US1999356A - Circular type tunnel kiln and method of operating same - Google Patents

Description

plfi my W35.. P. DH. DRESSLER Er AL gglg@ CIRCULAR-TYPE TUNNEL KILN AND METHOD OF OPERATING SAME Filed Sept. l5, 1935 5 Sheets-Sheet l ATTORNEY.

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CIRCULAR TYPE TUNNEL KILN AND METHOD OF OPERATING SAME Filed Sept. l5,A 1'933 3 Sheets-Shawl 2 l IN VEN TORS. PHM /P d H Off-SSL 5R [ow/1R@ HA /vFF BY m8/ A TTORNEY.

Apn 3(0), W3.. P. D'H. DRESSLER ET AL 3,999,356

CIRCULAR TYPETUNNEL KILN AND METHOD oF OPERATING SAME Filed sept. 15', 1955 3 sheets-sheet 3 wm n ,mfm E mi WA V 0 mi /m EN@ ,H .A \l m w t Q M @E MM Z M \b w Patented pr. 30, 1.935

^ PATENT OFFICE CERCA'ULAR TYPE TUNNEL KILN AND METHOD 0F OPERATING SAME PhilipV dI-Iuc Dressler and Edward A. Hani, Pittsburgh, Pa., assignors to Swindell-Dressler Corporation, Pittsburgh,

Pennsylvania Pa., a corporation 0f Application September 15, 1933, Serial No. 689,538

Claims.

The general object of the present invention is to provide an improved form of, and improved methods or" operating, a tunnel kiln of circular y type, in which thekiln chamber is in the form of circular arc, which ordinarily is of much greater extent than 180 but has its ends sep-arated by a gap for the loading of goods to be treated onto, and their kremoval from, cars employed to progressively advance the goods through the kiln chamber from the inlet end to the exit end of the latter.

Tunnel kilns in which the goods are transported on cars running on a straight trackway through a straight kiln chamber have long been known and are now in extensive use. For the general purposes for which such kilns are used, namely in firing and glazing china, in burning bricks, in annealing metal, and in analogous operations, kilns or" substantial capacity are required and the kiln chamber can seldom be less than 150 feet in length and is usually considerably longer and is sometimes more than twice that length. Y In some cases, space is not available for the use of a straight kiln of the required length. That and other reasons have resulted in numerous proposals, made from time to time in the past, for the use of circular tunnel kilns, in which the maximum horizontal dimension of the kiln chamber need be but little more than one-third of the length of the kiln chamber. Up to the present time, however, few circular kilns have been constructed and put into use.

All previously proposed circular tunnel kilns of which We have knowledge have included either a continuous annular hearth or goods carrier rotated `about the vertical axis of the kiln, or a continuous annular member for giving movement to goods-carrying cars of special construction which are moved in a continuous circular train along a continuous circular trackway. In general, the use of continuous circular means for moving the goods through the kiln chamber gives rise to diiiiculties as a result of thermal expansion and contraction, or at least requires the use of expediente which while minimizing the effect of such expansion and contraction, complicate the kiln construction and operation, and also requires complicated mechanism for giving motion to the hearth or cars on which the goods are moved through the kiln chamber. Y

Furthermore, no circular tunnel kiln of which we have knowledge has been devised or adapted to permit the movement of the goods through the kiln chamber on cars which on their emergence at the rexit end of the kiln canv be separated from the train of which they form a part, and which can be added to the rear end of theV train preparatory to their successive introduction into the kiln at the entrance end of the latter, as is done in the ordinary use of straight kilns. Such separation of cars from, and addition of cars to, the moving train of cars is desirable from time to time for car repair purposes, and under practical operation conditions it is frequently desirable to permit more time for loading and unloading a car than is available if the entire unloading and reloading operation must be performed while the car is moving at the train speed through the gap between the exit and entrance end of the kiln chamber. When cars can be so separated from and added to the train, it is possible, for example, to load and unload all or most of the cars moving through a kiln in twenty-four hours, or in a longer week end period, during one eight-hour loading and unloading shift, without interrupting the continuous operation of the kiln proper. the length of the above mentioned gap may be relatively long in some cases, in other cases it is necessarily quite short to provide the required kiln chamber length with particular maximum kiln chamber diameter permitted or madedesirable by special conditions.

