US2020140A - Continuous tunnel kiln - Google Patents

Description

Nov. 5, 1935.. P. D'H. DREssLER 2,020,140

CONTINUOUS TUNNEL KILN Filed March 28, 1954 5 Sheets-Sheet, 1

lNvENfroR PH/L/P C17-I. DREsLL-R BY s; AWM

ATTORNEY P. 'Dl-l. DREssLER 2,020,140

CONTINUOUS TUNNEL KILN Filed March 2s, 1954 s sheets-sheet 2 Nov. 5, 1935.

P. DH. DREssLE-R 2,020,140

CONTINUOUS TUNNEL KILN Filed March s, 1934 5 sheets-sheet s Nov. 5, 1935.

Patented Nov. 5, 1935 UNITED STATES CONTINUOUS TUNNEL KILN Philip dHuc Dressler, Pittsburgh, Pa., assignor to Swindell Dressler Corporation, Pittsburgh, Pa.,

a corporation of Pennsylvania Application March 28, 1934, Serial No. 717,707

` 17 claims. (c1. :z5- 142) The present invention relates to continuous tunnel kilns in which goods, for example ceramic ware to be fired or glazed, are subjected to a heat treatment by advancing them slowly through an elongated kiln chamber on a movable hearth formed by the work supporting platforms of a train of cars extending through the kiln chamber, cars being added to the train at the entrance end of the kiln and being separated from the train at the exit end of the kiln in accordance with the train movement through the kiln. More specifically, the invention relates to continuous tunnel kilns of the type including munie-heating provisions, whereby the burning gases and products of combustion formed by the combustion of the fuel burned in heating the kiln, are wholly or largely kept out of the kiln goods space or out of the high temperature portion, at least, of said space. y

The general object of the present invention is to improve kiln heating conditions, and the invention comprises a method of intensifying the supply of heat to spaces in the bodies of the kiln cars beneath their work supporting platforms, by the radiation of heat from the surfaces of bodies associated with the combustion chambers of the muiiie heating provisions. The invention in some of its forms, also provides for an intensification of the heat supply to said car body spaces, by the passage of heating gases through said spaces from one side of the kiln to its other side. The invention also comprises novel features of kiln construction and arrangement whereby the intensified supply of heat to said car body spaces is effected. Kilns of the general type above mentioned and having muille heating provisions are well known, and a specic object of the invention is to secure the desired improvements in heating conditions in kilns which in respect to major features of construction, of the kiln cars as well as the kiln proper, may follow the standard and approved practices of the art.

More specifically stated, the improvements in heating conditions which it is the main object of the invention to provide, are concerned with an increase in the rate at which heat is supplied to the kiln car bodies, relative to the rate at which heat is supp'ied to the goods space proper of the kiln. In kilns of the type for which the invention is especialy useful, the kiln cars employed include body portions of a Weight and heat absorbing capacity which are substantial in comparison with, and/are frequently considerably greater than the weight and heat absorbing capacity, respectively, of the goods supported by the cars. In the practical operation of such kilns, each car inserted in the entrance end of the kiln ordinarily has a car body temperature substantially below the temperature to which the goods on the car are to be heated. The proper heating of the goods neces- 5 sarily requires a substantial heating of the car bodies which if their upper or goods platform portions do not heat up as rapidly as the goods which they support, necessarily absorb heat from the goods in the lower portion of the goods space of the kiln, and thereby prevent the goods adjacent the car platforms from heating up uniformly with the goods higher up in the goods space and less subject to the heat absorbing effect of the car bodies. The invention is especially useful in tunnel kilns of relatively moderate or small length, and in which the kiln time cycle, i. e. the time required for the movement of a car through the kiln chamber, is relatively short, as in such kilns the rate at which the goods are heated up to the maximum goods temperature attained is relatively rapid, and the rapidity of car body heating required for a sufciently uniform goods heating effect is correspondingly increased. Moreover, in such kilns, the weight and heat absorbing capacity of the car bodies relative to the weight and `heat absorbing capacity of the goods is frequently,

and indeed usually, higher than in longer kilns operating with a substantially longer time cycle.

