US2571897A - Regenerative kiln - Google Patents

Description

Oct. 16, 1951 5 s, KlsTLER 2,571,897

REGENERATIVE KILN Filed Jan. 9, 1951 '5 Sheets-Sheet 1 Big] fizz/0 12b)" $AMUEL 5. K/5TLER fit torrze Oct. 16, 1951 s. s. KISTLER 2,571,897

REGENERATIVE KILN Filed Jan. 9, 1951 s Sheets-Shec 2 fizz/claw" SAMUEL 5 KLSTLER ,qccary y 1951 s. s. KlsTLER REGENERATIVE KILN i 5 m\\ Q vs 3 mm I I l l| v! m w 5 n NW SAMUEL 5. KISTLE nwyw z Aao r276 y Filed Jan. 9, 1951 Oct. 16, 1951 s. s. KISTLER 2,571,897

REGENERATIVE KILN Filed Jan. 9, 1951 5 Sheets-Sheet 4 I I Inmate? 5AMUEL S/(UTLER Patented Oct. 16, 19.51

- 2,571,897 7 REGENERATIVE KILN Samuel S. Kistler, West Boylston, Mass., assignor to Norton Company, Worcester, Mass., a corporation of Massachusetts Application January 9, 1951, Serial No. 205,210

17 Claims.

The invention relates to regenerative kilns, especially for firing w'are at high temperatures, of the order of cone 35 temperatures.

One object of the invention is to provide a kiln for the heat treatment of ceramic ware at cone 35 temperatures. Another object of the invention is to provide a kiln which can readily heat ware to a temperature of 1750 C. Another object of the invention is to provide a kiln, preferably of the above indicated characteristics, which is easily loaded and unloaded.

Another object of the invention is to provide an efficientkiln, for example one in which the exhaust gases pass to the outside air at temperatures of about 200 0., more or less, even while the temperature inside the kiln is at 1750 C., more or less. Another object of the invention is to provide a kiln of some of the above characteristics which will have a long useful life before it has to be rebuilt considering the high temperatures at which it is operated.

Another object of the invention is to provide a compact regenerative kiln. Another object of the invention is to provide a gas fired regenerative kiln of one or more of the characteristics indicated. Another object is to provide a kiln of the type indicated with mechanical features which render it highly practical and efficient in actual use. Another object is to provide an automatically operated and controlled regenerative kiln of the type indicated.

Another object of the invention is to provide a regenerative kiln having efiicient apparatus and arrangements for loading and unloading the ware. Another object is to provide a regenerative kiln with cars and tracks and at least two stations outside the firing chamber for the cars, whereby one car and its load can be cooling while another one is being unloaded or loaded.

Other objects will be in part obvious or in part pointed out hereinafter.

In the accompanying drawings illustrating one of many possible embodiments of the mechanical features of this invention,

Figure 1 is a plan view of the kiln and the loading and unloading mechanism thereof,

Figure 2 is a sectional view on an enlarged scale of a burner,

Figure 3 is a vertical sectional view of the fir ing portion of the kiln on an enlarged scale as compared with Figure 1, the section being taken on the line 33 of Figure 1,

Figure 4 is a vertical sectional view of the kiln on the same scale as Figure 3, the section being taken on the line 4-4 of Figure 1,

Figur 5 is a fragmentary sectional view on an enlarged scale of the pipe and fittings therefor that is shown at the lower right hand corner of Figure 4, the section being taken on the same line as Figure 4,

Figure 6 is a fragmentary detail, in section, of the door holding device, on an enlarged scale,

Figure 7 is a fragmentary elevation on an enlarged scale of the burner and pilot tube connections,

Figure 8 is a diagrammatic view of the cycle controlling mechanism,

Figure 9 is a fragmentary sectional View on an enlarged scale, the section being taken on the same'line as Figure 3,

Figure 10 is a front elevation of the door of the kiln,

Figure 11 is a sectional view on an enlarged scale taken on the line IIII of Figure 10.

Referring now to Figure 1, the parts of the entire apparatus comprise a kiln 10, a pair of kiln cars II, one of which is shown in Figure 1 and the other one in Figure 3, these cars I I having wheels l2 which are shown in Figure 3, a transfer car I3 having wheels I4 movable on a track comprising rails I5 and the'transfer car supporting rails It, a station I! having a track comprising rails I8 for the kiln cars II and a station I9 having a track comprising rails 20 for the kiln cars II. Also there is a track comprising rails 2! in the bottom of the kiln It for the kiln cars II, as shown in Figure 3. As indicated in Figure4, the rails I5 of the track for the transfer car I3 are at a lowlevel so that the rails It on the transfer car are on the same level as the rails 20 and 2I. Figure 1 shows by illustration of the ends of the rails 20 and 2| that the gauge of the tracks formed by the rails thereof is the same as the gauge of the track formed by the rails IE and likewise the gauge of the track formed by the rails I8 is the same as the gauge of the track formed by the rails I6. Thus, with the transfer car I3 located as shown in Figure 1 either kiln car II can be moved onto the transfer car I3 and a kiln car il can be moved into the kiln I0 whenever'the kiln It has no kiln car ll. Also the transfer car I3 can be moved to a position in front of station ll! to deliver a kiln car II thereto or receive one therefrom. It will now readily be appreciated that a kiln car II can be loaded with ware at station I1 or 9 while another kiln car II is in the kiln Ii) and when the war in the kiln I0 is fired, the kiln car II therein can readily be removed therefrom onto the transfer ashes? car 13, then transferred to whichever station I! or 19 is vacant for cooling of the ware, and thereafter th newly loaded kiln car II can be transferred by the transfer car 13 into the kiln It to fire a new load of ware while the old load is cooling down and is eventually replaced with green ware. Thus the kiln can be kept busy firing ware, with only short. intervals for transfer of kiln cars. It is quite within the scope of the invention to extend the track comprising the rails l5 and provide additional stations like the station 17 and additional kiln cars to as many as desired, but adequate results in ac tual practice have been achieved using only twov stations ii and i9 and two kiln cars H.

