US1525130A

US1525130A - Tunnel kiln

Info

Publication number: US1525130A
Application number: US445827A
Authority: US
Inventors: Winfield E Hinsdale
Original assignee: Individual
Current assignee: Individual
Priority date: 1921-02-17
Filing date: 1921-02-17
Publication date: 1925-02-03
Anticipated expiration: 1942-02-03

Description

Feb. 3. 1 925.

W. E. HINSDALE TUNNEL KILN 5 sheds-sheet 1 Filed Feb. 17, 1921 INVENTOR By Attorneys,

Gagw,

Feb. 3. 1925. 1,525,130

w. E. HlNsDALE TUNNEL KILN Filed Feb. 17, 1921 5 Sheets-Sheet 2 Feb. 3. 1925.

` w. E. HINSDALE TUNNEL KI LN By Attorneys,

am@ L OMA y INVENTOR Feb. s. 1925. 1,525,130 w. E. HINSDALE l TUNNEL KILN Filed Feb. 17, 1921 5 Sheets-Sheet 4 INVENTOR 1 @Md/L@ By A Horneys,

'Fem 3.1925 1,525,130

W. E. Hl NSDALE TUNNEL KILN Filed Feb. 17, 1921 5 ShetS-Shet 5 Fb@ J4.

INVENTOR is? By Attorneys,

Patented Feb. 3, 1925. A

UNITED STATES PATENT OFFICE.

TUNNEL KILN.

Application led February 17, 1921.

articles or materials to be subjected to heat' treatment are loaded on suitable cars and caused to progress contlnuously or intermittently through a tunnel chamber. In such kilns, it is customary to divide the structure longitudinally into three sections, of usually unequal length, the first section being that in which the material under treatment is first warmed and then pre-heated, this portion of the kiln being designated the heating or heating-up zone; the intermediate section, wherein vthe heat treatment is performed, will be herein referred to as the torridzone; the final section, in which the articles or materials, after heat treatment, are gradually cooled, is designated the cooling or cooling-01T zone.

Tunnel kilns have heretofore been of two types; namely, those in which direct combustion'has been maintained in the tunnel chamber, so that the ire gases or products of combustion have come into direct contact with the wares. or materials under treatment; and those of the muiile type, in which a thin inutile wall or partition has enclosed the tunnel chamber and separated it` from the adjacent chambers or flues in which the combustion occurs, and wherein circulate the fire gases or products of combustion.

The present invention provides improved constructions of tunnel kilns, its object being to avoid certain disadvantages heretofore inherent in kilns of this type, and to improve the eiciency, economy, certaint of operation, and ease of control of such kilns. More specifically, it aims to combine the advantages of both the combustionchamber type and-mule type 4or tunnel kilns, and produce such a kiln which, among other uses, shall be practicable and advantageous for the burning of chinaware, porcelain and other earthenware, while avoiding the necessity of enclosing such wares in the usual saggers or protecting boxes for sealing the Serial No. 445,827.

ware from the action of gases that may be present in the kiln. Other important ob- ]ects are to secure continuous operatior of the k1ln, to provide for ready inspectica of the interior parts during operation, to provide for repairs without lnecessitating the cooling down of the kiln, so as to avo'.`d loss of goods undergoing treatment at the time when .repairs become necessary, to insure durablhty of the members or elements of the tunnel, by enabling them to 'endure changes of temperature in heating or vcooling, to provide for vmaintaining a vsubstantially fixed atmosphere within the torrid zone, while maintaining a continuous but slow circulation of air through the tunnel for the removal of super-heated vapor given ol" from the advancing wares previous to their entering into the torrid Zone, and for enabling efficient control to be maintained of the temperature in the torrid zone, as well as of ,the duration vof time during which the goods are exposed to such temperature.

Toattain these advantages, the invention provides certain improved constructions, the nature of which -will be developed as the description proceeds. One important feature is the provision for heating the kiln electrically, by means of successive electric furnace units which may beindividually' inspected and controlled from the exterior, and which, inr case of need, may be individually removed and replaced without interrupting continuity of the heat treatment in the kiln.

In the accompanying dra-Wingspaplan is given in Fig. l and the other longitudinal views are divided into three equal portions, designated ,respectively as Figs. 2, 2a, 2b, etc., of which the first in each stance covers the entering portion of the kiln, in traversing which the goods are preheated;the second includes the torrid zone and more or less of the pre-heating zone and the initial portion'l of the cooling zone; and the third includes the major portion of the cooling4 Zone, leading to the exit or emerging end of the-tunnel.

Figure l, is a plan of the tunnel kiln. Figs. 2, 23 and 2b are a vertical longitudinal mid-section thereof.

Figs. 3, 3a and 3b are a longitudinal horizontal section, thev plane of which through `the torrid zone, is indicated by tie line 3* in Fig. 14.

in; g

Figs. 4, 42l and 4" show the the kiln in side elevation.

Fig. is an end view or elevation of the entering end.

Fig. 6 is a! transverse section on the line 6-6 of Fig. 3.

Fig. 7 is a transverse section on the line 7-7 of Fig. 3. Fig. 8 is a transverse section, in the plane of line 8 8 in Fig. 3.

Fig. 9 is a transverse section, on line 9 in Fig. 3.

Fig. 10 is a transverse section, on line l. in Fig. 3a.

Fig. 11 is a transverse section on the line 11-11 in Fig. ab.

' .'Figf12 is a transverse section on the line 12-.12 .in Fig. ab.

Fig. 13 is an elevation of the outlet on emerging end of the kiln.

Of the foregoing views, Fig. 1 is on a greatly reduced scale. Figs. 2-4 are on a larger scale, Figs. 5 and 13 are on an intermediate scale, and Figs. 6-12 are on a still larger scale.

Fig. 14 is a transverse section through the torrid Zone, on the line 14-14 in Figs. 3 and4, the electric furnace at the right being shown in itsl operative position, and that at the left removed for repairs; the view being on a larger scale than Figs. 6-12.

In the several views, the same reference letters or figures designate the same or corresponding parts, throughout.