A main object of the present invention is to provide a circular kiln in which goods are moved through the kiln chamber on short individual cars which can be separated from and added to the train of cars moving through the kiln, substantially as in the usual operation of a straight tunnel kiln. In so separating a car from, or adding it to the train, use may be made of a transfer table, movable transversely of the kiln track, either horizontally or vertically as conditions make desirable, to transfer the car between the kiln track and a storage track'at one side or at a different level from that of the kiln track.Y

Other main objects of the invention are topprovide a circular kiln which in its general construction and in the construction of the cars used, except for certain obviously necessary differences in form, may :follow the general practice, and make use of the experience developed in the extensive use of the straight tunnel kilns.

Specic objects of the invention are to provide simple and effective solutions for problems arising Vin the construction and operationV of a While circular kiln having the general characteristics of the present invention. One such specific object of the invention is the provision of simple and eiective means for preventing the cars in the circular train moving through the kiln from buckling or moving radially outward from the vertical axis of the kiln under the thrust of a propeller advancing the train by acting directly on the rear car thereof. Another specic object of the invention is to provide a propeller mechanism including a reciprocating car engaging element,

which may be substantially such as is used in straight kilns, but preferably includes special provisions accommodating the changes in position of each car occurring while the reciprocating propeller element is in direc'tfoperative engagement therewith. The train may be advanced by a single propeller mechanism acting on the car at the rear of the train and necessarily located adjacent the entranceend of the kiln, or part of the required train propulsive force may be furnished by such a propeller mechanism,

and the remainder by a second and generally sim-H ilar propeller mechanism acting on acar intermediate the ends of the train. Another specific object of the invention is to provide kiln cars with wheels which may be relatively adjusted for movement of the car along the circular kiln track or along a straight storage track on which it may be placed when out of the kiln chamber. Another specific object of the invention 1s a novel disposition of parts of the sand sealing means employed, as is usual in straight kilns, to prevent leakage through the vertical joints between the sides of the kiln car body and the adjacent walls'of the kiln structure.

In a kiln constructed and operated in Vaccordance with the present invention, all difficulties as a result of the thermal expansion and contraction in length of the individual kilncars are avoided by making the length of the train of cars moving through the kiln chamber such that the train extends less than 360 about the vertical axis of the kiln whereby a gap is left between the rear end of the rear car of the train and the front end of the front car of the train. This gap not only avoids the expansion and contraction diilculty referred to, but is frequently desirable because it permits of the passage of workmen Y through the gap between the space within and the space at the outer side without the circular kiln trackway. The space at the inner side of said trackway and at the concave side of the kiln chamber can be used for kiln car loading and unloading and other goods-handling purposes, to accommodate spur tracks for kiln cars undergoing repairs, and for analogous purposes.

The various features of novelty which characterize the present invention are pointed out with particularity in the claims annexed to and forming a part of this specification.v For a better understanding of the invention, however, its advantages and specic objects attained with its use,

reference should be had to the accompanying drawings and descriptive matter in which we have illustrated and described preferred embodiments of the present invention.

Of the drawings:

Fig. 1 is a plan view of a kiln;

Fig. 2 is a section on a line 2-2 of Fig. l;

Fig. 3 is a section generally similar to Fig. 2, of a kiln having heating means diering in type from that shown in Fig. 2;

Fig. 4 is a diagrammatic plan view of a kiln car;

Fig. 5 is a partial section takenl similarly to Fig. 2 but on a larger scale;

Fig. 6 is a plan, and Fig. '7 is a side elevation partly broken away and in section of a car propelling mechanism;'

' variations. great enough to permit workmen to move through Fig. 8 is a plan, and Fig. 9 an elevation di-V agrammatically illustrating a kiln installation comprising two associated kilns at different floor levels; and

Fig. 10 is a View generally similar to Fig. 4 illustrating a modified car arrangement.