The entire apparatus is preferably supported and integrated by a massive concrete base or floor 25 having (Figures 1 and 4) a deep pit 2G in the floor of which the rails are imbedded, a shallow pit 21' (Figure 1) in the floor of which the rails 18 are imbedded, a shallow pit 28 (Figures 1 and 4*) in the floor of which the rails 20 are imbedded; and a shallow pit 23 (Figures 3 and 4) in the floor of which the rails 21 are imbedded. Referring now to Figure 3*, the base 25 supports rectangular brick foundations 30, one on either side of and extending above the top level of the pit 29' which is rectangular. Supported on the flat tops of the foundations 30 are steel plates 31 to which are secured, on the inner sides of the foundations 30', elongated L-shaped irons 32 constituting troughs to receive sand and forming part of sand seals. The steel plates 31 may have downwardly extending portions 33 in contact with the outer sides of the foundations 30 securely to fix the irons 32 in place.

Still referrring to Figure 3; supported by the horizontal flat tops of the steel plates 3| are rectangular parallelepipedal' masses ofbricks 34. These masses 34 form the outside ofthe bottom portion of the kiln 10. Inside of the masses 34 and in contact with them and also supported by the horizontal steel-top plates 31' are brick masses 35 the inner surfaces of which are irregular orsteppedi This irregular or stepped shape may be varied almost at will the shape shown being one of many satisfactory shapes. However, straight'horizontal lines can be drawn anywhere on these inner surfaces; the irregularity being in the vertical direction. These irregular surfaces, in combination with complementary surfaces on the cars H, reduce loss of heat through radiation.

Supported by the horizontal fiat tops of the masses34 and 35 a-re rectangular parall'elepipedal masses of bricks 36 having horizontal holestherethrough for burner tubes 3.! and pilot light-- ing tubes- 38. Themasses 33 may be fiushwith the masses 34 on the outside, but in this em-- bodiment of the invention'they are stepped back from the masses 35 on the inside to provide spaces 39 into which the ends of burner tubes 21 project. The pilot tubes 38- are just above the burner tubes 3l as indicated in'F-igures 3 and- 4. Gas introduced alternatively into the right and left hand banks of burner tubes 3l-is ignited by the flames from the pilot tubes 33 until thekiln gets hot enough whereupon the pilot tubes 38 are withdrawn.

Referring to Figures 3 and 9, supported on the horizontal top surface of the brack masses 3B and flush with the vertical surfaces thereof are vertical brick walls 40. Spaced from the brick walls 40:and outside of themand alsorest 4 ing on the masses 36 are vertical brick walls 41 having on the bottom thereof cut-outs leaving channels 42 extending from the outside to inside of the walls 41. A brick arch 43 rests upon the two walls 40 extending from one to the other thereof, thus, with the walls 40 defining a kiln firing space 46; A brick arch. 4'! rests upon and extends between the two brick walls 41 but is spaced from the arch 43 as shown, leaving a complete air space 50 between the arche 43 and 4'! and between the walls 40 and 41, this space being open to the outside air via the channels 42. This space 5.0 serves as an insulator in so far as conduction is concerned and convection. currents are limited by the balanced nature of the space. Of course, radiation across the space 50 doestake-place but heat loss is great- 1y reduced; by the double walls and double arches.

Referring now to Figures 3 and 4, arch shaped angle irons 51 are fitted over the ends of the outer surface of the brick arch H to strengthen the structure; and for the same reason these angle iron 5| are connected by U-shaped girders 52' at an upper level, U-shaped girders 53 at a lower level and angle. iron girders 54 at the ends of the arch shaped angle irons 51'. These parts 51', 52, 53' and 54 are conveniently made of steel and are welded together to form a frame work. As a further measure to hold the walls and the arches in line I may, as shown in Figures 1 and 3, provide vertically extending steel I beams 55, imbedded in the concrete base 25' and in contact with the outside of the brick foundations 30; the brick masses 3'4 and 36' and welded tothe angle. iron girders 54. Asa further measure of strengthening the structure I may provide angle iron girders 56' and 5-1 extending horizontally and connecting the I-beams being welded thereto;