In generah the kiln is built at its ends with an outer shell of iron or steel plate, suitably strengthened by ribs, and, in the central portion exposed to heat, is constructed of suitable refractory material, with open-y ings formingl dead air spaces or fines, as will be described. in detail. The tunnel chamber has track rhils laid through it longitudinally, on which may travel the cars or platfrm's'ccarrying the material under treatment. At the entering end and at the outlet or emerging end are doors which may be closed in a nearly air-tight manner, after the introduction and discharge of successive cars.

Referring to the drawings, A designates the tunnel chamber, closed normally by a door a. at its entering end and by a door b at its outlet or emerging end. The wares are carried through. on cars B, of any suitable construction, having, as usual, a refractory bed or hearth, which, in use, forms the bottom of the tunnel chamber. The construction shown in Fig. 14 will serve as a suitable illustration of the cars, one of which is shown at B in Fig. 2a. In both these figures, the dotted outline r indicates the extreme dimension of the stack of goods or wares carried by the car, and very nearly filling the tunnel chamber A. The hearth portions of the successive cars fit together so as to form a continuous union.

The tunnel kiln is divided into a succession of 4sections or zones, which may differ in construction, as will now be described:

Of these zones, C is the first warming zone; D the second warming zone; E.the pre-heating zone; F the tiring or torrid zone; G the rst cooling `zone; H the second cooling zone; and J the iinal cooling zone, adjacent the outlet The first warming zone C is Shown in Figs. 1-4 and the left of Fig. 6. The portion C of the tunnel chamber A forms the inlet chamber of the tunnel. The construction of this zone is-shown as having side walls 20 of iron, which may be formed of cast-iron plates or sections bolted together with their flanges preferably on the inside, the better to interfere with any air currents that may seek to' fiow between the stacks of wares and the chamber wall, thus breaking .up such currents and forcing them towards and through the wares. The roof 21 is best constructed by crossingthe chamber with ordinary T-irons and bridging the spaces between with -ordinary flat arch hollow tiles. This style of roof prevents too rapid absorption of heat and gives economy of construction.

The second warming Zone D, which encloses a section D of the tunnel chamber A, is shown in Figs. 1-4 and the right of Fig. -G. The construction shown is the same as that of zone C, except that the walls 22 are double, being spaced Vpreferably about 6 apart, so as to enclose between them an air space or flue 23. At the entering end of zone D, the flues 23 on opposite sides open upwardly into an air box 24, Fig. 4, forming within it a cross-over flue 25, Figs. 2 and 6, which communicates with'the inlet of an exhaust fan 2G, the purpose of which is to exhaust the air from the air fiues 23 between the walls on opposite sides of the tunnel chamber. A.

Underlying zones Gand D, is a continuous foundation 29, Fig. 2, having side walls 30, which underlie the

iron panel walls

20, 22. .These iron walls are at one end firmly secured to the foundation ofthe first panel or panels nearest the pre-heating zone E, while the remainder of the iron work of these zones is free to expand longitudinally on such supporting base. For this purpose, the flanges of the cast iron plates may be united by bolts engaging enlarged or slotted bolt holes. as is common.

The pre-heating zone E is shown partly in Figs. 1-4 and partly in Figs. 2a-4a, and in the cross-sections Figs. 7 and 8.

The enclosed portion of the tunnel chamber A in zone E is lettered E. In this portion E of the tunnel chamber, the wares are progressively pre-heated as they approach the torrid zone. This pre-heating zone E is constructed with. an exterior shell or casing 32, of brick or tile masonry, suitably stiffened or reinforced by vT-iron vribs orv loads of stacks or wares earriedby the car platforms orfhearths, and the-wares are stacked 'to a height :to barelypass through the tunnel with safety. 'By reason thereof,

the successivecarloads of wares form, in efother framing 33. Toward the-hotter end,

i fectfa Yfairly tight closure or stopper for a refractory ning 35:-is provided, which may be made up of refractory brick Ortner-substantially preventing the flow 'of :air be- The `roof of zone E lis builtiof masonry in tween the stacks of wares and the inner arch'form, the thrust ofthe arch "being walls of .the tunnel chamber. This conditaken up by lateral members 36 of the metal tion continues until theV zone-E is reached,

Jframing, these .being shown as T-irons tying wherein the chamber E is abruptlyl widened' 1 f horizontallyH between the extended upper- (see Fig. 3), so that the advancing oarloids" .endsof the upright side -frames 33.- 1 The of wares enter'into a wider tunnel chamber,

masonry arch 3 has a lining 38 covering the which chamber, however, is etfectually .shut

bers C and D',

As the metal construction of zones C and; and wares illin D, andthe masonry Aconstruction otzone E, v '.1'he`inner re actory lining have different ratios of expansion,` and the hotter part o f the tunne .tinuation of the side linings 35. by

t ese chambers.'

chamber E -these zones are subjected to ywidely dissimiis free to expand longitudinally independlar temperatures, an' 'exglansion jointis ently of the outerv wall, as ithas no abutment Y formed at the junction o zones D and E. therewith, except where .the walls are wid- For urpose, the

masonryvwalls

32, 34 lened at 51 (Fig. 3") ad'acent to the entrance are exten ed so as tooverlap the end porto the firing chamber of the torrid zone. tion of the zone D, being extended inward at 40 to meet the outer wall 22, and rated from the preheating chamber by a hotter longitudinal portion, forminga cono from the first and second'warmin cham.A

the presence of t e cars The tiring chamber F is partiall. sepa- 3 5, enclosing an inwardly extending pier 41 on eaclrsrde, contraction-rin the wall at 52.v vThis conwhichmeetstheextended portion 22 of the tracted portion 'constitutes a portalto the w" inner wall of, 'the zone D. The. contact befillng Gham'bel'- Th Walls' 0f this portal tween the portions orY piers- 40, 41, and the 'are locatedfto -form a tunnel opening of 'respective walls of zone D, is a sliding corrpreferably the same dimensions as the walls tact, so that either section of the structure of the chambers Cf D, aifording'as'close an' may slide 'longitudinallywith diiferences of approach as is practicable to fthe load or "tern rature.- stack of wares (win Fig.'14), so asto form T e piers' 40 and 41 are longitudinally a partial seal around the'stacksof wares for separated (by preferably about slx feet) to obstructing, the HOW '0f 'air 'Passing' them; form on each side anintervening chamber In this manner, vthe tiring chamber is. apor air space 42; and the piers 40,A 41 areexproximately shut oi from the-.preheatng `tended overthe top, as'sh'own'- in Fig.- 2', chamber.-

forming larches 40', 41", the structure being n Y 'An expansion joint is formed between .the

icov

` extended upwardly at 43 and formin over tunnel walls ofthe preheating zone E and v.