In the drawings and referring rst to the arrangement shown in Figs. 1 and 2, A represents the kiln chamber, or kiln structure proper, which extends in the form of an arc for 340 or so about the vertical kiln axis a from the inlet end A to the exit end A2 of the kiln chamber, the extent of the gap between the entrance and exit ends of the kiln depending upon conditions of operation, as previously explained. Within the kiln chainber, track rails B curved about the axis a. form a trackway for the kiln cars C passing through the kiln; The rails B project from each end of the kiln chamber into suitable proximity with a transfer car E which. is radially movableon its supporting-rails D from a normal position in which the rails b on the transfer car unite with the rails B to form a continuous circular track about the axis a, into an` inner position in which the rails b register with the stub track rails F and F in:V

kiln chamber and thereby intermittently advance i said train of cars along the track rails B.

Advantageously, and particularly to facilitate the removal of cars and their loads in case of car wreckage, the kiln structure is of the type shown in Fig. 2 in that the kiln housing proper is mounted above the floor level on supporting iron work K and has its bottom at about the level of the bottom of the metallic car frames C' supporting the usual refractory upper portion of the hearth or goods-supporting platform formed by the car body. Y

In the condition of the apparatus shown in Fig. 1. the kiln car at the head of the train is almost but not quite centered on the transfer table E and has its front end separated froml the rear end of the car at the rear end of thetrain and about to be pushed into the entrance end of the kiln, by a short gap. The existence of that gap insures freedom for elongation and contraction in the length of the train as a whole and in the length of the individual cars due to temperature In most cases this gap should be the gap from the inner to the outer side of the track rails B. v

The kiln chamber is provided with suitable provisions for subjecting the wares moving through the chamber to the proper heat cycle, and ordinarily such a kiln chamber must com prise a heating-up zone, a high temperature zone, and a cooling zone. The character of the heating and cooling provisions of the kiln need not be illustrated or described in detail herein, however, as the present invention does not depend on theircharacter but permits the use of such provisionsin theV various forms in which they have been developed for use in ordinary straight tunnel kilns. In consequence, a transverse section of the kiln A at any point along its length may be'similar to a transverse section through an 'ordinary straight'kilnintended for the' same i'vi'ce and taken. at the same point along the length of the kiln, except for the special provisions, hereinafter described, for preventing the train of kiln cars from buckling or radial outward movement under the propeller thrust, and for the special provisions preferably employed, as hereinafter described, to prevent air or gas leakage through the vertical joints between the sidesy of the car bodies and the adjacent kiln walls.

Thus, for example, the section of the kiln A shown in Fig. 2 is in general like that of a standard open fire Dressler kiln of the so-called multiple burner type, having distributed fuel gas inlets I opening into the kiln chamberat different points along the length of thelatter and at different ele- Vati'ons, and uniting with air for combustion supplied through longitudinally extending channels J in the side walls of the kiln structure.

Fig. 3 illustrates by way of example, a crosssection Vof a Akiln with mule heating provisions which might be used in the kiln A in lieu of the heating provisions shown in Fig. 2. In the type of kiln shown in Fig.'3, the main heating effect is secured by the combustion of gas supplied through one or more inlets IA to each of the combustion chambers M extending longitudinally in the side walls of the high temperature portion of the kiln. In Fig. 3 auxiliary burner inlets IB are provided to secure an additional local heating effect. The combustion chambers M shown'in Fig. 3 are separated frcm'the kiln' chamber proper by a wall formed with uprisingY channels M open at top and bottom for the convection current circulation of the kiln atmosphere, as is customary in the well-known YDressler muifle heated kilns.

In accordance Vwith the present invention radial outward movementor buckling of the cars as a result of the propeller thrust on the car' forming the rear car of the train is prevented by means which comprise an abutment or thrust beam O curving about the kiln axis a and extending along the car pathway at its outer side in position for'engagement with bearing members P carried by the car. As shown the abutment member O is in the form of an I-beam having its web horizontal and being secured to the column portions of the kiln iron work K adjacent the pathway for the cars and below the level of the bottom of the kiln housing proper. The outer vertical ilange of the beam O bears against the iron work K and the inner flange of the beam forms a trackway for the thrust members P carried by the cars. The thrust members P are advantageously in the iorm of wheels having axles or supporting shafts P each mounted in a corresponding bracket P2 secured to the metallic frame member C' of the cars. Two thrust wheels may be mounted on each car, one. adjacent each end of the latter. To minimize friction losses, the thrust wheels P may have roller bearings.