Referring-now to Figure 4, resting on the floor of the pit 2'9 and extending across it at the far end thereof there is a rectangular parallelepipedal brick foundation 60; Referring also to Figure 5; there are two' rectangular orifices through this foundation 60 in which arelocated large steelair and gas pipes 61 which are rec tangularin cross'sectiorr. These pipes' 61- have e1bows-62 andfianges 63*whereby-t-hey are joined to flanges 64 on upwardly extending pipes 65c and 65b'. Steelplates 66 imbed'ded-in-the'foundation' (ill have horizontally extending studs 61 secured thereto which extend through flanges 68 secured to the'pipes 61 and which have springs fi'fl thereon backed by nuts 10 to urge the pipes 61' try the left of Figured, but permitting slight movement for thepurpose of making a tight seal with a portion of the kilncar' 11 for conducting airinto or exhaust gas from the kiln car;

Above the foundation 60 is a' mass" of bricks H- the inner surface of which is irregular or stepped. This irregular or stepped shape may be 'varied almost at will; the" shape shown being oneof 1 many satisfactory shapes; However, straight horizontal linescan' be drawn anywhere on this -inner surface'-the=irregularity being in' the vertical direction; This irregular" surface; in" combination with" complementary surfaces on the cars 11, reduces loss of heat through radiation.

Restingon the-rnass of bricks' 'll a-backwadl T2 made of brick-s: projecting forwardly from the otherwise inner plane surface of the back'wall '12 are-bricks 13 in a continuous course of bricks projecting into the air space 50 between-thewall'swo=and 4l"and Referring now to Figure 9' the arches 43 and 41. This construction prevents loss of hot gases from the furnace chamber into the air space 50 yet permitting an expansion joint I4 between the walls 40 and M, the arches 43 and 41, and the back wall I2. The outside arch 4'! caps the back wall I2 as indicated in Figure 4.

The bricks I3 also strengthen the arches 43 and 4'5, help to keep them from warping. Furthermore I find it is desirable to interlock the bricks of the arches 43 and 41 as by providing on each brick a projecting portion 15 and a recessed portion 16 so arranged as to interlock as shown in Figure 9. I

The kiln cars II are identical and are well illustrated in Figures 3 and 4. Flat car bottoms are formed by a plurality of (in this case nine) l-beams 85 running the length of the cars with three (or more or less) cross I-beams 8| extending transversely at one end of each car, a heavy perforated steel plate 82 and a heavy steel bottom plate 83. These parts are securely welded together to form a strong structure. Bearing brackets84, in pairs, are secured to the underside of the car bottoms and receive short axles 85, one for each wheel I2.

Side wall masses of bricks 81 rest on the car bottoms, one mass on each side of each car, and have inner surfaces which are vertical planes and outer surfaces formed complementary to the inner surfaces of the masses 35. A central wall of bricks 83 has vertical plane side walls and divides the space inside of each car into two parts, bounded by masses of bricks forming end walls 60 and SI. The spaces are further subdivided by brick walls 92, four in number on each side of each car in this embodiment of the invention, forming, in this embodiment, five chamhere on each side of each car. These chambers are filled with refractory pebbles or balls as illustrated in Figure 4. The pebbles or balls have not been illustrated in Figure 3 as to do so would confuse the drawing.

Welded to the edges of the steel plate 82 are depending strips of steel or iron 95 which project into the troughs 32 that are normally filled with sand, thus to form sand seals on either side of the kiln car II to keep the heat away from the steel parts including the wheels I2 of the underside of the kiln car II. The space underneath the kiln car I I, when it is in the kiln I I, is nowise connected to the kiln firing space 46 but on the other hand is in free communication with the outside air as will readily be seen from a, consideration of Figure 4.

Resting on the tops of the masses 90 and BI are two courses (more or less) of bricks I and MI respectively, extending from side to side of the cars II. Similarly, resting on the tops of each brick wall 92 are two courses (more or less) of bricks I52 extending from sideto side of the cars I I. Resting on top of the bricks I 00, IOI and I02 and on the wall 88 is a fiat top I03 of large refractory bricks. This structure leaves passages I54 from the chambers on each side of the cars I! to the spaces 39, there being in this embodiment of the invention, five passages I04 opposite three of which are the ends of the burner tubes by triangular pieces H5. This frame supports a sheet steel front IIB which is reinforced by a vertical central channel iron II! and transverse horizontal angle irons II 8, and the front '6 may be further reinforced by a rod I20 extending between brackets I2I welded to the pieces I II and I I2 and the rod I20 also extends through brackets I22 welded to the channel iron I". At the bottom of the frame, as shown in Figure 4, is a horizontal girder I24 welded to the pieces III, II2, I I3, and H4. This girder is I24 reinforced by a bottom plate I25 which rests upon the I-beams 8| when the door H0 is in place.

At the top of the door H0, as shown in Figures 4 and 10, flanges I26 are fastened to the pieces H2 and H3 and extending between the flanges I26 is a pin I2? which can be engaged by a hook to lift the door III) and remove it. This frame work made of steel is filled with and supports contiguous brick wall portions I28, I29 and I30. Referring especially to Figures 6, 7 and 10, bolts I3I are pivotally mounted on pins I32 secured to the I-beams 55 and can be moved into slots in plates I34 secured to the frame pieces II2 whereby springs I35 backed by nuts I36 on the bolts I3I will hold the door in place.