thetop, an extended flue or air cham r 44, firing zone F, being conveniently formed asv .shown in Fig.l 2. These air chambers between the portal 52 andthe expanded por- 23, 23. Extended through the remainder-of pansion .joint is formed by one wall overlapthe zone E, on each side of the tunnel champing the other with a sliding. lit admitting ber E,-are arranged hot air pipes 5:0,y of of expansion or contraction. 'In the con'- suitably refractory material, such as cast struction shown, the portal wall is' made rightl stacks, as shownin Figs. and 8v. -The embrace the end portion ofthe wall'l, -ends of these plpes are carried through the while the inner wall 54 is extended inside piers 41, and open freely into lthechambers thereof in such manner ,as to form a cham;

42, so that the hot air may flow fr omthem ber or liue 55l extending vertically vin each l into these chambersand thence through the side wall, these lilies bem Connected by an r.; lateral air lines 23. The total capacity of operhead flue,56 (F ig.l 2a The side.. flues the pipes 50 should approximately equal 55' open into the ends of the radiator pipes .42,44 communicate freely withthe airiiues tion 51, as shown in Figs. 2*, 3a.- 'I'his ex iron, these pipes being superposed in updouble,- an outer wall 53 being formed to that of the tlues 23. The pipes 50 on oppo- 50 on one side, and, on the other side, open p site sides. of the tunnel chamber converge into longitudinal llues 57 (shown in dotted slightlyas the carloads of Wares advance, lines Ain Fig. 28) these fines being extended,

being carried inside ofthe linings 35; through theside walls of the 'torrid zone/F The walls 20 of the zone C andthe conof the tunnel kiln structure.

tinuing walls of the zone D,\are equally The construction of this portion ,of the spaced apart, so that the tunnel chambers structure is shown -in cross section in Fig.

C, D are of uniform width, this width be- 9, a transverse arched chamber ,58 ybein ing barely sutliclent to safelyv enclose the formed at each side, in order teprovide su ficient lengthfor the portal 52, while avoid-l ing too massive masonry. At the opposite or outgoing end of the firing chamber F", the -structure is formed with a substantial duplication cf the portal 52, the second portal being marked 62, and having the same structure already described; that is to say, the side flues and overhead flue 56'are duplicated, these flues being marked and 66, respectively, and the longitudinal iues 57 .open in to these flues 65. A

The'

portals

52 and 62 are each'of a length equalling approximately the length of one of the cars B, and are formed with refractory inner walls and with suitable masonry outer walls, and overhead arch, as sliownin Fig.'

9. Thus, the overhead portion of each ort'al has an inner refractory arch 61, an an outer, or upper masonry arch 64, which arches sprin respectively from the inner partition wals and the outer side wall, asl

shown, so that they may expand and contract independently. Between these arches is a dead air space 6 3, affording heat insulation.

The torrid zone F, with its enclosed firing chamber F', will now be described:

The outer walls 7 0, suitably reinforced, as before, with steel framing, are erected on a succession of masonry arches 71,l springing from abutments 72, Fig. 4a .and over the top of the structure is carried a masonry arch 73, Fig. 14, springing from the reinforced upper portions of these walls. The inner or lining structure is constructed of the highest possible grade of refractory brick, and comprises Vside walls made hollow to enclose the longitudinal flues 57, having arched portions 76 beneath, coinciding in arrangement with the outer arches 71, and roofed over by a refractory arch 77 springing between the upper portions ofthe side walls, which portions are laterally reinforced against the outer side walls 70, as shown in Fig. 14. Between the arches 7 3 and 77 is a dead air space 78, forming a heat insulation. Also,V between the'lining wall and the outer wall, on each side, is an air chamber or cavity 79, forming normally a dead airspace on each side of the firing chamber. These several dead air spaces serve to insulate the interior walls, so as to preventloss of heat outwardly, thus protecting the outer walls and promoting economy in the operation of the kiln.

The firing chamber F has an average width somewhat greater than that of the narrowed ortals 52 and 62, and is partially subdivided) at each side to form a succession of

compartmentsl

80, 80, in which, respectively, are located the Vfiring furnaces 90, 90, ivhich will be more specifically described aber.

The compartments are, in part,- formed by piers 81, projecting inwardly from the side walls 75 -and coinciding longitudinally with the outer arch abutments 72. Thus, the compartments coincide in' number and position with the arches 71, which arches form a series of openings into the respective internal compartments,throughl which openings the firing furnaces may be introduced or removed. These arch openings in Vthe outer wall are rked 100, and those in the inner wall the inner furnace compartments are l arched over at 102, to form furnace chambers communicating with the firin chamber, When the furnaces 90 are in p ace, as shown at` the right in Fig. 14, Apartitions or doors 91 close the outer arches 100, and vpartitions or doors 92 close the inner arches' 101.

twelve firingfurnaces 90, six on eac side, but it will be understood that more or fewer may be dprovided, the important feature be# ing'to vide the heating meansinto units of suitable size to admit of ready control and to distribute the sources of heat along a considerable portion of the length of the tunnel, in order thatthe carloadsof' wares slowly advancing through the tunnel may be gradually raised in temperature in passing the successive furnace units. Each fur# refractory'bed portion 104 beneath the re-v spective compartments 80. Anti-friction rollers 9.6 or any other suitable means, may be provi ed to facilitate the movement of ,carriages 94 on' the runwaysv95. For moving the carriages, any suitable mechanical means may be provided, such as a screw 97 .engaged .by a .hand-Wheel 98 in a. well-.known man` By this means, the .several furnaces' ner. may be individually removed from their normal position', as shownat theright 'in Fig. 14, and carried outwardly tothe posi- .tion shownat the left in' that ligure, to permit `of in ection, renewal, or repairs. When any rnace 1s .thus removed, it is The kiln,y as Shown inthe. drawin has" highly important to. be able to immediately close the opening into the ring chamber, because the normal closures 91 and 92 `have (been taken away; forjthis purpose, a shutoff gate is. provided for each furnace Aopening, these gates being preferably constructed each as a vertically slidin' panel or slab 105, as shown in Fig. '14 which, in the normal-operation, is elevated to the position shown.. at the right in Fig. 14, or, immediately after the removal of a furnace unit, is lowered to the position shown in the left of that figure. These gates thus move in the lateral dead air chambers T9. being preferably of a thickness considerably less than the width of these chambers, so that, when elevated, a suitable dead air space remains. The bottoms of the dead air space between the