The present invention comprises and is primarily characterized by provisions made for heating the car bodies by radiation from the lower portions of the combustion chambers extending alongside of, and supplying heat to the high temperature portion of the goods space of the kiln. The invention in some forms of embodiment is further characterized by and consists in provisions whereby the heating of the car bodies by radiation, as mentioned above, is supplemcnted by a car body heating effect due to the movement of heating gases through channels in the car bodies beneath the work supporting platform of the latter.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages a-nd specific objects attained with it, refercnce should be had to the laccompanying drawings and descn'ptive matter in which I have illustrated and described preferred forms of embodiment of the invention.

Of the drawings.:

Fig. 1 is a plan section of one longitudinal portion, and Fig. 1A is a similar section of the remaining longitudinal portion, of a tunnel kiln, the section in each figure being taken on the level of the line I-I of Fig. 3;

Fig. 2 is a somewhat diagrammatic representation oi.' means which may be employed in withdrawing Waste heating gases from the kiln shown in Figs. 1 and 1A;

Fig. 3 is a transverse vertical section taken on the broken line 3-3 of Fig. l;

Fig. 4 is a partial sectional elevation on the line 4 4 of Fig. 3;

Fig. 5 is a partialsectional plan taken on the line 5 5 of Fig. 3, and on a larger scale than gFigs. l and 1A;

ing sections A', A2 and A3, respectively, extend" ing in the order named between the entrance and exit end of the kiln. Beneath the goods space of the kiln are track rails B for the kiln cars C. Each of the latter as shown comprise a metallic under structure in which the car wheels are mounted, a refractory body portion C', girders C2 extending transversely of the car and supported on the body C and supporting the goods supporting platform C4 oi.' the car, the girders C2 being spaced away from one another to provide channels C3 extending horizontally through the car structure between the body C' and platform C4. Openings C*s in the platform C4 permit of! circulation of the kiln atmosphere between the goods space proper, of which the car platforms C4 form the movable bottom wall and the channels C2, which communicate at their ends with spaces between the side edges of the platfonn C4` and the adjacent stationary portions of the kiln structure.

As shown and above described the kiln cars are' of the usual type, and in their general form may be like the cars shown, for example, in my prior patent, 1,521,216 granted December 30, 1924.

The features of kiln construction and arrangement shown in Figs. 1, 1A, 3, 4 and 5 follow the usual practice of the art also, in that the car bodies are formed with projecting shoulder portions Cs which coact with adjacent parts of bench portions A4 of the kiln structure to provide tortuous passages minimizing the tendency Ito air or gas flow between the level of the tops' of the car bodies and benches, and the space through which the metallic under structures of the car move. Metallic webs C'z extending longitudinally of the rails B and carried by the upper portions of the metallic car under structures dip into sand filled channels at the sides of the cars to provide sand seals D against the passage of gases or air between the goods space and the space through which the car wheels travel. As shown, in the high temperature secticn A2 of the kiln the space last mentioned is open to the atmosphere beneath the bench portions of the kiln.

Above each -bench A4 in the high temperature portion A2 of the kiln there is a combustion chamber E extending longitudinally of that secing kiln section A'. Suitable provisions are made 5' for effecting combustion in the combustion chambers E. The heating provisions shown in Figs. 1, 1A. 3 and 4 comprise a plurality of oil burners F extending into each combustion chamber E at intervals along the length of the latter. lo The details of the burner oil and air supply provisions need not be illustrated as they form no part of the present invention, but may be and ordinarily are in accordance with the usual practice of this art. 'I'he burning gases and products 15 of combustion are moved longitudinally of the combustion chambers and nues E to outlets adjacent the entrance end of the kiln-connected to a suitable draft creating means which may include an exhaust fan, but as shown consists 20 of a stack G3. As shown in Fig. 1, the stack is connected by a duct G2 to outlets G in the bottom wall of they ilues E, each outlet G being provided with an individual adjustable throttling damperG'. 25