In order to place the door '0 in position as shown in Figure 4. and to remove it therefrom, I preferably provide any suitable apparatus such as a chain hoist I40 movable along the track formed by an I-beam I4I which extends from a girder I42 in a concrete abutment I of the building to a supporting girder I44 secured from overhead in any suitable manner, not shown. The chain hoist I40 has rollers I45 permitting it to move along the I-beam I4I which is preferably horizontal so that a workman, without very much effort, can move the heavy door III] after it has been lifted. At the bottom of the chain hoist I4!) is of course a block having a hook, not shown, for engagement with the pin I21.

For moving the kiln cars II and the transfer car I3 I preferably provide, as shown in Figure 1, a drum I48 operated by an electric motor I49 through a speed reducing mechanism I50, the motor sprocket being connected to the reduction gear sprocket by means of a chain I5I. When a couple of turns of the rope I are placed around the drum I48 and the free end of the rope I55 is pulled, a hook I55 at the other end of the rope I55 will be pulled with a powerful force. The

hook I56 is engageable with either end of plates I51 welded to the ends of the I-beams SI of the kiln cars iI for pulling these kiln cars in either direction. The hook I55 is likewise engageable with frame members of the transfer car I3 to pull it in either direction.

Strategically located pulleys I60, I6I, I62, I53 and I64 provide means whereby the pull of the rope I55 can be exerted in appropriate directions to pull the respective cars along the respective tracks as desired. For pulling a kiln car II out of the kiln I0 and/or into the station I9, it is sufiicient to use the pulley I63. For pullin a kiln car II from the station I?) onto the transfer car I3 and/or into the kiln Iii, it is sufficient to use the pulleys I and I62. For pulling the transfer car I3 from the remote position opposite the station II to the position shown in Figure 1, it is sufficient to use the pulleys I60 and I6I. For pulling the transfer car I3 from the position opposite the station I9 to the position opposite the station II, it is sufficient to use the pulleys I63 and I64. For pulling a kiln car II. from the transfer car I3 into the station II, it is sufficient to use the pulley I63. For pulling a. kiln car II fromthe station I'I onto the transfer sense? 1 as i i, it is sane-lent to the suiieys its and 164-. y

it not believed to be necessary to describe specifically every meinbe'r or the transfer car 13 which is preferably an open steel framework construction and the design of which can be varied almost without limit. The framework journals a pair of axles I15 upon which the wheels i i are mounted and there no necessity for spring suspension Since the movement is always 510W. As illustrated in Figures 1 and 4, .I preferably provide a lever l'H pivoted at 112 to the transfer ca-r l3 and having one engaging .a fork H3 on a rod H4 slidable in brackets I15 secured to the transfer car 13. When the tramin car is is in position to bring the rails 16 in line with the rails 2e and 2t, movement of the lever Hi to the left, Figure 4,- causes the rod I 14 to engage a hole in the concrete base to :secu-r'e the transfer car i3 in position while moving a kiln car i I onto it or off it and by simply moving the lever I'll in the opposite direction the transfer car i3 is released.

Referring now to Figure 3, gas may be provided by a pipe having on the end thereof an elbow I80 "connected to a vertical pipe 18!, connected to a throttle and shut-off valve body I82, connected to a vertical pipe I83, connected to an elbow 184-, connected by a pipe not shown to an elbow 186-, connected by a short horizontal pipe =18! to a T--union I38, connected to a horizontal pipe 489, connected to an elbow 98, connected by a pipe not shown to an elbow I92 connected by a horizontal pipe let; to a T union H34, connected by a short vertical pipe. 95 to a T-union .208 which is connected by short horizontal pipes .201v to valves 232 by the action of which the gas is alternately supplied to the right and left hand sides of the kiln l3. Referring now to Figures 1 and 3, the valves 222 are connected lay-horizontal pipes 283 to elbows 264, which are connected by horizontal pipes 285 to elbows 206, which are connected by horizontal pipes 287 to elbows 238, which are connected by vertical pipes 209 to el bows me. These elbo-ws 2l 0, one on eachside of the kiln H are connected to short horizontal pipes 21 I, shown only in Figure 7 and only one pipe 2! l is shown. Figure 7 shows a portion of the left hand side of the kiln; the arrangement of pipes is the sarne on the right hand side.

Referring now to Figure '7, the pipes 2 are connectedto T -unions 212 which are connected to horizontal pipes 213, which are conne'c'te'd to T-unions 214, which are connected to h0rizoiita1 pipes 2K5 which are connected to elbows 2V6. Referring now to Figure 3, the T-1iriions2l4 are connected 'by couplings 2}? to burner tubes "31, and the T-unions 2i2 and elbows 2i5 are similarly connected to burner tubes 37.