arches

100, 100, are closed bytiles 106 which coincide with the movable beds 94, and afford complete parallel side walls between which the beds 94 may move. The movements of the gates may be performed in any convenient manner, the means for this purpose shown comprising, for each gate, a vertical rod 107, the lower end of which is imbedded in the gate, while the portion above the gate may slide in an iron tube 108, built into the masonry. and the portion which, when the gate is lifted, isabove this tube, is screwthreaded and engaged by the threaded hub of a wheel 109. having a bearing support 110 carried on the upper crossframing 111. By means of the gates 105, any furnace units may be removed without interfering with the operation of the kiln, by merely' droppingthe gate to close the opening and exclude cold air from the firing chamber. Gate 105 is thus lowered before` closure 92 is withdrawn from openin 100, to prevent any ingress of cold air to t 'e firing chamber, and any loss of heat therefrom.

The firing dfurnaces 90 may be`of any suitable or known construction, according to the .fuel or source of heat which is to be used. For many reasons, however, it is preferable to use electric furnaces, instead of those heated by gas or other fuel. The principal advantage of electric furnaces is that. in their use, there is, or need be, no discharge into the tiring -chamber of products of combustion s uch as mi ht injure the wares being fired. This avolds the necessity of-protecting the wares by en? closing them -in saggexs, or by constructing the kiln after the manner of mutle kilns, with a lining partition of thin refractory material tol separate the tunnel chamber from the lateral chambers in which the combustion' or heating takes place. The use of such inutile partition requires that the heating adjacent the tunnel chamber shall be carried to a higher temperature than that required in such chamber, inl order to overcome the obstruction to the flow of heat occasioned by the refractory lining- 93 are hollowed, and are extended longitudinally of the tunnel, the opposite ends of each hearth being entered byl conducting bars or pencils 120 of carbon. 'preferably in graphite form, which pass through holes 121 in the hearths and through suitably lined holes 122 in the partitions 92, and are carried by carbon holders 123, which may pass through suitably lined orv bushed holes 124 in the outer partitions 91. Each pair of these carbons constitutes a couple, to which electric current is conducted through any suitable conducting means, such as shown diagramatically in the form of wires at 125, in Figs; 4a and 14. Any suitable electric resistance material 99 is placed in t'he hollows of the hearths 93 and serves as the resistant connection between the ends of the respective carbon pencils which enter opposite ends of the hearth, this resistant material being heated to incandesence by the passageof the electric current.. As this material, broken or comminuted carbon is preferable.

Theresistant material 99 and the carbon pencils 120 need occasional renewal and this lis conveniently accomplished by withdrawing the furnace units, as shown at the left in Fig. 14, in the manner already described.

The first cooling`zone G extends from the outlet portal 62 for a suitable distance, connecting, at its outlet end, through an expansion joint, with the second cooling zone 'H. The enclosed portion G of the f tunnel chamber'constitutes a cooling chamber and is made wider and higher than the dimensions of the restricted opening through the portal 62, so that the inner walls 13G-of this chamber, and its roof lining or arch 131 (F ig. 10)- are at some distance away from the carloads of wares. The outer -walls 132 are of masonry suported b y lan external reinforcing steel raming, as before. At their entering end, these walls join the portal 62 by an overhangingslip connection to form an expansion jomt in a manner which maybe suhstantially a duplication, of the joint between the Wall 51 and" inner and

outer walls

53, 54 of the entering portal 52, already described. Fig. 10 1s a section at this slip joint portion of the portal. being taken through the outer wall 133 corresponding to 53) and inner Wall 134 (cor- .responding to 54), between which are formed the side connecting fines 65; the upper connectin flue 66 is formedbetweenthe inner arch 7 and an outer arch 136. Fig. 10.

The enclosing walls of the cooling zone G are traversed by a series of air heatingfiues 140, which are best formed by the use, for the inner lining Walls, of hollow refractory tiles 141, and similar tiles 142 to form the inner portion of the arched top. The cuter masonry wall 132 and outer arched masonry roof 137 are shown as directly adjoining these lining tiles.

The expansion joint 145 between the first cooling zone G and the second cooling zone H is formed, as best shown in Figs. 2", 3b, and 11, with an outer wall 146 and an inner or lining wall 147, which walls respectively embrace, with a slip connection, the side walls 151 of the cooling zone H In the construction shown, the outer walls 146 form a continuation of the outery walls 132, and may be built of masonry integral therewith; the inner walls 147 are extended inwardly from the tile linings 141-to the same extent as the inward projection of the

portals

52 and 62. This inward projection thus -orms an additional portal, designated 148. The outer and inner walls enclose a connecting iiue 160 on both sides and overhead, which iiue serves to connect, on the onediand, the ends of all the iues 140 traversing the zone G, and,on the other hand, a iue or flues 150, formed in the hollow or hollows, of the wall 151 and roof portion 152 of the zone H.

The second cooling zone H has its enclosed chamber H partially cut off from the iirst cooling chamber G', by the inter,- vening portal 148 in the same manner-1 that the first cooling chamber is cut off from the firing chamber. This zone H is best constructed of east iron plates or sections 153,

lin the same manner as the heating z one l?, except that, for this cooling zone, 1t 1s preferable to extend the same construction over the roof, as shown in section in Fig. 12. Thus, the segmental iron plates are spaced apart, forming between them the iiue vspaces 150, the roof plates 152 being similarly separated, and forming between them the overhead portion of this flue 150. rlhe side walls are built on a foundation 155 of masonry, which may be continuous with the foundation 155, shown in Figs. 10 and 11. The iron walls are fastened, at bottom, to this foundation, the fastening being rigid at the end 'portions nearest the zone G, the remainder of the side walls and top portions being free to move longitudinally with changes of temperature, tor which purpose longitudinally-slotted bolt-holes may be used.

