertically sliding elevators 119 and 120, guided upon vertical ways 121 and 122, and raised and lowered by means of chains 123, 124 running over pulleys 125, 126, the latter being power sprockets driven by a gear- train 127, 127 from a vertical shaft 128, to which is fixed said wheel 118. By revolving said wheel 118 the oven 110 may he raisedor lowered.

At their other ends the chains 123, 124 are connected to elevators 129, 130, upon which are trunnioned at 131 a companion even 132. Thus each oven counter-balances the other, and when either is raised the other is lowered. The oven 110 may be turned upon its trunnions by means of a crank 133, connected by means of a shaft 134 to a worm 135 meshing with a sector 136 on trunnion 111. The operation of ovens 110, 132 is the same, andat Figures 4 and 6 oven 132 is shown lowered and tilted backwardly to receive a carburized charge from one of the furnaces 100; the top door-cover 137 having been elevated by means of a hand-wheel 138, whose shaft 139 is provided with a worm 140, meshing with a sector 141 or the pintle of said cover 137. The chute 112 is inclined upwardly and rearwardly from compartment 20 to the retort 101, to receive the charge therefrom, whereby the cooling compartment 20 is filled with articles, as indicated at 21 (Figure 1). Then the oven 132 is restored to vertical position and the cold batch of work in compartment 22 thereof is pre-heated by means of the hot batch just received from the retort 101.

The ovens may be shifted as a unit to bring.

any compartment into register with any re tort, said ways 121, 122 being part of a frame,

tion (Figure 3) and to drop it to receiving position (Figure 4). Thecarriage may be driven along the tracks 149 by means of a hand-wheel 150 whose shaft 151 carries a pinion 152 in mesh with a driving gear 153 upon the shaft 154 of the flanged rolls 148.

W The cover 154 for the pre-heating compartment 22 may be raised by means of a hand-wheel 155 (similar to 138) and connected by shaft 156 and worm 157 to the cover.

The bottom cover 158 for each of the cooling compartments 20 may be similarly opened by means of a hand-wheel 159 and shaft 160, having a worm 161, meshing with a worm-wheel 162 on the pintle 163 of the cover.

For convenience in reaching the upper (-ontrols, the operator may use two platforms 164 and 165. There are both front and rear control shafts 128 for raising and lowering the ovens, as seen at Figure 4, each provided with a bottom hand-wheel 118, and also just above the platform with a midway hand-wheel 118. There are two sprockets 126 on the transverse shaft 166 which carry the large gears 127, Figure 4. An extra carriage-controlling hand-wheel 150 may be placed at top of shaft 151. above the platform 164, Figure 4.

Variations may be resorted to within the scope of the invention, and portions of the improvements may be used Without others.

Having thus described my invention, I claim:

1. In a carburizing apparatus, a tireless pre-heater having a compartment for receiving a deposit of exposed hot carburizcd metal articles from a carburizing furnace and also having a separate compartment for receiving a deposit of exposed fresh cold articles,

said compartments having an upper communicating passage for heated gas to circulate from the articles exposed in the cooling com-' deposit of exposed fresh cold articles,saidcompartments having an uppercommunicating passage for heating gas to circulate from the cooling compartment to the heating compartment, and a lower communicating passage for cooled gas to circulate simultaneously from the heating compartment to the cooling compartment, said compartments being continuous and said passages in theform of portings in the Wall that separates the compartments, each compartment having an opening for the receipt and withdrawal of the exposed articles, and closures for the openings.

3. A carburizing apparatus having a fireless pre-heater composed of separate closed compartments for receivmg 1n exposed condition hot batches of Work from a retort, and

separate closed compartments for receiving in exposed condition fresh cold batches of .work, said cold compartments being coupled with the hot compartments, means being pro-. vided for causing repeated circulation of gas between each hot compartment and its associated cold compartment, to transfer sub-' stantial heat from the hot articles to the cold articles.