A The construction of the burner tube's is shown in Figure 2 and referring new "to "that figure, each burner tube "comprises 'an cn'ts'rie shell 22a and an inside shell zz'llavmg aspace between through which'water is circulated. The burner tubes have threaded -endsj2'22 for ednnection to "the couplings 2H 'a'iidthidilgh tl'ile's'e threaded ends "2'22 pass "water inlet pipes 213. The pipes 223 fork into two branches 2'24 and 225 each of which leadfwaite'r tbthe space betweejn the "shells 2 2 9 "than 1 "waiterbuue't' pipes 226 discharge the "water n-omfthe turner "tubes. B'y constant circulation of cold water through the burner tubes 31 they are kept from ineltirrg ii oer tn nnuen'ce gfjtire intense hea'tin'the kiln. Burrier"6rifices2 21poiiitupwardandcom n'ect the insides of the burner tubes 31 to spaces 39. Large, very hot flames extend upwardly from the orifices 221 along the insides of the walls so and high up the brick arch 43 when the burner tubes are ignited and of course it is understood that during the firing of the kiln only one bank of burner tubes is flaming at any given time.

Referring to Figure '1, the Water inlet pipes 223 are connected to an elbow 228 and T-unions 229 which are connected together by piping 230 leadme to a source of water supply. Similarly pipes 226 are connected to T-unions 232 and piping 233 which discharges the water.

Referring now to Figure 3, the T-union I88 is connected by a vertical-pipe 235 to a throttle and shut-off valve body 236 and the T-union 194 is connected by a horizontal pipe 231, elbows and piping 238, a horizontal pipe 239, an elbow 240 to a vertical pipe 24! which is connected to a throttle and shut-off valve body 242. These valve bodies 242 are connected to piping 243 having both vertical and horizontal portions, 2. horizontal portion being shown in Figure 7. This piping 243 is,- on each side of the kiln l0, connected to flexible hoses 245 each one of which has on the end thereof a pilot lighting tube 38. These tubes -38 are plain steel tubes and of course when the valves 236 are turned on .gas emerges therefrom and can be ignited. Once the kiln It] gets near its top operating temperature these pilot tubes 38 are 'no longer needed because .gas emerging from the burner tubes 31 will immediately ignite in the atmosphere of air provided due to the intense heat of the kiln.

Referring now to Figure 1 and 3, overhead girders25il support steel rods 251 and 252 which support frames 253 and 254 which support centrifugal blowers 255 and 256. The inletof the blower 255 is indicated at 251 and the blower 2-55 draws air from 'the room in which the kiln H) is located and thus in winter months it draws warmer air than could be procured from outside. This, of course, ventilates the room where the kiln i6 is located but enough heat leaks out-of the kiln Ill to keep the room reasonably warm. The blower 255 discharges air into'apip'e 258 which is connected to a valve 258. The valve 269 is likewise connected by a pipe 231 to the inlet side of the'blower 256. The valve 258 is likewise connecte'd'to the pipes 65a and t-5b. The outlet side of the blower 256 is connected to -'a pipe 252 which i a Smokestack leading to outdoors. 'Ihus-the'exhaust gases are discharged outside of the building and they have'been-found to be at temperatures of the order of 200-C. while the temperature in the space 45 is at l750 G. lhis 'indicatesthe eflicienc'y of the kiln. Referring to FigdreL-the blower 255-is driven-by a moto'rf'fiiand'the blower 256 is driven bya motor 265. By-having two blowers the pressure in the kiln firing space 45 can be maintained at "atmospheric pressure. With'only one blower the pressure in the space 46 would be either above or below "atmospheric depending upon whether the blower were driving air into: or suck-'- ing'a'i'rbut-o'f the-kiln and in' such event there would either be=a tendency for air toleak-into the kiln or for hot gases to leak out of the kiln. By using two blowers I avoid these'undesired eifets.

When the kiln isoperating air is forced either intctne pipe ssa crime the pipefifib and 'combustion gasesare withdrawn from theothe'r one. Let 'it -be='-assumed, -'tl-re'r'efore, that air is being bidwn iiito -'-t-he pipe 65a *by the blower 1 255 and kiln these pebble beds are hot; thus the incoming air is heated and it passes through the passages 104 into the left-hand space 39. There the heated air meets the gas emerging from the burner orifices 221 and either the kiln is so hot that combustion results or else the pilot tubes 38 ignite the gas. In either event three roaring flames travel upwardly along the inside of the arch 43 and by the time the gases reach the opposite space 39 combustion is complete. The gases of combustion pass through the right-hand space 39 and through the right-hand passages 104 down into the five pebble beds in the chambers on the right-hand side of the kiln car 1!, thus heating these pebble beds. Of course the number of ebble beds could be more or less than five. The hot gases heat these pebble beds and then pas downwardly'through the perforated top plate 92 and out through the pine 95b. through the blower 256 and out through t e smokestack 262 which incidentally can he made of sheet steel whereas in most kilns reaching the same temperature as this one brick chimneys have to be used for the exhaust gases.

It has been found that good results are achieved if the flow of air and gas is reversed about every four minutes. Of course when air is sent to the left-hand pebble beds, gas is sent to the left-hand burners, and when air is sent to the right-hand pebble beds. gas is sent to t e right-hand burners. By reversing the flow of air and gas about every four minutes I am ohabled to heat the ware in the kiln firing space 43 to the high temperature of 1750" C. and yet the exhaust gases in the smokestack 262 remain at about 200 C. This constitutes a high order of efliciency.