The final cooling or cool zone J is a duplicate of the inlet zone C, except that it is preferable to form the roof of segmental cast iron plates 162, instead of masonry or tile. The enclosed tunnel Chamber J may be an uninterrupted continuation of the chamber H', and of equal width.

t the junction 163 between the zones and J, the outer wall 151 of the zone H is discontinued, while the inner wall is contin'ued as the wall 164 of. the yZone J. The space between these outer and inner walls is left open, to constitute an inlet 161 Jfor admitting air to the intervening space or air heating flue 150.

The outlet end of the zone J is closed by a suitable door h, which may be a duplicate of the inlet door.

The masonry construction throughout has its outer wall reinforced by sectional steel framing' 166 on the-sides and 167 overhead, this framing serving to resist the thrust of the archedmasory roofs in the manner well understood.

Having thus described the construction of the tunnel kiln, its operation may now be understood.-

Following iirst `the flow of the air through the longitudinal lues or spaces It is understood that the kiln, having been brought into full operation, contains a train of cars, ,each fully loaded with Astacks of wares in various stages' of heating and cooling, as will be more fully described below.

'The air entering at 161 into the wall space or flue y150, surrounding the cooling chamber H', flows slowly through this space into the connecting flue 160, thence subdivides and traverses the longitudinal heating lines 140, formed within the tile lining 141 of the cooling zone G; then, being united in the lateral iues and overhead equalizing Hue 66, the already highly heated air is caused to flow through the two lateral fines 57 traversing the walls of the firing chamber F', then entering the lateral lues 55 andl their connecting overhead fiue 56 and, being again subdivided, the air enters the multiple radiating pipes 50, through which it Hows Valong the opposite sides of the zone E; from these pipes, the air is discharged into lateral ues 42 and their overhead connection 44, and finally traverses the flue or air space 23 between the walls of the zone D, the air ciirrents being finally united in the i'lue 25, from which they are drawn to the suction fan 26, by which the current of air is maintained. During this flow of the air, it is iirst hea-ted, by taking up the heat radiated from the carloads of cooling wares in the cooling zones H and G, this heat being conducted to it through the lining walls of the chambers H', G; the highly heated air is then superheated while passing through the iiues: 57 traversing the lining of the tiring chamber; the air thus superheated then, in liowing through the radiating` pipes 50, gives out heat, which is radiatedl from these pipes to preheat ,the wares in the chamber E', and finally the air, now partially cooled, serves, while passing through the side flues 23,'to initially heat the wares traversing the first. heat chamber D'. Thus, the air first takes up heat from the cooling Wares, and later, by a reversal of this function, givesout heat to preheat the Ientering wares. In the tunnel chamber E', the

heated air is first carried throu' h the radiating pipes 50 (see Fig. 3) whi e these ipes are arranged Aclose, against the sides o the stacked wares; as the air loses heat, these pipes ecede from the sides ofthe cars (see igt will be noted that the cooling air, which afterwards becomes the heating air, isnot vitiated by products of combustion, nor in any way changed in character, so that, after being discharged from the fan, its remaining heat may be utilized for heating or drying, o1' for Vany purpose for which hot or warm air is available.

Now, following the progress of the wares through the kiln, it is to be observed that these travel in the contrary direction to the tlow of air. The successive carloads of wares are practically continuous, the wares being so piled as to allow inter-spaces through which the heated air within the tunnel chamber may' circulate. While other wares or materials may be treated, the present description will assume that the wares are porcelain or earthenware, to be fired. The successive cars are run in through the entrance door into the warming chamber C and this door closed. This chamber C receives its heat entirelyy by means of a certain amount ot' circulation from the end of the second warming zone D, the wares slowly warming up as they pass over approximately 2O feet of track, and then entering the second heating chamber D', where they first receive direct radiation from the side walls of the tunnel, where the latter are heated from the air circulating through the lues 23, on its way t0 thc fan 26, at which time the air has given up nearlyv all the heat it had gathered from the cooling zone and torrid zone. The iron walls of the tunnel in this' section D radiate the heat directly to the wares. this etiect being accompanied by convection by reason of the circulation of air in the tunnel chamber being upwards along both walls to a meeting of the lrespective cuirents at the top, and thence downward t rough the wares to the floor of the `car. and outward in both directions to the walls; this' rotary current being continuous and spontaneous. The tianged structure 0f the walls in this section D of the tunnel assists in breaking up the ascending air currents. and also provides increased radiating surface. It desired, the outer iron walls may be insulated b v an exterior covering of brick work or insulating material, asis Common.

The ware train is kept moving continuously or intermittently, and at a suitable rate throughout the length of the tunnel kiln. Continuous movement is preferred, and at a rate such that each car moves its own length in about one hour. Asthe'cars progress through the heating zone l),v they encounter continually hotter walls, from which there is a progressively higher heat radiation.v In time, each car passes lfrom the heating chamber D into the final preheatin chamber E, where the tunnel chamber su denly widens. In the progress of the carsthrough this chamber E', the Wares receive a continually incl/easing hea-t radiation from the cast iron radiating pipes .50, which, at the entering end, are somewhat separated laterally from' the loads of wares, and which gradually approach these as the cars advance. At about halfway through this chamber, the outer brick wall of the tunnel is reinforced by a tire brick lining 35 on the` side walls, and 38 at the roof, as, throughout the after portion of this chamber, the heat is elevated to a degree that would be injurious to common brick. Throughout this chamber, the same convective lateral circulation of air within the tunnel chamber and through the wares takes place, except that, as the heat is constantly becoming more intense, this circulation is probably more rapid and effective. In the final portion of this chamber, the radiatingy pipes are brought as close to the sides of the loads of wares as ossible, in order to make this lateral circulation the most effective.