When all the tracks on which the kiln cars run are similarly curved as` in the arrangement shown in Fig. l, the supporting wheels C2 for the kiln cars may be journalled in supports rigidly secured to metallic framework C' of the car, to turn about axis in xed relation to the latter and extending radially from the center axis a. of the kiln when the cars: are on. the circular track rails B. To facilitate movement of th i cars to be moved on straight storage, loading and unloading tracks as may be desirablein many instances, the axes of rotation of the wheels C2 may be made adjustable.

Thus asindicated in Figs. 4 and 5, the wheels C2 may be mounted in supports C5' which are pivotally mounted at C6 .in the metallic framework C ofthe car to turn with especia to. the latter about vertical axes. 'Arms C7 secured to the wheel support C5 are connected by linksI C8 to an operating lever C2 pivotally connected to the frame C at C1o and forming a means for simultaneousiy adjusting the planes of revolution of thewheels C2 about the axes of the pivotal connections CG for their supports C5 are required to enable the car to run on a track which is straight or which has any particular radius of curvature.

In its. movement through the kiln each car C is held in place on the track rails B as the result of the propeller thrust on' the car tending to move the car radially outward and the reaction to such movement furnished by the abutment O and thrust members P. In consequence, flanges on the wheels C2 are not then needed. All of the wheels C2 are advantageously flanged, however, even though intended to run only on similarly curved rails as shown in Fig. 1, in order that the wheels may be vkept in proper relation to the track rails of tracks such as the tracks F, F', G and G', and end portions of the track B which may project beyond the corresponding' ends of the abutment beam O, where no means other than the flanges are provided tokeep the wheels on the track. Where the iianged wheels are used the abutment member O and thrust members P should be so disposed as to prevent the flanges and particularly the flanges on the outer car wheels C2 from track rail engagement.

But for the necessity of providing for movement of cars on the transfer table E outward from the circular track way, the abutment O night extend in a circle entirely about the kiln axis a, assuming suitable expansion joints were provided in the abutment. The abutment O need not'extend out of the kiln housing at the exit end of the kiln, since a car at or immediately adjacent the head end of the train is not subjected to any substantial tendency to radial outward movement. At the entrance end of the kiln, however,

the abutment O should extend into position for Vengagement by the thrust blocks, or at least the front thrust block P of the rearmost car of the train which is acted upon by the propeller H.

The propeller H employed to move the cars through the kiln may be, and is, shown as generally similar to the hydraulic propellers commonly employed for the purpose in ordinary straight tunnel kilns. In essence, such a propeller comprises a cylinder and a plunger or ram piston H working therein and connected at the i front end of the cylinder to a ram head or part H2 adapted to engage a lug or shoulder C11 provided for the purpose on the underpart of the metallic framework C of each car engaged. In the particular constructions illustrated herein,

. two strokes of the propeller are required to advance the frame the length of one car and each car is therefore provided with two propeller engaging lugs or shoulders C11. To enable the propeller to be retracted and to pass under a lug or shoulder C11 at the rear of the yone previously engaged, the car engaging part H2 is pivotally connected to the propeller, plunger or ram as shown: in Figs. 6 and 7 so that it may tilt to clear the car shoulder or lug C11 past which the part H2 is moved on the retraction of the plunger. The part H2 is spring pressed or, as shown, is given a gravital bias into its normal position for engagement vwith the car shoulder C11. The

plunger. shown as provided atitsfront end with flanged pony truck wheels H3 running on supporting track rails H4. `Fo`r` use in a circular kiln, as shown, the track rails H4 are preferably curved circularly about the kiln center axis. To permit the wheels H3 to move along the curved track way, the portion of the ram carrying the wheels must be adjustable laterally relative to the propeller cylinder or the latter must be bodily adjustable. In the particular construction illustrated in Figs. 6 and '7, suitable bodily adjustment of the propeller cylinder is provided by Y means of a pivotal mounting H5 for the rear end of the cylinder permitting the latter to turn about a vertical axis as the wheels H3 move along the curved track rails H4. Y