The above described gas exhausting provisions may'follow the usual practices of the art. In particular, they may comprise a single outlet G from each combusti-on chamber extension e adja cent the inlet end of the kiln, or as shown each 30 chamber e may have two outlets G, one adjacent the entrance end of the kiln and the other more remote therefrom. In such case, gases are conveyed from the more remote outlet G to the conduit G2 by a bypass channel g formed in each 35 bench A4. In some cases, such provisions as have been referred to, are desirably supplemented by special gas discharge provisions hereinafter described and including features illustrated in Fig. 2. 40

The bottom outer side, and top wall of each combustion chamber E are shown as formed by corresponding portions of the main masonry wall structure of the kiln chamber. 'I'he inner wall of each combustion chamber E is formed by up- 45 rising hollow tile sections H which rest at their lower ends on chambered refractory bodies I. The latter rest directly on the corresponding bench portion A4 and extend upward from thev latter to a level slightly below the undersides of 50 the car platforms C4, which preferably overhang the inner ends of the members I as shown in Fig. 3.

As shown the tile like wall forming members H are inclined to the vertical and have their 55 upper ends in leaning engagement with a ledge or shoulder Als extending downward into the corresponding combustion chambery from the crown or roof of the kiln structure. The channels in the tiles H are open at their upper ends to the portion of the goods space between the two combustion chambers adjacent the top of the space. As shown the upper ends of the tiles H are beveled of! to facilitate the circulation of the kiln atmosphere in streams which enter the tile channels through inner side wall openings H in the latter adjacent the car platform levels, and which leave the tile channels at the upper ends of. the latter. vUse of such hollow tile combustion chamber Wall forming members is not new with me, but on the contrary is and long lhas been a customary vfeature of the well known Dressler muilie heated kilns and is disclosed, for example, in Patents No. 1,170,428, granted February 1, 1916, and No. 1,348,488, granted August 3, l1920.

In kilns constructed in accordance withh the present invention, the use of the wall forming tile members H give the same general advantages oi' augmenting and directing the goods space at- *mosphere circulation and oi' protecting the sides of the stack of goods in the cars against undue absorption of radiant heat from the combustion chambers with resultant local overheating of the goods, which have led to the extensive use of such wall forming members as combustion chamber walls in prior tunnel kilns.

The members I are formed with channels or chambers I' which extend transversely to the length of the kiln and are open at their goods space ends between the levels of the lower and upper sides of the car body channels C3, so that heat may be radiated through each channel I into the car chemicals C3 and against the adjacent ends of the channel separating girders C. as the car channel and girder ends successively move past said channel I. The heat thus radiatedagainst the upper portion ofthe car structures is radiated mainly by parts P and Io in line with the channels I' Aat the ends of the latter remote from the goods space. Each part Iz forms a combustion chamber wall part permanently closing communication between the corresponding combustion chamber E and channel I'. The parts I2 are ordinarily appreciably greater in number than the parts 12, each of the latter being associated with a channel I' between groups of channels I' having their inner ends closed by parts I2, as shown in Fig. 5. Each part 12 is a body of refractory material shaped to serve as a plug valve which in the position ol the parts 12 shown in full lines in Fig. 5, enters and closes the end of the corresponding channel I. The latter may be opened for the ow of heating gases between it and the corresponding combustion chamber, by moving the corresponding part 12 into the combustion chamber, as indicated in dotted lines in Fig. 5, and as shown in Fig. 6. Each part 12 may thus be moved between its channel closing and opening positions by a suitable implement extended into the com-v bustion chamber through a normally closed opening A formed for the purpose in the outer wall of the combustion chamber.

The parts I2 may be integral web portions of the corresponding members I, but advantageously and as shown are in-the form lof thin separately `formed plates, which may be cemented or otherwise permanently secured in place in the corresponding members I, as this makes lt possible to form the parts I2 of silicon carbide or Xother refractory material having a higher thermal conductivity than any material out of which it is ordinarily desirable from the commercial standpoint for use to make the members I. The high heat conducting capacity of the parts I,

resulting from their thinness and the high ther-V mal conductivity of material of which they are made, is desirable because it increases the temperature attained by, and therefore the heat radiating capacity of, the surface of each part I2 which faces and radiates heat through the corresponding channels I' into the car chanthe part P9 will ordinarily `be such that lthe lat- \ter has less heat conducting capacity than is lpossessed by a part I.