4. An apparatus for reclaiming heat from heat-treated metal articles and using the reclaimed heat in pre-heating other metal ar ticles, including a heat-treating retort mounted to swing about a horizontal axis so that the mouth may move up and down, and an oven having communicating compartments, one for receiving hot Work from the retort and the'other for receiving cold work to be heated up preparatory to discharging into said retort, said oven mounted to swing about a horizontal axis so that its mouth may move up and down for receiving work from and discharging work into the retort.

An apparatus for reclaimingheat from heat treated metal articles and using the reclaimed heat in pro-heating other metal ar-' and discharging work into the retort, and

being also mounted for raising and lowering.

6. An apparatus for reclaiming heat from heat-treated metal articles and using the reclaimed heat in pre-heating other metal articles, including a heat-treating retort mounted to swing about a horizontal axis, so that the mouth may move up and down, an oven having communicating compartments, one

for receiving hot work from the retort and the other for receiving cold work to beheated up preparatory to discharging into said retort,

said oven mounted to swing about a horizontal axis, so that its mouth may move up and down for receiving work from and discharging work into the retort, and being also mounted for raising and lowering, and a carriage upon which said oven is carried.

7. An apparatus for use with a battery of heat-treating furnaces mounted for swinging about horizontal axes, so that the mouth of each may move up and down, said apparatus including a plurality of ovens, each oven having communicating compartments, one for receivin hot work from the furnaces and the other %or receiving'cold work to be preheated by reclaiming heat from the hot Work, and elevators for said ovens, each oven being mounted for swinging upon its elevator for efi'ecting discharges. v

8. An apparatus for use with a battery of heat-treating furnaces mounted for swinging about horizontal axes, a plurality of ovens, each oven having communicating compartments, one for receiving hotwork from the furnaces and the other for receiving cold work tobe preheated by reclaiming heat from the hot work, elevators for said ovens, each oven being mounted for swinging upon its elevator for effecting discharges, and a carriage upon which said elevators are erected, said carriage arranged to present the ovens to different furnaces in the battery.

9. For use with a carburizing apparatus, a fireless work-pre-heater, including a closed draft-compartment to serve as a receptacle for confinlng in exposed condition a batch of hot carburized articles from a retort, and a closed draft-compartment to serve as a receptacle for confining in exposed condition a batch of fresh cold articles, passages being provided for effecting a thermo-syphon con- 1 stant circulation of gas through and between 0 said receptacles, and the batches of articles, and means for accelerating the circulation of gases.

- 10. For use with a carburlzing apparatus, a fireless work-pre-heater, including a draftcompartment for confining in exposed condition a batchof hot carburized articles from a retort, and a closed draft-compartment for confining in exposed condition a bath of fresh cold articles, the compartments having openings for charge and withdrawal of the articles and closures therefor, passages being providedfor effecting a thermo-syphon constant circulation of gas through and between said compartments, and a fan in the cold compartment for maintaining a constant circulation of gas between the compartments and through the batches of work.

11. For use with a carburizing apparatus, a fireless work-pre-heater formed to resist the high heat'of exposed metal articles received froma retort and having a closed compartment for confining said articles in exposed condition, and having another closed compartment for confining fresh cold articles in exposed condition, meansbeing provided for causing heated gas to circulate constantly through and from the cooling compartment to and through the pro-heating compartment and back to the cooling compartment, ackets of heat-resisting material enclosing said compartments, and separate heat-resisting removable closures for said compartments.

12. The combination of an oven formed to resist the high heat of metal articles received from a carburizing furnace in hot condition, said oven having a compartment for receiving said articles and having another compartment for receiving cold articles, means being provided in said oven for causing heated gas to flow from the cooling compartment to the preheating compartment and for the cooled gas to flow back from the preheating compartment to the cooling compartment, jackets of heat-resisting material enclosing said compartments, and a fan arranged in the lower part of the preheating compartment, said compartment having a grating covering the fan.