To prevent leakage through the vertical joints between the sides of the car bodies and the adjacent portions of the kiln structure, we make use of sand seals as is customary. The sand seal provisions at the inner or concave side of the kiln comprise a sand trough member OA extending longitudinally of the kiln and plates C12 secured to the inner sides of the car and dipping into the sand in the trough OA. The sand sealing provisions formed by the trough OA and plates C12 may be, and are shown as identical with sand sealing provisions heretofore employed in straight tunnels, except, of course, in that the trough OA is curved about the kiln axis.

The sand sealing provisions at the outer side of the train operate, in so far as the sand sealing function itself is concerned, like those at the inner side of the train, but advantageously the sand containing trough at the convex side of the kiln hasits outer wall formed by the outer vertical ange of the thrust beam O, and has its inner wall formed by a part OB secured to the member O between the vertical flanges of the latter and spaced at some distance away from the inner vertical ange of the member O. Advantageously and as shown, the member OB is the vertical ange of an angle bar which has its horizontal flange extending outwardly and secured to the web of the beam O. The space O5 between the member OB and the inner vertical flange of the member O serves as a receiving space for sand spilling over the top of the member OB. Such spillage from time to time is a 'common occurrence in the operation of kilns having sand sealing provisions and ordinarily is of no consequence. With applicants construction, however, such spillage might be detrimental because of the possibility that some of the sand spilling over the member OB might strike on the car carried thrust wheels P and work down into the bearings of the latter. This possibility is substantially eliminated by the provision of the spillage receiving space O5. Holes O6 may vbe formed at suitably close intervals along the length of the web portion ofthe member O forming the bottom wall of the space O5, so that the sand entering that space may escape through the holes O6 without coming into contact with the wheels-P.

The general operating characteristics and atvantages inherent in a circular tunnel kiln constructed in accordance with the present invention will be evident, it is` believed, to those skilled .in the art from what has already been said, The invention permits of a desirable exibility in operating conditions. For example, it is possible to operate the improved kiln without removing the kiln cars from the circular track way formed by the rails B and the transfer car rails b when this is desirable. In such a case, the cars must housing.

the goods on those cars.

be successively unloaded and reloaded' they move through the gap in the kiln housing between the entrance and the exit ends of the kiln Moreover with such operation, it is possible, whenever the occasion arises, to replace a car for repair purposes', by an extra car then put in place in the train. The transfer tableAE may be operated to replace one car of the train by another car for repair purposes or for other purposes without interfering with the regular but slow and intermittent motion of the train. The construction also permits the loading of cars not then on the kiln track with goods to be passed through the kiln and the storage of such loaded cars on one of the external storage tracks during the daytime, so that a single kiln attendant may keep the kiln in Voperation during the night by vtransferring the previously loaded cars onto the kiln track, as required for the replacement of cars successively emerging from the l kiln at its exit end, each car so removed from the train being placed on another storage track for Vthe subsequentV removal of the load of goods thereon which has been passed through the kiln. As will be apparent, it is possible to separate any two adjacent longitudinal sections of the Y train when necessary. This is importantin case of accident involving the wreckage of one or more of the cars within the kiln, or the dislocation of may be inserted from the open space beneath the kiln structure into position to jackapart adjacent cars of the train and thereby permit dislocated load portions to fall down onto the floor beneath the kiln structure. In this way the trackf way may be cleared for the movement of cars through thekiln. This permits the withdrawal, one at a time and at whichever end of the kiln is most convenient, of as many of the cars as it may be necessary to remove in order to restore,l

operative conditions without opening up the kiln chamber if, as is usually the case, the wrecking has not injured the kiln structure sufliciently to require substantial repairs to the latter.