To increase the absorption bythe car structures, and particularly by the goods platforms 5 C4 of the heat which is radiated through the channels I', I advantageously mount in the lower central portion of each channel C3 a refractory body ,of wedge shape with its apex or sharp edge uppermost and extending longitudinally of the car body. Each of the two inclined wedge surfaces C1 of the body'C is thus advantageously positioned to receive radiant heat from the adjacent members I or IA, and to reflect or reradiate the'heat so received upward against the l5 car platform C* and the upper portions of lthe girders C. lEach body C9 may well consist of a single piece of refractory material conveniently in the form of an inverted trough with closed ends, which is readily removable and re- 20 placeable if and-'when desirable. The use of such bodies C9 in the relation specied is of substantial practical importance. It has been found that in the operation of one kiln of the type illustrated in Figs. 1, 3 and 4, for example, 25 that as the goods treated are being heated up, the temperature of the goods adjacent the central portion'of each car platform averages from 30 to 40 hotter when the bodies C9 are in place than when they are removed, with conditions of 30 operation otherwise the same in each case. Such an increase in the temperature of the por- `tion of the goods which invariably tends to heat up less rapidly than the rest of the goods, as the latter are brought up to their maximum temperature, contributes substantially to a desirable uniformity of goods heating, and, in fact increases the kiln capacity by shortening the time cycle required to subject the goods to a given heat treatment.

Except in respect to special provisions, hereinafter described, which may be employed for withdrawing heating gases and regulating the pressures in the lues e, the general construction and arrangement of thepreheating section A of the kiln may be of any approved form customarily employed, or suitable for use, in a kiln of the general type disclosed. As shown, the iiues e have top, bottom and outer walls formed by the kiln wall structure as are the corresponding walls of the combustion chamber E. As shown also, the inner wall of each flue is formed by hollow tile members h which may be exactly like the tile members H-previously described, except that the members h have their lower ends extending into engagement with the corresponding bench portions Aof the kiln. and have their bottom side wall openings h between the levels of the tops and bottoms of the car channels C3. As shown, the inner ends of the members h are in leaning engagement with portions A50 projecting toward the goods space from the upper portions of the side walls of the kiln structure proper. The character of the cooling section A3 of the ,kiln forms no part of the present invention `and may be of any usual or other form suitable for use with the desired condition of kiln operation.

With the features of kiln construction and ar- 70 rangement shown in Figs. 1-6, the upper portions of the kiln cars may receive heat not only by radiation through the channels I', when desirable, but also as a result of the flow of heating gases from one combustion chamber E into the 75 4 otiiwtiirougii` some of the channels I' and, through carchannelsA. The special provisions for such flow of heating gases include the prev'iously mentioned members I, all or some of which may be adjusted to permit gas now through the corresponding channels I', and include provisions for preventing movement of the heating gases from -the channels C3 linto the goods space above the car platform C4, and include provisions for modifying lthe normally maintainedl balance between the gas pressures within the combustion chambers'E, so that' when the members I,2 are moved to their open position gases will pass into the channels C3 from one, and will pass from the channels C3 into the other of those combustion chambers.

In general, also, it is desirable to eliminate the flow obstructing effect of the bodies C. or to reduce that effect by reducing the height of the latter, andl as shown in Fig. 6` the bodies C are entirely removed, the additional heating effect of the. heating gas ow through the channels C3 being then relied upon to more than compensate for the loss of the localized heating action of the members C. n

The provisions illustrated for preventing gas ow between the goods space and the kiln chamber portion below the car platform C4 comprise refractory blocks Ca for closing the car platform openings C5, and means for maintaining sand seals J between the edges of the car platform C4 and the portions of the combustion chamber inner walls formed by the lower ends of the tile members H and the inner ends of the top wall `portions of the members I. The maintenance of such a sand seal J is facilitated by the fact that the sides of the car platform C4 overhang the members I.