13. A fireless work-pre-heaterformed to resist the high heat of metal articles received from a metal-heating retort, and having a closed compartment for confining a batch of said articles in exposed condition and having another closed compartment for confining a batch of cold articles in exposed condition, means being provided for causing gas heated by the hot articles to circulate continuously from the cooling compartment to and through the batch of cold exposed articles confined in the pro-heating compartment and back through the batch in the cooling compartment, said pre-heater being provided with means to supply inert gas thereto; a restricted vent being provided in the pre-heater to permit the replacement of gas and air by inert gas.

14. The combination of an oven formed to resist the high heat of metal articles received from a carburizing furnace in White-hot condition, said oven having a compartment for receiving said articles and having another compartment for receiving cold articles, means being provided in said oven for causing heated gas to flow from the cooling compartment to the preheating compartment and for the cooled gas to flow back from 'the preheating compartment to the cooling compartment, jackets of heat-resisting material enclosing said compartments, heat-resisting means insulating said compartments from each other and protecting the compartments against the escape of heat, and a metal shell enclosing said heat-resisting means, and said oven having at its bottom alayer of heat-retaining material upon which are supported the floors of the compartments, said floors having flanges keyed, in said material, each compartment having a cover in the form of refractory material, the lower part of each side Wall of each cover setting down Within an annular channel formed in the top of the compartment.

' 15. For use vwith a battery of tiltable furnaces, each containing a retort, the combination of a series of ovens, each having a cooling compartment and a pre-heating compartment, hoists upon which said ovens are mounted to tilt, covers for the tops and bottoms of the compartments in said ovens,

means for opening and closing each cover,

means for raising and lowering said hoists,

- a carriage for said hoists and said ovens, to

enable the different compartments to service different retorts in the battery; said hoists being connected so that when either is lifted the other is lowered; and means for tilting either oven upon its hoist;

16. The combination of an oven formed to resist the high heat of metal articles received from a carburizing furnace in white-hot condition, said oven having a compartment for receiving said articles and having another compartment for receiving cold articles, means being provided in said oven for causing heated gas to flow from the cooling compartment to the preheating compartment and for the cooled gas to flow back from the preheating compartment to the cooling compartment, jackets of heat-resisting material enclosing said compartments, heat-resisting means insulating said compartments from each other and protecting the compartments against the escape of heat, and a metal shell enclosing said heat-resisting means, and said oven having at its bottom a layer of heatretaining material.

17. The combination of an oven formed to resist the high heat of metal articles received from a carburizing furnace in White-hot condition, said oven having a compartment for receiving said articles and having another compartment for receiving cold articles, means being provided in said oven for causing heated gas to flow from the cooling compartment to the preheating compartment and fonthe cooled gas to flow back from the preheating compartment to the cooling compartment, jackets of heat-resisting material enclosing said compartments, heat-resisting means insulating said compartments from each other and protecting the compartments aganst the escape of heat, and a metal shell enclosing said heat-resisting means, and said oven having at its bottom a layer of heat-retaining material, each compartment having a cover in the form of an inverted metal bowl, said coverof sufficient thickness to retain the heat and being interiorly channelled around its under side, each compartment having at its top a depending annular vertical flange confined within said channel to retain the heat, the bottom of the cover being in the form of a cup setting within the flange and having an out-turned brim, the bottom of the cover setting down below said brim to form f for causing gas heated by the hot articles to circulate continuously through and from the batch in the cooling compartment to and through the batch in the pre-heating compartment and back to the cooling compartment, jackets of heat-resisting material enclosing said compartments, heat-resisting inc-ans insulating said compartments from each other and protecting the compartments against the escape of heat, top and bottom communicating draft-passages passing through said insulating means between said compartments, a metal shell enclosing said 'heatresisting means, and openable means for closing the tops of said compartments.