The smaller maximum horizontal dimension of a circular kiln as compared with the length of a straight kiln of the same capacity is of much practical importance in some cases, and particularly in cases in which it becomes desirable to replace existing round intermittent kilns with tunnel kilns and thereby increase the eiciency and capacity of the plant. For example, the removal from an existing installation of two side by side intermittent kilns 35 feet or so in diameter will ordnarily provide space for one of my improved circular kilns having three or four times the capacity of the intermittent kilns removed and In such a case, a jack requiring little or no more fuel for its operation at'full capacity than was required for capacity operation of the intermittent kilns replaced by The capacity for'removing cars from and putting other cars in vtheir place on the circular track way permits the loading and unloading operations tobe performed partly or wholly while the cars are on the'storage tracks, and thus makes it possible to diminish the distance between the entrance and exit ends of the kilns as compared with the distance between such kiln ends required when the loading and the unloading operations must be wholly performed while the cars loaded and unloaded are on the circular track way. This is important where space restrictions make it desirable to obtain the maximum kiln chamber lengthy with la given kiln chamber diameter. l

In practice the diametral distance between points on the center line of the kiln chamber 'and the opposite side of the axis h may vary widely with conditions of use, but ordinarily this distance may be expected torange between a 'minimum of 30 feet or so and a maximum of. 70 or 80 feet. Whether such diametral distance be smallr sents a biscuit kiln located on the lower floor,

disposition ofV their associated `repair and storage tracks to the kiln A previously described and have corresponding partsY similarly designated, except 'that the building space conditions made it necessary that the storge tracks GA, GB and GC associated with the kiln AA should extend alongside of the building'instead of circularly about thekiln axis, and except-that the kiln AA is provided with only one stub repair track 1i'.V The kiln AA, which 'is considerably smaller indiame-V ter thanl the kiln AB, has its vertical axis laterally displaced from the axis of the kiln A, thereby permitting rthe use of two elevators Q and QA for moving goods treated from one iioor level to the other, with the elevator Q at the inner side and the elevator QA at the outer side of the circular track way for the larger kiln AB.

As those skilled inthe' art understand, the

treatment of china successively in biscuit andY glost kilnsA involves numerous goods `handling operations including inspection and dipping ofV the goods between biscuit *and glost iiring, as

well as a car loading and unloading operation for i :each kiln'. With thekil'n arrangement'ilhtstrated in Figs.' 8 and9 the generally' circular space within'the two kilns -can Ibeeffectively utilized in eiecting some or all of the various` goods handling operations required in theoperation of the kilns.

In the modication illustrated in Fig. l0, the kiln car CA shown is formed at one end with a central nose'C13 and at its other'end with a corresponding central recess C14. In a train of such cars, oneof each two adjacent cars has itsl nose C13 received in the recess C11 of the other and this interlocking engagement of the .cars tends to prevent radial displacement of one car relative to the other and thusrnakes it possible to provide each car with a single thrust roller P located adjacent one end, and preferably adjacent the rear end, of the car. In general, however, we prefer the arrangement of Fig. Il to that .of Fig. l0 as the machining required with the .car of Fig. 4 is simpler'.

As previously indicated, in lieu of giving the train its advancing movements wholly by a single propeller like the propeller I-I located adjacent the entrance end Vof the kiln, we may employ a supplemental propeller HA located intermediate the ends of the kiln chamber, as shown in Fig. l.

The auxiliary propeller I-IA which may be similar in construction to the propeller I-I and which may be operated in synchronism with the latter by suitable pipe connections to a common pumping mechanism Y(not shown), is preferably not of suiicient power in normal operation to have any tendency to separate the section of the train ahead of it from the section of the train behind it, while at the same time exerting a substantial propulsion elect on the section of the train ahead. The propulsion effect furnished by the auxiliary propeller I-IA diminishes the duty and required capacity of the main propeller, and minimizes the maximum radial outward thrust 'exerted by the train against. the thrust abutment O. Advantageously the auxiliary propeller may be located. adjacent the exit portion of the furnace ory high temperature zone ci the kiln, where wrecks and dislodgment of goods from the kiln cars are most apt to occur, so that in case of a car wreck and with the main propeller held out of operation, the auxiliary propeller I-IA may be utilized in separating sections of the train for track cle'arage purposes.`