The'material designated generically as sana which is employed in the sand seals J, is preferably a granular refractory material such as course sand or bitstone or fire clay grog, sufficiently coarse so that there is no appreciable tendency for it to ily into contact with the goods or onto the car platforms when displaced. The sand for maintaining the sand seals J may be supplied through one or more of the channels in the wall forming tile members H. Usually it is suiiicient to introduce sand for the maintenance of the sand seals J through a tile channel in each combustion chamber wall adjacent the entrance end of the kiln section A1, but sand for such purpose may be introduced through other tile channels distributed along the length of the section A2 as conditions make desirable. As shown each tile channel through which sand is thus introduced may receive sand through a pipe K extending down the channel through the kiln roof and connected at its upper end to a sand hopper K provided at its bottom with a slide valve member K? adjusted for the intermittent or restricted flow of sand through the pipe K. 'I'he sand discharged byr the latter collects initially in the lower end of the tile channel and overflows from the latter through the corresponding tile wall opening H' onto the adjacent ledge formed by the inner end of the top wall of the members I. As shown the upper sides of the latter are recessed to form a sand receiving channel I3. The longitudinal movement of the car platforms C4 works the seal forming sand longitudinally of said ledge and,'with the arrangement shown will cause some sand spillage oif the inner edge of the ledge, but the rate at which sand is thus wasted from the sand seals J, with the relatively slow car movement, is quite slow, and the sand wasted does not interfere with the kiln operation. To prevent the sand wasted from the seals J from accumulating on the benches A4, the upper inner corner edges of the latter may be g54 bevelled off'as indicated at A40 in Fig. 8. Most of the waste sand from the seals J eventually works into and assists in maintaining the lower sand seals D, though the latter may be independently supplied with sand in the usual man- 10 ner (not illustrated) adjacent the inlet end of the kiln.

Ordinarily the sand seals J need not extend beyond the ends of the kiln section A', since while this theoretically permits of gas flow be- 15 tween the end portions of the goods space and the subjacent portions of the kiln chamber and be low the car platform C, longitudinal flow through said space is comparatively slow in any event, and with the normal kiln pressure condi- 20 tions maintained such flow as may occur is ordinarily insignificant and harmless.' Flow in either direction through any channel I' may be regulated or prevented by the adjustment of the corresponding plug damper member 12. 25

When a. kiln of the type shown in Figs. 1-6 is being operated with 'no discharge of heating gases from either combustion chamber E except through the usual outlets G, the dampers Gl associated with said outlets are normally adjusted 30 to maintain equal pressures in the combustion chambers E and flues e at the same points along the length of the flue system. To induce a ow of gases through the channels I and Cs from one combustion chamber E into the other when 35 all or some of the members 12 are moved into their open position, the pressures in the two combustion chambers E must be unbalanced. Such unbalance may be effected by increasing the exhaust suction on one combustion chamber relative to that on the other and this may advantageously be effected by provisions of the character illustrated in Figs. 1 and 2.

The means for the purpose illustrated comprise auxiliary outlets g' from each ue adjacent the 45 entrance end of the kiln but preferably more remote from the latter than the duct G3. As shown each outlet g' is connected to the stack G3 or other exhausting device by pipes G4 and G5, the latter forming the stem of a Y connection of which the two bifurcations are formed by the pipes G4 each of which is connected to a corresponding one of the outlets g. A pivoted damper L is mounted in the connection for adjustment between two positions, in one of which one outlet g is in free communication with the conduit G5 while communication between the other outlet g' and the pipe G5 is cut off. In the second position of the damper L, the last mentioned outlet g" is in free communication with the conduit Gf' and stack G3.

Inv order that the flow through the channels C3 between the two combustion chambers E may alternate in direction at regular intervals, as is obviously desirable from the standpoint of suitable heating uniformity, means are advantageously provided to shift the damper L back and forth between its positions at regular intervals. Various controlled relay mechanisms suitable for such use are known. 'I'he means diagrammati- 70 cally illustrated in Fig. 2 for the purpose comprise a constantly running timing motor M which in practice may be a synchronous alternating current motor having a suitably slow speed shaft M. The latter carries a cam M2 oscillating a 75 bifurcated lever M3 pivoted at M4 and connected by a link N to the damper L, so that the latter will be adjusted from one operative position to the other at the end of each half turn of the cam M2. The speed of the shaft M' will ordinarily be such that the damper L will be shifted from one position to another at intervals of 10 or 20 minutes or so.