19. For use with a case-hardening apparatus, a preheating oven formed to resist the high heat of metal articles received from a carburizing furnace, said oven having a closed compartment for receiving said articles and having another closed compartment for receiving fresh cold articles, means being provided for causing heated gas to circulate continuously through and from the cooling compartment to and through the preheating compartment and back to the cooling eompartment, heat-resisting means insulating said compartments from each other and protecting the compartments against the escape of heat, and a metal shell enclosing said heat resisting means,'said oven having at its bottom a layer of heat-retaining material upon which aresupported the flours of the compartments, said floors having flanges keyed in said material.

20. For use with a case-hardening apparatus, a preheating oven formed to resist the high heat of metal articles receivedfrom a carburizing furnace, said oven having a closed compartment for receiving said articles and having another closed compartment for receiving fresh cold articles,means being provided for causing heated gas to circulate continuously through and from the cooling compartment to and through the preheating compartment and back to the cooling compartment, each compartmenthaving a cover in the form of an inverted metal bowl, saId cover of sufficient thickness to retain the heat and having an interior channel around its under side, each compartment having at its top a depending annular vertical flange confined within said channel to retain the heat.

21. For use with a case-hardening apparatus, a preheating oven formed to resist the high heat of metal articles received from a carburizing furnace, said oven having a closed compartment for receiving said articles and having another closed compartment for receivingfresh cold articles, means being provided for causing heated gas to circulate continuously through and from the cooling compartment to and through the preheating compartment and back to the cooling compartment, each compartment having a cover in the form of an inverted metal bowl, said cover of sufficient thickness to retain the heat and having an interior channel around its under side,

each compartment having at its top a depending annular vertical flange confined within said channel to retain the heat, the

bottom of the cover being in the form of a tops and bottoms of the compartments in said ovens, and means for opening and closing each cover.

23. The combination of a series of ovens,

each having a cooling compartment and a preheating compartment, hoists upon which said ovens are mounted to tilt, covers for the tops and bottoms of the compartments in said ovens, means for opening and closing each cover, means for raising and lowering said hoists, and a carriage for said'hoists and said ovens, to enable the different compartments to service different retorts in a battery.

24. The combination of a series of ovens,

each having a cooling compartment and a preheating compartment, hoists upon which said ovens are mounted to tilt, covers for the tops and bottoms of the compartments in said ovens, means for opening and closing each cover, means for raising and lowering said hoists, and a carriage for said hoists and said ovens; to enable the different compartments to service different retorts in a batteryfsaid hoists being connected so that when either is lifted the other is lowered;

25. The combination of a series of ovens, each having a cooling compartment and a preheating compartment, hoists upon which said ovens are mounted to tilt, covers for the tops and bottoms of the compartments in said ovens, means for opening and closing each cover, means for raising and lowering said hoists, a carriage for said hoists and said ovens, to enable the different compartments to service different retorts in a battery,-and

means for tiltin either oven upon its hoist.

26. For a car urizing apparatus, a fireless preheating equipment for preparatory heating of a batch of confined cold articles by means of heat derived directly from a batch of confined articles in a hot condition, said equipment having means for causing a draft of gas heated by passage through the batch of heated articles to pass through the batch of cold articles to heat the latter, and including co-operative fiues, one flue forming a receptacle for confining the cold articles, and the other forming a receptacle for confining the hot articles, said flues having both top communication and bottom communication to establish a continuous circulation, up in one flue and down in the other, of the gases from the heated articles to the cold articles, each flue having a support upon which the articles may be depositedand directly exposed to the draft, and each flue also having an opening through which the batch of articles may be deposited and removed, and closures for the openings.

27. A fireless apparatus .for pre-heating cold articles preparatory to carburizing them, said apparatus having a flue forming a depository for confining in exposed condition hot metal articles from a furnace, and also having a separate flue serving as a depository for confining fresh cold articles in exposed condition, said fines having at one end a communicating passage for heated gas to pass from the cooling flue to the heating flue, and also having a communicating passage at the opposite end for cooler gas to pass simultaneously from the heating flue to the cooling flue.

GUSTAV W. SCHWAB.

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