In the types of circular kilns heretofore proposed in`which the movable goods transporting means includes a continuous circular member, it is essential that said means and the kiln charnber should be uniformly curved `about the kiln axis. Such vmathematical circularity, while ordif narilyfdesirable, is not essential with our irnproved kiln. l

While in accordance with the provisions of the statutes, we have illustrated and described the best forms of our invention now known to Us, it should be'apparent to those skilled in the art that changes in the for'rn of theapparatus described may be made without departing from the spirit of the inventio-nset forth in the aplpended claims and that certain features of the invention may sometimes be used to advantage without a corresponding use of other features.

VHaving now described our invention, what we claimv as new and desire to secure by Letters Patent, is: f

l. In the operation of a continuous tunnel kiln of the type comprising a circularly extending kiln chamber and a circularly extending track along which kiln cars are movable through said chamber, the methodwhich consists in moving kiln 'cars along said in a train shorter in length than said track and, as the motion the train proceeds, successively separating cars from the train at its head end and removing the Vcars so separated from the track for loading or repair purposes, and .successively placing cars on the track and adding themY to the train at its rear end to maintain the normal train length.

2.` A continuous tunnel kiln of the circular type comprising a circularly extending kiln chamber and a circularly extending track along which kiln cars are movable through said chamberl from the entrance to the exit ends of the latter, a train of kiln cars on said track shorter in length than the latter, means adjacentthe entrance end of the kiln for applying intermittent train advancin'g propeller thrusts to the rear car of the train, and means at the convex sideI of the train for engagement by the car bodies to hold the latter against movement outward from said track.

' 3. A continuous tunnel kiln of the circular type comprising a circularly extending kiln chamber and a circularly extending track along which kiln cars are movable through said chamber from the entrance to the exit ends ofthe latter, a train of kiln cars on said track shorter in length than the latter, means adjacent the entrance end of the kiln for applying intermittent train advancing propeller thrusts to the rear car of the train, means Aproviding a curved abutment track way at the convex side of said track and above the level of the latter, and roller members mounted. on said car bodies to turn about vertical axes while in engagement with said tracking, whereby said cars are held against movement outward from said track.- -f

4. A continuous tunnel kiln of the circular type comprising a circularly extending kiln chamber and a circular-track along which kiln cars are movable through said chamber and including a section movable transversely of its length into and'out of a position in which it may receive a car from or deliver a car toanadjacent portion of said track.

5. A continuous tunnel kiln of the circular type comprising a circularly extending kiln chamber, a kiln car storage track, and a circular track along which kiln cars are movable through said chamber and including a section movable transversely of its length between one positionin which it may receive a car from or deliver' a car to an adjacent portion of said circular track, and a seccnd'position in which it'may receive a car rom or deliver a car to said storage track.

V6. A tunnel kiln comprising an arc-shaped track for goods supporting cars, an arc-shaped kiln extending above said track, a track section movable from one position in which it extends between the ends of said arc-shaped track and mentioned track, and a track section movable between positions in one of which itrregisters with the ends of said arc-shaped track and unites with the latter to form a continuous track for kiln cars and other positions in which it registers respectively with said storage tracks to permit the movement to and from the latter of kiln cars from'and to said track section, respectively.

8. VIn a continuous tunnel kiln of the circular type, the combination with an arc-shaped kiln chamber of a circularly extending track, a train of kiln cars movable through said chamber on said track, said cars having thrust bearing rollers mounted on said cars to turn about vertical axes at the convex side of said train, a 'thrust beam' above extending along said track/at the convex side' of the kiln comprising a horizontal web por-v` tion and spaced apart uprising Y'flange 'portions,i

the frange portion at the concave side of the beam orminga track engaged by saidV rollers, apartition between said'ilanges and abovesaid webA unitingfwith said beam to forma sand containl' ing' trough space'between said'partition and the' outer'vertical iiange of the-beam and a' second space between said partition and the inner flange of the beam to receive sand spilling over the partition, and vertically disposed plate members carried at the outer sides oi the cars adapted to dip down into sand in the rst mentioned space and thereby form a sand seal preventing leakage through the joint between the outer sides of the car bodies and the adjacent portion of the kilnr structure. f l