To thus alternately diminish the pressure in the combustion chamber E and its extension e relative to the pressure in the other combustion chamber'and its extension, requires, in general, that the normal discharge outlet G should be throttled somewhat more than is necessary or desirable when the kiln is operated, as it may be, without such unbalancing of the pressures in the two combustion chambers E and their extension ues. i

In some cases, it is practical and desirable to pass heating gases through'the car channels C3 without unbalancing the pressures in the combustion chambers, and in Figs. 7 and 8, I have illustrated an arrangement for the purpose in which the heating gases passed through the car channels C3 are supplied by auxiliary burners O especially provided for the purpose. The burners are distributed at suitable intervals along the length of each combustion chamber E of the kiln shown in Figs. 7 and 8, burning gases and products of combustion from each burner being discharged into the open outer end of a corresponding channel I. As shown in Fig. 8, the channel I' thus utilized for the passage oi' heating gases is closed against communication with the corresponding combustion chamber space by a tube or pipe section P of suitable refractory material having one end in engagement with the corresponding member I, and extending outwardly from the latter through the lower portion of the corresponding combustion chamber E into the side wall of the kiln structure. At its outer end each pipe section P receives burning gases discharged by the delivery nozzle or outlet O of the corresponding burner O. The burner O includes a gas supply nozzle coaxial with the outlet O' and terminating in a burner block P which opens at its outer end into an air supply channel A6 formed in the side wall of the burner chamber and receiving air for combustion from the external atmosphere or preferably from the cooling section A3 of the kiln, as `conditions make desirable. The gas jet discharged by the pipe supply nozzle of each burner O into the burner outlet nozzle entrains or draws into the latter from the passage A6, the amount of air required for the combustion of the gas. As those skilled in the art will understand, kiln heating gas burners of the general type of the burners O are well known in the art and hence their operation need not be further explained herein.

The auxiliary burners O at one side of the kiln chamber section .A2 alternate with the burners O at the opposite side of the kiln section, and in preferred arrangements each channel C3 receiving burning gases at its outer end from a burner O is in register with a channel I at the opposite side of the kiln having in association therewith a plug valve member 12 positioned for the suitable inflow into the adjacent combustion chamber of the heating gases from the burner O in alignment therewith at the opposite side of the kiln. For the proper inflow into each combustion chamber E of burning gases from the burners O at the opposite side of the kiln, it is not only necessary to properly adjust the corresponding plug dampers 12, but also to maintain a proper pressure in the combustion chamber. 'I'he pressures deslrably maintained in the two combustion chambers. may be the same, however, and preferably are the same or approximately the same as the slightly subatmospheric pressure which would ordinarily be maintained in the combustion chambers E if their damper members 11 were not open to receive gases passing through the car channels C3.

The alternate direction of heating ow through each car channel C3 resulting from its successive movements from a position in which one end of the channel receives gases from an auxiliary 15 burner O at one side of the kiln into a position in which it receives gases at its opposite end from an auxiliary burner 0 at the opposite side of the kiln tends to a suitable uniformity in the upper portion of the car structure.

2 The arrangement shown in Figs. 7 and 8 is ob- 0 viously simpler than, and preferable from thc operative standpoint to the arrangement previously described, but in general the use of the arrangement shown in Figs. '1 and 8 is restricted to 25 Vnarily kept as small as possible. Moreover low capacity oil burners such as are required for the relatively small heating eiects which the burners O need to supply, vrequire considerable attention to keep them in proper operative condition. Where gas is employed as the kiln heating fluid, multiplication of the simple burners required is relatively unobjectionable from either the construction or operation standpoint, small gas burners being easy to maintain in operation. In heating kilns with gas, it is customary to supply air for the combustion of the gas which has been preheated in the cooling zone section of the kiln, and the combustion chambers are ordinarily operated under pressures below the pressure of the atmosphere, so that the use of the auxiliary burners O as illustrated in Figs. '7 and 8 requires no change in combustion chamber pressure conditions or in the draft regulating provisions used in connection with the combustion chambers E of the kiln.