In this section E of the tunnel is introduced an important improvement in such kilns:

The Ware entering the kiln is at a stage of process called chalk white; that is,`the clay is predried to a pointv where there isno apparent moisture present but molecular moisture remains. and, as the car progresses in the kiln, is liberated from the ware and is present as superheated vapor in the circulating air surrounding the ware train. It is necessary to remove this moisture; and for that purpose and also for the purpose of replenishing oxygen withinthe kiln, advantage is taken ota certain amount of air leakage at the doors at either end. also air leakage into the tunnel ata number of spy holes and a leakage in the side walls about the tire hearths in the torrid zone. A stack 170 is built over the tunnel at approximately one-third of the length of the preheating chamber E forward of the entrance to the torrid zone, and being connectedv directly with the interior ot' said chamber', creates an updraft which drawing on the tunnel interior produces a slow current from lboth ends, the current from the entranceend carryingI with it the molecular moisture vapor which, being always lighter than the normal air of the tunnel, readily finds its outlet to the stack, `while the current from the exit end, aiding primarily in cooling the ware on its way through the tunnel t0 the stack, takes up the peak heat of the torrid i zone and entering the preheating chamber tal the carload of wares is substantially cutYV off from external sources of heathfora suitable' time (preferably at least one hour), so

that during this time any irregularity in preheating of different portions of the wares 1s corrected` by4 mutualradi'ation and con-Y vection, thusmc'complishing an equalization of the preheating throughout theY load of wares. s

While in the torrid zone or firing chamber, the ware train is between two rows of direct ire from the furnaces 90, 90. The advancing Ware just enterin from the preheati'ng chamber receivesv t e direct heat from the first pairfof furnaces, and thereby is gradually elevated in temperature. Passing,l next, the second pair of furnaces, it is farther elevated in temperature, attaining its maximum temperature at thejfourth pair land maintaining this temperature past the thand sixth units (this action being modied in theY case of a greater or lesser number of' such units). During the latter part of their passage through the tiring chamber,

the waresare at incandescence, and, while passing throughY the outlet portal 62, the lining of which is incandescent, this incandescence is maintained, thus giving the wares a steady soak, Ywithout tire, for that period. This static heat treatment in the n outlet portal repeats in a manner the heat equalization occurring in the inlet portal, so. that-if the wares are unequally incandescent, or at unequal temperatures, this inequality is corrected by mutual radiation and by' convection.

On leaving this outlet portal, the wares 'i enter the first cooling chamber G', in which the heat radiated from the wares is taken up slowly1 by the hollow tile Wall and arch construction, and transmitted to the air circulating through the tlues formed in these hollow tiles. As the ware ytrain advances, the wares continue to'give up heat thus to the absorbent walls, the convective action now occurring by circulating up throughl the wares to the roof ,and down the sideso-the tunnel to the 'iioorof the car, thence returning to the roof; and, because otthis `circulation andlof the absenceof any'perceptible draft through the tunnel, the wares cool gradually and equally, thus avoiding danger of breakage through unequal contraction.

,This action proceeds progressively during the slow advance of the carloads of wares ation of air through thetunnel chamber.

On entering the second cooling chamber H', the wares continue to give out heat which, conducted through the inner iron Walls 'of this chamber, is taken up by the cool air circulating throu h the hollow space or iue 150 'in the side wa ls and roof. This construction rovides for ready and rapid absorption o heat from the walls so that, Whenthe latter have reached the end of this section at 163 and enter the single wall construction of the nal cool section J, the wares will have cooled to such 'an extent that, on their final passage through this section for a distance of about 2O feet (taking some 3 hours), the wares undergo a tempering rocess under cover which puts them in con ition for safe exit*V to the open air. Finally, as each car reaches the exit opening, the end door b is opened and the car run out and the' door 'then again tightly closed. Y*

The total length of the tunnel kiln and the roportionate lengths of the successive heating. zones of the torrid zone and of the cooling zones are matters which may be approximately arrived at by computation ased upon past experience' with tunnel kilns of other types, but which may be finally determined as to the best proportions only after a sufficient degree off'experience in the use of tunnel kilns of this improved type; and these proportions will be subject to variance according to the requirements Yof ditl'erent kinds of wares or different heat treatments tor which the kiln is to be used.

An important feature of the improved construction herein set forth is the provision 4of means forY protecting the tunnel structure against the injurious or destructive effects of expansion and contraction. To provide for expansion and contraction in longitudinal direction, the kiln is divided longitudinally into sections which, in their nature, are subject'ito varying temperatures in use, and, consequentlygto varyingdegrees of expansion and Ycontraction while heating up and codling down before and after a period of practical serviceL The construction of expansion joints at the meeting places of these successive sections, as already described, makes adequate provision for allowing for theeftects of expansion in this direction.

llO

Lateral and vertical expansion is also provided for; but, as there is little, if any, lateral movement of the walls or of the base foundations, the roof arches are the only members to be considered; and, since the thrust of the arches is always taken up against the steel reinforcement, it follows that the only movement due to expansion would be a bowing upwardly of the crowns of the successive arches. It is, therefore, seen that the tunnel structure is free to expand from its built dimensions to anew heated dimension, and, when cooled at any time, its dimensions are diminished from its expanded position,l this being taken up in the expansion joints and by, in some cases,

the opening of joints in the side walls, while the arch crown will lower somewhat in cooling; all parts of the structure, however, resuming their fixed expanded position when again heated.

ln order to provide for ready inspection of the tire hearths and of the wares in their progress through the firing chamber, suitable peep holes are provided in the sides and at thev ends of this chamber.l The lateral peep holes are best formed at 171, F igs. 2a and 4;, that is, through the stopperwalls or doors 91, 92, pertaining to the individual furnaces. End vpeep holes 172 are formed on opposite sides and at opposite ends of the firing chamber (see Fig. 3a.), these peep holes passing through end walls 173 forming the inner masonry members of the portals and G2 respectively. The arched recess 58. already referred to in describing the portal 52, and corresponding recess 68 pertainingto porta-1162, afford compartments opening externally which may be entered to make use of these spy holes. The provision of these -holes makes possible a ready inspection of the fire hearths from either end, and also enables a vision of the passing cars. As the spy holes at either end will sweep a tield of more than one-half the length of the tire chamber, it follows that the cars and wares in 'the firingchamber are always under visual inspection.

The improved'tunnel kiln herein set forth is designed and ideally adapted to maintain an intense heat in the torrid zone and a practically quiescent firing chamber from which no material loss of heat occurs; with the result that, when, in the original firing up of the kiln, the heat once reachesits peak, it may be maintained over long periods at relatively low cost of operation. In the firing chamber, the longitudinal flow of heated air, due to minute leakage through the end doors, furnace joints, peep holes and other interstices, is so slow that such longitudinal flow becomes negligible so far as a lfects the practical quiescence of the at mosphere within this chamber.