The mechanism for directing and reversing the fiow of air and gas is illustrated chiefly in Figure 8 which is diagrammatic. An electric motor 210 drives a pinion gear 211 which drives a large gear 212 which has a shaft 213 extended into a speed reducing mechanism 214 which has an output shaft 215 revolving once in every ei ht minutes. This rate of revolution of the shaft 215 can, however, be changed by turning a handwheel 218 as the s eed reducing mechanism 214 is preferably a variable one.

On this shaft 215 are cams 211, 218, 219 and 280. In order to show the shape of these cams the shaft 215 is shown in a series of sections, this being a diagrammatic presentation but which nevertheless clearly indicates the structure. The cam 211 operates a roller 28! carried by the movable element of a switch 282. The cam 218 operates a roller 283 carried by the movable element of a switch 284. The cam 219 operates a roller 285 carried by the movable element of a switch 288. The cam 280 operates a roller 281 carried by the movable element of a switch 288.

I provide a source of direct current electrical energy represented by positive power line 299 and negative power line 29!. The switch 232 is connected by wires 292 and 293 to the power line 290 and is connected by a wire 294 to a solenoid 295. The other end of this solenoid 295 is connected by a wire 296 and a wire 291 to the power line 29!. It will be apparent that when the switch 282 is closed, the solenoid 295 will be energized. The switch 284 is connected by a wire 298 to the wire 293 and is connected by a wire 299 to a solenoid 300 which is connected by a wire 30! to the wire 291 and therefore whenever the switch 284 is closed the solenoid 300 is energized.

Comparing now Figures 3 and 8, it will be seen that the solenoid 295 operates, through a link 302, a rotatable valve member 303 in the righthand valve 202, there being a spring 304 to close the right-hand valve 202 when the solenoid 295 is deenergized. Similarly it will be seen that the solenoid 300 is connected by a link 305 to a rotatable valve member 396 in the left hand valve 202 and a spring 301 closes the left-hand valve whenever the solenoid 300 is deenergized. The mechanical arrangement of these parts is clearly apparent in Figure 3. Figure 8 shows both valves 202 closed which is a state of affairs that lasts for a few seconds, say for about three seconds, to clear the firing space 46 of combustion gases before resuming firing. The solenoid 300 is about to be energized which will send gas to the lefthand side of the kiln.

Again referring to Figure 8, the switch 238 is about to close. This switch 288 is connected by a wire 310 to a normally closed relay switch 3!! having a relay coil 312, and the switch 311 is connected by a Wire 313 to the positive power line 290. The other side of the switch 286 is connected by a wire 314 to a reversible motor 315 having three terminals. The central terminal of the motor 315 is connected by a wire 316 to the negative power line 291 and hence, when the switch 286 closes, the motor 315 runs in a certain direction and that certain direction is clockwise to rotate a pinion 329 in a clockwise direction, to rotate a gear 321 in a counter-clockwise direction, to rotate a pinion 322 in'a counter-clockwise direction, to rotate a gear 323 in a clockwise direction. On this gear 323 is a lug 324 which is in engagement with a roller on a switch lever 325 and having a switch member 321 which, when the lug 324 is pressing against the roller on the lever 325, connects wires 330 and 33 1. The wire 33! is connected by a wire 332 to the positive power line 290 while the wire 330 is connected to a relay coil 333 of a normally closed relay switch 334. The other end of the coil 333 is connected by a wire 335 to the negative power line 29!. Consequently with the lug 324 engaging the roller on the lever 325 the switch 334 is open but it will close when the lug 324 leaves the roller on the lever 325.

Presently, through the action of the motor 315, the lug 324 will contact a roller on a lever 331 having a switch member 338 which when closedconnects a wire 339 connected to the wire 332 with a wire 340 leading to the relay coil 312 the other end of which is connected by a wire 34! to the negative power line 29!. Closing of the switch 338 energizes the relay coil 312 which opens the switch 311 thus breaking the circuit through the wires 314 and 318 to the motor 315 which stops the motor. Eventually, that is to say in the matter of about four minutes, the switch 288 opens again and the switch 288 closes by action of the cam 289 on the roller 281. This connects a wire 342 which extends to the third terminal of the motor 315 to a wire 343 running to the switch 334 the other side of which is connected by a wire 344 to the positive power line 290; Since this is a normally closed switch, and the switch 322i is open, electric current energizes the motor 3i 5 but this time in the opposite direction namely counter-clockwise which moves the gear 323 counterclockwise very quickly opening the switch 338 and deenergizing the relay coil 3!2. Ultimately, that is after a few seconds, the lug 324- again contacts the roller onthe switch 325 closing the switch 32'! which energizes the relay 333 opening the switch: 334' which stops the motor 315 until such time as the cam- 2'19 again closes the switch 286'.