While in accordance with the provisions of the statutes, I have illustrated and described the best form lof embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set'forth in the appended claims and that in some cases certain features of my invention may be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:-

1. In a continuous tunnel kiln, the combination with the kiln chamber, of kiln cars for moving goods through said chamber, said cars having goods supporting platforms and spaces beneath said platforms, combustion heating means for heating the goods without contact of the latter with the heating gases, combustion chambers at the opposite sides of said kiln chamber, and

bodies of highly heat conducting material associated with said chambers and receiving heat directly therefrom and radiating heat into said spaces. v

2. In a continuous tunnel kiln, the combination with the kiln chamber, of kiln cars for moving goods through said chamber and each comprising a goods supporting platform and transverse channels beneath said platform, combustion chambers at the opposite sides of said kiln chamber having thin heat radiating wall portions facing the ends of said channels, and means within and extending transversely of said channels adapted to absorb heat radiated into said channels and to radiate heat upward against the car platforms.

3. In a continuous tunnel kiln, the combination with the kiln chamber of kiln cars for moving goods through said chamber and each comprising a goods supporting platform and transverse channels beneath said platform, combustion chambers at the opposite sides of said kiln chamber having thin heat radiating wall portions facing the ends of said channels, and means within said channels having heat absorbing and radiating surfaces inclined downwardly and outwardly.

4. In a continuous tunnel kiln, the combination with the kiln chamber, of kiln cars for moving goods through said chamber and each comprising a goods supporting platform, and combustion means for heating the goods without contact therewith of the heating gases comprising combustion chambers at the opposite sides of said kiln chamber, each having an inner Wall comprising a portion of relatively low heat radiating'capacity above the car platform level and a portion of relatively high heat radiating capacity below said level and facing and adapted to radiate heat into the portion of the cars below said platforms. Y

5. In a continuous tunnel kiln, the combination with the kiln chamber, of kiln cars for moving goods through said chamber and each comprising a goods supporting platform, and combustion chambers at the opposite sides of said kiln chamber, each having an inner wallportion below the car platform level formed with a set of longitudinally distributed ports and a set of longitudinally distributed thin heat radiating wall parts between said ports and adapted to radiate heat into the portions of the cars below said platforms.

6. In a continuous tunnel kiln, the combination with the kiln chamber, of kiln cars for moving goods through said chamber and each comprising agoods supporting platform and transverse channels beneath said platform, and combustion heating means for heating the goods without contact of the latter with the heating gases, combustion chambers at the opposite sides of said kiln chamber having thin heat radiating wall portions facing the ends of said channels and formed of refractory ceramic material of relatively good heat conductivity.

7. In a continuous tunnel kiln, the combination with vthe kiln chamber, of kiln cars for moving goods through said chamber and each comprising a goods supporting platform and transverse channels beneath said platform, and combustion chambers at the opposite sides of said ing goods through said channels and each hav- 5 ing a goods supporting platform and transverse channels beneath the latter, and combustion chambers at opposite sides of the kiln chamber each including a wall portion at the level of said channels formed with openings distributed 10 along the length of the kiln and thin plates of refractory material of high thermal conductivity extending across said openings.

9. In a continuous tunnel kiln, the combination with the kiln chamber, of kiln cars for mov- 15 ing goods through said chamber and each in` cluding a goods supporting platform and transverse channels beneath the latter, and combustion chambers at the opposite sides of the kiln chamber having wall portions at the level of 20 said channels having ports therein distributed longitudinally of the kiln and portions alternating with said ports and radiating heat into said channels.