Bv referring to this atmosphere as quiescent. I do not negative the normal rotative circulation of air in transverse planes, by which the uniformity of heating and the equal incandescence of the wares throughout the stack thereof, is assured. Nor do I ignore the extremely slow flow of air, in volume equal to the aggregate in-leakage, toward the stack 170, already described.

It will be evident from the foregoing description, that the invention may be modified in construction, proportions and details in many ways, according to local conditions and the specific uses to which the tunnel 'kiln is to be applied. I desire it understood that all such modifications which are within the scope of the appended claims are to .be deemed within my invention.

`What' I claim is:

1. A tunnel kiln having a continuous tunnel chamber and successive cars traveling therethrough, the kiln comprising a heating zone, a torrid zone, and a cooling zone, having end doors, and the inlet and outlet portions of the tunnel chamber formed of minimum cross-section closely :approximating that of the carloads of stacked wares under treatment, lwhereby to substantially close the end port-ions of the tunnel and `prevent inflow of air toward the torrid zone, and the firing chamber at the torrid zone of greater cross-section, and having a dead air insulation surrounding the tunnel chamber, whereby when once heated to operative incandescence the..=.k iln yconserves heat and permits economic'operation, an-d means for absorbing heat radiated'A from the Wares traversing the cooling zone, conveying such heat past the firing chamber, and radiating it in the heating zone to preheat the Wares there- 2'. A tunnel kiln according to claim 1, the firing chamber being heated by multiple electric furnaces under independent control, whereby the advantages of electric heating` are rendered available under economic conditions.

3. A tunnel kiln having a tunnel chamber for the passage of cars traveling therethrough, comprising a heating Zone, a torrid zone. and a cooling Zone, the torrid zone formed as a firing chamber with a double arched roof and dead air insulation in such roof and in its side walls, and expansion joints of overlapping refractory masonry at the junction of the torrid zone and the heating and cooling zones.

4. A tunnel kiln formed with an expansion-joint where the torrid zone joins a portion of the kiln subject to less extreme temperature changes, and having a transverse chamber coinciding with such expansion joint. v

5. A tunnel kiln structurel comprising a torrid zoneforming the firing chamber, and preceding and succeeding zones which are normally subjected to lower temperatures, such zones partially separated by portals on both sides of the firing chamber adapted to closely enclose the carloads of wares to substantially cut off circulation of gases between such zones, and of a length such as to enclose a carload mass of wares, the tunnel structure formed between the torrid zone and the adjacent zones, with refractory masonry portions forming an expansion joint to enable the respective sections of the structure to expand or contract independently.

6.- A tunnel kiln structure according to claim 5, having longitudinal fines through the masonry walls, and having' transverse chambers at the expansion joints connecting the flues on opposite' sides of such joints.

7. A tunnel kiln structure divided transversely into longitudinal sections which are subject to diverse temperatures, such sections meeting with a double sliding joint. and a lateral flue chamber at such joint, whereby the movements due to temperature changes are taken up in such lateral chamber.

8. A tunnel kiln the torrid zone of which joins the preceding and succeeding portions of the kiln with expansion joints of -refractory masonry, having transverse chambers at the expansion joints, and longitudinal ues in the masonry walls, the flues on opposite sides of such joints communieating through said chambers. Y

9. A tunnel kiln the torrid zone of which is formed with a firing chamber partially separated from the preceding and succeeding zone by portals adapted to closely enclose t-he carloads of wares, such portals of a length such as to enclose a carload mass of wares and hold them in thermostatic condition for a timesufficient to effect equalization of temperatures.

10. A tunnel 'kiln having a heating zone and torrid zone, the tunnel chamber between such zones being contracted to form a portal closely approximately the cross-section of the carloads of wares, so as to substantially cut off circulation between such zones, and such portal of a length suficient to enclose the moving carload of wares and hold them in thermostatic condition for such time as to effect equalization oftheir temperatures.

11. A tunnel kiln having a torrid zone and a cooling zone, the tunnel chamber between such zones being contracted to form a portal closely approximating the crosssection of the carloads of wares, so as to substantially cnt off circulation between such zones, and such portal of a length sufficient to enclose the moving carload of wares and hold them in thermo-static condition for such time as to effect equalization of their temperatures.

12. A tunnel kiln having a heating zone, a torrid zone and a cooling zone, the torrid zone formed as a firing chamber of greater cross-section than the traveling carloads of wares, and such chamber formed with lateral compartments of greater width, independent portable heating units in such compartmentson opposite sides of the carloads, lateral openings to permit the remaval of any of such heating units, and means for closing such openings-- 13. A tunnel kiln the torrid zone of which is provided on opposite sides of the tunnel chamber with successive heating units, and means for permitting the removal of any one unit independently lof the others, and means for closing communication with the chamber upon the removal of such unit.

14. A tunnel kiln the torrid Zone of which is formed on opposite sides with successive furnace compartments, and independent furnace units in Such compartments.

15. A tunnel kiln the torrid zone of which is formed on opposite sides with successive furnace compartments, and independent furnace units in such compartments, such units being individually rcmovable.

1G. A tunnel kiln the torrid zone of which is formed on opposite sides with successive furnace compartments, and independent furnace units in such compartments. such units being individually removable, and means for closing off an)v cornpartment upon the removal of its furnace unit.

17. A tunnel kiln the torrid zone of which is formed on opposite sides with successive furnace compartments, and independent furnace units in such compartments, such units being individually removable, carriages for the individual furnace units, and closures on said carriages for the openings through which the units are removable.

18. A tunnel kiln according to claim 17, with independent closing means for shutting off any compartment when the furnace is removed.

19. A tunnel kiln having at its torrid zone on opposite sides a series of successive independent electricV furnaces, with means for controlling them individually, and means whereby said furnaces may be independently removed and replaced.

20. A tunnel kiln having at its torrid zone on opposite sides a plurality of electric furnace units, and means for controling the lindividual units independently, with openings through which such units are independently removable, and means for closing such openings.

2l. A tunnel kiln having at its torrid zone a plurality of electric furnace units, each unit independently removable, the kiln having openings for permitting their removal and movable doors for closing such openings 22. A tunnel kiln the chamber of which at itstorrid zone is formed with successive compartments, exterior openings communicating `with such compartments, doors for closing such openings, and electric furnace units movable through such openings into such compartments.