Secured tothe gear 323 is an arm 35! connected by a link 35! to an arm 35% operating a. rotatable valve member 353 in the air valve: 256. Thus, at the moment illustrated in Figure 8, the gas is shut off from both sides of the kiln and air is flowing into: the pipe 651) and thus to the righthand side of the: kiln, and this is the moment at the end of four minutes of firing at the righthand side of the kiln, but gas and air are immediately going to flow to the left-hand side of the kilnas the solenoid is about to be energized and the valve 353 is about tobe moved to cut off the air from the pipe 65b and direct it into the pipe 65a.

For checking the temperature of the kiln in various portions thereof, I may provide pyrometer tubes. For example extending through the back wall 12 there may be a large tube 355 and a small pyrometer' tube 356. These tubes will normally be plugged during operation of the furnace and they can be used to insert temperature instruments into the firing space 46. To determine the temperature of the pebble beds I may provide a plurality of pyrometer tubes 35!} and 35!, the former extending through the door H0 and the latter through the masses of brick 99, through the walls 92 and through the pebble beds themselves, and each tube 360 is aligned with a tube 38!. Various other instruments such as instruments to measure the flow of air and the flow of gas may be provided but I do not deem it necessary to discuss these further.

One of the principal functions of the space 53 and the channels 42 is to accelerate cooling of the kiln without shocking the ware. For this purpose I provide passages 355 at the top of the kiln through the arch 4'! and removable bricks 366 cover these passages 365 when the kiln is being fired. When the firing of the ware is deemed to be completed, the bricks 333 can be removed and air is immediately drawn by convection through the channels 42 and up the space 56 exhausting through the passages 355. This cools the kiln reasonably rapidly without, however, producing any heat shock on the ware.

The shape of the arches 43 and M is a catenary curve which is that shape most adequately supporting itself when embodied in an. arch. The flames readily flow over the inside surface of the arch 43 without excessive turbulence.

The various bricks of which the kiln l0 and the kiln car H are constructed should be sufiiciently refractory to withstand the temperature conditions involved. The bricks of the arch 43 have to withstand higher temperatures than the bricks of the arch 41. I have actually used alumina bricks for the walls Ml, for the arch 43, for the inner portion of the walls 4! and for the inner portion of the arch 41. I prefer refractory bricks for the brick masses 35 but the masses as can be made of less refractory material. A satisfactory material for outer bricks which are not subjected to quite so much intense heat is kaolin. However I believe thatit is preferableto use mullite bricks for the. most refractory portions of the kiln and of the kiln car because the coefiicient of expansion of mullite is less than that of alumina. I have used alumina bricks practically throughout in the construction of the kiln car H but again I believethat mullite bricks would be preferable. However, alumina bricks have been satisfactory although occasional replacements are necessary when using them.

As heretofore stated the kiln cycle is customarily about eight minutes for a complete cycle or four minutes for a half cycle. That is to say the firing is at the left-hand side for four min-utes and then at the right-hand. side for four minutes and then at the left-hand side for four minutes and so on. In operation of th kiln the top of the car H is piled high with kiln furniture and ware and it is customary to fire the kiln continuously for about thirty six hours which is deemed to give cone treatment to the ware because it takes about thirty three hours toheat up the ware to the required temperature of 1750" C.

One of the outstanding features of this regenerative kiln is the location of the heat exchangers in the kiln car. This concentrates a great deal of the heat below the fiat top H13 upon which the ware and kiln furniture rest. Since the top and sides of the stack of ware are surrounded by live flame and indeed the spaces between the stack of ware and the door H0 and the back wall R2 are likewise at or near top temperature, the ware is evenly heated from all sides simultaneously. Furthermore this means that when the door H0 is opened-a great many British thermal units of heat are removed from the kiln by moving the kiln car llout of it. Of course this is only done after the temperature inside of the kiln has fallen to about 500 C. In the open air the kiln car i l cools down rather quickly and when it has cooled the fired ware can be removed and the car again loaded with green ware and kiln furniture.

It has been mentioned that, with the kiln firing space 46 at a temperature of 1750" C. the gases of combustion go up the pipe or stack 262 at the remarkably low temperature of about 200 C. This is due to the short half cycle, namely four minutes and also to the size and depth of the pebble beds. In other words to achieve this objective the regenerator needs large pebble beds, preferably quite deep and capable of absorbin a large quantity of thermal units of heat (calories or British thermal units). It is a great convenience in construction and repair to have these pebble beds located in movable units such as the kiln cars ll. Another great advantage in the provision of kiln cars, even though the are stationary during firing, is that loading and unloading is speeded and facilitated. The workmen never have to enter the kiln ID except for repair, and by providing two kiln cars H, there does not need to be any waiting for loading, since one car can be loaded while the other one is in the kiln, and transfers can be quickly made by reason of the arrangement of tracks, stations and car moving mechanism.

The pipe a and the pipe 651) as well as the pipes 61 and the elbow 62 are in effect ducts and any other species of duct may be substituted. It will be noted that these ducts continue right to the underside of the heat exchangers since the space bounded by the central I-beam and the I-beams 80 under the inside edges of the masses 8'! constitute a duct. The ends of the pipes 61 13 are rectangular and extend from the central I- beam 80 to the I-beams 80 under the inner edge of the masses 81 so the two I-beams 80 interior of those mentioned do not block the fiow of air or gases at all.