9. In a continuous tunnel kiln of the circular mounted on said cars to turn about vertical'axes `at the convex side of said train, aV thrust beam above extending along said track at theconvex side of the kiln comprising a horizontal web por- Vtion and spaced apart uprising iiangeportions,

the flange portion at the concave side 4of Vthe beam forming a track engaged by said rollers, a

web uniting with said beam to form a sand containing 'trough space between said partition and'` the outer vertical flange of the beam and a second space between said partition and the inner iiange of the beam to receive sand spilling over the par- Ypartition between said flanges and above said tition, and vertically disposed plate members car-l ried at the outer sides of the cars adapted to dip down into sand in the-first mentioned space and thereby form a sand seal preventing leakage through the joint between the outer sides of the car bodies and theV adjacent portion of the kiln` structure, the portion of said web forming the bottom of said second space having apertures to permit the discharge of sand.

10.'In a tunnel kiln of the circular type, the

combination vof an arc-shaped track for the movement of kiln cars through the kiln Achamber o! said kiln, a storage track at one side of and diiering in curvature from the rst mentioned track,

a track section movable between a position which it registers with the ends of said arc-shaped track and uniteswith the latter to form a continuous'Av track for kiln cars land another position in which it registers with said storage track, and kiln cars movable along-saidtracks comprising car bodies and supporting wheels for said-bodies which are adjustable relative tothe latter to facilitate car movements along said arc-shaped track and along a track not similarly curved.

11. A tunnel'kiln comprising anarc-shapedkilnf chamber, 4an arc-shapedtrack for the Amovement of kiln' cars along said track through said kiln chamber, a storage track at vone side of and differing in curvature from the Iirst mentioned track,a track section movable between a position in which it registers with the ends of said arc-shaped track and unites with the latter` to form avcontinuous track for kiln cars and another position in which j it registers respectively with said storage track to permit the movement to vand from the-latter -of kiln cars from and to said track section, respectively, and kiln cars movable along said tracks and track sections comprising car bodies, and supporting wheels for said bodies and adjustable relative to the latter to facilitate car movements along the first mentioned track and along said storage track.

12. In a tunnel kiln of the circular type comprising a train of'kiln cars movable along a circularly extending path, train propulsive means adapted to exert a train advancing force in a direction substantially tangential to said path at one or more localized points along the length of the latter, and circularly disposed car guiding means co-acting with'the bodies of said cars to prevent movement of the latter radially outward from said path.

13. In a tunnel kiln of the circular type comprising a train of kiln cars movable along a circularly extending path, train propulsive means adapted to exert a train advancing force in a direction substantially tangential to said path at one or more localized points along the length of the latter, circularly disposed car guiding means and thrust rollers mounted on said cars and coacting with said guiding means, said rollers having antifriction bearings and being so disposed as to minimize dissipation ci the propulsive force in a direction radially to said path.

14. In a tunnel kiln of the circular type, the combination of a kiln chamber and a circularly extending track for the movement of kiln cars through said chamber in a train from the entrance to the exit end of the chamber, and means for giving motion to said train comprising a propeller located adjacent the entrance end of the kiln chamber and comprising a car engaging part movable forward and back along a path corresponding in curvature with the portion of said track along which the portion of a car engaged by it is moving, for successive engagement with cars successively at the rear of the train, and the advancement of the latter during successive forward movement of said part.

l5. In a continuous tunnel kiln of the circular type comprising a circularly extending kiln chamber and a circularly extending track along which kiln cars are movable through said chamber from the entrance to the exit ends of the latter and a train of kiln cars on said track, means for advancing said train along said track comprising a propeller adapted to act successively on the cars of said train successively adjacent the entrance end of the kiln and a second propeller adapted to act successively on the cars successively occupying a position intermediate the entrance and exit ends of said kiln chamber.

PHILIP DHUC DRESSLER. EDWARD A. HANFF.

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