23. A tunnel kiln having atl its torrid zone a plurality of electric fu-rnace units, each unit imlepemlently removable. and carriages` tor such furnace units.

24. A tunnel kiln having at its torrid zone a plurality of electric furnace units. cach unit independentlyremovable, and carriages` for such furnace units. the kiln having openings for passing such carriages and units. and doo-rs for closing such openings.

A tunnel kiln having at its torrid zone a plurality of independently removable electric furnace units` each such unit coinprising a hearth, carbon pencils leading to such hearth, and resistant material on said hearth bridging Said pencils.

26A A kiln according to claim 22, having lateral runways through said openings, and carriages for the furnace units traveling` in such runways.

i 27. A tunnel kiln having at its torrid zone a plurality of electric furnace units, each unit independently removable, and carriages for such furnace units, the kiln having openings for p'assinof such carriages and units, and doors for closing such openings carried on such carriages to close them when the units are in place. and separa-te means for closing such openings when the units are removed.

28. A tunnel kiln comprising a heating zone a torrid zone and a cooling zone, means for transmitting heat radiated bly the cooling wares to preheat the wares in the heating zone with electric furnaces for-heating the. torrid zone, whereby discharge of burning gases into the kiln is avoided, the kiln having suction means fo-r drawing air from the tunnel chamber at a point in the heating zone` the. ratbf suction graduated to remove v-apor being evaporated from the preheated 'wa-res Without material indraftl of hot gases into the heating zone from the torrid zone. .l

29. A tunnel kiln comprising'a heating zone, a torrid zone and a cooling zone, with electric furnaces for heating the torrid zone` whereby discharge of burning gases into-the kiln is avoided, the kiln having suction means for drawing air `from the tunnel chamber at a point closely pre-ceding thc torrid zone. its rate of suction graduated to be. only sullicient to remove inleaking air, but not sullicient to impair the normal convection etlect in the torrid zone chamber. .o

30. A tunnel kiln comprising a heating zone` a torrd zone and a cooling zone. the torrid zone and heating zone partially .separated by a portal adapted t-o closely enclose the carloads of ware-s to substantially cut olil circulation of gases between .such zones. and of a` length such as to enclose a carload mass of wares, with electric furnaces tor heating t-he torrid zone. whereby discharge of burning gases into the kiln is avoided. the kiln having suction means for drawing air from the tunnel chamber in the. heating zone.` its rate of suction graduated to be only sutiicient to remove inleaking air. but not snllicient to prevent the spontaneous lat- 'i eral circulation of, air within the tunnel chamber.

3l. A tunnel kiln comprising a heating zone.. a torri/d zone and a cooling zone. the torrid zone and heating zone partially separated by a portal adapted to closely enclose the carloads of wares to substantially cut ofi' circulation of gases between such zones. and of a length such as to enclose a carload mass of wares, with electric furnaces for -f heating the toi-rid zone, whereby discharge of burning gases into the kiln is avoided, the kiln having suction means for drawing air from the heating zone ot' the tunnel chamber at a point closely preceding the torrid zone, graduated to operate at a rate only sufficient to i'emoveinleaking air. whereby such air circulates slowly through the cooling chamber, the torrid chamber, and into the heating chamber.

32. A tunnel kiln having a heating zone, a torrid zone and a 'cooling zone with electric furnaces for heating the torrid zone Without discharge of combustion gases thereinto, the tunnel chambers contracted at the junction of the torrid zone with the heating and cooling -zones to form portals closely approximating the cross-section of the carloads oiwares, so as to substantially cut off circulation between such zones, and such portals of a length suflicient to enclose the moving wares and hold them in thermostatic condition for such time as to effect equalization of their temperatures, and suction means'for drawing air from the heat- 120 ing zone at a rate sufficient only to remove inleaking air, whereby to cause aslow circulation of air longitudinally of the torrid zone.

33. A tunnel kiln having a preliminary heating zone, an intermediate torrid zone. and a final cooling zone. the torrid zone having insulating walls to retain the heat, and air fines therein insulated from the exterior Walls,

and the preheating zone and cooling zone l having lining walls insulated from the exterior walls, and air flues'in their lining walls, and mearis'pfor circulating air first through the flues vof the 'cooling zone to absorb heat from the cooling wares, then through said iues passing the torrid zone, and'finally through the flues of the heating Zone to impart to the: wares approaching the torrid zone the heat taken up by the air.

34. A tunnel kiln according to claim 33, the lues passing the: torrid zone having no communication with the heating means.

35.*A tunnel kiln according to claim 33, the flues passing the torrid zone being formed in the lining walls thereof remote from. the source of heat.

36. A tunnel kiln according to claim 33, the lues in the heating zone being formed in the side liningv walls of the kiln.

37, A tunnel kiln according to claimr33, the means for circulating the air being a suction fan applied at the delivery from said 'flues in the heating zone. i

38. A tunnel kiln according to claim 33, the lines passing the torrid zone having no communication with the Yfiring chamber.

39. A tunnel kiln the firing chamber of vwhich has contracted portals i at opposite ends, with lateral recesses in such portals, and peep holes opening from such recesses into the ends of the chamber.

Y40. The torrid zone of a tunnel kiln having yits sides formed with successive abutments and arches thereover, side walls above said arches` an arched roof, and lining walls similarly arched to form successive compartments at the sides of the firing chamber, and removable closures for th lateral arched openings. Y i

41. A tunnel kiln having lateral openings int-o its firing chamber, movable doorsl for normally closing said openings, and extra closures movable into said openings before the removal of said doors, whereby to prevent'ingress of cold air. Y

42. A tunnel kiln having lateralY openings into its firing clamber, laterallyY removable furnace units having portions normally closing such openings, and extra closures movable into said openings before the removal of said normal closures. l

43. A tunnel kiln having lateral openings into its firing chamber, laterally removable furnace units having portions normally closing such openings, a movable bed carrying each such furnace unit and closure, and an extra closure for each opening, movable thereinto before the removal of said normal closure.

44. A tunnel kiln having its torridzone formed with inner and outer side walls, with dead air spaces between them, and having lateral openings in its side walls, furnace units accessible through said openings, and spaced closures for said openings having spaces between them forming continuations of said dead air spaces in the side walls.

In witness fwhereof, I have hereunto signed my name. Y

WINFIELD E. HNSDALE.