So far as certain features of the invention are concerned other types of heat exchangers could be used but the pebble beds have been found to be quite eificient in operation and are very cheap. While the description has mentioned the use of gas as fuel the kiln could be oil fired with no substantial change and therefore the burners 31 may be considered to be gas or oil burners.

The vertical brick walls 48 and 4! ar the side walls of the kiln while the arches 43 and 41 may be considered in efiect a top wall or a roof.

It will thus be seen that there has been provided by this invention heating appratus embodied in a regenerative kiln in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possibl embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth,

it is to be understood that all matter hereinbefore set forth is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. Heating apparatus comprisin a kiln having side top and back walls and a removable door, a track in the bottom of the kiln, a kiln car having wheels movable on said track, track means outside the kiln and alignable with the track in the kiln, a regenerator comprising at least two heat exchangers in the kiln car, means for forcing air through the exchangers alternately and into the kiln and for withdrawing waste gases through the exchangers alternately, and means for supplying fuel to the kiln for burning therein.

2. Heating apparatus according to claim 1 in which the heat exchangers are pebble beds.

3. Heating apparatus according to claim 2 in which the side and top walls are in the shape of an arch.

4. Heating apparatus according to claim 1 in which the side and top walls are in the shape of an arch.

5. Heating apparatus comprising a kiln, a first duct leading to the inside of the kiln, a second duct leading to the inside of the kiln, means to force air into the kiln and to withdraw combustion gases from the kiln said means being reversibly connectable to said ducts alternately to force air into the first duct while withdrawing gases from the second duct and to force air into the second duct while withdrawing gases from the first duct, a kiln car, a pair of heat exchangers in the kiln car each having an orifice alignable with one of said ducts when the kiln car is in the kiln, said kiln having a firing space, there being free inter-communication but at spaced locations between the kiln firing space and the heat exchangers, means to introduce fuel to said locations alternately, and operating mechanism to cause the air and fuel to go to first one location and then to the other one alternately to fire the kiln on the regenerative principle.

6. Heating apparatus comprising a kiln having an arch, a back wall, and a removable door, a bank of burners on one side of said arch, a bank of burners on the other side of said arch, a track in the kiln with rails parallel to the sides of the arch, a kiln car movable into and out of the klin on the track, a pair of heat exchangers in the kiln car, said heat exchangers connecting with passages leading to the burners, ducts connecting to the heat exchangers when the kiln car is in the kiln, valve means connecting the ducts, source of air under pressure connected to the valve, an exhaust stack connected to the valve, the valve being movable to connect the source of air to either duct while the other duct is connected to the exhaust stack, and valve means to connect fuel to either bank of burners.

'7. Heating apparatus as claimed in claim 6 having automatic control means to operate the valve connected to the ducts and automatic means to operate the valve means for the fuel synchronized to direct fuel and air to one side of said kiln for a certain time interval then to direct air and fuel to the other side of said kiln for a certain time interval.

8. Heating apparatus as claimed in claim '7 having two blowers, one forcing air into the kiln and the other withdrawing combustion gases from the kiln whereby to keep atmospheric pressure in the kiln.

9. Heating apparatus as claimed in claim 6 having two blowers, one forcing air into the kiln and the other withdrawing combustion gases from the kiln whereby to keep atmospheric pressure in the kiln.

10. A kiln car comprising a metal car bottom, a set of wheels supporting the car and connected to the car bottom, a mass of refractory material supported by the car bottom and shaped to provide a pair of spaces for heat exchanging means, heat exchanging means in each of said spaces, a pair of ducts formed in the car for conveying air to and exhaust gases from the heat exchanging means, and passages connected to the heat exchanging means remote from the ducts for delivering air to a kiln and collecting exhaust gases therefrom.

11. A kiln car as claimed in claim 10 in which the ducts are in the metal car bottom.

12. A kiln car as claimed in claim 11 in which the heat exchanging means constitute pebble beds.

13. A kiln car as claimed in claim 10 in which the heat exchanging means constitute pebble beds.

14. Heating apparatus comprising a kiln car, said kiln car having a set of wheels, a metal kiln car bottom supported on said wheels, a pair of refractory heat exchangers supported on said car bottom one on either side of said kiln car, a pair of ducts in said kiln car each open at one end of said car and each connected to one of the heat exchangers, a kiln having a track for the kiln car, a pair of ducts located in the kiln and having open ends in position to meet the open ends of the ducts in the kiln car when the kiln car is in the kiln, means to direct air through one duct in the kiln and to take exhaust gases through the other duct in the kiln and alternatable with respect to the ducts, and passages from the heat exchangers to the inside of the kiln.

15. Heating apparatus as claimed in claim 14 in which the ducts in the kiln car are in the metal bottom thereof.

16. Heating apparatus as claimed in claim 15 in which the heat exchangers are pebble beds.

17. Heating apparatus as claimed in claim 14 in which the heat exchangers are pebble beds.

SAMIUEL S. ICES'ILER.

No references cited.

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