10. In a continuous tunnel kiln, the combina- 25' tion with the kiln chamber, of kiln cars for moving goods through said chambers and each comprising a goods supporting platform and transverse channels beneath said platform of kiln, heating means comprising a combustion cham- 30 ber at one side of said chamber and having a lower wall portion adjacent and facing the ends of said channels and formed with ports distributed longitudinally of the kiln and including thin heat radiating portions between said ports. 35 means for effecting combustion within and withdrawing combustion products from said combustion chambers and means for passing hot gases through said channels and ports into said combustion chamber. y Y 40 11. In a continuous tunnel kiln, the combination with the kiln chamber, of kiln` cars for moving goods through said chambers and each comf prising a goods supporting platform and transverse channels beneath said platform of kiln, 45'

heating means comprising a combustion chamber at one side of said chamber and having a lower wall portion which is adjacent and faces the ends of said channels and which is formed with ports distributed longitudinally of the kiln and 50 which includes thin heat radiating portions between said ports, means for effecting combustion within said chamber and for maintaining a pressure therein which is different from the pressure in said channels. 55

12. In a continuous tunnel kiln, the combination with the kiln chamber, of kiln cars for moving goods through the kiln chamber and each comprising a goods supporting platform and transverse channels beneath said platform, kiln 60 heating means comprising combustion chambers at each side of the kiln chamber and each having a lower wall portion adjacent and facing the adjacent ends of said channels and formed with ports distributed iongitudmauy of the kun and 5 including heat radiating portions alternating with said ports, means for effecting combustion within said combustion chambers and means for maintaining different pressures in said combus- 7o ,tion chamber whereby heating gases will Ypass moving goods through the kiln chamber and each comprising a goods supporting platform and transverse channels beneath said platform, kiln heating means comprising combustion chambers at each side of the kiln chamber and each having a lower wall portion adjacent and facing the adjacent ends of said channels and formed with ports distributed longitudinally of the kiln and including heatradiating portions alternating with said ports, means for effecting combustion within said combustion chambers and means for periodically modifying the pressures in said combustion chambers to thereby pass heating gases between said combustion chambers through said channels alternately in opposite directions.

' 14. In a continuous tunnel kiln, the combination with the kiln chamber, of kiln cars for moving goods through said chamber and each comprising a goods supporting platform and transverse channels beneath said platform, a combustion chamber at each side of said kiln chamber having an inner wall portion below the car platform with a set of longitudinally distributed ports therein adapted to register with the corresponding ends of the said channels in the cars as the latter are progressively advanced through the kiln chamber, the ports in each of said wall portions being staggered with respect to those in the other wall portion, and means at each side of the kiln chamber for passing heating gases into the said ports at the opposite side of the kiln chamber through the corresponding car channels.

15. In a continuous tunnel kiln, the combination with the kiln chamber, of kiln cars for moving goods through said chamber and each comprising a. goods supporting platform and transverse channels beneath said platform, a combustion chamber at each side of said kiln chamber having an inner wall portion below the car platform with a set of longitudinally distributed ports therein adapted to register with the corresponding ends of the said channels lin the cars as the latter are progressively advanced through the kim chamber, the ports m' each of sala wan 5 portions being staggered with respect to those in the other wall portion, andgas burners at each side of the kiln chamber in register with the said ports at the opposite side of the kiln chamber for passing heating gases into the last mentioned 10 ports through the intervening car channels.

16. In the operation of a continuous tunnel kiln through which goods are moved on kiln cars having goods supporting platforms and car body spaces beneath said platforms, said kiln having 15 combustion chambers at its sides for heating the goods on said platforms, the method of intensifying the heat supplied to the portions of the goods immediately above said platforms which consists in radiating heat into said car body spaces from 20 highly-conducting heat radiating surfaces directly absorbing heat from said chambers while preventing the heating gases from coming into contact with the goods.

17. In the operation of a continuous tunnel 25 kiln through which goods are moved on kiln cars having goods supporting platforms and car body spaces beneath said platforms. said kiln having combustion chambers at its sides for heating the goods on said platforms, the method of intensify- Y9,0 ing the heat supplied to the portions of the' goods immediately above said platforms which consists in radiating heat into said car body` spaces from highly conducting heat radiating surfaces directly absorbing heat from said chambers and passing heating gases through said spaces from a portion of the kiln at one side lof said spaces to a portion of the kiln at the other side of said spaces.

PHILIP n'noc nnnssmn. o

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